COATING COMPOSITION, METHOD FOR THE PREPARATION THEREOF AND USE THEREOF IN ANTICORROSIVE PAINT

Abstract: The invention relates to a coating composition, a dispersion of electrically conductive particles in a dispersant, which consists of at least an electrically conductive polymer precipitated or adsorbed onto a first binder, containing a non-doping polymer, the coating composition containing 50 to 99 wt.% of a second binder, relative to the total amount of solid substance present, and the dispersant containing a non-aqueous solvent. The invention also relates to a process for preparing the coating composition and to the use thereof in an anticorrosive paint, to the anticorrosive paint based on the coating composition according to the invention and to the metal objects protected with it.

Description: COATING COMPOSITION. METHOD FOR THE PREPARATION THEREOF AND USE THEREOF IN ANTICORROSIVE PAINT The invention relates to a coating composition containing a dispersion of electrically conductive particles in a dispersant, which consists of at least an electrically conductive polymer precipitated or adsorbed onto a first binder, containing a non-doping polymer. Such a coating composition is known from EP-A-589, 529. The composition described herein consists of a dispersion of electrically conductive polymer precipitated or adsorbed onto a binder, consisting of a non-doping polymer. In 1981 already Mengoli et al . suggested in J. Appl. Polym. Sci. 1981, 26, 4247-4257, that conductive polymers could be used in the protecting of metals against corrosion. The first good results were however obtained only 10 years later, by Thompson, using a coating based on polyaniline, reported in Los Alamos National Report LA-UR-92-360. It was found that soft steel was in saline and acid environments protected against corrosion, even in places where scratches were made in the coating. The coating composition known from EP-A- 589,529 can also well be used to provide metals with a coating preventing corrosion. In particular because of the coating composition's high stability, a high concentration of conductive polymer can be obtained, as a result of which such a coating composition can be simply applied to an object, in a single layer homogeneously. A drawback of this known coating composition, however, is that the anticorrosive effect of a coating based on it is much poorer in a damp or wet environment than in a dry environment . In view of the fact that corrosion of metal generally occurs in a damp environment, this can be seen as a major drawback for the application as anticorrosive paint. The aim of the invention is to provide a coating composition that does not present said drawback. This aim is achieved according to the invention because the coating composition contains 50 to 99 wt.% of a second binder, relative to the total solid substance present, which consists of electrically non-conductive particles and the dispersant contains a non-aqueous solvent. The coating composition according to the invention ensures that the coating based on it shows a good anticorrosive effect in damp and wet environments. It has surprisingly been found that, in spite of the fact that the coating composition according to the invention shows no or only very little electric conductance, an excellent anticorrosive coating can nevertheless be obtained with it. A coating composition containing more than 99 wt.% of a second binder proved to afford little or no protection against corrosion, as did a coating composition that contained less than 50 wt.% of the second binder. Preferably the coating composition according to the invention contains 70-90 wt.% of the second binder. In this area a coating obtained with the coating composition proved to show good dry and wet adhesion, in addition to good protection against corrosion. A non-doping polymer is used as the first binder in the composition according to the invention. The non-doping polymer preferably has good coating properties. Such a polymer is for example chosen from the group comprising alkyd resins, polyester resins, amino resins, phenolic resins, polyurethane resins, epoxy resins, acrylate resins, cyclic rubbers, for example polyisoprene, natural rubber, silicone resins, polyvinyl chlorides, (poly) vinyl esters, for example polyvinyl acetate, polyolefines, which for example contain units chosen from the group comprising ethylene, propylene, butadiene and styrene, and hydrocarbon resins, for example (co) polymers of cyclopentadiene . The alkyd resins that can be used as the first binder in the dispersion of electrically conductive particles are for example composed of poly- ols, chosen from the group comprising glycerol, pentaerythritol, ethylene glycol, sorbitol, trimethylolethane, trimethylolpropane, dipentaery- thritol, tripentaerythritol, neopentyl glycol and diethylene glycol, and polycarboxylic acids or derivatives thereof, for example chosen from the group comprising phthalic anhydride, phthalic acid, isophthalic acid, maleic acid, maleic anhydride, fumaric acid, fumaric anhydride and fatty acids, for example linoleic acid and oleic acid. Possible preparation methods of the alkyd resins are known to a person skilled in the art and are for example described by H.F. Mark et al. in the Encyclopedia of Chemical Technology, 1978, Vol.2, pages 18-50. Suitable polyester resins are for example composed of dicarboxylic acid units or derivatives thereof, chosen from the group comprising maleic anhydride, fumaric acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid and tetrachlorophthalic acid, and diol units, for example chosen from the group comprising 1, 2-propanol, 1,3-butanol, ethylene glycol, neopentyl glycol, diethylene glycol, bisphenol-A and tricyclodecane dimethanol . Monofunctional and/or trifunctional monomer units may optionally also be used. Possible preparation methods of the polyester resins are known to a person skilled in the art and are for example described by the Oil and Colour Chemists' Association, Australia, in "Surface coatings, Vol.l - Raw materials and their usage", Chapman and Hall Ltd, 1983, pages 78-87. Suitable epoxy resins are for example derived from bisphenol-A and epichlorohydrin. Use may also be made of epoxidized aliphatic and cycloaliphatic dienes, for example 3,4-epoxycyclohexylmethyl-3, 4- epoxycyclohexane carboxylate and 4-epoxyethyl- 1, 2-epoxycyclohexane. Possible preparation methods of epoxy resins are known to a person skilled in the art and are for example described in Ullman's Encyclopedia of Industrial Chemistry, 1985, Vol.A9, pp. 547-563. Suitable polyuretha " ne resins are for example reaction products of isocyanates and polyols. The isocyanates are for example chosen from the group comprising 1, 6-hexamethylene diisocyanate, polymethylene polyphenylisocyanate, 4, 4 ' -methylenebis- (phenylisocyanate) , 1, 5-naphthalene diisocyanate, bitolylene diisocyanate, methylene- bis (cyclohexylisocyanate) , isophorone diisocyanate, trimethylhexamethylene diisocyanate, m-xylylene diisocyanate , 1,3 -bis (isocyanatomethyl) cyclohexane and 1,4-bis (isocyanatomethyl)cyclohexane. The polyols are usually chosen from the group comprising polyether polyols and polyester polyols. Possible preparation methods of polyurethane resins are for example described in Kirk Othmer's Encyclopedia of Chemical Technology, 1982, Vol.23, pages 576-608. A dispersion of a polyurethane resin can for example be stabilised by adding polyoxyethylene segments to the polyurethane chain as for example described by J. . Rosthauser et al . in Advances in Urethane Science and Technology, 1987, Stanford, Vol.10, pages 121-162, and by D. Dieterich in Progress in Organic Coatings, 1981, Vol.9, pages 291-332. The segments may be composed of modified diol or isocyanate units, but it is also possible to add monohydroxyl- functional polyoxyethylene polyethers directly onto the polyurethane chain. Suitable amino resins are for example reaction products of formaldehyde with compounds containing amino groups, for example melamine, benzoguanamine, glycoluril and urea. Amino resins and their preparation methods are for example described by the Oil and Colour Chemists' Association, Australia, in "Surface coatings, Vol.l - Raw materials and their usage", Chapman and Hall Ltd, 1983, pages 87-98. Suitable phenolic resins are for example reaction products of a phenol compound and an aldehyde compound or derivatives thereof. The phenol compound is for example chosen from the group comprising phenol, o-cresol, 2,4-xylenol, bisphenol-A, p-phenylphenol and p-tertiary-butylphenol. The aldehyde compound is for example formaldehyde. Phenolic resins and their preparation methods are for example described by the Oil and Colour Chemists' Association, Australia, in "Surface coatings, Vol.l - Raw materials and their usage", Chapman and Hall Ltd, 1983, pages 99-104. Suitable silicone resins are for example hydrolysis products of di- or trifunctional chlorosilanes. The chlorosilanes are to this end for example dissolved in an organic solvent such as toluene or xylene and subsequently hydrolysed with water. Silicone resins can also be prepared by treating alkoxysilanes, for example methoxy, ethoxy and/or propoxysilanes, with a strong acid in an aqueous medium and subsequently causing polymerisation to take place. Silicone resins and their preparation methods are for example described by the Oil and Colour Chemists ' Association, Australia, in "Surface coatings, Vol.l - Raw materials and their usage", Chapman and Hall Ltd, 1983, pages 134-143. Suitable acrylate resins are for example prepared through homopolymerisation of (meth) acrylate monomers, for example methyl methacrylate, ethyl methacrylate or ethyl acrylate, or copolymerisation of these monomers with monomers that can react with them, for example acrylonitrile, methacrylamide, maleic anhydride, aliphatic chains with a terminal acrylate group, methacrylic acid, vinyl acetate or styrene. Acrylate resins and their preparation methods are for example described by the Oil and Colour Chemists' Association, Australia, in "Surface coatings, Vol.l - Raw materials and their usage", Chapman and Hall Ltd, 1983, pages 144-157. The conductive polymer in the coating composition according to the invention consists of monomers . These monomers are for example chosen from the group comprising pyrrole, thiophene, indole, carbazole, furan, benzene, aniline, acetylene and derivatives of these monomers. In view of the level and the stability of the conductive properties, an electrically conductive polymer consisting of pyrrole, thiophene or aniline units or derivatives of these monomers is preferable. Examples of derivatives of these monomers are N-methylpyrrole, N-ethylpyrrole, N-n-propylpyrrole, N-n-butylpyrrole, N-phenylpyrrole, N-tolylpyrrole, N-naphthylpyrrole, 3 -methylpyrrole , 3 ,4-dimethylpyrrole, 3-ethylpyrrole, 3-n-propylpyrrole, 3-n-butylpyrrole, 3-phenylpyrrole, 3-tolylpyrrole, 3 -naphthylpyrrole, 3 -methoxypyrrole, 3 , 4-dimethoxypyrrole, 3-ethoxypyrrole, 3 -n-propoxypyrrole, 3-phenoxypyrrole, 3 -methyl-N-methylpyrrole, 3-methoxy-N-methylpyrrole, 3-chloropyrrole, 3-bromopyrrole, 3-methylthiopyrrole, 3 -methylthio-n-methylpyrrole, 2,2 ' -bithiophene, 3-methyl-2, 2 ' -bithiophene, 3,3' -dimethyl-2, 2 ' -bithiophene, 3 , 4-dimethyl-2 , 2 ' - bithiophene, 3 ,4-dimethyl-3 ' ,4 ' -dimethyl-2, 2 ' - bithiophene, 3 -methoxy-2 , 2 ' -bithiophene, 3,3' -dimethoxy-2, 2 ' -bithiophene, 2,2 ' , 5,2"-terthiophene, 3-methyl-2,2 ' , 5 ' , - 2"-terthiophene, 3,3' -dimethyl-2, 2 ' , 5 ' ,2"-terthiophene, 2-cyclohexylaniline, aniline, 4-propanoyl-aniline, 2- (methylamino) aniline, 2- (dimethylamino) -aniline, o-toluidine, 4-carboxyaniline, n-methyl-aniline, m-hexylaniline, 2-methyl-4-methoxy-carbonylaniline, n-propylaniline, n-hexylaniline, m-toluidine, o-ethylaniline, m-ethylaniline, o-ethoxyaniline, m-butylaniline, 5-chloro-2-ethoxyaniline, m-octylaniline, 4-bromoaniline, 2-bromoaniline, 3-bromoaniline, 3-acetamidoaniline, 4-acetamidoaniline, 5-chloro-2-methoxyaniline, 2-acetylaniline, 2, 5-dimethylaniline, 2, 3-dimethylaniline, N,N-dimethylaniline, 4-benzylaniline, 4-aminoaniline, 2-methyl- thiomethylaniline, 4- (2, 4 -dimethyl- phenyl) aniline, 2-ethylthioaniline, n-methyl-2,4-dimethylaniline, n-propyl-m-toluidine, n-methyl-o-cyanoaniline, 2, 5-dibutylaniline, 2 , 5-dimethoxyaniline, o-cyanoaniline, tetrahydronaphthylamine, 3-(n-butane sulphonic acid) aniline, 2 -thiomethylaniline, 2, 5-dichloroaniline, 2,4-dimethoxyaniline, 3-propoxymethylaniline, 4 -mercaptoaniline , 4 -methylthioaniline , 3 -phenoxyaniline , 4 -phenoxyaniline , n-hexyl-m-toluidine, 4-phenylthioaniline, n-octyl-m- toluidine , tetrahydrobenzo [c] thiophene , 4-trimethylsilylaniline and 3,4- (alkylene-vic-dioxy) thiophene. The electrically conductive polymer may optionally consist of a mixture of several of the aforementioned monomer units. The stabiliser of the first binder may be chosen within a wide range and may be physically adsorbed onto the binder particles (physically bound) or be incorporated in the binder (chemically bound) . The stabiliser may be an ionic stabiliser or a non- ionic stabiliser. The weight ratio of the electrically conductive polymer and the first binder may vary within a wide range. Usually this ratio will lie between 0.1:99.9 and 80:20, preferably between 0.1:99.9 and 40:60, more preferably between 10:90 and 25:75. It has however been found that a degree of variation in said weight ratio in the composition of the electrically charged particles or the use of several binders, onto which the electrically conductive polymer has been precipitated or adsorbed, does not offer a solution for the desired protection against corrosion under damp or wet conditions. Essential for the effect of the invention is that the coating composition contains 50 to 99 wt.% of a second binder, relative to the total amount of solid substance present, which second binder consists of electrically non-conductive particles. The aforementioned weight percentages are calculated on the basis of a coating composition from which the dispersant has been removed, resulting in a dry substance. The weight percentages mentioned in this application are understood to be the weight percentages based on the dry substance. The second binder may be chosen from the aforementioned group of suitable first binders . In this case the second binder may also consist of the same material as the first binder. In addition to the option of choosing a binder from the first group as the second binder it is also possible to opt for a two-component binder system. Examples of such a two-component binder system are epoxide-thiol, epoxide-amine, epoxide-polyamide, epoxide-acid, for example epoxide-carboxylic acid or epoxide-phosphoric acid, epoxide-anhydride, isocyanate- thiol, isocyanate-alcohol, isocyanate-amine, isocyanate-acid, anhydride-alcohol, anhydride-amine, anhydride-thiol or melamine-formaldehyde systems. The dispersant in the coating composition according to the invention contains a non-aqueous solvent . The dispersant is usually a mixture of the dispersant used for the dispersion of electrically conductive particles and the dispersant for the second binder. Aqueous dispersants for the second binder at least proved to be disadvantageous for obtaining a good adhesion of cured coating. The dispersant preferably contains no or virtually no water. This is achieved if the dispersion of electrically conductive particles is also dispersed in a non-aqueous solvent. It has been found that the wet adhesion in particular improves considerably as the dispersant contains less water. The invention also relates to a process for preparing a coating composition according to the invention. According to this process monomers are polymerised in a solution to form an electrically conductive polymer in the presence of a dispersion of a first binder that has been stabilised with a non-ionic stabiliser. This part of the process, in which the electrically conductive particles are prepared, is known and is described in detail in EP-A-589.529. The coating composition according to the invention is obtained because after the polymerisation of the monomers : - a second binder is added, the second binder being dispersed in a dispersant containing a non- aqueous solvent and the first binder containing a non-ionic stabiliser, or the dispersion precipitates, whether or not as a result of the addition of a strong base, after which the dispersion is again dispersed in a non- aqueous solvent containing an organic acid and a second binder, the second binder consisting of electrically non- conductive particles and the coating composition containing 50 to 99 wt.% of the second binder, relative to the total amount of solid substance present. If a second binder dispersed in a dispersant containing a non-aqueous solvent is added after the polymerisation of the monomers, the first binder contains a non-ionic stabiliser. As in EP-A- 589,529, this ensures the stability of the dispersion of electrically conductive particles. A non-ionic stabiliser is for example chosen from the group comprising alkylamines, alkyl- amides, (ethoxylated) alkylalcohols, alkylpyrrolidones, (ethoxylated) alkylphenols, polyoxyalkylesters, polyoxyalkylethers , glycolalkylethers , glycerolalkylethers, esters of fatty acids and (ethoxylated) sorbitanalkylates, (hydroxy(m) ethyl) cellulose, polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylamides. It is preferable to use polyoxyalkylethers on account of their high effectiveness. Extremely suitable polyoxyalkyl ethers are for example polyoxyethylene ethers, for example polyethylene glycol, alkoxypolyethylene glycol, for example methoxypolyethylene glycol, and ethylene oxide/propylene oxide copolymers. In other cases it is preferable to use polyoxyalkylesters on account of the fact that they are not very toxic . A survey of non-ionic stabilisers is given by Helmut Stache and Kurt Kosswig in the Tensid-Taschenbuch, Carl Hanser Verlag ien, 1990. If, after the polymerisation of the monomers, the dispersion precipitates, whether or not as a result of the addition of a strong base, it is possible to work without the presence of a non-ionic stabiliser in the first binder. If the first binder contains no stabiliser, or an ionic stabiliser, the dispersion will usually precipitate spontaneously after polymerisation. If the first binder contains a non-ionic stabiliser, the dispersion can be caused to precipitate by adding a strong base. A strong base may be for example alkali hydroxide . An ionic stabiliser may be an anionic or a cationic stabiliser. Suitable anionic stabilisers are for example alkyl sulphates and alkyl sulphonates, ethoxylated alkyl sulphates, alkyl sulphonates and alkyl phosphates, ethoxylated alkylcarboxylic acids and alkyl phenol carboxylic acids, ethoxylated alkyl phenol sulphates and alkyl phenol sulphonates, sulphosuccinates and salts of carboxylic acid. Suitable cationic stabilisers are for example primary, secondary, tertiary and quaternary ammonium salts, alkyl pyridinium salts and acetylated polyamines . Suitable stabilisers usually have a weight average molecular weight of between 100 and 1000000, preferably between 500 and 5000. A polymeric stabiliser that is suitable for the invention usually consists of monomer units containing 1-50 carbon atoms. This is preferably 1-20 carbon atoms. The polymeric stabiliser optionally contains several units containing different numbers of carbon atoms . An example of such a stabiliser is an ethylene oxide/propylene oxide copoly er. The stabiliser that is not chemically bound to the binder may have been added to the dispersion of binder particles in the usual manner. The stabiliser is preferably chemically bound to the binder employed. This can be realized by incorporating units of the stabiliser in the binder by adding the stabiliser during the polymerisation of the binder. It is also well possible to graft the stabiliser onto an already polymerised binder. The dispersion of binder particles usually contains between 1 and 35 wt.% stabiliser, based on the total weight of the binder plus the stabiliser. This is preferably 5-25 wt.%. The invention also relates to the use of the coating composition according to the invention in an anticorrosive paint. For the preparation of such a paint up to 60 and even up to 90 wt.% fillers and/or antioxidants may optionally also be added to the mixture of a first binder with an electrically conductive polymer and a second binder without a conductive polymer. Examples of fillers that may be added are talc, barium sulphate, calcium carbonate, fibres, (light-absorbing) pigments, for example titanium white, and coloured pigments like iron oxide and Siθ2, kaolin, wollastonite and glass. Adhesion- promoting agents, plasticisers, fillers, thickeners, surface-improving agents, antifoaming agents, anticorrosive agents, hardeners, drying agents, conductive materials, for example carbon black, conductive fibres and conductive flakes and stabilisers may also be added. The invention also relates to an anticorrosive paint containing the coating composition according to the invention. Such an anticorrosive paint is preferably used to protect metals like aluminium, copper or iron or alloys with these metals. For these metals in particular the electrically conductive polymer acts as a protective layer of a precious metal. The aforementioned anticorrosive paint can be cured at room temperature or at elevated temperature . Depending on the binder composition and the curing temperature, the curing can be accelerated by the presence of a curing catalyst. Examples of this are siccatives, bases, for example tertiary amines, acids, for example paratoluene sulphonic acid. The invention also relates to a coating based on the coating composition according to the invention and to metal objects at least parts of which are coated with this coating. The invention will be further elucidated with reference to some examples. The surface resistance, in Ohm/D, of the coated products was determined with the aid of the method described by H.H. ieder in Laboratory Notes on Electrical and Galvanomagnetic Measurements, Elsevier, New York, 1979. The adhesion was measured according to ISO 2409 (cross-cut tape test) , in which G=0 stands for excellent adhesion and G=5 for no adhesion. The values measured under dry conditions were obtained in a crosscut tape test before the (wet) corrosion test and the wet values were measured after the corrosion test. For the tests, unless otherwise indicated, the homogenised mixtures were applied to a standard steel plate (Q-panel R-46) with the aid of a coating knife, cured at room temperature and conditioned for 1 week. Next, the dry adhesion was determined with the aid of the cross-cut tape method. Two scratches were cut through the coating into the conditioned plates with the aid of a Stanley knife. The steel plates were subsequently for 3 days suspended in a 3.5% NaCl solution, through which a continuous stream of air bubbled, after which the plates were visually inspected to see whether any corrosion had taken place. "+" corrosion observable; "-" no corrosion observable. Next, the same plates were subjected to the "wet" cross-cut tape test. Example I A solution was prepared of 4.86 grams of FeCl 3 (from Merck, free of water) in 21.25 grams of demineralised water (solution A) . Next, a solution was prepared of 0.89 grams of pyrrole (from Aldrich, vacuum-distilled) in 19.34 grams of demineralised water (solution B) . At a temperature of 20°C solution A was added, drop by drop, to 20 grams of a dispersion of polyurethane (first binder) in water (Uraflex XP 401 UZ, DSM Resins, solids content 40%, average particle size 60nm, which had been stabilised by means of incorporated methoxypolyethylene glycol chains (M w =750 g/mol) . The addition of the drops took place while the dispersion was being stirred with the aid of a stirring bar. During the addition of the drops the temperature was kept at 20°C. The dispersion was yellow/green. After half an hour's stirring solution B was subsequently added, drop by drop, with stirring. After solution B had been added, the dispersion's colour changed to dark green and then black. After 20 hours' stirring at a temperature of 20°C, a portion of the dispersion was centrifuged for half an hour at a rate of 20000 rpm. Next, the supernatant water layer was poured away and the sediment (2.63 grams) was redispersed in 13.1 grams of demineralised water with the aid of an Ultra-Torrax T 25 (Janke & Kunkel JK Labortechnik) . A stable dispersion of electrically conductive particles containing 20 wt.% solids was obtained (solution C) . Example II A 20 wt.% solution of Uracron R Z 3410 (from DSM Resins) in 2-methoxypropanol was prepared as the second binder (solution D) . 1 wt.% paratoluenesulphonic acid was added to a mixture of solutions C and D (see Table 1 for the different mixing ratios) . The dispersion thus obtained was homogenised for 5 minutes using an Ultra-Torax. The results are given in Table l. Table 1 Example III As the second binder, a solution was prepared of 6.44 g of Uracron XP780CB (92% solids) and 11.58 g of Uracron XP770CB (50% solids) in 2-methoxy- propanol (total solids content 20%) (solution E) . Solutions C and E were mixed in different ratios (see Table 2) , after which the mixture was homogenised for 5 minutes using the Ultra-Torrax. The results of the corrosion test and the cross-cut tape test are given in Table 2. Table 2 Example IV Solution C was freeze-dried and redispersed to form a 20 wt.% dispersion of electrically conductive particles in methoxypropanol (solution F) . 1 wt.% paratoluenesulphonic acid was added to a mixture of solutions D and F (see Table 3 for the different mixing ratios) . The dispersion thus obtained was homogenised for 5 minutes using an Ultra-Torax. The results of the corrosion test and the cross-cut tape test are given in Table 3. Table 3 In all cases the presence of the electrically conductive particles proves to be essential for the corrosion resistance, as does the presence of at least 50 wt.% of the second binder. The wet adhesion moreover proves to be considerably better when use is made of a solvent free of water. Example V An NaOH solution was added to solution C to a pH of 14, after which the solution was after 1 day centrifuged at 1000 g. The centrifugate was decanted and the sediment was redispersed to form a 20 wt.% dispersion of electrically conductive particles in methoxypropanol (solution G) . 1 wt . % paratoluenesulphonic acid was added to a mixture of solutions D and G (see Table 4. for the different mixing ratios) . The dispersion thus obtained was homogenised for 5 minutes using an Ultra-Torax. The results of the corrosion test and the cross-cut tape test are given in Table 4. Table 4 resista adhesio adhesio nee n n (dry) (wet) Example VI A 50 wt.% solution of Epikote R 1001 in a (1/1, w/w) mixture of l-methoxy-2-propanol and propylene glycol methyl ether acetate was prepared (solution H) . 1 wt . % paratoluenesulphonic acid was added to solution G (solution I) . The coatings employed were prepared by adding to solution H an equimolar amount (relative to the number of epoxides) of isophorone diamine together with the required amount of solution I and were homogenised with the aid of a Dispermat R at 2000-4000 rpm. Then steel plates were sprayed with the aid of a spray gun. The coating obtained in this way was cured at 80°C for 30 minutes. There where a top clear coat (TCC; indicated by + in Table 5) was applied with the aid of the spray gun as an extra layer on top of the conductive layer, use was made of solution H and an equimolar amount of isophorone diamine, after which the top layer was cured for 30 min. at 80°C. All the plates were stored at room temperature for 4 weeks to ensure complete curing of the coating before a l-mm-wide cross-shaped incision was made (down to the iron) and the plates were exposed to the outdoor atmosphere for 9 months. The results are given in Table 5 Table 5 Experiments analogous to solution I were carried out for the purpose of comparing solution I (the conductive polymer is not dispersible in water) and solution C (the conductive, polymer is dispersible in water. The results are given in Table 6. Table 6 These experiments clearly show that the presence of the conductive polymer is essential for the resistance to corrosion. The experiments in Tables 5 and 6 also show that the resistance to corrosion is increased if the conductive polymer is no longer dispersible in water.

Claims: L A I M S 1. Coating composition containing a dispersion of electrically conductive particles in a dispersant, which consists of at least an electrically conductive polymer precipitated or adsorbed onto a first binder, containing a non- doping polymer, characterised in that the coating composition contains 50 to 99 wt.% of a second binder, relative to the total amount of solid substance present, and the dispersant contains a non-aqueous solvent. 2. Coating composition according to Claim 1, in which the dispersant contains no, or virtually no, water. 3. Process for preparing a coating composition according to Claim 1 or Claim 2 by polymerising monomers in a solution to form an electrically conductive polymer in the presence of a dispersion of a first binder that contains a non-doping polymer and has been stabilised with a non-ionic stabiliser, characterised in that, after the polymerisation of the monomers: -a second binder is added", the second binder being dispersed in a dispersant containing a non-aqueous solvent and the first binder containing a non- ionic stabiliser, -or the dispersion precipitates, whether or not as a result of the addition of a strong base, after which the dispersion is again dispersed in a non- aqueous solvent containing an organic acid and a second binder, the second binder consisting of electrically non- conductive particles and the coating composition containing 50 to 99 wt.% of the second binder, relative to the total amount of solid substance present . 4. Use of the coating composition according to Claim 1 or Claim 2 in an anticorrosive paint. 5. Use of the coating composition according to Claim 1 or Claim 2 for protecting metals like aluminium, copper and iron or alloys with these metals. 6. Anticorrosive paint containing the coating composition according to Claim 1 or Claim 2. 7. Coating based on the coating composition according to Claim 1 or Claim 2. 8. Metal objects at least parts of which are coated with the coating according to Claim 7.

Inventors: JANSEN JOHAN FRANZ GRADUS ANTO, JANSEN, JOHAN, FRANZ, GRADUS, ANTONIUS
Applicants: DSM NV, JANSEN JOHAN FRANZ GRADUS ANTO, DSM N.V., JANSEN, JOHAN, FRANZ, GRADUS, ANTONIUS
Application year: 1998
Main classification: C09D5
IPC codes: C09D5, C09D201