GB743922A - Phosphate plasticizers - Google Patents

Abstract

A composition comprises a thermoplastic material, e.g. a derivative of cellulose, plasticized with a bis-dipropyl phosphate of an alkylene or mono-oxa-alkylene glycol, said glycol having 4 to 8 carbon atoms in the molecule (see Group IV (b)). The cellulose derivatives include cellulose esters such as cellulose nitrate cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate-propionate and cellulose acetate butyrate as well as cellulose ethers such as ethyl cellulose and benzyl cellulose. Specified bis-dipropyl phosphates are those of 1,4 - butanediol, diethyleneglycol, 2,5 - hexanediol, and of dipropylene glycol. In examples plastic grade cellulose acetate is mixed with diethylene glycol-bis-dipropyl phosphate and butanediol-1,4-bis dipropyl phosphate respectively and pressed discs of good fire-resistance are prepared by moulding each mixture at 200 DEG C. for 15 minutes.ALSO:The invention comprises as new compounds bis-dipropyl phosphates of an alkylene or monooxa-alkylene glycol, said glycol having 4 to 8 carbon atoms in the molecule. Specified compounds are the dipropyl phosphates of 1,4-butanediol, diethylene glycol and 2,5-hexanediol and of dipropylene glycol. The products may be obtained by reacting 2 mols. of dipropyl chlorophosphate with one mol. of the glycol which may be tetramethylene; 3-oxa-1,5-pentylene; 3 - oxa - 1,5 - dimethyl - 1,5 - pentylene, hexamethylene; 2-ethyl hexamethylene; 2,2-diethyl trimethylene, or 5-oxa-1,7-heptylene, or diethylene glycol. The reaction is preferably carried out in the presence of an acid acceptor and mutual solvent such as pyridine. Examples describe the production of diethylene glycol bis-dipropyl phosphate and butanediol - 1,4 - bis-dipropyl phosphate by reacting the corresponding glycol with dipropylchlorophosphate in the presence of pyridine. The dipropyl chlorophosphate used is prepared by adding phosphorus trichloride gradually to n-propyl alcohol maintained at 8-11 DEG C. and then chlorinating by introducing chlorine under reduced pressure at 8-10 DEG C. until the reaction mixture turns yellow and a temperature drop is noted. Residual HCl is then removed and the product is then distilled under reduced pressure to yield dipropyl-chlorophosphate. The alkylene glycol phosphates are stated to be suitable as plasticizers for thermoplastic material particularly cellulose derivatives (see Group IV (a)).