AUTO-ADHESIVE COMPOSITION

Abstract: Auto-adhesive compositions are made of specific blends of low protein natural rubber latex in combination with at least one polymer. Proportions of these components may vary according to the requirements of the specific end products but in order to achieve the desired results of the present invention, at least 90.0 percent by weight of the low protein natural rubber latex and at least 1.0 percent by weight of the polymer are necessary in the adhesive. The low protein natural rubber latex can be present from 90.0 to 97.0 percent by weight and the polymer can be present from 3.0 to 10.0 percent by weight.

Description: AUTO-ADHESIVE COMPOSITION FIELD OF THE INVENTION This invention relates to novel auto-adhesive compositions that are especially formulated for use on skin More particularly, the present invention relates to adhesive compositions that comprise low protein natural rubber latex and at least one polymer "Auto-adhesive" as used herein is intended to mean an adhesive that bonds to itself or to a substrate and unwinds from itself and from the substrate without much effort BACKGROUND OF THE INVENTION The adhesive compositions of this invention are designed for cohesive elastic conforming bandages Such bandages adhere to themselves, but not to skin, hair or clothes Auto-adhesive bandages are used for dressing retention and are easy to apply especially on difficult parts of the body They are also used for fixation of padding material, cannulae and tubes, and for light compression and support bandages, and for application to the skin to protect wounds from contamination thereby reducing the danger of infection and guarding against further injury Natural rubber latex provides adhesive compositions with excellent auto-adhesion and non-residue properties, but the problem of allergic reaction to proteins in these natural rubber latex persists It is known in the prior art to reduce the protein content of natural rubber latex Several methods to remove these proteins are utilised including, for example, leaching, however the most efficient method is by enzyme treatment as it removes both water soluble and combined proteins Prior art examples of protein removal include complexing the proteins of natural rubber latex with e g ion exchange resins and thereafter separating the resulting protein-resin complex from the latex (as described in US Pat No 5,563,241 ), or by incubating the latex with a proteolytic enzyme in the presence of a combination of surfactants and then washing with water to remove both the protein combined with rubber molecules and the water-soluble proteins (as described by Shinichi Nakade "Progress in Prevention Developments Achieved in Low-Allergen NR Products" paper presented at "Latex Protein Allergy" Conference Amsterdam, Netherlands 19 February 1996) Other prior art methods of reducing the allergic affect of proteins in natural rubber latex, such as that exemplified by U S Pat no 5776484, rely on forming a barrier layer to prevent or minimise contact between the skin and the latex or by bonding the protein in natural rubber latex to a material, such as a copolymer, and thereby lessening the ability of the protein to be transported to the skin Although it is known to use low protein natural rubber latex in rubber products such as gloves to reduce the allergic affect of proteins, the use of such latex in auto-adhesives has heretofore not been considered viable due to the belief that they would impart poor auto-adhesion properties to such adhesives The drive and motivation as described in the prior art has been towards the continued use of protein-containing natural rubber latex in adhesive compositions combined with a means of preventing or minimising the transfer of proteins from the adhesive composition to the skin by utilising physical barriers or restraints This ensures the adhesive continues to obtain the benefits of auto-adhesion and elasticity known to be provided by protein-containing natural rubber latex It is to the prior-art problem of providing adhesives containing natural rubber latex whilst retaining the desired properties of auto adhesion and peel strength that the present invention is specifically directed SUMMARY OF THE INVENTION It has now been discovered that auto-adhesive dressings made from specific blends of a low protein natural rubber latex and one or more polymers possess good adhesion and non-residue properties According to the present invention, adhesives are made of specific blends of low protein natural rubber latex in combination with at least one polymer Proportions of these components may vary according to the requirements of the specific end products but in order to achieve the desired results of the present invention, at least 90 percent by weight of the low protein natural rubber latex and at least 1 percent by weight of the polymer are necessary in the adhesive The low protein natural rubber latex is preferably present from 90 to 99 percent by weight, more preferably from 90 to 97 percent by weight, and the polymer is preferably present from 1 to 10 percent by weight, more preferably from 3 to 10 percent by weight The adhesives of this invention are useful to prepare medical adhesive articles such as surgical bandages, athletic tapes, wound dressings and the like These adhesives may be coated onto any backing suitable for medical uses including occlusive (substantially non-breathable) and non-occlustve backings (breathable) Occlusive backings are also known as low porosity backings Non limiting examples of occlusive backings include films, foams and laminates thereof Non limiting examples of non- occlusive backings include woven substrates, non woven substrates or melt blown webs, foams and thermally embossed non woven substrates DETAILED DESCRIPTION OF THE INVENTION The present invention provides adhesive compositions comprising low-protein natural rubber latex and at least one polymer More particularly, the low-protein natural rubber latex content of the adhesive is at least 90 percent by weight, preferably from 90 to 99 percent by weight, more preferably from 90 to 97 percent by weight and the polymer is present in at least 1 percent by weight, preferably from 1 to 10 percent by weight, more preferably from 3 to 10 percent by weight The term "natural rubber latex" as used in this invention is the naturally occurring form of rubber, i e , cιs-1 ,4-polyιsoprene Amongst its natural sources is included the sap of the Havea brasiliensts rubber tree Natural rubber latex also comprises 1-2% proteins and it is known that some individuals are allergic to these proteins It is known to remove proteins from natural rubber latex, for example through incubation with a proteolytic enzyme in the presence of surfactants followed by washing with water This results in the removal of rubber proteins and water-soluble proteins The colloidal properties of the deproteinised natural rubber latex are maintained by addition of appropriate surfactants However, once the proteins have been removed the intrinsic properties of natural rubber latex are modified Such modification effectively reduces auto-adhesion and elasticity Deproteinised natural rubber latex is known and used to lessen the allergic effects of e g surgical gloves and similar rubber products However, it has not heretofore been known that such latex could be used in combination with polymers of this invention to provide adhesives having desirable properties The adhesive composition of this invention comprises deproteinised natural rubber latex and at least one polymer The adhesive is applied to a bandage to provide good auto-adhesion, low or no residue skin adhesion after peeling, good viscosity during production and good peel coating weight This invention provides the first adhesive product comprising deproteinised natural rubber latex having the above properties For the purpose of this invention, "polymer" refers to a homopolymer, a copolymer or an adhesive polymer as well as any mixtures or blends of one or more homopolymers, and/or one or more copolymers, and/or one or more adhesive polymers "Copolymer" refers to a polymeric material produced by the polymerisation of two or more dissimilar monomers, either with or without another functional group grafted thereto, as well as to a homopolymer with a functional group grafted thereto Thus, the term "copolymer" includes, without limitation, random copolymers, block copolymers, sequential copolymers, and graft copolymers Typical monomers include, but are not limited to, hydroxyl substituted C1 to C12 esters of acrylic and methacry c acids, vinyl esters (vinyl acetate and vinyl propionate), vinyl ethers, fumarates, maleates, styrene, acrylonitπle "Adhesive polymer" refers to a polymer that is inherently adhesive, or has been rendered adhesive by combining additives and/or modifiers with the polymer Examples of suitable additives and/or modifiers include, without limitation, tackifiers, plasticisers, stabilisers, cross-linking agents, and combinations thereof Typical polymers include, without limitation, for example, polyolefins, non-elastomeπc polyesters, non-elastomeπc polyamides, cellulosic derived polymers, vinyl acetates, acrylates, vinyl chlorides and polyvmyl alcohols Examples of trade name polymers suitable for use in the present invention include without limitation Vinamul 62118 a dextrine stabilised vinyl acetate-dibutyl maleate copolymer available from Vinamul, Vinamul 6152 a vinyl acetate-dibutyl maleate available from Vinamul, Airflex 920 a carboxylated Vinyl Acetate-Ethylene copolymer available from Air Product, Duroset 78-6964 E250 a ethylene / vinyl acetate copolymer available from National Starch and Chemical Company, Vinnapas LL8647 a mixture of copolymers of vinyl-acetate, acrylic acid ester and ethylene available from Wacker, Luphen D200A a polyurethane elastomer available from BASF, Aquastick 1120 a chloroprene and methacryhc acid copolymer available from DuPont Dow Elastomers, Synthomer VL10533 a carboxylated butadiene methyl methacrylate copolymer latex from available from Synthomer, Revacryl 239 a styrene / acrylic ester copolymer dispersion available from Harlow Chemical Company Other ingredients may be employed as desired and may include, for example, stabilisers, tackifiers, antioxidants, fibrous fillers, non-fibrous fillers, humectants, colorants, and deodorants or fragrances A typical stabiliser that may be utilised in the mix to form the compositions of the present invention includes, for example the trade name product, Nopco S This is a highly sulphated fatty acid used in rubber industry to stabilise lattices during compounding, storage and application and is available from Henkel Other stabilisers may include Dapro DF 900 from KRAHN CHEMIE GmbH and Byk-033 from BYK-CHEMIE GmbH Typical antioxidants and/or metal transition ion scavengers that may be utilised in the mix to form the compositions of the present invention includes, for example hindered phenols, amines, and sulfur and phosphorous hydroxide decomposers A list of common antioxidants is given in McCutcheon's Functional Materials (1991 ), pp 13-18 A suitable antioxidant is available under the trade name product, Dispersion 2074M from Vita Liquid Polymers, this is an aqueous dispersion of Zinc Dibutyl Dithiocarbamate The preparation according to the invention may also include a humectant Suitable humectants include glycerin, sorbitol, polyethylene glycol, propylene glycol, and other polyhydπc alcohols A suitable humectant is available under the trade name Polyethylene glycol 200 from ICI Surfactant - this is also called polyoxyethylene glycol Defoaming agents may be used in the mix The most common defoamers are given in McCutcheon's Functional Materials (1991), pgs 89-112 Typical defoamers include aluminium stearate, amyl alcohol, capπllic alcohol, capryl alcohol, castor oil, corn oil, decyl alcohol, diethylene glycol monolaurate, glyceryl monostearate, mineral oil, pine oil, polyalkyl glycol, silicone oils, steanc acid, sulfonic acid salts, tributyl citrate and , tributyl phosphate A suitable defoamer is available from Henkel under the trade name product Dehydran 1620 This is a blend of modified fatty alcohols and a polysiloxane The above additives and other components such as the cure activators, pH control agents, and silicone oils employed in the latex formulations of the present invention may be present in the range of from 2 percent by weight to 9 percent by weight of the latex The adhesive compositions of the invention may be prepared by mixing the latex and polymer, and any other desired ingredients, e g tackifiers, antioxidants, fillers etc in any convenient way (e g in a Sigma mixer) The mixing can be carried out in a liquid medium which is a solvent for some or all of the ingredients, or which is an aqueous medium Each of the ingredients can be added to the mixture as a solid, or as a molten liquid, or as a solution, emulsion or dispersion, as appropriate The resulting liquid mixture, i e solution, emulsion or dispersion in a liquid carrier, can be applied, if desired after further dilution, to the backing in conventional fashion, e g by spraying, painting, dipping or rolling EXAMPLES The following adhesive composition was prepared in accordance with the present invention KDP 150 is an highly deproteinised Natural Rubber Latex available from Kao Corporation under this trade name Revacryl 239 is a hard styr ene/acry c ester copolymer available from Harlow Chemical Company under this trade name Dehydran 1620 is a blend of modified fatty alcohols and a polysiloxane available from Henkel under this trade name 4 Nopco S is a highly sulphated fatty and is available from Henkel under this trade name 5 Dispersion 2074M is an aqueous dispersion of Zinc Dibutyl Dithiocarbamate available from Vita Liquid Polymers under this trade name This adhesive composition had a density of 0 95, a solids content of 59 to 62%, a pH of 9 5 to 10 5, and a viscosity in the range 80 to 130 cps The following Examples are based on the above formulation but with differing amounts (by Weight) of KDP 150 and/or Revacryl 239, or by replacing KDP 150 with LATZ Latex at the stated level (LATZ Latex is a low-ammonia protein-containing natural rubber latex available from Lewis and Peat under this trade name), or by replacing Revacryl 239 with another suitable polymer at the stated level Tpeel (ASTM D1876-61 T) refers to the force required to separate the adhesive to adhesive bond using paper strips that are 1 inch wide, 12 inches long and 30μm coated with the adhesive The specimens are bonded over 9 inches They are tested on an Instron tensometer 5 mm after bonding The paper strips are peeled apart and the force to do so recorded Higher Tpeel force means higher transfer from one side of the paper strip to the other Adhesives having Tpeel values between 2 and 4 N/25mm indicate acceptable tack levels and auto-adhesive properties The term "transfer" means auto-adhesion is higher than the adhesion between the adhesive and the paper Adhesion to skin was measured as follows tape samples 1 inch wide by 3 inches long were placed on the skin of a human subject using a predetermined constant pressure The tape was removed and a subjective evaluation of adhesion and residual tack was made and rated as no adhesion to skin. to 2 good adhesion; no tack. good adhesion; tack. ' = KDP 150 7 = Duroset 78-6964 2 = Revacryl 239 8 = Luphen D200A 3 = Vinamul 62118 9 = Vinamul 6152 4 = Aquastick 1120 10 = Synthomer VL10533 5 = Vinnapas LL8647 11 = LATZ Latex 6 = Airflex 920 Examples 1 to 13 were formulated according to the teachings of the present invention All of these formulations show Tpeel values between 2 and 4 N/25mm and have good skin adhesion with no residual tack In comparative Example 14, KDP 150 (highly deproteinised natural rubber latex) was substituted by a protein-containing natural rubber latex This formulation has a high Tpeel force and shows residual tack on skin Comparative Example 15 contains polymer and highly derproteinised latex according to the invention, but the latex is present at level less than the claimed amount This formulation has very low Tpeel force and shows no adhesion on skin Comparative Example 16 contains latex and polymer according to this invention, but both are present at levels outside their claimed amounts This formulation shows very high Tpeel force and shows residual tack on skin From the above Examples it is clearly seen that the key amount of low-protein natural rubber latex is 90 to 97 percent by weight and the key amount by weight of polymer is 1 to 6 percent by weight

Claims: CLAIMS 1 An adhesive composition which comprises a) at least 90% by weight of a low-protein natural rubber latex, and b) at least 1 % by weight of a polymer 2 An adhesive composition according to claim 1 wherein the low-protein natural rubber latex is present from 90% to 99% by weight 3 An adhesive composition according to claim 1 wherein the polymer is present from 1 % to 10% by weight 4 An adhesive composition according to claim 1 wherein the low-protein natural rubber latex is present from 90% to 97% by weight 5 An adhesive composition according to claim 1 wherein the polymer is present from 3% to 10% by weight 6 An adhesive composition according to any one of the preceding claims wherein the polymer is an adhesive polymer 7 An adhesive composition according to any one of the preceding claims, which is applied to a bandage, tape or wound dressing for use in the medical or surgical field

Inventors: BONNET FLORENCE, BONNET, FLORENCE
Applicants: BONNET FLORENCE, NAT STARCH & CHEMICAL INVEST, BONNET, FLORENCE, NATIONAL STARCH & CHEMICAL INVESTMENT
Application year: 2000
Main classification: A61L15
IPC codes: A61L15, C08C1, C09J107