Low dissipation factor electrostatic epoxy wire coating powder

Claim 1

A method of coating a metallic object with a coating of powder made by (A) preparing by dry mixing a composition which comprises: (1) about 20 to about 80 phr of a first diglycidyl ether of bisphenol A having an E.E.W. of at least 1600 and a Durran's softening point of at least 113° C; (2) about 10 to about 60 phr of a second diglycidyl ether of bisphenol A having an E.E.W. of 700 to 900 and a Durran's softening point of at least 112; and, (3) about 5 to about 50 phr of a third diglycidyl ether of bisphenol A having an E.E.W. of less than 1000 and a Durran's softening point of less than 105° C; (4) about 10 to about 60 phr of a preprepared epoxy ester, the epoxy portion of said ester being derived from a diglycidyl ether of bisphenol A having an E.E.W. of at least about 400 and a Durran's softening point of at least about 70, and the ester portion being derived from a dibasic acid having the formula HOOC--(CH 2 )m -- COOH, where m is about 18 to about 54; and (5) about 5 to about 20 phr of a curing agent for said diglycidyl ethers, at least about 10% by weight of the anhydride equivalent weight of said curing agent being selected from the group consisting of trimellitic anhydride, esterified trimellitic anhydride, and mixtures thereof; (B) hot melt mixing said composition; (C) cooling said composition to form a solid; and (D) grinding said composition into a powder having a particle size of about 5 to about 149 microns, said method comprising: (1) applying said coating powder to said metallic object with an electostatic means selected from the group consisting of a gun and a fluidized bed; and (2) heating said coating powder at about 200 to about 400° C for less than about 1 minute to melt and cure said powder.

Claim 2

A method of coating a metallic object with a coating of powder made by (A) preparing by dry mixing a composition which comprises: (1) about 20 to about 80 phr of a first diglycidyl ether of bisphenol A having an E.E.W. of at least 1600 and a Durran's softening point of at least 113° C; (2) about 10 to about 60 phr of a second diglycidyl ether of bisphenol A having an E.E.W. of 700 to 900 and a Durran's softening point of at least 112; and, (3) about 5 to about 50 phr of a third diglycidyl ether of bisphenol A having an E.E.W. of less than 1000 and a Durran's softening point of less than 105° C; (4) about 10 to about 60 phr of a preprepared epoxy ester, the epoxy portion of said ester being derived from a diglycidyl ether of bisphenol A having an E.E.W. of at least about 400 and a Durran's softening point of at least about 70, and the ester portion being derived from a dibasic acid having the formula HOOC--(CH 2 )m -- COOH, where m is about 18 to about 54; and (5) about 5 to about 20 phr of a curing agent for said diglycidyl ethers, at least about 10% by weight of the anhydride equivalent weight of said curing agent being selected from the group consisting of trimellitic anhydride, esterified trimellitic anhydride, and mixtures thereof; (B) hot melt mixing said composition; (C) cooling said composition to form a solid; and (D) grinding said composition into a powder having a particle size of about 5 to about 149 microns, said method comprising: (1) applying said coating powder to said metallic object with an electostatic means selected from the group consisting of a gun and a fluidized bed; and (2) heating said coating powder at about 200 to about 400° C for less than about 1 minute to melt and cure said powder.