Water-based extrusion primer for polyethylene

Abstract

The invention relates to a method of manufacturing a multilayer laminate, the multilayer laminate obtained by the method according to the invention and to forming an extrusion primer for making the multilayer laminate using an aqueous coating composition comprising at least one specific copolymer.

Claims

1. A method of manufacturing a multilayer laminate, comprising steps of: (i) providing a substrate comprising metal, polyethylene terephthalate, polyamide, polypropylene, polyamide or combinations thereof; (ii) applying an aqueous coating composition to at least one surface of the substrate, the aqueous coating comprising (a) at least one copolymer obtained by reacting at least one compound which is catechol or a derivative thereof with at least one polyethyleneimine and (b) water such that an amount of further components in the aqueous coating is below 5 wt.-%; (iii) subsequently drying the aqueous coating composition thereby forming a tack-free coating layer on the at least one surface of the substrate; then (iv) applying a polyolefin layer or polyolefin film onto the tack-free coating layer; and (v) applying pressure at 100 to 250 C. sufficient to melt the polyolefin layer or polyolefin film thereby forming a multilayer laminate; wherein the polyolefin layer or polyolefin film has a first surface and a second surface opposite the first surface, the first surface being corona or ozone treated and the polyolefin layer or polyolefin film being arranged such that the first surface contacts but does not adhere to the tack-free coating layer until step (v).

2. The method of claim 1, wherein the substrate is selected from oriented polyamide, cast polyamide, oriented polypropylene and combinations thereof.

3. The method of claim 1, wherein the aqueous coating composition contains the at least one copolymer in 0.01 to 1.1 wt.-%, based on total weight of the aqueous coating composition.

4. The method of claim 1, wherein the coating layer has an application weight of about 0.001 to 0.5 g/m.sup.2 and the drying step (iii) is performed at 35 to 100 C., for a time of up to 10 minutes.

5. The method of claim 1, wherein the drying step (iii) is performed at 50 to 90 C., for a time of up to 1 minute.

6. The method of claim 1, wherein the substrate is a metal film.

7. The method of claim 1, wherein the substrate is an aluminum film.

8. The method according to claim 7, wherein the substrate surface comprises a polyethylene terephthalate-aluminum prelaminate and the drying step is at 90 C. for 1 minute.

9. The method of claim 1, wherein the substrate is an aluminum film, bonded to a polyethylene terephthalate layer.

10. The method of claim 1, wherein the polyolefin layer or polyolefin film is (i) a polyethylene, polypropylene or polybutylene layer or film; or (ii) a pretreated polyolefin film.

11. The method of claim 10, wherein the polyolefin melt layer or polyolefin film is a polyethylene, polypropylene or polybutylene.

12. The method according to claim 1, wherein the at least one compound, which is catechol or a derivative thereof is selected from the group consisting of 4-(2-aminoethyl) benzene-1,2-diol, their salts and mixtures thereof.

13. The method according to claim 1, wherein the at least one compound, which is catechol or a derivative thereof comprises dopamine and the polyethyleneimine has a number average molecular weight of 200 to 100,000 g/mol or is an ethoxylated polyethyleneimine.

14. The method according to claim 1, wherein the amount of further components in the aqueous coating is below 1 wt.-%.

15. The method according to claim 1, wherein the amount of further components in the aqueous coating is below 0.001 wt.-%.

16. The method according to claim 1, wherein the at least one compound which is catechol or a derivative thereof to polyethyleneimine groups of the at least one polyethyleneimine is present in amounts such that there is a respective molar ratio from 1:0.05 to 1:25.

17. The method of claim 1, wherein step (v) is applied for up to 1 minute.

Description

EXAMPLES

Example 1

(1) General Information:

(2) The dopamine/polyethyleneimine copolymer containing primer has a solid content of approx. 11% (Primer according to the invention).

(3) Comparative Primer: PE extrusion primer Loctite Liofol A1883 (solid content 5% in deionized (DI) water)

(4) Primer according to the present invention used in different concentrations: Primer 1: Roller coater #5 approx. 0.1 g/m.sup.2 (dry) with a solid content of 1.1% in DI water. Primer 2: Roller coater #5 approx. 0.01 g/m.sup.2 (dry) with a solid content of 0.1% in DI water. Primer 3: Roller coater #5 approx. 0.001 g/m.sup.2 (dry) with a solid content of 0.01% in DI water. Primer 4: Roller coater #5 approx. 0.0001 g/m.sup.2 (dry) with a solid content of 0.001% in DI water.
Application and Testing:

(5) The primer solution (comparative primer and primer 1 to 4, respectively) was applied with a roller coater size #5 on the PET-aluminum prelaminate and the water was evaporated in oven at 90 C. for 1 minute. Then the corona treated side of the polyethylene (PE) was pressed against the coated aluminum surface with a hand roller. Due to the fact that the aluminum surface was tackfree, the polyolefin film did not stick. The resulting PET-Al/Primer/PE laminate was sealed with a Brugger machine for 1 s at 220 C. with 650 N pressure to melt the PE film. This procedure simulates the polyolefin extrusion process in the lab. At least 15 mm stripes were cut out of the laminates and the bond strength under the sealed area was measured with a tensile tester.

(6) Results:

(7) TABLE-US-00001 TABLE 1 Results of bond strength measurements using the extrusion primer for PE on PET-aluminum. Coating Bond weight strength Primer (dry) Structure (N/15 mm) Observations Comparative 0.01 g/m.sup.2 PET-Alu12 m/PE 0.4 no adhesion Example 1 to aluminum (AI), adhesive on PE Example 1 0.1 g/m.sup.2 PET-Alu12 m/PE 6.8 PE (Primer 1) elongation and tear in sealing area. Al surface nearly tackfree, Example 2 0.01 g/m.sup.2 PET-Alu12 m/PE 5.4 PE (Primer 2) elongation and tear in sealing area. Al surface tackfree, Example 3 0.001 g/m.sup.2 PET-Alu12 m/PE 6.1 PE (Primer 3) elongation and tear in sealing area. Al surface tackfree, Example 4 0.0001 g/m.sup.2 PET-Alu12 m/PE 2.4 Separation, (Primer 4) Al surface tackfree

(8) The primer according to the present invention showed improved adhesion results compared to the comparative example.

Example 2

(9) General Information:

(10) Primer like in example 1 were employed

(11) Application and Testing:

(12) The primer solution (Primer 1 and comparative primer 1 to 4, respectively) was applied with a roller coater size #5 on the PET film and the water was evaporated in oven at 90 C. for 1 minute. Then the corona treated side of the polyethylene (PE) was pressed against the coated PET surface with a hand roller. Due to the fact that the PET surface was tackfree, the polyolefin film did not stick. The resulting PET/primer/PE laminate was sealed with a Brugger machine for 1 s at 220 C. with 650 N pressure to melt the PE film. This procedure simulates the polyolefin extrusion process in the lab. At least 15 mm stripes were cut out of the laminates and the bond strength under the sealed area was measured with a tensile tester.

(13) Results:

(14) TABLE-US-00002 TABLE 2 Results of bond strength measurements, using the extrusion primer for PE on PET. Coating weight Bond strength Primer (dry) Structure [N/15 mm] Observations Comparative 0.01 g/m.sup.2 PET12 m/PE >4 PET tear Example 2 Comparative 0.01 g/m.sup.2 PET20 m/PE >4 PE elongation Example 3 and tear Example 5 0.1 g/m.sup.2 PET12 m/PE 5.9 PET tear (Primer 1) Example 6 0.01 g/m.sup.2 PET12 m/PE 4.8 PET tear (Primer 2) Example 7 0.1 g/m.sup.2 PET20 m/PE 6.2 PE elongation (Primer 1) and tear Example 8 0.01 g/m.sup.2 PET20 m/PE 6.0 PE elongation (Primer 2) and tear

(15) The primer according to the present invention showed improved adhesion results compared to the comparative examples.