ORTHOPAEDIC MATERIALS

Abstract: The present invention provides an orthopaedic bandage comprising a flexible substrate, a water curable silane functionalised prepolymer system and at least a water soluble halide salt as a catalyst.

Description: ORTHOPAEDIC MATERIALS This invention relates to orthopaedic casting and splinting bandages. In particular this invention relates to orthopaedic casting and splinting materials based on synthetic resins which, upon contact with water, will cross-link and harden to form a weight bearing support for a limb or body portion and to such resins which on contact with water will cross-link and harden. Resin based splinting and casting materials find wide use in the immobilisation of limbs, for example the fixation of fractured bones, immobilisation of injured joints and for the support of ligaments and muscies where it is necessary to encase the limb in a partially or completely surrounding rigid form or cast. There are several major considerations for a casting or splinting material. A suitable material should be easily handleable, with a reasonable setting time to allow sufficient time in the case of casting bandages to mould the bandage about the limb and it should be flexible and free of offensive chemicals which may affect the patient or practitioner applying the material. In addition it is desirable that during the forming of the cast the material does not generate an uncomfortable exothermic reaction and that it sets within a relatively short time under mild conditions. Splinting and casting materials comprising water activated synthetic polymers in which a cross-linkable prepolymer resin system is coated onto a suitable substrate are well known. The most favoured and commercially developed systems are those based on prepoiymers which contain isocyanate functional groups and which in the presence of cold water will cross-link to form urea \ bridges. The resin systems usually also contain a catalyst to speed up the cross-linking reaction and so that a weight bearing cast may be formed in as short a time as possible consistent with requirements for moulding and shaping the splint. The isocyanate linking reaction is usually an exothermic reaction. In meeting the working requirements for such resin systems the resin chemistry has to be carefully controlled so as to allow the resins to cure in a period of time which is acceptably short and yet not cure under conditions in which so much heat is evolved that the applied cast is uncomfortable to the wearer. A disadvantage of such systems is the relatively high exotherm generated on cuπng and that there is a perceived health hazard with the use of orthopaedic bandages compπsing isocyanate functionalised prepoiymers. It is therefore desirable to make a suitable splinting material without utilising isocyanate functionalised prepoiymers Examples of this approach include US Patent No 4411262 (von Bonin et al) wherein there are disclosed splinting and casting mateπals comprising substrates impregnated or coated with a reactive one component system, wherein inter alia the systems includes organic compounds with molecular weights greater than 10,000, comprising reactive groups which may be alkoxysiiane groups. It is taught that the organic compounds themselves were produced by an isocyanate functionalised reaction and thus any perceived health risk associated with isocyanate functionalised resins is not entirely removed without ensuring that the resins are fully reacted US Patent No 5,423,735 also describes materials of thts type, where the water reactive resin is an alkoxysiiane functionalised polyurethane/polyurea resin, produced by reacting isocyanate functionalised precursors Such resins potentially have the same problems which may be associated with other prior resins produced from isocyanate functionalised precursors The present invention seeks to provide an improved orthopaedic casting bandage with a resin system which overcomes the above mentioned disadvantages The use of alkoxysiiane groups as the water activated reactive hydrolysable groups, more specifically the use of methoxysilane as the hydrolysable group has been proposed in the art. The methoxysilane group has the advantage of being highly reactive with water without the need for catalysis, whereas higher molecular weight alkoxy substituents attached to the silane such as ethoxysilane or propoxysilane react more slowly and are not suitable for uncatalysed splinting and casting materials. One possible disadvantage with the use of methoxysilane functionalised materials however, is the evolution of methanol as a by-product during hydrolysis of the methoxysilane groups as illustrated below: i) RSi(OCH 3 ) 3 + H 2 O → RSi(OCH 3 ) 2 OH + CH 3 OH ii) RSi(OCH 3 ) 2 OH + RSi(OCH 3 ) 3 → RSi(OCH 3 ) 2 OSi (OCH 3 ) 2 R + CH 3 OH Methanol is a toxin in man, with potential to cause serious irreversible effects to the liver, central nervous systems and visual centres. It is a volatile compound, and thus patients and more possibly, plaster technicians could be exposed via inhalation as well as skin contact following its release from a setting casting material. The rate of metabolism and excretion of methanol is very low in man and thus repeated exposure to methanol may be regarded as having a cumulative effect. There would probably be only a single exposure for the patient but a casting technician would be repeatedly exposed as each new casting material was applied and therefore is deemed unacceptable. Thus it would be desirable to be able to use higher molecular weight hydrolysable organo-oxy groups as the water activated reactive groups in resins to be used for casting and splinting materials. Organo-oxy silanes are suitably defined as a group including alkoxysilanes [-Si-O-R] and acyloxysi lanes (-Si-O-C(O)-R], where R is an alkyl group aptly containing up to 10 carbon atoms. Organo- oxy silane groups cross-link in the presence of water to form siloxane [-Si-O-Si] links. A number of catalysts for the hydrolysis reaction have been proposed, for example^ertiary amine catalysts or acid catalysts. However, on their own they do not produce an acceptable cure profile for a casting material and often very high levels are required for the hydrolysis of organo-oxy silanes other than methoxysilane. Thus an object of the invention is to provide a casting system which does not suffer from the aforementioned disadvantages. In accordance with the present invention there is provided an orthopaedic casting bandage comprising a flexible substrate, a water curable organo-oxy silane functionalised prepolymer system and a catalyst component characterised in that said catalyst component comprises a water soluble halide salt. Further there is provided an orthopaedic casting bandage comprising a flexible substrate, a water curable organo-oxy silane functionalised prepolymer system and a catalyst component, characterised in that said catalyst comprises a water soluble alkali metal hahde salt. Although the splinting and casting material of the present invention is described in terms of "an orthcoaedic casting bandage", the term is also intended to embrace splints and braces, where such splints and braces do not necessarily surround the whole limb or other body portion. The catalyst of the present invention comprises a water soluble halide salt. Suitable water soluble halide salts include but are not limited to soluble alkali metal halide salts. Apt examples of metal salts include sodium, potassium, iron, copper and zinc salts because of their low costs. The catalyst of the present invention may further comprise a water soluble fluoride salt. By salts we include organic and inorganic halide salts. Suitable halide salts include quaternary ammonium salts and alkali metal salts amongst others. Apt examples of halides include but are not limited to the group comprising: caesium fluoride, sodium fluoride, potassium fluoride, potassium (hexa) fluoride zirconate, potassium (hexa) fluoride titanate, manganese (II) fluoride, zinc (II) fluoride, iron (III) fluoride, iron (II) fluoride, tin (II) fluoride, tetrabutylammonium fluoride, potassium chloride, ammonium chloride and acetyl chloride. Preferably the catalysts are potassium fluoride, sodium fluoride and caesium fluoride. The catalyst may be mixed into the organo-oxy silane functionalised prepolymer before reaction with water or may be added to the water used to react with the prepolymer. Suitable amounts of catalyst when mixed in with the prepolymer are 0.01 % w/w to 10.0% w/w more suitably 0.1% to 5.0% w/w. Suitable amounts of catalyst when added to water to make a solution are solutions of 0.01% to 10.0%, more suitably a 0.1% to 5.0% solution. The catalyst may be present as a single chemical species or a mixture. The catalyst is dispersed in the curable prepolymer of the invention using methods known to those skilled in the art. A problem often associated with the use of water soluble catalysts is where the shelf life of the curable prepolymer system is reduced due to the increased reactivity of the functionalised prepolymer with atmospheric moisture in the presence of such a catalyst. This may be avoided by coating the catalyst with a coating that is insoluble in atmospheric moisture and is soluble in water, or water pervious once the. coating is hydrated. A preferred feature of the present invention, although not essential is the pre-treatment of the selected water soluble halide catalyst with a hydrophilic coating, before dispersion in the prepolymer. This reduces the risk of ageing of the prepolymer system. The hydrophilic coating may be any suitable coating that will dissolve on contact with water or become hydrated with water such that the hydrated coating becomes water pervious, for example polyvinyl alcohol (PVA) or polyhydroxyethylmethacrylate (poly HEMA). The catalysts of the present invention may be suitable for a wide range of organo-oxy silane functionalised prepoiymers. Aptly the catalyst component as herein before described may additionally comprise a second catalyst component. The use of a second catalyst component may benefit the curing speed of the prepolymer system. The second catalyst component may be any catalyst that enhances the catalytic activity of the catalyst component of the present invention. Apt examples are hereinafter described. Suitably if two catalyst components are used, together they comprise less than 7.5% by weight of the prepolymer system. Aptly equal amounts of the catalysts are added to the resin system, for example 1.0%, 1.25%, 2% or 2.5% of each of the first and second catalyst by weight of the prepolymer system may be added. Reactive tertiary amine catalysts have been proposed for use in casting bandages, however such a use is accompanied by the possibility the catalyst may leach out or evaporate from the prepolymer system during curing or after curing. Such amines may have a strong odour and the potential inhalation and absorption toxicity of tertiary amines is well known. The use of a covalently bound-in tertiary amine catalyst would overcome the problems associated with the leaching of catalyst. By covalently bound-in is meant a catalyst that is covalently bound to the organo-oxy silane functionalised prepolymer. Thus according to a further embodiment of the present invention there is provided an orthopaedic casting bandage as herein before described additionally comprising a second catalyst wherein said second catalyst is covalently bound-in. The bound-in tertiary amine catalyst may be present at any appropriate location in the prepolymer. For example they may be introduced at an end of the prepolymer molecules via a capping reaction, they may be present on a side chain extending from the main polymer backbone, or may oe part of the polymer backbone itself. The tertiary amine catalyst may be optionally substituted with substituents which do not substantially adversely affect the reaction 8 of the tertiary amine catalyst with the prepolymer or the catalytic effect of the tertiary amine catalyst when present in the functionalised prepolymer system of the present invention. Appropriate tertiary amine catalysts for reacting with so as to form the prepoiymers of the present invention may include but are not limited to molecules with at least two functional secondary amine groups and/or at least one functional primary amine group, for example: 1 ,4-bis(3-aminopropyl)piperazine, 3-aminopropyl morpholine, 3,3-diamino-N-methyl dipropylamine, 1 -(2-aminoethyl)piperazine, 4-3(-aminopropyl)morpholine. The chemically bound-in tertiary amine catalysts may comprise a single species or mixture of species. Whatever species or tertiary amine containing molecules are utilised to prepare a bound-in catalyst, it is preferred that they comprise less than 10% by weight and more preferably from 0.1 to 5% by weight of the curable composition. The second catalyst component may suitably comprise other water soluble metal salts. Examples include but are not limited to copper salts for example copper II sulphate. The catalyst component of the present invention may be suitable for a wide range of organo-oxy silane functionalised prepoiymers. The prepoiymers employed in the present invention may be end capped with a an organo-oxy hydrolysable group as hereinafter described. Further, the prepoiymers may comprise pendant organo- oxy hydrolysable groups. Favoured end capping groups have the general formula -Si(OR)„, -Si(OCOR) n , -Si-0-Si(OR) n , -Si-O-Si(Rι) 3 . n (OR) nι Si(OC(R 3 )=C(Rι)(R 2 )n, where n has a value of 1 to 3 and each of R, R 1f R 2 . and R 3 may be the same or different and are alkyl groups aptly containing up to 10 carbon atoms. Preferably the hydrolysable alkoxy or acyloxy group is a C 2 - C 6 hydrocarbon group. More preferably the hydrolysable group is a C 2 - C β hydrocarbon alkoxy group and most preferably the hydrolysable group is an ethoxysilyl or propoxysilyl group. The prepoiymers used in the invention may be precured by the addition of water to cross-link a small percentage of the available organo-oxy silane groups. The advantage gained would be an increase in molecular weight, leading to an increase in viscosity. Examples of organo-oxy silane functionalised prepoiymers include organo-oxy silane functionalised polyurethanes, one component organo-oxy silane functionalised prepoiymers made by nucleophilic addition reactions and organo-oxy silane functionalised ionic based prepoiymers. Nucleophilic addition one component organo-oxy silane functionalised prepoiymers may be prepared by for example the reaction of nucleophiles with activated carbon-carbon based moieties or Michael-type reactions, where a least one of the reagents is terminated with a hydrolysable organo-oxy silane group. Patent Application PCT/GB96/00231 is incorporated herein by reference. Michael - type reactions may be defined as the reaction of a nucleophile with an α,β-unsaturated carbonyl moiety. Michael - type reactions may be exemplified by the reaction of acrylate or acrylamide reagents with reagents terminated with -SH, -NH 2 , -NHNH 2 , or >NH moieties. Preferred Michael - type reactions include the reactions of methacrylates, bisphenol A ethoxylate diacrylates, methylene bisacrylamides, bisacrylamide or diacrylate oligomers with amine functionalised oligomers such as aminoalkyl silanes. Apt nucleophilic reactions also comprise the reaction of nucleophiles with carbon-carbon based moieties, which are activated by ring strain or electron withdrawing effects. These include the reaction of reagents terminated with three membered heterocycles with reagents terminated with -SH, -NH 2 , -NH-NH 2 , >NΗ moieties where at least one of the reagents is further terminated with hydrolysable organo-oxy silane group. Suitable reactions include the reaction of organo-oxy terminated aminoalkylenesilanes with reagents terminated with three membered heterocycles such as epoxides or aziridines. Hydrolysable organo-oxy silane functionalised ionic based prepoiymers are a single component system where the group bearing the hydrolysable organo-oxy silane group is ionically bound to the prepolymer, rather than covalently bound to the prepolymer. The ionic based prepoiymers may suitably be made by for example the reaction of alkyl carboxylic acids with alkyl amines, where one or both of the reagents is terminated by a water hydrolysable organo-oxy silane group, to produce a salt complex, where a salt complex is defined as a prepolymer containing ionic linkages. The advantage conferred by ionic based prepoiymers is that the wetting out characteristics of the prepolymer are improved. Wetting out is defined as the ability of the prepolymer to take up water which in turn affects the rate at which the functionalised prepoiymers react with water. Hydrolysable organo-oxy silane functionalised prepoiymers, where the prepolymer carries pendant hydrolysable organo-oxy groups and is terminated with reactive amines may be further modified with an acid such as acid chlorides or acid anhydrides, for example, acetyl chloride. Acetyl chloride reacts with the terminating reactive amine groups liberating hydrogen chloride as a by-product, thereby producing an acidic environment which enhances the rate of the hydrolysis reaction, as herein before described. The preferred prepolymer systems are free of isocyanate moieties and thus perceived health hazards associated therewith are avoided. Preferred formulations of the prepolymer system may include a variety of additives conventional in the art. These additives may comprise fillers, pigments, fragrances, surfactants, lubricants or mixtures thereof. Suitable powdered fillers include talc, calcium carbonate, fumed silica sold under the trade name Cab-o-Sil™, alumina and fibrous reinforcing fillers such as wollastonites (calcium metasilicate), to impart desirable viscosity and handling characteristics. The fillers may be present as single chemical species or as mixtures and, when used, are aptly present in an amount of up to 50% w/w, preferably up to 20% w/w and aptly at least 1.0% w/w of the resin. The prepolymer system used for casting bandages according to the invention may be carried on any substrate suitable for a casting, splinting or bracing material. The prepolymer system may be coated, laminated, sprayed or impregnated onto a suitable substrate using conventional methods in the art. Aptly the casting materials of the invention are prepared by nip-coating the prepolymer on to the substrate. A preferred substrate is a flexible fabric carrier which may be a woven, knitted or non woven fabric which can carry enough of the prepolymer to ensure that the resultant cast has adequate strength. The substrate should be sufficiently porous to allow water to come into contact with the carried prepolymer when the formed bandage is immersed in water. The substrate may be in the form of tapes, bandages, sheets or other conventional forms, apt for preparing orthopaedic casting bandages, splinting materials or braces. Suitable materials for forming the substrate include polyester, nylon, polypropylene, polyamides, polyolefins and glass fibre or mixtures thereof. Examples of such substrates are disclosed in Patent Nos. US 4,427,002, US 4,627,424 and EP 326, 285. Aptly the substrate may be a mesh having openings through it to enable the water to penetrate into the rolled bandage to contact all of the prepolymer. The openings will also permit circulation of air to and evaporation of moisture from the skin beneath the cured cast. Preferably the mesh is of a loose weave or knit so as to allow at least partial impregnation as well as coating by the prepolymer. The amount of prepolymer carried by the substrate before curing may vary depending on the intrinsic properties of the prepolymer and shoutd be sufficient to ensure that the resultant cast has adequate strength. Suitable amounts range from 30 to 70% w/w which is calculated using the equation: weight of (substrate + prepolymer) - weight of (substrate) x 100 weight of (substrate + prepolymer) Preferably 35 to 70% w/w and most preferably 40 to 65% w/w of prepolymer are used. A hardened cast may be formed by wetting and shaping the wet material around a body member or part thereof and allowing the material to cure. Aptly wetting is achieved by immersing the material in water, and removing any excess water, for example, by squeezing the material several times before application to the body member. When removed from the water the material can be readily wrapped about a limb wherein the conventional underlying stockinette or padding is employed. An alternative method for forming a cast or splint comprises applying the material to the body member followed by spraying the material with water. The water used to wet the material may contain the catalyst, forming a solution as herein before described. The curing reaction of the prepolymer should be sufficiently slow to allow the material to be positioned and shaped before the material becomes unworkable. Suitable working times are aptly 1 to 6 minutes more aptly 2 minutes to 4 minutes. The curing reaction of the prepolymer should, however, be sufficiently fast to permit the formed cast or splint to become supportive and load-bearing as soon as possible after completion of working. Aptly the material will set and become supportive between 5 and 30 minutes, more aptly within 15 minutes and particularly in the case of a cast, will aptly become load-bearing within 60 minutes, more aptly after 10 minutes. The prepoiymers employed in the present invention possess the advantage that no methanol is generated during the curing reaction, and the further advantage in that the curing reaction is only slightly exothermic thus causing no harm or discomfort to the patient. The cast may be readily removed by conventional means such as by cutting with a conventional vibrating sawtooth disc. The orthopaedic casting material should be protected during storage from water and moisture vapour to prevent a premature setting taking place. The material can be conventionally packaged in heat sealed pouches such as metal foil polyethylene laminate pouches. The invention will now be described by way of example only and it should be understood that normal precautions for excluding moisture during chemical reactions were employed. Example 1 : Methylenebisacrylamide (109.3g, 0.71 mol) and 3-aminopropyltriethoxysilane (228.6g, 1.03 mot) were placed in a 1 litre resin flask fitted with an overhead air stirrer, a thermometer and a calcium chloride guard tube. The mixture was stirred at room temperature for 30 minutes before raising the temperature to 70°C, which was maintained for 48-72 hours, before cooling. The prepolymer prepared above was used for the following preparations: A) To 2g of the prepolymer was added 20mg of potassium fluoride which was mixed in thoroughly. 0.5cm 3 of water was added and the prepolymer cured in 10 minutes. B) To 2g of the prepolymer was added 0.5cm 3 of a 1 % solution of potassium fluoride in water and the prepolymer cured in 6 minutes. C) The prepolymer was coated onto a dry glass fibre bandage by passing the substrate through the prepolymer followed by passing the coated bandage through a nip roller, adjusted to a suitable pressure for obtaining a coating weight of 50-60% w/w. The prepolymer was set of by dipping the coated bandage in cold water and squeezing several times before application to a mandrel representing a limb. Example 2 • Methylenebisacrylamide (107.8g, 07 mol) and 3- amtnopropyltπethoxysilane (221.4g, 1.0 mol) were placed in a 1 litre resin flask fitted with an overhead air stirrer, a thermometer and a calcium chloride guard tube The mixture was stirred at room temperature for 30 minutes before raising the temperature to 70°C, which was maintained for 48 hours, before cooling to room temperature. Acetylchloπde (4.7g) was added dropwise over a period of 20 minutes. The prepolymer prepared above was used for the following preparation: A) To 2g of the prepolymer was added 20mg of potassium fluoride which was mixed in thoroughly 0 5cm 3 of water was added and the prepolymer cured in 2 minutes. B) The prepolymer was coated onto a dry glass fibre bandage by passing the substrate through the prepolymer followed by passing the coated bandage through a nip roller, adjusted to a suitable pressure for obtaining a coating weight of 50-60% w/w. The prepolymer was set of by dipping the coated bandage in cold water and squeezing several times before application to a mandrel representing a limb Example 3 . 3-amιnopropyltriethoxy silane (70g, 0.3 mol) mixed with methylene bisacrylamtde (32g, 0.2 mol) in an oven dried reaction vessel. The mixture was stirred and heated at 70°C for a total of 48 hours. After this time a prepolymer had formed. Anhydrous copper (II) sulphate (1g, 1% w/w) and potassium fluoride (1g, 1% w/w) were mixed in with the prepolymer To 2g of the prepolymer was added 0.5cm 3 of water and the prepolymer cured in 90 seconds. The prepolymer prepared above was coated onto a dry glass fibre bandage by passing the substrate through the prepolymer followed by passing the coated bandage through a nip roller, adjusted to a suitable pressure for obtaining a coating weight of 50- 60% w/w. The prepolymer was set off by dipping the coated bandage in cold water and squeezing several times before application to a mandrel representing a limb. Example 4: Methylenebisacrylamide (131g, 3.5 mol) 1-(2-aminoethyl) piperazine (21 g, 0.66 mol) and 3-aminopropyltriethoxysiiane (486g, 9 mol) were placed in a resin flask fitted with an overhead air stirrer, a thermometer and a calcium chloride guard tube. The mixture was stirred at room temperature for 30 minutes before raising the temperature to 70°C, which was maintained for 2 hours, before adding potassium fluoride (20g, 2% w/w). After 24 hours bisphenol A ethoxylated diacrylate (361 g, 3.5 mol) was added and after a further 20 hours acetylchloride (16g, 1.6% w/w) was added dropwise over a period of 20 minutes. The mixture was left stirring for 1 hour before cooling. The prepolymer prepared above had a viscosity of 67,000 mPa s and was coated onto a dry glass fibre bandage by passing the substrate through the prepolymer followed by passing the coated bandage through a nip roller, adjusted to a suitable pressure for obtaining a coating weight of 50-60% w/w. The prepolymer was set off by dipping the coated bandage in cold water and squeezing several times before application to a mandrel representing a limb. Example 5 : A) PolvHEMA coated potassium fluoride Preparation of polyHEMA coated potassium fluoride was carried out by charging a 3L resin flask with 2- hydroxyethylmethacrylate (250g), potassium fluoride (250g, 90μm sieved and milled) and dry ethyl acetate (2.5L). The flask was provided with a stirrer, purged thoroughly with nitrogen, and stirred for three hours, followed by addition of bis (4-t-butyl cyclohexyl) peroxydicarbonate (BCHPC, 2% by weight) and stirring for 5Y 2 hours at 55°C. At the end of the reaction bulking was evident. The material was collected by vacuum filtration and washed with ethyl acetate. The material was then dried for two days in a vacuum oven. The percentage yield was 96%. B) Methylene bisacrylamide (109.3g, 0.71 mol) and 3-aminopropyltriethoxysilane (228.6g, 1.03 mol) were placed in a 1 litre resin flask fitted with an overhead stirrer, a thermometer and a calcium chloride guard tube. The mixture was stirred at room temperature for 30 mintues before raising the temperature to 70°C which was maintained for 48- 72 hours, before cooling and adding polyHEMA coated potassium fluoride (13.5g, 4% w/w). The prepolymer prepared above was coated onto a dry glass fibre bandage by passing the substrate through the prepolymer followed by passing the coated bandage through a nip roller, adjusted to a suitable pressure for obtaining a coating weight of 50- 60% w/w. The prepolymer was set off by dipping the coated bandage in cold water and squeezing several times before application to a mandrel representing a limb. Example 6 : Methylenebisacrylamide (116g, 3.5 mol), bisphenol A ethoxylated diacrylate [321 g, 3.5 mol], 4-3)(aminopropyl) morpholine [31 g, 1 mol], potassium fluoride [27g, 3% w/w] and 3- aminopropyltriethoxysilane (431 g, 9 mol) were placed in a resin flask fitted with an overhead air stirrer, a thermometer and a calcium chloride guard tube. The mixture was stirred at room temperature for 30 minutes before raising the temperature to 70°C, which was maintained for 24 hours, before cooling to 40°C. Acetyl chloride [14g, 1% w/w] was added dropwise and left stirring for one hour before cooling. Example 7 : Preparation of an ionic based organo-oxy silane functionalised prepolymer — A polamic acid derivative of Jeffamine EDR-148 with maleic anhydride (11.2g, 0.03 mol) was reacted with 3-amino propyltriethyoxysilane (13.3g, 0.06 mol) in a 100% solids reaction by mixing the reagents in a dry reaction vessel, at room temperature under nitrogen. The mixture was left stirring for 10 hours. To 2g of the prepolymer was added 20mg of potassium fluoride which was mixed in thoroughly. 0.5cm 3 of water was added and the prepolymer cured in 6 minutes. Example 8 : Methylene bisacrylamide (77.5g, 0.5 mol) and aminopropyl triethoxysilane (222.5g, 1.0 mol) were placed in a 750cm 3 flange flask fitted with a calcium chloride guard tube and an overhead stirrer. The mixture was heated with stirring at 70°C for 48 hours to form a prepolymer. A) To 2g of the prepolymer prepared above was added ammonium chloride (0.2g, 10% w/w) which was mixed in thoroughly. 0.5cm 3 of water was added and the prepolymer cured in 10 minutes. B) To 2g of the prepolymer prepared above was added caesium fluoride (0.04g, 2% w/w) which was mixed in thoroughly. 0.5cm 3 of water was added and the prepolymer cured in 6 minutes, c) To 2g of the prepolymer prepared above was added potassium fluoride (0.04g, 2% w/w) which was mixed in thoroughly. 0.5cm 3 of water was added and the prepolymer cured in 7 minutes. D) To 2g of the prepolymer prepared above was added potassium chloride (0.04g, 2% w/w) and the prepolymer cured in 1.5 hours. E) To 2g of the prepolymer prepared above was added 0.5cm 3 of water and the prepolymer cured in 2 hours. Materials used in the above preparations 3-Aminopropyltriethoxysilane, obtainable from Hϋls UK. Methylene bisacrylamide, obtainable from Aldrich Chemical Co. Jeffamine EDR-148 is a polyethylene glycol diamine, obtainable from Huntsman Coφoration. Bisphenol A ethoxylate diacrylate [XEO/phenol], obtainable from Aldrich Chemical Co. 1-(2-amino ethyl) piperazine, obtainable from Aldrich Chemical Co. Cab-o-Sil™ is fumed silica obtainable from Cabot Corporation (USA) Potassium fluoride, obtainable from Aldrich Chemical Co. Copper (II) sulphate, obtainable from Aldrich Chemical Co. 4-3(amino propyl) morpholine, obtainable from Aldrich Chemical Co. Caesium fluoride, obtainable from Aldrich Chemical Co. Potassium chloride, obtainable from Aldrich Chemical Co.

Claims: CLAIMS 1. An orthopaedic casting bandage comprising a flexible substrate, a water curable organo-oxy silane functionalised prepolymer system and a catalyst component characterised in that said catalyst comprises a water soluble halide salt. 2. A bandage according to claim 1 wherein said catalyst comprises a water soluble alkali metal halide salt. 3. A bandage according to claim 1 wherein said catalyst comprises a water soluble fluoride salt. 4. A bandage according to claim 1 wherein the water soluble salt is selected from the group containing sodium fluoride, caesium fluoride, potassium fluoride, manganese (II) fluoride, iron (III) fluoride, tin (II) fluoride, zinc (II) fluoride, potassium hexa fluoride zirconate and potassium hexa fluoride titanate. 5. A bandage according to claim 1 wherein the catalyst is coated with a hydrophilic coating. 6. A bandage according to claim 5 wherein the hydrophilic coating comprises polyhydroxyethylmethacrylate. 7. A bandage according to claim 1 wherein the catalyst comprises less than 10% and at least 0.01 % by weight of the prepolymer. 8. A bandage according to claim 1 additionally comprising a second catalyst component. 9. A bandage according to claim 1 additionally comprising a second catalyst, wherein said second catalyst is covalently bound- in. 10. A bandage according to claim 9 wherein said catalyst comprises a tertiary amine catalyst. 11. A bandage according to claim 8 wherein said second catalyst comprises less than 10% and at least 0.01% by weight of the prepolymer. 12. A method for treating a fracture of a body part which comprises wetting the bandage according to claim 1 applying and shaping the bandage around the body part and allowing the bandage to set by curing of the prepolymer. 13. The use of a bandage according to claim 1 as an orthopaedic splinting material. 14. A bandage according to claim 1 wherein the flexible substrate is a woven, knitted or non-woven fabric.

Inventors: BENTLEY PETER HUBERT, PEEL CLAIRE, SHELVEY MICHAEL FRANCIS, WEST PETER JOHN, YEOMANS KEVIN ANDREW, BENTLEY, PETER, HUBERT, PEEL, CLAIRE, SHELVEY, MICHAEL, FRANCIS, WEST, PETER, JOHN, YEOMANS, KEVIN, ANDREW
Applicants: BENTLEY PETER HUBERT, PEEL CLAIRE, SHELVEY MICHAEL FRANCIS, SMITH & NEPHEW, WEST PETER JOHN, YEOMANS KEVIN ANDREW, BENTLEY, PETER, HUBERT, PEEL, CLAIRE, SHELVEY, MICHAEL, FRANCIS, SMITH & NEPHEW PLC, WEST, PETER, JOHN, YEOMANS, KEVIN, ANDREW
Application year: 1997
Main classification: A61F
IPC codes: A61L15