NO134659B - - Google Patents

Description

The present invention relates to a coating agent for the production of a coating that dries at room temperature by means of electrophoresis varnishing. The invention further relates to a method for producing this coating agent. To shorten the drying time, the covers can be cured at temperatures up to 85°C.

<p>coating of varnish and paint by electrophoresis is known, see e.g. "Technical Weekly" for 8 October 1964, pp. 881-884. In order to harden such covers, it has usually been necessary to use a longer baking time at temperatures above 120°C.

In Norwegian patent document no. 128,443, an anodic electrophoresis process is described, and according to this, burn-in varnish coatings were produced by using neutralized carboxylic acid resins.

In the British patents No. 1,161,819 and No. 1,168,269, the electrophoretic precipitation of acrylate polymers from neutralized aqueous solutions is described, but here the coatings must be baked in for at least 20 minutes at at least 170°C.

From the German specification no. 1,225,794, it is known about burn-in lacquers that contain castor oil-containing binders that are dissolved in organic solvents. The binders need temperatures of 150°C to harden. The castor oil is here - at least partially - chemically bound to a copolymer of several acrylic monomers (column 4, lines 48-52).

From French patent no. 1,504,895 it is known to secrete cationic polymers. But also .« such coatings separated at the cathode need high temperatures, i.e. above 170°C to cure.

In the British patents No. 1,139,432 and No. 1,159,930 it is true that burning temperatures as low as 80°C are mentioned (p. 5, line 19), but these have not been verified by examples. To harden the covers described in the examples, temperatures between 150°C and 180°C are necessary.

At temperatures below 100°C, however, the coatings do not harden and remain sticky. This results in coatings that do not have usable technological and corrosion protection properties.

Curing of burn-in coating requires high temperatures and

- thereby also high amounts of energy. The burn-in coating method is essentially limited to the layer application of metals. For electrophoretic varnishing of heat-sensitive substances, such as wood, rubber particles and plastic objects, burn-in can covers are usually not used. Here, air-dried coating agents must be used, and in the best case, the moon can work under temperatures up to 85°C. In order to expand the electrophoresis coating's field of application, it was desirable to find features that could harden completely at these low temperatures. Kt older proposal which does not belong to the state of the art (German patent no. 1,903,703), deals with burn-in varnishes, whose burn-in temperatures are 100 to 200°C, and which must be applied. metal parts by the electrophoresis method on the basis of an at least partially water-soluble or dispersible binder mixture, which consists of:

I. 10 to 50 wt-96 of at least one common phenolic resin and

II. 50 to 90% by weight of a copolymer consisting 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) 5-15% by weight of at least one copolymer in serbar a,{J-olefinic unsaturated carboxylic acid with 3-5 carbon atoms, (C) 3-20 wt-56 (meth)-acrylamide and/or N-methylol-(meth)-acrylamide and/or an ether of N-methylol-(meth)-acrylamide with alcohols of 1 -8 carbon atoms, and (D) 5 -20 wt-96 linseed oil and/or isomerized linseed oil and/or tallow oil and/or dehydrated castor oil,

and optionally up to 20 wt-56 of additional copolymerizable olefinic unsaturated compounds.

The French patent no. 1,573,573 belongs to the state of the art and deals with similar mixtures, although without component (D). They contain a fatty acid component, but this is present as a maleinized oil. ,

The object of the present invention is a coating agent for electrophoresis coating, comprising a water-dissolved or dispersed binder mixture of I. 10-50% of at least one common phenol/formaldehyde resin, preferably based on bisphenol A, and

II. 50-90% of a copolymer comprising

(A) 50-85% of at least one ester of acrylic or methacrylic acid and an alcohol with up to 10 carbon atoms, (B) 5-15% of at least one unsaturated carboxylic acid with 3-5 carbon atoms, (C) 3-20% ( meth-)-acrylamide and/or methylo-(meth)-acrylamide which is optionally etherified with an alcohol with

up to 8 carbon atoms, and

(D) 5-40% of additional copolymerizable compounds, and is characterized in that the copolymer's component (D) completely

or partly made up of

(E) 5-20% of at least one ester of unsaturated fatty acid,

and that the binder mixture further contains

III. cyclized rubber, in a proportion of 40-70 96, based on it

combined weight of I, II and III.

The coating agent according to the present invention is used for the production of at room temperature or at temperatures up to 85°C hardenable covers.

The coating agent according to the invention is particularly distinguished by having a good grip ("Umgriff", "throwing power") and good bath stability. The dispersion obtained is storage-stable for several months. The dispersed and neutralized mixture of phenolic resin I and copolymer II has a particularly good stability even with a solids content of less than 1096, a solids content that is very relevant when it is used for electrophoresis.

The mixture of phenolic resin I and copolymer II simultaneously acts as an emollient on the cyclo-rubber disease. It has surprisingly been shown that coatings obtained from dispersions according to the invention have a good covering ability and a very favorable hardness/impact resistance ratio. In the accelerated: climate test according to German Norm DIN 50018, the coatings were not yet attacked after 6 rounds in an S02/water vapor atmosphere, and Mari could not detect any loss of gloss either. Even after a stay in a humidity chamber at 40°C and 95% relative humidity for 1000 hours, the cover according to the invention was not attacked. In the salt spray test according to ASTM B 117-57 T, boards that were coated were only attacked after 168 hours.

Plastic objects, which were exposed to aluminum vapor in a high vacuum, were applied a layer of the coating agent according to the invention and mounted on a truck. In the course of a winter period, they were thus exposed to weather and wind for 6 months. The thus coated parts showed a better result than metallized objects which were coated with a layer of lacquer by a conventional spraying method.

As component I, the usual phenolic resins are suitable, i.e. condensation products of phenols and formalin, which are usually prepared from phenols and substituted phenols, such as e.g. phenol, cresol, xylenol, 2,2-bis-(p-hydroxyphenyl)-propane ("bisphenol A") and aqueous formaldehyde solutions in the presence of common basic contact agents, such as e.g. ammonia or water-insoluble amines (cf. e.g. K.Hultzsch "Chemie der Phenoharze", Springer Verlag 1950, p.118). As mentioned, phenolic resin is present in the binder mixture in a proportion of 10 to 50, preferably 20 - 35% by weight. •

The copolymer II of the binder mixture contains as component (A) 50 - 85, preferably 50 - 70% by weight of at least one ester of acrylic acid or methacrylic acid with alcohols with 1 - 10 carbon atoms. Particularly suitable are methanol, ethanol, propanol, n-butanol, isobutanol, tert-butanol, amyl alcohol, hexyl alcohol, cyclohexanol, heptanol, octanol, 2-ethylhexanol, nonanol and decanol. Mixtures of these esters can also be used. Particularly suitable are the esters of acrylic acid with n-butanol and isobutanol, as well as methacrylic acid methyl esters, respectively. mixtures of these esters.

As component (B), the copolymer II contains 5-15% by weight of at least one copolymerisable, ct,0-olefinic unsaturated carboxylic acid with 3-5 carbon atoms. Itaconic acid, citraconic acid, mesaconic acid and maleic acid and their half-esters can be broken down here. maleic anhydride. Acrylic acid and methacrylic acid are preferably used.

As component (C) in copolymer II, 3-20, preferably 5-15% by weight, (meth-)-acrylamide, and/or methylol-(meth)-acrylamide and/or an ether of methylol-(meth-) -acrylamide with alcohol with 1-8 carbon atoms, such as e.g. N-butoxymethyl methacrylic acid amide.

As a new component, the copolymer II according to the invention contains 5 - 20,. preferably 7-15 wt-?4, of an oil with at least one olefinic unsaturated fatty acid. Oils containing at least partially conjugated double bonds are preferably used. Such oils are soybean oil, linseed oil and preferably isomerized linseed oil, tall oil and tall oil distillates, such as e.g. the so-called intermediate fractions (which consist of a fatty acid/resin acid mixture with approx. 25 - 30% by weight of resin acid), dehydrated castor oil and the castor oil itself. According to Kaufmann and Baldes, <1>, Berichte der deutschen chemischen Gesellschaft", vol. 70, page 903 (1937), these unsaturated oils' content of conjugated double bonds can be determined using the diene number. The unsaturated oils preferred according to the invention have a diene number of

more than 5, preferably more than 10. The ricinoleic acid contained in castor oil can be converted into a fatty acid with two conjugated double bonds by splitting off water.

Besides the two conjugated double bonds, further isolated double bonds may occur in the preferred unsaturated oils.

Particular mention should be made of isomerized linseed oil with a diene number of 10 -

30 and/or tallow oil with a diene number from 10 - 15. However, it must be added here that copolymerization of acrylic monomers and various unsaturated oils, especially dehydrated castor oil,

has been known for a long time, as it is discussed in US patent no. 2,574,753.

Copolymer II can contain polymerized up to 35% by weight

of additional copolymerizable olefinic unsaturated compds.

As such, mention should be made of the usual vinyl compounds, such as vinyl esters, which e.g. vinyl pivalate, vinyl versatic ester and especially vinyl aromatics, such as e.g. styrene, vinyltoluene, p-chlorostyrene, as well as (meth-)-acrylonitrile. These compounds may contain

, several double bonds, such as butadiene or isoprene.

Preferred copolymers II contain e.g. 50 - 60% by weight isobutyl acrylate or n-butyl acrylate and 10 - 20% by weight methacrylic acid methyl ester or 60 - 70% by weight n-butyl acrylate, 7-15% by weight isomerized linseed oil (dient number 20 - 30) or dest. tall oil "intermediate fraction" or castor oil, 7-12% by weight acrylic acid and 5-15% by weight acrylamide or methacrylamide.

The production of copolymer II takes place from the individual components and according to usual methods, of which it is most appropriate

to use solution polymerization, i.e. that one polymerizes

in solvents in which both monomer and polymer are soluble.

Copolymer II usually exhibits a K value (according to H. Fikentscher) of 12 - 30, preferably 15 - 20. After the polymerisation, the major part of the solvent is distilled off. So much ammonia or organic base is added to the concentrated and still warm solution of copolymer II that

later dilution with water results in a stable solution or dispersion. For this, it is necessary to neutralize 1/3 of the carboxyl groups present in polymer II. As organic bases, organic amines, which are volatile, are particularly suitable

at burn-in temperatures of approx. 170°C, such as trialkylamines which may optionally be further substituted, such as e.g. dimethylethanolamine.

Copolymer II, which exists partly in the form of ammonium or amine salts, are mixed with phenol resin I in ordinary mixing equipment. 50-90, preferably 65-80, weight-% of copolymer II is combined with 10-50, preferably 20-35, weight-%, phenolic resin I (the weight percentages are calculated on the solids content).

For the production of the coating agent according to the invention, the cyclized rubber is first dissolved in organic solvents, after which phenol resin I and copolymer II are added to this solution. It is then further reacted with the organic amine until a pH value between 7 and 9 is obtained. This mixture is then dispersed with distilled and deionized water using a highly efficient agitator. The thus prepared dispersion is diluted with completely desalted water to a solids content of 8 - 16%, preferably 11 - 13%, whereby the emulsions for the dilution can be added to the pigment paste. Other substances can optionally be added to the emulsion, such as anti-foaming agent, coverage improvers, stabilizers and antioxidants.

The coating agent preferably has a conductivity value corresponding to approx. 1000 jum s cm""^. With electrophoresis painting, the object to be coated is connected as an anode, whereby the object is immersed in the coating agent. The deposition usually takes place in steel containers which are connected as a cathode. The bath temperature is between 20 and 50°C.

The objects to be coated can be made of metal, preferably pre-treated or non-pre-treated steel sheets, aluminum sheets and materials made of wood, rubber or plastic with conductive surfaces. Such objects are preferably made of rubber or plastic, the surface of which is provided with a metal cover.

The deposition usually takes place at a voltage between 50 and 150 volts, and after 2 minutes the object in question is evenly coated with a film that is between 20 and 35 pm, and which, after rinsing with water and drying in air at room temperature for 30 - 60 minutes, is non-stick, or as at temperatures up to 85°C

is quick-dried and hardened after 20 - 30 minutes.

In the example, the parts and percentages given are parts by weight and percentage by weight. This also applies to the patent requirements.

EXAMPLE

As phenolic resin component I, a yellow colored solution is used which has a solids content of 70%, and which is prepared from 200 parts of 2,2-bis-(p-hydroxyphenyl)-propane, 132 parts of 40% formalin and 19.65 parts of dimethylethanolamine at 70°C during two hours of stirring. 330 parts of this component are mixed with a copolymer II consisting of 322 parts of isobutyl acrylate, 53.6 parts of methyl methacrylate, 53.6 parts of isomerized linseed oil (dient number of about 25, determined according to Kaufman and Baldes), 53.6 parts of acrylamide and 53 .6 parts acrylic acid, which in the form of a solution in isopropanol and with a solids content of 85% is neutralized with 24.4 parts dimethylethanolamine. The final solids content of the mixture is 80%.

100 parts of this solution are mixed with 214 parts of a 70% solution of cyclokautjuk in petrol, and 50 parts of isodecyl alcohol and 3.5 parts of diisopropanolamine are added. With the help of a homogenizer, this solution is diluted with water to a solids content of 12% while simultaneously dispersing.

On • a deep-drawn plate of size (10 x 10) cm 2 which is connected as an anode, a separation is carried out at a separation voltage between 50 and 150 volts over the course of 2 minutes. After rinsing with water, a coating is obtained which, at room temperature, is non-sticky after 30 - 60 minutes, and which hardens overnight. The separated film can also be quickly used for 20 - 30 minutes at 80°C. The cover is fixed. In an accelerated climate test according to DIN 50018, the film is undamaged after 6 rounds. In the salt spray test according to ASTM B 117-57 T, no corrosion damage can be detected after 168 hours.

Claims (2)

1. Coating agent for electrophoresis coating, comprising a water-dissolved or dispersed binder mixture of 1. 10-50% of at least one common phenol/formaldehyde resin, preferably based on bisphenol A, and II. 50-90% of a copolymer comprising (A) 50-85% of at least one ester of acrylic or methacrylic acid and an alcohol with up to 10 carbon atoms, (B) 5-15% of at least one unsaturated carboxylic acid with 3-5 carbon atoms , (C) 3-20% (meth-)-acrylamide and/or methylol-(meth)-acrylamide which is optionally etherified with an alcohol with up to 8 carbon atoms, and (D) 5-40% of additional copolymerizable compounds, characterized in that the copolymer's component (D) is wholly or partly made up of (E) 5-20% of at least one ester of unsaturated fatty acid, and that the binder mixture further contains, III. cyclized rubber, in a proportion of 40-70%, based on the combined weight of I, II and III. 2. Process for producing the coating agent according to claim 1, characterized in that cyclized rubber (III) in the form of a solution in organic solvents is dispersed in a water-dissolved or dispersed binder mixture of I. 10-50% of at least one common phenol /formaldehyde resin, preferably on the basis of bisphenol A, and II. 50-90% of a copolymer comprising (A) 50-85% of at least one ester of acrylic or methacrylic acid and an alcohol with up to 10 carbon atoms, (B) 5-15% of at least one unsaturated carboxylic acid with 3-5 carbon atoms , (C) 3-20% (meth-)-acrylamide and/or methylol-(meth)T acrylamide which is optionally etherified with an alcohol with up to 8 carbon atoms, and in ; (D) 5-40% of further, copolymerizable compounds, ■>>y-f ' 0, component (D) being wholly or partly made up of : .; (E) 5-20 of at least one ester of unsaturated fatty acid, . ,. and when the cyclized rubber (III) is added in a proportion of 40-70 96, based on the combined weight of I, II and III.