JPH0827625A - Composite fiber and nonwoven web - Google Patents

Abstract

PURPOSE: To provide a conjugate fiber containing an ethylene polymer component and a propylene polymer component and highly crimpable even at fine deniers and provide a nonwoven fabric made from the fiber. CONSTITUTION: The objective highly crimpable conjugate fiber contains an ethylene polymer component and a propylene polymer component, the propylene polymer component contains a propylene polymer having a melt flow rate of about >=45 g/10 min at 230 deg.C and each of said components occupies a distinct section for substantially the entire length of said fiber.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to composite fibers containing high melt flow propylene polymers and nonwoven webs made therefrom.

[0002]

BACKGROUND OF THE INVENTION Composite fibers having two or more component polymers designed to benefit from a combination of the desired chemical and / or physical properties of the component polymers. Known in the art. Composite fibers and methods of making fabrics made therefrom are disclosed, for example, in U.S. Pat.No. 3,423,266 to Davis et al., Reissue Patent No. 30,955 to Stani Street and European Patent Application No. 0586924. . In addition to providing the combined desirable properties of the component polymers, composite fibers are heat crimped, especially when the fibers are made from component polymers that differ in crystallization, shrinkage and / or solidification properties. Thus, it may improve the tactile properties of nonwoven webs or fabrics made from fibers, including "cloth-like" texture, bulk and fullness. For example, European Patent Application No. 0586924 discloses thermally crimped composite fibers that are dimensionally stable.

Although methods of thermal crimping of composite fibers are known in the art, it is also known that the method of applying crimping by heat becomes very cumbersome as the thickness of the fibers decreases. . Thus, small denier fibers tend to form flat or dense nonwoven webs. Heat-crimped fine denier composite fibers can be produced by significantly reducing the throughput, ie the amount of polymer treated by the spinneret, or by increasing the treatment temperature of the polymer components. None of the alternatives is commercially desirable. Reduced throughput reduces the fiber production rate, and increased polymer processing temperature results in processing difficulties, such as thermal decomposition of the polymer, and increased spun fiber quenching requirements.
It is highly desirable to provide a method for making highly crimped conjugate fibers that can handle even fine denier with a high level of crimping and that does not require complex and / or cumbersome manufacturing steps. It is also highly desirable to provide a nonwoven web made from such fibers.

[0004]

The present invention provides highly crimpable conjugate fibers having an ethylene polymer component and a propylene polymer component. The propylene polymer component of the composite fiber comprises a propylene polymer having a melt flow rate at 230 ° C. of about 45 g / 10 minutes or more. The bicomponent fibers may be continuous spunbond filaments or staple fibers. Additionally, a nonwoven web processed from the composite fibers is provided. The bicomponent fibers of the present invention are highly crimpable, even at fine denier, to give soft, highly elastic nonwoven webs. As such, nonwoven webs made from composite fibers are very useful as various parts for diapers, sanitary napkins, disposable products including incontinence products, handkerchiefs, cover materials, garment materials, etc., and filters. Is.

The term "composite fiber" refers to a fiber that comprises at least two polymeric components that are arranged to occupy distinct portions of substantially the entire length of the fiber. Composite fibers are formed by simultaneously extruding at least two molten polymeric component compositions from multiple capillaries of a spinneret into multiple single multicomponent filaments or fibers. The term "spunbond fibrous web" refers to a non-woven fibrous web of small diameter filaments or fibers formed by extruding or melt spinning a molten thermoplastic polymer as filaments or fibers from multiple capillaries of a spinneret. Represents The extruded filaments are partially cooled and then rapidly drawn by a drawing mechanism or other known drawing mechanism. The drawn filaments are attached or placed on the forming surface in a random, isotropic fashion to form a loosely entangled fibrous web, which is then subjected to a bonding process to provide physical integrity and Provides dimensional stability. Suitable bonding processes for spunbond fibrous webs are known in the art and include calender bonding methods, ultrasonic bonding methods, hydroentangling methods, needle punching methods and through air bonding methods. The production of spunbond webs, for example,
U.S. Pat. No. 4,340,563 to Appel et al., U.S. Pat. No. 3,692,618 to Dauschner et al. And European Patent Application No. 0586924 to Kimbury Clarke. European Patent Application No. 0586924, which is incorporated herein by reference in its entirety, discloses a method of forming a spunbond fibrous web particularly suitable for the present invention.
Typically 10 spunbond filaments or fibers
has an average diameter of more than 55 μm and more than
Finer spunbond fibers can be produced. The term "bonded card staple fiber web"
2 represents a non-woven web formed from staple fibers. Staple fibers are commonly manufactured by melt spinning processes in which continuous fibers or filaments are manufactured and then often cut into staple lengths ranging from about 1 inch to about 8 inches. The continuous fiber forming process of the method is typically similar to the melt spinning process of conventional spunbond fiber web forming methods. The staple fibers are then carded and bonded to form a nonwoven web.

The present invention provides a nonwoven fibrous web of spunbond or staple bicomponent fibers that is highly crimpable even in fine denier. The fibrous web is
It not only provides improved texture properties, including softness and bulk, but also improved physical properties such as web uniformity and coverage. Although the bicomponent fibers of the present invention include an ethylene polymer component and a propylene polymer component, the bicomponent fibers may include additional polymer components selected from a wide variety of fiber forming polymers. Desirably, the composite fibers are from about 20% by weight, based on the total weight of the fibers.
Contains about 80% by weight ethylene polymer and about 80% to about 20% by weight propylene polymer. Propylene polymers suitable for the present invention are homopolymers and copolymers of propylene, which are known to be suitable for forming isotactic polypropylene, syndiotactic polypropylene and propylene copolymers in small amounts of one or more. Other monomers include, for example, ethylene, butylene, methyl acrylate-sodium co-allyl sulfonate, and propylene copolymers including styrene-co-styrene sulfonamide. Also, blends of these polymers are suitable. Further suitable propylene polymers are the above-mentioned propylene polymers blended with small amounts of ethylene alkyl acrylates such as ethylene ethyl acrylate; polybutylene; and / or ethylene-vinyl acetate. Of these suitable propylene polymers, isotactic polypropylene and propylene copolymers containing up to about 10 wt% ethylene are even more desirable.

In accordance with the present invention, the preferred propylene polymer has a higher melt flow rate than conventional fiber forming polypropylene. A suitable propylene polymer melt flow rate is AS
Measured according to TM D-1238 is about 45 g / 10 min or more at 230 ° C, desirably the melt flow rate is about 50 to about 200 g at 230 ° C.
/ 10 minutes, more preferably about 55 to about 175 g / 10 minutes at 230 ° C, and most preferably the melt flow rate is about 60 to about 60 at 230 ° C.
It is 150g / 10 minutes. If the melt flow rate of the propylene polymer is below a certain range, it is difficult to produce fine denier, for example, highly crimped composite fibers of 2.5 denier or less, using conventional fiber forming methods at commercial rates. And if the melt flow rate is higher than a certain more desired range, the physical incompatibility of the component polymer melts causes fiber spinning difficulties and also results in deformed fibers, or is entirely in the fiber spinning process. I may not pass. To a limited extent, the difficulties of spinning propylene polymers with melt flow rates above a certain range can be alleviated by using ethylene polymers with significantly higher melt flow rates. Surprisingly, the composite fibers of the present invention containing a high melt flow rate propylene polymer can be heat treated to contain a high level of crimp even in fine denier and thus be processed into an elastic fabric of fine denier fibers. . For example, the composite fiber may be treated even when the fiber size is reduced to about 2.5 denier or less, desirably about 2 denier or less, and more desirably about 1.5 denier.
1 per ounce, measured under a load of 0.025 psi
A fibrous web having a bulk of at least about 20 mils per square yard may be provided.

Ethylene polymers suitable for the present invention include fiber forming homopolymers of ethylene and ethylene and one or more comonomers such as butene, hexene, 4-methyl-1.
Pentene and octene, ethylene-vinyl acetate and ethylene alkyl acrylates, such as ethylene ethyl acrylate, and copolymers with blends thereof. Suitable ethylene polymers may be blended to include minor amounts of ethylene alkyl acrylates such as ethylene ethyl acrylate; polybutylene; and / or ethylene-vinyl acetate. More desirable ethylene polymers include high density polyethylene, linear low density polyethylene, medium density polyethylene, low density polyethylene and blends thereof, with the most preferred ethylene polymers being high density polyethylene and linear low density polyethylene.

Suitable fiber-forming polymers for the additional polymer component of the composite fiber of the present invention include polyolefins, polyesters, polyamides, acetals, acrylic polymers, polyvinyl chloride, vinyl acetate based polymers, and the like, as well as blends thereof. Is mentioned. Useful polyolefins include polyethylene such as high density polyethylene, medium density polyethylene, low density polyethylene and linear low density polyethylene; polypropylene such as isotactic polypropylene and syndiotactic polypropylene; polybutylene such as poly (1-butene). ) And poly (2-butene); polypentenes such as poly (2-pentene), and poly (4-methyl-1-pentene); and blends thereof. Beneficial vinyl acetate-based polymers include polyvinyl acetate; ethylene-vinyl acetate; saponified polyvinyl acetate or polyvinyl alcohol; ethylene-vinyl alcohol and blends thereof. Useful polyamides include nylon 6 and nylon 6 /
6, Nylon 10, Nylon 4/6, Nylon 10/10, Nylon 12, hydrophilic polyamide copolymers such as caprolactam and alkylene oxides such as ethylene oxide, copolymers and hexamethylene adipamide and alkylene oxide copolymers, and these Blends can be mentioned. As a beneficial polyester,
Included are polyethylene terephthalate, polybutylene terephthalate, and blends thereof. Acrylic polymers suitable for the present invention include ethylene acrylic acid, ethylene methacrylic acid, ethylene methyl methacrylate, and the like, as well as blends thereof. In addition, the fiber composition contains small amounts of compatibilizers, colorants, pigments, brighteners, UV stabilizers, antistatic agents, lubricants, antiwear agents, crimp inducers, nucleating agents, fillers. And other processing aids may be further contained.

The bicomponent fibers suitable for the present invention may have a side-by-side shape or an eccentric sheath-core shape. If a sheath-core configuration is utilized, an eccentric sheath-core configuration, i.e., non-concentrically arranged sheaths and cores, is more desirable. This is because the eccentric sheath-core fiber is easier to handle due to the heat crimping method. Suitable conjugate fibers are, for example, U.S. Pat.No. 3,423,266 to Davis et al., Reissue Pat.No. 30,955 to Stani Street, U.S. Pat.No. 4,189,338 to Ejima et al. And European Patent Application No. 0586924. Can be made by any of the known staple or continuous bicomponent fiber forming methods disclosed in US Pat. As is known in the art, crimping in composite fibers may be applied before, during or after the fibers are attached or placed to form the nonwoven web. However, it is highly desirable to crimp the composite fibers before they are formed into a nonwoven web. This is because the crimping method inherently causes shrinkage and dimensional change. Although the present invention is described in terms of thermal crimping methods, it should be noted that any known mechanical crimping method can also be utilized.

Referring to FIG. 1, the drawing illustrates a highly suitable process 10 for making highly suitable nonwoven composite fibrous webs, and more particularly bicomponent fibrous webs. A pair of extruders 12a
And 12b extrude the two polymer compositions separately, these compositions comprising a first hopper 14a and a second hopper 14b.
Separately, and the molten polymer composition is simultaneously fed to the spinneret 18 through conduits 16a and 16b. Suitable spinnerets for extruding bicomponent fibers are known in the art.
Briefly, the spinneret 18 has a housing containing a spin pack, which includes a plurality of plates and dies. The plate has a pattern of openings arranged to create a flow path for sending two polymers to a die having one or more rows of openings, which are designed according to the desired shape of the resulting bicomponent fiber. . A curtain of fibers is produced from the array of die openings and partially quenched by a quench air blower 20, or aspirator 22, before being fed to the fiber drawing unit. The quenching method not only partially quenches the fiber, but also causes latent helical crimping in the fiber. Fiber drawing units or aspirators suitable for use in melt spinning polymers are known in the art, and as a particularly suitable fiber drawing unit for the present invention, a European patent application published on 16 March 1994. No. 058692
Mention may be made of linear fiber aspirators of the type disclosed in specification No. 4, which is hereby incorporated by reference. Briefly, the fiber drawing unit 22 comprises an elongated vertical passage through which the filament is drawn by superheated intake air entering from the side of the passage from a temperature adjustable heater 24. Hot intake air draws filaments and ambient air through the fiber drawing unit 22. The temperature of the air supplied by the heater 24 is sufficient so that after some cooling by mixing with the cooler ambient air drawn with the filament, the air is needed to obtain the latent crimping of the filament. Heat to temperature. The temperature of the air from the heater can be varied to obtain different levels of crimp. In general, high air temperatures produce multiple crimps.

The process line 10 further includes an endless porous forming surface 26 located below the fiber drawing unit 22. Continuous fibers from the exit of the drawing unit are deposited on the forming surface 26 in a random fashion to produce a continuous web of uniform density and thickness. The fiber attachment method is
It may be assisted by a vacuum unit 30 located below the forming surface 26. If necessary, the resulting web is a roll
Light compression pressure may be applied at 32 to consolidate the web and impart additional physical integrity to the web prior to being subjected to the bonding process. The nonwoven web is then bonded, for example, by a through air bonding method. The generally described through air bonder 36 includes a perforated roll 38 (which receives a web) and a hood 40 surrounding the perforated roll. Heated air, which is high enough to melt the low melting component polymer of the composite fiber, is fed to the web through a perforated roll 38 and removed by a hood 40. The heated air melts the low melting polymer, which forms interfiber bonds in the web, especially at the locations where the fibers intersect. The through air bonding method is particularly suitable for producing elastic, evenly bonded spunbond webs. This is because these methods act uniformly on the interfiber bonds and do not use intermittently placed compressive pressure to act on the interfiber bonds. Also, unbonded nonwoven webs can be bonded with a calender bonder. Calender bonders typically combine a combination of heat and pressure to melt the fibers of a thermoplastic nonwoven web, thereby actuating two or more abutting heating elements that act on the bonded areas or locations in the web. It is a roll assembly device. The bond roll may be smooth to provide a uniformly bonded nonwoven web, or may include a pattern of raised bond points to provide a dot bonded web.

The soft, high modulus nonwoven webs of the present invention are disposable medical cloths such as surgical gowns, surgical drapes and sterile wraps; cover materials such as automobile and boat covers; protective garments such as cavalols, uniforms and aprons; And disposable protection products and personal protection products, such as diapers, training pants,
Very useful as various parts for sanitary napkins, incontinence products, handkerchiefs, etc. In addition, the elastic nonwoven web of the present invention containing fine denier fibers and having high bulk and improved uniformity over conventional spunbond composite fiber webs does not sacrifice web elasticity. It is very useful in filtration applications in that it provides pores between fine fibers evenly distributed at. The following examples are given for purposes of illustration and the invention is not limited thereto.

[0014]

【Example】

Example 1-2 (Ex1-Ex2) A point-bonded spunbonded fibrous web of rounded side-by-side conjugate fibers comprising 50 wt% linear low density polyethylene and 50 wt% polypropylene was prepared by the method shown in FIG. Was manufactured using. The two-component spinning die had a spinhole diameter of 0.6 mm, a 6: 1 L / D ratio and a spinhole density of 50 holes / inch. Linear Low Density Polyethylene (LLDPE), Aspan 6811A (which is available from Dow Chemical),
Contains 50% by weight TiO ₂ and 50% by weight polypropylene 2
Blended with wt% TiO ₂ concentrate and fed the mixture to the first single screw extruder. The LLDPE composition was extruded so that the extrudate had a melt temperature of about 221 ° C as it exited the extruder. Polypropylene X11029-20-1 (This is
Blended with ₂ % by weight of the above TiO ₂ concentrate having a melt flow rate (MFR) of about 65 g / 10 min at 230 ° C., available from Highmont, and the mixture was fed to a second single screw extruder. Supplied. The melting temperature of the polypropylene composition was maintained at 221 ° C for Example 1 and 241 ° C for Example 2. LLDPE and polypropylene extrudates were fed to a spinning die maintained at about 221 ° C. and spin hole throughput was measured in Example 1.
0.7 g / hole / min and 0.5 g / hole in Example 2
Kept at holes / min. The bicomponent fibers exiting the spinning die were quenched with a stream of air having a flow rate of 45 SCFM per inch spinneret width and a temperature of 18 ° C. Quenching air was applied about 5 inches below the spinneret. Quenched fibers were drawn, crimped in a suction unit using a stream of air heated to about 177 ° C. and supplied with a flow rate of 50.9 ft ³ / min / inch width.

The drawn and crimped fibers were then attached to the porous forming surface with the aid of a vacuum flow to form an unbonded fibrous web. The unbonded fibrous web was bonded by passing the web through a nip formed by two abutting bonding rolls, a smooth anvil roll and an embossing roll.
The raised bond points of the embossing roll covered about 15% of the total surface area and there were about 310 regularly spaced bond points per square inch. Both rolls were heated to about 121 ° C. and the pressure applied to the web was about 100 pounds per linear inch width. The bonded nonwoven webs, which had an average weight of about 1.0 ounces per square yard (osy), were tested for their bulk and average fiber size. The crimp level of the fibers forming the nonwoven web was measured indirectly by comparing the web bulk. This is because the bulk is directly related to the crimp level of the fiber,
Bulk is measured in mils under a load of 0.025 psi. The results are shown in Table 1. Control 1-2 (C1-C2) Except that Exon PP3445 polypropylene was used, the procedure outlined in Examples 1 and 2 was repeated to give Control 1-, respectively.
2 was produced. Polypropylene has a melt flow rate of about 35 g / min at 230 ° C and is a normal fiber brand polypropylene. The results are shown in Table 1.

[0016]

[Table 1] Polypropylene Example MFR throughput Fiber size Bulk (g / min) (g / hole / min) (denier) (mill) Ex1 65 0.7 2.5 20.3 Ex2 65 0.5 1.8 14.5 C1 35 0.7 2.8 11.8 C2 35 0.5 1.8 11.0

The result is that the bicomponent fibers containing high melt flow polypropylene provide a bulky nonwoven fabric and thus the fibers contain a higher level of crimping than bicomponent fibers made from conventional spunbond fiber forming fiber brand polypropylene. To demonstrate. Also, even though the difference in fiber size was very significant, C1 and C2 showed similar bulk values, indicating a difficulty in heat crimping fine denier fibers. Example 3-7 (Ex3-Ex7) Two kinds as shown in Table 2 except that the polymer treatment amount was kept at 0.7 g / hole / min and the melting temperature of the two-component polymer composition was kept at 221 ° C. An unbonded nonwoven web of side-by-side bicomponent fibers was prepared according to the operating summary of Example 1 using different grades of polypropylene from. In addition, the fiber size was adjusted by varying the flow rate of heated air supplied to the suction unit as shown in Table 2. Both 100 melt flow rate polypropylene resin and 65 melt flow rate polypropylene resin were obtained from Shell Chemical. The unbonded nonwoven web was then bonded by passing it through a through air bonder. The bonder exposed the nonwoven web to a stream of heated air having a temperature of about 132 ° C. and a flow rate of about 200 feet / minute. Average weight,
The fiber size and the bulk of the bonded web are measured, and the bulk is set to 1 os.
Normalized to y. Table 2 shows the results. Control 3-5 (C3-C5) Example 3 was repeated except that the polypropylene used was the 35 melt flow rate polypropylene disclosed in Control 1. Table 2 shows the results.

[0018]

[Table 2] Example of heated air fiber web Flow rate of PP MFR Size Weight Bulk (g / min) (ft ³ / min / (denier) (osy) (mil / osy) inch width) Ex3 100 37.3 2.0 2.03 36.5 Ex4 65 37.3 2.5 1.85 37.2 Ex5 100 42.9 1.9 1.89 37.4 Ex6 100 48.6 1.8 1.94 23.7 Ex7 65 48.6 1.9 2.18 23.6 C3 35 37.3 2.5 1.95 19.5 C4 35 42.9 2.2 2.03 14.5 C5 35 44.5 2.0 2.12 14.3

The results clearly demonstrate that using a high melt flow propylene polymer significantly improves the bulk of the composite fibrous web. For example, the fibers of Example 4 and Control 3 had the same fiber size, but the bulk of Example 4 was about 91% higher than that of Control 3.

[Brief description of drawings]

FIG. 1 illustrates a method suitable for making the composite fiber and nonwoven web of the present invention.

[Explanation of symbols]

 10 Non-woven composite fiber web manufacturing method 12a Extruder 12b Extruder 14a First hopper 14b Second hopper 16a Conduit 16b Conduit 18 Spinneret 20 Quenching air blower 22 Aspirator 24 Temperature adjustable heater 26 Forming surface 30 Vacuum unit 36 Through Air bonder 38 Perforated roll 40 Hood

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location D04H 1/42 X 3/00 CD D // A47L 13/16 A (72) Inventor Allen Edward Wright United States Georgia 30188 Woodstock Country Manor Coat 4142 (72) Inventor Simon Kwawe Ofos United States Georgia 30247 Lilburn Northwest India Way 1091

Claims (25)

[Claims] 1. A highly crimpable conjugate fiber comprising an ethylene polymer component and a propylene polymer component, comprising:
A composite fiber, wherein the propylene polymer component comprises a propylene polymer having a melt flow rate of about 45 g / 10 min or more at 230 ° C., each of the components occupying distinct portions over substantially the entire length of the fiber. 2. The conjugate fiber according to claim 1, wherein the conjugate fibers have a shape in which they are arranged side by side. 3. The conjugate fiber according to claim 1, wherein the conjugate fiber has an eccentric sheath-core shape. 4. The composite fiber of claim 1, wherein the propylene polymer is selected from the group consisting of propylene homopolymers and copolymers and blends thereof. 5. The composite fiber of claim 1, wherein the propylene polymer is selected from the group consisting of isotactic polypropylene and a propylene copolymer containing up to about 10 wt% ethylene. 6. The propylene polymer is about 50 at 230 ° C.
The composite fiber of claim 1, having a melt flow rate of about 200 g / 10 min. 7. The propylene polymer is about 55 at 230 ° C.
The composite fiber of claim 1, having a melt flow rate of about 175 g / 10 min. 8. The composite fiber of claim 1, wherein the ethylene polymer is selected from the group consisting of ethylene homopolymers and copolymers and blends thereof. 9. The composite fiber of claim 1, wherein the ethylene polymer is selected from the group consisting of high density polyethylene and linear low density polyethylene. 10. The composite fiber of claim 1, having a weight / unit length of about 2.5 denier or less. 11. The composite fiber according to claim 1, which is a heat-crimped fiber selected from the group consisting of spunbond filaments and staple fibers. 12. A non-woven web comprising highly crimped bicomponent fibers, said bicomponent fibers comprising an ethylene polymer component and a propylene polymer component, wherein said propylene polymer component at 230 ° C. is about 45 g / 10 min or more. A non-woven web having a melt flow rate of, each of said components occupying a distinct portion over substantially the entire length of said fiber. 13. The nonwoven web of claim 12, wherein the composite fibers are continuous fibers. 14. The nonwoven web of claim 12, wherein the composite fiber is staple fiber. 15. The nonwoven web of claim 12, wherein the composite fibers have a side-by-side configuration. 16. The nonwoven web of claim 12, wherein the composite fibers have an eccentric sheath-core shape. 17. The nonwoven web of claim 12 wherein the propylene polymer is selected from the group consisting of propylene homopolymers and copolymers and blends thereof. 18. The propylene polymer at about 230 ° C.
13. The nonwoven web of claim 12 having a melt flow rate of 50 to about 200 g / 10 minutes or more. 19. The nonwoven web of claim 12, wherein the ethylene polymer is selected from the group consisting of ethylene homopolymers and copolymers and blends thereof. 20. The nonwoven web of claim 12, wherein the composite fibers have a weight / unit length of about 2.5 denier or less. 21. The nonwoven web of claim 12, wherein the bicomponent fibers are heat crimped fibers selected from the group consisting of spunbond filaments and staple fibers. 22. A disposable product comprising the nonwoven web of claim 12. 23. A personal protection product comprising the nonwoven web of claim 12. 24. A disposable medical cloth product comprising the nonwoven web of claim 12. 25. A filter comprising the nonwoven web of claim 12.