WO2000004936A2

WO2000004936A2 - Textile including super absorbent fibers

Info

Publication number: WO2000004936A2
Application number: PCT/US1999/016184
Authority: WO
Inventors: Joseph P. Herlihy
Original assignee: Millennium Ground Control, Inc.
Priority date: 1998-07-22
Filing date: 1999-07-15
Publication date: 2000-02-03
Also published as: WO2000004936A3; CA2337915A1; WO2000004936B1

Abstract

A composite fabric includes a moisture permeable top layer and a bottom layer including super absorbent fibers. The layers are bound together by a moisture permeable adhesive layer, by being needle punched together or by heat sensitive fibers to which heat and pressure are applied in one or both of the top and bottom layers.

Description

TEXTILE INCLUDING SUPER ABSORBENT FIBERS

1. Field of the Invention

This application relates to a textile composite including super absorbent fibers. The textile is intended for use in the construction of clothing, linings, footwear, wipes, towels, filtration media, medical wraps, sport wraps, and other articles and apparel in which it is desired to promote absorption and transportation of fluids, such as body fluids, away from their source, such as the skin. The textile is suitable for use as insoles, sock liners, headbands, protective pads and the like.

2. Related Art Super absorbent polymers have the ability to absorb many times their own weight of aqueous fluids and retain this fluid when subjected to pressure. These polymers which are generally supplied in powder granule or bead form are mainly used in disposable hygienic products particularly baby diapers. More recently, super absorbent fibers have become available, but have not yet found wide application. Numerous attempts have been made to provide textiles which absorb liquids produced by the body, as in sweat bands, feminine hygiene products, diapers and shoe inserts, insoles or sock liners. For example, U.S. Patent No. 5,763,335 shows a material useable for, e.g., a shoe insert. It has a permeable cover layer over a foam layer with one or more sorbents dispersed throughout the foam matrix. U.S. Patent No. 4,531,738 teaches a product including stiffened cellulosic fibers interspersed with super absorbent polymer particles powder or granules.

Both patents teach away from a textile useable for clothing articles because of thickness, hand, density or stiffness.

In known products, a cover sheet, top sheet or the like on the side of an absorbent article in contact with the body is bonded peripherally to an absorbent core with an adhesive. See, for example, U.S. Patent No. 5,531 ,728. A peripheral bond is used because overall use of an adhesive which is restrictive to fluid flow would undesirably retard the flow of liquid through the cover sheet and into the absorbent core. For example, U.S. Patent No. 4, 551,191 discloses that absorbent rate and capacity are adversely affected by adhesives.

Accordingly, a need exists for a soft, highly absorbent structure capable of textile usage and exhibiting high integrity and thin construction. Such an absorbent textile product would readily find use in sock linings of shoes, where it would wick perspiration away from the foot.

Summary of the Invention

The present invention provides an improved composite fabric. The present invention may be realized in a composite fabric comprising a fluid permeable hydrophobic top layer; and an absorbent bottom layer including super absorbent polymer fibers. In some embodiments, the super absorbent fibers are included in an amount of about 5-60% by dry weight. In some embodiments, the top layer is permeable and hydrophobic, sustaining an air flow of 100-350 cubic feet per square foot per minute, measured under ASTM D737, and sustaining moisture vapor transmission of 50-150 grams per square meter per 24 hours, measured under ASTM E96(A). The super absorbent fibers can be needle-punched into the top layer from below to form the bottom layer.

The composite fabric can further comprise a moisture-permeable adhesive binding the top layer to the bottom layer. In embodiments using an adhesive binder, the adhesive binder can comprise a web of heat activated polyamide polyolefin. Alternatively, the adhesive can be another material having a glue line activation temperature of approximately 120°C. When an adhesive is used, it can be provided as a web having a basis weight of 0.6 to 1.5 ounces per square yard.

In some embodiments, the super absorbent fibers can be about 5-100 microns in diameter and about 0.25-0.50 inches long. The super absorbent fibers of some embodiments can further be characterized as absorbing about 200-300 grams of water per gram of fiber. In some embodiments the super absorbent fibers exhibit water retention rates at 0.5 PSI of 160- 250 grams of water per gram of fiber.

In embodiments not using a separate adhesive layer, the bottom layer can further comprise low melt temperature fibers, whereby the top and bottom layer are bonded together by heat and pressure applied to activate the low melt temperature fibers. The low melt - J - temperature fibers of such embodiments can be included in the bottom layer at 5-50% by dry weight.

The composites of various embodiments described above can further include an accessory layer bonded to the bottom layer. The accessory layer can add resilience, insulation, windproofing, water resistance, abrasion resistance, moldability or decoration to the composite.

The composites of various embodiments described above can also further include a dry solids addition. The dry solids addition can impart enhanced germicidal, bacteriological or odor control characteristics or change color when wetted.

Brief Description of the Drawings

In the drawings in which like reference designations indicate like elements:

Figs. 1 , 2, 3 and 4 are schematic representations of processes for manufacturing embodiments of the invention; Fig. 5 is a pictorial representation of a process for manufacturing a composite according to various aspects of the invention;

Fig. 6 is a cross-sectional side view of the bonded composite produced by the process depicted in Fig. 1 ;

Fig. 7 is an enlargement of Fig. 6 showing more detail; Fig. 8 A shows the structure of Fig. 7, immediately after a drop hits the composite; and

Fig. 8B shows the structure of Fig. 7, several seconds after the time depicted in Fig. 8A.

Detailed Description The present invention will be better understood upon reading the following detailed description of several embodiments thereof in connection with the drawings. The invention is first generally described, followed by a description of several methods of making embodiments thereof and detailed descriptions of several examples of textiles embodying the invention. Embodiments of the invention use super absorbent fibers. Fibers of about 50-100 microns diameter and about 0.25-0.50 in. length are preferred, although fibers of other dimensions can also be used. Super absorbent fibers have a number of interesting properties. Those which are particularly useful in connection with some embodiments of the invention include absorption of about 200-300 grams of water per gram of fiber and a retention at 0.5 PSI of about 160-250 grams of water per gram of fiber. The fiber surface has a crenulated surface structure with longitudinal grooves beneficial in transporting moisture along the surface. Fibers will absorb 95% of their capacity in 15 seconds compared to minutes for particles to absorb a similar amount. It has been discovered that fiber with a length to diameter ratio of at least 100 where fiber diameter is about 30 micron has approximately 8 times higher surface area, is less likely to migrate, is soft even with high levels of incorporation and is non abrasive, compared with super absorbent particles. Particles are difficult to incorporate, have a tendency to migrate, have little integrity, and tend to squeeze out under pressure.

The invention may thus be embodied in a layered composite which absorbs moisture and body fluids, gels them, and facilitates keeping the adjacent surfaces dry. The layered composite can include: 1. A hydrophobic fabric, or a dual-zoned fabric with an exposed surface of hydrophobic fibers and a lower surface of fibers of a different size or treated for surface hydrophillicity with a primary aim of moving moisture away from the top surface (i.e., transpiring moisture through the fabric),

2. An optional adhesive layer which permits moisture transpiration to continue through to the bottom layer,

3. A bottom layer of a fabric or sheet material consisting of super absorbent fibers and other non-absorbent fibers and/or absorbent such as polypropylene, polyester and the like,

4. An optional accessory layer, such as synthetic rubber, etc., which can impart additional desired properties. For example, the accessory layer can add resilience, insulation, windproofing, water resistance, abrasion resistance, moldability or decoration, and

5. Optional dry solids having germicidal, bacteriological or odor control properties or which change color when wet, useful in some applications. The aim of the total composite is to move moisture and body fluids away from the body surface and through the top layer to the super absorbent bottom layer below, keeping the body dry. As described below, it is possible to needle-punch super absorbent fibers directly into and through the bottom surface of the top layer so that the adhesive layer is eliminated. The bottom layer of the two-part fabric composite thus constructed consists of a top layer having a top surface adjacent a body part and super absorbent fibers to absorb and gel moisture and body fluids, keeping the top surface and the body dry.

Otherwise phrased, embodiments of the invention may include a fabric composite material comprising a super absorbent polymer fiber layer bonded to a less hydrophilic top cover with a permeable adhesive or other connection system in order to allow liquid penetration through the top layer and adhesive layer to the super absorbent layer, where it is absorbed and gelled. The super-absorbent layer consists of air-laid, wet-laid, carded thermal, chemically bonded, or needle-punched webs, or high-loft rolled goods consisting of super absorbent fibers blended with polyester or like non-absorbent fibers and/or rayon or like absorbent fibers in a ratio to best accomodate the end use. In one use, super absorbent fibers have been incorporated at 5-60% by weight super absorbent to non-absorbent material. Yet more preferably, the super absorbent fibers can be incorporated at 5-30% by weight.

In order to facilitate bonding the layers without use of an adhesive layer, the top or bottom layer may include some low melt temperature fibers, e.g. a low melt temperature polymer such as a polyamide polyolefin. In preferred constructions, the bottom layer, which preferably includes 5-60% by dry weight of super absorbent fibers, also preferably includes 5- 50%) by dry weight of low melt temperature fibers. The low melt temperature fibers may, for example, be a thermoplastic material. The layers are bonded together using heat and pressure such as described below.

Suitable super absorbent fibers are available from a number of sources. As noted above, FIBERSO B fibers from Camelot Technologies of Albert, Canada are presently preferred, but other types of super-absorbent fibers may be used, such as cross-linked carboxymcthyl-ccllulose and polymer-grafted cellulose (including hydrolyzcd polyacrylonitrile, polyacrylic esters, and polyacrylic and polymcthacrylic acids). See, for example, Chatterjce, Textile Science and Technology, vol. 7; U.S. Patent No. 4,036,588; and U.S. Patent No. 7.818,077. The top layer may consist of a fabric or film. The fabric may be woven, non-woven or υl^'knil material, synthetic or natural fiber. The film may be contiguous or perforated polymeric film. The top layer is selected to meet the needs of the particular end application for the composite. For example, if the end application is used as a sock liner in a shoe, the top layer may be any of a number of hydrophobic materials already used as sock liners. It is preferred that it be capable of sustaining an air flow of 100-350 cubic feet per minute, measured under ΛSTM D737 in effect on the date of filing this application. It is further preferred that the top layer have a moisture transmission rate of about 50-150 grams per square meter per 24 hours, measured under ASTM E96(A) in effect on the date of filing this application.

The permeable adhesive web is preferably a heat-activated dry film or liquid deposition such as a hot melt adhesive system, which is deposited between the top layer and the super-absorbent layer in a continuous process to bond the top layer to the super absorbent layer. The bond must be strong enough to prevent separation of the layers yet must readily pass liquids through the bond. A suitable adhesive is a dry film thermoplastic adhesive system such as Bostik SPA111. Similar adhesive thermoplastic hot melts or perforated films may be substituted by those skilled in the art. However, preferred adhesive films have a basis weight of about 0.6-1.5 ounces per square yard.

As shown in Fig. 1, the components of an embodiment of the invention are delivered into the process from stock rolls 101, 103 and 105. Stock roll 101 delivers a top layer 102, stock roll 103 delivers a web of heat-sensitive, moisture-permeable adhesive 104 and stock roll 105 delivers a fiber or web 106 of super absorbent fibers. Super absorbent fibers suitable for use in embodiments of the invention include FIBERSORB fibers, available from Camelot Technologies of Alberta, Canada. The top layer 102, adhesive web 104 and super absorbent fiber web 106 are brought together and advanced on a conveyor to a bonding station where the composite is preheated by heat source 107 and pressed or pressure-rolled together by squeeze rolls 108 to effect a tight bond between all elements. Additional super absorbent polymer in powder or other form may be metered onto the inside of either the top or bottom layer at locations 109 or 1 10 before the adhesive web 104 is applied. The entire composite then continues onto a take up roll 1 1 1 for use in subsequent products.

An alternative method of producing embodiments of the invention is shown in Fig. 2. Stock 102, 104, 106 is delivered from stock rolls 101, 103, 105, as before. Completed product is also accumulated on take-up roll 1 1 1 , as before. However, instead of heat source 107 and squeeze rolls 108, heated calendaring rolls 201 provide the heat and pressure to produce a bond between the stock 102, 104 and 106. As shown in Fig. 3, the top layer 102 can be needle punched from the bottom side with super absorbent fibers, to simplify the manufacturing process but still create a fabric composite with a hydrophobic top surface which is moisture permeable and a bottom layer which absorbs moisture and other body fluids and traps them in a gel form, keeping the top surface dry.

Top layer 102 is supplied from a stock roll 101 into a needle puncher 301 which pushes super absorbent fiber into the top layer 102 from below. The upper surface is largely free of super absorbent fiber, while the lower surface is largely covered with super absorbent fiber due to the needle puncher operating from that side. The completed composite is accumulated on take up roll 1 1 1 , as before.

In yet another method, illustrated in Fig. 4, using a needle puncher 301, a top layer 102 can be joined directly to a super absorbent web 106.

Fig. 5 illustrates pictorially the manufacturing process illustrated in schematic form in Fig. 2. Of particular note are the stock rolls 101, 103 and 105, from which top layer 102, adhesive web 104 and bottom layer 106 are supplied. They are bonded together by heat and pressure applied by calendaring rolls 201 to produce the composite fabric 501.

The structure of the composite fabric is shown schematically in Fig. 6. The bottom layer 601 contains super absorbent fibers. The top layer 602 is permeable to moisture. The bottom and top layers are bonded together, optionally by a layer of moisture permeable adhesive 603. This structure is illustrated in greater detail in Fig. 7. In the embodiment shown, the top layer 602 is a woven fabric having warp and weft fibers 701 and 702. The top layer 602 is in contact with the bottom layer 601 at point 703, through the adhesive layer 603, in this embodiment. Such direct contact is not necessary to the function of the invention, but helpful in transmitting moisture through the adhesive layer 603. The function of this embodiment is now described.

Absorption of a drop of water is now described in connection with Figs. 8 A and 8B. The drop 801 first contacts the top layer 602, as shown in Fig. 8A. The fabric of the top layer 602 is hydrophobic, allowing the water to pass through without wetting the fibers. The drop of water is brought into contact with the bottom layer 601 at contact point 703. The super absorbent fibers in bottom layer 601 rapidly take up the moisture, within seconds, as shown in Fig. 8R. Moisture is trapped 802 in the bottom layer 601 , and released again only slowly, through evaporation. The following examples indicate the utility of combining super absorbent polymer fibers contained in a fabric bonded to a cover stock where the cover stock (top layer) is in communication with a moisture source, draws moisture through cover stock, gels it into the bottom layer of composite leaving the cover stock dry.

Examples

Combinations of components of different composition were processed to evaluate the characteristics of retained weight absorption time and evaporative weight loss. The following descriptions define the test parameters and terms.

Retained Weight

The retained weight is the differential between saturated weight and wrung weight saturation was a one minute submersion in water and wringing was accomplished by a set of rolls set to squeeze out the maximum amount of water.

Absorption Time

Absorption time is the time in seconds to absorb a drop of water released 2 inches above the specimen.

Evaporative Weight Loss

The evaporative weight loss is the amount of retained water lost over a time period as a percent of the retained weight.

Processing For each example the bottom layer of the composite consisted of entangled synthetic fibers containing super absorbent polymer fibers in varying ratios.

The top layer or layer generally positioned in communication with a moisture source is selected by its abrasion resistance, tear strength, absorption speed, thickness, hand, and economics. The examples tested five top layer materials generally described as moisture wicking fabrics. Moisture wicking fabrics are fabrics designed to take a drop of moisture and quickly transport it to the opposite side spreading it out over a larger surface area. The top layer fabric should not be hydrophilic and would best be hydrophobic in its material of construction, its stmcture, or its post treatment. The goal is to draw moisture transport it through top layer and give it up to bottom layer where it is gelled by the super absorbent polymer fibers.

The bonding adhesive between the top layer and the bottom layer is fast acting adhesive, non water soluble, water permeable, flexible adhesive. The material selected was SPA III web adhesive. Application of heat through top, bottom or both layers by means of heated rolls produce a continuous web of roll goods composite. Those skilled in the art can readily substitute materials of construction with similar components without taking away from the spirit of the invention. A thin fabric like composite with soft hand wherein the top surface will readily accept, draw in, and pass through to lower layer moisture vapor or droplets. Said vapor or droplets are gelled within lower layer by super absorbent polymer. The gelled liquid will not rc-wct the lop layer under pressure yet will evaporate gelled moisture when exposed to air.

EXAMPLE 1

Samples were prepared from eight super absorbent fiber containing fabrics supplied by Knowlton Nonwovcns, Utica, NY of various thickness at approximately 60% parts/weight of super absorbent polymer fiber, bonded to ETC Fabric provided by SHEEHAN Sales, Beverly, MA, with a heat activated web adhesive SPA III from Bostik, Middleton, MA.

Table 1

Samples 1, 2, 3, 4 were calendered versions of samples 6, 5, 8 and 7, respectively, supplied by Knowlton.

EXAMPLE 2

A similar set of samples per example 1 were prepared from super absorbent fiber containing 4 fabrics supplied by Texel, Quebec, Canada.

Table 2 Evaluation of samples 1-12 indicated an average .46 grams of retained water per square inch of product with an average of 63 percent of retained water evaporating out within 8 hours.

EXAMPLE 3

A set of samples as in Example 1 were prepared from a Knowlton fabric in which the super absorbent fiber content was reduced from 60% as in example 1 to 15%. Four separate top cover layers were used consisting of:

Sample Top Cover Supplier

13 nylon Lee Fashions, NY

14 Nylon-Polypro Guilford, NC

15 Nylon Guilford, NC

16 Dri-Lex Faytex, MA

Table 3

It was concluded that in Examples 13- 16 with a lower percentage of super absorbent fibers, higher retained weight per square inch, and faster evaporative speeds that gel blocking was exhibited in samples 1-12.

Gel blocking occurs when super absorbent polymer is wetted and the fiber swells so as to inhibit further gelling.

EXAMPLE 4

A sample without the use of an adhesive web 104 was prepared. In this embodiment the bonding of top layer 102 to bottom layer 106 is accomplished by the selection of a thermally sensitive fiber mixed into the bottom layer 106. The bottom (absorbent) layer has been defined as an entangled roll goods comprising super absorbent fibers with synthetic fibers. Selection of a thermally sensitive synthetic fiber such as polypropylene or polyester with fusion temperatures of 100°C and 240°C respectively can be combined at up to 90 percent by weight with super absorbent fiber. The fiber mix of thermally sensitive and super absorbent fiber is entangled by air laying, wet laying needle punching or hydro entanglement. The resultant bottom layer is then processed as in the present invention whereby the heated rolls raises the temperature of the composite above the fusion temperature of the thermally sensitive synthetic fiber in the bottom layer causing some melting of thermally sensitive fiber creating a thermal bond.

A particular roll goods product containing a thermally sensitive fiber (fusible) polyester fiber content is available commercially and supplied as NLS 85, from BFF Nonwovens, Somerset, England.

A sample was prepared as follows:

Top cover layer nylon, Lee Fashions, NY

Table 4 EXAMPLE 5

A composite similar to Example 3, sample 16 was prepared in roll form 2-1/2" wide, 48" long. The roll was saturated and wrung out. It was then frozen and wrapped around an elbow joint on the arm. It was noted that the wrap imparted useful cold to the joint for about twice the time of a wrap not containing super absorbent polymer, thus demonstrating a clear advantage over an ordinary ice pack. A frozen pad or wrap of this construction imparts the cold storage capacity of ice without the liquefaction upon melting.

Having thus described several embodiments of the invention, various alternatives, modifications and improvements will readily occur to those skilled in the art. Such alterations, modifications and improvements are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description is by way of example only and is not intended as limiting. The invention is limited only as defined in the following claims and the equivalents thereto.

What is claimed is:

Claims

Clai s

1. A composite fabric comprising: a fluid permeable hydrophobic top layer; and an absorbent bottom layer including super absorbent polymer fibers.

2. The composite fabric of claim 1, wherein the super absorbent fibers are included in an amount of about 5-60% by dry weight.

3. The composite fabric of claim 1, wherein the top layer is permeable and hydrophobic, sustaining an air flow of 100-350 cubic feet per square foot per minute, measured under ASTM D737, an sustaining moisture vapor transmission of 50-150 grams per square meter per 24 hours, measured under ASTM E96(A).

4. The composite fabric of claim 1 , wherein the super absorbent fibers are needle- punched into the top layer from below to form the bottom layer.

5. The composite fabric of claim 1 , further comprising a moisture-permeable adhesive binding the top layer to the bottom layer.

6. The composite fabric of claim 5, wherein said adhesive binder comprises a web of heal activated polyamide polyolefin.

7. The composite fabric of claim 5, the adhesive having a glue line activation temperature of approximately 120┬░C.

8. The composite fabric of claim 5, the adhesive comprising a web having a basis weight of 0.6 to 1.5 ounces per square yard.

9. The composite fabric of claim 1 , wherein the super absorbent fibers are about 5-100 microns in diameter and about 0.25-0.50 inches long.

10. The composite fabric of claim 1 , wherein the super absorbent fibers absorb about 200- 300 grams of water per gram of fiber.

1 1. The composite fabric of claim 1 , wherein the super absorbent fibers exhibit water retention rates at 0.5 PSI of 160-250 grams of water per gram of fiber.

12. The composite fabric of claim 1 , the bottom layer further comprising: low melt temperature fibers, whereby the top and bottom layer are bonded together by heat and pressure applied to activate the low melt temperature fibers.

13. The composite fabric of claim 12, wherein the low melt temperature fibers are included in the bottom layer at 5-50% by dry weight.

14. The composite fabric of claim 12, wherein the super absorbent fibers are included in an amount of about 5-60%> by dry weight.

15. The composite fabric of claim 12, wherein the top layer is permeable and hydrophobic, sustaining an air flow of 100-350 cubic feet per square foot per minute, measured under ASTM D737, an sustaining moisture vapor transmission of 50-150 grams per square meter per 24 hours, measured under ASTM E96(A).

16. The composite fabric of claim 12, wherein the super absorbent fibers are needle- punched into the top layer from below to form the bottom layer.

17. The composite fabric of claim 12, further comprising a moisture-permeable adhesive binding the top layer to the bottom layer.

18. The composite fabric of claim 17, wherein said adhesive binder comprises a web of heat activated polyamide polyolefin.

19. The composite fabric of claim 17, the adhesive having a glue line activation temperature of approximately 120┬░C.

20. The composite fabric of claim 17, the adhesive comprising a web having a basis weight of 0.6 to 1.5 ounces per square yard.

21. The composite fabric of claim 12, wherein the super absorbent fibers are about 5-100 microns in diameter and about 0.25-0.50 inches long.

22. The composite fabric of claim 12, wherein the super absorbent fibers absorb about 200-300 grams of water per gram of fiber.

23. The composite fabric of claim 12, wherein the super absorbent fibers exhibit water retention rates at 0.5 PSI of 160-250 grams of water per gram of fiber.

24. The composite as in claim 1, further comprised of an accessory layer bonded to the bottom layer.

25. A composite as in claim 24, wherein the accessory layer adds resilience, insulation, windproofing, water resistance, abrasion resistance, moldability and or decoration to the composite.

26. A composite as in claim 1 , further comprised of a dry solids addition.

27. A composite as in claim 26, wherein the dry solids addition imparts enhanced germicidal, bacteriological or odor control characteristics or changes color when wetted.