GB2240032A - Applicator for liquids - Google Patents

Abstract

An applicator for liquids suitable for application to hard or soft surfaces, particularly parts of the human body, comprises a solid head (1) interconnected to a liquid reservoir (4). The head (1) comprises low density, porous, homogeneous cross-linked polymeric block material. The applicator is most suited for application of deodorants or antiperspirants to the underarm. <IMAGE>

Description

APPLICATOR SYSTEM FOR LIOUID This invention relates to an applicator system for a liquid suitable for application to hard or soft surfaces.

In particular the invention relates to an applicator system suitable for applying lotions and liquids to the human body, most particularly deodorant and antiperspirant systems.

As applicators for antiperspirant and deodorants it is known to use three types of system. Firstly, there are aerosols and pump sprays. Pressure in the liquid reservoir caused either by external or internal means causes a liquid spray to be ejected through a nozzle.

However, the nozzles are prone to blockages, particularly where there are solids suspended in the liquids.

Furthermore there is environmental concern about propellants used in aerosols.

Secondly there are solid sticks. These are pushed from a container and gradually worn down. There are problems in ensuring the stick stays attached to the ejector base and also in product texture to the body.

Thirdly, there are roll-on or ball applicators. In such applicators a liquid is dispensed from a reservoir via a rolling ball held in a cup or rim. By the nature of application the liquid must be quite sticky. This is found unacceptable by a number of users. Furthermore the texture of the ball itself is sometimes found unpleasant.

There is therefore a need for a novel type of liquid applicator which will have improved sensory properties and improved application characteristics in relation to current products.

We have now found that synthetic polymers of a certain structure can form effective and useful carriers and applicators for various liquid products, most particularly deodorant and antiperspirant systems.

According to the present invention there is provided a liquid application system comprising a reservoir for the liquid connected to a solid applicator head, said head comprising a porous homogeneous cross-linked polymeric block material, having a dry density of less than O.lg/cc and formed as a cross-l-nked porous structure having a pore volume of more than 9cc/g and an absorbency for hydrophobic liquids defined in terms of oleic acid of at least 7cc/g, said porous structure comprising interconnecting void spaces.

Preferably the applicator head is a monolithic body having a continuous structure formed by polymerization.

Particularly preferred is a carrier formed by polymerization of polymerizable material in an emulsion of which the polymerizable material forms the continuous phase, the voids in the carrier corresponding to the internal phase of the emulsion.

The advantages of a synthetic polymer as the applicator head, especially the preferred polymers mentioned above, are that high loadings of liquid can be achieved, e.g. at least 3g per g of carrier or even 8g per g of carrier or more, and that it is possible with precision to adjust the structure of the polymer to achieve desired liquid release rate characteristics.

Properties of the polymer which can be adjusted are pore size, void volume and cross-linking (which controls elasticity).

As mentioned above, preferred applicator heads used in the invention are formed by emulsion polymerisation with the polymerizable material as the continuous phase.

Examples of such carriers are those formed from vinyl monomers or as resorcinol/formaldehyde type condensation polymers. In the case of vinyl monomers, the continuous phase is the "oil" phase in the emulsion, which for condensation polymerization the continuous phase is the "water" phase. Processes of producing such polymer structures of high void volume are described in EP-A-60138 (vinyl polymers) and EP-A-289238 (condensation polymers).

It has been observed from microscopic inspection of samples of the porous polymer that it essentially comprises a series of substantially spherical, thin walled cavities having a plurality of holes in the walls interconnecting the adjacent cavities. The absorbency is related to the size of the cavities, expressed in terms of voids diameter, and the number and size of interlinkages.

The mechanism by which the holes form in the thin-walled cavities is not fully understood. However, experimental work suggests that it is related to the quantity of surfactant present and its compatability with the cross-linked polymer and, hence, also to the degree of cross-linking in the polymer. It is thought that prior to polymerisation the high internal phase emulsion consists of three main elements: monomer and surfactants in the continuous phase and water in the internal phase.

The continuous phase, which consists of a homogenous solution of surfactant and the monomer and cross-linking agent and, in this situation, the surfactant is compatible with the monomer mixture. It is thought that at this stage there are no interconnecting holes present in the external phase. During polymerisation chain propagation takes place and as the surfactant is not polymerisable and has no reactive sites in its structure, it cannot take part in the polymerisation reaction. As a result, the surfactant molecules separate because the surfactant is no longer compatible with the growing polymeric structure and is also insoluble in the water phase. Due to the nature of a surfactant, the aggregated molecules of surfactant remain part of the polymer phase and probably cause the production of weak spots and subsequent pinhole formation in the cross-linked polymer film.

The homogeneous structure of the porous polymer blocks provided by this invention can be contrasted with the structure obtained by compressing together polymer beads.

Clearly, when porous polymer beads are compressed and bonded together to form a block, many of the cavities and interconnecting pores on the surface of the beads will be blocked and form non-homogenous zones in the polymer block and the compressive forces applied will further increase the density of the porous polymer in these non-homogenous zones.

In the blocks provided by this invention the interior of the blocks is homogenous and, if the outer skin of the blocks, which is formed in contact with the container of the emulsion, is removed, then the blocks are homogenous and uniform in pore and cavity distribution.

In the present invention, applicator heads formed in this manner from vinyl polymers have been found most suitable. The monomer system may be either styrene alone or, preferably, styrene and an acrylate as co-monomers.

A cross-linking agent or agents, e.g. divinyl benzene, is used to provide the desired degree of rigidity and strength. Preferably the carrier has 74 to 98% void volume, more preferably 85 to 93%.

The amount of cross-linking agent or agents is preferably 2 - 20% by weight. The preferred carrier has void volume of 85-93% with from 5 to 15% crosslinking agent, to maximise liquid holding capacity while maintaining mechanical strength. At void volume greater than 93%, the polymers produced may be mechanically weak, especially when filled with perfume or other organic liquids but polymers prepared from greater than 93% internal phase emulsions can be employed provided that the levels of crosslinking agent are greater than 5%, and preferably at least 10% to improve the strength of the polymers. At crosslinking levels of only 5%, the 96% internal phase polymers are weak and prone to collapse on drying. This collapse may be irreversible or reversible.

In the latter case the polymer can be re-swollen with suitable organic liquids. At crosslinking agent levels less than 2%, the polymers may be too weak or too soft when impregnated with some organic liquids to support their own weight.

The size and shape of the carrier can have an important effect. Preferably, the ratio of external surface area of the carrier to bulk volume of the carrier 2 3 3 3 is in the range 3cm2:lcm3 to 0.5cm to lcm3.

An advantage of carrier used in the invention can be that the amount of the absorbed liquid component present is not so much that the carrier is wet to the touch at its external surface. The voids of the carrier fill with liquid material due to capillary action. There is no drainage back to the reservoir.

The structure and texture of the applicator head may be made in varying degrees of hardness according to the monomer types. Thus the ratio of styrene to ethyl hexyl acrylate could vary, for example, from 60:40 through to 40:60.

PREPARATION OF POLYMER The polymers can be prepared by first forming a water-in-oil high internal phase emulsion system where the oil phase is constituted by the monomer or mixture of monomers, together with a small amount of a cross-linking agent. The polymerisation initiator or catalyst can be dissolved in either the water phase or in the oil (monomer) phase. The high internal phase emulsion system is prepared by the slow addition of the aqueous internal phase to the oil (monomer) phase in which the emulsifying agent (surfactant) is preferably dissolved, using a moderate shear stirring. Conveniently the container in which the polymerisation is carried out is enclosed to minimise the loss of volatile monomers and the emulsions are thermally polymerised in the container.The water in the cavities or voids in the polymer structure can be exchanged for other liquids or readily removed by subjecting the polymer to a vacuum, or leaving the material to dry in a dry atmosphere at between about 30 and 600C. Surfactant used in the manufacture is preferably removed by washing. Liquids can then be reintroduced into the dried polymer, preferably after removing the air under reduced pressure.

SHAPE OF APPLICATOR HEAD The shape of the applicator head is preferably curved. The shape may either be carved from a block with a sharp blade or, preferably, moulded.

The head of the applicator is preferably covered with a cap which removably attaches to the main body of the reservoir. The presence of the cap provides a further method of moulding the applicator head. The cap is used to mould the shape of the applicator head as the unset polymer is poured thereinto. As the mix is dried the appropriate head shape is formed. The head shrinks back slightly from the cap and enables easy removal of the cap.

LIOUID RESERVOIR The liquid reservoir may be a moulded container suitable for holding liquids. Many types are known in the art. A preferred shape is shown in the accompanying drawings.

CONNECTION BETWEEN HEAD AND RESERVOIR In order that leakage of the liquid does not occur it is important that there is fluid tight fixing of the applicator head to the reservoir. This may be via a mounting to which the head is attached. The polymer material may extend into the reservoir like a wick, perhaps even filling the reservoir.

THE LIOUID The applicator may be used to supply liquid systems to hard or soft surfaces. The head is particularly suited for application of liquids to the human body.

These liquids include, for example, creams and lotions, soaps and fragrances. The most preferred liquids are deodorants and antiperspirants for underarm use.

Silicone or alcohol based systems are particularly preferred since they can be easily dispensed through the applicator head. The liquid phase may comprise an emollient material to provide desirable skin-feel qualities. Examples of emollients include isopropyl myristate or other fatty acid esters, such as dibutyl phthalate and di-isoprapyl adipate, but other materials well-known to those skilled in the art can also be used, for example cetyl alcohol. Further examples include those referred to in British Patent Specification No. 1393860 and US 4045548.

Various other suitable liquids are suggested in British Patent Specification Nos. 1411547, 1369872, 1341748, 1300260 and 1476117.

The liquids used may preferably comprise a deodorant agent. The deodorant may be a deodorant composition as defined and as described in GB-PS 2013493A.

Alternatively, the deodorant may be a particulate substance which may or may not also be an antiperspirant.

Suitable deodorant agents, not having an antiperspirant effect, are referred to in European Patent Publication No. 24175 and 24179. These applications relate particularly to the use as deodorants of the oxides, hydroxides and carbonates of magnesium and lanthanum, and zinc carbonate, respectively, but also refer to various other already known deodorant active materials such as zinc oxide and zinc phenolsulphonate.

The liquids may also comprise an antiperspirant material such as any of those mentioned in the specifications already referred to.

However, the antiperspirant active material preferably employed in the skin treatment product of this invention is desirably one which is highly active.

Antiperspirants falling into this category are special active forms of basic aluminium chloride having a particular distribution of polymeric species in aqueous solution and obtainable by the process of US Patent No. 4 359 456 (Gosling et al). The forms of basic aluminium chloride which have enhanced activity are those having a Band III Percent Aluminium Value (as determined by the chromatographic procedure described in the patent) of at least 208.

Other highly active antiperspirants are the aluminium zirconium chorhydrate complexes. Examples are aluminium zirconium trichlorhyrate, aluminium zirconium tetrachlorohydrate and aluminium zirconium pentachlorohydrate (these are CTFA generic names). These compounds may be combined with glycine to give for example the compounds known under the CTFA generic names aluminium zirconium trichlorohydrex-GLY. Methods for preparing aluminium zirconium chorohydrates are described in a number of patents, for example US Patent Nos. 4 028 390 (Armour) and 3 792 068 (Procter & Gamble).

Suitable aluminium zirconium chlorhydrate powders for use in the skin treatment products of this invention are available from the Rehseis Chemical Company under the trade names REZAL 36GP and REZAL 67P (REZAL is a trade mark).

The antiperspirant agent will usually be present in an amount in the range 2 to 50% by weight of the liquid.

It may be present as a powder or preferably in solution in an appropriate solvent.

The present invention will now be described in further detail and with reference to the accompanying drawings in which: Figure 1 shows a sectional view of an applicator Figure 2 shown an exploded view of a cap, applicator head and mounting base.

DETAILED DESCRIPTION The following vinyl-addition polymer systems were produced.: A: 60:40 poly(styrene-ethyl hexyl acrylate) B: 50:5C poly(styrene-ethyl hexyl acrylate) C: 40:60 poly(styrene-ethyl hexyl acrylate) All samples were prepared using 10% commercial divinylbenzene crosslinker containing 0.25 ml ethyl vinylbenzene and 2 g SPAN 80 (Trademark) surfactant to 11 mls monomer/crosslinker mix.

The samples were polymerised in situ according to detailed procedures set out in EP-A-289 238. Referring to Figures 1 and 2, the unset polymer mix was poured through the opening 2 of the mounting base 3 into the space enclosed by the cap 5 fixed removably onto the mounting base. After 9 hours at 600C the mix had polymerised in the cap to form a rigid porous head. The cap was removed and the applicator head 1 formed thereby and affixed to the mounting base was allowed to dry for three days. It was then washed to remove surfactant used in manufacutre an redried.

The applicator reservoir 4 was filled with an alcoholic base containing a perfume deodorant. The mounting base 3 with applicator head 1 attached was pressed onto the reservoir. The mounting base was sealed to the reservoir base using a flexible acetoxy-silicone rubber adhesive. The adhesive set after 30 minutes to form a fluid tight seal.

In order to deliver the liquid in the reservoir to the applicator head, the applicator was inverted and gently squeezed. Pressure to the head results in liquid delivery to the surface it is desired to treat.

Consumer testing showed a preference for polymer system A. This was judged to have a pleasant texture combined with a good delivery of product. Systems B and C in comparison were thought to be too spongy.

Claims (6)

Claims

1. A liquid applicator comprising a reservoir for a liquid connected to a solid applicator head, said head comprising a porous homogeneous cross-linked polymeric block material having a dry density of less than O.1g/cc and formed as a cross-linked porous structure having a pore volume of more than 9cc/g and an absorbency for hydrophobic liquids defined in terms of oleic acid of at least 7cc/g, said porous structure comprising interconnecting void spaces.

2. A liquid applicator as claimed in claim 1 wherein said liquid comprises a deodorant or antiperspirant material for underarm use.

Amendments to the claims have been filed as follows 1. A liquid applicator comprising a reservoir for a liquid connected to a solid applicator head, said head comprising a porous homogeneous cross-linked polymeric block material having a dry density of less than 0.1g/cc and formed as a cross-linked porous structure having a pore volume of more than 9cc/g and an absorbency for hydrophobic liquids defined in terms of oleic acid of at least 7cc/g, said porous structure comprising interconnecting void spaces.

2. A liquid applicator as claimed in claim 1, wherein the applicator head is formed from vinyl polymers.

3. A liquid applicator as claimed in claim 2, wherein the vinyl polymer is formed from a styrene monomer.

4. A liquid applicator as claimed in claim 2, wherein the vinyl polymer is formed from styrene and acrylate co-monomers.

5. A liquid applicator as claimed claim 2, wherein the applicator head is made from cross-linked styrene and ethyl hexyl acrylate monomers, in a ratio of from 60:40 to 40:60.

6. A liquid applicator as claimed in any of the preceding claims wherein said liquid comprises a deodorant or antiperspirant material for underarm use.