Patent GB-878115-A (GB)
Title: Improvements in and relating to polychloroformates
IPC: C08G64/24
Filed: 1959-12-07
Abstract: Synthetic resins are produced by reacting a glycol dihydric phenol, bisphenol or diamine with a polychloroformate of an alkylidene diphenol carbonate containing between 0,5 and 4 carbonate linkages per chloroformate group.  These polychloroformates are made by reacting phosgene with a dimetal salt of an alkylidene bis-phenol in aqueous solution maintained at pH9-12 by an alkaline buffer. Preferably the reaction medium contains an organic solvent.  In Example 9, a methylene chloride solution of the compound of the formula:  <FORM:0878115/IV (a)/1> is reacted at 25 DEG C. with hexamethylene glycol, in the presence of pyridine to produce a polycarbonate.  In Example 10 a similar dichloroformate to the above is reacted with 2, 2-bis (2, 3, 5, 6-tetrachloro-4-hydroxyphenyl)-propane.  These dichloroformates may be reacted with diamines to form products in which Bisphenol A carbonate residues are periodically interrupted by carbamate linkages.  Specified diamines are: piperazine, ethylene diamine, 1, 3-diaminopropane, hexamethylene diamine, methylene bisaniline, p, p1-diaminodiphenyl ether, and diamino derivatives of naphthalene, diphenyl and anthracene.ALSO:Polychloroformates of alkylidene diphenol carbonates, containing between 0.5 and 4 carbonate linkages per chloroformate group, are prepared by reacting phosgene with a dimetal salt of an alkylidene diphenol in an aqueous solution having its alkalinity regulated in the pH range of 9 to 12 by an alkaline buffer.  In Example1, an aqueous solution containing the di-sodium salt of p,p1-isopropylidene diphenol and sodium carbonate is mixed with methylene chloride, and then reacted with a solution of phosgene in methylene chloride, at a temperature of 0 DEG  to 15 DEG C. The molar ratio of phosgene to diphenol salt is 2:1.  The reaction product is washed with dilute sulphuric acid, and allowed to separate into two phases.  The organic phase is dried over magnesium perchlorate.  The methylene chloride is removed and there is obtained a bischloroformate having the structure <FORM:0878115/IV (b)/1> wherein the ratio of carbonate linkages to chloroformate groups is one to one.  In Example 4, the organic phase obtained by reacting 0.9 moles of p,p1-isopropylidene diphenol salt with 1.65 moles of phosgene is treated with three separate additions of heptane whereupon 3 precipitated products and a residual-product in the mother-liquor are separated.  The residual product has a carbonate to chloroformate ratio of 0.5; and two of the precipitated products have 4 carbonate linkages per chloroformate group.  In Example 8, the reaction is carried out by gradually adding gaseous phosgene and a separate stream of an aqueous solution of the di-sodium salt of p,p1-isopropylidene diphenol to a mixture of sodium carbonate, water and methylene chloride, the mixture being stirred and maintained at 8 DEG C. to 12 DEG C.  A list of other alkylidene diphenols, which may be employed in the reaction, is given.  The polychloroformate may be reacted with glycols, dihydric phenols, and diamines to form resins of high molecular weight (see Group IV(a)).