Heat transfer films for the dry coating of surfaces

Abstract

A heat transfer film having a) a carrier film, b) at least one coating layer arranged directly on the carrier film, and c) at least one hot-sealable polymer adhesive layer is disclosed. The coating layer is based on a non-aqueous, radiation-curable, liquid composition which contains at least 60 wt %, based on the total weight of the composition, of curable constituents selected from organic oligomers which have ethylenically unsaturated double bonds. Use of the heat transfer films for the dry coating of surfaces, production of such heat transfer films, and methods for coating or lacquering surfaces of objects using the heat transfer films are also disclosed.

Claims

1. A thermal transfer foil (1) comprising: a) a backing foil (2), b) at least one layer (3) of coating material arranged on the backing foil (2), c) at least one heat-sealable, polymeric adhesive layer (4), where the layer of coating material is based on a non-aqueous, radiation-curable, liquid composition which comprises at least 60% by weight, based on the total weight of the composition, of curable constituents selected from organic oligomers which have ethylenically unsaturated double bonds and mixtures of said oligomers with monomers which have at least one ethylenically unsaturated double bond, and where the heat-sealable polymeric adhesive layer (4) is based on at least two aqueous polymer dispersions, where at least one polymer dispersion comprises a UV-radiation-curable polymer in dispersed form, and where at least one other polymer dispersion comprises a self-crosslinking polymer in dispersed form.

2. The thermal transfer foil according to claim 1, wherein the radiation-curable composition which forms the layer of coating material comprises from 1.5 to 8 mols of ethylenically unsaturated double bonds per kg of the composition.

3. The thermal transfer foil according to claim 1, wherein the oligomers in the radiation-curable composition which forms the layer of coating material have an average of from 1.5 to 10, ethylenically unsaturated double bonds per molecule.

4. The thermal transfer foil according to claim 1, wherein the ethylenically unsaturated double bonds in the oligomers and in the monomers of the radiation-curable composition which forms the layer of coating material take the form of acrylic or methacrylic groups.

5. The thermal transfer foil according to claim 1, wherein the oligomers of the radiation-curable composition which forms the layer of coating material are selected from the group consisting of: polyether (meth)acrylates, polyester (meth)acrylates, epoxy (meth)acrylates, urethane (meth)acrylates, and unsaturated polyester resins, and mixtures of these.

6. The thermal transfer foil according to claim 5, wherein the radiation-curable composition which forms the layer of coating material comprises at least one oligomer selected from: polyester acrylates, urethane acrylates, and mixtures of these.

7. The thermal transfer foil according to claim 1, wherein the monomers are selected from esters of acrylic acid with mono- to hexahydric alcohols.

8. The thermal transfer foil according to claim 1, wherein the radiation-curable liquid composition comprises at least one photoinitiator which has an absorption band with a maximum .sub.max in the range from 220 to 420 nm.

9. The thermal transfer foil according to claim 1, wherein the thickness of the layer (3) of coating material is from 10 to 120 m.

10. The thermal transfer foil according to claim 1, which has a decorative layer between the layer (3) of coating material and the adhesive layer (4).

11. A process for the production of a thermal transfer foil according to claim 1, comprising: i. applying the non-aqueous, radiation-curable, liquid composition to provide a coating curable by high-energy radiation; ii. irradiating, by high-energy radiation, the curable coating obtained in step i., where the layer (3) of coating material is obtained; iii. optionally applying a decorative layer to the curable coating or to the layer (3) of coating material; and iv. applying the heat-sealable, polymeric adhesive layer (4).

12. The process according to claim 11, where the irradiation of the coating curable by high-energy radiation takes place is performed before the application of the adhesive layer and before the optional application of the decorative layer.

13. The process according to claim 11, where the manner of irradiation of the coating curable by high-energy radiation is sufficient to cause only partial polymerization of the ethylenically unsaturated double bonds comprised in the non-aqueous, radiation-curable, liquid composition.

14. A process for the coating of surfaces of articles, comprising: a) applying of the thermal transfer foil (1) according to claim 1 with the adhesive layer to the surface requiring coating; b) heat-sealing of the transfer foil, where a surface coated with the transfer foil is obtained; c) irradiating, with UV radiation or electron beams, of the surface coated with the transfer foil; d) optionally releasing the backing foil (2).

15. A method of dry coating an article comprising the use of a thermal transfer foil according to claim 1.

16. The thermal transfer foil according to claim 3, wherein the oligomers in the radiation-curable composition which forms the layer of coating material have an average of from 2 to 8 ethylenically unsaturated double bonds per molecule.

17. The thermal transfer foil according to claim 7, wherein the monomers are esters of acrylic acid with di- to tetrahydric aliphatic or cycloaliphatic alcohols.

18. The thermal transfer foil according to claim 1, where the UV-radiation-curable polymer is a polyether urethane acrylate.

Description

EXAMPLE 1: FOIL FOR USE AS COLOR COATING MATERIAL IN THE FURNITURE SECTOR

(1) Coating formulation 4 was applied with a layer thickness of 40 g/m.sup.2 to an uncolored polyethylene terephthalate backing foil with a layer thickness of 23 m. The foil thus coated was conducted at an advance velocity of 30 m/min past the Ga-doped mercury source in order to gel the layer of coating material.

(2) The UV-curable intaglio ink was then applied to the gelled layer of coating material. For curing, the foil thus printed was again conducted at an advance velocity of 30 m/min past the Ga-doped mercury source.

(3) Adhesive formulation 3 was then applied with a layer thickness of 15 g/m.sup.2 to the printed layer of coating material, and heat-dried.

EXAMPLE 2: FOIL FOR USE AS COLOR COATING MATERIAL IN THE FURNITURE SECTOR

(4) Coating formulation 5 was applied with a layer thickness of 70 g/m.sup.2 to an uncolored polyethylene terephthalate backing foil with a layer thickness of 23 m. The foil thus coated was conducted at an advance velocity of 30 m/min past the Ga-doped mercury source in order to gel the layer of coating material.

(5) The UV-curable intaglio ink was then applied to the gelled layer of coating material. For curing, the foil thus printed was again conducted at an advance velocity of 30 m/min past the Ga-doped mercury source.

(6) Adhesive formulation 3 was then applied with a layer thickness of 15 g/m.sup.2 to the printed layer of coating material, and heat-dried.

EXAMPLE 3: FOIL FOR USE AS CLEARCOAT MATERIAL IN THE FURNITURE SECTOR

(7) Coating formulation 6 was applied with a layer thickness of 40 g/m.sup.2 to an uncolored polyethylene terephthalate backing foil with a layer thickness of 23 m. The foil thus coated was conducted at an advance velocity of 30 m/min past the Ga-doped mercury source in order to gel the layer of coating material.

(8) Adhesive formulation 3 was then applied with a layer thickness of 15 g/m.sup.2 to the printed layer of coating material, and heat-dried.

EXAMPLE 4: FOIL FOR USE AS COLOR COATING MATERIAL IN THE OUTDOOR SECTOR

(9) Coating formulation 7 was applied with a layer thickness of 45 g/m.sup.2 to an uncolored polyethylene terephthalate backing foil with a layer thickness of 23 m. The foil thus coated was conducted at an advance velocity of 30 m/min past the Ga-doped mercury source in order to gel the layer of coating material.

(10) The UV-curable intaglio ink was then applied to the gelled layer of coating material. For curing, the foil thus printed was again conducted at an advance velocity of 30 m/min past the Ga-doped mercury source.

(11) Adhesive formulation 3 was then applied with a layer thickness of 15 g/m.sup.2 to the printed layer of coating material, and heat-dried.

(12) IV. Testing of the Foil Materials of the Invention:

(13) a) Testing of the Crosslinking of the Adhesive Layer

(14) The foil from example 3 was laminated to a sheet of beechwood by means of a heated roll (180 C., object temperature at most 50 C.). The foil thus laminated was then irradiated through the foil by conducting the laminated side at an advance velocity of 20 m/min past two UV sources (mercury source and Ga-doped mercury source) with respective power rating of 120 W/cm.

(15) The resultant sample was studied by means of ATR-FTIR spectroscopy using a FT-IR spectrometer from Nicolet (Nicolet 380) and a Golden Gate sample head. In comparison with an unirradiated sample, there was a significant discernible reduction of the absorption bands at 810 cm.sup.1 (>40%) and 1410 cm.sup.1 (>30%) characteristic of acrylate groups.

(16) b) Testing of the Stability of the Coating

(17) The following tests were undertaken:

(18) T1: Water resistance (24 h) in accordance with DIN 68861-1:2011-01. Evaluation used a scale from 1 (poor) to 5 (good).

(19) T2: Ethanol resistance (6 h) in accordance with DIN 68861-1:2011-01. Evaluation used a scale from 1 (poor) to 5 (good).

(20) T3: Ethyl acetate resistance (10 s) in accordance with DIN 68861-1:2011-01. Evaluation used a scale from 1 (poor) to 5 (good).

(21) T4: Hamberger plane test: in this test a tester similar to a coin is drawn across the surface to be tested at a prescribed angle with variable force. The test equipment allows continuously variable setting of the applied force. The force stated in newtons is the maximum force for which no surface damage is discernible.

(22) T5: Scratch resistance in the diamond test in accordance with EN 438-2:2005. The maximum force applied without leaving any continuous surface scratches is stated as the numerical value.

(23) T6: The crosscut test was carried out in accordance with DIN ISO 2409:2013. Evaluation used a scale from GTO (good adhesion) to GT5 (very severe breakaway of the coating).

(24) T7: Abrasion resistance by the falling sand method in accordance with DIN EN 14354:2005-03

(25) T8: Abrasion resistance by the S24 method in accordance with DIN 13329:2013-12

(26) Table T collates the results of the tests T1-T8.

(27) Sample 1:

(28) The foil from example 1 was laminated with application of constant pressure to a sheet of MDF by means of a heated roll (180 C., object temperature at most 50 C.). The sheet thus laminated was then irradiated through the foil by conducting the laminated side at an advance velocity of 20 m/min past two UV sources (mercury source and Ga-doped mercury source) with respective power rating of 120 W/cm. The backing foil was then removed.

(29) Comparative Sample Comp1:

(30) For comparative purposes, the foil from example 1 was laminated with application of the same pressure to a sheet of MDF by means of a heated roll (180 C., object temperature at most 50 C.) but no subsequent irradiation was undertaken here.

(31) Sample 2:

(32) The production process was analogous to that for the production of sample 1, but the foil from example 2 was used instead of the foil from example 1.

(33) Comparative Sample Comp2:

(34) The production process was analogous to that for the production of comparative sample comp1, but the foil from example 2 was used instead of the foil from example 1.

(35) Sample 3:

(36) The foil from example 3 was laminated with application of constant pressure to a sheet of beechwood by means of a heated roll (180 C., object temperature at most 50 C.).

(37) The sheet thus laminated was then irradiated through the foil by conducting the laminated side at an advance velocity of 20 m/min past two UV sources (mercury source and Ga-doped mercury source) with respective power rating of 120 W/cm. The backing foil was then removed.

(38) Comparative Sample Comp3:

(39) For comparative purposes, the foil from example 3 was laminated with application of the same pressure to a sheet of beechwood by means of a heated roll (180 C., object temperature at most 50 C.) but no subsequent irradiation was undertaken here.

(40) Sample 4:

(41) The foil from example 4 was laminated with application of constant pressure to a sheet of PVC by means of a heated roll (180 C., object temperature at most 50 C.). The sheet thus laminated was then irradiated through the foil by conducting the laminated side at an advance velocity of 15 m/min past two UV sources (mercury source and Ga-doped mercury source) with respective power rating of 120 W/cm. The backing foil was then removed.

(42) Comparative Sample Comp4:

(43) For comparative purposes, the foil from example 4 was laminated with application of the same pressure to a sheet of PVC by means of a heated roll (180 C., object temperature at most 50 C.) but no subsequent irradiation was undertaken here.

(44) TABLE-US-00016 TABLE T Results of tests T1-T8 UV T4 T5 T7 T8 Sample curing T1 T2 T3 [N] [N] T6 [rpm.sup.1] [rpm.sup.1] 1 yes 5 5 5 20 1.2 GT0 n.d. n.d. 2 yes 5 5 5 19 1.0 GT0 620 1600 3 yes 5 5 5 18 1.1 GT0 n.d. n.d. 4 yes 5 5 5 19 1.3 GT1 n.d. n.d. comp1 no 4-5 5 5 13 0.7 GT5 n.d. n.d. comp2 no 4-5 4-5 5 14 0.6 GT4 630 1550 comp3 no 4 4 5 13 0.7 GT4 n.d. n.d. comp4 no 5 5 5 13 0.7 GT3 n.d. n.d.

(45) The results show that good adhesion can be achieved only when the adhesive layer comprises a radiation-curable constituent which is crosslinked via irradiation with UV after lamination. This method moreover obtains better surface hardness values.