Aqueous stripping composition for metal surfaces

Abstract

The invention relates to an aqueous stripping composition for the removal of polymeric surface sealants on metal surfaces, said stripping composition comprising an alkalizing agent, a polymer splitting agent, a swelling agent, and a cloud point booster, wherein said polymer splitting agent is at least one gluconate wherein said swelling agent is at least one compound selected from the group consisting of glycol ethers and aliphatic alcohols having 3 to 9 carbon atoms. The inventive aqueous stripping composition is capable to remove polymeric sealants like e.g. polyurethane sealants, polyethylene sealants, polyethylene waxes, polyacrylic sealants, polysilicate sealants, and the like.

Claims

1. An aqueous stripping composition for the removal of polymeric surface sealants on metal surfaces, said stripping composition comprising: a) 30 to 300 g/L of an alkalizing agent, b) 1-100 g/L of a polymer splitting agent, wherein the polymer splitting agent is at least one gluconate, c) 5 to 150 g/L of a swelling agent, wherein the swelling agent is at least one compound selected from the group consisting of glycol ethers and mono-alcohols having 3 to 9 carbon atoms, d) a cloud point booster, wherein the cloud point booster is at least one alkylbenzenesulfonate according to formula I ##STR00004## wherein R.sub.1 and R.sub.2 are independently from each other H or a branched or unbranched C.sub.1 to C.sub.13 alkyl group, and M is at least one metal selected from the group consisting Li, Na, K, or a naphthyl sulfopropyl diether according to formula II ##STR00005## wherein m=1 to 11, and n=1 to 17 and M is at least one metal selected from the group consisting Li, Na, K, and e) 0.5 to 95 g/L of a surfactant.

2. The stripping composition according to claim 1 wherein the cloud point booster is the alkylbenzenesulfonate according to formula I.

3. The stripping composition according to claim 1, said composition having a pH-value of ≧13.

4. The stripping composition according to claim 1 wherein the surfactant is a non-ionic surfactant.

5. The stripping composition according to claim 1, wherein said surfactant is a polyglucoside according to formula III ##STR00006## wherein m=1 to 5, and n=5 to 15.

6. The stripping composition according to claim 1, wherein said surfactant is comprised in a concentration of ≦100 g/l.

7. The stripping composition according to claim 1, wherein the composition has a surface tension at 20° C. of ≦35 mN/m.

8. An aqueous stripping composition for the removal of polymeric surface sealants on metal surfaces, said stripping composition comprising an alkalizing agent, a polymer splitting agent, a swelling agent, and a cloud point booster, wherein said polymer splitting agent is at least one gluconate and wherein said swelling agent is at least one compound selected from the group consisting of glycol ethers and mono-alcohols having 3 to 9 carbon atoms, wherein the cloud point booster is a naphthyl sulfopropyl diether according to formula II ##STR00007## wherein m=1 to 11, and n=1 to 17 and M is at least one metal selected from the group consisting Li, Na, K.

9. The stripping composition according to claim 8, said composition having a pH-value of ≧13.

10. The stripping composition according to claim 8, wherein said polymer splitting agent is comprised in a concentration range of between ≧1 g/l and ≦100 g/l.

11. The stripping composition according to claim 8, wherein said swelling agent is comprised in a concentration range of between ≧1 g/l and ≦200 g/l.

12. The stripping composition according to claim 8, wherein said cloud point booster is comprised in a concentration range of between ≧1 g/l and ≦100 g/l.

13. The stripping composition according to claim 8, wherein the composition further contains a surfactant.

14. The stripping composition according to claim 13, wherein the surfactant is a polyglucoside according to formula III ##STR00008## wherein m=1 to 5, and n=5 to 15.

Description

EXAMPLE 1

(1) An aqueous stripping composition is provided by adding to 1000 ml tab water 50 g KOH as a alkalizing agent, 1 g potassium gluconate as a polymer splitting agent, 5 g ethylene glycol monoethyl ether as a swelling agent, 20 g of a cloud point booster according to general formula II (RALUFON NAPE 14-90, available from Raschig GmbH, Germany), and 8 g of a surfactant according to general formula III.

(2) A mild steel panel S235JR+AR plated with 10 m zinc from an alkaline zinc bath, passivated with PERMA PASS 3082 (a passivation commercial available from Enthone Inc., USA), sealed with ENSEAL 135 (a polyurethane based sealant commercial available from Enthone Inc., USA) and crosslinked in an oven was emerged in a solution according to example 1 at a temperature of 30° C. for 45 minutes. After removing the steel panel from the solution and rinsing in tab water, it was dipped in a copper sulfate solution. After removing the panel from the copper sulfate solution rinsing and drying it, a complete black conversion layer demonstrates the success of removing the sealant.