UV-CURABLE ADHESIVE COMPOSITION FOR DIGITAL PRINTING

Abstract

An adhesive composition polymerizable by applying ultraviolet radiation comprising an acrylate resin and a photoinitiator, said acrylate resin comprising at least one acrylate monomer, and optionally, an acrylate oligomer; a process for the application of a covering layer to a polymeric product comprising the step of applying the afore-mentioned adhesive composition above an ink layer for digital printing, preferably a U.V. ink, deposited on a surface of said planar substrate to define a printing pattern, thereby providing an interface layer between said planar substrate and said covering layer of subsequent application.

Claims

1. An adhesive composition polymerizable by applying ultraviolet radiation comprising an acrylate resin and a photoinitiator, said acrylate resin comprising at least one acrylate monomer, wherein said at least one acrylate monomer is selected from an alkyl acrylate, an alkyl methacrylate, a diol diacrylate, a diol dimethacrylate, a polyol diacrylate, a polyol dimethacrylate, a polyol triacrylate, a polyol dimethacrylate, a polyol trimethacrylate, or any combination thereof.

2. The adhesive composition according to claim 1, wherein said at least one acrylate monomer is a diol diacrylate, preferably said acrylate monomer being 1,6-hexanediol diacrylate, 3-methyl-1,5-pentanediyl acrylate, or any combination thereof.

3. The adhesive composition according to claim 1, wherein said photoinitiator is a Norrish type I photoinitiator or a Norrish type II photoinitiator.

4. The adhesive composition according to claim 3, wherein said photoinitiator is a compound belonging to the family of acyl phosphines, preferably said photoinitiator being selected from phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide or any combination thereof, more preferably said photoinitiator being phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

5. The adhesive composition according to claim 3, wherein said photoinitiator is a compound belonging to the family of thioxanthones, preferably said photoinitiator is selected from 4-isopropylthioxanthone, 2-isopropylthioxanthone or any combination thereof, more preferably said photoinitiator is 2-isopropylthioxanthone.

6. The adhesive composition according to claim 1, wherein said photoinitiator is present in an amount between 2% and 8%, preferably between 3% and 6%, by weight based on the total weight of the adhesive composition.

7. The adhesive composition according to claim 1, wherein said at least one acrylate monomer is present in an amount between 9% and 98%, preferably between 15% and 97%, more preferably between 20% and 80%, by weight based on the total weight of the adhesive composition.

8. The adhesive composition according to claim 1, wherein said acrylate resin comprises at least one acrylate oligomer, preferably said at least one acrylate oligomer being selected from polyurethane acrylate, epoxy acrylate, acryl acrylate, polyether acrylate, polyester acrylate, vinyl acrylate or any combination thereof.

9. The adhesive composition according to claim 8, wherein said at least one acrylate oligomer is present an amount between 1% and 88.5%, preferably between 15% and 75%, more preferably between 40% and 60%, by weight based on the total weight of the adhesive composition.

10. The adhesive composition according to claim 1, wherein said adhesive composition comprises at least one co-initiator, preferably said co-initiator being a tertiary amine, more preferably a tertiary alkylamine, and/or said adhesive composition comprises at least one modifying additive, preferably one organic modifying additive, more preferably said modifying additive being a vinyl copolymer.

11. The adhesive composition according to claim 1, wherein said composition consists of the following components, expressed in percentage by weight based on the total weight of the composition: TABLE-US-00011 acrylate monomer 9-98 acrylate oligomer 0-75 photoinitiator 2-8 co-initiator 0-12 modifying additive 0-30

12. A process for the application of a covering layer to a polymeric product comprising the steps of: providing a polymeric product in the form of a planar substrate of polymeric material with an ink layer for digital printing, preferably a U.V. ink, deposited on a surface of said planar substrate to define a printing pattern; applying, above said ink layer, the adhesive composition according to claim 1, thereby providing an interface layer; applying a covering layer of transparent polymeric material above said interface layer and as a protection of the printing pattern; being made to polymerize said interface layer by irradiating the covering layer so applied onto it with ultraviolet radiation, preferably said ultraviolet radiation having a wavelength between 150 nm and 420 nm.

13. The process for the application of a covering layer to a polymeric product according to claim 12, wherein said polymerization step said interface layer is carried out by means of a LED lamp or of a mercury-vapor lamp, preferably said mercury-vapor lamp concentrating a peak of power at a specific wavelength between 150 nm and 420 nm or said LED lamp concentrating a peak of power at a specific wavelength between 385 nm and 405 nm.

14. The process for the application of a covering layer to a polymeric product according to claim 12, wherein in said step of applying a covering layer of transparent polymeric material said covering layer is made of polyvinyl chloride, preferably said covering layer having a thickness lower than or equal to 7 mm.

15. A multilayer polymeric product, preferably in the form of a sheet or a panel, obtainable by the process according to claim 12.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0111] FIG. 1 shows a schematic view, with altered proportions to highlight the aspects of interest, of a polymeric product, in particular a PVC sheet, made according to the background art.

[0112] FIG. 2 shows a schematic view, with altered proportions to highlight the aspects of interest, of a polymeric product, in particular a PVC sheet, made according to the present invention.

[0113] FIG. 3 illustrates schematically a device to implement the application process of the covering layer according to the present invention.

DETAILED DESCRIPTION

[0114] The adhesive composition according to the present invention was used in a process for the application of a covering layer to a polymeric product, as described above in relation to the summary of the invention.

[0115] With reference to the attached FIG. 3, the process according to the invention was carried out with the aid of a device, which we identify globally with 100 for the application of a covering layer to a polymeric product 10, in particular a PVC sheet.

[0116] In the following description, terms such as above, below, lower, upper, or derivatives thereof are to be understood with reference to the normal configuration of use of the device 100 illustrated in the above figure.

[0117] The device 100 provides for advancing means, not shown because known per se, of a PVC planar substrate 11, of neutral coloration (for example white), along the different process stations.

[0118] A first process station is represented by a digital printer 1, illustrated schematically in the above-mentioned figure.

[0119] The digital printer presents in a known manner one or more printing modules, for example four printing modules relating to the different colors of a four-color printing. Each module comprises one or more print heads designed to release ink drops on the planar substrate 11 that passes under them.

[0120] Consistently, a color fixing station 2 is placed at the exit from the digital printer 1 and consists of an ultraviolet light lamp.

[0121] A different fixing station 2 may be provided according to the used ink type.

[0122] Downstream of the fixing station 2 an application station 3 of the interface layer 13 is provided. Such station consists of an application roller and a counterposed feedback roller, wherein the application roller is fed with the polymerizable adhesive composition according to the invention.

[0123] After the application station 3, a rolling station 4 is provided, constituted in a per se known manner by two rolling calenders.

[0124] In this station, the process provides for the coupling to a planar substrate 11 of a covering layer 14, fed continuously, to protect the already made printing pattern. The interface layer 13 is therefore placed between planar substrate 11 and covering layer 14, as shown in FIG. 2.

[0125] Finally, the device provides for a last polymerization station 5 of the interface layer 13, placed at the exit to the above-mentioned rolling rollers 4.

[0126] The polymerization station 5 may be an ultraviolet light lamp. For example, for the polymerization station 5 a LED lamp or a mercury-vapor lamp is used, which can concentrate the peak of power at a specific wavelength, comprised according to the project choices between 150 nm and 420 nm.

[0127] In particular, given the partially multi-chromatic nature of the emitted ultraviolet radiation, both the possible LED lamp and the possible mercury-vapor lamp can concentrate a plurality of power peaks at more specific wavelengths.

[0128] Specifically, the LED lamp can concentrate a plurality of power peaks at wavelength between 385 nm and 405 nm; vice versa, the mercury-vapor lamp can concentrate a plurality of power peaks at wavelength between 150 nm and 420 nm.

[0129] Experimental examples will now follow wherein different adhesive compositions according to the present invention were used in a process for applying a covering layer to a polymeric product to obtain a multilayer polymeric product comprising an interface layer consisting of a solidified polymeric adhesive formed by polymerizing and curing by U.V. irradiation the described adhesive composition.

Example 1

[0130] First, a polymeric product shaped as a planar substrate of polymeric material was provided, more precisely a polyvinyl chloride sheet of white color with a thickness of 70 μm.

[0131] The PVC sheet was then sent to the digital printer, within which a digital printing step was carried out.

[0132] During the digital printing step, on the upper surface of the PVC sheet a U.V. ink layer for CPUV-type digital printing was applied, supplied by INX International.

[0133] Within the color fixing station, with the aid of a 16-watt ultraviolet light LED lamp with double window (40 mm×200 mm), whose peak of power was set at a wavelength of 395 nm, the applied ink layer was then cured, defining a printing pattern.

[0134] Then, in the application station, on the ink layer, as well as on the remained free upper surface of the PVC sheet, an adhesive composition layer according to the invention was applied, consisting of the following components, indicated as a percentage by weight of the total weight of the composition:

TABLE-US-00002 acrylate monomer 1,6-hexandiol-diacrylate 94 photoinitiator Omnirad 819 6

[0135] wherein 1,6-hexandiol-diacrylate is supplied by Allnex, and Omnirad 819 is phenylbis(2,4,6-trimethylbenzoil)phosphine oxide, supplied by IGM Resins.

[0136] The PVC sheet was slid on the feedback roller at a speed of 40 m/min, while the application roller was fed with the adhesive composition of the previous paragraph.

[0137] The adhesive composition was applied according to a grammage of 12 g/m.sup.2. Then, on the interface layer a covering layer shaped as a PVC transparent sheet with a thickness of 700 μm was applied, protecting the printing pattern.

[0138] Further, in the following rolling station, the planar substrate was coupled to the previously applied covering layer.

[0139] Finally, the thus obtained multilayer polymeric product was sent to a polymerization station, i.e., to an ultraviolet light LED lamp, so that the adhesive composition constituting the interface layer was polymerized and cured.

[0140] The ultraviolet light LED lamp was set so to concentrate a peak of power at a wavelength of 395 nm; the lamp had a power of 16 watt and was of the double window type (40 mm×200 mm).

Example 2

[0141] In this example a multilayer polymeric panel was obtained carrying out a process comprising all the steps listed in the previous example, but according to the following technical specifications.

[0142] The adhesive composition according to the invention consisted of the following components, indicated as a percentage by weight of the total weight of the composition:

TABLE-US-00003 acrylate monomer 1,6-hexandiol-diacrylate 84.6 diluent Vinnol H 40/43 9.4 photoinitiator Omnirad 819 6

[0143] wherein 1,6-hexandiol-diacrylate is supplied by Allnex, Vinnol H 40/43 is a copolymer with about 66% by weight of vinyl chloride and about 34% by weight of vinyl acetate, supplied by Wacker; Omnirad 819 is phenyl bis(2,4,6-trimethylbenzoil)phosphine oxide, supplied by IGM Resins.

[0144] The PVC sheet was slid on the feedback roller at a speed of 30 m/min, while the application roller was fed with the above adhesive composition.

[0145] The adhesive composition was applied according to a grammage of 6 g/m.sup.2. Unless otherwise indicated, all other technical specifications coincided with those referred to in Example 1.

Example 3

[0146] In this example a multilayer polymeric panel was obtained carrying out a process comprising all the steps listed in Example 1, but according to the following technical specifications.

[0147] The adhesive composition according to the used invention consisted of the following components, indicated as a percentage by weight of the total weight of the composition:

TABLE-US-00004 acrylate monomer 1,6-hexandiol-diacrylate 65.8 modifying additive Vinnol H 40/43 28.2 photoinitiator Omnirad 819 6

[0148] wherein 1,6-hexandiol-diacrylate is supplied by Allnex, Vinnol H 40/43 is a copolymer with about 66% by weight of vinyl chloride and about 34% by weight of vinyl acetate, supplied by Wacker; Omnirad 819 is phenyl bis(2,4,6-trimethylbenzoil)phosphine oxide, supplied by IGM Resins.

[0149] The PVC sheet was slid on the feedback roller at a speed of 50 m/min, while the application roller was fed with the above adhesive composition.

[0150] The adhesive composition was applied according to a grammage of 6 g/m.sup.2.

[0151] Unless otherwise indicated, all other technical specifications coincided with those referred to in Example 1.

Example 4

[0152] In this example a multilayer polymeric panel was obtained carrying out a process comprising all the steps listed in Example 1, but according to the following technical specifications.

[0153] The adhesive composition according to the used invention consisted of the following components, indicated as a percentage by weight of the total weight of the composition:

TABLE-US-00005 acrylate monomer 1,6-hexandiol-diacrylate 54 acrylate oligomer Ebecryl 85 36 co-initiator Ebecryl P116 5 photoinitiator Omnirad 819 5

[0154] wherein 1,6-hexandiol-diacrylate is supplied by Allnex, Ebecryl 85 is an amine modified polyether acrylate supplied by Allnex; Ebecryl P116 is a tertiary amine supplied by Allnex and Omnirad 819 is phenyl bis(2,4,6-trimethylbenzoil)phosphine oxide, supplied by IGM Resins.

[0155] The PVC sheet was slid on the feedback roller at a speed of 50 m/min, while the application roller was fed with the above adhesive composition.

[0156] The adhesive composition was applied according to a grammage of 12 g/m.sup.2.

[0157] Unless otherwise indicated, all other technical specifications coincided with those referred to in Example 1.

Example 5

[0158] In this example a multilayer polymeric panel was obtained carrying out a process comprising all the steps listed in Example 1, but according to the following technical specifications.

[0159] The adhesive composition according to the used invention consisted of the following components, indicated as a percentage by weight of the total weight of the composition:

TABLE-US-00006 acrylate monomer 1,6-hexandiol-diacrylate 54 acrylate oligomer Ebecryl 820 36 co-initiator Ebecryl P116 5 photoinitiator Omnirad 819 5

[0160] wherein 1,6-hexandiol-diacrylate is supplied by Allnex, Ebecryl 820 is a polyester acrylate supplied by Allnex; Ebecryl P116 is a tertiary amine supplied by Allnex and Omnirad 819 is phenyl bis(2,4,6-trimethylbenzoil)phosphine oxide, supplied by IGM Resins.

[0161] The PVC sheet was slid on the feedback roller at a speed of 40 m/min, while the application roller was fed with the above adhesive composition.

[0162] The adhesive composition was applied according to a grammage of 24 g/m.sup.2.

[0163] Unless otherwise indicated, all other technical specifications coincided with those referred to in Example 1.

Example 6

[0164] In this example a multilayer polymeric panel was obtained carrying out a process comprising all the steps listed in Example 1, but according to the following technical specifications.

[0165] The adhesive composition according to the used invention consisted of the following components, indicated as a percentage by weight of the total weight of the composition:

TABLE-US-00007 acrylate monomer 1,6-hexandiol-diacrylate 54 acrylate oligomer Ebecryl 605 36 co-initiator Ebecryl P116 5 photoinitiator Omnirad 819 5

[0166] wherein 1,6-hexandiol-diacrylate is supplied by Allnex, Ebecryl 605 is bisphenol A epoxy diacrylate supplied by Allnex; Ebecryl P116 is a tertiary amine supplied by Allnex and Omnirad 819 is phenyl bis(2,4,6-trimethylbenzoil)phosphine oxide, supplied by IGM Resins.

[0167] The PVC sheet was slid on the feedback roller at a speed of 40 m/min, while the application roller was fed with the above adhesive composition.

[0168] The adhesive composition was applied according to a grammage of 24 g/m.sup.2.

[0169] Unless otherwise indicated, all other technical specifications coincided with those referred to in Example 1.

Example 7

[0170] In this example a multilayer polymeric panel was obtained carrying out a process comprising all the steps listed in Example 1, but according to the following technical specifications.

[0171] The adhesive composition according to the used invention consisted of the following components, indicated as a percentage by weight of the total weight of the composition:

TABLE-US-00008 acrylate monomer 1,6-hexandiol-diacrylate 56 acrylate oligomer Ebecryl 85 38 photoinitiator ITX 6

[0172] wherein 1,6-hexandiol-diacrylate is supplied by Allnex, Ebecryl 85 is an amine modified polyether acrylate supplied by Allnex; ITX is 2-isopropylthioxanthone supplied by Lambson.

[0173] The PVC sheet was slid on the feedback roller at a speed of 20 m/min, while the application roller was fed with the above adhesive composition.

[0174] The adhesive composition was applied according to a grammage of 12 g/m.sup.2.

[0175] Unless otherwise indicated, all other technical specifications coincided with those referred to in Example 1.

Example 8

[0176] In this example a multilayer polymeric panel was obtained carrying out a process comprising all the steps listed in Example 1, but according to the following technical specifications.

[0177] The adhesive composition according to the used invention consisted of the following components, indicated as a percentage by weight of the total weight of the composition:

TABLE-US-00009 acrylate monomer 3-methyl pentanediyl diacrylate 54 acrylate oligomer Ebecryl 85 36 co-initiator Ebecryl P116 5 photoinitiator Omnirad 819 5

[0178] wherein 3-methyl pentanediyl diacrylate is supplied by Arkema Sartomer; Ebecryl 85 is an amine modified polyether acrylate supplied by Allnex; Ebecryl P116 is a tertiary amine supplied by Allnex and Omnirad 819 is phenyl bis(2,4,6-trimethylbenzoil)phosphine oxide, supplied by IGM Resins.

[0179] The PVC sheet was slid on the feedback roller at a speed of 40 m/min, while the application roller was fed with the above adhesive composition.

[0180] The adhesive composition was applied according to a grammage of 32 g/m.sup.2.

[0181] Unless otherwise indicated, all other technical specifications coincided with those referred to in Example 1.

[0182] Adhesion Tests

[0183] For each of the multilayer polymeric products obtained in the previous Examples 1-8, adhesion tests were performed.

[0184] First, each of the multilayer polymeric products obtained in the previous Examples 1-8 was subjected to an embossing process, during which in a first time the various rolled products were place in an oven at 160° C. for 5 min.

[0185] Then, in a conventional way, different foldings were made on each led to temperature rolled product, so to simulate final application; further, the rolled products were cooled at room temperature.

[0186] Once room temperature was reached, the thus folded rolled products were subjected to peeling tests.

[0187] The peeling test was manually performed: the operation was carried out by taking the flap of each of the outermost layers that made up the laminate and pulling the flaps with a traction movement opposite to each other, until at least one of the flaps was broken.

[0188] Following the peeling test, the multilayer product could present itself in a substantially unaltered form at the level of coupling between the different layers that made it up, i.e., it did not delaminate, or in a partial or total delamination conformation.

[0189] The outcome of the performed embossing tests is summarized in the following Table 1.

TABLE-US-00010 TABLE 1 Sample Rolling Ex. 1 It does not delaminate Ex. 2 It does not delaminate Ex. 3 It does not delaminate Ex. 4 It does not delaminate Ex. 5 It does not delaminate Ex. 6 It does not delaminate Ex. 7 It does not delaminate Ex. 8 It does not delaminate

[0190] So, advantageously, it was proven that the multilayer polymeric products obtained by the afore-mentioned process and using the adhesive composition according to the invention for the realization of an interface layer between a planar polymeric substrate and a covering layer showed optimal properties from the adhesion point of view between the different layers that made them up.