WO2006081913A1

WO2006081913A1 - Multiphase toothpaste composition

Info

Publication number: WO2006081913A1
Application number: PCT/EP2006/000115
Authority: WO
Inventors: Rupesh Kumar Agarwal; Nand Sanmukhdas Bijlani; Donald Peter Gregory; Brian Groves
Original assignee: Unilever N.V.; Unilever Plc; Hindustan Lever Limited
Priority date: 2005-02-04
Filing date: 2006-01-06
Publication date: 2006-08-10

Abstract

Multiphase toothpaste composition comprising a first phase disposed co-axially within a second phase, the second phase being sufficiently clear such that the first phase can be visually perceived therethrough, the second phase comprising agglomerates .

Description

MULTIPHASE TOOTHPASTE COMPOSITION

The present invention relates to a multiphase toothpaste composition .

WO 99/01342 discloses apparatus for inserting plural materials into containers . The apparatus comprises a nozzle with a first hollow member and a second hollow member arranged inside the first hollow member. The nozzle is designed for directing the extrusion of multiple toothpaste phases into a toothpaste container with one phase being arranged within another.

Despite the prior art there remains the need for multiphase toothpaste compositions with improved visual and sensorial impact .

The present inventors have found that improved visual and sensorial impact is achieved with agglomerates . Accordingly and in a first aspect , the present invention provides a multiphase toothpaste according to claim 1.

The first phase is disposed co-axially within the second phase . By this is meant that the longitudinal axis of the ribbon as dispensed from the toothpaste container falls within the inner, first phase . Similarly, the general longitudinal axis of the toothpaste as stored within the toothpaste container falls within the inner, first phrase . Such alignment is understood to be judged by the eye and not mathematically. When looking at a section of the dispensed ribbon end-on the inner phase may extend towards or up to the exterior surface of the ribbon . Such extension may be radial , spiral or abstract and, where it is radial or spiral it may be regular or irregular . Regular radial extensions are the most preferred to the consumer . In addition the core may, in cross section be of any shape, for example, star-shaped, square shaped, triangular, etc . These shaped cores are a real plus to the younger consumers . However, it is most preferred that the inner phase comprises no extensions and instead provides nothing more than a regular core to the ribbon . This regular shape is less fussy and provide clean lines to the product which reinforces the impression of cleanliness that toothpastes aim to provide .

The agglomerates which provide the best impact sensorially contain only water insoluble particulates of low to medium structure, particularly those with low oil absorption capacity favoured as abrasives and polishing agents in dental formulations, bound together with water and dried are too weak to survive the normal processes in toothpaste manufacture and therefore would not be felt in the subsequent tooth cleaning process . Preferred agglomerates include those commercially available as BFG 50 ex. Ineos silicas .

The oil absorption is determined by the ASTM spatula rub- out method (American Society Of Test Material Standards D, 281) . The test is based on the principle of mixing linseed oil with the water insoluble particulate by rubbing with a spatula on a smooth surface until a stiff puttylike paste is formed which will not break or separate when it is cut with a spatula . The volume of oil used is converted to weight and expressed as g of oil / lOOg of water insoluble particulate .

The weight mean particle size of the water insoluble particulate before agglomeration is determined using a Malvern Mastersizer model X, made by Malvern Instruments , Malvern, Worcestershire with MS15 sample presentation unit .

The water insoluble particulates are dispersed ultrasonically in water for 5 minutes to form an aqueous suspension and then mechanically stirred before they are subj ected to the measurement procedure outlined in the instruction manual for the instrument , utilising a 45 mm lens in the detector system.

An accurate measure of the true particle size distribution of the granular composition is done using sieve analysis . One hundred grammes of the sample is placed on the top sieve of a series of BS sieves, at approximately 50 micron intervals between 45 and 600 microns . The sieves are arranged in order with the finest at the bottom and the coarsest at the top of the stack. The sieves are placed in a mechanical vibrator e .g. Inclyno Mechanical Sieve Shaker by Pascall Engineering Co Ltd. , covered with a lid and shaken for 10 minutes . Each sieve fraction is accurately weighed and the results calculated : % residue Wt . of residue *100 divided by the Wt . of sample .

A particle size distribution can then be plotted from the data . It is preferable that the granular composition should have a particle size distribution, as measured by sieve analysis , such that 95% of the granules are less than 400 microns and 95% of the particles are above 100 microns , most preferably microns . Owing to the porous nature of the agglomerates , it is possible for them to act as delivery vehicles for substances that give cosmetic benefits such as colouring pigments , flavours , perfumes or other cosmetic . The agglomerates can also contain other cosmetic and/or therapeutic dental and/or oral actives and release them into mouth. Such substances may be contained within the pores of the material . The inclusion of a material having a therapeutic or cosmetic effect on the gums or teeth or oral cavity into these agglomerates provides for a further benefit in that upon crushing or collapsing of these agglomerates, the therapeutic/cosmetic agent is slowly released, thus delivering the therapeutic agent over to the mouth over a longer period of time . Suitable examples of such therapeutic agents are zinc salts such as zinc citrate ; antimicrobial agents such as Triclosan; anti- caries agents such as sodium fluoride and sodium monofluorophosphate ; anti-plaque agents such as stannous pyrophosphate etc . In this respect it has surprisingly been found, that the inclusion of zinc citrate in the agglomerates (in an amount of up to 15 %, preferably up to 12 % by weight of the agglomerates) significantly reduced the level of astringency, perceived by trained panellists upon testing a toothpaste with such agglomerates for their sensory i properties . The addition of titanium dioxide as an opacifying agent at a concentration of 1 to 5% w/w, usually at the expense of the water insoluble particulates , ensures that the granules have a white appearance and therefore stand out in coloured toothpaste formulations .

If coloured granules are required, then suitable food grade coloured pigments , for example pigment dispersions under the Cosmenyl trade name or pigment powders under the Hostaperm trade name or Cosmetic Pink RC 01 (D & C Red No 30) supplied by Hoechst , can be added to the composition of the granule, without affecting the strength of the granule .

If titanium dioxide and therapeutic agent are omitted from the granular composition containing abrasive and thickening silicas , then the coarse particles are invisible in transparent gel formulations .

Moreover, the agglomerate strength can be varied over a wide range by changing the water insoluble particulate structure, i . e . low structure water insoluble particulates decrease strength whereas high structure water insoluble particulates increase agglomerate strength.

The use of water insoluble particulates which already have an approved role in toothpastes formulations , such as toothpaste abrasive silicas [e . g . Sorbosil AC77 (obtainable from Ineos Limited - England) ] as the low/medium structure component , is an added advantage since such silicas are capable of providing extra cleaning to the formulation and have good compatibility with the formulation . Indeed, _v- particularly preferred water insoluble particulates which make up the granular composition are mixtures of synthetic, amorphous thickening [e . g . Sorbosil TC15 (obtainable from Ineos Limited - England) ] and abrasive silicas .

The agglomerates should be insoluble in the medium of the toothpaste composition into which it is incorporated. In this context , " insoluble" means having insufficient solubility at ambient temperature in that the agglomerates remain undissolved or substantially undissolved in the composition such that their friability under the conditions of use of the composition and thus their ability to perform their cleaning/polishing function are not deleteriously affected. Preferably, the level of insolubility of the agglomerates extend to their insolubility in the oral environment in which the composition is used, which may frequently contain higher levels of water than for example a toothpaste, owing to the presence of saliva and added water frequently used in the brushing regime .

When the granules are incorporated in a toothpaste composition, it is important that they break down under the shear forces generated by the toothbrush in a relatively short period of time, whereby the gritty feel experienced by the user is eliminated.

This means, that the agglomerates should have a particle strength such that they will collapse within the range of shear and/or crush forces normally produced in the relevant brushing regime, since the considerably variable force^'s produced at a particular location over time enable at least some of the agglomerates to survive intact long enough to perform their cleaning function to a satisfactory degree . It is even possible to tailor the breakdown time of the agglomerates , such as to control the contact time for a given duration of brushing of the composition, by- controlling the average crush strength of the agglomerates , for example by selecting a particular type of source of the particulate materials and/or the manner in which they agglomerate in the manufacturing process .

If opaque granules are required, then titanium dioxide is added to the powder mixture . If coloured granules are required, a suitable food grade coloured pigment dispersion can be added . By drying the product after agglomeration, a granular composition is obtained which is stable in a toothpaste composition .

For incorporation into toothpastes , it is important that virtually all particles are below 600 pm, preferably below 400 pm since gritty particles give unpleasant mouth feel properties . A size reduction step utilizing minimum energy to prevent unnecessary breakdown of the agglomerate is therefore required.

Preferably, the first and second phases have specific densities of from 1.1 to 1.5 g/ml , more preferably from 1.2 to 1.4 g/ml and especially from 1.3 to 1.35 g/ml . These more preferred ranges provide the optimal density ranges for the production of a toothpaste according to the invention and which is stable post dispensing onto a toothbrush .

More preferably, the specific densities of the individual phases differ by no more than 20% , more preferably no more than 14% and especially no more than 8% of the specific density of the first phase .

Preferably, the phases according to the composition of the invention have viscosities as measured on a Brookfield RV

DV-I viscometer fitted with a Helipath stand and measured at 25⁰C and 5rpm using a T-D spindle from 180 000 Pa . s to 250 000 mPa . s , preferably from 200 000 to 240 000 mPa . s , moire preferably from 210 000 to 230 000 mPa . s and most preferably from 210 000 to 225 000 mPa . s . Such viscosities improve the performance with regard to extrusion into the container and also from the container by the consumer. These viscosity ranges provide the best extrusion performance for coaxially arranged phases as described herein . The extruded paste is stable and of consistent width on dispensing onto a toothbrush.

In a preferred embodiment the first phase constitutes up to 25% of the volume of the toothpaste composition . Should the inner phase constitute much more than 25% by volume of the composition the inner phase often appears to overwhelm the composition such that the outer phase is hardly noticed at all by the consumer . This is particularly the case when the outer phase is visually clear .

Preferably, the inner first phase constitutes from 11 to 20% and more preferably from 13 to 18% by volume of the toothpaste composition.

The first and second phases may be the same or different with regard to their principle components , i . e . thickeners , actives , structurants and abrasives . Where the first and second phases are essentially the same they may differ in minor components such as colours or flavours .

In an alternative preferred embodiment the inner, first phase is opaque . This adds a further benefit in that it creates a silvery effect at the interface between the two phases . This is especially so when the outer phase is visually clear and is an attractive effect for the consumer .

In an alternative preferred embodiment at least one of the phases is coloured. Preferably, the outer phase is coloured. This is even more preferred when the outer phase is visually clear . Preferred colours include green, red, orange, yellow, blue, gold and purple .

Preferably, the agglomerates are also coloured. More preferably, the agglomerates are the same colour as the inner phase of the toothpaste . Even more preferably, the second phase is coloured similarly to the core and agglomerates but with a lower saturation such that there is only a mildly perceived coloration in the outer phase but which still matches the colour of the core and agglomerates .

Even more preferably, the degree of coloration of the core and agglomerates is similar or identical such that it is perceived that they are made from the same phase .

In a further preferred embodiment either of the phases, especially when a visually clear phase is required, comprises abrasive silica . The particular abrasive silica used in the present invention is a silica with a low refractive index. It may be used as the sole abrasive silica, or in conjunction with a low level of other abrasive silicas, e .g . those according to EP 236 070. The low refractive index silicas , used as abrasives in the present invention are preferably silicas with an apparent refractive index (R. I . ) in the range of 1.41 - 1.47 , preferably 1.435 - 1.445 , preferably having a weight mean particle size of between 5 and 15 mm, a BET (nitrogen) surface area of between 10 and 100 m²/g and an oil absorption of about 70 - 150 cm³/l00 g, but abrasive silicas with a lower apparent refractive index may also be used . Typical examples of suitable low refractive index abrasive silicas (e . g . having an R. I . of between 1.435 and 1.445) are Tixosil 63 and 73 ex Rhone Poulenc ; Sident 10 ex Degussa; Zeodent 113 ex Zeofinn; Zeodent 124 ex Huber, Sorbosil AC 77 ex Crosfield Chemicals (having an R. I . of approximately 1.440) . The amount of these silicas in the composition generally ranges from 5-60% by weight , usually 5-20% by weight .

In a preferred embodiment the inner phase comprises chalk, preferably fine ground natural chalk. The inner composition will preferably comprise chalk at from 10 to 60 % by weight of the phase .

The phases of the composition according to the invention are manufactured using standard processes . They may be extruded into a container for dispensing by equipment such as that discussed in detail in WO 99/01342 , i . e . a coaxial nozzle assembly attached to standard equipment . The toothpaste composition according to the present invention can comprise an agent selected from the group consisting of anti-carries agents , tooth whitening agents , anti-tartar agents , anti-malodour agents , anti-gingivitis agents and mixtures thereof .

The toothpaste composition will comprise further ingredients which are common in the art , such as :

antimicrobial agents , e .g . chlorhexidine , sanguinarine extract , metronidazole, quaternary ammonium compounds , such as cetylpyridinium chloride; bis-guanides , such as chlorhexidine digluconate , hexetidine , octenidine, alexidine; and halogenated bisphenolic compounds , such as 2 , 2 ' methylenebis- (4-chloro-δ-bromophenol) ;

anti-inflammatory agents such as ibuprofen, flurbiprofen, aspirin, indomethacin etc . ;

anti-caries agents such as sodium- and stannous fluoride, aminefluorides , sodium monofluorophosphate, sodium trimeta phosphate and casein;

plague buffers such as urea, calcium lactate, calcium glycerophosphate and strontium polyacrylates ;

vitamins such as Vitamins A, C and E ;

plant extracts ; desensitising agents , e . g . potassium citrate, potassium chloride, potassium tartrate , potassium bicarbonate, potassium oxalate , potassium nitrate and strontium salts ;

anti-calculus agents , e .g . alkali-metal pyrophosphates , hypophosphite-containing polymers , organic phosphonates and phosphocitrates etc . ;

biomolecules , e . g . bacteriocins , antibodies , enzymes , etc . ;

flavours , e . g. peppermint and spearmint oils ;

proteinaceous materials such as collagen;

preservatives ;

opacifying agents ;

colouring agents ;

pH-adjusting agents ;

sweetening agents ;

pharmaceutically acceptable carriers , e . g . starch, sucrose, water or water/alcohol systems etc . ;

surfactants , such as anionic , nonionic, cationic and _v- zwitterionic or amphoteric surfactants ; particulate abrasive materials such as silicas , aluminas , calcium carbonates , dicalciumphosphates , calcium pyrophosphates , hydroxyapatites , trimetaphosphates , insoluble hexametaphosphates and so on, including agglomerated particulate abrasive materials , usually in amounts between 3 and 60% by weight of the oral care composition . Preferred abrasives are chalk and silica, more preferably fine ground natural chalk.

Humectants such as glycerol , sorbitol , propyleneglycol , xylitol , lactitol etc . ;

binders and thickeners such as sodium carboxymethyl- cellulose, hydroxyethyl cellulose (Natrosol^®) , xanthan gum, gum arabic etc . as well as synthetic polymers such as polyacrylates and carboxyvinyl polymers such as Carbopol^® ;

polymeric compounds which can enhance the delivery of active ingredients such as antimicrobial agents can also be included;

buffers and salts to buffer the pH and ionic strength of the oral care composition; and

other optional ingredients that may be included are e . g . bleaching agents such as peroxy compounds e . g . potassium peroxydiphosphate, effervescing systems such as sodium bicarbonate/citric acid systems, colour change systems_. , and so on. Liposomes may also be used to improve delivery or stability of active ingredients .

In a second aspect the present invention provides a toothpaste container comprising a first and second phase as described in the first aspect of the invention stored within a tubular container, the container comprising a tubular body which is crimped at one end and comprises a dispensing assembly at the other through which the composition is extruded by the consumer.

Preferably, the tubular container is transparent or translucent so that the inner phase can be seen within the outer phase within the container.

An embodiment of the invention is now discussed in the non- limiting example .

EXAMPLES

This composition comprises a first phase and a second phase . The second phase is visually clear and the inner phase is opaque . The composition comprises 85% v/v of the first phase and 15% v/v of the second phase .

Claims

1. Multiphase toothpaste composition comprising a first phase disposed co-axially within a second phase, the second phase being sufficiently clear such that the first phase can be visually perceived therethrough, the second phase comprising agglomerates .

2. Multiphase toothpaste according to claim 1 wherein the agglomerates are coloured .

3. Multiphase toothpaste according to claim 1 or 2 wherein the agglomerates are friable .

4. Multiphase toothpaste according to any preceding claim wherein the agglomerates comprise silica .

5. Multiphase toothpaste according to any preceding claim wherein the inner phase is coloured.

6. Multiphase toothpaste according to any preceding claim wherein the inner phase is opaque .

7. Multiphase toothpaste composition according to any preceding claim comprising a first phase disposed co- axially within a second phase, each of the phases having a viscosity of from 180 000 to 250 000 mPa . s .

8. Multiphase toothpaste composition according to any preceding claim wherein the first phase constitutes up to 25% by volume of the toothpaste, composition.

9. Multiphase toothpaste composition according to any preceding claim wherein the second phase comprises abrasive silica .

10. Multiphase toothpaste composition according to any preceding claim wherein the first phase comprises chalk as abrasive .

11. Multiphase toothpaste composition according to claim 10 wherein the chalk is fine ground natural chalk.

12. Multiphase toothpaste composition according to any preceding claim wherein the second phase comprises an abrasive silica having a Refractive Index of from 1.41 to 1.47.