CA2256414C - Process for producing fine fibers and fabrics thereof - Google Patents
Process for producing fine fibers and fabrics thereof Download PDFInfo
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- CA2256414C CA2256414C CA002256414A CA2256414A CA2256414C CA 2256414 C CA2256414 C CA 2256414C CA 002256414 A CA002256414 A CA 002256414A CA 2256414 A CA2256414 A CA 2256414A CA 2256414 C CA2256414 C CA 2256414C
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- fibers
- split
- filaments
- polymer
- split fibers
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Classifications
-
- D—TEXTILES; PAPER
- D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
- D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
- D04H3/00—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length
- D04H3/08—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of strengthening or consolidating
- D04H3/16—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of strengthening or consolidating with bonds between thermoplastic filaments produced in association with filament formation, e.g. immediately following extrusion
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/28—Formation of filaments, threads, or the like while mixing different spinning solutions or melts during the spinning operation; Spinnerette packs therefor
- D01D5/30—Conjugate filaments; Spinnerette packs therefor
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
- D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
- D01F8/06—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers with at least one polyolefin as constituent
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
- D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
- D01F8/12—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers with at least one polyamide as constituent
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
- D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
- D01F8/14—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers with at least one polyester as constituent
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
- Y10T442/60—Nonwoven fabric [i.e., nonwoven strand or fiber material]
- Y10T442/608—Including strand or fiber material which is of specific structural definition
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
- Y10T442/60—Nonwoven fabric [i.e., nonwoven strand or fiber material]
- Y10T442/637—Including strand or fiber material which is a monofilament composed of two or more polymeric materials in physically distinct relationship [e.g., sheath-core, side-by-side, islands-in-sea, fibrils-in-matrix, etc.] or composed of physical blend of chemically different polymeric materials or a physical blend of a polymeric material and a filler material
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
- Y10T442/60—Nonwoven fabric [i.e., nonwoven strand or fiber material]
- Y10T442/637—Including strand or fiber material which is a monofilament composed of two or more polymeric materials in physically distinct relationship [e.g., sheath-core, side-by-side, islands-in-sea, fibrils-in-matrix, etc.] or composed of physical blend of chemically different polymeric materials or a physical blend of a polymeric material and a filler material
- Y10T442/638—Side-by-side multicomponent strand or fiber material
Abstract
The disclosed invention relates to split fibers and improved means and methods for obtaining them as well as their use in nonwovens and incorporation into personal care and other products. Multicomponent filaments are formed including at least two incompatible components. These filaments are drawn under hot aqueous, for example, steam, conditions causing them to split into fibers containing the incompatible components. These fibers are collected as a fine fiber nonwoven which finds utility as a component of sanitary napkins, diapers and other products.
Description
PROCESS FOR PRODUCING FINE FIBERS AND FABRICS THEREOF
' s BACKGROUND OF THE INVENTION
The present invention is related to a process for producing fine denier fibers. More io specifically, the invention is related to a process for producing fine denier split fibers.
Nonwoven and woven fabrics containing split or fibrillated fine fibers exhibit highly desirable properties, including textural, barrier, visual and strength properties. There are different known processes for producing split fine fibers, and in general, split fibers are produced from is conjugate fibers which contain two or more incompatible polymer components or from an axially oriented film. For example, a known method for producing split fibrous structures includes the steps of forming splittable conjugate filaments into a fabric and then treating the fabric with an aqueous emulsion of benzyl alcohol or phenyl ethyl alcohol to split the conjugate filaments. Another known method has the steps of forming splittable conjugate filaments into a ao fibrous structure and then splitting the conjugate filaments by flexing or mechanically working the filaments in the dry state or in the presence of a hot aqueous solution.
Yet another commercially utilized method for producing split fine denier fibers is a needling process. In this process, conjugate fibers are hydraulically or mechanically needled to separate the different polymer components of the conjugate fibers. Further yet another method for producing fine as fibers, although it may not be a fiber splitting process, utilizes conjugate fibers that contain a solvent- or water-soluble polymer component. For example, a fibrous structure is produced from sheath-core conjugate fibers and then the fibrous structure is treated with a solvent that dissolves the sheath component to produce a fibrous structure of fine denier fibers of the core component.
Although different prior art processes, including the above described processes, for producing split or fibrillated fine denier fibers are known, each of the prior art processes suffers from one or more drawbacks including the use of chemicals, which may create disposal problems; a long fibrillation processing time; and/or a cumbersome hydraulic or mechanical fiber splitting 3 s process. Consequently, the prior art split fiber production processes are not highly economical and are not highly suitable for commercial scale productions. In addition, the prior art WO 98/01607 _ PCT/US97/10986 processes do not tend to produce uniformly split fibers and/or do not provide high levels of fiber splitting.
There remains a need for a production process that is economical and is not deleterious to the environment and that provides high levels of fiber splitting. Additionally, there remains a need for a fine fiber production process that is continuous and can be used in large commercial-scale productions.
SUMMARY OF THE INVENTION
io The present invention provides an in situ process for producing split filaments. The process contains the steps of melt spinning, such as by a spunbond process, multicomponent conjugate filaments including a plurality of distinct cross-sectional segments along their length with at least some adjacent segments being of incompatible compositions, one of which is is hydrophilic, and drawing them in the presence of a hot, aqueous split inducing medium so that segments disassociate into fine denier fibers which can be formed into nonwovens. The splittable fibers formed by such plurality of segments and nonwoven fabrics including resulting split fibers are also provided by the invention.
z o The term "steam" as used herein refers to both steam and a mixture of steam and air, unless otherwise indicated. The term "aqueous medium" as used herein indicates a liquid or gaseous medium that contains water or steam. The term "fibers" as used herein refers to both staple length fibers and continuous filaments, unless otherwise indicated. The term "spunbond fiber nonwoven fabric" refers to a nonwoven fiber fabric of small diameter filaments that are formed z 5 by extruding a molten thermoplastic polymer as filaments from a plurality of capillaries of a spinneret. The extruded filaments are cooled while being drawn by an eductive or other well-known drawing mechanism. The drawn filaments are deposited or laid onto a forming surface in a random, isotropic manner to form a loosely entangled fiber web, and then the laid fiber web is subjected to a bonding process to impart physical integrity and dimensional stability.
3 o The production of spunbond fabrics is disclosed, for example, in U.S. Pat.
Nos. 4,340,563 to Appel et al., 3,802,817 to Matsuki et al. and 3,692,618 to Dorschner et al.
Typically, spunbond fibers have a weight-per-unit-length in excess of 2 denier and up to about 6 denier or higher, although finer spunbond fibers can be produced. The term "staple fibers"
refers to discontinuous fibers, which typically have an average diameter similar to or somewhat smaller 35 than that of spunbond fibers. Staple fibers are produced with a conventional fiber spinning process and then cut to a staple length, less than about 8 inches. Such staple fibers are subsequently carded or air-laid and thermally or adhesively bonded to form a nonwoven fabric.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates one embodiment of a splitting system in accordance with the invention.
FIG. 2 illustrates a second embodiment including bonding means.
Zo DETAILED DESCRIPTION OF THE INVENTION
The present invention provides an in situ process for producing split filaments. The process has the steps of spinning splittable conjugate filaments and splitting the filaments before the split filaments are further processed, for example, into nonwoven webs, textile filaments or is staple fibers. The term "filament spinning process" as used herein indicates a conventional filament spinning process such as spunbonding that uses a spinneret and a filament drawing means to form filaments. The process includes the steps of forming filaments by passing melt-processed polymer compositions through a spinneret, cooling the filaments to substantially solidify the filaments, and then passing the cooled filaments through a drawing unit to a o attenuate the filaments and to impart molecular orientation in the polymers of the filaments.
The attenuating force can be applied mechanically, e.g., with godet rolls as in a continuous filament production process, but is preferably done pneumatically, e.g., with a pneumatic fiber drawing unit as in a spunbond filament production process. The term "substantially solidified"
as used herein indicates that at least 50% of the component polymers of the filaments are z5 solidified and the surtace temperature of the filaments is lower than the melting point (Tm) of the lowest melting component polymer. In accordance with the present invention, each of the splittable filaments contains at least two incompatible polymer component compositions, and at least one of the component compositions is hydrophilic. In addition, the component compositions are arranged to occupy distinct segments across the cross-section of the s o filament along the length thereof, and at least one segment of the fiber cross-section forms an unocclusive configuration such that the segment is not physically impeded from being separated from the filament. In accordance with the present invention, a conventional conjugate filament spinning process is modified to split the conjugate filaments of the present invention. The modification includes the step of applying a hot aqueous split-inducing medium 35 onto the filaments after the filaments are substantially solidified.
Desirably, the filaments are WO 98/01607 _ PCT/US97/10986 fully solidified before they are subjected to the split-inducing medium. The split-inducing medium is applied just prior to or during the filament drawing step.
The aqueous split-inducing media suitable for the invention include hot water, desirably hot water having a temperature of at least about 60°C. More desirably, the water has a temperature between about 65°C and 100°C. Additionally suitable media are steam and mixtures of steam and air that have a temperature higher than 60°C but lower than the melting temperature of the lowest melting polymer of the conjugate fiber. When an air and steam mixture medium is utilized, the temperature of the air that is mixed with steam can be adjusted to to change the temperature of the fibrillation-inducing medium. For example, the temperature of the air can be elevated to further increase the temperature of the steam-air mixture. The exposure to the aqueous split-inducing medium is controlled as to temperature and dwell time so as to avoid raising the temperature of the fibers above the melting point of the lowest melting component.
Turning to FIG. 1, there is illustrated a mechanically drawing continuous filament production process which has a hot aqueous split-inducing medium applying step. The split filament production apparatus 10 contains a spinneret 12 with spinning apertures through which at least two melt-processed polymer compositions are fed to form conjugate filaments 14. The z o melt-processed polymer compositions in each of the filaments 14 are arranged to occupy distinct segments across the cross-section of the filament along the length thereof. The compositions are quenched and solidified as the filaments move away from the spinneret 12.
Generally, cooling of the filaments 14 is facilitated by a transverse flow of cooling air 16 such that the filaments are substantially solidified when they reach a convergence guide 18. The z 5 filaments are then fed to a godet roll or take-up roll drawing assembly 20. Although not preferred, a godet roll assembly 20 may be used to apply a draw-down force on the filaments to draw and to impart molecular orientation in the component polymers of the filaments. Below the godet roll assembly 20, an aqueous medium injection means 22 is placed next to the drawn filaments. The injection means 22 applies an aqueous split-inducing medium onto the 3 o filaments such that the filaments are thoroughly contacted with the medium while under a drawing force and the segments of the filament split into split filaments. The split filaments are then processed further into yarns, staple fibers, tows and the like. The split-inducing medium supplied from the injection means 22 can be, for example, steam, a mixture of steam and air, or hot water.
_ WO 98/01607 - _ PCT/US97/10986 FIG. 2 illustrates a pneumatically draw filament production process modified with a hot aqueous split-inducing medium applying step. More specifically, Figure 2 illustrates a spunbond nonwoven web production process that applies the split-inducing medium white applying the drawing force. The process uses a spinneret filament production apparatus 42 s similar to the above-described continuous filament production apparatus.
However, the spunbond apparatus uses a pneumatic drawing unit 30, instead of the godet rolls. Generally described, the pneumatic drawing unit 30 has an elongated vertical passage through which the filaments are passed. In the vertical passage, drawing force is applied to the filaments by a high speed flow of drawing fluid 32, e.g., air, entering from the sides of the passage and to flowing downwardly through the passage. Suitable pneumatic drawing units for spunbond apparatus are disclosed, for example, in U.S. Pat. Nos. 3,692,618 to Dorschner et al., 4,340,5fi3 to Appei, et al. and 3,802,817 to Matsuki et al. In accordance with the present embodiment of the invention, the filament drawing air and the split-inducing medium are simultaneously applied through the pneumatic drawing unit 30, thereby drawing and splitting is the conjugate filaments simultaneously. The drawing air and the split-inducing medium can be supplied as a mixture, or a split-inducing medium can used as both the drawing air and the split-inducing medium.
The drawn, split filaments exiting the pneumatic unit 30 can be directly deposited on a forming s o surface 34 in random fashion to form a nonwoven web 36. The nonwoven web is then bonded using a conventional bonding process suitable for spunbond webs, e.g., calender bonding process, point bonding process and ultrasonic bonding process, to impart strength properties and physical integrity in the web. Additionally, a through-air bonding process can be utilized.
Figure 2 further illustrates an exemplary bonding process - a pattern bonding process. The 2s pattern bonding process employs at least two adjacently placed pattern bonding rolls 38, 40 for imparting bond points or regions at limited areas of the web by passing the web through the nip formed by the bonding rolls 38, 40. One or both of the roll pair may have a pattern of land areas and depressions on the surface and may be heated to an appropriate temperature.
3 o The bonding roll temperature and the nip pressure are selected so as to effect bonded regions without having undesirable accompanying side effects such as excessive shrinkage and web degradation. Although appropriate roll temperatures and nip pressures are generally influenced by parameters such as web speed, web basis weight, fiber characteristics, component polymers and the like, the roll temperature desirably is in the range between the 35 softening point and the crystalline melting point of the lowest melting component polymer. For example, desirable settings for bonding a fiber web that contains split polypropylene fibers, e.g., a web of polypropylene and polyamide split fibers, are a roll temperature in the range of about 125°C anc~a~bout 160°C and a pin pressure on the fabric in the range of about 350 kglcm2 and about 3,500 kg/cm2. Other exemplary bonding processes suitable for the present split fiber web are through-air bonding processes if the conjugate filaments are produced from s component compositions having different melting points. A typical through-air bonding process applies a flow of heated air onto the split fiber web to raise the temperature of the web to a level higher than the matting point of the lowest melting polymer of the web but below the melting point of the highest melting polymer of the web. A through-air bonding process may be employed so as not to apply any signficant compacting pressure and, thus, is highly io suitable for produdng a lofty bonded fabric particularly if the fibers are.crimped.
As another embodiment of the invention, the pneumatic drawing unit of a spunbond process can also be used to impart crimps in the filaments in addition to drawing and splitting the filaments if the component polymers for the conjugate filaments are selected from polymers zs having different themiai shrtnkage propert'es. When conjugate filaments are produced from polymers having different shrinkage properties, they form~latent crimpability.
The latent erimpability can be activated by utilizing heated drawing air or steam in the pneumatic drawing unit. The appropriate temperature of drawing air will vary depending on the selected component polymers. In general, a higher temperature produces a higher level of crimp, 2o provided that the fluid temperature is not so high as to melt the component polymers. U.S. Pat.
No. 5,382,400 to Pike et al. discloses a suitable process for produdng conjugate fibers and webs produced therefrom.
In accordance with the present invention, the splittable conjugate filaments can be 2s characterized in that at least one of the component polymer compositions of the conjugate filament is preferably hydrophilic. Hydrophilic polymers suitable for the present conjugate filament component compositions include both hydrophilic polymers and hydrophilicaliy modfied polymers. When hydrophobic or insufficiently hydrophilic polymers are utilized, at least one of the polymers needs to be hydrophilically modified. Desirably, the hydrophilic s o polymer component has an initial contact angle equal to or less than about 80°, more desirably equal to or less than about 75°, even more desirably equal to or less than about 80°, most desirably equal to or less than about 50°. The hydrophilicity of the hydrophilic component polymer can be measured in accordance with the ASTM D724-89 contact angle testing procedure on a elm produced by melt casting the polymer at the temperature of the spin pack 35 that is used to produce the conjugate filaments. The term "initial contact angle" as used herein indicates a contact angle measurement made within about 5 seconds of the application of water drops on west film specimen.
Inherently hydrophilic polymers suitable for the present invention include thermoplastic -polymers having the above-specified hydrophilicity. Such polymers include copolymers of caprolactam and alkyiene oxide diamine; e.g.; Hydrofil~ nylons, which are commercially available from Allied-Signal Inc.; copolymers of poly(oxyethylene) and polyurethane, polyamide, polyester or polyurea, e.g., absorbent thermoplastic polymers disclosed in U.S.
Pat. No. 4,767,825 to Pazos et al.; ethylene vinyl alcohol copolymers; and the like. U.S. Pat.
io No.4,767,825.
Hydrophilically modifiable polymers suitable for the present invention include polyoleflns, polyesters, polyamides, polycarbonates and copolymers and blends thereof.
Suitable polyolefins include polyethylene, e.g., high density polyethylene, medium density polyethylene, is low density polyethylene and linear low density polyethylene;
polypropylene, e.g., 'ssotactic polypropylene; syndiotactic polypropylene; blends of isotactic polypropylene and atadic polypropylene, and blends thereof; polybutylene; e.g., poly(1-butane) and poly(2-butane);
polypentene, e.g., pofy(1-pentane) and poiy(2-pentane); poly(3-methyl-1-pentane); poly(4-:
methyl-1-pentane); and copolymers and blends thereof. Suitable copolymers include random a o and block copolyrriers prepared from two or more different unsaturated olefin monomers, such as ethylenelpropylene and ethylenelbutylene copolymers. Suitable polyamides include nylon 6, nylon 6/6, nylon 4/6; nylon 11, nylon 12, nylon 6110, nylon S/12, nylon 12112, copolymers of caprolactam and alkylene oxide diamine, and the like, as well as blends and copolymers thereof. Suitable polyesters include polyethylene terephthalate, poiybutylene terephthalate, as polytetramethyiene terephthalate, pofycyclohexylene-1,4-dimethylene terephthalate, and isophthalate copolymers thereof, as well as blends thereof.
In accordance with the present invention, whena hydrophobic or insufficiently hydrophilic polymer is selected as the hydrophilic component of the splittable conjugate fiber, the polymer 3 o must be hydrophilically or wettably modified. One useful means for modifying the polymer is adding a hydrophilic modifying agent or hydrophilic modifier that renders the polymer hydrophilic. Suitable hydrophilic modifies include various surfactants.
Depending on the final use of the split fiber material; the surfactants can be fugitive or nonfugitive. Fugitive surfactants, i.e.; surfactants that wash off from the fiber surface, are suitable if the split fibers 3 s are used in single exposure applications or applications in which nonwettable or hydrophobic properties are desired, and nonfugitive surfactants; i:e., surFactants that permanently or semipermanentty adhere to the fiber surface, are suitable if the split fibers are used in applications in which more durably wettable or hydrophilic properties are desired. In addition, particularly suitable internally added surfactants are selected to have a low compatibility with the polymer of the hydrophilic component of the fiber since such surfactants readily migrate to s the surface of the fiber during the tuber spinning process. When a surfactant having a slow migration characteristic is utilized, the fibers may need to be heat treated or annealed to facilitate the migration of the surtactant to the surface: Such heat treatment is known in the art as a "blooming" process. Illustrative examples of suitable surfactants include silicon based surfactants, e.g., polyalkyfene-oxide modifted polydimethyl siloxane;
fluoroaliphatic surfactants, zo e.g., perfluoroalkyl polyatkylene oxides; and other surfactants, e.g., actyl-phenoxypolyethyoxy ethanol nonionic surfactants, alkyiaryl polyether alcohols; and polyethylene oxides.
Commercially available surfactants suitable for the present invention inGude various poly(ethytene oxide) based surtactants available under the trade-mark Triton~, e.g., grade.X-102, from Rohm and Haas Corp.; various polyethylene glycol based surfactants available is under the trade-mark:Emerest~, e.g., grades 2620 arid 2650, from Emery Industries; various polyaikylene oxide modified potydimethyisiloxane based urfactants available under the trade-mark .Masil~, e.g., SF-19, which is available from Mazer; polyalkylene oxide fatty acid derivatives available under the trade-mark PEG~, e.g. PEG 400, which is available from ICI;
sorbitan monooieate, e.g., Span 80, which is available from ICI; ethoxylated hydroxylated Tnn a o castor oil, e:g., G ~ 292; which is available from iCl; a mixture of sorbitan monooleate and ethoxylated hydroxylated castor oil, e.g:, Ahcovel~? Base N62, which is available from lCl;
polyoxyalkylene modfied ~uoroatiphatic surfactants which are available, e.g., from Minnesota Mining and Manufacturing Co.; and mixtures thereof:
' s BACKGROUND OF THE INVENTION
The present invention is related to a process for producing fine denier fibers. More io specifically, the invention is related to a process for producing fine denier split fibers.
Nonwoven and woven fabrics containing split or fibrillated fine fibers exhibit highly desirable properties, including textural, barrier, visual and strength properties. There are different known processes for producing split fine fibers, and in general, split fibers are produced from is conjugate fibers which contain two or more incompatible polymer components or from an axially oriented film. For example, a known method for producing split fibrous structures includes the steps of forming splittable conjugate filaments into a fabric and then treating the fabric with an aqueous emulsion of benzyl alcohol or phenyl ethyl alcohol to split the conjugate filaments. Another known method has the steps of forming splittable conjugate filaments into a ao fibrous structure and then splitting the conjugate filaments by flexing or mechanically working the filaments in the dry state or in the presence of a hot aqueous solution.
Yet another commercially utilized method for producing split fine denier fibers is a needling process. In this process, conjugate fibers are hydraulically or mechanically needled to separate the different polymer components of the conjugate fibers. Further yet another method for producing fine as fibers, although it may not be a fiber splitting process, utilizes conjugate fibers that contain a solvent- or water-soluble polymer component. For example, a fibrous structure is produced from sheath-core conjugate fibers and then the fibrous structure is treated with a solvent that dissolves the sheath component to produce a fibrous structure of fine denier fibers of the core component.
Although different prior art processes, including the above described processes, for producing split or fibrillated fine denier fibers are known, each of the prior art processes suffers from one or more drawbacks including the use of chemicals, which may create disposal problems; a long fibrillation processing time; and/or a cumbersome hydraulic or mechanical fiber splitting 3 s process. Consequently, the prior art split fiber production processes are not highly economical and are not highly suitable for commercial scale productions. In addition, the prior art WO 98/01607 _ PCT/US97/10986 processes do not tend to produce uniformly split fibers and/or do not provide high levels of fiber splitting.
There remains a need for a production process that is economical and is not deleterious to the environment and that provides high levels of fiber splitting. Additionally, there remains a need for a fine fiber production process that is continuous and can be used in large commercial-scale productions.
SUMMARY OF THE INVENTION
io The present invention provides an in situ process for producing split filaments. The process contains the steps of melt spinning, such as by a spunbond process, multicomponent conjugate filaments including a plurality of distinct cross-sectional segments along their length with at least some adjacent segments being of incompatible compositions, one of which is is hydrophilic, and drawing them in the presence of a hot, aqueous split inducing medium so that segments disassociate into fine denier fibers which can be formed into nonwovens. The splittable fibers formed by such plurality of segments and nonwoven fabrics including resulting split fibers are also provided by the invention.
z o The term "steam" as used herein refers to both steam and a mixture of steam and air, unless otherwise indicated. The term "aqueous medium" as used herein indicates a liquid or gaseous medium that contains water or steam. The term "fibers" as used herein refers to both staple length fibers and continuous filaments, unless otherwise indicated. The term "spunbond fiber nonwoven fabric" refers to a nonwoven fiber fabric of small diameter filaments that are formed z 5 by extruding a molten thermoplastic polymer as filaments from a plurality of capillaries of a spinneret. The extruded filaments are cooled while being drawn by an eductive or other well-known drawing mechanism. The drawn filaments are deposited or laid onto a forming surface in a random, isotropic manner to form a loosely entangled fiber web, and then the laid fiber web is subjected to a bonding process to impart physical integrity and dimensional stability.
3 o The production of spunbond fabrics is disclosed, for example, in U.S. Pat.
Nos. 4,340,563 to Appel et al., 3,802,817 to Matsuki et al. and 3,692,618 to Dorschner et al.
Typically, spunbond fibers have a weight-per-unit-length in excess of 2 denier and up to about 6 denier or higher, although finer spunbond fibers can be produced. The term "staple fibers"
refers to discontinuous fibers, which typically have an average diameter similar to or somewhat smaller 35 than that of spunbond fibers. Staple fibers are produced with a conventional fiber spinning process and then cut to a staple length, less than about 8 inches. Such staple fibers are subsequently carded or air-laid and thermally or adhesively bonded to form a nonwoven fabric.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates one embodiment of a splitting system in accordance with the invention.
FIG. 2 illustrates a second embodiment including bonding means.
Zo DETAILED DESCRIPTION OF THE INVENTION
The present invention provides an in situ process for producing split filaments. The process has the steps of spinning splittable conjugate filaments and splitting the filaments before the split filaments are further processed, for example, into nonwoven webs, textile filaments or is staple fibers. The term "filament spinning process" as used herein indicates a conventional filament spinning process such as spunbonding that uses a spinneret and a filament drawing means to form filaments. The process includes the steps of forming filaments by passing melt-processed polymer compositions through a spinneret, cooling the filaments to substantially solidify the filaments, and then passing the cooled filaments through a drawing unit to a o attenuate the filaments and to impart molecular orientation in the polymers of the filaments.
The attenuating force can be applied mechanically, e.g., with godet rolls as in a continuous filament production process, but is preferably done pneumatically, e.g., with a pneumatic fiber drawing unit as in a spunbond filament production process. The term "substantially solidified"
as used herein indicates that at least 50% of the component polymers of the filaments are z5 solidified and the surtace temperature of the filaments is lower than the melting point (Tm) of the lowest melting component polymer. In accordance with the present invention, each of the splittable filaments contains at least two incompatible polymer component compositions, and at least one of the component compositions is hydrophilic. In addition, the component compositions are arranged to occupy distinct segments across the cross-section of the s o filament along the length thereof, and at least one segment of the fiber cross-section forms an unocclusive configuration such that the segment is not physically impeded from being separated from the filament. In accordance with the present invention, a conventional conjugate filament spinning process is modified to split the conjugate filaments of the present invention. The modification includes the step of applying a hot aqueous split-inducing medium 35 onto the filaments after the filaments are substantially solidified.
Desirably, the filaments are WO 98/01607 _ PCT/US97/10986 fully solidified before they are subjected to the split-inducing medium. The split-inducing medium is applied just prior to or during the filament drawing step.
The aqueous split-inducing media suitable for the invention include hot water, desirably hot water having a temperature of at least about 60°C. More desirably, the water has a temperature between about 65°C and 100°C. Additionally suitable media are steam and mixtures of steam and air that have a temperature higher than 60°C but lower than the melting temperature of the lowest melting polymer of the conjugate fiber. When an air and steam mixture medium is utilized, the temperature of the air that is mixed with steam can be adjusted to to change the temperature of the fibrillation-inducing medium. For example, the temperature of the air can be elevated to further increase the temperature of the steam-air mixture. The exposure to the aqueous split-inducing medium is controlled as to temperature and dwell time so as to avoid raising the temperature of the fibers above the melting point of the lowest melting component.
Turning to FIG. 1, there is illustrated a mechanically drawing continuous filament production process which has a hot aqueous split-inducing medium applying step. The split filament production apparatus 10 contains a spinneret 12 with spinning apertures through which at least two melt-processed polymer compositions are fed to form conjugate filaments 14. The z o melt-processed polymer compositions in each of the filaments 14 are arranged to occupy distinct segments across the cross-section of the filament along the length thereof. The compositions are quenched and solidified as the filaments move away from the spinneret 12.
Generally, cooling of the filaments 14 is facilitated by a transverse flow of cooling air 16 such that the filaments are substantially solidified when they reach a convergence guide 18. The z 5 filaments are then fed to a godet roll or take-up roll drawing assembly 20. Although not preferred, a godet roll assembly 20 may be used to apply a draw-down force on the filaments to draw and to impart molecular orientation in the component polymers of the filaments. Below the godet roll assembly 20, an aqueous medium injection means 22 is placed next to the drawn filaments. The injection means 22 applies an aqueous split-inducing medium onto the 3 o filaments such that the filaments are thoroughly contacted with the medium while under a drawing force and the segments of the filament split into split filaments. The split filaments are then processed further into yarns, staple fibers, tows and the like. The split-inducing medium supplied from the injection means 22 can be, for example, steam, a mixture of steam and air, or hot water.
_ WO 98/01607 - _ PCT/US97/10986 FIG. 2 illustrates a pneumatically draw filament production process modified with a hot aqueous split-inducing medium applying step. More specifically, Figure 2 illustrates a spunbond nonwoven web production process that applies the split-inducing medium white applying the drawing force. The process uses a spinneret filament production apparatus 42 s similar to the above-described continuous filament production apparatus.
However, the spunbond apparatus uses a pneumatic drawing unit 30, instead of the godet rolls. Generally described, the pneumatic drawing unit 30 has an elongated vertical passage through which the filaments are passed. In the vertical passage, drawing force is applied to the filaments by a high speed flow of drawing fluid 32, e.g., air, entering from the sides of the passage and to flowing downwardly through the passage. Suitable pneumatic drawing units for spunbond apparatus are disclosed, for example, in U.S. Pat. Nos. 3,692,618 to Dorschner et al., 4,340,5fi3 to Appei, et al. and 3,802,817 to Matsuki et al. In accordance with the present embodiment of the invention, the filament drawing air and the split-inducing medium are simultaneously applied through the pneumatic drawing unit 30, thereby drawing and splitting is the conjugate filaments simultaneously. The drawing air and the split-inducing medium can be supplied as a mixture, or a split-inducing medium can used as both the drawing air and the split-inducing medium.
The drawn, split filaments exiting the pneumatic unit 30 can be directly deposited on a forming s o surface 34 in random fashion to form a nonwoven web 36. The nonwoven web is then bonded using a conventional bonding process suitable for spunbond webs, e.g., calender bonding process, point bonding process and ultrasonic bonding process, to impart strength properties and physical integrity in the web. Additionally, a through-air bonding process can be utilized.
Figure 2 further illustrates an exemplary bonding process - a pattern bonding process. The 2s pattern bonding process employs at least two adjacently placed pattern bonding rolls 38, 40 for imparting bond points or regions at limited areas of the web by passing the web through the nip formed by the bonding rolls 38, 40. One or both of the roll pair may have a pattern of land areas and depressions on the surface and may be heated to an appropriate temperature.
3 o The bonding roll temperature and the nip pressure are selected so as to effect bonded regions without having undesirable accompanying side effects such as excessive shrinkage and web degradation. Although appropriate roll temperatures and nip pressures are generally influenced by parameters such as web speed, web basis weight, fiber characteristics, component polymers and the like, the roll temperature desirably is in the range between the 35 softening point and the crystalline melting point of the lowest melting component polymer. For example, desirable settings for bonding a fiber web that contains split polypropylene fibers, e.g., a web of polypropylene and polyamide split fibers, are a roll temperature in the range of about 125°C anc~a~bout 160°C and a pin pressure on the fabric in the range of about 350 kglcm2 and about 3,500 kg/cm2. Other exemplary bonding processes suitable for the present split fiber web are through-air bonding processes if the conjugate filaments are produced from s component compositions having different melting points. A typical through-air bonding process applies a flow of heated air onto the split fiber web to raise the temperature of the web to a level higher than the matting point of the lowest melting polymer of the web but below the melting point of the highest melting polymer of the web. A through-air bonding process may be employed so as not to apply any signficant compacting pressure and, thus, is highly io suitable for produdng a lofty bonded fabric particularly if the fibers are.crimped.
As another embodiment of the invention, the pneumatic drawing unit of a spunbond process can also be used to impart crimps in the filaments in addition to drawing and splitting the filaments if the component polymers for the conjugate filaments are selected from polymers zs having different themiai shrtnkage propert'es. When conjugate filaments are produced from polymers having different shrinkage properties, they form~latent crimpability.
The latent erimpability can be activated by utilizing heated drawing air or steam in the pneumatic drawing unit. The appropriate temperature of drawing air will vary depending on the selected component polymers. In general, a higher temperature produces a higher level of crimp, 2o provided that the fluid temperature is not so high as to melt the component polymers. U.S. Pat.
No. 5,382,400 to Pike et al. discloses a suitable process for produdng conjugate fibers and webs produced therefrom.
In accordance with the present invention, the splittable conjugate filaments can be 2s characterized in that at least one of the component polymer compositions of the conjugate filament is preferably hydrophilic. Hydrophilic polymers suitable for the present conjugate filament component compositions include both hydrophilic polymers and hydrophilicaliy modfied polymers. When hydrophobic or insufficiently hydrophilic polymers are utilized, at least one of the polymers needs to be hydrophilically modified. Desirably, the hydrophilic s o polymer component has an initial contact angle equal to or less than about 80°, more desirably equal to or less than about 75°, even more desirably equal to or less than about 80°, most desirably equal to or less than about 50°. The hydrophilicity of the hydrophilic component polymer can be measured in accordance with the ASTM D724-89 contact angle testing procedure on a elm produced by melt casting the polymer at the temperature of the spin pack 35 that is used to produce the conjugate filaments. The term "initial contact angle" as used herein indicates a contact angle measurement made within about 5 seconds of the application of water drops on west film specimen.
Inherently hydrophilic polymers suitable for the present invention include thermoplastic -polymers having the above-specified hydrophilicity. Such polymers include copolymers of caprolactam and alkyiene oxide diamine; e.g.; Hydrofil~ nylons, which are commercially available from Allied-Signal Inc.; copolymers of poly(oxyethylene) and polyurethane, polyamide, polyester or polyurea, e.g., absorbent thermoplastic polymers disclosed in U.S.
Pat. No. 4,767,825 to Pazos et al.; ethylene vinyl alcohol copolymers; and the like. U.S. Pat.
io No.4,767,825.
Hydrophilically modifiable polymers suitable for the present invention include polyoleflns, polyesters, polyamides, polycarbonates and copolymers and blends thereof.
Suitable polyolefins include polyethylene, e.g., high density polyethylene, medium density polyethylene, is low density polyethylene and linear low density polyethylene;
polypropylene, e.g., 'ssotactic polypropylene; syndiotactic polypropylene; blends of isotactic polypropylene and atadic polypropylene, and blends thereof; polybutylene; e.g., poly(1-butane) and poly(2-butane);
polypentene, e.g., pofy(1-pentane) and poiy(2-pentane); poly(3-methyl-1-pentane); poly(4-:
methyl-1-pentane); and copolymers and blends thereof. Suitable copolymers include random a o and block copolyrriers prepared from two or more different unsaturated olefin monomers, such as ethylenelpropylene and ethylenelbutylene copolymers. Suitable polyamides include nylon 6, nylon 6/6, nylon 4/6; nylon 11, nylon 12, nylon 6110, nylon S/12, nylon 12112, copolymers of caprolactam and alkylene oxide diamine, and the like, as well as blends and copolymers thereof. Suitable polyesters include polyethylene terephthalate, poiybutylene terephthalate, as polytetramethyiene terephthalate, pofycyclohexylene-1,4-dimethylene terephthalate, and isophthalate copolymers thereof, as well as blends thereof.
In accordance with the present invention, whena hydrophobic or insufficiently hydrophilic polymer is selected as the hydrophilic component of the splittable conjugate fiber, the polymer 3 o must be hydrophilically or wettably modified. One useful means for modifying the polymer is adding a hydrophilic modifying agent or hydrophilic modifier that renders the polymer hydrophilic. Suitable hydrophilic modifies include various surfactants.
Depending on the final use of the split fiber material; the surfactants can be fugitive or nonfugitive. Fugitive surfactants, i.e.; surfactants that wash off from the fiber surface, are suitable if the split fibers 3 s are used in single exposure applications or applications in which nonwettable or hydrophobic properties are desired, and nonfugitive surfactants; i:e., surFactants that permanently or semipermanentty adhere to the fiber surface, are suitable if the split fibers are used in applications in which more durably wettable or hydrophilic properties are desired. In addition, particularly suitable internally added surfactants are selected to have a low compatibility with the polymer of the hydrophilic component of the fiber since such surfactants readily migrate to s the surface of the fiber during the tuber spinning process. When a surfactant having a slow migration characteristic is utilized, the fibers may need to be heat treated or annealed to facilitate the migration of the surtactant to the surface: Such heat treatment is known in the art as a "blooming" process. Illustrative examples of suitable surfactants include silicon based surfactants, e.g., polyalkyfene-oxide modifted polydimethyl siloxane;
fluoroaliphatic surfactants, zo e.g., perfluoroalkyl polyatkylene oxides; and other surfactants, e.g., actyl-phenoxypolyethyoxy ethanol nonionic surfactants, alkyiaryl polyether alcohols; and polyethylene oxides.
Commercially available surfactants suitable for the present invention inGude various poly(ethytene oxide) based surtactants available under the trade-mark Triton~, e.g., grade.X-102, from Rohm and Haas Corp.; various polyethylene glycol based surfactants available is under the trade-mark:Emerest~, e.g., grades 2620 arid 2650, from Emery Industries; various polyaikylene oxide modified potydimethyisiloxane based urfactants available under the trade-mark .Masil~, e.g., SF-19, which is available from Mazer; polyalkylene oxide fatty acid derivatives available under the trade-mark PEG~, e.g. PEG 400, which is available from ICI;
sorbitan monooieate, e.g., Span 80, which is available from ICI; ethoxylated hydroxylated Tnn a o castor oil, e:g., G ~ 292; which is available from iCl; a mixture of sorbitan monooleate and ethoxylated hydroxylated castor oil, e.g:, Ahcovel~? Base N62, which is available from lCl;
polyoxyalkylene modfied ~uoroatiphatic surfactants which are available, e.g., from Minnesota Mining and Manufacturing Co.; and mixtures thereof:
2 s The amount of surtactants required and the hydrophilicity of modified filaments for each application will vary depending on the type of surFactant and the type of polymer used: In general, filaments containing more hydrophilic or hydrophilically modified polymer components result in more spontaneous splitting. Consequently, a high level of a surfactant can be added to the polymer composition of the conjugate fibers provided that he surfactant level is not too 3 o high as to adversely affect he processibility of the polymer composition.
Typically, the amount of the surfactant suitable for the present fiber composition i5 in the range of from about Q.1 % to about 5%, desirably from about 0.3°t° to about 4°I°, by weight based on the weight of the polymer composition. The surfactant is thoroughly blended with the polymer composition before the composition is processed into filaments. For example, when a melt-extrusion 3 5 process far producing filaments is utilized, the surfactant is blended and melt-extruded with the polymer compositions in extruders and then spun into ftlaments.
a _ WO 98/01607 _ _ PCT/US97/10986 In accordance with the present invention, additional component polymers for the conjugate filaments are selected from hydrophilic and hydrophobic thermoplastic polymers that are incompatible with the hydrophilic component polymer of the conjugate fibers.
Suitable s polymers include the above illustrated hydrophilic polymers and hydrophobic polymers that are suitable for the hydrophilic component, provided that they are incompatible with the hydrophilic component polymer.
The term "incompatible polymers" as used herein indicates polymers that do not form or stay so as a miscible blend, i.e., immiscible, when melt blended. As a desirable embodiment of the present invention, differences in the polymer solubility parameter (8) are used to select suitably incompatible polymers. The polymer solubility parameters (8) of different polymers are well known in the art. A discussion of the solubility parameter is, for example, disclosed in Polymer:
Chemistry and Physics of Modern Materials, pages 142-145, by JMG Cowie, International i5 Textbook Co., Ltd., 1973. Desirably, the adjacently disposed polymer components of the present conjugate fiber have a difference in the solubility parameter of at least about 0.5 (cal/cm3)"~, more desirably at least about 1 (cal/cm3)"z, most desirably at least about 2 (cal/cm3)"z. The upper limit of the solubility parameter difference is not critical for the present invention since the higher the difference, the more spontaneous the splitting of the filament z o becomes.
Illustrative examples of particularly desirable pairs of incompatible polymers useful for the present invention include polyolefin-polyamide, e.g., polyethylene-nylon 6, polyethylene-nylon 6/6, polypropylene-nylon 6, polypropylene-nylon 6/6, polyethylene-a copolymer of caprolactam a5 and alkylene oxide diamine, and polypropylene -a copolymer of caprolactam and alkylene oxide diamine; polyoiefin-polyester, e.g., polyethylene-polyethylene terephthalate, polypropylene-polyethylene terephthalate, polyethylene-polybutylene terephthalate and polypropylene-polybutylene terephthalate; and polyamide-polyester, e.g., nylon 6-polyethylene terephthalate, nylon 6/6-polyethylene terephthalate, nylon 6-polybutylene terephthalate, nylon 3 0 6/6-polybutylene terephthalate, polyethylene terephthalate-a copolymer of caprolactam and alkylene oxide diamine, and polybutylene terephthalate-a copolymer of caprolactam and alkylene oxide diamine.
Fabrics or webs containing the present split filaments or staple fibers provide a combination of 35 desirable textural properties of conventional microfiber fabrics and desirable strength properties of highly oriented fiber fabrics. Especially with spunbond processes the split fiber WO 98/01607 _ PCT/US97/10986 fabric obtained by splitting prior to web forming exhibits desirable properties, such as uniformity of the fabric, uniform fiber coverage, barrier properties and high fiber surface area, that are akin to microfiber fabrics. in addition, unlike microfiber fabrics such as meltblown webs, the split fiber fabric also exhibits highly desirable strength properties, desirable hand and softness and can be produced to have different levels of loft. Many uses will be apparent, such as filter media, sorbent products, geotextiles, housewrap, synthetic paper, barrier and breathable barrier fabrics for personal care products and the like.
Furthermore, the present split fiber production process is highly advantageous over prior art io split fiber production processes. The present process is a flexible, noncompacting process that can be used to produce split fiber fabrics having a wide variety of loft and density. Unlike prior art needling processes for splitting fibers that inherently compact the precursor web, the present process does not apply compacting forces to split conjugate fibers.
Accordingly, the present process does not alter the loft of the precursor fiber web or fabric during the fiber i5 splitting process. In addition, the present process does not sacrifice the strength properties of the precursor fiber web. Unlike prior art solvent dissolving processes for producing fine fibers, the present process retains all of the polymeric components of the precursor conjugate fibers during the fiber splitting process. Consequently, the present process at least retains or even improves strength properties of the precursor web. This is because the present process a o retains the polymeric components of the precursor web while increasing the number of fiber strands, and because, as is known the art, a fabric having a higher number of fiber strands and thus having finer fibers is stronger than a coarse fiber fabric of the same polymer, the same basis weight and a similar level of molecular orientation and binding.
a s Fabrics containing the split fine fibers that exhibit the above-illustrated desirable properties are highly suitable for various uses as mentioned. For example, nonwoven fabrics containing the split fine fibers are highly suitable for various additional uses including disposable articles, e.g., protective garments, sterilization wraps, wiper cloths and covers for absorbent articles; and woven fabrics containing the split fine fibers that exhibit highly improved softness and s o uniformity are highly useful for soft apparels, dusting and wiper cloths and the like.
As another embodiment of the present invention, the soft, strong fine fiber fabric may be used as a laminate that contains at least one layer of the fine fiber fabric and at least one additional layer of another woven or nonwoven fabric or a film. The additional layer for the laminate is 3 s selected to impart additional and/or complementary properties, such as liquid andlor microbe barrier properties. The layers of the laminate can be bonded to form a unitary structure by a io ..onding process known in the art to t~ ~uifable for laminate structures, such as a thermal, ultrasonic or adhesive process.
A laminate structure highly suitable for the present invention is disclosed in U.S. Pat. No.
4,041,203 to l3rock et at. In adapting s the disclosure of U.S. Pat. No. 4,041;203, a pattern bonded laminate of at least one split continuous filament nonwoven web, e.g., split spunbond conjugate fiber web, and at feast one microfiber nonwoven web, e.g:, meitblowrt web; can be produced; and such laminate combines the strength and softness of the split fiber fabric and the breathable barrier properties of the micxofiber web. Alternatively, a breathable film can be Laminated to the fine i o f ber web to provide a breathable barrier laminate that exhibits a desirable combination of usefut properties, such as soft texture, strength and banter properties. As yet another embodiment of the present invention, the fine fiber fabric can be laminated to a non-breathable film to provide a strong, high bonier laminate having a Both-tike texture.
These laminate structures provide desirable Goth-like textural properties; improved strength properties and i5 high barrier properties. The laminate structures, consequently, are highly suitable for various uses including various skin-contacting applications, such as protective garments, covers for diapers, adult care products, training pants and sanitary napkins, various drapes, and the like.
'The following example is provided for illustration purposes and the invention is not limited 2 o thereto:
Example Hydrophilic modifying agent used:
TM
2s SF-19-ethoxylated polysiloxane, which is available from Mazer: SF-19 exhibited a contact angle of about 0°:
Testing Procedure:
~ o Contact Angle -measured in accordance with ASTM D724-89 using a 0.05 mm cast frlm produced from F~ocon's 3445 Polypropylene:
EXAMPLE 1 - - __ Crimped conjugate spunbond filarfients having a parent o~ initial denier of about 2 and including 50% by weight linear law density polyethylene and 54% by weight nylon 6 and s having a side-by-side configuration were produced. The linear low density polyethylene (LLDPE) was Dow Chem'ecal's LLDPE 6811A, and the nylon 6 used was custom polymerized polycaprolactam, which was produced by Nyltech, NH, and had a formic acid relative viscosity of 1.85. LLDPE was blended with 2°!o by weight of TiOz concentrate containing 50% by weight TiOZ and 50°~ by weight of potypropytene, and the mixture was fed into a first single saew to extruder. In addition, 2% by weight of SF-19 surfactant, as indicated in Table 1, was blended with the LLDPE composition before the composition was fed into the extruders.
The composition for Example 1 is shown in Table 1. The melt temperature of the LLDPE extrudate was about 232°C, and the melt temperature of the nylon 6 ex#rudate was about 232°C.
Is The extruded polymers were fed to a bicomponent spinning die and spun into round bicomponent fbers in accordance with the bicornponent spunbond fiber production process disclosed in afore-mentioned U.S. Patent 5,382,400. The bioomponent spinning die had a 0.6 mm spinhole diameter and a 4:1 UD raft. The spinhole throughput rate was 0.5 gramlhote/minute. The spinning die was maintained at 232°C. The bicomponent filaments ao exiting the spinning die were quenched by a flow of air having a flow rate of 0.5 m3lmin.lcm spinneret width and a temperature of 18°C. The quenching air was applied about 5 inches (about 12.7 cm) below the spinneret, and the quenched fibers were drawn in an aspirating unity of the ype which is described in U.S. Patent 3;802,817 to Matsukt et at. The quenched filaments were drawn with the flow of a 50:50 mixture of air and steam, which was heated to z 5 about 93°C, in the aspirating unit to attain crimped filaments of about 1 denier after splitting.
The drawn filaments were deposited onto a foraminous forming surface, forming a lofty weh of filaments.
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Typically, the amount of the surfactant suitable for the present fiber composition i5 in the range of from about Q.1 % to about 5%, desirably from about 0.3°t° to about 4°I°, by weight based on the weight of the polymer composition. The surfactant is thoroughly blended with the polymer composition before the composition is processed into filaments. For example, when a melt-extrusion 3 5 process far producing filaments is utilized, the surfactant is blended and melt-extruded with the polymer compositions in extruders and then spun into ftlaments.
a _ WO 98/01607 _ _ PCT/US97/10986 In accordance with the present invention, additional component polymers for the conjugate filaments are selected from hydrophilic and hydrophobic thermoplastic polymers that are incompatible with the hydrophilic component polymer of the conjugate fibers.
Suitable s polymers include the above illustrated hydrophilic polymers and hydrophobic polymers that are suitable for the hydrophilic component, provided that they are incompatible with the hydrophilic component polymer.
The term "incompatible polymers" as used herein indicates polymers that do not form or stay so as a miscible blend, i.e., immiscible, when melt blended. As a desirable embodiment of the present invention, differences in the polymer solubility parameter (8) are used to select suitably incompatible polymers. The polymer solubility parameters (8) of different polymers are well known in the art. A discussion of the solubility parameter is, for example, disclosed in Polymer:
Chemistry and Physics of Modern Materials, pages 142-145, by JMG Cowie, International i5 Textbook Co., Ltd., 1973. Desirably, the adjacently disposed polymer components of the present conjugate fiber have a difference in the solubility parameter of at least about 0.5 (cal/cm3)"~, more desirably at least about 1 (cal/cm3)"z, most desirably at least about 2 (cal/cm3)"z. The upper limit of the solubility parameter difference is not critical for the present invention since the higher the difference, the more spontaneous the splitting of the filament z o becomes.
Illustrative examples of particularly desirable pairs of incompatible polymers useful for the present invention include polyolefin-polyamide, e.g., polyethylene-nylon 6, polyethylene-nylon 6/6, polypropylene-nylon 6, polypropylene-nylon 6/6, polyethylene-a copolymer of caprolactam a5 and alkylene oxide diamine, and polypropylene -a copolymer of caprolactam and alkylene oxide diamine; polyoiefin-polyester, e.g., polyethylene-polyethylene terephthalate, polypropylene-polyethylene terephthalate, polyethylene-polybutylene terephthalate and polypropylene-polybutylene terephthalate; and polyamide-polyester, e.g., nylon 6-polyethylene terephthalate, nylon 6/6-polyethylene terephthalate, nylon 6-polybutylene terephthalate, nylon 3 0 6/6-polybutylene terephthalate, polyethylene terephthalate-a copolymer of caprolactam and alkylene oxide diamine, and polybutylene terephthalate-a copolymer of caprolactam and alkylene oxide diamine.
Fabrics or webs containing the present split filaments or staple fibers provide a combination of 35 desirable textural properties of conventional microfiber fabrics and desirable strength properties of highly oriented fiber fabrics. Especially with spunbond processes the split fiber WO 98/01607 _ PCT/US97/10986 fabric obtained by splitting prior to web forming exhibits desirable properties, such as uniformity of the fabric, uniform fiber coverage, barrier properties and high fiber surface area, that are akin to microfiber fabrics. in addition, unlike microfiber fabrics such as meltblown webs, the split fiber fabric also exhibits highly desirable strength properties, desirable hand and softness and can be produced to have different levels of loft. Many uses will be apparent, such as filter media, sorbent products, geotextiles, housewrap, synthetic paper, barrier and breathable barrier fabrics for personal care products and the like.
Furthermore, the present split fiber production process is highly advantageous over prior art io split fiber production processes. The present process is a flexible, noncompacting process that can be used to produce split fiber fabrics having a wide variety of loft and density. Unlike prior art needling processes for splitting fibers that inherently compact the precursor web, the present process does not apply compacting forces to split conjugate fibers.
Accordingly, the present process does not alter the loft of the precursor fiber web or fabric during the fiber i5 splitting process. In addition, the present process does not sacrifice the strength properties of the precursor fiber web. Unlike prior art solvent dissolving processes for producing fine fibers, the present process retains all of the polymeric components of the precursor conjugate fibers during the fiber splitting process. Consequently, the present process at least retains or even improves strength properties of the precursor web. This is because the present process a o retains the polymeric components of the precursor web while increasing the number of fiber strands, and because, as is known the art, a fabric having a higher number of fiber strands and thus having finer fibers is stronger than a coarse fiber fabric of the same polymer, the same basis weight and a similar level of molecular orientation and binding.
a s Fabrics containing the split fine fibers that exhibit the above-illustrated desirable properties are highly suitable for various uses as mentioned. For example, nonwoven fabrics containing the split fine fibers are highly suitable for various additional uses including disposable articles, e.g., protective garments, sterilization wraps, wiper cloths and covers for absorbent articles; and woven fabrics containing the split fine fibers that exhibit highly improved softness and s o uniformity are highly useful for soft apparels, dusting and wiper cloths and the like.
As another embodiment of the present invention, the soft, strong fine fiber fabric may be used as a laminate that contains at least one layer of the fine fiber fabric and at least one additional layer of another woven or nonwoven fabric or a film. The additional layer for the laminate is 3 s selected to impart additional and/or complementary properties, such as liquid andlor microbe barrier properties. The layers of the laminate can be bonded to form a unitary structure by a io ..onding process known in the art to t~ ~uifable for laminate structures, such as a thermal, ultrasonic or adhesive process.
A laminate structure highly suitable for the present invention is disclosed in U.S. Pat. No.
4,041,203 to l3rock et at. In adapting s the disclosure of U.S. Pat. No. 4,041;203, a pattern bonded laminate of at least one split continuous filament nonwoven web, e.g., split spunbond conjugate fiber web, and at feast one microfiber nonwoven web, e.g:, meitblowrt web; can be produced; and such laminate combines the strength and softness of the split fiber fabric and the breathable barrier properties of the micxofiber web. Alternatively, a breathable film can be Laminated to the fine i o f ber web to provide a breathable barrier laminate that exhibits a desirable combination of usefut properties, such as soft texture, strength and banter properties. As yet another embodiment of the present invention, the fine fiber fabric can be laminated to a non-breathable film to provide a strong, high bonier laminate having a Both-tike texture.
These laminate structures provide desirable Goth-like textural properties; improved strength properties and i5 high barrier properties. The laminate structures, consequently, are highly suitable for various uses including various skin-contacting applications, such as protective garments, covers for diapers, adult care products, training pants and sanitary napkins, various drapes, and the like.
'The following example is provided for illustration purposes and the invention is not limited 2 o thereto:
Example Hydrophilic modifying agent used:
TM
2s SF-19-ethoxylated polysiloxane, which is available from Mazer: SF-19 exhibited a contact angle of about 0°:
Testing Procedure:
~ o Contact Angle -measured in accordance with ASTM D724-89 using a 0.05 mm cast frlm produced from F~ocon's 3445 Polypropylene:
EXAMPLE 1 - - __ Crimped conjugate spunbond filarfients having a parent o~ initial denier of about 2 and including 50% by weight linear law density polyethylene and 54% by weight nylon 6 and s having a side-by-side configuration were produced. The linear low density polyethylene (LLDPE) was Dow Chem'ecal's LLDPE 6811A, and the nylon 6 used was custom polymerized polycaprolactam, which was produced by Nyltech, NH, and had a formic acid relative viscosity of 1.85. LLDPE was blended with 2°!o by weight of TiOz concentrate containing 50% by weight TiOZ and 50°~ by weight of potypropytene, and the mixture was fed into a first single saew to extruder. In addition, 2% by weight of SF-19 surfactant, as indicated in Table 1, was blended with the LLDPE composition before the composition was fed into the extruders.
The composition for Example 1 is shown in Table 1. The melt temperature of the LLDPE extrudate was about 232°C, and the melt temperature of the nylon 6 ex#rudate was about 232°C.
Is The extruded polymers were fed to a bicomponent spinning die and spun into round bicomponent fbers in accordance with the bicornponent spunbond fiber production process disclosed in afore-mentioned U.S. Patent 5,382,400. The bioomponent spinning die had a 0.6 mm spinhole diameter and a 4:1 UD raft. The spinhole throughput rate was 0.5 gramlhote/minute. The spinning die was maintained at 232°C. The bicomponent filaments ao exiting the spinning die were quenched by a flow of air having a flow rate of 0.5 m3lmin.lcm spinneret width and a temperature of 18°C. The quenching air was applied about 5 inches (about 12.7 cm) below the spinneret, and the quenched fibers were drawn in an aspirating unity of the ype which is described in U.S. Patent 3;802,817 to Matsukt et at. The quenched filaments were drawn with the flow of a 50:50 mixture of air and steam, which was heated to z 5 about 93°C, in the aspirating unit to attain crimped filaments of about 1 denier after splitting.
The drawn filaments were deposited onto a foraminous forming surface, forming a lofty weh of filaments.
_ WO 98/01607 _ _ PCT/US97/10986 a>
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Claims (17)
1. A process for producing split fibers, said process comprising:
a) melt spinning multicomponent conjugate filaments comprising a multitude of distinct cross-sectional segments along the length of said filaments, wherein adjacent distinct segments comprise incompatible polymer compositions at least one of which is hydrophilic;
and b) drawing the conjugate filaments in the presence of a aqueous fibrillation-inducing medium to split the filaments;
wherein said segments have an unocclusive configuration such that said segments are dissociable, and said segments dissociate in less than about 30 seconds when contacted with a hot aqueous fibrillation-inducing medium.
a) melt spinning multicomponent conjugate filaments comprising a multitude of distinct cross-sectional segments along the length of said filaments, wherein adjacent distinct segments comprise incompatible polymer compositions at least one of which is hydrophilic;
and b) drawing the conjugate filaments in the presence of a aqueous fibrillation-inducing medium to split the filaments;
wherein said segments have an unocclusive configuration such that said segments are dissociable, and said segments dissociate in less than about 30 seconds when contacted with a hot aqueous fibrillation-inducing medium.
2. The process for producing split fibers of claim 1 wherein at least one of said polymer compositions further comprises a hydrophilic modifier.
3. The process for producing split fibers of claim 2 wherein said incompatible polymer compositions comprise a first polymer composition, which comprises a first thermoplastic polymer, and a second polymer composition, which comprises a second thermoplastic polymer; and said first and second polymers are selected from polyolefin-polyamide, polyolefin-polyester and polyamide-polyester pairs.
4. The process for producing split fibers of claim 3 wherein said hydrophilic modifier is a surfactant.
5. The process for producing split fibers of claim 4 wherein said surfactant provides a water contact angle equal to or less than about 50° as measured in accordance with ASTM D724-89.
6. The process for producing split fibers of claim 5 wherein at least one of said first and second polymer compositions contains said surfactant between about 0.1% and about 5%
based on the total weight of said polymer composition.
based on the total weight of said polymer composition.
7. The process for producing split fibers of claim 3 wherein said first and second polymers have a solubility parameter difference of at least about 0.5 (cal th cm-3)1/2.
8. The process for producing split fibers of any one of claims 1 to 7, wherein said hot fibrillation-inducing medium comprises water or steam having a temperature of at least about 60°C.
9. A nonwoven fabric comprising split fibers produced with the process of any one of claims 1 to 8.
10. A process according to any one of claims 1 to 8, wherein said meltspinning step a) is effected by spunbonding said multicomponent conjugate filaments.
11. A process in accordance with any one of claims 1 to 7, wherein said hot fibrillation-inducing medium comprises steam and is the drawing medium.
12. A nonwoven fabric comprising split fibers produced in accordance with the process of claim 10 or 11.
13. A personal care product comprising the nonwoven fabric of claim 9 or 12.
14. A personal care product comprising split fibers made in accordance with the process of any one of claims 1 to 8.
15. A filter medium comprising split fibres made in accordance with the process of any one of claims 1 to 8.
16. A nonwoven fabric comprising fibers that have been split from multicomponent fibers by drawing said multicomponent fibers under hot aqueous conditions wherein at least two of said multipcomponents have a difference in solubility parameters of at least about 0.5 (cal/cm3)1/2.
17. The nonwoven fabric of claim 16, wherein said difference in solubility parameters is at least about 2 (cal/cm3)1/2.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/677,481 US5895710A (en) | 1996-07-10 | 1996-07-10 | Process for producing fine fibers and fabrics thereof |
| US08/677,481 | 1996-07-10 | ||
| PCT/US1997/010986 WO1998001607A1 (en) | 1996-07-10 | 1997-06-24 | Process for producing fine fibers and fabrics thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2256414A1 CA2256414A1 (en) | 1998-01-15 |
| CA2256414C true CA2256414C (en) | 2005-08-23 |
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ID=24718896
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002256414A Expired - Fee Related CA2256414C (en) | 1996-07-10 | 1997-06-24 | Process for producing fine fibers and fabrics thereof |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US5895710A (en) |
| EP (1) | EP0910687B1 (en) |
| KR (1) | KR100462734B1 (en) |
| CN (1) | CN1093893C (en) |
| AU (1) | AU714350B2 (en) |
| BR (1) | BR9710212A (en) |
| CA (1) | CA2256414C (en) |
| DE (1) | DE69717275T2 (en) |
| WO (1) | WO1998001607A1 (en) |
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- 1997-06-24 CN CN97196233A patent/CN1093893C/en not_active Expired - Fee Related
- 1997-06-24 EP EP97933162A patent/EP0910687B1/en not_active Expired - Lifetime
- 1997-06-24 AU AU36420/97A patent/AU714350B2/en not_active Ceased
- 1997-06-24 BR BR9710212-1A patent/BR9710212A/en not_active Application Discontinuation
- 1997-06-24 DE DE69717275T patent/DE69717275T2/en not_active Expired - Fee Related
- 1997-06-24 KR KR10-1999-7000147A patent/KR100462734B1/en not_active IP Right Cessation
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|---|---|
| DE69717275T2 (en) | 2003-08-28 |
| CA2256414A1 (en) | 1998-01-15 |
| CN1093893C (en) | 2002-11-06 |
| AU714350B2 (en) | 1999-12-23 |
| WO1998001607A1 (en) | 1998-01-15 |
| EP0910687B1 (en) | 2002-11-20 |
| US5895710A (en) | 1999-04-20 |
| EP0910687A1 (en) | 1999-04-28 |
| CN1225143A (en) | 1999-08-04 |
| KR100462734B1 (en) | 2004-12-20 |
| DE69717275D1 (en) | 2003-01-02 |
| AU3642097A (en) | 1998-02-02 |
| BR9710212A (en) | 2000-01-18 |
| KR20000023690A (en) | 2000-04-25 |
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