Toothpastes
United States Patent Venables et al.  
 TOOTHPASTES Inventors: Susan Mary Venables, Ascot;  
 Charles Andrew Watson, Ruislip, both of England Lever Brothers Company, New York, NY.  
 Filed: Nov. 24, 1972 Appl. 140.; 309,535  
 Related US. Application Data Continuation of Ser. No. 132,545. April 8, I971, abandoned.  
 Assignee:  
 US. Cl. 206/84; 424/49; 424/54; 206/277 Int. Cl A61k 7/16 Field of Search 424/49-58; 222/92; 206/277 References Cited UNITED STATES PATENTS l/l936 Jacobson 424/49 FOREIGN PATENTS OR APPLICATIONS 1.221816 9/1966 Germany 424/54 Primary E.\&#39;aminer-Richard L. Huff Attorney, Agent, or Firm-James J. Farrell, Esq.; Melvin H. Kurtz, Esq.; Arnold Grant, Esq.  
 [57] ABSTRACT A toothpaste containing glycerine, water and chloroform, characterised by the inclusion as a corrosion inhibitor to inhibit the corrosiveness of the toothpaste to aluminium of urea, biuret, geiatine, benzoic acid or a salt of benzoic acid.  
 3 Claims, No Drawings TOOTHPASTES This is a continuation, of application Ser. No. 132,545, filed Apr. 8, 1971, now abandoned. This invention relates to toothpastes.  
  Most toothpastes contain a proportion of water. the liquid phase consisting of a mixture of humectant and water. Glycerine and sorbitol are the most usual hu mectants, although others are occasionally used.  
  Chloroform is an ingredient commonly added to toothpastes for the purpose of improving the flavour. It is usually included in an amount in the range 0.5 to 4.0 percent by weight.  
  The inclusion of chloroform, however, can give rise to corrosion of aluminium tubes, aluminium being the most convenient and least expensive material for toothpaste packaging. lt has been suggested to mitigate this corrosion problem by the use of relatively high levels of glycerine in the liquid phase of the toothpaste. However, the use of the levels of glycerine results in products which are of high raw material cost, have a stringy fracture and are slow to disperse in the mouth. The problem of tube corrosion due to chloroform arises when water is present in the toothpaste at more than about 20 percent by weight of the liquid phase. The occurrence of corrosion is also especially marked at chloroform levels above about 1 percent by weight of the toothpaste. The problem of corrosion due to chloroform is one that has been known to toothpaste manufacturers for a long time.  
  It has now been found that corrosion of aluminium due to chloroform may be substanitially reduced in the case of toothpaste containing glycerine as humectant urea, biuret, gelatine or benzoic acid or a water-soluble salt of benzoic acid, or a mixture thereof, in the product.  
  Accordingly the present invention provides a toothpaste containing glycerine, water and chloroform having a reduced tendency to corrode aluminium comprising as corrosion inhibitor urea, biuret, gelatine, or benzoic acid or a water-soluble salt of benzoic acid.  
  The level of the urea, biuret, gelatine, benzoic acid or benzoic acid salt in the toothpaste required to give a corrosion inhibitive effect may be determined by experiment. The amount required is related somewhat to the amount of water in the toothpaste. Increasing amounts of inhibitor are required with the presence of greater amounts of water in the toothpaste. 1n usual commercial practice the amount of water may vary from about 25 percent to about percent by weight of the liquid phase of the toothpaste. Furthermore, the higher levels of chloroform in the range 0.5 to 4.0 percent generally tend to produce greater corrosion. However, as stated, for a particular combination of levels of water and chloroform, it is merely a maatter of simple experimentation to determine what level of the appropriateinhibitor is required to produce a substantial corrosion inhibitive effect.  
  A corrosion inhibitive effect is obtained in certain cases with a level of urea as. low as 0.1 percent by weight of the toothpaste although generally an amount of at least 0.5 percent by weight and in the range 0.5 to 2 percentwill be desirable. The chemically related compound biuret appears not to be quite so effective as urea on a weight for weight basis and biuret is recommended for use at a level of at least 0.5 percent by weight of the toothpaste, preferably an amount of from 1 to 2 percent by weight being used.  
  When using gelatine as the corrosion inhibitor, this material is desirably used at a level of at least 0.1 percent by weight of the toothpaste, the preferred amount being in the range 0.5 to 2 percent. Benzoic acid and its water-soluble salts are desirably used in an amount of at least 0.5 percent by weight of the toothpaste, the preferred levels for these inhibitors being from 1 to 5 percent by weight.  
  There is no advantage in using more of an inhibitor than is necessary to obtain the required reduction in corrosion. Amounts of corrosion inhibitior necessary are unlikely to be as high as 10&#39; percent and usually will not need to exceed 5 percent by weight of the toothpaste.  
  Apart from the corrosion inhibitor, the dentifrice of the invention will comprise the usual ingredients in the usual portions. Thus typically for a toothpaste in accordance with the invention, it will comprise, along with the inhibitor, preferably 15 to 40 percent by weight of glycerine, 30 to 60 percent by weight of an abrasive cleaning agent, 1 to 2.5 percent by weight of a surfaceactive agent, 0.5 to 4.0 percent by weight of chloro form, and the usual minor amounts of binding agent, flavouring agent and sweetening agent with the balance being water, the latter usually being present in an amount of about 8 to 30 percent by weight.  
  The following experiments illustrate the invention. Percentages are by weight.  
  Five base toothpastes were made having the following formulae:  
 The amount of chloroform varied due to the volatility of chloroform.  
  Other toothpastes in accordance with the invention were prepared by replacing a part of the abrasive by the corrosion inhibitor.  
  All the toothpastes were packed in unlacquered aluminium tubes and tested for corrosion by one or more of the following three test methods.  
 Test Method A Six tubes of the toothpaste under test were storred at 50C and 65C for up to 6 months and one tube of each test product at each temperature was opened every month and the inner walls were examined for corrosion.  
 Test Method B 216 and 72 tubes of the product under test were stored at 50C and 65C, respectively, and were examined for external signs of tube corrosion, i.e., perforation of the tube, at various intervals. The percentage of the number of tubes stored showing signs of corrosion was determined at each examination.  
 Test Method C Between 12 and 24 tubes of the toothpaste under test were stored at 65C and were examined at monthly intervals for external signs of tube corrosion. The percentage of the number of tubes sotred showing external signs of corrosion was determined at each examination.  
 The results obtained are given below.  
  The results obtained by Test Method A and B illustrating the effectiveness of urea are given in Tables 1 and 2. respectively.  
 TABLE 1 Extent of corrosion after storage at 65C for Toothl: Urea 1 month 3 months 6 months paste l moderate perforation perforation 0.1 slight slight slight l none very slight slight 2 none none none none none none ll 0 moderate perforation perforation 1 none none none 2 none none none lll 0 perforation perforation perforation 2 none none none IV 0 slight severe perforation 2 none none none V O perforation perforation perforation 1 none none none TABLE 2 of tubes perforated after storage for l2 months Toothpaste 7r Urea at C at 65C ll 0 60 86 2 O 0 The results obtained by Test Methods B and C illus- 65 trating the effectiveness of biuret as a corrosion inhibitor are given below in Tables 3 and 4, respectively.  
 TABLE 3 7: of No. of weeks Toothpaste Biuret tubes perforated storage at 65C 5 l 0 83 I4 2 21 14 3 l4 14 TABLE 4 of Storage time Toothpaste 7r Biuret tubes perforated (months) I 0 82 3 2 l3 3 l 5 4 0 3 ll 0 ll 3 l 0 3 2 0 3 lll 0 89 2 2 0 2 2O 4 0 2 The results obtained by Test Methods B and C illustrating the effectiveness of gelatine as a corrosion inhibitor are given below in Tables 5 and 6, respectively.  
 &#39; result after 2 months The results obtained by Test Methods A, B and C illustrating the effectiveness of sodium benzoate as a corrosion inhibitor are given below in Tables 7, 8, and 9, respectively.  
 TABLE 7 Extent of corrosion after storage at 50C for: Tooth- 7r Sodium 1 month 3 months 6 months paste Benzoate IV 0 slight slight slight 2 very slight none very slight 0 slight perforation perforation 2 slight none very slight Result after 2 months The results obtained by Test Method C illustrating the effectiveness of benzoic acid and a variety of watersoluble salts of benzoic acid as corrosion inhibitors are given below in Table 10. The results apply to the inclusion of the inhibitor at a level of 2 percent in Toothpaste 1.  
 TABLE 10 7r of tubes showing signs of corrosion after storage for 6 months Cation at 50C at 65C H 24 Li l 1 Na i2 42 K 5 5 NH. 0 0 Mg 0 5 Ca 0 l7 Sr 0 0 Zn 0 O Al 0 37 no inhibitor 52 93 While it has previously been proposed to include in toothpastes urea and biuret (as therapeutic agents), gelatin (as a binder) and sodium benzoate (as a preserving agent), the use of these materials as corrosion inhibitors in chloroform-containing toothpastes is believed to be original.  
 What is claimed is:  
 l. A toothpaste containing a. glycerine in an amount of about 15 percent to about 40 percent by weight of the toothpaste;  
 b. water in an amount of about 8 percent to about 30 percent by weight of the toothpaste, said amount of water consituting about 20 percent to about percent by weight of the liquid phase of the toothpaste;  
 c. chloroform in an amount of about 0.5 percent to about 4 percent by weight of the toothpaste; and  
 d. a corrosion inhibitor in an amount of about 0.1  
 percent to about 10 percent by weight of the toothpaste effective to inhibit corrosion of aluminium by the toothpaste, said corrosion inhibitor being selected from the group consisting of urea and biuret, said toothpaste being contained in an unlacquered aluminium tube.  
 2. A toothpaste containing a. glycerine in an amount of about 15 percent to about 40 percent by weight of the toothpaste;  
 b. water in an amount of about 8 percent to about 30 percent by weight of the toothpaste, said amount of water constituting about 20 percent to about 60 percent by weight of the liquid phase of the toothpaste;  
 c. chloroform in an amount of about 0.5 percent to about 4 percent by weight of the toothpaste; and d. a corrosion inhibitor in an amount of about 0.1  
 percent to about 10 percent by weight of the toothpaste effective to inhibit corrosion of aluminium by the toothpaste, said corrosion inhibitor consisting of gelatine, said toothpaste being contained in an unlacquered aluminium tube.  
 3. A toothpaste containing a. glycerine in an amount of about 15 percent to about 40 percent by weight of the toothpaste;  
 b. water in an amount of about 8 percent to about 30 percent by weight of the toothpaste, said amount of water consituting about 20 percent to about 60 percent by weight of the liquid phase of the toothpaste;  
 c. chloroform in an amount of about 0.5 percent to about 4 percent by weight of the toothpaste; and d. a corrosion inhibitor in an amount of about 0.5  
 percent to about 10 percent by weight of the toothpaste effective to inhibit corrosion of aluminium by the toothpaste, said corrosion inhibitor being selected from the group consisiting of benzoic acid and soluble salts of benzoic acid, said toothpaste being contained in an unlacquered aluminium tube.