US3229691A - Flexible absorbent sheet - Google Patents

Description

Jan. 18, 1966 A. cRowE, JR 3,229,691

FLEXIBLE ABSORBENT SHEET Filed July 10-, 1963 INVENTOR Quays A. (Row: JR.

ywz/zzam ATTO R N EY United States Patent 3,229,691 FLEXHBLE ABSGREENT SHEET George A. Crowe, .ilr., Plainfield, N..l., assignor to Johnson dz Johnson, a corporation of New Jersey Filed July 10, 1963, Ser. No. 293,948 17 Claims. (Cl. 128156) The present application is .a continuation-in-part of application Serial No. 159,117 filed December 13, 1961, and now abandoned. The present invention relates to air-pervious, resilient sheet materials which are absorbent on one side and water-repellent or nonabsorbing on the other.

For some surgical uses, it is highly desirable to have air-pervious, flexible, resilient protective coverings which are absorbent so as to remove body exudate, such as perspiration, and are at the same time water-repellent so as to prevent external wetting of the protected areas. Such materials are highly useful in protecting partiallycured wounds on which a scab has formed, bruises, and the like, and for other cushioning and protective uses as, for example, for use as underwraps under plastic casts and the like.

When applying a plaster cast, particularly where the cast is made of plaster of Paris, the wet plaster is applied to the injured member and then permitted to set, or harden, to stabilize the member into whatever position the physician has set the same. Not only do plaster of Paris compositions tend to generate some heat during the setting operation from which the underwrap protects the patient, but also after the cast has set and hardened, the same can be very uncomfortable unless there is a cushioning layer between the cast and the underlying skin of the patient. It is desirable to have an absorbent in contact with the skin of the patient so as to remove perspiration from the surface area under the cast. However, at the same time, it is desirable to have the cast material itself, when applied, not in contact with an absorbent which would remove moisture from the fresh, wet plaster of Paris when first applied as this may impair the homogeneous setting of the same. The underwrap should also be air-pervious so that moisture absorbed from the skin by the underlying absorbent layer can be vented to the atmosphere. The same problems are generally encountered in the protection of bruises and partially healed wounds where it is desirable to keep the same dry from the contact of water entering from outside of the wrap, while, at the same time, perspiration should be permitted to evaporate from the wound area.

Accordingly, it is one of the objects of the present invention to prepare a flexible, air-pervious, resilient protective cover that is water-repellent on one side and absorbent on the other. It is a further object to prepare a flexible, air-pervious, resilient protective cover that is not only water-absorbent on one side and water-repellent on the other side, but that is also a good insulator to protect from heat generated in the setting of casts. It is a still further object of the present invention to form protective sheet materials of the type described from open-cellular sponge sheets and absorbent or wettable fibers, the same being combined in such manner as to maintain a high degree of flexibility and conformity for the protective sheet. Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, wherein are set forth by way of illustration and example, certain embodiments of this invention.

Synthetic cellular sponge materials of varying types are presently available on the market. Many of these are soft and resilient and make excellent padding materials. However, many of the softer, more flexible and resilient 3,229,691 Patented Jan. 18, 1966 cellular sponge materials, such, for example, as flexible and resilient sponges formed of polyurethane esters and polyurethane ethers, nylon, rubber, polyethylene, polyvinyl chloride, and other foamable synthetic resin materials, are hydrophobic in nature and will not readily absorb fluids with which they are placed in contact. In accordance with the present invention, sheets of such resilient, flexible hydrophobic sponge materials, which are sufficiently open-cellular as to be readily pervious to air, are combined with a web of hydrophilic fibers to give a protective sheet product that is wateraabsorbent on one side and water-repellent on the other. By combining the web of hydrophilic fibers to the open-cellular sponge sheet by needling fibers of the web down into the sponge sheet without needling so deeply that the fiber bundles penetrate to the opposite surface of the sponge sheet, a bond can be obtained between the fiber web and the cellular sponge sheet which does not detract from the flexibility and resiliency of the final product nearly to the extent that a bond formed by cementing the two together would do. Also, the air permeability is not decreased by the needling process and, if anything, is slightly increased thereby whereas cement bonding tends to decrease air permeabilityv Besides bonding by needling, giving products of excellent air permeability where an open-cellular sponge sheet material is used, the bundles of hydrophilic fibers extending on up into the sponge material and terminating in the body of the sponge sheet help carry fluids up into the sponge sheet itself, where they can be more readily evaporated than if they were contained wholly on the surface of the sponge sheet.

As air permeability is an important characteristic of the protective cover sheets of the present invention, it is generally preferred that the products be formed by needling into a preformed sponge sheet rather than needling into a base sheet which is coated with a foamable material and the foamable material then foamed to form the sponge laminate. With the latter process, although a somewhat better bond may be obtained if the fibers are wetted by the material from which the sponge sheet is formed, formation of sponge sheets in this manner leaves a skim or skin over the surface of the sponge which is substantially air-impermeable. Any such skin would have to be removed or perforated before a suitable product could be obtained.

In making absorbent cellular sheet materials of the present invention, a layer or web of relatively hydrophilic or easily wetted fibers is placed on one surface of a sheet of cellular sponge material, and the sheet with the layer of hydrophilic fibers thereon is then needled by passing barbed needles down through the web of fibers into the sponge sheet to force a portion of the fibers, in the form of fiber bundles, down into the main body of the underlying sponge sheet. These fiber bundles, passing from the fiber layer down into the main body of the sponge sheet, not only act to bond the fiber layer to the underlying sponge sheet but also serve to carry moisture from the absorbent layer up into the sponge body to aid in evaporation of the same, It is found that when fluid is placed on the surface of the sponge sheet containing the web of hydrophilic fibers, not only does the web of hydrophilic fibers act to absorb the fluid but the fibers that penetrate into the main body of the cellular sponge sheet, in the form of fiber bundles, carry a substantial amount of fluid through the fiber bundles into the adjacent cells of the sponge material, thus substantially increasing the over-all absorptive capacity of the resulting product.

As the cellular sponge sheet is of relatively hydrophobic material, the Water can be brought into contact with the opposite side to that containing the web of hydrophilic fibers without any fluid passing through the product and wetting the fiber web contained on the other side. The

product thus prepared has both the advantages of a highly absorbent fabric as well as those of a water-repellent sheet. Also, as the only bonding between the fiber web and the foam sheet is that due to the fiber bundles extending down into the foam, there is no cement layer to act as a barrier and thus reduce the air permeability of the composite sheet material. As a result, the material is also highly -air pervious and any body fluids, such as perspiration, absorbed by the fiber layer and carried on up into the sponge body is readily evaporated.

In using the term hydrophilic fibers, those fibers or filaments, including continuous filaments, are intended which have the natural property of moving aqueous fluids along their length by capillary actions, either as single fibers or as fiber bundles, as well as those fibers or filaments which although normally not wetted by water, have been treated to make the same readily wettable so that they will move aqueous fluids along their surface by capillary action. It is generally preferred to use cellulosic fibers, such as the natural cellulosic fibers including cotton, ramie, jute, hemp, flax, and bagasse, and the synthetic cellulosic fibers, such as rayon and cellulose acetate.

Any cellular hydrophobic sponge material may be used that is sufiiciently flexible and resilient for the purpose intended. It is generally preferred, in practicing the present invention, to use sponge sheets formed of polyurethane polyethers or polyurethane polyesters, nylon, polyethylene, rubber, polyvinyl, chloride, and formalinized polyvinyl alcohol, or similar materials which will remain resilient and flexible. The preferred sponge materials are the polyurethane foams, where the foams are open-cellular, the polyurethane foams being either the polyurethane polyether or polyurethane polyester foam or sponge sheet products. Where the term open-cellular is used, this does not necessarily mean that all of the cell walls must be open to adjacent cells. However, a substantial portion of the cells should be open so as to give a sponge sheet ofiering only slight resistance to air flow therethrough. The sponge sheet from which the dressings of the present invention are made should have a resistance to air flow of less than 0.5 inch height of water. Resistance to air flow, where given in inch height of water in the present specification and claims, is the resistance offered to the flow of air at a velocity of 7.2 feet per second through a one-inch square section of sponge of 0.04 inch thickness. The water height is that shown by a water manometer measuring the pressure drop across the sponge sheet resulting from such resistance. In general, particular where the material is to be used for surgical dressings, the sponge should be readily flexible and conforming in sheets of about to /2 inch thickness and should be soft and resilient in nature. The material should be sufliciently flexible and conforming to fit over body contours and be sufliciently soft and resilient to act as a protective cushion without irritation, as would a stifl sponge structure. Accordingly, it is generally desired that the sponge material, where the products of the present invention are to be used in dressings, have a flexibility of 17-74% of original thickness and a resiliency of 78-98% of original thickness. The flexibility and resiliency are measured in the following manner. The original thickness is measured with a micrometer having a dead weight of 56.7 grams per square inch of sample. A 500 gram weight is added, and the thickness is read after 60 seconds to find flexibility. The 500 gram weight is removed, and after 60 seconds the thickness is read to find resiliency. Results are expressed in terms of percentage of original thickness.

In order to further illustrate the invention, reference is made to the drawings wherein are set forth by way of illustration and example certain embodiments thereof.

Referring to the drawings:

FIG. 1 is a perspective view of a sheet of material of the present invention;

FIG. 2 is a view taken along line 22 of FIG. 1;

FIG. 3 is a perspective view of a strip 'of sheet material of somewhat modified construction made in accordance with the present invention;

FIG. 4 illustrates an undercast wrap applied from a bandage strip of the present invention;

FIG. 5 is a perspective view of a cushion pad made in accordance with the present invention;

FIG. 6 illustrates one manner of applying the cushion pad of FIG. 5;

FIG. 7 is a modified form of cushion pad; and

FIG. 8 is a perspective view of a further modification of the present invention.

Referring to FIG. 1 of the drawings, there is illustrated an absorbent flexible sheet of the present invention, the sheet being in the form of an elongated bandage strip designed for wrapping around an injured member. The absorbent sheet of FIG. 1 consists of a base sheet 10 of open-cellular sponge material, such as a polyurethane foam sheet having a thickness of about to /2 inch, and having a resistance to air flow, prior to the manufacture of the composite sheet of FIG. 1, of not over 0.5 inch height of water. The open-cellular sponge sheet 10 has adhered to one side thereof a web 11 of nonwoven fibers, the web 11 of fibers being secured to the sponge sheet 10 by fiber bundles 12 which extend from the fiber web down into the sponge sheet. As part of the fibers which make up the fiber bundles 12 are also a part of the fiber web 11, these fibers act to bond the fiber web 11 to the spong sheet 10 through the fiber bundles which extend down into the same. The fiber bundles are formed as previously described by needling fibers from the fiber web 11 down into the sponge base sheet 10, care being taken to adjust the depth of the penetration of the needles to such that the fiber bundles stop short of the surface 15 of the base sponge sheet.

The fibers used in forming the fiber web preferably have a fiber length of about A2 to 3 inches and a denier of about 1 to 10. The fibers, in the form of the bundles 12, are pushed down into the base sponge sheet 10 through the use of needles containing barbs thereon which catch the fibers and force the same down through the sponge sheet in somewhat of a U configuration. In forming these needled products, it is generally preferred that there be at least 50 needle penetrations per square inch. The downwardly extending fibers forming the fiber bundles 12 not only serve to lock the fiber web 11 onto the base sheet 10 but also act to draw fluids up onto the sponge body where the same can be more readily dissipated through evaporation through the open-cellular sponge sheet. As previously indicated, in needling the fibers from web 11 down into the sponge sheet, the needle penetration should be such that a space 13 remains between the ends 14 of the fiber bundles 12 and the surface 15 of the sponge sheet 10, as best illustrated in FIG. 2.

As the material from which the sponge sheet is formed is relative-1y nonwettable, fluids will not readily pass therethrough. As a result, the surface 15 acts as a fluid barrier preventing fluids from passing on through the composite sheet to the bundle ends 14 or the absorbent fiber web 11. When sheet materials of this type are used and the fiber web 11 is brought into contact with a surface containing fluids, the fluids are absorbed by the fiber web 11. Some of the absorbed fluids pass on up into the sponge sheet 10 by means of the fiber bundles 12. As these fiber bundles do not extend completely through the sponge sheet 10, any moisture contacting the other side 13 of the composite sheet will not enter the same because of the hydrohobic nature of the sponge material. As air can readily pass through the cellular sponge sheet 10, moisture can pass from the penetrating fiber bundles 12 in the form of water vapor on out through the surface 15 of the composite sheet, thus removing moisture absorbed by fiber web 11 from the surface with which it is in contact. Composite absorbent water-repellent sheet materials of this type are not only suitable for bandaging, as previously discussed, but are also suitable for the formation of hygienic products, such as sanitary napkins, or any other use where it is desired that the sheet materials be substantially water-impermeable or waterrepellent on one side and absorbent to water or body fluids on the other.

In FIG. 3 is illustrated a bandage Wrap somewhat similar to that illustrated in FIGS. 1 and 2 but differing therefrom primarily in that the fiber web 19 does not extend to the edges of the composite sheet material. In the embodiment illustrated in FIG. 3, the fiber web 19 terminates short of the edges 16 of the underlying base sponge sheet 17 leaving a margin 18 extending between the fiber Web and the edge 16 of the base sponge sheet. With this construction, when the bandage is wrapped around an injured member, as for example illustrated in FIG. 4, the margin 18, which is not covered by the fiber web 19 and is formed solely of hydrophobic sponge material, contacts the underlying surface on which it is wrapped. This is either the surface of the wrapped member or the hydrophobic surface 20 of the sponge sheet, with the result that when the bandage is applied the absorbent fiber web 11 is completely enclosed. The bandage wrap of FIG. 3 thus provides a wrap that is completely water-impervious, all of the absorbent fibers being enclosed therein and being protected from being wetted even with water contacting the edge of the bandage.

In FIG. 5, a relatively small protective pad is illustrated for application over a bruise or a partially healed wound for protecting the same. In the cushion pad of FIG. 5, the fiber web 21, which is formed in the same manner as the fiber webs of FIGS. 1 and 3, terminates short of the edges 22 of the pad leaving a margin 23 which extends around the same and which is free of fibers. When the protective pad of FIG. 5 is applied over an injured member, as illustrated in FIG. 6, the fiber-free marginal edge 23 contacts the underlying skin forming a barrier to water penetration and completely enclosing the underlying absorbent fiber Web 21 thus insuring that the same remains dry even where water is spilled on the protective cushion dressing during, for example, washing of the injured member. As illustrated in FIG. 6, the pad 25 of FIG. 5 is applied, sponge surface 26 on the outside, to the underlying member through means of tape strips or the like 24.

The embodiment illustrated in FIG. 7 is similar to that illustrated in FIG. 6 but differs therefrom primarily in that the fiber-free border 27 is covered with a pressuresensitive adhesive 28. A protective cover sheet 29 is then applied over the pressure-sensitive adhesive to protect the same until the protective pad is to be used. When the protective pad of FIG. 7 is to be used, the protective cover 29 is removed exposing the pressure-sensitive adhesive surface 28 and the absorbent fiber web 30. The protective pad may then be placed over the wound, the pressuresensitive adhesive adhering the pad to the underlying skin and acting to seal off the absorbent web 30 from the outside access of Water. Any of the pressure-sensitive adhesives conventionally used in the preparation of adhesive bandages and the like may be employed for the protective cover sheet 29. The sponge sheet 31 is of hydrophobic open-cellular sponge material as in the previously described modifications.

The bandage wrap of FIG. 3 may be further modified so as to provide a pressure-sensitive adhesive coating over the margin 18. A bandage wrap so formed may be rolled on itself with an interliner, not shown, over the pressuresensitive adhesive to protect the same until the bandage is to be used, or the surface 20 of the bandage wrap, opposite to that containing the absorbent fiber Web 19, may be treated with a release agent which will release from the pressure-sensitive adhesive used in coating the marginal areas 18, in much the same manner that release agents are used for treating the backs of adhesive tapes so that the same will readily unwind when rolled on themselves.

A still further modification is illustrated in FIG. 8. In this modification, relatively large sheets of composite Water-absorbent-water-repellent sheet material 32 is prepared having areas covered with absorbent fiber webs 34 which are needled into the base sponge sheet in the same manner as that described for the preparation of the material of FIG. 1. These areas 34 are separated by areas 33 free from such fiber Web. Such large composite sheets may be used as such for treating a large surface or may be cut into smaller sheets or single pads by cutting along the areas 33 which contain no fiber Webs, so as to give smaller composite sheet dressings or the like wherein the fiber Web area is completely surrounded by a nonfiber-containing area. Such composite sheets may also be made by coating the fiber-free areas 33 with pressure-sensitive ad hesive in much the same manner that the fiber-free area 27 of the small dressing of FIG. 7 is coated and the whole may then be protected by a cover sheet, such as 29 of FIG. 7, or by rolling on itself and using an interliner or a back sizing to prevent adherence of the pressure-sensitive adhesive coating to the back 36 of the cellular sponge sheet 37 when the composite sheet is rolled on itself.

Although, as illustrated in FIG. 8, the absorbent fiber webs 34 are in the form of small rectangular patches, the same may be in the form of individual fiber web strips extending substantially the full length of the composite sheet.

Having thus described my invention, I claim:

1. A composite flexible, resilient, air-pervious sheet having a water-absorbent side and a Water-nonabsorbent side and comprising a hydrophobic sheet of open-cellular sponge material having adhered to one side thereof a web of hydrophilic fibers, said sheet of open-cellular sponge material having a resistance to air flow of not over 0.5 inch of water height and said Web of hydrophilic fibers being adhered to said sheet of open-cellular sponge material by fibers from said fiber Web extending as individual fiber bundles into the main body of said sheet of cellular sponge material, the ends of said bundles terminating short of the surface of said sponge sheet opposite tothe surface containing said fiber Web, said composite sheet having an air permeability of not appreciably less than the air permeability of said open-cellular sponge sheet.

2. A composite sheet of claim 1 in which the sheet of open-cellular sponge has a flexibility of 17-74% and a resiliency of at least 78%.

3. A composite sheet of claim 1 in which said composite sheet contains a margin between the edge of said fiber web and the edge of said sponge sheet, said margin being free of fibers of said Web.

4. A composite sheet of claim 3 in which said composite sheet is in the form of a bandage strip.

5. A bandage strip of claim 4 in which said fiber free margin is coated with a pressure-sensitive adhesive.

6. A dressing comprising a sheet of hydrophobic cellular sponge material,

an absorbent fiber web on one side of said sponge sheet,

a fiber-free border extending around said fiber web between the edge thereof and the edge of said sponge sheet,

fiber bundles extending from said fiber web down into said sponge sheet and terminating in the main body thereof,

said fiber bundles acting to bond said fiber Web to said sponge sheet.

7. A dressing pad of claim 6 in which said fiber-free border is coated with a pressure-sensitive adhesive.

8. A dressing pad of claim 7 in which said pressuresensitive adhesive is protected with a removable cover member.

9. A dressing pad of claim 7 in which the back of said sponge sheet, opposite to the surface containing said absorbent fiber web, is coated with a release agent releasable from said pressure-sensitive adhesive coating to ermit said dressing pad to be rolled on itself.

10. A dressing of claim 6 in which said sheet of cellular sponge material contains a plurality of separate absorbent fiber webs, each separated from the other by a fiber-free area.

11. A dressing of claim 10 in which said fiber-free areas are coated with a pressure-sensitive adhesive.

12. A dressing of claim 6 in which said sponge sheet has a resistance to air flow of not over 0.50 inch of water height.

13. A dressing of claim 12 in which said sponge sheet has a, flexibility of 1774% and a resiliency of 78-98%.

14. A dressing of claim 13 in which said sponge sheet is a polyurethane sponge.

15. A dressing of claim 13 in which said fiber web is 5 a fiber length of /2 inch to 3 inches and a denier of 1 to 6.

References (Iited by the Examiner UNITED STATES PATENTS 1,857,281 5/1932 Johnson 161-154 2,951,278 9/1960 Hoffman 28-79 3,059,312 10/ 1962 Jamieson 2879 ADELE M. EAGER, Primary Examiner.

Claims (1)

1. A COMPOSITE FLEXIBLE, RESILIENT, AIR-PERVIOUS SHEET HAVING A WATER-ABSORBENT SIDE AND A WTER-NONABSORBENT SIDE AND COMPRISING AHYDROPHOBIC SHEET OF OPEN-CELLULAR SPONGE MATERIAL HAVING ADHERED TO ONE SIDE THEREOF A WEB OF HYDROPHILIC FIBERS, SAID SHEET OF OPEN-CELLULAR SPONGE MATERIAL HAVING A RESISTANCE TO AIR FLOW OFNOTE OVER 0.5 INCH OF WATER HEIGHT AND SAID WEB OF HYDROPHILIC FIBERS BEING ADHERED TO SAID SHEET OF OPEN-CELLULAR SPONGE MATERIAL BY FIBERS FROM SAID FIBER WEB EXTENDING AS INDIVIDUAL FIBER BUNDLES INTO THE MAIN BODY OF SAID SHEET OF CELLULAR SPONGE MATERIAL, THE ENDS OF SAID BUNDLES TERMINATING SHORT OF THE SURFACE OF SAID SPONGE SHEET OPPOSITE TO THE SURFACE CONTAINING SAID FIBER WEB, SAID COMPOSITE SHEET HAVING AN AIR PERMEABILITY OF NOT APPRECIABLY LESS THAN THE AIR PERMEABILITY OF SAID OPEN-CELLULAR SPONGE SHEET.

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