NO162493B - TOOTHPASTE. - Google Patents

Description

Sodium carboxymethylcellulose has been used as a gelling agent in toothpastes because it is readily available and because of the generally satisfactory rheological properties it contributes to toothpastes, especially when they are stored and used under temperate climate conditions. Under tropical climate conditions, sodium carboxymethylcellulose can be subjected to decomposition by the action of cellulase.

Toothpastes made with a variety of grades of sodium carboxymethylcellulose tend to have a coarse appearance (soft lumps or chunks) even at room temperature, especially when subjected to dynamic aging which involves extruding 2 cm strips of toothpaste from a tube two times daily for 2 weeks, which is a condition that simulates the normal use of toothpaste by a single person.

Even grades of sodium carboxymethyl cellulose such as

are not exposed to such a roughness transition during dynamic ageing, may exhibit other rheological problems, e.g.

poor "set" qualities, i.e. rapid settling of the extruded cream into a flat ribbon or thickening as time passes.

It is worth noting that roughening by dynamic aging can especially be observed when the toothpaste contains a compound that provides fluoride ions, and a calcium phosphate is present as a polishing material. Small problems thus occur when fluorine is obtained from sodium monofluorophosphate or a mixture of sodium monofluorophosphate and sodium fluoride and the polishing agent is a silicon dioxide-containing material.

However, the problem can be easily observed when fluoride is obtained from sodium monofluorophosphate or a mixture of sodium monofluorophosphate and sodium fluoride in a toothpaste containing at least 35% by weight

of a calcium phosphate as a polishing material, such as dicalcium phosphate.

Attempts to overcome the roughness problem without causing other problems, such as poor "set", by mixing different grades of sodium carboxymethyl cellulose or by mixing sodium carboxymethyl cellulose with other gelling agents, such as a synthetic, inorganic, silicate clay (e.g., material

(shelter "

ales sold under the trademarks Laponite^ and Veequm ), thickeners, such as silicon dioxide thickeners sold under the trademark "Zeosyl", such as "Zeosyl" 200,

or Tixosir^, soiti e.g. Tixosir^ 33J, or under the trade name "HDK N20" or a material with a liquid phase,

such as polyethylene glycol 600, has not been satisfactory.

Hydroxyethylcellulose has been proposed as an alternative gelling agent to sodium carboxymethylcellulose, among others

(s)

grades of hydroxyethylcellulose, such as Natrosol M, have been used in commercial toothpastes, and grades have been described e.g. in US Patents 3862307 (Natrosol<*>^G) and 3070510 (viscosity 75-125 eps - Brookfield, 20°C, 2% in water) and 4022881 (Natrosol<*>^ 250 H which is a high viscosity material). Although generally satisfactory, such grades of hydroxyethylcellulose can be prone to causing toothpastes to suffer "rheology elongation" by forming a visible "tail" when filled into containers and when extruded onto a toothbrush.

For example, "stringing" has been described in US Patent 4,022,881 for toothpastes containing a thickening medium mixture of 30% hydroxyethylcellulose and 70% sodium carboxymethylcellulose. A non-string-like toothpaste containing calcium carbonate as an abrasive together with a thickener mixture of 10% hydroxyethylcellulose and 90% sodium carboxymethylcellulose has also been described.

According to the invention, a toothpaste is provided with

a gelling agent mixture which shows little susceptibility to becoming coarse during aging and which at the same time has other desired rheological properties, such as good "stability", absence of formation of a "tail" on an extruded band of toothpaste bg good band gloss. Moreover, a toothpaste can be easily prepared with this mixture without significant modification of methods used when sodium carboxymethyl cellulose is the only gelling agent. The gel material with which sodium carboxymethyl cellulose can be advantageously mixed in a particular weight ratio is hydroxyethyl cellulose. This material, although generally a good material, has not been completely satisfactory in terms of

rheological trade-offs when used alone or in admixture with thickening or gelling materials other than sodium carboxymethylcellulose. Dentifrices containing hydroxy-ethyl cellulose grades such as Natrosoil<®> 250 M, dicalcium phosphate and a fluoride-releasing compound actually exhibit "tailing" and/or low "set strength" when such grades as Natroso]® 250 M are the sole gelling agent or is present together with sodium carboxymethylcellulose in a weight ratio between sodium carboxymethylcellulose and hydroxyethylcellulose (Natrosol 250 M or a similar material) of less than approx. 2:3, e.g. within the range 1:10-3:7.

In the above-mentioned US patent document 4022881, a dentifrice is described containing as a thickener 5-30% hydroxyethylcellulose with high viscosity (e.g. Natrosof* 250 H) and 70-95% sodium carboxymethylcellulose to stabilize the sodium carboxymethylcellulose against degradation. However, such relative amounts (e.g. 10:1 and 7:3) are not satisfactory because they do not lead to the avoidance of surface roughness which, however, is avoided according to the present invention.

It is an advantage of the present invention that it provides a gelling agent system for a toothpaste which remains smooth during dynamic aging and has other generally desirable rheological properties.

Further advantage of the invention is achieved because the toothpaste contains a starting material for fluorine, i.e. sodium monofluorophosphate or a binary starting material for fluorine consisting of sodium monofluorophosphate and sodium fluoride, and a polishing agent which includes a calcium phosphate.

The invention thus concerns a toothpaste which is characterized by the fact that it comprises a compound which provides at least 100 ppm fluorine and is selected from the group consisting of sodium monofluorophosphate bg a mixture of sodium monofluorophosphate and sodium fluoride in which 30-40% by weight of fluorine is obtained from the sodium fluoride, 40-75% by weight % polishing agent containing a calcium phosphate in an amount of at least 35% by weight of the toothpaste, a dentifrice carrier comprising 20-80% by weight, based on the weight of the toothpaste, of a liquid phase containing water, humectant or a mixture thereof, and 0.5-5 .0% by weight based on the weight of the toothpaste, of a gelling agent containing sodium carboxymethylcellulose and hydroxyethylcellulose, each present in a 3:2-2:3 weight ratio with respect to the other.

The above numerical references to viscosity refer to viscosities measured with a Brookfield viscometer for a 2% by weight aqueous solution at 25°C.

The gel agent is present in the toothpaste in an amount of 0.5-

5, preferably 0.8-2, and most preferably 0.9-1.1, wt%,

and the ratio of sodium carboxymethylcellulose to hydroxyethylcellulose is 3:2-2:3, typically 1:1, and preferably from below 1:1 to 2:3 (eg, 49:51, 9:11 or 2:3).

Sodium carboxymethyl cellulose is commercially available under the names CMC-7MXF and 7MFD, and these are preferred qualities for use according to the invention.

The qualities can have a degree of polymerization of around 500, corresponding to a molecular weight of around 100,000. The viscosity is from medium to high, e.g. 300-3000 eps or more, typically 300-1200 eps, and preferably 300-500 eps (Brookfield, 2%, 25°C). The CMC-7MXF contains approx. 0.7 sodium carboxymethyl groups per anhydroglucose unit.

In the table below, desirable commercial grades of sodium carboxymethyl cellulose (CMC) are given (where the viscosity has been measured using an apparatus other than a Brookfield viscometer in a 2% by weight aqueous solution at 25°C, the differences are indicated):

Hydroxyethylcellulose is commercially available under the trade name Natrosol<®> 2 50 M and is a preferred quality for the toothpaste according to the invention.

The qualities can have a degree of polymerization of approx. 750 corresponding to a molecular weight of approx. 190,000. The viscosity is from medium to high, e.g. 3000-12000 eps or more, typically 3000-7000 eps, and preferably 4500-6500 eps (Brookfield, 2%, 25°C). When the viscosity is measured with a device other than a Brookfield viscometer in a 2% by weight aqueous solution at 25°C, the differences are indicated.

In the table below, desired commercial qualities of hydroxyethyl cellulose (HEC) are reproduced:

The sodium carboxymethyl cellulose and the hydroxyethyl cellulose can be mixed mechanically with each other before they are mixed with the liquid phase of the toothpaste carrier or they can be mixed separately with the liquid phase.

The advantageous rheological properties which can be achieved according to the present invention are manifested in the toothpaste containing a compound which provides at least 100 ppm, typically 100-10,000 ppm, and more typically 750-2,000 ppm, fluorine. Sodium monofluorophosphate or a mixture of sodium monofluorophosphate and sodium fluoride is used in the toothpaste according to the invention. The advantageous rheological properties obtained according to the invention are also apparent because a calcium phosphate polishing agent, especially dicalcium phosphate, is present in an amount of at least 35% by weight of the toothpaste.

The toothpaste contains at least 35 preferably 40-50,

% by weight of a dentally acceptable, water-insoluble polishing material consisting of a calcium phosphate, such as dicalcium phosphate in dihydrated or anhydrous form

or as mixtures thereof in any ratio, tricalcium phosphate or calcium pyrophosphate. Dicalcium phosphate is most often used, generally in the form of the dihydrate. Dicalcium phosphate is typically the only polishing agent, but if desired, smaller amounts (e.g. up to 5% by weight of the toothpaste and up to 12% by weight of the total amount of polishing material) of other dental care-acceptable, water-insoluble polishing agents can be used that are not in significantly adversely affects the ability of the toothpaste according to the invention to promote oral hygiene. Typical polishing agents are aluminum oxide, silicon dioxide or sodium aluminum silicate etc. A small amount of hydrated aluminum oxide, e.g.

about. 1%, will also inhibit or even eliminate the tendency of some toothpastes to separate or "bleed" in the tubes.

The toothpaste typically contains sodium monofluorophosphate or a mixture of sodium monofluorophosphate and sodium fluoride in an amount sufficient to obtain 100-10,000, e.g. 750-2000, especially 1400-2000, which e.g. 1400-1670, ppm fluorine. A binary fluoride system of sodium monofluorophosphate and sodium fluoride can advantageously be used, in which 30-40% of the fluorine, e.g. 30-35%, i.e. 300-580 ppm, is obtained from sodium fluoride.

The mixed gelling agent system is particularly advantageous as a gelling component in toothpastes containing the binary fluoride mixture and the dicalcium phosphate polishing agent described in British Patent Specification 2068727A. In a typical toothpaste, sodium monofluorophosphate is thus typically used in the binary system in such an amount that this gives 700-1090 ppm of fluoride in the toothpaste, in which the total amount of fluoride is 1000-1670 ppm, with 30-35% of the total amount of fluoride being obtained from sodium fluoride ( 300-580 ppm). This corresponds to 0.5-1.2

wt% sodium monofluorophosphate and 0.05-0.11 wt% sodium fluoride. Of these, the toothpaste preferably contains 1000-1500, more preferably 950-1000, ppm fluorine from sodium monofluorophosphate and 450-500 ppm fluorine from sodium fluoride.

Sodium monofluorophosphate, which has the formula Na2P03F, can

as a commercial product have widely varying purity. It can be used with any suitable purity, provided that any contamination will not adversely affect the desired properties to a significant extent. In general, the purity should be at least 80% by weight. In order to achieve the best results, it should be at least 85% by weight, preferably at least 90% by weight, of sodium monofluoride, etc., with the rest being mainly impurities or by-products from the manufacture, such as sodium fluoride and water-soluble sodium phosphate salt. Expressed in another way, the sodium monofluorophosphate used should have a total fluoride content of more than 12%, preferably more than 12.7%, a free sodium fluoride content of not more than 1.5%, preferably not more than 1.2%, and a sodium monofluorophosphate content of at least 12%, preferably at least 12.1%, all calculated as fluoride.

As indicated above, sodium fluoride in the binary mixture is a fluorine-containing component that is separate from sodium monofluoride, etc. 300-580 ppm fluorine is preferably obtained in the toothpaste from sodium fluoride.

In the toothpastes, the toothpaste carrier comprises a liquid phase in an appropriate amount in relation to the gel agents to form an extrudable, creamy mass with the desired consistency. In general, the liquids in the toothpaste will mainly comprise water, glycerol, sorbitol, polyethylene glycol 400, propylene glycol or a similar liquid, including suitable mixtures thereof. It is generally advantageous to use a mixture of water and a humectant, such as glycerol or sorbitol, and then typically 10-30% by weight of water and 15-50% by weight of humectant. It is preferred to use glycerol or sorbitol. The total liquid content must be 20-80% by weight of the toothpaste.

Any suitable surfactant or cleansing material may be present in the toothpaste.

Such compatible materials are desired to provide additional cleaning, foaming or antibacterial properties depending on the particular type of surfactant and are selected accordingly. These cleaning materials are usually water-soluble compounds,

and they can be anionic, nonionic or cationic. It is generally preferred to use the water-soluble, synthetic, organic surfactants which are not soaps. Suitable cleaning materials are known and include e.g. the water-soluble salts of higher fatty acid monoglyceride monosulfate (eg sodium coconut fatty acid monoglyceride monosulfate),

higher alkyl sulfate (eg sodium lauryl sulfate) or alkyl aryl sulfonate (eg sodium dodecylbenzene sulfonate or higher fatty acid esters of 1,2-dihydroxypropane sulfonate) etc.

Additional surfactants include i

essentially saturated, higher, aliphatic acylamides of lower, aliphatic aminocarboxylic acid compounds, such as those having 12-16 carbon atoms in the acyl radical. The amino acid part is generally written from the lower, aliphatic, saturated monoaminocarboxylic acids with 2-6 carbon atoms, usually from the monocarboxylic acid compounds. Suitable compounds are the fatty acid amides of glycine, sarcosine, alanine, 3-aminopropanoic acid or valine with 12-16 carbon atoms in the acyl group. However, it is preferred to use N-lauroyl-, -myristoyl-

or -palmitoylsarcoside compounds to achieve optimal effects.

The amide compound can be used in the form of the free acid or preferably in the form of its water-soluble salts,

such as the alkali metal, ammonium, amine or alkylolamine salts. Specific examples of these are the sodium or potassium N-lauroyl, myristoyl or palmitoyl sarcosides, ammonium or ethanolamine N-lauroyl glycide or alanine. For convenience, reference to "aminocarboxylic acid compound" or "sarcoside" etc. shall apply to such compounds which have a free carboxyl group, or the water-soluble carboxylate salts.

Such materials are used in pure or substantially pure form. They should be as free as practicable from soap or similar higher fatty acid material which tends to reduce the activity of these compounds. According to common practice, the amount of such a higher fatty acid material is less than 15% by weight of the amide and insufficient to significantly adversely affect it, preferably less than 10% of the amide material.

Various other materials can be incorporated into the tooth creams according to the invention. Examples of these are coloring or whitening agents, preservatives, stabilizers, tetrasodium pyrophosphate, silicones, chlorophyll compounds or ammoniacal materials, such as urea, diammonium phosphate or mixtures thereof. These auxiliary additives are incorporated into the present toothpastes in quantities which will not significantly adversely affect the desired properties and characteristics, and they can be suitably selected and used in normal quantities.

For certain purposes, it may be desirable to incorporate antibacterial agents into the toothpastes according to the invention. Typical antibacterial agents that can be used in amounts of 0.001-5, preferably 0.05-1, % by weight of the dentifrice include

N<1->4 (chlorobenzyl) - N<5> - (2,4-dichlorobenzyl)-bigunaid, p-chlorophenylbiguanide,

4-chlorobenzyhydrylbiguanide,

4-chlorobenzyhydrylguanylurea,

N-3-lauroxypropyl-N<5->p-chlorobenzylbiguanide, 1,6-di-p-chlorophenylbiguanidehexane,

1-(lauryldimethylammonium)-8-(p-chlorobenzyldimethylammonium)-octane dichloride,

5,6*dichloro-2-guanidinebenzimidazole,

N<1->p-chlorophenyl-N<5->laurylbiguanide,

5-amino-1,3-bis(2-ethylhexyl)-5-methylhexahydropyrimidine

or their non-toxic acid addition salts.

Any suitable flavoring or sweetening materials can be used to flavor the dentifrices according to the invention. Examples of suitable flavoring materials include the flavoring oils, e.g. oils of spearmint, peppermint, wintergreen, sassafras, clove, sage, eucalyptus, marjoram, cinnamon, lemon or orange, and also methyl salicylate. Suitable sweeteners include sucrose, lactose, maltose, sorbitol, sodium cylamate, sodium saccharin dipeptides according to US patent document 3939261 or oxathiazone salts according to US patent document 3932606. It is advantageous that the flavoring and sweetening materials together comprise 0.01-5% or more of the dentifrices according to the invention.

The toothpastes must have a pH that allows them to be used in practice. A pH range of 5-9 is particularly favorable. The reference to pH applies to the pH determined directly on the toothpaste. If desired, such materials as benzoic acid or citric acid can be added to regulate the pH in general to e.g. 5.5-6.5.

The toothpaste is typically packaged in a collapsible tube, such as a lined or unlined aluminum or lead tube, or in laminated tubes in general.

In the examples below, the toothpastes were produced in the usual way, and all quantities of the various constituent parts are based on weight if nothing else is stated.

In Examples 1-3, mixed gelling agent, calcium phosphate and a single or binary starting material for fluorine were used.

Example 1

The following toothpastes are produced using usual methods for the production of toothpastes, where the sodium carboxymethylcellulose and hydroxyethylcellulose components are added separately to a previously formed mixture of glycerol and water. They are filled in aluminum toothpaste tubes and aged dynamically by extruding a 2 cm toothpaste band twice a day and five days per week for two weeks.

After dynamic aging for two weeks, the surfaces of the toothpastes are smooth and rheologically acceptable. The creams do not form a tail when extruded from the tube and show good stability on toothbrushes.

Similar rheological effects occur at a weight ratio between the sodium carboxymethyl cellulose and the hydroxyethyl cellulose of 3:2.

When the recipes are changed so that the weight ratio between carboxymethylcellulose is greater than 3:2 (7:3 and 10:1), surface roughness is observed during dynamic aging. When only the sodium carboxymethylcellulose is present as gelling agent

(0.9 part), the surface may become rough after dynamic aging i

Two weeks.

When the amount of sodium carboxymethyl cellulose in relation to the hydroxyethyl cellulose is below 2:3, the toothpastes will not show good stability, but will quickly settle in the form of flat bands. Moreover, when the extrusion is finished,

the bands will form tails. Tailing also occurs when the hydroxyethyl cellulose is the only gelling agent.

Example 2

The toothpaste A according to example 1 is changed by using 0.36 part sodium carboxymethylcellulose and 0.54 part hydroxyethylcellulose. The surface is smooth, the toothpaste does not form a tail, and it has good stability.

Example 3

The toothpaste A according to example 1 is changed by using 0.45 part sodium carboxymethylcellulose (7 MFD) and 0.45 part hydroxyethylcellulose (250 M). The surface is smooth, and the toothpaste does not show tail formation and has good stability.

A similar desired rheology is observed when the toothpaste A according to example 1 is changed by using 0.5 part sodium carboxymethylcellulose (7MF) and 0.5 part hydroxyethylcellulose (250 MR) together with 0.25 part tetrasodium pyrophosphate.

Similar effects to those described in Examples 1-3 are obtained when other grades of sodium carboxymethylcellulose (eg 7m::f, Walocel<®> CRT 1000 PAA 107, "Nymcel" XMF.33 or "Akucel" AC 632) and of hydroxyethylcellulose (e.g. Natrosol<®> 250 HR, Natrosol<®> 2 50 HHR or Tylose<®>H4000P) are used.

Analogous effects to those described in examples 1-3 are obtained when 1.15 parts of sodium monofluorophosphate are present and sodium fluoride is omitted.

Claims (5)

1. Toothpaste, characterized in that it comprises a compound which provides at least 100 ppm fluorine and is selected from the group consisting of sodium monofluorophosphate and a mixture of sodium monofluorophosphate and sodium fluoride in which 30-40% by weight of fluorine is obtained from the sodium fluoride, 40-75% by weight of polishing agent containing a calcium phosphate in an amount of at least 35% by weight of the toothpaste, a dentifrice carrier comprising 20-80% by weight, based on the weight of the toothpaste, of a liquid phase containing water, humectant or a mixture thereof, and 0.5-5.0% by weight, based on the weight of the toothpaste, of a gelling agent containing sodium carboxymethylcellulose and hydroxyethylcellulose, each of which is present in a 3:2-2:3 weight ratio with respect to the other. 2. Toothpaste according to claim 1, characterized in that the gelling agent contains sodium carboxymethylcellulose and hydroxyethylcellulose in a weight ratio of 49:51-2:3. 3. Toothpaste according to claim 2, characterized in that 75 0-2,000 ppm ionic fluorine is obtained from a fluorine starting material consisting of sodium monofluorophosphate or a mixture of sodium monofluorophosphate and sodium fluoride in which 30-40, preferably 30-35, weight% of the fluorine is obtained from the sodium fluoride. 4- Toothpaste according to claim 2 or 3, characterized in that dicalcium phosphate is present as a polishing agent in an amount of 40-50% by weight. 5. Toothpaste according to claims 1-4, characterized in that the sodium carboxymethyl cellulose has a viscosity of 300-500 eps and the hydroxyethyl cellulose a viscosity of 4500-6500 eps, each viscosity having been determined by measurement with a Brookfield viscometer at 25°C for a 2% aqueous solution.