Patent GB-935386-A (GB)
Title: Plastic tablet coating
IPC: A61K9/28
Filed: 1960-08-23
Abstract: A liquid for coating composition for applying a thin, colour-stable plastic film to solid medicaments, comprises a volatile organic solvent containing a water-dispersible, non-toxic, filmforming plastic, a physiologically acceptable colouring agent, and a complexing agent which comprises tannin when the colouring agent either forms an aqueous solution having a pH greater than 7 or contains basic nitrogen, and which comprises albumin when the colouring agent either forms an aqueous solution of pH less than 7 or contains sulphonic acid groups.  Film-forming plastics suitable include those of Specification 762,229, which are combinations of a water-soluble wax-like material, e.g. polyethylene glycol and glyceryl monostearate, and cellulose esterified partially with a lower aliphatic mono-carboxylic acid and partially with a polycarboxylic acid, e.g. cellulose acetatephthalate combinations of a copolymer of maleic anhydride and ethylene with partial hydrolysis products thereof according to U.S.A. Specification 2,857,365, the combination of water-soluble waxes and a cellulose ester of aliphatic carboxylic acids having 1-4 carbon atoms, e.g. cellulose acetate, acrylic polymers and copolymers, e.g. methyl methacrylate, methyl methacrylate/methacrylic acid, methyl acrylate/methyl methacrylate, and vinyl polymers, e.g. polyvinyl pyrollidene/vinyl acetate with a water-soluble wax.  Cellulose acetate phthalate with propylene glycol is used as a plastic material in the examples.  The composition may contain both tannin and albumin.  Suitable solvents include 1-4 carbon atom alkanols, e.g. methanol, ethanol, n- and isopropanol, acetone, methylene chloride, methyl ethyl acetone, and ethyl acetate. A mixture of acetone with an alkanol is preferred.  A preferred liquid coating composition comprises 180-250 parts by weight of the film-forming plastic, 0,04-4,0 parts by weight of the colouring agent, and 5-30 parts by weight of the complexing agent or agents in 1,000 parts by volume of the solution.  The dried coating prepared therefrom may contain 88-97% plastic, 0,051,5% colouring agent and 2,5-10,5% by weight of complexing agent.  A liquid coating composition containing other additives may be used, e.g. silicone resins, long-chain fatty acids, long-chain metallic soaps and long-chain alcohols as gloss-producing agents, titanium dioxide, calcium carbonate, dehydrated calcium sulphate, and dicalcium phosphate as opaquing agents, "Bentone" (Registered Trade Mark), and alkyl ammonium montmorillonite and Veegum, a colloidal magnesium aluminium silicate, as suspending agents, plasticizers, e.g. mineral oil, castor oil, polyethylene and polypropylene glycols, and glycerine and sweetening agents, e.g. vanillin, saccharin, sodium cyclohexyl sulphamate, coumarin and heliotropin.  Such a liquid coating composition may contain, in addition to the plastic, colouring agents and complexing agents present, 15-25 g. plasticizer, 5-15 g. opaquing agents, 2-5 g. flavouring agents and 5-10 g. wetting agents per litre of solution.  The dried coating prepared therefrom may contain 75-85% plastic, 0,02-1,0% colouring agent, 2-8% complexing agent, and 13-16% by weight tableting excipients and adjuvants.  Tablets so coated show a reduced tendency to fading of the colouring agent on exposure to ultra-violet light.  U.S.A. Specifications 2,093,462 2,093,464 and 2,126,460 also are referred to.ALSO:Solid medicaments having a reduced tendency to fading of the colouring agent on exposure to ultra-violet light are made by the use of a liquid coating composition comprising a volatile organic solvent containing a water-dispersible, non-toxic, film-forming plastic, a physiologically acceptable colouring agent, and a complexing agent which comprises tannin when the colouring agent either forms an aqueous solution having a pH greater than 7 or contains basic nitrogen, and which comprises albumin when the colouring agent either forms an aqueous solution of pH less than 7 or contains sulphonic acid groups.  Film-forming plastics suitable include those of Specification 762,229, which are combinations of a water-soluble wax-like material, e.g. polyethylene glycol and glyceryl monostearate, and cellulose esterified partially with a lower aliphatic mono-carboxylic acid and partially with a polycarboxylic acid, e.g. cellulose acetate-phthalate combinations of a copolymer of maleic anhydride and ethylene with partial hydrolysis products thereof according to U.S.A. Specification 2,857,365, the combination of water-soluble waxes and a cellulose ester of aliphatic carboxylic acids having 1-4 carbon atoms, e.g. cellulose acetate, acrylic polymers and copolymers, e.g. methyl methacrylate, methyl methacrylate/methacrylic acid, methyl acrylate/methyl methacrylate, and vinyl polymers, e.g. polyvinyl pyrollidene/vinyl acetate with a water-soluble wax.  Cellulose acetate phthalate with propylene glycol is used as a plastic material in the examples.  The composition may contain both tannin and albumin.  Suitable solvents include 1-4 carbon atom alkanols, e.g. methanol, ethanol, n- and iso-propanol, acetone, methylene chloride, methyl ethyl acetone, and ethyl acetate. A mixture of acetone with an alkanol is preferred.  A preferred liquid coating composition comprises 180-250 parts by weight of the film-forming plastic, 0.04-4.0 parts by weight of the colouring agent, and 5-30 parts by weight of the complexing agent or agents in 1000 parts volume of the solution.  The dried coating prepared therefrom may contain 88-97% plastic, 0.05-1.5% colouring agent and 2.5-10.5% by weight of complexing agent.  A liquid coating composition containing other additives may be used, e.g. silicone resins, long-chain fatty acids, long-chain metallic soaps and long-chain alcohols as gloss-producing agents, titanium dioxide, calcium carbonate, dehydrated calcium sulphate, and dicalcium phosphate as opaquing agents, "Bentone" (Registered Trade Mark), and alkyl ammonium montmorillonite and Veegum, a colloidal magnesium aluminium silicate, as suspending agents, plasticizers, e.g. mineral oil, castor oil, polyethylene and polypropylene glycols, and glycerine and sweetening agents, e.g. vanillin, saccharin, sodium cyclohexyl sulphamate, coumarin and heliotropin. Such a liquid coating composition may contain, in addition to the plastic, colouring agents and complexing agents present, 15-25 g. plasticizer, 5-15 g. opaquing agents, 2-5 g. flavouring agents and 5-10 g. wetting agents per litre of solution.  The dried coating prepared therefrom may contain 78-85% plastic, 0.02-1.0% colouring agent, 2-8% complexing agent, and 13-16% by weight tableting excipients and adjuvants.  U.S.A. Specifications 2,093,462, 2,093,464 and 2,126,460 also are referred to.