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, comprising at least one copolymer obtained by reacting at least one compound which is catechol or a derivative thereof with at least one polyethyleneimine, to at least one surface of the substrate; (iii) subsequently drying the aqueous coating composition thereby forming a coating layer on the at least one surface of the substrate; then (iv) applying a polyolefin melt or polyolefin film onto the coating layer; and (v) applying pressure sufficient to form a multilayer laminate.

2. The method of claim 1, wherein the substrate is selected from metal, 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 0.001 to 50 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 metal substrate is a metal film.

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

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

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

10. The method of claim 1, wherein one side of the polyolefin film or polyolefin melt is corona or ozone treated.

11. A multilayer laminate, obtained by the method of claim 1.

12. A method of forming a tack-free metal to polyolefin extrusion primer on a metal surface comprising steps of: a. obtaining an aqueous coating composition comprising at least one copolymer reaction product of at least one compound, which is catechol or a derivative thereof with at least one polyethyleneimine; b. applying the aqueous coating composition on a substrate comprising a metal surface and optionally further comprising polyethylene terephthalate, polypropylene or polyamide substrate surfaces; c. drying the aqueous coating composition on the substrate surface thereby forming a tack-free extrusion primer adhered on at least the metal surface generating a primed substrate for extrusion bonding with a polyolefin layer or film; and d. optionally, rerolling the primed substrate.

13. The method according to claim 7, wherein the at least one compound, which is catechol or a derivative thereof is selected from the group consisting of dopamine, 4-(2-aminoethyl)benzene-1,2-diol, their salts and mixtures thereof.

14. The method according to claim 7, wherein the polyethyleneimine has a number average molecular weight of 200 to 100,000 g/mol or is an ethoxylated polyethyleneimine.

15. 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.

Description

EXAMPLES

Example 1

General Information:

[0077] The dopamine/polyethyleneimine copolymer containing primer has a solid content of approx. 11% (Primer according to the invention).

[0078] Comparative Primer: PE extrusion primer Loctite Liofol A1883 (solid content 5% in deionized (DI) water)

[0079] Primer according to the present invention used in different concentrations: [0080] Primer 1: Roller coater #5 approx. 0.1 g/m.sup.2 (dry) with a solid content of 1.1% in DI water. [0081] Primer 2: Roller coater #5 approx. 0.01 g/m.sup.2 (dry) with a solid content of 0.1% in DI water. [0082] Primer 3: Roller coater #5 approx. 0.001 g/m.sup.2 (dry) with a solid content of 0.01% in DI water. [0083] 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:

[0084] 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.

Results:

[0085]

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 μm/PE 0.4 no adhesion Example 1 to aluminum (AI), adhesive on PE Example 1    0.1 g/m.sup.2 PET-Alu12 μm/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 μm/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 μm/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 μm/PE 2.4 Separation, (Primer 4) Al surface tackfree

[0086] The primer according to the present invention showed improved adhesion results compared to the comparative example.

Example 2

General Information:

[0087] Primer like in example 1 were employed

Application and Testing:

[0088] 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.

Results:

[0089]

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 μm/PE >4 PET tear Example 2 Comparative 0.01 g/m.sup.2 PET20 μm/PE >4 PE elongation Example 3 and tear Example 5  0.1 g/m.sup.2 PET12 μm/PE 5.9 PET tear (Primer 1) Example 6 0.01 g/m.sup.2 PET12 μm/PE 4.8 PET tear (Primer 2) Example 7  0.1 g/m.sup.2 PET20 μm/PE 6.2 PE elongation (Primer 1) and tear Example 8 0.01 g/m.sup.2 PET20 μm/PE 6.0 PE elongation (Primer 2) and tear

[0090] The primer according to the present invention showed improved adhesion results compared to the comparative examples.