US3369547A - Extensible sheet material - Google Patents

Description

Feb. 20, 1968 Y G. H. SACK ETAL 3,369,547

EXTENS IBLE SHEET MATERIAL Filed Aug. 27, 1964 557 22/ 2/ l L31@ T1 :1.7.

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3,369,547 EXTENSIBLE SHEET MATERIAL Georges Henri Sack, Highland Park, and Gerald Joseph Liloia, North Brunswick, NJ., assignor to Johnson & Johnson, a corporation of New Jersey Filed Aug. 27, 1964, Ser. No. 392,514 9 Claims. (Cl. 12S- 296) ABSTRACT F THE DISCLSURE A dressing is disclosed which is of the type having a layer of elastomeric material, suitably polyurethane foam, and a nonwoven fibrous web heat sealed together to form an integral structure. In the dressings disclosed, the elastomeric material is adhesively bonded to the fibrous web at a plurality of discrete spaced peripherally located areas and the fibrous and elastomeric material lying between .the heat sealed areas is either left unbonded or is removed. The improved dressings thus pro vided have higher flexibility and extensibility than prior art dressings of this type by virtue of which they may conform more readily to various body contours.

The present invention relates to extensible sheet materials and bandages, dressings, and the like, formed by the same. More particularly, the invention relates to extensible sheet materials having at least one intermediate layer of non-elastic fibers contained between two mutualiy bonded extensible outside layers.

Extensible sheet materials are used for many purposes; however, they are particularly useful in the preparation of surgical dressings and the like. For example, in the treatment of wounds it is often desirable to protect the wound with a resilient absorbent cushion that will draw wound exudate away from the wound site. At the same time, the dressing must be extensible so that it may easily be applied to all parts of the body. It has heretofore been possible to obtain the desired properties by the use of a dressing comprising an absorbent tibrous material contained between two porous, extensible covering layers. It has also been possible to provide extensible sheet materials having properties designed for other uses by the proper choice of materials to be used in the intermediate fiberlayer, and the extensible outsidel ayer.

When producing structures of this sort, it is usually desirable to bond the two covering layers together at the edge of the sheet to present a compact sealed body. Since many of the extensible coverings used are heat scalable, it is particularly convenient to eiect the body by heat sealing methods. In the past, such sealing has been accomplished by pressing the two outside layers and the intermediate fiber layer together at a narrow border at the edges of the sheet while maintaining the same at elevated temperatures. This method provides a continuous seal around the entire periphery of the sheet.

When the extensible outside layers are bonded to the layer of non-elastic fibers, movement of the extensible outside layers is restricted by the non-elastic fibers. Although only the areas which are so sealed become directly restricted and non-extensible, these areas, as described above, constitute a continuous border around the sheet and thus the extensibility of the body of the dressing is likewise affected. Not only are dressings so made nonextensible; but due to the restriction on the edges, the dressing can not be easily twisted so as to conform easily to body parts.

A second convenient method of bonding is by the use of non-elastic adhesives or cements. Seals of these materials have also been in the form of a continuous border at the edges of the sheet, and since the layer of adhesive or cementitious material is non-elastic, movement of the bonded strip and hence the body of the sheet is again restricted. Any rigid edge bond structure produces this vsame result.

It is therefore an object of this invention to provide a method of bonding a layer of non-elastic libers to a layer of extensible material by heat sealing the edges of the various layers together to form a sealed composite body without destroying the extensibility of the resulting sheet material.

It is a further object of this invention to provide a method of bonding a layer of non-elastic fibers to a layer of extensible material by sealing the edges of the various layers together with a non-elastic sealing material such as an adhesive or cement, to form a sealed composite body, without destroying the extensibility of the resulting sheet material.

It is a still further object of this invention to provide a compact sheet material which is easily extensible and conformable to body parts comprising an intermediate layer of non-elastic fibers contained between two eX- tensible outside layers, wherein the various layers are sealed together at the edges.

It has now been discovered that these objects may be fulfilled by forming a discontinuous bond between a layer of non-elastic Iibers and a layer of extensible material in a border around the edges of the composite sheet.

The inventive concept will be more easily understood by reference to the accompanying drawings wherein:

FIGURE l is a view in perspective of a prior art sheet material having a continuous seal around the edges of the composite body.

FIGURE 2 is a cross section ot the sheet material of FIGURE l taken along line 2 2.

FIGURE 3 is a view in perspective of one form of the sheet material of this invention having a discontinuous heat seal around the edges of the composite body formed by the platen illustrated in FIGURE 9.

FIGURE 4 is a single line cross section of the sheet material or FIGURE 3 taken along the line 4-4.

FIGURE 5 is a single line cross section corresponding to that in FIGURE 4 when the dressing is in the stretched position.

FIGURE 6 is a view in perspective of another sheet material of this invention having a discontinuous seal around the edges of the composite body formed by the platen illustrated in FIGURE 8.

FIGURE 7 is a cross section of the sheet material of FIGURE 6 taken along the line 7 7.

FIGURE 8 is a side view of a pair of platens used in sealing the sheet material of this invention illustrated in FIGURE 6.

FIGURE 9 is a View of another pair of platens used in sealing the sheet material of this invention illustrated in FIGURE 3.

Referring now to the drawings, FIGURES 1 and 2 illustrate a sheet material 12 comprising an intermediate layer 16 of non-elastic fibers contained between a top extensible covering layer 14 and a bottom extensible covering layer 15 of polyurethane sponge. The two extensible layers and the layer of non-elastic ibers are bonded together by a continuous heat seal 17 along the edges. Due to the restriction imposed on the movement of the extensible material where bonded to non-elastic iibers, the Sealed areas at the edges are non-extensible. Since this area constitutes a continuous border around the sheet, the movement of the body 13 of the sheet is similarly restricted, and is nonextensible and relatively nonconformable.

together at small discrete, discontinuous areas 21 at the edges of the sheet; the bonded edge areas 21` alternating between non-bonded edge areas 22. Although the extensibility of the laminate has been destroyed in the bonded areas 21,` said property is retained in the non-bonded areas 22.

The extensibility of the sheet is best illustrated by FIGURES 4 and 5. When it is attempted to extend the sheet in the direction indicated by arrows 23, the nonbonded areas 22, originally having width y, are extended with width y-iwhile the width x of bonded areas 21 remains constant. There being substantially `less restriction on the extensibility of the edges of the sheet, the body of the sheet, is readily extensible.

FIGURES 6 and 7 present a preferred sheet material of this invention. The two extensible layers have been bonded to the fiber layer at small discrete, discontinuous areas 31 along the edges of the sheet. Small discrete portions of both` the fiber layer and the extensible layers have been removed, leaving notches 32 between said bonded areas where the various layers are not sealed together. The notches at the edges impart added conformability to the sheet material.

In addition to the embodiments illustrated,fmany other forms of these sheet materials having a discontinuous bond along the edges are included within the inventive concept. For example, limited extensibility can be obtained by introducing the discontinuities in the form of slits in the otherwise continuousbond. The inventive concept should not be limited to the preferred embodiments JV heretofore described.

This method may be used to bond one or more layers of any` extensible material toone or more layers of nonelastic tibers; and is especially useful with heat scalable substances, such as the polyurethane lesters and ethers, rubber, and polyvinyl chloride.

The size and frequency of the discontinuities in the bonded edge areas depends upon the degree of conformability and extensibility desired. An additional factor is the necessity or desirability of producing a tightly bonded and compact unit. Conformability will vary directly with the number of discrete areas, while extensibility will vary inversely with the percentage of the edgs which is bonded.

Sheet materials having bonded areas disposed between non-bonded areas may be produced by positioning the various layers one on top of the other, and pressing the layers between a set of heated dies, such as those shown in FIGURES 8 and 9. In FIGURE 9, there is illustrated a pair of platens consisting of upper platen 45 and lower platen 46. Both platens contain blunt protuberances 47. When a pair of platens of this type is used, the resulting sheet material will be similar to that illustratedin FIG- URES 3 through 5, the sheet being bonded where the blunt protuberances of the upper platen Contact those of the lower.

FIGURE 8 illustrates a pair of platen consisting of upper and lower platen 42. Upper platen 40 contains blunt protuberances 41, having length z; while lower platen 42 contains slightly longer blunt protuberances 43, having z-i. The later protuberances `are on the order of .0001 of an inch longer than the former. When this pair of platens is used, a sheet material resembling that illustrated in FIGURES 6 and 7 is obtained. The area contacted by protuberances 41 becomes heat sealed, while the area contacted by the slightly longer protuberances 43, under much greater pressure because of the greater length of protuberances 43, meltsand is disintegrated.

If it is desired, the sheetmaterial may be heat sealed in a continuous strip around the periphery, and subsequently contacted by the die system shownin FIGURE 8, so as to disintegrate small discrete areas of the bondedstrip.

Whether it is necessary to heat only one or both dies depends upon the properties of the materials to be sealed. In the case of such materials as the polyurethanes, which are poor condutcors of heat, it is necessary to heat both dies. The temperature to which the dies must be heated will depend upon the melting point of the substance to be sealed.. In general, the temperatures used will vary from between about 50 Fahrenheit to about 200 Fahrenheit above the softening point. In the case of the polyurethanes, this would be from about 400 vFahrenheit to about 600 Fahrenheit.

The pressure to which the material must be subjected depends upon whether the notched or unnotched product` is being produced. In the case of the latter, the pressures are conventionalheat sealing pressures; however, in the, case of the` former, the pressures are substantially higher;` in general, on the order of v1,000 to 2,000 pounds per square inch, and preferably about 1,500 pounds per square inch.

The method described has been found to be particular-` ly useful with respect to surgical dressings of the type described in United States Patent 3,122,140 and 3,122,- 141, issued to G. A. Crowe. In those dressings7 a flexible web of hydrophilic fibers is contained between extensible and resilient sheets of cellular sponge material. The material is preferably polyurethane. The sheet has been subjected to the action of a needle loom so that the hydrophilic fibers extend through the sponge material and are thereby anchored to it. When these fibers are in contact with the wound site, body fluids present thereon are absorbed by capillary action into the absorbent intermediate layer, thus cleaning the wound site. In this dressing, where extensibility is important, it is necessary to bond the two polyurethane players together so as to present a compact sealed absorbent body. Since the polyurethane foam is heat activatable, the layer of fibers and the outside layers may be sealed bythe method of this invention without destroying the extensibility of thedressing.

When effecting a seal with adhesive or cement, the sealing material may be applied in a discontinuous pattern at the edge of the sheet and the positioned layers passed through a series of rollers; or the adhesive or cement may be applied in a continuous strip and small areas of bonded material removed or slits provided subsequent to sealing.

The invention will be further illustrated in greater detail by the following example. It should be understood that although the example may `describe some of the more specific features of the invention, they are given only for the purpose of illustration and the invention should not be construed as limited thereto.

EXAMPLE Prior arr A sheet of polyurethane foam having a thickness of 5/128 inch is used as the extensible material. A web of blended carded polypropyleney fibers, having a denier of 1.5 and a fiber length of 11/2 inches, and carded rayon fibers, having a denier of 3 and a fiber length of 1%'6 inches, placedon top of a sheet of polyurethane foam.

The sheet of polyurethane foam with the fiber webs is passed through a needling machine, each needle having 9 barbs. The needles are made to penetrate the foam sheet and the web .from the surface containing the web; the barbs on the needles being in such a position so as to draw fibers down through the sponge sheet, they fibers not extending more than 1/16 inch from the opposite surface, The needling is carried out to give a needle penetration every .232 inch in the direction of fiber orientation. The product so prepared-has a series of fiber bundles extending from the rayon fiber web and the polypropylene fiber web which just penetrate the opposite surface of the sponge sheet.

A two inch by four inch strip is cut from thesheet material. Two opposing edges are in turn passed between a set of heated rollers in such a way so that a continuous heat seal, having a width of 1/16 inch is produced along those edges. The speed of the roller is 5 feet per minute;

and the temperature is 520 Fahrenheit. rPhe pressure at the nip is 50 pounds.

A one inch by one inch sample is cut from the strip so that one edge of the sample contains a heat seal 1/16 inch wide along the entire edge. The sample is tested for extensibility in an lnstron Tester at a rate of pull of 2 inches per minute, and a tensile stress of 700 grams. The test consists of measuring the elongation obtainable before any damage, such as rupturing of the heat sealed area, occurs. The one inch long sample was elongated to 1.312 inches in the direction parallel to the heat sealed edge before such damage occurred. The laminate therefore has an extensibility of 31.2% in the direction parallel to the heat sealed edge.

Dressings of this invention A second two inch by four inch strip is cut from the sheet material described in the example. Two opposing edges of the sample are in turn positioned between a set of platens similar to those described in FIGURE 8. The upper platen has 8 protuberances per inch, in the form of semi-circles 7AM of an inch in diameter; while the lower platen has 8 slightly longer protuberances per inch, each protuberance on the lower platen being .0001 of an inch longer than the protuberances on the upper platen. The protuberances on the lower platen are shaped so as to fit snugly into the spaces between the protuberances on the upper platen. Both dies are heated to 520 Fahrenheit. The strip is pressured between the heated dies at 1,000 pounds per square inch. Contact time is 0.6 second. The heat sealed strip has a series of small discrete bonded areas on the edges separated by a series of non-bonded areas.

A one inch by one inch sample is cut from the strip so that one entire edge is heat sealed as described above. The elongation is measured essentially as described in the example. The one inch by one inch sample was elongated to 3.9 inches in a direction parallel to the heat sealed edge before rupturing of the material in the body of the sample occurred. No rupture occurred in the heat sealed areas. The laminate, therefore, has an extensibility of 290% in the direction parallel to the heat sealed edge.

Although several specific examples of the inventive concept have been described, the same should not be construed as limited thereby to the specific features mentioned therein, but to include various other equivalent features as set forth in the claims appended hereto. It is understood that any suitable changes may -be made without departing from the spirit and scope of the invention.

What is claimed is:

1. An extensible pad for use as a dressing, or the like, comprising at least one layer of elastomeric material adhesively bonded to at least one nonwoven brous web, said adhesive bond being present in a border along the edges of said pad, the bonded portion of said pad being essentially inextensible and substantially stiffer than the nonbonded portion thereof said nonbonded areas being highly extensible, said adhesive bond along said edges being intermittent to provide flexibility and extensibility to the dressing.

2. The pad of claim ll wherein said elastomeric material is thermoplastic and wherein said bond is a pressure bonded heat seal.

3. The pad of claim 2 wherein a fibrous web is contained between and bonded to two layers of elastomeric material.

4. An extensible pad for use as a dressing, or the like, comprising at least one layer of elastomeric material adhesively bonded to at least one nonwoven fibrous web, said adhesive bond being present at small, discontinuous, discrete areas around the edges of the sheet disposed between unbonded areas, the bonded portion of said pad being essentially inextensible and substantially stiffer than the nonbonded portions thereof and said unbonded areas being highly extensible.

5. The pad of claim 4 wherein said elastomeric material is thermoplastic and wherein said `bond is a pressure bonded heat seal.

6. The pad of claim 5 wherein a fibrous web is contained between and bonded to two layers of elastomeric material.

7. The pad of claim 4 in which the unbonded portion of the lborder of said pad, disposed 4between said bonded areas of said border of said pad, has been removed.

S. An extensible absorbent pad for use'as a dressing, or the like, comprising an absorbent intermediate fibrous web contained between flexible sheets of thermoplastic cellular sponge material, the fibers from said intermediate fibrous web extending through said sheet of cellular sponge material to the opposite surface thereof, whereby when the ends of said fibers which extend through to the opposite surface of said cellular sponge sheet are wetted, liuid is drawn up into said absorbent layer, said fibrous web being adhesively bonded to the layers of cellular sponge in a border along the edges or" the sheet, said bond along said edges being present at small, discontinuous discrete areas disposed between unbonded areas.

9. The pad of claim 8 in which said sheet of cellular i sponge material is polyurethane foam.

References Cited UNITED STATES PATENTS 2,120,949 6/1938 Hayden 123-290 2,896,618 7/1959 Schaefer 128-296 2,973,760 3/1961 Dudley 12S-2.90 3,122,142 2/1964 Crowe 12S- 296 3,156,242 11/1964 `Crowe 128-296 3,248,757 5/1966 Salcer 264-16l FOREIGN PATENTS 371,555 10/1963 Switzerland.

RCHARD A. GAUDET, Primary Examiner. C. F. ROSENBAUM, Examiner.

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