Patent GB-1035877-A (GB)
Title: Method of manufacturing contact lenses from hydrogels capable of swelling
IPC: B29D11/00
Filed: 1964-09-07
Abstract: A contact lens is made from hydrogels which when in a swollen condition are transparent, soft and elastic, by preparing the hydrogel in a substantially unswollen condition, working it mechanically to shape, e.g. by moulding, and then swelling, washing and immersing the lens in a solution substantially isotonic to living human tissue.  In one example 58 parts of ethylene glycol monomethacrylate, 17 parts of di-ethylene glycol monomethacrylate, 0.4 part of di-ethyleneglycol di-methacrylate, 21.7 parts of 1% aqueous ammonium persulphate solution and 3 parts of dimethylamino ethyl acetate are mixed at 0 DEG  C., which mixture after cooling is formed into a transparent gel.  After the temperature is raised to 40 DEG  C., the gel is stored for at least a week at 20-25 DEG  C. and at 30-40% relative humidity, and after being worked into the desired shape the lens is immersed in a physiologic solution until osmotic equilibrium is reached.  In another example 55 parts of ethyleneglycol monomethacrylate, 20 parts of di-ethyleneglycol monomethacrylate, 0.3 part of ethyleneglycol di-methacrylate, 20 parts of water, 2 parts of a 5% aqueous potassium pyrosulphite solution, 2.6 parts of a 5% aqueous ammonium persulphate solution are mixed at 20 DEG  C.  Then 0.05 parts of a 0.1% aqueous solution of copper dichloride dihydrate is added.  In a further example the mixture contains 75 parts of ethyleneglycol monomethacrylate, 13 parts of diethyleneglycol monomethacrylate, 10 parts of triethyleneglycol monomethacrylate, 0.4 part of dietheleneglycol dimethacrylate, 0.4 part of dibenzoxylperoxide, 1.2 parts of p-toluenesulphonic acid and 0.05 part of a 5% solution obtained by dissolving copper benzoate and pyridine in water.  In a further example a 2% solution of polyvinyl alcohol is pressure filtered and then evaporated to a 50% concentrate which is then mixed with 1% of oxalic acid.  The oxylic acid may be replaced by 0.5% glyoxal computed on polyvinyl alcohol dry content.  The polyvinyl alcohol of this example may be replaced by a 2% dextran solution.  In another example, a monomeric mixture of 70 parts of ethyleneglycol monomethacrylate, 20.5 parts of diethyleneglycol monomethacrylate and 0.5 part of diethyleneglycol dimethacrylate, cooled to - 10 DEG  C. is mixed with 1 part of methyl ethyl ketone peracetal dissolved in 5 parts of ethylene glycol and with 3 parts of dimethylamine ethyl-acetate. In another example a mixture of 95 parts ethyleneglycol monomethacrylate, 4.5 parts ethyleneglycol, 0.5 part ethyleneglycol di-methacrylate and 0.01 part di-benzoxylperoxide is bubbled with pure nitrogen before being poured into a mould. This mixture may be replaced by one containing 80 parts ethyleneglycol monomethacrylate, 20 parts diethyleneglycol monomethacrylate, 0.4 part ethyleneglycol di-methacrylate and 0.01 part azo-bisisobutyronitrile. In a further example 75 parts ethyleneglycol monomethacrylate, 20 parts methacrylamide, 4.5 parts acrylamide and 0.5 part ethylene glycol di-methacrylate are mixed at between 40 DEG and 60 DEG  C. and 0.01 part dibenzoxl peroxide are added.  Suitable monomers are stated to be monallyl esters of organic dicarboxylic or tricarboxylic hydroxy acids, such as tartaric, malic or citric acid with a diallyl ester of the same or similar acid, and further examples are allyl ethers of sorbitol, mannitol and other poly-hydroxylic sugars, glycol monoesters of polymerizable olefinic acids such as itaconic or maleinic acid with a small amount of a glycol diester of such acids, bis-ethylene glycol itaconate, such lower molecular oligoesters and polyesters of polymerizable dicarboxylic acids as itaconic acid with a cross-linking agent such as N,N-methylene-bis-methacrylamide or low molecular polyvinylalcohol methacrylate.