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
1996-06-05
1998-01-13
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...
524539, 524555, 524591, 524839, 524840, 525123, 525127, 525130, C08L 7500
Patent
active
057080720
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/AT94/00186 filed Dec. 5, 1994, published as WO95/16004 Jun. 15, 1995.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for the preparation of water-dilutable coating binders based on oligourethane-acrylate copolymers, and to the coating binders preparable by this process and to their use in the formulation of storing enamels.
2. Description of Related Art
From the extensive patent literature it is evident that coating binders containing urethane groups and proportions of acrylate copolymers are becoming increasingly important, in the form of dispersions, for the formulation of high-grade, water-thinnable, oven-drying topcoats. Examples which may be mentioned are the products as described in DE 3210051 A1, DE 3628124 A1, DE 3628125 A1, DE 3841540 A1, DE 4223182 C1, EP 0226171 B1, EP 0297576 B1 and EP 0438090 A1. Coating binders of this kind are in many cases encountered as mixtures in which the binder components are not sufficiently compatible, and coating materials formulated with these binders have too short a shelf life.
U.S. Pat. No. 4,317,895 recommends thermoplastic acrylic-urethane copolymers as non-water-dilutable binders for automotive topcoats, the solvents preferably employed being ketones and acetates.
Products analogous to these but dilutable in water are known from U.S. Pat. No. 4,318,833. They are obtained by polymerization of ethylenically unsaturated monomers, preferably (meth)acrylates, in the presence of polyurethanes whose dilutability in water is achieved by the incorporation of dimethylolpropionic acid.
SUMMARY OF THE INVENTION
It has now been found that water-dilutable acrylic-urethane copolymers can be prepared by using as starting product a water-insoluble oligourethane and by introducing carboxyl groups into the binder by means of the additional use of (meth)acrylic acid in the monomer mixture.
The present invention accordingly relates to a process for the preparation of coating binders which are based on oligourethane-acrylate copolymers and which are dilutable in water following at least partial neutralization of the carboxyl groups, which process is characterized in that
(A) a monomer mixture containing have 2 to 4 carbon atoms, radicals have 2 to 4 carbon atoms, styrene, the number 100, and the components (Aa) to (Ad) being selected such that in theory a corresponding acrylate copolymer would have an acid number of from 30 to 90 mg of KOH/g, a hydroxyl number of from 30 to 50 mg of KOH/g and a glass transition temperature of from -5.degree. to +25.degree. C., free-radical polymerization initiator and of a
(B) water-insoluble oligourethane which has been obtained by the reaction of an aliphatic ester diol or of a mixture of such diols with diisocyanates, contains no free isocyanate groups and has a hydroxyl number of from 110 to 150 mg of KOH/g, a nitrogen content of from 2.8 to 3.7% by weight and
a molecular mass of from 750 to 1000, (AB) is from 35 to 60% by weight and said end product has an acid number of from 15 to 45 mg of KOH/g, a hydroxyl number of from 75 to 110 mg of KOH/g and an intrinsic viscosity (1.5% strength in chloroform/20.degree. C.) of from 13.5 to 16.5 ml/g.
The invention furthermore relates to the water-dilutable coating binders preparable by this process and to their use, in combination with crosslinking components and, if desired, with other coating binders, in the formulation of storing enamels.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The polymerization of a specific monomer mixture is thus carried out in the presence of the water-insoluble oligourethane, the polymer which forms acting increasingly as emulsifier for the water-insoluble oligourethane, which is incompatible in a mixture with the corresponding acrylate copolymer (see Comparative Examples).
The raw materials and preparation methods used for the process according to the invention are known in principle to the person skilled in the art, so that reference need only be made to specific selection criteria.
In
REFERENCES:
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patent: 4489135 (1984-12-01), Drexler et al.
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patent: 4851460 (1989-07-01), Stranghoner et al.
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patent: 4981885 (1991-01-01), Engel et al.
patent: 5334420 (1994-08-01), Hartung et al.
patent: 5342882 (1994-08-01), Gobel et al.
Hiden Hans
Luttenberger Johann
Tulacs Laszlo
Wilfinger Werner
Cain Edward J.
Vianova Resins Aktiengesellschaft
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