A method for preparing a color paste for an automotive color-changing film

Abstract

The application discloses a preparation method of a color paste for a car color-changing film, which comprises the following steps: a) uniformly stirring and mixing resin, solvent, wetting agent, dispersing agent, ultraviolet absorber, hindered amine light stabilizer and heat stabilizer; b) adding pigments and modified titanium dioxide and uniformly stirring and mixing; and c) adding the obtained mixture into a grinding machine, using zirconium dioxide as a medium grinding ball to grind the mixture, so as to obtain the color paste for the car color-changing film; the resin is organic silicon-acrylic acid composite modified polyurethane resin; and the modified titanium dioxide is obtained by coating a lanthanum oxide layer, a zirconium dioxide layer and a magnesium-aluminum LDH layer on the surface of titanium dioxide in sequence. The color paste prepared by the method can be used as a base film raw material for preparing the car color-changing film, and can effectively enhance the weather resistance of the base film of the car color-changing film.

Description

Technical Field

[0001] This invention relates to a method for preparing color paste for automotive color change films, belonging to the field of automotive color change film technology. Background Technology

[0002] To meet users' personalized needs for car colors, the current main method is to apply a color-changing film to the car's paint surface. Car color-changing films mainly consist of a substrate, a base film, and a protective film. The base film is the main component of the color-changing film, and its material is primarily thermoplastic polyurethane (TPU) or polyvinyl chloride (PVC).

[0003] Traditional car wrapping films primarily focus on color richness, color saturation, and color difference. However, with the development of car wrapping films, there is now a requirement for them to have certain protective functions. For example, after the wrapping film is applied, it isolates the car paint from the air, leaving only the wrapping film itself exposed. Over long-term use, it will be affected by factors such as ultraviolet rays, water, oxygen, and temperature, causing structural changes and shortening its lifespan. To ensure that the wrapping film can be used for a long time, it needs to have excellent weather resistance.

[0004] The raw materials for automotive color-change film base films mainly include base film resin, plasticizer, color paste, and solvent. Among these, color paste plays a crucial role, not only in providing basic coloring but also significantly influencing the product performance of the base film. Therefore, it is necessary to develop a color paste suitable for automotive color-change films to improve their weather resistance. Summary of the Invention

[0005] In view of the above-mentioned problems in the existing technology, the purpose of this invention is to provide a method for preparing color paste for automotive color change film.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a color paste for automotive color-changing films includes the following steps:

[0008] a) Mix 50-60 parts by weight of resin, 20-30 parts by weight of solvent, 0.4-0.6 parts by weight of wetting agent, 1-3 parts by weight of dispersant, 1-3 parts by weight of ultraviolet absorber, 1-3 parts by weight of hindered amine light stabilizer and 0.5-1.5 parts by weight of heat stabilizer evenly.

[0009] b) Add 10-20 parts by weight of pigment and 6-8 parts by weight of modified titanium dioxide, and stir to mix evenly;

[0010] c) Add the obtained mixture to a grinder and grind the mixture using zirconium dioxide as the grinding media to obtain a color paste for automotive color change film;

[0011] In step a), the resin is a silicone-acrylic acid composite modified polyurethane resin. This silicone-acrylic acid composite modified polyurethane resin is obtained by first reacting isophorone diisocyanate, polytetrahydrofuran diol, polycarbonate diol, dimethylolpropionic acid, and hydroxyl-terminated polydimethylsiloxane to obtain a silicone-modified polyurethane prepolymer. Then, the silicone-modified polyurethane prepolymer is polymerized with acrylic monomers. The acrylic monomers consist of cyclohexyl methacrylate, styrene, butyl methacrylate, methyl methacrylate, lauryl methacrylate, glycidyl methacrylate, methacrylic acid, hydroxypropyl methacrylate, and methoxy polyethylene glycol methacrylate. The solvent is a mixed solvent of ethyl acetate: n-propyl acetate: isopropanol in a mass ratio of 5:3:2.

[0012] In step b), the modified titanium dioxide is obtained by sequentially coating the surface of titanium dioxide with a lanthanum oxide layer, a zirconium dioxide layer, and a magnesium aluminum LDH layer.

[0013] In one embodiment, in step a), the wetting agent is the silicone wetting agent Tego-4100, the dispersant is BYK-333, the ultraviolet absorber is 2-hydroxy-4-(2-hydroxyethoxy)benzotriazole, and the hindered amine light stabilizer is 2,2,6,6-tetramethylpiperidine methacrylate.

[0014] In one embodiment, in step a), the heat stabilizer is a calcium-zinc composite heat stabilizer.

[0015] In a preferred embodiment, the calcium-zinc composite heat stabilizer is a composition of calcium cyanurate, zinc acetylacetone, calcium stearate, and zinc stearate in a mass ratio of 4:1:1.5:1.

[0016] In one embodiment, step a) of preparing the organosilicon-acrylic composite modified polyurethane resin includes the following steps:

[0017] 1) Under nitrogen protection, 31-33 parts by weight of isophorone diisocyanate (IPDI), 11-13 parts by weight of polytetrahydrofuran diol, 11-13 parts by weight of polycarbonate diol, 4-6 parts by weight of dimethylolpropionic acid (DMPA), 7-9 parts by weight of hydroxyl-terminated polydimethylsiloxane (PDMS-OH) and 40-50 parts by weight of propylene glycol methyl ether acetate are added to the reactor and stirred until homogeneous. Then the temperature is raised to 75-85℃, 0.05-0.1 parts by weight of catalyst are added, and the mixture is kept at this temperature and stirred for 2-3 hours. The reaction is then stopped, and the temperature is lowered to 45-55℃ to obtain the organosilicon-modified polyurethane prepolymer for later use.

[0018] 2) Mix 14-16 parts by weight of cyclohexyl methacrylate (CHMA), 19-21 parts by weight of butyl methacrylate (BMA), 14-16 parts by weight of methyl methacrylate (MMA), 4-6 parts by weight of lauryl methacrylate (LMA), 2-4 parts by weight of glycidyl methacrylate (GMA), 1.5-2.5 parts by weight of methacrylic acid (MAA), 4-6 parts by weight of hydroxypropyl methacrylate (HPMA), 4-6 parts by weight of methoxy polyethylene glycol methacrylate (PEGMA), and 14-1 Mix 6 parts by weight of propylene glycol methyl ether (PM) evenly to obtain a monomer solution; mix 1.2-1.6 parts by weight of initiator and 4-6 parts by weight of propylene glycol methyl ether (PM) evenly to obtain an initiator solution; add 14-16 parts by weight of propylene glycol methyl ether (PM) to a reactor, heat to 80-85℃, and then simultaneously add the monomer solution and initiator solution dropwise to the reactor, controlling the addition to be completed within 2-3 hours. After the addition is completed, keep the temperature and stir the reaction for 2-3 hours, then stop the reaction and cool to 45-55℃ to obtain an acrylic acid copolymer solution for later use.

[0019] 3) Heat the silicone-modified polyurethane prepolymer obtained in step 1) to 75-85℃, slowly add the acrylic copolymer solution obtained in step 2), control the adding time to 2-3 hours, and after the addition is complete, keep it warm and stir for 2-3 hours, then cool it to 38-42℃, add N,N-dimethylethanolamine to neutralize to pH=8-9, then slowly add 90-110 parts by mass of deionized water, continue stirring for 30 minutes, filter and discharge to obtain silicone-acrylic composite modified polyurethane resin.

[0020] In a preferred embodiment, in step 1), the hexamethylene diisocyanate used is a hexamethylene diisocyanate trimer (i.e., HDI trimer, for example, Desmodur N3300, Desmodur N3600), the polytetrahydrofuran diol used has a relative molecular weight of 1000, and the polycarbonate polyol used has a relative molecular weight of 2000.

[0021] In a preferred embodiment, in step 1), the catalyst used is a bismuth-based catalyst, such as K-KAT®348.

[0022] In a preferred embodiment, in step 2), the methoxy polyethylene glycol methacrylate used has a relative molecular weight of 1000.

[0023] In a preferred embodiment, in step 2), the initiator used is a compound of tert-butyl peroxide and benzoyl peroxide in a mass ratio of 3:1.

[0024] In one embodiment, step b) uses pigments including inorganic pigments (e.g., carbon black) and organic pigments (e.g., pigment red 122, pigment orange 43, pigment yellow 12, pigment green 7, pigment blue 15, pigment violet 23, etc.), wherein the pigments are pigments modified with diazonium salts.

[0025] In a preferred embodiment, the diazonium salt is selected from any one of 4-chloroaniline diazonium hexafluorophosphate, 4-nitroaniline diazonium tetrafluoroborate, p-aminoaniline diazonium salt, p-aminobenzenesulfonic acid diazonium salt, and p-aminobenzoic acid polymethyl ethylene glycol ester diazonium salt (the relative molecular mass of the polymethyl ethylene glycol fragment is 1000 to 2000).

[0026] In a preferred embodiment, the diazonium salt modified pigment comprises the following steps: reacting the pigment and the diazonium salt in water at a reaction temperature of room temperature to 90°C; after the reaction is complete, collecting the solid product to obtain the modified pigment, wherein the mass ratio of diazonium salt to pigment is 1:3 to 1:30.

[0027] In one embodiment, step b) of the preparation of the modified titanium dioxide includes the following steps:

[0028] ① Preparation of lanthanum oxide-coated titanium dioxide material: Nano-titanium dioxide was dispersed in water to obtain a titanium dioxide slurry with a concentration of 240-260 g / L; the titanium dioxide slurry was heated to 55-65℃, polycarboxylate dispersant was added, and the mixture was stirred for 15-25 minutes. Ammonia water was added to adjust the pH of the slurry to 9.0 and stabilize it. 0.1M lanthanum nitrate aqueous solution was slowly added dropwise, maintaining pH=9.0 throughout the process. After the addition was completed, the mixture was aged at 55-65℃ for 30-90 minutes, filtered, washed, dried, and ground to obtain lanthanum oxide-coated titanium dioxide material, denoted as: La2O3 / TiO2;

[0029] ② Preparation of zirconium dioxide / lanthanum oxide-coated titanium dioxide material: Lanthanum oxide-coated titanium dioxide material was dispersed in water to obtain a slurry with a concentration of 240-260 g / L; the obtained slurry was heated to 55-65℃, polycarboxylate dispersant was added, and the mixture was stirred for 15-25 minutes. Ammonia water was added to adjust the pH of the slurry to 9.0 and stabilize it. 0.5M zirconium oxynitrate aqueous solution was slowly added dropwise, and the pH was maintained at 9.0 throughout the process. After the addition was completed, the mixture was aged at 55-65℃ for 30-90 minutes, filtered, washed, dried, and ground to obtain zirconium dioxide / lanthanum oxide-coated titanium dioxide material, denoted as: ZrO2 / La2O3 / TiO2;

[0030] ③ Preparation of magnesium aluminum LDH / zirconium dioxide / lanthanum oxide-coated titanium dioxide material: The zirconium dioxide / lanthanum oxide-coated titanium dioxide material was dispersed in water to obtain a slurry with a concentration of 80-120 g / L; a magnesium aluminum nitrate solution with a total metal ion concentration of 0.3 M was prepared, wherein Mg 2+ :Al 3+ The molar ratio of urea and sodium dodecyl sulfate was 2:1. The mixture was stirred and mixed evenly to obtain a salt solution. The obtained salt solution was added to the obtained slurry and stirred at 75-85℃ for 8-15 hours. The reaction was then stopped, and the reaction solution was allowed to cool naturally to room temperature and aged for 3-5 hours. After centrifugation, washing, and drying, a magnesium-aluminum LDH / zirconium dioxide / lanthanum oxide-coated titanium dioxide material was obtained, denoted as: Mg-Al LDH / ZrO2 / La2O3 / TiO2.

[0031] In a preferred embodiment, in step ①, the coating amount of lanthanum oxide is 0.15-0.25 wt%, based on titanium dioxide.

[0032] In a preferred embodiment, in step ②, the coating amount of zirconium dioxide is 0.5-1 wt%, based on titanium dioxide.

[0033] In a preferred embodiment, in step ③, the coating amount of magnesium aluminum LDH is 3.0-5.0 wt% based on titanium dioxide.

[0034] In a preferred embodiment, in step ③, the molar ratio of urea to nitrate ions added to the salt solution is 3:1.

[0035] Compared with the prior art, the present invention has the following significant advantages:

[0036] This invention uses silicone-acrylic acid composite modified polyurethane resin as the main body, and combines the silicone-acrylic acid composite modified polyurethane resin with modified titanium dioxide, pigments and other components to prepare a color paste. The prepared color paste can be used to prepare the base film raw material for automotive color change film, which can effectively enhance the weather resistance of automotive color change film base film and has extremely strong industrial application value.

[0037] Example 1

[0038] I. Preparation of Organosilicon-Acrylic Composite Modified Polyurethane Resin

[0039] 1) Under nitrogen protection, 32 parts by weight of isophorone diisocyanate (Desmodur N3300), 12 parts by weight of polytetrahydrofuran diol (relative molecular mass of 1000), 12 parts by weight of polycarbonate diol (relative molecular mass of 2000), 5 parts by weight of dimethylolpropionic acid (DMPA), 8 parts by weight of hydroxyl-terminated polydimethylsiloxane (PDMS-OH, relative molecular mass of 1000) and 45 parts by weight of propylene glycol methyl ether acetate were added to the reactor and stirred until homogeneous. Then the temperature was raised to 80°C, and 0.08 parts by weight of catalyst (K-KAT®348) were added. The mixture was kept at this temperature and stirred for 2.5 hours. The reaction was then stopped, and the temperature was lowered to 50°C to obtain the silicone-modified polyurethane prepolymer for later use.

[0040] 2) Mix 15 parts by weight of cyclohexyl methacrylate (CHMA), 20 parts by weight of butyl methacrylate (BMA), 15 parts by weight of methyl methacrylate (MMA), 5 parts by weight of lauryl methacrylate (LMA), 3 parts by weight of glycidyl methacrylate (GMA), 2 parts by weight of methacrylic acid (MAA), 5 parts by weight of hydroxypropyl methacrylate (HPMA), 5 parts by weight of methoxy polyethylene glycol methacrylate (PEGMA, relative molecular weight 1000) and 15 parts by weight of propylene glycol methyl ether (PM). Mix thoroughly to obtain a monomer solution; mix 1.4 parts by mass of initiator (a compound of tert-butyl peroxide and benzoyl peroxide in a mass ratio of 3:1) and 5 parts by mass of propylene glycol methyl ether (PM) thoroughly to obtain an initiator solution; add 15 parts by mass of propylene glycol methyl ether (PM) to the reactor, heat to 80°C, and then simultaneously add the monomer solution and initiator solution to the reactor, controlling the addition to be completed within 3 hours. After the addition is completed, keep warm and stir the reaction for 2.5 hours, stop the reaction, cool to 50°C, and obtain an acrylic copolymer solution for later use;

[0041] 3) Heat the silicone-modified polyurethane prepolymer obtained in step 1) to 80°C, slowly add the acrylic copolymer solution obtained in step 2), control the addition time to 2.5 hours, and after the addition is complete, keep it at the temperature and stir for 2.5 hours. Then cool it down to 40°C, add N,N-dimethylethanolamine to neutralize to pH=8-9, and then slowly add 100 parts by mass of deionized water. Continue stirring for 30 minutes, filter and discharge to obtain silicone-acrylic composite modified polyurethane resin.

[0042] II. Preparation of Modified Carbon Black

[0043] Two parts by mass of carbon black were mixed with 14 parts by mass of water to obtain a slurry. 0.11 parts by mass of 4-chloroaniline diazonium hexafluorophosphate was dissolved in 7 parts by mass of water to obtain a diazonium salt aqueous solution. The obtained diazonium salt aqueous solution was added to the slurry, and the mixture was stirred at room temperature for 20 minutes. The reaction was then stopped, filtered, and the filter cake was extracted with tetrahydrofuran in a Soxhlet extractor. After extraction, the residue was dried in an oven to obtain modified carbon black.

[0044] III. Preparation of Modified Titanium Dioxide (Mg-Al LDH / ZrO2 / La2O3 / TiO2)

[0045] ① Preparation of lanthanum oxide-coated titanium dioxide material: Nano-titanium dioxide was dispersed in water to obtain a titanium dioxide slurry with a concentration of 250 g / L; the titanium dioxide slurry was heated to 60℃, and polycarboxylate dispersant was added (slurry:dispersant mass ratio of 35:0.1), stirred for 20 minutes, and 2M ammonia water was added to adjust the pH of the slurry to 9.0 and stabilize it. 0.1M lanthanum nitrate aqueous solution was slowly added dropwise (the La2O3 coating amount was controlled to be 0.2wt% of TiO2, and the dropping rate was controlled at 0.5 mL / min), and the pH was maintained at 9.0 throughout the process. After the addition was completed, it was aged at 60℃ for 60 minutes, filtered, washed (washed with deionized water and ethanol), dried (vacuum dried at 80℃ for 12 hours), and ground to obtain lanthanum oxide-coated titanium dioxide material, denoted as: La2O3 / TiO2;

[0046] ② Preparation of zirconium dioxide / lanthanum oxide-coated titanium dioxide material: Lanthanum oxide-coated titanium dioxide material was dispersed in water to obtain a slurry with a concentration of 250 g / L; the obtained slurry was heated to 60℃, polycarboxylate dispersant was added (slurry:dispersant mass ratio of 35:0.1), stirred for 20 minutes, 2M ammonia water was added to adjust the pH of the slurry to 9.0 and stabilize it, and 0.5M zirconium oxynitrate aqueous solution was slowly added dropwise (controlling the ZrO2 coating amount to 0.8wt% of TiO2, and the dropping rate to 1.0 mL / min), maintaining pH=9.0 throughout the process. After the addition was completed, it was aged at 60℃ for 60 minutes, filtered, washed, dried (vacuum dried at 80℃ for 12 hours), and ground to obtain zirconium dioxide / lanthanum oxide-coated titanium dioxide material, denoted as: ZrO2 / La2O3 / TiO2;

[0047] ③ Preparation of magnesium aluminum LDH / zirconium dioxide / lanthanum oxide-coated titanium dioxide material: The zirconium dioxide / lanthanum oxide-coated titanium dioxide material was dispersed in water to obtain a slurry with a concentration of 100 g / L; a magnesium aluminum nitrate solution with a total metal ion concentration of 0.3 M was prepared, wherein Mg 2+ :Al 3+ The molar ratio is 2:1, and urea (urea and NO3) is added. -The molar ratio of magnesium aluminum nitrate (3:1) and sodium dodecyl sulfate (0.1 wt% of the total magnesium aluminum nitrate) were stirred and mixed evenly to obtain a salt solution. The obtained salt solution was added to the obtained slurry (controlling the magnesium aluminum LDH coating amount to 4 wt% of TiO2), and the reaction was stirred at 80℃ for 12 hours. The reaction was then stopped, and the reaction solution was naturally cooled to room temperature, aged for 4 hours, centrifuged, washed, and dried (vacuum dried at 80℃ for 12 hours) to obtain a magnesium aluminum LDH / zirconium dioxide / lanthanum oxide coated titanium dioxide material, denoted as: Mg-Al LDH / ZrO2 / La2O3 / TiO2.

[0048] IV. Preparation of Color Paste

[0049] a) Mix 50 parts by weight of silicone-acrylic acid composite modified polyurethane resin, 20 parts by weight of solvent (a mixed solvent of ethyl acetate: n-propyl acetate: isopropanol in a mass ratio of 5:3:2), 0.4 parts by weight of wetting agent (silicone wetting agent Tego-4100), 1 part by weight of dispersant (BYK-333), 1 part by weight of ultraviolet absorber (2-hydroxy-4-(2-hydroxyethoxy)benzotriazole), 1 part by weight of hindered amine light stabilizer (2,2,6,6-tetramethylpiperidin methacrylate), and 0.5 parts by weight of heat stabilizer (a composition of calcium cyanurate: zinc acetylacetone: calcium stearate: zinc stearate in a mass ratio of 4:1:1.5:1) until homogeneous.

[0050] b) Add 10 parts by weight of modified carbon black and 6 parts by weight of modified titanium dioxide (Mg-Al LDH / ZrO2 / La2O3 / TiO2), and stir to mix evenly;

[0051] c) Add the obtained mixture to a grinder and grind the mixture using zirconium dioxide as the grinding media until the particle size is less than 0.5 μm to obtain a color paste for automotive color change film.

[0052] Example 2

[0053] The difference between this embodiment and Embodiment 1 is that:

[0054] 1) The pigment used in the color paste is modified pigment blue 15, and the modification method is as follows:

[0055] 1.68 parts by weight of NaNO2 were dissolved in 75 parts by weight of water. 20 parts by weight of Pigment Blue 15 and 4 parts by weight of sodium p-aminobenzenesulfonate (sodium p-aminobenzenesulfonate reacts with NaNO2 in water to form a diazonium salt of p-aminobenzenesulfonic acid) were added to the solution. The mixture was heated to 70°C with stirring to form a uniform slurry. Then, 30% HCl was added to adjust the pH of the system to 2. The mixture was kept at this temperature and stirred for 1 hour to stop the reaction. The mixture was filtered, and the filter cake was extracted with tetrahydrofuran in a Soxhlet extractor. After extraction, the residue was dried in an oven at 70°C to obtain modified Pigment Blue 15.

[0056] 2) The preparation of the color paste is as follows:

[0057] a) Mix 55 parts by weight of silicone-acrylic acid composite modified polyurethane resin, 25 parts by weight of solvent (a mixed solvent of ethyl acetate: n-propyl acetate: isopropanol in a mass ratio of 5:3:2), 0.5 parts by weight of wetting agent (silicone wetting agent Tego-4100), 2 parts by weight of dispersant (BYK-333), 2 parts by weight of ultraviolet absorber (2-hydroxy-4-(2-hydroxyethoxy)benzotriazole), 2 parts by weight of hindered amine light stabilizer (2,2,6,6-tetramethylpiperidin methacrylate), and 1 part by weight of heat stabilizer (a composition of calcium cyanurate: zinc acetylacetone: calcium stearate: zinc stearate in a mass ratio of 4:1:1.5:1) until homogeneous.

[0058] b) Add 15 parts by weight of modified pigment blue and 7 parts by weight of modified titanium dioxide (Mg-Al LDH / ZrO2 / La2O3 / TiO2), and stir to mix evenly;

[0059] c) Add the obtained mixture to a grinder and grind the mixture using zirconium dioxide as the grinding media until the particle size is less than 0.5 μm to obtain a color paste for automotive color change film.

[0060] Example 3

[0061] The difference between this embodiment and Embodiment 1 is that:

[0062] 1) The pigment used in the color paste is modified pigment Violet 23, and the modification method is as follows:

[0063] Mix 80 parts by weight of pigment Violet 23 with 800 parts by weight of water to form a paste, and set aside.

[0064] Eight parts by mass of polymethyl methacrylate p-aminobenzoate were dissolved in 100 parts by mass of HCl (concentration of 1%), and then 0.6 parts by mass of NaNO2 were added at 0°C. The mixture was stirred and reacted for 20 minutes to obtain the diazonium salt of polymethyl methacrylate p-aminobenzoate.

[0065] Add the diazonium salt to the pigment paste and react at room temperature for 30 minutes. Adjust the pH to 5-6 and continue stirring for another 30 minutes. Then raise the temperature to 50°C and continue the reaction until the diazonium salt is no longer detected in the reaction solution. Adjust the pH to 7, filter, wash with water until the conductivity of the filtrate is less than 30µS / cm, and dry at 80°C to obtain the modified pigment Violet 23.

[0066] 2) The preparation of the color paste is as follows:

[0067] a) Mix 60 parts by weight of silicone-acrylic acid composite modified polyurethane resin, 30 parts by weight of solvent (a mixed solvent of ethyl acetate: n-propyl acetate: isopropanol in a mass ratio of 5:3:2), 0.6 parts by weight of wetting agent (silicone wetting agent Tego-4100), 3 parts by weight of dispersant (BYK-333), 3 parts by weight of ultraviolet absorber (2-hydroxy-4-(2-hydroxyethoxy)benzotriazole), 3 parts by weight of hindered amine light stabilizer (2,2,6,6-tetramethylpiperidin methacrylate), and 1.5 parts by weight of heat stabilizer (a composition of calcium cyanurate: zinc acetylacetone: calcium stearate: zinc stearate in a mass ratio of 4:1:1.5:1) until homogeneous.

[0068] b) Add 20 parts by weight of modified pigment Violet 23 and 8 parts by weight of modified titanium dioxide (Mg-Al LDH / ZrO2 / La2O3 / TiO2), and stir to mix evenly;

[0069] c) Add the obtained mixture to a grinder and grind the mixture using zirconium dioxide as the grinding media until the particle size is less than 0.5 μm to obtain a color paste for automotive color change film.

[0070] Comparative Example 1

[0071] The difference between this comparative example and Example 1 is as follows:

[0072] Covestro 2110 waterborne polyurethane resin was used instead of the self-made silicone-acrylic composite modified polyurethane resin in Example 1.

[0073] Comparative Example 2

[0074] The difference between this comparative example and Example 1 is as follows:

[0075] Ordinary nano-titanium dioxide was used instead of the self-made modified titanium dioxide (Mg-Al LDH / ZrO2 / La2O3 / TiO2) in Example 1.

[0076] Comparative Example 3

[0077] The difference between this comparative example and Example 1 is as follows:

[0078] Unmodified ordinary carbon black was used instead of the modified carbon black prepared in Example 1.

[0079] Comparative Example 4

[0080] The difference between this comparative example and Example 1 is as follows:

[0081] Covestro 2110 waterborne polyurethane resin was used instead of the self-made silicone-acrylic composite modified polyurethane resin in Example 1. Ordinary nano titanium dioxide was used instead of the self-made modified titanium dioxide (Mg-Al LDH / ZrO2 / La2O3 / TiO2) in Example 1. Unmodified ordinary carbon black was used instead of the self-made modified carbon black in Example 1. Ordinary heat stabilizer (a composition of calcium stearate and zinc stearate in a mass ratio of 1.5:1) was used instead of the calcium-zinc composite heat stabilizer (a composition of calcium cyanurate, zinc acetylacetone, calcium stearate, and zinc stearate in a mass ratio of 4:1:1.5:1) in Example 1.

[0082] Performance testing:

[0083] 1) Preparation of PVC base film:

[0084] 100 parts by weight of PVC powder and 50 parts by weight of plasticizer (DINP) were stirred for 10 minutes to make them uniformly mixed. Then, 0.3 parts by weight of antioxidant (antioxidant 1010), 0.3 parts by weight of anti-yellowing agent (UV329), and 5 parts by weight of color paste prepared in the example or comparative example were added and stirred for 10 minutes to make them uniformly mixed. Then, vacuum was applied and stirring was continued under vacuum conditions for 20 minutes to obtain PVC coating. Then, a PVC coating with a thickness of 100 μm was uniformly coated on the substrate by slit coating. The coating was dried and cured in sequence at temperatures of 60℃ / 80℃ / 80℃ / 90℃ / 90℃ / 60℃ to form a PVC base film for automotive color change film (this invention only examines the effect of color paste in automotive color change film on the performance of PVC base film, therefore only the PVC base film is prepared, and the color change film as a whole is not prepared).

[0085] 2) UV aging test:

[0086] According to the testing standard ASTM G154, the UV aging test was conducted on the PVC base films prepared using the color pastes of Examples 1-3 and Comparative Examples 1-4 using a QUV accelerated aging test chamber. The test conditions were as follows: UV light source: UVB-313 lamp (wavelength 313nm); cycle program: 60℃ UV irradiation for 4 hours → 50℃ condensation for 4 hours (repeated cycle); total test duration: 1500 hours; color difference change (ΔE) was measured by a colorimeter, gloss loss rate was detected by a gloss meter, and chalking level was detected by visual inspection + tape adhesion method, thereby determining the UV aging resistance of the PVC base film. The test results are shown in Table 1.

[0087] 3) Damp heat aging test:

[0088] According to the testing standard ASTM D2247, PVC base films prepared using the color pastes of Examples 1-3 and Comparative Examples 1-4 were subjected to damp heat aging tests using a constant temperature and humidity chamber. The test conditions were: test temperature: 85℃ ± 2℃; test humidity: 85% RH ± 5%; test duration: 1000 hours. The color difference change (ΔE) was measured using a colorimeter, the gloss loss rate was detected using a gloss meter, and the chalking level was detected by visual inspection and tape adhesion method, thereby determining the damp heat aging resistance of the PVC base film. The test results are shown in Table 1.

[0089] Table 1. UV aging and damp heat aging test data of PVC base films prepared using the color pastes of Examples 1-3 and Comparative Examples 1-4

[0090]

[0091] As can be seen from Table 1, after UV aging and damp heat aging tests, the PVC base film prepared using the color pastes of Examples 1-3 showed better color difference, gloss loss rate and chalking grade than the PVC base film prepared using the color pastes of Comparative Examples 1-4. Therefore, the PVC base film prepared using the color pastes of Examples 1-3 has better UV aging resistance and damp heat aging resistance than the PVC base film prepared using the color pastes of Comparative Examples 1-4.

[0092] In summary, the PVC-based films prepared using the color pastes of Examples 1-3 of this invention exhibit better weather resistance than those prepared using the color pastes of Comparative Examples 1-4. Therefore, the color pastes of Examples 1-3 of this invention can effectively improve the weather resistance of PVC-based films when used for preparation. This may be because:

[0093] Compared with the waterborne polyurethane resins in Comparative Examples 1 and 4, the silicone-acrylic composite modified polyurethane resins used in Examples 1-3, after being modified by silicone and acrylic composite, have excellent UV aging resistance and hydrolysis resistance, thus effectively improving the overall weather resistance of PVC base film.

[0094] Compared to the ordinary nano-titanium dioxide in Comparative Examples 2 and 4, the modified titanium dioxide (Mg-Al LDH / ZrO2 / La2O3 / TiO2) used in Examples 1-3 has a surface coating of Mg-Al LDH / ZrO2 / La2O3 that can effectively improve the photostability of TiO2, inhibit photocatalytic activity, effectively provide barrier properties, and delay the penetration of water vapor and ultraviolet rays, thereby effectively improving the overall weather resistance of PVC base film.

[0095] The pigments used in Examples 1-3 were modified with diazonium salts. Compared with the ordinary pigments in Comparative Examples 3 and 4 that were not modified with diazonium salts, the pigments effectively improved the dispersibility and stability of the pigments in the resin, reduced agglomeration, thereby enhancing the UV shielding effect and thus effectively improving the overall weather resistance of the PVC base film.

[0096] The heat stabilizers used in Examples 1-3 (a composition of calcium cyanurate, zinc acetylacetone, calcium stearate, and zinc stearate in a mass ratio of 4:1:1.5:1) have a stronger synergistic effect among their components and superior heat and light resistance compared to the heat stabilizers used in Comparative Example 4 (a composition of calcium stearate and zinc stearate in a mass ratio of 1.5:1), thus effectively improving the overall weather resistance of the PVC base film.

[0097] Finally, it should be noted that the above are only some preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing a color paste for automotive color-changing films, characterized in that, Includes the following steps: a) Mix 50-60 parts by weight of resin, 20-30 parts by weight of solvent, 0.4-0.6 parts by weight of wetting agent, 1-3 parts by weight of dispersant, 1-3 parts by weight of ultraviolet absorber, 1-3 parts by weight of hindered amine light stabilizer and 0.5-1.5 parts by weight of heat stabilizer evenly. b) Add 10-20 parts by weight of pigment and 6-8 parts by weight of modified titanium dioxide, and stir to mix evenly. c) Add the obtained mixture to a grinder and grind the mixture using zirconium dioxide as the grinding media to obtain a color paste for automotive color change film; In step a), the resin is a silicone-acrylic acid composite modified polyurethane resin. This silicone-acrylic acid composite modified polyurethane resin is obtained by first reacting isophorone diisocyanate, polytetrahydrofuran diol, polycarbonate diol, dimethylolpropionic acid, and hydroxyl-terminated polydimethylsiloxane to obtain a silicone-modified polyurethane prepolymer. Then, the silicone-modified polyurethane prepolymer is polymerized with acrylic monomers. The acrylic monomers are composed of cyclohexyl methacrylate, styrene, butyl methacrylate, methyl methacrylate, lauryl methacrylate, glycidyl methacrylate, methacrylic acid, hydroxypropyl methacrylate, and methoxy polyethylene glycol methacrylate. The solvent is a mixed solvent of ethyl acetate: n-propyl acetate: isopropanol in a mass ratio of 5:3:

2. The heat stabilizer is a calcium-zinc composite heat stabilizer, which is a composition of calcium cyanurate: zinc acetylacetone: calcium stearate: zinc stearate in a mass ratio of 4:1:1.5:

1. In step b), the modified titanium dioxide is obtained by sequentially coating the surface of titanium dioxide with a lanthanum oxide layer, a zirconium dioxide layer, and a magnesium aluminum LDH layer; the pigments used include inorganic pigments and organic pigments, and the pigments are pigments modified with diazonium salts, wherein the diazonium salts are selected from any one of 4-chloroaniline diazonium hexafluorophosphate, 4-nitroaniline diazonium tetrafluoroborate, p-aminoaniline diazonium salt, p-aminobenzenesulfonic acid diazonium salt, and p-aminobenzoic acid polymethyl methacrylate diazonium salt.

2. The method for preparing color paste for automotive color-changing film according to claim 1, characterized in that: In step a), the wetting agent is the silicone wetting agent Tego-4100, the dispersant is BYK-333, the ultraviolet absorber is 2-hydroxy-4-(2-hydroxyethoxy)benzotriazole, and the hindered amine light stabilizer is 2,2,6,6-tetramethylpiperidine methacrylate.

3. The method for preparing color paste for automotive color-changing film according to claim 1, characterized in that, In step a), the preparation of the organosilicon-acrylic composite modified polyurethane resin includes the following steps: 1) Under nitrogen protection, 31-33 parts by weight of isophorone diisocyanate, 11-13 parts by weight of polytetrahydrofuran diol, 11-13 parts by weight of polycarbonate diol, 4-6 parts by weight of dimethylolpropionic acid, 7-9 parts by weight of hydroxyl-terminated polydimethylsiloxane, and 40-50 parts by weight of propylene glycol methyl ether acetate are added to the reactor and stirred until homogeneous. Then the temperature is raised to 75-85℃, 0.05-0.1 parts by weight of catalyst are added, and the mixture is kept at this temperature and stirred for 2-3 hours. The reaction is then stopped, and the temperature is lowered to 45-55℃ to obtain the organosilicon-modified polyurethane prepolymer for later use. 2) Mix 14-16 parts by weight of cyclohexyl methacrylate, 19-21 parts by weight of butyl methacrylate, 14-16 parts by weight of methyl methacrylate, 4-6 parts by weight of lauryl methacrylate, 2-4 parts by weight of glycidyl methacrylate, 1.5-2.5 parts by weight of methacrylic acid, 4-6 parts by weight of hydroxypropyl methacrylate, 4-6 parts by weight of methoxy polyethylene glycol methacrylate, and 14-16 parts by weight of propylene glycol methyl ether until homogeneous to obtain... To obtain the monomer solution, mix 1.2-1.6 parts by weight of initiator and 4-6 parts by weight of propylene glycol methyl ether evenly to obtain an initiator solution; add 14-16 parts by weight of propylene glycol methyl ether to the reactor, heat to 80-85℃, and then simultaneously add the monomer solution and initiator solution to the reactor dropwise, controlling the addition to be completed within 2-3 hours. After the addition is completed, keep the temperature and stir the reaction for 2-3 hours, then stop the reaction and cool down to 45-55℃ to obtain an acrylic acid copolymer solution for later use. 3) Heat the silicone-modified polyurethane prepolymer obtained in step 1) to 75-85℃, slowly add the acrylic copolymer solution obtained in step 2), control the adding time to 2-3 hours, and after the addition is complete, keep it warm and stir for 2-3 hours, then cool it to 38-42℃, add N,N-dimethylethanolamine to neutralize to pH=8-9, then slowly add 90-110 parts by mass of deionized water, continue stirring for 30 minutes, filter and discharge to obtain silicone-acrylic composite modified polyurethane resin.

4. The method for preparing color paste for automotive color-changing film according to claim 3, characterized in that, In step 2), the initiator used is a compound of tert-butyl peroxide and benzoyl peroxide in a mass ratio of 3:

1.

5. The method for preparing color paste for automotive color-changing film according to claim 1, characterized in that, In step b), the preparation of the modified titanium dioxide includes the following steps: ① Preparation of lanthanum oxide-coated titanium dioxide material: Nano-titanium dioxide was dispersed in water to obtain a titanium dioxide slurry with a concentration of 240-260 g / L; the titanium dioxide slurry was heated to 55-65℃, polycarboxylate dispersant was added, and the mixture was stirred for 15-25 minutes. Ammonia water was added to adjust the pH of the slurry to 9.0 and stabilize it. 0.1M lanthanum nitrate aqueous solution was slowly added dropwise, maintaining pH=9.0 throughout the process. After the addition was completed, the mixture was aged at 55-65℃ for 30-90 minutes, filtered, washed, dried, and ground to obtain lanthanum oxide-coated titanium dioxide material, denoted as: La2O3 / TiO2; ② Preparation of zirconium dioxide / lanthanum oxide-coated titanium dioxide material: Lanthanum oxide-coated titanium dioxide material was dispersed in water to obtain a slurry with a concentration of 240-260 g / L; the obtained slurry was heated to 55-65℃, polycarboxylate dispersant was added, and the mixture was stirred for 15-25 minutes. Ammonia water was added to adjust the pH of the slurry to 9.0 and stabilize it. 0.5M zirconium oxynitrate aqueous solution was slowly added dropwise, and the pH was maintained at 9.0 throughout the process. After the addition was completed, the mixture was aged at 55-65℃ for 30-90 minutes, filtered, washed, dried, and ground to obtain zirconium dioxide / lanthanum oxide-coated titanium dioxide material, denoted as: ZrO2 / La2O3 / TiO2; ③ Preparation of magnesium aluminum LDH / zirconium dioxide / lanthanum oxide coated titanium dioxide material: Disperse the zirconium dioxide / lanthanum oxide coated titanium dioxide material in water to obtain a slurry with a concentration of 80-120 g / L; Prepare a magnesium aluminum nitrate solution with a total metal ion concentration of 0.3 M, wherein Mg 2+ :Al 3+ The molar ratio of urea and sodium dodecyl sulfate was 2:

1. The mixture was stirred and mixed evenly to obtain a salt solution. The obtained salt solution was added to the obtained slurry and stirred at 75-85℃ for 8-15 hours. The reaction was then stopped, and the reaction solution was allowed to cool naturally to room temperature and aged for 3-5 hours. After centrifugation, washing, and drying, a magnesium-aluminum LDH / zirconium dioxide / lanthanum oxide-coated titanium dioxide material was obtained, denoted as: Mg-Al LDH / ZrO2 / La2O3 / TiO2.

6. The method for preparing color paste for automotive color-changing film according to claim 5, characterized in that: In step ①, based on titanium dioxide, the coating amount of lanthanum oxide is 0.15-0.25 wt%; in step ②, based on titanium dioxide, the coating amount of zirconium dioxide is 0.5-1 wt%; in step ③, based on titanium dioxide, the coating amount of magnesium aluminum LDH is 3.0-5.0 wt%.

Images