Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1992-11-30
1996-03-26
Cain, Edward J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524458, 524556, 4273722, 427380, 4273837, 4273855, 4273881, 4273882, 4273884, 4274071, C08K 320
Patent
active
055021018
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the production of a multicoat protective and/or decorative finish in which basecoat, and subsequently
This process represents the well-known basecoat/clearcoat process which is employed especially in the automotive industry for the production of high-quality finishes, in particular of metallic finishes (cf. for example EP-A-38,127, EP-A-89,497 and DE-A-3,628,124).
The invention also relates to aqueous paints which can be used as basecoats in the above process.
The basecoat/clearcoat process under discussion employs predominantly basecoats which contain exclusively organic solvents as thinners and/or solvents.
The paint industry has striven for ecological and economic reasons to replace as large a part of the organic solvents as possible by water. There is a great demand for aqueous basecoats which can be used in the basecoat/clearcoat process described above. An essential feature of the basecoat/clearcoat process lies in the fact that the transparent topcoat is applied to the basecoat before the latter has been baked, and only then are the basecoat and topcoat baked together (wet-on-wet process).
The object forming the basis of the present invention consists in providing novel aqueous paints which can be used as basecoats in the basecoat/clearcoat process. Surprisingly, this object is achieved by the provision of aqueous pigmented paints comprising a water-thinnable polyacrylate resin which can be obtained by adding, either consecutively or alternately in part amounts, unsaturated monomer which contains at least one carboxyl group per molecule and is copolymerizable with (b1), (b2), (b3) and (a2), or a mixture of such monomers, together with monomer which is free from carboxyl groups and is copolymerizable with (b1), (b2), (b3) and (a1), or a mixture of such monomers, and
(meth)acrylic acid ester which is copolymerizable with (b2), (b3), (a1) and (a2) and is essentially free from carboxyl groups, or a mixture of such (meth)acrylic acid esters, and monomer which is copolymerizable with (b1), (b3), (a1) and (a2), contains at least one hydroxyl group per molecule and is essentially free from carboxyl groups, or a mixture of such monomers, and unsaturated monomer which is copolymerizable with (b1), (b2), (a1) and (a2), is essentially free from carboxyl groups and is different from (b1) and (b2), or a mixture of such monomers, in the presence of at least one polymerization initiator and, the resultant polyacrylate resin and dispersing it in water, the sum of the proportions by weight of (a1), (a2), (b1), (b2) and (b3) always being 100% by weight and the type and amount of (b1), (b2), (b3), (a1) and (a2) being chosen so that the polyacrylate resin has a hydroxyl value of 0 to 200, preferably of 20 to 120, an acid value of 20 to 100, preferably of 25 to 50, and a glass transition temperature (T.sub.G) of -40.degree. C. to +60.degree. C., preferably of -20.degree. C. to +40.degree. C.
The water-thinnable polyacrylate resins used according to the invention allow the formulation of basecoats which possess-especially in comparison with known basecoats comprising polyacrylate resins-a higher solids content and a lower tendency to form runs. In addition, the use of the water-thinnable polyacrylate resins according to the invention, especially in polyurethane-containing basecoats, provides stabilization against a fluctuating shearing stress. Compared with the state of the art, a smaller reduction in viscosity, or no reduction at all, occurs especially on exposure to weak shearing forces. This results in improved sedimentation behavior, simpler handling and increased application reliability.
A more detailed description of the preparation of the water-thinnable polyacrylate resins essential to the invention is preceded by an explanation of two of the terms used: for "methacrylic acid or acrylic acid". indicate that the components (b1), (b2) and (b3) may have a low carboxyl group content (but no higher than would cause the polyacrylate resin prepared from the components (b1), (b2) and
REFERENCES:
patent: 4521489 (1985-06-01), Rehfuss et al.
patent: 4677004 (1987-06-01), Das et al.
patent: 4730020 (1988-03-01), Wilfinger et al.
patent: 4798748 (1989-01-01), Claar et al.
patent: 4978708 (1990-12-01), Fowler et al.
Dobbelstein, deceased Arnold
Eikelmann Klaus
Lassmann Walter
Niemann Ju/ rgen
Piontek Susanne
BASF Lacke & Farben AG
Cain Edward J.
Sabourin Anne Gerry
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