MULTICOLOURED PAINT COMPOSITION

Abstract: There is described a paint formulation comprising a thickener adapted to increase in elasticity at pH greater than 7. The thickener comprises a cationic gum which is treated so as to be soluble only under acidic conditions. The paint formulation comprises an inner phase, which is adapted to increase in elasticity and produces a heterochromatic effect, and an outer phase comprising a sequestering agent and an anionic thickener. There is also described a process for the manufacture of the inner and outer phases and a process for the manufacture of a paint formulation.

Description: MULTICOLOURED PAINT COMPOSITION This invention relates to paint compositions and, in particular, heterochromatic, or multicoloured paint compositions and to methods of their manufacture. The invention also relates to the novel use of certain ingredients in the manufacture of paint compositions. It is known to manufacture paints which comprise different coloured particles wherein the particles are kept separate in such a way that they can be applied, without stirring, by use of a low pressure spray application to a desired surface. Such compositions produce a multicoloured decorative finish. However, such systems generally require the use of a solvent/water based technology. Since it is undesirable to use organic solvents, efforts have been made to produce All Aqueous Multicolour (AAMc) paints. Such paints are described in European Patent Application No. 85106538J (EP 0 182 962) which describes a paint comprising an anionic pigmented base dispersed in a cationic medium. European Patent Application No. 91830148.2 also describes an AAMc paint which comprises a pigmented base dispersed in a precipitating solution containing borate ions. Indeed conventionally known heterochromatic paint formulations use borax or borate ions. Also, such formulations are disadvantageous in that they produce large inelastic fleck paints which are undesirably very textured. However, known AAMc formulations and methods have been unsuccessful due to the fact that large fleck type particles, which can be produced using solvent based formulations, cannot be successfully produced in water based systems. So far, it has not been possible to reproduce the effect of solvent/water based systems in AAMc paints. In summary, the problems with prior art systems include, inter alia, (i) particles drying to give a highly textured finish; (ii) particles blocking the spray equipment due to their highly gelatinous nature; (iii) particles breaking down in size when applied through spray equipment; (iv) settlement of particles on storage requiring long mixing times before use; (v) transfer of colour from one coloured particle to another; (vi) strong odour caused by coalescing solvents in the formulation. This present invention provides a water based alternative to current solvent/water based systems whilst maintaining the pattern and texture previously only obtainable using solvent/water based systems. The paint compositions described herein contain less than 0.1% Volatile Organic Compound (VOCs) and are therefore extremely safe to use, are virtually odour free and are not harmful to the environment. We have especially found that paint formulations can be manufactured using 'delayed solubility' gums which are soluble at low pH and undergo a change in rheology at higher pHs. According to the invention we provide a paint formulation comprising at least a thickener adapted to increase in elasticity at pH greater than 7. It is preferred that the increase in elasticity occurs at between pH 7 and 9, e.g. pH 8. A preferred thickener for use in the formulation of the invention is a cationic guar gum and preferably one which is treated so as to be soluble only under acidic conditions. Such gums include galactomannan gums and particularly a galactomannan gum which is not completely solubilised. At, for example, pH's higher than 8, the rheology of the gum is elastic and at significantly higher pH, the material becomes unhandleable. The galactomannan gum is preferably a specially treated gum such that the gum is only soluble under acidic conditions. At a pH of less than 8, in particular a neutral or acidic pH then the gum behaves in a thixotropic manner. At a pH of greater than 8 the rheology becomes elastic. The gum is preferably treated by coating it to increase the time before the gum dissolves. A preferred gum which may be mentioned is JAGUAR C-13S available from Rhone Poulenc in the UK. Although other gums may be used such as GUAR CAT 10, N- HANCE 3205, these are found to be not quite as suitable as the JAGUAR gum. According to a further feature of the invention we provide a paint formulation as hereinbefore described comprising an inner phase which is adapted to increase in elasticity and an outer phase. In particular such a two phase paint formulation comprises an inner phase adapted to produce a multicolour effect and is thixotropically soluble at low pH and substantially elastic at high pH; and an outer, high pH phase. In use, when the high pH outer phase comes into contact with the low pH inner phase, the pH of the inner phase is increased thus increasing the elasticity. The inner and outer phases can preferably be charged. Thus, according to a further feature of the invention we provide a paint formulation comprising an inner phase adapted to produce the multicolour effect and which is cationically charged and an outer phase which is anionically charged. The charged phases are particularly advantageous in that they can keep separate the individual particles and prevent transfer of colourant between them. A preferred paint formulation is one in which the inner phase comprises JAGUAR C13 S. According to a further feature of the invention we provide a paint formulation as hereinbefore described comprising; an inner phase comprising a delayed solubility cationic guar gum thickener, a dispersant, a pigment and a polymer emulsion; and an outer phase comprising a sequestering agent and a second thickener, which second thickener may be anionic. The ratio of the inner phase to the outer phase may be from 1 :99 to 75:25, preferably from 5:95 to 66:33. An especially preferred ratio is 15:85. For a more washable paint, increased amounts of the polymer emulsion may be added to the fleck paint, thus for example, a mixture of fleck paint/polymer emulsion may be prepared in the ratio of from 75:25 to 95:5 fleck paint to polymer emulsion, preferably from 80:20 to 90: 10 and especially 85:15. The inner phase will be an aqueous phase and will generally comprise from 80 to 90 parts by weight (w/w) of water, e.g. 85 w/w water; from 1 to 2 w/w of a thickener, preferably from 1.5 to 2 w/w and especially, 1.75 w/w; from 0J to l .Ow/w of a dispersant, preferably from 0J to 0.6 w/w, e.g. 04 w/w; from 2 to 3 w/w of pigment, preferably from 2.25 to 2.75 w/w, especially 2.5 to 2.1 w/w; and from 8 to 9 w/w of a polymer emulsion, preferably from 8.5 to 9 w/w and especially from 8.8 to 9 w/w. The outer phase will generally comprise from 0J to 1 w/w of a sequestering agent, preferably from 0J to 0.7 w/w, more preferably from 0.5 to 0.1 w/w, e.g. 0.6; and from 0J to 2 w/w of a thickener, from 0.5 to 1.5 w/w of a thickener, e.g. 1 w/w. According to a further feature of the invention we provide a process of manufacturing a paint formulation as hereinbefore described which comprises; preparation of an inner phase comprising at least one pigment and a thickener and adjusting the pH down to allow the guar gum thickener to solubilise; preparation of an outer phase comprising at least an aqueous medium of pH greater than 7; and mixing the inner and outer phases. In particular the process of the invention comprises; (i) preparation of an inner phase by mixing in an aqueous medium a dispersant and a pigment followed by the addition of a guar gum thickener and adjusting the pH as appropriate to less than 6 until the thickener is fully dissolved and then readjusting the mixture to a neutral pH of 7 to 7.5; and (ii) preparation of an outer phase by mixing a sequestering agent in an aqueous medium and adding a gellant followed by a second thickener, which second thickener may be anionic. Conventionally known pigments may be used although the preferred pigment is titanium dioxide. The inner phase can be tinted to produce any colour. If a pigment is omitted, pearlescent dispersions can be added to produce metallic effects. It is possible that the outer phase may be pigmented. However, such pigmentation may mask the colour of the flecks pigmented in the inner phase. Thus, it is preferable that the pigmentation is in the inner phase only. The tinted base paints used in the invention can utilise conventional amounts of coloured dispersions known per se. In preparation of the inner phase any conventionally known dispersants may be used, such as one or more acrylic polymers. As described earlier, the inner phase thickener may be a galactomannan gum or a blend of galactomannan gums, which gums will be cationic. The polymer emulsion may, for example, be a polymeric dispersion of copolymers of vinyl acetate and ethylene in water. Conventionally known acidifying agents may be used, for example, a carboxylic acid and similarly conventionally known neutralising agents may be used, for example, a hydroxide such as sodium hydroxide. In preparation of the outer phase conventionally known sequestering agents used in paint formulations may be used, such as, tetrasodium pyrophosphate. The gellant may be a silicate such as anhydrous sodium lithium magnesium fluoro-silicate. The second thickener may be a cellulose, such as sodium salt of a cellulose ether. Other excipients may be included in the inner phase and/or the outer phase, such as a biocide, for example, a solution of n-formals and isothiazolones, may optionally be used in the mixture; similarly, a defoamer such as mineral oil may also optionally be used. The shape of the flecks produced can be controlled by the way the inner phase is added to the outer phase. If the inner phase is injected into the outer phase, thin string like particles are produced. Whereas, if the inner phase is, for example, simply poured into the outer phase and then mixed together, irregular shaped flecks of an even size are produced. This type of manufacture is mentioned in European Patent application No. 85196538.3. The key ingredients in the inner phase are:- a) the cationic guar gum, we have found one grade that gives especially satisfactory results; b) the polymer emulsion, this does not require any coalescing solvent and therefore allows the formulation to be solvent free; and c) the dispersant, this should be highly effective and allow the pigment to be dispersed thoroughly and prevent it being flocculated by the guar gum. The key ingredients in the outer phase are:- a) the sequestering agent, this stops the gellant reacting to give too strong a gel; and b) the thickener, which in combination with gellant produces a soft gel which suspends the flecks to produce a stable paint. The use of a cationic guar gum, such as JAGUAR C13 S, in paint formulations is novel per se. Thus according to a yet further feature of the invention we provide the use of a cationic guar gum, treated so as to be soluble only under acidic conditions, in the manufacture of a paint formulation. The formulations according to the invention may be applied using conventional methods however it is preferred that, in use, the paint would be applied using a spray gun. Thus we further provide a method of applying a paint formulation according to the invention which comprises the use of a paint spray gun containing a paint formulation comprising an inner phase and an outer phase as hereinbefore described. The formulations according to the invention are advantageous in that the problems mentioned have been overcome by: a) reducing the solid content of the particles to such an extent as to reduce the texture of the finish to a minimal amount; b) eliminating the need for a Borate ion to be used as a precipitant. Therefore producing particles which have a high viscosity without gelation which pass through spray equipment without blockages; c) producing a formulation in which the coloured particles are suspended eliminating the need for stirring; d) producing a formulation in which the particles and their surrounding phase are of opposite charges eliminating pigment transfer within the paint; and/or e) eliminating the need for any coalescing solvents in the formulation, by the use of polymer emulsions which film form without any solvent at room temperature. The invention will now be described but in no way limited with reference to the following examples. Example la) Preparation of Inner Pigmented Phase The inner phase, or pigmented phase, consisted of the following ingredients: Ingredient Parts bv weight Water 84.78 Dispersant a 0.44 Pigment b 2.66 Thickener c 1.77 Biocide d 0.44 Acidifying agent c 0.44 dependent on amount necessary to achieve spec. Neutralising agent f 0.5 dependent on amount necessary to achieve spec. Polymer emulsion g 8.87 Defoamer h 0J Method An acrylic polymer dispersant was added to water whilst mixing slowly on high speed dispenser a titanium dioxide pigment was slowly added. Mixing was continued until all lumps have disappeared. A cationic glactomannan blend thickener was added to the above dispersion and then a biocide (a solution of n-formals and isothiazolones). The dispersion thickened and the mixing speed was increased to maintain vortex. The pH was measured and a carboxylic acid acidifying agent was added as necessary to adjust the pH to 6. When the gellant was fully dissolved, then a sodium hydroxide neutralising agent was added until the pH returned to 7.0 - 7.5. Care was taken not to exceed this. A polymer emulsion (a polymeric dispersion of copolymers of vinyl acetate and ethylene in water) was added to the dispersion followed by a mineral oil defoamer. The inner phase is preferably tinted to produce the coloured particles, using aqueous pigment dispersions. Example lb) Preparation of Outer Phase The outer phase consisted of the following ingredients: Ingredient Parts by weight Water 96 Sequestering agent a 0.6 Gellant b 2.0 Thickener c 1.0 Biocide d 0.3 Defoamer c 0.1 Method A tetrasodium pyrophosphate sequestering agent was slowly added to water with stirring. When fully a gellant, anhydrous sodium lithium magnesium fluoro-silicate was added. When this had fully dissolved a sodium salt of a cellulose ether thickener was ~ followed by a biocide (a solution of N-formals and isothiazolones) and a mineral oil defoamer. Example 2 Preparation of grey tint base paint Ingredient Parts by weight 1) Inner phase 99.82 2) Black dispersion 0.078 3) Yellow oxide disp. 0J01 4) Blue dispersion 0.001 Method To an inner phase according to Example la) was added under slow speed mixing a black dispersion, yellow oxide disp., and blue dispersion. Example 3 Preparation of pink tint base paint Ingredient Parts by weight 1) Inner phase 99.69 2) Red dispersion 0J 3) Yellow dispersion 0J Method To an inner phase according to Example 1 a) was added under slow speed mixing a red dispersion and a yellow dispersion. Example 4 Preparation of fleck production paint Ingredient Parts by weight 1 ) Grey tint base 7.5 2) Pink tint base 1.5 1 ) Outer phase 85 Method Using standard Portaspray plus extra spray equipment each coloured base was injected into the outer phase whilst it was being stirred, the size and shape of the particles produced was controlled by the jet size and the speed of the mixer. Example 5 Modification of fleck production paint After the correct fleck size was achieved, and extra addition of polymer emulsion was made to increase the washability of the dried film. Ingredient Parts by weight 1) Fleck paint 85 2) Polymer emulsion 15 The polymer emulsion was added slowly to the fleck paint whilst under slow stirring until homogenous.

Claims: CLAIMS 1. A paint formulation comprising at least a thickener adapted to increase in elasticity at pH greater than 7. 2. A paint formulation according to Claim 1 wherein the increase in elasticity occurs at pH greater than 8. 3. A paint formulation according to Claim 1 wherein the increase in elasticity occurs at between pH 7 and 9. 4. A paint formulation according to any one of the preceding claims wherein the thickener comprises a cationic gum. 5. A paint formulation according to Claim 4 wherein the gum is a cationic guar gum. 6. A paint formulation according to Claim 4 wherein the cationic gum is treated so as to be soluble only under acidic conditions. 7. A paint formulation according to Claim 4 wherein the cationic gum is JAGUAR C13 S. 8. A paint formulation according to Claim 1 comprising an inner phase which is adapted to increase in elasticity and an outer phase. 9. A paint formulation according to Claim 8 wherein the inner phase comprises a cationic guar gum. 10. A paint formulation according to Claim 9 wherein the inner phase comprises JAGUAR C13 S. 11. A paint formulation according to Claim 8 wherein the inner phase is adapted to produce a heterochromatic effect. 12. A paint formulation according to claim 8 comprising; an inner phase comprising a delayed solubility cationic guar gum thickener, a dispersant, a pigment and a polymer emulsion; and an outer phase comprising a sequestering agent and a second thickener. 13. A paint formulation according to claim 12 wherein the second thickener is anionic. 14. The use of a cationic guar gum, treated so as to be soluble only under acidic conditions, in the manufacture of a paint formulation. 15. A process for the manufacture of a paint formulation according to Claim 8 which comprises; preparation of an inner phase comprising at least one pigment and a thickener and adjusting the pH down to allow the guar gum thickener to solubilise; preparation of an outer phase comprising at least an aqueous medium of pH greater than 7; and mixing the inner and outer phases. 16. A process for the preparation of an inner phase according to Claim 15. 17. A process for the preparation of an outer phase according to Claim 15. 18. An inner phase for use in a formulation according to Claim 8 which comprises a delayed solubility cationic guar gum thickener, a dispersant, a pigment and a polymer emulsion. 19. An outer phase for use in a formulation according to Claim 8 which comprises a sequestering agent and a second thickener. 20. A method of applying a paint formulation according to Claim 8 which comprises mixing an inner phase and an outer phase in a paint spray gum. 21. A paint formulation substantially as described with reference to the accompanying examples.

Inventors: LOMAX JIM, LOMAX, JIM
Applicants: KALON DECORATIVE PRODUCTS, LOMAX JIM, LOMAX, JIM
Application year: 1999
Main classification: C09D7
IPC codes: C09D5, C09D7