Patent GB-1358750-A (GB)
Title: Process for preparing an organosol
IPC: C08J3/12
Filed: 1971-07-09
Abstract: 1358750 Graft copolymer organosols E I DU PONT DE NEMOURS & CO 9 July 1971 [10 July 1970] 32358/71 Heading C3G A process for preparing a self-stabilized organosol comprises (A) copolymerizing a polymeric backbone segment in which the polymeric backbone segment is soluble ("active solvent"); (B) copolymerizing a polymeric graft segment(s) to said backbone segment thereby forming a graft copolymer solution; (C) effecting further copolymerization to increase the conversion to a graft copolymer of unreacted monomers remaining from step (B), and (D) inverting the graft copolymer into an organosol by adding an organic solvent which is a non-solvent for one of the segments of the graft copolymer (" non-active solvent ") to said graft copolymer solution to form a solvent blend such that said solvent blend is a non-solvent for one of the segments of the graft copolymer taken as a separate entity and a solvent for the other segment of the graft copolymer if taken as a separate entity. The copolymerizing of the monomers in step (A) may occur as a two-step procedure. The monomers are dissolved under reflux in an active solvent and a catalyst is added to the solution in two separate additions. The grafting of the monomer to the polymeric backbone is carried out under free radical conditions. Numerous grafting monomers are specified, e.g. acrylic acid, methacrylic acid and their amides and nitriles, 2-ethylhexyl acrylate, butyl acrylate, vinyl acetate, styrene, α-methyl styrene, vinyl toluene, and 3-(2-methacryloxyethyl) - 2,2 - spirocyclohexyl - oxazolidine. Typically 20-60% of the graft monomers will remain in the unreacted state after grafting in which case additional backbone monomers may be added to effect further graft polymerization. Prior to the inversion step maximum conversion of the monomers may be accomplished by continuing the reaction process for 60-120 minutes, the temperature of the reaction mixture being maintained from reflux temperature of the mixture to not lower than 20‹ C. below the reflux temperature of the mixture. The active solvent may be an ester, ketone or an aromatic hydrocarbon. In the inversion step (D) the solvent used may be pentane, hexane, VM and P naphtha, petroleum ethers, mineral spirits, aliphatic alcohols or mixtures thereof. The non-active solvent should preferably be added in an amount 25-95% by weight of the total solvent blend in the organosol. Example (1) describes the preparation of a graft polymer comprising a copolymeric backbone of methyl methacrylate and allyl methacrylate and a graft component comprising 2-ethylhexyl acrylate units and using methyl ethyl ketone and a paraffin hydrocarbon as active and non-active solvents respectively. Example 2 describes the preparation of a graft polymer comprising a copolymeric backbone of methyl methacrylate, diethylaminoethyl methacrylate and allyl methacrylate and a graft component comprising 2- ethylhexyl acrylate and methyl methacrylate units using the same solvents as in Example 1. Pure solvent is added as the final step of the process illustrated in the examples.