| 摘要 |
The invention relates to a method for coating a metallic surface with an aqueous composition for pretreating before applying another coating or for treating said metallic surface. In addition to water, the composition contains: a) at least one hydrolyzable or at least partially hydrolyzed silane; b) at least one metal chelate; c) at least one organic film former, and; d) at least one long-chain alcohol that serves as a film forming aid. The unsoiled, scoured, cleaned and/or pretreated metallic surface is brought into contact with the aqueous composition so that a film forms on the metallic surface, which is subsequently dried, compacted in part or completely by film formation and, if necessary, additionally hardened. The dried and, if necessary, additionally hardened film has a layer thickness ranging from 0.01 to 10 μm. The invention also relates to corresponding aqueous compositions. |
| 主权项 |
1. A process comprising
contacting a metallic surface that is at least one of clean, pickled, cleaned or pretreated with an aqueous composition having a solids content to form a film on the metallic surface to form a coated substrate, which is then dried to partly or completely compact the formed dried film,
wherein the dried film has a layer thickness in the range from 0.01 to 10 μm, for pretreatment before a further coating or for treatment, wherein the aqueous composition has a pH of from 4 to 9.5 and is largely or completely free of chromium(VI) compounds, and comprises water and:
a) at least one hydrolyzable or at least partly hydrolyzed silane, wherein said partly hydrolyzed silane is an epoxy silane;b) a metal chelate selected from the group consisting of a metal lactate; a metal ammonium lactate, a metal citrate, a metal dialkylcitrate, and a metal dialkylester-citrate;c) an organic film-forming agent comprising at least one of a water-soluble, organic polymer, a water-dispersible organic polymer, a water soluble organic copolymer, or a water-dispersible organic-copolymer with an acid number in the range from 3 to 250 and wherein the organic film-forming agent, based on the solids the composition, is present in an amount of >45 wt. % and contains an acid group, wherein said organic film-forming agent further comprises at least one member selected from the group consisting of acrylic-polyester-polyurethane copolymer, acrylic-polyester-polyurethane-styrene copolymer, acrylic acid ester, acrylic acid ester-methacrylic acid ester, optionally with at least one of free acids or acrylonitrile, ethylene-acrylic mixture, ethylene-acrylic copolymer, ethylene-acrylic-polyester copolymer, ethylene-acrylic-polyurethane copolymer, ethylene-acrylic-polyester-polyurethane copolymer, ethylene-acrylic-polyester-polyurethane-styrene copolymer, ethylene-acrylic-styrene copolymer, polyester resins with free carboxyl groups combined with melamine-formaldehyde resins, a synthetic resin mixture or copolymer based on acrylate and styrene, a synthetic resin mixture or copolymer based on styrene-butadiene, a synthetic resin mixture or copolymer of acrylate and epoxide, an acrylic-modified polyester containing carboxyl groups together with melamine-formaldehyde and ethylene-acrylic copolymer, polycarbonate-polyurethane, polyester-polyurethane, styrene, styrene-vinyl acetate, vinyl acetate, vinyl ester and vinyl ether;
d) a long-chain alcohol; ande) an inorganic compound, wherein the inorganic compound is in particle form,wherein the aqueous composition further comprises a crosslinking agent based on a hafnium cation, wherein the content of the crosslinking agent in the aqueous composition is in the range from 0.01 to 3 wt. %,wherein the organic film-forming agent contains a content of at least one copolymer with an acid number in the range from 3 to 80 to the extent of at least 50 wt. % of the synthetic resins added, wherein the content of the at least one silane in the aqueous composition, including the reaction products formed therefrom, is from 0.1 to 50 g/l, and wherein the molecular weights of the synthetic resins added are in the range of at least 1,000 u. |
