DK142585B - COATING AGENT FOR ELECTROPHORETIC COATING OF ELECTRIC CONDUCTIVE ITEMS AND PROCEDURE FOR MANUFACTURING THE AGENT - Google Patents

Description

(11) PUBLICATION 142585 (Ai

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\ Ra / DENMARK (ευ int.ci.3 c 09 d 5 / ao '(21) Application No 2704/71 (22) Filed on 3 · Jun. 1971 (24) Running Day 3 · Jun. 1971 (44) The application presented and ... q_

the petition published on 24 · nOV · 1 ytjU

DIRECTORATE OF

PATENT AND TRADE MARKET (30) Priority requested from it

4. Jun. 1970, 2027428, DE

(71) BASF FARBEN + FASERN AKTIENGESELTSCHAFT, Hamburg-Wandebek, Neumarkt 30, DE.

(72) Inventor: Peter Fritsche, Lange S trass e 93, 4403 Hiltrup, DE.

(74) Plenipotentiary in the proceedings:

International Patent Office.

(54) Coating agent for electrophoretic coating of electrically conductive articles and method of preparation of the agent.

The present invention relates to a coating agent for the electrophoretic coating of electrically conductive articles as well as to a method of making this agent. With the agent, at room temperature, drying wires are applied to the electrically conductive articles used as anode, especially with metal surfaces or metal objects. These coatings can also be cured to shorten the drying time at temperatures up to 85 ° C.

Methods for electrophoretic preparation of coatings on metallic workpieces by immersing the article used as anode in an electrode bath are known. To cure such coatings, it has heretofore been required to be burned at temperatures above 120 ° C for extended periods of time. The known electro-dip coating methods have so far received only burn-in coatings. Thus, Swiss Patent No. 419,770 discloses a method for electrophoretic preparation of an artificial resin coating using burn-in varnish containing as a binder, acrylic resin, alkali resin or maleate oils alone or in combination with urea resins or melamine resins. These coatings are burned at least 1/2 hour at least 120 or 130 ° G. Also, United States Patent No. 3,230,162 discloses an anodic electrocoating process in which the use of neutralized polycarboxylic acid resins is used for coating paint coatings.

British Patent Nos. 1,151,819 and 1,168,269 describe the electrophoretic separation of acrylate polymers by their neutralized aqueous solutions, but again, the coatings must be burned for at least 170 minutes at at least 170 ° C to obtain cured films.

At temperatures below 100¾, the known separated coatings remain sticky and do not cure. This gives coatings without any useful technological and anti-corrosion properties. In order to cure burn-in coatings, high temperatures are required and thus also high energy amounts. The use of burn-in coatings is essentially limited to the coating of metals. For electrode coating of heat sensitive substances, such as wood fabrics, rubber suede or plastics and plastic articles, burn-in coatings generally cannot be used. Air drying coatings must be used here, and at most can be operated at slightly elevated temperatures up to a maximum of 85 ° C. Otherwise, the objects to be coated will be damaged.

The forced drying of air-drying coatings at elevated temperature up to 85 ° C is meanwhile necessary to achieve certain mechanical and corrosion protection properties. In order to increase the scope of electrode coating, it was desirable to find air-drying electrode coatings.

This is achieved by providing the coating composition of the invention which is an agent based on at least partially in the form of salts of inorganic bases or ammonia and / or volatile organic water-soluble amines in water dissolved or dispersed binder mixture of I) 10 to 50 % by weight of at least one commonly used phenolic resin and II) 50 to 90% by weight of a mixture polymer of A) 50 to 85% by weight of at least one ester of acrylic or methacrylic acid with alcohols having 1-10 carbon atoms, B) 5 to 20% by weight of at least one oil containing olefinic unsaturated fatty acids, C) 5 to 15% by weight of at least one copolymer resin, α, β-olefinic unsaturated carboxylic acid having 3-5 carbon atoms, D) 3 to 20% by weight (meth) -) - acrylamine and / or methylol (meth -) - acrylamide optionally etherified with alcohols of 1-8 carbon atoms and optionally E) up to 20% by weight of other copolymerizable olefinically unsaturated compounds.

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This agent is peculiar in that the mixture further contains cyclo-rubber dispersed in such an amount that the total binder composition consists of 40 to 70% by weight of cyclo-rubber and 60-30% by weight of the mixture of I and II.

The process according to the invention for the preparation of this coating agent is characterized by dispersing the cyclo rubber in the form of a solution in organic solvents in the at least partially in the form of salts of inorganic bases or ammonia and / or volatile organic water-soluble amines dissolved in water or dispersed binder mixture of I and II.

The coatings made with the coating agent according to the invention can be cured in air at room temperature. In addition, they can be subjected to accelerated curing at up to 85 ° C. The coating agent according to the invention is particularly distinguished by its good permeability and bath stability. The resulting dispersion is stock stable for a period of several months. The mixture of phenolic resin I and mixture polymerate II, which serves as a dispersion medium, provides, in the neutralized form, a particularly excellent stabilization of the dispersion even at low solids content of less than 10% solids, as it is especially used for electrode coating.

The mixture of phenolic resin I and mixture polymerate II simultaneously acts as a plasticizer for the cyclo rubber. Surprisingly, the coatings prepared by the coating agent according to the invention exhibit a good confluence and a very favorable relationship between hardness and impact resistance. In a short weathering test according to the German standard DIN 50018, after 6 rounds in a SO 2 water vapor atmosphere, the coating was not yet attacked and without significant loss of luster. Also, after a test in a "Dauers sauna" at 40 ° C and 95% relative humidity for 1000 hours, the metal parts coated with the invention were affected. In the salt spray test after ASTM B 117-57 T, the coated parts were only attacked after 168 hours.

Aluminum in high vacuum evaporated plastic parts was coated with the coating composition according to the invention and mounted on trucks and exposed to the weather for a period of 6 months during a winter period. The agent coated parts in the test showed better results than such metallized plastic parts, which were coated with a lacquer layer by a conventional spraying method.

As component I, commonly used phenolic resins, ie. condensation products of phenols and formalin, commonly prepared from phenols and substituted phenols, such as e.g. phenol, cresol, xylenol, 2,2-bis (p-hydroxyphenyl) propane, and an aqueous formaldehyde solution in the presence of common basic contacting agents such as e.g. ammonia or water-soluble amines (compare, e.g., K. Hultzsch "Chemie der Phenol resin", Springer Verlag 195o, p.

118). The phenolic resin is present in the binder mixture serving as a dispersant in an amount of from about 10% to 5% by weight, preferably 20% to 35% by weight.

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Mixture polymerizate II in the binder mixture contains as component A) preferably polymerized 50 to 70% by weight of the indicated ester. As esters of acrylic acid or methacrylic acid, esters of straight chain, branched or cyclic alcohols, such as, for example, methanol, ethanol, propanol, n-butanol, iso-butanol, tert-butanol, amyl alcohol, hexyl alcohol, cyclohexanol, heptanol, are suitable. -nol, 2-ethylhexanol, nonanol and decanol, as well as mixtures of these esters. Particularly suitable are esters of acrylic acid and n-butanol or isobutanol as well as methacrylic acid methyl ester or mixtures of these esters.

As component B), the blend polymerized II preferably contains 7-15% by weight of the oil specified. Preferably suitable are oils containing at least partially conjugated double bonds. As such oils are soy oil, linseed oil and preferably isomerized linseed oil, tall oil and tall oil distillates such as e.g. the so-called intermediate fraction, which consists of a fatty acid / resin acid mixture with approx. 25-30% by weight of resin acid, dehydrated castor oil and castor oil. The content of conjugated double bonds in these unsaturated oils may e.g. is determined by determining the number by the method of Kaufmann and Baldes, Berichte der deutschen chemischen Gesellschaft, 70, page 903 (1937). The oils preferably used according to the invention generally have a number of more than 5, preferably of more than 10. Ricinolic acid, which is found in castor oil, can be converted into a fatty acid with two conjugated double bonds by water decomposition.

In addition to the two conjugation to each other double bonds, other isolated double bonds may be present in the preferably unsaturated oils used. For the coating agent according to the invention, it has been found that isomerized linseed oil having a number of 10 to 30 and / or tall oil having a number of 10 to 15 is particularly suitable.

As the carboxylic acid used in component C) it is suitable, for example, itaconic acid, citraconic acid, mesaconic acid and maleic acid, its semesters or maleic anhydride and preferably acrylic acid and methacrylic acid.

As component D), in blend polymerize II, polymerized preferably is 5-15% by weight of the indicated optionally etherified amide with an alcohol, for example, N-butoxymethylmethacrylic acid amide.

As the olefinically unsaturated compound of component E), the common copolymerizable vinyl compounds such as vinyl ester, e.g. vinyl pivalate, vinyl versatile ester, and especially vinyl aromatics such as e.g. styrene, vinyltoluene, p-chlorostyrene, and (meth-) acrylonitrile, as well as copolymerizable compounds containing several double bonds, such as e.g. butadiene or isoprene.

Preferred blend polymerisates II contain inpolymerized e.g. 50-60 wt% isobutyl acrylate or n-butyl acrylate and 10 to 20 wt% methacrylic acid methyl ester or 60 to 70 wt% n-butyl acrylate as component A), 7 to 15 wt% isomerized linseed oil (number 20 to 30) or distilled tall oil "intermediate fraction" or castor oil as component B), 7-12 weight-7. acrylic acid as component C) and 5-15. acrylamide or methacrylamide as component D).

The preparation of blend polymerized IT is based on the individual components generally by conventional methods, conveniently by solution polymerization, ie. are polymerized in solvents in which both the monomers and the polymerizers are soluble. Suitable solvents are e.g. alcohols, ethers and / or ketones or mixtures of these solvents. The boiling point of these suitable solvents or solvent mixtures is conveniently in a range of from ca. 50-120 ° C. For preparing blend polymerate II, the conventional radical-forming polymerization initiators, such as organic peroxides, e.g. benzoyl peroxide, cyclohexanone peroxide, ditert.-butyl peroxide, organic hydroperoxides, e.g. cumole hydroperoxide, as well as aliphatic azo compounds such as e.g. azodiisosmørsyrenitril. These polymerization initiators are conveniently used in amounts from 0.5 to 5 weight-7. calculated on the basis of the total amount of monomers.

The monomers to be polymerized are contained in said solvents or solvent mixtures in general in an amount of approx. The solution polymerization is conveniently carried out at temperatures which are in the range between boiling temperatures of the solutions, so that the reaction heat can be dissipated by boiling. One may bring the entire initiator-containing monomer solution to polymerization at the same time, but it is advisable, however, to first polymerize only part of the monomer solution or to start with the solvent, and then add the monomer mixture or the remainder of the monomer mixture little by little, so that it can be more easily controlled by the heat of polymerization occurring. It is frequently appropriate to carry out the polymerization in the presence of small amounts of conventional regulators. As a regulating agent, e.g. n- or tert-dodecylmercaptan and diisopropylxanthogen disulfide. These regulators are generally used in amounts from 0.5 to 3 weight-7. calculated on the basis of the total amount of monomers.

Mixture polymerizate II generally exhibits a K value measured by the method of 12 to 30, preferably 15-20, set by H. Fikentscher (cf. Cellulose Chemistry _13_58 (1932)). After the polymerization, most of the solvent is distilled off. The concentrated, yet hot solution of the mixture polymerate II is added with so much ammonia or a volatile organic base that a later solution or dispersion is obtained with water. For this, it is necessary to neutralize approx. one-third of the carboxyl groups present in blend polymer II. As organic bases, there are suitable organic amines which are volatile at burn-in temperatures of approx. 170 ° C, such as e.g. optionally further substituted trialkylamine such as e.g. dimethylethanolamine.

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The mixture of ammonium or amine salt partially added in the form of ammonium or amine salts is mixed with phenolic resin I in ordinary mixing assemblies with stirring, combining 50-90, preferably 65-80, wt.% Of mixture polymerisate II with 10-50, preferably 20-35% by weight of phenolic resin I (both calculated on the solids content).

To prepare the coating agent of the invention, cyclo rubber is then dissolved in organic solvents and mixed in the solution of phenolic resin I and blend polymer II. Then, further react with the organic amine until a pH of between 7 and 9. This mixture is then dispersed with vigorous stirring with distilled deionized water, the dispersion thus prepared is diluted with completely desalted water to a solids content of 8-16%. , preferably 11-13%, the pigment material being further admixed prior to dilution. Optionally, the emulsion may be added to other conventional additives such as phenolic resins, maize alkyd resins, maleized oil, acrylate or methacrylate polymers, antifoaming agents, process enhancers, stabilizers and antioxidants.

The coating agent preferably has a conductivity of about 1000p S cm. For electrode coating, the article to be coated is designed as anode and dipped in the coating agent. The separation is generally done in steel vessels which are designed as cathode. The bath temperature is between 20 and 50 ° C.

The articles to be coated may consist of metals, preferably pretreated or non-treated iron or steel sheets and aluminum sheets, or of wood materials, rubber, plastics or conductive surfaces. Preferably, such articles are made of rubber, plastic or plastic, the surface of which is provided with a metal coating. The separation is usually carried out at a voltage between 50 and 150 volts. After approx. For 2 minutes, the article to be coated has a uniform coating having a film thickness between 2o and 35yu, which coating - after rinsing with water for 3o to 6o minutes in air at room temperature or accelerated dried at temperatures up to 85 ° C - after 2o to 3o minutes is cured.

The parts and percentages given in the examples are parts by weight and percentages by weight.

Example 1 1) Preparation of phenolic resin component I (condensate A) 200 parts of 2,2-bis (p-hydroxyphenyl) propane, 132 parts of 40% formalin and 19.65 parts of dimethylethanolamine is stirred at 70 ° C for 2 hours. A yellowish solution having a solids content of 70% is obtained.

B) Preparation of a Binder Mixture of a Mixture Polymerate and Condensate A.

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132 parts of boiling isopropanol are allowed to run for 2 hours in a solution of 322 parts of isobutyl acrylate, 53.6 parts of methyl methacrylate, 53.6 parts of isomerized linseed oil, which has a determined diet of Kaufmann and Baldes of approx. 25, 53.6 parts of acrylamide, 53.6 parts of acrylic acid, 5.36 parts of azodiisobutyric acid nitrile and 10.72 parts of ditert.-butyl peroxide in 134 parts of isopropanol as the mixture is constantly refluxed. After another 2 hours, the solids content is checked. If this has not yet reached 65%, add 2.68 parts of azodic acid butyric acid nitrile suspended in 12 parts of isopropanol and boil for another 4 hours. When the solids content has reached 65%, the material is polymerized. Distill approx. 195 parts of solvent towards the end, possibly under low vacuum. At a final solids content of 85%, after cooling to 60 - 70 C, 24.4 parts of dimethylethanolamine are stirred and mixed with 330 parts of condensate A. The final solids content is 80%.

C) Preparation of the coating.

214 Parts of a 70% solution of cyclo rubber in gasoline are mixed with 100 parts of solution B and 50 parts of isodecyl alcohol and 3.5 parts of diisopropanolamine are added.

Using a homogenizer, this solution is diluted with water to a solids content of 12% and uniformly dispersed.

2 On one piece of 10 x 10 cm depth-of-draft, designed as anode, a discharge occurs at a separation voltage between 50 and 150 volts and 2 minutes of separation time. After rinsing with water, a coating is obtained which after 30 to 60 minutes at room temperature is non-sticky and after one night is cured.

The separated film can also be cured accelerated for 20 to 30 minutes at a temperature of 80 ° C. The cover is grip tight. In a short-term weather test according to DIN 50018, the film is impeccable after 6 rounds. After 168 hours with a salt spray test according to ASTM B 117-57 T no corrosion can be noticed.

Example 2 A) Condensate B.

A mixture of 223 parts of 37% formalin, 111 parts of phenol, 27.7 parts of 2,2-bis (p-hydroxyphenyl) propane and 10.3 parts of dimethylethanolamine is stirred at 45 ° C for approx. 15 hours under nitrogen. The condensation product must be able to be diluted with water in a ratio of at least 3: 1 and have a free formaldehyde content of approx. 8 to 9% (determined by the hydroxylamine hydrochloride method). Solid content is approx. 45%.

B) Example 1 was repeated only with the difference that condensate A was used instead of condensate B. Prior to dilution with water, pigment with 60 parts of titanium dioxide was used. An impeccable air-drying film was also obtained which, in the salt spray test after ASTM-B-117-57 T after 16 hours, showed no signs of corrosion.