Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1998-09-28
2000-11-14
Dawson, Robert
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
525100, 525101, 525106, 525474, 525479, 525902, 524837, C08L 8304, C08F 800, C08F28312, C08G 7704, C08G 7738
Patent
active
061471429
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to the use of precrosslinked silicone elastomer particles with an organic-polymer shell as a formulating constituent in aqueous coating compositions based on water-soluble or water-dilutable binders.
BACKGROUND ART
Aqueous coating materials comprise binders which are either soluble in or dilutable in water; the water-dilutable binders include resin components and resins which have been emulsified or rendered self-emulsifiable, and aqueous dispersions. Examples of water-soluble binders are modified alkyd resins, acrylate resins, linear and branched saturated polyester resins, epoxy resins, shellac and modified phenolic resins. Examples of water-dilutable binders are--optionally modified--dispersed or water-dispersible, unsaturated and saturated polyester resins, alkyd resin emulsions, polyurethane dispersions, one-component epoxy resin emulsions, emulsifiable two-component epoxy resin systems, dispersible alkyd, phenolic, melamine and urea resins, (meth)acrylate dispersions, (meth)acrylate copolymer dispersions, polystyrene and styrene copolymer dispersions, poly(vinyl ether) dispersions, and polyvinyl chloride and polyvinylidene chloride dispersions.
In addition to water-soluble or water-dilutable binders, aqueous coating materials generally include pigments, fillers, water-soluble crosslinkers and crosslinking catalysts, and further additives such as, for example, levelling assistants, devolatilizing assistants and wetting agents.
These compositions are applied in aqueous form, for example to metallic substrates, mineral substrates, plastics, wood, paper or glass. Following application, the aqueous film dries to a solid coating film. Films which dry at ambient temperature (room temperature) after drying in air, are optionally subjected to thermal conditioning/post-drying at temperatures up to 100.degree. C. For other types of aqueous coating material, even higher temperatures (120-220.degree. C.) may be necessary for film formation, if the latter requires the chemical reaction (post-crosslinking) of two or more binder components.
The water-soluble and water-dilutable binders listed predominantly comprise thermoplastic or thermosetting polymers, which are generally hard but brittle. To improve the film properties, therefore, impact modification of the polymer systems is frequently necessary. Silicones are known as modifiers for thermoplastics and thermosets and are of particular interest since they not only increase the impact strength but also improve low-temperature flexibility, weathering stability, stability to fluctuating temperature stress and chemical resistance of thermoplastic or thermosetting organic-polymer systems. Generally disadvantageous, however, is the fundamental incompatibility of silicones with organic polymers. The incompatibility may induce flow defects in the course of use, while migration of the silicones gives rise to adhesion problems and problems associated with overcoatability.
In DE-A 3922285 (=GB-A 2222167) (Dow Corning, laid open on Jan. 25, 1990) the known incompatibility of siloxanes with organic polymers is exploited for decorative purposes; it describes a coating composition composed of polydiorganosiloxane and of an aqueous dispersion of a film-forming polymeric material, for obtaining a hammered surface effect. Polysiloxanes of this kind are not suitable for the impact modification of aqueous coating materials, since the polysiloxane is present in emulsified form as a liquid in the water phase rather than as discrete particles. In the amount which needs to be used for impact modification, these compounds are exuded from the coating film.
EP-A 586048 (Shin Etsu, published on Mar. 9, 1994) describes diol-functional silicone oils as additives to aqueous coating materials for lowering the surface tension and improving the substrate wettability; in this established utility, these siloxanes show better flow properties than polyether-modified silicone oils. Siloxanes of this kind, present in emulsified form, are unsuitable for impact m
REFERENCES:
patent: 4748215 (1988-05-01), Lindner et al.
patent: 4803233 (1989-02-01), Narula et al.
patent: 5202368 (1993-04-01), Davies et al.
patent: 5223586 (1993-06-01), Maufner et al.
patent: 5587424 (1996-12-01), Langstein et al.
patent: 5973068 (1999-10-01), Yamaya et al.
patent: 5981659 (1999-11-01), Geck et al.
Derwent Abstract Corresp. to FR 1505881 A # 68-86404 P.
Derwent Abstract Corresp. to DE 2310213 A # 73-58541 U.
Deubzer Bernward
Geck Michael
Goeblmeier Walter
Oswaldbauer Helmut
Patrick Ekkehard
Dawson Robert
Robertson Jeffrey B.
Wacker-Chemie GmbH
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