Digital printing PET (Polyethylene Terephthalate) decorative plate with high paint film adhesion and preparation method thereof

Abstract

The invention belongs to the technical field of polymer composite materials and building decoration materials, and discloses a digital printing PET decorative plate with high paint film adhesion. The decorative plate comprises a base material, a surface decorative layer and a back paint layer, wherein the surface decorative layer sequentially comprises a second adhesion primer layer, a white primer layer, a pattern printing layer, a wear-resistant primer layer, a 3D texture layer and a finish paint layer; the back paint layer is attached to the mute pad through the adhesive layer. According to the invention, sanding pretreatment is carried out on the PET base material, the two-component polyurethane is adopted to attach the primer, and deep cross-linking curing is realized through reaction of hydroxyl and isocyanate groups, so that the adhesive force of a paint film is obviously improved, and a cross-cut test reaches 5B. Meanwhile, the front and back coatings are designed to effectively balance stress and prevent the plate from warping. The invention also discloses a preparation method of the decorative plate, the prepared decorative plate has the characteristics of good wear resistance, excellent decorative effect, environmental protection and the like, and is suitable for the fields of home decoration and tools, and the comprehensive performance and market competitiveness of the digital printing PET decorative plate are integrally improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer composite materials and building decoration materials, and relates to a high polymer decorative plate, in particular to a digital printing PET decorative plate with high paint film adhesion and a preparation method thereof. BACKGROUND

[0002] Polyethylene terephthalate (PET) is an environmentally friendly polymer material composed of C, H and O elements. Due to its non-toxic and harmless characteristics, it is often used in beverage bottles, food packaging containers, etc. The digital printing PET decorative plate is a new type of environmentally friendly building material made of recycled r-PET plastic (such as recycled beverage bottles) and pure new material PET resin as the main raw material, combined with natural stone powder, through high temperature and high pressure extrusion molding, and combined with multi-channel digital coating process, which is widely used in home decoration and industrial fields.

[0003] Although PET is a polar polymer, the symmetry and geometric regularity of the molecular structure make it easy to orient and crystallize, and the surface energy is low, the wetting ability of the ordinary UV coating is poor, the firmness of the UV coating after curing is poor, and the problem of coating peeling off easily occurs, as disclosed in patent CN115991954A. The existing technology often adopts the method of first performing adhesion bottom treatment on the PET substrate and then coating the subsequent coating, but the single-component UV coating often has insufficient deep curing, which affects the adhesion of the coating and the substrate, leading to the failure of the hundred grid test, and seriously affecting the application of the product.

[0004] To overcome the above-mentioned defects, the application provides a digital printing PET decorative plate and a preparation method thereof by substrate sanding pretreatment combined with two-component adhesion primer and front and back coating stress balance design. SUMMARY

[0005] In view of the problems of poor adhesion of the UV coating on the PET substrate, easy peeling and warping of the plate in the prior art, the purpose of the application is to disclose a digital printing PET decorative plate with strong paint film adhesion, good wear resistance, excellent decoration and stable size, and a preparation method thereof.

[0006] TECHNICAL SCHEME

[0007] The application discloses a digital printing PET decorative plate with high paint film adhesion, which comprises, from bottom to top, a soundproof pad, a substrate and a surface decoration layer, wherein the surface decoration layer comprises a second adhesion primer layer, a white primer layer, a pattern printing layer, a wear-resistant primer layer, a 3D texture layer and a topcoat layer; the back surface of the substrate is provided with a back paint layer; the soundproof pad is attached to the back paint layer through a glue adhesive layer; the substrate comprises PET resin and fillers; the PET resin is recycled r-PET, pure new material PET resin or a combination of both; the fillers are at least one of calcium carbonate powder, talc powder, wollastonite, kaolin, mica, diatomite, carbon black, biomass charcoal, silicon dioxide and wood powder; and the adhesion primer layer, the white primer layer, the wear-resistant primer layer, the 3D texture layer, the topcoat layer and the back paint layer are all formed of photocuring resin.

[0008] In the preferred disclosure of the application, the white primer layer comprises a first white primer layer, a second white primer layer and a third white primer layer which are overlaid on the second adhesion primer layer; the wear-resistant primer layer comprises a first wear-resistant primer layer and a second wear-resistant primer layer which are overlaid on the pattern printing layer; and the back paint layer comprises a first adhesion primer layer which is overlaid on the back surface of the substrate and a pull-back paint layer which is overlaid on the first adhesion primer layer.

[0009] In the preferred disclosure of the application, the surface hardness of the substrate is not less than 75HD of Shore hardness, the static bending strength is not less than 22 MPa, and the elastic modulus is not less than 3500 MPa.

[0010] In the preferred disclosure of the application, the adhesion primer layer is formed by mixing component A and component B at a mass ratio of 1:1 to 2:1; wherein the component A comprises multifunctional hydroxyl-containing polyurethane acrylate with a hydroxyl value of 70-80 mgKOH / g; and the component B comprises isocyanate multimer with an NCO content of 18-23%.

[0011] Further, the component A comprises, in terms of mass fraction, 65-75 parts of polyurethane acrylate, 3-6 parts of photoinitiator, 1-3 parts of silane coupling agent and 20-30 parts of active diluent; and the component B comprises, in terms of mass fraction, 55-65 parts of isocyanate multimer, 10-15 parts of diisocyanate, 20-40 parts of solvent and 0.1-0.5 parts of catalyst.

[0012] In the preferred disclosure of the application, the white primer layer comprises, in terms of mass fraction, 30-40 parts of polyurethane acrylate, 10-20 parts of epoxy acrylate, 25-35 parts of titanium white powder, 3-5 parts of photoinitiator and 15-20 parts of active diluent. The titanium white powder (preferably rutile type, D50=3μm) provides whiteness, hiding power and enhances ink adhesion.

[0013] The preferred disclosed example of the application, the wear-resistant primer layer comprises, in parts by mass: polyurethane acrylate 40-50 parts, acrylate 10-15 parts, alumina micropowder 10-15 parts, silica micropowder 10-15 parts, photoinitiator 3-5 parts, active diluent 15-20 parts.

[0014] The preferred disclosed example of the application, the photocuring resin of the 3D texture layer comprises, in parts by mass: epoxy acrylate 55-65 parts, acrylate 15-20 parts, nano-silica 3-5 parts, photoinitiator 5-6 parts, active diluent 10-15 parts. Epoxy acrylate provides high hardness, and nano-silica improves wear resistance and adjusts lightness.

[0015] The alumina and silica micropowder (D50=38μm) improves wear resistance and scratch resistance.

[0016] The preferred disclosed example of the application, the soundproof pad is at least one of 1mm thick 7.5 times foaming IXPE film or 1mm thick r-PET non-woven fabric (gram weight 150-200g / m 2 ), and is attached by roll coating with A / B two-component polyurethane adhesive (A:B mass ratio 3-6:1, preferably 5:1).

[0017] One of the key improvements of the application is that the adhesive primer layer is a two-component system mixed by A component and B component in a mass ratio of 1:1 to 2:1.

[0018] The A component contains multifunctional hydroxyl-containing polyurethane acrylate (hydroxyl value 70-80mgKOH / g), photoinitiator, silane coupling agent and active diluent.

[0019] The B component contains isocyanate multimer (NCO content 18-23%), diisocyanate, solvent and catalyst.

[0020] This two-component design forms urethane bonds and urea bonds by the reaction of hydroxyl groups and NCO groups, realizes deep cross-linking and curing, and forms mechanical bite force with the sanded PET surface, significantly improving the adhesion.

[0021] The second key improvement of the application is that the substrate has a coating (surface decoration layer and back paint layer) on both the front and back surfaces, and a soundproof pad is attached outside the back paint layer through an adhesive layer. This design can form an up-down shrinkage balance force during the curing process of the coating, effectively solving the problems of plate surface bending and surface tile (warpage).

[0022] The second object of the application is also to disclose a preparation method of the digital printing PET decorative plate with high paint film adhesion.

[0023] A preparation method of a digital printing PET decorative plate with high paint film adhesion, comprising the following steps:

[0024] S1, providing a PET substrate, and pre-treating a back surface of the substrate;

[0025] S2, roll coating an adhesion primer on the pre-treated back surface of the substrate, and light curing to form a first adhesion primer layer, roll coating a back lacquer primer on the first adhesion primer layer, and light curing to form a back lacquer layer;

[0026] S3, turning over the substrate, pre-treating a front surface thereof, roll coating an adhesion primer on the pre-treated front surface, and light curing to form a second adhesion primer layer, roll coating three layers of white primer on the surface of the second adhesion primer layer in sequence, and light curing respectively to form a white primer layer;

[0027] S4, performing inkjet printing on the surface of the white primer layer, and light curing to form a pattern printing layer, roll coating two layers of wear-resistant primer on the surface of the pattern printing layer in sequence, and light curing respectively to form a wear-resistant primer layer;

[0028] S5, roll coating a light-curing resin for forming a 3D texture layer on the surface of the wear-resistant primer layer, spraying an inhibitor containing a polymerization inhibitor or a ultraviolet light absorber by using a 3D printer, light curing, treating the surface by using a steel brush and a hair brush, removing the resin which is not completely cured to form a 3D texture layer, and cleaning and blowing dry the plate surface;

[0029] S6, roll coating a topcoat, and light curing to form a topcoat layer;

[0030] S7, performing slotting, chamfering and pasting a mute pad on the cured plate to obtain the product.

[0031] In the step S1, the PET substrate is PET or r-PET, the filler is 300-800 mesh calcium carbonate, and the mass ratio of PET: calcium carbonate is 1:3-4.5; and the PET substrate can be a single layer or a multi-layer (such as A-B-A structure) co-extrusion structure.

[0032] In the step S2, the pre-treatment is polishing treatment, and a sand belt machine is used, the grit size of the sandpaper is 220-280 mesh, and the polishing roller maintains a contact pressure of 0.05-0.2 MPa with the substrate.

[0033] In the steps S2 and S3, the adhesion primer has a mass ratio of A component to B component of 1:1 to 2:1; the A component includes, in terms of mass fraction, 65-75 parts of polyurethane acrylate, 3-6 parts of a photo initiator, 1-3 parts of a silane coupling agent, and 20-30 parts of an active diluent; and the B component includes, in terms of mass fraction, 55-65 parts of an isocyanate polymer, 10-15 parts of a diisocyanate, 20-40 parts of a solvent, and 0.1-0.5 parts of a catalyst.

[0034] In the step S7, the mute pad adopts at least one of 1mm thick 7.5 times foaming IXPE film or 1mm thick r-PET non-woven fabric, and is attached by roll coating using A / B two-component polyurethane adhesive, and the mass ratio of the A component and the B component is 3-6:1.

[0035] Advantages

[0036] The disclosed digital printing PET decorative plate has the following advantages: high adhesion: through sanding treatment of the PET substrate and application of A / B two-component polyurethane adhesion primer, the synergistic effect of mechanical engagement and chemical deep curing (formation of urethane bond and urea bond) is utilized, effectively solving the problems of poor wettability, low adhesion and easy falling of ordinary UV coating on PET substrate. The crosshatch test can reach 5B (no falling). Excellent wear resistance: by setting a special wear-resistant primer layer (containing alumina and silica powder), and by controlling the coating amount, it can flexibly meet the different wear resistance requirements. Good dimensional stability: by setting a back coating layer on the back of the substrate, the stress generated by the surface paint layer curing shrinkage is effectively balanced, solving the problem of plate warping (face bending, face tile). Fine decoration: through multi-layer white primer to ensure the color rendering of the pattern, combined with unique 3D texture manufacturing process (inhibitor spraying + mechanical brushing), clear three-dimensional texture effect can be achieved. Environmental protection and sustainability: the substrate can use a large amount of recycled r-PET, meeting the green environmental protection requirements. Synergistic effect of each layer: through professional design of each coating layer (adhesion primer, white primer, wear-resistant primer, 3D texture layer), each layer can best realize its predetermined function, and the overall performance and market competitiveness of the digital printing PET decorative plate are improved. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 . The structure of the digital printing PET decorative plate with high paint film adhesion is shown in the figure, wherein the component identifiers are as follows: 01-substrate, 02-back paint layer, 02-1-first adhesion primer layer, 02-2-back paint layer, 03-surface decoration layer, 03-1-second adhesion primer layer, 03-2-first white primer layer, 03-3-second white primer layer, 03-4-third white primer layer, 03-5-pattern printing layer, 03-6-first wear-resistant primer layer, 03-7-second wear-resistant primer layer, 03-8-3D texture layer, 03-9-topcoat layer, 04-adhesive layer, 05-mute pad. DETAILED DESCRIPTION

[0038] The application will be described in detail below with reference to the examples, so that those skilled in the art can better understand the application, but the application is not limited to the following examples.

[0039] The experimental methods in the following examples, unless otherwise specified, are generally performed according to routine conditions or according to the conditions recommended by the manufacturer. All percentages and parts are by mass unless otherwise specified.

[0040] In the examples, the materials used, unless otherwise specified, are commercially available.

[0041] The test methods are as follows:

[0042] Adhesion: Refers to the standard ASTM D 3359 crosshatch method.

[0043] Surface hardness: Determined using a Shore hardness meter.

[0044] Static strength and elastic modulus: Determined in accordance with the relevant ASTM standards.

[0045] Example 1

[0046] A digital printing PET decorative sheet with high paint film adhesion, from bottom to top, includes a soundproof pad 05, an adhesive layer 04, a back paint layer 02, a substrate 01, and a surface decoration layer 03; wherein the back paint layer 02 is a two-layer structure. The surface decoration layer 03 is a 9-layer structure. The back paint layer 02 is on the back of the substrate, and the back paint layer 02 includes a first adhesion primer layer 02-1 covering the substrate and a pull-back paint layer 02-2 covering the first adhesion primer layer 02-1; the surface decoration layer 03 includes a second adhesion primer layer 03-1 covering the surface of the substrate, and a first white primer layer 03-2, a second white primer layer 03-3, a third white primer layer 03-4, a pattern printing layer 03-5, a first wear-resistant primer layer 03-6, a second wear-resistant primer layer 03-7, a 3D texture layer 03-8, and a topcoat layer 03-9 stacked one by one upwards. The first adhesion primer layer 02-1 and the second adhesion primer layer 03-1 use the same formula and process. Typically, the thickness of the back paint layer 02 is 20-80 pm, the thickness of the surface decoration layer is 200-300 pm, and the thickness of the adhesive layer is 20-40 pm. The above coating thickness is achieved by the respective coating amount.

[0047] Example 2

[0048] A digitally printed PET decorative panel with high paint film adhesion, wherein the base resin of the substrate 01 is at least one of PET and r-PET, and the filler is 300-800 mesh calcium carbonate. In the embodiment, the substrate thickness is 4.8 mm, with a single-layer structure. The base resin of the substrate is r-PET bottle flake material, and the filler is 400 mesh calcium carbonate; the mass ratio of r-PET to calcium carbonate is 1:3.5. The adhesion primer layer is composed of component A and component B mixed in a mass ratio of 1:1 to 2:1; wherein component A contains a multifunctional hydroxyl-containing polyurethane acrylate with a hydroxyl value of 70-80 mgKOH / g; and component B contains an isocyanate polymer with an NCO content of 18-23%.

[0049] Example 3

[0050] A digitally printed PET decorative panel with high paint film adhesion, wherein the surface decorative layer 03 comprises a second adhesion primer layer 03-1, a white primer layer, a pattern printing layer 03-5, a wear-resistant primer layer, a 3D texture layer 03-8, and a topcoat layer 03-9; a back paint layer 02 is provided on the back side of the substrate 01; the back paint layer 02 is roll-pressed with the sound-absorbing pad 05 through an adhesive layer 04; the substrate 01 comprises PET resin and filler; the PET resin is recycled r-PET, pure virgin PET resin, or a combination of the two; the filler is at least one selected from calcium carbonate powder, talc powder, wollastonite, kaolin, mica, diatomaceous earth, carbon black, biochar, silica, and wood flour; the adhesion primer layer, white primer layer, wear-resistant primer layer, 3D texture layer, topcoat layer, and back paint layer are all formed by photocuring resin.

[0051] Example 4

[0052] A digitally printed PET decorative panel with high paint film adhesion, such as Figure 1As shown, from bottom to top, it includes a sound-absorbing pad 05, an adhesive layer 04, a back coating layer 02, a substrate 01, and a surface decoration layer 03; wherein the back coating layer 02 is a two-layer structure. The surface decoration layer 03 is a nine-layer structure. The back coating layer 02 is on the back side of the substrate and includes a first adhesive primer layer 02-1 covering the substrate and a backing paint layer 02-2 covering the first adhesive primer layer 02-1; the surface decoration layer 03 includes a second adhesive primer layer 03-1 covering the surface of the substrate, and layers stacked upwards: a first white primer layer 03-2, a second white primer layer 03-3, a third white primer layer 03-4, a pattern printing layer 03-5, a first wear-resistant primer layer 03-6, a second wear-resistant primer layer 03-7, a 3D texture layer 03-8, and a topcoat layer 03-9. The first adhesive primer layer 02-1 and the second adhesive primer layer 03-1 are made using the same formula and process. Typically, the thickness of the back coating layer (02) is 20~80µm, the thickness of the surface decorative layer is 200~300µm, and the thickness of the adhesive layer is 20~40µm. These coating thicknesses are achieved through the application rate of each layer.

[0053] The aforementioned coatings, such as the adhesion primer layer, white primer layer, and abrasion-resistant primer layer, are all formed by roller coating with UV-cured resin and then UV-cured. However, each coating has a different function, which leads to differences in the formulation of each coating. For example, the adhesion primer layer (including the first adhesion primer layer 02-1 and the second adhesion primer layer 03-1) mainly enhances the adhesion between the PET substrate and the coating and prevents peeling. The film-forming material is mainly composed of UV-cured polyurethane acrylate oligomers and isocyanates that participate in the addition reaction. The polyurethane acrylate oligomers are polyfunctional polyurethane acrylate resins containing hydroxyl groups, with a hydroxyl value of 70-80 mgKOH / g. Multifunctionality refers to difunctionality, and may contain small amounts of trifunctional, tetrafunctional, and hexafunctional groups. The isocyanate is composed of isocyanate polymers and diisocyanates, with isocyanate polymers being the main component. The isocyanate polymers mainly refer to trimers, usually HDI trimers, IPDI trimers, or H12MDI trimers, etc. The white primer layer (comprising the first white primer layer 03-2, the second white primer layer 03-3, and the third white primer layer 03-4) primarily functions to cover the PET substrate, providing a uniform white background and enhancing ink color development. The film-forming material is mainly a combination of polyurethane acrylate and epoxy acrylate, with polyurethane acrylate being the majority. Titanium dioxide is used as the filler, specifically rutile type with a D50 of 3μm, mainly to provide whiteness and hiding power, ensuring vibrant colors and no show-through in subsequent printed patterns. The abrasion-resistant primer layer (comprising the first abrasion-resistant primer layer 03-6 and the second abrasion-resistant primer layer 03-7) primarily protects the printed pattern from scratches and chemical corrosion. The film-forming material is mainly polyurethane acrylate monomers and multifunctional acrylate monomers, with polyurethane acrylate monomers being the majority. Multifunctional acrylate monomers mainly refer to tetrafunctional monomers, with a small amount of trifunctional and hexafunctional monomers. The 3D texture layer primarily serves to achieve a three-dimensional texture effect, ensuring clear and non-sticky textures during wire drawing and facilitating uniform sinking during mechanical wire drawing. The film-forming material mainly consists of epoxy acrylate and multifunctional acrylate monomers, with epoxy acrylate monomers being the majority. The multifunctional acrylate monomers primarily refer to hexamidocity, with a small amount of trifunctional, tetrafunctional, and pentafunctional monomers. The fillers are silica micropowder and alumina micropowder, with a particle size D50 of 38 μm. The reactive diluent is interchangeable across formulations, typically 1,6-hexanediol diacrylate (HDDA). The photoinitiator is also interchangeable, typically TPO with an absorption wavelength of 365-420 nm.

[0054] Unlike the coatings mentioned above, the pattern printing layer 03-5 is formed by inkjet printing using an industrial inkjet printer and then curing. The ink used in industrial inkjet printers is a UV-curable pigment, with a viscosity typically controlled between 5 and 25 cp at 25°C. The film-forming substance is mainly polyurethane acrylate.

[0055] It should be noted that although the 3D texture layer 03-8 is achieved through roller coating, roller coating does not immediately create a three-dimensional effect. It requires an industrial inkjet printer to spray ink containing polymerization inhibitors and / or UV absorbers onto specific areas, causing the ink-coated areas to not cure or not completely cure, thus distinguishing them from the cured areas. Then, the uncured or incompletely cured areas can be brushed away with a steel brush and a bristle brush, creating a 3D textured effect on this layer, which is the 3D texture layer 03-8. The realization of this 3D effect, as described above, is defined as a sunken process.

[0056] The matrix resin of the substrate 01 is at least one of PET and r-PET, and the filler is 300~800 mesh calcium carbonate. In the embodiment, the substrate thickness is 4.8 mm, with a single-layer structure. The base resin of the substrate is r-PET bottle flake material, and the filler is 400 mesh calcium carbonate. The mass ratio of r-PET to calcium carbonate is 1:3.5.

[0057] Example 5

[0058] A method for preparing a digitally printed PET decorative panel with high paint film adhesion includes the following steps:

[0059] (a) Substrate preparation

[0060] A single-layer structural substrate 01 with a thickness of 4.8 mm is provided. Its base resin is r-PET bottle flake material and its filler is 400 mesh calcium carbonate powder. The mass ratio of r-PET to calcium carbonate is 1:3.5. The surface hardness of the substrate is 78HD, the static bending strength is 25MPa, and the elastic modulus is 3800MPa.

[0061] (II) Preparation of digitally printed PET decorative panels

[0062] Backside treatment:

[0063] S2 Grinding: The back surface of substrate 01 is ground using a 240-grit belt sander, with the surface roughness Ra controlled at 1.0~1.5μm. The grinding roller maintains a contact pressure of 0.1MPa with the substrate.

[0064] S3 First Adhesion Primer Layer: A two-component adhesion primer is roller-coated onto the back surface of the treated substrate, with a coating weight of 20 g / m². 2 Subsequently, it was cured by irradiation with a 395nm UV lamp at an energy of 200mJ / cm². 2 This forms the first adhesive primer layer 02-1 (dry film thickness approximately 10-15 μm).

[0065] Adhesion primer formulation (component A and component B are mixed in a mass ratio of 5:3):

[0066] Component A: 70 parts of multifunctional hydroxyl-containing polyurethane acrylate (hydroxyl value 75mgKOH / g, difunctionality), 4 parts of photoinitiator TPO, 2 parts of silane coupling agent KH-550, 24 parts of reactive diluent HDDA, and 0.3 parts of polymeric defoamer.

[0067] Component B: 58 parts of isocyanate polymer (HDI trimer, NCO content 20%), 12 parts of diisocyanate (IPDI), 20 parts of ethyl acetate solvent, 10 parts of PMA solvent, and 0.2 parts of DBTL catalyst.

[0068] S4 Backing Coating Layer: Roller-coated backing primer (formula can be the same as the second bonding primer layer or other commonly used backing primer formulations) is applied over the first bonding primer layer 02-1, with a coating amount of 20g / m². 2 Curing was performed using a 395nm UV lamp with an energy of 600mJ / cm². 2 This forms a backing paint layer 02-2 (dry film thickness approximately 10-15 μm).

[0069] Front treatment and decorative layer construction:

[0070] S5 Flipping and Front Treatment: Flip the substrate 180° with the front side facing up using a flipping machine. Perform the same sanding treatment as S2 on the front side of the substrate (240-grit sanding belt, Ra=1.0~1.5μm). Then, roll-coat the same primer as S3 (coating amount 20g / m²). 2 With a curing energy of 200 mJ / cm², a second adhesive primer layer 03-1 is formed (dry film thickness approximately 10-15 μm).

[0071] S6 White Primer Layer: Roller-coating white primer (coating amount 15g / m²) is applied to the surface of the second primer layer 03-1. 2 Cured by irradiation with a 395nm UV lamp (energy 600mJ / cm). 2 The first white primer layer 03-2 is formed; this process is repeated twice to form the second white primer layer 03-3 and the third white primer layer 03-4 (total dry film thickness is about 30-40μm).

[0072] White primer formulation: 36 parts polyurethane acrylate (hexafunctional), 15 parts epoxy acrylate (bisphenol A type diacrylate), 30 parts titanium dioxide (rutile type, D50=3μm), 4 parts photoinitiator TPO, and 15 parts reactive diluent HDDA.

[0073] S7 Pattern Printing Layer: On the surface of the third white primer layer 03-4, a UV-curable color paste (viscosity approximately 15cp@25℃, film-forming substance mainly polyurethane acrylate) is printed using an industrial inkjet printer, with an inkjet volume of 5g / m². 2After being cured by light, a pattern printing layer 03-5 is formed.

[0074] S8 Abrasion-resistant primer layer: Roller-coated abrasion-resistant primer (coating amount 35g / m²) onto the surface of pattern printing layer 03-5. 2 Cured by irradiation with a 395nm UV lamp (energy 600mJ / cm). 2 The first wear-resistant primer layer 03-6 is formed; this process is repeated once to form the second wear-resistant primer layer 03-7 (total dry film thickness is about 50-60μm).

[0075] Abrasion-resistant primer formulation: 45 parts polyurethane acrylate (hexafunctional), 12 parts acrylate (PETA), 12 parts alumina micro powder (D50=38μm), 12 parts silica micro powder (D50=38μm), 4 parts photoinitiator TPO, and 15 parts reactive diluent HDDA.

[0076] S9-S11 form a 3D texture layer:

[0077] S9: Roll-coat the surface of the second wear-resistant primer layer 03-7 with a UV-curable resin for the 3D texture layer (coating amount 40g / m²). 2 At this time, light curing is not performed.

[0078] 3D texture layer photocurable resin formulation: 55 parts epoxy acrylate (bisphenol A type diacrylate), 20 parts acrylate (DPHA), 5 parts nano silica (1250 mesh), 5 parts photoinitiator TPO, 15 parts reactive diluent HDDA, and 0.3 parts defoamer.

[0079] S10: Use a 3D printer to spray an inhibitor containing polymerization inhibitors and ultraviolet absorbers onto specific areas.

[0080] S11: The surface is cured by light using a 395nm UV lamp, and then treated with a steel brush (5m / min) and a bristle brush (20m / min) to remove the incompletely cured resin paste, forming a 3D textured layer 03-8 with a three-dimensional uneven effect.

[0081] S12 Cleaning and Drying: Clean the board surface to remove residue, then dry it.

[0082] S13 Topcoat Layer: Roller-applied topcoat (common UV topcoat formulations can be used, coating amount 20g / m²) 2 Curing was performed using a 395nm UV lamp (energy 800mJ / cm). 2 ), forming the topcoat layer 03-9.

[0083] Post-processing (S14):

[0084] The obtained board is grooved and chamfered. Then, using an A / B two-component polyurethane adhesive (component A is mainly a mixture of polyester / polyether polyol, component B is mainly MDI, A:B=5:1), a 1mm thick IXPE sound-absorbing pad 05 with a foaming rate of 7.5 times is bonded to the back paint layer 02-2 by a roll pressing process, forming an adhesive layer 04 (approximately 30μm thick) in the middle, finally obtaining a digitally printed PET decorative board.

[0085] (III) Performance Testing

[0086] The digitally printed PET decorative panel obtained in Example 1 was subjected to a cross-cut adhesion test (ASTM D 3359), and the result was 5B (no peeling), indicating that the paint film adhesion was excellent.

[0087] Comparative Example 1

[0088] The preparation method is basically the same as in Example 5, except that:

[0089] In S2, the back surface of the substrate is not sanded, and the first adhesion primer is directly applied by roller.

[0090] In S5, the front side of the substrate is not sanded, and the second primer is directly applied by roller.

[0091] The cross-cut test result was 4B (dropout <5%).

[0092] Comparative Example 2

[0093] The preparation method is basically the same as in Example 5, except that:

[0094] The adhesion primers used in S3 and S5 are single-component, with the following formulation: 60 parts polyurethane acrylate (hexafunctional), 5 parts photoinitiator TPO, 2 parts silane coupling agent KH-550, and 33 parts reactive diluent HDDA.

[0095] The cross-linking test result was 2B (15%~35% shedding).

[0096] Comparative Example 3

[0097] The preparation method is basically the same as that of Comparative Example 2, except that:

[0098] Sanding is not performed in S2 and S5.

[0099] The cross-linking test result was 1B (35%~65% shedding).

[0100] Analysis of test results

[0101] The table below summarizes the results of the 100-grid test for Example 5 and Comparative Examples 1-3:

[0102]

[0103] It can be seen from the above table:

[0104] The synergistic effect of sanding and two-component adhesion primer is crucial: Example 5 (sanding + two-component) performed best (5B).

[0105] Chemical deep cross-linking can partially compensate for insufficient mechanical interlocking: Comparative Example 1 (unsanded + two components) still achieved 4B, which is better than the single-component system.

[0106] Deep cross-linking curing has a significant impact on adhesion: the adhesion of single-component primers (comparative examples 2-3) decreased significantly, especially when unsanded (comparative example 3) the adhesion was only 1B.

[0107] Practical applications require a balance between sanding and two-component primers: To ensure the durability of the coating film in high-abrasion environments such as floors, it is recommended to use sanding and a two-component primer formulation.

[0108] The above embodiments and comparative examples fully illustrate the technical solution of the present invention, especially the application of sanding pretreatment and two-component adhesive primer, which have outstanding and unexpected effects on solving the problem of poor adhesion of UV coatings on PET substrates.

[0109] The embodiments described above are merely specific implementations of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A digitally printed PET decorative panel with high paint film adhesion, comprising, from bottom to top, a sound-absorbing pad (05), a substrate (01), and a surface decorative layer (03), characterized in that: The surface decorative layer (03) comprises a second adhesive primer layer (03-1), a white primer layer, a pattern printing layer (03-5), a wear-resistant primer layer, a 3D texture layer (03-8), and a topcoat layer (03-9); a back coating layer (02) is provided on the back side of the substrate (01); the back coating layer (02) is rolled and bonded to the sound-absorbing pad (05) by an adhesive layer (04); the substrate (01) comprises PET resin and filler; the PET resin is recycled r-PET, pure virgin PET resin, or a combination of the two; the filler is at least one of calcium carbonate powder, talc powder, wollastonite, kaolin, mica, diatomaceous earth, carbon black, biochar, silica, and wood flour; the adhesive primer layer, white primer layer, wear-resistant primer layer, 3D texture layer, topcoat layer, and back coating layer are all formed by photocuring resin.

2. The digitally printed PET decorative panel with high paint film adhesion according to claim 1, characterized in that: The white primer layer includes a first white primer layer (03-2), a second white primer layer (03-3), and a third white primer layer (03-4) covering the second adhesive primer layer (03-1); the abrasion-resistant primer layer includes a first abrasion-resistant primer layer (03-6) and a second abrasion-resistant primer layer (03-7) covering the pattern printing layer (03-5); the back paint layer (02) includes a first adhesive primer layer (02-1) covering the back surface of the substrate (01) and a backing paint layer (02-2) covering the first adhesive primer layer (02-1).

3. The digitally printed PET decorative panel with high paint film adhesion according to claim 1, characterized in that: The surface hardness of the substrate (01) is not less than Shore hardness 75HD, static bending strength is not less than 22MPa, and elastic modulus is not less than 3500MPa.

4. The digitally printed PET decorative panel with high paint film adhesion according to claim 1, characterized in that: The adhesive primer layer is composed of component A and component B mixed in a mass ratio of 1:1 to 2:1; wherein component A contains a multifunctional hydroxyl-containing polyurethane acrylate with a hydroxyl value of 70-80 mgKOH / g; component B contains an isocyanate polymer with an NCO content of 18-23%; further, component A comprises, by mass parts: 65-75 parts of polyurethane acrylate, 3-6 parts of photoinitiator, 1-3 parts of silane coupling agent, and 20-30 parts of reactive diluent; component B comprises, by mass parts: 55-65 parts of isocyanate polymer, 10-15 parts of diisocyanate, 20-40 parts of solvent, and 0.1-0.5 parts of catalyst.

5. The digitally printed PET decorative panel with high paint film adhesion according to claim 1, characterized in that: The white primer layer comprises, by weight parts: 30-40 parts polyurethane acrylate, 10-20 parts epoxy acrylate, 25-35 parts titanium dioxide, 3-5 parts photoinitiator, and 15-20 parts reactive diluent; the wear-resistant primer layer comprises, by weight parts: 40-50 parts polyurethane acrylate, 10-15 parts acrylate, 10-15 parts alumina micro powder, 10-15 parts silica micro powder, 3-5 parts photoinitiator, and 15-20 parts reactive diluent; the photocurable resin of the 3D texture layer comprises, by weight parts: 55-65 parts epoxy acrylate, 15-20 parts acrylate, 3-5 parts nano silica, 5-6 parts photoinitiator, and 10-15 parts reactive diluent.

6. The digitally printed PET decorative panel with high paint film adhesion according to claim 1, characterized in that: The sound-absorbing pad (05) is a 1mm thick 7.5x expanded IXPE film or a 1mm thick film with a basis weight of 150-200g / m³. 2 At least one of the r-PET nonwoven fabrics is roll-coated and bonded using an A / B two-component polyurethane adhesive.

7. A method for preparing a digitally printed PET decorative panel with high paint film adhesion as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Provide a PET substrate (01) and pre-treat the back surface of the substrate (01); S2. Apply an adhesive primer to the back surface of the pretreated substrate (01) by roller coating and cure by light to form a first adhesive primer layer (02-1). Apply a back paint primer to the first adhesive primer layer (02-1) by roller coating and cure by light to form a back paint layer (02-2). S3. Turn the substrate (01) over, pre-treat its front side, roll coat the adhering primer, and cure it by light to form the second adhering primer layer (03-1); roll coat three layers of white primer on the surface of the second adhering primer layer (03-1) and cure them by light to form a white primer layer. S4. Inkjet printing is performed on the surface of the white primer layer, and light curing is performed to form a pattern printing layer (03-5); two layers of wear-resistant primer are sequentially rolled onto the surface of the pattern printing layer (03-5) and light cured separately to form a wear-resistant primer layer. S5. Roll-coat the wear-resistant primer layer with a light-curing resin to form a 3D texture layer. Spray an inhibitor containing a polymerization inhibitor or a UV absorber with a 3D printer. Cure by light. Treat the surface with a steel brush and a brush to remove the incompletely cured resin and form a 3D texture layer (03-8). Clean and dry the board surface. S6. Roller-apply topcoat and light-curing to form topcoat layer (03-9). S7. After curing, the board is grooved, chamfered and covered with sound-absorbing pads (05) to obtain the final product.

8. The method for preparing a digitally printed PET decorative panel with high paint film adhesion according to claim 7, characterized in that: In step S1, the PET substrate is PET or r-PET, the filler is 300-800 mesh calcium carbonate, and the mass ratio of PET:calcium carbonate is 1:3-4.5; it is a single-layer or multi-layer co-extruded structure.

9. The method for preparing a digitally printed PET decorative panel with high paint film adhesion according to claim 7, characterized in that: In step S2, the pretreatment is a polishing process, which is carried out using a belt sander with a sandpaper grit size of 220-280 mesh. The sanding roller maintains a contact pressure of 0.05-0.2 MPa with the substrate.

10. The method for preparing a digitally printed PET decorative panel with high paint film adhesion according to claim 7, characterized in that: In steps S2 and S3, the adhesive primer has a mass ratio of component A to component B of 1:1 to 2:

1. The A component, by mass parts, comprises: 65-75 parts of polyurethane acrylate, 3-6 parts of photoinitiator, 1-3 parts of silane coupling agent, and 20-30 parts of reactive diluent; the B component, by mass parts, comprises: 55-65 parts of isocyanate polymer, 10-15 parts of diisocyanate, 20-40 parts of solvent, and 0.1-0.5 parts of catalyst; in step S7, the sound-absorbing pad (05) is made of at least one of a 1mm thick 7.5x foamed IXPE film or a 1mm thick r-PET nonwoven fabric, and is rolled and bonded using an A / B two-component polyurethane adhesive, wherein the mass ratio of the A component to the B component is 3-6:1.

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