DE1646174C3 - Production of electrophoretically depositable coatings - Google Patents

Description

moderately by polymerization in water-soluble solvents. Used in water-insoluble solvents polymerized, these are largely removed in vacuo after the end of the reaction and passed through replaces water-soluble solvents.

The peroxides or azo compounds which give free radicals by thermal decomposition or by redox reactions can serve as accelerators; the regulator is preferably 2 to 6 ¹ V ₀ tert. Dodecyl mercaptan used. These amounts of regulator ensure the formation of polymers in the optimum molecular weight range of 5000 to 15000.

The finished polymer is treated with formaldehyde, as paraformalehyde, or as alcoholic or aqueous Formaldehyde solution can be applied, implemented in alcoholic solution, with the Reaction released water is continuously distilled off. The end of this reaction can be recognized by the fact that it has not occurred the formation of water. The amount of formaldehyde is calculated so that 1 to 2.5 moles per mole of amide Formaldehyde.

The alcohols suitable for etherification preferably have 1 to 6 carbon atoms.

Another embodiment for the preparation of the water-thinnable resins is that the Polymers are completely or partially neutralized with bases before the reaction with formaldehyde. Suitable bases are ammonia and primary, secondary and tertiary amines and alkanolamines, of which triethylamine and dimethylethanoiamine may be mentioned as examples.

If the neutralization is only carried out after the reaction with formaldehyde, the the above-mentioned bases for use.

After the electrophoretic application of the resin, which is described in more detail in Example 1. will the deposited film is baked at temperatures of 120 to 200 C.

The following examples serve to explain the invention in more detail, the numerical data being based on each other Refer to parts by weight.

example 1

70 parts of butanol,
8 parts acrylic acid,

15 parts of acrylamide,

25 parts of styrene,

25 parts of butyl acrylate,

27 parts of ethyl acrylate,
1 part di-tert-butyl peroxide,
5 parts tert. Dodecyl mercaptan.

♦ 5

50

The acrylamide is dissolved in the butanol and the remaining reactants are added. After presenting one Part of the mixture, the polymerization is initiated by heating and when it reaches At reflux temperature, the remainder of the mixture was added over a period of 2 to 3 hours. The completeness the polymerization is controlled via the solids content, with possibly also accelerators must be given in.

After the end of polymerization; one adds the viscous clear solution to 12.7 parts of paraformaldehyde and keeps the reaction mixture at reflux temperature as long as until no more water separates out (about 2 to 3 hours). By applying a vacuum part of the butanol is drawn off and the solution is concentrated as much as possible. After neutralization with The resin is soluble in dimethylethanoiamine.

To use this low molecular weight resin by the electrophoretic process, it is _{pigmented with TiO 2} , diluted to about 10% with water and the object to be painted, connected as an anode, is immersed. After applying a voltage of 100 to 150 volts, the resin separates evenly as a dense film of about 25μ within a very short time. It is rinsed off with water and the film is cured at 160.degree. The coating becomes pure white, hard, shiny, elastic and has a smooth surface.

If the pigmented lacquer is applied by dipping or spraying, it is obtained after baking also smooth and glossy coatings, but the opposite of the electrophoretically deposited Films have significantly poorer elasticity.

Example 2
(Comparative example)

70 parts of butanol,

8 parts of acrylic acid.
15 parts of acrylamide,
25 parts of styrene,
25 parts of butyl acrylate,
27 parts of acrylic acid ether.

1 part di-tert-butyl peroxide.

1 part tert. Dodecyl mercaptan.

The use of the lower amount of regulator gives copolymers with a significantly higher amount Molecular weight.

This approach is polymerized in the same way as the approach from Example 1 and the reaction is also carried out with paraformaldehyde and neutralization in the same way. "

In the case of the electrophoretic deposition of this higher molecular weight resin as in Example 1, the disadvantage of the higher molecular weight becomes apparent, because when curing at 160 ^° C., matt, wrinkled coatings are obtained whose mechanical properties correspond to those of the coatings of the low molecular weight resin from Example 1.

If the pigmented lacquer is applied by dipping or spraying, elastic, glossy surfaces are obtained Coatings with a smooth surface.

Claims (1)

Ιλ formaldehyde unoccupied copolymers of acrylic and / or methacrylamide and at least two others. Claims: ethylenically unsaturated monomers, of which one is an ethylenically unsaturated carboxylic acid, ι c " _nt " 7 _{,, ca z} from ~> 0 to 6.0% tertiary 1-dodecyl. Use of water-thinnable amine salts 5 with additive of copolymer reacted with formaldehyde! - ^me ™ ^a . ^pt Jf: _lekulareewic ht for heat-curing lacquers made of acrylamide and / or methacrylamide and Das Mo. - "" ^^ _between 20,000 and id i d ahlh saturated resins lie - saten from acrylamide and / or methacrylamide and "" ^^ _between 20,000 and at least two other ethylenically unsaturated resins lieg - ^ _ofrjda , _D j _ges ,, 36.141 / 1964). M di an ethylenic un f ™ ^ at least two anren y gg ^ _ofrjda , _D j _ges ,, 36.141 / 1964). Monomers, one of which has an ethylene un- f ™ ^ _djeser limit, the brittleness of the is saturated carboxylic acid, with the addition of 2.0% uniernaiD ^ ^ _{Rißbi] d} up to 6.0% tertiary dodecyl mercaptan for Her- Har * ™ J ° 'temperature change, and at higher position of electrophoretically separable over- at sclr ° » ^e ™ '* ^P _{, the} handling by the züeen on electrically conductive surfaces. MοIekulargevvi ™ ^te "J I The method according to claim 1, characterized by ^^^ f ^ Sung "certain test conditions draws. that Copolymerisatam.nsalze with j> up to 15 ° ^u " ^h 7 _d " _t Zimabc certain compounds 20 percent by weight of acrylic and / or methacrylic- S ^ " ^d J _Ha ~ _{d the} molecular weight far- Amide monomer units are used ^ has a decisive influence 3 The method according to claim 1 and / or 2, da- g ^ molecular weight practice compounds with characterized by that Copolymensatamm- on Jas ^M «. > eb _agation coefficient (so-called salts, the m, t 1 to 2 5 moles of formaldehyde per mole "especially s higher *> _m * . ^ _{wobe ,? m} t ^^^ the an slung ^ acry. am ^^ aten des obe. Proverbs 1 to 3, characterized in that
Copolymerisutamine salts are used, which are drawn from about 0.7 in addition to acrylamide monomer units acrylic acid, 25 on the Acrylic acid butyl ester, acrylic acid ethyl ester and It is now surprising that resins with essential Contain styrene monomer units. lower degrees of polymerization than electrophoresis coatings applied at the table do not have the disadvantages, or only to a much lesser extent, such as 30 the coatings applied by spraying, dipping and other methods of resins from the same drigen degree of polymerization (see. Examples 1 and 2). On the other hand, however, in contrast to the resins, they have a higher degree of polymerisation than smooth films Let 35 separate. It is known, water-thinnable resins from their In the German Auslegeschriften 1 083 548 and aqueous solutions by applying a 1089 549 is the implementation of acrylic and / or to deposit voltage on conductive objects. methacrylamide-containing polymers in alcoholic Baking at higher temperatures gives a solution containing formaldehyde. The after hard, glossy films are used, but the resins produced in these published publications dissolve use of alkyd resins !! some yellowing only in organic solvents, but are in show, so that ksine pure white shades get water-insoluble. Will the acidic polybe be able. merisate by neutralization with suitable If acrylates and bases are converted into your soaps as water-thinnable resins, they become if it is set, it is water-soluble for reasons of a constant bath temperature and for electrophoretic application heating advantageous, self-hardening process suitable. to use component systems, among which the neutralization of carboxyl-containing resins Acrylamide polymers are of greatest importance, for example, in German patent specification 859 954, sit. With these solution polymers the her- in the French patent 901 476 and in the Positioning of pure white coatings possible, but results in 5 "German Auslegeschrift 1 053 696 described. films with the usual degrees of polymerisation.In particular, copolymers of acrylic heavily disturbed surfaces, such as orange peel, matte and / or methacrylamide produced, with the amounts Spots, pimples or wrinkles, the resins on these monomers are preferably 5 to 20 percent by weight for the electrophoretic application process. As ethylenically unsaturated acids make suitable. 55, for example, acrylic, methacrylic, Maiein- It has now been found that water-thinned or fumaric acid and the half-esters of the last two acrylamide polymers of particularly low mole-mentioned acids can be used as other comonomers of acylcular weight electrophoretically as smooth films and / or methacrylic acid esters, preferably lower high layer thickness and after the alcohols (up to C-8). In addition, Malein or Stoving coatings with good hardness, elasticity and 60 fumaric acid esters, styrene and its derivatives, such as. B. Adhesion result in the case of pig- \ -Methylstyrene or vinyltoluene, as comonomers mented systems are of a pure white color. As suitable. Another advantage of these resins is shown that the amount of unsaturated acid is so too an addition of other components with a crosslinking effect is measured so that the polymers are neutralized it is not necessary what are water-soluble for the electrophoretic 65 sation, whereby the lower limit Application of the resins is a particular advantage. depending on the type of comonomers and at about In the case of the resins used, there is an acidity of 3 percent by weight, If the amine salts are water-dilutable with The production of the polymers is