IE48240B1 - Dental cream formulation - Google Patents

Abstract

A toothpaste which, apart from 20-75% by weight of an abrasive containing calcium carbonate and 0.1 to 5% by weight of a surface-active agent including sodium C10-C18-alkyl sulphate with a wide alkyl chain distribution, ranging from C10 to C18, contains 0.2 to 1% by weight of a pyrophosphate or an anionic phosphate ester is distinguished by a smooth texture and by a low tendency to granulation. The latter remains small even on storage at low temperatures. In addition, the toothpaste has desirable rheological properties.

Description

This invention relates to a dental cream composition having a desirable rheological character. In particular it relates to a dental cream composition of smooth texture with little tendency to form grain, particularly upon aging at low temperatures.

Calcium carbonate or chalk has long been used as a dental polishing agent. In earlier times, in spite of its effectiveness in polishing teeth, it had disadvantages in that it tended to make dental cream somewhat slimy in feel. More recently, however, grades of calcium carbonate have come into use which substantially avoid this problem.

Nevertheless, it has been observed that in dental creams containing calcium carbonate, including modern grades of the material, when the cream further contains sodium lauryl sulphate as a surface active agent, and particularly sodium lauryl sulphate having a broad distribution of alkyl chain lengths, such as about 1-8% (ηθ; '40-70% C12; 13-30% C^; 5-16% Clg; and 0-23% C]8; grain formation does occur after storage at low temperatures e.g. between about • . -7 to 7°C.

It is an object of this invention to provide a dental cream composition comprising calcium carbonate and sodium lauryl sulphate having a broad distribution of alkyl chain lengths which composition has desirable rheological characteristics and is substantially grain free.

According to the present invention a dental cream composition comprises from 20 to 75% by weight of a calcium carbonate polishing material, from 0.1 to 5% by weight of a surface active material including sodium lauryl sulphate having a broad distribution of alkyl groups containing 10-18 carbon atoms, the content being about to 70% by weight, and from 0.2 to 1% by weight of an additive which is an M4 pyrophosphate or an anionic phosphate ester comprising a mixture of monoester of the formula R(0C2H4)n0P-0M and OM diester of the formula R(0C2H4)n0-P-0(C2H40)nR OM wherein M is hydrogen, alkali metal or ammonium, R is an alkyl group of 10-20 carbon atoms and n is an integer from 1 to 6.

Calcium carbonate is available in various grades, particularly as precipitated chalk. For example, grades may have an apparent density of about 0.47-0.61 gms/cc; a flow point of about 19 to 25; a moisture loss at 105°C of about 1 to 2%; a particle size such that at least 99.7% of the particles are finer than 74 microns (pass through U.S. 200 sieve), the median size is about 4 to 9 microns and not more than 90% are less than 18 microns; and the material is composed of calcite and aragonite in a ratio of from about 1:9 to 3:1, typically about 1:10, 1:1 or 3:1. Suitable grades are available from John and E. Sturge Ltd., Birmingham, England, for instance as Sturcal H and from Johann Schaefer Kalkwerke, Diez, West Germany as Schaefer AC.

The polishing material preferably comprises from 40 to'55%, of the dental cream and preferably at least about 95% of the polishing material is calcium carbonate. In addition to calcium carbonate the polishing material may optionally contain as up to about 5% of its content an additional polishing agent such as di calcium phosphate (anhydrous or dihydrate), tricalcium phosphate, dimagnesium phosphate, trimagnesium phosphate, insoluble sodium metaphosphate, hydrated alumina or silica.

Sodium lauryl sulphate has long been used in dental cream compositions but it has generally been used as a narrow cut material in which at least 90%, even 99%, of the alkyl groups are C^· Dental creams containing calcium carbonate and narrow cut sodium lauryl sulphate often do not become grainy, even upon aging at low temperatures. It is when the sodium lauryl sulphate of broad alkyl distribution is employed, that the problem of grain upon aging at low temperatures can be recognized. A particular sodium lauryl sulphate employed for the present invention contains about 3% C-jqJ 56% C·^; 21% C·^; 9% and 11% C^g alkyl groups and is commercially available in the form of needles as LZV from Marchon Division of Albright and Wilson, Whitehaven, England. Further broad cut grades of sodium lauryl sulphate which may be employed are Tensopol ACL 17 front Tensia SiA., Liege, Belgium and Texapon ZHC from Henkel and Cie,, .Dusseldorf, West Germany. Such grades of sodium lauryl sulphate include about 40 to 70$ C12 of their alkyl distribution. More particularly, they typically have an alkyl distribution of about 1 to 8% 4 to 70% C^S 13 to 30% C^; to 16% Clg; and 0 to 23% Ο^θ. The alkyl groups are substantially straight chain (normal).

In addition to sodium lauryl sulphate of broad alkyl distribution, the dental cream optionally may include an additional surface active agent. Such agents may include anionic materials, for instance, water-soluble salts of higher fatty acid monoglyceride monosulphate (e.g., sodium coconut fatty acid monoglyceride monosulphate), alkyl aryl sulphonate (e.g., sodium dodecyl benzene sulphonate), higher fatty acid esters of 1,2-dihydroxy propane sulphonate (e.g., sodium coconut fatty acid ester of 1,2-dihydroxy propane sulphonate) or anionic phosphate ester of the type indicated above which is also effective as an additive to reduce grain formation.

A nonionic or ampholytic surface active agent may also be present, such agents including nonionic agents such as sorbitan monostearate with approximately 60 moles of ethylene oxide, condensates of ethylene oxide with propylene glycol (available under the trademark Pluronics”) and amphoteric agents such as quaternized imidazole derivatives which are available under the trademark “Hiranol such as Miranol C2M. It is preferred that the total amount of surface active agent does not exceed about 5% by weight of the oral composition. The total surface active material content of the dental cream is about 0.1 to 5% by weight. Preferably about 1 to 2% by weight of sodium lauryl sulphate of broad alkyl distribution is present.

The additive which reduces the grain formation upon aging at low temperature, such as about -7 to 7°C, is a phosphate material, particularly a pyrophosphate or the anionic phosphate ester mixture of monoester and diester as defined above. When the anionic phosphate ester is employed, it may also serve as part of the surface active material.

The pyrophosphate may be tetrasodium pyrophosphate in its anhydrous or hydrated forms. (Na^O? -,^0) is a preferred material.

The corresponding tri polyphosphate is not believed to be effective in grain reduction.

The anionic phosphate esters are mixtures of mono and di-esters of the formulas hereinabove set forth. They are available from M0D0 Kemi Aktiebolaget, formerly Berol Aktiebolaget, of Sweden under the name Berol and may include an anionic tri ester moiety too, as well as some non-ionic portion. Berol 729 has alkyl chain lengths of 16 to 18 carbon atoms and contains series of 4 ethylene oxide units. Since the acid form of Berol 729 typically provides a completed oral preparation with a pH below 6, this material is generally used in neutralized or partially neutralized form in order to assure a pH above about 6 to the completed oral preparation.

Further anionic phosphate esters which may be used in acid or neutralized forms are Berol 525 which contains alkyl groups of 10 to 18 carbon atoms and series of 5 ethylene oxide units and Berol 513 which contains alkyl groups of 16 to 18 carbon atoms. However, use of Berol 525 may also provide a completed oral preparation with a pH below 6 and it is preferred to use it in neutralized or partially neutralized form. Further Berol anionic phosphate esters are available as Berol 521, Berol 724 and Berol 733. The weight ratio of monoester to diester may vary, typically from about 1:10 to 10:1.

The grain reduction additive is employed in amount of from 0.2 to 1 % by weight, preferably about 0.2 to 0.5$. When a dentifrice containing calcium carbonate and sodium lauryl sulphate having a broad alkyl group distribution, but not including the anti-grain additive is prepared, grain formation can be observed after aging for one month at a low temperature, such as about -7 to 7°C, typically 4°C.

The dental cream includes as a vehicle for the polishing material, grain reduction additive and other ingredients, liquids and solids proportioned to form an extrudable creamy mass of desirable consistency. In general, liquids in the dental cream will comprise chiefly water, glycerine, sorbitol, propylene glycol, or the like, including suitable mixtures thereof. It is advantageous usually to use a mixture of both water and a binder or humectant such as glycerine and/or sorbitol. It is preferred to use glycerine or mixtures of glycerine with sorbitol. The humectant is generally used in an amount between about 20 and 25% and preferably about 22%. The total liquid content will generally be about 20 to 65% by weight of the formulation, with water being in an amount to bring the total of components to 100%.

It is preferred to use also a gelling agent in dental creams such as the natural and synthetic gum and gum-like materials, e.g.

Irish moss, gum tragacanth, sodium carboxymethylcellulose, polyvinyl pyrrolidone, starch and the like; all being referred to as gum. The Irish moss and sodium carboxymethylcellulose are compatible particularly and are preferred gelling agents. The gum content is usually in an amount up to about 10% and preferably about 0.5 to 5% by weight of the formulation, with gum in an amount of about 0.9 to 1.3% especially preferred.

The total of liquid and gelling agent (gum) form the dental cream vehicle in which the other components are dispersed or dissolved.

Various other materials may be incorporated in the dental creams of this invention. Examples thereof are colouring or whitening agents, flavours, sweeteners, preservatives, silicones, chlorophyll compounds and ammoniated materials such as urea, diammoniumphosphate and mixtures thereof. These adjuvants are incorporated in the instant compositions in amounts which do not substantially adversely affect the properties and characteristics of the particular type of preparation involved.

A fluoride-providing compound may also be present. These compounds may be slightly soluble in water or may be fully water-soluble. They are characterized by their ability to release fluoride ions in water and by substantial freedom from reaction with other compounds of the oral preparation. Among these materials are inorganic fluoride salts, such as suitable alkali metal, alkaline earth metal, and heavy metal salts, for example, sodium fluoride, potassium fluoride, ammonium fluoride, a copper fluoride such as cuprous fluoride, zinc fluoride, a tin fluoride such as stannous fluoride, or stannous chlorofluoride, barium fluoride, sodium fluorosilicate, ammonium fluorosilicate, sodium fluorozirconate, sodium monofluorophosphate, aluminium mono-and di-fluorophosphate, and fluorinated sodium calcium pyrophosphate. Alkali metal and tin fluorides, such as sodium and stannous fluorides and also sodium monofluorophosphate are preferred.

The following specific examples are further illustrative of the nature of the present invention but it is understood that the invention is not limited thereto. Oral compositions are prepared in the usual manner, except as indicated, and all amounts and proportions are by weight except as otherwise indicated.

EXAMPLE The following dentifrices were prepared and placed in unlined aluminium tubes: 48340 Components Parts A B C Glyceri ne 6.060 6.060 6.060 Sodium carboxymethyl cellulose 1.200 1.200 1.200 Sodium saccharin 0.200 0.200 0.200 Sodium silicate 0.200 0.200 0.200 Sorbitol (70%) 16.000 16.000 16.000 Tetrasodium pyrophosphate - 0.500 - Berol 513* - - 0.500 Deionized water 23.433 22.933 22.933 Calcium carbonate** 42.000 42.000 42.000 Sodium lauryl sulphate LZV*** 1.807 1.807 1.807 Flavour 1.100 1.100 1.100 PH 8.65 9.44 8.20 *Berol 513, employed in dentifrice C is a mixture of anionic phosphate monoesters and diesters of the earlier indicated formulas in which the alkyl group contains 16 to 18 carbon atoms. It is a pasty material with a density of about 1.050/cm3 at 30°C. It is available from MoDo Kemi Aktiebolaget, of Sweden.

**The calcium carbonate employed in dentrifices A, B and C is Sturcal H chalk, available from John & E. Sturge Ltd., Birmingham, England.

***The sodium lauryl sulphate employed in dentrifices A, B and C is LZV, a broad-cut needle material available from Marchon Division of Albright and Wilson.

After aging for three months at 4°C, dentifrice A has an appearance which can be noticed as somewhat rough and grainy. On the other hand, the presence of tetrasodium pyrophosphate in dentifrice B and of Berol 513 in dentifrice C, reduces grain, such that after storage for three months at 4°C, dentifrice B is slightly rough only at the tube nozzle, but is otherwise satisfactory and indeed shiny; dentifrice C is satisfactory and shiny after storage for three months at 4°C.

Likewise, improvements are observed when tetrasodium pyrophosphate or the organic phosphate ester is present in dentifrices containing calcium carbonate available as Schaefer AC and broad cut sodium lauryl sulphate, including LZV as well as needles of Tensapol ACL7 available from Tensia, S.A., Liege, Belgium and needles of Texapon ZHC, available from Henkel and Cie., Dusseldorf, West Germany.

A grain problem also exists when the formula contains 40% calcium carbonate, such as Sturcal H and 2% dicalcium phosphate as polishing materials and broad-cut sodium lauryl sulphate, such as LZV, which problem is reduced by the presence of tetrasodium pyrophosphate or the organic phosphate ester.

Claims (6)

1. I. A dental cream composition comprising from 20 to 75% by weight of a calcium carbonate polishing material and from 0.1 to 5% by weight of a surface active material including sodium lauryl sulphate having a 5 broad distribution of alkyl groups containing 10 to 18 carbon atoms, the C^ content being 40 to 70% by weight, .and 0.
2. 2. To 1% by weight of an additive which is an M^ pyrophosphate or an anionic phosphate ester comprising a mixture of monoester of the formula II R(0C 2 H 4 ) n 0P-0M OM diester of the formula and II wherein M is hydrogen, alkali metal or ammonium, R is an alkyl group of 10 to 20 carbon atoms and n is an integer from 1 to 6. 15 2. A dental cream composition as claimed in Claim 1 wherein the polishing agent is present in amount of from 40 to 55% by weight of the dental cream and at least 95% by weight of the polishing material is calcium carbonate.
3. 3. A dental cream composition as claimed in Claim 1 or Claim 2 20 wherein the distribution of alkyl groups in the sodium lauryl sulphate is: C 10 1 to 8% C 12 40 to 70% C 14 13 to 30% C 16 5 to 16% C 18 0 to 23%; and the said alkyl groups are substantially straight chains.
4. 4. A dental cream composition as claimed in any of Claims 1 to 3 wherein the additive is tetrasodium pyrophosphate. 10
5. 5. A dental cream composition as claimed in any of Claims 1 to 3 wherein the additive is an anionic phosphate ester, and R contains 16 to 18 carbon atoms.
6. 6. A dental cream composition substantially as described in formulation δ or C of the Example.