JPH04228617A - Two-component elastomer fiber - Google Patents

Abstract

PURPOSE: To provide a method for producing an elastomeric fiber useful for producing a pair of stockings, etc. CONSTITUTION: This bicomponent elastomeric fiber is obtained by coextrusion molding of an elastomer consisting of (a) 100 pts.wt. functionalized and selectively hydrogenated block copolymer comprising (i) at least 2 blocks consisting of predominantly polymerized monovinyl aromatic monomer units, (ii) at least one block consisting of predominantly, before its hydrogenation, polymerized conjugated diolefin monomer units and (iii) 2-20 acid or anhydride groups on average per 1 molecule of the polymer, and (b) 30-300 pts.wt. nylon.

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to elastic fibers and, in particular, to methods for producing such elastic fibers.

High modulus fibers are useful in making support pantyhose and stockings. Until recently, supporting pantyhose were expensive, clumsy, and had to be manufactured in a variety of sizes to provide a snug fit for the majority of potential customers. Most support pantyhose were made from fibers with a spandex core coated with nylon. Spandex is a polyurethane block copolymer. The fibers are bulky and expensive to manufacture. Improved fibers were produced by coextruding polyurethane block copolymers and nylon to produce fibers that were part polyurethane and part nylon. The fiber is cooled and then stretched. After stretching, nylon does not shrink the way polyurethane does. Therefore, upon relaxation, this bicomponent fiber produces a helix in which the outer half of the helix is nylon and the inner half is polyurethane. Such fibers are described in U.S. Patent No. 3,987,14.
It is stated in No. 1. These fibers are relatively inexpensive to produce, can be made in very small diameters, and have excellent extensibility. The commercialization of these fibers has made it possible to create pantyhose that fit most people in smaller sizes.
Officially, they are now available at a relatively low price with a level of support that can only be found in support pantyhose, but they are still not thin enough to satisfy consumers. These fibers have only been commercially available for a few years, barely making ends meet. Until now, only very specific polyurethanes have been used in these fibers due to the stringent requirements of coextrudability, thermal stability and adhesion to nylon. The different swellability of the two polymeric components suggests that they must be strongly adhered to each other or they will separate upon shrinkage.

Attempts to coextrude hydrogenated block copolymers of styrene and butadiene with nylon to produce fibers with superior elasticity than those produced from polyurethane block copolymers have been unsuccessful. Styrene and butadiene block copolymers are not as expensive as polyurethanes suitable for coextrusion. They also have a narrower molecular weight distribution and are therefore more processable. Hydrogenated block copolymers of monovinyl aromatics and conjugated diolefins are also more thermally stable at higher temperatures than polyurethanes. This allows coextrusion over a wide range of temperatures, and also allows coextrusion of nylon 6-6, which can be melt processed at temperatures above which polyurethane is thermally stable. It is therefore desirable to produce coextruded fibers of nylon and these block copolymers, but attempts have not been successful due to shrinkage separation of these two fiber components.

It is therefore an object of the present invention to provide elastic fibers that can be produced by coextrusion of monovinyl aromatic compound-conjugated block copolymers and nylon.

As a result of extensive research experiments, it has surprisingly been found that by introducing polar functionality into block copolymers of monovinyl aromatic compounds and conjugated diolefins, excellent elastic binary components composed of these polymers can be obtained. It has been found that sufficient adhesion can be obtained to form fibers.

Therefore, the present invention provides (a) (i) at least two polymerizable monovinyl aromatic monomer units consisting mainly of polymerizable monovinyl aromatic monomer units;
(ii) at least one block consisting primarily of polymerizable conjugated diolefin monomer units prior to hydrogenation; and (iii) an acid or 100 parts by weight of a functionalized, selectively hydrogenated block copolymer comprising anhydride groups; and (b) a range of 30 to 300 parts by weight of nylon. It is something.

The block copolymer, which is the main component of the fiber of the present invention, comprises at least two monovinyl aromatic compound blocks of sufficient molecular weight to form a separate domain from the rubbery conjugated diolefin phase. include.

[0008] The domains of these monovinyl aromatic compounds have a glass transition temperature that exceeds the usable temperature of the polymer;
It serves to connect rubber-like conjugated diolefin polymer blocks to each other. This gives the polymer properties similar to vulcanized rubber, which has high elongation before break and high recovery from stress.

Although the monovinyl aromatic block may have a low molecular weight when it has a polar functional group, it is generally thought that monovinyl aromatic blocks having a number average molecular weight of 2000 or more form separate domains. This is because polar functional groups increase the incompatibility between the domains and the conjugated diolefin phase when they are primarily present within the monovinyl aromatic block. As long as the solubility parameters of the monovinyl aromatic blocks remain sufficiently different from those of the conjugated diolefin blocks forming the separate domains, these blocks may be copolymer blocks of one or more monovinyl aromatic compounds or other It may also be a copolymer with a polymerizable monomer. Therefore, as long as the block consists primarily of a monovinyl aromatic compound, it may contain other monomer units. As used herein, primarily refers to about 75% (or more) by weight.

[0010] Vinyl aromatic hydrocarbons forming the base of the monivinyl aromatic block include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, Vinylnaphthalene, vinylanthracene, etc. may be mentioned. Styrene is preferred because of its availability and relatively low cost. Polystyrene also has a fairly high glass transition temperature and minimal miscibility with conjugated diolefin blocks.

The conjugated diolefin blocks are preferably based on isoprene and/or butadiene and may therefore include polyisoprene, polybutadiene or butadiene-isoprene copolymer blocks.

The conjugated diolefin block may also contain other types of monomers so long as they have solubility parameters sufficiently different from those of the monovinyl aromatic block. The conjugated diolefin blocks are primarily conjugated diolefin monomer units, and again, about 75% by weight is usually sufficient. The number average molecular weight of the conjugated diolefin block is 20,000 to 150,000
, preferably from 30,000 to 75,000.

Block copolymers having a variety of structures, such as those having linear or radial structures and forming monovinyl aromatic domains, are believed to be useful in making the fibers of this invention. In linear block copolymers,
At least some of the conjugated diolefin blocks are believed to be attached at each end to the monovinyl aromatic domain, whereas in radial block copolymers,
The monovinyl aromatic blocks are preferably connected at the outer ends of the arms of the block copolymer.

The monovinyl aromatic content of the block copolymer ranges from 10 to 45% by weight, preferably from 10 to 33% by weight.
It can vary within a range of weight percentages. If the content is low, the formation of monovinyl aromatic domains will be insufficient, and if the content is high, the polymer will be hard and inelastic.

As mentioned above, the production of block copolymers is known, for example in US Pat. No. 3,390,207.
It is suitably carried out by anionic polymerization in an inert solvent using an alkyllithium initiator, as described in 1999.

When butadiene is used as the conjugated diolefin, a polar modifier can be used in the polymerization solution to change the vinyl content of the polybutadiene block produced.

Although the block copolymers of the present invention can be utilized in unhydrogenated form, it is preferred that they be hydrogenated. Unhydrogenated block copolymers have limited extrusion temperatures and are susceptible to decomposition by oxygen and light. Therefore, fibers obtained from unhydrogenated block copolymers have a limited pot life.

Hydrogenation removes 90% of the initial ethylenic unsaturation.
% and less than 10% of the initial aromatic unsaturation is preferred. Furthermore, hydrogenation preferably removes at least 98% of the original ethylenic unsaturation and no more than 1% of the original aromatic unsaturation.

Retaining aromatic unsaturation is preferred because retaining aromatic unsaturation results in a higher glass transition temperature of the monovinyl aromatic domain and lower hydrogen consumption.

Hydrogenation can be carried out by several known methods. In particular, the method described in US Pat. No. 3,113,986 can be used.

Acid or anhydride functionality may be introduced into the block copolymer by any method known in the art. Since the purpose of the functionality is to induce adhesion of the polyamide, the functionality can be introduced into one type of block or into both types of blocks.

One method for producing functionalized, selectively hydrogenated block copolymers is to copolymerize monomers containing functional groups with monovinyl aromatic or conjugated diolefin monomers. Next, the obtained polymer is hydrogenated. When utilizing this method, the functional group should not interfere with the hydrogenation step and should be convertible to an acceptable acid or anhydride functionality after hydrogenation.

Another preferred method of introducing functionality into block copolymers is by melt grafting an α,β-unsaturated carboxylic acid or anhydride onto the polymer in the presence or absence of a free radical initiator. It consists of doing. Methods using free radical initiators are preferred because they can be carried out with minimal residence time in the extruder. A preferred α,β-unsaturated carboxylic acid or anhydride is maleic anhydride.

The functionality of the carboxylic acid or anhydride can also be improved by reacting the block copolymer with a metal alkyl in an inert solvent and then displacing the metal ion with an electrophile such as carbon dioxide. It can be introduced into the block copolymer by forming a lithium salt. The lithium salt may then be acidified by contacting with an organic acid. Such a method is known from US Pat. No. 4,868,245.

A method for introducing sulfonic acid functionality into the block copolymers used in the present invention is described in US Pat. No. 3,87
No. 0,841, a block copolymer and acyl sulfate (RCO2 SO3 H) are reacted to add a sulfonic acid group (-SO3 H) to the aromatic ring of the polymer,
It consists of liberating an organic acid (RCO2H).

Block copolymers can also be functionalized by reacting hydrogenated block copolymers with azidosulfonyl benzoates.

The number of functional groups present in each polymer molecule is
ranging from 2 to 20 on average, preferably from 2 to 16 on average
and more preferably 4 to 12 on average. Low functionality results in insufficient adhesion between the polymer phases, but higher contents are not necessary for good adhesion and are unfavorable for elasticity.

A wide variety of nylons or polyamides that may be incorporated into the fibers of the present invention include polyhexamethylene adipic acid amide (nylon 6-6), polypyrrolidone (nylon 4), polycaprolactam (nylon 6), polyheptolactam. (Nylon 7) Polycapryllactam (Nylon 8), Polynonanolactam (Nylon 9), Polyundecanolactam (Nylon 11), Polydodecanolactam (Nylon 12), Polyhexamethyleneazelaic acid amide (Nylon 6-9) , polyhexamethylene sebacic acid amide (nylon 6-10), polyhexamethylene isophthalic acid amide (nylon 6-iP), polymethaxylylene adipic acid amide (nylon MXD-6), heximethylene diamine and n-dodecanedioic acid polyamide (nylon 6-12), dodecamethylene diamine and n-
Included are polyamides with dodecanedioic acid (nylon 12-12) and Qiana®.

For example, the following copolymer: hexamethyleneadipic acid amide/caprolactam (nylon 6-6/6)
, hexamethylene adipic acid amide/hexamethylene-
Isophthalic acid amide (nylon-6-6iP), hexamethylene adipic acid amide/hexamethylene terephthalic acid amide (nylon 6-6/6T), hexamethylene adipic acid amide/hexamethylene azelaic acid amide (nylon 6-6/6) -9), nylon copolymers such as hexamethylene adipic amide/hexamethylene azelaic amide/caprolactam (nylon 6-6/6-9/6) may also be used.

Preferred nylons include 6, 6-6, 11 and 12.

The polyamide used in the composition of the invention preferably has a number average molecular weight (Mn) of at least 10,000, and more preferably has a molecular weight (Mn) in the range of 20,000 to 50,000. preferable. Furthermore,
Such polyamides preferably have an equivalent content of amine of 0.1 meq/g or less.

It is necessary that the fibers of this invention contain a sufficient amount of block copolymer to provide excellent elasticity. The fiber contains a sufficient amount of nylon to give the fiber a silky appearance and good strength. Generally, the fibers consist of block copolymers in the range of 20-77% by weight of the fibers. Preferably 25-75% by weight of the fibers and more preferably 50-60% by weight are block copolymers. Preferably 20-75% by weight of the fibers are nylon. More preferably, 25-65% by weight of the fibers are nylon, and most preferably 40-50% by weight of the fibers are nylon. The amount of nylon per 100 parts by weight of the block copolymer ranges from 30 to 300 parts by weight, preferably 100 parts by weight.
Parts by weight.

The fibers of the present invention are coextruded to form filaments by methods known in the art. After the block copolymer and nylon are extruded and cooled below their melting temperature, the fibers are "drawn" or stretched to at least twice their original length.
tch). Preferably, the fibers have an original length of
It is enlarged between 5 times. Upon relaxation, the fibers assume a helix configuration.

[0034] The polymeric components of the fibers are preferably arranged in close proximity, although an enclosed form is not preferred for the final fiber product, especially if it is nylon that surrounds some of the block copolymer.

The fibers may be used without further processing, but may be woven or crimped by several known methods.

The fiber of the present invention has an initial diameter of 0.02 mm.
It can be coextruded to a range of .about.0.05 mm. This fine fiber can be knitted into elastic pantyhose or stockings, which are thin and provide excellent support. Of course, even larger diameter fibers can be made to provide greater strength at the expense of thinness.

Although the fibers of the present invention are preferably extruded to have a circular cross section, other cross sections are possible and can be used. A shape with a large surface area reflects light well and appears to be more glossy. Sharp crevices, such as star-shaped sections, are undesirable because they trap dirt and appear to stain easily. Stretching and relaxing the fibers, of course, further alters the cross-section of the fibers.

The two polymer melts to be coextruded must have similar viscosities at acceptable extrusion temperatures. The melt viscosity of the block copolymer can be adjusted by changing the styrene content, the molecular weight of the block copolymer, or by adding plasticizers. In general, relatively low molecular weight block copolymers are preferred because they eliminate or minimize the need for the use of plasticizers. A number average molecular weight in the range of 30,000 to 185,000 is preferred, and a number average molecular weight of 45,000 to 85,000 is more preferred, since the melt viscosity of the polymer having such a molecular weight is higher than that of normal grades of nylon. This is because the melt viscosity is closer to that of

[0039] Acceptable extrusion temperature, for example 250°C
The melt viscosity ratio of block copolymer to nylon is 3
:1 to 1:3 is preferable. Furthermore, this ratio is 1.5:
The range of 1 to 1:1.5 is preferable. When a plasticizer is used with either polymer, melt viscosity ratios in the above range can be achieved.

The plasticizer that may be used must not be volatile at the extrusion temperature and must not act as a mold release agent at the interface of the two polymer phases. The processing oil acts as a mold release agent and destroys the adhesion between the polymer phases. This occurs when the oil vaporizes in the die and condenses at the polymer interface. Therefore, a process oil is required that has an initial boiling point above the extruder die temperature. When using process oil, the initial boiling point is 2.
Those having a temperature of 30°C or higher are preferred.

The fibers may be dyed using known dyes for nylon, including acid dyes. Acid dyes generally do not stain the exposed block copolymer surface, which is another advantage of the fibers of the present invention. Because undyed block copolymers are translucent, products made from knitted or woven fibers appear thinner than articles made from all nylon fibers.

Other additives and treatments known to be useful for polymeric fibers may also be incorporated into the fibers of this invention. These include matting additives, pigments, dyes, antistatic additives, flame retardants, brightening agents, carbon black and fillers in combinations thereof.

The fibers of the present invention may be knitted or woven into fabrics. The fabric is useful as socks, stockings or pantyhose for men or women. The fibers have the excellent silky appearance typical of nylon fibers, but are more elastic than nylon-covered spandex fibers.

The block copolymers of the present invention are more thermally stable at high temperatures than polyurethanes previously used in coextruded nylon fibers. nylon 6-6
Although nylons such as Nylon 6-6 cannot be coextruded with polyurethane due to the high melting temperature of Nylon 6-6, Nylon 6-6 and the block copolymers of the present invention can be coextruded.

The polyurethane component of the prior art fibers is also more expensive than the block copolymer portion of the fibers of the present invention. Therefore, the fibers of the present invention can be produced at lower cost than prior art coextruded fibers.

The fibers of the present invention and articles made therefrom exhibited excellent "strength", hysteresis, fit, appearance, durability, fit resistance, and abrasion resistance.

EXAMPLE Preparation of Elastic Nylon 6-Functional Block Copolymer Fiber Bumek copolymer is a triblock of styrene and butadiene having a number average molecular weight of about 52,000 and containing 30% by weight styrene. there were. The terminal blocks were polystyrene blocks of approximately equal molecular weight. The block copolymer was selectively hydrogenated to remove more than 99% of the original ethylenic unsaturation and less than 5% of the original aromatic unsaturation. The hydrogenated block copolymer was grafted during coextrusion with maleic anhydride in the presence of a peroxide free radical initiator to contain about 2% functionality by weight as maleic anhydride.

In an attempt, DSM 473GL (nylon 6 commercially available from Enka) and 50/50m/
Fibers were coextruded using m ratio functional block copolymers. This coextrusion attempt was unsuccessful because the block copolymer was more viscous than nylon.

Next, 85 parts by weight of the functional block copolymer was added to a process oil having an initial boiling point of about 240°C, namely Dr.
The melt viscosity of the block copolymer was reduced to that of nylon 6 by mixing with akol 4465.

Fibers were produced by coextrusion of nylon and oil-containing functionalized polymer in a 50/50 m/m ratio through a 126-hole spinneret with circular holes of 0.035 mm diameter. The fibers were then cooled and the 126 fiber bundle was wound into a spool. If you enlarge the bundle,
Each fiber does not assume a helical structure due to relaxation, but
Each fiber was separated from the bundle, stretched to approximately three times its length, and then, when relaxed, assumed a neat helical structure with excellent elasticity.

Claims (17)

[Claims] 1. (a) (i) at least two blocks consisting primarily of polymerizable monovinyl aromatic monomer units; (ii) at least one block consisting primarily of polymerizable conjugated diolefin monomer units prior to hydrogenation; and (iii) on average ranging from 2 to 20 acid or anhydride groups per polymer molecule. 100 parts by weight; and (b) a coextruded elastic fiber in the range of 30 to 300 parts by weight of nylon. 2. The fiber of claim 1, wherein the selectively hydrogenated block copolymer is saturated with 90% or more of ethylenic unsaturation and 10% or less of aromatic unsaturation. 3. Fibers according to claim 1 or 2, wherein the fibers have an average diameter in the range from 0.02 mm to 0.05 mm. 4. The fiber according to claim 1, having a helical structure. 5. The fiber according to claim 4, wherein the coextruded fiber is elongated to a length that is at least twice its original length, and then the fiber is relaxed to form a helical structure. . 6. The fiber according to claim 1, wherein the block copolymer is a triblock copolymer. 7. A fiber according to claim 6, wherein the central block of the triblock copolymer is, prior to hydrogenation, primarily polybutadiene, polyisoprene or butadiene-isoprene copolymer. 8. A fiber according to claim 6, wherein the end blocks of the triblock copolymer are primarily polystyrene. [Claim 9] Claim 1 wherein the nylon is nylon 6.
9. The fiber according to any one of items 1 to 8. 10. A fiber according to claim 1, which has a substantially circular cross-section before drawing. 11. A fiber according to claim 1, wherein the block copolymer contains on average from 2 to 16, preferably from 4 to 12, functional groups per polymer molecule. . 12. A fiber according to claim 1, wherein the block copolymer is functionalized by melt grafting maleic anhydride onto a hydrogenated block copolymer. 13. The fiber of claim 12, wherein the melt grafting is carried out in the presence of a free radical initiator. 14. Block copolymer versus nylon 2
The ratio of melt viscosity at 50°C is 1.5:1 to 1:1.
14. The fiber according to any one of claims 1 to 13, wherein the fiber is in the range of 5. 15. Plasticizing in an amount sufficient to reduce the ratio of the melt viscosity at 250° C. of the block copolymer to the melt viscosity at 250° C. of the nylon to within the range of 1:1.5 to 1.5:1. The fiber according to any one of claims 1 to 13, further comprising an agent. 16. A knitted or woven fabric comprising the fiber according to any one of claims 1 to 15. 17. Stockings or pantyhose made of the fiber according to any one of claims 1 to 15.