Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1994-03-14
1998-08-11
Gulakowski, Randy
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
523412, 525438, 525531, 525529, 525530, C08K 320, C08K28300
Patent
active
057928045
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the preparation of an aqueous coating composition containing a carboxyl-containing epoxy resin, optionally crosslinking agents, organic solvents, optionally conventional assistants and additives, and optionally pigments and fillers, in which the organic binder solution is neutralized by means of a tertiary amine with supply of heat. The invention furthermore relates to the aqueous coating compositions prepared by the process, and to the use of the compositions for coating packaging containers, preferably for coating cans.
U.S. Pat. No. 4,212,781 discloses aqueous packaging-container coating agents whose binders are prepared by free-radical polymerization of ethylenically unsaturated monomers, some of which contain carboxyl groups, in the presence of an epoxy resin, using at least 3% by weight, based on the total weight of the monomers, of peroxidic initiators. According to the U.S. Patent, the organic solution of the resultant binder mixture is dispersed in water using neutralizers, for example tertiary amines. The organic binder solution here is preferably introduced into a mixture of water and dimethylethanolamine. However, it is also possible to add the amine with a little water with vigorous stirring to the organic solution; U.S. Pat. No. 4,212,781 makes the global statement that warming may optionally be effected during this operation. In the examples of U.S. Pat. No. 4,212,781, the neutralization is carried out by adding the organic binder solution, cooled to 85.degree. C., dropwise to the amine/water mixture, during which the temperature of the resultant mixture increases to 50.degree. C. The aqueous coating agents contain crosslinking agents, preferably amino plastic resins.
U.S. Pat. No. 4,076,676 discloses aqueous can coatings which contain products of the reaction of epoxy resins containing on average 2 terminal glycidyl groups, for example the epoxy resins obtainable under the trade name Epon 1004 and Epon 1007, with tertiary amines. The reaction products are adducts containing quaternary ammonium groups. The compositions disclosed in U.S. Pat. No. 4,076,676 contain amino resins as crosslinking agents. The epoxy resins used in U.S. Pat. No. 4,076,676 contain no acid groups; the water-dispersibility is caused exclusively by the quaternary ammonium groups. The reaction between the epoxy resins and the tertiary amine is preferably carried out in the temperature range from 70.degree. to 80.degree. C.
U.S. Pat. No. 4,247,439 and U.S. Pat. No. 4,302,373 disclose aqueous packaging-container coating compositions based on carboxyl-containing polymers, polyepoxides and tertiary amines. The compositions may be self-crosslinking. The compositions are preferably prepared by dissolving the epoxy resin in the COOH prepolymer and organic solvents, and adding the tertiary amine in water to the mixture, preferably at temperatures between 50.degree. C. and 100.degree. C. The coating agents contain polymeric quaternary ammonium amine salts of polymeric acids. The use of the COOH group-containing prepolymers is regarded as disadvantageous in the aqueous coating agents since they must be prepared in a separate reaction step. In any case, a single-step process is preferred for the preparation of the binder mixtures.
Finally, WO 89/1498 relates to aqueous dispersions which are suitable as coating agents for metal containers for storing foodstuffs and beverages. The coating compositions contain binder mixtures prepared by addition polymerization of relatively inexpensive monomers, such as, for example, styrene, in a reaction medium containing modified epoxy resins. These are obtained by reaction of some of the epoxide groups with ethylenically unsaturated monomers containing groups which are reactive with epoxide groups, such as, for example, unsaturated carboxylic acids, and reaction of further epoxide groups with tertiary amines and with a preaddition polymer which contains carboxyl groups and contributes to the water-dispersibility. The compositions of WO 89/1498 may be
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Cibura Klaus
Dartmann Holger Herbert
Figge Hans Jurgen
Willmer Regina
BASF Lacke & Farben AG
Gulakowski Randy
Sabourin Anne Gerry
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