Acrylic resin composition for protective film, pressure-sensitive adhesive, and protective film

Abstract

The application provides an acrylic resin composition for protective film, pressure-sensitive adhesive and protective film. The acrylic resin composition comprises, in parts by weight: 94-97.5 parts of acrylic ester copolymer, 0.9-1.9 parts of catalyst, 0.78-1.9 parts of curing agent and 0.9-1.9 parts of inhibitor; wherein the acid value of the acrylic ester copolymer is <0.5 mgKOH / g; and the viscosity of the acrylic ester copolymer is ≤100 mPa·s when the solid content is 35%. The application optimizes the formula of the acrylic resin composition for protective film, solves the key problems of the existing acrylic resin for protective film in application, including the dilution requirement before coating caused by high viscosity, the increase of the cost of using release film material caused by slow curing speed and insufficient cohesion, and the influence of the product appearance and performance caused by the residual adhesive layer after film peeling.

Description

Technical Field

[0001] This invention relates to the field of protective film technology, and more specifically, to an acrylic resin composition for protective films, a pressure-sensitive adhesive, and a protective film. Background Technology

[0002] Protective film, as an important surface protection material, is widely used in industries such as electronics, construction, automotive, and home appliances. Its main function is to prevent products from being scratched or damaged during transportation, handling, warehousing, and display, thereby maintaining the product's appearance and performance. Protective film typically consists of a substrate and a pressure-sensitive adhesive. It must not only be inert to the surface of the protected material, not causing a chemical reaction, but also possess good adhesion to ensure it adheres firmly during product handling and processing, without peeling or falling off. Furthermore, the protective film should have excellent weather resistance, maintaining good tack stability even under long-term exposure or harsh conditions, ensuring easy removal without leaving any adhesive residue on the protected material surface, thus avoiding affecting the product's final use.

[0003] Chinese patent CN110607146B discloses a pressure-sensitive adhesive for PET protective films and its preparation method. The adhesive is synthesized using a solution polymerization process. However, this adhesive has a slow curing rate, requiring a release film to cover it after coating and allowing it to mature for a period of time before use. This leads to increased production costs and resource consumption. Furthermore, the release film used during the maturation process must be discarded later, further contributing to resource waste and environmental pollution.

[0004] Currently, most adhesives used in the preparation of protective films on the market have a solid content of around 40% and a viscosity of over 1000 mPa·s. To ensure smoothness during coating and avoid clogging of the micro-dip coating head, the adhesive usually needs to be diluted to a solid content of about 20% before coating. This process not only increases production costs, but the diluent used in the dilution process also requires further RTO incineration or condensation recovery treatment during the drying stage. In addition, the coating speed of protective films is usually above 40 m / min, and they are directly wound after high-speed coating. This requires the adhesive layer to have high cohesion immediately after leaving the machine to adapt to the short drying tunnel time and the winding conditions without release film protection. However, when unwinding some products after winding, the adhesive layer is easily adhered to the back of the substrate, resulting in phenomena such as fogging and ring marks on the film surface, affecting the appearance and performance of the product.

[0005] Therefore, there is an urgent need to develop pressure-sensitive adhesives for protective films that have lower viscosity, simpler application processes, and faster curing and maturation rates. Summary of the Invention

[0006] The main objective of this invention is to provide an acrylic resin composition for protective films, a pressure-sensitive adhesive, and a protective film, in order to solve the problems of high viscosity, complex application process, and low curing rate of adhesives for protective films in the prior art.

[0007] To achieve the above objectives, according to one aspect of the present invention, an acrylic resin composition for protective films is provided, comprising, by weight, 94 to 97.5 parts of an acrylate copolymer, 0.9 to 1.9 parts of a catalyst, 0.78 to 1.9 parts of a curing agent, and 0.9 to 1.9 parts of an inhibitor; wherein the acid value of the acrylate copolymer is <0.5 mg KOH / g; and the viscosity of the acrylate copolymer at a solid content of 35% is ≤100 mPa·s.

[0008] Further, the acid value of the acrylate copolymer is 0.05~0.3 mgKOH / g; and / or, the viscosity of the acrylate copolymer at a solid content of 35% is 20~100 mPa·s; and / or, the weight average molecular weight of the acrylate copolymer is 100000 g / mol~300000 g / mol, preferably 110000 g / mol~230000 g / mol.

[0009] Furthermore, the catalyst content in the acrylic resin composition is 0.97~1.26% by weight.

[0010] Furthermore, the acrylate copolymer is obtained by polymerization of acrylate monomers and functional monomers; the mass ratio of acrylate monomers to functional monomers is (32~35):(2.3~3).

[0011] Further, the acrylate monomer is selected from any one or more of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, isopropyl acrylate, isopropyl methacrylate, butyl acrylate, butyl methacrylate, hexyl acrylate, hexyl methacrylate, heptyl acrylate, heptyl methacrylate, isooctyl acrylate, octyl methacrylate, nonyl acrylate, nonyl methacrylate, decyl acrylate, decyl methacrylate, lauryl acrylate, and lauryl methacrylate; and / or, the functional monomer is selected from styrene, acrylamide, N-hydroxymethylacrylamide, acetic acid, etc. Vinyl acrylate, tetrahydrofuran acrylate, tetrahydrofuran methacrylate, isobornyl acrylate, isobornyl methacrylate, dimethylaminomethyl acrylate, dimethylaminomethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminomethyl acrylate, diethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate.

[0012] Furthermore, the catalyst comprises an organotin compound and a solvent; the mass ratio of the organotin compound to the solvent is (0.5~1):(9~10.5); the organotin compound is selected from any one or more of dibutyltin dilaurate, dimethyltin dineodecanate, and dioctyltin oxide.

[0013] Furthermore, the curing agent is a polyisocyanate curing agent; the polyisocyanate curing agent is hexamethylene diisocyanate.

[0014] Further, the inhibitor is an organic acid with a boiling point of 100~145℃; preferably, the inhibitor is selected from any one or more of formic acid, acetic acid and propionic acid.

[0015] According to another aspect of the present invention, a pressure-sensitive adhesive is provided, which is prepared from a pressure-sensitive adhesive composition comprising the above-described acrylic resin composition for protective films.

[0016] According to another aspect of the present invention, a protective film is provided, comprising a substrate and a pressure-sensitive adhesive, wherein the pressure-sensitive adhesive is the aforementioned pressure-sensitive adhesive.

[0017] By applying the technical solution of this invention, this application solves key problems in the application of existing acrylic resins for protective films by optimizing the formulation of the acrylic resin composition. These problems include the need for dilution before coating due to high viscosity, which leads to increased production costs and a heavier environmental burden; slow curing speed and insufficient cohesion, resulting in increased material costs due to the use of release films; and residual adhesive layers after film removal affecting the product's appearance and performance. The resulting acrylic resin exhibits excellent environmental performance, high production efficiency, and good economic benefits, making it suitable for the efficient production of PET protective films and meeting the industry's demand for high-quality, low-cost, and low-energy-consumption protective film materials. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0019] As mentioned in the background section, existing protective film adhesives suffer from problems such as high viscosity, complex application process, and low curing rate. In order to solve the above problems, this application provides an acrylic resin composition for protective films, a pressure-sensitive adhesive, and a protective film.

[0020] In a typical embodiment of this application, an acrylic resin composition for protective film is provided, comprising, by weight: 94-97.5 parts of an acrylate copolymer, 0.9-1.9 parts of a catalyst, 0.78-1.9 parts of a curing agent, and 0.9-1.9 parts of an inhibitor; wherein the acid value of the acrylate copolymer is <0.5 mg KOH / g; and the viscosity of the acrylate copolymer at a solid content of 35% is ≤100 mPa·s.

[0021] The acrylic resin composition for protective films of this application controls the addition ratio of each component within the aforementioned range, enabling the acid value and viscosity of the acrylate copolymer at a solid content of 35% to reach the aforementioned range. This allows for direct coating without dilution during use. Furthermore, the acrylic resin composition for protective films exhibits excellent curing speed and cohesive strength, allowing for direct winding without the need for additional release film protection. The optimized proportions of the acrylic resin composition effectively simplify the production process of the protective film, reducing the consumption of diluent and release film materials during production, thereby contributing to lower production costs.

[0022] Specifically, in the acrylic resin composition for protective films, the acrylate copolymer serves as the base component, ensuring the adhesive performance and stability of the formed protective film. Controlling the amount of acrylate copolymer added within the aforementioned range improves the rheological properties of the acrylic resin composition for protective films, allowing the adhesive to maintain a low viscosity even at high solids content. This enables the acrylic resin composition for protective films to be directly coated without dilution, reducing the cost of diluents and environmental impact. Furthermore, controlling the acid value of the acrylate copolymer within the aforementioned range results in a lower free acid content in the acrylic resin composition for protective films, thereby increasing the curing speed of the adhesive and the cohesive strength of the adhesive layer. Simultaneously, it avoids interference with the activity of the curing agent due to excessively high acid values, thus reducing the problem of residual adhesive when removing the protective film. Controlling the viscosity of the acrylate copolymer at a solids content of 35% within the aforementioned range allows the acrylic resin composition to be directly coated without dilution, significantly reducing the amount of diluent used and the need for RTO incineration or condensation recovery treatment, thereby reducing production costs and environmental impact. At the same time, low viscosity also helps to improve the uniformity of coating and the leveling of the adhesive layer, avoiding scratches and unevenness.

[0023] Furthermore, the catalyst in the acrylic resin composition for protective films can further accelerate the curing reaction rate of the polymer, resulting in a better curing speed during the preparation of the protective film. The curing agent can undergo further cross-linking with the acrylate copolymer, enabling the formation of a denser network structure within the protective film, thereby enhancing the cohesiveness and adhesion of the protective film layer and improving its stability. In addition, the curing agent can further reduce the curing time of the acrylic resin composition, thus reducing energy consumption and time costs during the curing process. Inhibitors can prevent premature curing of the composition during storage or mixing, thereby extending the shelf life of the acrylic resin composition and reducing waste and costs caused by glue solidification in production.

[0024] The synergistic effect of the above components enables the acrylic resin composition for protective films to be directly coated without dilution during use. It also exhibits excellent curing rate and cohesive strength, allowing for direct winding without the need for additional release film protection. The optimized proportions of the acrylic resin composition effectively simplify the production process of the protective film, reduce the consumption of diluent and release film materials during production, and thus help lower the production cost.

[0025] In summary, this application addresses key issues in the application of existing acrylic resins for protective films by optimizing the formulation of the acrylic resin composition. These issues include the need for pre-coating dilution due to high viscosity, leading to increased production costs and environmental burden; slow curing speed and insufficient cohesion resulting in increased material costs due to the use of release films; and residual adhesive layers after film removal affecting product appearance and performance. The resulting acrylic resin exhibits excellent environmental performance, high production efficiency, and good economic benefits, making it suitable for the efficient production of PET protective films and meeting the demand for high-quality, low-cost, and low-energy-consumption protective film materials.

[0026] In one embodiment of this application, the acid value of the acrylate copolymer is 0.05~0.3 mgKOH / g.

[0027] In one embodiment of this application, the viscosity of the acrylate copolymer at a solid content of 35% is 20~100 mPa·s.

[0028] In one embodiment of this application, the weight-average molecular weight of the acrylate copolymer is 100,000 g / mol to 300,000 g / mol, preferably 110,000 g / mol to 230,000 g / mol.

[0029] Preferably, the acid value of the acrylate copolymer should be within the aforementioned range. This not only helps to achieve a lower free acid content in the acrylic resin composition, thereby increasing the curing speed of the adhesive and the cohesive strength of the adhesive layer, but also helps to reduce the interference of excessively high acid values ​​on the activity of the curing agent, thus reducing the problem of residual adhesive when the protective film is removed. Controlling the viscosity of the acrylate copolymer at a solid content of 35% simplifies the application process of the acrylic resin composition, allowing it to be directly applied to the machine without dilution, significantly reducing the amount of diluent used and mitigating a series of problems associated with diluent use. By controlling the acid value of the acrylate copolymer and its viscosity at a solid content of 35% within the aforementioned range, the viscosity and weather resistance of the protective film are improved.

[0030] The above viscosity was tested at a temperature of 25±0.5℃.

[0031] Controlling the weight-average molecular weight of the acrylate copolymer within the aforementioned range helps improve the adhesive strength and stability of the acrylic resin composition, while also enhancing its rheological properties, thus facilitating coating. Furthermore, controlling the molecular weight of the acrylate copolymer within this range helps reduce the precipitation of small molecules from the adhesive layer when used in protective films, thereby reducing contamination of the protected surface, and also helps minimize the decrease in coating uniformity and leveling caused by increased viscosity of the acrylic resin composition.

[0032] In one embodiment of this application, the catalyst content in the acrylic resin composition is 0.97~1.26% by weight.

[0033] Preferably controlling the weight content of the catalyst in the acrylic resin composition within the above range helps to further accelerate the curing reaction rate of the polymer, enabling the acrylic resin composition to have a better curing speed when preparing the protective film. It also helps to make the formed protective film have better cohesion, stability and long-term performance, thereby helping to better reduce energy consumption and time costs in production and improve product quality.

[0034] In one embodiment of this application, the acrylate copolymer is obtained by polymerization of acrylate monomers and functional monomers; the mass ratio of acrylate monomers to functional monomers is (32~35):(2.3~3).

[0035] The introduction of functional monomers provides additional chemical properties to acrylate copolymers, thereby enhancing the adhesive's adhesion, stability, weather resistance, and other properties. Functional monomers (such as hydroxyethyl acrylate and hydroxypropyl acrylate) typically contain reactive functional groups such as hydroxyl groups, which can crosslink with the curing agent during the formation of the protective film, creating a more stable network structure. This, in turn, helps to improve the cohesiveness and adhesive strength of the adhesive layer. Controlling the acrylate monomers and functional monomers in the acrylate copolymer within the aforementioned ranges helps the acrylic resin composition maintain good rheological properties while also promoting the formation of a sufficient crosslinked network in the protective film, thus further improving the performance of the protective film.

[0036] The preparation method of acrylate copolymer includes the following steps: mixing acrylate monomers, functional monomers, initiators and solvents to obtain a mixed solution; subjecting the mixed solution to a polymerization reaction at a first temperature to obtain a reaction solution; and cooling the reaction solution to obtain the acrylate copolymer.

[0037] By weight, the mixed solution contains 32-35 parts of acrylate monomer, 2.3-3.0 parts of functional monomer, 0.15-0.25 parts of initiator, and 60-65 parts of solvent.

[0038] Preferably, in the actual preparation process, the initiator is added in batches, and is respectively designated as the first initiator, the second initiator, and the third initiator; the solvent is added in batches, and is respectively designated as the first solvent, the second solvent, the third solvent, and the fourth solvent; the preparation method of the acrylate copolymer includes the following steps: mixing the acrylate monomer, the functional monomer, the first solvent, and the first initiator to obtain a first mixed solution; adding the first mixed solution dropwise to a reaction vessel containing the second solvent to carry out a first reaction to obtain a first reaction slurry; continuing to add the second initiator and the third solvent to the first reaction slurry to carry out a second reaction to obtain a second reaction slurry; continuing to add the third initiator and the fourth solvent to the second reaction slurry to carry out a third reaction to obtain a reaction solution; and obtaining the acrylate copolymer after cooling the reaction solution. Preferably, the mass ratio of the first initiator, the second initiator, and the third initiator is (8~14):(4~6):(3~5). The mass ratio of the first solvent, the second solvent, the third solvent, the fourth solvent, and the fifth solvent is (18~54):(2~34):(1~2):(1~2):(4~14). Preferably, the dropping time is 1-2 hours; preferably, the first reaction time is 1-1.5 hours; preferably, the second reaction time is 1-1.5 hours; preferably, the third reaction time is 3-4.5 hours. Following the above operating steps, the initiator is added in batches. Adding the above-mentioned amount of initiator in the first reaction helps to maintain a low monomer concentration in the reaction vessel, resulting in a relatively uniform molecular weight distribution of the acrylate copolymer and thus stable performance of the acrylate copolymer. The molecular weight is controlled by adjusting the monomer concentration through controlling the dropping rate. Timely replenishment of the initiator in the second and third reactions helps to increase the free radical concentration, initiating the remaining small amount of monomer and thus improving the conversion rate. This makes it easier to control the acidity and viscosity of the acrylate copolymer, thereby resulting in better performance of the protective film prepared from the acrylic resin composition.

[0039] Preferably, the polymerization reaction temperature is 77~79℃ and the time is 5~7h; preferably, the polymerization reaction is carried out in a gaseous atmosphere; preferably, the gas is any one or more of nitrogen, argon and helium. Controlling the parameters in the preparation process within the above range can improve the performance of the obtained acrylate copolymer, and its use in the preparation of protective films can improve the performance of the prepared protective films.

[0040] The initiator is selected from any one or more of azobisisobutyronitrile, azobisisoheptanenitrile, azobisisovaleratenitrile, benzoyl peroxide, and 1,4-(di-tert-butylperoxide)cyclohexane. The solvent includes, but is not limited to, ethyl acetate.

[0041] In one embodiment of this application, the acrylate monomer is selected from any one or more of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, isopropyl acrylate, isopropyl methacrylate, butyl acrylate, butyl methacrylate, hexyl acrylate, hexyl methacrylate, heptyl acrylate, heptyl methacrylate, isooctyl acrylate, octyl methacrylate, nonyl acrylate, nonyl methacrylate, decyl acrylate, decyl methacrylate, lauryl acrylate, and lauryl methacrylate; preferably, the functional monomer is selected from styrene, acrylamide, N-hydroxymethylacrylamide, and styrene. The amine, vinyl acetate, tetrahydrofuran acrylate, tetrahydrofuran methacrylate, isobornyl acrylate, isobornyl methacrylate, dimethylaminomethyl acrylate, dimethylaminomethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminomethyl acrylate, diethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate.

[0042] Using the above-mentioned acrylate monomers, functional monomers, initiators and solvents to prepare acrylate copolymers can improve the performance of acrylate copolymers, thereby helping to further improve the performance of protective films.

[0043] In one embodiment of this application, the catalyst comprises an organotin compound and a solvent, wherein the mass ratio of the organotin compound to the solvent is (0.5~1):(9~10.5); the organotin compound is selected from any one or more of dibutyltin dilaurate, dimethyltin dineodecanate, and dioctyltin oxide.

[0044] Solvents include, but are not limited to, toluene. Preferably, organotin compounds are within the above-mentioned range, which helps to further accelerate the curing reaction rate of the polymer, thereby increasing the curing speed of the acrylic resin composition in the preparation of the protective film.

[0045] In one embodiment of this application, the curing agent is a polyisocyanate curing agent; the polyisocyanate curing agent is hexamethylene diisocyanate.

[0046] The preferred type of curing agent falls within the aforementioned range, which facilitates further cross-linking with the acrylate copolymer, resulting in a denser network structure within the protective film. This enhances the cohesiveness and adhesion of the protective film layer, thereby improving its stability. Furthermore, the aforementioned types of curing agents help to further reduce the curing time of the acrylic resin composition, thereby reducing energy consumption and time costs during the curing process.

[0047] In one embodiment of this application, the inhibitor is an organic acid with a boiling point of 100-145°C; preferably, the inhibitor is selected from any one or more of formic acid, acetic acid, and propionic acid.

[0048] Controlling the boiling point of the organic acid within the aforementioned range helps the acrylic resin composition to evaporate from the reaction system in a timely manner during the formation of the protective film, thereby facilitating a better curing reaction. The aforementioned inhibitors also help reduce premature curing of the acrylic resin composition for the protective film during storage or mixing, thus extending its shelf life and reducing waste and costs caused by adhesive solidification in production.

[0049] In another typical embodiment of this application, a pressure-sensitive adhesive is provided, which is prepared from a pressure-sensitive adhesive composition comprising the above-mentioned acrylic resin composition for protective film.

[0050] The pressure-sensitive adhesive prepared from the acrylic resin composition for protective film provided in this application has a fast curing speed, strong cohesion of the adhesive layer, high curing degree, and stable adhesion. It can also achieve direct coating without dilution and direct winding without the need for additional release film protection, effectively simplifying the problems of complex process, high cost and low efficiency in the preparation of protective film.

[0051] In another typical embodiment of this application, a protective film is provided, comprising a substrate and a pressure-sensitive adhesive, wherein the pressure-sensitive adhesive is the pressure-sensitive adhesive described above.

[0052] The protective film of this application provides better protection for materials, thus enabling its wider application in fields such as electronics, construction, automobiles, and home appliances. Furthermore, the protective film exhibits excellent weather resistance, maintaining good adhesion even under prolonged exposure or harsh conditions, ensuring easy removal without leaving any adhesive residue on the surface of the protected material.

[0053] Preparation method of protective film: The protective film is prepared by mixing an acrylic resin composition with the substrate and then coating it onto the substrate surface, followed by drying. The coating amount is 4-5 g / m². 3 ; and / or, the drying temperature is 140~150℃; the time is 20~50s.

[0054] Controlling the drying temperature and time, as well as the coating amount, within the above ranges helps to improve the quality of the protective film.

[0055] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0056] Example 1

[0057] (1) Preparation of acrylate copolymer

[0058] Raw materials: By weight, 32.3 parts acrylate monomer (9.8 parts butyl acrylate, 22.5 parts isooctyl acrylate), 2.7 parts functional monomer (hydroxyethyl acrylate), 0.18 parts initiator (azobisisobutyronitrile), and 64.82 parts solvent (ethyl acetate). The initiators are divided into a first initiator, a second initiator, and a third initiator with a mass ratio of 8:5:5. The solvents are divided into a first solvent, a second solvent, a third solvent, a fourth solvent, and a fifth solvent with a mass ratio of 43:10:2:2:7.

[0059] The second solvent was placed in a reactor, and the reactor system was purged with nitrogen for 20 minutes. The system was then heated to 78°C. The acrylate monomer, functional monomer, first initiator, and first solvent were mixed to obtain a first mixed solution. This first mixed solution was added dropwise to the heated reactor system over 1.5 hours. After the addition was complete, the reaction was continued at this temperature for 1 hour to obtain a first reaction slurry. The second initiator was dissolved in a third solvent and added to the first reaction slurry, and the reaction was continued at this temperature for 1 hour to obtain a second reaction slurry. The third initiator was then dissolved in a fourth solvent and added to the second reaction slurry, and the reaction was continued at this temperature for 3.5 hours to obtain a reaction solution. The remaining fifth solvent was added to the reactor as a diluent, and the mixture was cooled and discharged to obtain the acrylate copolymer, denoted as A-1. A-1: ​​weight-average molecular weight is 140,000 g / mol, acid value is 0.2 mg KOH / g, and viscosity is 41 mPa·s at 35% solid content.

[0060] (2) By weight, the acrylic resin composition for protective film consists of 97.28 parts of acrylate copolymer A-1, 0.97 parts of catalyst (toluene solution of dibutyltin dilaurate with a mass content of 10%), 0.78 parts of curing agent (hexamethylene diisocyanate) and 0.97 parts of inhibitor (glacial acetic acid).

[0061] After thoroughly mixing the above-mentioned components in the acrylic resin composition for protective film according to the specified ratio, the mixture is uniformly coated onto the surface of a 50µm thick polyethylene terephthalate (PET) film, with a coating weight of 5g / m². 3 After coating, it is dried at 145°C for 30 seconds to form a pressure-sensitive adhesive, which is then applied to the back of a 50µm thick PET film to obtain a protective film.

[0062] Example 2

[0063] The difference from Example 1 is that,

[0064] (1) Preparation of acrylate copolymer: By weight, 32 parts of acrylate monomer (2.1 parts of methyl methacrylate, 7.7 parts of butyl acrylate, and 22.2 parts of isooctyl acrylate), 2.7 parts of functional monomer (hydroxyethyl methacrylate), 0.32 parts of initiator (azobisisobutyronitrile), and 64.98 parts of solvent (ethyl acetate) were used to obtain the acrylate copolymer, denoted as A-2. A-2: weight average molecular weight is 180,000 g / mol, acid value is 0.15 mg KOH / g, and viscosity is 77 mPa·s when solid content is 35%. Replacing acrylate copolymer A-1 with acrylate copolymer A-2, a protective film was finally obtained.

[0065] Example 3

[0066] The difference from Example 1 is that,

[0067] (1) Preparation of acrylate copolymer: By weight, 32.7 parts of acrylate monomer (including 5 parts of methyl methacrylate, 7 parts of butyl acrylate, and 20.7 parts of isooctyl acrylate), 2.3 parts of functional monomer (including 1 part of acrylamide and 1.3 parts of hydroxyethyl methacrylate), 0.22 parts of initiator (azobisisobutyronitrile), and 64.78 parts of solvent (ethyl acetate) were used to obtain the acrylate copolymer, denoted as A-3. A-3: weight average molecular weight is 120000 g / mol, acid value is 0.12 mg KOH / g, and viscosity is 55 mPa·s when solid content is 35%. Replacing acrylate copolymer A-1 with acrylate copolymer A-3, a protective film was finally obtained.

[0068] Example 4

[0069] The difference from Example 1 is that,

[0070] (1) Preparation of acrylate copolymer: By weight, 32.3 parts of acrylate monomer (including 1.7 parts of methyl methacrylate, 7.7 parts of butyl acrylate, and 22.9 parts of isooctyl acrylate), 2.7 parts of functional monomer (including 1.4 parts of acrylamide and 1.3 parts of hydroxyethyl methacrylate), 0.18 parts of initiator (azobisisobutyronitrile), and 64.82 parts of solvent (ethyl acetate) were used to obtain the acrylate copolymer, denoted as A-4. A-4: weight average molecular weight is 150,000 g / mol, acid value is 0.22 mg KOH / g, and viscosity is 85 mPa·s when solid content is 35%. Replacing acrylate copolymer A-1 with acrylate copolymer A-4, a protective film was finally obtained.

[0071] Example 5

[0072] The difference from Example 1 is that,

[0073] (1) Preparation of acrylate copolymer: By weight, 33 parts of acrylate monomer (including 1 part of methyl methacrylate, 9.5 parts of butyl acrylate, and 22.5 parts of isooctyl acrylate), 3 parts of functional monomer (including 1.7 parts of acrylamide and 1.3 parts of hydroxyethyl methacrylate), 0.21 parts of initiator (azobisisobutyronitrile), and 63.79 parts of solvent (ethyl acetate) were used to obtain the acrylate copolymer, denoted as A-5. A-5: weight average molecular weight is 170,000 g / mol, acid value is 0.18 mg KOH / g, and viscosity is 76 mPa·s when solid content is 35%. Replacing acrylate copolymer A-1 with acrylate copolymer A-5, a protective film was finally obtained.

[0074] Example 6

[0075] The difference from Example 5 is that, by weight, the acrylic resin composition for the protective film consists of 94 parts of acrylate copolymer A-5, 0.9 parts of catalyst (10% by weight of dimethyltin dinedecanoate in toluene solution), 0.8 parts of curing agent (hexamethylene diisocyanate), and 0.9 parts of inhibitor (formic acid), ultimately yielding the protective film.

[0076] Example 7

[0077] The difference from Example 5 is that, by weight, the acrylic resin composition for the protective film consists of 97.5 parts of acrylate copolymer A-5, 1.9 parts of catalyst (toluene solution of dioctyltin oxide with a weight content of 10%), 1.9 parts of curing agent (hexamethylene diisocyanate) and 1.9 parts of inhibitor (propionic acid), ultimately yielding a protective film.

[0078] Example 8

[0079] The difference from Example 5 is that, by weight, the acrylic resin composition for the protective film consists of 96 parts of acrylate copolymer A-5, 1.26 parts of catalyst, 1.2 parts of curing agent and 1.43 parts of inhibitor, with the catalyst content being 1.26% by weight, ultimately yielding a protective film.

[0080] Example 9

[0081] The difference from Example 5 is that (1) the acrylate copolymer was prepared: the total weight of the acrylate monomer and the functional monomer was 37 parts, the mass ratio of the acrylate monomer and the functional monomer was 34:3, and the final acrylate copolymer A-6 was obtained. A-6: weight average molecular weight was 220000 g / mol, acid value was 0.25 mg KOH / g, and viscosity was 92 mPa·s when the solid content was 35%. The acrylate copolymer A-5 was replaced with the acrylate copolymer A-6, and the final protective film was obtained.

[0082] Example 10

[0083] The difference from Example 5 is that (1) the acrylate copolymer was prepared: the total weight of the acrylate monomer and the functional monomer was 37 parts, the mass ratio of the acrylate monomer and the functional monomer was 35:2, and the acrylate copolymer A-7 was finally obtained. A-6: weight average molecular weight was 300000 g / mol, acid value was 0.3 mg KOH / g, and viscosity was 100 mPa·s when the solid content was 35%. The acrylate copolymer A-5 was replaced with the acrylate copolymer A-7, and a protective film was finally obtained.

[0084] Comparative Example 1

[0085] The difference from Example 1 is that no catalyst is added to the acrylic resin composition for the protective film, and a protective film is finally obtained.

[0086] Comparative Example 2

[0087] The difference from Example 1 is that, by weight, the acrylic resin composition for the protective film consists of 97.27 parts of acrylate copolymer A-1, 1.05 parts of catalyst (toluene solution of 10% dibutyltin dilaurate), 0.7 parts of curing agent (toluene diisocyanate), and 0.97 parts of inhibitor (glacial acetic acid), ultimately yielding the protective film.

[0088] Comparative Example 3

[0089] The difference from Example 1 is that no inhibitor is added to the acrylic resin composition for the protective film, and a protective film is finally obtained.

[0090] Comparative Example 4

[0091] The difference from Example 1 is that the acrylate copolymer A-1 in the acrylic resin composition was replaced with PS-8243 adhesive (Kunshan Shimei New Material Technology Co., Ltd., solid content: 30%, viscosity: 2300mPa·s), and the protective film was finally obtained.

[0092] Comparative Example 5

[0093] The difference from Example 1 is that, by weight, the acrylic resin composition for the protective film consists of 49.31 parts of PS-8243 adhesive (Kunshan Shimei New Material Technology Co., Ltd., solid content: 30%, viscosity: 2300 mPa·s), 0.49 parts of catalyst (toluene solution of dibutyltin dilaurate with a weight content of 10%), 0.39 parts of curing agent (hexamethylene diisocyanate), 0.49 parts of inhibitor (glacial acetic acid), and 49.31 parts of diluent (ethyl acetate), ultimately yielding the protective film.

[0094] Comparative Example 6

[0095] The difference from Example 1 is that the catalyst is 0.1 parts by weight, and a protective film is finally obtained.

[0096] Comparative Example 7

[0097] The difference from Example 1 is that the acid value of the acrylate copolymer is 1 mg KOH / g, and the viscosity is 120 mPa·s when the solid content is 35%, resulting in a protective film.

[0098] Test method:

[0099] The weight-average molecular weight, acid value, solid content, and viscosity of the obtained acrylate copolymer were tested:

[0100] 1) Viscosity test: According to GB / T 2794-2022, the test temperature is 25℃, and a single-cylinder rotational viscometer is used for testing.

[0101] 2) Weight-average molecular weight: Polymethyl methacrylate was used as a standard to create a working curve, and the weight was measured using Shimadzu LC-20A liquid chromatography.

[0102] 3) Solid content: The mass percentage of non-volatile components was measured after drying at 150℃ for 1 hour.

[0103] The properties of the pressure-sensitive adhesive and protective film prepared above were tested, and the test results are shown in Table 1.

[0104] 1) Adhesive flowability after 3 hours of compounding: After the adhesive is compounded, it is sealed and placed in a 30℃ water bath for three hours. Then, it is taken out and quickly cooled to 25℃. If there are no scratches on the adhesive layer, the flowability is considered good. If there are some scratches on the adhesive layer, the flowability is poor. If it cannot be coated, it is considered that it has solidified.

[0105] 2) Appearance after drying: Observe the protective film after drying. If the adhesive layer is flat and smooth, it is considered to be in a flat state. If there are strip-shaped scratches parallel to the coating direction, it is considered to have scratches.

[0106] 3) Appearance after unwinding: After drying, cover the adhesive layer with a 50µm thick PET backing and roll it back and forth three times using a 2kg roller. After leaving it at room temperature for 20 minutes, quickly tear off the PET backing and observe the appearance of the adhesive layer and the PET backing under light. If the adhesive layer is flat and smooth and there is no adhesive layer on the PET backing, the appearance is considered clean. If there are bubble-like marks on the adhesive layer and there is no adhesive layer on the PET backing, the appearance is considered to have ring marks. If the adhesive layer is torn and there is adhesive transferred from the PET backing, the appearance is considered to have residual adhesive.

[0107] 4) Peel force test of pressure-sensitive adhesive: The test shall be conducted in accordance with the test method in GB / T 2792-2014.

[0108] Table 1

[0109]

[0110] As can be seen from the above, the leveling properties, adhesion, appearance after unwinding, and fluidity of the acrylic resin composition for the protective film of this application are all superior to existing adhesives. Furthermore, the solid content of current protective film adhesives is mostly around 40%, and the viscosity is mostly above 1000 mPa·s. During use, the solid content needs to be diluted to 20% (as in Comparative Example 5) to achieve a scratch-free coating surface. In contrast, the acrylic resin composition for the protective film of this application, after coating, achieves rapid curing, high curing degree, and high stability after drying at 145°C for 30 seconds. The protective film of the embodiments of this application shows little change in its resistance to double 85 for 7 days.

[0111] The curing agent toluene diisocyanate in Comparative Example 2 has two active isocyanate groups. However, due to the steric hindrance effect of the benzene ring and methyl group, the isocyanate groups are difficult to achieve rapid curing, and the peel strength will decrease significantly after 1 day of curing.

[0112] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0113] This application addresses key issues in the application of existing acrylic resins for protective films by optimizing the formulation of the acrylic resin composition. These issues include the need for pre-coating dilution due to high viscosity, leading to increased production costs and environmental burden; slow curing speed and insufficient cohesion resulting in increased material costs due to the use of release films; and residual adhesive layers after film removal affecting product appearance and performance. The resulting acrylic resin exhibits excellent environmental performance, high production efficiency, and good economic benefits, making it suitable for the efficient production of PET protective films and meeting the industry's demand for high-quality, low-cost, and low-energy-consumption protective film materials.

[0114] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An acrylic resin composition for protective films, characterized in that, The acrylic resin composition comprises, by weight, 94-97.5 parts of an acrylate copolymer, 0.9-1.9 parts of a catalyst, 0.78-1.9 parts of a curing agent, and 0.9-1.9 parts of an inhibitor; The acrylate copolymer has an acid value of <0.5 mg KOH / g and a viscosity of ≤100 mPa·s when the solid content is 35%.

2. The acrylic resin composition for protective film according to claim 1, characterized in that, The acrylate copolymer has an acid value of 0.05~0.3 mgKOH / g; and / or, the acrylate copolymer has a viscosity of 20~100 mPa·s when the solid content is 35%; and / or, the acrylate copolymer has a weight-average molecular weight of 100000 g / mol~300000 g / mol, preferably 110000 g / mol~230000 g / mol.

3. The acrylic resin composition for protective film according to claim 1, characterized in that, The catalyst in the acrylic resin composition has a weight content of 0.97~1.26%.

4. The acrylic resin composition for protective films according to any one of claims 1 to 3, characterized in that, The acrylate copolymer is obtained by polymerization of acrylate monomers and functional monomers; the mass ratio of the acrylate monomers to the functional monomers is (32~35):(2.3~3).

5. The acrylic resin composition for protective film according to claim 4, characterized in that, The acrylate monomer is selected from any one or more of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, isopropyl acrylate, isopropyl methacrylate, butyl acrylate, butyl methacrylate, hexyl acrylate, hexyl methacrylate, heptyl acrylate, heptyl methacrylate, isooctyl acrylate, octyl methacrylate, nonyl acrylate, nonyl methacrylate, decyl acrylate, decyl methacrylate, lauryl acrylate, and lauryl methacrylate. And / or, the functional monomer is selected from any one or more of styrene, acrylamide, N-hydroxymethylacrylamide, vinyl acetate, tetrahydrofuran acrylate, tetrahydrofuran methacrylate, isobornyl acrylate, isobornyl methacrylate, dimethylaminomethyl acrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminomethyl acrylate, diethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate.

6. The acrylic resin composition for protective films according to any one of claims 1 to 5, characterized in that, The catalyst comprises an organotin compound and a solvent; the mass ratio of the organotin compound to the solvent is (0.5~1):(9~10.5); the organotin compound is selected from any one or more of dibutyltin dilaurate, dimethyltin dineodecanate, and dioctyltin oxide.

7. The acrylic resin composition for protective films according to any one of claims 1 to 6, characterized in that, The curing agent is a polyisocyanate curing agent; the polyisocyanate curing agent is hexamethylene diisocyanate.

8. The acrylic resin composition for protective films according to any one of claims 1 to 7, characterized in that, The inhibitor is an organic acid with a boiling point of 100-145°C; preferably, the inhibitor is selected from any one or more of formic acid, acetic acid, and propionic acid.

9. A pressure-sensitive adhesive, prepared from a pressure-sensitive adhesive composition, characterized in that, The pressure-sensitive adhesive composition comprises the acrylic resin composition for protective films according to any one of claims 1 to 8.

10. A protective film, comprising a substrate and a pressure-sensitive adhesive, characterized in that, The pressure-sensitive adhesive is the pressure-sensitive adhesive according to claim 9.

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