Acrylic acid protective film and preparation method thereof

Abstract

The invention relates to the field of high polymer materials, in particular to an acrylic protective film and a preparation method thereof.The acrylic protective film comprises a base material layer, a primer modification layer and an acrylic pressure-sensitive adhesive layer, and the primer modification layer is prepared from, by weight, 30-40 parts of polyurethane resin; 10 to 15 parts of acrylate copolymer resin; 2-5 parts of a silane coupling agent; 1-3 parts of a curing agent; 40 to 55 parts of a solvent; the acrylic pressure-sensitive adhesive layer is composed of the following raw materials in parts by weight: 40-50 parts of butyl acrylate; 20 to 30 parts of 2-ethylhexyl acrylate; 5 to 10 parts of methyl methacrylate; 3 to 8 parts of hydroxyethyl acrylate; 1-3 parts of a crosslinking monomer; 0.2 to 0.5 part of an initiator; the surface activity of a base material is improved through plasma modification, the adhesive force of an adhesive layer-base material interface is improved by 30% or above in cooperation with the bridging effect of the primer modification layer, the cohesion strength of the adhesive layer is optimized through addition of the cross-linking monomer, and no adhesive scraps are left and no powder falls off after die cutting.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, and more particularly to an acrylic protective film and its preparation method. Background Technology

[0002] Acrylic protective films, with their excellent transparency, weather resistance, and adhesion, are widely used for process protection and end-product protection of various products. In practical applications, the protective film needs to be die-cut into specific sizes and shapes to fit the appearance of the protected product.

[0003] However, during the die-cutting process, traditional acrylic protective films are prone to "powdering," resulting in adhesive layer breakage and residue, due to insufficient adhesion between the pressure-sensitive adhesive layer and the substrate, and low cohesive strength of the adhesive layer itself. This powdering can contaminate the surface of the protected product or subsequent processing equipment, leading to decreased product yield and increased processing costs. Furthermore, the residual adhesive residue is difficult to clean, severely affecting the appearance and performance of the final product. This negative impact is particularly pronounced in high-end fields such as optical displays and precision electronics.

[0004] Currently, the industry often improves cohesive strength by increasing the crosslinking density of the adhesive layer. However, excessive crosslinking can lead to decreased adhesion of the protective film and leave residue when removed. Another approach involves coating the substrate surface with a primer to enhance interfacial adhesion, but this increases production steps and costs, and some primers pose environmental risks. Therefore, developing an acrylic protective film that combines high die-cutting anti-dust properties, stable adhesion, and easy removal has become a pressing technical challenge for the industry. Summary of the Invention

[0005] The purpose of this invention is to solve the problems existing in the prior art by proposing an acrylic protective film and its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides an acrylic protective film, comprising a substrate layer, a primer modification layer, and an acrylic pressure-sensitive adhesive layer. The primer modification layer is composed of the following raw materials in parts by weight: polyurethane resin: 30-40 parts; acrylate copolymer resin: 10-15 parts; silane coupling agent: 2-5 parts; curing agent: 1-3 parts; solvent: 40-55 parts. The acrylic pressure-sensitive adhesive layer is composed of the following raw materials in parts by weight: butyl acrylate: 40-50 parts; isooctyl acrylate: 20-30 parts; methyl methacrylate: 5-10 parts; hydroxyethyl acrylate: 3-8 parts; crosslinking monomer: 1-3 parts; initiator: 0.2-0.5 parts; solvent: 30-40 parts.

[0007] Furthermore, the silane coupling agent is γ-aminopropyltriethoxysilane.

[0008] Furthermore, the crosslinking monomer is ethylene glycol diacrylate or trimethylolpropane triacrylate.

[0009] A method for preparing an acrylic protective film as described above includes the following steps: 1. Substrate modification: The biaxially oriented PET film was subjected to corona treatment and plasma modification in sequence; 2. Primer coating: Mix the primer modification layer raw materials evenly, coat them onto the surface of the modified substrate, and dry and cure. 3. Adhesive coating: Apply acrylic pressure-sensitive adhesive emulsion to the surface of the primer modification layer, dry and cure it, then attach the release film and cure it in a 50°C curing chamber for 48 hours to obtain the finished product.

[0010] Furthermore, the thickness of the biaxially oriented PET film is 30-50 μm. After corona treatment, it is treated with 180-200W plasma for 12-15 seconds, and the surface tension of the substrate reaches 53-55 mN / m.

[0011] Furthermore, the coating amount of the primer modification layer is 0.5-1.2 g / m², and the drying conditions are 80-100℃ for 1-2 min.

[0012] Furthermore, the coating thickness of the acrylic pressure-sensitive adhesive layer is 10-20 μm, and the drying conditions are 100-120°C for 2-3 minutes.

[0013] The beneficial effects of the acrylic protective film and its preparation method proposed in this invention are as follows: This invention enhances the surface activity of the substrate through plasma modification, and with the bridging effect of the primer modification layer, the adhesion between the adhesive layer and the substrate is increased by more than 30%. The addition of cross-linked monomers optimizes the cohesive strength of the adhesive layer, and there is no adhesive residue or powder shedding after die cutting. The adhesive formulation of this invention balances adhesion and cohesive strength, with an adhesion force of 100-2000gf / 25mm on different material surfaces such as metal, glass, and plastic. There is no adhesive residue after the protective film is removed, and it will not contaminate the protected product. This invention requires no additional complex processes, and the raw materials for the primer modification layer do not contain heavy metals or harmful solvents, comply with RoHS environmental standards, and are suitable for large-scale industrial production. The acrylic protective film of the present invention has excellent overall performance. The light transmittance of the protective film is ≥92%, the haze is ≤2%, and the adhesion change rate is ≤10% after being placed in an environment of 60℃ and 90%RH for 72 hours. It also has good weather resistance. Detailed Implementation

[0014] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0015] An acrylic protective film includes a substrate layer, a primer modification layer, and an acrylic pressure-sensitive adhesive layer. The primer modification layer is composed of the following raw materials in parts by weight: polyurethane resin: 30-40 parts; acrylate copolymer resin: 10-15 parts; silane coupling agent: 2-5 parts; curing agent: 1-3 parts; solvent: 40-55 parts. The acrylic pressure-sensitive adhesive layer is composed of the following raw materials in parts by weight: butyl acrylate: 40-50 parts; isooctyl acrylate: 20-30 parts; methyl methacrylate: 5-10 parts; hydroxyethyl acrylate: 3-8 parts; crosslinking monomer: 1-3 parts; initiator: 0.2-0.5 parts; solvent: 30-40 parts.

[0016] In an optional embodiment of the present invention, the silane coupling agent is γ-aminopropyltriethoxysilane, which is used to enhance the interfacial compatibility between the primer modification layer and the substrate layer and the acrylic pressure-sensitive adhesive layer.

[0017] In an optional embodiment of the present invention, the crosslinking monomer is ethylene glycol diacrylate or trimethylolpropane triacrylate, used to enhance the cohesive strength of the acrylic pressure-sensitive adhesive layer.

[0018] A method for preparing an acrylic protective film as described above includes the following steps: 1. Substrate modification: The biaxially oriented PET film was subjected to corona treatment and plasma modification in sequence; 2. Primer coating: Mix the primer modification layer raw materials evenly, coat them onto the surface of the modified substrate, and dry and cure. 3. Adhesive coating: Apply acrylic pressure-sensitive adhesive emulsion to the surface of the primer modification layer, dry and cure it, then attach the release film and cure it in a 50°C curing chamber for 48 hours to obtain the finished product.

[0019] In an optional embodiment of the present invention, the thickness of the biaxially oriented PET film is 30-50 μm. After corona treatment, it is treated with 180-200W plasma for 12-15 seconds to achieve a substrate surface tension of 53-55 mN / m, thereby increasing the content of active groups on the substrate surface.

[0020] In an optional embodiment of the present invention, the coating amount of the primer modification layer is 0.5-1.2 g / m², and the drying conditions are 80-100°C for 1-2 min. After the raw materials of the primer modification layer are mixed evenly, they are coated onto the modified surface of the substrate layer by microgravure coating to form the primer modification layer.

[0021] In an optional embodiment of the present invention, the coating thickness of the acrylic pressure-sensitive adhesive layer is 10-20 μm, and the drying conditions are 100-120°C for 2-3 minutes. After mixing the raw materials of the acrylic pressure-sensitive adhesive layer, the temperature is raised to 70-80°C under a nitrogen atmosphere, and an initiator is added to carry out a polymerization reaction for 4-6 hours to obtain an acrylic pressure-sensitive adhesive emulsion with a solid content of 35%-45%. The pressure-sensitive adhesive emulsion is coated on the surface of the primer modification layer, and after cooling, a release film is laminated to obtain the finished protective film. Example

[0022] 1. Substrate treatment: 50μm thick biaxially oriented PET film was selected, and after corona treatment, it was treated with 200W plasma for 15s, and the surface tension of the substrate reached 55mN / m.

[0023] 2. Preparation of the base coating modification layer: Weigh 35 parts of polyurethane resin, 12 parts of acrylate copolymer resin, 3 parts of γ-aminopropyltriethoxysilane, 2 parts of curing agent, and 48 parts of ethyl acetate according to the weight ratio. Mix them evenly and then apply them to the surface of the PET substrate by microgravity coating with a coating amount of 0.8 g / m². Dry at 90℃ for 1.5 min.

[0024] 3. Preparation of pressure-sensitive adhesive layer: Weigh 45 parts by weight of butyl acrylate, 25 parts by weight of isooctyl acrylate, 8 parts by weight of methyl methacrylate, 5 parts by weight of hydroxyethyl acrylate, 2 parts by weight of ethylene glycol diacrylate, 0.3 parts by weight of azobisisobutyronitrile, and 35 parts by weight of ethyl acetate. Polymerize at 75°C for 5 hours under a nitrogen atmosphere to obtain a pressure-sensitive adhesive emulsion with a solid content of 40%. Coat the emulsion onto the surface of the primer modification layer with a coating thickness of 15 μm, dry at 110°C for 2.5 min, attach the release film, and cure in a curing chamber at 50°C for 48 hours to obtain the finished protective film. Example

[0025] 1. Substrate treatment: 30μm thick biaxially oriented PET film was selected, and after corona treatment, it was treated with 180W plasma for 12s, and the surface tension of the substrate reached 53mN / m.

[0026] 2. Preparation of the base coat modification layer: Weigh 32 parts of polyurethane resin, 10 parts of acrylate copolymer resin, 2 parts of γ-aminopropyltriethoxysilane, 1 part of curing agent, and 55 parts of ethyl acetate according to the weight ratio. Mix them evenly and then apply them to the surface of the PET substrate by micro-gravure coating with a coating amount of 0.6 g / m². Dry at 85℃ for 1 min.

[0027] 3. Preparation of pressure-sensitive adhesive layer: Weigh 42 parts by weight of butyl acrylate, 28 parts by weight of isooctyl acrylate, 6 parts by weight of methyl methacrylate, 4 parts by weight of hydroxyethyl acrylate, 1.5 parts by weight of trimethylolpropane triacrylate, 0.25 parts by weight of azobisisobutyronitrile, and 32 parts by weight of ethyl acetate. Polymerize at 72℃ for 4.5h under nitrogen atmosphere to obtain a pressure-sensitive adhesive emulsion with a solid content of 38%. Coat the emulsion onto the surface of the primer modification layer with a coating thickness of 12µm, dry at 105℃ for 2min, attach the release film, and cure in a curing chamber at 50℃ for 48h to obtain the finished protective film.

[0028] Comparative Example 1 The difference from Example 1 is that the substrate was not plasma modified and the primer modification layer does not contain silane coupling agent.

[0029] Performance testing The protective films of Example 1, Example 2, and Comparative Example 1 were subjected to performance tests. The test methods and results are as follows: Test Project Test methods Example 1 Example 2 Comparative Example 1 180° peel strength test GB / T 2792-2014 600gf / 25mm 450gf / 25mm 800gf / 25mm Anti-powdering performance Microscopic observation after die-cutting No glue residue No glue residue Multiple glue residues Light transmittance GB / T 2410-2008 92.4% 92.7% 91.8% Weather resistance Change in adhesive strength after 72 hours at 60℃ / 90%RH 6% 7% 13% After systematic performance testing of Examples 1, 2, and Comparative Example 1, the results show that its overall performance is significantly better than that of the comparative example that did not adopt the complete technical solution. The specific test results are as follows: Regarding the 180° peel strength, Examples 1 and 2 achieved 600 gf / 25 mm and 450 gf / 25 mm, respectively. While Comparative Example 1 exhibited a higher peel strength (800 gf / 25 mm), its excessively high adhesive strength often resulted in difficulty in removal or the risk of residue, which is detrimental to the removability requirements in practical applications. The embodiments of this invention maintain moderate adhesive strength while ensuring no residue remains after removal of the protective film, making it suitable for applications requiring high surface cleanliness.

[0030] In the crucial die-cutting anti-dust performance test, neither Example 1 nor Example 2 showed any adhesive residue after die-cutting, demonstrating excellent anti-dust performance. However, Comparative Example 1 showed multiple adhesive residues under the same test conditions, indicating insufficient cohesive strength of the adhesive layer or poor interfacial adhesion, making it prone to contamination during processing. This demonstrates that the present invention, through plasma modification to enhance the surface activity of the substrate and in conjunction with a primer modification layer containing a silane coupling agent, significantly improves the interfacial bonding between the adhesive layer and the substrate, effectively suppressing adhesive layer breakage and dusting during the die-cutting process.

[0031] In terms of optical performance, the transmittance of Example 1 and Example 2 is 92.4% and 92.7% respectively, which is better than 91.8% of Comparative Example 1. This shows that the present invention achieves high adhesion and anti-powdering without sacrificing the transparency of the protective film, and is suitable for fields such as optical displays where transmittance is strictly required.

[0032] In the weather resistance test, after being placed in an environment of 60°C and 90%RH for 72 hours, the adhesive strength change rates of Examples 1 and 2 were 6% and 7%, respectively, while the change rate of Comparative Example 1 reached 13%. This indicates that the protective film of the present invention can still maintain stable adhesive performance under high temperature and high humidity environments, and its weather resistance is significantly improved, which is beneficial for long-term storage and reliability in harsh environments.

[0033] In summary, this invention significantly improves the anti-powdering performance and weather resistance of the protective film during die-cutting by modifying the substrate surface, optimizing the base coating, and adjusting the adhesive formulation, while maintaining good adhesion and high light transmittance.

[0034] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An acrylic protective film, comprising a substrate layer, a primer modification layer, and an acrylic pressure-sensitive adhesive layer, characterized in that: The primer modification layer is composed of the following raw materials in parts by weight: polyurethane resin: 30-40 parts; acrylate copolymer resin: 10-15 parts; Silane coupling agent: 2-5 parts; Hardener: 1-3 parts; Solvent: 40-55 parts; The acrylic pressure-sensitive adhesive layer is composed of the following raw materials in parts by weight: butyl acrylate: 40-50 parts; isooctyl acrylate: 20-30 parts; methyl methacrylate: 5-10 parts; hydroxyethyl acrylate: 3-8 parts. Cross-linked monomers: 1-3 parts; Initiator: 0.2-0.5 parts; Solvent: 30-40 parts.

2. The acrylic protective film according to claim 1, characterized in that: The silane coupling agent is γ-aminopropyltriethoxysilane.

3. The acrylic protective film according to claim 1, characterized in that: The cross-linking monomer is ethylene glycol diacrylate or trimethylolpropane triacrylate.

4. A method for preparing an acrylic protective film as described in any one of claims 1-3, characterized in that: Includes the following steps, Substrate modification: The biaxially oriented PET film was subjected to corona treatment and plasma modification in sequence; Primer coating: Mix the primer modification material evenly, coat it onto the modified substrate surface, and dry and cure. Adhesive coating: Apply acrylic pressure-sensitive adhesive emulsion to the surface of the primer modification layer, dry and cure it, then attach the release film and cure it in a 50℃ curing chamber for 48 hours to obtain the finished product.

5. The method for preparing an acrylic protective film according to claim 4, characterized in that: The biaxially oriented PET film has a thickness of 30-50 μm. After corona treatment, it is treated with 180-200W plasma for 12-15 seconds, resulting in a substrate surface tension of 53-55 mN / m.

6. The method for preparing an acrylic protective film according to claim 4, characterized in that: The coating amount of the primer modification layer is 0.5-1.2 g / m², and the drying conditions are 80-100℃ for 1-2 min.

7. The method for preparing an acrylic protective film according to claim 4, characterized in that: The coating thickness of the acrylic pressure-sensitive adhesive layer is 10-20 μm, and the drying conditions are 2-3 min at 100-120℃.