GB631365A - Improvements in or relating to the production of transparent synthetic resins - Google Patents

Abstract

Transparent artificial resins are obtained by condensing an aldehyde, urea (and/or thiourea), and up to 50 mol. per cent (based on the total urea or thiourea in the reaction mixture) of one or more polyfunctional urea derivatives of the formula (H2N.CX.NH)nR, where R is a di- or bi-valent hydrocarbon radical, X is an oxygen or sulphur atom and n is 2 or 3. The polyfunctional urea derivatives may be added to an initial urea and/or thiourea condensate which is then condensed further. The radical R may be derived from ethane, isoprene, butane, cetane, decane, ethylene, butene, octene, decene, benzene, cyclohexane, toluene, 2 : 5-dimethyl-cyclohexane, cyclopentane, cyclohexene, or cyclopentene. Urea-derivatives specified are 1,4-butylene diurea, 1,3-pentylene diurea, 1,4,6-triureido hexane, 1,2-phenylene diurea, 1,5,7-triureido decane, 2,4-pentylene diurea, 2,6-heptylene diurea, 1,4-butylene dithiourea, 1,3- or 1,5-naphthylene dithiourea, 1,3-heptylene diurea, 1,2,4-triureido naphthalene, 1,5-heptylene dithiourea, ethylene diurea, 1,3,5-triureido heptane, 1,3-octylene diurea, 1,5-decylene diurea, 2,4-pentylene dithiourea, ethylene dithiourea, 1,3,5-trithioureido heptane. Suitable aldehydes include formaldehyde, acetaldehyde, propion-aldehyde, 2-pentenal, 2-butyraldehyde, 2,4-pentanediol, caproaldehyde, valeraldehyde, crotonaldehyde, 2 - furaldehyde, octanal, heptanal. The reaction may be performed in solution in water, alcohols, toluene, dioxane, hexane. Suitable catalysts for the condensation are alkali or alkaline earth metal hydroxides, oxides, alkali metal alcoholates, or quaternary ammonium bases, and for the polymerization, hydrochloric, sulphuric, acetic, lactic, or peracetic acid, to bring the pH to 4 to 6.5. Plasticizers such as glycerol may be added. In examples: (1) urea, formaldehyde, and caustic soda are reacted at room temperature, the product acidified with lactic acid, then heated with ethylene diurea, allowed to stand, and dehydrated. The product is cast and cured at 70 DEG C.; (2) urea, ethylene diurea, formaldehyde, and caustic soda are reacted together, the product acidified with lactic acid, heated, and then part of the water removed under alkaline conditions and the remainder under acid conditions, the resin finally being cast and cured at 70 DEG C. Specification 506,507 is referred to.