Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1994-02-01
1997-11-25
Sellers, Robert E.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525 65, 525108, 525111, 525117, 525118, 525119, 525209, 525438, C08L 3302, C08L 3314, C08L 6308, C08L 6702
Patent
active
056914199
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to coating agents which comprise, as the binding agent, at least one polymer containing carboxyl groups and, as the hardener, at least one epoxy resin having on average more than one epoxide group per molecule.
The present invention furthermore relates to processes for the preparation of these coating agents and to their use, and to processes for coating substrates.
Very high quality requirements are imposed in particular on coating agents which are employed in the field of automobile repair painting. Thus, these coating agents must be curable at low temperatures (.ltoreq.100.degree. C., preferably .ltoreq.80.degree. C.) and at the same time already be dry to dust and tack-free after less than 7 hours. A good resistance to solvents, resistance to weathering, resistance to taping, resistance to yellowing and sandability, and a low intrinsic color of the resulting coatings are furthermore required. It must be possible, furthermore, to paint over the coatings, in order thus to guarantee that paint damage in the adjacent region and in the region of the repair paint can also be repaired.
Coating agents based on acrylate copolymers containing carboxyl groups and on epoxy resins which are also used in the field of automobile repair painting have been known for a long time and are described, for example, in EP-B-51 275, EP-A-123793, DE-OS 26 35 177, JP-OS 76 338/77, WO 87/02041 and WO 89/08132. However, these known coating agents have only a low stability to weathering and a low surface slip, and as a result a poor resistance of the resulting coatings to chemicals. Compatibility problems moreover occur between the acrylate copolymers containing carboxyl groups and some epoxy resins.
Coating agents for coating automobiles are furthermore known from EP-A 358153, these comprising either a) a copolymer which is obtainable using polysiloxane macromonomers having at least two functional groups per molecule and vinyl monomers containing epoxide groups, or b) 1 mixture of a polymer (1) based on polysiloxane macromonomers having at least two functional groups and a polymer (2) based on vinyl monomers containing epoxide groups. These coating agents furthermore contain an aluminum chelate compound and/or a titanium chelate compound and/or a zirconium chelate compound as the hardener.
Since the functional groups of the polysiloxane macromonomers contribute toward crosslinking of the coating agents, a very high content of this polysiloxane macromonomer in the copolymer is required to guarantee adequate crosslinking. On the other hand, crosslinking of the coating agents by a carboxy/epoxy reaction is not described in EP-A-358153. These moisture-hardening coating agents known from EP-A-358153 furthermore have the disadvantage of a lower storage stability after drums have been opened and higher production costs of the coating agents.
Moisture-hardening coating agents furthermore are known from DE-OS 38 39 215, these comprising, as the binding agent, a resin which is obtainable by polymerization of a vinyl monomer containing alkoxysilane and/or a polysiloxane macromonomer with a vinyl monomer containing epoxide groups in the presence of a resin containing carboxyl groups. These coating agents in turn contain a chelate compound as the hardener.
A coating agent based on acrylate copolymers containing hydroxyl groups and on polyisocyanates furthermore is known from JP-OS 2163177, this being employed, in particular, as a house paint. The coatings here are distinguished by an improved stability to weathering, which is achieved by copolymerization of 0.5 to 15% by weight of a polysiloxane macromonomer into the acrylate copolymer containing hydroxyl groups. It is also known from U.S. Pat. No. 4,754,014 that the weathering resistance of coating agents based on acrylate copolymers containing hydroxyl groups can be improved by modification with polysiloxane macromonomers. However, coating agents based on acrylate copolymers containing carboxyl groups and on epoxy resins are not described in JP-OS 2163177 and U.
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Brunnemann Michael
Engelke Stephan
Holst Andreas
Rotter Olaf
BASF Lacke & Farben AG
Budde Anna M.
Sabourin Anne Gerry
Sellers Robert E.
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