AU645264B2 - Method for making biocomponent fibers - Google Patents

Description

WO 92/02669 PCT/US90/04410 METHOD FOR MAKING BICOMPONENT FIBERS The present invention pertains to dyeable thermoplastic bicomponent fibers and a method of preparation. These bicomponent fibers are characterized by contacting under thermally bonding conditions a first component comprising at least one high performance thermoplastic polymer, and 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 and into fiber having a round. oval.

trilobal. triangular. dog-boned, flat or hollow shape and a sheath/core or side-by-side configuration. The bicomponent fiber can be coextruded using melt blown.

spunbond or staple fiber manufacturing process conditions. The present 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. 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 WO 92/02669 PCT/US90/04410 -2generally 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 crystalline).

The largely crystalline types of polypropylene (PP), including both isotactic and syndiotactic, have found wide acceptance in certain applications in the form of fibers.

Other 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 (g/cc) and linear low density polyethylene (LLDPE) having 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 with 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 o,p-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 WO 92/02669 P(7/US90/04410 -3introduced 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 polyethylenesknown 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 concomitant high melt elasticity, LDPE is cifficult to form into a fiber and has inferior properties as.compared to LLDPE, HDPE and PP fibers.

One application of certain fibers such as, for example, polyvinyl chloride, low melting polyester and polyvinylacetate, has been the use of such fibers as binder fibers by blending the binder fiber with high performance natural and/or synthetic fibers such as polyesters polyethylene terephthalate (PET) or polybutylene terephthalate polyamides, cellulosics cotton). modified cellulosics rayon), wool or the like, and heating 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 WOD 92/02669 PCT/US90/04410 -4formation of microglobules or beads of the olefin fiber.

Moreover, it is difficult to achieve suitable thermalbonding 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 to dye. because there are no sites for the specific attraction of dye molecules, 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 melt before extrusion, and much effort has gone into pigmentation technology for dispersing a dye into the polyolefin fiber. This has largely been unsuccessful because of the poor lightfastness. poor fastness to dry cleaning, generally low color build-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 typically fabricated commercially by melt spinning. In this procedure, each molten polymer is extruded through a die, a spinnerette, with subsequent drawing of the molten extrudate, solidification 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 WO 92/02669 PCT/US90/04410 filament industry, the following definitions apply to the terms used herein: A "monofilament" (also known as "monofil") refers to an individual strand of denier greater than 15, usually greater than A "fine denier fiber or "filament" refers to a strand of denier less than A "multi-filament" (or "multifil") refers to simultaneously formed fine denier filaments spun in a bundle of fibers, generally containing at least 3, preferably at least 15-100 fibers and can be several hundred or several thousand'; An "extruded strand" refers to an extrudate formed by passing polymer through a forming-orifice.

such as a die; A "bicomponent fiber" refers to a fiber comprising two polymer components, each in a continuous phase, e.g. side-by-side or sheath/core: A "bicomponent staple fiber" refers to a fine denier strand which have been formed at, or cut to.

staple lengths of generally one to eight inches (2.5 to 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, round, trilobal, triangular, dog-boned, flat or hollow. The configuration of these bicomponent fibers or bicomponent staple fibers can be symmetric sheath/core or side-by-side) or they can be WO 92/02669 PCT/US90/04410 -6asymmetric a crescent/moon configuration within a fiber having 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: Encyclopedia of Polymer Science and Technology, Interscience, New York. vol. 6 (1967), pp.

505-555 and vol. 9 (1968), pp. 403-440; Kirk-Othmer Encyclooedia of Chemical Technology, vol. 16 for "Olefin Fibers". John Wiley and Sons, New York, 1981. 3rd edition; Man Made and Fiber and Textile Dictionary, Celanese Corporation: Fundamentals of Fibre Formation--The Science of Fibre Spinning and Drawing, Adrezij Ziabicki, John Wiley and Sons, London/New York, 1976; Man Made Fibres, by R. W. Moncrieff, John Wiley and Sons. London/New York, 1975.

Other references relevant to this disclosure 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, and polymer uniformity: 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 WO 92/02669 PC/US90/04410 -7anhydride 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 145 0 C to give a bulky non-woven fabric.

However, polypropylene is disadvantageous in some applications because of its relatively high melting point (1450C), and because of the relatively poor hand or feel imparted to fabrics made thereof. Poor hand is manifested in a relatively rough and inflexible fabric, as opposed to a smooth and flexible fabric.

U.S. Patent No. 4,684,576 describes the use of blends of HDPE grafted with maleic acid or maleic anhydride to give rise to succinic acid or succinic anhydride groups along the polymer chain with other olefin polymers as an adhesive, for example. in extrusion coating of articles, as adhesive layers in films and packaging, as hot melt coatings, as wire and cable interlayers, and in other similar applications.

Similar references describing adhesive blends containing HDPE grafted with unsaturated carboxylic 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 first component being at least one high performance thermoplastic polymer, and a second component which is olefinic and which forms at least a portion of the fiber's surface characterized by 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 SWO 92/02669 PCT/US90/04410 -8superior 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 and 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 can be a polyester (such as polyethylene terephthalate or polybutylene terephthalate) or a polyamide (such as nylon). Component can be 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. 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 PET or PBT), polyamides nylon), cellulosics cotton), modified cellulosics rayon), wool or the like, by blending dyeable thermoplastic bicomponent 2 fibers of the present invention used as binder fibers with the hi h performance, fibe rs nd heating the fibrous Aure -he m ltto Pini 6 mixture to therma ly weld the binder fiber to the high performance fibers.

In still another aspect, the invention provides a fabric comprising dyeable thermoplastic bicomponent fibers.

In still another aspect, the invention provides a fabric comprising dyeable thermoplastic bicomponent 9 fibers as binder fiber blended with performance fibers, wherein the bicomponent binder fibers 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 at least one grafted linear ethylene polymer having pendant succinic acid or succinic anhydride groups and at least one ungrafted linear ethylene po.ymer.

In yet another aspect, there is provided a bicomponent fiber, wherein at least one component is characterised as an adhesive polymer blend comprising at least one grafted linear ethylene polymer having pendant succinic acid or succinic anhydride groups and at least one ungrafted linear ethylene polymer.

In yet a further aspect, there is provided a method for dyeing a thermoplastic bicomponent fiber, comprising contacting said thermoplastic bicomponent fiber containing an adhesive polymer blend with a water soluble cationic dye, wherein said 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.

The linear ethylene polymers used for grafting can be linear HDPE and/or LLDPE.

The density of linear HDPE before grafting can be about 0.94 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 conditions and the like. The linear ethylene polymer before grafting has a melt index (MI) measured at 190 0 C/2.16kg 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 (N:\LIBZ]00094:ER 9of 3 WO 92/02669 PCr/ US90/0410 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 190 0 C/2.16 kg (also known as condition 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 succinic acid or succinic anhydride groups may be done by methods described in the art which generally involve reacting maleic acid or maleic anhydride in admixture with heated polymer, generally using a peroxide or free radical initiator to accelerate the grafting. The maleic acid and maleic anhydride compounds are known in ti:se 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 in 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 WO 92/02669 PC/US90/04410 -11reacted with the linear ethylene polymer(s) at molten temperatures to produce and extrude the grafted polymer.

The anhydride or acid groups of the grafted ,ipolymer generally comprise from about 0.001 to about 10 weight percent, preferably from about 0.01 to about weight percent, and especially 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 chain, as opposed to the carboxylic ac d groups obtained by the bulk copolymerization of ethylene with an .a-ethylenically unsaturated carboxylic acid such as acrylic acid as disclosed in European Patent 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 employed singly or as a component in a polymer blend with other linear ethylene polymers. The polymer blend preferably contains from about 0.5 to about ;9.5 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 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 PCT/US90/04410 -12- The LLDPE employed either as the grafted linear ethylene 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 LLDPE, preferably from about 1 to about 20 weight percent, and most preferably from about 2 to about 15 weight percent.

The grafted linear ethylene polymer 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 polymer 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 e-.ruders, Brabender mixers, Banbury mixers, roll mills and the like.

The high performance thermoplastic polymer 3 useful as such as.the second component of the dyeable thermoplastic bicomponent fiber of the present invention can be a polyester PET or PBT) or a polyamide nylon). The high performance thermoplastic polymer can be used as one component of the bicomponent fiber by contacting it with the grafted linear ethylene WO 92/02669 PCT/US90/4~410 -13polymer(s) under thermally bonding conditions, such as that enc tered when coextruding bicomponent fiber using a Uicomponent 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 polymer is a polymer blend of grafted linear HDPE blended with ungrafted LLDPE. Additionally, the high performance thermoplastic polymer used in making the bicomponent fiber of 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 polymer through a die to form a fiber is effected using conventional equipment such as. for example, extruders. gear pumps and the like. It is preferred to employ separate extruders, which feed gear pumps to supply the separate molten polymer streams to the die. The grafted linear ethylene polymer or polymer blend is preferably mixed in a mixing zone of the extruder and/or in a static mixer, for example.

upstream of the gear 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 surface. In a bicomponent staple fiber forming process.

the fibers are taken up on a godet which draws down the fibers in proportion to the speed of the take-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 WO 92/02669 PC'/US90/04410 -14melt blown process, air is ejected'at the surface of the spinner-ette 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 molecules for good tenacity. It is not generally sufficient to solidify the fibers without significant extension before take-up, as the fine strands which are formed thereby can hardly be cold drawn, i.e. in a solid state below the melting temperature of the polymer, because of their low tenacity. On the other hand, when the fibers are drawn' down in the molten state, the result ng strands can more readily be cold drawn because of the improved tenacity imparted by the melt drawing.

Melt drawdowns of up to about 1:1000 may be employed depending upon spinnerette die diameter and spinning velocity, preferably from about 1:10 to about 1:200, and especially 1:20 to 1:100.

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 annealed by employing a 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, WO 92/02669 PCr/US90/04410 respectively. Similar texturizing is effected in the melt blown process by the cooling fluid which is in shear with the molten polymer strands, and which may also randomly delinearize th 'ibers prior to their solidification.

The bicomponent fibers so formed by the abovedescribed 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, preferably in the range of from 1 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 the present invention have a wide variety of potential applications. For 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 emr.oyed 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 cotton), wool, modified cellulosics such as rayon and rayon acetate, WO 92/02669 PCT/US90/0410 -16and the like. The oicomponent 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 linear ethylene polymer component relative to the performance fiber. The relative proportions of the binder fiber of the present invention employed in admixture with performance fibers in a fiber blend will depend on the desired application and capabilities of the resulting fiber mixture and/or fabric obtained thereby. It is preferred to employ from a'_ut 5 to about 95 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 parts by weight binder fiber, and especially 5 to parts by weight binder fiber.

In preparing non-woven fabrics from the bicomponent binder fiber/performance fiber blend of the invention, there are several important considerations.

Where 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 least one grafted linear ethylene polymer having pendant succinic acid or anhydride groups to adhere to the o'.her 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 the core of a M'O 92/02669 PCT/US90/04410 bicomponent fiber) protrudes from the cut edge. the fiber will creat-e an irritation when worn next to the skin. The irritation is especially pronounced wnen the core compornent is a high performance thermoplastic such as PET. When ungrafted linear eithyl ene polymer and PET are made. respectively, into a sheath/core bicomponent fiber and cut into shor. staple fiber. the core of PET orctrudes beyon-d the c ut edge. The enhanced ad.hesiLon of the gzrafted li;near ethylene polymer component to the PET component jsed in making the dyeable thermoplastic bicomponent fiber of thpresen: invention reduces HET Protrusion beyond the fioDer after cutting- and thus ena .bles' fabrics and fiber blends rto e mace wnicn can be more comfortably worn next the skin.

The ability f t-he bicomponent binder fibers to adhere to the performance fibers is ano:_- er imocrtant -onsideration. Ad'hesion- and 4iyeazili'ty can g-enerally be= controlled by varying the acid content of the binder 2) -fiber, either by the levlel of graft of ma=leic acid or anhydride in the grate linear ethylene polymer. or by tne proportion of the zrafted Linear ethylene polymer olendeJ i~ the unr-raf--d 1inear ethylene pooimer in tebicoononent binder' fibers. ;n typical non-..oven fatrics obtained by thermall'; bond2inc- the oei'formance fieswith a bicomponent binder fiber. the ability of thne binder fibers to bond together the performance fibers depends largely on the thermal bonding of the 3~performance fibers tog-ether by the bincer fibers. In typical prior art non-w.-oven -fabrics employing binder 'ibers. the binder fiber therma'll bonds Derformance fibers togethter by least partially melting to form -lobules cr teads which encapsulate the perf ormance fibers. The binder fibers of" the oresen:. invent-ion WO 92/02669 PCT//US90/04410 -18enhance 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 adhesion in which the bicomponent binder fibers largely retain their fibrous form, and the resulting non-woven fabric is characterized by a reduced number of globules or beads formed by the melting of the lower melting component of the bicomponent binder fibers.

It is also important for one component of the bicomponent binder fiber to have a relatively broad melting point range or thermal bonding window, particularly where hot calendaring is employed to obtain a thermal bonding of a non-woven or woven fabric. A good indication of melting point range rr thermal bonding window is the difference between the Vicat softening point and the peak melting point determined by differential scanning calorimetry (DSC). Narrow melting point ranges present a difficult 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 2 formed between the bicomponent binder fibers and 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 one component of the bicomponent binder fiber material can be achieved without a complete melting. A melting point WO 92/02669 PCT/US90/010 range of at least 7.5 0 C is desired for proper thermal bonding, and preferably a sufficiently broad melting point range that a minimum 10 0 C 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 present invention is that one component has generally higher melt viscosity than fibers consisting of ungrafted LLDPE and/or ungrafted linear HDPE. In Saddition 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.

and the like.

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 medium. The aqueous mediui can contain surfactants, if desired, to promote contact.

The invention is illustrated by way of, but not limited to, the examples which follow.

EXAMPLE 1 A linear HDPE ethylene/propylene copolymer (the "base" polymer), having a MI of about 25 minutes and density of 0.955 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 22500 (the temperature ranged from about WO 92/02669 PPUS90/04410 1800 to about 250°C) using a Werner-Pfleiderer twin-screw devolatization extruder. The final incorporated concentration of maleic anhydride is about 1% 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 samples are blended having compositions ranging from MAH-grafted linear HDPE concentrate to 50% MAH-grafted linear HDPE concentrate in various LLDPE resins at a melt temperature of 170 0 C. The blends are useful as at least one component in a bicomponent fiber, wherein at least one other component is a performance polymer component, such as PBT or PET.

Examole 2 Ten percent of a grafted linear HDPE (ethylene/propylene copolymer, MI of 25 grams/10 minutes before grafting, density of 0.955 g/cc before grafting) having about 1% by weight succinic acid groups is blended with about 90% by weight of an ungrafted LLDPE (ethylene/octene 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 polymer 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 Scellulosics, formed into batts and oven bonded. The batts are found to be well-bonded and have good physical integrity.

WO 92/02669 PCr/US90/0441 0 -21- Example 3 Linear HDPE (ethylene-propylene copolymer. MI of 25 grams/10 minutes, 0.955 g/cc 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 LLDPE (ethylene-octene copolymer.- MI of 18 grams/10 minutes, 0.930 g/cc density) to produce polymer blends containing 0.05%. 0.15%, and 0.4% by weight of the succinic acid. The grafted linear HDPE/LLDPE polymer blend samples are coextruded with PET to produce sideby-side bicomponent fibrous material. The adhesion between fibers in a heat-bonded 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 heatbonded bat strength occurs when using bicomponent fiber having a succinic acid level of about 0.1% by weight.

Example 4 Linear HDPE (ethylene-propylene copolymer. MI of 25 grams/10 minutes. C.955 g/cc density) is grafted with maleic anhydride to provide about 1% by weight succinic anhydride groups along the polymer chain.

Portions of the grafted linear HDPE are blended with amounts of ungrafted LLDPE (ethylene-octene copolymer, MI of 18 grams/10 minutes, 0.930 g/cc density) to produce polymer blends containing 0.05%, 0.15%, S0.2%, and.0.5% by weight of the succinic acid groups.

Polymer blends of the grafted linear HDPE with the ungrafted LLDPE can be coextruded as the sheath layer in a bicomponent spunbond system using a PET as the core layer. The resultant thermally bonded fabric has a bonded fabric strength higher than that obtained using WO 92/02669 PCT/US90/04410 -22ungrafted linear ethylene polymer alone as the sheath resin.

Example LLDPE (ethylene-octene copolymer, MI of 18 grams/10 minutes, 0.930 g/cc density) does not accept dye when treated with Basic Violet III (a basic dye also known as Crystal Violet) at 800C for 15 minutes in the presence of a drop of dide'vl dimethyl ammonium chloride used as a wetting agent. When blended with enough LLDPE grafted with maleic anhydride to provide a polymer blend having about 0.15% by weight succinic acid groups, the resulting polymer blend, when treated in the same manner as immediately above, became dyed to a blue/purple color. The dye does not readily leach out, even when placed in boiling water for 10-15 minutes. Other water soluble cationic dyes dyes which are typically referred to as "basic dyes" in the industry) can be similarly used to dye the novel bicomponent fibers.

Claims (24)

1. A method for making a dyeable thermoplastic bicomponent fiber by contacting under thermally bonding conditions at least one polyester or polyamide polymer, and an olefinic polymer which forms at least a portion of the fiber's surface characterized by including at least one grafted linear ethylene polymer having pendant succinic acid or succinic anhydride groups.

2. The method defined by claim 1 wherein said bicomponent fiber is prepared by coextruding and 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 claims 1 to 3 wherein is a polyester.

The method defined by claim 4 wherein is polyethylene terephthalate or polybutylene terephthalate.

6. The method defined by any one of claims 1 to 5 wherein includes at least one ungrafted linear ethylene polymer.

7. The method defined by claim 6 wherein is a polymer blend of a grafted linear high density ethylene polymer and an ungrafted linear low density ethylene polymer.

8. The method defined by any one of claims 1 to 7 wherein said fiber is formed under melt blown, spunbond or staple fiber manufacturing process conditions.

9. A method for making a dyeable thermoplastic bicomponent fiber, substantially as hereinbefore described with reference to any one of the Examples.

A dyeable thermoplastic bicomponent fiber obtainable by the method of any one of the preceding claims.

11. A bicomponent fiber, wherein at least one component is characterised as an S adhesive polymer blend comprising at least one grafted linear ethylene polymer having pendant succinic acid or succinic anhydride groups and at least one ungrafted linear ethylene polymer.

12. The bicomponent fiber defined by claim 11, wherein one of the components comprises an ungrafted linear ethylene polymer.

13. The bicomponent fiber of claim 12, wherein one of the components is a polymer blend of grafted linear high density ethylene polymer and an ungrafted linear low density ethylene polymer.

14. The bicomponent fiber of claim 11 characterised in that the adhesive polymer blend forms at least a portion of the fiber's surface.

S N:\LIBZ100094:ER 23 of 3 The bicomponent fiber of claim 14 further characterised in that the fiber has a round, oval, trilobal, triangular, dog-boned, flat or hollow shape and a symmetrical or asymmetrical sheath/core or side-by-side configuration.

16. A bicomponent fiber as defined in claim 11 and substantially as herein described with reference to any one of the examples.

17. A dyeable thermoplastic bicomponent fiber, substantially as hereinbefore described with reference to any one of the Examples.

18. The fiber of any one of claims 10 to 16 dyed by contacting said fiber with a water soluble cationic dye.

19. The fiber of any one of claims 10 to 18 in the form of a fabric.

A method of bonding high performance fibers selected from polyester, polyamide, cellulosic or wool, or a mixture thereof by blending such high performance fibers with the bicomponent fibers of any one of claims 10 to 17 and heating the fibrous mixture to near the melting point of the bicomponent "bers to thermally bond the bicomponent fibers to the high performance fibers.

21. Bonded bicomponent fibers and high performance fibers when obtained by the method of claim

22. A method for dyeing a thermoplastic bicomponent fiber containing an adhesive polymer blend which includes least one grafted linear ethylene polymer hav ig pendant succinic acid or succinic anhydride groups and at least one ungrafted linear ethylene polymer comprising contacting said fiber with a water soluble cationic dye.

23. A melthod for dyeing a thermoplastic bicomponent fiber, substantially as hereinbefore described with reference to Example

24. A dyed thermoplastic bicomponent fiber when prepared by the method of claim 22 or claim 23. Dated 5 November, 1993 The Dow Chemical Company Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON N 0094E 24 of 3 N 1N:\LtBZ1000 94.ER 24 ol 3 INTERNATIONAL SEARCH REPORT International Application No. PCT/US90/04410 I. CLASSIFICATION OF SUBJECT MATTER (it several classificlion symbols apply.indicate all) 6 According to Inlernntional Patent Classification (IPC) or to both Nalional Classification and IPC IPC D01F 8/06, 8/12, 8/14 U.S. CL. 428/373; 525/74 II FIELDS SEARCHED Minimum Documentation Searched 7 Classification System Ciassifkiatlon Symbols U.S. 428/273; 525/74 Documentation Searched otthl than Minimum Documentilion to the Extent that such Documents are Included in the Fields Searched S tll. DOCUMENTS CONSIDERED TO BE RELEVANT' Category Citation of Document, with indication, where appropriate, of the relevant passages 12 Relevant to Claim No. 1 A US, A, 3,968,307 (MATSUI ET AL) 06 JULY 1976 A US, A, 4,424,257 (BACH) 03 JANUARY 1984 A US, A, 4,230,830 (TANNY ET AL) 28 OCTOBER 1980 A US, A, 4,397,916 (NAGANO) 09 AUGUST 1983 A US, A, 4,452,942 (SHIDA ET AL) 05 JUNE 1984 A US, A, 4,500,384 (TOMIOKA ET AL) 19 FEBRUARY 1985 A EP, A, 0 248 598 (UNITIKA LTD.) 09 DECEMBER 1987 A DE, A, 3544523 (HENSEN ET AL) 26 JUNE 1986 Special categories of cited documents: 10 later document published after the international filing date document defining the general state ot the art which is not or priority date and not in conflict with the application but considered to be o particular relevance cited to understand the principle or theory underlying the invention earlier document but published on or after the international document of particular relevance; the claimed invention filing date cannot be considered novel or cannot be considared to document which may throw doubts on priority claim(s) or involve an inventive step which is cited to establish the publcatior' date 1o another documnt: ol particular relevance; the claimed invention citation or other special reason (as specified) cannot be considered to involve an inventive step when the document referring to an oral disclosur. use, exhibition or document is combined uitn one or more other such docu- other means ments, such combination being obvious to a person skilled document published prior to the international filing date but in the art. later than the priority date claimed document member of the same patent family IV. CERTIFICATION Date of the Actual Completion of the International Search Date of Mailing of this International Search Report 03 OCTOBER 1990 20 F-3 1991 International Searching Authority Signature of Au orized Offcer ISA/US Carmen J. Seccuro International Aoolicallon No. PCT/US90/04410 FURTHER INFORMATION .ONTINUED FROM THE SECOND SHEET I -I V.4 OBSERVATIONS WHERE CERTAIN CLAIMS WERE FOUND UNSEARCHABLE This internanional search report has not been established in resoect of certain claims under Article 17(2) for the following reasons: I Claim numoers ecause iney relate to subject i-atter reoulred to oe searched oy this Authority, namely: 2.j Claim numbers 13 because they relate to parts of the international application that do not comply with the prescribed require- meni to sucn an axtent that no meaningful international search can be carried out specifically: It is not clear whether Claim 13 calls for the use of the blend to prepare dyeable fibers or further modifies Claim 1 to includb a process step of adding a dye or .".rther defines component of Claim 1. 3J Claim numoers 8 1 because mey are depenaenr claims not drated in acco lance with me second and third sentences of PCTRule6.4(a). and 14 and VI.] OBSERVATIONSWHERE UNITY OF INVENTION IS LACKING2 I This International Searching Authority found multiple inventions in this international application as follows: .0 As all required additional search fees were timely paid by the applicant, this international search report covers all searchable claims of the international application. As only some of the required additional search fees were timclt paid by the applicant, this international search report covers only those claims of the international application for which fees were paid, specifically claims: 3.r- No required additional search fees were timely paid hy the applicant. Consequently, this international search report is restricted to the invention first mentioned in the claims; it is covered by claim numbers: 4 As all searchableclaims could be searched without ffort lustilying an andiional lee, the Internationnl Searching Authority dio not invite payment of any additional lee. Remark on Protest The additional search lees were accompanied hy applicant's protest. SNo nrotest accompanied the payment of additional search lees, Form PCTl/SA,210 (LsuLoian L s heer (Rev. 11.87)