TPU (thermoplastic polyurethane) film adaptive to pressure-sensitive adhesive and preparation process of TPU film

Abstract

The invention relates to a TPU film matched with a pressure-sensitive adhesive and a preparation process of the TPU film, and belongs to the technical field of TPU films. A formula of the TPU film comprises the following components in parts by weight: 80 to 90 parts of TPU, 10 to 15 parts of tetrahydrofuran copolyether, 5 to 8 parts of fluorinated acrylate, 2 to 5 parts of modified SiO2 particles, 1 to 2 parts of a silane coupling agent KH560 and 0.5 to 1 part of a dispersing agent, and the dispersing agent is ethylene bis stearamide. The TPU film prepared by the process disclosed by the invention has the characteristic of good adhesion with a pressure-sensitive adhesive, and also has good flame retardance and mechanical properties.

Description

Technical Field

[0001] The invention belongs to the technical field of TPU films and relates to a TPU film adapted for pressure-sensitive adhesive and a preparation process thereof. Background Art

[0002] Pressure-sensitive adhesive is a functional material that can achieve bonding without solvents, heating or curing. Its core performance indicators include initial adhesion, sustained adhesion, peel strength and environmental aging resistance. In high-end application scenarios such as automotive paint protection film, medical dressings, and electronic screen protection films, pressure-sensitive adhesives need to form a stable and long-lasting bonding interface with the substrate to meet the challenges of complex environments. However, the interfacial compatibility, chemical bonding ability and physical adsorption between the substrate and the pressure-sensitive adhesive directly affect the overall performance of the composite film, becoming a key technical bottleneck restricting the development of the industry. Therefore, there is an urgent need to develop a TPU film suitable for pressure-sensitive adhesives and its preparation process. Summary of the Invention

[0003] The purpose of the present invention is to provide a TPU film adapted to a pressure-sensitive adhesive and a preparation process thereof, which has the characteristics of good adhesion with the pressure-sensitive adhesive.

[0004] The purpose of the present invention can be achieved through the following technical solutions: A TPU film suitable for pressure-sensitive adhesive, the formula of the TPU film is as follows: in parts by weight, 80-90 parts of TPU, 10-15 parts of tetrahydrofuran copolyether, 5-8 parts of fluoroacrylate, 2-5 parts of modified SiO2 particles, 1-2 parts of silane coupling agent KH560, and 0.5-1 part of dispersant. The preparation method of the modified SiO2 particles is as follows: S1-1: 20-30 parts by weight of anhydrous ethanol, 5-10 parts by weight of deionized water, and 1-2 parts by weight of 30 wt% ammonia water were added to a three-necked flask, and the mixture was stirred at 500-600 rpm in a water bath at 30-40°C for 30-60 min. 3-5 parts by weight of ethyl orthosilicate was added dropwise, and the mixture was stirred in a water bath for 6-8 h. The mixture was then washed with deionized water and ethanol, and then dried in vacuo at 60°C for 12 h to obtain SiO2 particles. S1-2: 3-Methacryloxypropyltrimethoxysilane was mixed with ethanol, and SiO2 particles were added to obtain a solid content of 5-10 wt%. The mixture was stirred at 50-60°C for 6-8 h, centrifuged, washed with ethanol, and dried at 60°C for 12 h to obtain particles A. S1-3: 10-20 parts by weight of microparticles A were dispersed in 100-150 parts by weight of Tris-HCl buffer with a pH of 8-8.5, and sonicated for 30 min. Dopamine hydrochloride was then added, and the mixture was stirred in the dark at 25-35°C for 20-24 h, during which the pH was maintained within the range of 8.5±0.2. The mixture was centrifuged and dialyzed for 48 h, and then freeze-dried at -40°C for 12 h to obtain microparticles B. S1-4: 5-10 parts by weight of the microparticles B are added to 100 parts by weight of a phytic acid aqueous solution, stirred at 60° C. for 10-12 hours, washed with deionized water, and dried at 60° C. for 12 hours to obtain the modified SiO 2 microparticles.

[0005] As a preferred technical solution of the present invention, the dispersant is ethylene bisstearamide.

[0006] As a preferred technical solution of the present invention, the dripping speed of the ethyl orthosilicate in S1-1 is 1-2 mL / min.

[0007] As a preferred technical solution of the present invention, in S1-2, 3-methacryloxypropyltrimethoxysilane and ethanol are mixed in a volume ratio of 1:(8~10).

[0008] As a preferred technical solution of the present invention, the amount of dopamine hydrochloride added in S1-3 is 0.2 to 0.3 times the mass of the microparticles A.

[0009] As a preferred technical solution of the present invention, the dialysis purification in S1-3 uses a dialysis bag with a molecular weight cut-off of 1000.

[0010] As a preferred technical solution of the present invention, the mass fraction of phytic acid in the phytic acid aqueous solution in S1-4 is 10%.

[0011] A preparation process of a TPU film suitable for pressure-sensitive adhesive, the specific steps of the preparation process are as follows: S8-1: Place TPU particles in a ball mill and mill for 3-4 hours at a ball mill speed of 150-250 rpm. Then, add fluoroacrylate, modified SiO2 particles, dispersant and tetrahydrofuran copolyether in sequence and stir for 30-60 minutes to obtain mixture C; S8-2: Add mixture C to a high-speed mixer, then add silane coupling agent KH560, and mix at 80°C for 2-3 hours to obtain a masterbatch; S8-3: The masterbatch is cast into TPU film through an extruder through a direct casting process, and no embossing treatment is performed at the three rollers; S8-4: After extrusion casting, corona treatment is performed at a power of 1.5-2 kW and a speed of 8-10 m / min, followed by standing for 12-14 hours, cooling and winding, and packaging the finished product to obtain the TPU film.

[0012] As a preferred technical solution of the present invention, the stirring speed in S8-1 is 200~300 rpm.

[0013] As a preferred technical solution of the present invention, the mixing speed in S8-2 is 800~1000 rpm.

[0014] By adjusting the amount of ammonia and the reaction time, monodisperse SiO2 is prepared, which can be used as a rigid core layer to enhance the wear resistance of the film, reduce the friction coefficient, and indirectly improve the bonding durability. The abundant hydroxyl groups on the SiO2 surface provide active sites for the subsequent silanization reaction. 3-Methacryloxypropyltrimethoxysilane is mixed with ethanol, added to SiO2 rice particles, and washed and dried after the reaction to obtain microparticles A. 3-Methacryloxypropyltrimethoxysilane is used as a silane coupling agent, and its methoxy group reacts with the hydroxyl group on the SiO2 surface to form a covalent bond, and the terminal double bond provides an active site for subsequent polymerization. 3-Methacryloxypropyltrimethoxysilane modification improves the compatibility of SiO2 with the TPU substrate, reduces interface defects, and improves bonding strength.

[0015] Dopamine hydrochloride self-polymerizes into polydopamine under weakly alkaline conditions, and the catechol groups impart biomimetic adhesion properties to the microparticles. The PDA coating significantly enhances interfacial adhesion through catechol-metal ion coordination bonds and hydrogen bonds. Furthermore, the carbonized PDA forms a residual carbon layer that blocks heat transfer.

[0016] Phytic acid, a multidentate ligand, reacts its phosphate groups with the hydroxyl groups on the SiO2 surface, introducing negative charges and improving the dispersion of the particles in the TPU. Phytic acid treatment indirectly improves bonding strength by enhancing particle dispersion and reducing interfacial defects. Furthermore, phytic acid, a phosphorus-based flame retardant, decomposes during combustion to form polyphosphoric acid, which promotes the dehydration and carbonization of the TPU, forming a flame-retardant layer and significantly reducing smoke density.

[0017] Dopamine and phytic acid exhibit a synergistic effect. PDA provides chemical bonding sites, while phytic acid enhances dispersibility. The combined effect significantly improves peel strength. The modified particle surface is closer to that of the pressure-sensitive adhesive, promoting wetting and adhesion. Furthermore, phytic acid and SiO2 form a Si-OP network during combustion, enhancing the stability of the char layer. Phytic acid decomposes to produce NH3 and H2O, which dilute the combustible gas concentration and delay combustion.

[0018] Introducing corona treatment into the TPU film preparation process introduces polar groups onto the surface, enhancing the adhesion of the pressure-sensitive adhesive. The static process relaxes stress within the film, significantly reducing residual stress and minimizing deformation during subsequent processing.

[0019] Beneficial effects: The present invention uses a monodisperse SiO2 core layer to reduce the friction coefficient and enhance wear resistance through a rigid structure, and its surface hydroxyl groups provide reaction sites for subsequent functionalization; 3-methacryloxypropyltrimethoxysilane coupling agent improves compatibility with TPU through chemical bonding, reduces interface defects, and enhances peel strength; dopamine self-polymerizes to form a polydopamine coating, and uses catechol groups to construct a dual adhesion mechanism of chemical bonding and hydrogen bonding, while forming a thermal barrier layer after carbonization; phytic acid introduces phosphate groups to give the particles negative charge, optimize dispersibility, and indirectly strengthen interface bonding. Its phosphorus-based flame retardant properties significantly enhance flame retardancy through catalytic carbonization and gas dilution effects, and reduce smoke density. Dopamine and phytic acid work synergistically to match the surface energy with the pressure-sensitive adhesive, promote wetting and adhesion, and form a Si-OP network during combustion to enhance the stability of the carbon layer, ultimately achieving a simultaneous improvement in peel strength and flame retardancy. DETAILED DESCRIPTION

[0020] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0021] Example 1 A TPU film suitable for pressure-sensitive adhesive, the formula of the TPU film is as follows: in parts by weight, 85 parts of TPU, 12 parts of tetrahydrofuran copolyether, 7 parts of fluoroacrylate, 3 parts of modified SiO2 particles, 1.5 parts of silane coupling agent KH560, and 0.8 parts of ethylene bisstearamide. The preparation method of the modified SiO2 particles is as follows: S1-1: 25 parts by weight of anhydrous ethanol, 8 parts by weight of deionized water, and 1.5 parts by weight of 30 wt% ammonia water were added to a three-necked flask, and the mixture was stirred at 550 rpm in a 35°C water bath for 45 min. 4 parts by weight of ethyl orthosilicate was added dropwise at a rate of 1.5 mL / min, and the mixture was stirred in the water bath for 7 h. The mixture was then washed with deionized water and ethanol, and then dried in vacuo at 60°C for 12 h to obtain SiO2 particles. S1-2: 3-Methacryloxypropyltrimethoxysilane and ethanol were mixed in a volume ratio of 1:9, SiO2 particles were added to make the solid content 8 wt%, and the mixture was stirred at 55°C for 7 h, centrifuged and washed with ethanol, and then dried at 60°C for 12 h to obtain particles A; S1-3: 15 parts by weight of microparticles A were dispersed in 120 parts by weight of Tris-HCl buffer with a pH of 8.3, and the mixture was sonicated for 30 min. Then, 0.25 times the mass of dopamine hydrochloride of microparticles A was added. The mixture was incubated at 30°C in the dark with stirring for 22 h, during which the pH was maintained within the range of 8.5 ± 0.2. The mixture was centrifuged and dialyzed for 48 h using a dialysis bag with a molecular weight cut-off of 1000. The mixture was then freeze-dried at -40°C for 12 h to obtain microparticles B. S1-4: 8 parts by weight of the particles B were added to 100 parts by weight of a 10% phytic acid aqueous solution, stirred at 60° C. for 11 h, washed with deionized water, and dried at 60° C. for 12 h to obtain the modified SiO 2 particles.

[0022] A preparation process of a TPU film suitable for pressure-sensitive adhesive, the specific steps of the preparation process are as follows: S8-1: TPU particles were ball milled for 3.5 h at a speed of 200 rpm, followed by the addition of fluoroacrylate, modified SiO2 particles, dispersant, and tetrahydrofuran copolyether, and stirred for 45 min at a speed of 250 rpm to obtain mixture C; S8-2: Add mixture C to a high-speed mixer, add silane coupling agent KH560, and mix at 80°C for 2.5 hours at a mixing speed of 900 rpm to obtain a masterbatch; S8-3: The masterbatch is cast into TPU film through an extruder through a direct casting process, and no embossing treatment is performed at the three rollers; S8-4: After extrusion casting, corona treatment was performed at a power of 1.8 kW and a speed of 9 m / min, followed by standing for 13 h, cooling and winding, and packaging the finished product to obtain the TPU film.

[0023] Example 2 A TPU film suitable for pressure-sensitive adhesive, the formula of the TPU film is as follows: in parts by weight, 80 parts of TPU, 10 parts of tetrahydrofuran copolyether, 5 parts of fluoroacrylate, 2 parts of modified SiO2 particles, 1 part of silane coupling agent KH560, and 0.5 parts of ethylene bisstearamide. The preparation method of the modified SiO2 particles is as follows: S1-1: 20 parts by weight of anhydrous ethanol, 5 parts by weight of deionized water, and 1 part by weight of 30 wt% ammonia water were added to a three-necked flask, and the mixture was stirred at 500 rpm in a 30°C water bath for 30 min. 3 parts by weight of ethyl orthosilicate was added dropwise at a rate of 1 mL / min, and the mixture was stirred in the water bath for 6 h. The mixture was then washed with deionized water and ethanol, and then dried in vacuo at 60°C for 12 h to obtain SiO2 particles. S1-2: 3-Methacryloxypropyltrimethoxysilane and ethanol were mixed in a volume ratio of 1:8, SiO2 particles were added to make the solid content 5 wt%, and the mixture was stirred at 50°C for 6 h. The mixture was centrifuged and washed with ethanol, and then dried at 60°C for 12 h to obtain particles A. S1-3: 10 parts by weight of microparticles A were dispersed in 100 parts by weight of Tris-HCl buffer with a pH of 8, and sonicated for 30 min. Then, 0.2 times the mass of dopamine hydrochloride of microparticles A was added. The mixture was incubated at 25°C in the dark with stirring for 20 h, during which the pH was maintained within the range of 8.5 ± 0.2. The mixture was centrifuged and dialyzed for 48 h using a dialysis bag with a molecular weight cutoff of 1000. The mixture was then freeze-dried at -40°C for 12 h to obtain microparticles B. S1-4: 5 parts by weight of the particles B were added to 100 parts by weight of a 10% phytic acid aqueous solution, stirred at 60° C. for 10 h, washed with deionized water, and dried at 60° C. for 12 h to obtain the modified SiO 2 particles.

[0024] A preparation process of a TPU film suitable for pressure-sensitive adhesive, the specific steps of the preparation process are as follows: S8-1: TPU particles were ball milled for 3 h at a speed of 150 rpm, followed by the addition of fluoroacrylate, modified SiO2 particles, dispersant, and tetrahydrofuran copolyether, and stirred for 30 min at a speed of 200 rpm to obtain mixture C; S8-2: Add mixture C to a high-speed mixer, add silane coupling agent KH560, and mix at 80°C for 2 h at a mixing speed of 800 rpm to obtain a masterbatch; S8-3: The masterbatch is cast into TPU film through an extruder through a direct casting process, and no embossing treatment is performed at the three rollers; S8-4: After extrusion casting, corona treatment is performed at a power of 1.5 kW and a speed of 8 m / min, followed by standing for 12 h, cooling and winding, and packaging the finished product to obtain the TPU film.

[0025] Example 3 A TPU film suitable for pressure-sensitive adhesive, the formula of the TPU film is as follows: in parts by weight, 90 parts of TPU, 15 parts of tetrahydrofuran copolyether, 8 parts of fluoroacrylate, 5 parts of modified SiO2 particles, 2 parts of silane coupling agent KH560, and 1 part of ethylene bisstearamide. The preparation method of the modified SiO2 particles is as follows: S1-1: 30 parts by weight of anhydrous ethanol, 10 parts by weight of deionized water, and 2 parts by weight of 30 wt% ammonia water were added to a three-necked flask, and the mixture was stirred at 600 rpm in a 40°C water bath for 60 min. 5 parts by weight of ethyl orthosilicate was added dropwise at a rate of 2 mL / min, and the mixture was stirred in the water bath for 8 h. The mixture was then washed with deionized water and ethanol, and then dried in vacuo at 60°C for 12 h to obtain SiO2 particles. S1-2: 3-Methacryloxypropyltrimethoxysilane and ethanol were mixed in a volume ratio of 1:10, SiO2 particles were added to make the solid content 10 wt%, and the mixture was stirred at 60°C for 8 h. The mixture was centrifuged and washed with ethanol, and then dried at 60°C for 12 h to obtain particles A. S1-3: 20 parts by weight of microparticles A were dispersed in 150 parts by weight of Tris-HCl buffer with a pH of 8.5, and the mixture was sonicated for 30 min. Then, 0.3 times the mass of dopamine hydrochloride of microparticles A was added. The mixture was incubated at 35°C in the dark with stirring for 24 h, during which the pH was maintained within the range of 8.5±0.2. The mixture was centrifuged and dialyzed for 48 h using a dialysis bag with a molecular weight cutoff of 1000. The mixture was then freeze-dried at -40°C for 12 h to obtain microparticles B. S1-4: 10 parts by weight of the particles B were added to 100 parts by weight of a 10% phytic acid aqueous solution, stirred at 60° C. for 12 h, washed with deionized water, and dried at 60° C. for 12 h to obtain the modified SiO 2 particles.

[0026] A preparation process of a TPU film suitable for pressure-sensitive adhesive, the specific steps of the preparation process are as follows: S8-1: TPU particles were ball milled for 4 h at a speed of 250 rpm, followed by the addition of fluoroacrylate, modified SiO2 particles, dispersant, and tetrahydrofuran copolyether, and stirred for 60 min at a speed of 300 rpm to obtain mixture C; S8-2: Add mixture C to a high-speed mixer, add silane coupling agent KH560, and mix at 80°C for 3 h at a mixing speed of 1000 rpm to obtain a masterbatch; S8-3: The masterbatch is cast into TPU film through an extruder through a direct casting process, and no embossing treatment is performed at the three rollers; S8-4: After extrusion casting, corona treatment is performed at a power of 2 kW and a speed of 10 m / min, followed by standing for 14 h, cooling and winding, and packaging the finished product to obtain the TPU film.

[0027] Comparative Example 1 Unmodified SiO2 particles were used instead of modified SiO2 particles, and the remaining steps were consistent with those in Example 1.

[0028] Comparative Example 2 Dopamine hydrochloride was not added during the preparation of the modified SiO2 particles, and the remaining steps were the same as those in Example 1.

[0029] Comparative Example 3 No phytic acid aqueous solution was added during the preparation of the modified SiO2 particles, and the remaining steps were the same as those in Example 1.

[0030] Comparative Example 4 The preparation process steps do not involve corona treatment, and the remaining steps are the same as those in Example 1.

[0031] Comparative Example 5 The silane coupling agent KH560 was not added, and the remaining steps were the same as those in Example 1.

[0032] Performance Testing The samples prepared in the Examples and Comparative Examples were conditioned at (23±2)°C and (50±10)% RH for 48 hours. The tape peel strength of the Examples and Comparative Examples was tested according to GB / T 2791; the flame retardancy of the Examples and Comparative Examples was tested according to GB 8410-2006; and the hardness of the Examples and Comparative Examples was tested according to ASTM D2240. The specific experimental data are summarized in the following table.

[0033] It can be seen from the data of the examples and comparative examples that the TPU film prepared in the present invention has the characteristics of good adhesion to pressure-sensitive adhesives and also has good flame retardancy and mechanical properties.

[0034] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A TPU film suitable for pressure-sensitive adhesive, characterized in that: The formula of the TPU film is as follows: in parts by weight, 80-90 parts of TPU, 10-15 parts of tetrahydrofuran copolyether, 5-8 parts of fluoroacrylate, 2-5 parts of modified SiO2 particles, 1-2 parts of silane coupling agent KH560, and 0.5-1 part of dispersant. The preparation method of the modified SiO2 particles is as follows: S1-1: 20-30 parts by weight of anhydrous ethanol, 5-10 parts by weight of deionized water, and 1-2 parts by weight of 30 wt% ammonia water were added to a three-necked flask, and the mixture was stirred at 500-600 rpm in a water bath at 30-40°C for 30-60 min. 3-5 parts by weight of ethyl orthosilicate was added dropwise, and the mixture was stirred in a water bath for 6-8 h. The mixture was then washed with deionized water and ethanol, and then dried in vacuo at 60°C for 12 h to obtain SiO2 particles. S1-2: 3-Methacryloxypropyltrimethoxysilane was mixed with ethanol, and SiO2 particles were added to obtain a solid content of 5-10 wt%. The mixture was stirred at 50-60°C for 6-8 h, centrifuged, washed with ethanol, and dried at 60°C for 12 h to obtain particles A. S1-3: 10-20 parts by weight of microparticles A were dispersed in 100-150 parts by weight of Tris-HCl buffer with a pH of 8-8.5, and sonicated for 30 min. Dopamine hydrochloride was then added, and the mixture was stirred in the dark at 25-35°C for 20-24 h, during which the pH was maintained within the range of 8.5±0.

2. The mixture was centrifuged and dialyzed for 48 h, and then freeze-dried at -40°C for 12 h to obtain microparticles B. S1-4: 5-10 parts by weight of the microparticles B are added to 100 parts by weight of a phytic acid aqueous solution, stirred at 60° C. for 10-12 hours, washed with deionized water, and dried at 60° C. for 12 hours to obtain the modified SiO 2 microparticles.

2. The TPU film adapted for pressure-sensitive adhesive according to claim 1, characterized in that: The dispersant is ethylene bisstearamide.

3. The TPU film adapted for pressure-sensitive adhesive according to claim 1, characterized in that: The dropping speed of the ethyl orthosilicate in S1-1 is 1-2 mL / min.

4. The TPU film adapted for pressure-sensitive adhesive according to claim 1, characterized in that: In the S1-2, 3-methacryloxypropyltrimethoxysilane and ethanol are mixed in a volume ratio of 1:(8-10).

5. The TPU film adapted for pressure-sensitive adhesive according to claim 1, characterized in that: The amount of dopamine hydrochloride added in S1-3 is 0.2 to 0.3 times the mass of the microparticles A.

6. The TPU film adapted for pressure-sensitive adhesive according to claim 1, characterized in that: The dialysis purification in S1-3 uses a dialysis bag with a molecular weight cut-off of 1000.

7. The TPU film adapted for pressure-sensitive adhesive according to claim 1, characterized in that: The mass fraction of phytic acid in the phytic acid aqueous solution in S1-4 is 10%.

8. A process for preparing a TPU film suitable for pressure-sensitive adhesive according to any one of claims 1 to 7, characterized in that: The specific steps of the preparation process are as follows: S8-1: Place TPU particles in a ball mill and mill for 3-4 hours at a ball mill speed of 150-250 rpm. Then, add fluoroacrylate, modified SiO2 particles, dispersant and tetrahydrofuran copolyether in sequence and stir for 30-60 minutes to obtain mixture C; S8-2: Add mixture C to a high-speed mixer, then add silane coupling agent KH560, and mix at 80°C for 2-3 hours to obtain a masterbatch; S8-3: The masterbatch is cast into TPU film through an extruder through a direct casting process, and no embossing treatment is performed at the three rollers; S8-4: After extrusion casting, corona treatment is performed at a power of 1.5-2 kW and a speed of 8-10 m / min, followed by standing for 12-14 hours, cooling and winding, and packaging the finished product to obtain the TPU film.

9. The process for preparing a TPU film suitable for pressure-sensitive adhesive according to claim 8, characterized in that: The stirring speed in S8-1 is 200-300 rpm.

10. The process for preparing a TPU film suitable for pressure-sensitive adhesive according to claim 8, characterized in that: The mixing speed in S8-2 is 800-1000 rpm.

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