Photocurable adhesive composition for acrylic substrate, method for preparing the same, and use thereof

Abstract

The embodiment of the present application provides a photocuring type glue composition for acrylic substrate and a preparation method and application thereof, and belongs to the technical field of resin glue coating process.The photocuring type glue composition comprises the following components in weight percentage: a photoinitiator, 4-8 parts; an active monomer, 45-60 parts; a styrene-acrylonitrile copolymer resin, 10-30 parts; a polyester acrylate, 10-35 parts; and a polyurethane acrylate, 5-15 parts.The specific proportioning synergy of the SAN resin, the polyester acrylate and the polyurethane acrylate realizes high adhesion, high wear resistance and high light transmittance of the acrylic substrate, and the VOC is free and the UV curing can be performed at one time.

Description

Technical Field

[0001] This invention relates to the technical field of resin adhesive coating processes, and particularly to a photocurable adhesive composition for acrylic substrates, its preparation method, and its application. Background Technology

[0002] Polymethyl methacrylate (PMMA), commonly known as plexiglass, is a thermoplastic polymer compound polymerized from methyl methacrylate. PMMA possesses excellent transparency (visible light transmittance can reach over 92%), good chemical stability, mechanical properties, and weather resistance. It also boasts a beautiful appearance and is easy to process, making it widely used in construction, lighting, and medical fields. In the electronics industry, it is used as a cover for mobile phone cases, screen windows, and display light guide plates.

[0003] Ultraviolet (UV) curing technology boasts advantages such as rapid curing, low energy consumption, high efficiency, and zero pollution, making it an environmentally friendly green technology. However, existing UV-curable coatings or transfer adhesives for PMMA materials generally suffer from poor adhesion to PMMA substrates. This is because PMMA materials have a relatively rigid structure, making it difficult for general coatings and inks to penetrate. UV resins, on the other hand, typically contain polyurethane or polyester structures, which differ significantly in structure. The chain segments do not easily form mechanical entanglement, and there is a lack of reactive covalent bonds, thus hindering adhesion. During the curing process, UV coatings rely on double bond addition reactions, resulting in strong volume shrinkage. This intense shrinkage of the coating coupled with the relaxation of the substrate leads to shear stress at the interface, ultimately causing adhesion failure.

[0004] To improve adhesion, existing technologies typically employ the following methods: first, preheating the PMMA substrate before application to accelerate the diffusion and penetration of UV adhesive onto the substrate surface; second, using a free radical-cationic hybrid curing system, utilizing the dark polymerization reaction of the cationic components after light exposure for post-curing; and third, adding adhesion promoters such as silane coupling agents. However, all of these existing technologies suffer from technical drawbacks such as cumbersome processes, long production cycles, and high production costs, and their adhesion improvement effect is very limited.

[0005] In view of this, a novel photocurable adhesive composition for acrylic substrates, its preparation method, and its application are proposed to solve all or part of the above problems. Summary of the Invention

[0006] To address at least one of the aforementioned problems and deficiencies in the prior art, embodiments of the present invention provide a photocurable adhesive composition for acrylic substrates, its preparation method, and its application. A five-component synergistic system is constructed using photoinitiators, active monomers, styrene-acrylonitrile copolymer (SAN) resin, polyester acrylate, and polyurethane acrylate in specific weight ratios. Utilizing the close proximity of the benzene ring groups of SAN resin to the solubility parameters of PMMA, a mechanical hinge interlock is formed. Furthermore, the strong polar nitrile groups generate intermolecular attraction with the polyurethane / ester bonds in the UV resin. This achieves excellent adhesion (5B) to PMMA substrates, good abrasion resistance (RCA test 150-200 times), and high light transmittance (above 96%). Simultaneously, it achieves 100% solids content, no VOC emissions, one-time UV curing, and eliminates the need for substrate preheating and post-curing, significantly simplifying the construction process, reducing production costs, and improving production efficiency. The technical solution is as follows:

[0007] According to one aspect of the present invention, a photocurable adhesive composition for use on acrylic substrates is provided. The photocurable adhesive composition comprises, by weight, the following components:

[0008] Photoinitiator, 4-8 parts;

[0009] Active monomer, 45-60 parts;

[0010] Styrene-acrylonitrile copolymer resin, 10-30 parts;

[0011] Polyester acrylate, 10-35 parts;

[0012] Polyurethane acrylate, 5-15 parts.

[0013] According to another aspect of the present invention, a method for preparing a photocurable adhesive composition for an acrylic substrate is provided. This preparation method is used to prepare the photocurable adhesive composition described above. The preparation method includes the following steps:

[0014] Step S100: Mix a portion of the active monomer with the photoinitiator to completely dissolve the photoinitiator, thereby obtaining a photoinitiator mixture;

[0015] Step S200: Mix the remaining active monomer with the styrene-acrylonitrile copolymer resin and disperse it at 55-60℃ and 800-1200 rpm for 1-2 hours to completely dissolve the styrene-acrylonitrile copolymer resin and obtain a styrene-acrylonitrile copolymer resin mixture.

[0016] Step S300: Mix the photoinitiator mixture with the styrene-acrylonitrile copolymer resin mixture and stir until homogeneous;

[0017] Step S400: Add polyester acrylate and polyurethane acrylate to the mixture obtained in step S300, disperse evenly, and obtain a light-curing adhesive composition.

[0018] According to another aspect of the present invention, an application of a photocurable adhesive composition in the transfer or coating of decorative patterns on the surface of an acrylic substrate is provided. The photocurable adhesive composition is either the photocurable adhesive composition described above or a photocurable adhesive composition prepared according to the preparation method described above.

[0019] The photocurable adhesive composition for acrylic substrates, its preparation method, and its application provided by the embodiments of the present invention have at least one or a portion of the following advantages:

[0020] (1) By using a specific weight ratio of photoinitiator, active monomer, SAN resin, polyester acrylate and polyurethane acrylate, the adhesive composition has excellent adhesion, wear resistance and curing efficiency. It is a 100% solid content, solvent-free system with no VOC volatilization during the curing process, and is environmentally friendly.

[0021] (2) The relative density of SAN resin is 1.06-1.08, and the tensile strength is 700-820 kg / cm². 2 Flexural strength is 1000-1350 kg / cm² 2 With a Rockwell hardness of 78-85, a heat distortion temperature of 89-100℃, and a melt index of 1-5 g / 10min, SAN resin exhibits the best compatibility with UV resin within this range. It dissolves fully in the active monomer and can provide sufficient structural support and wear-resistant foundation for the coating.

[0022] (3) The active monomers are selected from 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, N,N-dimethylacrylamide, tetrahydrofuran acrylate, and vinylcaprolactam. Low-functionality active monomers are used to reduce viscosity, dissolve photoinitiators, and promote adhesion. High-functionality active monomers increase hardness while maintaining viscosity to meet different construction needs.

[0023] (4) The photoinitiator is selected from benzoin dimethyl ether, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, and 1-hydroxy-cyclohexylbenzophenone. It has the effect of absorbing ultraviolet light at a wavelength of 250-400 nm, has good thermal stability, low yellowing, good solubility in active monomers, is easy to store, does not produce crystal precipitation, and can be used in combination for LED light curing.

[0024] (5) Polyester acrylate has a viscosity of 1500-80000 mPa·s at 25℃, a refractive index of 1.44-1.53, and a functionality of 2-4. It has low odor, low irritation, good wettability and flexibility, good adhesion to plastic substrates, and can improve the curing rate; Polyurethane acrylate has a functionality of 2-10, a viscosity of 2000-80000 mPa·s at 25℃, and a refractive index of 1.44-1.53. It can improve the physical and chemical properties of coating such as hardness, wear resistance and water resistance.

[0025] (6) The UV-curable adhesive composition is a 100% solids-containing, solvent-free system. After one-time UV curing, the adhesion to PMMA substrate reaches 5B (standard GB / T 13217.7-2023), the RCA abrasion resistance test is 150-200 times, the light transmittance is over 96%, and the overall performance is excellent.

[0026] (7) The light-curing adhesive composition is a 100% solid content, solvent-free system and does not contain silane coupling agents, which avoids the defects of silane coupling agents being easy to hydrolyze and sensitive to temperature, humidity and storage. At the same time, it simplifies the formulation composition, reduces the cost of raw materials, and the product shelf life can reach more than 12 months.

[0027] (8) The preparation method of the present invention is to obtain a photoinitiator mixture by mixing and dissolving a portion of the active monomer with the photoinitiator, and then dispersing the remaining active monomer with SAN resin at 55-60℃ and 800-1200 rpm for 0.5-1.5 hours to completely dissolve the SAN resin. Then, the two mixtures are mixed and polyester acrylate and polyurethane acrylate are added and dispersed evenly. The process is simple, the operation is controllable, and it is easy to industrialize. It can also ensure the full dispersion of each component and the uniformity and stability of the system.

[0028] (9) Disperse at a speed of 750-850 rpm for 20-40 minutes to ensure that the components are fully mixed and uniform. This process is mild and energy-efficient, avoiding local overheating and component degradation that may be caused by high-speed dispersion.

[0029] (10) The light-curing adhesive composition of the present invention can be applied to the transfer or coating of decorative textures on the surface of PMMA substrate. During construction, it only needs to be cured by ultraviolet light once. No substrate preheating treatment or post-curing is required, which greatly simplifies the production process, shortens the production cycle, reduces production costs, and improves production efficiency. Attached Figure Description

[0030] These and / or other aspects and advantages of the present invention will become apparent and readily understood from the following description of preferred embodiments taken in conjunction with the accompanying drawings, in which:

[0031] Figure 1 This is a flowchart illustrating the steps of a method for preparing a photocurable adhesive composition according to an embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram illustrating the principle of applying the photocurable adhesive composition of the present invention using an imprinting method. Detailed Implementation

[0033] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. In this specification, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the present invention and should not be construed as a limitation thereof.

[0034] The embodiments of the present invention address the technical problems of poor adhesion of existing UV-curable adhesives to PMMA (acrylic sheet) materials and the high production costs and low production efficiency caused by the need for additional processing steps such as pre-baking or post-curing. The present invention provides a UV-curable adhesive composition for acrylic substrates and its preparation method. The UV-curable adhesive composition of the present invention aims to achieve the following objectives:

[0035] ①100% solid content, no added solvents, no VOC volatilization, all resin and active monomer components participate in the reaction;

[0036] ② Excellent adhesion to raw acrylic sheets, reaching level 5B;

[0037] ③ Good abrasion resistance, RCA test 150-200 times;

[0038] ④ Recoatability: After the light-curing adhesive composition is fully cured, it has excellent adhesion to common brand plastic printing inks as a substrate;

[0039] ⑤ Construction is simple and convenient. It uses ultraviolet light for one-time curing, without the need for substrate preheating or post-curing, saving time and improving production efficiency.

[0040] The photocurable adhesive composition provided by this invention comprises, by weight, the following components: 4-8 parts photoinitiator; 45-60 parts reactive monomer; 10-30 parts SAN resin (styrene-acrylonitrile copolymer resin); 10-35 parts polyester acrylate; and 5-15 parts polyurethane acrylate. The details of each component are described below:

[0041] The photoinitiator is selected from one or any mixture of benzoin dimethyl ether (651), 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (819), 2-hydroxy-2-methyl-1-phenylpropanone (1173), and 1-hydroxy-cyclohexylbenzophenone (184). The above-mentioned photoinitiators exhibit absorption of ultraviolet light at wavelengths of 250-400 nm, good thermal stability, low yellowing, good solubility in active monomers, and are easy to store without crystal precipitation. For LED curing, multiple photoinitiators can be used in combination.

[0042] The active monomer is selected from one or any mixture thereof, including 1,6-hexanediol diacrylate (HDDA), 1,4-butanediol diacrylate (BDDA), pentaerythritol triacrylate (PETA), trimethylolpropane triacrylate (TMPTA), dipentaerythritol hexaacrylate (DPHA), N,N-dimethylacrylamide (DMAA), tetrahydrofuran acrylate (THFA), and vinylcaprolactam (NVC). Low-functionality active monomers are mainly used to reduce viscosity, dissolve photoinitiators, and promote adhesion; high-functionality active monomers can increase hardness while maintaining viscosity.

[0043] SAN resin (styrene-acrylonitrile copolymer resin) has a relative density of 1.06-1.08 and a tensile strength of 700-820 kg / cm². 2 The bending strength is 1000-1350 kg / cm². 2 The Rockwell hardness is 78-85, the heat distortion temperature is 89-100℃, and the melt flow index is 1-5 g / 10min. SAN resin mainly functions to increase adhesion to PMMA materials, assist in abrasion resistance, and provide recoatability for printing inks. SAN resin is mainly formed by the addition polymerization of styrene and acrylonitrile monomers, with styrene accounting for 20-80% and acrylonitrile accounting for 20-80%. Resins with this main structure, polymerized from these two monomers, and those used in combination with UV resins are all within the scope of protection of this invention.

[0044] Polyester acrylate, used as the main resin, is characterized by low odor and low irritation, as well as good wetting and flexibility, exhibiting good adhesion to plastic substrates and improving curing speed. Its viscosity at 25°C is 1500-80000 mPa·s, its refractive index is 1.44-1.53, and its functionality is 2-4 functionalities. For example, Runao Chemical FSP7241 can be selected as the polyester acrylate in the embodiments of this invention.

[0045] Polyurethane acrylates are mainly used to improve the hardness, abrasion resistance, and water resistance of coatings. They have a functionality of 2-10, a viscosity of 2000-80000 mPa·s at 25°C, and a refractive index of 1.44-1.53. For example, Runao Chemical's FSP3897 and FSP2159 can be selected as the polyurethane acrylates in the embodiments of this invention.

[0046] It should be noted that the UV resins used in the embodiments of the present invention are not limited to brands and models such as FSP2159, FSP3897, and FSP7241. Those skilled in the art will understand that polyurethane acrylate resins are typically produced by reacting long-chain diols with diisocyanates, followed by end-capping with hydroxyl acrylates; polyester acrylates are typically obtained from polyester diols and acrylic acid, or by reacting hydroxyl acrylates with acid anhydrides, followed by esterification with polyester diols. Products with such structures or their modified forms can be used in the embodiments of the present invention.

[0047] Typically, acrylic materials are polymerized from methyl methacrylate monomers, which are relatively hard among organic materials, making them difficult for general coatings and inks to penetrate. UV resins, on the other hand, generally contain polyurethane or polyester structures. The structures of these two materials differ significantly, making it difficult for the chain segments to form mechanical entanglement and lacking reactive covalent bonds, thus hindering adhesion. UV coatings rely on double bond addition reactions, which involve strong shrinkage. This intense shrinkage of the coating while the substrate relaxes leads to shear stress at the interface, ultimately causing adhesion failure. Higher functionality resins or monomers exhibit more severe shrinkage, resulting in poorer adhesion and ultimately hindering the improvement of abrasion resistance.

[0048] While synthetic methods or modified grafting can improve coating adhesion to some extent, the monomer ratios and parameter control in chemical synthesis are quite complex, and product stability requires long-term exploration and adjustment. A single resin typically cannot meet all requirements, and the final formulation often relies on blending to adjust performance, resulting in a disproportionate input-output ratio.

[0049] To overcome the aforementioned problems, the inventors conducted extensive research and experimental screening, discovering that styrene-acrylonitrile copolymer (SAN) resin can form a high-performance blend system with the polyester acrylate and polyurethane acrylate main resins in this invention. The mechanism of action lies in the fact that the SAN resin molecule contains moderately polar benzene ring macromolecular groups on its side chains, making it less prone to crystallization and exhibiting good transparency. Simultaneously, it contains strongly polar nitrile groups, which can generate intermolecular attraction with the polyurethane and ester bonds in the UV resin.

[0050] Furthermore, the solubility parameter of polystyrene segments in SAN resin is 17.4-19×10⁻⁶. 3 (J / m) 3 ) 1 / 2 The solubility parameters of the polyacrylonitrile segments are 25.6-31.5×10⁻⁶.3 (J / m) 3 ) 1 / 2 This characteristic gives it broad compatibility in oil-based systems, expanding the range of UV resins available. Meanwhile, PMMA has a solubility parameter of 18.4 × 10⁻⁶. 3 (J / m) 3 ) 1 / 2 Because of its similarity to polystyrene, SAN resin can form a good mechanical hinge interlock with the PMMA substrate, thus significantly increasing interfacial adhesion. Furthermore, SAN resin also acts as a good "bridging" agent between the coating and subsequent printing inks, thereby giving the coating excellent recoatability.

[0051] After identifying SAN resin as a key component, this invention further optimized its ratio with the main resin. SAN resin and polyester acrylate form the main structural components of the system. SAN resin provides adhesion and some abrasion resistance, while the lower functionality and softer chain segments of polyester acrylate help release curing stress, which is beneficial for adhesion stability. Polyurethane acrylate has high functionality and can reinforce abrasion resistance, but its addition amount must be strictly controlled, otherwise it can easily lead to coating brittleness. The final ratio was obtained by systematically balancing adhesion, abrasion resistance, and component compatibility stability.

[0052] See Figure 1 The main steps of the preparation method of the light-curable adhesive composition are shown.

[0053] The embodiments of the present invention also provide a method for preparing the photocurable adhesive composition, comprising the following steps:

[0054] Step S100: Prepare a photoinitiator mixture.

[0055] Mix a portion of the active monomer with the photoinitiator until the photoinitiator is completely dissolved and there are no particles in the solution to obtain a photoinitiator mixture, and let it stand for later use.

[0056] Step S200: Prepare SAN resin mixture.

[0057] The remaining active monomers are mixed with SAN resin, and the mixture is heated to 55-60°C at a disperser speed of 800-1200 rpm and maintained for 0.5-1.5 hours (preferably 1 hour) to completely dissolve the SAN resin particles, thus obtaining a SAN resin mixture.

[0058] Step S300: Mix evenly.

[0059] The photoinitiator mixture from step S100 is mixed with the SAN resin mixture from step S200 and stirred until homogeneous.

[0060] Step S400: Add the remaining components.

[0061] Polyester acrylate and polyurethane acrylate are added to the mixture obtained after stirring in step S300. The mixture is dispersed for 20-40 minutes (preferably 30 minutes) at a speed of 750-850 rpm (preferably 800 rpm) in a disperser until it is fully mixed. This yields the light-curing adhesive composition of each embodiment of the present invention.

[0062] The following provides a detailed description through multiple embodiments and comparative examples:

[0063] Those skilled in the art will understand that, in the following embodiments, the commercially available product grades of SAN resin include, but are not limited to: Formosa Plastics NX3400, NX3200, NF2200, NF2100, Chi Mei PN-106, PN-107, PN-117, PN-118L150, PN-127, PN-128L150, PN-138H, AS D-168, AS D-178, and others such as AS-115, DG-AS106, 80HF, etc.

[0064] Example 1:

[0065] Dissolve 2 parts of photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2 parts of 1-hydroxy-cyclohexylbenzophenone in 10 parts of 1,6-hexanediol diacrylate until no particles remain in the solution. Let the photoinitiator mixture stand before use.

[0066] Take another 15 parts of N,N-dimethylacrylamide, 10 parts of 1,6-hexanediol diacrylate and 25 parts of SAN resin and mix them. The disperser speed is 800-1200 rpm and the temperature is raised to 55-60℃. Keep it for 1 hour to completely dissolve the resin particles. Then add it to the photoinitiator mixture and stir evenly.

[0067] Add 15 parts of polyester acrylate FSP7241, 10 parts of polyurethane acrylate FSP3897, 5 parts of dipentaerythritol hexaacrylate, and 12 parts of trimethylolpropane triacrylate to the above mixture. Disperse at 800 rpm for 30 minutes to mix thoroughly.

[0068] Finally, the film is coated onto the PMMA material by imprinting, with a film thickness of 4-8 μm.

[0069] Example 2:

[0070] Dissolve 2 parts of photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 1 part of benzoin dimethyl ether, and 2 parts of 1-hydroxy-cyclohexylbenzophenone in 12 parts of 1,6-hexanediol diacrylate until no particles remain in the solution. Let the photoinitiator mixture stand for later use.

[0071] Take another 15 parts of N,N-dimethylacrylamide, 5 parts of 1,4-butanediol diacrylate and 20 parts of SAN resin and mix them. The disperser speed is 800-1200 rpm and the temperature is raised to 55-60℃. Maintain this temperature for 1 hour to completely dissolve the resin particles. Then add the mixture to the photoinitiator mixture and stir evenly.

[0072] Add 25 parts of polyester acrylate FSP7241, 10 parts of polyurethane acrylate FSP3897, 8 parts of dipentaerythritol hexaacrylate, and 10 parts of trimethylolpropane triacrylate to the above mixture. Disperse at 800 rpm for 30 minutes to mix thoroughly.

[0073] Finally, the film is coated onto the PMMA material by imprinting, with a film thickness of 4-8 μm.

[0074] Example 3:

[0075] Dissolve 3 parts of photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 3 parts of 2-hydroxy-2-methyl-1-phenylpropanone in 15 parts of 1,6-hexanediol diacrylate until no particles remain in the solution. Let the photoinitiator mixture stand before use.

[0076] Take another 15 parts of vinyl caprolactam and 15 parts of SAN resin and mix them. Use a disperser with a speed of 800-1200 rpm and a temperature of 55-60℃ for 1 hour to completely dissolve the resin particles. Then add the mixture to the photoinitiator mixture and stir evenly.

[0077] Add 20 parts of polyester acrylate FSP7241, 15 parts of polyurethane acrylate FSP2159, 15 parts of dipentaerythritol hexaacrylate, and 5 parts of pentaerythritol triacrylate to the above mixture. Disperse at 800 rpm for 30 minutes to ensure thorough mixing.

[0078] Finally, the film is coated onto the PMMA material by imprinting, with a film thickness of 4-8 μm.

[0079] Example 4:

[0080] Dissolve 2.5 parts of photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2.5 parts of 2-hydroxy-2-methyl-1-phenylpropanone in 15 parts of 1,6-hexanediol diacrylate until no particles remain in the solution. Let the photoinitiator mixture stand before use.

[0081] Take another 7 parts of vinylcaprolactam, 10 parts of tetrahydrofuran acrylate and 17 parts of SAN resin and mix them. The disperser speed is 800-1200 rpm and the temperature is raised to 55-60℃. Maintain this temperature for 1 hour to completely dissolve the resin particles. Then add the mixture to the photoinitiator mixture and stir evenly.

[0082] Add 27 parts of polyester acrylate FSP7241, 12 parts of polyurethane acrylate FSP3897, 8 parts of dipentaerythritol hexaacrylate, and 6 parts of pentaerythritol triacrylate to the above mixture. Disperse at 800 rpm for 30 minutes to ensure thorough mixing.

[0083] Finally, the film is coated onto the PMMA material by imprinting, with a film thickness of 4-8 μm.

[0084] Example 5:

[0085] Dissolve 2.5 parts of photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2.5 parts of benzoin dimethyl ether in 13 parts of 1,6-hexanediol diacrylate until no particles remain in the solution. Let the photoinitiator mixture stand for later use.

[0086] Take another 14 parts of N,N-dimethylacrylamide, 14 parts of vinylcaprolactam and 28 parts of SAN resin and mix them. The disperser speed is 800-1200 rpm and the temperature is raised to 55-60℃. Keep it for 1 hour to completely dissolve the resin particles. Then add it to the photoinitiator mixture and stir evenly.

[0087] Add 18 parts of polyester acrylate FSP7241, 13 parts of polyurethane acrylate FSP2159, 9 parts of dipentaerythritol hexaacrylate, and 10 parts of trimethylolpropane triacrylate to the above mixture. Disperse at 800 rpm for 30 minutes to ensure thorough mixing.

[0088] Finally, the film is coated onto the PMMA material by imprinting, with a film thickness of 4-8 μm.

[0089] Comparative Example 1:

[0090] Comparative Example 1 does not contain SAN resin.

[0091] Use 10 parts of 1,6-hexanediol diacrylate and 15 parts of vinylcaprolactam to fully dissolve 2.5 parts of photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2.5 parts of 1-hydroxy-cyclohexylbenzophenone until there are no particles in the solution.

[0092] Then, while maintaining a low speed of 600 rpm in the disperser, add the following in sequence: 15 parts of trimethylolpropane triacrylate, 10 parts of dipentaerythritol hexaacrylate, 25 parts of polyester acrylate FSP7241, 8 parts of polyurethane acrylate FSP2159, and 7 parts of polyurethane acrylate FSP3897. Increase the speed of the disperser to 800 rpm and disperse for 30 minutes to mix thoroughly.

[0093] Finally, the film is coated onto the PMMA material by imprinting, with a film thickness of 4-8 μm.

[0094] Comparative Example 2:

[0095] Comparative Example 2 did not contain SAN resin and the resin ratio was adjusted.

[0096] Dissolve 2 parts of photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 3 parts of 1-hydroxy-cyclohexylbenzophenone in 8 parts of 1,6-hexanediol diacrylate and 15 parts of vinylcaprolactam until no particles remain in the solution.

[0097] Then, while keeping the disperser at a low speed of 600 rpm, add the following in sequence: 15 parts N,N-dimethylacrylamide, 15 parts trimethylolpropane triacrylate, 30 parts polyester acrylate FSP7241, and 15 parts polyurethane acrylate FSP3897. Increase the disperser speed to 800 rpm and disperse for 30 minutes to mix thoroughly.

[0098] Finally, the film is coated onto the PMMA material by imprinting, with a film thickness of 4-8 μm.

[0099] Comparative Example 3

[0100] The PMMA material (substrate) in Comparative Example 3 was preheated.

[0101] Use 10 parts of 1,6-hexanediol diacrylate and 15 parts of vinylcaprolactam to fully dissolve 2.5 parts of photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2.5 parts of 1-hydroxy-cyclohexylbenzophenone until there are no particles in the solution.

[0102] Then, while maintaining a low speed of 600 rpm in the disperser, add the following in sequence: 15 parts of trimethylolpropane triacrylate, 10 parts of dipentaerythritol hexaacrylate, 25 parts of polyester acrylate FSP7241, 8 parts of polyurethane acrylate FSP2159, and 7 parts of polyurethane acrylate FSP3897. Increase the speed of the disperser to 800 rpm and disperse for 30 minutes to mix thoroughly.

[0103] After preheating the PMMA material board in a 50℃ oven for 50-60 minutes, apply the prepared UV transfer adhesive of Comparative Example 3 onto the PMMA material by imprinting, with a film thickness of 4-8μm.

[0104] The test results of the above embodiments and comparative examples are shown in Table 1:

[0105] Table 1 Performance test results of UV-curable adhesive compositions

[0106]

[0107] In the above performance tests, the adhesion test was performed according to standard GB / T 13217.7-2023. The RCA abrasion test refers to the paper tape abrasion test, recording the number of times the coating is worn through. Recoating performance refers to the adhesion after the adhesive composition has been fully cured on a PMMA board and then re-imprinted with the adhesive or printed with other plastic inks, also performed according to standard GB / T13217.7-2023. Based on the test results of the above examples and comparative examples, it can be seen that the photocurable adhesive composition of the present invention achieves excellent performance without the need for acrylic substrate pretreatment during application.

[0108] In Comparative Example 1, although the inclusion of 18.9% hexafunctional monomers and decafunctional resin FSP2159, among other highly functional reactive groups, was intended to improve abrasion resistance, actual tests often showed that the coating only penetrated after 30-40 abrasion cycles. This is because the UV coating lacks a strong bond with the substrate. Although the overall strength and hardness of the coating are improved, slippage occurs between the coating and the substrate under repeated friction during testing, resulting in poor abrasion resistance.

[0109] In Comparative Example 2, no high-functionality monomers or resins were added, and the amount of FSP3897 resin with good extensibility was doubled to fully offset the internal shrinkage problem of the system. The test results showed that while the adhesion was improved, the abrasion resistance did not meet the standard.

[0110] Comparative Example 3 and Comparative Example 1 had the same components and dosages, the difference being that the PMMA material plate was preheated. The test results showed that the adhesion and abrasion resistance were improved to a limited extent, but still not as good as the above embodiments.

[0111] See Figure 2 The diagram illustrates the principle of applying the photocurable adhesive composition of the present invention using an imprinting method.

[0112] In specific applications, the photocurable adhesive composition of the present invention, such as... Figure 2As shown, the application is typically done using a transfer (imprinting) method. The process is as follows: First, the photocurable adhesive composition prepared in this embodiment is uniformly coated onto the surface of the PMMA material, forming a coating (adhesive layer) with a thickness of 4-8 μm. Then, a release film (e.g., PET or PP release film) is placed over the adhesive layer as a transfer carrier, positioning the adhesive layer between the release film and the PMMA material (i.e.,...). Figure 2 (The three-layer structure shown); then, after passing through or peeling off the release film, it is cured in one step using ultraviolet light.

[0113] The curing conditions for the photocurable adhesive composition of this invention are relatively relaxed. Mercury lamps, halogen lamps, or LED lamps can be used, with an irradiation distance of 10cm, a medium power of 20-50W, and a cumulative energy of 500-800mJ / cm. 2 After curing, the release film is peeled off, and the UV-cured adhesive layer (decorative texture layer or coating layer) is firmly adhered to the PMMA material surface. The adhesive composition of the present invention does not require substrate preheating during application, does not require post-curing, and has excellent adhesion after curing (up to 5B), with a shelf life of at least 12 months after curing.

[0114] This invention employs a pure free radical, one-time photocuring method, eliminating the need for post-curing. Compared to the higher cost of cationic systems, the SAN resin used in this invention is inexpensive, resulting in significant cost reduction.

[0115] Furthermore, the combination of SAN and UV resin in this invention already meets the adhesion requirements, so there is no need to add other adhesion promoters, such as silane coupling agents.

[0116] The photocurable adhesive composition for acrylic substrates, its preparation method, and its application provided by the embodiments of the present invention have at least one or a portion of the following advantages:

[0117] (1) By using a specific weight ratio of photoinitiator, active monomer, SAN resin, polyester acrylate and polyurethane acrylate, the adhesive composition has excellent adhesion, wear resistance and curing efficiency. It is a 100% solid content, solvent-free system with no VOC volatilization during the curing process, and is environmentally friendly.

[0118] (2) The relative density of SAN resin is 1.06-1.08, and the tensile strength is 700-820 kg / cm². 2 Flexural strength is 1000-1350 kg / cm² 2With a Rockwell hardness of 78-85, a heat distortion temperature of 89-100℃, and a melt index of 1-5 g / 10min, SAN resin exhibits the best compatibility with UV resin within this range. It dissolves fully in the active monomer and can provide sufficient structural support and wear-resistant foundation for the coating.

[0119] (3) The active monomers are selected from 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, N,N-dimethylacrylamide, tetrahydrofuran acrylate, and vinylcaprolactam. Low-functionality active monomers are used to reduce viscosity, dissolve photoinitiators, and promote adhesion. High-functionality active monomers increase hardness while maintaining viscosity to meet different construction needs.

[0120] (4) The photoinitiator is selected from benzoin dimethyl ether, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, and 1-hydroxy-cyclohexylbenzophenone. It has the effect of absorbing ultraviolet light at a wavelength of 250-400 nm, has good thermal stability, low yellowing, good solubility in active monomers, is easy to store, does not produce crystal precipitation, and can be used in combination for LED light curing.

[0121] (5) Polyester acrylate has a viscosity of 1500-80000 mPa·s at 25℃, a refractive index of 1.44-1.53, and a functionality of 2-4. It has low odor, low irritation, good wettability and flexibility, good adhesion to plastic substrates, and can improve the curing rate; Polyurethane acrylate has a functionality of 2-10, a viscosity of 2000-80000 mPa·s at 25℃, and a refractive index of 1.44-1.53. It can improve the physical and chemical properties of coating such as hardness, wear resistance and water resistance.

[0122] (6) The UV-curable adhesive composition is a 100% solids-containing, solvent-free system. After one-time UV curing, the adhesion to PMMA substrate reaches 5B (standard GB / T 13217.7-2023), the RCA abrasion resistance test is 150-200 times, the light transmittance is over 96%, and the overall performance is excellent.

[0123] (7) The light-curing adhesive composition is a 100% solid content, solvent-free system and does not contain silane coupling agents, which avoids the defects of silane coupling agents being easy to hydrolyze and sensitive to temperature, humidity and storage. At the same time, it simplifies the formulation composition, reduces the cost of raw materials, and the product shelf life can reach more than 12 months.

[0124] (8) The preparation method of the present invention is to obtain a photoinitiator mixture by mixing and dissolving a portion of the active monomer with the photoinitiator, and then dispersing the remaining active monomer with SAN resin at 55-60℃ and 800-1200 rpm for 0.5-1.5 hours to completely dissolve the SAN resin. Then, the two mixtures are mixed and polyester acrylate and polyurethane acrylate are added and dispersed evenly. The process is simple, the operation is controllable, and it is easy to industrialize. It can also ensure the full dispersion of each component and the uniformity and stability of the system.

[0125] (9) Disperse at a speed of 750-850 rpm for 20-40 minutes to ensure that the components are fully mixed and uniform. This process is mild and energy-efficient, avoiding local overheating and component degradation that may be caused by high-speed dispersion.

[0126] (10) The light-curing adhesive composition of the present invention can be applied to the transfer or coating of decorative textures on the surface of PMMA substrate. During construction, it only needs to be cured by ultraviolet light once. No substrate preheating treatment or post-curing is required, which greatly simplifies the production process, shortens the production cycle, reduces production costs, and improves production efficiency.

[0127] While some embodiments of the present general inventive concept have been shown and described, those skilled in the art will understand that changes may be made to these embodiments without departing from the principles and spirit of the present general inventive concept, the scope of which is defined by the claims and their equivalents.

Claims

1. A photocurable adhesive composition for acrylic substrates, characterized in that, The light-curing adhesive composition comprises the following components in parts by weight: Photoinitiator, 4-8 parts; Active monomer, 45-60 parts; Styrene-acrylonitrile copolymer resin, 10-30 parts; Polyester acrylate, 10-35 parts; Polyurethane acrylate, 5-15 parts.

2. The photocurable adhesive composition according to claim 1, characterized in that, The styrene-acrylonitrile copolymer resin has a relative density of 1.06-1.08, a tensile strength of 700-820 kg / cm 2 , a bending strength of 1000-1350 kg / cm 2 , a Rockwell hardness of 78-85, a heat distortion temperature of 89-100°C, and a melt index of 1-5 g / 10 min.

3. The photocurable adhesive composition according to claim 1, characterized in that, The active monomer is any one or any combination thereof, of 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, N,N-dimethylacrylamide, tetrahydrofuran acrylate, and vinylcaprolactam.

4. The photocurable adhesive composition according to claim 1, characterized in that, The photoinitiator is any one or any combination thereof of benzoin dimethyl ether, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, and 1-hydroxy-cyclohexylbenzophenone.

5. The photocurable adhesive composition according to claim 1, characterized in that, The polyester acrylate has a viscosity of 1500-80000 mPa·s at 25°C, a refractive index of 1.44-1.53, and a functionality of 2-4. The polyurethane acrylate has a viscosity of 2000-80000 mPa·s at 25°C, a refractive index of 1.44-1.53, and a functionality of 2-10.

6. The light-curing adhesive composition according to any one of claims 1-5, characterized in that, The photocurable adhesive composition is a 100% solids, solvent-free system. After being cured by ultraviolet light in one step, the light-curing adhesive composition achieves an adhesion of 5B to acrylic substrates, a paper tape abrasion resistance test of 150-200 cycles, and a light transmittance of ≥96%.

7. The photocurable adhesive composition according to claim 6, characterized in that, The photocurable adhesive composition does not contain silane coupling agents.

8. A method for preparing a photocurable adhesive composition for an acrylic substrate, said preparation method being used to prepare a photocurable adhesive composition according to any one of claims 1-7, characterized in that, The preparation method includes the following steps: Step S100: Mix a portion of the active monomer with the photoinitiator to completely dissolve the photoinitiator, thereby obtaining a photoinitiator mixture; Step S200: Mix the remaining active monomer with the styrene-acrylonitrile copolymer resin and disperse it at 55-60℃ and 800-1200 rpm for 0.5-1.5 hours to completely dissolve the styrene-acrylonitrile copolymer resin and obtain a styrene-acrylonitrile copolymer resin mixture. Step S300: Mix the photoinitiator mixture with the styrene-acrylonitrile copolymer resin mixture and stir until homogeneous; Step S400: Add polyester acrylate and polyurethane acrylate to the mixture obtained in step S300, disperse evenly, and obtain the light-curing adhesive composition.

9. The preparation method according to claim 8, characterized in that, In step S400, the rotation speed for uniform dispersion is 750-850 rpm, and the dispersion time is 20-40 minutes.

10. The application of a light-curing adhesive composition in the transfer or coating of decorative patterns on acrylic substrates, characterized in that, The photocurable adhesive composition is a photocurable adhesive composition according to any one of claims 1-7 or a photocurable adhesive composition prepared by the preparation method according to any one of claims 8-9.

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