An acrylate copolymer, a preparation method thereof, and a UV-cured pressure-sensitive adhesive and a UV-cured protective film

Abstract

The application provides an acrylate copolymer, a preparation method thereof and ultraviolet light curing pressure sensitive adhesive and protective film, and relates to the technical field of adhesives.The acrylate copolymer provided by the application comprises the following preparation raw materials in mass fraction: 98-100 parts of acrylate monomer, 0.01-2 parts of chain transfer agent and 0.01-2 parts of photoinitiator; the acrylate monomer comprises the following monomers in mass percentage: 66-70% of 2-ethylhexyl acrylate, 28-30% of isobornyl acrylate and 1-4% of beta-acryloyloxypropionic acid.The application provides an ultraviolet light curing pressure sensitive adhesive, and components thereof comprise the acrylate copolymer, active diluent and photoinitiator.The ultraviolet light curing pressure sensitive adhesive provided by the application is a solvent-free system, and the protective film obtained by the ultraviolet light curing mode has very low peeling force, good re-peeling property, and good weather resistance and air exhaust property.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and in particular to an acrylate copolymer, its preparation method, and a UV-curable pressure-sensitive adhesive and a UV-curable protective film. Background Technology

[0002] Pressure-sensitive adhesive films are widely used in packaging, encapsulation, commercial labeling, and product protection, and are closely related to daily life. Solvent-based pressure-sensitive adhesive protective films contain a large amount of volatile solvents, which can cause serious environmental pollution. With the continuous improvement of living standards, environmental protection is receiving increasing attention. Therefore, solvent-free, pollution-free, environmentally friendly, and safe UV-curable pressure-sensitive adhesive films are playing an increasingly important role.

[0003] Currently, UV-cured pressure-sensitive adhesive films have poor re-peelability, making re-peeling difficult or impossible. At the same time, they have poor weather resistance and cannot meet the increasingly stringent usage requirements as protective films. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide an acrylate copolymer, its preparation method, and a UV-curable pressure-sensitive adhesive and a UV-curable protective film. The UV-curable pressure-sensitive adhesive and UV-curable protective film formed from the acrylate copolymer provided by this invention have the characteristics of good re-peelability and good weather resistance.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides an acrylate copolymer comprising the following raw materials in parts by weight: 98-100 parts of acrylate monomers, 0.01-2 parts of chain transfer agent, and 0.01-2 parts of photoinitiator; The acrylate monomers include the following monomers in the following mass percentages: 66-70% 2-ethylhexyl acrylate, 28-30% isobornyl acrylate, and 1-4% β-acryloyloxypropionic acid.

[0006] Preferably, the acrylate monomers comprise the following monomers in weight percentages: 70% 2-ethylhexyl acrylate, 28-29% isobornyl acrylate, and 1-2% β-acryloyloxypropionic acid.

[0007] Preferably, the chain transfer agent is n-dodecyl mercaptan; the photoinitiator is one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinobenzylphenyl)butanone, 2,2-dimethoxyacetophenone, 2,2-diethoxyacetophenone, benzoin methyl ether, and benzoin ethyl ether.

[0008] Preferably, the viscosity of the acrylate copolymer at 25°C is 120~475 cps.

[0009] This invention provides a method for preparing the acrylate copolymer described above, comprising the following steps: The acrylate monomers, chain transfer agents, and photoinitiators are mixed, and a copolymerization reaction is initiated by ultraviolet light irradiation to obtain the acrylate copolymer.

[0010] Preferably, the wavelength of the ultraviolet light is 200~400nm, and the light intensity is 5~15W / cm. 2 The ultraviolet irradiation time is until the copolymer system obtained by mixing is heated to 10~15°C.

[0011] This invention provides a UV-curable pressure-sensitive adhesive, wherein the components of the UV-curable pressure-sensitive adhesive include an acrylate copolymer, a reactive diluent, and a photoinitiator; the mass ratio of the acrylate copolymer to the reactive diluent is (98~104):(0.1~3), and the mass of the photoinitiator is 0.05~2% of the mass of the UV-curable pressure-sensitive adhesive; the acrylate copolymer is the acrylate copolymer described in the above technical solution or the acrylate copolymer prepared by the preparation method described in the above technical solution.

[0012] Preferably, the reactive diluent is one or more of 1,6-hexanediol diacrylate, polypropylene glycol diacrylate, polyethylene glycol diacrylate, triethylene glycol diacrylate, 1,4-butanediol diacrylate, 3-hydroxy-2,2-dimethylpropyl-3-hydroxy-2,2-dimethylpropyl diacrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, and pentaerythritol tetraacrylate. The photoinitiator is one or more of the following: 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinobenzylphenyl)butanone, 2,2-dimethoxyacetophenone, 2,2-diethoxyacetophenone, benzoin methyl ether, and benzoin ethyl ether.

[0013] The present invention provides a peelable UV-curable protective film, comprising a substrate layer, an intermediate layer and a release film layer stacked sequentially, wherein the intermediate layer is an adhesive film layer formed by UV curing of the UV-curable pressure-sensitive adhesive described in the above technical solution.

[0014] Preferably, the thickness of the adhesive film layer is 5~20μm.

[0015] This invention provides an acrylate copolymer comprising the following raw materials in parts by weight: 98-100 parts of acrylate monomers, 0.01-2 parts of chain transfer agent, and 0.01-2 parts of photoinitiator; wherein the acrylate monomers comprise the following monomers in weight percentages: 66-70% 2-ethylhexyl acrylate, 28-30% isobornyl acrylate, and 1-4% β-acryloyloxypropionic acid. This invention uses acrylate monomers, a blend of 2-ethylhexyl acrylate, isobornyl acrylate, and β-acryloyloxypropionic acid in a specific ratio, as reactive monomers. These acrylate monomers form the main chain and control the glass transition temperature. β-acryloyloxypropionic acid not only participates in the polymerization reaction to form copolymers but also has a low glass transition temperature (Tg) (approximately 37°C). Its addition significantly improves the flexibility and elasticity of the final polymer. The carboxyl groups at the molecular ends can interact strongly with the surfaces of various substrates such as metals, glass, and wood, thereby greatly enhancing the adhesion between the adhesive and the substrate and improving the adhesive's weather resistance. 2-ethylhexyl acrylate provides a flexible carbon chain backbone, while isobornyl acrylate provides a rigid carbon chain backbone. The chain transfer agent effectively controls the molecular weight and molecular weight distribution. During the chain growth process of the free radical reaction, it terminates the original chain and initiates a new chain, thereby effectively reducing the average molecular weight of the polymer and consequently reducing the polymer viscosity. Lower viscosity polymers are beneficial for coating. This invention utilizes the combined action of various raw materials to enable the UV-curable pressure-sensitive adhesive and UV-curable protective film formed from the provided acrylate copolymer to possess excellent re-peelability and weather resistance.

[0016] This invention provides a UV-curable pressure-sensitive adhesive, wherein the components of the UV-curable pressure-sensitive adhesive include the acrylate copolymer, reactive diluent, and photoinitiator described in the above technical solution. The UV-curable pressure-sensitive adhesive provided by this invention is a solvent-free system, and the protective film obtained by UV curing has extremely low peel strength, good re-peelability, and good weather resistance and air release properties.

[0017] The results of the examples show that the UV-curable protective film formed by the UV-curable pressure-sensitive adhesive has a 180° peel strength of 0.161~0.265 N / 25mm (glass), an air permeability of over 96%, and no ghosting or adhesive residue after being placed in a temperature and humidity environment of 60℃ / 90%RH and 85℃ / 85%RH for 7 days. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the peelable UV-curable protective film provided by the present invention. Figure 1 In the middle, 1-substrate layer, 2-intermediate layer (adhesive film layer), 3-release film layer. Detailed Implementation

[0019] This invention provides an acrylate copolymer comprising the following raw materials in parts by weight: 98-100 parts of acrylate monomers, 0.01-2 parts of chain transfer agent, and 0.01-2 parts of photoinitiator (denoted as the first photoinitiator); The acrylate monomers include the following monomers in the following mass percentages: 66-70% 2-ethylhexyl acrylate, 28-30% isobornyl acrylate, and 1-4% β-acryloyloxypropionic acid.

[0020] Unless otherwise specified, all raw materials involved in this invention are commercially available products well known in the art.

[0021] The raw materials for preparing the acrylate copolymer provided by the present invention include 98 to 100 parts of acrylate monomers, which can be 98, 99 or 100 parts by mass.

[0022] In this invention, the acrylate monomers comprise the following monomers in the following mass percentages: 66-70% 2-ethylhexyl acrylate, 28-30% isobornyl acrylate, and 1-4% β-acryloyloxypropionic acid. The mass percentage of 2-ethylhexyl acrylate in the acrylate monomers can be 66%, 66.7%, 67%, 68%, 69%, or 70%, preferably 70%; the mass percentage of isobornyl acrylate can be 28%, 29%, or 30%, preferably 28-29%; and the mass percentage of β-acryloyloxypropionic acid can be 1%, 2%, 3%, 3.3%, or 4%, preferably 1-2%. This invention controls the proportions of 2-ethylhexyl acrylate, isobornyl acrylate, and β-acryloyloxypropionic acid within the above ranges to ensure the material has suitable peel strength while avoiding contamination caused by excessive small molecule residues.

[0023] In this invention, the acrylate monomers constitute the main chain and regulate the glass transition temperature; among them, β-acryloyloxypropionic acid can not only participate in the polymerization reaction to form copolymers, but also has a low glass transition temperature (Tg) (about 37°C). Its addition can significantly improve the flexibility and elasticity of the final polymer. The carboxyl groups at the molecular ends can have strong physical or chemical interactions with the surfaces of various substrates such as metal, glass, and wood, thereby greatly enhancing the adhesion between the adhesive and the substrate and improving the weather resistance of the adhesive.

[0024] Based on 1 part by mass of the acrylate monomers, the raw materials for preparing the acrylate copolymers provided by this invention include 0.01 to 2 parts of chain transfer agent, which can be 0.1, 0.2, 0.4, 0.5, or 1 part. In this invention, the chain transfer agent is preferably n-dodecyl mercaptan; the chain transfer agent can effectively control the molecular weight and molecular weight distribution, terminating the original chain and starting a new chain during the chain growth process of the free radical reaction, thereby effectively reducing the average molecular weight of the polymer and thus reducing the polymer viscosity. The molecular weight of the polymer directly affects the performance of the polymer, so the amount of chain transfer agent needs to be precisely controlled. By controlling the amount of chain transfer agent within the above range, this invention can obtain acrylate copolymers with a weight-average molecular weight of 20,000 to 200,000 (specifically 30,000 to 95,000), which have moderate viscosity, are easy to apply, and can undergo secondary crosslinking under the action of photoinitiators and reactive diluents to obtain a protective film adhesive with low peel strength and low exudation.

[0025] Based on 1 part by mass of the acrylate monomers, the raw materials for preparing the acrylate copolymers provided by the present invention include 0.01 to 2 parts of a first photoinitiator, which can be 0.05, 0.1, 0.5, 0.9, 1, or 1.5 parts. In the present invention, the first photoinitiator is preferably one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinobenzylphenyl)butanone, 2,2-dimethoxyacetophenone, 2,2-diethoxyacetophenone, benzoin methyl ether, and benzoin ethyl ether. In this invention, the first photoinitiator functions as follows: (1) absorbing UV light to generate active species: under UV irradiation, the photoinitiator decomposes (e.g., α-decomposition type) or abstracts hydrogen to generate free radicals, initiating monomer polymerization; (2) controlling reaction time: the start and stop of polymerization can be precisely controlled by switching on and off the UV light source (e.g., UV lamp), which is suitable for continuous coating-curing processes. Photoinitiator residues or degradation products may migrate, affecting environmental resistance testing (e.g., causing fogging or yellowing). Therefore, this invention uses a low-migration, high-efficiency decomposition type photoinitiator and controls the dosage.

[0026] In this invention, the viscosity of the acrylate copolymer at 25°C is 120~475 cps, and can be 220~315 cps. This invention controls the viscosity of the acrylate copolymer within the above range to facilitate coating.

[0027] This invention provides a method for preparing the acrylate copolymer described above, comprising the following steps: The acrylate monomer, chain transfer agent, and first photoinitiator are mixed, and a copolymerization reaction is initiated by ultraviolet light irradiation to obtain the acrylate copolymer.

[0028] In this invention, the mixing of the acrylate monomer, chain transfer agent and first photoinitiator is preferably carried out under nitrogen protection at room temperature. The mixing is preferably stirred, and the stirring speed can be 100 r / min, and the stirring time can be 20~40 min, specifically 30 min. The stirring ensures that the raw materials are mixed evenly.

[0029] In this invention, the wavelength of the ultraviolet light is preferably 200~400nm, and can be 365nm, and the light intensity is preferably 5~15W / cm². 2 It can be 10W / cm 2 The ultraviolet irradiation time is preferably until the temperature of the copolymer system obtained by mixing is raised to 10~15°C (that is, the ultraviolet light source irradiation is stopped when the system temperature is raised to 10~15°C). The present invention controls the viscosity of the prepared acrylate copolymer to be 120~475cps (25°C) by controlling the exothermic reaction.

[0030] This invention provides a UV-curable pressure-sensitive adhesive, wherein the components of the UV-curable pressure-sensitive adhesive include an acrylate copolymer, a reactive diluent, and a photoinitiator (denoted as the second photoinitiator); the mass ratio of the acrylate copolymer to the reactive diluent is (98~104):(0.1~3), and the mass of the second photoinitiator is 0.05~2% of the mass of the UV-curable pressure-sensitive adhesive; the acrylate copolymer is the acrylate copolymer described in the above technical solution or the acrylate copolymer prepared by the preparation method described in the above technical solution.

[0031] In this invention, the mass ratio of the acrylate copolymer to the reactive diluent can be (98~104):(0.1~1), specifically 101.3:(0.35~0.7). The mass of the second photoinitiator can be 0.1~1% of the mass of the UV-curable pressure-sensitive adhesive, specifically 0.15~0.5%. This invention initiates the reaction between the reactive diluent and the acrylate copolymer through the second photoinitiator. The reactive diluent reacts with multiple acrylate copolymers to obtain a highly three-dimensional network crosslinked adhesive with extremely low peel strength. The efficient reaction results in minimal small molecule residue and excellent weather resistance. If the proportion of reactive diluent is too low, the degree of crosslinking is insufficient, leading to poor weather resistance; if the proportion is too high, the adhesive will be over-crosslinked, losing its creep space and becoming unadhesive. The second photoinitiator is also a crucial condition for initiating the reaction; excessively high or low proportions will cause crosslinking problems, thus affecting the final performance.

[0032] In this invention, the reactive diluent is preferably one or more of the following: 1,6-hexanediol diacrylate, polypropylene glycol diacrylate, polyethylene glycol diacrylate, triethylene glycol diacrylate, 1,4-butanediol diacrylate, 3-hydroxy-2,2-dimethylpropyl-3-hydroxy-2,2-dimethylpropyl diacrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, and pentaerythritol tetraacrylate. The second photoinitiator is preferably one or more of the following: 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinobenzylphenyl)butanone, 2,2-dimethoxyacetophenone, 2,2-diethoxyacetophenone, benzoin methyl ether, and benzoin ethyl ether. The acrylic copolymer and reactive diluent undergo secondary crosslinking under the action of the second photoinitiator, increasing the degree of crosslinking, enhancing cohesion, reducing small molecule residues, and obtaining an adhesive with low peel strength and low pollution.

[0033] This invention provides a method for preparing the UV-curable pressure-sensitive adhesive described in the above technical solution, comprising the following steps: The acrylate copolymer, reactive diluent, and second photoinitiator are mixed and defoamed to obtain the UV-curable pressure-sensitive adhesive.

[0034] In this invention, the mixing of the acrylate copolymer, reactive diluent, and second photoinitiator is preferably carried out at room temperature under stirring conditions. The stirring speed can be 100 r / min, and the time is sufficient to ensure that all components are mixed evenly. In this invention, the defoaming is preferably carried out under static conditions, and the defoaming time is preferably 20-40 min, specifically until no obvious bubbles are visible to the naked eye.

[0035] This invention provides a peelable UV-curable protective film, comprising a substrate layer, an intermediate layer, and a release film layer stacked sequentially. The intermediate layer is a film layer formed by UV-curable pressure-sensitive adhesive as described in the above technical solutions or UV-curable pressure-sensitive adhesive prepared by the preparation method described in the above technical solutions and then cured with UV light.

[0036] Figure 1 This is a schematic diagram of the structure of the peelable UV-curable protective film provided by the present invention. Figure 1 In the middle, 1-substrate layer, 2-intermediate layer (adhesive film layer), 3-release film layer.

[0037] This invention does not have any special requirements for the materials of the substrate layer and the release film layer; any materials well known to those skilled in the art can be used. For example, the substrate layer can be a polyester film, and the release film layer can be a polyester release film. This invention also does not have any special requirements for the thickness of the substrate layer and the release film layer; conventional thickness settings in the art can be used.

[0038] In this invention, the thickness of the adhesive film layer is preferably 5~20μm, and can be 8~10μm. Excessive thickness of the adhesive film layer will affect peel strength and contamination.

[0039] This invention also provides a method for preparing the peelable UV-curable protective film described in the above technical solution, comprising the following steps: The UV-curable pressure-sensitive adhesive is coated on the surface of the substrate layer, the pressure-sensitive adhesive is bonded to the release film layer, and the resulting composite film is cured with UV light to obtain the peelable UV-curable protective film.

[0040] In this invention, the coating can be performed using a coating machine; the curing energy for ultraviolet light curing is preferably 2000 mJ / cm². 2 Complete curing is achieved through ultraviolet light curing.

[0041] The UV-curable protective film provided by this invention has good re-peelability, weather resistance and air release properties.

[0042] To further illustrate the present invention, the following detailed description, in conjunction with examples, of the acrylate copolymers, their preparation methods, UV-curable pressure-sensitive adhesives, and UV-curable protective films provided by the present invention, should not be construed as limiting the scope of protection of the present invention.

[0043] Example 1 Step 1: The raw material composition of the acrylate copolymer is as follows: 66.7 kg of 2-ethylhexyl acrylate, 30 kg of isobornyl acrylate, 3.3 kg of β-acryloyloxypropionic acid, 0.4 kg of n-dodecyl mercaptan, and 0.9 kg of 1-hydroxycyclohexylphenyl ketone. The preparation method is as follows: accurately weigh all raw materials, and stir the above raw materials uniformly in a reaction vessel at room temperature under nitrogen for 30 min at a stirring speed of 100 r / min, using a wavelength of 365 nm and a light intensity of 10 W / cm. 2 Irradiation with ultraviolet light source was carried out, and the irradiation was stopped when the temperature of the reactor was raised to 10°C, resulting in an acrylate copolymer with a viscosity of 120 cps (25°C) and a weight-average molecular weight of 30,000.

[0044] Step 2: Preparation of UV-curable protective film: After cooling the prepared acrylate copolymer to room temperature, add 0.35 kg of 1,6-hexanediol diacrylate and 0.15 kg of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide. Stir evenly in a mixing tank (stirring speed: 100 r / min), allow to stand to defoam, and obtain UV-curable pressure-sensitive adhesive. Then, coat the UV-curable pressure-sensitive adhesive onto a polyester film using a coating machine, and laminate it with a polyester release film to obtain a coating film with one side of polyester film, one side of polyester release film, and the middle of UV-curable pressure-sensitive adhesive (adhesive layer thickness: 8 μm). Finally, use a UV curing machine for complete curing at a curing energy of 2000 mJ / cm². 2 Thus, a UV-curable protective film is obtained.

[0045] Examples 2-6 and Comparative Example 1 The raw material compositions for preparing the acrylate copolymer and UV-curable protective film in Examples 2-6 and Comparative Example 1 are shown in Table 1, and the preparation steps are the same as in Example 1. The difference between Comparative Example 1 and the Examples is that acrylic acid is used instead of β-acryloyloxypropionic acid.

[0046] Table 1. Raw material composition of Examples 2-6 and Comparative Example 1 (all raw material units are kg).

[0047] Performance testing The UV-curable protective films prepared in Examples 1-6 and Comparative Example 1 were subjected to performance tests, including peel strength, air release, and weather resistance. The test methods are as follows: Peel strength: The standard GB / T2792-2014 was adopted, and the test time was 20 minutes.

[0048] Air release test: Attach a 50×50mm protective film to a glass plate, observe and count the number, size and distribution of internal bubbles under a standard light source, and calculate the area of ​​the bubbles. Air release (%) = (area of ​​protective film - sum of bubble areas) / area of ​​protective film.

[0049] Re-peelability: The peel strength was tested again 72 hours after the glass plate was attached, according to standard GB / T2792-2014.

[0050] Weather resistance: After attaching the glass plate, place it in the corresponding temperature and humidity equipment, remove it after the predetermined time, and observe the surface after cooling to room temperature for 30 minutes.

[0051] The test results are shown in Table 2.

[0052] Table 2 shows the performance test results of the UV-curable protective films prepared in Examples 1-6 and Comparative Example 1.

[0053] As shown in Table 2, the present invention provides a UV-curable protective film with ultra-low peel strength, good re-peeling performance, good air release properties, and good weather resistance. In contrast, Comparative Example 1 uses acrylic acid instead of β-acryloyloxypropionic acid to prepare an acrylate copolymer, resulting in a protective film with higher peel strength, poorer air release properties, and ghosting in the weather resistance test, which will affect the subsequent use of the adhered object.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An acrylate copolymer, characterized in that, The preparation raw materials include the following parts by weight: 98-100 parts of acrylate monomers, 0.01-2 parts of chain transfer agent, and 0.01-2 parts of photoinitiator; The acrylate monomers include the following monomers in the following mass percentages: 66-70% 2-ethylhexyl acrylate, 28-30% isobornyl acrylate, and 1-4% β-acryloyloxypropionic acid.

2. The acrylate copolymer according to claim 1, characterized in that, The acrylate monomers include the following monomers in the following mass percentages: 70% 2-ethylhexyl acrylate, 28-29% isobornyl acrylate, and 1-2% β-acryloyloxypropionic acid.

3. The acrylate copolymer according to claim 1, characterized in that, The chain transfer agent is n-dodecyl mercaptan; the photoinitiator is one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinobenzylphenyl)butanone, 2,2-dimethoxyacetophenone, 2,2-diethoxyacetophenone, benzoin methyl ether, and benzoin ethyl ether.

4. The acrylate copolymer according to any one of claims 1 to 3, characterized in that, The viscosity of the acrylate copolymer at 25°C is 120~475 cps.

5. A method for preparing the acrylate copolymer according to any one of claims 1 to 4, characterized in that, Includes the following steps: The acrylate monomers, chain transfer agents, and photoinitiators are mixed, and a copolymerization reaction is initiated by ultraviolet light irradiation to obtain the acrylate copolymer.

6. The preparation method according to claim 5, characterized in that, The ultraviolet light has a wavelength of 200~400nm and a light intensity of 5~15W / cm. 2 The ultraviolet irradiation time is until the copolymer system obtained by mixing is heated to 10~15°C.

7. A UV-curable pressure-sensitive adhesive, characterized in that, The UV-curable pressure-sensitive adhesive comprises an acrylate copolymer, a reactive diluent, and a photoinitiator; the mass ratio of the acrylate copolymer to the reactive diluent is (98~104):(0.1~3), and the mass of the photoinitiator is 0.05~2% of the mass of the UV-curable pressure-sensitive adhesive; the acrylate copolymer is the acrylate copolymer according to any one of claims 1 to 4 or the acrylate copolymer prepared by the preparation method according to claim 5 or 6.

8. The UV-curable pressure-sensitive adhesive according to claim 7, characterized in that, The reactive diluent is one or more of 1,6-hexanediol diacrylate, polypropylene glycol diacrylate, polyethylene glycol diacrylate, triethylene glycol diacrylate, 1,4-butanediol diacrylate, 3-hydroxy-2,2-dimethylpropyl-3-hydroxy-2,2-dimethylpropyl diacrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, and pentaerythritol tetraacrylate; the photoinitiator is one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinobenzylphenyl)butanone, 2,2-dimethoxyacetophenone, 2,2-diethoxyacetophenone, benzoin methyl ether, and benzoin ethyl ether.

9. A peelable ultraviolet-curable protective film, characterized in that, It includes a substrate layer, an intermediate layer and a release film layer stacked in sequence, wherein the intermediate layer is an adhesive film layer formed by UV curing of the UV-curable pressure-sensitive adhesive as described in claim 7 or 8.

10. The peelable UV-curable protective film according to claim 9, characterized in that, The thickness of the adhesive film layer is 5~20μm.

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