Patent GB-630026-A (GB)
Title: Improvements in the production of resinous articles
IPC: B29C39/00
Filed: 1947-01-29
Abstract: An article made of resin of the type having the group CH2=C< is provided with a coating of solvent-resistant, abrasion-resistant hard resin obtained by polymerizing a film or layer containing (a) one or more compounds having two or more unconjugated CH2=C< groups per molecule, or (b) a mixture of (a) with a compound containing the group CH2=C< or (c) a partial polymer of these compounds or mixtures, by the following process: One or more sides of a casting cell or mould are coated with a film or layer of the coating resin which is in the unpolymerized or partly polymerized state, and then the resin which is to form the main body of the article and which is in the form of a polymerizable dough, liquid or jelly which will swell the coating resin is introduced into the cell or mould.  The whole is then subjected to polymerization.  The main body resin may be polymethyl methacrylate, polystyrene or polyvinyl acetate, or compounds having more than one CH2=C< group per molecule, e.g. polymers of allyl methacrylate, diallyl fumarate, glycol dimethacrylate or dimethacrylic esters of low molecular weight, ethylene glycol-phthalic acid polyesters, and if doughy or liquid, may be a mixture or solution of polymer in monomer or, if a jelly, may be a gel of liquid monomer and polymer.  Compounds (a) above may be allyl methacrylate, diallyl fumarate, glycol dimethacrylate, the dimethacrylic esters mentioned above, di(allyl glycollyl) succinate, or non-crystalline solids obtained by reacting polymethyl methacrylate with allyl alcohol or polyvinyl acetate with methacrylic acid under ester-interchange conditions.  Mixture (b) may contain compounds (a) plus methyl methacrylate with or without one or more other CH2=C< compounds, or may contain polyesters of maleic or fumaric acids and dihydric alcohols, e.g. polyethyl and polypropyl maleate and styrene.  The film or layer may be obtained by solvent-casting the non-crystalline solids on the mould side, or by spreading a film of viscous liquid, e.g. the dimethacrylic esters mentioned above, on the mould side; this liquid film may be partly polymerized to the gel state before the body resin is cast and, to prevent inhibition of polymerization by air, the film may be covered with "Cellophane" (Registered Trade Mark) or detergent-coated glass during gelation.  The jelly may be injected into moulds and casting cells or placed therein as preforms, the polymerization being effected by heat, light or catalyst with or without pressure, or may be homogenized in situ from liquid monomer and polymer.  The invention may be carried out by using the process described in Specification 582,248 (making optical elements) a coated preform being moulded in a mould coated internally with the film.  In an example, a solution containing methyl methacrylate monomer, the dimethacrylic esters mentioned above and benzoyl peroxide is poured on to a level flat glass plate surrounded by a gasket, the film so obtained is partly polymerized by heat, the gasket is removed and the glass plate with the film on its surface is used, with another glass plate and a separating gasket, to make a cell.  Into the cell is cast a solution consisting of methyl methacrylate monomer and polymer, dibutyl phthalate and benzoyl peroxide, and the whole is polymerized by heat to produce a methyl methacrylate polymer sheet coated on one side with a hard solvent-resistant film.  Specifications 460,239, 491,739, 567,778, 574,692, 581,251, 588,658, 588,660, 595,881, 596,467, 599,837, 606,716, 606,717, 607,888 and 612,070 are referred to.ALSO:An article made of resin of the type having the group CH2=C< is provided with a coating of solvent-resistant, abrasion-resistant hard resin obtained by polymerizing a film or layer containing (a) one or more compounds having two or more unconjugated CH2=C< groups per molecule or (b) a mixture of (a) with a compound containing the group CH2=C< or (c) a partial polymer of these compounds or mixtures, by the following process:-One or more sides of a casting cell or mould are coated with a film or layer of the coating resin which is in the unpolymerized or partly polymerized state, and then the resin which is to form the main body of the article and which is in the form of a polymerizable dough, liquid or jelly which will swell the coating resin is introduced into the cell or mould.  The whole is then subjected to polymerization.  The main body resin may be polymethyl methacrylate, polystyrene or polyvinyl acetate, or compounds having more than one CH2=C< group per molecule, e.g. polymers of allyl methacrylate, diallyl fumarate, glycol dimethacrylate or dimethacrylic esters of low molecular weight ethylene glycol-phthalic acid polyesters, and, if doughy or liquid, may be a mixture or solution of polymer in monomer, or, if a jelly, may be a gel of liquid monomer and polymer.  Compounds (a) above may be allyl methacrylate, diallyl fumarate, glycol dimethacrylate, the dimethacrylic esters mentioned above, di (allyl glycollyl) succinate, or non-crystalline solids obtained by reacting polymethyl methacrylate with allyl alcohol or polyvinyl acetate with methacrylic acid under ester-interchange conditions. Mixture (b) may contain compounds (a) plus methyl methacrylate with or without one or more other CH2=C< compounds, or may contain polyesters of maleic or fumaric acids and dihydric alcohols, e.g. polyethyl and polypropyl maleate, and styrene.  The film or layer may be obtained by solvent-casting the noncrystalline solids on the mould side, or by spreading a film of viscous liquid, e.g. the dimethacrylic esters mentioned above, on the mould side; this liquid film may be partly polymerized to the gel state before the body resin is cast and, to prevent inhibition of polymerization by air, the film may be covered with "Cellophane" (Registered Trade Mark) or detergent-coated glass during gelation.  The jelly may be injected into moulds and casting cells or placed therein as preforms, the polymerization being effected by heat, light or catalyst with or without pressure, or may be homogenized in situ from liquid monomer and polymer.  The invention may be carried out by using the process described in Specification 582,248 (making optical elements) a coated preform being moulded in a mould coated internally with the film.  In an example, a solution containing methyl methacrylate monomer, the dimethacrylic esters mentioned above and benzoyl peroxide is poured on to a level flat glass plate surrounded by a gasket, the film so obtained is partly polymerized by heat, the gasket is removed and the glass plate with the film on its surface is used, with another glass plate and a separating gasket, to make a cell.  Into the cell is cast a solution consisting of methyl methacrylate monomer and polymer, dibutyl phthalate and benzoyl peroxide, and the whole is polymerized by heat to produce a methyl methacrylate polymer sheet coated on one side with a hard solvent-resistant film.  Specifications 460,239; 491,739, 567,778, 574,692, (all in Group IV], 581,251; 588,658, 588,660, 595,881, 596,467, 599,837, [all in Group IV], 606,716, 606,717, 607,888 and 612,070, [all in Group IV (a)], also are referred to.