Pressure-sensitive adhesive for PVC color-changing car film and preparation method thereof

Abstract

The present application relates to the technical field of pressure sensitive adhesive, in particular to a pressure sensitive adhesive for PVC color-changing car film and a preparation method thereof, wherein the preparation raw materials include, by weight: 60-85 parts of soft monomer, 5-15 parts of hard monomer, 5-15 parts of functional monomer, 3-10 parts of modified monomer, 0.01-0.5 parts of initiator, 0.1-0.5 parts of crosslinking agent, 0.1-0.5 parts of antioxidant, and 150-250 parts of solvent.The present application can effectively avoid the precipitation of plasticizer in the PVC base material by limiting the modified monomer to include acrylamide compounds containing C3-C8 alkyl substituents, and further optimizes the construction adaptability and long-term stability of the pressure sensitive adhesive.

Description

Technical Field

[0001] This invention relates to the field of pressure-sensitive adhesive technology, specifically to a pressure-sensitive adhesive for PVC color-changing car wrap film and its preparation method. Background Technology

[0002] PVC color-change car wraps hold a significant share of the personalized car modification market due to their economic advantages. Their adhesion stability and lifespan largely depend on the performance of the matching pressure-sensitive adhesive. The industry has clear technical requirements for these pressure-sensitive adhesives: they must possess low initial tack to meet the need for rework during installation; high holding power and high cohesive strength to ensure long-term adhesion without peeling; resistance to the leaching of plasticizers (28%–32%) from the PVC substrate to prevent peel strength degradation or residue issues; and resistance to outdoor UV radiation, humid and hot environments, and extreme temperature differences to ensure stable long-term performance. As the automotive aftermarket demands higher lifespans for color-change films, there is still a need for further breakthroughs in the aging resistance of existing pressure-sensitive adhesives. Therefore, developing a high-performance pressure-sensitive adhesive that maintains core properties such as plasticizer resistance and aging resistance while further optimizing installation compatibility and long-term stability has become a key direction for the development of the PVC color-change car wrap industry.

[0003] Currently, the mainstream solutions in the market are mainly acrylic pressure-sensitive adhesives, such as the acrylic pressure-sensitive adhesive for PVC color-changing films and its preparation method disclosed in Chinese invention patent application CN117004349A. This method controls the product's number-average molecular weight to 40,000-60,000 and glass transition temperature to -30℃ to -45℃ by adjusting the ratio of 35-85 parts soft monomers, 10-25 parts hard monomers, and 2-9 parts functional monomers, combined with 140-160 parts solvent and 0.5-1.5 parts initiator. This achieves excellent plasticizer resistance and over 520 hours of resistance to damp heat aging. However, this solution has limitations in its resistance to plasticizer degradation, its relatively small molecular weight and poor tackiness, and it does not address the technical shortcomings of optimizing low-temperature performance. Summary of the Invention

[0004] The first aspect of this invention provides a pressure-sensitive adhesive for PVC color-changing car wrap film, wherein the raw materials for preparation, by weight, include: 60-85 parts of soft monomer, 5-15 parts of hard monomer, 5-15 parts of functional monomer, 3-10 parts of modified monomer, 0.01-0.5 parts of initiator, 0.1-0.5 parts of crosslinking agent, 0.1-0.5 parts of antioxidant, and 150-250 parts of solvent.

[0005] The solvent content in the raw materials is 30-70 wt%.

[0006] Optionally, the solvent content in the raw materials is 60-70 wt%.

[0007] The soft monomer includes branched alkyl acrylates containing 5-8 carbon atoms.

[0008] Optionally, the branched alkyl acrylate containing 5-8 carbon atoms includes at least one of 2-ethylhexyl acrylate, isooctyl acrylate, isoheptyl acrylate, 3,5,5-trimethylhexyl acrylate, and isoamyl acrylate.

[0009] Currently, PVC color-changing car wraps commonly use acrylic solvent-based pressure-sensitive adhesives as the bonding layer. However, the plasticizers added to the film are prone to migration and precipitation, leading to a decrease in the peel strength of the pressure-sensitive adhesive. This invention has found that by limiting the modified monomers to acrylamide compounds containing C3-C8 alkyl substituents, the precipitation of plasticizers from the PVC substrate can be effectively avoided, further optimizing the application compatibility and long-term stability of the pressure-sensitive adhesive. On the one hand, the acrylamide group possesses excellent copolymerization compatibility, enabling efficient polymerization with acrylate main monomers, hard monomers, and functional monomers, and stably anchoring within the pressure-sensitive adhesive molecular chain, preventing the migration and loss of modified components. On the other hand, the C3-C8 alkyl substituents impart appropriate hydrophobicity and steric hindrance to the molecular chain, significantly reducing the solubility parameter matching between the pressure-sensitive adhesive and the phthalic plasticizer in the PVC substrate, weakening the thermodynamic driving force for plasticizer penetration and swelling into the adhesive layer, and inhibiting adhesive layer softening and cohesive attenuation from the source. Furthermore, the steric hindrance of the alkyl chain inhibits excessive molecular chain entanglement or slippage, allowing the adhesive layer to maintain good flexibility while strengthening cohesive strength. In addition, the synergistic effect of these modified monomers, functional monomers, and crosslinking agents further optimizes the stability of the three-dimensional network structure of the pressure-sensitive adhesive, reducing chain segment degradation caused by small amounts of plasticizer penetration during long-term use, ultimately achieving a synergistic improvement in anti-plasticizer precipitation, ease of application, and long-term bonding stability.

[0010] The modified monomers include acrylamide compounds containing C3-C8 alkyl substituents.

[0011] The acrylamide compounds containing C3-C8 alkyl substituents include at least one of N-tert-butylacrylamide, N-isopropylacrylamide, N-cyclohexylacrylamide, N-tert-pentylacrylamide, and N-n-butylacrylamide.

[0012] The crosslinking agent includes organotitanium compounds containing β-diketone chelating ligands.

[0013] The organotitanium compounds containing β-diketone chelating ligands include at least one of bis(acetylacetonyl)diisopropoxytitanate, bis(acetylacetonyl)dibutoxytitanate, tri(acetylacetonyl)isopropyl titanate, bis(acetylacetonyl)diisopropoxyzirconate, and tetra(acetylacetonyl) titanate.

[0014] The hard monomer includes at least one of methyl methacrylate, ethyl methacrylate, propyl methacrylate, isobutyl methacrylate, methyl acrylate, and tert-butyl methacrylate.

[0015] The functional monomers include carboxyl-containing acrylic functional monomers, hydroxyl-containing acrylate functional monomers, and epoxy-containing acrylate functional monomers.

[0016] The weight ratio of the carboxyl-containing acrylic functional monomer, the hydroxyl-containing acrylate functional monomer, and the epoxy-containing acrylate functional monomer is 5:(2-6):(0.5-3).

[0017] The carboxyl-containing acrylic functional monomers include at least one of methacrylic acid, β-carboxyethyl acrylate, itaconic acid, and maleic anhydride.

[0018] The hydroxyl-containing acrylate functional monomers include at least one of hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and 4-hydroxybutyl acrylate.

[0019] The epoxy-containing acrylate functional monomers include at least one of glycidyl acrylate, 3,4-epoxycyclohexyl methyl methacrylate, glycidyl isobutylene ester, and allyl glycidyl ether.

[0020] The initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, di-tert-butyl peroxide, diisopropylbenzene peroxide, and tert-butyl peroxide.

[0021] The antioxidants include at least one of antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 3114, antioxidant DLTP, and antioxidant BHT.

[0022] The solvent includes at least one of ethyl acetate, toluene, butyl acetate, acetone, cyclohexanone, and xylene.

[0023] Optionally, the solvent includes ethyl acetate and toluene, wherein the mass ratio of ethyl acetate to toluene is 7:(1-5).

[0024] The second aspect of the present invention provides a method for preparing a pressure-sensitive adhesive, comprising the following steps: mixing a soft monomer, a hard monomer, a functional monomer, and a solvent comprising 50-60% of the total solvent to obtain a first mixture; dissolving an initiator in a solvent comprising 10-20% of the total solvent to obtain an initiator solution; dissolving a crosslinking agent and an antioxidant in a solvent comprising 5-15% of the total solvent to obtain a second mixture; adding the initiator solution dropwise to the first mixture to react, and adding the remaining solvent after the reaction to obtain a third mixture; and adding the second mixture to the third mixture and mixing them evenly.

[0025] The dripping time is 2-4 hours.

[0026] The reaction is carried out at a temperature of 65-100℃ for 1-3 hours.

[0027] Optionally, the reaction temperature is 75-95°C.

[0028] Beneficial effects 1. By limiting the modified monomers to acrylamide compounds containing C3-C8 alkyl substituents, this invention can effectively prevent the precipitation of plasticizers in PVC substrates, and further optimize the application compatibility and long-term stability of pressure-sensitive adhesives.

[0029] 2. By limiting the soft monomer to include branched alkyl acrylates containing 5-8 carbon atoms, the present invention can improve the low-temperature resistance of pressure-sensitive adhesives.

[0030] 3. By limiting the crosslinking agent to include organotitanium compounds containing β-diketone chelating ligands, this invention can balance the high-temperature tack and high-temperature aging properties of pressure-sensitive adhesives, while effectively reducing the amount of residual adhesive.

[0031] 4. By limiting the functional monomers to include carboxyl-containing acrylic functional monomers, hydroxyl-containing acrylate functional monomers, and epoxy-containing acrylate functional monomers, and by limiting the compounding ratio, the peel strength reduction rate of the pressure-sensitive adhesive after being placed at 60°C for 5 days is controlled within 15%.

[0032] 5. The pressure-sensitive adhesive of the present invention is suitable for bonding PVC color-changing car wrap film, and has excellent resistance to plasticizer interference and strong environmental stability. Detailed Implementation

[0033] Example 1, Comparative Examples 1-4 A pressure-sensitive adhesive for PVC color-changing car wrap film, the raw materials for preparation are shown in Table 1 by weight, " / " indicates no addition.

[0034] Table 1

[0035] The mass ratio of ethyl acetate to toluene is 7:3.

[0036] A method for preparing pressure-sensitive adhesive for PVC color-changing car wrap film includes the following steps: 1. Premixing: Add the soft monomer, hard monomer and functional monomer to the reactor according to the ratio, add solvent accounting for 60% of the total solvent, and stir to dissolve.

[0037] 2. Droplet polymerization: Heat the reactor to 78±2℃ and purge with nitrogen for 30 min to remove oxygen; dissolve the initiator in a solvent accounting for 20% of the total solvent and add it dropwise to the reactor at a uniform rate over 3 h.

[0038] 3. Incubation and curing: After dripping, raise the temperature to 85℃ and keep it warm for 2 hours.

[0039] 4. Post-crosslinking treatment: Add solvent accounting for 10% of the total solvent, cool to 50℃, then use the remaining solvent to dissolve the crosslinking agent and antioxidant, add the dissolved solvent to the reaction vessel, and stir for 30 minutes.

[0040] 5. Discharge: Cool to room temperature and discharge.

[0041] Performance testing methods The pressure-sensitive adhesives prepared in the examples and comparative examples were coated on substrates and their performance was tested. The test data are listed in Table 2, with " / " indicating that no test was performed.

[0042] The steps for coating the substrate are as follows: Transfer coating of 50μm release PET mesh film to 150μm PVC color-changing car wrap film; dry coating thickness: 25±2μm; curing conditions: 50℃×48h The testing method is as follows: 1. Peel strength: ASTM D3330, for coated films, test the peel strength initially (after 20 min) and after 24 h.

[0043] 2. Low temperature resistance: After 24 hours at -15℃, observe whether it becomes brittle and the peel strength retention rate.

[0044] 3. Resistance to plasticizer migration: Changes in peel strength after accelerated precipitation at 60℃ for 5 days.

[0045] 4. Double 85 test: After being placed under double 85 conditions for 7 days, the change in peel strength and residual adhesiveness are tested.

[0046] 5. Adhesive adhesion strength: Check for residual adhesive after 30 bonding cycles.

[0047] 6.80℃ High Temperature Adhesion Holding Time: Hang a 1kg weight on the adhesive film and place it in a high temperature adhesion holding time test chamber. Set the temperature to 80℃ and test the adhesion holding time according to GB / T 4851-2014.

[0048] 7. Initial tack ring: Tested according to GB / T 31125-2014.

[0049] Performance test data Table 2

Claims

1. A pressure-sensitive adhesive for PVC color-changing car wrap film, characterized in that, The raw materials for preparation, by weight, include: 60-85 parts of soft monomer, 5-15 parts of hard monomer, 5-15 parts of functional monomer, 3-10 parts of modified monomer, 0.01-0.5 parts of initiator, 0.1-0.5 parts of crosslinking agent, 0.1-0.5 parts of antioxidant, and 150-250 parts of solvent; the modified monomer includes acrylamide compounds containing C3-C8 alkyl substituents.

2. The pressure-sensitive adhesive according to claim 1, characterized in that, The soft monomer includes branched alkyl acrylates containing 5-8 carbon atoms.

3. The pressure-sensitive adhesive according to claim 2, characterized in that, The crosslinking agent includes organotitanium compounds containing β-diketone chelating ligands.

4. The pressure-sensitive adhesive according to claim 3, characterized in that, The functional monomers include carboxyl-containing acrylic functional monomers, hydroxyl-containing acrylate functional monomers, and epoxy-containing acrylate functional monomers.

5. The pressure-sensitive adhesive according to claim 4, characterized in that, The weight ratio of the carboxyl-containing acrylic functional monomer, the hydroxyl-containing acrylate functional monomer, and the epoxy-containing acrylate functional monomer is 5:(2-6):(0.5-3).

6. The pressure-sensitive adhesive according to claim 1 or 5, characterized in that, The solvent content in the raw materials is 30-70 wt%.

7. The pressure-sensitive adhesive according to claim 1, characterized in that, The initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, di-tert-butyl peroxide, diisopropylbenzene peroxide, and tert-butyl peroxide.

8. The pressure-sensitive adhesive according to claim 1, characterized in that, The solvent includes at least one of ethyl acetate, toluene, butyl acetate, acetone, cyclohexanone, and xylene.

9. A method for preparing a pressure-sensitive adhesive according to any one of claims 1-8, characterized in that, Includes the following steps: The soft monomer, hard monomer, functional monomer, and solvent accounting for 50-60% of the total solvent are mixed evenly to obtain a first mixture; the initiator is dissolved in solvent accounting for 10-20% of the total solvent to obtain an initiator solution; the crosslinking agent and antioxidant are dissolved in solvent accounting for 5-15% of the total solvent to obtain a second mixture; the initiator solution is added dropwise to the first mixture to carry out the reaction, and the remaining solvent is added after the reaction to obtain a third mixture; the second mixture is added to the third mixture and mixed evenly.

10. The method for preparing the pressure-sensitive adhesive according to claim 9, characterized in that, The dripping time is 2-4 hours.

Images