Patent GB-576228-A (GB)
Title: Improvements in and relating to the manufacture of artificial, rubber-like materials
IPC: C08L89/00
Filed: 1943-12-10
Abstract: Artificial rubber-like substances are made by heating proteins or amino acids such as glycine obtained by their hydrolysis with an aliphatic polycarboxylic acid, which, in the case of a dibasic acid, has at least four carbon atoms between the two carboxyl groups, and then further heating the reaction product with one or more polyhydric alcohols.  Suitable proteins are bone glue, gelatin, collagen, keratin, casein or gluten.  Suitable polybasic acids are adipic, azelaic, sebacic, or citric.  Suitable polyhydric alcohols are glycerin, triethanolamine, ethylene glycol, trimethylene glycol, or sorbitol.  Monooleic or similar mono-ester of glycerine may be used yielding water-resistant products.  The reaction may be discontinued before gelation occurs, yielding a viscous liquid product soluble in alcohol or acetone and useful as an adhesive for surgical plasters. Continuing heating until gelation is imminent yields a fusible product which is soft and elastic when cold.  It is also soluble in alcohol or acetone and may be spread as coating either hot or as a solution.  Discontinuing heating just after gelation yields a soft, tacky, elastic, rubber-like solid, not readily fusible and insoluble in water, alcohol or the usual organic solvents. Continuing heating after gelation makes the product harder and less tacky.  Modifying agents may be added before, during or after the reaction.  These are linoleic or other long-chain aliphatic acid.  Drying acids yield an air-drying product.  Non-drying acids, e.g. oleic yield products which are not readily oxidisable, but all the acid-modified products can be dried by heating with benzoyl peroxide.  Alternative procedures for modification or to treat a product, obtained by stopping heating when gelation is imminent and dissolved in pyridine with an acid chloride, e.g. oleyl chloride, or to treat a similar product dissolved in alcohol or acetone and modified with a long-chain aliphatic acid or not with chromium chloride.  A similar product modified with an unsaturated long-chain acid may be dissolved in chloroform and treated with sulphur monochloride.  Addition of ammonium persulphate after gelation of the reaction mixture facilitates hardening on heating.  Using glycerine as the polyhydric alcohol and adipic acid as the polybasic acid, about one-third of the adipic acid may be replaced by phthalic acid yielding a product capable of being drawn into very fine threads.  Certain substances, preferably added after gelation and followed by continued heating, act analogously to vulcanizing agents with natural rubber.  These are phosphorus pentoxide, phosphorus tri- or penta-sulphide or sodium bisulphite.  Preferably, these substances are used together with carbon black.  The products may be mixed with softeners, e.g. butyl lactate, tricresyl phosphate, chlornaphthalene, or stearic acid and fillers, e.g. calcined bone or china clay.  Examples 1, 5 and 13 describe the preparation of products by condensing gelatin and adipic acid and condensing the product with glycerine.  Example 7 is similar, but employs sorbitol in place of glycerine and example 6 uses powdered horn in place of gelatine.  Example 9 uses glue as the protein and trimethylene glycol as the polyhydric alcohol and example 10 uses glycine and ethylene glycol respectively.  Example 8 illustrates the addition of linoleic acid and example 12 shows the effect of heating the product of example 8 with benzoyl peroxide. Example 3 employs glue, azelaic acid and glycerine, and example 4 is similar, but substitutes for azelaic acid, the mixture of acids obtained by oxidising oleic acid with nitric acid.  Examples 2 and 11 describe products from glue, sebacic acid and glycerine, and example 13 from glue, sebacic acid and monoolein.  Examples 14, 15 describe vulcanization of the product of example 5 with soft carbon black, stearic acid and different proportions of phosphorus pentoxide. Examples 17-21 all describe treatments or applications of the product of example 2.  Example 17 treats a solution of this product with oleyl chloride, example 18 uses a benzene-alcohol solution of the example 2 product for coating metal.  Example 19 incorporates phosphorus pentoxide with the product of example 2 and uses it by heating under pressure to bond two pieces of metal together.  Example 20 bonds metal to rubber by applying a benzene-alcohol solution of the example 2 product to aluminium and a solution of chromic chloride, or of an aluminium or caesium salt to a strip of rubber. Pressing the surfaces together for a few days formed a flexible, solvent-resistant joint.  Example 21 adds the product of example 2 to a lacquer containing nitrocellulose, ethyl lactate, butyl acetate, toluene and acetone.  It states that cellulose acetate may be similarly used in place of nitrocellulose.