Process of stabilization of anhydrous dibasic calcium phosphate against fluorine ions with azacycloalkane-2,2-diphosphonic acids

Abstract

A process for stabilizing anhydrous dibasic calcium phosphate against reaction with fluorine ions comprising treating an aqueous suspension of anhydrous dibasic calcium phosphate at a pH of from 5 to 10 with an azacycloalkane-2,2-diphosphonic acid of the formula ##STR1## wherein n is an integer from 3 to 5, or a water-soluble salt thereof, in an amount of from 0.01% to 5% by weight with reference to the anhydrous dibasic calcium phosphate; as well as tooth cleaning preparation containing the stabilized anhydrous dibasic calcium phosphate.RELATED ARTAnhydrous dibasic calcium phosphate having the formula CaHPO.sub.4 is a polishing substance frequently utilized in tooth cleaning preparations as, for example, toothpastes and powders. For this purpose it may be used alone or in admixture with other polishing substances as, for example, silica gel or plastics cleaning substances. If soluble fluorides or other compounds providing fluorine ions are added to these tooth cleaning preparations as anti-caries substances, the fluorine contained therein may be inactivated by conversion into the soluble and inactive calcium fluoride. The process thereby occurring may be represented by the following empirical reaction:CaHPO.sub.4 + 2 NaF .fwdarw. CaF.sub.2 + Na.sub.2 HPO.sub.4the speed of this inactivation reaction is influenced by several circumstances such as temperature, pH value of the mixture and its composition.For the use of a polishing agent as cleaning material in toothcleaning preparations, its abrasive behavior is of decisive importance, since products to be used for this purpose must only have an abrasive power which does not cause damage to the teeth. Owing to its favorable abrasive behavior, anhydrous dibasic calcium phosphate already enjoys great popularity as a cleaning material in tooth cleaning preparations. Its property of making the fluorine-containing compounds used for control of caries in the tooth cleaning preparation inactive or at least strongly reducing their action is, however, extremely undesirable. The problem, therefore, exists of finding ways and means largely to stop this inactivation of the fluorine-containing added substances.OBJECTS OF THE INVENTIONAn object of the present invention is the development of a process for stabilizing anhydrous dibasic calcium phosphate against reaction with fluorine ions consisting essentially of suspending anhydrous dibasic calcium phosphate in an aqueous medium at a pH of from 5 to 10, containing from 0.01% to 5% by weight based on the content of dibasic calcium phosphate of an azacycloalkane-2,2-diphosphonic compound selected from the group consisting of (A) compounds of the formula ##STR2## wherein n is an integer from 3 to 5, and (B) water-soluble salts thereof, and separating said stabilized anhydrous dibasic calcium phosphate.Another object of the present invention is the obtaining of a stabilized anhydrous dibasic calcium phosphate.A further object of the present invention is the obtaining of tooth cleaning preparations containing a stabilized anhydrous dibasic calcium phosphate.These and other objects of the present invention will become more apparent as the description thereof proceeds.

Description

Claims

1. A process for stabilizing anhydrous dibasic calcium phosphate against reaction with fluorine ions consisting essentially of suspending anhydrous dibasic calcium phosphate in an aqueous medium at a pH of from 5 to 10, containing from 0.01% to 5% by weight based on the content of dibasic calcium phosphate of an azacycloalkane-2,2-diphosphonic compound selected from the group consisting of (A) compounds of the formula ##STR9## wherein n is an integer from 3 to 5, and (B) water-soluble salts thereof, and separating said stabilized anhydrous dibasic calcium phosphate.

2. The process of claim 1 wherein said pH is between 6 to 8.

3. The process of claim 1 wherein the amount of said azacycloalkane-2,2-diphosphonic compound is from 0.1% to 2% by weight based on the content of anhydrous dibasic calcium phosphate.

4. The process of claim 1 wherein said water-soluble salts are selected from the group consisting of the alkali metal salts and ammonium salts.

5. An anhydrous dibasic calcium phosphate stabilized against reaction with fluorine ions by an azacycloalkane-2,2-diphosphonic acid produced by the process of suspending anhydrous dibasic calcium phosphate in an aqueous medium at a pH of from 5 to 10, containing from 0.01% to 5% by weight based on the content of dibasic calcium phosphate of an azacycloalkane-2,2-diphosphonic compound selected from the group consisting of (A) compounds of the formula ##STR10## wherein n is an integer from 3 to 5, and (B) water-soluble salts thereof, and separating said stabilized anhydrous dibasic calcium phosphate.