ACETIC NITRILE FIBRE AND PREPARATION METHOD THEREFOR

Description

TECHNICAL FIELD

[0001] The present invention relates to a fibrous material, in particular to a fiber of polyacrylonitrile - cellulose acetate and preparation method thereof.

BACKGROUND

[0002] Acrylic fiber is one of principal varieties of synthetic fiber in the world, which is soft in hand feel, bright in color and luster and relatively good in strength and elasticity and has a good reputation as "artificial wool". However, acrylic fiber macromolecule has irregular helical conformation and has no true crystalline structures. The strength of the acrylic fiber is much higher than that of natural fiber and regenerated fiber, the acid resistance of the acrylic fiber is good, and the weather resistance is good. And feedstock polyacrylonitrile (PAN) contains a large number of hydrophobic groups, so that the acrylic fiber is relatively poor in hygroscopicity and extremely easily generate static electricity. The static electricity can cause the fiber to wind or block up a machine element and affect the successful proceeding of a weaving process. And due to the accumulation of electrostatic charges on clothing, wearers easily feel uncomfortable, so that the wearability of acrylic-fiber textiles is lowered, and thus, the further development of the acrylic-fiber textiles is limited.

[0003] An important method for modifying the antistatic property of the acrylic fiber is to blend an antistatic agent and an acrylic fiber spinning stock solution and then carry out spinning to obtain fiber. At present, a frequently-used blended type antistatic agent is carbon black. For example, CN101805935A discloses a novel antistatic acrylic fiber and a preparation method thereof. The acrylic fiber comprises carbon nano-tubes and carbon black, wherein the weight percent of the carbon nano-tubes is 1-15%, the weight percent of the carbon black is 1-3%, and the weight percent of polyacrylonitrile is 82-98%. However, the prepared fiber is black, so that the use of the prepared fiber is limited.

[0004] In addition, the antistatic property of the acrylic fiber can also be improved by proper physical and chemical methods, but that causes environmental pollutions of different degrees. A doctoral dissertation, i.e., plasma antistatic treatment of acrylic fiber proposes provides a method for improving the antistatic property of the acrylic fiber through carrying out surface modification on the acrylic fiber by adopting a low-temperature plasma technology. As an environment-friendly new technology, the low-temperature plasma technology is water-saving, energy-saving and pollution-free and has remarkable economic and environmental protection effects. However, the method is relatively high in requirements and has certain difficulty in actual popularized application.

[0005] Cellulose acetate fiber is good in hygroscopicity, has a moisture regain of 6%, can be dyed with disperse dyes and has good wearability. Filaments are elegant in luster and soft in hand feel, have good drapability, look exactly like real silk, are suitable for producing underwear, bathrobes, children's wear, lady's garments, indoor decorative fabrics and the like and can also be used for producing cigarette filters. However, the cellulose acetate fiber is low in strength and poor in wearability.

[0006] Discussion on a spinning process of hygroscopic acrylic fiber, issued by Wang, Zuowu, discloses hygroscopic acrylic fiber prepared through compounding two feedstocks, i.e., polyacrylonitrile and cellulose acetate. However, composite fibers are two or more incompatible polymers in the same fiber section. Moreover, due to the low moisture regain of the hygroscopic acrylic fiber has, there are a serious phenomenon of flying flowers and static electricity in each procedure of the spinning process. Especially in high speed parallel machine spinning system, drafting fiber strands output from a former roller are more prominent in electrostatic phenomenon and extremely easily wind rollers and leather rollers, so that production is difficult, and the yarn evenness is seriously deteriorated.

[0007] In a master's dissertation, i.e., research on hydrophilic copolyacrylonitrile fiber, copolyacrylonitrile is prepared by an aqueous-phase precipitation polymerization method in a manner of taking acrylonitrile (AN), a potential crosslinker (2-hydroxypropyl acrylate) and vinyl acetate (VAc) as monomers and taking sodium chlorate (NaClO₃) as an initiator. The copolyacrylonitrile fiber, which has relatively high water absorption and water retention capacity, is free of irritation and has certain strength, is obtained through preparing copolyacrylonitrile (CPAN) fiber and CPAN/cellulose acetate (CA) blended fiber (CPAN-CA) containing crosslinker through wet spinning by taking N, N-dimethylacetamide (DMAc) as a solvent, preparing copolyacrylonitrile fiber with a crosslinked structure through post-crosslinking and subjecting the fiber to basic hydrolysis. However, during the preparation of copolyacrylonitrile, a front crosslinking agent and an initiator are required to be added, and the aqueous-phase precipitation polymerization method is required to be adopted, so that the preparation method is complicated; and the blended fiber, which has relatively high water absorption and water retention capacity, is free of irritation and has certain strength, can only be obtained through further carrying out post-crosslinking and carrying out basic hydrolysis on the fiber after the copolyacrylonitrile (CPAN) fiber and CPAN/cellulose acetate (CA) blended fiber containing crosslinker are prepared by wet spinning. According to the method, the front crosslinking agent and the initiator are required to be added during the preparation of copolyacrylonitrile, the preparation method is complicated, reactions of multiple steps, i.e., aqueous-phase precipitation polymerization, wet spinning, post-crosslinking and basic hydrolysis are required to be adopted, and the condition that hydrolysis is an indispensable step for preparing the polyacrylonitrile hydrophilic fiber is pointed out. However, when the content of cellulose acetate in the prepared blended fiber is 5%, the strength of the blended fiber is maximized and is only 1.4cN/dtex, and then, the strength is lowered along with the increase of the cellulose acetate content.

[0008] At present, the textile industry in our country is confronted with product structure adjustment; and in order to adapt market competition at home and abroad and improve economic benefits of enterprises, it is urgent to develop fiber with excellent characteristics of the cellulose acetate fiber, excellent characteristics of the acrylic fiber, and other improved comprehensive performance such as antistatic properties and strength, so as to meet market demands, and a relatively simple preparation method is needed to be provided.

[0009] Therefore, the present invention is provided.

SUMMARY

[0010] A first object of the present invention is to provide a polyacrylonitrile-cellulose acetate fiber to overcome the defects that acrylic fiber is poor in hygroscopicity, and likely to cause static electricity; and meanwhile, to overcome the disadvantages that pure cellulose acetate fiber is low in strength and poor in wearability.

[0011] A second object of the present invention is to provide a preparation method of the polyacrylonitrile-cellulose acetate fiber. The method is simple and feasible and is easy to control in process.

[0012] In order to achieve the first object of the present invention, the present invention adopts a technical scheme as follows:

a fiber of polyacrylonitrile-cellulose acetate is provided, wherein the polyacrylonitrile-cellulose acetate fiber is composed of polyacrylonitrile and cellulose acetate, wherein a mass ratio of the cellulose acetate to the polyacrylonitrile is arbitrary, preferably (15-35wt%):(65-85wt%), more preferably (15-30wt%):(70-85wt%).

[0013] The polyacrylonitrile-cellulose acetate fiber has a break strength of 2.3CN/dtex to 3.0CN/dtex, a breaking elongation of 32-40%, a moisture regain of 2-3% and a specific resistance of 9.0× 10⁸Ω•CM to 4.8×10⁹Ω•CM.

[0014] The fiber of polyacrylonitrile-cellulose acetate is prepared through dissolving polyacrylonitrile and cellulose acetate with a solvent to obtain a colloid and then carrying out wet spinning.

[0015] Polyacrylonitrile is prepared from acrylonitrile and vinyl acetate, wherein a mass ratio of the acrylonitrile to the vinyl acetate is (92-94wt%):(6-8wt%).

[0016] A ratio of the sum of the masses of polyacrylonitrile and cellulose acetate to the mass of the solvent is (20-25.5):(74.5-80).

[0017] The fiber of polyacrylonitrile-cellulose acetate provided by the present invention has the advantages of light weight, warm keeping, good weather resistance, good acid/base resistance, good drapability, difficulty in wrinkling, etc.; and not only is a domestic gap filled up, but also a novel fibrous raw material is provided for the textile industry.

[0018] In order to achieve the second object of the present invention, the present invention adopts a technical scheme as follows:

a preparation method of the fiber of polyacrylonitrile-cellulose acetate, provided by the present invention, comprises the following steps:

1) mixing 92-94wt% of acrylonitrile monomer and 6-8wt% of vinyl acetate monomer to obtain a mixture, regulating the concentration of the mixture to 30-40wt%, and then carrying out an aqueous-phase suspension polymerization reaction continuously; and subjecting to a chelation reaction for termination to obtain a polymer, removing unreacted monomer, and then carrying out water washing, filtering, granulation shaping and baking to obtain powdery polyacrylonitrile;

2) mixing the powdery polyacrylonitrile, cellulose acetate and a solvent, and carrying out heating, cooling and filtering to obtain a spinning stock solution; and

3) subjecting the spinning stock solution to temperature adjustment and pressure adjustment, carrying out spinning after filtering, and then carrying out double-diffusion shaping in a coagulating bath, water washing, drafting, oiling, baking, curling and setting, thereby preparing the fiber of polyacrylonitrile-cellulose acetate.

[0019] According to the preparation method, in step 1), the aqueous-phase suspension polymerization reaction is carried out at a temperature of 58 DEG C to 62 DEG C and at a pH value of 2.5 to 3.5.

[0020] In step 2), a mass ratio of cellulose acetate to the powdery polyacrylonitrile is arbitrary, preferably (15-35wt%):(65-85wt%), more preferably (15-30wt%):(70-85wt%).

[0021] A ratio of the sum of the masses of the powdery polyacrylonitrile and cellulose acetate to the mass of the solvent is (20-25.5):(74.5-80); the solvent is selected from dimethylacetamide, dimethyl sulfoxide, dimethylformamide or sodium thiocyanate; the heating means heating up to a temperature of 80 DEG C to 90 DEG C; and the cooling means cooling down to a temperature of 70 DEG C to 80 DEG C.

[0022] In step 3), the spinning is carried out at a temperature of 80 DEG C to 97 DEG C under a pressure of 0.7MPa to 0.9MPa. The coagulating bath is selected from an aqueous solution of dimethylacetamide, dimethyl sulfoxide, dimethylformamide or sodium thiocyanate and has a concentration of 30-55wt% and a temperature of 25 DEG C to 50 DEG C. The temperature adjustment means adjusting a temperature to 80 DEG C to 97 DEG C and the pressure adjustment means adjusting a pressure to 0.7MPa to 0.9MPa. A drafting ratio is 4 to 10; and the setting is carried out under a pressure of 200KPa to 330KPa.

[0023] The technical schemes of the present invention are described below in detail.

[0024] Due to the characteristics of poor water absorption and hygroscopicity, low moisture regain, antistatic properties and the like, the range of application of ordinary polyacrylonitrile fiber is restricted. The hygroscopicity and antistatic properties of the fiber have a certain internal relationship, so that the other properties can be greatly improved through improving the water absorption and hygroscopicity of the polyacrylonitrile fiber. A variety of hygroscopic fibers prepared through blending polyacrylonitrile and cellulose acetate are disclosed in the prior art, and many articles in the prior art indicate that the break strength of the hygroscopic fiber is maximized and is only 1.4cN/dtex when the content of cellulose acetate is 5%. And then the strength is lowered along with the increase of the cellulose acetate content. Therefore, in the prior art, in view of a strength problem, a relatively high cellulose acetate mass ratio is not taken into account any more generally during the preparation of the fiber of polyacrylonitrile-cellulose acetate. At present, it is urgent to develop fiber with excellent characteristics of cellulose acetate fiber, excellent characteristics of acrylic fibers and other improved comprehensive performance such as antistatic properties and strength, so as to meet market demands, and how to develop becomes the most critical problem.

[0025] The present invention firstly provides a fiber of polyacrylonitrile-cellulose acetate which is composed of polyacrylonitrile and cellulose acetate, wherein a mass ratio of cellulose acetate to polyacrylonitrile is arbitrary, preferably (15-35wt%):(65-85wt%), more preferably (15-30wt%):(70-85wt%).

[0026] Through a great deal of tests, the inventor pleasantly and surprisedly discovers that, by adopting a relatively high cellulose acetate mass ratio, the strength of the fiber of polyacrylonitrile-cellulose acetate is increased, and the elongation, moisture regain and specific resistance of the polyacrylonitrile-cellulose acetate fiber are better and exceed expected ranges.

[0027] The polyacrylonitrile-cellulose acetate fiber provided by the present invention has good comprehensive performance and has a break strength of 2.3CN/dtex to 3.0CN/dtex, a breaking elongation of 32-40%, a moisture regain of 2-3% and a specific resistance of 9.0×10⁸Ω•CM to 4.8x 10⁹Ω•CM.

[0028] According to the present invention, the determination of break strength and breaking elongation is carried out according to provisions of GB/T 14337; the determination of moisture regain is carried out according to provisions of GB/T 6503; and the determination of specific resistance is carried out according to provisions of GB/T 14342-1993.

[0029] Concretely, the fiber of polyacrylonitrile-cellulose acetate is prepared through dissolving polyacrylonitrile and cellulose acetate with a solvent to obtain a colloid and then carrying out wet spinning.

[0030] In the prior art, blended fiber of polyacrylonitrile and cellulose acetate is generally prepared through carrying out wet spinning, then, carrying out post-crosslinking, and then, carrying out basic hydrolysis, wherein the condition that hydrolysis is an indispensable step for preparing the polyacrylonitrile hydrophilic fiber is pointed out. However, the fiber of polyacrylonitrile-cellulose acetate provided by the present invention can be obtained through only dissolving polyacrylonitrile and cellulose acetate with a solvent to obtain a colloid and then carrying out wet spinning without crosslinking, post-crosslinking and basic hydrolysis. The process route is simple, so that processing steps are greatly simplified, the working efficiency is increased, and batch production is facilitated; and physical indexes of the produced polyacrylonitrile-cellulose acetate fiber are closer to indexes of the conventional acrylic fiber.

[0031] Further, polyacrylonitrile isformed from acrylonitrile and vinyl acetate, wherein a mass ratio of acrylonitrile to vinyl acetate is (92-94wt%):(6-8wt%).

[0032] In the prior art, polyacrylonitrile is generally prepared from acrylonitrile, vinyl acetate and other ingredients such as a front crosslinking agent, an initiator, three single auxiliaries, an oxidant and a reducer. In the present invention, polyacrylonitrile is prepared from acrylonitrile and vinyl acetate which are in a mass ratio of (92-94wt%):(6-8wt%).

[0033] A ratio of the sum of the masses of polyacrylonitrile and cellulose acetate to the mass of the solvent is (20-25.5):(74.5-80).

[0034] The present invention further provides a preparation method of the fiber of polyacrylonitrile-cellulose acetate. The method is simple and feasible and is easy to control in process.

[0035] The preparation method of the polyacrylonitrile-cellulose acetate fiber, provided by the present invention, comprises the following steps:

1) mixing, 92-94wt% of acrylonitrile monomer and 6-8wt% of vinyl acetate monomer to obtain a mixture, regulating the concentration of the mixture to 30-40wt%, and then carrying out an aqueous-phase suspension polymerization reaction continuously; and subjecting to a chelation reaction for termination to obtain a polymer, removing unreacted monomer, and then carrying out water washing, filtering, granulation shaping and baking to obtain powdery polyacrylonitrile;

2) mixing the powdery polyacrylonitrile, cellulose acetate and a solvent, and carrying out heating, cooling and filtering to obtain a spinning stock solution; and

3) subjecting the spinning stock solution to temperature adjustment and pressure adjustment, carrying out spinning after filtering, then carrying out double-diffusion shaping in a coagulating bath, water washing, drafting, oiling, baking, curling and setting, thereby obtaining the fiber of polyacrylonitrile-cellulose acetate.

[0036] In the prior art, copolyacrylonitrile is prepared by an aqueous-phase precipitation polymerization method, taking acrylonitrile (AN), a potential crosslinker (2-hydroxypropyl acrylate) and vinyl acetate (VAc) as monomers and taking sodium chlorate (NaClO₃) as an initiator. Copolyacrylonitrile (CPAN) fiber and CPAN/cellulose acetate (CA) blended fiber (CPAN-CA) with crosslinker is obtained through wet spinning by taking N, N-dimethylacetamide (DMAc) as a solvent, and then the copolyacrylonitrile-base fiber with a crosslinked structure is prepared by post-crosslinking, and is subjected to basic hydrolysis to obtain copolyacrylonitrile-base fiber, which has relatively high water absorption and water retention capacity and certain strength.preparing According to the method, a front crosslinking agent and the initiator are required to be added during the preparation of copolyacrylonitrile, the preparation method is complicated, and reactions of multiple steps, i.e., aqueous-phase precipitation polymerization, wet spinning, post-crosslinking and basic hydrolysis are required to be adopted. The condition that hydrolysis is an indispensable step for preparing the polyacrylonitrile hydrophilic fiber is emphasized. Obviously, in the prior art, it is generally believed that hydrolysis is an indispensable step for preparing the polyacrylonitrile hydrophilic fiber.

[0037] According to the present invention, through regulating a process, a proportioning ratio and the like, the fiber of polyacrylonitrile-cellulose acetate can be obtained by only adopting two monomers, i.e., acrylonitrile and vinyl acetate, carrying out aqueous-phase suspension polymerization to obtain polyacrylonitrile and then subjecting polyacrylonitrile and cellulose acetate to wet spinning without crosslinking, post-crosslinking and basic hydrolysis. The process route is simple, so that processing steps are greatly simplified, the working efficiency is increased, and batch production is facilitated; and physical indexes of the produced fiber of polyacrylonitrile-cellulose acetate are closer to indexes of the conventional acrylic fiber.

[0038] Further, according to the preparation method, in step 1), the aqueous-phase suspension polymerization reaction is carried out at a temperature of 58 DEG C to 62 DEG C and at a pH value of 2.5 to 3.5.

[0039] In step 2), a mass ratio of cellulose acetate to the powdery polyacrylonitrile is arbitrary, preferably (15-35wt%):(65-85wt%), more preferably (15-30wt%):(70-85wt%).

[0040] A ratio of the sum of the masses of the powdery polyacrylonitrile and cellulose acetate to the mass of the solvent is (20-25.5):(74.5-80); the solvent is selected from dimethylacetamide, dimethyl sulfoxide, dimethylformamide or sodium thiocyanate; the heating means heating up to a temperature of 80 DEG C to 90 DEG C; and the cooling means cooling down to a temperature of 70 DEG C to 80 DEG C.

[0041] In step 3), the spinning is carried out at a temperature of 80 DEG C to 97 DEG C under a pressure of 0.7MPa to 0.9MPa. The coagulating bath is selected from an aqueous solution of dimethylacetamide, dimethyl sulfoxide, dimethylformamide or sodium thiocyanate and has a concentration of 30-55wt% and a temperature of 25 DEG C to 50 DEG C. The temperature adjustment means adjusting a temperature to 80 DEG C to 97 DEG C and the pressure adjustment means adjusting a pressure to 0.7MPa to 0.9MPa. A drafting ratio is 4 to 10; and the setting is carried out under a pressure of 200KPa to 330KPa.

[0042] The preparation method provided by the present invention is simple and feasible in process, and the prepared polyacrylonitrile-cellulose acetate fiber is good in comprehensive performance and has a break strength of 2.3CN/dtex to 3.0CN/dtex, a breaking elongation of 32-40%, a moisture regain of 2-3% and a specific resistance of 9.0×10⁸Ω•CM to 4.8×10⁹Ω•CM.

[0043] Compared with the prior art, the fiber of polyacrylonitrile-cellulose acetate and the preparation method thereof have the following advantages:

(1) The fiber of polyacrylonitrile-cellulose acetate produced by the present invention has some characteristics of acrylic fiber and overcomes the defects that the acrylic fiber is poor in hygroscopicity and likely to cause static electricity.

(2) Not only is the strength of the fiber of polyacrylonitrile-cellulose acetate provided by the present invention improved, but also the fiber of polyacrylonitrile-cellulose acetate has better properties, i.e., elongation, moisture regain and specific resistance.

(3) The fiber of polyacrylonitrile-cellulose acetate produced by the preparation method in the present invention has some characteristics of cellulose acetate fiber, and is good in drapability, is not prone to wrinkling and overcomes the disadvantages, i.e., low strength, poor acid resistance and poor weather resistance of the cellulose acetate fiber.

(4) The preparation method is simple and feasible in process and easy to control, existing devices such as existing spinning are used for production, and the continuity of production of downstream procedures cannot be affected.

DETAILED DESCRIPTION

[0044] Detailed embodiments of the invention are as follows, and the embodiments are used for further describing the present invention rather than limiting the present invention.

Embodiment 1: preparation of a fiber of polyacrylonitrile-acetate

[0045] 

1) Production of a polymer: 92wt% of acrylonitrile monomer and 8wt% of vinyl acetate monomer were mixed to obtain a mixture, and the concentration of the mixture was regulated to 30-40wt%, and the mixture was carried out an aqueous-phase suspension polymerization reaction continuously at a temperature of 58 DEG C to 62 DEG C and a pH value of 2.5-3.5, and was subjected to a chelation reaction for termination to obtain a polymer. The monomers unreacted was removed with a stripper, and then, salts and moisture were removed by washing and filtering, then powdery polyacrylonitrile was obtained by carrying out granulation shaping and baking.

2) The powdery polyacrylonitrile, cellulose acetate and a solvent, i.e., dimethylacetamide were mixed, in accordance with a ratio of the sum of the masses of the powdery polyacrylonitrile and cellulose acetate (85wt%:15wt%) to the mass of dimethylacetamide being 20wt%:80wt%. The mixture was heated up to a temperature of 80 DEG C to completely dissolve polyacrylonitrile and cellulose acetate in the solvent dimethylacetamide, and carried out cooling to a temperature of 70 DEG C, and then carried out filtering to obtain a spinning stock solution.

3) The spinning stock solution was subjected to temperature adjustment and pressure adjustment, carryied out filtering, and then carried out spinning at a temperature of 80 DEG C to 97 DEG C and under a pressure of 0.7MPa to 0.9MPa in accordance with a ratio of the powdery polyacrylonitrile to cellulose acetate being 85wt%:15wt%. The fiber of polyacrylonitrile-acetate is obtained by double-diffusion shaping in a coagulating bath (the coagulating bath was an aqueous solution of dimethylacetamide and had a concentration of 30-55wt% and a temperature of 25 DEG C to 50 DEG C), water washing, drafting, oiling, baking, curling and setting, wherein a drafting ratio was 10, and the setting was carried out under a setting pressure of 200KPa.

Embodiment 2: preparation of a fiber of polyacrylonitrile-acetate

[0046] 

1) Production of a polymer: 94wt% of acrylonitrile monomer and 6wt% of vinyl acetate monomer were mixed to obtain a mixture, and the concentration of the mixture was regulated to 30-40wt%, and the mixture was carried out an aqueous-phase suspension polymerization reaction continuously at a temperature of 58 DEG C to 62 DEG C and at a pH value of 2.5-3.5; and was subjected to a chelation reaction for termination to obtain a polymer. The monomers unreacted was removed with a stripper, and then salts and moisture were removed by washing and filtering. Powdery polyacrylonitrile was obtained by carrying out granulation shaping, baking.

2) The powdery polyacrylonitrile, cellulose acetate and a solvent, i.e., dimethylacetamide were mixed, in accordance with a ratio of the sum of the masses of the powdery polyacrylonitrile and cellulose acetate (80wt%:20wt%) to the mass of dimethylacetamide being 23wt%:77wt%., The mixture was heated up to a temperature of 80 DEG C to completely dissolve polyacrylonitrile and cellulose acetate in the solvent dimethylacetamide, and carried out cooling to a temperature of 70 DEG C, and carried out filtering to obtain a spinning stock solution; and

3) The spinning stock solution was subjected to temperature adjustment and pressure adjustment, carried out filtering, and then carried out spinning at a temperature of 80 DEG C to 97 DEG C under a pressure of 0.7MPa to 0.9MPa in accordance with a ratio of the powdery polyacrylonitrile to cellulose acetate being 80wt%: 20wt%. The fiber of polyacrylonitrile-cellulose acetate is obtained by carrying out double-diffusion shaping in a coagulating bath (the coagulating bath was an aqueous solution of dimethylacetamide and had a concentration of 30-55wt% and a temperature of 25 DEG C to 50 DEG C), water washing, drafting, oiling, baking, curling and setting, wherein a drafting ratio was 4, and the setting was carried out under a setting pressure of 330KPa.

Embodiment 3: preparation of a fiber of polyacrylonitrile-cellulose acetate

[0047] 

1) Production of a polymer: 93wt% of acrylonitrile monomer and 7wt% of vinyl acetate monomer were mixed to obtain a mixture, and the concentration of the mixture was regulated to 30-40wt%, and the mixture was carried out an aqueous-phase suspension polymerization reaction continuously at a temperature of 58 DEG C to 62 DEG C and at a pH value of 2.5-3.5; and was subjected to a chelation reaction for termination to obtain a polymer. The monomers unreacted was removed with a stripper, and then salts and moisture were removed by washing and filtering. Powdery polyacrylonitrile is obtained by carrying out granulation shaping, and baking.

2) The powdery polyacrylonitrile, cellulose acetate and a solvent, i.e., dimethylacetamide were mixed, in accordance with a ratio of the sum of the masses of the powdery polymer and cellulose acetate (75wt%: 25wt%) to the mass of the dimethylacetamide being 25.5wt%: 74.5wt%. The mixture was heated up to a temperature of 80 DEG C to completely dissolve polyacrylonitrile and cellulose acetate in the solvent dimethylacetamide, and carried out cooling to a temperature of 70 DEG C, and carried out filtering to obtain a spinning stock solution.

3) The spinning stock solution was subjected to temperature adjustment and pressure adjustment, carried out filtering, and then carried out spinning at a temperature of 80 DEG C to 97 DEG C under a pressure of 0.7MPa to 0.9MPa in accordance with a ratio of the powdery polyacrylonitrile to cellulose acetate being 75wt%: 25wt%. The polyacrylonitrile-cellulose acetate fiber is obtained by carrying out double-diffusion shaping in a coagulating bath (the coagulating bath was an aqueous solution of dimethylacetamide and had a concentration of 30-55wt% and a temperature of 25 DEG C to 50 DEG C), water washing, drafting, oiling, baking, curling and setting, wherein a drafting ratio was 8, and the setting was carried out under a setting pressure of 250KPa.

Embodiment 4: preparation of a fiber of polyacrylonitrile-cellulose acetate

[0048] 

1) Production of a polymer: 93.5wt% of acrylonitrile monomer and 6.5wt% of vinyl acetate monomer were mixed to obtain a mixture, and the concentration of the mixture was regulated to 30-40wt%, and the mixture was carried out an aqueous-phase suspension polymerization reaction continuously at a temperature of 58 DEG C to 62 DEG C and at a pH value of 2.5-3.5; and was subjected to a chelation reaction for termination to obtain a polymer. The monomers unreacted was removed with a stripper, and then salts and moisture were removed by washing and filtering. Powdery polyacrylonitrile is obtained by carrying out granulation shaping, and baking.

2) The powdery polyacrylonitrile, cellulose acetate and a solvent, i.e., dimethylacetamide were mixed, in accordance with a ratio of the sum of the masses of the powdery polyacrylonitrile and cellulose acetate (70wt%:30wt%) to mass of dimethylacetamide being 25wt%: 75wt%. The mixture was heated up to a temperature of 80 DEG C to completely dissolve polyacrylonitrile and cellulose acetate in the solvent dimethylacetamide, and carried out cooling to a temperature of 70 DEG C, and carried out filtering to obtain a spinning stock solution.

3) The spinning stock solution was subjected to temperature adjustment and pressure adjustment, carried out filtering, and then carried out spinning at a temperature of 80 DEG C to 97 DEG C under a pressure of 0.7MPa to 0.9MPa in accordance with a ratio of the powdery polyacrylonitrile to cellulose acetate being 70wt%: 30wt%. The fiber of polyacrylonitrile-cellulose acetate is obtained by carrying out double-diffusion shaping in a coagulating bath (the coagulating bath was an aqueous solution of dimethylacetamide and had a concentration of 30-55wt% and a temperature of 25 DEG C to 50 DEG C), water washing, drafting, oiling, baking, curling and setting, wherein a drafting ratio was 6, and the setting was carried out under a setting pressure of 280KPa.

Embodiment 5: preparation of a fiber of polyacrylonitrile-cellulose acetate

[0049] 

1) Production of a polymer: 92.5wt% of acrylonitrile monomer and 7.5wt% of vinyl acetate monomer were mixed to obtain a mixture, and the concentration of the mixture was regulated to 30-40wt%, and the mixture was carried out an aqueous-phase suspension polymerization reaction continuously at a temperature of 58 DEG C to 62 DEG C at a pH value of 2.5∼3.5; and was subjected to a chelation reaction for termination to obtain a polymer. The monomers unreacted was removed with a stripper, and then, salts and moisture were removed by a water-washing filter. Powdery polyacrylonitrile is obtained by carrying out granulation shaping, and baking.

2) The powdery polyacrylonitrile, cellulose acetate and a solvent, i.e., dimethylacetamide were mixed, in accordance with that a ratio of the sum of the masses of the powdery polyacrylonitrile and cellulose acetate (65wt%: 35wt%) to the mass of dimethylacetamide being 25wt%: 75wt%. The mixture was heated up to a temperature of 80 DEG C to completely dissolve polyacrylonitrile and cellulose acetate in the solvent dimethylacetamide, and then carried out cooling to a temperature of 70 DEG C, and carried out filtering to obtain a spinning stock solution.

3) The spinning stock solution was subjected to temperature adjustment and pressure adjustment, carried out filtering, and then, carried out spinning at a temperature of 80 DEG C to 97 DEG C under a pressure of 0.7MPa to 0.9MPa in accordance with a ratio of the powdery polyacrylonitrile to cellulose acetate being 65wt%: 35wt%. The fiber of polyacrylonitrile-cellulose acetate is obtained by carrying out double-diffusion shaping in a coagulating bath (the coagulating bath was an aqueous solution of dimethylacetamide and had a concentration of 30-55wt% and a temperature of 25 DEG C to 50 DEG C), water washing, drafting, oiling, baking, curling and setting, wherein a drafting ratiowas 7, and the setting was carried out under a setting pressure of 300KPa.

Embodiment 6: preparation of a fiber of polyacrylonitrile-cellulose acetate

[0050] According to the method of embodiments 1 to 5, except replacing the solvent dimethylacetamide with dimethyl sulfoxide, dimethylformamide or sodium thiocyanate, the fiber polyacrylonitrile-cellulose acetate can be prepared.

Comparative Example: preparation of polyacrylonitrile-acetate fiber according to a method in the prior art

[0051] Polyacrylonitrile was prepared by the means of an intermittent aqueous-phase precipitation polymerization method. Specifically, white powdery polyacrylonitrile was prepared by controlling a temperature in a four-mouthed flask to 45+/-2 DEG C through a constant-temperature circulating water bath, then adding acrylonitrile (AN), vinyl acetate (VAc) and a potential crosslinker (HQ) into the flask according to a certain ratio under nitrogen protection, adjusting a pH value to about 2, and adding an initiator, i.e., NaClO₃-Na₂SO₃ to initiate a polymerization reaction, controlling polymerization time to 1.5 hours, adding NaOH to terminate the reaction, and then carrying out filtering and baking.

[0052] The blended fiber was obtained as the following step: blending the prepared white powdery polyacrylonitrile and cellulose acetate separately according to mass ratios of 85/15, 80/20, 75/25, 70/30 and 65/35, preparing a DMAc spinning solution according to a concentration of 20%, putting the spinning solution into a spinning kettle, carrying out uniform stirring and mixing at a certain rate of revolution to obtain a brown and transparent uniform solution, carrying out vacuumized deaeration at a temperature of 60 DEG C, spinning nascent fiber by a wet spinning process in a manner of taking a 40% DMAc aqueous solution as a coagulating bath, and carried out coagulating shaping, drafting, relaxing and drying to obtain the blended fiber.

[0053] Blended fiber with a crosslinked network structure was obtained through naturally airing the above-mentioned prepared fiber, and subjecting the aired fiber to crosslinking for appropriate time in a baking oven with a temperature of 180 DEG C to allow functional groups inside fiber macromolecules to be subjected to a dehydrated crosslinking reaction.

[0054] Blended fiber with hydrophilicity was obtained through putting blended staple fiber into alkali liquor tanks of different concentrations and different temperatures, controlling hydrolysis time, taking out the hydrolyzed fiber, neutralizing residual alkali liquor on the surface of the fiber with hydrochloric acid, sufficiently washing the fiber with distilled water, and carrying out natural air-drying.

Test Example 1

[0055] In the test example, properties of fiber prepared by the method provided by the present invention and properties of fiber prepared by a method in the prior art were surveyed under the condition that blending ratios of polyacrylonitrile and cellulose acetate in the methods were the same.

[0056] Test samples: the fiber of polyacrylonitrile-cellulose acetate provided by the present invention was prepared through blending polyacrylonitrile and cellulose acetate separately according to mass ratios of 85/15, 80/20, 75/25, 70/30 and 65/35 according to the method provided by the embodiment 1 of the present invention.

[0057] Control samples: the blended fiber in the prior art was prepared through blending polyacrylonitrile and cellulose acetate separately according to mass ratios of 85/15, 80/20, 75/25, 70/30 and 65/35 according to the method provided by the comparative example.

[0058] Main technical indexes of the test samples and main technical indexes of the control samples (specifications are all 1.33dtex) were tested by adopting a determination method frequently used in the art, and results were shown in a table 1 as follows. Wherein, the determination of break strength and breaking elongation are carried out according to provisions of GB/T 14337; the determination of moisture regain is carried out according to provisions of GB/T 6503; and the determination of specific resistance is carried out according to provisions of GB/T 14342-1993.

Table 1

Blending ratio	Sample	Size (dtex)	Break strength (CN/dtex)	Breaking elongation (%)	Moisture regain (%)	Specific resistance (Ω•CM)
85/15	test	1.33	2.81	36	2.00	4.73×109
	control	1.08	2.01	30	1.12	4.15×1011
80/20	test	1.35	2.91	37	2.10	5.51 ×109
	control	1.12	2.12	31	1.03	5.23×1011
75/25	test	1.31	2.95	38	2.63	9.27×108
	control	1.15	2.33	33	0.92	7.31×1011
70/30	test	1.37	2.97	39	2.53	5.77×108
	control	1.18	2.41	35	0.86	8.18×1011
65/35	test	1.29	2.93	36	2.69	6.89×109
	control	1.10	2.31	30	0.75	9.17×1011

Note: blending ratio means w (polyacrylonitrile)/w (cellulose acetate)

[0059] From the above-mentioned test results, it is observed that the comprehensive performance of the fiber of polyacrylonitrile-cellulose acetate prepared by the method provided by the present invention is better under the condition that blending ratios of polyacrylonitrile and cellulose acetate are the same.

Test Example 2

[0060] In the test example, main technical indexes of the fiber of polyacrylonitrile-cellulose acetate prepared by the method provided by the present invention and main technical indexes of the conventional acrylic fiber and cellulose acetate fiber were tested separately, and results were separately shown in a table 2 and a table 3 as follows. Determination provisions were the same as those in the test example 1.

Table 2: Main technical indexes of the polyacrylonitrile-cellulose acetate fiber prepared by the method provided by the present invention and main technical indexes of the conventional acrylic fiber

Specifica tions (dtex)	Variety (glazed)	Size (dtex)	Break strength (CN/dtex)	Breaking elongation (%)	Moisture regain (%)	Specific resistance (Ω•CM)
1.33	polyacrylonitril e-cellulose acetate fiber	1.4	2.5	34	2.63	9.27×108
1.33	conventional acrylic fiber	1.31	2.69	35	0.81	2.75×1012
1.67	polyacrylonitril e-cellulose acetate fiber	1.78	2.68	36	2.1	4.73×109
1.67	conventional acrylic fiber	1.70	2.71	38	0.93	9.13×1011

Table 3: Main technical indexes of the fiber of polyacrylonitrile-cellulose acetate prepared by the method provided by the present invention and main technical indexes of the conventional cellulose acetate fiber

Specifications (dtex)	Variety (glazed)	Break strength (CN/dtex)	Breaking elongation (%)	Moisture regain (%)	Specific resistance (Ω•CM)
0.89-16.67	polyacrylonitrile -cellulose acetate fiber	2-3.2	30-45	2-4	9.27×108
4.2-6.5	conventional acetate fiber	1-2	26-32	6-7	1.50×1010

Test Example 3

[0061] In the test example, the effect of the different ratio of polyacrylonitrile and cellulose acetate on the antistatic properties of prepared polyacrylonitrile-cellulose acetate fiber was investigated.

[0062] In the test example, the fiber of polyacrylonitrile-cellulose acetate was prepared from polyacrylonitrile and cellulose acetate in different proportioning ratios according to the method provided by the embodiment 1, the moisture regain and specific resistance of the fiber of polyacrylonitrile-cellulose acetate were investigated, and results were shown in a table 4. Determination provisions were the same as those in the test example 1.

Table 4: Influence on the moisture regain and specific resistance of the fiber polyacrylonitrile-cellulose acetate caused by different proportioning ratios of polyacrylonitrile and cellulose acetate

w (polyacrylonitrile)/w (cellulose acetate)	Moisture regain (%)	Specific resistance (Ω•CM)
100/0	0.89	1.12×1013
95/5	1.05	5.88×1011
90/10	1.47	8.91×1010
85/15	2.00	4.73×109
80/20	2.10	5.51×109
75/25	2.63	9.27×108
70/30	2.53	5.77×108
65/35	2.69	6.89×109
60/40	2.71	6.17×108

[0063] From the above-mentioned test results, it is observed that different proportioning ratios of polyacrylonitrile and cellulose acetate have certain influence on the moisture regain and specific resistance of the prepared fiber of polyacrylonitrile-cellulose acetate. Along with increase of the cellulose acetate content, the moisture regain of the fiber of polyacrylonitrile-cellulose acetate is improved, and the specific resistance is reduced. However, in view of that situation that the cellulose acetate content is continued to be increased, the amount of pores of the blended fibers is increased, the degree of etching is relatively increased, and thus, the break strength of the fiber is lowered. Therefore, in the present invention, a mass ratio of cellulose acetate to polyacrylonitrile is preferably (15-35wt%):(65-85wt%), more preferably (15-30wt%):(70-85wt%).

Claims

1. A fiber of polyacrylonitrile - cellulose acetate, composing of polyacrylonitrile and cellulose acetate, wherein a mass ratio of the cellulose acetate to the polyacrylonitrile is arbitrary, preferably (15-35wt%):(65-85wt%), more preferably (15-30wt%):(70-85wt%).

2. The fiber of polyacrylonitrile - cellulose acetate according to claim 1, characterized in that the polyacrylonitrile-cellulose acetate fiber has a break strength of 2.3CN/dtex to 3.0CN/dtex, a breaking elongation of 32-40%, a moisture regain of 2-3% and a specific resistance of 9.0×10⁸Ω•CM to 4.8×10⁹Ω•CM.

3. The fiber of polyacrylonitrile - cellulose acetate according to claim 1 or 2, characterized in that the polyacrylonitrile-cellulose acetate fiber is prepared through dissolving polyacrylonitrile and cellulose acetate with a solvent to obtain a colloid and then carrying out wet spinning.

4. The fiber of polyacrylonitrile - cellulose acetate according to claim 3, characterized in that polyacrylonitrile is formed from acrylonitrile and vinyl acetate, wherein a mass ratio of the acrylonitrile to the vinyl acetate is (92-94wt%):(6-8wt%).

5. The fiber of polyacrylonitrile - cellulose acetate according to claim 3 or 4, characterized in that a ratio of the sum of the masses of the polyacrylonitrile and the cellulose acetate to the mass of the solvent is (20-25.5):(74.5-80).

6. A method for preparing the fiber of polyacrylonitrile - cellulose acetate according to any one of claims 1 to 5, comprising the following steps:

1) mixing 92-94wt% of acrylonitrile monomer with 6-8wt% of vinyl acetate monomer to obtain a mixture, regulating a concentration of the mixture to 30-40wt%, carrying out an aqueous-phase suspension polymerization reaction continuously to obtain a polymer; and subjecting the polymer obtained after the reaction to a chelation reaction for termination, removing unreacted monomers, and then carrying out water washing, filtering, granulation shaping and baking to obtain powdery polyacrylonitrile;

2) mixing the powdery polyacrylonitrile, cellulose acetate and a solvent, and carrying out heating, cooling and filtering to obtain a spinning stock solution; and

3) subjecting the spinning stock solution to temperature adjustment and pressure adjustment, carrying out spinning after filtering, carrying out double-diffusion shaping in a coagulating bath, water washing, drafting, oiling, baking, curling and setting, thereby obtaining the fiber of polyacrylonitrile -cellulose acetate.

6. The method according to claim 6, characterized in that in step 1), the aqueous-phase suspension polymerization reaction is carried out at a temperature of 58 DEG C to 62 DEG C and at a pH value of 2.5 to 3.5.

7. The method according to claim 6, characterized in that in step 2), a mass ratio of the cellulose acetate to the powdery polyacrylonitrile is arbitrary, preferably (15-35wt%):(65-85wt%), more preferably (15-30wt%):(70-85wt%).

9. The method according to claim 8, characterized in that a ratio of the sum of the masses of the powdery polyacrylonitrile and cellulose acetate to the mass of the solvent is (20-25.5):(74.5-80);
the solvent is select from a group consisting of dimethylacetamide, dimethyl sulfoxide, dimethylformamide or sodium thiocyanate; a heating process is carried out heating up to a temperature of 80 DEG C to 90 DEG C; and a cooling process is carried out cooling down to a temperature of 70 DEG C to 80 DEG C.

10. The method according to claim 6, characterized in that in step 3), a spinning process is carried out at a temperature of 80 DEG C to 97 DEG C and under a pressure of 0.7MPa to 0.9MPa;
the coagulating bath is selected from an aqueous solution of dimethylacetamide, dimethyl sulfoxide, dimethylformamide or sodium thiocyanate and has a concentration of 30-55wt% and a temperature of 25 DEG C to 50 DEG C;
the temperature adjustment is carried out adjusting a temperature to 80 DEG C to 97 DEG C and the pressure adjustment is carried out adjusting a pressure to 0.7MPa to 0.9MPa; a drafting ratio is 4 to 10; and the setting is carried out under a pressure of 200KPa to 330KPa.