Method for the formulation and preparation of heterochromatic paints and related products

Abstract: In the paint-formulation method disclosed, an anionic cellulose thickener contained in the base is made to react with the inorganic salts of heavy or trivalent metals or with cationic surface-active agents, which are contained in a reactive emulsion medium. The method can be carried into effect in a variety of ways, all of which resulting in a stable heterochromatic paint giving a mono- or polychrome ground, with additional colours superimposed at random in a speckled, dropped or filiform pattern, or with star or disc shapes &c.

Description: The invention relates to a method of formulating and preparing heterochromatic paints and other related products-that is, a new process for the manufacture of general purpose multicolour paints such as are used in the construction, woodworking, plastics and mechanical engineering industries, etc. The paints obtainable via such a process likewise constitute property to be protected by the appended claims. It is known from US-A-3,458,328 an aqueous multicolour coating composition of two or more phases consisting of at least one dispersed phase consisting of discrete globules or droplets of an aqueous film-former and containing therein a hydrophilic colloid, which dispersed phase is dispersed in an aqueous dispersing medium. At least some of the dispersed globules are different in colour from the dispersing medium and a substantial number of said globules are at least about 25 micrometers in size. It is also known from GB-A-2 078 243 a multicolor coating composition of the type in which a number of discrete coloured globules of a size visible to the naked eye are dispersed in an aqueous medium of a colour different from that of the globules. The globules comprise a mixed organic complex reaction product resulting from both ionic and non-colloid reactions of two polyelectrolytes of opposite charges and a reactant which forms a complex with one of the polyelectrolytes and are of sufficient strength and fluidity as to not subdivide substantially when brushed or rolled on a desired substrate. In the above-described multicolor coating compositions, the dispersion of the coloured globules or droplets in the dispersing medium is a physical process, thermodynamically unstable, thus the coloured particles may mingle together with detriment of the polychrome effect and stability cannot, in general, be ensured beyond 6 to 12 months. Furthermore, no possibility exists with such prior art paints of modifying the shape of the particles, which are predominantly spherical, and as a result, somewhat limited in aesthetic potential, not to mention the fact that it is impossible to obtain spherical particles of a diameter noticeably greater than 2 mm. The density of the dispersing phase and dispersed phase and the viscosity of the paint must be closely monitored in order to avoid sedimentation, hence coalescence of colour particles, and the production of chromatic effects other than those initially intended. Again the determining nature of numerous variable factors and the unstable nature of the dispersion are instrumental in the production of numerous batches of paint which fail to match the effects of earlier batches of the same type. The prior art stands in need of improvement in view of the possibility of producing paints which afford a high polychromatic potential, variety of visual effects, long term stability. From the foregoing, one may discern the need for a solution to the problem posed by a search for polychrome paints wherein the suspended particles afford greater variety of patterns and shapes (speckled, dropped or filiform, star or disc, etc.) and possess greater long-term stability (two or three years and more) the characteristics of which can be reproduced exactly even following a long time lapse. The invention solves the problem thus outlined by adoption of a new method for the formulation of heterochromatic paints which renders greater variety and long-term stability of the shape of particles feasible by chemical reaction. The method consists in bringing about a reaction between an anionic cellulose thickener contained in the base and cationic salts of heavy or trivalent metal dissolved in the reactive medium, the excess of cationic salts being neutralized by calcium carbonate. The reaction results in the formation of non-soluble precipitates consituting a random dispersion of colour particles. The method of formulating heterochromatic paints according to the invention envisages two components, the first of which being the "base", the second of which being a "reactive medium" split into two parts A and B. The heterochromatic paint is produced by an appropriate blending of the two components, and, according to the ultimate manner of carrying the method into effect, stable heterochromatic dispersions of non-soluble precipitates are produced which, when applied, exhibit a mono- or polychrome ground with a random dispersion of colour particles creating a speckled, dropped or filiform pattern, or appearing in star, disc or other shapes. Advantages of the invention are: ample variety of random particles shapes, obtained with the extruders employed for admixing the bases; conservation of the shape of particles in suspension for ultra-long periods; and dependability and repeatability of the manufacturing process and the results thereof. The invention will now be described in detail, by way of example, with the aid of three accompanying sheets of drawings which illustrate black-and-white reproductions of heterochromatic-type paint-finishes formulated both with prior art methods, and with the method described herein. Figs. 1 and 2 are specimens of a speckled-type finish given by a heterochromatic paint, formulated according to prior art methods, using a solvent medium; Figs. 3 and 4 are specimens of a speckled-type finish given by a heterochromatic paint formulated according to a first version A of the method disclosed; Figs. 5, 6, 7 and 8 are specimens of a dropped-type finish given by a heterochromatic paint formulated according to a second version B of the method disclosed; Figs. 9, 10, 11 and 12 are specimens of a filiform-type finish given by a heterochromatic paint formulated according to a third version C of the method disclosed. The method is carried into effect as follows. Thy heterochromatic paint, a water paint, is obtained by appropriate blending of base and reactive medium. Formulation of the reactive medium (expressed in pp% and listed in admixing sequence) Part A Sufficient water to reach 100 Bacteriocide (optional) 0.010 to 0.300 Nonionic cellulose ether (e.g. cellulose or polysaccharide alkyl or hydroxyalkyl) (optional) 0.050 to 4.000 Part B Water 1.000 to 70.000 Inorganic salt (of heavy or trivalent metal) 1.000 to 30.000 total pp 100 The following is an example of the formulation of a heterochromatic paint according to the invention. Components are expressed in pp%. The method claimed herein is divided into three stages, the first two of which being preparation of one or more bases (i.e. two or more colours), and preparation of the reactive medium and admixture of the base thereto. The third stage may be carried out in a number of ways (version A, B, or C &c.) which will differ in terms of the admixture sequence or of the manner in which components are blended, thereby obtaining the polymorphous application typical of a heterochromatic paint according to the invention. Method of preparing the base (stage 1) Bases are produced in given colours such as will obtain the multicolour effect sought after. The base mixture is prepared utilizing the process currently adopted for blending water paints. Use is made of a vessel, together with a dispersion apparatus which keeps the mixture on the move and refines the entire bulk, whose speed of rotation can be varied between, say, 0 and 2000 min⁻¹, and whose rotary dispersion-paddle is adjustable for height within the vessel. The apparatus also incorporates a rotor for dispersion of the pigments. The base is formulated according to the sequence listed above. Admixture of the single components must be subject to complete solution or dispersion of the component previously introduced. The colour in question can be obtained utilizing either organic or inorganic pigments, or suitably-proportioned combinations of the two, in order to achieve the tone, saturation and luminosity sought after. When admixed to the reactive medium, the base duly reacts with cations in the salts thereby forming non-soluble precipitates, a process which can be assisted by admixture to the base of an emulsion having similar polarity to the cellulose. Method of preparing the reactive medium (stage II) The reactive medium is prepared by way of the process currently utilized in the paint manufacturing industry. The non-ionic cellulose ether (alkyl or hydroxyalkyl of cellulose or polysaccharide) is dissolved in a plastic or stainless steel vessel. There is no special need to utilize a cellulose thickener in the reactive medium in order to render particles insoluble, though it is important that the cellulose thickener should be added when seeking to control the shape of the particles, if degeneration into unwanted shapes is to be avoided. Preparation of part A being under way, the cationic compound (e.g. an inorganic salt of heavy or trivalent metal, is prepared in a separate plastic or stainless steel vessel, and then added slowly to a part A which will be kept gently stirring all the while. The reactive medium is formulated according to the sequence listed above. Method of preparing the heterochromatic paint (stage III) Whatever the morphology of the heterochromatic paint in production, the method of its preparation is one whereby the various colour bases are admixed to the reactive medium in a stir-and-disperse apparatus consisting of a plastic or stainless steel vessel provided with a height-adjustable rotor, or with paddles located at various heights, whose speed of rotation is variable between 0 and 2000 min⁻¹. The admixing sequence for components must correspond to that listed above, and each single component must dissolve and/or blend and/or react fully before the following component is introduced. Versions of the method of preparing heterochromatic paints It is in stage III of the process that polymorphous characteristics of the paint are determined. Different particle shapes are obtainable from the one method of formulation by admixing the base to the reactive medium in different ways, and stirring the medium at varying speeds and by different means. Adopting version A which provides a heterochromatic emulsion giving the speckled type of finish reproduced in Figs 3 and 4 in black & white photocopy, the rotor must be capable of producing a significant level of dispersion -viz, Lenhard and Cowles type, or emulsifying, centrifugal, radial, biconical, trapezoidal &c... With the reactive medium poured into the vessel, the dispersion rotor is made to turn at 800 min⁻¹ or more whereupon base colour 1 is admixed, by manual means or utilizing a pump, such as to react gradually with the inorganic salt and split up into particles whose size will diminish the longer the stirring action is continued; and/or the higher the speed of rotation becomes. The same procedure is adopted for other bases (colour 2, colour 3, &c.), however many, in due proportion. By keeping a record of the pump flow rate and the speed of rotation, there will be no difficulty in repeating the manufacturing process in such a way as to obtain an identical morphology and colour specification. Adopting version B which provides a heterochromatic emulsion giving the dropped type of finish reproduced in Figs, 5, 6, 7 and 8 in black & white photocopy, the rotor must be of a design such as to blend without occasioning dispersion, such as the impeller type, having vanes either in V-formation or angled, or one of the various anchor types, so-called, or an auger-type, or a turbine type having vertical and contoured blades, vertical radial blades, inclined radial blades &c. With the reactive medium poured into the vessel, the rotor is made to turn at a low speed (40 to 80 min⁻¹) the exact setting of which will also depend upon the type of vanes, and adjusted so as to invest the mixture with as laminar a motion as possible-i.e. without any vortex being set up. The bases are now admixed in succession (colours 1, 2, 3...), being extruded in solid and/or liquid state from nozzles of appropriate diameter (e.g. 2 to 4 mm) which may be immersed directly into the medium, or installed at surface level, or even marginally thereabove, say, 5 cm or more. In view of the fact that the morphology of particles held in suspension will depend upon the nozzle diameter and the speed of rotation, physical parameters such as these must be maintained constant if repeatability of the batch specification is to be ensured. Adopting version C , one obtains the filiform type of multicolour finish reproduced in Figs. 9, 10, 11 and 12 in black & white photocopy. The paint providing the filiform finish of Fig. 9 is formulated from the heterochromatic components already described, whilst in that providing the filiform finish of Figs. 10 and 12, though formulated in the same manner, different proportions are utilized; the quantity of colour 1 (white) is reduced in favour of colour 2 (blue) and colour 3 (grey). The filiform particles are obtained by applying version B, though utilizing nozzles of much smaller diameter, say, 0.3 to 0.8 mm. Before extruding the filiform particles, one can give the paint ground colour a substantially uniform appearance (Figs. 9 to 12) by proceeding as follows. With the reactive medium poured into the vessel, a turbine is fitted to the blender shaft whose design is such as to produce a strong dispersive action (version A ) with the rotor turning at maximum speed (1400 min⁻¹ at least). Base colour 1 is now admixed, and the refining action is made to continue, thereby producing particles of such fineness that, applying the finish, a ground of uniform appearance can be obtained against which the random filiform splashes will stand out in contrast. At this juncture, the high speed dispersion turbine must be replaced with a low speed blend-only rotor (version B ). The random filiform particles are not obtained, following dispersion of dour 1, by the admixture of colour 2 and colour 3, extruding the relative bases from small-diameter nozzles as afore-mentioned. The length of the filiform particles is determined by their viscosity and by the speed of reaction with the medium; their random diameter is dependent upon the diameter of the nozzles. Thus, combining versions A, B and C as described, together with other such 'versions' which may be deduced in the light of the foregoing, regarding the shape and diameter of nozzles or means of extrusion generally, and the colours of different bases, it becomes possible to obtain an infinite variety of patterns and chromatic effects. The following formulations are those employed for the finishes illustrated in the drawings. Formulation of white base component-colour 1 (Figs. 4, 6, 9, 10 & 12) Water 80.100 Bacteriocide 0.200 Sodium carboxymethylcellulose 1.000 Inorganic pigment-titanium dioxide 6.000 Mica 1.500 Coalescent 0.500 Defoaming agent 0.400 Copolymer-anionic vinyl-ethylene acetate with 50% suspended solids 10.000 Corrosion inhibitor 0.300 total pp 100 Formulation of blue base component-colour 2 (Figs. 4, 6, 9, 10 & 12) Water 80.100 Bacteriocide 0.200 Sodium carboxymethylcellulose 1.000 Inorganic pigment-titanium dioxide 5.800 Organic pigment-phthalocyanine blue 0.200 Mica 1.500 Coalescent 0.500 Defoaming agent 0.400 Copolymer-anionic vinyl-ethylene acetate with 50% suspended solids 10.000 Corrosion inhibitor 0.300 total pp 100 Formulation of grey base component-colour 3 (Figs. 4, 6, 9, 10 & 12) Water 80.000 Bacteriocide 0.200 Sodium carboxymethylcellulose 1.000 Inorganic pigment-titanium dioxide 5.000 Inorganic pigment-yellow ferrous oxide 0.100 Inorganic pigment-black ferrous oxide 1.000 Mica 1.500 Coalescent 0.500 Defoaming agent 0.400 Copolymer-anionic vinyl-ethylene acetate with 50% suspended solids 10.000 Corrosion inhibitor 0.300 total pp 100 Formulation of reactive medium (Figs. 4, 6, 9, 10 & 12) Part A Water 59.400 polygalactomannan hydroxyalkyl 0.600 Part B Water 30.000 Aluminium sulphate-Al₂ (SO₄)₃ 10.000 total pp 100 Formulation of heterochromatic paint (Figs. 4, 6, 9, 10 & 12) Reactive medium 10.000 White base-colour 1 60.000 Blue base-colour 2 6.600 Grey base-colour 3 5.000 Micronized calcium carbonate 3.000 Defoaming agent 0.200 Coalescent 0.500 Copolymer-styrene acrylic suspension containing 50% solids 12.000 Solution of bentonite-10% in water 0.800 Solution of polygalactomannan hydroxyalkyl-60% in ethanol 0.400 Bacteriocide 0.200 Solution of caustic soda-30% in water 1.000 Corrosion inhibitor 0.300 total pp 100 Figs. 5, 7, 8 and 11 show further examples of paint finishes affording different colour combinations, obtained with heterochromatic emulsions according to the invention. When carrying the invention into effect, materials, details, may all differ from those described, but technically equivalent whilst by no means straying from within the bounds of protection afforded to the invention by claims appended. The following variation might be applied in the case of the speckled multi-colour finish illustrated in black & white photocopy in Figs. 3 and 4, bearing in mind that variations of this nature fall within the scope of the method and the different versions of its implementation disclosed in the foregoing pages. Formulation of the bases and of the reactive medium remain unaltered. Stage III on the other hand, in which formulation of the heterochromatic paint is brought about, remains substantially unaltered in terms of total quantities introduced, though the sequence of mixing single components is modified. Variation on the formulation of heterochromatic paint (as in Fig. 4) Base-colour 1 60.000 Reactive medium 5.000 Calcium carbonate 1.500 Base-colour 2 6.600 Reactive medium 3.000 Calcium carbonate 0.500 Base -colour 3 5.000 Reactive medium 2.000 Calcium carbonate 1.000 Defoaming agent 0.200 Coalescent 0.500 Copolymer-styrene acrylic suspension containing 50% solids 12.000 Solution of bentonite-10% in water 0.800 Solution of polygalactomannan hydroxyalkyl-60% in ethanol 0.400 Bacteriocide 0.200 Solution of caustic soda-30% in water 1.000 Corrosion inhibitor 0.300 total pp 100 The variation thus formulated (version D) is carried into effect as follows. Base colour 1 is poured into a plastic or stainless steel vessel, care having been taken to fit the blender with a turbine designed to provide a strong dispersive action. The rotor is made to turn at 800 min⁻¹ or more, and introduction of the reactive medium commenced. As the medium gradually comes into contact with the base, a reaction takes place which produces the finely divided particles. Granulometry being obtained as required, the rotor speed is duly reduced, whereupon the reaction is neutralized by admixture of the calcium carbonate. Base colour 2 is now added, the rotor speed once again increased, and the reactive medium introduced. Having obtained the requisite granulometry, rotor speed is lowered, whereupon the reaction is neutralized by admixture of the calcium carbonate. This cycle is duly repeated for each base utilized. With the granulated colour particles formed, the paint is integrated by admixture of the remaining components listed. As far as regards the sequence of admixture in each formulation disclosed, this happens to be the most convenient in each case. Heterochromatic paints are obtainable nonetheless implementing changes in the sequence that remain compatible with the method.

Claims: Method for the formulation and preparation of heterochromatic paints and related products consisting of a dispersion of colour particles in an aqueous dispersing medium, the method comprising reacting one or more base mediums containing an anionic cellulose thickener, each of said base mediums, when more than one is used, being of a different colour, with a reactive medium comprising an inorganic salt, characterised in that an inorganic salt of heavy or trivalent metal is used and calcium carbonate is added immediately to the reaction product to neutralize excess cationic salts, said inorganic salt being used in an amount sufficient to form reaction products consisting essentially of non-soluble precipitated colour particles. Method as in claim 1 wherein the base and the reactive medium are obtained by formulation of the following components, expressed quantitatively in parts per hundred by weight (ppt) and listed in the preferred sequence of admixing. Reactive medium Part A Sufficient water to reach 100 Bacteriocide 0.010 to 0.300 Non-ionic cellulose ether (e.g. cellulose or polysaccaride alkyl or hydroxyalkyl) (optional) 0.050 to 4.000 Part B Water 1.000 to 70.000 Inorganic salt (of heavy or trivalent metal) 1.000 to 30.000 Total pp 100 Heterochromatic paint as in claims 1 and 2, characterized in that it is formulated from the following components in parts per hundred by weight, listed in preferred sequence of admixing. Heterochromatic paint as in claim 3 wherein the formulation in pp% is as follows. Sufficient water to reach 100 Bacteriocide 0.014 to 0.850 Non-ionic cellulose ether 0.031 to 3.600 Solution of inorganic salt (of heavy or trivalent metal) in water 0.020 to 9.000 Ionic cellulose ether 0.020 to 5.400 Inorganic and organic pigments 0.080 to 18.000 Mica 0.080 to 5.400 Micronized calcium carbonate 0.100 to 6.000 Defoaming agent 0.054 to 1.220 Coalescent 0.070 to 1.900 Copolymer emulsion containing 50% dispersed solids 2.400 to 48.000 Bentonite 0.010 to 0.500 Caustic soda 0.015 to 0.900 Corrosion inhibitor 0.014 to 1.050 total pp 100 Method according to claims 1 or 2 characterized in that two or more base mediums of different colours are admixed in succession to the reactive medium in a stir-and-disperse apparatus consisting of a plastic or stainless steel vessel provided with a rotor capable of producing a significant level of dispersion and turning at a high speed of 800 min⁻¹ or more, thus obtaining a speckled finish. Method according to claims 1 or 2 characterized in that two or more base mediums of different colour are admixed in succession to the reactive medium, whilst invested with laminar motion, in a stir-and-disperse apparatus consisting of a plastic or stainless steel vessel provided with a rotor designed to produce a blending action only at low speed of 40 to 80 min⁻¹, and that the bases are extruded from nozzles having a diameter of 2 to 4mm, which may be either immersed directlly into the medium, or disposed at surface level thereof, or located marginally thereabove, thereby producing particles of a medium size order and obtaining a dropped finish. Method according to claims 1 or 2 characterized in that a first base for the ground colour is admixed to the reactive medium and finely dispersed in a stir-and-disperse apparatus consisting of a plastic or stainless steel vessel provided with a rotor designed to produce a strong dispersive action, turning at an extra high speed of 1400min⁻¹ or more whereupon the aforesaid rotor is replaced by a rotor designed to produce blending action only, turning at low speed of 40 to 80min⁻¹, with other bases of different colour being admixed in succession to the reactive medium; and that the other bases are extruded from nozzles of small diameter of 0.3 to 0.8mm, either immersed directly into the reactive medium , or disposed at surface level thereof, or located marginally thereabove, thus obtaining a random dispersion of colour particles creating a filiform finish of appearring in star, disc or other shapes, depending upon the cross section of said nozzles. Method according to claims 1 or 2 characterized in that a first base is introduced in a stir-and-disperse apparatus consisting of a plastic or stainless steel vessel provided with a rotor designed to produce a strong dispersive action and turning at a high speed of 800min or more; and that a proportion of the reactive medium is admixed to the first base, whereupon, having obtained the requisite granulometry, the rotor speed is lowered and the reaction is neutralized with calcium carbonate; and that the above cycle is repeated for the second and subsequent bases, thus obtaining a speckled finish. Heterochromatic paint obtained according to the method of claim 5, characterized in that it ehxibits a speckled type of finish. Heterochromatic paint obtained according to the method of claim 6, characterized in that it exhibits a dropped type of finish. Heterochromatic paint obtained according to the method of claim 7, characterized in that it exhibits colour particles creating a filiform type finish or appearing in star, disc or other shapes. Heterochromatic paint obtained according to the method of claim 8, characterized in that it exhibits a speckled type of finish.

Inventors: ROSSETTI EDOARDO, ROSSETTI, EDOARDO
Applicants: BRIDGEFIELD BV, SPETRA SRL, BRIDGEFIELD B.V., SPETRA S.R.L.
Application year: 1985
Main classification: C09D5
IPC codes: C09D5