Lamination of substrates

Abstract

There is disclosed a method for laminating a substrate comprising acrylate groups on a surface, comprising: a) providing a substrate with acrylate groups, b) applying a liquid formulation comprising a diacrylate and a Norrish type-II photoinitiator, c) applying a foil on the applied liquid, wherein the foil comprises polypropylene and / or polyethylene, and which is treated with corona and / or flame-treatment, d) irradiating the substrate with actinic radiation on the applied foil to initiate a reaction to cure the liquid formulation. Improved adhesion of the foil is achieved.

Description

[0001] LAMINATION OF SUBSTRATES

[0002] Technical f ield

[0003] The present invention relates to a method for laminating a foil onto a substrate with acrylate groups , such as a printed substrate . Laminated products are also encompassed .

[0004] Background

[0005] Printed substrates including digitally printed substrates are sometimes laminated in order to protect the graphics from abrasion, chemicals , and UV exposure . Abrasion and detergents can rub or wash the pigment of f of the prints if not laminated . Any printed graphic installed in an environment in which the f inal product will be washed, walked on, or exposed to dirt and debris are often laminated . With aqueous inkj et prints , an overlaminate can also protect from UV exposure and extend the outdoor life of the ink .

[0006] Suf f icient time for the solvent to evaporate from the prints is typically allowed before laminating .

[0007] EP 3 655 247 discloses a method of coating a substrate , said method comprising the steps of a) providing a substrate , said substrate comprising at least one secondary amine , at least a fraction of the at least one secondary amines is at the surface of the substrate , b) contacting the substrate surface with a compound comprising at least one carbon- carbon double bond, wherein an electron withdrawing group is on at least one side of the carbon- carbon double bond, so that a complex is formed between nitrogen in the secondary amine and the carbon- carbon double bond, c) initiating a reaction to form a covalent bond by reaction of nitrogen in the secondary amine and the carbon- carbon double bond, by subj ecting at least a part of the formed complexes to actinic radiation, wherein the wavelength of the actinic radiation is adapted to be absorbed by the complex . It should be noted that the actinic radiation passes an applied solution so that it reaches the surface of the substrate .

[0008] JP2014196451 discloses an adhesive sheet and a laminate using a pressure- sensitive adhesive layer that is curable by active energy rays . The adhesive composition includes a (meth) acrylic acid ester copolymer with a weight average molecular weight of 200 , 000 to 900 , 000 , containing 5 to 20 wt% of (meth) acrylic acid, an active energy ray- curable component , and a crosslinking agent . The adhesive layer has a thickness of 50 to 400 pm and is thermally crosslinked to provide excellent step- following properties , resistance to wet heat whitening , and durability . It is aimed to improve adhesion between protective panels and display modules by eliminating air gaps and enhancing image quality . The laminate is formed by curing the adhesive layer with active energy rays , resulting in enhanced durability and conformability to uneven surfaces . In particular there is in one example disclosed use of polyethylene glycol diacrylate together with Irgacure 184 , which is a Norrish type I photoinitiator .

[0009] EP 3 845 392 discloses a method for producing printed matter that enhances both laminate adhesion and image quality . The process involves forming a printing layer on a non-absorbent or slightly absorbent base material using inkj et printing with an active ray- curable ink . The printing layer is then irradiated with an active ray to achieve a polymerization rate of 5% to 80% for the photopolymerizable compound in the ink . A laminate f ilm is applied over the printing layer with an adhesive layer in between, followed by a second active ray irradiation from either the laminate film side or the base material side to further increase the polymerization rate, enhancing adhesion and durability. The ink used may be radical-curable or cation-curable and can include a gelling agent for improved quality. The method aims to prevent laminate film peeling, improve image durability, and enhance the anchoring effect, resulting in strong mechanical bonding at the adhesive interface. The overall objective is to optimize the balance between curing and adhesion, ensuring high-quality printed materials with improved laminate adhesion and image quality.

[0010] US 5,475,038 discloses a polyurethane oligomer composition useful as a print laminating adhesive. The composition comprises a monoacrylate and an UV photoinitiator amongst other ingredients. In the examples, the photoinitiator is a Norrish type I photoinitiator in the form of Darocure 1173 which is 2-hydroxy-2-methyl-l-phenyl-propane-l-one .

[0011] The Norrish type I reaction is the photochemical cleavage or homolysis of aldehydes and ketones into two free radical intermediates (a-scission) . The carbonyl group accepts a photon and is excited to a photochemical singlet state. Through intersystem crossing the triplet state can be obtained. On cleavage of the a-carbon bond from either state, two radical fragments are obtained.

[0012] For some print laminating adhesives it is a problem that they cure or react in such a way that film is formed, which gives less adhesion of the laminated foil. Even though the technology according to the state of the art works f ine , there is still room for an improvement regarding the function and adhesion of certain laminating adhesives .

[0013] Summary

[0014] It is an obj ect of the present invention to alleviate at least some of the disadvantages in the prior art and provide a method for laminating a substrate comprising acrylate groups on a surface .

[0015] In a f irst aspect there is provided a method for laminating a substrate comprising acrylate groups on a surface , said method comprising the steps of a) providing a substrate , wherein at least a part of the surface of the substrate comprises acrylate groups , b) applying a layer of a liquid formulation on at least a part of the substrate , the liquid formulation comprising at least one diacrylate and at least one Norrish type- II photoinitiator , c) applying a foil on the applied liquid formulation, wherein the foil comprises at least one polymer selected from the group consisting of polypropylene and polyethylene , and wherein the foil before the application is treated with at least one method selected from the group consisting of corona and f lame- treatment on at least the side to be contacted with the applied liquid, d) irradiating the substrate with actinic radiation on the applied foil to initiate a reaction to cure the liquid formulation.

[0016] In a second aspect there is provided a substrate laminated as described above.

[0017] An advantage is that the adhesion is improved.

[0018] Brief description of the drawing

[0019] Aspects and embodiments will be described with reference to the following drawing in which:

[0020] Figure 1 shows a schematic view of a laminated substrate according to the invention. There are shown the following parts :

[0021] 1) Foil transparent to the relevant wavelength so that actinic radiation can reach through the foil to a sufficient extent so that a curing reaction occurs.

[0022] 2) Activated surface, i.e. a surface treated with corona and / or flame on the side to be contacted with the applied liquid formulation.

[0023] 3) Lamination glue, i.e. the applied liquid formulation to be cured.

[0024] 4) Residual acrylate groups. At least a part of the surface of the substrate comprises acrylate groups.

[0025] 5) Substrate.

[0026] Detailed description

[0027] Before the invention is disclosed and described in detail, it is to be understood that this invention is not limited to particular compounds, configura ions, method steps, substrates, and materials disclosed herein as such compounds, configurations, method steps, substrates, and materials may vary somewhat. It is also to be understood that the terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting since the scope of the present invention is limited only by the appended claims.

[0028] It must be noted that, as used in this specification and the appended claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise .

[0029] If nothing else is defined, any terms and scientific terminology used herein are intended to have the meanings commonly understood by those of skill in the art to which this invention pertains.

[0030] As used herein (meth) acrylate is a general term that encompasses both acrylate and methacrylate. Acrylates include the salts, esters, and conjugate bases of acrylic acid. Polyacrylates are also encompassed. A diacrylate is one compound that contains two acrylate (-COOCH=CH2) functional groups.

[0031] As used herein a Norrish type II-initiator is a photoinitiator which is activated by actinic radiation and forms free radicals by hydrogen abstraction from a second compound that becomes the actual initiating free radical . This second compound is called a polymerization synergist. By UV- irradiation the Norrish type II photoinitiator abstracts a hydrogen atom from the employed synergist forming two radicals. These radicals can then initiate the polymerization reaction. Type II photoinitiators normally are not incorporated during the reaction but the synergist is. (Norrish Type II photoinitiators should not be confused with Norrish Type I initiators, which undergo direct cleavage without requiring a synergist.)

[0032] As used herein a partially cured UV-curing ink is an ink which is cured by irradiation with UV-radiation, and which is irradiated only to such an extent that the curing reaction has not fully completed so that a part of the UV-curing ink is still uncured and so that it is possible to irradiate the UV-curing ink further at a later stage to complete the curing .

[0033] As used herein polypropylene refers to poly(l- methylethylene) .

[0034] As used herein polyethylene refers to poly (methylene) .

[0035] In the first aspect there is provided a method for laminating a substrate comprising acrylate groups on a surface, said method comprising the steps of a) providing a substrate, wherein at least a part of the surface of the substrate comprises acrylate groups , b) applying a layer of a liquid formulation on at least a part of the substrate, the liquid formulation comprising at least one diacrylate and at least one Norrish type-II photoinitiator, c) applying a foil on the applied liquid formulation, wherein the foil comprises at least one polymer selected from the group consisting of polypropylene and polyethylene , and wherein the foil before the application is treated with at least one method selected from the group consisting of corona and f lame- treatment on at least the side to be contacted with the applied liquid, d) irradiating the substrate with actinic radiation on the applied foil to initiate a reaction to cure the liquid formulation .

[0036] The substrate is substrate with acrylate groups . The substrate can be made of any material as long as there are acrylate groups on its surface . Polymeric substrates as well as any other substrates are encompassed . The acrylate groups are either provided by the material of the substrate , or added afterwards by applying some kind of coating on the substrate .

[0037] In one embodiment , the substrate is printed with an ink , which is cured by irradiation with UV . This procedure is standard in the art and it follows known and well established methods for printing . It is also known in the art that the UV- curable ink is not necessarily fully cured before it is laminated with a foil .

[0038] If used, a UV- curable ink is not fully cured in step a) . A skilled person can determine roughly the dose required to cure the ink by simple standard methods and then the skilled person can select a lower UV-dose for the curing so that the UV- curable ink is not fully cured in step a) . In the art a printed substrate is commonly protected by applying a coating on top . The manufacturer of the ink normally informs how much the ink should be cured, i . e . cured partially on order to obtain suitable adhesion to the next layer . The same can be applied in the present invention . Further , the ink can be tested, if the ink is fully cured it is less sensitive to scratches compared to a partially cured ink .

[0039] In step b) there is applied a layer of a liquid formulation . The liquid formulation is applied on the substrate and on the parts of the substrate , which are intended to be laminated by a foil in the next step . The liquid formulation is applied by known standard methods . The liquid formulation comprises at least one diacrylate and at least one Norrish type- II photoinitiator . The amount of photoinitiator is as known in the art in an amount , which is able to initiate a reaction upon irradiation .

[0040] After the liquid formulation has been applied in step b) , then a foil is applied on the liquid formulation . The foil is a thin sheet of material . Before the foil is applied, the foil is treated with corona and / or f lame- treatment . The corona treatment and / or f lame treatment creates additional reactive groups on the surface of the foil . The corona treatment and f lame treatment creates peroxides and a number of other reactive groups on the surface of the foil . At least the side of the foil , which is intended to be contacted with the liquid formulation is treated . Other parts can be treated optionally if convenient . The foil comprises at least one polymer selected from the group consisting of polypropylene and polyethylene . In one embodiment , the foil comprises polypropylene . In one embodiment , the foil comprises polyethylene . In one embodiment , the foil comprises a mixture of polyethylene and polyethylene . In one embodiment , the foil consists of polypropylene . In one embodiment , the foil consists of polyethylene . In one embodiment , the foil consists of a mixture of polypropylene and polyethylene . The foil is transparent to actinic radiation so that a fraction of actinic radiation will reach through the foil to such an extent that the curing reaction can occur in the applied liquid formulation . The foil does not block actinic radiation . The foil is without additives that blocks actinic radiation, or at least with suf f iciently low levels of additives that block actinic radiation so that a curing reaction can occur in the liquid formulation when irradiated through the foil .

[0041] The foil is preferably applied so that no air bubbles are trapped between the foil and the substrate . This is common practice when laminating substrates .

[0042] When the foil is applied on the liquid formulation, the substrate including the liquid formulation and the foil are irradiated with actinic radiation . Since the foil is transparent to the actinic radiation it will to some extent reach through the foil . Typically the foil is very thin and transmits a high fraction of the actinic radiation . The actinic radiation will also to some extent reach through the liquid formulation, which is between the foil and the partially cured ink . Since the liquid formulation comprises a photoinitiator , it will absorb the actinic radiation at wavelengths where the photoinitiator absorbs radiation . However if the applied layer of the liquid formulation is thin so that a certain fraction of the actinic radiation reaches through the applied liquid formulation, then also the uncured UV- curable ink will react . The actinic radiation will induce a reaction of the photoinitiator in the liquid formulation . In some embodiments , the actinic radiation will also induce a reaction of the uncured UV- curable ink .

[0043] In the reaction the diacrylate will react as well as the acrylate groups . The diacrylate will form a polymer . Further the photoinitiator will react with the peroxides created on the foil . This will give a lamination adhesive , which is f irmly bound both to the foil and to the ink on the substrate . Thus a laminated printed substrate with excellent adhesion can be achieved .

[0044] The wavelength of the actinic radiation should be adapted to the photoinitiator . In one embodiment , the actinic radiation is also adapted to the UV- curable ink . A photoinitiator and an UV- curable ink absorbs certain wavelengths and is thereby able to induce a reaction . In practice the actinic radiation is UV- radiation and the wavelength is adapted by selecting a broad spectrum UV- lamp which are well known in the art . It is for instance also possible to use a narrow spectrum UV-diode which emits wavelengths adapted to the photoinitiator and optionally to the UV- curable ink .

[0045] In one embodiment the actinic radiation reaches the partially uncured ink and induces a reaction thereof , this contributes to creating bonds between the ink and the diacrylate . In an alternative embodiment , the actinic radiation does not reach the partially uncured ink to any signif icant extent and in this case the photoinitiator in the applied liquid formulation induces a reaction so that bonds between the ink and the diacrylate can form anyway . In the latter case the unreacted groups of the ink can serve as reactive groups for a reaction with the diacrylate .

[0046] The acrylate groups on the surface of the substrate can be created in many dif ferent ways . In one embodiment the substrate itself comprises acrylate groups . In another embodiment a partially cured UV- curing ink comprises acrylate groups on the substrate . In yet another embodiment a coating comprising acrylate groups is applied on the substrate and / or on an ink on the substrate . Such a coating comprises acrylate groups on its surface after application and optional or partial curing . In one embodiment a coating which reacts with the substrate is applied . After the reaction acrylate groups are on the surface .

[0047] In one embodiment , at least a part of the surface of the substrate is provided with a partially cured UV- curing ink , wherein a surface of the partially cured UV- curing ink comprises acrylate groups .

[0048] In one embodiment , the acrylate groups of at least a part of the surface of the substrate are provided in step a) by applying a coating comprising acrylate groups .

[0049] In one embodiment , the substrate comprises melamine and wherein the acrylate groups of at least a part of the surface of the substrate are provided in step a) by applying a coating , which provides acrylate groups .

[0050] In one embodiment , the liquid formulation is applied in a thickness of 1 - 100 pm, preferably 5 - 50 pm . This is a suitable thickness both with respect to application of the liquid and the transmittance of the actinic radiation . In one embodiment , the thickness of the foil is 1 mm or less . If the foil is much thicker than 1 mm, such as 5 mm or higher the transmittance of the foil may become too low so that the actinic radiation does not reach the applied liquid formulation to a suf f icient extent . In one embodiment , the thickness of the foil is 0 . 5 mm or less . In another embodiment , the thickness of the foil is 0 . 2 mm or less .

[0051] In one embodiment , the foil and the applied liquid formulation is suf f iciently transparent to actinic radiation so that the irradiation in step d) at least to some extent cures an optionally applied UV- curing ink . If the actinic radiation reaches through both the applied foil and the applied liquid formulation, then it will cause a reaction in the optionally applied UV- curable ink , which reaction will improve the adhesion further .

[0052] In the second aspect there is provided a substrate laminated as described above .

[0053] Other features and uses of the invention and their associated advantages will be evident to a person skilled in the art upon reading the description and the examples .

[0054] It is to be understood that this invention is not limited to the particular embodiments shown here . The embodiments are provided for illustrative purposes and are not intended to limit the scope of the invention since the scope of the present invention is limited by the appended claims .

[0055] All percentages are calculated by weight throughout the description and the claims . Examples

[0056] Example 1

[0057] Formulation 1 : (applied liquid formulation) 1 | 1 1 | I 1

[0058] SR 508 is dipropylene Glycol Diacrylate (DPGDA) from Arkema® , France , MBF is methylbenzoyl formate from IGM resins , Holland Aerosil R972 is a surface modif ied fumed silica from Evonik , Germany .

[0059] Substrate : An extruded polypropylene sheet with a partially cured digitally printed UV- ink .

[0060] Foil : Polypropylene foil , 300 microns thick , Corona treated .

[0061] Corona treatment : PP foil was corona treated with Multidyne 1000 a small corona machine from 3DT® , USA . The substrate was secured on a non- conductive rubber sheet and the corona tip was placed 10 mm from the substrate . The corona discharge was started and the corona tip was moved over the substrate 4 times back and forth for a total of 8 passes at a speed of 10 cm in 5 seconds .

[0062] Curing : A conveyor belt equipped 120 W / cm medium pressure mercury lamp was used for curing in all examples .

[0063] 22 pm formulation 1 was applied on the substrate . Onto this wet coating , a corona treated PP foil was laminated by hand where care was taken to remove air bubbles. The substrate was treated in an UV-oven at 2x 50% UV at 9.9 m / min giving a dose of 200 mJ / cm2(UVA) . The UV-source was a broad- spectrum UV- lamp and the dose was measured in the UVA- range.

[0064] A second curing experiment was performed but without adding the sheet so that formulation 1 was subjected to atmospheric conditions .

[0065] Peel test: For the peel test a PCE-PST 1 from PCE instruments, Germany, was used. Briefly, a 60 mm length of foil is separated from the substrate and inserted into a holder that tightly grips the foil. The machine is started and the force required to peel off the foil is recorded. 1 N / mm is considered a commercially viable result. A normal failure mode is that the PP foil breaks, which corresponds to values higher than 1 N / mm.

[0066] Boiling test: The full assembly (substrate, formulation 1, foil) was put in boiling water for 1 hr and peel strength was evaluated once the sample had cooled to room temperature and the assembly had dried.

[0067] Example 2 (Comparative)

[0068] Formulation 1 : | | | | | | | SR9020 is Glycerol propoxylate triacrylate, i.e. a triacrylate and thus not according to the invention. MBF is methylbenzoyl formate from IGM resins, Holland. Aerosil R972 is a surface modified fumed silica from Evonik, Germany. BYK 361 is a surface active agent. BYK 1790 is a defoamer suitable for radiation curing systems.

[0069] All tests performed as above

[0070] Comment: when film formation is too fast, bonding reactions to the foil is slowed down due to the rapid increase in viscosity which lowers monomer diffusion rates and depletion of reactive groups that are used up in crosslinking reactions instead of bonding reactions.

[0071] Example 3

[0072] Formulation 1 : SR 508 is DiPropylene Glycol Diacrylate (DPGDA) from Arkema®, France, MBF is Methylbenzoyl formate from IGM resins, Holland Aerosil R972 is a surface modified fumed silica from Evonik, Germany .

[0073] Substrate: An extruded polypropylene sheet with a partially cured digitally printed UV-ink.

[0074] Second layer: UL 1117 Foil: Polypropylene foil, 300 microns thick, Corona treated.

[0075] Corona treatment: PP foil was corona treated with Multidyne 1000 a small corona machine from 3DT®, USA. The substrate was secured on a non conductive rubber sheet and the corona tip was placed 10mm from the substrate. The corona discharge was started and the corona tip was moved over the substrate 4 times back and forth for a total of 8 passes at a speed of 10 cm in 5 seconds .

[0076] Curing: A conveyor belt equipped 120 W / cm medium pressure mercury lamp was used for curing in all examples.

[0077] A layer of 22 pm UL1117, an UV curing acrylate sealer from Sherwin Williams was applied using a rod. The UL 1117 was partially cured at 1 pass 50% 9.9 m / min giving a dose of 100mJ / cm2(UVA) . UL1117 is a hard and tough, low yellowing sealer for wood parquet. The UL1117-coating will comprise acrylate groups both before and after curing.

[0078] 22 pm formulation 1 was applied on the substrate. Onto this wet coating, a corona treated PP foil was laminated by hand where care was taken to remove air bubbles. The substrate was treated in an UV-oven at 2x 50% UV at 9.9 m / min giving a dose of 200 mJ / cm2(UVA) .

[0079] Peel test: For the peel test a PCE-PST 1 from PCE instruments, Germany, was used. Briefly, a 60 mm length of foil is separated from the substrate and inserted into a holder that tightly grips the foil. The machine is started and the force required to peel off the foil is recorded. lN / mm is considered a commercially viable result. The failure mode in Example 3 is that the print is torn off the PP substrate at 0.9 N / mm.

[0080] Example 4

[0081] Formulation 1 :

[0082] SR 508 is DiPropylene Glycol Diacrylate (DPGDA) from Arkema®, France, MBF is Methylbenzoyl formate from IGM resins, Holland Aerosil R972 is a surface modified fumed silica from Evonik, Germany .

[0083] Substrate: White (article number 1000) 12 mm MDF Melamine Formaldehyde furniture panel from Egger Melamine primer: lg / m2Duoprime 1814, from Mercene Coatings AB. Duoprime 1814 is a melamine-primer which converts inert melamine groups to reactive acrylate groups . The primer- treated substrate thus comprises acrylate groups .

[0084] Foil : Polypropylene foil , 300 microns thick , Corona treated .

[0085] Corona treatment : PP foil was corona treated with Multidyne 1000 a small corona machine from 3DT® , USA . The substrate was secured on a non conductive rubber sheet and the corona tip was placed 10mm from the substrate . The corona discharge was started and the corona tip was moved over the substrate 4 times back and forth for a total of 8 passes at a speed of 10 cm in 5 seconds .

[0086] Curing : A conveyor belt equipped 120 W / cm medium pressure mercury lamp was used for curing in all examples .

[0087] Duoprime 1814 was cured 2x 4m / min 100% power , giving a dose of 900 mJ / cm2(UVA) .

[0088] 22 pm formulation 1 was applied on the primed melamine substrate . Onto this wet coating , a corona treated PP foil was laminated by hand where care was taken to remove air bubbles . The substrate was treated in an UV-oven at 2x 50% UV at 9 . 9 m / min giving a dose of 200 mJ / cm2(UVA) .

[0089] Peel test : For the peel test a PCE- PST 1 from PCE instruments , Germany, was used . Brief ly, a 60 mm length of foil is separated from the substrate and inserted into a holder that tightly grips the foil . The machine is started and the force required to peel of f the foil is recorded . lN / mm is considered a commercially viable result . The failure mode in Example 4 is that the PP foil breaks , which corresponds to values higher than 1 N / mm .

[0090] Example 5 Formulation 3 :

[0091] LR8981 is a polyester acrylate for the formulation of radiation curable coatings and printing inks for wood, wood based products , paper and plastics from BASF , Germany . Sr 508 is DiPropylene Glycol Diacrylate (DPGDA) from Arkema® , HEMA is Hydoxy methyl methacrylate from SigmaAldrich, Germany, France , MBF is Methylbenzoyl formate from IGM resins , Holland, Irgacure 819 is Phenylbis (2 , 4 , 6- trimethylbenzoyl ) hosphine oxide from IGM resins, Holland Wollastonite M1250 is a wollastonite filler from Imerys, France .

[0092] Substrate: An extruded polypropylene sheet with a partially cured digitally printed UV-ink.

[0093] Foil: Polypropylene foil, 300 microns thick, Corona treated.

[0094] Corona treatment: PP foil was corona treated with Multidyne 1000 a small corona machine from 3DT®, USA. The substrate was secured on a non- conductive rubber sheet and the corona tip was placed 10 mm from the substrate. The corona discharge was started and the corona tip was moved over the substrate 4 times back and forth for a total of 8 passes at a speed of 10 cm in 5 seconds .

[0095] Curing: A conveyor belt equipped 120 W / cm medium pressure mercury lamp was used for curing in all examples.

[0096] 30 pm formulation 1 was applied on the substrate. Onto this wet coating, a corona treated PP foil was laminated by hand where care was taken to remove air bubbles. The substrate was treated in an UV-oven at 2x 50% UV at 9.9 m / min giving a dose of 200 mJ / cm2(UVA) . The UV-source was a broad- spectrum UV- lamp and the dose was measured in the UVA- range.

[0097] Peel test: For the peel test a PCE-PST 1 from PCE instruments, Germany, was used. Briefly, a 60 mm length of foil is separated from the substrate and inserted into a holder that tightly grips the foil. The machine is started and the force required to peel off the foil is recorded. lN / mm is considered a commercially viable result . The failure mode in Example 5 is that the partially cured printed ink on a base coat is peeled of f from the extruded polypropylene substrate , which corresponds to values higher than 1 N / mm .

[0098] Example 5 shows that adding a Norrish type 1 initiator , an acrylate oligomer and an inorganic f iller does not prevent the function of the lamination glue .

Claims

Claims1. A method for laminating a substrate (5) comprising acrylate groups (4) on a surface, said method comprising the steps of a) providing a substrate (5) , wherein at least a part of the surface of the substrate comprises acrylate groups (4) , b) applying a layer of a liquid formulation (3) on at least a part of the substrate (5) , the liquid formulation (3) comprising at least one diacrylate and at least one Norrish type-II photoinitiator, c) applying a foil (1) on the applied liquid formulation (3) , wherein the foil (1) comprises at least one polymer selected from the group consisting of polypropylene and polyethylene, and wherein the foil (1) before the application is treated with at least one method selected from the group consisting of corona and flametreatment on at least the side (2) to be contacted with the applied liquid (3) , d) irradiating the substrate with actinic radiation on the applied foil (1) to initiate a reaction to cure the liquid formulation (3) .

2. The method according to claim 1, wherein at least a part of the surface of the substrate (1) is provided with a partially cured UV-curing ink.

3. The method according to claim 2, wherein a surface of the partially cured UV-curing ink comprises acrylate groups .

4. The method according to any one of claims 1 or 2 , wherein the acrylate groups of at least a part of the surface of the substrate are provided in step a) by applying a coating comprising acrylate groups.

5. The method according to claim 1, wherein the substrate (1) comprises melamine and wherein the acrylate groups of at least a part of the surface of the substrate are provided in step a) by applying a coating, which provides acrylate groups .

6. The method according to any one of claims 1-5, wherein the layer of the liquid formulation (3) is applied in a thickness of 1-100 pm, preferably 5-50 pm.

7. The method according to any one of claims 1-6, wherein the foil (1) comprises polypropylene.

8. The method according to any one of claims 1-7, wherein the thickness of the foil (1) is 1 mm or less.

9. The method according to any one of claims 1-8, wherein the foil (1) and the applied liquid formulation (3) is sufficiently transparent to actinic radiation so that the irradiation in step d) at least to some extent cures the UV- curing ink.

10. A substrate laminated according to any one of claims 1-9.

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