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
1994-03-10
1996-02-27
Seidleck, James 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...
524839, 524840, 525440, 525454, 528 45, 528 67, 528 71, C08L 7506, C08G 1880
Patent
active
054949564
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the preparation of water-dilutable coating binders and to their use for formulating stoving enamels, especially water-thinnable fillers for automotive coating.
The binders contain a reaction product of a polyurethane resin containing carboxyl groups and at least one terminal, blocked isocyanate group (polycarboxyl component) with a polyester carrying hydroxyl groups (polyhydroxyl component), which product is water-dilutable after neutralization of the carboxyl groups, and a crosslinking component.
Binder combinations comprising a polycarboxyl component, a polyhydroxyl component and a crosslinking component are described, for example, in AT Patent 328 587, AT Patent 388 738, AT Patent 388 382 and in EP-A2-0 330 139.
The use of such binder combinations achieves rheological properties, in the coating materials, which are advantageous for application, and achieves a very good adhesive strength of the baked coating films to a metallic substrate or to a primer and in relation to subsequent coats, thus enabling the formulation of high-quality, water-thinnable fillers, as are used by the motor-vehicle industry.
The requirements placed on water-thinnable fillers by users in industry are subject to continual changes, and great efforts are required to provide products which can be employed completely, or almost, universally.
Surprisingly it has now been found that, by making a specific selection of the binder components and by specific process steps for the combination of these binder components, it is possible to achieve further improvements in the storage stability of the coating materials.
The present invention accordingly relates to a process for the preparation of water-dilutable coating binders which contain a reaction product of a polycarboxyl component with a polyhydroxyl component and contain a crosslinking component, which process is characterized in that polyurethane resin which contains carboxyl groups corresponding to an acid number of from 70 to 160 mg of KOH/g and contains, in the molecule, at least one terminal blocked isocyanate group but neither free hydroxyl groups nor fatty acid radicals having more than 12 C atoms, and has an intrinsic viscosity of from 6.5 to 12.0 ml/g, preferably from 8.0 to 11.0 ml/g, measured in N,N-dimethylformamide (DMF) at 20.degree. C., are reacted with polyester resin which may be urethane-modified and has a hydroxyl number of from 50 to 500 mg of KOH/g, an acid number of less than 20 mg of KOH/g and an intrinsic viscosity of from 8.0 to 13.0 ml/g, preferably from 9.5 to 12.0 ml/g, measured in N,N-dimethylformamide (DMF) at 20.degree. C. at a temperature of between 90.degree. and 170.degree. C., preferably at a temperature which is from 10.degree. to 20.degree. C. above the temperature at which the blocking agent for the terminal isocyanate groups of component (A) is eliminated, up to an intrinsic viscosity of from 13.5 to 18.0 ml/g, preferably from 14.5 to 16.5 ml/g, measured in N,N-dimethylformamide (DMF) at 20.degree. C., without exceeding the limit of solubility in water, and subsequently partial or complete neutralization of the carboxyl groups with an inorganic or organic base, but before addition of a significant proportion of water, are mixed at from 40.degree. to 100.degree. C. with water-dilutable, and the mixture is diluted with water to a solids content suitable for its further processing, and (B) and of (I) and (II), based on solids, being in each case 100.
The invention also relates to the water-dilutable coating binders prepared by the process according to the invention and to their use for formulating water-thinnable stoving enamels, especially for formulating water-thinnable fillers (primer surfacers) for automotive coating.
By an additional, hydrolysis-stable linkage of the polycarboxyl component (A) with the polyhydroxyl component (B), via the urethane group, by the selection of specific raw materials for the polycarboxyl component (A) in order to improve the compatibility of the reaction product (I) with the cros
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Dworak Gert
Goldner Wolfgang
Staritzbichler Werner
Seidleck James J.
Sergent Rabon
Vianova Kunstharz A.G.
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