Method and apparatus for dewatering of a finely - to - a very finely granular solid material - liquid - mixture

摘要

A polyalkylene terephthalate is made by heating a glycol of formula HO-(CH2)nOH (where n=2-10) with a terephthalic acid anhydride or derivative thereof having the formula FORM:0801412/IV (a)/1 where R is a hydroxyl group, a chlorine atom or or an acyloxy group and R1 is an acyl, p-carbonylbenzoic acid, p-carbonylbenzoic acid ethyl ester or p-carbonylbenzoic chloride group and X is 1-100. The derivative may be (1) a mixed anhydride of terephthalic acid of formula FORM:0801412/IV (a)/2 where n=1-4 (obtained by reacting terephthalic acid with the anhydride of a fatty acid): (2) diterephthalic anhydride or a mixed anhydride of acetic and terephthalic acid of formula FORM:0801412/IV (a)/3 (obtained by oxidizing the anhydride of p-methyl benzoic acid); or (3) a polyterephthalic anhydride of formula FORM:0801412/IV (a)/4 (obtained by treating diterephthaloyl chloride with a stoichiometric equivalent or water or alkali followed by spontaneous polymerization). Reaction between the glycol and the terephthalic anhydride (or derivative) may be effected in presence of antimony oxide and preferably the latter part of the reaction is effected in vacuo and a current of an inert gas. Specifications 578,079, 590,451, [both in Group IV], and 630,992 are referred to.ALSO:The Specification describes the preparation of the following compounds: (1) a mixed anhydride of terephthalic acid of formula: FORM:0801412/IV (b)/1 where n=1-4 and X=1-100 and R is an -OH group, or FORM:0801412/IV (b)/2 obtained by heating terephthalic acid with the anhydride of a lower fatty acid; (2) a mixture of diterephthalic acid anhydride and mixed anhydrides of acetic and terephthalic acid of the formul : FORM:0801412/IV (b)/3 and FORM:0801412/IV (b)/4 which is obtained by dissolving the anhydride of p-methyl benzoic acid in acetic anhydride, adding cobalt acetate, and passing a stream of oxygen through the boiling reaction mixture while continuously distilling off liquid. By boiling the product with water, pure diterephthalic anhydride is obtained, whilst by adding further acetic anhydride during the distillation the pure mixed anhydride is obtained; (3) a polyterephthalic acid anhydride of formula: FORM:0801412/IV (b)/5 which is obtained by adding water or a mixture of water and pyridine to terephthalic acid dichloride dissolved in dioxane, allowing an exothermic reaction to take place, adding further dioxane and boiling the reaction mixture; (4) the anhydride of p-methyl benzoic acid which is made by heating p-methyl benzoic acid with acetic anhydride. Specifications 578,079, 590,451, [both in Group IV], and 630,992, [Group IV (a)] are referred to.