MXPA05001376A

MXPA05001376A - Multi-component fibers and non-woven webs made therefrom.

Info

Publication number: MXPA05001376A
Application number: MXPA05001376A
Authority: MX
Inventors: John Sayovitz
Original assignee: Kimberly Clark Co
Priority date: 2002-08-21
Filing date: 2003-06-25
Publication date: 2005-04-28
Also published as: EP1530655A1; JP2005536657A; BR0313263A; AU2003253716A1; US20040038612A1; AU2003253716B2; CN1675414A; CN1311112C; WO2004018746A1; KR20050056950A

Abstract

Bicomponent spunbond filaments and non-woven webs made from the filaments are disclosed. The spunbond filaments include a core polymer and a sheath polymer. Both the core polymer and the sheath polymer are made primarily from polypropylene polymers. For instance, the sheath polymer can be a randomized copolymer of polypropylene and ethylene. The ethylene can be present in the sheath polymer in an amount of less than about 2% by weight. The core polymer, on the other hand, can be a polypropylene polymer having a melting temperature than the sheath polymer.

Description

FIBERS OF MULTIPLE COMPONENTS AND NON-WOVEN FABRICS MADE OF THE SAME Background of the Invention Non-woven fabrics made of polymeric materials are used to make a variety of products, which desirably have particular levels of softness, strength, uniformity, liquid handling properties such as absorbency, and other physical properties. Such products include towels, industrial wipes, incontinence products, infant care products such as baby diapers, absorbent women's care products and garments such as medical clothing. These products are often made with multiple layers of non-woven fabric to obtain the desired combination of properties.

In many applications, non-woven fabrics are created from spunbonded filaments that are formed by spinning with melted thermoplastic materials. The methods for making non-woven fabrics bonded with yarn are well known and are described, for example, in U.S. Patent Nos. 4,692,618 issued to Dorschner et al .; 4,340,563 granted to Appel and others and 5,418,045 granted to Pike and others, which are incorporated herein by reference. Spunbonded nonwoven polymeric fabrics are formed by extruding thermoplastic materials through a spinning organ and pulling the extruded material into filaments with a high velocity air stream to form a random fabric on a collector surface.

In some applications, in order to produce spunbonded materials with desired combinations of softness, strength and absorbency, spunbond nonwoven webs are formed of multi-component filaments such as two-component filaments. The two component filaments are filaments made from a first and a second polymer component which remain distinct within the filament. For example, in one embodiment, the filament may be in a sheath and core arrangement in which a first polymer component constitutes the core and a second polymer component constitutes the sheath.

In the past, very useful bicomponent spunbond filaments have been made containing a core polymer made of polyethylene and a sheath polymer made of polypropylene. The sheath polymer generally has a melting temperature lower than that of the core polymer to allow the filaments to be easily thermally bonded together. The sheath polymer also provides softness to the resulting non-woven fabric. The core polymer, on the other hand, provides the resistance to the fabric.

Even though the yarn-bonded filaments described above and the non-woven fabrics made of the filaments have provided great advances in the art, further improvements are still required. In particular, there is a need for a less expensive alternative to the yarn-bonded filament described above having properties essentially equal to or better than those of yarn-linked filaments made in the past.

Synthesis of the Invention In general, the present invention is directed to filaments of multiple components joined with spinning and to non-woven fabrics made of the filaments. For example, in one embodiment, the present invention is directed to a non-woven fabric containing filaments of continuous polymeric multiple components. The polymeric filaments include a sheath polymer and a core polymer. The shell polymer comprises a copolymer of a polypropylene polymer and a monomer. The core polymer on the other hand, comprises a polypropylene polymer. In general, the core polymer has a melting temperature that is at least about 8 ° C higher than the melting temperature of the sheath polymer. When combined to form a non-woven fabric, the filaments can be thermally melted together.

The sheath polymer may be present in the continuous filament in an amount of from about 20% by weight to about 70% by weight, and particularly from about 40% by weight to about 60% by weight. In one embodiment, the sheath polymer may comprise a random polymer of the polypropylene and the monomer. The monomer can be, for example, ethylene.

For example, in one embodiment of the present invention, the sheath polymer is a random copolymer of polypropylene and ethylene. Ethylene is present in the sheath polymer in an amount of less than about 2% by weight and particularly less than about 1.8% by weight. It has been discovered by the present inventors that various benefits and advantages are achieved and the amount of ethylene present in the sheath polymer is below about 2% by weight.

The core polymer, on the other hand, can be about 98% by weight of polypropylene. For example, in one embodiment, the core polymer can be a metallocene-catalyzed polypropylene.

The melt flow rate of the sheath polymer and the core polymer can be from about 30 grams per 10 minutes to about 40 grams per 10 minutes, and particularly from about 30 grams per 10 minutes to about 35 minutes. grams for 10 minutes. The sheath polymer can have a melting temperature of from about 110 ° C to about 150 ° C. As stated above, the core polymer can have a melting temperature that is at least about 8 ° C greater than the melting temperature of the sheath polymer. While various articles may be made in accordance with the present invention, the teachings of the present invention are particularly suitable for the formation of spunbonded fibers and particularly continuous filaments spun-bonded.

Other features and aspects of the present invention are discussed in more detail below.

Brief Description of the Drawings A complete and enabling description of the present invention, including the best mode, directed to one with ordinary skill in the art is more particularly set forth in the remainder of the description, which refers to the accompanying figures in which: Figure 1 is a cross-sectional view of an incorporation of a bicomponent filament made in accordance with the present invention; Y Figure 2 is a schematic drawing of an embodiment of a process line that can be used to make filaments according to the present invention.

The repeated use of the reference characters in the present description and in the drawings is intended to represent the same or analogous elements of the invention.

Detailed description It is understood by one of ordinary skill in the art that the present discussion is a description of the example embodiments only, and that it is not intended to limit the broader aspects of the present invention, whose broader aspects are involved in the constructions. of example.

In general, the present invention is directed to non-woven fabrics made of multi-component polymer filaments. Non-woven fabrics are made to have a desired balance of physical properties. In general, multi-component polymer filaments are continuous bicomponent filaments containing a core polymer surrounded by a sheath polymer. In accordance with the present invention, both the core polymer and the shell polymer contain polypropylene primarily. For example, the sheath polymer may be a random polypropylene copolymer, while the core polymer may be a crystalline polypropylene polymer having a relatively high melting point.

The present inventors have discovered that when using polypropylene polymers selected to build the bicomponent filaments, non-woven fabrics can be formed having improved strength and tear properties compared to non-woven fabrics made of monocomponent filaments, while also being soft and absorbent. Of a particular advantage, non-woven fabrics with improved properties can be formed according to the present invention using relatively inexpensive polypropylene materials, as opposed to resorting to the use of more expensive exotic polymers to improve the bond or toughness.

Referring to Figure 1, there is shown an embodiment of a cross section of a filament indicated with the number generally made in accordance with the present invention. As illustrated, the filament 100 is a bicomponent filament that includes a core polymer 200 surrounded by a sheath polymer 300. As described above, in accordance with the present invention, the core polymer 200 and the sheath polymer 300 they are both made primarily from polypropylene polymers. Further, in one embodiment, the filament 100 is a filament attached with spinning which may be continuous.

As shown, copolymer 200 and sheath polymer 300 are arranged in different areas across the cross section of filament 100. Both polymers extend the full distance of filament 100. In this embodiment, core polymer 200 is shown essentially concentric with the sheath polymer 300. It should be understood, however, that the core polymer and sheath polymer can be placed in several other arrangements. For example, the core polymer 200 and the sheath polymer 300 can also be placed in an eccentric array.

In general, the sheath polymer 300 has a melting temperature lower than that of the core polymer 200. In this manner, the sheath polymer 300 of a filament can easily melt and fuse with the sheath polymer of an adjacent filament during the formation of non-woven fabrics. Bonding can occur between adjacent filaments without the melting of the core polymer 200, which provides the filament with increased strength.

The sheath polymer 300 used to make the filaments and the non-woven fabrics according to the present invention primarily contain a polypropylene polymer, such as a crystalline polypropylene. The polypropylene polymer should have a relatively low melting temperature, such as a melting temperature of less than about 150 ° C. Specifically, the melting temperature of the polypropylene sheath polymer can be from about 110 ° C to about 150 ° C and more particularly from about 120 ° C to about 135 ° C. The melt flow rate of the polymer can be from about 30 g / 10 minutes to about 40 g / 10 minutes, and particularly from about 30 g / 10 minutes to about 35 g / 10 minutes. The melt flow ranges described above are particularly well suited for the formation of filaments attached with spinning in melt spinning operations.

In one embodiment, the sheath polymer is a copolymer of polypropylene and a monomer, particularly a random copolymer of a polypropylene and a monomer. The monomer can be, for example, ethylene or butene. The amount of monomer contained within the random polypropylene copolymer should be relatively low in some applications. Specifically, it has been discovered that the present inventors that the monomer must be present within the random copolymer in an amount of less than about 2% by weight, particularly less than about 1.8% by weight. For example, in one embodiment, the monomer may be ethylene and may be contained in the random copolymer in an amount of less than about 1.6% by weight.

The lower levels of monomer contained within the random copolymer provide several benefits and advantages of the present invention. For example, when the monomer is present in an amount greater than about 2% by weight, it has been noted that the filaments lose some strength and softness. In addition, the filaments tend not to be effectively cooled during the formation. It is believed that better binding characteristics between the copolymer and the sheath polymer are achieved when the polymer is present in an amount of less than about 2% by weight.

In one embodiment of the present invention, the sheath polymer may be a random copolymer of polypropylene and ethylene sold by Dow Chemical under the product number 6D43. The Dow Chemical 6D43 polymer, however, contains ethylene in an amount of about 3.2% by weight. Therefore, when used in the present invention, greater amounts of polypropylene or other suitable polymer can be added to the product in order to reduce the monomer levels.

In general, the sheath polymer should contain polypropylene in an amount of about 95% by weight. In addition to polypropylene, the sheath polymer may contain a monomer as described above and other additional additives. Such additives may include antioxidants, heat stabilizers, other stabilizers and the like.

The sheath polymer not only provides softness to the spunbonded filaments and non-woven fabrics made in accordance with the present invention, but also improves the strength of the fabrics. For example, due to its lower melting temperature, the sheath polymer has a softer feel. In addition, also because the sheath polymer has a lower melting temperature, the sheath polymer is well adapted to melt and fuse with adjacent fibers. In fact, since the sheath polymer can be easily melted with other filament fibers during bonding, the non-woven fabrics formed in accordance with the present invention have greater integrity and firmness.

As described above, the core polymer 200 also shown in Figure 1 also primarily contains polypropylene. Compared to the sheath polymer, however, the core polymer generally has a melting temperature higher than that of the sheath polymer. For example, the core polymer may have a melting temperature that is at least about 8 ° C higher than the melting temperature of the sheath polymer, and particularly may have a melting temperature of from about 8 ° C. higher than about 15 ° C higher than that of the sheath polymer. For example, the core polymer can have a melting temperature of more than about 150 ° C, and particularly more than about 155 ° C.

During the thermal bonding of the filaments made in accordance with the present invention, the core polymer generally does not melt or significantly degrade. The core polymer is present in the filament in order to increase the strength of the filament and increase the strength of the non-woven fabrics made of the filaments.

In one embodiment, the core polymer contains a polypropylene homopolymer in an amount of at least about 95% by weight. Other polymers and additives can be combined with the core polymer in relatively small amounts. In order to facilitate the formation of filaments attached with spinning, particularly continuous filaments in a spinning operation with melt, the core polymer can have a melt flow rate of from about 30 grams per 10 minutes to about 40 grams. for 10 minutes, and particularly from about 33 grams per 10 minutes to about 39 grams per 10 minutes.

The polypropylene contained in the core polymer can be a Ziegler-Natta catalyzed polymer or, alternatively, it can be a metallocene catalyzed polymer. Metallocene catalyzed polymers provide several ntages including offering the possibility of providing a polymer with a relatively low molecular weight distribution. In one embodiment, the core polymer is the product number 3155 or 3854 marketed by Exxon Corporation.

In general, the sheath polymer is present in the filament in an amount of from about 20% to about 70% by weight and particularly in an amount of from about 40% to about 60% by weight.

The teachings of the present invention are particularly well suited for producing continuous melt spun filaments, such as spunbond filaments. Referring to Figure 2, a process line generally 10 is illustrated for preparing spunbonded filaments according to the present invention. The process line 10 is arranged to produce continuous bicomponent filaments and to produce non-woven fabrics made of spunbonded filaments. In this embodiment, the process line 10 includes a pair of extruders 12A and 12B for separately extruding a sheath polymer and a core polymer. The sheath polymer is fed to the extruder 12A from a first hopper 14A and the core polymer is fed to the extruder 12B from the second hopper 14B.

The shell polymer and the core polymer are fed from the extruders 12A and 12B through the polymer conduit 16A and 15B to a spin organ 18. Generally described, in one embodiment, the spin member 18 includes a box containing a spin pack which includes a plurality of plates stacked one on top of the other with a pattern of openings arranged to create flow paths for directing the polymer components through the spin organ. The spinning organ 18 has the openings arranged in one or more rows. The openings of the spinning member form a curtain extending downwards from filaments when the polymers are extruded through the spinning organ.

In the illustrated embodiment, the process line 10 also includes a cooling blower 20 positioned on one side of the filament curtain extending from the spinning member 18. The air from the cooling air blower 20 cools the filaments extending from the spinning member 18. The cooler can be directed from one side of the filament curtain as shown in Figure 2 or from both sides of the filament curtain.

The process line may further include a fiber pull or vacuum unit 22 positioned below the spin organ that receives the cooled filaments. Fiber pulling units or vacuums for use in melt spinning polymers are well known as discussed above.

Generally described, the fiber pull unit 22 includes an elongated vertical conduit through which the filaments are pulled by sucking the air that enters from the sides of the conduit and flows down through the conduit. A heater 24 can supply the hot suction air to the fiber pulling unit 22. The hot suction air pulls the filaments and ambient air through the fiber pulling unit.

A perforated forming surface 26 is positioned below the fiber pulling unit 22 and receives the continuous filaments from the outlet opening of the fiber pulling unit. The forming surface 26 moves around the guide roller 28. A vacuum 30 placed below the forming surface 26 where the filaments are deposited pulls the filaments against the forming surface.

In the embodiment illustrated in Figure 2, the process line 10 further includes a compression roller 32 which, together with the forwardmost of the guide rollers 28, receives the fabric as the fabric is pulled out of the forming surface 26. From the compression roller 32, the fabric is fed to a winding roller 42 to take the finished fabric. Prior to winding the fabric on the roll 42, the process line may also include some type of bonding apparatus such as the thermal point bonding rolls and / or an air bond. Thermal point joiners and air linkers are well known to those skilled in the art and are not discussed in detail here.

To operate the process line 10, the hoppers 14A and 14B are filled with the respective polymer components. The core polymer and the shell polymer are melted and extruded by the respective extruders 12A and 12B through the polymer conduit 16A and 16B and the spin organ 18. During extrusion, the polymers are heated to temperatures sufficient for the Polymers are flowable.

As the extruded filaments extend below the spinning member 18, a stream of air from the cooling blower 20 at least partially cools the filaments. The cooling air, for example, can flow in a direction essentially perpendicular to the length of the filaments. The temperature of the cooling air can be from about 45 ° F to about 90 ° F and can be at a rate of from about 100 to about 400 feet per minute.

After cooling, the filaments are pulled into the vertical conduit of the fiber pulling unit 22 by a flow of hot air from the heater 24 through the fiber pulling unit. It should be understood, however, that the use of fiber pull unit is optional. When present in the system, the fiber pull unit can be used, for example, to make the filaments slightly curly. After leaving the fiber pulling unit 22, the filaments are deposited on the moving forming surface 26. The vacuum 20 pulls the filaments against the forming surface to form a nonwoven and unbonded web of continuous filaments. The fabric is then slightly compressed by the compression roller 32. Then, the fabric can be joined together using any suitable technique such as thermally bonded knit rolls or by using the linker through air. When the linker is used through air, air having a temperature above the melting temperature of the sheath polymer and below the melting temperature of the core polymer is directed from a cover and through the fabric. The hot air melts the sheath polymer thus forming bonds between the bicomponent filaments to integrate the fabric. The temperature of the air flowing through the joiner can be from about 230 ° F to about 280 ° F and can be at a speed of from about 100 to about 500 feet per minute.

Finally, the finished fabric is wound on the furling roller 42 and is ready for further treatment or use. Spunbond non-woven fabrics constructed in accordance with the present invention have been found to offer several advantages and benefits. For example, non-woven fabrics have been found to have increased tensile strength and tear resistance relative to fabrics made only with a polypropylene polymer. In fact, fabrics have exhibited properties that are favorably comparable to conventionally made bicomponent filaments. Since the filaments of the present invention, however, are made almost exclusively of polypropylene polymers, the filaments are relatively inexpensive to produce.

Yarn-bonded non-woven fabrics made in accordance with the present invention can be used in numerous applications. For example, fabrics joined with yarn can be used to make personal care items and garment materials. Personal care items include products for infant care such as disposable baby diapers, child care products such as underpants, and adult care products such as incontinence products. and the products for the care of women. Suitable medical garments include medical clothing, work clothes and the like.

In one embodiment, the spunbonded non-woven fabrics made in accordance with the present invention can be combined with other fabrics to form laminates. For example, fabrics bonded with yarn can be laminated to other fabrics joined with yarn or other meltblown fabrics. In a particular embodiment, for example, a spunbonded / meltblown / spunbonded laminate is formed containing the non-woven fabrics of the present invention. The basis weight of the non-woven fabrics can be, for example, from about 0.25 ounces per square yard to about 3 ounces per square yard and particularly from about 0.50 ounces per square yard to about 2 ounces per square yard. . In one embodiment, for example, a spunbond / meltblown / spunbonded laminate can be formed in which each layer has a basis weight of about 1 ounce per square yard.

These and other modifications and variations of the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention, which is particularly set forth in the appended claims. In addition, it should be understood that the aspects of the various incorporations can be exchanged both in whole or in part. In addition, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and that it is not intended to limit the invention thus described in such appended claims.

Claims

R E I V I N D I C A C I O N S

1. A non-woven fabric comprising continuous polymer filaments. The polymeric filaments comprise multiple component filaments including a sheath polymer and a core polymer, the sheath polymer comprises a polypropylene copolymer polymer and a monomer, the core polymer comprises a polypropylene polymer, the core polymer has a temperature of melt that is at least about 15 ° F higher than the melting temperature of the sheath polymer, the polymer filaments continue to be melted together.

2. A non-woven fabric as claimed in clause 1, characterized in that the sheath polymer comprises a random copolymer.

3. A non-woven fabric as claimed in clause 2, characterized in that the monomer comprises ethylene.

4. A non-woven fabric as claimed in clause 2, characterized in that the monomer is present in the sheath polymer in an amount of less than about 2% by weight.

5. A non-woven fabric as claimed in clause 3, characterized in that the monomer is present in the sheath polymer in an amount of less than about 2% by weight.

6. A non-woven fabric as claimed in clause 1, characterized in that the continuous filaments comprise filaments joined with spinning.

7. A non-woven fabric as claimed in clause 1, characterized in that the sheath polymer and the core polymer have a melt flow rate of from about 30 g / 10 minutes to about 35 g / 10 minutes.

8. A non-woven fabric as claimed in clause 1, characterized in that the sheath polymer has a melting temperature of from about 110 ° C to about 150 ° C.

9. A non-woven fabric as claimed in clause 1, characterized in that the core polymer comprises a metallocene-catalyzed polypropylene.

10. A non-woven fabric as claimed in clause 1, characterized in that the core polymer comprises polypropylene and an amount of at least 98% by weight.

11. A non-woven fabric as claimed in clause 1, characterized in that the sheath polymer comprises from about 20% by weight to about 70% by weight of the continuous filaments.

12. A non-woven fabric comprising polymeric fibers, the polymeric fibers comprise multi-component fibers including a sheath polymer and a core polymer, the sheath polymer comprises a random polymer of a polypropylene polymer and ethylene, the ethylene being present in the sheath polymer in an amount of less than about 2% by weight, the core polymer comprises a polypropylene polymer, the core polymer has a melting temperature that is at least about 15 ° F higher than the melting temperature of the sheath polymer, the polymer fibers being melted and bound.

13. A non-woven fabric as claimed in clause 12, characterized in that the ethylene is present in the sheath polymer in an amount of less than about 1.8% by weight.

14. A non-woven fabric as claimed in clause 12, characterized in that the fibers of multiple components are continuous filaments.

15. A non-woven fabric as claimed in clause 12, characterized in that the fibers of multiple components are spun-bonded fibers.

16. A non-woven fabric as claimed in clause 12, characterized in that the sheath polymer and the core polymer have a melt flow rate of from about 30 g / 1 minutes to about 35 g / 10 minutes.

17. A non-woven fabric as claimed in clause 12, characterized in that the sheath polymer has a melting temperature of from about 110 ° C to about 150 ° C.

18. A non-woven fabric as claimed in clause 12, characterized in that the core polymer comprises melalocene-catalyzed polypropylene.

19. A non-woven fabric comprising continuous polymeric filaments, the polymeric filaments are formed by being extruded through a spinning organ, the polymeric filaments comprise filaments of multiple components including a sheath polymer and a core polymer, the polymer of The sheath comprises a random copolymer of a polypropylene polymer ethylene, the ethylene being present in the sheath polymer in an amount of less than about 2% by weight, the core polymer comprises a polypropylene polymer, the polypropylene being present in the core polymer in an amount of at least 95% by weight, the core polymer having a melting temperature that is at least about 15 ° F higher than the melting temperature of the sheath polymer, the polymer Core and sheath polymer have a melt flow rate of at least 30 g / 10 minutes, polymer filaments continuous coss being fused together to form the non-woven fabric.

20. A non-woven fabric as claimed in clause 19, characterized in that the sheath polymer has a melting temperature of from about 110 ° C to about 150 ° C.

21. A non-woven fabric as claimed in clause 19, characterized in that the core polymer comprises a metallocene-catalyzed polypropylene.

22. A non-woven fabric as claimed in clause 19, characterized in that the sheath polymer comprises from about 20% by weight to about 70% by weight of the continuous filaments.

23. A non-woven fabric as claimed in clause 19, characterized in that the ethylene is present in the sheath polymer in an amount of less than about 1. 8% by weight.

24. A fiber that includes: A filament bonded with bicomponent yarn including a sheath polymer and a core polymer, the sheath polymer comprises a random copolymer of a polypropylene polymer and ethylene, the ethylene being present in the sheath polymer in an amount of less than of about 2% by weight, the core polymer comprises a polypropylene polymer, the core polymer has a melting temperature that is at least about 15 ° F higher than the melting temperature of the sheath polymer.

25. A fiber as claimed in clause 24, characterized in that the ethylene is present in the sheath polymer in an amount of less than about 1.8% by weight.

26. A fiber as claimed in clause 24, characterized in that the sheath polymer and the core polymer have a melt flow rate of from about 30 g / 10 minutes to about 35 g / 10 minutes.

27. A fiber as claimed in clause 24, characterized in that the sheath polymer has a melting temperature of from about 110 ° C to about 150 ° C.

28. A fiber as claimed in clause 24, characterized in that the core polymer comprises metallocene-catalyzed polypropylene.

29. A fiber as claimed in clause 24, characterized in that the sheath polymer comprises from about 20% by weight to about 70% by weight of the continuous filaments. SUMMARY Bundled filaments with bicomponent yarn and non-woven fabrics made of the filaments are described. Spunbonded filaments include a core polymer and a sheath polymer. Both the core polymer and the sheath polymer are made primarily of polypropylene polymers. For example, the sheath polymer may be a random copolymer of polypropylene and ethylene. Ethylene may be present in the sheath polymer in an amount of less than about 2% by weight. The core polymer, on the other hand, may be a polypropylene polymer having a melting temperature that is greater than that of the sheath polymer.