Patent GB-1115305-A (GB)
Title: Release coating composition
IPC: C09J7/40
Filed: 1965-08-25
Abstract: A coating composition comprises a minor proportion of a release agent copolymer consisting essentially of stearyl methacrylate and acrylonitrile in proportion within the range from 50 parts by weight of stearyl methacrylate and 50 parts by weight of acrylonitrile to 80 parts by weight of stearyl methacrylate and 20 parts by weight of acrylonitrile, and a major proportion of a film-forming composition incompatible with the polymer in the dry state of the release coating but sufficiently compatible therewith in the coating solution to allow the release coating to be coated on the backing without gross separation of the copolymer from the film-forming composition during coating.  By stearyl methacrylate is meant octadecyl methacrylate or octadecyl methacrylate containing higher alkyl methacrylates having at least 12 carbon atoms and consisting predominantly of octadecyl methacrylate. Suitable film-forming compositions are certain curable compositions based primarily on alkyd resins.  These include in addition to the alkyd resins a formaldehyde resin condensate, such as an alcoholated urea-formaldehyde or melamine-formaldehyde resin.  The ratio of alkyd resin to formaldehyde resin may be between 90 to 10 and 50 to 50 parts by weight respectively.  The release coating composition may also include catalyst for curing the film former, such as an alkyl acid phosphate and also pigments and colouring agents.  The composition may contain 1-25% by weight of release agent.  Solvents may be aromatic hydrocarbons, ketones and esters and may include a proportion of aliphatic or naphthenic hydrocarbon.ALSO:A porous backing has a release coating composition on at least one surface of the backing comprising a minor proportion of a release agent copolymer consisting essentially of stearyl methacrylate and acrylonitrile in proportion within the range from 50 parts by weight of stearyl methacrylate and 50 parts by weight of acrylonitrile to 80 parts by weight of stearyl methacrylate and 20 parts by weight of acrylonitrile, and a major proportion of a film forming composition incompatible with the polymer in the dry state of the release coating but sufficiently compatible therewith in the coating solution to allow the release coating to be coated on the backing without gross separation of the copolymer from the film forming composition during coating.  By stearyl methacrylate is meant octadecyl methacrylate or octadecyl methacrylate containing higher alkyl methacrylates having at least 12 carbon atoms and consisting predominantly of octadecyl methacrylate.  Suitable film-forming compositions are certain curable compositions based primarily on alkyd resins.  These include, in addition to the alkyl resins a formaldehyde resin condensate, such as an alcoholated urea-formaldehyde or melamime-formaldehyde.  The ratio of alkyd resin and formaldehyde resin may be from 90 to 10 and 50 to 50 parts by weight respectively.  The release coating composition may also include catalyst for curing the film former, such as an alkyl acid phosphate and also pigments and colouring agents.  The composition may contain 1-25% by weight of release agent.  The coating may be in amount 0.05 to 1.0 ounce per square yard. Coating may be by clearance coating, knife coating or air knife coating followed by drying by passage through a circulating air oven or oven steam heated cans. Solvents may be aromatic hydrocarbons, ketones and esters and may include a proportion of aliphatic or naphthenic hydrocarbon.  Curing may be for 15 secs. at 325 DEG F.  The backing may be creped paper and the coating may be on both surfaces or on one surface of the backing.  The other surface may be coated with a pressure sensitive adhesive, and a primer layer may be applied before the adhesive layer or the release coating layer.