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
1996-06-24
1998-09-22
Warzel, Mark L.
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...
524560, 524531, 524556, 525207, 525208, 525221, 525222, 427402, 4274071, 427410, C08L 3300
Patent
active
058114840
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the preparation of water-dilutable coating binders based on acrylate copolymers and to their use for the formulation of water-thinnable baking enamels having a low content of organic auxiliary solvents.
Water-dilutable binders which are obtained by partial condensation of a polycarboxy component, which is soluble in water following neutralization of the carboxyl groups, with a resin-like polyhydroxy component which is essentially not dilutable in water, and which are distinguished by favourable viscosity characteristics on dilution with water, are claimed in a series of protective documents, for example in AT Patent 328 587, AT Patent 379 607, AT Patent 388 738, AT Patent 388 382 and EP 0 496 079 A2.
The preparation of acrylate copolymers in accordance with EP 0 496 079 A2 requires a high level of concomitant analytical control measures in order to ensure that the quality of these products remains constant.
It has now been found that it is possible, by reacting a polycarboxy component with a polyhydroxy component which contains epoxide groups, to carry out the preparation of such water-dilutable acrylate copolymers in a more simple, more rapid and more reproducible manner.
The invention accordingly relates to a process for the preparation of water-dilutable coating binders based on acrylate copolymers, which are obtained by reacting a polycarboxy component with a polyhydroxy component followed by at least partial neutralization of the carboxyl groups, which is characterized in that copolymer as polycarboxy component having an acid number of from 70 to 240 mg of KOH/g, preferably from 100 to 200 mg of KOH/g, which has been prepared in the form of a solution polymer from
(Aa) from 67 to 90% by weight of alkyl (meth)acrylates which contain an alkyl radical of 1 to 12 carbon atoms, it being possible for these esters to be replaced in a proportion of up to 50% by weight by aromatic vinyl compounds, preferably styrene, and
(Ab) from 10 to 33% by weight of .alpha.,.beta.-ethylenically unsaturated carboxylic acids, preferably (meth)acrylic acid, copolymer as polyhydroxy component having a hydroxyl number of from 90 to 250 mg of KOH/g, preferably from 110 to 180 mg of KOH/g, and an epoxide equivalent of from 0.7 to 26.0 milliequivalents/100 g of solids, which has been prepared in the form of a solution polymer from
(Ba) from 40 to 79.9% by weight of alkyl (meth)acrylates which contain an alkyl radical of 1 to 12 carbon atoms, it being possible for these esters to be replaced in a proportion of up to 50% by weight of aromatic vinyl compounds, preferably styrene,
(Bb) from 20 to 59.9% by weight of monoesters of (meth)acrylic acid with diols, which contain an alkylene radical of 2 to 4 carbon atoms or an oxyalkylene radical of 6 to 12 carbon atoms, and
(Bc) from 0.1 to 3% by weight of a monomer which contains epoxide groups,
the data for the acid number and hydroxyl number always relating to the solids content and the sums of the percentages for components (A) and (B) and, respectively, (Aa) and (Ab) and (Ba) to (Bc) necessarily giving 100 in each case, KOH/g, the solvent is removed in vacuo until the solids content of the batch is at least 95% by weight, the batch is diluted with an auxiliary solvent to a solids content of from 85 to 93% by weight, and then the mixture is maintained at a temperature of from 100.degree. to 150.degree. C., preferably from 110.degree. to 130.degree. C., until the epoxide equivalent of the batch has fallen to less than 0.2 milliequivalent/100 g of solids.
The invention also relates to the use of the binders prepared by this process, in combination with crosslinking components and optionally with other coating binders, for the formulation of water-thinnable baking enamels having a low content of organic auxiliary solvents.
In comparison with the process described in EP 0 496 079 A2 it is possible with the aid of the process according to the invention to prepare water-dilutable acrylate copolymers of similar composition with a simple procedure, a shor
Gossak Kurt
Kriessmann Ingo
Wilfinger Werner
Vianova Resins Aktiengesellschaft
Warzel Mark L.
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