COIL COATING PROCESS

Abstract

The present invention relates to a method for surface coating a plane metal substrate, the method comprising the following steps: Providing a coiled plane metal substrate; unwinding the coiled plane metal substrate; applying a polyester based adhesive onto a top surface of the unwound plane metal substrate, and laminating a film comprising a base acrylic layer onto the polyester based adhesive, thereby forming a laminated assembly. The invention further relates to a pre-coated metal substrate obtainable by the method according to the invention, and to a product comprising a pre-coated metal substrate according to the invention.

Claims

1. A method for surface coating a plane metal substrate, the method comprising the steps of: providing a coiled plane metal substrate; unwinding the coiled plane metal substrate; applying a polyester based adhesive onto a top surface of the unwound plane metal substrate, and laminating a film comprising a base acrylic layer onto the polyester based adhesive, thereby forming a laminated assembly, wherein the polyester based adhesive and the film comprising a base acrylic layer each comprise less than 15 wt % of plasticizer.

2. Method according to claim 1, wherein no plasticizer is incorporated in the laminated assembly.

3. Method according to claim 1, wherein the top surface of the plane metal substrate comprises a metal substrate primer.

4. Method according to claim 1, wherein the film comprises a base acrylic layer primer.

5. Method according to claim 1, wherein the polyester based adhesive comprises an aromatic acid component, wherein the aromatic acid component comprises a combination of terephtalic acid and isophtalic acid.

6. Method according to claim 1, wherein the base acrylic layer comprises a methacrylate, polymethyl methacrylate (PMMA), and/or, wherein the base acrylic layer comprises one or more pigments.

7. Method according to claim 1, wherein the film further comprises one or more of the following: an ink layer at least partially covering the base acrylic layer, a top acrylic layer covering the previous layers, a fluorinated top layer covering the previous layers.

8. Method according to claim 1, further comprising embossing the laminated assembly.

9. Method according to claim 1, further comprising applying a strippable film covering one or more lower layers of the laminated assembly.

10. Method according to claim 1, Further comprising applying a backing coating to a bottom surface of the plane metal substrate.

11. Method according to claim 1, further comprising rewinding the laminated assembly resulting in a laminate coil.

12. Method according to claim 1, further comprising cutting the laminated assembly to produce slit coils.

13. Method according to claim 1, further comprising cutting the laminated assembly to produce pre-coated metal sheets.

14. A pre-coated metal substrate obtainable by the method of any one of the preceding claims, the pre-coated metal substrate comprising a plane metal substrate, a polyester based adhesive layer covering the plane metal substrate, a film comprising a base acrylic layer, the base acrylic layer coveting the polyester based adhesive layer, wherein the polyester based adhesive layer and the film comprising a base acrylic layer each comprise less than 15 wt %.

15. A product comprising a pre-coated metal substrate according to claim 14.

16. A product according to claim 15, which is a facade panel, preferably a structured facade panel.

17. Method according to claim 2, wherein the film comprises a base acrylic layer primer.

18. Method according to claim 1, wherein the aromatic acid component comprises a combination of terephtalic acid and isophtalic acid.

19. Method according to claim 6, wherein the base acrylic layer comprises a methacrylate, polymethyl methacrylate (PMMA).

20. Method according to claim 7, wherein the fluorinated top layer comprises polyvinylidene fluoride (PVDF) or polyvinyl fluoride (PVF).

Description

BRIEF DESCRIPTION OF THE FIGURES

[0065] FIG. 1: Schematic picture of a coil coating line.

[0066] FIG. 2: Schematic picture of a laminated assembly according to the invention.

DETAILED DESCRIPTION OF THE FIGURES

[0067] FIG. 1 depicts a typical coil coating line for carrying out a process according to the invention. In the embodiment shown, a coil 2 of a plane metal substrate 1 is unwound and transported through the line in transport direction 19. The substrate is degreased in degreasing zone 4, washed in washing zone 5, rinsed in rinsing zone 6, and subsequently passivated and dried in passivation zone 7 and drying zone 8, respectively. A primer 23 is applied by reverse roller coat in zone 9, cured by heating in primer heating zone 10, and cooled with water in primer cooling zone 11. In the depicted embodiment, the adhesive 24 and a back-coat 30 are applied simultaneously in adhesive and back-coat coating zones 12 and 13, respectively. Both the adhesive 24 and back-coat 30 are applied by reverse roller coat. Subsequent heating is performed in adhesive heating zone 14. The film 31 is laminated onto the metal substrate 1 in lamination zone 15. Subsequent cooling is performed by cooling with water in laminate cooling zone 16, followed by drying in laminate drying zone 17. A strippable film 29 is applied in strippable film lamination zone 18. The metal substrate is rewound onto coil 3.

[0068] FIG. 2 depicts an embodiment of a laminated assembly 21 according to the invention. Shown are the plane metal substrate 1, of which a first surface 32 is subsequently covered by a layer of metal substrate primer 23, polyester based adhesive layer 24, film 31, and strippable film 29. The second surface 33 is covered by a backing coating 30. Film 31 comprises in order layers 34, 25, 26, 27, and 28, i.e. base acrylic layer primer 34, base acrylic layer 25, ink layer 26, top acrylic layer 27 and fluorinated top layer 28.

Materials

[0069] Multilayer film—Multilayer, plasticizer free, film comprising in order: a pigmented PMMA base layer, a printing ink layer, a transparent PMMA layer, a transparent PVDF top layer.

[0070] Polyester based adhesive—Commercially available polyester based adhesive comprising terephthalic acid, isophthalic acid, (in a ratio of between 1:1 and 2:1), and neopentyl glycol as main components, according to the most preferred embodiments of the invention.

[0071] Comparative Adhesive 1—Commercially available acrylic based adhesive.

[0072] Comparative Adhesive 2—Commercially available vinylic based adhesive.

[0073] Comparative Paint 3—Polyester resin comprising >25 wt % of plasticizer.

Example 1

[0074] A coil of galvanized steel was unwound, degreased and pre-treated by a passivant liquid, a primer was applied by using a reverse roll coating process typically at a line speed of 20 m/min resulting in a film thickness of 8 μm. The primer was cured at a temperature of up to 232° C. for a total of 30 sec. Then the coil was cooled down by water and dried up. The polyester based adhesive was applied in a film thickness of 8 μm by using a reverse roll coating process at a line speed of 20 m/min, curing it up to 232° C. for a total of 30 sec. Then the film was laminated immediately outside the oven. Then the coil was cooled down by water and dried up. A protective film was applied in line and the coil was rewound.

Comparative Examples

[0075] Comparative examples were prepared in a similar fashion as for example 1, however, the adhesives were comparative adhesive 1, and comparative adhesive 2, respectively. A further comparative example is prepared which comprises comparative paint 3.

TABLE-US-00001 TABLE 1 ex1 c1 c2 c3 Corrosion resistance  750 h  750 h  500 h  <500 h EN13523-8 (ASTM B117) Condensation resistance at 38° C. 1500 h 1500 h 1000 h <1000 h ISO 6270 (ASTM D585)

[0076] As can be seen from table 1, the vinylic based adhesive provided acceptable corrosion resistance and condensation resistance properties. However, both example 1 as well as the acrylic based adhesive provided for excellent corrosion resistance and condensation resistance. The acrylic based adhesive is however undesirable for use on a coil coating line because such an adhesive is not compatible with other frequently used adhesives in coil coating. Therefore, the polyester based adhesive has the advantage of providing excellent corrosion resistance as well as condensation resistance, while being compatible with other frequently used adhesives.

[0077] When instead of an adhesive, a plastisol paint is used (c3), the corrosion and condensation resistance provide inferior results. Moreover, the aesthetic properties of example c3 are inferior to those of the other examples.

[0078] The invention furthermore relates to the following clauses:

1. A method for surface coating a plane metal substrate, the method comprising the steps of: [0079] providing a coiled plane metal substrate; [0080] unwinding the coiled plane metal substrate; [0081] applying a polyester based adhesive onto a top surface of the unwound plane metal substrate, and [0082] laminating a film comprising a base acrylic layer onto the polyester based adhesive, thereby forming a laminated assembly.
2. Method according to clause 1, wherein the top surface of the plane metal substrate comprises a metal substrate primer.
3. Method according to clause 1 or 2, wherein the film comprises a base acrylic layer primer.
4. Method according to any one of the preceding clauses, wherein the polyester based adhesive comprises an aromatic acid component.
5. Method according to clause 4, wherein the aromatic acid component comprises a combination of terephtalic acid and isophtalic acid.
6. Method according to clause 5, wherein the weight ratio of terephthalic acid:isophtalic acid is in the range of 1:1 to 1:2, preferably 1:1.2 to 1:2.
7. Method according to any one of the preceding clauses, wherein the base acrylic layer comprises a methacrylate, preferably polymethyl methacrylate (PMMA).
8. Method according to any one of the preceding clauses, wherein the base acrylic layer comprises one or more pigments.
9. Method according to any one of the preceding clauses, wherein the film further comprises an ink layer at least partially covering the base acrylic layer.
10. Method according to any one of the preceding clauses, wherein the film further comprises a top acrylic layer covering the previous layers, preferably wherein the top acrylic layer is a clear layer.
11. Method according to any one of the preceding clauses, wherein the film further comprises a fluorinated top layer covering the previous layers, the top layer preferably comprising polyvinylidene fluoride (PVDF) or polyvinyl fluoride (PVF), more preferably PVDF.
12. Method according to any one of the preceding clauses, further comprising embossing the laminated assembly.
13. Method according to any one of the preceding clauses, further comprising applying a strippable film covering the lower layers.
14. Method according to any one of the preceding clauses, further comprising applying a backing coating to a bottom surface of the plane metal substrate.
15. Method according to any one of the preceding clauses, further comprising rewinding the laminated assembly resulting in a laminate coil.
16. Method according to any one of the preceding clauses, further comprising cutting the laminated assembly to produce slit coils.
17. Method according to any one of the preceding clauses, further comprising cutting the laminated assembly to produce pre-coated metal sheets.
18. Pre-coated metal substrate obtainable by the method of any one of the preceding clauses, the pre-coated metal substrate comprising

[0083] a plane metal substrate,

[0084] a polyester based adhesive layer covering the plane metal substrate,

[0085] a film comprising a base acrylic layer, the base acrylic layer covering the polyester based adhesive layer.

19. Pre-coated metal substrate according to clause 18, wherein the top surface of the plane metal substrate comprises a metal substrate primer.
20. Pre-coated metal substrate according to clause 18 or 19, wherein the film comprises a base acrylic layer primer.
21. Pre-coated metal substrate according to any one of clauses 18-20, wherein the polyester based adhesive comprises an aromatic acid component.
22. Pre-coated metal substrate according to any one of clauses 18-21, wherein the aromatic acid component comprises a combination of terephtalic acid and isophtalic acid.
23. Pre-coated metal substrate according to any one of clauses 18-22, wherein the weight ratio of terephthalic acid:isophtalic acid is in the range of 1:1 to 1:2, preferably 1:1.2 to 1:2.
24. Pre-coated metal substrate according to any one of clauses 18-23, wherein the base acrylic layer comprises a methacrylate, preferably polymethyl methacrylate (PMMA).
25. Pre-coated metal substrate according to any one of clauses 18-24, wherein the base acrylic layer comprises one or more pigments.
26. Pre-coated metal substrate according to any one of clauses 18-25, wherein the film further comprises an ink layer at least partially covering the base acrylic layer.
27. Pre-coated metal substrate according to any one of clauses 18-26, wherein the film further comprises a top acrylic layer covering the previous layers, preferably wherein the top acrylic layer is a clear layer.
28. Pre-coated metal substrate according to any one of clauses 18-27, wherein the film further comprises a fluorinated top layer covering the previous layers, the top layer preferably comprising polyvinylidene fluoride (PVDF) or polyvinyl fluoride (PVF), more preferably PVDF.
29. Product comprising a pre-coated metal substrate according to any one of clauses 18-28.
30. Product according to clause 29, which is a façade panel, preferably a structured façade panel.