BANDAGE

Abstract: A bandage which has been rendered elastic by inclusion therein of an elastomeric polymer film. The elastomeric polymer film may be present as an array of long strips from 1 to 5 mm in width placed from 1 to 6 mm apart to run the length of the bandage. Preferably the elastomeric polymer film is present as a ribbon which contains longitudinal slits. This ribbon adhered to the fabric of the bandage using heat and pressure contracts and the slits open providing the ribbon with an open area of from 25 to 75% within the bandage. A process for manufacturing the bandage by extending the elastomeric polymer film, adhering it to a fabric and then allowing the combination to relax to form the elastic bandage is described.

Description: BANDAGE The present invention is concerned with elastic compression bandages and methods for their manufacture. Elastic bandages in both adhesive and non-adhesive forms are used to provide support, assist in the healing of strained muscles and in the treatment of various venous conditions where it is important to maintain an effective level of compressive force for long periods of time. Previously known and commercially available elastic bandages have employed crimped yarns, high twist cotton yarns or elastic threads to provide elasticity in the bandage. None of these types of bandage has proved entirely satisfactory. -Elastic woven bandages containing crimped yarns have relatively poor elastic properties. Bandages containing high twist cotton yarns which are shrunk during processing are expensive to manufacture and also have relatively poor elastic properties and are adversely affected by moisture. Elastic bandages formed by weaving elastic warp threads under* tension into a woven structure have good elastic properties but are expensive to produce, can cause local constriction at the location of individual threads and are difficult to apply at an even and acceptable tension. It has now been discovered that if the material conferring elasticity to a bandage is in the form of thin, narrow, strips of elastomeric polymer film or a ribbon of elastomeric polymer film containing longitudinal slits and which are bonded over their length to a fabric material, a bandage may be obtained which is easy to manufacture, can be prepared either as a conventional strip bandage or as a tubular bandage and can provide superior elastic properties. Accordingly in one aspect the present invention provides a bandage which has been rendered elastic by • inclusion therein of strips of elastomeric polymer film. Accordingly in another aspect the present invention provides a bandage which has been rendered elastic by inclusion therein of a ribbon of elastomeric polymer film containing longitudinal slits. A strip when used herein refer to a generally flat piece of film of rectangular or elliptical cross-section and whose length is orders of magnitude greater than its width. A slit ribbon when used herein is a flat piece of film of greater length than width in which the slits run along the length of the ribbon from near to one end to near to the other end as a continuous uninterupted slit. A slit ribbon of this type is therefore to be thought of as a number of strips joined together at their ends. Surprisingly it has been found that if the included elastic ribbon or strips are formed from a non-linear elastomeric polymer, bandages are obtained which have extremely useful elastic properties which have hitherto not been recognised in the bandage art. The term non-linear elastomeric polymer when used herein means a polymer whose force-extension relationship is non-linear, that is, when the force-extension relationship is determined by stretching a sample of the polymer using an Instron (trade mark) and represented graphically, the graph shows two regions. In the first region, at low extension, the slope of the graph is steep; at large extension, the slope of the graph is shallower. Suitable non-linear elastomeric polymers for use in this invention have been found to have a force extension relationship when represented graphically, comprising a steep linear slope up to about 100? extension but to have a shallow linear slope above 100$ extension so that little additional force is required to provide extra extension. When such elastomeric polymers are used in a bandage of the present invention it has been found that the risk of applying the bandage at too great a pressure is reduced so that the bandage may be applied safely by an unskilled person. The bandages have good relaxation properties which maintain the compression on a limb for an extended period. As hereinbefore suggested, one function of a compression bandage is to provide pressure on a limb to prevent pooling of blood in the peripheral veins and to promote return in the deep veins. To achieve this the pressure should be graduated from the distal to the proximal end of a limb, with the highest pressure applied at the extremity and the pressure decreasing as the radius of the limb increases. Linear bandages are able to achieve this pressure gradient because as the bandage is applied the tension can be varied by stretching according to the radius of curvature of the part of the limb being covered. The tension in tubular bandages cannot be adjusted in the above manner by varying the stretching as the amount of stretch is defined solely by the ratio of the radius of the limb to the initial radius of the bandage. It has been found that by forming a tubular bandage in which are included a slit ribbon or strip of an elastomeric polymer, as described above, an elastic bandage is formed in which there is graduated compression along the limb as required. In yet another aspect therefore the present invention provides a tubular bandage which has been rendered elastic by inclusion therein strips of elastomeric polymer film. In a further aspect therefore the present invention provides a tubular bandage which has been rendered elastic by inclusion therein a ribbon of elastomeric polymer film containing longitudinal slits. The ribbon or strips for inclusion in the bandages of the present invention may be formed from any elastomeric polymer including natural and synthetic rubbers. Preferred elastomers are those which are found to have non-linear force-extension curves as hereinbefore described. Particularly preferred elastomeric polymers are styrene-butadiene-styrene (SBS) block copolymers which are available commercially as Kratons (trade mark) and Cariflexes (trade mark). If the elastomer material is present as strips, the strips may be rectangular in cross-section in which case the strip may have a width of from 1 to 5 mm or may be circular or elliptical in which case the diameter of the strip may be from 1 to 4 mm. Suitably the strips may have a weight per unit area of between 90 and 500 gsm, and preferably between 100 and 250 gsm. If the elastomer material is present as a ribbon, the ribbon may be rectangular in cross-section in which case the ribbon may have a short side corresponding to the thickness of the ribbon of 1 to 5 mm and a long side substantially equal to the width of the bandage which may be from 5 cm to 20 cm, more suitably 8 to 15 cm for example 10 cm. Suitably the ribbon will have a weight per unit area of between 20 and 150 gsm, and preferably between 30 and 60 gsm; for example 30, 40 50 or 60 gsm. Aptly the ribbons or strips may be cast from solution in which case it may be necessary to build the strip up from several layers cast one on top of the other until the required weight per unit area is achieved. In this method of manufacture the use of a solvent means that the layers are securely adhered together and the strips do not delaminate. It is preferred to cast the elastomeric polymer as a ribbon, or strip because if the ribbon or strip is formed by extrusion the non-linear orce-extension curve property may be lost and with it the preferred elastic properties conferred to the bandages by the ribbon or strip. Aptly the ribbon or strips may be bonded on only one surface to a fabric but preferably the ribbon or strips will be bonded to a fabric on both sides. Suitably the strips will be placed along the length of the fabric and then bonded to the fabric. Suitably the strips will be placed parallel to each other and bonded to the fabric. Suitably the strips are from 1 to 6 mm wide, with a similar distance between adjacent strips. l Suitably the ribbon or strips may be bonded to the fabric by means of a thermoplastic-elastomeric polymer which is tacky at a lower temperature than the melting point of the polymer forming the ribbon or strip. A suitable bonding agent is a thermoplastic elastomeric polyurethane for example a linear polyether of polyester polyurethane. The polyurethane may be coated on to one or both sides of the ribbon or strip as appropriate. Suitably the bonding agent will be present at a weight per unit area of from 8 to 20 gsm and more suitably 10 to 15 gsm. Aptly the coated ribbon contains slits running in the longitudinal direction of the ribbon ' about 0.3 cm apart. Unslit regions are left at each end of the ribbon which act as handles to facilitate the manufacturing processes. The fabric may be woven or non-woven. It is preferred to use non-woven fabrics in the bandages of this invention. A suitable non-woven fabric will generally have a weight per unit area of from 10 gsm to 80 gsm and more aptly from 12 gsm to 60 gsm, for example 18 gsm to 45 gsm. The non-woven fabric employed may aptly have absorbent properties. Suitable non-woven fabrics include those made from cellulosic fibres such as viscose rayon fibres, 0 polyester fibres or polyolefin fibres for example polypropylene, or other flexible material. Preferred non-woven fabrics include apertured non-woven fabrics such as those made from bonded viscose filaments. A suitable fabric of this type is 15 . available as Bemliese (trade mark) from Asahi Chemical Industry Co. A second preferred non-woven fabric is a spun-bonded polyester available as Sontara (trade mark) from Du Pont de Nemours Ltd. A third preferred non-woven fabric may be formed from polyolefin fibres 20 by bonding or entanglement of the fibres. Fabrics formed from polypropylene fibres are available as Lutrasil (trade mark) and Suominen (trade mark) . The elastic bandages in the first aspect of the invention may be prepared in the following manner. The elastomer is cast from solution in a suitable solvent as a large flat sheet or in the form of a multitude of strips of the appropriate width if a multicompartment casting unit is available. The weight per unit area of elastomer is in the range 150 to 350 gsm so that multiple casting operations may be required to give a multilaminate, but which will not by virtue of its method of manufacture delaminate. If the elastomer is prepared as a large flat film an adhesive may be applied to one surface of the film which may then be cut into strips of the appropriate width. The strips are stretched to an extension of between 100? and 350$ and bonded to a fabric. The strips are placed parallel to each other from 1 to 6 mm apart. When all the strips are in place, the resulting bandage is allowed to contract in length. Alternatively if the strips are formed as narrow strips the adhesive may be applied to the fabric material first and the stretched strips adhered to the fabric material. The combined strips and fabric are allowed to relax as before. The elastic bandages of the second aspect of the invention may be prepared in the following manner. The elastomer is cast from solution in a suitable solvent as a large flat sheet. The weight per unit area of elastomer is now in the range 20 to 150 gsm so that multiple casting operations may be required to give a multilaminate of the correct weight, but which will not by virtue of its method of manufacture delaminate. If the elastomer is prepared as a large flat film the bonding agent may be applied to one or both surfaces of the film which may then be cut into ribbons of the appropriate width. Slits are then cut in the longitudinal direction along the ribbon to leave uncut regions at either end. The ribbon is stretched to an extension of between 100? and 350? and bonded to a fabric by means of the application of heat and pressure. The heat and pressure cause the bonding agent to bond the ribbon to the fabric but they also cause the elastomeric polymer film to shrink resulting in the slits opening. The ribbon within the bandage may suitably then have an open area of about 25? to 75? and preferably 30? to 60? for example 50?. The resulting bandage is allowed to contract in length. The above method may be used to prepare linear bandages. Tubular bandages may be prepared by making linear bandages as described above and then bringing two opposed edges of the linear bandage together to form a cylinder with the slit ribbon or strips of elastomeric polymer running circumferentially. The two edges may then be secured together for example with adhesive, a heat seal, stitching or a zip mechanism. Alternatively a ribbon or strip of elastomeric polymer may be wrapped spirally round a former, for example a cylinder, and an adhesive coated non-woven fabric adhered to the spiral ribbon. The ribbon or strips may be bonded to the fabric by any conventional means. For slit ribbons heat bonding is preferred using a bonding agent as hereinbefore described. For the strips attachment by means of an adhesive, for example using an acrylic ester copolymer adhesive, is preferred. I n another aspect therefore the present invention provides a method of forming an elastic bandage by including in a bandage strips of an elastomeric polymeric material. In another aspect therefore the present invention provides a method of forming an elastic bandage by including in a bandage a ribbon of an elastomeric polymeric material containing longitudinal slits. Suitable elastomeric polymeric materials include those as hereinbefore defined. Suitably the method comprises bonding the elastomeric polymer ribbon when stretched from 100 to 350? extension to a fabric material and allowing the bondage so formed to relax. Example 1 A solution of a styrene-butadiene-styrene block copolymer was prepared using IMS as a solvent at 40? solids. This solution was then cast from a conventional spreading box to form a film of the styrene-butadiene-styrene copolymer. Several passes were made with the spreading box until a film having a weight per unit area of 150 gsm (approximately) was achieved. A film of adhesive, formed by the polymerisation of 47 parts by weight n-butyl acrylate, 47 parts by weight 2-ethyl hexyl acrylate and 6 parts by weight acrylic acid in acetone, was coated onto the block copolymer film using a knife over flat bed coating unit. The adhesive coated film was then cut longitudinally into strips approximately 2mm wide. The strips were then stretched to 100? extension and adhered to an appropriately shaped piece of a Bemliese apertured fabric. The strips were placed parallel to each other and approximately 2mm apart. When all the strips were in place the resulting bandage was allowed to contract. This bandage was able to extend to 100? extension but any further extension was prevented by the inextensibility of apertured fabric. Example 2 A similar bandage was prepare as described in Example 1 except that this time the strips were stretched to 200? extension. Instead of allowing the bandage to relax after placing the strips onto one piece of apertured non-woven fabric, a second non-woven fabric coated with the acrylic ester copolymer adhesive described in Example 1 was placed over the strips of elastomeric polymer so that both sides of the strip were adhered to non-woven fabric. The bandage material was then allowed to contract in length ' . Example 3 Strips of a styrene-butadiene-styrene block copolymer are prepared using a multi-compartmental spreading box, to give strips which are approximately 2mm wide. A film of adhesive formed from the copolymer described in Example 1 is coated onto a polypropylene non-woven fabric using a knife over flat bed coating unit. The strips of block copolymer are extended to 1 0? and adhered to the non-woven fabric parallel to each other and spaced approximately 2mm apart. When all the strips were in place the resulting bandage is allowed to contract. Example 4 A bandage was formed by a similar method to that described in Example 2. The relaxed bandage was formed into a cylinder so that the elastic strips ran circumferentially around the cylinder. The two opposed edges of the bandage were stitched together so as to provide a tubular bandage. Example 5 A long thin strip of elastomeric polymer about 2mm wide is wound round a cylindrical former in the form of a spiral. A piece of non-woven fabric is coated with an acrylic ester polymer adhesive and placed around the former so as to adhere the non-woven fabric to the spiral elastomeric polymer strip. The edges of the non-woven fabric are heat sealed together and the strip allowed to relax by removing the bandage from the former. .A tubular bandage is thus produced. Example 6 A solution of a styrene-butadiene-styrene block copolymer was prepared using IMS as a solvent at 40? solids. This solution was then cast from a conventional spreading box to form a film of the styrene-butadiene-styrene copolymer. Several passes were made with tr ' . e spreading box until a film having a weight per unit area of 150 gsm (approximately) was achieved. A coating of a polyurethane polymer (Estane 571 F, trade mark) was appl-ied to the film prepared above at a weight per unit area of 10 gsm. The coate film was then cut longitudinally into ribbons approximately 10 cm wide. The ribbon was then stretched tc 100? extension. A series ofr slits was cut into the coated ribbon running so that the slits ran longitudinally along the ribbon approximately 0.3 cm apart and bonded by heat and pressure to an appropriately shaped piece of a Bemliese apertured fabric. The ribbon was placed along the length of the bandage. When all the ribbon was in place the resulting bandage was allowed to contract. This bandage was able to extend to 100? extension but any further extension was prevented by the inextensibility of the apertured fabric. Example 7 A bandage was prepared as described in Example 1 except that the ribbon was coated on both sides with the polyurethane and then the slits were cut into the laminate ribbon. The laminate was stretched to 200? extension and placed between two appropriately sized pieces of non-woven fabriq. The pieces were bonded to the slit ribbon by heat and pressure to form the bandage. Example 8 A bandage was formed by a similar method to that described in Example 2. The relaxed bandage was formed into a cylinder so that the elastic ribbon ran circumrerentially around the cylinder. The two opposed edges ofr the bandage were stitched together so as to provide a tubular bandage. Example 9 A long thin ribbon of elastomeric polymer containing longitudinal slits and about 10 cm wide is wound round a cylindrical former in the form of a spiral. A piece of non-woven fabric is coated with an acrylic ester polymer adhesive and placed around the former so as to adhere the non-woven fabric to the spiral elastomeric polymer ribbon. The edges of the non-woven fabric are heat sealed together and the strip allowed to rela by removing the bandage from the former. A tubular bandage is thus produced.

Claims: CLAIMS 1. A bandage which has been rendered elastic by inclusion therein of strips of elastomeric polymer film. 2. A bandage which has been rendered elastic by inclusion therein of a ribbon of elastomeric polymer film. containing longitudinal slits. 3. A bandage as claimed in either of claims 1 or 2 in which the elastomeric polymer film is formed from a non-linear elastomeric polymer as herein defined. 4. A bandage as claimed in claim 3 in which the elastomeric polymer is a styrene-butadiene-styrene block copolymer. 5. A bandage as claimed in claim 1 in which the strips are from 1 to 5 mm in width and have a weight per unit area of from 90 to 500 gsm. 6. A bandage as claimed in claim 2 in which the ribbon is substantially equal to the width of the bandage and has a weight per unit area of from 20 to 150 gsm. 7. A bandage as claimed in either of claims 1 or 2 in which the elastomeric polymer film is coated on one or both sides with a bonding agent whereby the film may be bonded on one or both sides to a fabri 8. A bandage as claimed in claim 7 in which the bondin agent is a linear polyether or polyester polyurethane which is tacky at a lower temperature than the melting point of the elastomeric polymer and is present at a weight per unit area of from 8 to 20 gsm. 9. A bandage as claimed in claim 7 in which the fabric is a non-woven fabric which has a weight per unit area of from 10 gsm to 80 gsm. 10. A bandage as claimed in claim 2 in .which the ribbo has an open area of from 25% to 75% after inclusion in t banαage. 11. A bandage as claimed in either of claims 1 or 2 in which the bandage is in the form of a tubular bandage 12. A process for the preparation of an elastic bandag which process comprises taking strips of elastomeric polymeric film, stretching to an extension of between 100% and 350%, bonding to a fabric at a distance of from 1 to 6 mm between each strip and then allowing the bandage to relax. 13. A process as claimed in claim 12 in which the strips are bonded to the fabric by means of an acrylate ester copolymer. 14. A process for the preparation of an elastic bandage which process comprises coating a ribbon of elastomeric polymer film with a bonding agent, cutting longitudinal slits through the elastomeric polymer film and bonding agent, stretching to an extension of between 100% and 350%, bonding to a fabric under the influence of heat and pressure and allowing the bandage to relax whereby " the ribbon shows an open area within the bandage of from 25% to 75%. 15. A process as claimed in claim 14 in which the bonding agent is a polyether or polyester polyurethane.

Inventors: DANIEL CHRISTOPHER, DANIEL, CHRISTOPHER
Applicants: SMITH & NEPHEW ASS, SMITH AND NEPHEW ASSOCIATED COMPANIES PLC.
Application year: 1987
Main classification: A61F13
IPC codes: A61F13