BADGE- and BPA-free can coating
View Patent ↗The present invention relates to a composition, which is useful for producing coatings for metal sheet substrates of metal cans for storing and/or transporting food or beverages or a lid thereof, and which comprises the following components: (a) 30 to 90 wt. % of a polyvinylchloride-(PVC)-polymer, (b) 7 to 25 wt. % of an acrylic resin, (c) 3 to 40 wt. % of a crosslinking agent, which is produced from phenol, para-tert.-butylphenol, xylenol or a mixture thereof, and formaldehyde, (d) 0 to 8 wt. % additive, (e) 0 to 50 wt. % pigment and (f) a solvent-component, where all weight percentages are on the basis of the total dry weight of the coating composition (without solvents) and the composition is substantially free of bisphenol-A-diglycidyl-ether (“BADGE”) and also substantially free of bisphenol-A-resins. The composition provides metal can coatings that have suitable flexibility, scratch resistance, adherence and sterilization resistance when processed in contact with food. The coatings are suitable for three-piece cans as well as deep-drawn metal cans. In particular they are, however, useful for lids that are to be torn open due to their extraordinary flexibility and sterilization resistance.
1. A coating composition, which is useful for coating a metal substrate, which coating composition comprises:
(a) 30 to 90 wt. % of a polyvinylchloride polymer,
(b) 7 to 25 wt. % of an acrylic resin,
(c) 3 to 40 wt. % of a crosslinking agent, which is produced from phenol, para-tert.-butylphenol, xylenol or a mixture thereof, and formaldehyde,
(d) 0 to 8 wt. % additive,
(e) 0 to 50 wt. % pigment and
(f) a solvent-component,
where all weight percentages are on the basis of the total dry weight of the coating composition (without solvents) and the composition is substantially free of bisphenol-A-diglycidyl-ether (“BADGE”) and also substantially free of bisphenol-A-resins and other epoxy groups.
2. The coating composition of claim 1 wherein the acrylic resin is selected from methylmethacrylate, ethylmethacrylate, propylmethacrylate or butylmethacrylate resins or blends thereof.
3. The coating composition of claim 1 wherein the acrylic resin is present in an amount of from 5 to 18 wt. %.
4. The coating composition of claim 1 wherein the crosslinking component is present in an amount of from 8 to 25 wt. %.
5. The coating composition of claim 1 which further comprises additives selected from the group of accelerators for controlling the rate of the crosslinking reaction, lubricants, surfactants, adhesion promoters, stabilizing agents, defoamers, softening agents and mixtures thereof.
6. The coating composition of claim 1 wherein the polyvinylchloride polymer is a polyvinylchloride homopolymer.
7. The coating composition of claim 6 wherein the polyvinylchloride polymer is present in an amount of from 55 to 80 wt. %.
8. The coating composition of claim 1 comprising 55 to 80 wt. % polyvinylchloride polymer, 5 to 18 wt. % acrylic resin, and 8 to 25 wt. % crosslinking agent.
9. The coating composition of claim 8 wherein the polyvinylchloride polymer is a polyvinylchloride photopolymer and wherein the acrylic resin is selected from methylmethacrylate, ethylmethacrylate, propylmethacrylate or butylmethacrylate resins or blends thereof.
10. A method for producing a coated metal substrate which comprises applying a coating composition onto the metal substrate and heating the coated metal substrate, wherein the coating composition comprises:
(g) 30 to 90 wt. % of a polyvinylchloride polymer,
(h) 7 to 25 wt. % of an acrylic resin,
(i) 3 to 40 wt. % of a crosslinking agent, which is produced from phenol, para-tert.-butylphenol, xylenol or a mixture thereof, and formaldehyde,
(j) 0 to 8 wt. % additive,
(k) 0 to 50 wt. % pigment and
(l) a solvent-component,
where all weight percentages are on the basis of the total dry weight of the coating composition (without solvents) and the composition is substantially free of bisphenol-A-diglycidyl-ether (“BADGE”) and also substantially free of bisphenol-A-resins and other epoxy groups.
11. The method of claim 10 , wherein the metal substrate comprises tin-plated or chromium-plated steel or aluminum.
12. The method of claim 10 which comprises heating the coated metal substrate for 10 to 20 minutes at a temperature of from 150 to 250° C.
13. The method of claim of claim 10 wherein the coating composition comprises 55 to 80 wt. % polyvinylchloride polymer, 5 to 18 wt. % acrylic resin, and 8 to 25 wt. % crosslinking agent.
14. The method of claim 13 wherein the polyvinylchloride polymer is a polyvinylchloride photopolymer and wherein the acrylic resin is selected from methylmethacrylate, ethylmethacrylate, propylmethacrylate or butylmethacrylate resins or blends thereof.
15. A coated metal substrate, which has been coated with a coating composition comprising:
(m) 30 to 90 wt. % of a polyvinylchloride polymer,
(n) 7 to 25 wt. % of an acrylic resin,
(o) 3 to 40 wt. % of a crosslinking agent, which is produced from phenol, para-tert.-butylphenol, xylenol or a mixture thereof, and formaldehyde,
(p) 0 to 8 wt. % additive,
(q) 0 to 50 wt. % pigment and
(r) a solvent-component,
where all weight percentages are on the basis of the total dry weight of the coating composition (without solvents) and the composition is substantially free of bisphenol-A-diglycidyl-ether (“BADGE”) and also substantially free of bisphenol-A-resins and other epoxy groups.
16. The coated metal substrate of claim 15 , characterized in that it is a metal can or can lid intended for storing and/or transporting food or beverages.
17. The coated metal substrate of claim 15 wherein the coating composition comprises 55 to 80 wt. % polyvinylchloride polymer, 5 to 18 wt. % acrylic resin, and 8 to 25 wt. % crosslinking agent.
18. The coated metal substrate of claim 17 wherein the polyvinylchloride polymer is a polyvinylchloride photopolymer and wherein the acrylic resin is selected from methylmethacrylate, ethylmethacrylate, propylmethacrylate or butylmethacrylate resins or blends thereof.