Chemistry: electrical and wave energy – Processes and products – Electrostatic field or electrical discharge
Patent
1992-07-28
1994-06-28
Marquis, Melvyn I.
Chemistry: electrical and wave energy
Processes and products
Electrostatic field or electrical discharge
523404, 525484, 525524, 525526, C25D 1306
Patent
active
053244044
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the coating of electrically conducting substrates in which electrocoating paint,
The invention also relates to an aqueous paint, an epoxide-amine adduct and the use of the epoxide-amine adduct as grinding resin for the production of aqueous pigment pastes.
The cathodic electrocoating process described above is known (cf. for example DE-OS-3,518,732, DE-OS-3,518,770, EP-A-4,090, EP-A-12,463 and EP-A-262,069) and is employed in particular for the priming of automobile bodies. The resultant paint films are usually coated with at least one filler coat and at least one topcoat.
The object of the present invention is to provide a novel cathodic electrocoating process. The object of the invention comprises in particular the provision of novel aqueous paints for the electrocoating process described above.
Surprisingly, this object is achieved by a cathodic electrocoating process wherein the aqueous electrocoating paint is produced using a pigment paste which contains as grinding resin an at least partially protonated epoxide-amine adduct which is obtainable by reacting at least one epoxide group in the molecule, or a mixture of such glycidyl ethers, more than 1.0 epoxide groups in the molecule, or a mixture of such polyglycidyl ethers and mixture of such compounds is obtained in which on statistical average at least 2.0 primary amino groups of the component (C) are incorporated in a chain-extending function with the formation of tertiary amino groups and the resultant epoxide-amine adduct is at least partially protonated. The paint films produced by the process according to the invention are distinguished in particular by the fact that, surprisingly, they possess high stone chip resistance (both as a single-coat coating and in a multicoat paint system), high flexibility and good corrosion resistance. The electrocoating paints used according to the invention are distinguished by high dielectric strength, good throwing power and low organic solvent contents. The high stone chip resistance of the resultant coatings in particular could not have been foreseen in view of the fact that high flexibility of the electrocoating paint film is no guarantee of high stone chip resistance--especially in multicoat coatings. EP-A-253,404 describes electrocoating paints which contain a cationic reaction product from a diglycidyl ether of a diphenol, a diglycidyl ether of a polyol, a diphenol and a nucleophilic compound. There are great differences between the chemical structure of the reaction products described in EP-A-253,404 and the chemical structure of the grinding resins according to the invention.
The electrocoating paints used according to the invention contain at least one cathodically depositable synthetic resin, at least one crosslinking agent and pigments, if appropriate, as well as, if appropriate, fillers and other generally wellknown additives such as antifoams, flow-control agents etc.
The pigments and fillers are incorporated in the electrocoating paints in the form of pigment pastes. The pigment pastes are produced--as a person skilled in the art is aware of--by grinding the pigments in the presence of a suitable grinding resin.
It is an essential part of the invention that the electrocoating paints are produced by the use of a pigment paste which contains as grinding resin an at least partially protonated epoxide-amine adduct which is obtainable by reacting at least one epoxide group in the molecule, or a mixture of such glycidyl ethers, more than 1.0 epoxide groups in the molecule, or a mixture of such polyglycidyl ethers and mixture of such compounds is obtained in which on statistical average at least 2.0 primary amino groups of the component (C) are incorporated in a chain-extending function with the formation of tertiary amino groups and the resultant epoxide-amine adduct is at least partially protonated.
The grinding resins used according to the invention are prepared by reacting the components (A), (B) and (C) with each other in such a stoichiometric ratio that an epox
REFERENCES:
patent: 4659800 (1987-04-01), Daimer et al.
patent: 4661541 (1987-04-01), Batzill et al.
patent: 4824927 (1989-04-01), Dobbelstein et al.
Brucken Thomas
Heimann Ulrich
Jouck Walter
Ott Gunther
Reiter Udo
Aylward David
BASF Lacke & Farben Aktiengesellschaft
Marquis Melvyn I.
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