HK1148984B

HK1148984B - Multilayer variable stretch nonwoven fabric composites

Info

Publication number: HK1148984B
Application number: HK11103210.5A
Authority: HK
Inventors: Peter W. Pascavage
Original assignee: Invista Technologies S.À R.L.
Priority date: 2007-09-07
Filing date: 2008-09-04
Publication date: 2015-04-24

Description

Multilayer variable stretch nonwoven fabric composite

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to provisional application No. 60/970,554 filed on 7/9/2007. Thus, provisional application No. 60/970,554 is incorporated by reference herein in its entirety.

Technical Field

The present invention relates to multi-layer nonwoven fabric composites in which certain nonwoven layers containing fibers are of a certain type and laid in a specific pattern and orientation to provide unique tensile properties to the composite. The resulting nonwoven composite has acceptable tensile strength and can have widely variable tensile characteristics.

Background

Stretchable nonwoven fabrics are benefiting from the rapid growth of the health care industry. Most products in use have longitudinal stretch capability, e.g. Kimberly ClarkAnd "Flex-All" products, or cross-direction stretch, such as "Golden Phoenix" or "Tredegar" nonwoven-elastomeric film laminates. Stretchable nonwoven fabrics stretched in one or several directions provide valuable functionality for health care related products as well as opening new end uses such as garments of such stretchable nonwoven fabrics.

Known techniques for preparing stretchable nonwoven fabrics include those based on laminating an elastic film to a nonwoven, a fiber to a nonwoven, or multiple nonwoven layers, each layer having characteristic properties designed to perform certain functions. A well-known form of multilayer nonwoven composite construction consists of a meltblown elastic inner layer surrounded by two outer layers of spunbond, hard (i.e., no measurable stretchability) fibers. By laminating the elastic layer to the spunbond outer layer, the extensible nonwoven fabric in this form may have unidirectional stretch in either the machine direction or the cross direction when the elastic layer is in a stretched configuration.

Commercial producers have also made fully elastic multidirectional spunbond nonwoven fabrics by using elastic thermoplastic polymers in a conventional spunbond process. However, some of these products, while exhibiting excellent elasticity, also have rubber-like handles with unpleasant elastic polymer characteristics. The use of an elastic polymer in the inner nonwoven layer, which is shielded by the outer nonwoven layer of stiff fibers, avoids this problem, particularly if stiff fibers of low denier are used.

The variation in the stretch properties of the multi-layer nonwoven web may be provided by varying the orientation of inelastic hard filaments or fibers formed as the nonwoven outer layers of a laminate composite having one or more elastic inner layers. Such outer layer hard filaments or fibers, oriented such that they are primarily aligned in the machine direction, will tend to minimize or eliminate the tendency of the nonwoven composite to stretch in the machine direction while still maintaining the ability of the composite to stretch somewhat in the cross direction. Nonwoven composite webs of this type have been disclosed, for example, in U.S. patent No. 5,393,599.

The variation in tensile properties typically used in such multi-layer composites can also be provided by utilizing fibers in one or more nonwoven outer layers of such composites, which are bicomponent and/or somewhat elastic in the composite, regardless of fiber orientation. In such nonwoven structures, there remains a need to balance the desirable tensile properties of the nonwoven fabric and to avoid undesirable tactile, hand or aesthetic characteristics in the outer layer fibers used.

While techniques for making multilayer nonwoven composites having primarily unidirectional, e.g., cross-machine direction, or multidirectional, e.g., isotropic, stretch properties with certain fiber types and orientations in each composite layer have utility, to meet the needs and requirements of potential use, it would be desirable and useful to identify additional types of such nonwoven composite structures where the stretch properties and fiber composition may be altered. Such composites would be those that can be made using conventional spunbond and meltblown apparatuses and processes without the need for additional post-web preparation processing steps that add time and expense to induce the desired tensile properties.

Summary of The Invention

The present invention relates to nonwoven fabric composites, in particular to such composites of the spunbond-meltblown (SM), spunbond-meltblown-Spunbond (SMs) or spunbond-meltblown-spunbond (SMMS) type in general. Such fabric composites are prepared by forming or assembling the layers of the composite in the machine direction.

In one embodiment, such nonwoven fabric composites comprise: a) at least one inner layer comprising meltblown fibers; and b) at least one outer layer disposed on one side of the at least one inner layer. One or more of the outer layers are formed from spunbond, continuous filament fibers comprising different fibers formed from at least two different types of polymeric materials.

Such spunbond fibers are deposited during the formation of one or more outer layers so as to form a plurality of discrete, substantially parallel stripes of fibers within each outer layer. One of the at least two fiber strands has a polymer composition that is different and distinct from the other of the at least two fiber strands due to the inclusion therein of fibers formed of different types of polymer materials.

Substantially parallel, distinct fiber stripes are deposited during the formation of one or more outer layers so as to be oriented primarily in the machine direction of the nonwoven fabric composite. The inner and outer layers of the composite fabric are bonded together by heat, adhesive, ultrasonic or mechanical bonding.

In another inventive embodiment, the nonwoven fabric composite herein comprises: a) at least one inner layer comprising elastic meltblown fibers; and b) two outer layers disposed on opposite sides of the at least one inner layer. At least one of the two outer layers comprises spunbond, continuous filament fibers comprising first spunbond fibers formed of a first type of polymeric material and second spunbond fibers formed of a second type of polymeric material. The second type of polymeric material is different from the first type of polymeric material.

The spunbond fibers are deposited during the formation of at least one outer layer to form a plurality of alternating, discontinuous, substantially parallel stripes of fibers within the outer layer or layers. Such alternating fiber strips are formed from alternating first and second spunbond fibers. Moreover, during the formation of one or more outer layers, these alternating, discontinuous, substantially parallel strips of fibers are deposited so as to be oriented primarily in the machine direction of the nonwoven fabric composite. All nonwoven composite layers are bonded together by heat, adhesive, ultrasonic or mechanical bonding methods.

The composites herein may exhibit variable amounts of stretch in both the machine and cross directions depending on the polymer composition of the spunbond fibers of the different fiber stripes in the meltblown inner layer or layers and the spunbond outer layer or layers. Selection of the appropriate type of polymer composition for the various fibers within the composite structure can result in achieving a desired ratio of selection of machine direction stretch to cross direction stretch for such nonwoven fabric composites.

The invention requests protection:

1. a multilayer nonwoven fabric composite prepared by forming the layers of the composite in a machine direction comprising a machine direction and a cross direction, exhibiting stretch in both the machine direction and the cross direction, the cross direction stretch ranging from about 100% to about 250%, the machine direction stretch being less than 50%, the multilayer nonwoven fabric composite comprising:

a) at least one inner layer comprising meltblown fibers; and

b) at least one outer layer comprising spunbond, continuous filament fibers and disposed on one side of the at least one inner layer;

wherein the spunbond fibers in the at least one outer layer comprise different fibers formed from at least two different types of polymeric materials; and

wherein said spunbond fibers are deposited during the formation of said at least one outer layer to form a plurality of discrete, substantially parallel stripes of fibers within said at least one outer layer, and wherein one of at least two of said stripes has a polymer composition that is different from and distinct from the other of said at least two stripes due to the inclusion therein of fibers formed of different types of polymeric materials, wherein one of said stripes comprises an elastomeric polymer; and

wherein parallel strips of spunbond fibers within each spunbond layer are oriented primarily in the machine direction by maintaining the orientation of the strips of fibers substantially parallel to the machine direction of the substrate upon which such strips of spunbond fibers have been deposited to form the spunbond layer; and

wherein the spunbond layers each independently exhibit a ratio of machine direction tensile strength to cross direction tensile strength of at least about 1.25: 1; and

wherein during the formation of the at least one outer layer, the substantially parallel stripes of different fibers are deposited so as to be oriented primarily in the machine direction of the nonwoven fabric composite; and

wherein the at least one inner layer and the at least one outer layer of the fabric are bonded together via heat, adhesive, ultrasonic, or mechanical bonding methods.

2. The fabric composite of item 1 wherein in at least one of the outer layers, one type of the spunbond fiber stripes comprises polypropylene and the other type of stripes comprises polypropylene blended with the elastic polymer.

3. The fabric composite of item 2, wherein the spunbond fibers in each of the outer layers are independently partially attenuated to an average of about 1.8 to about 3.0 denier per filament.

4. The fabric composite of item 3, wherein in the at least one outer layer, one type of spunbond fiber sliver comprises a blend of polypropylene with a copolymer of: copolymers of ethylene and propylene, or copolymers of ethylene and/or propylene with at least one other alpha-olefin.

5. The fabric composite of item 3 wherein in one or both of the outer layers, one type of spunbond fiber strip comprises multicomponent fibers that each comprise at least one elastic polymer and at least one different inelastic polymer.

6. The fabric composite of item 5 wherein one type of spunbond multicomponent fiber sliver comprises bicomponent fibers comprising an elastomeric polymer core selected from the group consisting of polyesters, polyurethanes, polyamides, copolymers of ethylene with at least one vinyl monomer, and A-B-A' block copolymers, and a non-elastomeric sheath comprising a non-elastomeric polyolefin,

wherein A and A' are the same or different and each represents a thermoplastic polymer endblock and B represents an elastomeric polymer midblock.

7. The fabric composite of item 3, wherein the spunbond fibers in the stripes of the at least one outer layer independently comprise a polymer or combination of polymers having a melt flow rate of about 20 to about 80.

8. The fabric composite of item 1, wherein the spunbond fibers are extruded in an alternating pattern of parallel stripes as two types of filament stripes.

9. The fabric composite of item 1, wherein the spunbond layers each independently have from about 5 to about 45g/m²The basis weight of (a).

10. The fabric composite of item 1, wherein the fibers of the at least one meltblown layer comprise a polymeric material selected from the group consisting of elastic polyolefins, elastic polyesters, elastic polyurethanes, elastic polyamides, elastic copolymers of ethylene and at least one vinyl monomer, and elastic A-B-A' block copolymers,

11. The fabric composite of item 10, wherein the fibers of the at least one meltblown layer comprise an elastic polyolefin selected from random copolymers of ethylene and propylene or random copolymers of ethylene and/or propylene and at least one other alpha-olefin, and blends of the random copolymers with isotactic polypropylene.

12. The fabric composite of item 10, wherein the meltblown fibers in the at least one inner layer comprise multicomponent fibers that each comprise at least one elastic polymer and at least one different inelastic polymer.

13. The fabric composite of item 12, wherein the meltblown multicomponent fibers are bicomponent fibers comprising an elastomeric polymer core selected from the group consisting of polyesters, polyurethanes, polyamides, copolymers of ethylene with at least one vinyl monomer, and a-B-a' block copolymers, and a non-elastomeric sheath comprising a non-elastomeric polyolefin.

14. The fabric composite of item 13, wherein the bicomponent fibers comprise a sheath of polypropylene.

15. The fabric composite of item 10, having a meltblown inner layer, the meltblown inner layer having a basis weight of about 5 to about 40oz/yd²。

16. The fabric composite of item 1 wherein the composite layers have been thermally bonded using a discontinuous pattern of points, lines, or other patterns of intermittent bonds.

17. The fabric composite of item 16, wherein the layers of the composite have been thermally bonded together by passing the layers through a nip formed by a patterned calender roll and a smooth roll, or between two patterned rolls, and heating at least some of the rolls.

18. The fabric composite of clause 17, wherein the thermal bonding is achieved using a roll bonding temperature of about 110 ℃ to 130 ℃ and a bonding nip pressure of about 100-.

19. The fabric composite of item 1 wherein two spunbond layers and one meltblown layer each comprise about 5-60% by weight of the composite, the composite being in the SMS configuration with three layers together comprising 100% of the SMS composite.

20. The fabric composite of item 1, having a basis weight of from about 10 to about 300 grams per meter²(gsm)。

21. A multilayer nonwoven fabric composite prepared by forming the layers of the composite in a machine direction comprising a machine direction and a cross-machine direction, the fabric exhibiting stretch in both the machine direction and the cross-machine direction, the cross-machine direction stretch ranging from about 100% to about 250%, the machine direction stretch being less than 50%, the multilayer nonwoven fabric composite comprising:

a) at least one inner layer comprising elastic meltblown fibers; and

b) two outer layers each comprising spunbond, continuous filament fibers, and each outer layer disposed on opposite sides of the at least one inner layer;

wherein the spunbond fibers in at least one of the outer layers comprise first spunbond fibers comprising a first type of polymeric material comprising an elastomeric polymer and second spunbond fibers formed from a second type of polymeric material different from the first type of polymeric material; and

wherein during the formation of at least one of the outer layers, the spunbond fibers are deposited so as to form a plurality of alternating, discontinuous, substantially parallel stripes of fibers within at least one of the outer layers, the alternating stripes being formed by alternating first spunbond fibers and second spunbond fibers; and

wherein during the formation of at least one of the outer layers, the alternating, discontinuous, substantially parallel strips of fibers are deposited so as to be oriented primarily in the machine direction of the nonwoven fabric composite; and

wherein all layers of the nonwoven fabric composite are bonded together via thermal, adhesive, ultrasonic, or mechanical bonding methods.

22. The fabric composite of item 21, wherein at least one of said outer layers comprises alternating stripes of substantially uniform width from about 50 to about 150 per meter of the cross-sectional width of said outer layer.

Detailed Description

The nonwoven fabric composites herein and the individual layers therein and their components and features may be described using conventional terminology commonly used in connection with articles of this type. Some of the commonly used terms used in the description of the composite articles herein are defined as follows:

as used herein, the term "nonwoven" fabric, layer or web refers to a fabric, layer or web having individual fibers or threads structures that are interlaid, but not in an identifiable manner as in a knitted fabric. Nonwoven fabrics, layers, or webs have been formed from many processes such as, for example, meltblowing processes, spunbonding processes, and bonded carded web processes. Usually in terms of ounces of materialFraction/code²(osy) or g/m²(gsm) to express the basis weight of the nonwoven fabric, layer or web. To convert osy to gsm, the osy value is multiplied by 33.91.

The nonwoven fabrics, layers or webs described herein comprise an array of fibers or filaments. The terms "fiber" and "filament" are used interchangeably herein.

As used herein, the term "meltblown fibers" refers to fibers formed by the process of: the molten thermoplastic material is extruded as molten threads or filaments through a plurality of fine, usually circular, die capillaries into converging high velocity, usually hot, gas (e.g. air) streams which attenuate the filaments of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter, for example, less than about 1.0 denier per filament. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly disbursed meltblown fibers. This process is disclosed, for example, in U.S. Pat. No. 3,849,241 to Butin et al. Meltblown fibers are microfibers which may be continuous or discontinuous and are generally tacky when deposited onto a collecting surface.

As used herein, the term "spunbond fibers" refers to small diameter fibers formed by the following process: molten thermoplastic material is extruded as filaments from a plurality of fine, usually circular capillaries of a spinneret with the diameter of the extruded filaments then being rapidly reduced in diameter by methods such as those in the following patents: U.S. Pat. Nos. 4,340,563 to Appel et al; U.S. Pat. Nos. 3,692,618 to Dorschner et al; U.S. Pat. Nos. 3,802,817 to Matsuki et al; U.S. Pat. nos. 3,338,992 and 3,341,394 to Kinney; U.S. Pat. No. 3,502,763 to Hartman; and U.S. Pat. No. 3,542,615 to Dobo et al. Spunbond fibers are generally not tacky when they are deposited onto a collecting surface. Spunbond fibers are generally continuous.

For both spunbond and meltblown fibers, fiber diameter is typically expressed in microns (μm). Fiber size is also characterized by the term "denier". As used herein, "denier" refers to the weight in grams of a single filament or fiber per 9000 meters.

The fibers used to form the spunbond and meltblown layers of the composites herein are made from polymeric materials. As used herein, the term "polymer" generally includes, but is not limited to, homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc. and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term "polymer" shall include all possible molecular geometric configurations. These configurations include, but are not limited to isotactic, syndiotactic and random symmetries.

One or more meltblown layers

The nonwoven fabric composites herein essentially comprise at least one inner layer comprising a meltblown web. Such meltblown fibers are preferably elastic and may be formed from any of a variety of elastic thermoplastic polymers. Generally any suitable elastic fiber forming resin or blend containing such resins may be used for the elastic meltblown fibers. Such materials include elastic polyolefins, elastic polyesters, elastic polyurethanes, elastic polyamides, elastic copolymers of ethylene with at least one vinyl monomer, and elastic A-B-A 'block copolymers, where A and A' are the same or different thermoplastic polymers.

One preferred type of elastomeric polymer for the meltblown layer comprises an elastomeric polyolefin. Such materials include random polyolefin copolymers, such as copolymers of ethylene and propylene or copolymers of ethylene and/or propylene and at least one other alpha-olefin. Polyolefin copolymers of this type include the ExxonMobil Chemical Company under the trade name ExxonMobilMarketed under the trade name Dow chemical CompanyThose that are on the market. Blends of such random copolymers with isotactic polypropylene may also be used as polymers that can form meltblown nonwoven layers.

In other cases, the elastic meltblown fibers of one or more inner layers may be prepared from block copolymers having the general formula a-B-a ', where a and a' are each thermoplastic polymer endblocks comprising a styrenic moiety such as a poly (vinyl aromatic hydrocarbon), where B is an elastomeric polymer midblock such as a conjugated diene or lower olefin polymer. The block copolymer may be, for example, available under the trademark PolytetrafluoroethyleneG (polystyrene/poly (ethylenebutylene)/polystyrene) block copolymer from Shell Chemical Company. One such block copolymer may be, for exampleG-1657。

Other exemplary elastomeric materials that may be used for the meltblown inner layer or layers include polyurethane elastomeric materials, such as those available under the trademark PURGoodrich from b.f.&Co. those obtained; polyamide elastic materials, e.g. under the trade markThose available from the Rilsan Company; and polyester elastic materials, e.g. under the trade markFrom e.i. dupont De Nemours&Those available from Company. The formation of elastic meltblown fibers from polyester elastic materials is disclosed, for example, in U.S. patent No. 4,741,949 to Morman et al, which is incorporated herein by reference.

Useful elastomeric polymers also include, for example, elastomeric copolymers of ethylene with at least one vinyl monomer such as vinyl acetate, unsaturated aliphatic monocarboxylic acids, and esters of such monocarboxylic acids. The formation of elastomeric copolymers and elastomeric meltblown fibers from those elastomeric copolymers is disclosed, for example, in U.S. Pat. No. 4,803,117, also incorporated herein by reference.

In certain preferred embodiments herein, the fibers used in one or more meltblown layers of the composites herein may be multicomponent fibers. As used herein, the term "multicomponent fiber" refers to a fiber that is formed from at least two different, e.g., immiscible, component polymers or the same polymer, having different characteristics or additives, extruded from separate extruders but spun together to form one fiber or filament. Multicomponent fibers are also sometimes referred to as conjugate fibers or bicomponent fibers, although more than two components may be used.

In multicomponent fibers, the different polymers can be arranged in substantially constantly positioned distinct zones across the cross-section of the multicomponent fiber and extend continuously along the length of the multicomponent fiber. The configuration of the multicomponent fiber can be, for example, a concentric or eccentric sheath/core arrangement in which one polymer is surrounded by another; or may be a side-by-side, "islands-in-the-sea" arrangement; or arranged in pie wedges or strips on round, oval or rectangular cross-section fibers; or other configurations. Multicomponent fibers are taught in U.S. Pat. No. 5,108,820 to Kaneko et al and U.S. Pat. No. 5,336,552 to Strack et al. Conjugate fibers are also taught in U.S. Pat. No. 5,382,400 to Pike et al. All of these patents are incorporated herein by reference.

By using two (or more) polymers of different expansion and contraction rates, the combined fibers can be used to create crimp in the fiber. The bicomponent fibers in one or more of the meltblown layers herein may also comprise a relatively elastic polymer as one component and a different relatively inelastic polymer as another component thereof. For example, the bicomponent fibers used in one or more meltblown layers may comprise an elastomeric polymer such asThe core of the block copolymer is,the core is surrounded by a sheath of a different and immiscible, relatively inelastic polymer such as polypropylene.

For bicomponent fibers, the polymers may be present in the proportions of 75/25, 50/50, 25/75, or any other desired proportion. Further, any given component of a multicomponent fiber may desirably comprise two or more polymers as the multicomponent blend components.

The elastic fibers within one or more meltblown inner layers of the composites herein will typically be microfibers having an average denier per filament of less than about 1.0. They may be formed using 35-75 holes per inch (hpi) melt-jet dies. The basis weight of the meltblown inner layer or layers will generally be from about 5 to about 40oz/yd²More preferably from about 10 to about 30oz/yd²。

The fabric composites herein may comprise more than one inner layer. For example, the composite material herein may be an SMMS configuration with two different meltblown inner layers therein.

Spunbond layer

The fabric composites herein will also comprise at least one outer layer disposed on one side of at least one meltblown inner layer. Preferably, the fabric composites herein will comprise two outer layers of spunbond fibers disposed on opposite sides of at least one meltblown inner layer. Various spunbonding techniques exist, but all typically include basic steps including extruding continuous filaments, quenching the filaments, drawing or attenuating the filaments by a high velocity fluid, and collecting the filaments as fibers on a surface, e.g., forming a strand or other substrate, to form a web. Exemplary spunbonding processes known in the art include the Lurgi spunbonding process, wherein a plurality of circular or tubular venturi nozzles attenuate the filaments; and slot draw spunbond, in which a plurality of tube attenuators (attentuators) are replaced with slot-like attenuators that extend in the weft direction of the machine.

Any spunbonding technique known in the art may be used to form the spunbond outer layers of the composite of the present invention. Exemplary spunbond is described, for example, in the following patentsThe technology comprises the following steps: U.S. Pat. Nos. 4,340,563 and 4,405,297 to Appel et al; U.S. Pat. Nos. 4,692,106 and 78 to Grabowski et alUs patent No. 4,820,459. All of these patents are incorporated herein by reference. The spunbond web can be made or formed in-line and in sequence with one or more elastic meltblown layers.

Any polymer or polymer blend or other combination of polymers capable of being melt spun to form substantially continuous filaments can be used to form the spunbond outer layers of the composites herein. Examples of polymers that may be suitable for forming the spunbond web include polyesters, acrylics, polyamides, polyolefins such as polyethylene, polypropylene, copolymers thereof, and the like, or other thermoplastic polymers, as well as copolymers and blends and combinations of these and other thermoplastic polymers.

As with the fibers used in one or more meltblown layers of the composites herein, the spunbond fibers of the outer layer can also comprise multicomponent fibers as described above. Spunbond multicomponent fibers are those which are: the fibers are formed from different incompatible polymers so as to have different regions of the two or more incompatible polymers comprising the spunbond fibers. Suitable bicomponent fibers for the spunbond layer can, for example, comprise the same types that can be used for one or more of the meltblown layersCore/polypropylene sheath fiber.

Whatever the polymer composition of the filaments used to make the spunbond layer of the composite material herein, such polymeric materials will generally exhibit a melt flow rate of from about 20 to about 55. More preferably, the melt flow rate of the polymer used in the spunbond layer will be from about 25 to about 35. Herein, melt flow rate (mfr) can be determined using the ASTM D-01238-04c method entitled Standard test method for determining melt flow rates of thermoplastics by extrusion plastographs.

The spunbond filaments of the spinneret are preferably only partially attenuated prior to being laid down as fibers to form a spunbond nonwoven web for one or more outer layers of the composite material. For purposes herein, such filaments are locally attenuated if they are stretched to only an average of no less than about 1.8 denier per filament. More preferably, the spunbond filaments used herein for the outer layer are locally attenuated to an average denier per filament of from about 1.8 to about 3.0. By using only partially attenuated fibers in the spunbond layer, the resulting fabric composite can exhibit additional attenuation and stretch when elongated in the cross direction.

An essential feature of the invention is that it is in the form of a plurality of discrete, substantially parallel stripes or rows within which at least one outer layer of spunbond fibers is deposited. Furthermore, at least two of these strips will have mutually different polymer compositions. This difference in polymer composition is caused by two different strands, each comprising fibers that differ from each other by being formed from two different types of polymer materials. Preferably at least one, and preferably both outer spunbond layers will comprise at least 10, more preferably at least 25, discrete, substantially parallel stripes or rows.

For the purposes of the present invention, two polymer types are different from each other provided that they exhibit different and distinguishable chemical, physical, rheological, microstructural, functional or performance characteristics. The polymer types may be different and distinguishable provided and because they have different monomer types and contents, molecular weights, tacticity or other molecular arrangements, crystallinity, melting points, glass transition temperatures, viscosities, melt flow rates, elastic characteristics, and the like. In fact, two aliquots of the same polymeric material may become different polymer types, provided they have been treated in different ways, for example by tapering (stretching) them to different degrees.

In a preferred embodiment, the first set of spunbond fibers will comprise one polymer type and the second set of spunbond fibers will comprise a second polymer type. For example, certain spunbond fibersThe fibers may comprise substantially 100% polypropylene. Other spunbond fibers can comprise compatible blends of polypropylene with elastomeric polymers, such as copolymers of ethylene and propylene or copolymers of ethylene and/or propylene with at least one other alpha-olefin. As indicated above, with respect to elastomers that may be used in the meltblown layer, elastomeric polyolefin copolymers of this type include those available under the trade name ExxonMobil Chemical CompanyThose that are on the market. If such compatible blends of polypropylene with other polymeric materials are used in a population of spunbond layer fibers, it is preferred that such fibers have a polypropylene content of from about 5% to about 90% by weight.

The spunbond fiber stripes deposited to form one or more outer layers can comprise those of three or more different polymer types. Preferably, however, one or more of the outer layers will only comprise two types of stripes deposited in a parallel alternating pattern of stripes, for example in an ABABA or like configuration. More preferably, the two types of strips will be uniform in width. Typically, there are from about 50 to about 150, more preferably from about 70 to about 140, stripes of uniform width and alternating pattern per meter of outer layer cross-sectional width.

Discrete stripes of spunbond fibers can be formed with one or more spinning beams fed by two or more separate extruders that provide two or more different types of polymers for spinning. If a single manifold is used, the manifold can be divided to spin separate polymer filament types in a desired striping relationship. If two manifolds are used, they can be positioned to provide separate rows of filaments for deposition in the desired filament stripe pattern. This type of device is described, for example, in U.S. patent No. 6,872,339, which is incorporated herein by reference.

The fiber stripes in one or more outer spunbond layers of the fabric composite herein are also oriented primarily in the machine direction of the one or more outer spunbond layers. Given that the resulting spunbond web exhibits anisotropic properties, the stripes and fibers in these layers are considered to be oriented primarily in the machine direction. Thus, for example, such spunbond webs used herein will exhibit a ratio of machine direction tensile strength (break strength) to cross direction tensile strength (break strength) of at least about 1.25: 1. More preferably, the ratio of the MD to CD tensile strength of the spunbond web for the composites herein will be from about 1.5: 1 to about 2.5: 1.

Various techniques and apparatus types may be used to form a spunbond web having stripes of filaments/fibers oriented primarily in the machine direction. Such techniques and device types may include those of: these techniques and apparatus alter or change the degree to which the stripes of spunbond filaments are spread, mixed or randomly oriented prior to being laid down or deposited on a forming wire, belt, substrate or other collecting surface to form the desired spunbond web. The simplest way to influence the machine direction orientation of the spunbond fiber strands in the spunbond layer is to exclude various conventional methods commonly used in the spunbond art to randomize the drawn spunbond fibers prior to their deposition. In this manner, the fiber strands of the attenuator may be oriented in a substantially parallel relationship with the longitudinal direction of the substrate upon which such fiber strands are deposited.

Deflector plates or other mechanical elements may also be used to control the orientation of the spunbond filament strands deposited onto the forming substrate. Such methods are shown, for example, in U.S. patent nos. 5,366,793 and 7,172,398 and in U.S. patent publication No. 2006/0137808. Changing the direction of the air flow is shown in U.S. patent No. 6,524,521 to adjust the placement of the spunbond filament strips and thereby affect the longitudinal orientation of the placed filaments. All of these patents and publications are incorporated herein by reference.

The spunbond layers of the composites herein will each independently have from about 5 to about 45g/m²The basis weight of (a).

Fabric composite component

After the spunbond webs used as the outer layers of the composites herein have been formed or are being formed, they are placed in layered, face-to-face relationship with at least one elastic layer to form the fabric composites herein. The layers can be joined together using techniques familiar to those skilled in the art to produce, for example, SMS laminates. The spunbond and meltblown layers can be formed and joined using the in-line process described in U.S. patent No. 4,041,203, or any suitable alternative process. Any of the spunbond and meltblown layers can be formed in-line. The layers may be sequentially overlaid and bonded to each other. U.S. patent No. 6,770,156 describes a suitable multi-station apparatus for preparing the SMS-type fabric composite herein.

The laminated layers are generally bonded together in discrete, discontinuous bond areas by standard bonding techniques, including heat, adhesive, ultrasonic, or mechanical bonding methods. Preferably, the composites herein are formed by thermally bonding one or more elastic inner layers to two spunbond outer layers. In one embodiment, the laminated composite is thermally bonded using a discontinuous pattern of dots, lines, or other patterns of intermittent bonds using methods known in the art. Intermittent thermal bonds may be formed by: applying heat and pressure at discrete points on the surface of the spunbond web, such as by passing the layered structure through a nip formed by a patterned calender (calendar) roll and a smooth roll or a nip formed between two patterned rolls; one or both of the rollers are heated to thermally bond the fabric.

The bonding conditions and bonding pattern may be selected to provide a desired combination of strength, softness, and drape in the bonded fabric. For the fabric composites of the present invention, it has been found that a roll bonding temperature of 110 ℃ to 130 ℃ and a bonding nip pressure of about 100-. The optimum bonding temperature and pressure are a function of the line speed during bonding, and faster line speeds generally require higher bonding temperatures.

The fabric composites herein can also be thermally bonded with ultrasonic energy, for example by passing the fabric composite between a horn (horn) and a rotating backing roll, for example a backing roll having a raised pattern on its surface. Alternatively, the fabric composites herein may be bonded using flow-through bonding methods known in the art, wherein a heated gas, such as air, is passed through the fabric while the fabric is supported on a porous surface at a temperature sufficient to bond the fibers together where their cross-over points contact each other.

The fabric composites herein may have a density of about 10-300 grams/meter depending on the end use application²(gsm), or from about 15 to 200gsm, or from about 20 to 100gsm, or from about 25 to 50gsm basis weight. The basis weight of the composites herein is generally substantially uniform across the surface area of the composite.

For example, the spunbond and meltblown layers can each comprise about 5% to 60% by weight of the preferred SMS-type laminate, or about 15% to 50% by weight of the laminate, or about 20% to 40% by weight of the laminate, and the three layers together comprise 100% of the SMS laminate. The fabric composites herein can have various stretch properties in both the machine direction and the cross direction. In one embodiment, the composite herein may exhibit a stretch of about 50% to about 250% in the transverse direction, with a minimum stretch of, for example, less than 50% in the machine direction.

Examples

An SMS fabric composite having a basis weight of 85gsm was prepared from two outer spunbond layers made from alternating polypropylene (Exxon Mobile Chemical Company)) Strands of filaments and tapes comprising about 25% of this polypropylene with random ethylene/propylene copolymer (of ExxonMobil Chemical Company)2230) Filament strands of the blend of (a). The inner web of the composite comprises elastic meltblown fibers,the fibers comprise the same random ethylene/propylene copolymer (of ExxonMobil Chemical Company)2230). The composite material is prepared on line by the following method: a first spunbond layer was laid on a one meter wide web-formed belt, a layer of meltblown elastic filaments was laid on the first spunbond layer, and finally a second spunbond outer layer was laid on a forming web of meltblown fibers. This sequential formation of SMS fabric composites of this type is carried out in a similar plant arrangement as described in us patent No. 6,427,745.

The filaments of the two spunbond layers were laid in discontinuous alternating stripes of the two polymer types. The strips were uniform in width, 78 strips per meter of spunbond layer cross-sectional width. The filament strands of the spunbond layer are directed through the spinning distance (attenuator to belt) to the forming belt (or to the web layer thereon) and, without any fiber randomization or diffuser means present, thus providing fiber strand orientation primarily in the machine direction within the spunbond layer.

The elastic polymer blend filaments of the meltblown layer were formed using a 50 hole per inch (hpi) melt-blown die. The meltblown layer is formed to make the randomly oriented fibers therein isotropic.

The meltblown layer comprised 20% by weight of the SMS composite. The SMS layers were bonded together using a fixed crown calender (calendar) with a pattern. The resulting SMS composite had 180% stretch in the transverse direction and less than 50% stretch in the machine direction.

Claims

a) at least one inner layer comprising meltblown fibers; and

2. The fabric composite of claim 1 wherein in at least one of said outer layers one type of said stripes of spunbond fibers comprises polypropylene and the other type of stripe comprises polypropylene blended with said elastomeric polymer.

3. The fabric composite of claim 2 wherein said spunbond fibers in each of said outer layers are independently locally attenuated to an average of from about 1.8 to about 3.0 denier per filament.

4. The fabric composite of claim 3 wherein in the at least one outer layer, one type of spunbond fiber stripe comprises a blend of polypropylene with a copolymer of: copolymers of ethylene and propylene, or copolymers of ethylene and/or propylene with at least one other alpha-olefin.

5. The fabric composite of claim 3 wherein one type of spunbond fiber strip in one or both of the outer layers comprises multicomponent fibers each comprising at least one elastic polymer and at least one different inelastic polymer.

6. The fabric composite of claim 5 wherein one type of spunbond multicomponent fiber sliver comprises bicomponent fibers comprising an elastomeric polymer core selected from the group consisting of polyesters, polyurethanes, polyamides, copolymers of ethylene with at least one vinyl monomer, and A-B-A' block copolymers, and a non-elastomeric sheath comprising a non-elastomeric polyolefin,

7. The fabric composite of claim 3 wherein the spunbond fibers in the stripes of the at least one outer layer independently comprise a polymer or combination of polymers having a melt flow rate of from about 20 to about 80.

8. The fabric composite of claim 1 wherein said spunbond fibers are extruded as stripes of two types of filaments in an alternating pattern of parallel stripes.

9. The fabric composite of claim 1 wherein each of said spunbond layers independently has from about 5 to about 45g/m²The basis weight of (a).

10. The fabric composite of claim 1 wherein the fibers of the at least one meltblown layer comprise a polymeric material selected from the group consisting of elastic polyolefins, elastic polyesters, elastic polyurethanes, elastic polyamides, elastic copolymers of ethylene and at least one vinyl monomer, and elastic A-B-A' block copolymers,

11. The fabric composite of claim 10 wherein the fibers of the at least one meltblown layer comprise an elastic polyolefin selected from the group consisting of random copolymers of ethylene and propylene or random copolymers of ethylene and/or propylene and at least one other alpha-olefin, and blends of the random copolymers with isotactic polypropylene.

12. The fabric composite of claim 10 wherein said meltblown fibers in said at least one inner layer comprise multicomponent fibers each comprising at least one elastic polymer and at least one different inelastic polymer.

13. The fabric composite of claim 12 wherein the meltblown multicomponent fibers are bicomponent fibers comprising an elastomeric polymeric core selected from the group consisting of polyesters, polyurethanes, polyamides, copolymers of ethylene with at least one vinyl monomer and a-B-a' block copolymers and a non-elastomeric sheath comprising a non-elastomeric polyolefin.

14. The fabric composite of claim 13 wherein said bicomponent fibers comprise a sheath of polypropylene.

15. The fabric composite of claim 10A material, said fabric composite having a meltblown inner layer, said meltblown inner layer having a basis weight of from about 5 to about 40oz/yd²。

16. The fabric composite of claim 1 wherein said composite layer has been thermally bonded using a discontinuous pattern of points, lines or other patterns of intermittent bonds.

17. The fabric composite of claim 16 wherein the layers of the composite have been thermally bonded together by passing the layers through a nip formed by a patterned calender roll and a smooth roll, or between two patterned rolls, and heating at least some of the rolls.

18. The fabric composite of claim 17 wherein said thermal bonding is accomplished using a roll bonding temperature of about 110 ℃ to 130 ℃ and a bonding nip pressure of about 100-.

19. The fabric composite of claim 1 wherein two spunbond layers and one meltblown layer each comprise about 5-60% by weight of the composite, the composite being in the SMS configuration with three layers together comprising 100% of the SMS composite.

20. The fabric composite of claim 1 having a basis weight of from about 10 to about 300 grams per meter²(gsm)。

a) at least one inner layer comprising elastic meltblown fibers; and

22. The fabric composite of claim 21 wherein at least one of said outer layers comprises alternating stripes of substantially uniform width from about 50 to about 150 per meter of cross-sectional width of said outer layer.