WO2003066796A1

WO2003066796A1 - Opacifiers

Info

Publication number: WO2003066796A1
Application number: PCT/EP2003/001185
Authority: WO
Inventors: Kevan Hatchman
Original assignee: Huntsman International Llc
Priority date: 2002-02-09
Filing date: 2003-02-06
Publication date: 2003-08-14
Also published as: AU2003210218A1

Abstract

A non-ionic based suspension of an opacifier (e.g. pearliser) with high payload comprises from 15 to about 40% by weight EDGS, Less than 12%, and more usually less than 7% by weight EGMS and 5 to 30% by weight of non-ionic surfactant. The aqueous medium containing the surfactant has a cloud point greater than 50°C, e.g. greater than 70°C.

Description

OPACIFIERS

This invention relates to opacifiers, which can be suspended in liquids to provide an opaque, creamy visual effect and conceal inhomogeneities. The invention, in its preferred embodiment, relates to pearhsers.

Pearhsers are a species of opacifier, which typically comprise small, thin, transparent platelet crystals, which can be suspended in a parallel configuration. When so suspended, light falling on the crystals undergoes complex multiple reflections within the substrate, similar to those which occur in a pearl and giving rise to similar optical interference effects.

Natural pearls comprise alternate layers of calcium carbonate and protein. Artificial pearhsers include guanine/hypoxanthine crystals extracted from fish scales, mica, various salts of lead, zinc, mercury and bismuth (e.g. bismuth oxychloride), titanium oxide and various fatty acid derivatives such as magnesium stearate, coconut monoethanolamide, ethylene glycol distearate , ethylene glycol monostearate and polyethyleneglycol stearates. Fish scale extracts are too expensive and the inorganic pearhsers are either too toxic for general use in toiletries e.g. lead, mercury, or relatively ineffective e.g. bismuth. The fatty acid derivatives are therefore now the most widely used pearhsers. In addition to the chemical nature and physical form of the pearliser the manner in which it is suspended has an important effect on its visual impact. Difficulty is sometimes encountered obtaining the desired effect when incorporating pearhsers into aqueous formulations.

Conventional fatty acid derived pearhsers are supplied as solids, which are usually added to a heated formulation above their melting point and recrystallised in situ. The conditions of crystallisation and especially the amount and nature of the agitation applied must be carefully controlled in order to obtain an acceptable result. This makes it difficult to obtain consistent effects and renders solid pearhsers inconvenient to use.

Attempts have been made to prepare liquid concentrates or suspensions, which can be added directly to shampoo formulations without heating. While more convenient for the user, such concentrates face the manufacturer with problems of obtaining a high and consistent pearl effect, similar to those which confront the user of conventional solid pearhsers. Difficulty is also encountered in maintaining the particles in stable suspension and preventing sedimentation.

Commercial products addressing the above problems, based on the teaching, for example, of WO 01 / 25378, have required the use of anionic surfactants, such as alkyl ether sulphates. However, for many potential applications, the presence of anionic surfactants is unacceptable or undesirable.

US 4 777 038 describes a non-ionic aqueous pearliser suspension, but it has not proved possible, following the teaching of this document, to achieve commercially viable payloads of the glycol stearate pearliser. At concentrations of glycol stearates above about 10% by weight, these suspensions become unacceptably viscous and / or difficult to dilute or incorporate into the end formulation.

Commercial glycol stearate pearhsers all comprise mixtures of ethylene glycol mono stearate (EGMS) and ethylene glycol distearate (EGDS), together sometimes with polyethylene glycol stearates, in varying proportions. Those skilled in the art are aware that homologues, such as palmitates, arachi dates and behenates are substantially equivalent to the corresponding stearates, but are very unlikely to be used in practice on economic grounds, as well as being technically less preferred. The invention will therefore be described with particular reference to stearate esters, but it is to be understood that references herein to "stearates" are intended to embrace the equivalent esters of other C16-22 fatty acids, and mixtures thereof, whenever the context permits. Expressions such as EGMS and EGDS are to be similarly construed. The aforesaid ethylene glycol, and polyethylene glycol, stearates, and their equivalents will be referred to collectively herein as "glycol ester opacifiers".

In the following discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, coupled with an indication that one of said values is more highly preferred than the other, is to be construed as an implied statement that each intermediate value of said parameter, lying between the more preferred and the less preferred of said alternatives, is itself preferred to said less preferred value and also to each value lying between said less preferred value and said intermediate value.

We have now discovered that it is possible to make non-ionic glycol ester opacifier suspensions with commercially viable concentrations of opacifier by selecting surfactants with a sufficiently high cloud point and by keeping the total concentration of EGMS below 8%.

Our invention provides an aqueous glycol ester opacifier suspension, which comprises an aqueous non-ionic surfactant medium and suspended solid glycol ester opacifier characterised in that the aqueous medium comprises from 5 to 30% by weight total, based on the total weight of the suspension, of non-ionic surfactant and has a cloud point greater than 50°C, said suspension containing a total of from 0 to 12% EGMS and greater than 15% EGDS by weight, based on the total weight of the suspension.

The EGDS is preferably present in a proportion of more thanl6%, more preferably more than 17%, even more preferably more than 20%, more preferably still, more than 25%, most preferably more than 28% by weight, based on the total weight of the suspension. The upper limit of the EGDS concentration depends on the nature of the aqueous medium, including the presence of any deflocculants, and also on the maximum viscosity that is acceptable to the end user. For example, EGDS concentrations as high as 40%, or even higher, can be envisaged. In practice the EGDS concentration is preferably less than 38%, more preferably less than 36%, most preferably less than 35%, by weight, based on the total weight of the suspension.

The amount of EGMS is critical to obtaining an acceptable viscosity and good pearl effects. Whereas it is possible to obtain suspensions up to about 12% EGMS if sufficient deflocculant and/ or dispersant is used, and/ or if relatively low total payloads and/ or relatively high viscosity can be tolerated, we generally prefer that the concentration of EGMS is below 10%. It is more preferably less than 9%, even more preferably less than 8% and most preferably less than 7%, and, for best mobility at high payloads, is preferably as low as possible. However, for a good pearl effect, it is preferred to include at least 2%, more preferably at least 3%, even more preferably at least 4%, most preferably at least 5%, EGMS by weight of the suspension.

The aqueous medium, including any dissolved electrolyte, hydrotrope, EGMS, or other soluble ingredients, as well as the non -ionic surfactant, when separated from suspended solids, e.g. by centrifuging at 20,000G, should preferably have a cloud point greater than 55°C, more preferably greater than 60°C, even more preferably greater than 65°C, most preferably greater than 70°C, e.g. 80 to 100°C.

The non-ionic surfactant is usually present as a clear, optically isotropic Ll-phase. However, if a relatively hydrophobic surfactant is present, the concentration of surfactant is high and / or there is a high enough level of electrolyte, the surfactant may form a structured system, usually a lamellar (G- or Lα) or dispersed lamellar, or spherulitic (i.e. comprising dispersed concentrically layered spheroids) phase. These are typically optically anisotropic. In the absence of the glycol stearates, the non-ionic surfactant and water may, according to an embodiment of the invention, form a clear, optically isotropic micellar solution, which exhibits small angle X-ray diffraction peaks, having a spacing characteristic of hexagonal symmetry. Such systems are believed to comprise prolate micelles in a substantially or predominantly parallel orientation. Such LI -phases lie close to the Ll/M-phase boundary and may be regarded as precursors of the M-phase. They will be referred to herein as "protohexagonal". We believe that, in the presence of dissolved ethylene glycol monostearate, the protohexagonal-phase forms lamellar or spherulitic structured systems.

The concentration of non-ionic surfactant in the aqueous phase is preferably greater than 8% by weight, based on the total weight of the suspension, more preferably greater than 10%, even more preferably more than 12%, most preferably more than 15%), but preferably less than 28%, more preferably less than 25%, even more preferably less than 23%, most preferably less than 20%. In addition to any dissolved portion of the EGMS, the non-ionic surfactant preferably comprises at least one ethoxylated surfactant, preferably a C ₈to25, especially oto∑o, straight or branched chain alcohol, 1 to 60 mole, preferably 2 to 20 mole, ethoxylate. The alcohol may be fatty alcohol or synthetic e.g. branched chain alcohol. Preferably the non-ionic surfactant has a mean HLB greater than 3, more preferably greater than 6, most preferably greater than 8, but preferably less than 16, more preferably less than 15, most preferably less than 12. We particularly prefer mixtures of two or more non-ionic surfactants having a weighted mean HLB in accordance with the above values.

Other ethoxylate and/or propoxylated non-ionic surfactants, which may be present, include Cβ- alkylphenol ethoxylates, ethoxylated fatty acids, ethoxylated amines, ethoxylated alkanolamides, ethoxylated alkyl sorbitan and/or glyceryl esters and propylene oxide / ethylene oxide block co-polymers.

Other non-ionic surfactants, which may be present, include amine oxides, fatty alkanolamides such as coconut monoethanolamide, and coconut diethanolamide, alkyl polyglycosides, sugar esters and alkylaminoethyl fructosides and glucosides.

In particular it has been discovered that the viscosity of the suspension may be reduced, and the maximum practicable payload of opacifier thereby increased, if a non-ionic or anionic deflocculant is included. The latter may comprise one or two fatty alkyl or alkenyl groups linked to a large (e.g. more than lOOamu, preferably more than 200, more preferably more than 300, even more preferably more than 400, yet more preferably more than 500, most preferably more than 600amu) non-ionic or anionic hydrophilic group.

Examples include alkyl polyglycosides, polyglyceryl esters, sorbitan esters, polyethylene glycol esters, thiol polyacrylates, alkyl polyethoxylates and sucrose esters. We generally prefer that the deflocculant has an HLB greater than 12, more preferably greater than 13, even more preferably greater than 14, most preferably greater than 15. Additionally or alternatively to the deflocculant, the composition may contain a non- ionic dispersant, which has an HLB below 10, preferably below 8, more preferably below 7, even more preferably below 6, most preferably below 5, but above 1.1 preferably above 1.5, more preferably above 2, still more preferably above 3, most preferably above 4. Examples of suitable dispersants include glyceryl and poly (e.g. 2 to 5, preferably 3 to 4 mole) glyceryl esters, especially of one or preferably more fatty acids, such as stearic, oleic, erucic or isostearic acid. Polyglyceryl esters of dimerised unsaturated fatty acids, such as dimerised linoleic acid, and their (preferably longer chain, i.e. C_14-24) fatty acid derivatives, such as diisostearoyl polyglyceryl-3 dimer dilinoleate, are particularly preferred. Also of use as dispersants are sorbitan mono-, or preferably di-, esters of (preferably longer chain) fatty acids.

. The proportion of the added deflocculant and /or dispersant is preferably less than 2%, more preferably less than 1%, even more preferably less than 0.7%, most preferably less than 0.5%, by weight, based on the weight of the suspension

We prefer that the weight ratio of suspended glycol stearate to non-ionic surfactant in the aqueous phase be greater than 1:1, more preferably greater than 1.5:1, even more preferably greater than 1.7: 1, more preferably still, greater than 2:1, most preferably greater than 2.2:1, but preferably less than 3: 1, more preferably less than 2.7: 1, even more preferably less than 2.5:1, more preferably still, less than 2.4:1, most preferably less than 2.3: 1.

The aqueous medium may comprise dissolved electrolyte, which may improve the stability of the suspension, e.g. by contributing to the structuring of the surfactant. The electrolyte may, for instance comprise sodium chloride or any other water soluble salt of an alkali metal, e.g. sodium or potassium, or of ammonium and a strong acid. It may comprise a water-soluble citrate, acetate, acrylate, lactate, borate, carbonate, silicate, phosphate, pyrophosphate, polyphosphate, phosphonate or any other water- soluble salt in concentrations up to saturation, compatible with a stable, pourable suspension. The aqueous medium may additionally comprise a preservative. Solvents are preferably absent, but may sometimes be used in small quantities to improve mobility. For example, alcohols such as ethanol or isopropanol, glycols such as ethylene or propylene glycol, glycerol, polyethylene glycols and glycol ethers may be present, sometimes in concentrations as high as 10% by weight, but more usually less than 5%, especially less than 2%, e.g. less than 1%. Hydrotropes, such as urea, or toluene-, cumene- or xylene- sulphonates are not normally needed, but could be added in amounts up to about 5% by weight, e.g. 0.1 to 2%, if desired.

It is also possible to suspend other solids, e.g. polyethylene glycol distearates or other co-opacifiers or pearhsers, in addition to the ethylene glycol stearates, especially fatty acid alkanolamides, e.g. if a metallic sheen is desired.

In principle the suspensions of the invention can contain any chemically compatible ingredient that may be required or tolerated in the customer's formulation, including minor proportions, e.g. up to 10% by weight, preferably less than 8%, more preferably less than 5%, most preferably less than 2%, of anionic and / or amphoteric surfactants, or of cationic surfactants. However, we strongly prefer to include only the minimum number of essential ingredients, so as to give the customer maximum flexibility. In general these essential ingredients are water, non-ionic surfactant and glycol stearates, together, usually, with preservative and, sometimes, electrolyte. We prefer that the suspensions be substantially free from ionic surfactants, e.g. containing less than 2%, preferably less than 1.5%, more preferably less than 1%, even more preferably less than 0.7%, more preferably still less than 0.5%, most preferably less than 0.4%, by weight , based on the total weight of the suspension.

The suspensions of the invention are preferably made by mixing the ingredients at, or raising a mixture of the ingredients to, a temperature above the melting point of the EGDS, e.g. above 60°C, preferably above 70°C, typically 80 to 90°C, stirring the mixture to disperse the molten wax and cooling to re-crystallise the wax. In general, where a good pearl effect is required, we prefer to cool the mixture slowly, e.g. less than 0.5°C per minute, preferably less than 0.2°C, especially between 0.15 and 0.01°C per minute. In particular we prefer to cool most slowly at, and just below, the temperature at which the glycol stearate crystallises. We particularly prefer to hold the mixture at a temperature slightly below the crystallisation temperature, e.g. between 55and 60°C, for from 1 to 4 hours

The invention will be illustrated by the following examples in which all percentages are by weight based on the total weight of the suspension:

EXAMPLE 1

A mixture of:

C 12- 14alky 1 12 mole ethoxylate 15%

EGDS 24% EGMS 6%

Water balance

was heated to 85° with stirring to disperse the molten wax. The mixture was cooled, with further stirring, at a rate of 0.1°C per minute, to a temperature of58°C. After 1.5 hours stirring at 55-58°C, the mixture was cooled to 30°C, at a rate of 0.05°C per minute. A stable, mobile pearl concentrate was obtained.

EXAMPLE π

A mixture of:

Was mixed and cooled as described in Example I. The product had a pH, at 10% dilution, of 4.8, and a viscosity of 8 Pas. EXAMPLE πi

A mixture of:

Was mixed and cooled as in example 1. The product had a viscosity (Brookfield, spindle 3, 20°C, 30sec) of 3Pas, a 10% dilution pH of 5, and a particle size of 10 to 20μ.

Claims

-1- CLAIMS

1. An aqueous glycol ester opacifier suspension, which comprises an aqueous non-ionic surfactant medium and suspended solid glycol ester opacifier characterised in that the aqueous medium comprises from 5 to 30% by weight total, based on the total weight of the suspension, of non-ionic surfactant and has a cloud point greater than 50°C, said suspension containing a total of from 0 to 12%) EGMS and more than 15 % EGDS by weight, based on the total weight of the suspension.

2. A suspension according to claim 1, characterised in that the proportion of EGDS is between 20% and 38% by weight based on the total weight of the suspension

3. A suspension according to either of claims 1 and 2, characterised in that the proportion of EGMS is from 2 to 8% by weight based on the total weight of the suspension.

4. A suspension according to any foregoing claim characterised in that the concentration of non-ionic surfactant in the aqueous phase is from 10% to 25%» by weight, based on the total weight of the suspension.

5. A suspension according to any foregoing claim characterised in that the weight ratio of suspended glycol stearate to non-ionic surfactant in the aqueous phase is greater than 1:1 but less than 2.7:1