KR20050056950A - Multi-component fibers and non-woven webs made therefrom - Google Patents

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

MULTI-COMPONENT FIBERS AND NON-WOVEN WEBS MADE THEREFROM

Nonwoven fabrics made from polymeric materials are used to make a variety of products in which it is desirable to have liquid handling properties such as softness, strength, uniformity, absorbency, and other physical properties. Such products include towels, industrial wipes, incontinence products, baby hygiene products such as baby diapers, absorbent feminine hygiene products and clothing such as medical garments. These products are often made with multiple layers of nonwoven fabrics to achieve the desired combination of properties.

In many applications, nonwoven fabrics are produced from spunbond filaments formed by melt spun thermoplastic materials. Is not a method for producing a spunbond nonwoven fabric, and is disclosed in U.S. Patent No. 5,418,045, issued to U.S. Patent No. 4,340,563 No. and Pike, etc. issued to such example D'such as U.S. Patent No. 4,692,618, issued to swineo, eopel All of which are hereby incorporated by reference. Spunbond nonwoven polymer webs are formed by extruding thermoplastic material through a spinneret and drawing the extruded material into the filaments as a high speed stream to form a random web on the collecting surface.

In some applications, spunbond nonwoven fabrics are formed from multicomponent filaments, such as bicomponent filaments, to produce spunbond materials that relate to a desired combination of ductility, strength, and absorbency. Bicomponent filaments are filaments made from the first and second polymer components that remain discrete in the filament. For example, in one embodiment, the filaments may be in the shell and core arrangement in which the first polymer component makes up the core and the second polymer component makes up the sheath.

To date, very useful bicomponent spunbond filaments have been prepared comprising a core polymer made from polyethylene and a shell polymer made from polypropylene. The shell polymer generally has a lower melting temperature than the core polymer so that the filaments are easily thermally bonded together. The outer polymer also provides ductility to the final nonwoven web. On the other hand, the core polymer provides strength to the web.

Spunbond filaments and nonwoven webs made from the filaments described above provide significant advances in the art, but further improvements are still needed. In particular, there is a need for an inexpensive alternative to the spunbond filaments described above having substantially the same or superior properties as spunbond filaments made in the past.

1 is a cross-sectional view of one embodiment of a bicomponent filament made in accordance with the present invention.

2 is a schematic diagram of one embodiment of a process line that may be used to produce filaments in accordance with the present invention.

In general, the present invention relates to spunbond multicomponent filaments and nonwoven webs made from filaments. For example, in one embodiment, the present invention relates to a nonwoven web comprising continuous polymeric multicomponent filaments. Polymeric filaments include shell polymers and core polymers. Shell polymers include copolymers of polypropylene and monomers. In contrast, the core polymer comprises a polypropylene polymer. In general, the core polymer has a melting temperature at least about 8 ° C. (15 ° F.) above the melting temperature of the shell polymer. When combined to form a nonwoven web, the filaments can be thermally fused together.

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

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

In contrast, the core copolymer may be about 98% by weight polypropylene. For example, in one embodiment, the core polymer can be a metallocene catalyzed polypropylene.

The melt flow rate of the shell polymer and the core polymer can be from about 30 g / 10 minutes to about 40 g / 10 minutes and in particular from about 30 g / 10 minutes to about 35 g / 10 minutes. The shell polymer may have a melting temperature of about 110 ° C to about 150 ° C. As mentioned above, the core polymer may have a melting temperature at least about 8 ° C. above the melting temperature of the shell polymer. Although various products can be prepared according to the present invention, the disclosure is particularly suitable for the formation of spunbond fibers and in particular spunbond continuous filaments.

Hereinafter, other features and aspects of the present invention will be discussed in detail.

The complete and legitimate disclosure of the invention, including the best mode of the invention, which is intended for those skilled in the art, is described in particular in the remainder of the specification with reference to the accompanying drawings.

Repeat use of reference numerals in the specification and drawings of the present invention is intended to represent the same or similar elements of the present invention.

It is to be understood by those skilled in the art that the discussion of the present invention is merely illustrative of exemplary embodiments and is not intended to limit the broad aspects of the present invention and that the broad aspects are practiced in the exemplary configurations.

In general, the present invention relates to nonwoven webs made from multicomponent polymer filaments. Nonwoven webs are made to balance the desired physical properties. Generally, multicomponent polymer filaments are continuous bicomponent filaments comprising a core polymer surrounded by a shell polymer. According to the invention, all core polymers and shell polymers mainly comprise polypropylene. For example, the shell polymer may be a random polymer of polypropylene and the core polymer may be a crystalline polypropylene polymer having a relatively high melting point.

The inventors of the present invention find that nonwoven webs having improved strength and bursting properties can be formed compared to nonwoven webs made from monocomponent filaments while maintaining ductility and absorbency when using polypropylene polymers selected to make up bicomponent filaments. Revealed. Among certain advantages, nonwoven webs associated with improved properties can be formed in accordance with the present invention using relatively inexpensive polypropylene materials as opposed to relying on the use of expensive foreign polymers to improve bonding or viscosity.

1, one embodiment of a cross section of a filament 100 generally manufactured in accordance with the present invention is shown. As shown, the filament 100 is a bicomponent filament comprising the core polymer 200 surrounded by the shell polymer 300. As mentioned above, according to the present invention, both the core polymer 200 and the shell polymer 300 are mainly made from polypropylene polymers. Furthermore, in one embodiment, the filament 100 is a spunbond filament, which may be continuous.

As shown, the core polymer 200 and the shell polymer 300 are arranged in separate regions that cross the cross section of the filament 100. All polymers extend the entire distance of the filament 100. In this embodiment, the core polymer 200 is shown to be substantially concentric with the shell polymer 300. However, it should be understood that the core polymer and the shell polymer may be placed in a variety of different arrangements. For example, core polymer 200 and sheath polymer 300 may also be placed in an eccentric array configuration.

In general, the shell polymer 300 has a lower melting temperature than the core polymer 200. In this manner, the sheath polymer 300 of one filament can be easily melted and fused with the sheath polymer of adjacent filaments during formation of the nonwoven web. Bonding may occur between adjacent filaments without melting the core polymer 200 which provides increased strength to the filaments.

The shell polymer 300 used to make the filament and nonwoven webs according to the present invention mainly comprises polypropylene polymers such as crystalline polypropylene. The polypropylene polymer should have a relatively low melting temperature, such as a melting temperature of less than about 150 ° C. In particular, the melting temperature of the polypropylene shell polymer may be from about 110 ° C to about 150 ° C and in particular from about 120 ° C to about 135 ° C. The melt flow rate of the polymer may be from about 30 g / 10 minutes to about 40 g / 10 minutes and in particular from about 30 g / 10 minutes to about 35 g / 10 minutes. The aforementioned melt flow range is particularly suitable for the formation of spunbond filaments in melt spinning operations.

In one embodiment, the outer polymer is a copolymer of polypropylene and monomers, in particular a random copolymer of polypropylene and monomers. The monomer may for example be ethylene or butene. The amount of monomer included in the random polypropylene copolymer is relatively low in some applications. Specifically, it has been found by the inventors that the monomer should be present in the random copolymer in an amount of less than about 2% by weight, in particular about 1.8% by weight. For example, in one embodiment, the monomer may be ethylene and may be included in the random copolymer in an amount of less than about 1.6 weight percent.

Low levels of monomers included in random copolymers provide various benefits and advantages of the present invention. For example, it was recognized that when the monomer is present in an amount greater than about 2% by weight, the filaments lose some strength and ductility. Furthermore, the filaments tend not to be rapidly cooled effectively during formation. It is believed that good binding properties between the core polymer and the shell polymer are achieved when the monomer is present in an amount of less than about 2% by weight.

In one embodiment of the present invention, the shell polymer may be a random copolymer of polypropylene and ethylene sold by Dow Chemical under product number 6D43. However, Dow Chemical's 6D43 polymer comprises ethylene in an amount of about 3.2% by weight. As such, when used in the present invention, significant amounts of polypropylene or another suitable polymer may be added to the article to reduce monomer levels.

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

The shell polymer not only provides ductility to the spunbond filaments and nonwoven webs made in accordance with the present invention but also improves the toughness of the web. For example, due to its low melting temperature, the shell polymer has a soft feel. Furthermore, because the shell polymer has a low melting temperature, the shell polymer is suitable for melting and fusing with adjacent fibers. In fact, the sheath polymer can easily melt with other filament fibers during bonding, so the nonwoven webs formed in accordance with the present invention have great integrity and toughness.

As mentioned above, the core polymer 200 as shown in FIG. 1 also mainly comprises polypropylene. However, compared to the shell polymer, the core polymer generally has a higher melting temperature than the shell polymer. For example, the core polymer may have a melting temperature at least about 8 ° C. (15 ° F.) higher than the melting temperature of the shell polymer, and in particular may have a melting temperature about 8 ° C. to about 15 ° C. higher than the shell polymer. For example, the core polymer may have a melting temperature above about 150 ° C. and in particular above about 155 ° C.

During the thermal bonding of the filaments made according to the invention, the core polymer generally does not severely melt or degrade. The core polymer is present in the filament to increase the strength of the filament and to increase the strength of the nonwoven web made from the filament.

In one embodiment, the core polymer comprises a homopolymer of polypropylene in an amount of at least about 95% by weight. Other polymers and additives may be combined with the core polymer in relatively small amounts. To facilitate the formation of spunbond filaments, particularly continuous filaments in melt spinning operations, the core polymer may be from about 30 g / 10 minutes to about 40 g / 10 minutes and in particular from about 33 g / 10 minutes to about 39 g / 10 minutes. It can have a melt flow rate of.

The polypropylene included in the core polymer may be a Ziegler-Natta catalyzed polymer or may be a metallocene catalyzed polymer. Metallocene catalyzed polymers offer a variety of advantages, including the possibility of providing polymers associated with relatively low molecular weight distributions. In one embodiment, the core polymer is product number 3155 or 3854 sold by Exxon Corporation.

Generally, the shell polymer is present in the filaments in an amount of about 20% to about 70% by weight and in particular about 40% to about 60% by weight.

The disclosure of the present invention is particularly suitable for producing continuous melt spun filaments such as spunbond filaments. 2, a process line 10 for preparing spunbond filaments in accordance with the present invention is shown. Process line 10 is arranged to produce bicomponent continuous filaments and to produce nonwoven webs made from spunbond filaments. In this embodiment, process line 10 includes a pair of extruders 12A, 12B that extrude the shell polymer and the core polymer separately. The outer polymer is transferred from the first hopper 14A into the extruder 12A and the core polymer is transferred from the second hopper 14B into the extruder 12B.

The shell polymer and core polymer are transferred from the extruders 12A, 12B to the spinneret 18 through the polymer conduits 16A, 16B. Generally speaking, in one embodiment, the spinneret 18 has a spin pack with a plurality of plates stacked up and down with openings in a predetermined pattern arranged to create a flow path guiding the polymer component through the spinneret. And a housing. Spinnerets 18 have openings arranged in one or more rows. The spinneret opening forms a curtain extending downward of the filament when the polymer is extruded through the spinneret.

In the illustrated embodiment, the process line 10 may also include a rapid cooling blower 20 positioned adjacent to a curtain of filaments extending from the spinneret 18. The air from the quench air blower 20 rapidly cools the filaments extending from the spinneret 18. The rapid coolant may be guided from one side of the filament curtain or from both sides of the filament curtain as shown in FIG.

The process line may further comprise a fiber suction unit or inhaler 22 positioned below the spinneret containing the rapidly cooled filaments. Fiber suction units or inhalers used in melt spinning polymers are well known as described above.

Generally speaking, the fiber suction unit 22 includes an elongated vertical passageway through which the filaments are drawn in by sucking air flowing from both sides of the passageway and flowing downwardly through the passageway. The heater 24 can supply the hot suction air to the fiber suction unit 22. The hot intake air sucks the filament and the ambient air through the fiber suction unit.

The porous forming surface 26 is located below the fiber suction unit 22 and receives continuous filaments from the outlet opening of the fiber suction unit. The forming surface 26 is moved around the guide roll 28. The vacuum chamber 30 located below the forming surface 26 on which the filaments are deposited sucks the filaments against the forming surface.

In the embodiment shown in FIG. 2, the process line 10 further comprises a compression roller 32 which receives the web together with the foremost of the guide roller 28 as the web is drawn off from the forming surface 26 and sucked. do. From the compression roller 32, the web is transferred to a winding roll 42 which winds up the finished fabric. Prior to winding the web onto the roll 42, the process line may further comprise some form of bonding device, such as a hot spot bonding roller and / or a through air coupler. Heat point couplers and through air couplers are well known to those skilled in the art and are not disclosed in detail herein.

To operate the process line 10, the hoppers 14A and 14B are filled with respective polymer components. The core polymer and sheath polymer are melted and extruded by respective extruders 12A, 12B through polymer conduits 16A, 16B and spinnerets 18. During extrusion, the polymer is heated to a temperature sufficient to allow the polymer to flow.

As the extruded filaments extend below the spinneret 18, a stream of air from the rapid cooling blower 920 at least partially rapidly cools the filaments. For example, rapid cooling air can be flowed in a direction substantially perpendicular to the length of the filament. The temperature of the quench air can be between about 7 ° C. (45 ° F.) and about 32 ° C. (90 ° F.) and can be between about 30 m / min (100 ft / min) and 122 m / min (400 ft / min). have.

After the rapid cooling, the filaments are sucked into the vertical passage of the fiber suction unit 22 by the flow of hot air from the heater 24 through the fiber suction unit. However, it should be understood that the use of a fiber suction unit is optional. When present in the system, the fiber suction unit can be used, for example, to cause the filament to be slightly crimped. After exiting the fiber suction unit 22, the filaments are deposited onto the forming surface 26 to be moved. The vacuum chamber 20 draws the filaments against the forming surface to form an unbonded nonwoven web of continuous filaments. Next, the web is compressed by the compression roller 32. The webs can then be joined together using any suitable technique, such as by using a hot spot bonding roller or by using a through air coupler. When using a through air coupler, air having a temperature above the melting temperature of the shell polymer and below the melting temperature of the core polymer is drawn from the hood and through the web. Hot air melts the shell polymer forming a bond between the bicomponent filaments to unite the web. The temperature of the air flowing through the coupler may be between about 110 ° C. (230 ° F.) and about 138 ° C. (280 ° F.) and between about 30 m / min (100 ft / min) and 152 m / min (500 ft / min). It can be speed.

Finally, the finished web is wound into a winding roller 42 and ready for further processing or use. Spunbonded nonwoven webs constructed in accordance with the present invention have been found to provide various advantages and benefits. For example, nonwoven webs have been found to have increased tensile and burst strength with respect to webs made only of polypropylene polymers. In fact, the webs exhibited comparable properties to bicomponent filaments made according to conventional methods. However, because the filaments of the present invention are made exclusively of polypropylene polymers, the filaments are produced relatively inexpensively.

Spunbond nonwoven webs made in accordance with the present invention may be used in a number of applications. For example, spunbond webs can be used to make personal care products and garment materials. Personal hygiene products include infant hygiene products, such as disposable diapers, baby hygiene products, such as training pants, and adult hygiene products, such as incontinence products and feminine hygiene products. Suitable clothing includes medical clothing, work products, and the like.

In one embodiment, the spunbond nonwoven webs according to the present invention can be combined with other webs to form laminates. For example, spunbond webs can be laminated to other spunbond webs or meltblown webs. For example, in one specific embodiment, spunbond / meltblown / spunbond laminates are formed that include the nonwoven webs of the present invention. The basis weight of the nonwoven web may be, for example, 0.25 OSY to about 3 OSY and especially about 0.50 OSY to about 2 OSY. For example, in one embodiment, a spunbond / meltblown / spunbond stack can be formed in which each layer has a basis weight of about 1 OSY.

These and other modifications and variations of the present invention can be made by those skilled in the art without departing from the spirit and scope of the invention as specifically described within the appended claims. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those skilled in the art will understand that the foregoing descriptions are merely examples and are not intended to limit the invention further described within this appended claims.

Claims (29)

Nonwoven web comprising continuous polymeric filaments, The polymer filament comprises a multicomponent filament having a sheath polymer and a core polymer, the sheath polymer comprises a copolymer of polypropylene and a monomer, the core polymer comprises a polypropylene polymer, and the core polymer is above the melting temperature of the sheath polymer. A nonwoven web having a melting temperature as high as at least about 8 ° C. (15 ° F.), wherein the continuous polymer filaments are fused together. The nonwoven web of claim 1 wherein the jacketed polymer comprises a random copolymer. The nonwoven web of claim 2 wherein the monomer comprises ethylene. The nonwoven web of claim 2 wherein the monomer is present in the shell polymer in an amount of less than about 2% by weight. 4. The nonwoven web of claim 3 wherein the monomer is present in the shell polymer in an amount of less than about 2% by weight. The nonwoven web of claim 1 wherein the continuous filament comprises a spunbond filament. The nonwoven web of claim 1 wherein the shell polymer and core polymer have a melt flow rate of about 30 g / 10 minutes to about 35 g / 10 minutes. The nonwoven web of claim 1, wherein the outer polymer has a melting temperature of about 110 ° C. to about 150 ° C. 3. The nonwoven web of claim 1 wherein the core polymer comprises a metallocene catalyzed polypropylene. The nonwoven web of claim 1 wherein the core polymer comprises polypropylene in an amount of at least 98% by weight. The nonwoven web of claim 1 wherein the skin polymer comprises from about 20 wt% to about 70 wt% continuous filaments. Nonwoven web comprising polymeric fibers, The polymeric fiber comprises a multicomponent filament having a sheath polymer and a core polymer, the sheath polymer comprises a random copolymer of polypropylene polymer and ethylene, ethylene is present in the sheath polymer in an amount of less than 2% by weight, and the core polymer And a polypropylene polymer, the core polymer having a melting temperature at least about 8 ° C. (15 ° F.) above the melting temperature of the shell polymer, wherein the polymer fibers are fused together. 13. The nonwoven web of claim 12 wherein ethylene is present in the shell polymer in an amount of less than about 1.8% by weight. The nonwoven web of claim 12 wherein the multicomponent fiber is a continuous filament. The nonwoven web of claim 12 wherein the multicomponent fiber is a spunbond fiber. The nonwoven web of claim 12 wherein the skin polymer and the core polymer have a melt flow rate of about 30 g / 10 minutes to about 35 g / 10 minutes. The nonwoven web of claim 12 wherein the skin polymer has a melting temperature of about 110 ° C. to about 150 ° C. 13. The nonwoven web of claim 12 wherein the core polymer comprises a metallocene catalyzed polypropylene. Nonwoven web comprising continuous polymeric filaments, The polymer filament is formed by extruding through a spinneret, the polymer filament comprises a multicomponent filament having a sheath polymer and a core polymer, the sheath polymer comprising a random copolymer of polypropylene polymer and ethylene, ethylene being about 2 weights Present in the shell polymer in an amount of less than%, the core polymer comprises a polypropylene polymer, the polypropylene is present in the core polymer in an amount of at least 95% by weight, and the core polymer is at least about 8 ° C. above the melting temperature of the shell polymer A nonwoven web having a melting temperature as high as (15 ° F.), the core polymer and the shell polymer having a melt flow rate of at least 30 g / 10 minutes, and the continuous polymer filaments are fused together to form a nonwoven web. The nonwoven web of claim 19 wherein the skin polymer has a melting temperature of about 110 ° C. to about 150 ° C. 20. The nonwoven web of claim 19 wherein the core polymer comprises a metallocene catalyzed polypropylene. 20. The nonwoven web of claim 19 wherein the shell polymer comprises from about 20% to about 70% by weight continuous filaments. 20. The nonwoven web of claim 19 wherein ethylene is present in the shell polymer in an amount of less than about 1.8 weight percent. The bicomponent spunbond filament comprises a sheath polymer and a core polymer, the sheath polymer comprises a random copolymer of polypropylene polymer and ethylene, ethylene is present in the sheath polymer in an amount of less than about 2% by weight and the core polymer is A polypropylene polymer, wherein the core polymer has a melting temperature at least about 8 ° C. (15 ° F.) above the melting temperature of the shell polymer. The fiber of claim 24 wherein the ethylene is present in the shell polymer in an amount of less than about 1.8% by weight. The fiber of claim 24 wherein the shell polymer and the core polymer have a melt flow rate of about 30 g / 10 minutes to about 35 g / 10 minutes. The fiber of claim 24, wherein the shell polymer has a melting temperature of about 110 ° C. to about 150 ° C. 25. The fiber of claim 24 wherein the core polymer comprises a metallocene catalyzed polypropylene. The fiber of claim 24 wherein the shell polymer comprises from about 20 wt% to about 70 wt% continuous filament.