MODIFIED POLYESTER FIBER, OPAL FINISHED WOVEN AND KNITTED FABRIC CONTAINING THE FIBER, AND METHOD FOR PRODUCING SAME

Abstract

 As a fiber for weight reduction, a modified polyester fiber, which is obtained by copolymerizing: ethylene terephthalate as a main constitutional unit; equal to or more than 12 mol% and equal to or less than 25 mol% of an aliphatic dicarboxylic acid having equal to or more than 4 and equal to or less than 8 carbon atoms; and equal to or more than 2 mol% and equal to or less than 5 mol% of a metal sulfonate group-containing aromatic dicarboxylic acid, is used. This modified polyester fiber has a single fiber fineness of equal to or more than 0.6 dtex and equal to or less than 3.5 dtex. A mixed woven or knitted fabric composed of two or more types of fibers, which are the modified polyester fiber, a regular polyester fiber, and optionally, a polyurethane fiber, is capable of exhibiting good etching finish properties by using an etching finish agent that contains an etching finish accelerator, for example, a Mei printer OP-2 (manufactured by Meisei Chemical Works, Ltd.) and sodium carbonate, and also exhibits low reduction in strength of non-etching finished parts.

Description

Technical Field

[0001] The invention relates to an easily alkali soluble polyester fiber having high etching finish properties, etching finished woven and knitted fabrics which contain said fiber and a method for producing the woven and knitted fabrics.

Background Art

[0002] In general, etching finishing which includes: printing an etching paste on a woven or knitted fabric composed of two or more types of fibers including a fiber having high etching finish properties and a fiber hard to be etched in a patterned manner; and embrittling and removing the fiber having high etching finish properties; is also called opal finishing. The etching finishing has been widely known as processing for forming a watermark pattern or a highly stretchable part. A chemical reaction in the etching finishing varies depending on types of fibers. For example, a method for removing a polyester fiber is also referred to as alkali weight reduction. The method is alkaline hydrolysis which uses sodium hydroxide, potassium hydroxide and the like. On the other hand, in order to remove a cellulosic fiber such as cotton and acetate, acid hydrolysis, dissolution by carbonization or a hot organic solvent and the like have been utilized.

[0003] As etching finishing for a woven or knitted fabric made of a polyester fiber, a method which includes: printing an etching paste on a woven or knitted fabric composed of a modified polyester fiber having high etching finish properties and an unmodified polyester fiber having low etching finish properties in a patterned manner; and removing the modified polyester fiber having high etching finish properties; has been known. As such a method, a method which includes: printing a paste liquid containing sodium hydroxide or potassium hydroxide as an etching finish agent; and performing heat treatment; has been known.

[0004] However, the method, which uses sodium hydroxide or potassium hydroxide when performing etching finishing by utilizing a difference in hydrolyzability between the modified polyester fiber having high etching finish properties and the unmodified polyester fiber having low etching finish properties, may even embrittle the unmodified polyester fiber. Accordingly, the method has a problem which may cause reduction in strength and etching defect. In addition, sodium hydroxide and potassium hydroxide are strong alkaline substances, and therefore, they have high toxicity and irritancy to human, and also have high influence on aquatic environment.

[0005] On the other hand, in order to improve dyeability of a polyethylene terephthalate fiber, which has been dyed under high temperature and high pressure by a disperse dye, such that the fiber is capable of being dyed by dyeing under normal pressure by using a disperse dye and a cationic dye, a modified polyester fiber which is obtained by copolymerizing a polyethylene terephthalate with 0.4 to 5 mol% of 5-sodium sulfoisophthalic acid and 2 to 15 mol% of adipic acid has been known, for example, by JP S61-239015 A (Patent Document 1), JP H08-269820 A (Patent Document 2), JP 2013-18802 A (Patent Document 3) and the like.

[0006] Such a modified polyester fiber has been diversified from the point of view of dyeing, because types of dyes which can be applied to the fiber increase. In addition, the modified polyester fiber has been also used for combined use of a polyethylene terephthalate fiber having high chemical resistance and a fiber having low chemical resistance in opal finishing. However, a conventional modified polyester fiber has been not sufficiently satisfied yet in terms of etching removal properties by an alkali when performing opal finishing. Accordingly, a modified polyester fiber, which maintains physical properties of the fiber as much as possible and which is etching removed more easily, has been required in order to diversify opal finished products.

[0007] In addition, for example, according to JP 2000-096439 A (Patent Document 4), with regard to etching finishing of a modified polyester fiber in a woven or knitted fabric in which a fabric is composed of the modified polyester fiber and an unmodified polyester fiber, etching finishing which uses an etching finish agent containing guanidine carbonate has been proposed. However, etching finishing by using guanidine carbonate is good in etching finish properties of the modified polyester, but there has been a problem that the unmodified polyester tends to embrittle, which causes the reduction in strength.

[0008] Further, according to JP 2000-282377 A (Patent Document 5), in etching finishing of a modified polyester fiber in a woven or knitted fabric which contains an normal pressure cation-dyeable polyester fiber as an essential component, a method which includes: printing a paste liquid containing a quaternary ammonium salt; performing heat treatment; and after that, performing alkali weight reduction to remove the modified polyester fiber; has been proposed. However, since the method is alkali weight reductionprocessing which uses sodium hydroxide, there has been a problem that strength of the modified polyester fiber and an unmodified polyester fiber cannot be maintained.

[0009] Furthermore, for example, according to JP 2008-038332 A (Patent Document 6), in etching finishing of a modified polyester fiber in a woven or knitted fabric composed of the modified polyester fiber and an unmodified polyester fiber, it has been proposed to perform etching finishing by a method which includes making an etching finish agent containing at least one of guanidine carbonate, sodium hydroxide, and potassium hydroxide adhere to the fabric by inkjet textile printing. In the method, etching finishing is performed by controlling an adhesion amount of the etching finish agent by inkjet textile printing. However, in order to maintain strength of the unmodified polyester fiber, fineness of the unmodified polyester fiber has been made larger. Alternatively, a bicomponent filament yarn in which a core part is an unmodified polyester fiber and a sheath part is a modified polyester fiber has been used such that the etching finish agent adheres only to the modified polyester fiber, or other methods have been used. In any case, there has been a problem that embrittlement of the unmodified polyester fiber cannot be prevented.

[0010] In addition, for example, according to WO 2007/086593 A (Patent Document 7), a method in which a fabric to which etching finishing is performed is composed of a non-elastic fiber and an elastic fiber has been proposed. In the fabric, a cation dyeable polyester fiber, which is a fiber capable of being etched, and a nylon fiber, which is a fiber not capable of being etched, are used as the non-elastic fiber, and an ether-based polyurethane fiber is used as the elastic fiber. There has been a problem that the cation dyeable polyester fiber and the polyurethane fiber, which are not the subjects of etching tend to be etched when sodium hydroxide is used as the etching finish agent, which causes reduction in elasticity and strength.

Citation List

Patent Document

[0011] 

Patent Document 1: JP S61-239015 A

Patent Document 2: JP H08-269820 A

Patent Document 3: JP 2013-18802 A

Patent Document 4: JP 2000-096439 A

Patent Document 5: JP 2000-282377 A

Patent Document 6: JP 2008-038332 A

Patent Document 7: WO 2007/086593 A

Summary of Invention

Technical Problem

[0012] One object of the invention is to provide an easily alkali soluble modified polyester fiber which is used as a fiber having low chemical resistance in opal finishing and is capable of being easily etching-removed by an alkali. Conventionally, an aliphatic dicarboxylic acid and a metal sulfonate group-containing aromatic dicarboxylic acid are copolymer components which are known to have modifying effects of dyeability of a polyethylene terephthalate fiber. However, it is found that when specific amounts of the aliphatic dicarboxylic acid and the metal sulfonate group-containing aromatic dicarboxylic acid are used, the modifying effects of dyeability are maintained, and further, it is found that an easily alkali soluble fiber, which can be easily etching-removed, can be obtained, and thus the invention has been completed.

[0013] In addition, as described above, there has been a problem that in etching finishing which includes etching a modified polyester fiber, sufficient etching can be achieved only in the case when a strong alkali is used. On the contrary, when the strong alkali is used, there has been a problem that strength of a fabric which has been subjected to etching finishing tends to decrease. In view of this situation, another object of the invention is to provide etching finished woven and knitted fabrics having high etching finish properties, which can be easily etched even when a weak alkali is used, by using a modified polyester fiber having sufficient etching finish properties, while preventing reduction in strength of fibers in parts containing an unmodified polyester fiber other than etchedparts . In addition, another object of the invention is to provide a method for producing the etching finished woven and knitted fabrics.

Solution to Problem

[0014] In conventional technologies, in etching finishing of a woven or knitted fabric composed of a modified polyester fiber and an unmodified polyester fiber, in order to prevent the unmodified polyester fiber from being embrittled, a method which includes: printing an alkali weight reduction accelerator without using a strong alkaline substance such as sodium hydroxide and potassium hydroxide in an etching paste; performing heat treatment; and promoting alkali weight reduction of printed parts at the time of the alkali weight reduction after the printing and the heat treatment; has been considered. However, the inventors have focused on further modification of a modified polyester fiber, and have conducted various studies and experiments. As a result, the inventors have found that alkali weight reduction of a certain modified polyester fiber can be performed in a certain pH range, without using a strong alkaline substance such as sodium hydroxide and potassium hydroxide, and without an influence of reduction in strength of an unmodified polyester fiber and a polyurethane fiber. The inventors have found that the alkali weight reduction only of the modified polyester fiber can be achieved.

[0015] The modified polyester fiber according to the invention is a modified polyester fiber characterized by having a weight reduction ratio of equal to or more than 5% and equal to or less than 15%, the weight reduction ratio being obtained by the following measuring method:
<measuring method of weight reduction ratio of fiber>
the measuring method of the weight reduction ratio including adding 100 g of a fiber to 2 L of an aqueous solution including 40 g/L of sodium carbonate; heating an obtained mixture at 100°C for 30 minutes; performing drying treatment at 80°C for 60 minutes; and after that, measuring a fiber mass A g.

[0016] It is preferable that the modified polyester fiber according to the invention is characterized in that the modified polyester fiber is composed of a modified polyester obtained by copolymerizing: ethylene terephthalate as a main constitutional unit; equal to or more than 12 mol% and equal to or less than 25 mol% of an aliphatic dicarboxylic acid having 4 to 8 carbon atoms; and equal to or more than 2 mol% and equal to or less than 5 mol% of a metal sulfonate group-containing aromatic dicarboxylic acid.

[0017] It is preferable that the modified polyester fiber according to the invention is characterized in that the aliphatic dicarboxylic acid is adipic acid, and the metal sulfonate group-containing aromatic dicarboxylic acid is 5-sodium sulfoisophthalic acid.

[0018] It is preferable that the modified polyester fiber according to the invention is characterized by having a content of diethylene glycol of equal to or more than 0.5 mass% and equal to or less than 3.0 mass%.

[0019] It is preferable that the modified polyester fiber according to the invention has a single fiber fineness of equal to or more than 0.6 dtex and equal to or less than 3.5 dtex, a fiber strength of equal to or more than 2.0 cN/dtex and equal to or less than 3.5 cN/dtex, and a fiber elongation of equal to or more than 25% and equal to or less than 45%.

[0020] It is preferable that the modified polyester fiber according to the invention is characterized in that the modified polyester fiber contains lithium acetate and diethylene glycol, and a content of the lithium acetate is 50 to 120 ppm in terms of lithium atom content.

[0021] The woven or knitted fabric according to the invention contains a modified polyester fiber and a fiber not for weight reduction, characterized in that: the modified polyester fiber has a weight reduction ratio of equal to or more than 5% and equal to or less than 15% and the fiber not for weight reduction has a weight reduction ratio of equal to or more than 0% and less than 5%; a content of the modified polyester fiber in the woven or knitted fabric is equal to or more than 5 mass% and equal to or less than 50 mass%; a content of the fiber not for weight reduction in the woven or knitted fabric is equal to or more than 50 mass% and equal to or less than 95 mass%; and the weight reduction ratio is obtained by the following measuring method:
<measuring method of weight reduction ratio of fiber>
the measuring method of the weight reduction ratio including: adding 100 g of a fiber to 2 L of an aqueous solution including 40 g/L of sodium carbonate; heating an obtained mixture at 100°C for 30 minutes; performing drying treatment at 80°C for 60 minutes; and after that, measuring a fiber mass A g.

[0022] The woven or knitted fabric according to the invention contains a modified polyester fiber and a fiber not for weight reduction, characterized in that: the modified polyester fiber has a weight reduction ratio of equal to or more than 5% and equal to or less than 15% and the fiber not for weight reduction has a weight reduction ratio of equal to or more than 0% and less than 5%; the woven or knitted fabric has an etching finished part of the modified polyester fiber; a weight reduction ratio of the modified polyester fiber in the etching finished part to the modified polyester fiber in a non-etching finished part is equal to or more than 50 mass% and equal to or less than 100 mass%; and the weight reduction ratio is obtained by the above-described measuring method of the weight reduction ratio of the fiber.

[0023] It is preferable that the woven or knitted fabric according to the invention is characterized in that a difference between said weight reduction ratio of the modified polyester fiber and said weight reduction ratio of the non-etched fiber is equal to or more than 5%.

[0024] It is preferable that the woven or knitted fabric according to the invention is characterized in that a burst strength of the woven or knitted fabric in the etching finished part is equal to or more than 250 kPa and equal to or less than 900 kPa.

[0025] It is preferable that the woven or knitted fabric according to the inventionhas a strength retention ratio of aburst strength of the woven or knitted fabric in the etching finished part to a burst strength of the woven or knitted fabric in the non-etching finished part of equal to or more than 50%.

[0026] It is preferable that the woven or knitted fabric according to the invention is characterized in that the modified polyester fiber is a modified polyester that is obtained by copolymerizing: ethylene terephthalate as a main constitutional unit; equal to or more than 16 mol% and equal to or less than 25 mol% of an aliphatic dicarboxylic acid having 4 to 8 carbon atoms; and equal to or more than 2 mol% and equal to or less than 5 mol% of a metal sulfonate group-containing aromatic dicarboxylic acid.

[0027] It is preferable that the woven or knitted fabric according to the invention is characterized in that the fiber not for weight reduction contains equal to or more than 50 mass% and equal to or less than 95 mass% of synthetic fibers.

[0028] It is preferable that the woven or knitted fabric according to the invention is characterized in that the synthetic fiber is at least one of a regular polyester fiber, a polyamide fiber, an elastic fiber, a polyolefin fiber, and an acrylic fiber.

[0029] It is preferable that the woven or knitted fabric according to the invention is characterized in that a single fiber fineness of the modified polyester fiber is equal to or more than 0.6 dtex and equal to or less than 3.5 dtex.

[0030] It is preferable that the woven or knitted fabric according to the invention is characterized in that the elastic fiber is composed of any one of a polyurethane fiber, a polytrimethylene terephthalate fiber, and a polybutylene terephthalate fiber.

[0031] It is preferable that the method for producing the woven or knitted fabric according to the invention includes: printing an etching finish agent on a cloth that contains a modified polyester fiber having a weight reduction ratio of equal to or more than 5% and equal to or less than 15% and a fiber not for weight reduction; and performing weight reduction processing by supplying a superheated steam to a part on which the etching finish agent is printed; the method being characterized in that: the etching finish agent has a pH of equal to or more than 8 and equal to or less than 13 ; the heatingmethod includes supplying a superheated steam of equal to or higher than 150°C and equal to or lower than 200°C; the heating time is equal to or more than 5 minutes and equal to or less than 15 minutes; and the weight reduction ratio is obtained by the above-described measuring method of the weight reduction ratio of the fiber.

Advantageous Effects of Invention

[0032] According to the invention, in etching finishing of a woven or knitted fabric containing a modified polyester fiber, it is possible that reduction in strength of parts other than etched parts of the modified polyester fiber does not occur. In addition, it is possible that reduction in strength of etched parts of the woven or knitted fabric containing a fiber other than the modified polyester fiber does not occur. At the same time, a good etching action can be obtained. According to the invention, it is possible to obtain an etching finished product of which the modified polyester fiber is etched well without causing reduction in strength.

Description of Embodiments

[0033] The modified polyester fiber according to the invention is a modified polyester fiber characterized by having a weight reduction ratio of equal to or more than 5% and equal to or less than 15%, the weight reduction ratio being obtained by the following measuring method:
<measuring method of weight reduction ratio of fiber>
the measuring method of the weight reduction ratio including: adding 100 g of a fiber to 2 L of an aqueous solution including 40 g/L of sodium carbonate; heating an obtained mixture at 100°C for 30 minutes; performing drying treatment at 80°C for 60 minutes; and after that, measuring a fiber mass A g.

[0034] When the modified polyester fiber according to the invention has the weight reduction ratio of equal to or more than 5%, weight-reduction of the modified polyester fiber is capable of being performed with an alkali easily, and deterioration in physical properties of a fiber not for weight reduction can be suppressed. In addition, when the weight reduction ratio is equal to or less than 15%, reduction in strength of the modified polyester fiber according to the invention is low, and it is possible to suppress thread breakage inaproduction process of a woven or knitted fabric.

[0035] From the above points of view, the weight reduction ratio of the fiber is more preferably equal to or more than 7% and equal to or less than 13%, and is even more preferably equal to or more than 8% and equal to or less than 11%.

[0036] It is preferable that the modified polyester fiber according to the invention is composed of a modified polyester obtained by copolymerizing: ethylene terephthalate as a main constitutional unit; equal to or more than 12 mol% and equal to or less than 25 mol% of an aliphatic dicarboxylic acid having 4 to 8 carbon atoms; and equal to or more than 2 mol% and equal to or less than 5 mol% of a metal sulfonate group-containing aromatic dicarboxylic acid.

[0037] It is preferable that the modified polyester fiber according to the invention is characterized in that the aliphatic dicarboxylic acid is adipic acid, and the metal sulfonate group-containing aromatic dicarboxylic acid is 5-sodium sulfoisophthalic acid.

[0038]  The aliphatic dicarboxylic acid having 4 to 8 carbon atoms, which is a copolymer component, increases alkali solubility of the polyester fiber by disturbing an amorphous structure of the fiber. Examples of the aliphatic dicarboxylic acid having 4 to 8 carbon atoms include succinic acid, glutaric acid, adipic acid, pimelicacid, and suberic acid, and particularly preferable examples of the aliphatic dicarboxylic acid having 4 to 8 carbon atoms include adipic acid.

[0039] An amount of the copolymerized aliphatic dicarboxylic acid having 4 to 8 carbon atoms is equal to or more than 16 mol% and equal to or less than 25 mol%, and is preferably, equal to or more than 18 mol% and equal to or less than 20 mol%. When the amount of the copolymerized aliphatic dicarboxylic acid having 4 to 8 carbon atoms is within this range, significant deterioration in dynamic and heat characteristics is suppressed, and the amorphous structure of the fiber is disturbed, which contributes to improvement of dyeability with a disperse dye and a cationic dye. In addition, alkali solubility of the fiber is significantly increased. When the amount of the copolymerized aliphatic dicarboxylic acid having 4 to 8 carbon atoms is equal to or more than 16 mol%, it becomes easy to obtain a solubility with an alkali easily suitable for opal finishing. When the amount of the copolymerized aliphatic dicarboxylic acid having 4 to 8 carbon atoms is equal to or less than 25 mol%, it becomes easy to maintain physical properties, fastness properties, and heat characteristics such as heat resistance of the fiber, which are required to be used as a fiber.

[0040] The metal sulfonate group-containing aromatic dicarboxylic acid, which is the other copolymer component, is a component which acts as a cationic dye-dyeing site since a metal sulfonate group is introduced into a fiber. In addition, the metal sulfonate group-containing aromatic dicarboxylic acid is a component which makes it possible to dye a polyethylene terephthalate fiber with a cationic dye under normal pressure. Further, the metal sulfonate group, together with an aromatic ring, is introduced into the fiber, and makes it possible to improve dyeability with a disperse dye. Furthermore, the temperature on dying can be lowered. In addition, the metal sulfonate group-containing aromatic dicarboxylic acid also contributes to improvement of alkali solubility of the fiber. Examples of the metal sulfonate group-containing aromatic dicarboxylic acid include, 5-sodium sulfoisophthalic acid, potassium sulfoterephthalic acid, sodium sulfonaphthalene dicarboxylic acid and the like. Particularly preferable examples of the metal sulfonate group-containing aromatic dicarboxylic acid include 5-sodium sulfoisophthalic acid.

[0041] An amount of the copolymerized metal sulfonate group-containing aromatic dicarboxylic acid is equal to or more than 2 mol% and equal to or less than 5 mol%. When the amount of the copolymerized metal sulfonate group-containing aromatic dicarboxylic acid is equal to or more than 2 mol%, it becomes easy to obtain sufficient dyeability with a cationic dye. In addition, it tends to be easy to lower a temperature on dying with a disperse dye sufficiently. When the amount of the copolymerized metal sulfonate group-containing aromatic dicarboxylic acid is equal to or less than 5 mol%, it tends to be easy to decrease the thread breakage during spinning and the occurrence of fuzz.

[0042] The production of the modified polyester according to the invention can be achieved by a known method which is the same as the production of a polyethylene terephthalate. In other words, when terephthalic acid is used, a method which includes causing an esterification reaction of terephthalic acid with ethylene glycol is employed. Alternatively, when dimethyl terephthalate, which is an ester, is used, a method which includes causing a transesterification reaction between dimethyl terephthalate and ethylene glycol, and thereafter, performing a polycondensation reaction is employed.

[0043] The aliphatic dicarboxylic acidhaving4 to 8 carbon atoms, which is a copolymer component, can be added at an arbitrary stage before completion of the polycondensation. For example, the aliphatic dicarboxylic acid having 4 to 8 carbon atoms is added as a slurry in ethylene glycol at the time of starting the esterification reaction between terephthalic acid and ethylene glycol. Alternatively, the aliphatic dicarboxylic acid having 4 to 8 carbon atoms is added as a dispersion or a solution of the aliphatic dicarboxylic acid or bis-hydroxy dicarbonate in ethylene glycol to bis(β-hydroxyethyl)terephthalate which is generated by the esterification reaction between terephthalic acid and ethylene glycol. Meanwhile, when producing the modified polyester, a gloss reducing agent, an antistatic agent, a flame retardant, a pigment and the like may be added at an arbitrary stage before completion of the polycondensation.

[0044] Similarly, the metal sulfonate group-containing aromatic dicarboxylic acid, which is a copolymer component in producing the modified polyester, can be added at an arbitrary stage before completion of the polycondensation.

[0045] For example, the metal sulfonate group-containing aromatic dicarboxylic acid is added as a slurry in ethylene glycol at the time of starting the esterification reaction between terephthalic acid and ethylene glycol. Alternatively, the metal sulfonate group-containing aromatic dicarboxylic acid is added as a dispersion or a solution of the metal sulfonate group-containing aromatic dicarboxylic acid dimethyl ester or diglycol ester in ethylene glycol to bis(β-hydroxyethyl)terephthalate which is generated by the esterification reaction between terephthalic acid and ethylene glycol.

[0046] It is preferable that the modified polyester fiber according to the invention has a content of diethylene glycol of equal to or more than 0.5 mass% and equal to or less than 3.0 mass%.

[0047] When producing the modified polyester, especially when producing the modified polyester by a direct esterification method, diethylene glycol, which is produced by dehydrative dimerization of ethylene glycol, is produced as a by-product, and remains in the subsequent polycondensation reaction system.

[0048] When the content of diethylene glycol in the modified polyester fiber according to the invention is equal to or less than 3.0 mass%, deterioration in a fiber strength can be suppressed. From the above points of view, the content of diethylene glycol in the modified polyester fiber is more preferably equal to or less than 2.5 mass%, and is further more preferably equal to or less than 2.0 mass%.

[0049] Preferable examples of the method for suppressing the by-production of diethylene glycol include a method which includes adding a weak acid salt or a hydroxide of an alkali metal or an alkali earth metal to the reaction system during the esterification reaction. In particular, sodium hydroxide, sodium acetate, lithium acetate and the like are effective for suppressing the by-production of diethylene glycol, and are preferably used when the content of dicarboxylic acids, which are copolymer components, is equal to or more than 10 mol%. In the invention, lithium acetate is more preferably used.

[0050] It is preferable that the modified polyester fiber according to the invention contains lithium acetate and a content of the lithium acetate is 50 to 120 ppm in terms of lithium atom content.

[0051] The content of lithium acetate is preferably 50 to 150 ppm to a polymer composition in terms of lithium atom content, is more preferably 100 to 150 ppm, and is even more preferably 120 to 150 ppm. When such an amount of lithium acetate is added and contained, the modified polyester having a content of ethylene glycol of equal to or more than 0.5 mass% and equal to or less than 3.0 mass% can be obtained.

[0052] It is preferable that the modified polyester fiber according to the invention has a single fiber fineness of equal to or more than 0.6 dtex and equal to or less than 3.5 dtex, a fiber strength of equal to or more than 2 cN/dtex and equal to or less than 3.5 cN/dtex, and a fiber elongation of equal to or more than 25% and equal to or less than 45%.

[0053] It is preferable that the modified polyester fiber according to the invention has a single fiber fineness of equal to or more than 0.6 dtex, because a fiber strength can be maintained and the manufacturability of a woven or knitted fabric is good. It is preferable that the modified polyester fiber according to the invention has a single fiber fineness of equal to or less than 3.5 dtex, because the weight reduction processability is good. From the above points of view, the single fiber fineness is more preferably equal to or more than 1 dtex and equal to or less than 3 dtex, and is further more preferably equal to or more than 1.3 dtex and equal to or less than 2.5 dtex.

[0054] It is preferable that the modified polyester fiber according to the invention has a fiber strength of equal to or more than 2 cN/dtex and equal to or less than 3.5 cN/dtex, because there is no problem in the manufacturability of a woven or knitted fabric . It is more preferable that the modified polyester fiber according to the invention has a fiber strength of equal to or more than 2.3 cN/dtex and equal to or less than 3 cN/dtex. In addition, it is preferable that the modified polyester fiber according to the invention has an elongation of equal to or more than 25% and equal to or less than 45%, because the manufacturability of a woven or knitted fabric is good. It is more preferable that the modified polyester fiber according to the invention has an elongation of equal to or more than 30% and equal to or less than 40%.

[0055] The modified polyester according to the invention is produced through, for example, the following production steps:

the step of supplying a slurry of terephthalic acid and ethylene glycol into an esterification reaction vessel in which bis(β-hydroxyethyl)terephthalate and an oligomer thereof are present, and causing an esterification reaction at a temperature around 250°C for 3 to 8 hours to give a reaction product having an esterification rate of equal to or more than 95%; the step of transferring the esterification reaction product to a polymerization vessel, adding each of an aliphatic dicarboxylic acid and a metal sulfonate group-containing aromatic dicarboxylic acid, which are copolymer components, lithium acetate, magnesium acetate, triethyl phosphate, and germanium dioxide as a solution or a dispersion in ethylene glycol, and thereafter, adding antimony trioxide, which is a polymerization catalyst, as a dispersion in ethylene glycol, raising the temperature, and performing a polycondensation reaction at a temperature around 270°C under reduced pressure until a polycondensate reaches a predetermined limiting viscosity; and after that,

the step of removing the polycondensate to give a strand and making the strand as a chip.

[0056] The modified polyester fiber according to the invention can be obtained by a known melt spinning method similar to a method for producing a polyethylene terephthalate fiber. As a method for making a yarn which includes spinning by extruding a modified polyester chip from a spinning hole of a spinning nozzle and subsequent drawing, a known method may be also employed. For example, for the production of the modified polyester fiber, a condition of: a spinning temperature of 240 to 300°C; a spinning speed of 1,000 to 2,000 m/min; a drawing temperature of 60 to 90°C; a drawing speed of 400 to 1,000 m/min; a drawing ratio of 1.8 to 3.5 times; a drawing ratio of 0.65 to 0.80 times the maximum drawing ratio; and a heat set temperature of 110 to 160°C; is used. Here, the maximum drawing ratio refers to a ratio obtained when drawing is performed until an undrawn yarn is cut at a drawing temperature of 80°C, a heat set temperature of 145°C, and a drawing speed of 600 m/min.

[0057] In a yarn manufacturing process, a method which includes winding an undrawn yarn after spinning once and then drawing, a method which includes drawing without winding an undrawn yarn after spinning, a method which includes winding a yarn as a half undrawn yarn by high speed spinning at a spinning speed of equal to or more than 2,000 m/min, a method which includes high speed spinning and drawing without winding, or a similar method may be employed.

[0058] The modified polyester fiber according to the invention is suitably used for opal finishing in which a part of component fibers of a woven or knitted fabric is etching removed. Accordingly, a single fiber fineness of the modified polyester fiber, or when the form of the fiber is a filament yarn, a single yarn fineness, is preferably equal to or more than 0.6 dtex and equal to or less than 3.5 dtex because etching removal of the fiber is easy. The cross sectional shape of the modified polyester fiber may be any shapes including a circular shape, a flat shape, a triangle shape, a Y-shape, a multilobed shape and the like. In addition, the form of the modified polyester fiber may be any of a short fiber, and a filament. When the form of the fiber is a filament, the filament yarn may be subjected to crimping processing or false twist processing.

[0059] The modified polyester fiber according to the invention has easy dyeability, that is, capability of being dyed with a disperse dye under normal pressure, as well as dyeability, that is, capability of being dyed with a cationic dye under normal pressure. At the same time, the modified polyester fiber according to the invention has solubility with an alkali easily, that is, capability of being etching removed easily. Accordingly, when a mixed woven or knitted fabric, which is obtained by combined weaving or knitting of the modified polyester fiber according to the invention with another fiber having high chemical resistance, is subj ected to opal finishing, opal finished products having various colors and color tones can be obtained by adding a disperse dye or a cationic dye to an etching paste or a paste containing an etching finish accelerator for printing. Especially preferable examples of the fiber having high chemical resistance which is used in combination include a polyethylene terephthalate fiber. Accordingly, the modified polyester fiber according to the invention is capable of producing an opal finished product of a mixed woven or knitted fabric consisting only of polyester fibers, by being combined with a polyethylene terephthalate fiber. In addition, the modified polyester fiber according to the invention may be used in combination with another fiber having low chemical resistance or another fiber having different chemical resistance, for example, wool, silk, cotton, rayon, an acetate fiber, a polyamide fiber or the like, other than a fiber having high chemical resistance, according to the need. The modified polyester fiber according to the invention is capable of producing an opal finished product having various colors, color tones, and textures, by adding a dye suitable for the fiber to be combined to an etching paste.

[0060] In addition, the modified polyester fiber according to the invention makes it possible to obtain an opal finished product having stretchability due to its solubility with an alkali easily. The opal finished product having stretchability can be obtained by combining the modified polyester fiber with a polyethylene terephthalate fiber and a polyurethane fiber and performing opal finishing under a mild alkali treatment condition such that a highly stretchable part in which only the modified polyester fiber is etching removed is formed without embrittling the polyurethane fiber. The polyurethane fiber which is used may be any of a polyether-based polyurethane fiber, and a polyester-based polyurethane fiber.

[0061] For opal finishing performed on a mixed woven or knitted fabric obtained by combined weaving or knitting of the modified polyester fiber according to the invention with a polyethylene terephthalate fiber, and optionally, a polyurethane fiber, for example, a method which includes the steps of printing an etching paste which contains sodium hydroxide as an etching agent, drying, etching treating by wet heating or dry heating, and soaping and washing with water; a method which includes the steps of printing a paste containing an etching finish accelerator, drying and heat treating, soaping and washing with water, and alkali weight reduction treating (etching treating) with sodium hydroxide; and the like may be employed. However, conditions of the methods vary depending on a woven or knitted fabric texture, a mixing ratio of fibers, an etching pattern, a use or the like. In the case of opal finishing of a mixed woven or knitted fabric composed of the modified polyester fiber according to the invention, a polyethylene terephthalate fiber, and optionally, a polyurethane fiber, the alkali weight reduction treatment (etching treatment) in the latter method may be performed by alkali weight reduction processing which is generally applied to a woven or knitted fabric of a polyester fiber, and the latter method is more preferably employed. When opal finishing is performed, a dye may be appropriately added to an etching paste or a paste containing an etching finish accelerator such that etching and coloring of a non-etched fiber are performed simultaneously. In addition, dying maybe combinedly performed before or after opal finishing. As a result, an opal finished product which has various colors, a low single fiber fineness, as well as a high-grade sense can be obtained.

[0062] Examples of the opal finished product of the mixed woven or knitted fabric obtained by using the modified polyester fiber according to the invention include an embroidery lace, an outerwear as well as an innerwear such as lingerie, a foundation, a swimsuit, an underwear for sports, a bodysuit, a leotard, tights for sports and a girdle.

[0063] The woven or knitted fabric according to the invention is a woven or knitted fabric containing a modified polyester fiber and a fiber not for weight reduction, characterized in that: the modified polyester fiber has a weight reduction ratio of equal to or more than 5% and equal to or less than 15% and the fiber not for weight reduction has a weight reduction ratio of equal to or more than 0% and less than 5%; a content of the modified polyester fiber in the woven or knitted fabric is equal to or more than 5 mass% and equal to or less than 50 mass%; a content of the fiber not for weight reduction in the woven or knitted fabric is equal to or more than 50 mass% and equal to or less than 95 mass%; and the weight reduction ratio is obtained by the following measuring method:
<measuring method of weight reduction ratio of fiber>
the measuring method of the weight reduction ratio including: adding 100 g of a fiber to 2 L of an aqueous solution including 40 g/L of sodium carbonate; heating an obtained mixture at 100°C for 30 minutes; performing drying treatment at 80°C for 60 minutes; and after that, measuring a fiber mass A g.

[0064] The woven or knitted fabric according to the invention contains the fiber not for weight reduction having the weight reduction ratio of equal to or more than 0% and less than 5%, and therefore, when the modified polyester fiber according to the invention is subjected to weight reduction with an alkali, the fiber not for weight reduction remains and etching finishing can be performed.

[0065] From the above point of view, the weight reduction ratio of the fiber not for weight reduction is more preferably equal to or less than 4%, and is further more preferably equal to or less than 3%.

[0066] In addition, when the content of the modified polyester fiber in the woven or knitted fabric is equal to or more than 5 mass%, an effect of etching finishing tends to be easily exhibited. Further, when the content of the modified polyester fiber in the woven or knitted fabric is equal to or less than 50 mass%, the non-etched fiber remains sufficiently, and therefore, strength of the woven or knitted fabric can be maintained sufficiently.

[0067] From the above points of view, the content of the modified polyester fiber in the woven or knitted fabric is more preferably equal to or more than 10 mass% and equal to or less than 40 mass%, and is even more preferably equal to or more than 15 mass% and equal to or less than 30 mass%.

[0068] The woven or knitted fabric according to the invention is a woven or knitted fabric containing a modified polyester fiber and a fiber not for weight reduction, characterized in that: the modified polyester fiber has a weight reduction ratio of equal to or more than 5% and equal to or less than 15% and the fiber not for weight reduction has a weight reduction ratio of equal to or more than 0% and less than 5%; the woven or knitted fabric has an etching finished part of the modified polyester fiber; a weight reduction ratio of the modified polyester fiber in the etching finished part to the modified polyester fiber in a non-etching finished part is equal to or more than 50 mass% and equal to or less than 100 mass%; and the weight reduction ratio is obtained by the following measuring method:
<measuring method of weight reduction ratio of fiber>
the measuring method of the weight reduction ratio including: adding 100 g of a fiber to 2 L of an aqueous solution including40 g/Lof sodium carbonate; heating an obtained mixture at 100°C for 30 minutes; performing drying treatment at 80°C for 60 minutes; and after that, measuring a fiber mass A g.

[0069] The woven or knitted fabric according to the invention having the etching finished part has a weight reduction ratio of the modified polyester fiber in the etching finished part to the modified polyester fiber in the non-etching finished part of equal to or more than 50 mass% and equal to or less than 100 mass%.

[0070] When the weight reduction ratio is 50%, an effect of weight reduction processing on a woven fabric is sufficient. When the weight reduction ratio is 100%, there is no modified polyester fiber in the etching finished part, and such a state is preferable. However, from the point of view of a designing effect on the woven or knitted fabric, it is preferable to make at least a part of the modified polyester remain in the etching finished part.

[0071] It is preferable that the woven or knitted fabric according to the invention has a burst strength of the woven or knitted fabric in the etching finished part of equal to or more than 250 kPa and equal to or less than 900 kPa.

[0072] When the burst strength is equal to or more than 250 kPa, the strength has no problem for the woven or knitted fabric to be used as a product. In addition, when the burst strength is 900 kPa, the strength is sufficient for the woven or knitted fabric to be used.

[0073] From the above points of view, the burst strength is preferably equal to or more than 400 kPa, and is more preferably equal to or more than 600 kPa.

[0074] It is preferable that the woven or knitted fabric according to the invention has a strength retention ratio of a burst strength of the woven or knitted fabric in the etching finished part to a burst strength of the woven or knitted fabric in the non-etching finished part of equal to or more than 50%.

[0075] When the strength retention ratio of the burst strength of the woven or knitted fabric in the etching finished part to the burst strength of the woven or knitted fabric in the non-etching finished part is equal to or more than 50%, the break of the woven or knitted fabric due to the excess stress concentration to the etching finished part is suppressed.

[0076] From the above points of view, the strength retention ratio is more preferably equal to or more than 70%, and is further more preferably equal to or more than 85%.

[0077] It is preferable that the woven or knitted fabric according to the invention is characterized in that the modified polyester fiber is a modified polyester fiber that is obtained by copolymerizing: ethylene terephthalate as a main constitutional unit; equal to or more than 16 mol% and equal to or less than 25 mol% of an aliphatic dicarboxylic acid having 4 to 8 carbon atoms; and equal to or more than 2 mol% and equal to or less than 5 mol% of a metal sulfonate group-containing aromatic dicarboxylic acid.

[0078] When the modified polyester fiber has an amount of the copolymerized aliphatic dicarboxylic acid having 4 to 8 carbon atoms of equal to or more than 16 mol%, weight reduction tends to be easily performed even in a range of pH equal to or more than 9 and equal to or less than 13. When the amount of the copolymerized aliphatic dicarboxylic acid having 4 to 8 carbon atoms is equal to or less than 25 mol%, thread breakage of said fiber during spinning canbe suppressed, and productivity becomes good.

[0079] From the above points of view, it is more preferable that the amount of the copolymerized aliphatic dicarboxylic acid having 4 to 8 carbon atoms is equal to or less than 20 mol%.

[0080] It is preferable that the woven or knitted fabric according to the invention is characterized in that the fiber not for weight reduction contains equal to or more than 50 mass% and equal to or less than 95 mass% of synthetic fibers.

[0081] When the content of the synthetic fiber in the woven or knitted fabric is equal to or more than 50 mass%, deterioration in the burst strength of the etching finished part can be suppressed. In addition, when the content of the synthetic fiber is equal to or less than 95 mass%, an etched fiber can be contained, and therefore, it becomes possible to exhibit effects of etching finishing easily. From the above points of view, the content of the synthetic fiber is more preferably equal to or more than 60 mass% and equal to or less than 80 mass%.

[0082] It is preferable that the woven or knitted fabric according to the invention is characterized in that the synthetic fiber is at least one of a regular polyester fiber, a polyamide fiber, an elastic fiber, a polyolefin fiber, and an acrylic fiber.

[0083] Among the above, from the point of view of strength, the synthetic fiber is preferably a regular polyester fiber, and from the point of view of exhibiting stretchability, the synthetic fiber is preferably an elastic fiber.

[0084] It is preferable that the woven or knitted fabric according to the invention is characterized in that a single fiber fineness of the modified polyester fiber is equal to or more than 0.6 dtex and equal to or less than 3.5 dtex.

[0085] When the single fiber fineness is equal to or more than 0.6 dtex, strength of the woven or knitted fabric can be increased, and when the single fiber fineness is equal to or less than 3.5 dtex, etching finish properties become good, and the texture of the woven or knitted fabric tends to be easily made to be soft.

[0086] From the above points of view, it is more preferable that the single fiber fineness is equal to or more than 0.9 dtex and equal to or less than 2.5 dtex.

[0087] It is preferable that the woven or knitted fabric according to the invention is characterized in that the elastic fiber is anyone of apolyurethane fiber, a polytrimethylene terephthalate fiber, and a polybutylene terephthalate fiber, as described above.

[0088] It is preferable that the woven or knitted fabric according to the invention is composed of the modified polyester fiber, the regular polyester fiber and the polyurethane fiber. When the woven or knitted fabric has the above-described constitution, the woven or knitted fabric which has stretchability, high strength, and a soft texture can be obtained.

[0089] The method for producing the woven or knitted fabric according to the invention is a method for producing a woven or knitted fabric, the method including: printing an etching finish agent on a cloth that contains a modified polyester fiber, which is weight reduced under a condition of pH of equal to or more than 8 and equal to or less than 13, and a fiber not for weight reduction; and performing weight reduction processing by supplying a superheated steam to a part on which the etching finish agent is printed; the method being characterized in that: the etching finish agent has a pH of equal to or more than 8 and equal to or less than 13 ; the heating method includes supplying a superheated steam of equal to or higher than 150°C and equal to or lower than 200°C; and the heating time is equal to or more than 5 minutes and equal to or less than 15 minutes.

[0090]  The heating method includes supplying a superheated steam of equal to or higher than 150°C and equal to or lower than 200°C onto a part on which an etching finish agent is printed. When the temperature of the superheated steam is equal to or higher than 150°C, etching finish properties becomes good, and when the temperature of the superheated steam is equal to or lower than 200°C, it becomes possible to prevent the texture of the polyester fiber from becoming hard.

[0091] It is preferable that the heating time is equal to or more than 5 minutes and equal to or less than 15 minutes.

[0092] When the heating time is equal to or more than 5 minutes, etching finish properties become good, and when the heating time is equal to or less than 15 minutes, reduction in strength of the non-etching finished part can be suppressed.

[0093] An etching finish agent is characterized by containing a pasting agent and a component having an etching action in a specific range of pH (pH of equal to or more than 8 and equal to or less than 13) except for guanidine carbonate. It is preferable that the component having the etching action is one or two types selected from sodium carbonate and potassium carbonate, and it is more preferable that the component having the etching action is one type which is sodium carbonate. An amount of sodium carbonate or potassium carbonate used may be adjusted depending on the mass of the modified polyester fiber to be etched. In general, it is preferable that the amount of sodium carbonate or potassium carbonate used may be in a range of equal to or more than 5 mass% and equal to or less than 15 mass% to the amount of the etching finish agent. The etching finish agent may contain an etching finish accelerator, according to the need. The etching finish accelerator is not particularly limited, and a commercially available etching finishaccelerator may be used. For example, it is preferable that the etching finish accelerator is a Mei printer OP-2 manufactured by Meisei Chemical Works, Ltd.

[0094] Examples of the pasting agent contained in the etching finish agent which may be used include a natural pasting agent, a processed pasting agent, a semisynthetic pasting agent, and a synthetic pasting agent. Examples of the pasting agent include a locust bean gum based pasting agent, a starch based pasting agent, a dextrin based pasting agent, a crystal gum based pasting agent, a tragacanth gum based pasting agent, a cellulose based pasting agent, carboxymethyl cellulose, polyvinyl alcohol, sodium polyacrylate and the like. The pasting agent may be used alone or two or more types of them may be used. A ratio of the pasting agent is not particularly limited as long as a viscosity suitable for printing the etching finish agent and performing heat treatment can be maintained. For example, it is preferable that the pasting agent is contained in a ratio equal to or more than 1 mass% and equal to or less than 10 mass% to the etching finish agent.

[0095] The etching finish agent may further contain other compounds such as a dye.

[0096] A method for etching finishing which includes using the above-described etching finish agent is described hereinbelow.

[0097] The above-described etching finish agent is preferably applied to a woven or knitted fabric containing a modified polyester fiber.

[0098] A fiber which is used in combination with the modified polyester fiber is not particularly limited as long as the fiber has a weight reduction resistant property different from the modified polyester fiber. Examples of the fiber which may be used in combination with the modified polyester fiber include an unmodified polyester fiber (which is composed of an unmodified polyethylene terephthalate, and is also referred to as a regular polyester fiber), a polyamide fiber, a polytrimethylene terephthalate fiber, a polybutylene terephthalate fiber, a polypropylene fiber, a polyethylene fiber, a polyurethane fiber and the like. The modified polyester fiber and the above-described fiber are combined by an arbitrary method such as mixed spinning, mixed fiber producing, intertwisting and the like to give a woven or knitted fabric composed of a yarn, a staple yarn and the like. Then, the woven or knitted fabric is subjected to etching finishing. As the above-described woven or knitted fabric, a fabric which is dyed may be used, according to the need. Dying is performed by a known arbitrary method on all parts or one part of the fabric by plain dyeing or printing.

[0099] Etching finishing may be performed by using the above-described etching finish agent, according to a known method which generally includes printing, heat treating, and washing. In the step of printing, an etching finish agent is printed on a woven or knitted fabric containing a modified polyester fiber in a shape in accordance with a desired pattern. For printing the etching finish agent, a printing method, a spraying method and the like may be used. The printing method is not particularly limited, and a frame mold printing method, a flat screen printing method, a rotary screen printing method, a roller printing method and the like may be used. An adhesion amount of the etching finish agent onto the woven or knitted fabric may be determined arbitrarily depending on the printing method, the woven or knitted structure of the fabric, and the desired pattern.

[0100] For example, when the flat screen printing method is employed, a viscosity of the etching finish agent, a hardness of a rubber squeegee, a pressure of a rubber squeegee whenprinting of the etching finish agent is performed, and a printing speed of a squeegee are determined, depending on the woven or knitted structure to which printing is performed, a mesh of a flame mold which prints a desired pattern and the like. Then, the etching finish agent is applied on the fabric in a desired pattern uniformly. In order to confirm that the etching finish agent is uniformly adhered to the fabric, confirmation of whether there is a blur in a printed part, confirmation of whether there is a difference in a pattern between the right and left of the rubber squeegee, confirmation of whether the etching finish agent is permeated uniformly into the back surface of the printed part and the like visually are performed. In addition, a coloring paste which does not contain an etching finish agent maybe printed onto a part other than the adhered part of the etching finish agent, in a shape in accordance with a desired pattern. A method for printing the coloring paste is not particularly limited, and the same printing method as that of the etching finish agent may be employed. After printing the etching finish agent and the coloring paste to the woven or knitted fabric, the woven or knitted fabric is appropriately dried, and thereafter, heat treating is performed.

[0101] Examples of the heat treating method include a baking method, a steam method, a HT steam method and the like. The HT steam method is more preferably employed.

[0102]  After the heat treating step, removal of the modified polyester fiber which is embrittled on the printed parts, removal of a dye unfixed to the fiber, which is a dye used in combination with the etching finish agent, and washing of a pasting agent used for a coloring paste which is used for parts other than the adhesion part of the etching finish agent, the dye unfixed to the fiber and the like are performed. A washing method is not particularly limited, and washing is performed by a known method. Examples of the washing method include washing with 2 g/L of a surfactant, alkali washing with 2 g/L of a surfactant and 2 g/L of soda ash, acidic washing with 2 g/L of a surfactant and 2 g/L of acetic acid (90%), alkali reduction washing with 2 g/L of a surfactant, 2 g/L of soda ash, and 2 g/L of hydrosulfite or thiourea dioxide, and acidic reduction washing with 2 g/L of a surfactant, 2 g/L of acetic acid (90%) and 4 g/L of rongalite. A washing temperature is preferably equal to or higher than 60°C and equal to or lower than 100°C, and a washing time is preferably equal to or more than 5 minutes and equal to or less than 30 minutes. After that, washing with water, dehydrating and drying are performed.

[0103] Examples of the surfactant used for washing include a nonionic surfactant, an anionic surfactant, a cationic surfactant, and an amphoteric surfactant. The surfactant may be used alone or two or more types of them may be used in combination.

[0104] Examples of the nonionic surfactant include: an ether type nonionic surfactant such as a higher alcohol alkylene oxide adduct, an alkylphenol alkylene oxide adduct, a styrenated alkylphenol alkylene oxide adduct, a styrenated phenol alkylene oxide adduct, a higher alkylamine alkylene oxide adduct; an ether ester type nonionic surfactant such as a fatty acid alkylene oxide adduct, a polyalcohol fatty acid ester alkylene oxide adduct, a fatty acid amide alkylene oxide adduct, and an alkylene oxide adduct of anoil and fat; apolyalkylene glycol type nonionic surfactant such as a polypropylene glycol ethylene oxide adduct; an ester type nonionic surfactant such as a fatty acid ester of glycerol, a fatty acid ester of pentaerythritol, a fatty acid ester of sorbitol, a fatty acid ester of sorbitan, and a fatty acid ester of sucrose; other nonionic surfactants such as an alkyl ether of a polyalcohol, and a fatty acid amide of alkanolamines. Examples of the alkylene oxide include ethylene oxide, propylene oxide, and butylene oxide. A form of an adduct of the alkylene oxide may be a random adduct of two or more types or may be a block adduct.

[0105] Examples of the anionic surfactant include: an anionic surfactant of a carboxylate such as a fatty acid soap; a sulfuric acid ester salt such as a sulfuric acid ester salt of a higher alcohol, a sulfuric acid ester salt of a higher alcohol alkylene oxide adduct, a sulfuric acid ester salt of a polyoxyalkylene ether, a sulfuric acid ester salt of a phenol alkylene oxide adduct, a sulfuric acid ester salt of an alkylphenol alkylene oxide adduct, a sulfuric acid ester salt of a styrenated alkylphenol alkylene oxide adduct, a sulfuric acid ester salt of a styrenated phenol alkylene oxide adduct, a sulfuric acid ester salt of a polyalcohol alkylene oxide adduct, a sulfated oil, a sulfated fatty acid ester, a sulfated fatty acid, and a sulfated olefin; an anionic surfactant of a salt of a sulfonic acid ester such as a formalin condensate such as an alkylbenzene sulfonate, an alkylnaphthalene sulfonate, and a naphthalene sulfonic acid, and a sulfonate such as an α-olefin sulfonate, a paraffin sulfonate, and a salt of sulfosuccinate diester; a salt of a phosphoric acid ester such as sodium methyl oleoyl taurate, a salt of a phosphoric acid ester of a higher alcohol, a salt of a phosphoric acid ester of a polyoxyalkylene ether, a salt of a phosphoric acid ester of a phenol alkylene oxide adduct, a salt of a phosphoric acid ester of an alkylphenol alkylene oxide adduct, a salt of a phosphoric acid ester of a styrenated alkylphenol alkylene oxide adduct, a salt of a phosphoric acid ester of a styrenated phenol alkylene oxide adduct, and a salt of a phosphoric acid ester of a polyalcohol alkylene oxide adduct; and other anionic surfactants such as N-methyltaurine oleate, and N-methyltaurine stearate. Examples of the alkylene oxide include ethylene oxide, propylene oxide, and butylene oxide. A form of an adduct of the alkylene oxide may be a random adduct of two or more types or may be a block adduct. Examples of the salt include: an alkali metal salt such as a lithium salt, a sodium salt, and a potassium salt; an ammonium salt, and an amine salt such as a salt of a primary amine such as a methylamine salt, an ethylamine salt, a propylamine salt, a butylamine salt, and an allylamine salt; a salt of a secondary amine such as a dimethylamine salt, a diethylamine salt, a dipropylamine salt, a dibutylamine salt, and a diallylamine salt; a salt of a tertiary amine such as a trimethylamine salt, a triethylamine salt, a tripropylamine salt, and a tributylamine salt; and a salt of an alkanolamine such as a monoethanolamine salt, a diethanolamine salt, and a triethanolamine salt.

[0106] Examples of the cationic surfactant include a quarternary ammonium salt of an alkyl ether, a quarternary ammonium salt of an alkylamide, a quarternary ammonium salt of a dialkyl ester, a quarternary ammonium salt of a dialkyl imidazoline, an alkylamide amine, an alkyl ether amine, an alkylamide guanidine, and an arginine derivative.

[0107] Examples of the amphoteric surfactant include an alkylbetaine type surfactant, an amidopropylbetaine type surfactant, an imidazolinium betaine type surfactant and the like.

[0108] By the above-described processing method, an etching finished product from which the modified polyester fiber in the part where the etching finish agent is printed is removed can be obtained. The obtained etching finished product is subjected to, according to the need, a known treatment such as dyeing and final finishing.

Examples

[0109] The invention is more specifically described hereinbelow by referring to Examples. However, the invention is not limited to these Examples. Meanwhile, methods for measuring and evaluating various characteristic values in Examples are as follows.

(Limiting viscosity [η])

[0110] A temperature of a modified polyester was adjusted to 20°C in a mixed solvent of phenol/tetrachloroethane = 1/1, and a limiting viscosity was measured by the Ubbelohde method.

(Content of diethylene glycol (hereinafter, abbreviated as DEG))

[0111] An obtained modified polyester was subj ected to alkaline hydrolysis, and thereafter, each number of moles of ethylene glycol and DEG was quantified by using a Gas Chromatograph GC-9A manufactured by Shimadzu Corporation, and a content of DEG was obtained as a ratio (%) of the number of moles of DEG to the total number of moles of ethylene glycol and DEG.

(Glass transition temperature Tg)

[0112] A glass transition temperature Tg (°C) of a modified polyester was measured by using a Differential Scanning Calorimeter DSC 220 manufactured by Seiko Instruments Inc., at a temperature raising rate of 10°C/min.

(Strength and elongation)

[0113] A strength (cN/dtex) and an elongation (%) were measured according to JIS L1013 by using a tension tester Tensilon UTM-4-100 type manufactured by ORIENTEC CORPORATION.

(Alkali weight reduction ratio)

[0114] A weight reduction ratio of a fiber on which alkali weight reduction was performed was calculated as a weight reduction ratio (%) from a mass of the fiber before treatment and that of the fiber after treatment according to the following formula:

[0115] It is preferable that alkali weight reduction is performed by making a fiber to take the form of a knitted fabric from the point of view of handleability.

(Burst strength)

[0116] A burst strength was measured according to the Mullen method of JIS L 1018.

(Burst strength retention ratio)

[0117] 

(Example 1)

[0118] To an esterification reaction vessel in which bis(β-hydroxyethyl)terephthalate and oligomers thereof were present, a slurry of terephthalic acid (hereinafter abbreviated as TPA) and ethylene glycol (hereinafter abbreviated as EG) at a molar ratio of 1/1.6 was supplied continuously, and an esterification reaction was performed under a condition of a temperature of 250°C, a pressure of 0.1 Pa, and a residence time of 8 hours. Then, 15.4 kg of the obtained esterification reaction product was transferred to a polycondensation reaction vessel, and 4.6 kg of an EG dispersion in which a concentration of adipic acid (hereinafter abbreviated as ADA) was adjusted to 50 mass% was added thereto. In addition, in order to suppress the by-production of DEG, lithium acetate was added such that a concentration of lithium acetate was 120 ppm in terms of lithium atom content. After that, the mixture was stirred and mixed at a temperature of 230°C for 5 minutes, and thereafter, as stabilizers, 120 ppm of magnesium acetate in terms of magnesium atom content, 140 ppm of triethyl phosphate in terms of phosphorus atom content and 30 ppm of germanium dioxide in terms of germanium atom content were added, and 2.6 kg of an EG solution of 5-sodium sulfoisophthalic acid (hereinafter abbreviated as SIP) in which a concentration of the EG ester of SIP was adjusted to 35 mass% was added, and then the mixture was stirred and mixed at a temperature of 230°C. Then, as a polycondensation catalyst, 400 ppm of antimony trioxide was added, and thereafter, the pressure was gradually reduced such that the reduced pressure after 60 minutes was equal to or less than 1.2 hPa. The mixture was stirred and mixed, and thereafter, the temperature was raised to a temperature of 270°C, and a polycondensation reaction was performed until a polycondensate reached a predetermined limiting viscosity [η]. As a result, a modified polyester having an amount of the copolymerized ADA of 18 mol%, and an amount of the copolymerized SIP of 2.5 mol% was obtained, and the modified polyester was made to be a chip. Polymer physical properties of the modified polyester were shown in Table 1.

[0119] The obtained chip of the modified polyester was subjected to spinning by using a spinning nozzle with a circular shape of a hole and the number of holes of 24 at a spinning temperature of 255°C, and a spinning speed of 1,800 m/min. The undrawn yarn was subjected to drawing at a drawing temperature of 65°C, a drawing ratio of 2.28 times, and a ratio of a drawing ratio to the maximum drawing ratio (an MDR ratio) of 0.72 times. Then, heat setting was performed at 150°C to give a modified polyester fiber having 84 dtex/24 f (a single yarn fineness of 3.5 dtex) .

[0120] A weft knitted fabric of the modified polyester fiber was produced, and 10 g of the knitted fabric was subjected to soaking treatment in 1 L of an aqueous solution of sodium hydroxide at a concentration of 10 g/L, at a temperature of 98°C for 20 minutes. Thereafter, the knitted fabric was subjected to washing with water, dehydrating, and drying. A weight reduction ratio was measured according to the following formula:

[0121] Physical properties of the obtained modified polyester filament yarn were shown in Table 1.

(Example 2)

[0122] By using the modified polyester chip obtained in Example 1, spinning and drawing were performed in the same manner as Example 1 except that an amount of a polymer discharged during spinning was changed to 2/5 of that in Example 1 to give a modified polyester filament yarn having 33 dtex/24 f (a single yarn fineness of 1.38 dtex). Physical properties of the obtained modified polyester filament yarn were shown in Table 1.

(Example 3)

[0123] A modified polyester in which 16 mol% of ADA and 2.25 mol% of SIP were copolymerized was obtained and was made to be a chip in the same manner as Example 1, except that 15.9 kg of the esterification reaction product obtained in Example 1 was transferred to the polycondensation reaction vessel, and an addition amount of the EG dispersion of ADA was changed to 4.1 kg and an addition amount of the EG solution of SIP was changed to 2.4 kg. Polymer physical properties of the modified polyester are shown in Table 1. By using the obtained modified polyester chip, spinning and drawing were performed in the same manner as Example 1 except that a spinning speed during spinning was changed to 1,200 m/min. As a result, a modified polyester filament yarn having 84 dtex/24 f (a single yarn fineness of 3.5 dtex) was obtained. Physical properties of the obtained modified polyester filament yarn were shown in Table 1.

(Comparative Example 1)

[0124] A modified polyester in which 14 mol% of ADA and 2. 0 mol% of SIP were copolymerized was obtained and was made to be a chip in the same manner as Example 1, except that 16.4 kg of the esterification reaction product obtained in Example 1 was transferred to the polycondensation reaction vessel, and an addition amount of the EG dispersion of ADA was changed to 3.6 kg and an addition amount of the EG solution of SIP was changed to 2.1 kg. Polymer physical properties of the modified polyester were shown in Table 1. By using the obtained modified polyester chip, spinning and drawing were performed under a spinning condition and a drawing condition shown in Table 1. As a result, a modified polyester filament yarn having 84 dtex/24 f (a single yarn fineness of 3.5 dtex) was obtained. Physical properties of the obtained modified polyester filament yarn were shown in Table 1.

(Comparative Example 2)

[0125] A modified polyester in which 10 mol% of ADA and 2.0 mol% of SIP were copolymerized was obtained and was made to be a chip in the same manner as Example 1, except that 16.9 kg of the esterification reaction product obtained in Example 1 was transferred to the polycondensation reaction vessel, and an addition amount of the EG dispersion of ADA was changed to 2.6 kg and an addition amount of the EG solution of SIP was changed to 2.1 kg. Polymer physical properties of the modified polyester were shown in Table 1. By using the obtained modified polyester chip, spinning and drawing were performed under a spinning condition and a drawing condition shown in Table 1. As a result, a modified polyester filament yarn having 84 dtex/24 f (a single yarn fineness of 3.5 dtex) was obtained. Physical properties of the obtained modified polyester filament yarn were shown in Table 1.

(Comparative Example 3)

[0126] A modified polyester in which 5 mol% of ADA and 2.25 mol% of SIP were copolymerized was obtained and was made to be a chip in the same manner as Example 1, except that 17.6 kg of the esterification reaction product obtained in Example 1 was transferred to the polycondensation reaction vessel, and an addition amount of the EG dispersion of ADA was changed to 1.3 kg and an addition amount of the EG solution of SIP was changed to 2.3 kg. Polymer physical properties of the modified polyester were shown in Table 1. By using the obtained modified polyester chip, spinning and drawing were performed under a spinning condition and a drawing condition shown in Table 1. As a result, a modified polyester filament yarn having 84 dtex/24 f (a single yarn fineness of 3.5 dtex) was obtained.

[0127] Said fiber has copolymer components of a polyester fiber which is cation dyeable under normal pressure, which is generally used in the market.

[0128] Physical properties of the obtained modified polyester filament yarn were shown in Table 1.

[Table 1]

	Copolymer components		Polymer physical properties			Spinning condition		Drawing condition			Filament physical properties
	ADA	SIP	DEG	Tg	[η]	Temperature	Speed	Temperature	Drawing ratio	MDR ratio	Single fiber fineness	Strength	Elongation	Weight reduction ratio
	mol%	mol%	%	°C		°C	(m/min)	°C	Times	Times	dtex	cN/dtex	%	%
Example 1	18	2.5	1.24	46	0.558	255	1800	65	2.28	0.72	3.5	2.43	34.6	22.5
Example 2	18	2.5	1.38	47	0.565	255	1800	65	2.19	0.72	1.38	2.32	31.2	27.6
Example 3	16	2.25	1.30	48	0.562	255	1200	65	2.79	0.75	3.5	2.45	43.4	12.5
Comparative Example 1	14	2.0	1.33	50	0.613	255	1200	75	1.89	0.76	3.5	1.56	32.9	11.7
Comparative Example 2	10	2.0	1.34	56	0.543	270	1200	71	2.34	0.7	3.5	2.02	29.0	7.1
Comparative Example 3	5	2.25	2.40	70	0.544	283	1800	82	2.55	0.71	3.5	2.99	32.0	6.3

*ADA: adipic acid SIP: 5-sodium sulfoisophthalic acid DEG: diethylene glycol

(Example 4)

[0129] 48 filaments of a modified polyester fiber having a fineness of 84 dtex which was composed of a modified polyester resin obtained by copolymerizing ethylene terephthalate as a main constitutional unit, 16 mol% of ADA and 2.5 mol% of SIP were knitted to give a weft knitted fabric having a Jersey stitch structure.

[0130] Alkali weight reduction processing was performed on 100 g of the weft knitted fabric by using a Mini Color dyeing machine (manufactured by Texam Technical Research Institute, Co. Ltd. , a multicolor rotation pot dyeing test machine), at a concentration of sodium carbonate of 40 g/L, in a mass ratio of the weft knitted fabric to the sodium carbonate aqueous solution of 1 : 20, at a temperature of the aqueous solution of 100°C × 30 minutes. Then, washing with water, dehydrating, and drying treatment at 80°C for 60 minutes were performed to give a processed knitted fabric.

[0131] In addition, alkali weight reduction processing was also performed by using an aqueous solution of each of potassium carbonate, and sodium hydroxide instead of sodium carbonate in the same manner to give a knitted fabric.

[0132] The pH of each of the aqueous solutions, and the weight reduction ratio of each of the modified polyester fibers are shown in Table 2.

[0133] Weight reduction ratio (%) = { (mass of weft knitted fabric before alkali weight reduction processing - mass of processed knitted fabric after alkali weight reduction processing) /mass of weft knitted fabric before alkali weight reductionprocessing} × 100.

(Comparative Example 4)

[0134] A processed knitted fabric was obtained in the same manner as Example 4 except that, as yarns used for the weft knitted fabric, 48 filaments of a cation dyeable polyester fiber having a fineness of 84 dtex composed of a polyester resin obtained by copolymerizing ethylene terephthalate as a main constitutional unit, 5 mol% of ADA and 2.3 mol% of SIP were used.

[0135] The weight reduction ratio is shown in Table 2.

(Comparative Example 5)

[0136] As yarns used for the weft knitted fabric, yarns composed of a polyethylene terephthalate fiber (an unmodified polyethylene terephthalate) were used. Hereinafter, the polyethylene terephthalate fiber is also referred to as "a regular polyester fiber". A processed knitted fabric was obtained in the same manner as Example 4 except that the yarns composed of the regular polyester fiber were constituted by those manufactured by TEIJIN LIMITED., and 36 filaments each having a fineness of 84 dtex were used.

[0137] The weight reduction ratio is shown in Table 2.

[Table 2]

	Fiber	Copolymer components		Weight reduction ratio (%)
		ADA	SIP	Sodium carbonate 40 g/L	Potassium carbonate 40 g/L	Sodium hydroxide 10g/L
		mol%	mol%	pH of aqueous solution = 11.8	pH of aqueous solution = 11.8	pH of aqueous solution = 13.8
Example 4	Modified polyester	16	2.5	9%	8%	39%
Comparative Example 4	Cation dyeable polyester	5	2.3	3%	2%	20%
Comparative Example 5	Regular polyester	0	0	0%	0%	1%

[0138] As shown in Table 2, when alkali weight reduction was performed by using sodium carbonate, the result was that the modified polyester fiber of Example 4 had a higher weight reduction ratio than the generally used cation dyeable polyester fiber of Comparative Example 4, and the regular polyester fiber of Comparative Example 5 was not capable of being alkali weight reduced by using sodium carbonate. In addition, when alkali weight reduction was performed by using potassium carbonate, the result was that the modified polyester fiber of Example 4 had a higher weight reduction ratio than the generally used cation dyeable polyester fiber of Comparative Example 4, and the weight reduction ratio of the generally used cation dyeable polyester fiber of Comparative Example 4 was as low as 2% when being weight reduced by using potassium carbonate, as shown in Table 2. When alkali weight reduction was performed by using sodium hydroxide, the modified polyester fiber of Example 4 exhibited a higher weight reduction ratio than the generally used cation dyeable polyester fiber of Comparative Example 4, and the regular polyester fiber of Comparative Example 5.

(Example 5)

[0139] Etching finishing which dissolves a modified polyester fiber was performed by using a warp knitted fabric obtained by using the modified polyester fiber used in Example 4 and the regular polyester fiber used in Comparative Example 5 (the modified polyester fiber = 16.7%, and the regular polyester fiber = 83.4%) and using an etching finish agent having the following composition. The composition of the etching finish agent was shown in Table 3.

• Sorbitose C-5 (10% aqueous solution) (manufactured by AVEBE Co., Ltd.) 50 mass%
• Sodium carbonate (manufactured by Tokuyama Corporation, trade name: soda ash) 10 mass%
• Water 40 mass%

[0140] A square pattern was printed on the knitted fabric to be treated with the above-described etching finish agent, and drying at 110°C × 2 minutes was performed. Then, a superheated steam treatment was performed by using a HT steamer at 180°C × 8 minutes. After that, washing was performed at 80°C × 20 minutes by using a soaping bath containing 2 g/L of Laccol ISF (manufactured by Meisei Chemical Works, Ltd., a nonionic surfactant), and thereafter, washing with water, dehydrating, and drying were performed to give a processed warp knitted fabric which was etching finished.

[0141] Evaluation: Etching finish properties were evaluated visually. As evaluation criteria, as shown in Table 3, with regard to etching finish properties, when a fiber on which etching is performed in printed parts cannot be visually confirmed, the etching finish property was marked by ⊙, when etching can be performed though a little residue can be confirmed visually, and the knitted fabric can be determined as capable of being used as a commercial product, the etching finish property was marked by ○, and when etching cannot be performed and a residue can be visually confirmed, and the knitted fabric can be determined as incapable of being used as a commercial product, the etching finish property was marked by ×. In addition, the burst strength in the etching finished part was measured according to the Mullen method of JIS L 1018. The results are shown in Table 3. The burst strength of the processed knitted fabric in the non-etching finished part was 755 kPa.

(Example 6)

[0142] An etching finished knitted fabric was obtained in the same manner as Example 5 except that the composition of a paste liquid was changed to that shown in Table 3, that is, an etching finish accelerator (manufacturedbyMeisei Chemical Works, Ltd. a Mei printer OP-2) was used. The evaluation of the etching finish properties is shown in Table 3.

[0143] By using the etching finish accelerator, etching finish properties which were similar to etching finish properties exhibited when a strong alkali was used were obtained. On the other hand, deterioration in the burst strength was little.

(Comparative Examples 6 and 7)

[0144] Etching finishing was performed in the same manner as Example 5 except that each composition of the etching finish agents and each of conditions were changed to those shown in Table 3. Then, the obtained etching finished knitted fabric was evaluated. The results are shown in Table 3.

[0145] Since a strong alkali was used, etching finish properties were good, but deterioration in the burst strength was large.

[Table 3]

Composition of paste liquid	Example 5	Example 6	Comparative Example 6	Comparative Example 7
Sorbitose C-5 (10% aqueous solution)	50	50	50	50
Sodium carbonate	10	10
Guanidine carbonate			10
Sodium hydroxide				10
Etching finish accelerator (Mei printer OP-2)		20
Water	40	20	40	40
pH of finish agent	12.0	12.2	11.8	14.5
Etching finish properties	○	⊙	⊙	⊙
Burst strength (kPa)	755	628	39	265
Strength ratio (%)	94.0	78.0	4.9	33.0

[0146] As shown in Table 3, in Example 5 in which only sodium carbonate was contained, etching finishing was capable of being performed, and reduction in strength in the etched part was also low. On the other hand, in Comparative Example 6 in which guanidine carbonate was used as well as Comparative Example 7 in which sodium hydroxide was used, etching finish properties of the etched parts were good, but extreme reduction in strength in the etched parts was observed.

[0147] The finish agent which used guanidine carbonate had a pH of 11.8, but it is known that guanidine carbonate becomes a strong alkali when being heated. Accordingly, deterioration in the burst strength became large.

[0148] In addition, in Example 6 in which a Mei printer OP-2, which is an etching finish accelerator, and sodium carbonate were contained, good etching finish properties were able to be obtained, and reduction in strength in the etched parts was also little.

(Example 7)

[0149] Etching finishing was performed in the same manner as Example 6 except that a knitted fabric (50% modified polyester fiber/500 regular polyester fiber) obtained by using the modified polyester fiber that is the same as Example 4 and the regular polyester fiber (manufactured by TEIJIN LIMITED., 84 dtex) that is the same as Comparative Example 5 was used as a knitted fabric to be treated. Then, an etching finished knitted fabric was obtained. The evaluation of the etching finish properties is shown in Table 4. With regard to the evaluation of etching finish properties, no fiber was capable of being confirmed visually in printed parts to which etching was performed, and therefore, the evaluation result was ⊙.

(Comparative Examples 8 to 11)

[0150] An etching finished fabric was obtained in the same manner as Example 5 except that the modified polyester fiber used in Example 5 was changed to each of polyester fibers shown in Table 4. The evaluation of the etching finish properties is shown in Table 4.

[Table 4]

	Fiber for etching	Etching finish properties
Example 7	Modified polyester fiber	⊙
Comparative Example 8	Polyester fiber cation dyeable under normal pressure (manufactured by KB SEIREN, LTD.)	×
Comparative Example 9	Polyester fiber cation dyeable under normal pressure (manufactured by MITSUBISHI RAYON CO., LTD.: AHY)	×
Comparative Example 10	Polyester fiber cation dyeable under high pressure (manufactured by Huvis Corp)	×
Comparative Example 11	Polyester fiber cation dyeable under high pressure (manufactured by Nan Ya Plastics Corporation)	×

Industrial Applicability

[0151] According to the invention, it is possible to obtain an etching finished cloth with good etching finish properties of a modified polyester fiber by using the certain modified polyester fiber as a modif iedpolyester fiber, without performing alkali weight reduction on a woven or knitted fabric composed of the modifiedpolyester fiber and an unmodified polyester fiber and without causing embrittlement of the unmodified polyester fiber, while removing only the modified polyester fiber in printed parts. Since no strong alkaline substance which has high toxicity to human is used, it becomes possible to perform etching finishing with high safety in operation.

Claims

1. A modified polyester fiber characterized by having a weight reduction ratio of equal to or more than 5% and equal to or less than 15%, the weight reduction ratio being measured by:
adding 100 g of a fiber to 2 L of an aqueous solution including 40 g/L of sodium carbonate; heating an obtained mixture at 100°C for 30 minutes; performing drying treatment at 80°C for 60 minutes; and after that, measuring a fiber mass A g,

2. The modified polyester fiber according to claim 1, characterized in that the modified polyester fiber is composed of a modified polyester obtained by copolymerizing: ethylene terephthalate as a main constitutional unit; equal to or more than 12 mol% and equal to or less than 25 mol% of an aliphatic dicarboxylic acid having 4 to 8 carbon atoms; and equal to or more than 2 mol% and equal to or less than 5 mol% of a metal sulfonate group-containing aromatic dicarboxylic acid.

3. The modified polyester fiber according to claim 2, characterized in that the aliphatic dicarboxylic acid is adipic acid, and the metal sulfonate group-containing aromatic dicarboxylic acid is 5-sodium sulfoisophthalic acid.

4. The modified polyester fiber according to any one of claims 1 to 3, characterized by having a content of diethylene glycol of equal to or more than 0.5 mass% and equal to or less than 3.0 mass%.

5. The modified polyester fiber according to any one of claims 1 to 4, characterized by having a single fiber fineness of equal to or more than 0.6 dtex and equal to or less than 3.5 dtex, a fiber strength of equal to or more than 2.0 cN/dtex and equal to or less than 3.5 cN/dtex, and a fiber elongation of equal to or more than 25% and equal to or less than 45%.

6. The modified polyester fiber according to anyone of claims 1 to 5, characterized in that the modified polyester fiber contains lithium acetate and a content of the lithium acetate is 50 to 120 ppm in terms of lithium atom content.

7. A woven or knitted fabric containing a modified polyester fiber and a fiber not for weight reduction, characterized in that: the modified polyester fiber has a weight reduction ratio of equal to or more than 5% and equal to or less than 15% and the fiber not for weight reduction has a weight reduction ratio of equal to or more than 0% and less than 5%; a content of the modified polyester fiber in the woven or knitted fabric is equal to or more than 5 mass% and equal to or less than 50 mass%; a content of the fiber not for weight reduction in the woven or knitted fabric is equal to or more than 50 mass% and equal to or less than 95 mass%; and the weight reduction ratio is measured by the following measuring method:
<measuring method of weight reduction ratio>
the measuring method of the weight reduction ratio including: adding 100 g of a fiber to 2 L of an aqueous solution including 40 g/L of sodium carbonate; heating an obtained mixture at 100°C for 30 minutes; performing drying treatment at 80°C for 60 minutes; and after that, measuring a fiber mass A g,

8. A woven or knitted fabric containing a modified polyester fiber and a fiber not for weight reduction, characterized in that: the modified polyester fiber has a weight reduction ratio of equal to or more than 5% and equal to or less than 15% and the fiber not for weight reduction has a weight reduction ratio of equal to or more than 0% and less than 5%; the woven or knitted fabric has an etching finished part of the modified polyester fiber; a weight reduction ratio of the modified polyester fiber in the etching finished part to the modified polyester fiber in a non-etching finished part is equal to or more than 50 mass% and equal to or less than 100 mass%; and the weight reduction ratio is measured by the following measuring method:
<measuring method of weight reduction ratio>
the measuring method of the weight reduction ratio including: adding 100 g of a fiber to 2 L of an aqueous solution including 40 g/L of sodium carbonate; heating an obtained mixture at 100°C for 30 minutes; performing drying treatment at 80°C for 60 minutes; and after that, measuring a fiber mass A g,

9. The woven or knitted fabric according to claim 7 or 8, characterized in that a difference between said weight reduction ratio of the modified polyester fiber and said weight reduction ratio of the non-etched fiber is equal to or more than 5%.

10. The woven or knitted fabric according to claim 8 or 9, characterized in that a burst strength of the woven or knitted fabric in the etching finished part is equal to or more than 250 kPa and equal to or less than 900 kPa.

11. The woven or knitted fabric according to any one of claims 8 to 10, characterized in that a strength retention ratio of a burst strength of the woven or knitted fabric in the etching finished part to a burst strength of the woven or knitted fabric in the non-etching finished part is equal to or more than 50%.

12. The woven or knitted fabric according to any one of claims 8 to 11, characterized in that the modified polyester fiber is a modified polyester that is obtained by copolymerizing: ethylene terephthalate as a main constitutional unit; equal to or more than 16 mol% and equal to or less than 25 mol% of an aliphatic dicarboxylic acid having equal to or more than 4 and equal to or less than 8 carbon atoms; and equal to or more than 2 mol% and equal to or less than 5 mol% of a metal sulfonate group-containing aromatic dicarboxylic acid.

13. The woven or knitted fabric according to any one of claims 8 to 12, characterized in that the fiber not for weight reduction contains equal to or more than 50 mass% and equal to or less than 95 mass% of synthetic fibers.

14. The woven or knitted fabric according to claim 13, characterized in that the synthetic fiber is at least one of a regular polyester fiber, a polyamide fiber, an elastic fiber, a polyolefin fiber, and an acrylic fiber.

15. The woven or knitted fabric according to any one of claims 8 to 14, characterized in that a single fiber fineness of the modified polyester fiber is equal to or more than 0.6 dtex and equal to or less than 3.5 dtex.

16. The woven or knitted fabric according to claim 14 or 15, characterized in that the elastic fiber is any one of a polyurethane fiber, a polytrimethylene terephthalate fiber, and a polybutylene terephthalate fiber.

17. A method for producing a woven or knitted fabric, the method including: printing an etching finish agent on a cloth that contains a modified polyester fiber having a weight reduction ratio of equal to or more than 5% and equal to or less than 15% and a fiber not for weight reduction; and performing weight reduction processing by supplying a superheated steam to a part on which the etching finish agent is printed; the method being characterized in that: the etching finish agent has a pH of equal to or more than 8 and equal to or less than 13; the heating method includes supplying a superheated steam of equal to or higher than 150°C and equal to or lower than 200°C; the heating time is equal to or more than 5 minutes and equal to or less than 15 minutes; and the weight reduction ratio is measured by the following measuring method:
<measuring method of weight reduction ratio>
the measuring method of the weight reduction ratio including: adding 100 g of a fiber to 2 L of an aqueous solution including 40 g/L of sodium carbonate; heating an obtained mixture at 100°C for 30 minutes; performing drying treatment at 80°C for 60 minutes; and after that, measuring a fiber mass A g,