Method of priming or one-coat painting of plastics using water-b

Details Method of priming or one-coat painting of plastics using water-b Method of priming or one-coat painting of plastics using water-b

1993-04-06

1994-10-18

Lusignan, Michael

Stock material or miscellaneous articles

Composite

Of epoxy ether

427386, 4273935, 4274121, 428414, B32B 2738

Patent

active

053567145

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a method of priming or one-coat painting of plastics using water-borne paints, and to the use of a water-borne paint for priming or one-coat painting of plastics.
Plastics are increasingly used in virtually all areas, in particular in automobile production. In motor vehicles, the aim is for there to be no differentiation between the plastic parts and the metallic parts of the body, either optically or through lower resistance to stone chipping, weathering, etc. In order to achieve this, attempts have been made to paint the plastic parts so that there is no differentiation between them and the metallic parts of the body with respect to appearance and resistance to stone chipping, weathering, etc. However, simple overcoating using the paints employed for the metallic parts is unsuccessful due to adhesion problems and/or poor low-temperature impact resistance and/or poor resistance to stone chipping. In order to overcome these problems, plastic parts are painted with a primer, which can then be overcoated with a top coat. For ecological and economic reasons, it is desired to employ water-borne paints for the primer. When water-borne paints are used for priming of plastics, poor notched impact strength and/or poor adhesion between the substrate and primer, in particular between the primer and the top coat applied thereto, are repeatedly observed.
The object of the present invention is to provide water-borne paints which are suitable for priming or one-coat painting of plastics. These paints Should allow, in particular, plastics to be primed in such a manner that no, or greatly reduced, problems occur with respect to low-temperature impact resistance and/or adhesion.
This object is achieved, surprisingly, by a method of priming or one-coat painting of plastics using water-borne paints which comprises employing a water-borne paint which contains an at least partially protonated product of the reaction of from 5 to 45% by weight and a butadiene content of from 55 to 95% by weight which contains, per molecule, on average from 1.4 to 3.0 primary and/or secondary amino groups, and optionally tertiary amino groups, and has a number average molecular weight of from 500 to 15,000, or a mixture of such butadiene-acrylonitrile copolymers, and from 140 to 10,000 and contains, on statistical average, at least 1.5 epoxide groups per molecule, selected from the group comprising ethers to react with a polyphenol and reacting the resultant product with epichlorohydrin, propylene oxide, tetrahydrofuran or other cyclic ethers, or a mixture of such organic compounds, reaction product in such amounts that from 1.05 to 20 equivalents of reactive amine hydrogen atoms from component (A) are present per equivalent of epoxide groups from component (B).
Suitable compounds for component (A) are butadiene-acrylonitrile copolymers containing from 5 to 45% by weight, preferably from 10 to 30% by weight, of acrylonitrile and from 55 to 95% by weight, preferably from 70 to 90% by weight, of butadiene and containing, per molecule, on average 1.4-3.0 primary and/or secondary amino groups, and, if appropriate, tertiary amino groups. The number average molecular weight of the copolymers is advantageously 500-15,000, preferably 2,000-8,000.
The copolymers containing amino groups can be obtained, for example, by reacting butadiene-acrylonitrile copolymers containing carboxyl groups with diamines. Such butadiene-acrylonitrile copolymers containing amino groups are commercially available (for example HYCAR.RTM. ATBN 1300 X 16, 1300 X 21 and 1300 X 35).
In addition, butadiene-acrylonitrile copolymers containing amino groups can be prepared by partial hydrogenation of butadiene-acrylonitrile copolymers or by the addition reaction of primary amines with butadiene-acrylonitrile copolymers containing epoxide groups.
It is also possible to employ mixtures of butadiene-acrylonitrile copolymers containing primary and/or secondary amino groups as component (A).
As component (B), organic compounds which have a number average molecular

REFERENCES:
patent: 4085018 (1978-04-01), Ariga et al.
patent: 4214039 (1980-07-01), Steiner et al.
patent: 4518724 (1985-05-01), Kuwajima et al.
patent: 4696763 (1987-09-01), Bentley et al.

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