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AssigneeDynamit Nobel Aktiengesellschaft
InventorsKlaus Bruning, Karl-Gunter Sturm, Siegfried Hahn
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An improvement in a process for coating a substrate by a powder coating process wherein a polyester powder is applied to said substrate which improvement comprises using as the polyester powder a partially crystalline powder of a polyester condensation product of an acid component comprising an acid or ester of at least terephthalic acid and a diol component at least 50 molar percent of which is 1,4-butanediol; a polyester coating powder which is a partially crystalline polyester of an acid component at least part of which is an acid or ester of terephthalic acid and a diol component at least 50 molar percent of which is 1,4-butanediol, said powder having a glass transition temperature between -20.degree. and +50.degree. C., measured as the attenuation maximum in accordance with Deutsche Industrie Norm 53,445 a reduced n.sub.red viscosity of at least 0.6, measured in a 1 weight percent solution of a mixture of 60 parts by weight phenol and 40 parts by weight phenol and 40 parts by weight 1,1,2,2-tetrachloroethane at 25.degree. C. and a melting maximum, determined by differential thermoanalysis, of about 150.degree. to 200.degree. C.
In a process for coating a substrate by a powder coating process wherein a polyester powder is applied to said substrate, the improvement which comprises using as the polyester powder a powder consisting essentially of a partially crystalline powder of an acid component comprising an acid or ester of at least 60 mole percent of which is terephthalic acid and a diol component of at least 50 mole percent of which is 1,4-butanediol, said polyester having a glass transition temperature of between +20.degree. and +50.degree. C, as measured at the attenuation maximum in accordance with Deutche Industrie Norm 53,445, a reduced .eta..sub.red viscosity of 0.7 to 1.0, as determined in a one weight percent solution in a mixture of 60 parts by weight phenol and 40 parts by weight 1,1,2,2-tetrachloroethane at 25.degree. C and melting maximum as determined by differential thermoanalysis of 170 to 190.degree. C, said powder having a grain size of 10-300 microns and being in admixture with a leveling agent.
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