METHOD AND DEVICE FOR CURING A COATING, AND LAMINATE OBTAINED THEREWITH

Abstract

The present invention is related to a method of curing a coated product comprising a substrate and a UV-curable coating composition applied onto a surface of said substrate, the method comprising the steps of transporting said coated product, by means of a web path, into a curing unit comprising a rotating unit, preferably a cylindrical body, and a treatment area formed between said rotating unit and said web path, said rotating unit and said web path having an even surface, wherein said coated product when being transported through said treatment area contacts the rotating unit and the web path so that no free areas between the coated product and the cylindrical body and the web path are present in said treatment area, and UV-curing said coated product present in said treatment area.

Claims

1. A method of curing a coated product comprising a substrate and a UV-curable coating composition applied onto a surface of said substrate, the method comprising the steps: a) transporting said coated product, by means of a flexographic, rotary screen or offset printing onto a web path, into a curing unit comprising a rotating unit, preferably a cylindrical body, and a treatment area formed between said rotating unit and said web path, said rotating unit and said web path having an even surface, wherein said coated product when being transported through said treatment area contacts the rotating unit and the web path so that no free areas between the coated product and the rotating unit and the web path are present in said treatment area, and b) UV-curing, preferably using at least one LED, said coated product present in said treatment area.

2. The method according to claim 1, wherein said UV-curing is performed with a UV lamp that is provided in the interior of the cylindrical body, and said cylindrical body being permeable for UV radiation.

3. The method according to claim 1, wherein said UV-curing is performed with a LED lamp.

4. The method according to claim 1, wherein said UV-curable coating composition comprises a photoinitiator in an amount from 0.01 to 10% by weight, preferably 0.1 to 3% by weight, of the entire amount of the UV-curable composition.

5. The method according to claim 1, wherein during step b) in said treatment area formed between said rotating unit and said web path, at the site of irradiation of the coated product with UV-light, oxygen is present in an amount of less than 200 ppm, preferably less than 100 ppm and most preferably 0 ppm.

6. The method according to claim 1, wherein said UV-curable coating composition is applied onto said surface of said substrate in a printing unit that is located in-line upstream said treatment area.

7. The method according to claim 1, wherein said coated product is transported through said treatment area with a speed of 100-1000 fpm, preferably 200 to 400 fpm.

8. The method according to claim 1, wherein said coated product is cured in step b) with LED light having a wavelength in the range from 360 to 400 nm, preferably 380-395 nm.

9. A product comprising a substrate and a UV-cured coating composition applied onto a surface of said substrate, obtainable by a method according to claim 1.

10. The product according to claim 9, wherein said product has a gloss in the range from 80 to 120 degrees when measured on a BYK gloss meter at 60 degree angle.

11. The product according to claim 9, wherein said product has a rub resistance in the range of 500 to 1000 Sutherland rubs with 2 lb weight.

12. A device for performing a method according to claim 1, comprising a curing unit, wherein said curing unit comprises a rotating unit, preferably a cylindrical body, and a web path, said rotating unit and said web path having an even surface, a UV lamp, preferably LED, and a treatment area formed between said rotating unit and said web path.

13. The device according to claim 12, wherein said UV lamp is provided in the interior of the cylindrical body, and said cylindrical body is permeable for UV radiation.

14. The device according to claim 12, wherein said UV lamp is a LED lamp.

15. The device according to claim 12, further comprising a printing unit that is located in-line upstream said treatment area of said curing unit.

16. The method according to claim 2, wherein said UV-curing is performed with a LED lamp.

17. The product according to claim 10, wherein said product has a rub resistance in the range of 500 to 1000 Sutherland rubs with 2 lb weight.

18. The device according to claim 13, wherein said UV lamp is a LED lamp.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0074] The present invention will now be explained below in more detail with reference to non-limiting drawings and examples.

[0075] FIG. 1 is a front view of an embodiment of a device with a curing unit according to the present invention

[0076] FIG. 2 is a side view of the embodiment of FIG. 1

[0077] FIG. 3 is a schematic representation of a device according to the present invention comprising a printing unit and a curing unit

[0078] FIG. 4 is a schematic representation of a coated product according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0079] In FIG. 1, a front view of an embodiment of a device 1 with a curing unit according to the present invention is shown. Said curing unit comprises a cylindrical body 2 as a rotating unit, which here is transparent and hollow so that a LED serving as UV lamp 5 can be arranged within said cylindrical body 2.

[0080] A web path 3 transports a coated product 11 comprising a substrate 11a and a UV-curable coating 11b into a treatment area 4 between said cylindrical body 2 and said web path 3. In said treatment area 4, the coated product 11 is irradiated with LED light 6.

[0081] A pressure roller 12 is provided underneath the web path 3 in order to press the coated product 11 comprising a substrate 11a and a UV-curable coating 11b against the cylindrical body 2, thus reducing or completely eliminating the amount of oxygen in the treatment area 4.

[0082] In FIG. 2, a side view of the embodiment of FIG. 1 is shown, wherein same reference numbers denote the same components.

[0083] In FIG. 2, the cylindrical body 2 is fastened to a frame 7 via bearings 8a, 8b that are connected with side faces 2a, 2b of said cylindrical body 2. Side face 2a is removable so as to allow access in the inner space of the cylindrical body 2. In said inner space, a support 9 in the form a slide for the LED light 5 is attached (by fixing means not shown).

[0084] In FIG. 3, a schematic representation of a device 1 according to the present invention comprising a printing unit 10 and a curing unit is shown, wherein same reference numbers denote the same components.

[0085] In FIG. 3, a substrate 11a is transported by the web path 3 into the printing unit 10, where a UV-curable coating is applied. Then, the coated product 11 is transported in-line into the treatment area 4, where it is cured by LED light 6 from the UV lamp 5 provided within the cylindrical body 2.

[0086] In FIG. 4, a schematic representation of a coated product 11 according to the present invention is shown, wherein same reference numbers denote the same components.

[0087] The coated product 11 consists of a substrate 11a and a UV-curable coating 11b applied to a surface of said substrate 11.

Example 1

[0088] In a device as shown in example 1, a white polypropylene film was provided in a conventional printing unit (flexographic printing unit with a chamber system and an anilox roller of 400 lines/inch; 4.5 bcm) with a UV-curable coating, so that a coating layer was applied.

[0089] The coated PE film was conveyed, with a speed of 125 fpm, to a curing unit that comprised a cylinder made of quartz glass with a diameter of 200 mm and a wall thickness of 3 mm, and a LED lamp (Phoseon Firepower FP601 20 watt/cm.sup.2 lamp) in said cylinder. Said LED lamp emitted UV light having a wavelength of 395 nm.

[0090] The coated PE film was pressed against the surface of the cylinder with the aid of a pressure roller (rubber roller with durometer hardness of 90) that was applied with a pressure of 60-100 psi) and a web tension of 56 psi against the uncoated surface of the PE film. Under this condition, the coated PE film was irradiated with UV light emitted from the LED in the interior of the cylinder with a power of 100%.

[0091] The resulting cured product was conveyed out of the curing area and evaluated for its gloss and rub resistance by the methods described herein. The obtained product had a gloss of about 100 degrees when measured on a BYK gloss meter at 60 degree angle, and a rub resistance of 500-1000 Sutherland rubs with 2 lb weight. Rub resistance was also measured with MEK rubs. MEK rub testing is performed with a 2 pound ball pen hammer with a cheese cloth on one end that previously immersed in MEK and then placed on the surface of the print. The hammer is pulled back and forth, thus allowing the weight of hammer to press against the printed surface with the MEK soaked cheese cloth. One rub is one back and forth movement of the hammer.