Method for manufacturing coated can lids

Patent metadata

Field	Value
Publication number	US-9889468-B2
Application number	US-201514739202-A
Country	US
Kind code	B2
Filing date	Jun 15, 2015
Priority date	Dec 17, 2012
Publication date	Feb 13, 2018
Grant date	Feb 13, 2018

Abstract

The present invention relates to a method for manufacturing coated can lids from aluminum strip, and is based on the finding that flexible, easily formable coatings having high abrasion resistance result from the use of water-based lacquers containing a copolymer or a copolymer mixture of at least one aliphatic, acyclic alkene with at least one α,β-unsaturated carboxylic acid in water-dispersed form, and a curing system. In a preferred embodiment of the method, the application of a primer coating can be dispensed with entirely when water-soluble compounds of the elements Zr and/or Ti in the lacquer are used as the curing system.

First claim

The invention claimed is:

1. A method for manufacturing a coated can lid from an aluminum strip, comprising:
1) initially applying a lacquer formulation to an aluminum strip and curing said lacquer formulation thereon; wherein the lacquer formulation is a water-based lacquer comprising, in addition to water, components:
a) a copolymer or a copolymer mixture of at least one aliphatic, acyclic alkene with at least one α,β-unsaturated carboxylic acid in water-dispersed form, wherein the copolymer or the copolymer mixture has acid groups that are at least 20% neutralized, but not more than 60% neutralized, and has an acid number of at least 20 mg KOH/g but not greater than 200 mg KOH/g; and
b) at least one water-soluble curing agent,

wherein dispersed polymeric components of the water-based lacquer have a D 50 value of less than 0.5 μm and not less than 0.1 μm; and
2) after step 1) punching lid material from the aluminum strip and forming the lid material into a can lid.

2. The method according to claim 1 , wherein the at least one water-soluble curing agent is selected from the group of consisting of aminoplasts, carbodiimides and mixtures thereof.

3. The method according to claim 1 , wherein the at least one water-soluble curing agent is selected from the group of consisting of polymers vinyl alcohol, copolymers of vinyl alcohol and mixtures thereof, having a hydroxyl number of at least 100 mg KOH/g.

4. The method according to claim 1 , wherein the acid groups of the copolymer or the copolymer mixture are at least 30% neutralized but not more than 50% neutralized such that the copolymer or the copolymer mixture is self-emulsifying and the lacquer formulation contains no emulsifiers and/or no organic solvents.

5. The method according to claim 4 , wherein the lacquer formulation further comprises ammonia, amines, metallic Al, metallic Zn, water-soluble oxides of elements Li, Na, K, Mg, Ca, Fe(II), and Sn(II), and water-soluble hydroxides of elements Li, Na, K, Mg, Ca, Fe(II), and Sn(II) as a neutralizing agent for the acid groups of the copolymer or the copolymer mixture.

6. The method according to claim 5 , wherein the neutralizing agent is selected from ammonia and/or amines.

7. The method according to claim 6 , wherein the neutralizing agent comprises amines selected from morpholine, hydrazine, hydroxylamine, monoethanolamine, diethanolamine, triethanolamine, dimethylethanolamine, and/or diethylethanolamine.

8. The method according to claim 1 , wherein the copolymer or the copolymer mixture has a glass transition temperature of not greater than 80° C.

9. The method according to claim 1 , wherein the at least one aliphatic, acyclic alkene is selected from ethene, propene, 1-butene, 2-butene, isobutene, 1,3-butadiene, and/or 2-methyl-1,3-butadiene.

10. The method according to claim 1 , wherein the α,β-unsaturated carboxylic acids are selected from cinnamic acid, crotonic acid, fumaric acid, itaconic acid, maleic acid, acrylic acid, and/or methacrylic acid.

11. The method according to claim 1 , wherein the at least one aliphatic, acyclic alkenes is present in in the copolymer or in the copolymer mixture in a weight fraction of at least 40% by weight, but not greater than 95% by weight.

12. The method according to claim 1 , wherein the lacquer formulation comprises at least 40% by weight water and:
a) 4-30% by weight of said copolymer or the copolymer mixture;
b) 2-20% by weight of said at least one water-soluble curing agent;

said lacquer formulation further comprising:
c) not greater than 5% by weight of emulsifiers selected from nonionic amphiphiles having an HLB value of at least 8;
d) not greater than 10% by weight of organic water-miscible solvents;
e) not greater than 10% by weight of auxiliary substances selected from the group consisting of wetting agents, leveling agents, defoaming agents, catalysts, film-forming agents, stabilizers, neutralizing agents and mixtures thereof.

13. The method according to claim 1 , wherein prior to application of the lacquer formulation, the aluminum strip does not undergo a wet chemical treatment step which results in a conversion coating of at least 5 mg/m 2 , based on metal elements which are not components of the aluminum strip.

14. The method according to claim 1 , wherein the lacquer formulation is applied to the aluminum strip in an amount sufficient to produce a dry can coating layer of at least 2 g/m 2 , but not greater than 20 g/m 2 .

15. The method according to claim 1 , wherein the aluminum strip is coated on both sides with the lacquer formulation.

16. A method for manufacturing a coated can lid from an aluminum strip, comprising:
1) initially applying a lacquer formulation to an aluminum strip and curing said lacquer formulation thereon; wherein the lacquer formulation is a water-based lacquer comprising, in addition to water, components:
a) a copolymer or a copolymer mixture of at least one aliphatic, acyclic alkene with at least one α,β-unsaturated carboxylic acid in water-dispersed form, wherein the copolymer or the copolymer mixture has acid groups that are at least 20% neutralized, but not more than 60% neutralized, and has an acid number of at least 20 mg KOH/g but not greater than 200 mg KOH/g; and
b) at least one water-soluble curing agent,

wherein dispersed polymeric components of the water-based lacquer have a D 50 value of less than 1 μm; and
2) after step 1) punching lid material from the aluminum strip and forming the lid material into a can lid;

wherein the at least one water-soluble curing agent is selected from inorganic compounds of elements Zr and/or Ti.

17. The method according to claim 16 , wherein the inorganic compounds of elements Zr and/or Ti are selected from alkoxides and/or carbonates.

18. The method according to claim 16 , wherein the inorganic compounds of elements Zr and/or Ti are selected from the group consisting of tetrabutoxy zirconate, tetrapropoxy zirconate, tetrabutoxy titanate, tetrapropoxy titanate, ammonium zirconium carbonate, ammonium titanium carbonate and mixtures thereof.

Assignees

• Henkel Ag & Co Kgaa

Inventors

• De Zeeuw Ard
• Moeller Thomas
• Auweiler Nicole

Classifications

• B05D3/12

  by mechanical means · CPC title

• C08L29/04

  Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids · CPC title

• B05D1/02

  performed by spraying · CPC title

• B05D2252/10

  Applying the material on both sides · CPC title

• B05D2202/25

  based on Al · CPC title