Patent GB-1142687-A (GB)
Title: Improvements in or relating to the preparation of fluorophosphates
Inventor: ROHLFS HANS ADOLF
IPC: C01B25/455
Filed: 1966-03-09
Abstract: 1,142,687. Ammonium and metal fluorophosphates. CHEMISCHE WERKE ALBERT. 9 March, 1966, No. 10375/66. Heading C1A. Fluorophosphates of ammonium and metals or compositions containing them, in which the ratio of "metal" equivalents (i.e. NH 4 + metal)/P = (0À7-2À5)/1 and P/F BOUND  where the F is bound directly to P = 1/(0À5-2) and P/F TOTAL  = 1/(0À5-3) and F BOUND /F TOTAL  = (0À5-1)/1, are prepared by reacting (A) a phosphoric acid, an ammonium phosphate, a metal phosphate, or an adduct of at least one organic nitrogen compound which is capable of releasing ammonia on heating or a mixture of two or more such phosphorus containing compounds with (B) hydrogen fluoride, an ammonium or a metal fluoride, or mixture of such fluorides, which expression fluoride includes complex fluorides such as silicafluorides but excludes addition products of neutral fluorides with hydrogen fluoride such as bifluorides, and at least where (A) and (B) do not contain a sufficient amount of metal equivalents to comply with the above ratio with (C) at least one basic reacting metal hydroxide, basic salt or metal salt of which the acid component escapes under the conditions used, at a temperature within the range from 140‹ C. up to 600‹ C. that is below the temperature at which the fluorophosphate loses fluorine, the atomic ratio of P: F in the starting materials being not greater than 1 : 0À5; metal + NH4 / P = (0À7- 2À5): 1 and at least one acid hydrogen atom being present in the starting materials for every two P atoms contained therein. Preferred reactants are ammonium, alkali metal, or alkaline earth metal acid phosphates with H : P = 1 : 1, and hydrofluoric acid and preferred temp. ranges are 170-600‹ C., 170- 300‹ C., and 200-400‹ C. for different types of starting material. In a modification of the process, an alkali metal or an ammonium phosphate, both of which contain at least 1 H atom for each P atom they contain is reacted with a silico fluoride at a temp. of 400- 800‹ C. The F TOTAL /P ratio in the starting material may be 1: 20 but is preferably 1 : (1- 8) and the (NH 4 +metal)/P ratio is preferably (1-2): 1 and the ratio of F BOUND /F TOTAL is preferably (0À8-1): 1. Other preferred M<SP>I</SP>: P : F ratios are quoted and preferred types of starting material are indicated, e.g. phosphoric acid at least 15% by wt. H 3 PO 4  and hydrofluoric acid at least 15% by wt. HF. The starting materials may, however, be anhydrous. The reaction may be carried out at ambient, at reduced or elevated pressure, e.g. between 10 mm. Hg and 100 atmos (gauge). Reactant (C) may be an alkali or alkaline earth metal hydroxide or a salt of such a metal which decomposes to yield a gaseous compound under the conditions used. The nitrogen compound which may be the phosphorus adduct or reactant (C) is preferably hydrazine or has one of the formulµ in which X represents O, S or NH, R 1  = H, alkyl, alkoxy, acid amide, i.e. -CONH 2 , which may be bound to C = X by an alkylene group, an NH 2  group, an NH, NH 2  group or an R 2  is an NH 2  group, an SNH 4  group, or an ONH 4  group. R 3 ,R 4 ,R 5  each represent OH or NH 2  groups and may be the same or different. R 6  represent H, an alkyl group, an acid amide group as above, an NH 2  group or an NH-NH 2  group, the alkyl, alkoxy and acid amide groups of R 1  and R 6  each having not more than 3 carbon atoms and in which either of radical R 1  and R 6  on the one hand and X on the other hand together may be combined to represent a single nitrogen atom. The above materials may be used in an amount such that N : P in reaction mix is not greater than 5 to 1, preferably (0À3-3): 1. The above nitrogen containing materials are exemplified by urea, thiourea and formamide. The product of the above process is used as a tooth-paste additive.