Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
  • D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
  • D01F8/10—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers with at least one other macromolecular compound obtained by reactions only involving carbon-to-carbon unsaturated bonds as constituent
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
  • D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
  • D01F8/12—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers with at least one polyamide as constituent

Definitions

• This invention relates to an elastomeric fibre and to a particular process to produce this elastomeric fibre.
• the bicomponent fibre therefore forms a helix upon relaxation with the yielded nylon half on the outside of the helix and the polyurethane on the inside.
• a fibre is disclosed in U.S. Patent No. 3,987,141.
• These fibres are relatively inexpensive to produce, can be made in very small diameters, and have excellent elongation properties.
• the commercialization of these fibres has resulted in the availability of relatively inexpensive pantyhose with a few sizes fitting most of the population with a level of support formally only available in support pantyhose, and yet a sheerness which is satisfactory to consumers.
• These fibres were only commercially available for a few years, however, due to marginal economics.
• Hydrogenated block copolymers of styrene and butadiene have been coextruded with nylon in unsuccessful attempts to produce fibres having elastomeric properties superior to those produced from polyurethane block copolymers.
• Block copolymers of styrene and butadiene are less expensive than the polyurethanes which are suitable for coextrusion. They also have a much narrower molecular weight distributions, and therefore have much better processability properties.
• Hydrogenated block copolymers of monovinyl aromatics and conjugated diolefins are also thermally stable to higher temperatures than polyurethanes.
• the invention provides a coextruded elastomeric fibre comprising:
• the block copolymer on which the fibres of the present invention are based must comprise at least two monovinyl aromatic blocks of a molecular weight high enough to form domains separate from the rubbery conjugated diolefin phase. These monovinyl aromatic domains have glass transition temperatures which exceed service temperatures of the polymer, and serve to tie together the rubbery conjugated diolefin polymer blocks. This results in a polymer having properties similar to vulcanized rubber, with high elongations before break, and high recovery from stress. Monovinyl aromatic blocks having number average molecular weights greater than 2000 will generally form separate domains, although lower molecular weights are possible when the monovinyl aromatic blocks contain polar functionality.
• These blocks may be copolymer blocks of more than one monovinyl aromatic, or copolymers with other polymerizable monomers, so long as the solubility parameters of the monovinyl aromatic blocks remain sufficiently varied from the solubility parameters of the conjugated diolefin blocks for separate domains to form.
• Other monomer units may therefore be included so long as the block predominantly comprises monovinyl aromatics. Predominantly, as it is used here is about 75 percent by weight.
• Vinyl aromatic hydrocarbons on which the monovinyl aromatic blocks may be based include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, alpha-methylstyrene, vinylnaphthalene, vinylanthracene and the like. Styrene is preferred due to its availability and relatively low cost. Polystyrene also has a reasonably high glass transition temperature and is least compatible with conjugated diolefin blocks.
• the conjugated diolefin blocks are preferably based on isoprene and/or butadiene and may thus comprise polyisoprene, polybutadiene or a butadiene-isoprene copolymer block.
• the conjugated diolefin blocks may also contain other monomer types, provided the solubility parameters remain sufficiently different from the solubility parameters of the monovinyl aromatic blocks.
• the conjugated diolefin blocks must be predominantly conjugated diolefin monomer units, and again, about 75 percent by weight is generally sufficient.
• the number average molecular weights of the conjugated diolefin blocks may vary in the range of from 20,000 to 150,000, and preferably from 30,000 to 75,000.
• Block copolymers having various structures may be utilized in the preparation of the fibres of the present invention, such as those having a linear or a radial structure, provided such polymers form monovinyl aromatic domains.
• the linear block copolymers at least some of the conjugated diolefin blocks should be anchored at each end to those monovinyl aromatic domains, while with the radial block copolymers the monovinyl aromatic blocks are preferably at the outer ends of the arms of the block copolymer.
• the monovinyl aromatic content of the block copolymer may vary in the range of from 10 to 45 percent by weight and preferably from 10 to 33 percent by weight. Lower contents result in insufficient monovinyl aromatic domain formation and higher contents result in a polymer which is hard and inelastic.
• a polar modifier may be utilized in the polymerization solution to alter the vinyl content of the resultant polybutadiene block.
• the block copolymer of the present invention may be utilized in an unhydrogenated form, but hydrogenation is preferred. Unhydrogenated block copolymers have limited extrusion temperatures and are susceptible to degradation by oxygen and light. A fibre made from an unhydrogenated block copolymer would therefore have a limited useful life.
• the hydrogenation is preferably a selective hydrogenation, with greater than 90 percent of the initial ethylenic unsaturation and less than 10 percent of the initial aromatic unsaturation being hydrogenated. More preferably, the hydrogenation will eliminate greater than 98 percent of the initial ethylenic unsaturation and less than 1 percent of the initial aromatic unsaturation.
• the aromatic unsaturation is preferably retained because the retention of aromatic unsaturation results in a greater glass transition temperature of the monovinyl aromatic domains and reduces hydrogen consumption.
• Hydrogenation may be accomplished by any known method.
• the methods disclosed in U.S. Patent No. 3,113,986 may be utilized.
• the acid or anhydride functionality may be incorporated into the block copolymer by any method known in the art. Because the purpose of the functionality is to cause adhesion to the polyamide, the functionality may be incorporated into either of the types of blocks, or into both types of blocks.
• One of the methods for the preparation of the functionalized selectively hydrogenated block copolymers comprises copolymerizing functional group containing monomers with the monovinyl aromatic or conjugated diolefin monomers, followed by hydrogenating the resultant polymer.
• the functional group must be one which does not effect the hydrogenation process, and can be converted to an acceptable acid or anhydride functional group after hydrogenation.
• Another and preferred method to incorporate functionality into the block copolymer comprises the melt grafting of an alpha-beta unsaturated carboxylic acid or anhydride onto the polymer in the presence or absence of a free radical initiator.
• the method, using a free radical initiator, is preferred because it can be carried out in an extruder with a minimal residence time.
• the preferred alpha-beta unsaturated carboxylic acid or anhydride is maleic anhydride.
• Carboxylic acid or anhydride functionality may also be incorporated into the block copolymer by reacting the block copolymer with a metal alkyl in an inert solvent, and then replacing the metal ion with an electrophile such as carbon dioxide, to form a lithium salt of carboxylic acid, which may then be acidified by contact with an organic acid.
• a metal alkyl in an inert solvent
• an electrophile such as carbon dioxide
• a method to incorporate sulphonic acid functionality into the block copolymers for use in this invention has been described in U.S. Patent No. 3,870,841, and comprises reacting the block copolymer with acyl sulphate (RCO2SO3H), which adds a sulphonic acid (-SO3H) group to the aromatic ring of the polymer, and releases the organic acid (RCO2H).
• RCO2SO3H acyl sulphate
• the block copolymers may also be functionalized by reacting the hydrogenated block copolymers with an azidosulphonylbenzoate.
• the number of functional groups present in each polymer molecule should be, on average, in the range of from 2 to 20, and more preferably on average from 2 to 16, and more preferably on average from 4 to 12. Less functionality results in insufficient adhesion between the polymer phases where as higher levels are not required for good adhesion and are detrimental to elastomeric properties.
• nylons or polyamides which may be incorporated in the fibres of the present invention include: polyhexamethylene adipamide (nylon 6-6), polypyrrolidone (nylon 4), polycaprolactam (nylon 6), polyheptolactam (nylon 7), polycapryllactam (nylon 8), polynonanolactam (nylon 9), polyundecanolactam (nylon 11), polydodecanolactam (nylon 12), polyhexamethylene azelaamide (nylon 6-9), polyhexamethylene sebacamide (nylon 6-10), polyhexamethylene isophthalamide (nylon 6-iP), polymethaxylylene adipamide (nylon MXD-6), polyamide of hexamethylenediamine and n-dodecanedioic acid (nylon 6-12), polyamide of dodecamethylenediamine and n-dodecanedioic acid (nylon 12-12) and Qiana (Q
• Nylon copolymers may also be used, for example, copolymers of the following: hexamethylene adipamide/caprolactam (nylon 6-6/6), hexamethylene adipamide/hexamethylene-isophthalamide (nylon 6-6 iP), hexamethylene adipamide/hexamethyleneterephthalamide (nylon 6-6/6T), hexamethylene adipamide/hexamethylene-azelaamide (nylon 6-6/6-9), hexamethylene adipamide/hexamethyleneazelaamide/caprolactam (nylon 6-6/6-9/6). Mixtures of different nylons may also be utilized.
• Preferred nylons include 6,6-6, 11 and 12.
• the polyamides which are employed in the compositions of the invention preferably have number average molecular weight (M n ) of at least 10,000 and more preferably have molecular weights (M n ) in the range of from 20,000 to 50,000.
• such polyamides preferably have amine equivalent contents of 0.1 milliequivalents per gram or less.
• the fibres of the present invention must contain a sufficient amount of block copolymer to result in excellent elasticity. They must contain a sufficient amount of nylon to impart a silk-like look to the fibre and impart good strength.
• the fibre comprises in the range of from 20 to 77 percent by weight of the fibre should be block copolymer. Preferably, from 25 to 75 percent by weight and more preferably, from 50 to 60 percent by weight of the fibre is block copolymer. Preferably, from 20 to 75 percent by weight of the fibre is nylon. More preferably, from 25 to 65 percent by weight of the fibre is nylon and most preferably, from 40 to 50 percent by weight of the fibre is nylon. Based on 100 parts by weight of block copolymer, the amount of nylon is in the range of from 30 to 300 parts by weight and preferably 100 parts by weight.
• the fibre of this invention is coextruded to form a filament by methods well known in the art. After being extruded and cooled to below the melting temperature of the block copolymer and nylon, the fibre is "drawn", or stretched to over two times its original length. Preferably, the fibre is drawn to between 3 and 5 times its original length. Upon relaxation, the fibre will take on a helix configuration.
• the polymeric components of the fibres are preferably in a side by side configuration although some wrap-around will not be detrimental to the final fibre product, particularly if it is the nylon which is enclosing a portion of the block copolymer.
• the fibres may be textured or crimped by any known methods although the fibre is usable without such further processing.
• the fibre of this invention may be co-extruded to an initial diameter of in the range of from 0.02 mm to 0.05 mm.
• This fine fibre can be knit into elastic pantyhoses or stockings, which are sheer and yet provide excellent support. Of course, greater diameter fibres can be produced to result in greater strength at the expense of sheerness.
• the fibres of this invention are preferably extruded with a round cross section, but other cross sections are known and usable. Shapes with broad surfaces reflect light better and appear to have more luster. Sharp crevices, such as star-shaped cross sections, tend to trap dirt and appear dirty easily and are therefore not preferred. The drawing and relaxation of the fibres will, of course, further alter the cross section of the fibres.
• the melt viscosity of the block copolymer may be adjusted by varying the styrene content, and the molecular weight of the block copolymer, or by adding plasticizers. Generally, relatively low molecular weight block copolymers are preferred in order to eliminate or minimize the need for plasticizers. Number average molecular weights in the range of from 30,000 to 185,000 are preferred, and number average molecular weights of 45,000 to 85,000 are more preferred because the melt viscosities of polymers having such molecular weights are closer to those of the common grades of nylons.
• the ratio of the melt viscosity of the block copolymer to that of the nylon at an acceptable extrusion temperature, for example 250 °C, should be in the range of from 3:1 to 1:3. More preferably, this ratio is in the range of from 1.5:1 to 1:1.5. Plasticizers may be utilized with either polymer to achieve a melt viscosity ratio in these ranges.
• Acceptable plasticisers must not be volatile at extrusion temperatures, and must not act as a release agent at the interface between the two polymer phases. Processing oils may act as release agents, and destroy the adhesion between the polymer phases. This happens when the oils vaporize in the die, and concentrate at the polymer interface. Processing oils with initial boiling points above the extruder die temperatures are therefore required. Preferably, when a processing oil is utilized, it has an initial boiling point of 230 °C or greater.
• the fibres may be dyed with dyes known to be useful with nylons, including acidic dyes.
• the acidic dyes will generally not dye any block copolymer surface which remains exposed, which is another advantage of the fibre of this invention. Because the undyed block copolymer is translucent, the product knit or weaved from the fibre appears even more sheer than an article made of a fibre which is all nylon.
• additives and treatments known to be useful for polymeric fibres may also be incorporated into the fibres of the present invention. These include delustering additives, pigments, dyes, antistatic additives, flame-retarding additives, brighteners, carbon black and fillers along with combinations of these.
• the fibre of the present invention may be knit or woven into fabrics.
• the fabrics are useful as men's or ladies' socks, stockings or pantyhose.
• the fibres have an excellent silk-like appearance which is typical of nylon fibres, but even greater elasticity than nylon wrapped spandex fibres.
• the block copolymers of the present invention are thermally stable at higher temperatures than polyurethanes which have previously been utilized in coextruded nylon fibres. Nylons such as nylon 6-6 could not be coextruded with polyurethanes due to the high melt temperature of nylon 6-6, whereas nylon 6-6 and the present block copolymers can be coextruded.
• the polyurethane component of prior art fibres is also more expensive than the block copolymer portion of the fibre of the present invention.
• the fibre of the present invention is therefore produced at a lower cost than the prior art coextruded fibres.
• the fibres of this invention demonstrate excellent "power”, hysteresis, fit-range, appearance, durability, fit and abrasion resistance.
• the block copolymer was a triblock of styrene and butadiene having a number average molecular weight of about 52,000 and 30% by weight styrene content.
• the end blocks were about equal molecular weight polystyrene blocks.
• the block copolymer was selectively hydrogenated, removing more than 99% of the initial ethylenic unsaturation and less than 5% of the initial aromatic unsaturation.
• the hydrogenated block copolymer had been extruder grafted with maleic anhydride in the presence of a peroxide free radical initiator and contained about 2% by weight of functionality as maleic anhydride.
• the fibre was prepared by coextrusion of the nylon and the oil-containing functionalized polymer in a 50/50 m/m ratio, through a 126 hole spinneret having 0.035 mm diameter round holes. The fibres were then cooled and put on a spool in a bundle of the 126 fibres. If the bundle was drawn, the individual fibres would not assume the helical configuration upon relaxation, but when individual fibres were separated from the bundle and drawn to about three times its length and relaxed, it assumed a tight helical configuration with excellent elastomeric properties.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Artificial Filaments (AREA)
• Socks And Pantyhose (AREA)
• Undergarments, Swaddling Clothes, Handkerchiefs Or Underwear Materials (AREA)
• Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)
• Multicomponent Fibers (AREA)

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Cited By (3)

Citations (2)

• 1991
  • 1991-06-12 EP EP19910201454 patent/EP0461726A3/en not_active Withdrawn
  • 1991-06-12 JP JP14020891A patent/JPH04228617A/ja active Pending

Patent Citations (2)

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