Patent GB-883558-A (GB)
Title: Improvements in the production of photopolymerisable compositions
IPC: C08F251/00
Filed: 1959-05-20
Abstract: An addition photopolymerizable composition is made by mixing together a cellulose partial ester of a saturated aliphatic carboxylic acid having 2-4 carbon atoms, a dicarboxylic acid anhydride, an addition polymerisable ethylenically unsaturated compound, and an esterification catalyst, and heating the mixture to 85-180 DEG C for a period between 0,5-60 mins. sufficient to cause further esterification of the cellulose partial ester, without charring, and, at any stage in the process, including that at which esterification occurs and that subsequent to the esterification, incorporating an addition polymerisation initiator which is activatable by actinic light but has no significant thermal activity at the esterification temperature. Preferably, the cellulose ester is a cellulose acetate having a degree of substitution about 1,85, but cellulose acetate propionate, cellulose acetate butyrate, cellulose propionate and cellulose butyrate, having some free hydroxy groups, may be used. The preferred dicarboxylic acid anhydride is succinic anhydride, but others specified include maleic, glutaric and phthalic anhydrides. The ethylenically unsaturated compound is preferably triethylene glycol diacrylate, but others specified include ethylene glycol diacrylate, diethylene glycol diacrylate, tetramethylene glycol diacrylate, diallyl itaconate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, and tetramethylene glycol dimethacrylate.  As esterification catalyst a tertiary amine or metal salt may be used.  Specified catalysts include diethyl cyclohexylamine, pyridine, triethylamine, trimethylamine acetate and pyridine acetate, sodium and potassium carbonates, phosphates, borates and acetates, and calcium and magnesium acetates. Addition polymerization initiators specified include anthraquinone, 1-chloro-anthraquinone, 2-chloranthraquinone, 2-methylanthraquinone, 2-tertbutyl-anthraquinone, octamethylanthraquinone, 1,4-naphthoquinone, 9,10-phenanthrenequinone, 1,2-benzanthraquinone, 2,3-benzanthraquinone, 2-methyl-1,4-naphthoquinone, 2,3-dichloronaphthoquinone, 1,4-dimethylanthraquinone, 2,3-dimethylanthraquinone, 2-phenylanthraquinone, 2,3 diphenylanthraquinone the sodium salt of anthraquinone-a -sulphonic acid, 3-chloro-2-methyl anthraquinone, retenequinone, 7,8,9,10-tetrahydronaphthacenequinone, and 1,2,3,4-tetrahydrobenz[a ]anthracene-7, 12-dione.  The mixture may also contain the anhydride of a monocarboxylic acid having 2-18, preferably 2-4, carbon atoms, and a saturated plasticizer, e.g. triacetin, glyceryl tributyrate, triethylene glycol dipropionate, triphenyl phosphate and dimethyl phthalate.  The ethylenically unsaturated compound may be rendered resistant to polymerization at the esterification temperature by incorporating a thermal polymerization inhibitor, e.g. p-methoxy phenol.  The cellulose ester and ethylenically unsaturated compound may be mixed in the presence of water or a water-miscible swelling agent for the cellulose ester, e.g. methanol, ethanol or propanol, and the content of water or water-miscible swelling agent reduced to 4% or less of the weight of the total composition before the dicarboxylic acid anhydride is added.  In a preferred series of methods, the cellulose partial ester is mixed with the ethylenically unsaturated compound, the addition polymerization initiator and a thermal polymerization inhibitor, and water in amount 1/2 -10 times the weight of the cellulose ester; then (a) the mixture is milled at 105-160 DEG C. until its water content has been reduced at least to 4% of the weight of the total composition, part of the dicarboxylic acid anhydride is added and the mixture is milled at 105-160 DEG C. for 5-15 mins; the remainder of the acid anhydride and an esterification catalyst are added; and the mixture is milled until esterification is substantially complete.  Alternatively, (b) the mixture is milled at 105-160 DEG C. until its water content has been reduced at least to 4% of the weight of the total composition, the dicarboxylic acid anhydride is added, the resulting mixture is heated and milled for 5-10 mins. to reduce its moisture content below 0,5%, an esterification catalyst is added, and milling is continued until the esterification reaction is substantially complete. Alternatively, (c) a proportion of the final photopolymerizable mixture obtained in a previous run is added, the mixture milled at 100-160 DEG C. until its water content has been reduced at least to 4% of the weight of the total composition, the dicarboxylic acid anhydride and esterification catalyst are mixed in, and the mixture milled until esterification is substantially complete. In a further method the cellulose partial ester is mixed with the ethylenically unsaturated compound, a thermal polymerization inhibitor, an esterification catalyst, and water in amount 1/2 to 10 or more times the weight of the cellulose ester, the mixture slurried for 30-60 mins., the resulting impregnated cellulose ester filtered off and dried until the water content of the composition is below 0,3% by weight of the total composition, the addition polymerization initiator, additional thermal polymerization inhibitor and the anhydride are added and the mixture is milled at 125-135 DEG  C. until esterification is substantially complete.  In this method, or in methods (a), (b) and (c) above, the addition polymerization initiator may alternatively be added after esterification is substantially complete.  A layer of a composition made according to the invention may be pressed to form a photpolymerisable sheet (see Group XX).  Specifications 741,294, 741,441 and 843,238 are referred to.