Nonaqueous paints

Details Nonaqueous paints Nonaqueous paints

1996-02-20

1998-07-14

Niland, Patrick D.

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...

525123, 525124, 525455, 528 45, C08J 300, C08K 320, C08L 7500, C08F 830

Patent

active

057805415

DESCRIPTION:

BRIEF SUMMARY
The invention relates to nonaqueous paints comprising group-containing synthetic resins
JP-A-2-242867 describes nonaqueous paints containing (A) a hydroxyl group-containing synthetic resin, (B) an amino resin, (C) a blocked polyisocyanate and (D) pigments, in which context components (B) and (C) are to be selected such that the temperature at which a chemical reaction between (A) and (C) ensues should be not more than 20.degree. C. below and not more than 50.degree. C. above the temperature at which a chemical reaction between (A) and (B) ensues.
The nonaqueous paints described in JP-A-2-242867 give coatings which, in particular with regard to their resistance to organic solvents and acids, their scratch resistance and their tendency to yellowing, are in need of improvement.
DE-B-26 39 491 describes nonaqueous coatings materials which contain a hydroxyl group-containing polyester resin and/or alkyd resin, hexamethylene diisocyanate blocked with an alkyl acetoacetate, and/or 2,2,4 trimethylhexamethylene diisocyanate blocked with an alkyl acetoacetate, and an amino resin. The coatings obtained using these coating materials undergo yellowing, especially when elevated baking temperatures and/or prolonged baking times are employed, and are to be improved in particular with regard to their resistance to acids and organic solvents and with regard to their scratch resistance.
The present invention relates to nonaqueous paints of the type mentioned at the beginning, which are characterized in that component (C) contains both isocyanate groups blocked with a blocking agent (I) and isocyanate groups blocked with a blocking agent (II), in which context malonates, contains active methylene groups, or is an oxime, or is a mixture of these blocking agents, and the isocyanate groups blocked with (II) is between 1.0:1.0 and 9.0:1.0.
The coatings which can be produced using the paints according to the invention are distinguished by a high degree of hardness, high gloss, good adhesion, good topcoat holdout, good scratch resistance and good resistance to climatic effects, to organic solvents and to acids, and a high resistance to yellowing (especially to yellowing occurring as a result of high baking temperatures and/or as a result of long baking times). The nonaqueous paints according to the invention are also distinguished by high storage stability and can also be processed well with a low content (e.g. less than 50% by weight) of organic solvents.
Component (A) may in principle be any hydroxyl group-containing synthetic resin which is suitable for transparent topcoats, or a mixture of such synthetic resins. As component (A) it is preferred to employ hydroxyl group-containing polyester resins and/or hydroxyl group-containing alkyd resins and/or hydroxyl group-containing polyacrylate resins, and mixtures of these resins. The synthetic resins employed as component (A) generally have hydroxyl numbers of from 40 to 240, preferably from 60 to 150, and number-average molecular weights of from 1500 to 30,000, preferably from 2000 to 15,000, particularly preferably from 2500 to 7500.
Hydroxyl group-containing polyester resins, alkyd resins and polyacrylate resins are well known. Examples of such resins and their preparation are described in, for example, JP-A-2-24 28 67, DE-B-26 39 491 and in the patent documents specified on page 6 in lines 31 to 36.
As component (A) it is particularly preferred to employ polyacrylate resins which can be prepared by polymerizing cycloalkyl acrylate or of an alkyl or cycloalkyl methacrylate having 1 to 18, preferably 4 to 13, carbon atoms in the alkyl or cycloalkyl radical, or mixtures of such monomers, hydroxyalkyl acrylate or of a hydroxyalkyl methacrylate having 2 to 4 carbon atoms in the hydroxyalkyl radical, or mixtures of such monomers, acid or methacrylic acid, or mixtures of these monomers, and unsaturated monomers which are different from (a), (b) and (c) and are copolymerizable with (a), (b) and (c), or mixtures of such monomers preferably from 60 to 150, acid numbers of from 0 to 35, pre

REFERENCES:
patent: 4677180 (1987-06-01), Schmitt et al.

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