GB2144333A - Functional agglomerated speckles, dentifrices containing them, and processes and apparatuses - Google Patents

Abstract

Functional agglomerated speckles, for incorporation in dentifrices, include agglomerates of a water insoluble powdered functional material and water insoluble, ethanol soluble ethyl cellulose, and may sometimes preferably also include a water soluble binder, such as polyvinyl pyrrolidone. These speckles are formed into a stream, which is directed on to a stream of a dental composition so that the speckles are insufficient to cover the stream of the dental composition, whereby the 2 streams are adhered together to produce a dentifrice. <IMAGE>

Description

1 GB 2 144 333 A 1

SPECIFICATION

Functional Agglomerated Speckles, Dentifrices Containing Them, and Process and Apparatuses The present invention relates to functional agglomerated speckles for incorporation in dentifrices. More particularly, it relates to such speckles and to dentifrices containing them, wherein the speckles are made from a water insoluble powdered functional material, such as a dental polishing agent, and water insoluble, ethanol soluble ethyl cellulose, preferably with a water soluble binder, such as polyvinyl pyrrolidone. The invention also relates to processes and apparatuses for manufacturing such speckles and such dentifrices and to such dentifrices packaged in dispensing containers, such as transparent or translucent containers through which the speckles in a transparent or translucent gel dentifrice may be viewed. To obtain desired visual effects the speckles will usually be of a colour which contrasts with the rest of the dentifrice.

Prior art toothpastes and gels which incorporated contrastingly coloured speckles are known. Although such speckles in some cases are primarily for aesthetic effects, they may be based on functional components, such as polishing agents. In the past various speckled dentifrices have included speckles which were initially palpable but became impalable during toothbrushing. Although such products have met with technical approval it has also been found desirable to market another type of speckled dentifrice, like that of this invention, in which the 100 speckles, although readily visible and discrete, are impalpable initially, as well as subsequently, during brushing of the teeth.

Dentifrices containing visible and palpable, substantially water-insoluble, agglomerated 105 particles of polishing agents have been described in the prior art. Binding agents have been mentioned as employed in the manufacture of dental speckles and among the water soluble binders methyl cellulose and polyvinyl pyrrolidone 110 WVP) have been mentioned. However, methyl cellulose is water soluble and therefore does not provide a speckle which maintains integrity during lengthy processing. A dentifrice containing encapsulated sweetener has been described in the art, wherein ethyl cellulose was mentioned among various other materials useful for coating the sweetener to make the spheres. Water soluble and water insoluble binders for dental speckles have been disclosed together in the art but ethyl cellulose was not mentioned in such disclosure. Toothpaste formulations having dispersed therein visible agglomerated particles of dental polishing agent are known and advantages of both water soluble and water insoluble agglomerating or binding agents were recognized but ethyl cellulose was not suggested for use as a binder in such disclosures. Microencapsulation of sodium fluoride by lower alkyl cellulose, such as ethyl cellulose, and dispersing of the capsules in a dentifrice has been suggested but such suggestion was not relevant to agglomerating materials to produce dental speckles.

The present invention is one wherein ethyl cellulose, which is water insoluble but ethanol soluble, is utilized as an agglomerating agent for a functional water insoluble powdered dentifrice material made into dentifrice speckles of improved properties. Prior speckles, made with water soluble binders, such as methyl cellulose, could disintegrate during processing after mixing in with other dentifrice components, such as those in previously formulated gel or paste media, if the speckled dentifrice was held too long in the processing equipment, which can happen, as when mechanical breakdowns of processing equipment occur. Such losses of integrity of the speckles could take place because such dentifrices contain water, which can solubilize the water soluble binders of the speckles and lead to separation of the component particles of the speckles. The dissolving of the binder can be minimized in such cases by prompt processing but when filling line holdups cause processing times to be increased losses of product could result. Dentifrice speckles made with ordinary water insoluble binding agents, as disclosed in the art (such art does not disclose ethyl cellulose), when dispersed in dentifrice gels or pastes tend to be palpable, and although that may often be desirable, in some dentifrices, e.g. those intended for use by persons with sensitive gingiva, it is not.

The ethyl cellulose employed as a binder for functional speckles in accordance with the present invention satisfactorily maintains the integrity of the speckles in aqueous dentifrice media for a sufficiently long time to allow processing after incorporation of the speckles in the dentifrice. Yet, apparently because of the presence of components of the dentifrice which tend to soften the speckles on storage, such as flavouring agents, and in some cases, surface active agents, the speckles in the dentifrice are softened sufficiently during storage so that, although they maintain their integrity and independence and their distinctly separate appearances until the product is used, they are impalpable and are readily disintegrated during toothbrushing.

In some preferred formulations, such as those which may contain lesser proportions of flavouring agents (and dental detergent and any other solvents or lipophiles) or in those dentifrices including materials of lower solubilizing (for ethyl cellulose) properties, the presence of an auxiliary binder which is water soluble, e.g. PVP, can produce the desired impalpability. Still the speckles' integrity will be maintained due to the presence of the ethyl cellulose.

Once made, preferably by a process which comprises -moistening- a water insoluble functional material in powdered form (or a mixture of such functional powder and water soluble binder) with a solution of water insoluble 2 GB 2 144 333 A 2 ethyl cellulose in a volatile solvent, compacting, converting to particulate form and drying, the speckles may be controllably directed onto a stream oi dentifrice and adhered thereto to distribute them evenly, and preferably certain apparatuses will be used.

In accordance with the present invention functional agglomerated speckles, for incorporation in dentifrices, comprise agglomerates of a water insoluble powdered 75 functional material and water insoluble, ethanol soluble ethyl cellulose, sometimes preferably with a water soluble binder also being present.

The functional agglomerated speckles are comprised of two essential components, a water insoluble powdered functional material and a water insoluble, ethanol soluble ethyl cellulose.

The first may be characterized as the functional bodying agent and the second as the binder.

Various functional materials, all of which are preferably water insoluble, or at least, slowly soluble, can be employed, including colourants, such as pigments, germicides, ion exchange agents, polymeric materials (which may contain other active components, sometimes water soluble materials), and flavourings, but it is highly preferred that the functional base material for the speckles be a polishing agent or include a major proportion thereof. Of the polishing agents, normally utilized in dry powder form to make the agglomerated speckles, those preferred are dicalcium phosphate, tricalcium phosphate, insoluble sodium metaphosphate, alumina, silica, magnesium carbonate, calcium carbonate, calcium pyrophosphate, bentonite and zirconium silicate, and suitable mixtures thereof. Both anhydrous or calcined forms of these materials, such as calcined alumina, and hydrated forms, such as dicalcium phosphate dihydrate, may be employed but the anhydrous or calcined materials are often preferred. Because the agglomerates will normally desirably be opaque there is no need to match refractive indices with those of the dentifrice vehicles (including other components, too) but "transparent" polishing agents, with such a matching refractive index, e.g. 1.44 to 1.47, may be used to make transparent or translucent speckles, as well as being used in making a clear gel dentifrice body containing polishing agent.

Such "transparent" polishing agents include colloidal silicas and those sold under the trademark Syloid (Registered Trade Mark), as Syloids 63, 65, 72 and 74, under the mark Santocel (Registered Trade Mark), as Santocel 100, and as Zeo (Registered Trade Mark) 49, Zeo 120 113 and Zeo 119, and Zeodent (Registered Trade Mark). Also, synthetic alkali metal aluminosilicate complexes may be particularly useful, because they have refractive indices close to those of dental vehicles including water, glycerol, 125 sorbitol and gelling agent, which are those normally employed in the manufacture of dentifrices.

The water insoluble, powdered functional material utilized to make the present speckles will 130 normally be of initial particle sizes in the range of 0.5 to 20 microns, preferably being within the range of 1 to 10 microns, and more preferably of 2 to 8 microns. However, in some instances larger particle sizes may be employed, as when the agglomerating operation tends to size-reduce some of the powder, as may happen in mixing before actual agglomeration begins.

The binding agent for the present speckles is ethyl cellulose. This effective binder is water insoluble but is soluble in ethanol, and is gradually soluble in an aqueous glycerol-sorbitol medium which also contains "solvents" for it, such as flavourings and surfactants, which are usually present in the dentifrices of this invention. Such ethyl cellulose will usually have an ethoxy content in the range of about 45 to 50%, preferably 48 to 50% or 48 to 49.5%. In a preferred ethyl cellulose, such as that marketed by The Dow Chemical Company under the trade name Ethocel Standard 10 Premium Ethyl Cellulose, the ethoxyl content is in the range of 48.0 to 49.5%; the viscosity is 9 to 11 centipoises; the moisture content is 2% maximum; chloride, as NaCl is 0.15% maximum; and ash content is 0.15% maximum.

Ethyl cellulose resins suitable for use as binders for the present speckles are available commercially as white to light tan granular powders of a degree of etherification such that there are 2.25 to 2.58 ethoxy groups per anhydroglucose unit, which corresponds to 45.0 to 49.5% ethoxy content (by weight). Of two such grades of ethyl cellulose the materials which are preferred for the practice of the present invention have ethoxy contents in the range of 48.0 to 49.5% (by weight), and less preferred materials ars of ethoxy contents in the 46.0 to 46.5% range. Of course, such products are available in different viscosity ranges, usually from 3 to 110 centipoises, with the less preferred material tending to be more viscous.

The preferred or "standard" grade of ethyl cellulose tends to be soluble in aromatic hydrocarbons, hydroaromatic hydrocarbons, chlorinated aliphatic hydrocarbons and naval stores. It is also soluble in monohydric aliphatic alcohols, such as ethanol; monohydric cyclic alcohols, such as benzyl alcohol, phenylethyl alcohol and pine oil; ether alcohols, such as glycol ethers; ethers, such as diethyl cellosolve; esters, especially acetates, such as isopropyi acetate and see-amyl acetate and esters of hydroxy acids, such as methyl salicylate; and ketones, such as cyclohexanone and acetophenone. Generally, the less preferred or "medium" ethoxy grade of ethyl cellulose is less soluble than the standard grade and so may be more suited for use when greater proportions of solubilizing materials are present in the dentifrice formulation.

The water soluble binders which are useful for making the combination binder sometimes preferably utilized for production of the speckles of this invention include, among others, gum acacia; gelatin; starches, both natural and 3 GB 2 144 333 A 3 modified; alkali metal carboxymethyl celluloses, particularly sodium carboxymethyl cellulose; polyethylene glycols; sugars, such as glucose and sucrose; methyl cellulose; carboxyethyl hydroxyethyl celluloses; alginates, particularly sodium alginate; polyvinyl alcohol; carrageenam, preferably Irish moss; xanthan gums, gum tragacanth; and PVP. It has been found that PVP is stable in the presence of ethyl cellulose, does not bleed excessively from the speckles in which it is incorporated as a binder in combination with ethyl cellulose, and lends itself to use to adjust the binding properties of the combination binder, so as to make such binder readily adaptable for employment in the same desired total proportion in a variety of dentifrice formulations, wherein the proportion of ethyl cellulose to PVP may be adjusted accordingly. Also important is the characteristic of the combination binder in the speckles of the present invention of being 85 sufficiently hard and firm so that during processing the speckles do not dissolve excessively and yet are sufficiently softenable on storage in the dentifrice in which they are incorporated so that they become impalpable by the time the dentifrice is used. They do not soften excessively so as to cause streaking in the tube or during discharge, but by adjustment of the proportion of ethyl cellulose to PVPI increasing the PVP, controlled streaking, if desirable, may sometimes be obtained.

PVP will usually be of molecular weights in the 30,000 to 50,000 range and the PVP preferably employed in the present invention is of a molecular weight of about 40,000. Such a 100 product, which is marketed by GAF Corporation under the trademark Plasclone (Registered Trade Mark), as Plasdone K 29-32 and K 26-28, has average molecular weights.designated by indicated K values, with K-30 being equivalent to about 40,000. PVP is available as a light coloured powder containing less than 5% moisture, 12.6+0.4% of nitrogen, less than 2 parts per million of arsenic and less than 20 p.p.m. of heavy metals. It is soluble in cold water and in a variety 110 of organic alcohols, acids, ether-alcohols, ketonealcohols, chlorinated hydrocarbons, esters and ketones, but is insoluble in hydrocarbons and some ethers, chlorinated hydrocarbons, ketones and esters. it is compatible with various natural and synthetic resins, and inorganic salts and with many synthetic organic detergents, including those commonly employed as dental detergents, e.g sodium higher fatty alcohol sulphates and poly-loweralkoxylated alcohol sulphates.

Although it might have been expected that the best speckles would be made from the least soluble binder material, it has been found that ethyl cellulose, as described herein, makes speckles of ideal properties, which maintain their individuality and integrity while being processed and during storage, but which are also essentially impalpable during use of the dentifrice in brushing. If desired, the character of the speckles may be changed, as by modifying the degree of ethoxy content of the ethyl cellulose and/or by blending with it other substantially water insoluble binders of known types. Similarly, as when the content of lipophilic materials in the dentifrice (less speckles) is less, so that the speckles are less likely to become impalpable on storage, water soluble binder, e.g. PVP, may be used with the ethyl cellulose to increase the softening of the speckles. Such regulation of speckle properties may also be effected by using more water soluble binder(s) or more of such binder(s) or by changing the molecular weight thereof (as by lowering the molecular weight of the PVP). The properties of the speckles may also be regulated by adjusting the proportions of functional material and the binder, as will be referred to subsequently. Thus, agglomerates may be made which will be stable during processing after mixing, such as deaerating and filling, yet which will break up rapdify after the dental cream is extruded from its container or, if desired, such breaking up may be retarded so that the agglomerates will feel harder and somewhat firmer to the user during brushing of his teeth. It is normally highly preferable for the speckles to be essentially impalpable on use, while still maintaining their identity in the dentifrice.

The binder will normally be of particle size like that of the functional powdered material of the speckles, especially if the agglomerates are to be made, at least in part, by compacting of powdered materials. Because normally the speckles will be made by utilizing an alcoholic solution of the ethyl cellulose, the particle sizes thereof may be of relatively little importance. However, when water soluble binder is present it is considered that its sizes are preferably like those of the functional material.

The speckles, while sometimes white or colourless and possibly even translucent or transparent, or approaching such appearances, may also be coloured, normally due to containing a suitable proportion of dye or pigment or a mixture of dyes and/or pigments. Any non-toxic dye or pigment of a suitable colour, usually a strong colour, such as one of a suitable hue, with a Munsell chroma greater than 4 and a Munsell value in the 4 to 7 range, may be utilized, and in some instances weak colours or pastels maybe satisfactory or desirable. it is usually best to employ a dye or pigment which is approved for drug and cosmetic use (D&C) or for food, drug and cosmetic use (FD&C), Representative of suitable dyes are D&C Reds No's 2, 3, 6, 7, 8, 9, 10, 11, 12 13,19,30,31, 36 and 37; D&C Blue No. 1; FD&C Blues No's 1 and 2; FD&C Reds No's 1, 2 and 3; FD&C Yellow No. 5; cosmetic green oxide; and cosmetic red oxide. Pigments of the foregoing dyes, known as lakes, are also suitable for use in colouring the speckles but normally the dyes will be preferred. The above mentioned pigments are often composed of dyes supported on a finely powdered insoluble carrier and the pigments are dispersed rather than dissolved in the medium to 4 GB 2 144 333 A 4 be coloured. The particle sizes of pigments employed may be within the range previously given for the polishing agents or may be sized like the binder. Sizes may be finer, e.g. in the 0.01 to 1 micron range. Particle sizes of dyes may be similar but because they are normally employed in a dissolved state, in water or solvent, preferably being oil soluble and being dissolved in the appropriate solvent, sizes are not important as long as the powder or particles are small enough so as to make the dye readily soluble in the solvent chosen.

The speckles of this invention may be made by any suitable method, either wet or dry processes.

When ethyl cellulose is the sole binder and a wet granulation process is employed the ethyl cellulose, in dry powder form, is first preferably blended with polishing agent and dye or pigment, if present, and ethanol. Water and/or lipophilic solvent may be present with the ethanol and a dye or pigment for colouring the speckles may also be present. Alternatively, and often preferably, an ethanol solution of ethyl cellulose may have a suitable dye or pigment and the polishing agent admixed with it. The proportions of components will be such as to result in speckles of the desired composition and from the proportion of solvent(s) will normally be from 5 to 50% of the mix, preferably 5 to 25% thereof. The production of the dispersion may be by means of a Hobart mixer, Dravo pan, or other suitable mixing device or granulator for wetting powder(s), and the order of addition of the various components of the dispersion may be adjusted as best benefits the mixing or blending apparatus employed. A preferred way of producing the speckles is by forcing the "wetted" mix of polishing agent and ethyl cellulose (with dye or pigment, if used) through a screen having uniform openings, which usually will be in the range of 105 about 150 to 2,000 microns (about in the No. 10 to 100 sieve range, U.S. Sieve Series) and the 11 extruded" agglomerates are then dried, usually either in air or in an oven. Instead of screens other means, such as pressure extruders, may be employed for extruding or otherwise pelletizing the mix, after which the particles resulting are dried. The particles are then classified into desired size range, normally in the No's. 10 (having openings 2.0 mms across) to 80 (having openings 177 microns across), preferably No's. 40 (having openings 0.42 mms across) to 80 and more preferably No's. 30 (having openings 0.59 mms across) to 60 (having openings 0.25 mms across) (U.S. Sieve Series). Of course, if the wet mass is formed in a Dravo pan the forced screening or other extruding may be omitted. Generally, when the particle sizes are larger than 2,000 microns (No. 10 sieve) they will be less satisfactory for introduction into the oval cavity of a user and when less than about 177 microns in diameter (No. 80 sieve) they will not be as readily apparent and hence, will not be of as attractive an appearance.

Instead of employing the wet granulation 130 process a dry or slugging process may be utilized, wherein the components of the speckles may be pressed to large tablet size and such tablet may then be broken up, with particles thereof in the desired size range being separated from the others. In such tableting process it may be desirable to employ a water insoluble lubricant. Such as talc, magnesium stearate, calcium stearate or stearic acid, which also helps to facilitate agglomeration. Similarly, such materials and other water insoluble adjuvants may be present when wet granulation methods are used. The speckles made are preferably dry, containing no moisture, but moisture contents of up to 10%, e.g. 1 to 5%, may be present without causing any serious adverse affects on the properties of the speckles.

The proportions in the speckles of water insoluble powdered functional material, such as dental polishing agent, and binder, such as ethyl cellulose or ethyl cellulose plus water soluble binder, will be such that the binder will be the minor component of the speckles and the powdered functional material will be the major component thereof (although allowance should be made for the presence of other materials too, such as colours and adjuvants). Generally, the dental polishing agent of functional material is from 75 to 80 to 98% of the speckles, preferably 85 to 97% thereof, the binder or combination of binders will be 2 to 20% of the speckles, preferably 3 to 15% thereof and the colourant will be 0 to 5% of the speckles, such as about 0.05 to 1 % thereof, all on a dry basis, free of water and ethanol or other solvent. When the combination of binders is present the proportion of ethyl cellulose to water soluble binder (PVP) is in the range of 1:10 to 10:1, preferably 1:5 to 5:1, more preferably 1:2 to 2:1, and most preferably 1:2 to 1:2, e.g. 2:3.

The dentifrice in which the speckles are distributed may be any suitable such product, because in the present invention in acts primarily as the medium for the speckles, maintaining them independent, individual and separate, while performing its normal dentifrice functions. Opaque dentifrices are useful media for the present speckles but it is highly preferred that the dentifrice be transparent or translucent and normally be of a type characterized as a gel. Dentifrices normally comprise water, humectant, gelling agent, dental detergent and a dental polishing agent, usually with flavouring and/or colouring too. Among various functional adjuvants are fluorides, stabilizers, anti-caries agents and antibacterial compounds.

The water employed will preferably be deionized water, although city waters, both soft and hard, may also be utilized. The gelling agent is normally a water soluble natural or synthetic gum or gum-like material, among which are carrageenan, gum tragacanth, xanthan gum, alginates, alkali metal carboxymethyl cellulose (preferably sodium carboxymethyl cellulose), hydroxymethyl carboxyethyl cellulose, polyvinyl GB 2 144 333 A 5 pyrrolidone, starch, and hydrophillic colloidal carboxyvinyl polymers, such as those sold under the trademarks Carbopol (Registered Trade Mark) 934 and 940. Although various polyols may be utilized as humectants those preferred are of 3 to 6 carbon atoms and 3 to 6 hydroxyl groups per molecule, and those of choice are glycerol and sorbitol. The glycerol is in normal liquid state, generally being about 99% or more pure, and sorbitol, normally being a solid, is frequently utilized as a 70% aqueous solution thereof (70% sorbitol, 30% water). The three mentioned components may be considered as the main constituents of the dentifrice vehicle, in which flavour and detergent may also be incorporated.

Such detergent may include a soap but normally will be a non-soap synthetic organic surface active agent having detersive properties.

Preferably such detergent will be of the anionic type, although nonionic detergents are also useful, ampholytic detergents can be employed, and cationic detergents can be acceptable under some circumstances.

The preferred anionic detergents are specially useful because they combine excellent cleaning 90 action and foaming properties. Normally, such compounds include hydrophilically and lipophilically balanced moieties, with the lipophilic moiety usually being a higher fatty alkyl or allyl of 10 to 18 carbon atoms, preferably 12 to 16 carbon atoms, and the hydrophile being alkali metal, e.g. sodium, potassium, or ammonium or lower alkanolammonium. Suitable such anionic detergents are: the water soluble salts (normally alkali metal and preferably sodium or potassium) 100 of higher fatty acid monoglyceride sulphates, such as the sodium salt of the monosulphated monoglyceride of hydrogenated coconut oil fatty acids; higher alkyl sulphates, such as sodium lauryl sulphate; alkylaryl sulphonates, such as sodium linear dodecyl benzene sulphonate; higher alkyl sulphoacetates; higher fatty acid ester 1,2dihydroxypropane sulphonates; the sodium salts of sulphated polyethoxylated alcohols; and the substantially saturated higher aliphatic acylamides of lower aliphatic aminocarboxylic acid compounds, such as N-lauroyl sarcosine, and the sodium, potassium and ethanolamine salts of N-lauroyl-, N-myristoyl-, and N-palmitoyl sarcosine, all of which sarcosine compounds are 115 preferably substantially free from soap or similar higher fatty acid material. Among the nonionic detergents, ethoxylated sorbitan monostearate, with approximately 20 mols of ethylene oxide per mol; condensates of ethylene oxide with propylene oxide and propylene glycol (such as those sold under the name Pluronic (Registered Trade Mark)); polyethoxylated higher fatty alcohols, such as those sold under the name Neodol (Registered Trade Mark) (23-6.5 and 45 125 11, for example); and condensation products of a lpha-olefin oxides containing 10 to 20 carbon atoms, polyhydric alcohols containing 2 to 10 carbon atoms and 2 to 6 hydroxyl groups, and either ethylene oxide or heteric mixtures of 130 ethylene oxide and propylene oxide, are useful. Quaternized imidazoyl derivatives, such as Miranol (Registered Trade Mark) C2M, and other Mironals represent useful amphoteric detergents and the quaternary ammonium halides, such as dimethyl dicetyl ammonium bromide, represent cationic detergents.

The various polishing agents, which are dispersed in the dentifrice vehicle (or vehicle plus detergent and any other adjuvants) are those previously described for conversion to speckle form. Also useful in such group of materials are synthetic finely divided silicas, such as those sold under the trademarks Cab-O-Sil (Registered Trade Mark) M-5, Syloid 244, Syloid 266, Aerosil (Registered Trade Mark) D-200, Zeosyl (Registered Trade Mark) 200 and Zeothix (Registered Trade Mark) 265, which are normally utilized for only a small percentage of the polishing agent, normally being no more than 1 to 9% by weight of the total dentifrice, and which are useful for thickening or gelling the vehicle and improving the clarity of the dentifrice.

The dentifrices of this invention will normally contain suitable flavouring and/or sweetening materials. Examples of flavours include the flavouring oils, such as those of spearmint, peppermit, wintergreen, sassafras, clove, sage, eucalyptus, cinnamon, lemon and orange, and the sweeting agents include sucrose, lactose, maitose and saccharin. Desirably for fluoride dentifrices there will also be present sodiumfluoride, stannous fluoride. potassium fluoride, potassium stannous fluoride, sodium hexafluorostannate, stannous chlorofluoride and/or sodium monofluorophosphate.

The flavouring materials include various well known essential oils, mainly terpenes; esters, alcohols, aldehydes, ketones, and other aromatic substances, many of which emit aromatic odours and fragrances. Because flavour is a simultaneous physiological and psychological response obtained from the present of a substance in the mouth and depends on the senses of taste, smell and feel, with smell often being of primary importance, it is not surprising that aromatic materials are important components of flavours. In the present case advantage is taken of this fact and of the chemical natures of such materials which, as was previously indicated in the discussion of solubilities of ethyl cellulose, permits the ethyl cellulose binder in the present speckles to be slowly solubilized by the solubilizing substances in the flavouring material, causing softening of the speckles but not causing their disintegration. For example, the terpenes, which are hydrocarbons and which constitute an important class of perfumery orflavour materials, are good solvents for the ethyl cellulose of this invention, as are many other flavouring materials, such as those previously named (as flavouring oils) above, and others well known to the perfumery and flavouring arts. By utilizing the flavouring essences in the dentifrice composition to soften the ethyl cellulose speckles and thereby 6 GB 2 144 333 A 6 make them impalpable, which is an aim of this invention, it is unnecessary to add another component to the dentifrice or the speckles for this purpose. Also, because of the relatively small proportion of flavouring material normally present in a dentifrice, with the proportion of the lipophilic part of the flavour often being lower, a desirable slow softening of the speckle particles can result, usually due to a relatively low mass transfer rate for the -solvent- material, which transfer rate is especially slowed due to the gelatinous nature of the dentifrice. Thus, even if some flavouring material at the interface with the speckle started to soften the ethyl cellulose thereof while the dentifrice was being blended, the flavour solution of ethyl cellulose would soon become saturated and thus would inhibit further quick dissolving of the ethyl cellulose. Still with the passage of the normal time a dentifrice spends in storage before sale and use, which time will often be at least about 2 weeks and sometimes more (with certain dentifrice formulas it is desirable to allow them to age to improve flavour and product uniformity), the speckles become impalpable, yet remain distinct.

In the preceding discussion references were made to the ethyl cellulose binder but it is recognized that sometimes a water soluble binder, such as PVP, will also be present and the references were also meant to apply to such speckles and speckled dentifrices. In such products the ethyl cellulose holds the speckle together until it is -solubilized- by the lipophiles in the dentifrice, and the PVP allows less ethyl cellulose to be used and facilitates the desired softening of speckles in dentifrices containing lesser proportions of solubilizing flavouring and other lipophiles.

Although it is considered that the flavouring materials, particularly the lipophiles, which exert substantial solvent action on ethyl cellulose, are the most important slowly solubilizing components of the present dentifrice, the surface active agent component, which includes a lipophilic moiety, may also have an appreciable solubilizing effect and by means of its wetting action, may promote mass transfer in a dentifrice tube and thereby increase the solubility rate of the ethyl cellulose. It is also possible that combinations of other constituents of the 115 dentifrice, including some of the sweetening agents and vehicle components, will further assist in solubilization of the ethyl cellulose to the extent desired, while not promoting premature softening of the speckles.

Colourants, such as those previously mentioned with respect to the speckles, may be employed, normally in lesser proportion, so as to provide a base which contrasts with the speckles.

Various other adjuvant materials may be present in the dentifrice, including preservatives, silicones, chlorophyll compounds and ammoniated materials. Normally, when a gel dentifrice is made which is intended to be transparent or translucent, the polishing agent chosen will be one having an index or refraction closely matching that of the rest of the dentifrice medium. Of course, in such clear gel formulations the amount present of insoluble materials which would cloud the gel will normally be minimized. When the pH of the dentifrice is adjusted, (the pH desirably being within the range of 3 to 10, more desirably from 3.5 to 5 when stannous ions are present, and 4.5 to 7 in the absence of such ions), organic acids, such as citric, malonic, and fumaric acids, may be employed.

In the dentifrice of this invention a dental polishing agent is uniformly distributed throughout the vehicle of water, humectant and gelling agent, with a dental detergent and the desired proportion of flavour already in it. Then the spedkies, which also preferably contain a polishing agent (and often of a different type from that in the body of the dentifrice), are uniformly distributed throughout the dentifrice, usually comprising 0. 1 to 10% of the dentifrice, preferably 0.5 to 5% thereof, more preferably 1 to 3% thereof and most preferably 1.5 to 2.5% thereof. The dental base will usually comprise:

about 5 to 30% water, preferably 10 to 25% and more preferably 10 to 20%; about 20 to 70% of humectant, preferably polyol humectant, more preferably 45 to 65% thereof and most preferably 50 to 60% thereof; and about 0. 1 to 5% of gelling agent, preferably 0. 1 to 1 % and more preferably 0.2 to 0.5% thereof. The humectant is preferably a mixture of glycerol and sorbitoi wherein the glycerol content is 5 to 40% of the dental base, preferably 20 to 30%, and the sorbitol content is 5 to 50%, preferably 25 to 35%. The preferred gelling agent is sodium carboxymethyl cellulose, and a preferred proportion thereof utilized is about 0.3 to 0.4%. The dental detergent content will normally be from 0.5 to 5%, preferably 0.5 to 3%, and a preferred such detergent is sodium lauryl sulphate. The polishing agent in the dentifrice base, exclusive of that in the speckles, is normally 10 to 40%, preferably 15 to 30% and most preferably 20 to 25%, including Syloid 244 type silicas, which are also employed for thickening. Various other materials, including flavours (usually 0.5 to 2%), colour, preservatives, sweeteners, and tooth hardeners (fluorides) will normally total no more:than 10% of the dentifrice, preferably being from 2 to 7% thereof. Utilizing the proportions of the various constituents within the ranges given, with respect to the speckles and the medium in which they are distributed, results in an attractive product which is stable during storage and in which the speckles are uniformly and attractively distributed.

To prepare the speckled dentifrice, after first producing the speckles, is comparatively simple but an important consideration is that minimal mechanical agitation should be employed so as to prevent or delay any disintegration, softening and solubilization of the speckles in the dentifrice. It is considered that lipophilic materials and solvents present, such as those in flavouring oils, will slowly solubilize ethyl ceifu lose, but not to an 7 GB 2 144 333 A 7 objectionable extent in the absence of vigorous agitation in processing. If the dentifrice is at an elevated temperature during such mixing, possibly due to manufacturing limitations in processing, it is even more important to minimize 70 agitation. However, when the ethyl cellulose binder or combination binder is used in the manufacture of the speckles, manufacturing restrictions may be less stringent, but care should still be exercised. Suitable equipment for distributing the speckles throughout the dentifrice may include conventional Banbury or dough mixers operated at low speeds but other gently operated blenders may also be used providing that mixing is controlled so as to prevent 80 substantial breakdowns, dissolvings or disintegrations of the speckles. When such mixers are used mixing blade speed will normally be of the order of one to five revolutions per minute (r.p.m.) and mixing will last from one to five minutes. After completion of the blending the dentifrice is deaerated and filled into containers, such as transparent resilient or collapsible tubes.

If vacuum is employed during mixing operations deaeration may be omitted.

Although the manufacturing apparatus and process above are standard for making speckled dentifrices, it is much preferred to employ methods that have recently been invented for facilitating blending of the speckles into the dental gel body without excessive agitation. Such processes and apparatuses, and other aspects of the present invention have been set forth in the following description and the rest of this specification, and the invention will be readily understood from these, taken in conjunction with the drawings.

Thus the invention may be put into practice in various ways and a number of specific embodiments will be described to illustrate the invention with reference to the accompanying examples and drawings in which:

Figure 1 is a perspective view of a tube of dental gel of this invention, including a removed cap, and a toothbrush; Figure 2 is a schematic representation of an apparatus in accordance with the present invention for making a speckled dentifrice from a dental composition and previously produced speckles; Figure 3 is an enlarged perspective view of a portion of the "speckling apparatus" of this invention, illustrating application of speckles to a gel stream or ribbon; Figure 4 is a schematic representation of 120 another embodiment of apparatus in accordance with the present invention for making a speckled dentifrice; and Figure 5 is an enlarged perspective view of a portion of the "speckling apparatus" of Figure 4, illustrating application of the speckles to gel streams or ribbons.

In Figure 1 there is shown a clear walled container 11, which is made of transparent polymeric material (PVC), including a body 13, a130 shoulder 15, a threaded neck 17 and a cap 19, with the cap having been removed from the tube. Although it is preferred to make the packaged dentrifice by utilizing a deformable tube of clear or translucent synthetic organic polymeric material, such as polyvinyl chloride, polyethylene, polyvinylidine chloride or similar material through which the attractive appearing speckled dentifrice may be viewed, collapsible opaque tubes, such as those of aluminium or other metal, may also be used. As illustrated, some of the dentifrice 21 is being dispensed from the tube 11 through the neck 17 onto the bristles of a toothbrush 12. In the dentifrice there are clearly shown speckles 23 in accordance with the present invention in the continuous dentifrice medium 25. It is to be noted that such speckles are initially impalpable although they are easily visible. During toothbrushing they break down into smaller entities of essentially the same sizes as the component polishing agent. Of course, the speckle polishing agent acts together with that in the dental gel to help clean and polish the teeth.

In Figure 2 there are shown gel-making vessel 111, which often preferably will be a Hobart or Dopp mixer, in which the various components of the dental composition, including vehicle, gelling agent, polishing agent, flavour, colour, detergent, preservative and any other adjuvants, are mixed together, sometimes under vacuum, to form a composition to which speckles, preferably functional speckles, such as those based on a dental polishing agent, are to be added, to make a speckled dentifrice. A variable speed motor and/or drive 113 powers a positive displacement pump 115, at a controllable speed, to deliver the gel to an outlet 117, preferably a somewhat restricted flat orifice, through which it is extruded or discharged as a flat ribbon or other suitable stream 119 onto which speckles 121, in discrete bit or particulate form, are deposited. A pump 115 may be set to control the gel feed rate and by also controlling the feed rate of the speckles the desired proportion of speckles may be continuously added to the flowing gel. Preferably the pump 115 will be one which subjects the gel to little or no shearing action, so as to maintain its consistency (viscosity), and screw pumps with walls of elastomer are preferred, such as those of the Moyno (Mono) type. The gel feeding outlet means or extruder 117 is preferably enclosed in a walled vessel or container 123 and usually will be so positioned therein that ribbons of gel containing speckles on the surface thereof, produced in such vessel, will fall vertically to the bottom thereof near the centre of the vessel, from which they may be removed through a central outlet 125.

The speckles to be added to the dental gel in prescribed proportion are contained in a hopper 127 for a controllable flow rate feeder 129, preferably a helix type, including a speed control 13 1, which feeder discharges the speckles at a desired controlled rate through an outlet 133 onto a funnel shaped directing means 135, which 8 GB 2 144 333 A 8 shapes the discharge stream of speckles as desired so that as they leave it they form a falling stream or curtain which matches the ribbon of gel flowing from the outlet 117 preferably being such that the speckles fall substantially vertically to deposit on and become adhered to the inner portion of the gel ribbon, with none missing contact wtih the gel, Preferably the speckle curtain covers a substantial part, e. g. 40 to 95% preferably 60 to 90% of the width of the gel ribbon, and the curtain should not be so wide as to result in any substantial proportion of the speckles missing the ribbon. However, it will be desirable to have the curtain be of a width only slightly less than the ribbon when feasible, e.g. 80 80 to 90%. Lines 137, 139 and 141 connect to vacuum sources 143 and 145, respectively but while the use of vacuum is desirable to prevent air bubbles from entering the dentifrice, with careful processing the infiltration of such bubbles may be avoided without the use of vacuum. After the speckled dentifrice is dropped through the outlet 126, a pump 147, which is preferably a screw pump, such as one of the Moyno type, powered by variable speed motor 149, pumps the product in a gentle manner to a static mixer 15 1, preferably of the Kenics type, where it is gently blended without disintegration or solubilization of the speckles therein, and is uniformly mixed. It then passes through a line 153 to a receiver 155, 95 which may be the feed tank for a tube filling machine, not illustrated.

In Figure 3 the gel feeding means 157 includes a delivery tube 159 and a nozzle portion 117, with such nozzle including a flat rectangularly shaped opening 16 1. The gel feeding means and the opening in the discharge "nozzle" portion thereof may be adjustable. Thus, the feed direction could be changed as desired, and the angle of discharge could be varied but the feed direction should have a horizontal component and is usually from 0 to 45 1, e.g. 10 to 30', from the horizontal. Also, the rectangular orifice can be changed in size, so as to be more restricted, but care should be exercised to keep the gel ribbon coherent so that the ribbon will not be thin beyond the gel strength. Usually it will be from 1 mm to 1 cm thick, e.g. 2 to 6 mm. The stream or ribbon of gel is directed so that the stream or curtain of speckles may fall on it correctly, 115 preferably when the speckles are falling substantially vertically and the gel is moving in a direction with a horizontal component, so that the gel passes under the failing speckles, which contact it and adhere to it. The gel ribbon 163 is shown falling downwardly and to the right, while the speckles 165 fall on to it from a discharge spout 167 of the directing means 135 (see Figure 2).

In Figure 4, there is shown a gel-making vessel 211, which may be like that of Figure 2 and functions similarly. Valves 213 and 215 in the line 217, together with a controllable speed positive displacement pump 219, allow recycling of the gel through the mixer, if desired. Lines 220 and 221, and valves 222 and 223 permit discharge of130 the dental gel (or paste) for cleaning or production of a dentrifrice not containing any speckles. The line 225 and the valve 227, when opened, with the valves 215, 222 and 223 closed and with the valve 213 open, the gel pump 219 operative and the mixing means 211 containing dental gel, allow delivery of the gel at a controlled rate to gel feeding means 229 and through the line 231 to a similar but opposing gel feeding means 233, both of which means include relatively restricted and flattened orifices or nozzles, as better illustrated in Figure 5. They also desirably include additional supporting means for the gel as it leaves the nozzles to help it maintain its ribbon shape and to guide it's flow. The pump 219 may be set to control the gel feed rate so that by controlling the feed rate of the speckles the desired proportion of speckles may be continuously added to the flowing gel. Preferably, the pump 219 will be like the pump 115, previously described. The gel feeding means or extruders 229 and 233 and the line 231 are preferably enclosed in a walled vessel or container 235 and usually will be centrally positioned therein so that sandwiches of gel with speckles in the interior thereof, produced in such vessel, will fall vertically or substantially vertically to the bottom thereof near the centre of the vessel, from which they may be removed through an outlet communicating with the line 237. The outlet (unnumbered) is at the base of the vessel and it is preferable that the gel feeding means 233 terminate near the outlet to diminish rippling of the ribbon sandwich containing speckles which can cause air entrainment (when vacuum is not employed). Also it is preferred that the outlet shape match the ribbon shape (usually flat rectangular) and be orientated with it to minimize obstructions to dentifrice withdrawal from the walled vessel, and so to minimize holdup time, air entrapment, and speckle binder solubilization.

The speckles to be added to the dental gel in the prescribed proportion are contained in a hopper 230 of a controllable flow rate feeder 232, preferably of a helix type, including speed control and motor combination 234, which feeder discharges the speckles at a desired controlled rate through an outlet of a tube 236 onto a distributor 238, which spreads them out so that, as they leave it, they form a failing stream or thin curtain which matches in size and orientation the ribbons produced by the nozzles 229 and 233. I nstead of a helical feeder, other feeders of screw, belt or vibratory types are also useful. The line 228 connects to a vacuum source, which, like the vacuum line 259 may or may not be activated or connected.

The valves 239 and 241 are provided to selectively allow dropping of the product through the line 243 or communication with the pump 245, which is preferably of the Moyno type. A screw pump 245, powered by a motor 247, pumps the product in a gentle manner through a line 249 to a static mixer 25 1, preferably of the Kenics type, where it is gently blended without 9 GB 2 144 333 A 9 disintegration or solubilization of the speckles therein, and is uniformly mixed. It then passes through a line 253 to a receiver 255, which may be the feed tank for a tube filling machine, not 5 illustrated.

Although the apparatus of the invention may be used and the process thereof may be practiced without employing vacuum, often it will be desirable to avoid the intrusion of air into the dental materials and the entire operation or any part of it may be under vacuum. Desirably, the speckles feeder and speckles "applicator" will be under vacuum and accordingly, the vacuum lines or taps 259 and 228 are indicated in the drawing.

In Figure 5 the gel feeding means 229 and 233 include nozzle portions 275 and 277 having restricted flat openings 263 and 265, respectively, with the nozzle portions, as illustrated, having connected to them supporting guides 267 and 269, respectively, which may be adjustable, and which facilitate proper directing of the ribbons or webs of gel so that the curtain or screen of speckles may fall on them correctly. The gel ribbon on the guide 267 is designated by the numeral 271 and is shown without speckles 90 having been deposited on it. A similar ribbon 272 on the guide 269 discharges its gel ribbon below the discharge from the first guide, and near to the outlet from the vessel. Preferably, the curtain of speckles drops vertically or substantially vertically onto the get ribbon 271 after that ribbon has left the guide 267 but while it is still moving in a direction with a horizontal component, e.g. at 601 from the horizontal. However, if care is exercised some speckles can be dropped onto the gel 271 while it is still in contact with the support. As the gel ribbon 271 with adherent speckles falls vertically or substantially vertically it contacts the ribbon 272 and the two ribbons sandwich the speckles between them. To avoid rippling, which can cause air entrapment, the guide 269 may preferably extend, either straight or as a convex curve, to near (usually within 5 to 25 cm) of the outlet opening from the vessel and the gel ribbon passes through the oriented and similarly shaped outlet without rippling, with the discharge rate being kept the same as the sum of the addition rates. The rates of feeds (and thicknesses) of the gel ribbons may be about the same or may be varied with such relative rates usually being within the 1:4 to 4:1 range. The controlled and proportioned feed of discrete speckles passes from the delivery tube 236 onto the distributor 238, which is shown in the form of an expanding chute, including side walls 279 and 281, bottom 283 and dividing pegs 285, located in a "Pascal's triangle" arrangement. The speckles and the gel feeding means and the openings in the discharge 11 nozzle" portions of such gel feeding means may be adjustable, as described with respect to Figure 3. The first or upper stream of speckles, usually 0.5 to 5 mm thick, may fall on it correctly, preferably when the speckles are failing substantially vertically and the gel is moving in a direction with a horizontal component, so that the 130 gel passes under the falling speckles, which contact it and adhere to it. The gel ribbon 271 is shown failing downwardly and to the right, while speckles 273 fall onto it from the distributor 238 of directing means 235 (Figure 4), and the ribbon 272 falls downwardly and to the left below the ribbon 27 1.

The described apparatuses of Figures 2 to 5 and the corresponding processes allow the manufacture of speckled dentifrices to be effected efficiently and quickly without the need for any use of any conventionally shearing mixing apparatus. Also, the speckles do not clump together and neither are they disintegrated, and because the process is a speedy one the product is quickly processed and may be filled into tubes before any appreciable softening or solubilizing of the dentifrice binder occurs. Thus, the preferred clear gel dentifrice, usually with individually visible, separate functional speckels attractively distributed therein, is obtained, without any clouding of it due to breaking up of speckles and distribution of the finely divided functional material, such as polishing agent, through the dentifrice.

Other advantages of this invention include the immobilization of the speckles with respect to the gel ribbon, and resulting lesser dissolving of any binder utilized in any solvent materials that may be present in the gel. The feeding of the gel in an arc that becomes vertical above a vessel outlet after the speckles have been deposited diminishes residence time in the apparatus before removal and thereby diminishes such dissolving,of the binder for the speckles and prevents distinegration of the speckles. Also, the sandwiching effect, as illustrated in Figures 4 and 5, results in an even better distribution of speckles in the dental material, and is especially good for dental compositions to which the speckles are not strongly adherent.

In accordance with a broad process aspect of the invention, the manufacturing of a dentifrice containing dispersed discrete speckles therein comprises producing a stream of a gel or paste dental composition containing a gelling agent which helps to make the surfaces thereof adhesive for the speckles, which dental composition constitues a major proportion of the dentifrice, producing a stream of speckles to be distributed throughout the dentifrice, directing the said stream of speckles onto a surface of the stream of the dental composition and controlling the relative feed rates and the proportions of the streams of dental composition and the speckles to be dispersed in the dentifrice so that when the stream of speckles contacts the stream of dental composition the speckles are insufficient to cover the dental composition surface, so that the speckles adhere to the dental composition stream and there is produced a dentifrice containing the speckles in desired proportion distributed in it. An apparatus for carrying out the described process comprises means for producing a moving or flowing stream of a dental composition, which is GB 2 144 333 A 10 usually a dentifrice except for speckles to be distributed therein, and is of such a nature that the speckles will adhere to it. In such an apparatus a stream or ribbon of dental gel is produced by forcing it through an appropriate orifice so that it is extruded from the said orifice in the desired shape, preferably as a flat ribbon, the stream or curtain of speckles is of particle sizes within the No. 10 to 80 sieve range, U.S. Sieve Series, the said speckles are directed onto the gel ribbon in such manner as to be distributed evenly over the inner portion of the surface of the flowing ribbon so as to adhere to the said ribbon, and the ribbon of gel with adherent speckles thereon is collected in a walled vessel from which it is continuously removed as more gel containing speckles is added thereto or created therein. In Oreferred embodiments of the invention the speckles are sandwiched between dentifrice ribbons and the speckles are formed into a uniform failing curtain by means of a Pascal's triangle arrangement of barriers.

The following examples illustrate but do not limit the invention. Throughout the specification, including the working examples, and in the claims, all parts are by weight, unless otherwise indicated.

EXAMPLE 1 A

Five parts of ethyl cellulose (10 centipoises), of the physical characteristics described previously in the specification and in powder form, were dissolved in five parts of ethanol (95%) and were mixed in a Hobart mixer with 95 parts of calcined alumina (Microgrit WCA 9F) of particle size in the range of 0.5 to 10 microns and having an average particle size in the range of 3 to 5 microns. Mixing was continued for about four minutes until the blend was uniform, after which the mix was forced through a No. 10 (U.S. Sieve Series) screen and the "extruded" material was oven dried for one hour at 651C. The dried agglomerates were then screened through a No. 30 screen and the cut that rests on a No. 60 screen, namely the dried speckles comprising the calcined alumina and ethyl cellulose, was collected. The speckles produced were of angular shapes, with the ratios of maximum length to maximum width usually being within the 1 to 2 range and most of the particles being of such a ratio within the 1.1 to 1.5 range. The angularity of the particles maybe a factor in making the dentifrices so attractive in appearance, at least for some consumers.

A transparent (or translucent) dentifrice base (all components except speckles), was made of 95 the following formula: Component Parts by Weight Glycerol (99.3% pure) Sodium carboxymethyl

cellulose Sorbitol (70% aqueous solution Polyethylene glycol 600 Water Sodium saccharin Sodium benzoate Blue dye (FDEtC Blue No. 1 % 1 % aqueous solution Sodium m onoff uorophosp hate (1 to 60 microns) Silicon dioxide (Zeo 49) Synthetic silica (Syloid 244) Sodium lauryi sulphate Flavour (spearmint, peppermint, 75 wintergreen, clove, etc., as desired) 25.00 0.35 36.04 3.00 3.00 0.25 0.50 0.20 0.76 18.00 5.50 1.20 1.20 95.00 Five parts of the described speckles, with particle sizes -30 +60 (U.S. Sieve Series), were gently blended in a slow moving mixer (about two r.p.m.) with 95 parts of the described dentifrice base, after which the mix was deaerated and automatically filled into capped collapsible tubes which were then sealed. During the mixing, deaeration and tube filling steps the speckles, which are substantially evenly distributed through the dentifrice, remains discrete, independent and undissolved in the dentifrice base so that when the tube was opened, after filling, and preferably, after storage for about a month, and the dentifrice was squeezed through the discharge opening thereof, the speckles appeared to have retained their initial integrity, contrasting with the bluish gel. When the product was evaluated immediately after filling, and without being stored, the speckles were palpable but, upon storage before GB 2 144 333 A 11 use, for period from two weeks to a year or more, were sufficiently softened, as by solubilization of the ethyl cellulose by the flavouring oil, sometimes with the aid of the dental detergent or other surface active agent that may be present, the other components, so as to appear distinct and not---smeared-,but yet to be satisfactorily impalpable. During toothbrushing with the dentifrice the speckle particles were readily reduced in size, were not irritating to the gingiva, 75 and were readily dischargeable from the oral cavity on completion of brushing.

Although the presence of the anionic detergent in the dental base may be of assistance, it is thought that the controlling component of such 80 base is the 1.2% of flavouring agent present. A proportion of such an agent or a mixture thereof from 0.5 to 2%, preferably 0.8 to 1.5%, of which at least half is normally active as a solvent for ethyl cellulose, is desirable for best speckle dispersions, and the flavour will usually include over 50% and often over 80% of solubilizing hydrocarbons, esters, alcohols and aldehydes.

The manufacturing method described for the dentifrice, in which the speckles are dispersed in the body of the gel, is one in which the mixing operation should be watched to make sure that the speckles are not disintegrating and, at any sign of this happening mixing should be halted and, providing that the dentifrice appearance is not significantly adversely affected, usually by being made unacceptably cloudy, filling of the tubes should be undertaken promptly. In steam employing the described mixing method it will often be preferable to utilize other processing techniques, previously referred to herein, wherein 100 a regulated even "fan" of speckles is deposited by means of gravity on a continuously failing extruded ribbon of gel, to which the speckles adhere, so asto obtain uniformity of distribution of the speckles in the dentifrice.

When the speckled dentifrice of this invention is packed in a collapsible aluminium tube the speckles in the dentifrice are not visible until discharge from the tube but at that time they are maintained discrete in the extruded toothpaste ribbon and impart to it an attractive and distinctive appearance. However, when instead of the normal aluminium tubes one employs resilient transparent tubes, such as tubes of polyvinyl chloride or other suitable polymer, the speckles can be seen through the tubes and through the transparent gel dentifrice base, and their movements, on discharge, can be observed. This provides an additional aesthetic benefit and helps to make toothbrushing more interesting, especially for children. Additionally, the functional 120 speckles act as a reminder to the person using the dentifrice of the presence of polishing agent or other functional constituent in the dentifrice and thereby help to remind him of the importance of brushing so that such component may be 125 effective.

The formula given above is one for a gel dentifrice in which the normal 41.04% of sorbital solution had been reduced to 36.04% to allow for the introduction of the 5% of speckles. The effect of this change in the formulation is to maintain the percentages of the other dentifrice components the same as in an unspeckled product, with the exception of the major component, the sorbitol solution. It is considered that with other variations in the contents of speckles in such dentifrices such procedure for modifying the formula may continue to be followed. However, it is also feasible to start with the initial gel formulation, e.g. containing 41.04% of sorbitol solution, and reduce each of the components proportionally to allow for the introduction of the desired percentage of speckles.

EXAMPLE 1 B

In a variation of the above described Example 1 A 1 % of ultramarine blue pigment was employed in place of 1 % of the Microgrit, so that the speckles were of a definite blue colouration.

In place of the described proportion of ultramarine blue one may use 0.5 to 2.0% of that pigment or mixtures of pigment(s) and polishing agent(s) of proportions from 1:10 to 10:1 may be used. Alternatively, about 0. 1 to 1 % of any suitable water insoluble (or oil soluble) dye may be employed. In such cases the dye solution may be omitted from the dentifrice base formula or may be present, providing enough contrast between the speckles and the base is obtainable.

Of course, the various components of the formula may be replaced by others, such as those previously described, and useful products will also be obtained. For example, the different mentioned pigments and dyes may be employed, the sodium lauryl sulphate may be replaced by sodium ethoxylated higher fatty alcohol sulphate or sodium hydrogenated coconut oil fatty acids monoglyceride monosulphate, and the polishing agents may be replaced by dicalcium phosphate dihydate and/or dicalcium phosphate (anhydrous) or mixtures thereof. Proportions of the various components may be modified by 10%, 20%, or 30%, so long as they are maintained within the ranges previously recited, and the results are satisfactorily products of similar properties, although those of the proportions of this example are preferred.

EXAMPLE 2A

Parts of anhydrous dicalcium phosphate and 15 parts of dicalcium phosphate dihydrate, both having average ultimate particle sizes of about 4 microns, were mixed with 10 parts of ethyl cellulose and 10 parts of ethyl alcohol in a Hobart mixer. Alternatively, and preferably, the ethanol and ethyl cellulose may be premixed and then may be admixed with a previously made blend of the di-calcium phosphates. The mass formed was forced through a screen having uniform openings of 2,000 microns and was then oven dried for one hour at 651C. The dried agglomerates were then screened through a screen having uniform 12 GB 2 144 333 A 12 openings of 420 microns and those agglomerates which do not pass through a screen having uniform openings of 177 microns were collected. Next, the agglomerated functional particles resulting were mixed with a dentifrice base of the formula given in Example 1, with the exception that the polishing agent in such base was replaced by sodium aluminosilicate, such as that marketed under the trade name Zeolite (Registered Trade Mark) 4A, and the percentage of speckles in the final product was 2% (with the sorbital solution present being increased by 3%).

EXAMPLES 2B, 2C and 2D In variations of this formula there may be substituted for the polishing agent of the speckles, hydrated alumina having an average particle size less than about 10 microns, calcium carbonate having particles substantially all of which are less than about 7.4 microns in diameter, or insoluble sodium metaphosphate having an average particle size of about 5 microns (all such sizes being ultimate particle sizes).

The dentifrices of this example were speckled, transparent or translucent products and were aesthetically pleasing in appearance. The visible particles of the agglomerated polishing agents (for which other functional insoluble materials may be substituted in whole or in part) where substantially uniformly dispersed in the dentifrice base as visibly separate entities and were not substantially impalpable upon use, after three months' storage.

EXAMPLE 3

Instead of dissolving the ethyl cellulose in the ethanol or other suitable solvent, agglomerates were made by blending the polishing agent and ethyl cellulose, sometimes with a reduced proportion of ethanol present, to form a powder blend. Such blend was compressed in a rotary tablet press to form slugs, about 6 mm thick and 25 mm in diameter. The slugs were then granulated in an oscillating granulator to form smaller particles, preferably such as will pass through a No. 30 screen and rest on a No. 60 or No. 80 screen. This technique for making the speckles may also be applied to any of the speckle 110 formulas given in the preceding examples. Although the binding effect of the ethyl cellulose might not be as great, the products of this example are also satisfactory for incorporation in dentifrices to contribute their aesthetic advantages and functional effects. If the binding effect of the ethyl cellulose in the foregoing formulas is not sufficient, the proportion thereof present maybe increased, sometimes upto 100 or 200%, but such increases involve additional expenses and therefore the "wet" method, in which solutions of ethyl cellulose in ethanol or other suitable solvents are employed, is often preferred.

EXAMPLE 4

Parts of calcined alumina (Microgrit WCA 9F) of particle size in the range of 0.5 to 10 microns and an average particle size in the range of 3 to 5 microns were blended with three parts of powdered polyvinyl pyrrolidone, obtained from GAF Corp., and marketed by them under the designation Plasdone K-29-32. Two parts of ethyl cellulose powder of the type mentioned in Example 1 were dissolved in five parts of ethanol (95%) and the PVP- alumina blend was mixed with the solution in a Hobart mixer. Mixing was continued for about four minutes until the blend was uniform, after which the mix was force through a No. 10 screen and the -extrudedmaterial was oven dried, as described in Example 1. The dried agglomerates were then screened and collected, as described in Example 1. The speckles produced were of angular shapes, with the ratios of maximurn length to maximum width usually being like those of Example 1. A transparent (or translucent) dentifrice base (all components except speckles) was made like that of Example 1, except for the presence of 39.04 parts of sorbitol solution instead of 36.04 parts thereof.

Two parts of the described speckles, with particle sizes -30 +60 (U.S. Sieve Series), were gently blended in a slow moving mixer (about two r.p.m.) with 98 parts of the described dentifrice base, after which the mix was deaerated and automatically filled into capped collapsible tubes which were then sealed. The processing employed was like that described in Example 1.

When the product was evalutated immediately after filling, and without being stored, the speckles are palpable but, upon storage before use, for periods from two weeks to a year or more, they were sufficiently softened to be impalpable, as by solubilization of the PVP by the moisture present and solubilization of the ethyl cellulose by the flavouring oil, both solubilizations apparently sometimes being with the aid of the dental detergent or other surface active agent that may be present, and sometimes assisted by other components too.

When the proportion of flavour in the dental gel base was decreased to 0. 6%, half that of the above formula, the PVP-ethyl cellulose binder system for the speckles still was effective and they were satisfactorily impalpable on storage. The system was also effective when the flavour concentration was varied to 0.3%,0.9% and 1.5%. However, the greater proportions of flavour (and/or other lipophile solvents) may cause somewhat earlier solubilization than preferred, in which case the proportions of PVP and ethyl cellulose will preferably be varied, to 2 parts PVP and 3 parts ethyl cellulose, for example. Similarly, if the palpability of the speckles should increase to more than desired they may be made softer by increasing the PVP proportion, e.g. to twice the ethyl cellulose. The concentrations of speckles and the sizes thereof may be changed, within the ranges previously given. Also, others of the materials previously listed may be substituted for the alumina polishing agent, including other types 13 GB 2 144 333 A 13 of water insoluble functional substances. The variations in formulations and procedures described in Example 1 are also applicable to this 65 example and the products obtained are also 5 useful speckles and speckled dentifrices.

EXAMPLE 5 parts of anhydrous dicalcium phosphate and 15 parts of dicalcium phosphate dihydrate, both having average ultimate particle sizes of about 4 microns, were mixed with 5 parts of ethyl cellulose, 5 parts of PVP and 10 parts of ethyl alcohol in a Hobart mixer. Alternatively, and preferably, ethanol and ethyl cellulose may be premixed and then may be admixed with a previously made blend of the dicalcium phosphates with PVP. The mass formed was forced through a screen having uniform openings of 2,000 microns and was then oven dried for one 80 hour at 601C. The dried agglomerates were then screen through a screen having uniform openings of 420 microns and those agglomerates which do not pass through a screen having uniform openings of 177 microns were collected. Next, the agglomerated functional particles resulting were mixed with a dentifrice base of the formula given in Example 4, with the exception that the polishing agent in such base was replaced by sodium aluminosilicate, such as that marketed under the trade name Zeolite 4A.

The dentifrices of this example were speckled, transparent or translucent products and aesthetically pleasing in appearance. When formula and processing variations were made, as 95 in Example 2, good products also resulted, of the desired properties.

EXAMPLE 6

The functional polishing agent constituent of Example 5 was replaced by a mixture of ten parts of anhydrous dicalcium phosphate and 90 parts of calcium carbonate, with the same total proportion of polishing agent being employed; otherwise the same procedure was followed. The products resulting were similarly satisfactory in functional effects and were aesthetically pleasing in appearance. Similar results were obtained when different mixtures of the disclosed polishing agents were substituted for the present mixing in the speckles, and when proportions thereof were varied.

EXAMPLE 7

Instead of dissolving the ethyl cellulose and PVP in ethanol or other suitable solvent, agglomerates like those of Example 6 were made by blending the polishing agent, PVP and ethyl cellulose, sometimes with a reduced proportion of ethanol present, to form a powder blend. Such blend was compressed in a rotary tablet press to 120 form slugs, about 6 mm thick and 25 mm in diameter. The slugs were then granulated in an oscillating granulator to form smaller particles, preferably such as will pass through a No. 40 screen and rest on a No. 60 or No. 80 screen.

Although the binding effects of the PVP and ethyl cellulose might not be as great, the products of this example were also satisfactory for incorporation in dentifrices to contribute their aesthetic advantages and functional effects. If the binding effects of the PVP and ethyl cellulose in the foregoing formulas are not sufficient, the proportions thereof present may be increased, sometimes up to 100 or 200%, but such increases involve additional expenses and therefore the "wet" method, in which solutions of PVP and ethyl cellulose in ethanol or other suitable solvents are employed, is often preferred.

EXAMPLE 8

In the preceding examples, the polyvinyl pyrrolidone, the water soluble binder portion of the combination binder, is partially replaced (50%) or entirely replaced by the following water soluble binders: gum acacia, gelatin, corn starch, sodium carboxymethyl cellulose, sodium alginate, polyvinyl alcohol, carrageenan, xanthan gum and gum tragacanth. The speckles made, when incorporated in gel dentifrices like those previously described in these examples, sufficiently retain their individuality and integrity during processing but become impalpable on storage in the dentifrice, while still retaining their original shapes, in the same manner as the speckles made with PVP-ethyl cellulose combination binders. However, it is considered that the PVP- ethyl cellulose combination binder is generally superior in its combination of desirable features, including processing stability, compatibility with dentifrice components, and conversion from palpability to impalpability without loss of speckle integrity and without significant change in appearance.

EXAMPLE 9

Speckles of various compositions were compared to those based on ethyl cellulose and PVP. The speckles in accordance with the invention were made in generally the manner as described in Example 4, by the wet method, and the speckle formula included 95% of calcined alumina, 2% of ethyl cellulose and 3% of PVP, with such materials being the same as those used in Example 4. The speckles of the comparative experiments were also made by the wet method, except for one type, which will be indicated, which was made by the dry or "slugging" method of Example 7.

The speckles were tested by weighing out 100 milligrams of each type, separately placing them on glass slides, adding to each four drops of water, covering each slide with another slide, and noting the time of physical change and the type of physical change in the granules. When 2% of sodium carboxymethyl cellulose was employed as the binder the speckles lost integrity within fifteen seconds, which is also the case with the speckles bound with 2% of hydroxpropyl methyl cellulose, but that took two minutes. Speckles made with a binder comprising 2% of methyl cellulose and 3% 14 GB 2 144 333 A 14 of PVP soften, swell and lose integrity after about two minutes and when 5% of PVP is employed as the sole binder speckles made with it soften after eight minutes. When the binder is 1 % of methyl cellulose (400 centiposes), the speckles lose integrity after a little more than five minutes and when the binder is changed to 10% of polyethylene glycol 6, 000, with 1 % of magnesium stearate, with the speckles being made by "slugging", they lose integrity after nineteen minutes. The "control" speckles of this invention, including 2% of ethyl cellulose and 3% of PVP, when subjected to the same test, were still intact after over six hours.

EXAMPLE 10

In a process of this invention in which the.apparatus of Figures 2 and 3 was employed, a speckled clear gel dentifrice was made of the formula and by the method described in Example 1. The various gel (or paste) components were mixed together in the mixer 111 and were pumped, preferably by a Moyno type pump, to the extruder, which terminated in a flat "slit" nozzle, as illustrated, with a relatively narrow rectangular opening. Preferably, such a nozzle will be inclined downwardly from the horizontal at an angle of about 10 to 45 0, e.g. 30 0.

The feed rate of the speckle feeding mechanism, an Acrisan helix feeder, was adjusted to correspond to the gel feed rate. Thus, when, for 95 example, a 3% speckle content in the dentifrice was desired, if the feed rate of the gel was 3 kilograms per minute, then the speckles were fed at the rate of 93 grams per minute. Conventional electronic or mechanical means may be employed to maintain the desired feeds ratio, or to adjust it if changes in such proportions are desired for different products.

In the drawing the feeding mechanism for the speckles is shown only schematically in Figure 2 105 and only the end thereof is shown in Figure 3 but various types of feeds, including screw, belt, weighing belt, electronically controlled gravimetric feeders, and others may be used and the discharge pattern may be changed. The discharge will be such that few, if any, speckles will fall past the gel and the gel stream will hold the impinging speckles. Also, the speckles will fall separately and the gel will be moving fast enough underneath them, at a speed usually of 10 to 100 cm/second, e.g. 20 to 50 cm/sec, that individual speckles strike the gel and adhere to it, with very few hitting other held speckles and bouncing off them. Also, all or almost all of such bouncing speckles will subsequently adhere to the dental composition.

The falling speckled gel, with the speckles adherent to it, does not remain for a long period of time in the walled vessel in which or above which the speckling apparatus is located because it drops through the centre of such vessel and most of it proceeds almost directly to the outlet. This short residence time in the "speckling vessel" is highly desirable and helps to maintain the integrity of the speckles in the dentifrice. While residence times in the vessel may vary, typical times are in the range of 20 seconds to 2 minutes, the shorter the better. Such quick throughput, the absence of mobile speckles and the central gel discharge from the vessel also help to avoid aggregation of speckles into objectionable clumps. The additional volume of the walled vessel is for holding gel which may be fed into it during periods when filling equipment may be temporarily halted a nd before feed to the vessel can be stopped. Thus, often the walled vessel may contain only a small proportion of speckled gel, e.g. 10 to 25% of its volume. Alternatively, other material may act as a "wall" bounding the speckled gel, within the vessel.

After leaving the speckling vessel the gel is gently pumped by a M-yno type pump and passes through a static mixer, to assure complete mixing. The preferred static mixer, a Kenics mixer, is like that described in the March 19, 1973 edition of Chemical Engineering in an article entitled Handling Viscous Materials - Motionless Mixer for Viscous Polymers. Although it is desirable to utilize a mixer prior to discharging the gel to a filling machine or suitable container before such machine, the present process and apparatus, without such mixer, can often sufficiently distribute the speckles throughout the gel so that in some instances the mixer is not employed.

The conditions of operations are not considered to be critical but usually the vacuum employed will be within the range of about 300 to 700 mm of mercury, e.g. 400 to 600 mm Hg. The temperatures rnay be about room temperature or l 00 higher, e.g. in the range of 100 to 400C. The pressure of extrusion of the gel varies with the gel viscosity but from 0.03 to 0.7 kilogram per square centimetre is considered to be a reasonable range.

The various piece of equipment of this invention, because they are employed in processing an oral product, should be constructed of noncorroding and safe materials. If has been found that stainless steel components are highly preferable and the mixers, extruders, pumps and valves, and any other parts that contact liquid or gel materials, will preferably be made of stainless steel, such as is normally employed in the food processing industry.

When a 2% speckled clear dentifrice (containing silicon dioxide, sorbitol, glycerol, CMC, sodium lauryl sulphate, flavour and water in.the gel, and alumina and ethyl cellulose in the speckles), like that described in Example 1, is made with the apparatus described herein, the product resulting will be just as desired, with the speckles being regularly distributed through the clear gel and with no cloudiness or disintegrated speckles noted. Similar results are obtainable when other speckled dentifrices, such as those of the prior art and of Examples 2-9, are produced, utilizing the apparatus and process of this invention, as illustrated.

In practicing the process of the present GB 2 144 333 A 15 invention, while it will be preferred for the dental gel or paste to be in flat ribbon form, it is understood that variations of such form may be utilized, such as arced ribbons and even cylindrical or tubular streams. Also, while it is preferred that the stream or curtain of speckles be a suitably thin straight curtain of such material, e.g. 0.1 mm to 1 cm, e.g. 0.5 to 5 mm, in thickness, failing by gravity, the speckles may be forcefully directed onto the dentifrice. For example, in some instances, a vertically moving stream of dentifrice may have speckles directed onto it horizontally, with those not adhering being collected for recycling. The dental material stream may be given a rotary motion so that it -picks up" 80 about its entire exposed surface speckles unidirectionally aimed at it. Conveyed speckle particles can impact a gel stream and deposit on it, immobile and discrete. Yet, while such variations of the invention are operative, the process described and illustrated herein is considered to be superior.

The proportion of speckles fed to the moving ribbon or web of gel dentifrice will be a minor proportion, compared to the complete dentifrice 90 containing speckles, and compared to the gel fed. The feed rate of the speckles will usually be adjusted so that the amount of speckles directed onto the gel will be insufficient to cover it and preferably will be insufficient to cover more than 95 half the area of the portion of the gel exposed to the curtain of speckles when such curtain contacts the gel. While, as we mentioned previously, different ways of adhering the speckles to the gel ribbon have been mentioned, it 100 is highly preferable that the speckles be dropped vertically in a curtain onto a ribbon of gel, with the gel moving in a direction with a horizontal component. Such direction may be horizontal or -- have a significant horizontal component with the 105 gel failing after having picked up the speckles, but normally an inclination from the horizontal, e.g.

to 601, will be preferred for the gel, with the speckles failing vertically, after having been discharged from a delivery apparatus. The 110 viscosity of the gel is not critical, so long as the speckles sufficiently adhere to it, and the sizes of the particles are not critical, but normally they are in the No's. 10 to 80 sieve size range, preferably 30 to 80, and more preferably 30 to 60. The 115 speckles are preferably sharp edged and in failing onto the gel stream they become partially embedded therein, immediately being rendered immobile, but similar good results may also be obtained when rounded speckles are used.

Although the speckles used are preferably visible 120 in a clear gel, which makes the product aesthetically attractive, they may be of an index of refraction which renders them invisible. Thus, the designation "speckles" includes visible and invisible discrete particles of various materials, 125 with agglomerates of finely divided polishing agents being preferred. Also, while it is preferred that they be agglomerates of finely divided polishing agent and binder they may comprise other "active" components, such as therapeutic agents, colourants, flavours and fluorides.

It is contemplated that the dentifrice material on which speckles are deposited will be all the dentifrice, except speckles, but this is not necessary. It is possible that some dental components may be blended in with the other dentifrice materials after addition of the speckles. For example, it may be desirable to blend in the flavouring, which may contain some volatile components, before the Kenics mixer but after any application of vacuum to the product during the depositing of the speckles. Such a procedure has the advantages of preserving the flavour and preventing losses of more volatile components thereof due to theapplication of the vacuum in the speckling operation, and any flavour components which would solubilize the binder of the speckles would have less processing time contact with them. Yet, the Kenics or other relatively low shear static mixer would blend the flavouring sufficiently evenly throughout the dentifrice. Similarly, other components, usually minor adjuvant components, may be added to the dentifrice subsequent to the incorportion of the speckles therein.

The walled vessel mentioned, into which the speckled dentifrice falls, may be under vacuum or may be open to the atmosphere. The speckling apparatus may have a reservoir underneath it, rather than being enclosed in a vessel. However, it is preferred that such equipment be covered and under vacuum, when air entrapment would otherwise be a problem. It acts as a container for the speckling apparatus, in addition to being a vessel to hold the resulting product. The present process and apparatus lend themselves to use for making a variety of different dentifrice formulas containing different proportions of speckles. To vary the speckles concentration is a simple matter, since it involves only changing the speed of the speckles feeder and controlling the gel feed rate accordingly.

Among the various advantages of the invention are increased efficiency of operation, diminution of employment of moving part mixers and the stabilization of the dental gel or paste. It is known that various dentif rices are thinned by excessive mechanical working and the present blending operation for adding speckles to the dentifrice avoids such working and allows maintenance of the desired viscosity of the dental gel.

EXAMPLE 11

A process for making a speckled dentifrice is carried out as in Example 10 but the apparatus employed is that illustrated in Figures 4 and 5. Therefore two gel ribbons are produced, each with half of the total dentifrice (less speckles) in it. The flat slit nozzles are inclined downwardly at about 301 from the horizontal. The gel speed will be about 20 to 50 cm/second and the gel will preferably be adhesive enough and conditions will be so controlled that most of the speckles striking the first gel stream will adhere to it, with the 16 GB 2 144 333 A 16 balance (or essentially all the balance) being sandwiched in place by the other gel stream.

The speckle feed, as shown in Figure 5, is a chute with pegs located thereon in Pascal triangle arrangement. It is downwardly inclined at an angle of about 301 from the horizontal, and is about 90% of the width, at the delivery end, of the gel streams. Of course, while the Pascal triangle arrangement of pegs is preferred other feeders may also be employed.

The dentifrice resulting has all the advantages of that of Example 10. Additionally, the process and apparatus of the present example are especially suitable for holding speckles to the gel dentifrices in ordered arrangement and uniform distribution therein when the gel is not strongly adhesive. Thereby "bouncing off" of the speckles is avoided, saving losses of speckles and the need to recycle or scrap unadhered speckles.

Additionally, even with non-adhesive gels (and/or non-adherent speckles) the final product can be controlled so as to have a consistent and desired content of the speckles therein (because speckle losses are minimized).

Claims (11)

1. A process for manufacturing a dentifrice containing dispersed discrete speckles therein which comprises producing a stream of a gel or paste dental composition containing a gelling agent which helps to make surfaces thereof adhesive for the speckles, which dental composition constitutes a major proportion of the dentifrice, producing a stream of speckles to be distributed throughout the dentifrice, directing the said stream of speckles onto a surface of the stream of the dental composition and controlling the relative feed rates and the proportions of the streams of dental composition and the speckles to be dispersed in the dentifrice so that when the stream of speckles contacts the stream of dental 105 composition the speckles are insufficient so cover the dental composition surface, so that the speckles adhere to the dental composition stream and there is produced a dentifrice containing the speckles in desired proportion distributed in it. 110

2. A process according to Claim 1 wherein the stream is a ribbon of gel and constitutes all the dentifrice except for the speckles to be distributed therein, the ribbon of such gel is produced by forcing it through a suitably shaped orifice so that 115 it is extruded from the said orifice as a ribbon which flows in a direction having a horizontal component, the stream of speckles has particle sizes less than 2 mms and greater than 175 microns, the said speckles are in the form of a falling curtain directed so as to fall downwardly onto the gel ribbon in such manner as to be distributed evenly over a substantial portion of the width of the flowing ribbon and adhered to the said ribbon while being insufficient to cover 125 more than half of the area of the ribbon surface presented to it, and the ribbon of gel with adherent speckles thereon is collected in a walled vessel from which it is continuously removed as additional gel containing speckles is added thereto, which vessel is under vacuum.

3. A process for manufacturing a dentifrice containing dispersed discrete speckles therein which comprises producing a plurality of ribbon shapes streams of a gel or paste dental composition which constitutes a major proportion of a dentifrice, producing a stream of speckles to be distributed through the dentifrice, directing the said stream of soeckles onto a surface of at least one of the streams of gel or paste dental composition and controlling the relative feed rates and the proportions of the gel or paste dental composition and the speckles to be dispersed therein so that when the stream of speckles contacts the stream of gel or paste the speckles are insufficient to cover the ribbon surface presented to the curtain, so that the speckles adhere to the gel or paste ribbon, the bringing together at least two of the plurality of streams of the dental composition so that major surfaces thereof adhere together and sandwich the speckles between them.

4. A process as claimed in Claim 3 in which the streams of gel or paste dental composition are a pair of ribbons or gel continuously flowing in partially opposing directions having horizontal components, and the stream of speckles is directed so as to fall downwardly onto one of the flowing gel ribbons and the amount of speckles in the failing curtain is insufficient to cover more than half of the area of the ribbon surface presented to it.

5. A process as claimed in Claim 2 substantially as specifically described herein with reference to any one of Examples 1 to 8, 10 or 11.

6. Apparatus for manufacturing dentifrice containing dispersed speckles therein which comprises means for producing a stream of gel or paste dental composition, means for producing a stream of speckles to be distributed throughout a dentifrice and for directing the said stream onto a surface of the stream of dental composition, where such speckles will be held, and means for controlling relative feed rates and proportions of the dental composition and the speckles to be dispersed therein, so that when the stream of speckles contacts the stream of dental composition the speckles are insufficient to cover the dental composition surface, and the speckles may adhere to the dental composition stream, and by use of such apparatus there may be produced a dentifrice containing speckles in desired proportion distributed in it.

7. Apparatus as claimed in Claim 6 in which the means for producing the stream of gel or paste dental composition produces a gel ribbon and includes an extruder for extruding it in a direction having a horizontal component, the means for producing the stream of speckles produces a curtain of speckles and includes a helix or screw feeder and means for distributing the speckles fed thereby into a curtain of width slightly less than the width of the gel ribbon, and which apparatus includes a walled vessel above 17 GB 2 144 333 A 17 which or in which the means for extruding the gel and the means for producing the curtain of speckles are located.

8. Apparatus as claimed in Claim 7 in which the means for producing the curtain of speckles directs such speckles downwardly so that they fall in a vertical curtain onto the gel ribbon, the walled vessel has an outlet opening at the bottom 40 thereof, and the means for producing the gel ribbon directs it so that after the speckles contact the ribbon and are held by it, the ribbon falls vertically toward the outlet from the walled vessel and which comprises means for maintaining the 45 walled vessel under vacuum, a screw pump and a static mixer, the screw pump being located in communication with an outlet from the walled vessel in which the speckled dentifrice is made so as continuously to withdraw the dentifrice from so such vessel and pump it through the static mixer without disintegrating or dissolving speckles thereof in the dentifrice, so that the dentifrice may be delivered to a tube filling machine without objectionable change in the appearance in the 55 speckles.

9. Apparatus for manufacturing dentifrice containing dispersed speckles therein which comprises means for producing a plurality of streams of gel or paste dental compositions, means for producing a stream of speckles to be distributed throughout a dentifrice and for directing the said speckle stream onto a surface of a stream of gel or paste dental material, means for controlling relative feed rates and the proportions of the gel or paste dental material and the speckles to be distributed therein, so that when the curtain of speckles contacts the stream of gel or paste the speckles are insufficient to cover the stream surface presented to the curtain and the speckles adhere to the gel or paste of the stream, and means for directing a separate stream of gel so that it adheres to the gel to which the speckles are adhered and sandwiches the speckles between the streams, so that there is produced a gel or paste dentifrice containing speckles in desired proportion distributed in it.

10. Apparatus as claimed in Claim 9 in which the means for producing the streams of dental composition produces a pair of ribbons of gel continuously flowing in directions having horizontal components, the means for producing a stream of speckles and directing them onto the surface of a ribbon of gel directs the speckles to fall downwardly as a curtain onto such flowing gel ribbon and the means for controlling the relative feed rates and proportions of the gel and speckles controls them so that the amount of speckles in the failing curtain is insufficient to cover more than half of the area of the ribbon surface presented to it.

11. Apparatus as claimed in Claim 6 substantially as specifically described herein with reference to Figures 2 and 3 or 4 and 5 of the accompanying drawings.

Printed in the United Kingdom for Her Majesty's Stationery Office, Demand No. 8818935, 3/1985. Contractor's Code No. 6378. Published by the Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.