GB460239A - Improvements in or relating to the production of cast synthetic resins - Google Patents

Abstract

<PICT:0460239/IV/1> Shaped resin masses of substantial thickness are cast from polymerizable unsaturated organic compounds having an exothermic reaction and tending to contract during polymerization by disposing the compound in a fluid state in a thin layer in a mould which leaves only the upper surface unconfined, polymerizing the layer to form a solid body, superposing a second thin layer and polymerizing the same, and continuing the process until a body of the desired thickness is produced. The compound may be used in a partly polymerized syrupy condition. In an example, for producing a rod from methyl methacrylate, a lead mould is used of the kind described in Specification 460,240, [Group XXII]. Liquid resin is poured into the mould and is polymerized for 24 hours at 70 DEG C., thus contracting to form a layer 14 about 0,5 inches thick. A second layer 15 is then poured in and polymerized and finally a third layer which fills the mould and the filling space 13. The finished rod may be turned and ground. The various layers used may be of contrasting colours. The compounds used may comprise acrylic and methacrylic acids their homologues and derivatives, including esters such as methyl, ethyl, butyl or phenyl methacrylate, glycol di-methacrylate, vinyl acetate, chloroacetate or chloride, styrene, a -methyl styrene, methyl vinyl ketone, divinyl acetylene, ethylene oxide, acrolein, and dimethyl itaconate. Plasticizers, colouring matter &c. may be added and polymerization may be performed by heat alone or by light, catalysts, &c. Rods, tubes, and other shaped articles may be produced. Specification 433,540 also is referred to.