| 摘要 |
<p>A dry fluidisable pulverulent mass comprises (1) at least one polyepoxide containing only vicinal epoxy groups and having an epoxy e.g univalency greater than 1.0, (2) at least one epoxy curing agent, (3) at least one thixotropic agent selected from colloidal silica, organic complexes of bentonite and attapulgite and (4) at least one coalescing and anti-cratering agent which is a thermoplastic resin e.g. polyvinyl butyral resin. The composition may additionally contain a partly reacted mixture of a polyepoxide and curing agent and also a small amount of a normally liquid polyepoxide. Many polyepoxides are listed. The curing agents specified are dicyandiamide, phenol-blocked polyisocyanate resins, pyromellitic dianhydride, diamino diphenyl sulphone, meta phenylene diamine, 4,41 methylene dianiline and reaction products of boron trifluoride with ethylamine and polyhydric alcohols. Titanium dioxide and phthalocyanine green pigments may be included in the composition. The composition may be prepared by (1) individually pulverising the components and then blending the powders; (2) fusing the components together, cooling and pulverising; or (3) milling the components at an elevated temperature, cooling and pulverising.ALSO:A process for coating articles, e.g. steel probes, comprises immersing the heated article into a fluidized bed of a dry pulverulent mass comprising (1) at least polyepoxide containing only vicinal epoxy groups and having an epoxy equivalency greater than 1,0, (2) at least one epoxy curing agent, (3) at least one thixotropic agent selected from colloidal silica, organic complexes of bentonite and attapulgite, and (4) a coalescing and anticratering agent which is a thermoplastic resin (e.g. polyvinyl butyral resin), removing coated article from the fluidized bed and maintaining the article at a sufficient temperature to cure the coating. Before coating the article may be degreased by use of a solvent and cleaned and roughened by sand or metal grit blasting or acid etching. The article may be masked using a silicone resin and may be kept in motion in the bed. The composition may additionally contain a partly reacted mixture of an epoxy compound and curing agent. Many polyepoxides are listed. The curing agents specified are dicyandiamide, phenol-blocked polyisocyanate resins, pyromellitic dianhydride, diaminodiphenylsulphone, meta phenylene diamine, 4,41 methylene di-aniline and reaction products of boron trifluoride with ethylamine and polyhydric alcohols. Other compounds which may be included in the composition are titanium dioxide phthalocyanine green.</p> |
