CA2067398A1 - Method for making bicomponent fibers - Google Patents
Method for making bicomponent fibersInfo
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- CA2067398A1 CA2067398A1 CA002067398A CA2067398A CA2067398A1 CA 2067398 A1 CA2067398 A1 CA 2067398A1 CA 002067398 A CA002067398 A CA 002067398A CA 2067398 A CA2067398 A CA 2067398A CA 2067398 A1 CA2067398 A1 CA 2067398A1
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- fiber
- fibers
- polymer
- linear ethylene
- bicomponent
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Abstract
A method is disclosed for making thermoplastic bicomponent fibers by contacting under thermally bonding conditions (a) a first component being at least one high performance thermoplastic polymer, such as PET, PBT, nylon or the like, and (b) a second component which is olefinic and which forms at least a portion of the fiber's surface characterized by (b) including at least one grafted linear ethylene polymer having pendant succinic acid or succinic anhydride groups; whereby the fiber is dyeable. The bicomponent fibers made by this process can be in a variety of shapes (e.g., round, oval, trilobal, flat, or hollow) and configurations (e.g., symmetrical sheath/core or side-by-side or asymmetrical crescent/moon). The succinic acid or succinic anhydride groups are provided by grafting, respectively, maleic acid or maleic anhydride onto the linear ethylene polymers especially by a process wherein the grafting is done in a twin-screw, co-rotating extruder with the maleic acid or maleic anhydride being injected into a pressured zone of the extruder. The acid containing grafted linear ethylene polymer or polymer blends are dyeable in contradistinction to ungrafted linear ethylene polymers.
Description
2 ~
W092/02669 PCr/US90/0~10 MÉTHOD FOR MA~ING ~lCOMPON~NT FI~ERS
The preser.t inver.ticn pertains tc ~yeabie thermoplastic bicomponent fibers ar,a a method of preparatior.. These bicomponent fibers are characterized by contacting under thermally bonding conditions (a) a first component comprising at least one high performance thermoplastic polymer. and (b) a second component comprising at least one grafted linear ethylene polymer having pendant succinic acid or succinic anhydride groups. The bicomponent fibers can be prepared by coextruding (a) and (b) lnto fiber having a round. oval.
trilobal. triangular. dog-boned. flat or hollow shape and a sheath/core or side-by-side configuratior.. ~he bicomponent fiber can be coextruded using me' blown.
spunbond or staple fiber manufacturing process conditions. The presen~ invention also pertains to a method of bonding high performance fibers using the dyeable thermoplastic bicomponent fibers of the present invention as binder fibers.
Various olefin fibers. i.e... fibers in which the fiber-forming substance is any long chain, synthetic polymer of at least 85 weight percent ethylene.
propylene, or other olefin units, are known from the prior art. The.mechanical properties of such fibers are W092/02669 2 0 6 7 ~ ~ ~ PCT/US90/0~10 generally related in large part to the morphology of the polymer. especially molecular orientation and crystallinity. Thus, crystalline polypropylene fibers and filaments are items of commerce and have been used in making products such as ropes ! non-woven fabrics. and woven fabrics. Polypropylene is known to exist as atactic (largely amorphous). syndiotactic (largely crystalline), and isotactic (also largely crys~alline).
The largely crystalline types o~ poiypropylene (PP).
including both isotactic and syndiotactic~ have found wide accep~ance in certain applications in tne ~or~i of fibers.
Othe~r types of polyolefins which have been suitably formed into fibers include linear ethylene polymers. such as linear high density polyethylene (HDPE) having a density in the range of 0.941-0.965 grams/cubic centimeter ~s!cc) and linear low density polyethylene (LLDPE) ha~ing a density typically in the range of low density polyethylene (LDPE) and linear medium density polyethylene (LMDPE). or from 0.91 g/cc to 0.94 g~cc. The densities of the linear ethylene polymers are measured in accordance "ith ASTM D-792 and defined as in ASTM D-1248. These polymers are prepared using coordination catalysts and are generally known as linear polymers because of the substantial absence of branched chains of polymerized monomer pendant from the main polymer backbone. LLDPE is a linear low density ethylene polymer wherein ethylene has been polymerized along with minor amounts of a,~-ethylenically unsaturated alkenes having from three to twelve carbon (C3-C12) atoms per alkene molecule, and more typically four to eight (C4-C8). Although LLDPE contains short chain branching due to the pendant side groups 2/02 2~3~
W09 669 PCTtUS90/0~10 introduced by the alkene comonomer and exhibits characteristics of low density polyethylene such as toughness and low modulus, it generally retains much of the strength, crystallinity. and extensibility normally found in HDPE homopolymers. In contrast, polyethylene prepared with the use of a free radical initiator, such as peroxide, gives rise to highly branched polyeJhylenes known as low density polyethylene (LDPE~ and sometimes as high pressure polyethylene (HPPE) and ICI-type polyethylenes. Because of unsuitable morphology.
notably long chain branching and concom -ant hi=:n me!~
elasticity, LDPE is difficuit to form into a fiber and has inferior properties as compared to LLDPE. HDPE and PP fibers.
One appiication of certain fibers such as. for example. polyvinyl chloride. low melting polyester and polyvinylacetate. has been the use of such fiberâ as binder fibers by blending the binder fiber with high performance natural and/or synthetic fibers such as polyesters (e.g.. polyethylene terephthalate (PET) or polybutylene terephthalate (PBT)). polvamides.
cellulosics (e.g.. cotton). modified cellùlosics (e.g..
rayon), wool or the like, and heatins the fibrous mixture to near the melting point of the binder fiber to thermally weld the binder fiber to the high performance fiber. This procedure has found particular application in non-woven fabrics prepared from performance fibers which would otherwise tend to separate easily in the fabric. However. because of the unavailability of reactive sites in the olefin fibers, the bonding of olefin fibers to the performance fibers is characterized by encapsulation of the performance fiber by the melted olefin fiber at the thermal bonding site by the 2~)~7~
W092l02669 PC~/US90/0~10 formation of microglobules or beads of the olefin fiber.
Moreover. it is difficult to achieve suitable thermal bonding in this fashion because of the poor wettability of a polar performance fiber by a nonpolar olefin fiber.
Another problem which has hampered the acceptance of olefin fibers is a lack of dyeability.
Olefin fibers are inherently difficult ~o dve. because there are no sites for the specific attraction of dye molecules, i.e.~ there are no hydrogen bonding or ionic groups, and dyeing can only take place by virtue of weak van der Waals forces. Usually. such fibers are colored by adding pigments to the polyolefin meit befor~
extrusion. and much effort has gone nt3 pigmentation technology for dispersing a dye into the polyolefin fiber. This has largeiy been unsuccessful because of - the poor lightfastness. poor fastness to dry cleaning.
generally low color bu id-up. stiffness, a necessitY for continuous production changes. poor color uniformity, possible loss of fiber strength and the involvement of large inventories.
Bicomponent fibers are tyDically fabricated commercially by melt spinning. In th s procedure, each molten polymer is extruded through a die. e.g., a spinnerette, with subsequent drawing of the molten extrudate, solid-fication of the extrudate by heat transfer to a surrounding fluid medium. and taking up of the solid extrudate. Melt spinning may also include 3 cold drawing, heat treating, texturizing and/or cutting.
~ An important aspect of melt spinning is the orientation ; of the polymer molecules by drawing the polymer in the molten state as it leaves the spinnerette. In accordance with standard terminology of the fiber and .
W092/02669 PCT/US90/0~1 filament industry, the following definitions apply to the terms used herein:
A "monofilament" (also known as "monofil") refers to an individual strand of der.ier greate~ than 1~, usually greater than 30:
A "fine denier fiber or "filament" refers to a strand of denier less than 15:
A "multi-filament" (or "multifil") refers to simultaneously formed fine denier filaments spun in 2 bundle of fibers, generally containir.g a~ le~st 3.
preferably at least 15-lO0 fibers and can be se~/eral hundred or several thousand:
An "extruded strand" refers to an extrudate formed by passing polyme~ through a forming-orific2.
such as a die:
A "bicomponent fiber" refers to a fiber comprising two polymer componencs. each in a continuous phase. e.g. side-by-side or sheath/core:
A "bicomponent staple fi~er" refers to a fine 2~ denier strand which have been formed at. or cu~ to.
staple lengths of generally one to eight inches (2.7 to 20 cm).
The shapes of these bicomponent fibers.
extruded strands and bicomponent staple fibers can be any which is convenient to the producer for the intended end use, e.g.~ round, trilobal, triangular. dog-boned, flat or hollow. The configuration of these bicomponent fibers or bicomponent stapie fibers can be symmetric (e.g., sheath/core or side-by-side) or they can be ~7 ~
W092/02669 PCT/US90/0~10 asymmetric (e.g.. a crescent/moon con~iguration within a fiber h~aving an overall round shape).
Convenient references relating to fibers and filaments, including those of man made thermoplastics, and incorporated herein by reference, are, for example:
(a) Encvclopedla of Polvme~ Science and Technolo~. Interscience. New York. vol. 6 (1967) . pp.
505-555 and vol. 9 (1968), pp. 403-440:
10 .
(b) Kirk-Othmer Enc-Jclopedia of Chemical Technolo~v. vol. 16 for "Olefin Fibers". John Wiley and Sons, New York. 1981. 3rd edition;
~5 (c) Man Made and Fiber and Textile Dictionarv.
Celanese Corporation:
(d) Fundamentals of Fibre Formation--The Science of Fibre Spinning and Drawing. Adrezi, Ziabicki.
John Wiley and Sons. London~New York. 1976;
(e) Man Made Fibres. by R. W. Moncrieff.
John Wiley and Sons. London/New York, 1975.
Other references relevant to this disclosure 2~ include U.S. Patent No. 4.644.045 which describes spun bonded non-woven webs of LLDPE having a critical combination of percent crystallinity, cone die melt flow, die swell, relation of die swell to melt index, ~ .30 and polymer unifor~ity: European Patent Application No.
-~87304728.6 which describes a non-woven fabric formed of heat bonded bicomponent filaments having a sheath of LLDPE and a core of polyethylene terephthalate.
In CA 91 :22388p (1979) there is described a fiber comprising polypropylene and ethylene-maleic W092/02669 ~r~ PcT/US90/O44lO
anhydride graft copolymer spun at a 50:50 ratio and drawn 300 percent at 100~C. and a blend of the drawn fibers and rayon at a 40:60 weight ratio carded and heated at 145C to give a bulky non-woven fabric.
However, polypropylene is disadvantageous in some applications because of its relatively high melting point (145CC). and because of the relatively poor hand or feel imparted to fabrics made thereof. Poor hand is manifested in a relati~ely rough and inflexible fabric, as opposed to a smooth and flexible fabric.
U.S. Patent No. 4.684,576 describes the use of ~lends of HDPE grafted with maleic acid or maleic anhydride to give rise to succinic acid or succinic 5 anhydride groups along the polymer chain with other olefin polymers as an adhesive, for example~ in extrusion coating of art~cles. as adhesive layers in - films and packaging, as hot mel~ coatings. as wire and cable interlayers, and in other similar applications.
20 Similar references describing adhesive blends containing HDPE grafted with unsaturated carboxyiic acids, primarily for laminate structures. include U.S. Patent Nos. 4.460.632; 4.394.485: and 4,230,830 and U.K. Patent Application Nos . 2.081,723 and 2.113,696.
A method has now been discovered for making thermoplastic bicomponent fibers by contacting under thermally bonding conditions (a) a first component being at least one high performance thermoplastic polymer, and 3 (b) a second component which is olefinic and which forms at least a portion of the fiber's surface characterized by (b) including at least one grafted linear ethylene polymer having pendant succinic acid or succinic anhydride groups; whereby the fiber is dyeable. These novel dyeable thermoplastic bicomponent fibers have ':~
, .
,' .
W092/02669 2 ~ ~ 7 ~ PCT/USgo/o~lo ' superior hand, a relatively low melting or bonding temperature~ superior adhesive properties. superior dyeability and superior adhesion of the components within the bicomponent fiber. The bicomponent fiber can be prepared by coextruding (a) and (b) into a fiber having a symmetrical or asymmetrical sheath/core or side-by-side configuration and a round. oval. trilobal.
triangular, dog-boned~ flat or hollow shape. Component (a) can be a polvester (such as polyethylene terephthalate or polybutylene terephthalate) or a pol-iamide (such âS rylon). Componen' (b) can be a polymer blend of a grafted linear ethyler.e ?olymer having pendant succinic acid or succinic anhydride groups and at least one ungrafted linear ethylene polymer. The bicomponent fiber can be formed under melt blown. spunbond or staple manufacturing process conditions.
In a further aspect of the invention, there is provided a method of bonding high performance natural and/or synthetic fibers such as polyester (e.g.. PET or PB,), polyamides (e.g.. nylon). cellulosics (e.g..
cotton). modified cellulosics (e.g.. rayon). wool or the like. by blending dyeable thermoplastic bicomponent fibers of the present invention used as binder fibers with the high performance fibers and heating the fibrous mixture to thermally weld the binder fiber to the high performance fibers.
Tn still another aspect. the invention provides a fabric comprising dyeable thermoplastic bicomponent fibers.
In still another aspect, the invention provides a :abric comprising dyeable thermoplastic bicomponent .
- . .
.
, 2 ~ '3 i W092/02669 PCT/US90/0~10 _g_ fibers as binder fiber blended with performance fibers.
wherein the bicomponent binder ~ibers are bonded to the performance fibers.
In a still further aspect of the invention.
there is provided an adhesive polymer blend for use as a component in making the dyeable thermoplastic bicomponent fibers. The polymer blend comprises (a) at least one grafted linear ethylene polymer having pendant succinic acid or succinic anhydride groups and (b) at least one ungrafted linear ethylene polymer.
In yet another aspect. there s provided a dyeable thermoplastic bicomponent fiber characterized b~
(a) a first component comprising at leas~ one high performance thermoplastic polymer. and (b) a second component comprising at leas~ one grafted linear ethylene polymer having pendant succinic acid or succinic anhydride groups which have been contacted under thermally bonding conditions.
The linear ethylene polvmers used for grafting can be linear HDPE and/or LLDPE. The density of linear HDPE before grafting can be about O.g4 to 0.97 g/cc. but is typically between about 0.945 and 0.965 g/cc. while that of LLDPE before grafting can be about 0.88 to 0.94 g/cc, but is typically between about 0.91 and 0.94 g/cc. Typically, linear HDPE and LLDPE will have about the same density before and after grafting. but this can vary depending on the particular linear ethylene polymer properties, graft level, grafting cond~itions and the i- like. The linear ethylene polymer before grafting has a melt index (MI) measured at 190~C/2.16 kg from about 0.1 to about 1000 grams/10 minutes, but typically less after grafting. For example, linear HDPE with a 25 MI and a .
., , ~ . . . .
W092/02669 2 ~ ~ ~ 3 ~ ~ PCT/US90/0~10 -0.955 g/cc density grafted to a level of about 1 weight percent maleic anhydride (MAH) has a MI after grafting of about 16-18 grams/10 minutes. Melt index herein is measured in accordance with ASTM D1238 condition 190C/2.16 kg (also known as condition "E"). The MI of the ungrafted linear ethylene polymer used for grafting is selected depending on the specific melt spinning procedure employed and whether or not the grafted linear ethylene polymer is employed alone or in a blend with another linear ethylene polymer.
The grafting of succinie acid or succinic anhydride groups may be done by methods described in the art which ~enerally involve reac~ing malei^ acid cr maleic anhydride in admixture with heated polymer.
generally using a peroxide or free radical initiator to accelerate the graftlng. The maleic acid and maieic anhydride compounds are known in these relevant arts as having their olefin unsaturation sites conjugated to the acid groups. Fumaric acid. an isomer of maleic acid which is also conjugated. gives off water and rearranges to form maleic anhydride when heated. and thus is operable in the present invention. Grafting may be effected in the presence of oxygen, air hydroperoxides.
or other free radical initiators. or i,n the essential absence of these materials when the mixture of monomer and polymer is maintained under high shear and heat conditions. A convenient method for producing the graft polymer is extrusion machinery, although Brabender mixers or Banbury mixers. roll mills and the like may also be used for forming the graft polymer. It is preferred to employ a twin-screw devolatilizing extruder (such as a Werner-Pfleiderer twin-screw extruder) wherein maleic acid or maleic anhydride is mixed and ~ o ~
W092/02669 PCT/US90/0~10 reacted with the linear ethylene polymer(s) at molten temperatures to produce and extrude the grafted polymer.
The anhydride or acid groups of the grafted polymer generally comprise from about 0.001 to about 10 wei~ht percent, preferably from about 0.01 to about 5 weight percent. and especiaily from 0.1 to about 1 weight percent of the grafted polymer. The grafted polymer is characterized by the presence of pendant succinic acid or anhydride groups along the polymer 0 chain. as opposed to the carboxylic acid groups obtained by the bulk copolymerization of ethvlene ~ith an ethylenically unsaturated carboxylic acid such as acrylic acid as disclosed in Furopean ~atent Application number 88116222.6 (EP Publication number 0 311 860 A2).
Grafted linear HDPE is the preferred grafted linear ethylene polymer.
The grafted linear ethylene polymer(s) can be - 20 employed singly or as a component in a polymer blend with other linear ethylene polymers. The polymer blend preferably contains from abou~ 0.5 to about 99.~ weight percent of the grafted linear ethylene polymer. more preferably from about 1 to 50 weight percent grafted linear ethylene polymer~ and especially from about 2 to 15 weight percent grafted linear ethylene polymer. The polymer blend may also include conventional additives, such as dyes, pigments, antioxidants, UV stabilizers, spin finishes, and the like and/or relatively minor 3 proportions of other fiber forming polymers which do not significantly alter the melting properties of the blend ; or the improved hand obtained~in fabrics containing fibers employing LLDPE as a polymer blend component.
- WO 92/02669 2 ~ S 7 ~ f ~ PCT/US90/0~10 The LLDPE employed either as the grafted linear ethylen~e polymer component or as the ungrafted component in the dyeable thermoplastic bicomponent fiber, comprises at least a minor amount of a C3-C 2 olefinically unsaturated alkene, preferably a C4-C8 olefinically unsaturated alkene. and 1-octene is especially preferred. The alkene may constitute from about 0.5 to about 35 percent by weight of the L~DPE, preferably from about l to about 20 weight percent. and most preferably from about 2 to about 15 weight percent.
The grafted linear ethylene polymer (e.g., grafted linear HDPE) and the ungrafted linear ethylene polymer (such as ungrafted LLDPE) may be blended together prior to extrusion, either by melt blending or dry blending. Dry blending of pellets of the grafted linear ethylene polvmer and the ungrafted linear ethylene polymer prior to extrusion is generally adequate where the melt indices of the blend components are similar. and there will generally be no advantage in melt blending such blend constituents prior to extrusion. However. where melt blending may be desired, as in the case of grafted linear HDPE and LLDPE or dissimilar melt indices, melt blending may be accomplished with conventional blending equipment, such as, for example. mixing extruders, Brabender mixers, Banbury mixers, roll mills and the like.
The high performance thermoplastic polymer useful as such as the second component of the dyeable thermoplastic bicomponent fiber of the present invention can be a polyester (e.g., PET or PBT) or a polyamide (e.g., nylon). The high performance thermoplastic polymer can be used as one component of the bicomponent fiber by contacting it with the grafted linear ethylene W092/02669 2 V ~ 7 ~ ~ ~ PCT/US90/0~10 polymer(s) under thermally bonding conditions. such as that encountered when coextruding bicomponent fiber using a bicomponent staple fiber die. The high performance polymer can either component of a sheath/core configuration or it can be either component of a side-by-side configuration. The high performanc thermoplastic polymer can be chosen to provide stiffness in the bicomponent fiber, especially when the grafted linear ethylene polvmer is a polymer blenà of grafted linear HDPE blended with ungrafted LLDP~. Additionallv.
the high performance thermopiastic polymer used in making the bicomponent fiber cf the present invention can be the same polymer as that used for making high performance fiber which is blended with the bicomponent fiber.
Extrusion of the poiymer through a die to form a fiber is effected using con~entiona' eauipment such as. for example. extruders. gear pumps and the like. It 2C is preferred to employ separate extruders. which feed gear pumcs to supplv the separate molten polymer streams to the die. The grafted linear ethylena polvmer or polymer blend is preferablv mixed in a mixing zone of the extruder and/or in a statlc mixer. for example.
upstream of the gezr pump in order to obtain a more ; uniform dispersion of the polymer components.
- Following extrusion through the die. the fiber is taken up in solid form on a godet or another take-up 3 surface. In a bicomponent staple fiber forming process.
the fibers are taken up on a godet which draws down the fibers in proportion to ~he speed of the tak,e-up godet.
In the spunbond process. the fibers are collected in a jet, such as, for example. an air gun, and blown onto a take-up surface such as a roller or moving belt. In the .
~a~
WOg2/02669 PCT/US90/04410 melt blown process, air is ejected at the surface of the spinnerette which serves to simultaneously draw down and cool the fibers as they are deposited on a take-up surface in the path of the cooling air. Regardless of the type of melt spinning procedure which is used, it is important that the fibers be partially melt drawn in a molten state, i.e. before solidification occurs. At least some drawdown is necessary in order to orient the polymer ~olecules ~^or good tenacity. It is not generally sufficient to sGlidify the fibers withou~
significant extension before take-u?. as ~;~^ fine strands which are forme~ tnereby can hardly be colc drawn. i.e. in a solid state below the melting temFerature of the polvmer. because of the:r low tenacity. On the other hand~ when the fibers are draws down in the molten state. the resulting strands can mone ; readily be cold drawn because of the im?roved tenzcity imparted by the melt drawing.
Melt drawdowns of up to about 1:1000 mav be employed depending upon spinnerette die diameten and spinning velocity. preferably from about 1:10 ~o about 1:200, and especially 1:20 to 1:10G.
Where the bicomponent staple-forming process is employed. it may be desirable to cold draw the strands with conventional drawing equipment. such as. for example. sequential godets operating at differential speeds. The strands may also be heat treated or 3 annealed by employing 5 heated godet. The strands may further be texturized, such as. for example. by crimping and cutting the strand or strands to form staple. In the spun bonded or air jet processes, cold drawing of the solidified strands and texturizing is effected in the air~jet and by impact on the take-up surface, 2~ ~3v~
W092/02669 PCT/US9~/0~10 respectively. Similar texturizing is effected in the melt blown process by the cooling fluid whicn is in shear with the molten polymer strands. and which may also randomly delinearize the fibers ?rior to their solidification.
The bicomponent fibers so formed by the above-described process also constitute a part of the present invention. The bicomponent fibers are generally fine denier filaments of 15 denier or less down to fractional deniers. preferabiy in the range of rom l to 10 denier.
although this will depend on the desired properties of the fibers and the specific application in which they are to be used.
The bicomponent fibers of tne present invention have a wide variety of potential applications. ~or example. the bicomponent fibers may be formed into a batt and heat treated by calendaring on a heated.
embossed roller to form a fabric. The batts may also be heat bonded-, for example. by infrared light, ultrasound or the like, to obtain a high loft fabric. The fibers may also be empioyed in conventional textile processing such as carding. sizing. weaving and the like. Woven fabrics made from the bicomponent fibers of the present invention may also be heat treated to alter the properties of the resulting fabric.
A preferred embodiment of the invention resides in the employment of the bicomponent fibers formed according to the process of the invention in binder fiber applications with high performance natural and~or synthetic fibers such as, for example, polyamides~
polyesters, silk, cellulosics (e.g. cotton), wool.
modified cellulosics such as rayon and rayon acetate.
W092~02669 2 0 5 ~ 3 ~ 3 PCT/US90/0~10 ' and the like. The bicomponent fibers of the present invention find particular advantage as binder fibers owing to their adhesion to performance fibers and dyeability thereof which is enhanced by the presence of the acid groups in the grafted linear ethylene polymer component and the relatively lower melting temperature or range of the grafted iinear ethylene polymer component relative to the performance fiber. The relative proportions of tne binder fiDer of the present invention employed in admixture with performance fibers in a fiber blend wi;l depend on the desired application and capabilities of the resulting fiber mixture and/or fabric obtained thereby. It is preferred to employ from about ~ to about g~ parts by weight of the binder fiber per 100 parts by weight of the binder fiber/performance fiber mixture, more preferably from about 5 to about 53 parts by weight binder fiber. and especia~ly 5 to 1 parts by weight binder fiber.
j 20 In preparing non-woven fabrics from the bicomponent binder fiber/performance fiber blend of the invention, there are several important considera~ions.
Wheré the binder fibers are in staple form~ there should be no fusing of the fibers when they are cut into staple, and the crimp imparted to the binder fibers should be sufficient for blending with the performance fibers to obtain good distribution of the fibers.
The ability of the component comprising at 3 least one grafted linear ethylene polymer having pendant succinic acid or anhydride groups to adhere to the other component of at least one high performance thermoplastic polymer is an important consideration in cutting of bicomponent staple fiber. When bicomponent staple fiber is cut and one of the components (e.g., the core of a ' ' ` ''' 2~7~
~'092/02669 PCT/US90/04410 bicomponent .'iber) protrudes from t;ne cuv e~ge~ the .lber will creare ar. irrita~ion when worrl ne~ ~o the skin. ThC irr.taticn is especially pronounced .Jnen the ^ore compor.ent is a :qioh performanc- thermopias~,~c such 2S PE.. 'when ungr~fted linear -thylene ?olymer and PET
are made. respectiveiv, into 3 sheath/core bicomponent f.Der and cu~ into shor- sta?le fibcr. the core Gi' PET
2rctrrudes beyond the cu. edge. lhe er,nanced a~ir.es;on G' t.qe graf~Qr 1 near e,.qyiQne ?oi~Jmer componen ~o ~he .-E.
c~mponer.~ _aed in makin the dyeaDle ther.rnop'las'lc , ~, _~comron-n~ ^ b-r o^ -'h- ?r-,en- inve-l or. rcr~c_a ?EI
pro~rusio-. D-~/on~ _in, fiDer' _fter cuttin, -r.d r,hus -naDle, fabr~cs and 'i3er b'ends ,- ~e ~arQ ~.;h~C.^ can be mor- comfort2bly wor.-. next to th_ s'r~in.
,, ~ he abl L_'y ^f ~r~e bicomponer.' bindc- bers ~c~
ad'r.erQ -o tr.- ?er,ormance iibers is anG~ncr im?cntant cor.sider tion. Acr.esio.-. and ~yea~-`i r- c7n 3cn r~i~ y controllec b-; varyiqO ~.^- acid CorltQr.t o- tne binscr 2~ .iber. e;.~her b. tne 'evel o.' gra.~ o. m-lelc -cid or anhydrid_ in the gra ~-- linear _ :n~,~lene polymer. or b~-tne prGpcr ior. o'` th- -r~fted _in-_r e'r.vien~ -.o'.ymer ~iende~ .!i'r. thQ ur.gr-:'~,ed lincar e~h~yierl_ ?oivmer i,.
~.he bico...-o:le-it 5indQ: i' Ders. r. .,ypic^l non-:~ovcn 2~ fabrlcs ob ain_d bf tr.erma"-J bond ng tr.- perforl,.ancc :irers wi'h a bicomponerlt binaer f~'ber. the abilit~y ~f 'he binder fibers to 5Ond to-,ether tne ?erformance ibers de?ends large'y on the thermal bon-lng o the ?erfor~ance ~ibers ~oge her r~y ~he ~incer fibera. In tJpica_ pri^r ar~ r.on.-.~oven faDrlcs ei,.ploying binder fibers. tr.- 5inder fiDer therca'ly Doncs performlance fibers to~ether bj a, ieas~ ?ar r ia L iy me!ting ~o form globules cr beads which encapsulate ~he ?erformance fibers. Thne binder fibers of the present inven~ion 20~7~
enhance the non-woven fabric by providing great adhesion of the binder fiber to the performance fiber. Employing the binder fibers of the present invention. it is also possible to obtain thermal bonding of the binder fiber to a performance fiber by partial melting and contact - 5 adhesion in which the bicomponent binder fibers largely retain their fibrous form. and the resulting non-woverl fabric is characterized 5y a reduced number of Olobules or beads formed by the meiting of the iower melting component of the bicomponent binder fibers.
-t is also importan~ for one componen~ OA th~
bicomponent binder fiber to have a relatively broad melting point range or tnhermai Donding window.
particularly where hot calendaring is employed to obtain a thermal bonding of a non-woven or woven fabric. A
good indication of meltina point range or thermai bonding window is the dlfference between th- Vicat softening point and the peak melting point determined by dlfferential scanning calorime~ry (DSC). Narrow melting point ranges present a difficu ~ target for process bonding equipment such as a calendar roll. and even slight variations in the temperature of bonding equipment can result in an insufficient bond to be formed betwee.n the bicomponent binder fibers ar.d the performance fibers. If too low a temperature is : ~ .
employed, the bicomponent binder-fibers will not ~sufficiently fuse. whereas when too high a temperature is employed, one component of the bicomponent binder fiber may completely melt and run right out of the performance fiber batt. Thus. a broad melting point range is desired in order that partial fusion of on-component of the bicomponent binder fiber materia1 car.
be achieved without a complete melting. A melting point .
:
' ~ W092/02669 ~ ~ 7 3 ~ g PCT/US90/04410 _ 1 9--range of at least 7.5C is desired for proper thermal bonding. and preferably a sufficiently broad melting point range that a minimum 10C bonding window is obtained.
Another important characteristic of bicomponent binder fibers is that when they are melted in equipment-such as a calendar roll, one of the components will have a sufficient melt viscosity to be retained in the fiber matrix and not readily flow therefrom. An important advantage of the bicomponent binder fibers of the preser.t invention is tha one component has generally higher me:t viscosity than fibers consisting of ungrafted LLDPE and/or ungrafted iinear HDPE. In addition to using a calendar roll. bonding of the present binder fibers can also be obtained using other bonding techniques. e.g. with hot air. infrared heaters.
ard the like.
2~ The thermoplastic bicomponent fibers of the invention can be dyed by contacting them with a water soluble ionic dye. preferably a water soluble cationic dye. in a suitable aqueous medlu~.. The aqueous medium can contain surfactants, i; desired. to promote contact.
The invention is illustrated by way of, but not limited to, the examples which follow.
3 A linear HDPE ethylene~propylene copolymer (the "base" polymer), having a MI of about 25 grams/10 minutes and density of O.g55 g~cc. is extruded with maleic anhydride (3.0 pounds per hour) and dicumyl peroxide (0.3 pounds per hour) at an average melt temperature of 225C (the temperature ranged from about 2~73~
w0~2/02669 PCT/US90/04410 180 to about 250C) using a Werner-Pfleiderer twin-screw devolatization extruder. The final incorporated concentration of maleic anhydride is about 110 by weight (as determined by titration) and has a MI of about - 16-18 grams/10 minutes: this is called the MAH-grafted linear HDPE concentrate.
Using a 6-inch Farrell two-roll mill. 250 gram sampies are blended ha~ing compositions ranging from ,%
MAH-grafted linear HDPE concentrate to 50~ MAH-grafted linear HDPE concentrate in v2rious LLDPE resins 2t a me't temperature of 170~ he ~lends are useful 2S 2' least one component in 2 bicomponent fiber, wherein at least one other component is a perîormance poiymer component. such as PBT or PET.
ExamDle 2 Ten percent of a grafted linear HDPE
(ethylene/propylene copolymer. MI of 2~ grams,'10 mlnutes before grafting. densitv of 0.955 g/cc before grafting) having about 1% bv weight succinic acid groups is biended with about 9C,~ by weight of an ungrafted LLDPE
(ethyleneioctene copolymer. MI of 18 grams/10 minutes.
0.930 g/cc density) to form a polymer blend having about 0.1~ by weight succinic acid groups. The polvmer blend is then used as a sheath component in a bicomponent staple fiber spinning operation. with the core component being PET. The sheath/core bicomponent fibers are blended with other performance fibers such as PET or 3 cellulosics, formed into batts and oven bonded. The batts are found to be weIi-bonded and have good physical integrity.
2~5i73~
Example 3 Linear HDPE (ethylene-propylene copolymer. MI
of 25 grams/10 minutes, 0.95~ gicc density) is grafted with maleic acid to provide succinic acid groups along the polymer chain. Portions of the grafted linear HDPE
are then blended with amounts of ungrafted LLDP~
(ethylene-octene copolvmer. MI of 18 grams,'10 minutes.
0.930 g/cc density) to produ^_ polymer blends containlng o.o5aO. 0.1~. 0.157c. 0.2~. and 0.4% by weight of the succinic acid. The grafted linear HDPEi'LLDPE polymer bler.d samples are coextrud-a .with PE t~ ?roduce sid--by-side bicomponent fibrous materia'. The adhesion between fibers in a heat-Donded bat of the fibrous material is appreciably better than that obtained in comparison by using the same linear HDPE and LLDPE
without any grafted acid groups. The maximum heat-bonded bat strength occurs when usinO bi~omponent fiber having a succinic acid level of about 0.1~ by weigh~.
ExamDle 4 Linear HDPE (eth~lene-p.opylene copol~mer. Ml of 25 grams/10 minutes. C.?,-,i g~cc densitv) is grafted wlth male-c anhvdride ~o ?ro~.~d^ abou~ l~s DV weigh' succinic anhydride groups aiong ths polymer chain.
Portions of the grafted linear HDP' are blended with amounts of ungrafted LLDPE (e~hylene-octene copolymer.
MI of 18 grams/10 minutes. 0.930 gicc density) to produce polymer blends containing 0.05~. 0.1~. 0.15~.
0.2%~ and 0.5% by weight of the succinic acid groups.
Polym~r blends of the grafted linear HDPE with the ungrafted LLDPE can be coextruded as the sheath layer in a bicomponer.t spunbond system using a PET as the cor-layer. The resultant thermally bonded fabric has a bonded fabric strength higher than that obtained using W092/02669 RCT/US90/n4410 -~2-ungrafted linear ethylene polymer alone as the sheath resin.
Example 5 LLDPE (ethylene-octene copolymer. MI of 18 grams/lO minutes. O.93O g/cc density) does not accept dye when treated with Basic Viole~ III (a basic dye also known as Crystal ~ioiet~ at 80C for 15 minutes in the presence of a dro? of didec~vi dimethyl ammonium chloriae used as a wetting agen'. When blended wlth enough LLDPE
gra~ted w.tn maleic anhydride to providc a r,olvmer blend having about 0.157O Dy weight succinic acid groups. the resulting polymer blend. when treated in the same manner as immediately above. became dyed to a biue,purpie color. The dye does not readily leach out. even when placed in boiling water for 10-15 minutes. Other water soluble cationic dyes (i.e.. dyes which ane typically referred to as "basic dyes" in the :ndustry` can be similarly used to dye the novel bicomponent fibers.
3o
W092/02669 PCr/US90/0~10 MÉTHOD FOR MA~ING ~lCOMPON~NT FI~ERS
The preser.t inver.ticn pertains tc ~yeabie thermoplastic bicomponent fibers ar,a a method of preparatior.. These bicomponent fibers are characterized by contacting under thermally bonding conditions (a) a first component comprising at least one high performance thermoplastic polymer. and (b) a second component comprising at least one grafted linear ethylene polymer having pendant succinic acid or succinic anhydride groups. The bicomponent fibers can be prepared by coextruding (a) and (b) lnto fiber having a round. oval.
trilobal. triangular. dog-boned. flat or hollow shape and a sheath/core or side-by-side configuratior.. ~he bicomponent fiber can be coextruded using me' blown.
spunbond or staple fiber manufacturing process conditions. The presen~ invention also pertains to a method of bonding high performance fibers using the dyeable thermoplastic bicomponent fibers of the present invention as binder fibers.
Various olefin fibers. i.e... fibers in which the fiber-forming substance is any long chain, synthetic polymer of at least 85 weight percent ethylene.
propylene, or other olefin units, are known from the prior art. The.mechanical properties of such fibers are W092/02669 2 0 6 7 ~ ~ ~ PCT/US90/0~10 generally related in large part to the morphology of the polymer. especially molecular orientation and crystallinity. Thus, crystalline polypropylene fibers and filaments are items of commerce and have been used in making products such as ropes ! non-woven fabrics. and woven fabrics. Polypropylene is known to exist as atactic (largely amorphous). syndiotactic (largely crystalline), and isotactic (also largely crys~alline).
The largely crystalline types o~ poiypropylene (PP).
including both isotactic and syndiotactic~ have found wide accep~ance in certain applications in tne ~or~i of fibers.
Othe~r types of polyolefins which have been suitably formed into fibers include linear ethylene polymers. such as linear high density polyethylene (HDPE) having a density in the range of 0.941-0.965 grams/cubic centimeter ~s!cc) and linear low density polyethylene (LLDPE) ha~ing a density typically in the range of low density polyethylene (LDPE) and linear medium density polyethylene (LMDPE). or from 0.91 g/cc to 0.94 g~cc. The densities of the linear ethylene polymers are measured in accordance "ith ASTM D-792 and defined as in ASTM D-1248. These polymers are prepared using coordination catalysts and are generally known as linear polymers because of the substantial absence of branched chains of polymerized monomer pendant from the main polymer backbone. LLDPE is a linear low density ethylene polymer wherein ethylene has been polymerized along with minor amounts of a,~-ethylenically unsaturated alkenes having from three to twelve carbon (C3-C12) atoms per alkene molecule, and more typically four to eight (C4-C8). Although LLDPE contains short chain branching due to the pendant side groups 2/02 2~3~
W09 669 PCTtUS90/0~10 introduced by the alkene comonomer and exhibits characteristics of low density polyethylene such as toughness and low modulus, it generally retains much of the strength, crystallinity. and extensibility normally found in HDPE homopolymers. In contrast, polyethylene prepared with the use of a free radical initiator, such as peroxide, gives rise to highly branched polyeJhylenes known as low density polyethylene (LDPE~ and sometimes as high pressure polyethylene (HPPE) and ICI-type polyethylenes. Because of unsuitable morphology.
notably long chain branching and concom -ant hi=:n me!~
elasticity, LDPE is difficuit to form into a fiber and has inferior properties as compared to LLDPE. HDPE and PP fibers.
One appiication of certain fibers such as. for example. polyvinyl chloride. low melting polyester and polyvinylacetate. has been the use of such fiberâ as binder fibers by blending the binder fiber with high performance natural and/or synthetic fibers such as polyesters (e.g.. polyethylene terephthalate (PET) or polybutylene terephthalate (PBT)). polvamides.
cellulosics (e.g.. cotton). modified cellùlosics (e.g..
rayon), wool or the like, and heatins the fibrous mixture to near the melting point of the binder fiber to thermally weld the binder fiber to the high performance fiber. This procedure has found particular application in non-woven fabrics prepared from performance fibers which would otherwise tend to separate easily in the fabric. However. because of the unavailability of reactive sites in the olefin fibers, the bonding of olefin fibers to the performance fibers is characterized by encapsulation of the performance fiber by the melted olefin fiber at the thermal bonding site by the 2~)~7~
W092l02669 PC~/US90/0~10 formation of microglobules or beads of the olefin fiber.
Moreover. it is difficult to achieve suitable thermal bonding in this fashion because of the poor wettability of a polar performance fiber by a nonpolar olefin fiber.
Another problem which has hampered the acceptance of olefin fibers is a lack of dyeability.
Olefin fibers are inherently difficult ~o dve. because there are no sites for the specific attraction of dye molecules, i.e.~ there are no hydrogen bonding or ionic groups, and dyeing can only take place by virtue of weak van der Waals forces. Usually. such fibers are colored by adding pigments to the polyolefin meit befor~
extrusion. and much effort has gone nt3 pigmentation technology for dispersing a dye into the polyolefin fiber. This has largeiy been unsuccessful because of - the poor lightfastness. poor fastness to dry cleaning.
generally low color bu id-up. stiffness, a necessitY for continuous production changes. poor color uniformity, possible loss of fiber strength and the involvement of large inventories.
Bicomponent fibers are tyDically fabricated commercially by melt spinning. In th s procedure, each molten polymer is extruded through a die. e.g., a spinnerette, with subsequent drawing of the molten extrudate, solid-fication of the extrudate by heat transfer to a surrounding fluid medium. and taking up of the solid extrudate. Melt spinning may also include 3 cold drawing, heat treating, texturizing and/or cutting.
~ An important aspect of melt spinning is the orientation ; of the polymer molecules by drawing the polymer in the molten state as it leaves the spinnerette. In accordance with standard terminology of the fiber and .
W092/02669 PCT/US90/0~1 filament industry, the following definitions apply to the terms used herein:
A "monofilament" (also known as "monofil") refers to an individual strand of der.ier greate~ than 1~, usually greater than 30:
A "fine denier fiber or "filament" refers to a strand of denier less than 15:
A "multi-filament" (or "multifil") refers to simultaneously formed fine denier filaments spun in 2 bundle of fibers, generally containir.g a~ le~st 3.
preferably at least 15-lO0 fibers and can be se~/eral hundred or several thousand:
An "extruded strand" refers to an extrudate formed by passing polyme~ through a forming-orific2.
such as a die:
A "bicomponent fiber" refers to a fiber comprising two polymer componencs. each in a continuous phase. e.g. side-by-side or sheath/core:
A "bicomponent staple fi~er" refers to a fine 2~ denier strand which have been formed at. or cu~ to.
staple lengths of generally one to eight inches (2.7 to 20 cm).
The shapes of these bicomponent fibers.
extruded strands and bicomponent staple fibers can be any which is convenient to the producer for the intended end use, e.g.~ round, trilobal, triangular. dog-boned, flat or hollow. The configuration of these bicomponent fibers or bicomponent stapie fibers can be symmetric (e.g., sheath/core or side-by-side) or they can be ~7 ~
W092/02669 PCT/US90/0~10 asymmetric (e.g.. a crescent/moon con~iguration within a fiber h~aving an overall round shape).
Convenient references relating to fibers and filaments, including those of man made thermoplastics, and incorporated herein by reference, are, for example:
(a) Encvclopedla of Polvme~ Science and Technolo~. Interscience. New York. vol. 6 (1967) . pp.
505-555 and vol. 9 (1968), pp. 403-440:
10 .
(b) Kirk-Othmer Enc-Jclopedia of Chemical Technolo~v. vol. 16 for "Olefin Fibers". John Wiley and Sons, New York. 1981. 3rd edition;
~5 (c) Man Made and Fiber and Textile Dictionarv.
Celanese Corporation:
(d) Fundamentals of Fibre Formation--The Science of Fibre Spinning and Drawing. Adrezi, Ziabicki.
John Wiley and Sons. London~New York. 1976;
(e) Man Made Fibres. by R. W. Moncrieff.
John Wiley and Sons. London/New York, 1975.
Other references relevant to this disclosure 2~ include U.S. Patent No. 4.644.045 which describes spun bonded non-woven webs of LLDPE having a critical combination of percent crystallinity, cone die melt flow, die swell, relation of die swell to melt index, ~ .30 and polymer unifor~ity: European Patent Application No.
-~87304728.6 which describes a non-woven fabric formed of heat bonded bicomponent filaments having a sheath of LLDPE and a core of polyethylene terephthalate.
In CA 91 :22388p (1979) there is described a fiber comprising polypropylene and ethylene-maleic W092/02669 ~r~ PcT/US90/O44lO
anhydride graft copolymer spun at a 50:50 ratio and drawn 300 percent at 100~C. and a blend of the drawn fibers and rayon at a 40:60 weight ratio carded and heated at 145C to give a bulky non-woven fabric.
However, polypropylene is disadvantageous in some applications because of its relatively high melting point (145CC). and because of the relatively poor hand or feel imparted to fabrics made thereof. Poor hand is manifested in a relati~ely rough and inflexible fabric, as opposed to a smooth and flexible fabric.
U.S. Patent No. 4.684,576 describes the use of ~lends of HDPE grafted with maleic acid or maleic anhydride to give rise to succinic acid or succinic 5 anhydride groups along the polymer chain with other olefin polymers as an adhesive, for example~ in extrusion coating of art~cles. as adhesive layers in - films and packaging, as hot mel~ coatings. as wire and cable interlayers, and in other similar applications.
20 Similar references describing adhesive blends containing HDPE grafted with unsaturated carboxyiic acids, primarily for laminate structures. include U.S. Patent Nos. 4.460.632; 4.394.485: and 4,230,830 and U.K. Patent Application Nos . 2.081,723 and 2.113,696.
A method has now been discovered for making thermoplastic bicomponent fibers by contacting under thermally bonding conditions (a) a first component being at least one high performance thermoplastic polymer, and 3 (b) a second component which is olefinic and which forms at least a portion of the fiber's surface characterized by (b) including at least one grafted linear ethylene polymer having pendant succinic acid or succinic anhydride groups; whereby the fiber is dyeable. These novel dyeable thermoplastic bicomponent fibers have ':~
, .
,' .
W092/02669 2 ~ ~ 7 ~ PCT/USgo/o~lo ' superior hand, a relatively low melting or bonding temperature~ superior adhesive properties. superior dyeability and superior adhesion of the components within the bicomponent fiber. The bicomponent fiber can be prepared by coextruding (a) and (b) into a fiber having a symmetrical or asymmetrical sheath/core or side-by-side configuration and a round. oval. trilobal.
triangular, dog-boned~ flat or hollow shape. Component (a) can be a polvester (such as polyethylene terephthalate or polybutylene terephthalate) or a pol-iamide (such âS rylon). Componen' (b) can be a polymer blend of a grafted linear ethyler.e ?olymer having pendant succinic acid or succinic anhydride groups and at least one ungrafted linear ethylene polymer. The bicomponent fiber can be formed under melt blown. spunbond or staple manufacturing process conditions.
In a further aspect of the invention, there is provided a method of bonding high performance natural and/or synthetic fibers such as polyester (e.g.. PET or PB,), polyamides (e.g.. nylon). cellulosics (e.g..
cotton). modified cellulosics (e.g.. rayon). wool or the like. by blending dyeable thermoplastic bicomponent fibers of the present invention used as binder fibers with the high performance fibers and heating the fibrous mixture to thermally weld the binder fiber to the high performance fibers.
Tn still another aspect. the invention provides a fabric comprising dyeable thermoplastic bicomponent fibers.
In still another aspect, the invention provides a :abric comprising dyeable thermoplastic bicomponent .
- . .
.
, 2 ~ '3 i W092/02669 PCT/US90/0~10 _g_ fibers as binder fiber blended with performance fibers.
wherein the bicomponent binder ~ibers are bonded to the performance fibers.
In a still further aspect of the invention.
there is provided an adhesive polymer blend for use as a component in making the dyeable thermoplastic bicomponent fibers. The polymer blend comprises (a) at least one grafted linear ethylene polymer having pendant succinic acid or succinic anhydride groups and (b) at least one ungrafted linear ethylene polymer.
In yet another aspect. there s provided a dyeable thermoplastic bicomponent fiber characterized b~
(a) a first component comprising at leas~ one high performance thermoplastic polymer. and (b) a second component comprising at leas~ one grafted linear ethylene polymer having pendant succinic acid or succinic anhydride groups which have been contacted under thermally bonding conditions.
The linear ethylene polvmers used for grafting can be linear HDPE and/or LLDPE. The density of linear HDPE before grafting can be about O.g4 to 0.97 g/cc. but is typically between about 0.945 and 0.965 g/cc. while that of LLDPE before grafting can be about 0.88 to 0.94 g/cc, but is typically between about 0.91 and 0.94 g/cc. Typically, linear HDPE and LLDPE will have about the same density before and after grafting. but this can vary depending on the particular linear ethylene polymer properties, graft level, grafting cond~itions and the i- like. The linear ethylene polymer before grafting has a melt index (MI) measured at 190~C/2.16 kg from about 0.1 to about 1000 grams/10 minutes, but typically less after grafting. For example, linear HDPE with a 25 MI and a .
., , ~ . . . .
W092/02669 2 ~ ~ ~ 3 ~ ~ PCT/US90/0~10 -0.955 g/cc density grafted to a level of about 1 weight percent maleic anhydride (MAH) has a MI after grafting of about 16-18 grams/10 minutes. Melt index herein is measured in accordance with ASTM D1238 condition 190C/2.16 kg (also known as condition "E"). The MI of the ungrafted linear ethylene polymer used for grafting is selected depending on the specific melt spinning procedure employed and whether or not the grafted linear ethylene polymer is employed alone or in a blend with another linear ethylene polymer.
The grafting of succinie acid or succinic anhydride groups may be done by methods described in the art which ~enerally involve reac~ing malei^ acid cr maleic anhydride in admixture with heated polymer.
generally using a peroxide or free radical initiator to accelerate the graftlng. The maleic acid and maieic anhydride compounds are known in these relevant arts as having their olefin unsaturation sites conjugated to the acid groups. Fumaric acid. an isomer of maleic acid which is also conjugated. gives off water and rearranges to form maleic anhydride when heated. and thus is operable in the present invention. Grafting may be effected in the presence of oxygen, air hydroperoxides.
or other free radical initiators. or i,n the essential absence of these materials when the mixture of monomer and polymer is maintained under high shear and heat conditions. A convenient method for producing the graft polymer is extrusion machinery, although Brabender mixers or Banbury mixers. roll mills and the like may also be used for forming the graft polymer. It is preferred to employ a twin-screw devolatilizing extruder (such as a Werner-Pfleiderer twin-screw extruder) wherein maleic acid or maleic anhydride is mixed and ~ o ~
W092/02669 PCT/US90/0~10 reacted with the linear ethylene polymer(s) at molten temperatures to produce and extrude the grafted polymer.
The anhydride or acid groups of the grafted polymer generally comprise from about 0.001 to about 10 wei~ht percent, preferably from about 0.01 to about 5 weight percent. and especiaily from 0.1 to about 1 weight percent of the grafted polymer. The grafted polymer is characterized by the presence of pendant succinic acid or anhydride groups along the polymer 0 chain. as opposed to the carboxylic acid groups obtained by the bulk copolymerization of ethvlene ~ith an ethylenically unsaturated carboxylic acid such as acrylic acid as disclosed in Furopean ~atent Application number 88116222.6 (EP Publication number 0 311 860 A2).
Grafted linear HDPE is the preferred grafted linear ethylene polymer.
The grafted linear ethylene polymer(s) can be - 20 employed singly or as a component in a polymer blend with other linear ethylene polymers. The polymer blend preferably contains from abou~ 0.5 to about 99.~ weight percent of the grafted linear ethylene polymer. more preferably from about 1 to 50 weight percent grafted linear ethylene polymer~ and especially from about 2 to 15 weight percent grafted linear ethylene polymer. The polymer blend may also include conventional additives, such as dyes, pigments, antioxidants, UV stabilizers, spin finishes, and the like and/or relatively minor 3 proportions of other fiber forming polymers which do not significantly alter the melting properties of the blend ; or the improved hand obtained~in fabrics containing fibers employing LLDPE as a polymer blend component.
- WO 92/02669 2 ~ S 7 ~ f ~ PCT/US90/0~10 The LLDPE employed either as the grafted linear ethylen~e polymer component or as the ungrafted component in the dyeable thermoplastic bicomponent fiber, comprises at least a minor amount of a C3-C 2 olefinically unsaturated alkene, preferably a C4-C8 olefinically unsaturated alkene. and 1-octene is especially preferred. The alkene may constitute from about 0.5 to about 35 percent by weight of the L~DPE, preferably from about l to about 20 weight percent. and most preferably from about 2 to about 15 weight percent.
The grafted linear ethylene polymer (e.g., grafted linear HDPE) and the ungrafted linear ethylene polymer (such as ungrafted LLDPE) may be blended together prior to extrusion, either by melt blending or dry blending. Dry blending of pellets of the grafted linear ethylene polvmer and the ungrafted linear ethylene polymer prior to extrusion is generally adequate where the melt indices of the blend components are similar. and there will generally be no advantage in melt blending such blend constituents prior to extrusion. However. where melt blending may be desired, as in the case of grafted linear HDPE and LLDPE or dissimilar melt indices, melt blending may be accomplished with conventional blending equipment, such as, for example. mixing extruders, Brabender mixers, Banbury mixers, roll mills and the like.
The high performance thermoplastic polymer useful as such as the second component of the dyeable thermoplastic bicomponent fiber of the present invention can be a polyester (e.g., PET or PBT) or a polyamide (e.g., nylon). The high performance thermoplastic polymer can be used as one component of the bicomponent fiber by contacting it with the grafted linear ethylene W092/02669 2 V ~ 7 ~ ~ ~ PCT/US90/0~10 polymer(s) under thermally bonding conditions. such as that encountered when coextruding bicomponent fiber using a bicomponent staple fiber die. The high performance polymer can either component of a sheath/core configuration or it can be either component of a side-by-side configuration. The high performanc thermoplastic polymer can be chosen to provide stiffness in the bicomponent fiber, especially when the grafted linear ethylene polvmer is a polymer blenà of grafted linear HDPE blended with ungrafted LLDP~. Additionallv.
the high performance thermopiastic polymer used in making the bicomponent fiber cf the present invention can be the same polymer as that used for making high performance fiber which is blended with the bicomponent fiber.
Extrusion of the poiymer through a die to form a fiber is effected using con~entiona' eauipment such as. for example. extruders. gear pumps and the like. It 2C is preferred to employ separate extruders. which feed gear pumcs to supplv the separate molten polymer streams to the die. The grafted linear ethylena polvmer or polymer blend is preferablv mixed in a mixing zone of the extruder and/or in a statlc mixer. for example.
upstream of the gezr pump in order to obtain a more ; uniform dispersion of the polymer components.
- Following extrusion through the die. the fiber is taken up in solid form on a godet or another take-up 3 surface. In a bicomponent staple fiber forming process.
the fibers are taken up on a godet which draws down the fibers in proportion to ~he speed of the tak,e-up godet.
In the spunbond process. the fibers are collected in a jet, such as, for example. an air gun, and blown onto a take-up surface such as a roller or moving belt. In the .
~a~
WOg2/02669 PCT/US90/04410 melt blown process, air is ejected at the surface of the spinnerette which serves to simultaneously draw down and cool the fibers as they are deposited on a take-up surface in the path of the cooling air. Regardless of the type of melt spinning procedure which is used, it is important that the fibers be partially melt drawn in a molten state, i.e. before solidification occurs. At least some drawdown is necessary in order to orient the polymer ~olecules ~^or good tenacity. It is not generally sufficient to sGlidify the fibers withou~
significant extension before take-u?. as ~;~^ fine strands which are forme~ tnereby can hardly be colc drawn. i.e. in a solid state below the melting temFerature of the polvmer. because of the:r low tenacity. On the other hand~ when the fibers are draws down in the molten state. the resulting strands can mone ; readily be cold drawn because of the im?roved tenzcity imparted by the melt drawing.
Melt drawdowns of up to about 1:1000 mav be employed depending upon spinnerette die diameten and spinning velocity. preferably from about 1:10 ~o about 1:200, and especially 1:20 to 1:10G.
Where the bicomponent staple-forming process is employed. it may be desirable to cold draw the strands with conventional drawing equipment. such as. for example. sequential godets operating at differential speeds. The strands may also be heat treated or 3 annealed by employing 5 heated godet. The strands may further be texturized, such as. for example. by crimping and cutting the strand or strands to form staple. In the spun bonded or air jet processes, cold drawing of the solidified strands and texturizing is effected in the air~jet and by impact on the take-up surface, 2~ ~3v~
W092/02669 PCT/US9~/0~10 respectively. Similar texturizing is effected in the melt blown process by the cooling fluid whicn is in shear with the molten polymer strands. and which may also randomly delinearize the fibers ?rior to their solidification.
The bicomponent fibers so formed by the above-described process also constitute a part of the present invention. The bicomponent fibers are generally fine denier filaments of 15 denier or less down to fractional deniers. preferabiy in the range of rom l to 10 denier.
although this will depend on the desired properties of the fibers and the specific application in which they are to be used.
The bicomponent fibers of tne present invention have a wide variety of potential applications. ~or example. the bicomponent fibers may be formed into a batt and heat treated by calendaring on a heated.
embossed roller to form a fabric. The batts may also be heat bonded-, for example. by infrared light, ultrasound or the like, to obtain a high loft fabric. The fibers may also be empioyed in conventional textile processing such as carding. sizing. weaving and the like. Woven fabrics made from the bicomponent fibers of the present invention may also be heat treated to alter the properties of the resulting fabric.
A preferred embodiment of the invention resides in the employment of the bicomponent fibers formed according to the process of the invention in binder fiber applications with high performance natural and~or synthetic fibers such as, for example, polyamides~
polyesters, silk, cellulosics (e.g. cotton), wool.
modified cellulosics such as rayon and rayon acetate.
W092~02669 2 0 5 ~ 3 ~ 3 PCT/US90/0~10 ' and the like. The bicomponent fibers of the present invention find particular advantage as binder fibers owing to their adhesion to performance fibers and dyeability thereof which is enhanced by the presence of the acid groups in the grafted linear ethylene polymer component and the relatively lower melting temperature or range of the grafted iinear ethylene polymer component relative to the performance fiber. The relative proportions of tne binder fiDer of the present invention employed in admixture with performance fibers in a fiber blend wi;l depend on the desired application and capabilities of the resulting fiber mixture and/or fabric obtained thereby. It is preferred to employ from about ~ to about g~ parts by weight of the binder fiber per 100 parts by weight of the binder fiber/performance fiber mixture, more preferably from about 5 to about 53 parts by weight binder fiber. and especia~ly 5 to 1 parts by weight binder fiber.
j 20 In preparing non-woven fabrics from the bicomponent binder fiber/performance fiber blend of the invention, there are several important considera~ions.
Wheré the binder fibers are in staple form~ there should be no fusing of the fibers when they are cut into staple, and the crimp imparted to the binder fibers should be sufficient for blending with the performance fibers to obtain good distribution of the fibers.
The ability of the component comprising at 3 least one grafted linear ethylene polymer having pendant succinic acid or anhydride groups to adhere to the other component of at least one high performance thermoplastic polymer is an important consideration in cutting of bicomponent staple fiber. When bicomponent staple fiber is cut and one of the components (e.g., the core of a ' ' ` ''' 2~7~
~'092/02669 PCT/US90/04410 bicomponent .'iber) protrudes from t;ne cuv e~ge~ the .lber will creare ar. irrita~ion when worrl ne~ ~o the skin. ThC irr.taticn is especially pronounced .Jnen the ^ore compor.ent is a :qioh performanc- thermopias~,~c such 2S PE.. 'when ungr~fted linear -thylene ?olymer and PET
are made. respectiveiv, into 3 sheath/core bicomponent f.Der and cu~ into shor- sta?le fibcr. the core Gi' PET
2rctrrudes beyond the cu. edge. lhe er,nanced a~ir.es;on G' t.qe graf~Qr 1 near e,.qyiQne ?oi~Jmer componen ~o ~he .-E.
c~mponer.~ _aed in makin the dyeaDle ther.rnop'las'lc , ~, _~comron-n~ ^ b-r o^ -'h- ?r-,en- inve-l or. rcr~c_a ?EI
pro~rusio-. D-~/on~ _in, fiDer' _fter cuttin, -r.d r,hus -naDle, fabr~cs and 'i3er b'ends ,- ~e ~arQ ~.;h~C.^ can be mor- comfort2bly wor.-. next to th_ s'r~in.
,, ~ he abl L_'y ^f ~r~e bicomponer.' bindc- bers ~c~
ad'r.erQ -o tr.- ?er,ormance iibers is anG~ncr im?cntant cor.sider tion. Acr.esio.-. and ~yea~-`i r- c7n 3cn r~i~ y controllec b-; varyiqO ~.^- acid CorltQr.t o- tne binscr 2~ .iber. e;.~her b. tne 'evel o.' gra.~ o. m-lelc -cid or anhydrid_ in the gra ~-- linear _ :n~,~lene polymer. or b~-tne prGpcr ior. o'` th- -r~fted _in-_r e'r.vien~ -.o'.ymer ~iende~ .!i'r. thQ ur.gr-:'~,ed lincar e~h~yierl_ ?oivmer i,.
~.he bico...-o:le-it 5indQ: i' Ders. r. .,ypic^l non-:~ovcn 2~ fabrlcs ob ain_d bf tr.erma"-J bond ng tr.- perforl,.ancc :irers wi'h a bicomponerlt binaer f~'ber. the abilit~y ~f 'he binder fibers to 5Ond to-,ether tne ?erformance ibers de?ends large'y on the thermal bon-lng o the ?erfor~ance ~ibers ~oge her r~y ~he ~incer fibera. In tJpica_ pri^r ar~ r.on.-.~oven faDrlcs ei,.ploying binder fibers. tr.- 5inder fiDer therca'ly Doncs performlance fibers to~ether bj a, ieas~ ?ar r ia L iy me!ting ~o form globules cr beads which encapsulate ~he ?erformance fibers. Thne binder fibers of the present inven~ion 20~7~
enhance the non-woven fabric by providing great adhesion of the binder fiber to the performance fiber. Employing the binder fibers of the present invention. it is also possible to obtain thermal bonding of the binder fiber to a performance fiber by partial melting and contact - 5 adhesion in which the bicomponent binder fibers largely retain their fibrous form. and the resulting non-woverl fabric is characterized 5y a reduced number of Olobules or beads formed by the meiting of the iower melting component of the bicomponent binder fibers.
-t is also importan~ for one componen~ OA th~
bicomponent binder fiber to have a relatively broad melting point range or tnhermai Donding window.
particularly where hot calendaring is employed to obtain a thermal bonding of a non-woven or woven fabric. A
good indication of meltina point range or thermai bonding window is the dlfference between th- Vicat softening point and the peak melting point determined by dlfferential scanning calorime~ry (DSC). Narrow melting point ranges present a difficu ~ target for process bonding equipment such as a calendar roll. and even slight variations in the temperature of bonding equipment can result in an insufficient bond to be formed betwee.n the bicomponent binder fibers ar.d the performance fibers. If too low a temperature is : ~ .
employed, the bicomponent binder-fibers will not ~sufficiently fuse. whereas when too high a temperature is employed, one component of the bicomponent binder fiber may completely melt and run right out of the performance fiber batt. Thus. a broad melting point range is desired in order that partial fusion of on-component of the bicomponent binder fiber materia1 car.
be achieved without a complete melting. A melting point .
:
' ~ W092/02669 ~ ~ 7 3 ~ g PCT/US90/04410 _ 1 9--range of at least 7.5C is desired for proper thermal bonding. and preferably a sufficiently broad melting point range that a minimum 10C bonding window is obtained.
Another important characteristic of bicomponent binder fibers is that when they are melted in equipment-such as a calendar roll, one of the components will have a sufficient melt viscosity to be retained in the fiber matrix and not readily flow therefrom. An important advantage of the bicomponent binder fibers of the preser.t invention is tha one component has generally higher me:t viscosity than fibers consisting of ungrafted LLDPE and/or ungrafted iinear HDPE. In addition to using a calendar roll. bonding of the present binder fibers can also be obtained using other bonding techniques. e.g. with hot air. infrared heaters.
ard the like.
2~ The thermoplastic bicomponent fibers of the invention can be dyed by contacting them with a water soluble ionic dye. preferably a water soluble cationic dye. in a suitable aqueous medlu~.. The aqueous medium can contain surfactants, i; desired. to promote contact.
The invention is illustrated by way of, but not limited to, the examples which follow.
3 A linear HDPE ethylene~propylene copolymer (the "base" polymer), having a MI of about 25 grams/10 minutes and density of O.g55 g~cc. is extruded with maleic anhydride (3.0 pounds per hour) and dicumyl peroxide (0.3 pounds per hour) at an average melt temperature of 225C (the temperature ranged from about 2~73~
w0~2/02669 PCT/US90/04410 180 to about 250C) using a Werner-Pfleiderer twin-screw devolatization extruder. The final incorporated concentration of maleic anhydride is about 110 by weight (as determined by titration) and has a MI of about - 16-18 grams/10 minutes: this is called the MAH-grafted linear HDPE concentrate.
Using a 6-inch Farrell two-roll mill. 250 gram sampies are blended ha~ing compositions ranging from ,%
MAH-grafted linear HDPE concentrate to 50~ MAH-grafted linear HDPE concentrate in v2rious LLDPE resins 2t a me't temperature of 170~ he ~lends are useful 2S 2' least one component in 2 bicomponent fiber, wherein at least one other component is a perîormance poiymer component. such as PBT or PET.
ExamDle 2 Ten percent of a grafted linear HDPE
(ethylene/propylene copolymer. MI of 2~ grams,'10 mlnutes before grafting. densitv of 0.955 g/cc before grafting) having about 1% bv weight succinic acid groups is biended with about 9C,~ by weight of an ungrafted LLDPE
(ethyleneioctene copolymer. MI of 18 grams/10 minutes.
0.930 g/cc density) to form a polymer blend having about 0.1~ by weight succinic acid groups. The polvmer blend is then used as a sheath component in a bicomponent staple fiber spinning operation. with the core component being PET. The sheath/core bicomponent fibers are blended with other performance fibers such as PET or 3 cellulosics, formed into batts and oven bonded. The batts are found to be weIi-bonded and have good physical integrity.
2~5i73~
Example 3 Linear HDPE (ethylene-propylene copolymer. MI
of 25 grams/10 minutes, 0.95~ gicc density) is grafted with maleic acid to provide succinic acid groups along the polymer chain. Portions of the grafted linear HDPE
are then blended with amounts of ungrafted LLDP~
(ethylene-octene copolvmer. MI of 18 grams,'10 minutes.
0.930 g/cc density) to produ^_ polymer blends containlng o.o5aO. 0.1~. 0.157c. 0.2~. and 0.4% by weight of the succinic acid. The grafted linear HDPEi'LLDPE polymer bler.d samples are coextrud-a .with PE t~ ?roduce sid--by-side bicomponent fibrous materia'. The adhesion between fibers in a heat-Donded bat of the fibrous material is appreciably better than that obtained in comparison by using the same linear HDPE and LLDPE
without any grafted acid groups. The maximum heat-bonded bat strength occurs when usinO bi~omponent fiber having a succinic acid level of about 0.1~ by weigh~.
ExamDle 4 Linear HDPE (eth~lene-p.opylene copol~mer. Ml of 25 grams/10 minutes. C.?,-,i g~cc densitv) is grafted wlth male-c anhvdride ~o ?ro~.~d^ abou~ l~s DV weigh' succinic anhydride groups aiong ths polymer chain.
Portions of the grafted linear HDP' are blended with amounts of ungrafted LLDPE (e~hylene-octene copolymer.
MI of 18 grams/10 minutes. 0.930 gicc density) to produce polymer blends containing 0.05~. 0.1~. 0.15~.
0.2%~ and 0.5% by weight of the succinic acid groups.
Polym~r blends of the grafted linear HDPE with the ungrafted LLDPE can be coextruded as the sheath layer in a bicomponer.t spunbond system using a PET as the cor-layer. The resultant thermally bonded fabric has a bonded fabric strength higher than that obtained using W092/02669 RCT/US90/n4410 -~2-ungrafted linear ethylene polymer alone as the sheath resin.
Example 5 LLDPE (ethylene-octene copolymer. MI of 18 grams/lO minutes. O.93O g/cc density) does not accept dye when treated with Basic Viole~ III (a basic dye also known as Crystal ~ioiet~ at 80C for 15 minutes in the presence of a dro? of didec~vi dimethyl ammonium chloriae used as a wetting agen'. When blended wlth enough LLDPE
gra~ted w.tn maleic anhydride to providc a r,olvmer blend having about 0.157O Dy weight succinic acid groups. the resulting polymer blend. when treated in the same manner as immediately above. became dyed to a biue,purpie color. The dye does not readily leach out. even when placed in boiling water for 10-15 minutes. Other water soluble cationic dyes (i.e.. dyes which ane typically referred to as "basic dyes" in the :ndustry` can be similarly used to dye the novel bicomponent fibers.
3o
Claims (15)
1. A method for making a thermoplastic bicomponent fiber by contacting under thermally bonding conditions (a) a first component being at least one high performance thermoplastic polymer, and (b) a second component which is olefinic and which forms at least a portion of the fiber's surface characterized by (b) including at least one grafted linear ethylene polymer having pendant succinic acid or succinic anhydride groups: whereby the fiber is dyeable.
2. The method defined by Claim 1 wherein said bicomponent fiber is prepared by coextruding (a) and (b) into a fiber having a round, oval, trilobal, triangular. dog-boned, flat or hollow shape and a symmetrical or asymmetrical sheath/core or side-by-side configuration.
3. The method defined by Claim 2 wherein said bicomponent fiber has a round shape and a sheath/core configuration.
4. The method defined by any one of the preceding Claims wherein (a) is a polyester or a polyamide.
5. The method defined by Claim 1 wherein said bicomponent fiber is prepared by coextruding (a) and (b) into a fiber having a sheath/core configuration, and wherein (a) is a polyester, and wherein (b) includes a polymer blend of a grafted linear ethylene polymer having pendant succinic acid or succinic anhydride groups and at least one ungrafted linear ethylene polymer.
6. The method defined by Claim 5 wherein (a) is polyethylene terephthalate or polybutylene terephthalate and wherein (b) is a polymer blend of a grafted linear high density ethylene polymer and an ungrafted linear low density ethylene polymer.
7. The method defined by Claim 2 wherein said fiber is formed under melt blown, spunbond or staple fiber manufacturing process conditions.
8. The dyeable thermoplastic bicomponent fiber obtainable by the method of any one of the preceding Claims.
9. A method of bonding high performance fibers by blending the high performance fibers with binder fibers and heating the fibrous mixture to near the melting point of the binder fibers to thermally bond the binder fibers to the high performance fibers characterized by providing the dyeable thermoplastic bicomponent fibers of Claim 8 as the binder fibers.
10. The method defined by Claim 9 wherein said high performance fiber is a polyester, polyamide, cellulosic or wool, or a mixture thereof.
11. The product obtainable by the method of Claims 9 or 10.
12. An adhesive polymer blend for fiber forming use in (b) of the method of Claim 1 wherein the blend includes at least one grafted linear ethylene polymer having pendant succinic acid or succinic anhydride groups and at least one ungrafted linear ethylene polymer.
13. Use of an adhesive polymer blend in preparing dyeable fibers in (b) of the method of Claim 1 by contacting said fiber with a water soluble cationic dye wherein the blend includes at least one grafted linear ethylene polymer having pendant succinic acid or succinic anhydride groups and at least one ungrafted linear ethylene polymer.
14. The fiber of Claim 8 for dyeing use by contacting said fiber with a water soluble cationic dye.
15. The fiber of Claim 8 in the form of a fabric.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002067398A CA2067398A1 (en) | 1990-08-07 | 1990-08-07 | Method for making bicomponent fibers |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002067398A CA2067398A1 (en) | 1990-08-07 | 1990-08-07 | Method for making bicomponent fibers |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2067398A1 true CA2067398A1 (en) | 1992-02-08 |
Family
ID=4149720
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002067398A Abandoned CA2067398A1 (en) | 1990-08-07 | 1990-08-07 | Method for making bicomponent fibers |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2067398A1 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5336552A (en) | 1992-08-26 | 1994-08-09 | Kimberly-Clark Corporation | Nonwoven fabric made with multicomponent polymeric strands including a blend of polyolefin and ethylene alkyl acrylate copolymer |
| US5382400A (en) | 1992-08-21 | 1995-01-17 | Kimberly-Clark Corporation | Nonwoven multicomponent polymeric fabric and method for making same |
| US5405682A (en) | 1992-08-26 | 1995-04-11 | Kimberly Clark Corporation | Nonwoven fabric made with multicomponent polymeric strands including a blend of polyolefin and elastomeric thermoplastic material |
| US5643662A (en) | 1992-11-12 | 1997-07-01 | Kimberly-Clark Corporation | Hydrophilic, multicomponent polymeric strands and nonwoven fabrics made therewith |
| US6500538B1 (en) | 1992-12-28 | 2002-12-31 | Kimberly-Clark Worldwide, Inc. | Polymeric strands including a propylene polymer composition and nonwoven fabric and articles made therewith |
-
1990
- 1990-08-07 CA CA002067398A patent/CA2067398A1/en not_active Abandoned
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5382400A (en) | 1992-08-21 | 1995-01-17 | Kimberly-Clark Corporation | Nonwoven multicomponent polymeric fabric and method for making same |
| US5418045A (en) | 1992-08-21 | 1995-05-23 | Kimberly-Clark Corporation | Nonwoven multicomponent polymeric fabric |
| US5336552A (en) | 1992-08-26 | 1994-08-09 | Kimberly-Clark Corporation | Nonwoven fabric made with multicomponent polymeric strands including a blend of polyolefin and ethylene alkyl acrylate copolymer |
| US5405682A (en) | 1992-08-26 | 1995-04-11 | Kimberly Clark Corporation | Nonwoven fabric made with multicomponent polymeric strands including a blend of polyolefin and elastomeric thermoplastic material |
| US5425987A (en) | 1992-08-26 | 1995-06-20 | Kimberly-Clark Corporation | Nonwoven fabric made with multicomponent polymeric strands including a blend of polyolefin and elastomeric thermoplastic material |
| US5643662A (en) | 1992-11-12 | 1997-07-01 | Kimberly-Clark Corporation | Hydrophilic, multicomponent polymeric strands and nonwoven fabrics made therewith |
| US6500538B1 (en) | 1992-12-28 | 2002-12-31 | Kimberly-Clark Worldwide, Inc. | Polymeric strands including a propylene polymer composition and nonwoven fabric and articles made therewith |
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