Patent GB-1358921-A (GB)
Title: Process for preparing an organosol
IPC: C08F2/08
Filed: 1971-07-07
Abstract: 1358921 Graft copolymer organosols E I DU PONT DE NEMOURS & CO 7 July 1971 [8 July 1970] 31891/71 Heading C3G A process for preparing a self-stabilized organosol comprises: (A) copolymerizing a polymeric backbone segment in an organic solvent 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) 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, and (D) postreacting to increase conversion of unreacted monomers to a graft copolymer. 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, ½-methyl styrene, vinyl toluene and 3-(2-methacryloxyethyl) - 2,2 - spirocyclohexyl - oxazolidine. Typically 20-60% of the graft monomer will remain in the unreacted state after grafting in which case additional backbone monomers may be added to effect further graft polymerization. In the inversion step (C) the solvent used may be pentane, hexane, VM and P naphtha, petroleum ethers, mineral spirits, aliphatic alcohols or mixtures thereof. The active solvent may be selected from esters, ketones, benzene and toluene. The non-active solvent should preferably be added in an amount 25-95% by weight of the total solvent blend in the organosol. Maximum conversion of the monomers may then be accomplished by maintaining the temperature of the reaction mixture from reflux temperature of the mixture to not lower than 20‹ C. below the reflux temperature of the mixture. A free radical catalyst may be added along with a suitable nonactive organic solvent. Example (1) describes the preparation of a graft polymer comprising a copolymeric backbone of methyl methacrylate and allyl methacrylate and a graft segment comprising 2-ethylhexyl acrylate units and using methyl ethyl ketone and a specific paraffin as the 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 segment comprising 2-ethylhexyl acrylate and methyl methacrylate units and using methyl ethyl ketone and VM and P naphtha as the active and non- active solvents respectively. The non-active solvent is added to the reaction mixture mixed with a free radical catalyst to effect step (D) of the process.