Latent contractable elastomers, composite yarns therefrom and methods of formation and use

Description

[0001] Elastic yarns, notably spandex yarns, are frequently used in a variety of woven and knitted articles, especially garments, to enhance fit, comfort, and/or-to provide compression support. The use of such yarns is relatively expensive, not only because of the cost of the fiber, but also because in order to obtain the maximum benefits of the elastic properties of the yarn, the yarn must be woven or knitted in a stretched condition, requiring specially adapted machinery, which operates at processing speeds less than those employed with conventional non-elastic yarns.

[0002] In contrast, the yarns of the invention can be processed in a non-stretched mode, as a conventional yarn, and when formed into a processed, e.g., woven, knitted or tufted article, can be contracted to provide an elastic particle.

[0003] Composite yarns comprising elastic yarns and a covering of entangled relatively inelastic filaments are disclosed in U.S. Patent No. 3,940,917. These yarns are formed by conducting the entangling step when the elastic yarn is in a stretched condition.

[0004] This invention relates to melt extruded latent contractable filaments which are formed by melt extruding certain segmented physically crosslinked thermoplastic polymers to form filaments, which filaments, when heat processed at elevated temperatures, significantly contract to yield an elastic filament. This invention also relates to the formation of composite covered yarn comprising the latent contractable melt extruded filaments. In addition, this invention relates to processes for forming articles from the latent contractable filaments or covered yarns and subsequently contracting the yarns to form an elastic article.

[0005] Accordingly, in one aspect the present invention provides a method of forming an elastic filament which comprises melt extruding a segmented inherently elastic polyester-polyester or polyester-polyether thermoplastic polymer which contains interspersed relatively hard segments and relatively soft segments and then without prior deliberate drawing exposing the melt extruded polymer to an elevated temperature in the range of from 40°C to 125°C to linearly contract the melt extruded polymer at least 15% to provide an elastic filament.

[0006] In another aspect the present invention provides a method of forming a composite elastic yarn wherein a melt extruded segmented inherently elastic polyester-polyester or polyester-polyether thermoplastic polymer is associated with inelastic fibres or filaments and without prior deliberate drawing the composite yarn is subjected to exposure to an elevated temperature in the range of from 40° to 125°C to cause the melt extruded polymer filament to cause by at least 15% in length.

[0007] In a further aspect the present invention provides a process for combining a latent contractable melt extruded filament formed from a segmented inherently elastic polyester-polyester or polyester-polyether thermoplastic polymer which contains interspersed relatively hard segments and relatively soft segments with a relatively inelastic synthetic polymer filament to produce a composite yarn which comprises continuously feeding at least one latent contractable melt extruded filament at a first predetermined feed rate and at least one relatively inelastic filament and at a second predetermined feed rate through a jetted high velocity fluid and impinging the jetted fluid on the filament axis at an angle of 90° + 45° to separate the inelastic filaments and entangle the inelastic filaments around the melt extruded filament at spaced intervals; the rate of feed of the inelastic filaments being adjusted with respect to the rate of feed of the melt extruded filaments so that the rate of feed of the inelastic filaments is less than twice the rate of feed of the melt extruded filament and is a rate such that when the resultant composite yarn is exposed without prior deliberate drawing to an elevated contraction inducing temperature the melt extruded filament is contracted at least 15% to provide an elastic filament and when the resultant composite yarn is stretched the inelastic filaments become load-bearing at a predetermined percent of elastic stretching below the break elongation of the elastic filament.

[0008] In a still further aspect the present invention provides a process of forming a stretchable textile article which comprises forming a predetermined over-sized article with yarns comprising a latent contractable filament formed form a segmented inherently elastic polyester-polyester or polyester-polyether thermoplastic polymer which contains interspersed relatively hard segments and relatively soft segments which contracts at least 15% as compared to its original length when exposed without prior deliberate drawing to an elevated contraction inducing temperature to provide an elastic filament and exposing the resultant textile article to an elevated temperature sufficient to contract the latent contractable filament at lest 15% to form a stretchable article of a desired size.

[0009] While not intending to be bound by any theory, it is believed that during melt extrusion, the ordinarily relatively unoriented soft segment is oriented, at least to some degree, followed by cooling, which fixes the filament in a relatively oriented state. When the filament is subjected to heat processing at an elevated temperature, the orientation of the soft segment created by the melt extrusion is dissipated, causing contraction of the filament and the creation of substantially increased elastic properties in the filament.

[0010] It is believed that the polyester-polyester or polyester-polyether polymers which can be employed are polymers consisting of a hard segment and a soft segment capable of forming one phase in the melt, which yield a poorly phase separated morphology when quenched and that, upon latent contraction by a heat treatment, produce a well phase separated morphology.

[0011] A particularly useful class of elastomers are described in U.S. Patent No. 4262114. These elastomers comprise thermoplastics segmented copolyester polyethers, consisting essentially of a multiplicity of randomly occurring intrachain segments of long-chain (soft segments) and short chains (hard segments) ester units, the long-chain ester units being represented by the following structure:

where L is- a divalent radical remaining after the removal of terminal hydroxyl groups from poly(oxyalkylene) glycols having at least 1 nitrogen containing ring per molecule, a carbon to nitrogen ratio in the range of from 3/1 to 350/1, and a molecular weight in the range of from 200 to 8,000, and R is a divalent radical remaining after the removal of the carboxyl groups from a dicarboxylic acid having a molecular weight of less than 300.

[0012] Short-chain ester units are represented by the following structure:

where E is a divalent radical remaining after the removal of hydroxyl groups from a low molecular weight diol having from 2 to 15 carbon atoms per molecule and a molecular weight in the range of from 50 to 250, and R is the divalent radical described for (a) above.

[0013] The introduction of a foreign repeat unit in the back bone of a crystallizable soft segment, such as a polyether, has an effect on the soft segment crystallization process. Such a foreign unit must be stable to processing temperatures and must not be so rigid as to reduce the mobility (raise the glass transition temperature) of the soft segment itself. The foregoing unit should be nonreactive during the synthesis of the segmented thermoplastic elastomer, and should be present in a concentration of at least 1 unit per polyether molecule

[0014] The polyether unit (or -OLO- in formula (a) above) of the soft segment may be represented by the following structures, in which the foreign unit X is alkoxylated:



In (c), the unit X is placed near the center of the polyether chain, and may be one foreign unit or a series of foreign units covalently linked together. In (d), the unit x is one or more foregin repeat units as in (c), but these units are placed along the length of the linear polyether chain.

[0015] In both formulae (c) and (d), X is a nitrogen containing heterocyclic ring, giving the polyether soft segment a carbon to nitrogen ratio in the range of from 3/1 to 350/1, and a molecular weight in the range of from 200 to 8,000. The sum of m plus n is within the range of 5 to 180, and x in formula (d) has a maximum value of 10.

[0016] The nature of X is such that it may covalently enter the polyether chain to influence crystallization. Covalent links to the polyether in (c) or (d) may be an amide link or imide link, both of which are capable of withstanding high temperature processing. These links, the polyester units themselves, and the foreign unit(s) X in (c) or (d) form the soft segment.

[0017] The introduction of the repeat unit X into the poly(oxyethylene) chain, where X is greatly different from poly(oxyethylene), disrupts the chain regularity and suppresses the melting point of the soft segment, preventing crystallization at room temperature. This allows the use of higher molecular weight polyethers, or stated differently, lower mole percentage of the soft segment. The lower mole percentage of the soft segment increases the melting point of the copolymer due to the higher mole percentage of the hard segment. Also, a more regular chain is obtained, which may result in better separation of the hard and soft phases. Better phase separation results in a higher tenacity, a lower glass transition temperature for the soft segment, and an improved elastomeric performance.

[0018] The term "foreign repeat unit" as applied to the soft segments refers to heterocyclic, nitrogen- containing rings which may covalently link (as amide or imide) along the soft segment chain as described previously. Representative units are: 1,3-divalent-5,5-dialkylhydantoin (including alkyl groups connected in a cyclic fashion to the 5,5 positions); 2,5-divalent-1,3,4-triazole; 2,5-divalent-1,3,4-thiadiazole; 2,5-divalent-1,3,4-thiadiazole; 1,3-divalent-1,2,4-triazolidine-3,5-dione; 4,5-divalent-1,2-isothiazole, 4,5-divalent-1,2-oxazole, 4,5-divalent-1,3-diazole-; 2,5-divalent-1,3-oxazole; 2,4-divalent-imidazole; divalent (N position) hypoxanthine; and 2,5-divalent-1,3-thiazole. A preferred unit is 5,5-dialkyl hydantoin having the following formula:

wherein R' and R" are lower alkyl, e.g., methyl, ethyl, propyl, which can be converted to a polyoxyalkylene glycol represented by (e) or (f) by oxyalkylation with ethylene oxide as disclosed in the above mentioned U.S. Patent No. 4262114.

[0019] The term "long-chain ester units" as applied to units in the copolymer chain refers to the reaction product of a long chain glycol with a dicarboxylic acid. Such "long-chain ester units", which are selected from repeating units in the copolyesters of this invention, correspond to formula (a) above. The long-chain glycols are polymeric glycols having terminal hydroxy groups and a molecular weight about 400 and preferably of from 1,000 to 3,000 for (c). The long-chain glycol used to prepare the copolyesters of this invention are poly(oxyalkylene) glycols having foreign repeat units represented by formulas (e) and (f).

[0020] The poly(oxyalkylene) glycols have carbon to nitrogen ratios in the range of from 3/1 to 350/1, molecular, weights in the range of from 200 to 8,000 m plus n is within the range of from 5 to 180, and x in formula (f) has a maximum value of 10. In a preferred embodiment, the poly(oxyalkylene) glycols have carbon to nitrogen ratios in the range of from 8.5/1 to 23/1 and molecular weights in the range of from 450 to 8,000. Representative long-chain glycols are poly(oxyethylene)glycol, poly(oxypropylene) glycol, poly(oxymethylethylene) glycol, poly(oxytetramethylene) glycol, and random or block copolymers of ethylene oxide and 1,2-propylene oxide.

[0021] The term "short-chain ester units" as applied to units in the copolymer chain refers to low molecular weight compounds for polymer chain units having molecular weights of less than about 500. They are made by reacting a low molecular weight diol (below about 250) with a dicarboxylic acid to form ester units represented by the formula (b) above.

[0022] Included among the low molecular weight diols which react to form the short-chain ester units are cyclic, alicyclic, and aromatic dihydroxy compounds. Preferred are diols containing from 2 to 15 carbon atoms, such as ethylene, propylene, 1,4-butane, pentamethylene, 2,2-dimethyl trimethylene, hexamethylene, and decamethylene glycol, dihydroxycyclohexane, cyclohexane dimethanol, resorcinol, hydroquinone, 1,5-dihydroxy naphthaline, etc. Especially preferred are aliphatic diols containing from 2 to 8 carbon atoms. Equivalent ester-forming derivatives of diols are useful (e.g., ethylene oxide or ethylene carbonate can be used in place of ethylene glycol). The term "low molecular weight diols" as used herein includes such equivalent ester-forming derivatives; provided, however, that the molecular weight requirement pertains to diol only and not to its derivatives.

[0023] Dicarboxylic acids which are reacted with the forgoing long-chain glycols (L in formula a) and low molecular weight diols (E in formula b) are aliphatic, cycloaliphatic, or aromatic dicarboxylic acids of a low molecular weight, i.e., having a molecular weight of less than about 300. The term "dicarboxylic acids" as used herein includes equivalents of carboxylic acids having 2 functional carboxyl groups which perform substantially like dicarboxylic acids in reaction with glycols and diols in forming copolyester polymers. These equivalents include esters and ester-forming derivatives, such as acid halides and anhydrides. The molecular weight requirement pertains to the acid, and not to its equivalent ester or ester-forming derivative. Thus, an ester of a dicarboxylic acid having a molecular weight above 300 or an acid equivalent of a dicarboxylic acid having a molecular weight above 300 are included, provided the corresponding acid has a molecular weight below about 300. The dicarboxylic acids may contain any substituent groups or combinations which do not substantially interfere with the copolyester polymer formation and the use of the polymer.

[0024] Aliphatic dicarboxylic acids, as the term is used herein, refers to the carboxylic acids having 2 carboxyl groups, each attached to a saturated carbon atom. If the carbon atom to which the carboxylic acid group is attached is saturated and is in a ring, the acid is cycloaliphatic. Aliphatic or cycloaliphatic acids having conjugated unsaturation often can be used, provided that they are thermally stable at polymerization temperatures and do not undergo homopolymerization.

[0025] Aromatic dicarboxylic acids, as the term is used herein, are dicarboxylic acids having 2 carboxyl groups attached to a carbon atom in an isolated or fused benzene ring. It is not necessary that both functional carboxyl groups be attached to the same aromatic ring, and where more than 1 ring is present, they can be joined by aliphatic or aromatic divalent radicals, such as -0- or-S02 .

[0026] Representative aliphatic and cycloaliphatic acids which can be used for this invention are sebasic acid, 1,3-cyclohexane dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid, adipic acid, glutaric acid, succinic acid, carbonic acid, oxalic acid, azelaic acid, dimethylmalonic acid, allylmalonic acid, 4-cyclohexene-1, 2-dicarboxylic acid, 2-ethyl suberic acid, 2,2,3,3-tetramethyl succinic acid, cyclopentane dicarboxylic acid, decahydro-1, 5-naphthalene dicarboxylic acid, 4,4'-bicyclohexyl dicarboxylic acid, decahydro-2,6-naphthalene dicarboxylic acid, 4,4'-methylene bis(cyclohexane carboxylic acid), 3,4-furan dicarboxylic acid, and 1,1-cyclobutane dicarboxylic acid. Preferred aliphatic acids are cyclohexane-dicarboxylic acids and adipic acid.

[0027] Representative aromatic dicarboxylic acids which can be used include terephthalic phthalic and isophthalic acids, dibenzoic acid, substituted dicarboxylic acids with two benzene nuclei such as Bis(p-carboxyphenyl)methane, p-oxy-(p-carboxyphenyl)benzoic acid, ethylene-Bis (p-oxybenzoic acid), 1,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, phen- anthrene dicarboxylic acid, anthracene dicarboxylic acid, 4,4'-sulfonyl dibenzoic acid, and C₁-C₁₂ alkyl and ring substitution derivatives thereof, such as halo, alkoxy; and aryl derivatives. Hydroxy acids such as (β-hydroxy ethoxy) benzoic acid can also be used, provided an aromatic dicarboxylic acid is also present.

[0028] Aromatic dicarboxylic acids are a preferred class for preparing the copolyester polymers. Among the aromatic acids, those with from 8 to 16 carbon atoms are preferred, particularly the phenylene dicarboxylic acids, i.e., terephthalic, phthalic and isophthalic acids.

[0029] The polymers described herein can be made conveniently by a conventional ester interchange such as that described in U.S. Patent No. 3,763,109. Other special polymerization techniques, for example, interfacial polymerization, may prove useful for the preparation of specific polymers. Both batch and continuous methods may be used for any stage of copolyester polymer preparation. Polycondensation of prepolymers can also be accomplished in the solid phase by heatng divided solid prepolymer in a vacuum or in a stream of inert gas to remove liberated low molecular weight diol. This method has the advantage of reducing degradation, because it must be used at temperatures below the softening point of the prepolymer.

[0030] Although the copolyesters possess many desirable properties, it is advisable to stabilize certain of the compositions to heat or ultraviolet radiation, and this can be done by incorporating stabilizers into the polyester compositions. Satisfactory stabilizers comprise phenols and their derivatives, amines and their derivatives, compounds containing both hydroxyl and amine groups, hydroxyazine, oximes, polymeric phenolic esters and salts of multivalent metals in which the metal is in its lower valent state. Particularly useful stabilizers of the preferred segmented co-polyester polyethers are derivatives of 2,2,6,6-tetramethyl piperidine.

[0031] The properties of these copolyesters can be modified by the incorporation of various conventional inorganic compounds such as titanium dioxide, carbon black, silica gel, alumina, clays, and chopped fiberglass.

[0032] A particularly preferred polymer within the above described class is a polymer consisting essentially of from 30% to 60% by weight of polybutyleneterephthalate units and from 40% to 70% by weight of hydantoin polyether units and further characterised as above.

[0033] Another group of polyester-polyether polymers are the so-called Hytrel type copolyesters which contain a dimethyl-terephthalate-polytetramethylene ether glycol (molecular weight about 600 to 3000) derived soft segment and a dimethyl-terephthalate-1,4 butanediol derived hard segment. Preferably, these polymers contain at least 40% soft segment.

[0034] Similar polyethylene terephthalate-polytetramethylene glycol copolymers as well as other polyester-polyether polymers are described in U.S. Patent Nos. 3,880,976, 3,023,192, 3,651,014 and 3,701,755.

[0035] Urethane based elastomers, assuming that they can be melt extruded to provide sufficient phase separation to display elasticity upon melt extrusion, will display the latent contraction phenomenon of this invention.

[0036] Yet another useful polymer group are segmented polyester copolymers, having both polyester hard segments and polyester soft segments. Segmented polymers of this type can be prepared by forming acide chloride terminated hard segments, for example, formed by reacting terephthalic acid chloride with ethylene glycol and then reacting this hard segment with a soft segment polyester, for example, hydroxyl terminated polybutyleneadipate. Preferably, these polyester-polyethers contain at least 35% soft segment and most preferably at least 40% soft segment.

[0037] Using the method of the invention the latent contractable filaments are formed by melt extruding the inherently elastomeric polymer in a conventional manner, preferably to form a filament having a denier of less than 300, preferably between 2 and 250 denier, and most preferably between 10 and about 75 denier.

[0038] The resultant_melt extruded filaments at least have a reduced degree of elasticity as compared to the subsequent contracted filament.

[0039] The latent contractable, melt extruded filaments are contracted without prior deliberate drawing by heat processing at an elevated temperature which is a contraction inducing temperature below the polymer softening temperature generally in the range of from 40°C to 125°C, preferably from 80° to 100°C and for a time sufficient to contract the length of the melt extruded filament at least 25% and preferably at least 40% as compared to its precontracted length. Generally, the temperature employed is at least 15°C lower than the polymer softening point. The time required for contraction varies with the type of polymer and the temperature. Thirty minutes at 90°-100°C is generally effective to obtain significant contraction. As most filaments employed in a fabric are at some point wet processed, the preferred method of the invention comprises processing the filaments in an aqueous medium at a contraction-inducing temperature of at least 40°C to 60°C for a time sufficient to cause the filament to contract linearly at least 15% and preferably at least 40% of its original length.

[0040] The contractable inherently elastic filaments of the invention are especially useful in the formation of a stretchable textile article which comprises forming a predetermined over-sized article with yarns comprising a latent contractable filament which contracts at least 15% as compared to its original length when exposed to a contraction inducing temperature to provide an elastic filament and exposing the resultant textile article to an elevated temperature sufficient to contract the latent contractable filament at least 15% to form a stretchable article of the desired size. Usually the contractable filament is employed in conjunction with other inelastic yarns and is interspersed unidirectionally or multidirectionally within the textile article.

[0041] In a preferred embodiment, the melt extruded filaments, prior to wet processing, are processed into a textile article, either as the sole filament, or most usually intermixed with other fibers, typically in a manner such that the melt extruded latent contractable filament is unidirectionally or biaxially directed and spaced apart within the textile to provide a desired stretch characteristic to the fabric, in a manner generally known in the textile art. However, contrary to the conventional practice, the textile articles of the invention are processed to a relaxed size which is larger than the desired finished end product. The woven, knitted or otherwise processed textile product is then subjected to wet processing at a temperature and for a time sufficient to cause the melt extruded elastomeric polymer to contract and achieve its ultimate desired elasticity. As a result of this contraction, the dimensions of the textile article are reduced resulting in a textile article having the desired dimensions and elastic stretchability.

[0042] It is to be noted that the wet processing step of the invention need not be carried out as a separate step, but can be and most desirably is conducted in conjunction with at least one other aqueous, elevated temperature treatment step such as washing, dyeing, sizing or the like.

[0043] The original precontracted dimensions of the textile article can be readily determined based upon the latent contraction characteristics of the particular melt extruded elastomeric polymer employed and the quantity of polymer filaments per unit area, coupled with the heat processing conditions employed. If necessary, a few trials will readily determine the necessary originally woven or knitted textile dimensions required to achieve a heat processed elastically stretchable textile article-having the desired finished dimensions.

[0044] The heat-processed contracted elastic filaments of the invention have an elastic modulus of at least about .01 g/D preferably between 0.05 g/D and 0.5 g/D and most preferably between 0.2 g/D and 0.4 g/D measured at 100% extension. The preferred filaments of the invention are those which have a medium elastic modulus, i.e. between 0.2 g/D and 0.4 g/d at 100% extension. These filaments provide processed articles which provide relatively high compression and relatively low extension.

[0045] Many different textile fabrics and types of garments made therefrom utilizing the contractable elastic filaments of the invention having useful stretch properties are contemplated, including some desirably having relatively high compression forces at low elongation. Some typical uses of stretch fabrics falling within the invention include undergarments, such as panty hose, girdles, bras and waist bands; outergarments, such as socks, jeans, ski apparel, swimsuits, tube tops, etc.; and elastic bandages. The contractable elastic filaments themselves may be especially useful in certain applications, e.g., elastic string for packaging, and label cords.

[0046] The latent-contractable filaments of this invention can be processed into a textile product as extruded. However, in order to protect the filament from abrasion, to provide strength at a maximum extension so that the filament will not be broken, to provide lower running friction and to enhance the appearance and feel of a textile, it is desirable to cover the filaments of the invention with relatively inelastic filaments (i.e., hard fibers) which can be any of the synthetic filaments or fibers commonly used for textile purposes. Elastic yarn covering techniques are known in the art. However, in the prior processes, the elastic yarn was covered in a stretched condition in order to prevent the covering hard fibers from retarding the desired extensibility.

[0047] In the present invention, the latent-contractable elastic filaments are covered in their melt extruded precontracted state. If desired, the elastic filaments of the invention may be single wrapped with a yarn, i.e., one or more covering yarns being wrapped spirally in a single direction with the elastic filament, or double covered, an additional yarn also being wrapped about the composite yarn with an opposite direction of false twist from the first cover yarn. These wrapping procedures are carried out upon the latent-contractable elastic filaments in an essentially unstretched state in a manner such that the wet processed contracted elastic filaments when stretched will be limited in its extensibility by the extensibility of the wrapping hard fiber yarns.

[0048] In the preferred assembling process of the invention, the precontraction melt extruded filaments of the invention are comingled with at least one and preferably at least three relatively inelastic filaments (hard fibers) to protect the elastic filament and provide desirable textile properties. The resultant composite yarn upon heat (preferably wet) processing yields a contracted bulky, elastic yarn which is capable of being extended at least 50% and preferably 100% of its contracted relaxed length when stretched until the relatively inelastic filaments first become load bearing. When stretched until the hard fibers firt become load-bearing, the composite yarn is characterized by load-bearing, relatively inelastic filaments entangled with the elastic yarn in intermittent zones of random braided structure and otherwise extending substantially parallel to the elastic yarn, there being an average entanglement spacing of less than 10 centimeters and the filaments being free from crunodal or other surface loops when the composite yarn is examined in the stretched condition.

[0049] The composite yarn preferably has substantially zero unidirectional torque. The relatively inelastic filaments preferably have crimp when relaxed. The crimp is preferably such that the relatively inelastic filaments form undulations and twist pigtails when the composite yarn is relaxed. In accordance with a preferred embodiment, the relatively inelastic filaments form reversing helical coils when the composite yarn is relaxed.

[0050] The relatively inelastic filaments may be bicomponent filaments which crimp when relaxed before or after crimp development.

[0051] The composite yarn after latent contraction preferably has a break elongation of 50 to 350 percent or more. Generally, the elastic portion of the composite yarn shows no evidence of crimp, twist or torque produced by the operation of combining the hard fiber filaments with the elastic yarn.

[0052] The composite yarn of this invention can be produced at feed rates of up to about 2000 meters per minute, or higher, by continuously feeding the elastic yarn with the relatively inelastic filaments through jetted high velocity fluid and impinging the jetted fluid on the yarn axis at an angle of 90° ± 45° to entangle the filaments around the elastic yarn in intermittent zones of random braided structure. Usually, the precontraction melt extruded filament is fed to the jetted fluid under predetermined tension sufficient to stretch the filament, if desired, or merely to maintain it relatively taut. The relatively inelastic filaments (hard fibers) are simultaneously fed at a rate which is approximately equal to the rate at which the melt extruded filament is fed or which provides a net overfeed of hard fibers to be jetted fluid. Preferably, the composite yarn is wound on a package under controlled tension.

[0053] Suitable hard filber filaments or fibers include any synthetic textile filaments or fibers of relatively inelastic material such as nylon, e.g. nylon 6 and nylon 6,6; a polyester, e.g., polybutylene terephthalate, and polyethylene terephthalate, polypropylene, cellulose acetate; regenerated cellulose, etc. The hard fiber filaments may be fed to the jetted fluid as a single filament or as a bundle of preferably at least three filaments and may be of more than one material. The bundle preferably has less than 1 turn per 5 centimeters of twist and the filaments must be capable of being separated by the jetted fluid.

[0054] If desired, two or more precontraction melt extruded filaments may be fed and comingled with the inelastic filaments, the plurality of melt extruded filaments being separated at least temporarily by the jetted fluid to, if desired, insert portions of the relatively inelastic filaments between the melt extruded filaments.

[0055] The fluid used is preferably compressed air, although other fluids can be used; it is usually used at ambient temperature. The fluid is preferably impinged on the yarn from more than one direction, each substantially perpendicular to the yarn axis.

[0056] The rate of feed of the inelastic filaments in relation to the precontraction melt extruded filament is determined by the degree of extension desired in the composite yarn before the inelastic filaments become load-bearing. For any given filament and intended heat processing conditions, one can determine the amount of contraction to be obtained. Since it is desired that the contracted elastic filament of the invention be extendable at least 50% and preferably between about 100% and 350%, the amount of inelastic filament fed should be that amount which becomes load-bearing at the desired maximum extension of the contracted elastic filament.

[0057] Thus, since typically the desired extensibility of the contracted elastic filament is the contracted relaxed length multiplied by about 1.75 to about 6 and, since typically the contracted relaxed length of the heat processed elastic filament is 40% to 75% of the precontraction melt extruded filament length, the desired rate of feed of the inelastic filament and the precontraction melt extruded filament can be readily calculated for a given desired composite yarn. For example, if a heat processed elastic filament is contracted 50% based on the starting melt extruded filament and the desired extensibility is 100% (contracted length x2) the rates of feed of the inelastic filaments and the melt extruded filament should be equal. On the other hand, if the desired extensibility of the 50% contracted relaxed elastic filament is 150% (contracted relaxed length x2.5), the rate of feed of the inelastic filaments should be 25% greater than the rate of feed of the melt extruded filament. These calculations assume no extensibility is inherent in the inelastic companion filament. However, where the inelastic companion filament is crimped or otherwise yieldable, obviously the relative feed rates must be adjusted to attain the desired maximum extensibility of the resultant composite yarn.

[0058] In order that the relatively inelastic yarn protects the elastic filament from breaking, it is preferable that the elastic filament be intermingled with the inelastic yarn in a manner so that the relatively inelastic yarn becomes load-bearing at at least less than about 95% of the break elongation of the elastic filament.

Figure 1 is a schematic representation of a process for entangling a hard fiber yarn about an uncontracted melt extruded filament of the invention; and

Figure 2 illustrates a composite yarn obtained by the process of Figure 1.

[0059] With reference to Figure 1, a precontraction melt extruded filament 1 of the invention, from a supply source, is supplied, at a given rate, by driven feed roll 2 to a fluid jet intermingling device 7, while relatively inelastic filaments 3, from a supply source, are supplied at a given rate by rolls 4, 5 and 6, the same as or different from the melt extruded filament supply rate to the fluid jet intermingling device 7. The two filament supplies pass through a fluid intermingling jet with the device 7, which may have filament guides at the entrance and exit to center the filaments within the jet which intermingles the hard fiber filaments with the melt extruded filament. The resultant composite yarn 8 then passes one or more wraps about roll 9 and then to a windup device and package 10.

[0060] With reference to Figure 2, a useful composite yarn comprises, for example, two heat contracted elastic filaments 11 and 12, intermingled with five inelastic filaments 13, 14, 15, 16 and 17.

[0061] The fluid jet intermingling device may be one of those described in U.S. Patent Nos. 3,364,537 and 3,115,691 U.S. Patent No. 3.426,405, for example, in which one or more fluid streams impinge on the yarn line at an angle of 90° ± 45°. The essential requirement is that the hard fiber filaments be subjected to a fluid stream having an appreciable component of force at right angles to the filaments to separate them and force them around the inherently elastic yarn and around and between other hard fiber filaments to intermingle the hard fiber filaments by a random braiding action intermittently along the length of the composite yarn. If fluid jets are directed at the yarns at an angle of less than 45°, the fluid forces parallel to the yarns tend to be greater than those transverse to the yarns, thereby tensioning the filaments and tending to form stable loops rather than braiding them. It is also necessary to avoid a predominantly uni- directionial fluid twisting vortex, since such actions tends to wrap the filaments around the yarn rather than randomly braiding them. Jets having a unidirectional twisting effect are suitable for the present process only when a yarn oscillates rapidly between a region of fluid torque operating in one direction and a region of opposite torque, as described in U.S. Patent No. 2,990,671.

[0062] While in the intermingling process, the melt extruded filament and the inelastic companion filaments can be fed at greatly varying rates relative to each other, because of the subsequent contractability of the melt extruded filament it is not necessary to overfeed the inelastic companion filaments at rates as high as heretofore considered appropriate. Thus, a preferred process comprises continuously feeding at least one of the melt extruded filaments at a first predetermined feed rate and relatively inelastic filaments at a second predetermined feed rate through jetted high velocity fluid to entangle the inelastic filament around the melt extruded filament at spaced intervals, the rate of feed of the inelastic filaments being adjusted to the rate of feed of the melt extruded filaments so that the rate of feed of the inelastic filaments is less than twice the rate of feed of the melt extruded filament and is a rate such that after the resultant composite yarn is exposed to an elevated contraction inducing temperature whereby the melt extruded filament is contracted at least about 15% to provide an elastic filament, when the resultant composite yarn is stretched, the inelastic filaments become load-bearing at a predetermined percent of elastic stretching below the break elongation of the elastic filament. That is, to say, the precontraction melt spun filament and inelastic filament are fed at rates adjusted to form a composite yarn which has the desired elastic extensibility properties after the composite yarns has been heat treated to contract the melt spun filament. Because the elastic filament formed by the heat treatment is shortened, the inelastic filament need not be overfed or at least need not be overfed at high rates to achieve the desired elastic extensibility. In any event, upon stretching, it is desired that the inelastic filaments become load bearing before the break elongation of the elastic filament is reached.

[0063] The hard fiber multifilaments consists of relatively inelastic continuous filaments of any commonly available textile material. Nylon is generally preferred because of its high strength and low friction. Either uncrimped or crimped yarn may be employed, but crimped-or crimpable yarns must be capable of being held loop-free at the tension required to entangle the filament around the core and wind the composite yarn on a package. The tension-stable textured yarn described in U.S. Patent No. 2,783,609, for example, which has a crunodal surface loops when held at tension, is unsatisfactory for the purpose of the present invention. Two or more different multifilaments yarns may be employed, for example, nylon to give strength at ultimate extension and cullose acetate to provide luxurious textile aesthetics when the fabric is relaxed. Two yarns having differential shrinkage properties may be employed for certain effects. For .example, an untextured polyester yarn having high potential shrinkage may be fed with a textured nylon yarn and be entangled around a melt extruded core yarn wherein both hard fiber yarns are at the same tension during entangling and, in contract to those of U.S. Patent No. 2,783,609 remain loop free when wound on the package. When the yarn is made into fabric, and the fabric is heat treated under relaxed conditions, the polyester will shrink while the nylon develops crimp. When the treated fabric is then stretched, the polyester will become the load-bearing member to limit the ultimate extension of the composite yarn and will permit the textured nylon to retain a degree of crimp and bulk even at ultimate extension of the composite.

[0064] When the hard fiber component of the present invention composite yarn is crimpled or crimpable, the retractive power of such yarn may be less than that normally required when these filaments are used alone, since the elastic portion of the present composite yarn furnishes the major retractive power of the composite. The hard fiber filaments, therefore, need only have sufficient crimping ability to form the crimps, twists, or coils desired for imparting bulk, opacity or tactile aesthetics to the final fabric. These filaments, therefore, will be processed at higher speeds or under less stringent texturing conditions than would normally be required. This may permit falsetwist texturing, for example, to be performed on hard fiber which is then fed directly into the entangling step in a single continuous process.

[0065] There should be at least one and preferably at least three hard filaments. More filaments are generally desirable to provide more chances for intermingling, and more thorough protection for the elastic yarn. Low denier per filament in the hard fiber yarn is generally conductive to better intermingling, the smaller filaments being more easily formed into a random braid. In the case of stretch textured or bicomponent yarns, low denier per filament favours formation of small, fine coils when relaxed. Low bending modulus in the hard fiber filaments is also conductive to improved intermingling.

[0066] The hard fiber feed yarns should have low twist, preferably not more than 0.4 to 1.0 turns per 5 centimeters known as "producer twist", or most preferably zero twist. High twist interferes with opening of the filament bundle during the process of intermingling and surrounding the elastic core. Feed yarns having zero or low twist may interlace as described in U.S. Patent No. 2,985,995, but they should not have such a large degree of interlace that thefilaments are unable to separate for random braiding in the present process. For the present purposes, a yarn having the lowest degree of interlace consistent with processing, winding, and unwinding is preferred, no interlace being most preferable.

[0067] The yarns should not have size or finish of such a cohesive nature that it prevents the bundle from opening during the intermingling process although certain finishes may be desirable which allow the bundle to open but aid in retaining intermingling subsequently. Finishes disclosed in U.S. Patent 3,701,248, for example, may be used to improve the performance of yarns of this invention.

[0068] Yet another useful process for providing a covered yarn comprises spinning cut or staple fibres about the contractable inherently elastic filament by techniques known in the art as "core spinning". Core spinning is described in U.S. Patents 3,380,244; 3,009,311; 3,017,740; and 3,038,295. It is noted that while it has generally been considered necessary to stretch the core filament (elastic filament) to provide a useful composite core-spun elastic yarn, in the present invention, if desired, it not necessary to appreciably stretch the melt extruded filament during the core spinning process. The latent contraction, when heat activated subsequent to core-spinning the relatively inelastic staple fibres about the melt extruded filament, allows subsequent elastic extension of the resultant core-spun yarn before the inelastic yarn becomes load bearing.

[0069] There follow a number of Examples which illustrates the invention and what are now considered its best embodiments. As throughout the specification, all parts and percentages are by weight, and all temperatures are degrees Centigrade, unless otherwise specified.

Example 1

[0070] An ester interchange reactor was charged with 38.9 pounds of dimethylterephthalate, 10.5 kilograms of 1,4-butane diol, 29.9 kilograms of Dantocol DHE 20, i.e.:

where m + n = 20, as well as 220 grams of Antioxidant 330, 220 grams of Tinuvin 770, U.V. light stabilizer and 160 grams of titanium dioxide delusterant. The ester interchange reaction was conducted to recover about 12 pounds of methanol. The resultant reaction product was transferred to a polycondensation vessel and the reaction continued to recover about 4.8 kilograms of 1,4-butanediol and about 46 kilograms of the elastomeric polymer. (TINUVIN is a Registered Trade Mark).

[0071] With reference to Figure 3, the above 40 wt% PBT―60 wt% HPOE elastomer in the form of polymer chips stored in bunker (A) were extruded through a 1.27 cm extruder (B), the zones I, II and III of the extruder being at temperatures of 215°C, 218°C and 220°C, respectively. The extruder melt temperature was 205-207°C, and the pump yield for a 50 denier elastic yarn was 2.0 g/min. The polymer was extruded through a 2-hole spinneret (250 µ x 440 u) into a water bath (C) which was at room temperature (-22°C). The water bath temperature was maintained at approximately 20-22°C by constant inflow and outflow of water. The distance between the spinneret and the water bath was approximately 5 inches. A standard polyester finish was applied by means of a kiss-roll finish applicator (D). The speed of the two godets (E and F) is 500 meters/min. The elastic yarn was tangled with the companion yarn (G), 20/5 cationic dyeable textured nylon, by feeding both the yarns through a tangling jet (H). The air pressure for tangling used was 60 psi. The combined yarn was wound on a 15 cm long tube (0.63 cm thickness) using a Leesona winder (J).

[0072] An elastic yarn package containing the combination of the above elastic filament and companion filament in a total denier of 60, which is 40 denier 2 filament (abbreviated as 40/2 elsewhere herein) elastic yarn and 20/5 stretch nylon cationic dyeable companion yarn, was positioned on a horizontal creel of a four-feed high speed (800 rpm) 51 gauge panty hose machine. The elastic yarn was knit in every fourth course of the panty portion at about 3 gram tension. The other 3 feeds knitted a 50 denier stretch nylon cationic dyeable filament yarn. The stitch construction was set on a 1 x 1 rib.

[0073] The band was made in a 3 x 1 construction of a conventional 560 denier base spandex with a 50 denier cationic dyeable nylon filament, so that the entire panty hose top could be dyed with basic dyes for style purposes. The leg portion, knitted from regular dyeable nylon stretch filament yarn, plain or in combination with regular nylon covered spandex, can be dyed with acid dyes. After knitting, the toes of the hosiery panels were closed and the panty portions were slit to construct the total panty hose panty, while a pre- knitted cotton crotch was sewn in.

[0074] The completed panty hose garment was dyed starting with clean hosiery paddle dyeing machines.

[0075] Dyeing formulations were added and initial dyeing was run for 10-15 minutes. The bath temperature was raised to 100°C at a rate of about 20° per minute, at which temperature the hose were dyed for 30 to 40 minutes. The latent contraction of the elastic filaments occurred during the dyeing step.

[0076] After draining the bath, and. gradually cooling the yarn, two 5-minute rinses were given wherein the final rinse a 2% softener or finish was added for hand and stretch performance.

[0077] Additional samples were made, as above, in which the ratio of hard segments to soft segments were 50:50 and 60:40, respectively. The boiling water contraction of the 50:50 PBT/HPOE was 37%, while that of the 60:40 PBT/HPOE was 17%.

Example 2

[0078] Exposing the elastic composite yarn of Example 1 in straight but relaxed condition to dry hot air at 240°F (115.6°C) for 30 minutes produced the same yarn contraction as exposing the yarn in straight relaxed condition for 30 minutes in boiling water. As was the case with the boiled-off elastic yarn, the hot air contraction was also completely recoverable.

[0079] In addition, the elastic modulus of the elastic filament and the composite yarn of Example 1 were studied. On the linear elongation/load tester, Instron Model 1140 with reversing program possibilities, stress/strain diagrams were made from melt spun elastic yarn with and without companion yarn. (INSTRON is a Registered Trade Mark). Both yarn types were measured before and after boil-off. The yarn in this example was a 50/2 elastic yarn with a 20/5 textured nylon companion yarn. The boiled-off yarn contraction measured 41.1 %. The denier of the elastic yarn after boil-off measured 83.

[0080] In Figure 4, both the original and boiled-off elastic yarns were elongated to the breaking point. The original 5 cm gauge length for the untreated elastic yarn, the solid line, was reduced to 3 cm, to adjust for contraction of the boiled-off elastic yarn, the dotted line. The diagram shows a reduction in the elastic force for the boiled-off yarn, a reduction in modulus, and a breaking elongation of 560%, which is 2 times the elongation of the untreated elastic yarn of 280%. The crosshead and chart speeds during the measuring were both 50 cm per minute.

[0081] In Figure 5, the same yarn types were measured under the same conditions as was the case in Figure 4, with the exception of the setting for maximum elongation. In this example, the Instron was reversed at reaching 80% of the breaking elongation in order to measure the relaxation modulus. The chart the crosshead speeds of the return part of the cycle were maintained at 50 cm/minute.

[0082] In Figure 6, the combination of 50/2 elastic yarn with the 20/5 stretch nylon companion yarn was subjected to the stress/strain test. Because of the higher stress forces and the lower elongation of the composite yarn, the full-scale load was doubled and the crosshead speed reduced at 10 cm/minute. One unit (1.5 cm) of the "force" coordinate represents a load of 20 grams, while 3 cms of the "elongation" coordinate equals 20% elongation for the 3-cm sample length of the contraction adjusted boiled-off yarn, the dotted line. For the 5-cm gauge length of the original sample, the solid line, 20% elongation,equals 5 cm on the horizontal coordinate. Also, here the chart direction was reversed after reaching 80% of the breaking elongations for the respective samples in order to exhibit the contraction modulus. The diagram of the boiled-off yarn exhibits the typical elastic characteristics of the elastic composite yarn in finished fabrics. Eighty percent of the breaking elongation measures, in this case, 136% stretch at a load of 70 grams. In textile garment applications, the elastic yarn will usually perform in the 60%-100% elongation range and between 10-25 grams elastic force.

Example 3

[0083] A comparison of elastomeric yarns for contraction after exposure to various fabric processing conditions was made. Three fabric processes were simulated: atmospheric dyeing alone, atmospheric dyeing followed by hot air drying and pressure dyeing. These test exposures were carried out, comparing a 40% polybutyelene terephthalate hard segment, 60% hydantoin polyether soft segment segmented copolyester elastomer yarn (PBT/HPOE) prepared in accordance with U.S. Patent No. 4262114, filed December 20, 1978, and two non-melt extruded elastomers, Globe Manufacturing 70/1 S5 Lot 525 Glospan spandex, and duPont 70/8 Type 126 Lycra spandex. These three yarns were exposed to the three fabric processing conditions at no extension (relaxed). Exposures were conducted on 25-meter skeins. Length measurements were made using a 20-gram weight for load. The resultant contraction data follow: .

[0084] The primary observation resulting from this data was a confirmation that, when exposed to a boiling water process for one hour, the untensioned PBT/HPOE elastomeric yarn contracts to approximately 50% of its original length: This is in marked contrast to less than 10% contraction for duPont's Lycra. (LYCRA is a Registered Trade Mark). The contraction of elastomeric yarns upon exposure to atmospheric boiling water processes appears to be fully recoverable as stretch - the property most desirable in elastomeric yarns. In order to verify this fact, modified elongation tests were used.

[0085] In order to demonstrate that the latent contraction developed under atmospheric dyeing conditions would be fully recoverable as stretch; the yarns exposed to the three fabric processes above were tested for elongation, but under conditions which corrected the developed contraction of the yarns. In simple terms, when a developed specimen was tested in the tensile testing machine, the gauge length was reduced by the percentage which the yarn had contracted. The other machine settings were unaltered. Thus if 1.0 in of PBT/HPOE elastomeric yarn would stretch to 2.5 in before breaking, and if the developed contraction is fully recoverable, then 0.5 in of the developed PBT-HPOE should stretch to a length of 2.5 in before breaking. The developed yarn could be said to have twice the elongation of the undeveloped yarns. Or, if the elongations are both reported on the basis of the gauge length used for testing the undeveloped yarn (as is done in the following data table), both undeveloped and developed yarns would be said to have 250% elongation, showing that no total extensibility was lost during contraction:

The data in this table demonstrates that the contraction was fully recoverable as stretch.

[0086] In addition elongation, breaking strength tests were also conducted, the results of which follow:

Example 4

[0087] Samples of Hytrei (Registered Trade Mark) polyether: polyester (polyester hard segments:poly(ethylene terephthalate); polyether soft segments:poly(tetrahydrofuran)) (for preparation, see U.S. Patent 3,763,109) were extruded in the manner generally shown in Example 1 and separate samples of the extruded filament exposed to hot air (80°C) and boiling water for 30 minutes and the extent of latent contraction measures:

Example 5

[0088] In the general manner of Example 1, a segmented polyether: polyester was prepared consisting of 40% polybutyleneterephthalate hard segment and 60% polyoxyethyethylene (mol. wt. 1000) soft segment. The polymer was melt extruded into a 40 denier filament using a small laboratory ram extruder. Due to the long residence time inherent in the use of this extruder, a relatively weak fiber was produced having a tenacity (gm/denier) of about 0.2, and an elastic modulus at 100% extension of 0.1 gram/denier. The filament, upon exposure to boiling water for 30 minutes was an elastic filament which displayed a 33% contraction from its pre heat exposure length.

Example 6

[0089] A 60% poly(butyleneterephthalate) 40% poly(butylene adipate) polyester: polyester with soft and hard segments formed through urethane links was melt spun in a Killian ½-inch extruder at 210°C through a 1000 p x 3000 µ spinneret, into water at ambient temperature, and taken up at 300 meter/minutes, to yield a filament having a denier of 73. The filament, upon exposure to boiling water for 30 minutes, displayed a 33% contraction of its original length. The filament prior to heat treatment had an elongation of 213% and after heat treatment had an elongation of 382%. The relative viscosity is converted to intrinsic viscosity using the following modification of the Bellmeyer equation when the solution concentration is 1%:

where (η) = intrinsic viscosity and In = the natural logarithm. Intrinsic viscosity was measured using a 60/ 40 phenol/1,1,2,2 tetrachloroethane mixed solvent containing 5.0 ml of Karl Fischer reagent per liter of solvent. 0.18 to 0.22 grams of the dry polymer chips were weighed into a flask and the phenol/ tetrachloroethane solvent containing Karl Fischer reagent added to make a one percent solution. The samples were oscillated on a hot plate at 90 to 95°C until completely dissolved. The samples were cooled and relative viscosity determined in a Ubbelohde viscometer in a constant temperature bath at 25 ± 0.1°C. Care is taken to minimise the exposure to moisture during the entire procedure.

Claims

1. A method of forming an elastic filament which comprises melt extruding a segmented inherently elastic polyester-polyester or polyester-polyether thermoplastic polymer and exposing the melt extruded polymer to an elevated temperature characterized in that the thermoplastic polymer contains interspersed relatively hard segments and relatively soft segments and without prior deliberate drawing the melt extruded polymer is exposed to an elevated temperature in the range of from 40° to 125°C to linearly contract the melt extruded polymer at least 15% to provide an elastic filament.

2. A method as claimed in claim 1 wherein the melt extruded polymer is a segmented thermoplastic copolyester consisting essentially of a multiplicity of recurring long-chain ester units and short-chain ester units joined head to tail through ester linkages, the long-chain ester units comprising from 40-70% by weight of the copolyester and being represented by the formula:

and the short-chain ester units being represented by the formula:

where L in the long-chain unit is a divalent radical remaining after removal of terminal hydroxyl groups from a poly-(oxyalkylene) glycol having at least one nitrogen containing ring per molecule, a carbon to nitrogen ratio in the range of from 3/1 to 350/1, and a number average molecular weight in the range of from 200 to 8,000; R is a divalent radical remaining after the removal of carboxyl groups from a dicarboxylic acid having a molecular weight of less than 300; and E in the short-chain unit is a divalent radical remaining after the removal of hydroxyl groups from a low molecular weight diol having from 2 to 15 carbon atoms per molecule and a molecular weight of less than 250.

3. A method as claimed in claim 2 wherein in the long-chain ester units and short-chain ester units forming the polymer, substantially all of the dicarboxylic acid is terephthalic acid and wherein in the short-chain ester units forming the polymer, substantially all of the diol having a molecular weight of less than 250 is 1,4-butane diol.

4. A method as claimed in claim 2 wherein in the long-chain ester units forming the polymer the group -OLO- is a poly(oxyalkylene) glycol unit formed by the oxyalkylation of:

wherein R' and R" are C₁-₃ lower alkyl groups.

5. A method as claimed in any one of claims 1 to 4 wherein the polymer is subjected to a temperature in the range of from 80° to 100°C.

6. A method as claimed in any one of claims 1 to 4 wherein the polymer is exposed to a temperature of at least 40° to 60°C for a time sufficient to contract the length of the melt extruded filament by at least 40% as compared to its uncontracted length.

7. A method of forming a composite elastic yarn wherein a melt extruded, segmented inherently elastic polyester-polyester or polyester-polyether thermoplastic polymer is associated with inelastic fibres or filaments and the composite yarn exposed to an elevated temperature, characterized in that the thermoplastic polymer contains interspersed relatively hard segments and relatively soft segments and without prior deliberate drawing the composite yarn is subjected to exposure to an elevated temperature in the range of from 40°C to 125°C to cause the melt extruded polymer filament to contract by at least 15% in length.

8. A process for combining a latent contractable melt extruded filament formed from a segmented inherently elastic polyester-polyester or polyester-polyether thermoplastic polymer with a relatively inelastic synthetic polymer filament to produce a composite yarn which comprises continuously feeding at least one latent contractable melt extruded filament at a first predetermined feed rate and at least one relatively inelastic filament at a second predetermined feed rate through a jetted high velocity fluid and impinging the jetted fluid on the filament axis at an angle of 90° ± 45° to separate the inelastic filaments and entangle the inelastic filaments around the melt extruded filament at spaced intervals; the rate of feed of the inelastic filaments being adjusted with respect to the rate of feed of the melt extruded filaments so that the rate of feed of the inelastic filaments is less than twice the rate of feed of the melt extruded filament characterized in that the thermoplastic polymer contains interspersed relatively hard segments and relatively soft segments and when the resultant composite yarn is exposed without prior deliberate drawing to an elevated temperature in the range of from 40° to 125°C the melt extruded filament is contracted at least 15% to provide an elastic filament and when the resultant composite yarn is stretched the inelastic filaments become load-bearing at a. predetermined percent of elastic stretching below the break elongation of the elastic filament.

9. A process as claimed in claim 8 wherein the melt extruded filament and the inelastic filament are fed at about the same rate.

10. A process of forming a stretchable textile article which comprises forming a predetermined over-sized article with yarns comprising a latent contractable filament formed from a segmented inherently elastic polyester-polyester or polyester-polyether thermoplastic polymer and exposing the resultant textile article to an elevated temperature sufficient to contract the latent contractable filament, characterized in that the thermoplastic polymer contains interspersed relatively hard segments and relatively soft segments and contracts at least 15% as compared to its original length when exposed without prior deliberate drawing to an elevated temperature in the range of from 40° to 125°C, thereby to form a stretchable article of a desired size.

11. A process as claimed in claim 10 wherein the latent contractable filament is covered with a relatively inelastic companion filament or fiber.

Ansprüche

1. Verfahren zur Erzeugung eines elastischen Fadens (Filaments), wobei ein segmentiertes, inhärent elastisches thermoplastisches Polyester-Polyester- oder Polyester-Polyäther-Polymer schmelzextrudiert und das schmelzextrudierte Polymer einer erhöhten Temperatur ausgesetzt wird, dadurch gekennzeichnet, daß das thermoplastische Polymer verhältnismäßig harte und verhältnismäßig weiche Segmente eingestreut enthält und daß das schmelzextrudierte Polymer, ohne daß es zuvor absichtlich gezogen wird, einer erhöhten Temperatur im Bereich von 40-125°C ausgesetzt wird, um das schmelzextrudierte Polymer um mindestens 15% linear zu kontrahieren und um einen elastischen Faden zu erzeugen.

2. Verfahren nach Anspruch 1, worin das schmelzextrudierte Polymer einen segmentierten thermoplastischen Co-Polyester darstellt, der im wesentlichen aus einer Vielzahl von wiederkehrenden langkettigen und kurzkettigen Estereinheiten besteht, welche über Esterbindungen "Kopf-an-Schwanz" miteinander verbunden sind, wobei die langkettigen Estereinheiten mindestens 40 bis 70 Gew.-% des CoPolyesters ausmachen und durch die Formel

dargestellt sind und wobei die kurzkettigen Estereinheiten durch die Formel

dargestellt sind, worin bedeuten:

L in der langkettigen Einheit bedeutet einen zweiwertigen Rest, der nach Entfernung der entständigen Hydroxylgruppen aus einem Poly-(Oxyalkylen)-Glykol hinterbleibt und der mindestens einen stickstoffhaltigen Ring je Molekül, ein Kohlenstoff/Stickstoff-Verhältnis im Bereich von 3/1 zu 350/1 sowie ein numerisches durchschnittliches Molekulargewicht im Bereich von 200 bis 8000 aufweist;

R bedeutet einen zweiwertigen Rest, der nach Entfernung der Carboxylgruppen aus einer Dicarbonsäure hinterbleibt und der ein Molekulargewicht von weniger als 300 hat;

und E in der kurzkettigen Einheit bedeutet einen zweiwertigen Rest, der nach Entfernung der Hydroxylgruppen aus einem niedrigmolekularen Diol hinterbleibt und der 2 bis 15 Kohlenstoffatome je Molekül enthält und ein Molekulargewicht von weniger als 250 hat.

3. Verfahren nach Anspruch 2, worin in den langkettigen und in den kurzkettigen Estereinheiten, die das Polymer bilden, praktisch die gesamte Dicarbonsäure Terephthalsäure darstellt und worin in den kurzkettigen Estereinheiten, die das Polymer bilden, praktisch der gesamte Diol mit einem Molekulargewicht von weniger als 250 1,4-Butandiol darstellt.

4. Verfahren nach Anspruch 2, worin in den langkettigen Estereinheiten, die das Polymer bilden, die Gruppe -OLO- eine Poly-(Oxyalkylen)-Glykol-Einheit darstellt, die durch die Oxyalkilierung von

gebildet worden ist, worin R' und R" niedere Alkylgruppen mit 1 bis 3 C-Atomen darstellen.

5. Verfahren nach einem der Ansprüche 1 bis 4, worin das Polymer einer Temperatur im Bereich von 80 bis 100°C ausgesetzt wird.

6. Verfahren nach einem der Ansprüche 1 bis 4, worin das Polymer einer Temperatur von mindestens 40 bis 60°C ausgesetzt wird, und zwar über einen Zeitraum, der ausreicht, um die Länge des schmelzextrudierten Fadens um mindestens 40%, verglichen mit der Länge im nicht-kontrahierten Zustand, zu kontrahieren.

7. Verfahren zur Herstellung eines elastischen Verbundgarns, worin ein schmelzextrudiertes, segmentiertes, inhärent elastisches thermoplastisches Polyester-Polyester- oder Polyester-Polyäther-Polymer mit unelastischen Fasern oder Fäden vereinigt und das zusammengesetzte Garn einer erhöhten Temperatur ausgesetzt wird, dadurch gekennzeichnet, daß das thermoplastische Polymer verhältnismäßig harte und verhältnismäßig weiche Segmente eingestreut enthält und daß das schmelzextrudierte Polymer, ohne daß es zuvor absichtlich gezogen wird, einer erhöhten Temperatur im Bereich von 40-125°C ausgesetzt wird, um den schmelzextrudierten polymeren Faden um mindestens 15% seiner Länge zu kontrahieren.

8. Verfahren zum Vereinigen eines latent kontrahierbaren, schmelzextrudierten Fadens, der aus einem segmentierten, inhärent elastischen, thermoplastischen Polyester-Polyester- oder Polyester-Polyäther-Polymer gebildet ist, mit einer verhältnismäßig unelastischen, synthetischen Polymerfaden, um ein Verbundgarn herzustellen, wobei mindestens ein latent kontrahierbarer, schmelzextrudierter Faden mit einer esten, vorherbestimmten Zugabegeschwindigkeit und mindestens ein verhältnismäßig unelastischer Faden mit einer zeitlich vorherbestimmten Zugabegeschwindigkeit kontinuierlich durch einen Fluidstrahl mit hoher Geschwindigkeit geleitet werden, wobei der Fluidstrahl unter einem Winkel von 90° ± 45° auf die Fadenachse auftrifft, um die unelastischen Fäden zu trennen und um die unelastischen Fäden um den schmelzextrudierten Faden zu verwickeln; wobei die Zugabegeschwindigkeit der unelastischen Fäden gegenüber der Zugabegeschwindigkeit der schmelzextrudierten Fäden so eingestellt wird, daß die Zugabegeschwindigkeit der unelastischen Fäden weniger als das Doppelte der Zugabegeschwindigkeit der schmelzextrudierten Fäden beträgt; dadurch gekennzeichnet, daß das thermoplastische Polymer verhältnismäßig harte und verhältnismäßig weiche eingestreute Segmente enthält und daß, wenn das erhaltene Verbundgarn, ohne daß es zuvor absichtlich gezogen wurde, einer erhöhten Temperatur im Bereich von 40 bis 125°C ausgesetzt wird, der schmelzextrudierte Faden um mindestens 15% kontrahiert wird, um einen elastischen Faden zu erzeugen, und, wenn das erhaltene Verbundgarn gestreckt wird, die unelastischen Fäden bei einem vorherbestimmten prozentualen Anteil an elastischer Streckung unterhalb der Bruchdehnung des elastischen Fadens die Last aufnehmen.

9. Verfahren nach Anspruch 8, worin der schmelzextrudierte Faden und der unelastische Faden mit etwa der gleichen Geschwindigkeit zugeführt werden.

10. Verfahren zur Erzeugung eines streckbaren Textilgegenstandes, wobei ein vorherbestimmter Gegenstand in Übergröße mit Garnen, enthaltend latent kontrahierbare Fäden aus einem segmentierten, inhärent elastischen, thermoplastischen Polyester-Polyester- oder Polyester-Polyäther-Polymer erzeugt und der erhaltene Textilgegenstand einer erhöhten Temperatur ausgesetzt wird, die ausreicht, um den latent kontrahierbaren Faden zu kontrahieren, dadurch gekennzeichnet, daß das thermoplastische Polymer verhältnismäßig harte und verhältnismäßig weiche Segmente eingestreut .enthält und um mindestens 15%, bezogen auf seine ursprüngliche Länge, kontrahiert, wenn es, ohne daß es zuvor absichtlich gezogen wird, einer erhöhten Temperatur im Bereich von 40 bis 125°C ausgesetzt wird, um einen streckbaren Gegenstand mit der gewünschten Größe zu bilden.

11. Verfahren nach Anspruch 10, worin der latent kontrahierbare Faden mit einem verhältnismäßig unelastischen Begleitfaden oder -faser bedeckt wird.

Revendications

1. Procédé de formation d'un filament élastique, qui comprend l'extrusion à l'état fondu d'un polymère thermoplastique à élasticité propre, segmenté et de type polyester-polyester ou polyester-polyéther, et l'exposition du polymère extrudé à l'état fondu à une température élevée, caractérisé en ce que le polymère thermoplastique contient des segments relativement durs et des segments relativement mous entremmêlés, et, sans étirage préalable délibéré, le polymère extrudé à l'état fondu est exposé à une température élevée comprise entre 40 et 125°C afin que le polymère extrudé à l'état fondu soit contracté linéairement d'au moins 15% et forme un filament élastique.

2. Procédé selon la revendication 1, dans lequel le polymère extrudé à l'état fondu est un copolyester thermoplastique segmenté essentiellement constitué de motifs ester à chaîne longue et des motifs ester à châine courte récurrents, reliés par des liaisons ester par leurs extrémités, les motifs ester à chaîne longue forment 40 à 70% du poids du copolyester et étant représentés par la formule:

et les motifs ester à chaîne courte étant représentés par la formule:

L du motif à chaîne longue étant un radical bivalent restant après enlèvement des groupes hydroxyle terminaux d'un poly(oxyalkylène)glycol ayant au moins un noyau contenant de l'azote par molécule, un rapport carbone/azote compris entre 3/1 et 350/1 et une masse moléculaire moyenne en nombre comprise entre 200 et 3000, R étant un radical-bivalent restant après l'enlèvement des groupes carboxyle d'un acide dicarboxylique ayant une masse moléculaire inférieure à 300, et E du motif à chaîne courte étant un radical bivalent restant après l'enlèvement des groupes hydroxyle d'un diol de faible masse moléculaire ayant 2 à 15 atomes de carbone par molécule et une masse moléculaire inférieure à 250.

3. Procédé selon la revendication 2, caractérisé en ce que, dans les motifs ester à châine longue et à chaîne courte formant le polymère, la totalité pratiquement de l'acide dicarboxylique est l'acide téréphtalique, et dans lequel, dans les motifs ester à chaîne courte formant le polymère, la totalité du diol pratiquement ayant une masse moléculaire inférieure à 250 est le 1,4-butanediol.

4. Procédé selon la revendication 2, caractérisé en ce que, dans les motifs ester à chaîne longue formant le polymère, le groupe -OLO- est un motif poly(oxyalkylène) glycol formé par oxyalkylation de:

R' et R" étant des groupes alkyle inférieurs en C₁-_3'

5. Procédé selon l'une quelconque des revendications 1 à 4, dans lequel le polymère est soumis à une température comprise entre 80 et 100°C.

6. Procédé selon l'une quelconque des revendications 1 à 4, dans lequel le polymère est exposé à une température d'au moins 40 à 60°C pendant un temps qui suffit pour que la longueur du filament extrudé à l'état fondu se contracte d'au moins 40% par rapport à la longueur à l'état non contracté.

7. Procédé de formation d'un fil élastique composite dans lequel un polymère thermoplastique à élasticité propre, segmenté, extrudé à l'état fondu et de type polyester-polyester ou polyester-polyéther est associé à des filaments ou fibres non élastiques et le fil composite est exposé à une température élevée, caractérisé en ce que le polymère thermoplastique contient des segments entremmêlés relativement durs et relativement mous et, sans étirage préalable délibéré, le fil composite est soumis à une exposition à une température élevée comprise entre 40 et 125°C afin que le filament polymère extrudé à l'état fondu se contracte d'au moins 15% de sa longueur.

8. Procédé de combinaison d'un filament extrudé à l'état fondu et à contraction latente, formé à partir d'un polymère thermoplastique à élasticité propre, segmenté et de type polyester-polyester ou polyester-polyéther, ayant un filament de polymère de synthèse relativement non élastique, afin qu'un fil composite soit formé, le procédé comprenant l'avance continue d'au moins un filament extrudé à l'état fondu et à contraction latente à une première vitesse prédéterminée d'avance et d'au moins un filament relativement non élastique à une seconde vitesse prédéterminée d'avance, dans un jet de fluide à grande vitesse, et la projection du jet de fluide sur l'axe du filament avec un angle de 90 ± 45° afin que les filaments non élastiques soient séparés et que les filaments non élastiques s'entremmêlent autour du filament extrudé à l'état fondu, à certains intervalles, la vitesse d'avance des filaments non élastiques étant ajustée par rapport à la vitesse d'avance des filaments extrudés à l'état fondu afin que la vitesse d'avance des filaments non élastiques soit inférieure au double de la vitesse d'avance du filament extrudé à l'état fondu, caractérisé en ce que le polymère thermoplastique contient des segments entremmêlés relativement durs et relativement mous et, lorsque le fil composite résultant est exposé sans étirage préalable délibéré à une température élevée comprise entre 40 et 125°C, le filament extrudé à l'état fondu est contracté d'au moins 15% afin qu'il forme un filament élastique et, lorsque le fil composite résultant est allongé, les filaments non élastiques commencent à supporter les forces avec un pourcentage prédéterminé d'allongement élastique au-dessous de l'allongement à la rupture du filament élastique.

9. Procédé selon la revendication 8, dans lequel le filament extrudé à l'état fondu et le filament non élastique avancent à la même vitesse environ.

10. Procédé de formation d'un article textile qui peut s'allonger, comprenant la formation d'un article surdimensionné prédéterminé à l'aide de fils contenant un filament à contraction latente formé d'un . polymère thermoplastique à élasticité propre, segmenté et de type polyester-polyester ou polyester-polyéther, et l'exposition de l'article textile résultant à une température élevée qui suffit à la contraction du filament à contraction latente, caractérisé en ce que le polymère thermoplastique contient des segments entremmêlés relativement durs et relativement mous et se contracte d'au moins 15% par rapport à sa longueur originale lorsqu'il est exposé sans étirage préalable délibéré, à une température élevée comprise entre 40 et 125°C, si bien qu'un article qui peut s'allonger, ayant la dimension voulue, est formé.

11. Procédé selon la revendication 10, dans lequel le filament à contraction latente est recouvert de fibre ou d'un filament associé relativement non élastique.

Drawing