High-transmittance tpe protective film for liquid crystal light guide plate and preparation method of high-transmittance tpe protective film

Abstract

The invention relates to the field of protective films, and discloses a liquid crystal light guide plate high-transmittance tpe protective film and a preparation method thereof.The protective film comprises SEBS, polypropylene, modified halloysite nanotubes, modified silicon dioxide and auxiliaries; the modified halloysite nanotube is prepared by reacting a functional additive prepared by grafting an isocyanato antioxidant component and a modified benzothiazole-containing monomer with 3-chloropropyltrimethoxysilane, and then grafting on the surface of the halloysite nanotube; the isocyanated antioxidant component is prepared by reacting 3-(3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid with N-hydroxymethyl acrylamide, then reacting the product with 2-mercaptoethanol to obtain a hydroxylated antioxidant component, and then reacting the hydroxylated antioxidant component with isophorone diisocyanate; the modified benzothiazole-containing monomer is prepared by reacting 2-aminobenzothiazole with bromoacetyl bromide and then reacting with 3, 5-dihydroxybenzylamine, and the protective film prepared by the invention has good thermo-oxidative aging resistance, antibacterial property, heat resistance and tensile property.

Description

Technical Field

[0001] The present invention belongs to the technical field of protective films, and particularly relates to a high-transparency TPE protective film for a liquid crystal light guide plate and a preparation method thereof. Background Art

[0002] The light guide plate applied to the liquid crystal screens of mobile phones, cameras and other digital electronic products is a product with high transparency and high cleanliness, and it has very high requirements for the production environment and surface quality. However, during the processing, handling and transportation of the light guide plate, it is inevitable to come into contact and friction with some parts of the equipment, or due to improper operation, resulting in scratches on its surface or adhesion of dust, oil stains, etc., so it is necessary to attach a protective film on the surface of the light guide plate.

[0003] Thermoplastic elastomer is a new type of polymer material that combines the high strength of plastics and the high elasticity of rubbers, and at the same time has excellent processability and recyclability, thus receiving extensive attention in various fields such as electronic products, automobiles, aerospace, and daily necessities. At present, after the protective film applied to the light guide plate is attached to the surface of the light guide plate, over time, the protective film will age under the influence of temperature, resulting in the phenomenon that the protective film cannot be peeled off smoothly after use and residual glue appears, affecting the quality of the light guide plate. The existing technology improves the aging resistance of the protective film by adding small molecules such as hindered phenol antioxidants and amine antioxidants as antioxidant components. However, hindered phenol antioxidants and amine antioxidants are prone to volatilization and migration during the processing and subsequent use of the protective film, and the long-term antioxidant performance of the protective film cannot be guaranteed. Therefore, there are still difficulties in practical applications, and the existing thermoplastic elastomer protective films have problems such as poor heat resistance, low tensile strength, and insufficient antibacterial effect, which limit their scope of use to a certain extent. Summary of the Invention

[0004] To solve the deficiencies mentioned in the above background art, the purpose of the present invention is to provide a high-transparency TPE protective film for a liquid crystal light guide plate and a preparation method thereof. By adding modified halloysite nanotubes and modified silica, the protective film is given good heat and oxygen aging resistance, antibacterial performance, heat resistance and tensile performance.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A high-transparency TPE protective film for a liquid crystal light guide plate comprises the following components in parts by weight: 45 - 60 parts of SEBS elastomer, 8 - 12 parts of polypropylene, 5 - 10 parts of modified halloysite nanotubes, 2 - 5 parts of modified silica, 1 - 5 parts of lubricant, and 5 - 15 parts of plasticizer;

[0007] The modified halloysite nanotubes are prepared by grafting a modified silane coupling agent, which is formed by the substitution reaction of a functional additive and 3-chloropropyltrimethoxysilane, onto the surface of halloysite nanotubes; the functional additive is prepared by grafting an isocyanated antioxidant component and a modified benzothiazole monomer through a chemical reaction.

[0008] The isocyanated antioxidant component is prepared by reacting 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid and N-hydroxymethylacrylamide through an esterification reaction, then reacting with 2-mercaptoethanol through a thiol-ene click reaction to obtain a hydroxylated antioxidant component, and then reacting isophorone diisocyanate with the hydroxylated antioxidant component; the modified benzothiazole monomer is prepared by reacting 2-aminobenzothiazole and bromoacetyl bromide through a substitution reaction and further reacting with 3,5-dihydroxybenzylamine through a substitution reaction.

[0009] The modified silica is prepared by using the sol-gel method to coat silica particles formed by the hydrolysis of tetraethyl orthosilicate on a polyacrylic acid core.

[0010] Preferably, the lubricant is one or a combination of stearic acid, polyethylene wax, oxidized polyethylene wax, paraffin wax, etc.; the plasticizer is one or a combination of dibutyl phthalate, diisononyl phthalate, tributyl citrate, acetyl tributyl citrate, etc.

[0011] Preferably, the preparation method of the modified halloysite nanotubes includes the following steps:

[0012] A. Take the isocyanated antioxidant component, the modified benzothiazole monomer and toluene in a reactor, then add a mixed solution of dibutyltin dilaurate and toluene, place it at 45-55 °C and stir for 10-12 h. After the reaction is completed, carry out rotary evaporation, washing and drying to prepare the functional additive.

[0013] B. Take the functional additive, 3-chloropropyltrimethoxysilane, triethylamine and tetrahydrofuran in a reactor, place it in a nitrogen atmosphere at 70-85 °C and stir for 5-8 h. After the reaction is completed, carry out suction filtration, washing and drying to prepare the modified silane coupling agent.

[0014] C. Take the halloysite nanotubes and ultrasonically disperse them in a mixed solution of absolute ethanol and deionized water, then add the modified silane coupling agent, place it at 60-75 °C and stir for 3-6 h. After the reaction is completed, carry out centrifugation, washing and drying to prepare the modified halloysite nanotubes.

[0015] Preferably, the preparation method of the isocyanated antioxidant component in step A includes the following steps:

[0016] (1) Take 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, 4-dimethylaminopyridine and dichloromethane in a reactor, place it under the conditions of 0-4 °C and nitrogen atmosphere, stir and dissolve, then add a mixed solution of 1-ethyl-3(3-dimethylpropylamine)carbodiimide and dichloromethane, stir for 1.5-2 h, and then take N-hydroxymethylacrylamide dissolved in dichloromethane and add it to the reactor, react at 18-22 °C for 3-4 h. After the reaction is completed, filter, rotary evaporate and purify to prepare a double-bond grafted antioxidant component;

[0017] (2) Take the double-bond grafted antioxidant component and 2-mercaptoethanol in a reactor, add toluene solvent, heat up to 45-55 °C, add a mixed solution of triethylamine and toluene, stir and react for 4-6 h. After the reaction is completed, carry out rotary evaporation under reduced pressure and purification to remove the unreacted substances, and prepare a hydroxylated antioxidant component;

[0018] (3) Take the hydroxylated antioxidant component, isophorone diisocyanate and toluene in a reactor, then add a mixed solution of dibutyltin dilaurate and toluene, place it at 55-65 °C and stir and react for 4-6 h. After the reaction is completed, carry out rotary evaporation, washing and drying to prepare an isocyanated antioxidant component.

[0019] Preferably, in the step (1), the molar ratio of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid to N-hydroxymethylacrylamide is 1:1-1.5; in the step (2), the molar ratio of the double-bond grafted antioxidant component to 2-mercaptoethanol is 1:1.5-2.

[0020] Preferably, in the step (3), the molar ratio of the hydroxylated antioxidant component to isophorone diisocyanate is 1-1.1:1.

[0021] Preferably, the preparation method of the modified benzothiazole monomer in the step A includes the following steps:

[0022] ① Take 2-aminobenzothiazole and triethylamine in a reactor, add dichloromethane solvent, under the condition of ice-water bath, dropwise add a mixed solution of bromoacetyl bromide and dichloromethane, stir and react for 0.5-1 h. After the reaction is completed, carry out rotary evaporation under reduced pressure and purification to prepare a benzothiazole monomer;

[0023] ② Take the benzothiazole monomer, 3,5-dihydroxybenzylamine and sodium carbonate in a reactor, add a mixed solvent of N,N-dimethylformamide and tetrahydrofuran, place it at 55-70 °C and react for 2-3 h. After the reaction is completed, carry out rotary evaporation, washing, drying and purification to prepare a modified benzothiazole monomer.

[0024] Preferably, in step ①, the molar ratio of 2-aminobenzothiazole to bromoacetyl bromide is 1:1-1.2; and in step ②, the molar ratio of benzothiazole monomer to 3,5-dihydroxybenzylamine is 1:1-1.2.

[0025] Preferably, the preparation method of the modified silica comprises the following steps: dissolving polyacrylic acid in ammonia water, adding anhydrous ethanol and mixing, then adding tetraethyl orthosilicate in batches under magnetic stirring, adjusting the pH value of the system to 5.5-6 with acetic acid after reacting for 8-10 hours, placing the obtained mixed sol at 55-65° C. and stirring for 0.5-1 hour, cooling in ice water after the reaction is completed, and ultrasonically dispersing for 15-20 minutes to prepare modified silica.

[0026] A method for preparing a high-transmittance TPE protective film for a liquid crystal light guide plate comprises the following steps:

[0027] S1. Weigh each component by weight, add SEBS elastomer, polypropylene, modified halloysite nanotubes, modified silica, lubricant and plasticizer into a mixer, and mix at 50-65° C. for 8-12 minutes to obtain a premix;

[0028] S2, extruding and granulating the premixed material in a twin-screw extruder at 185-220° C. to obtain a mixed material;

[0029] S3, blow molding the mixture to prepare a high-transmittance TPE protective film for a liquid crystal light guide plate.

[0030] Beneficial effects of the present invention:

[0031] The present invention utilizes hindered phenol antioxidant 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid and N-hydroxymethyl acrylamide to undergo esterification reaction to prepare a double-bond grafted antioxidant component, and then the double-bond grafted antioxidant component and 2-mercaptoethanol undergo thiol-ene click reaction to prepare a hydroxylated antioxidant component, and then utilizes isophorone diisocyanate, which is directly connected to the cyclohexane ring and has high activity, to react with the hydroxyl group in the hydroxylated antioxidant component to prepare an isocyanato antioxidant component. At the same time, the present invention utilizes the amino group in 2-aminobenzothiazole and the bromine of the acyl bromide group in bromoacetyl bromide to undergo substitution reaction to prepare a benzothiazole-containing monomer, and then utilizes the amino group in 3,5-dihydroxybenzylamine and the ungrafted bromine atom in the benzothiazole-containing monomer to further undergo substitution reaction to prepare a modified benzothiazole-containing monomer.

[0032] The present invention utilizes the reaction between the isocyanate groups in the isocyanated antioxidant component and the hydroxyl groups in the modified benzothiazole monomer to prepare a functional additive. Then, the un-grafted hydroxyl groups in the functional additive react with the chlorine atoms in 3-chloropropyltrimethoxysilane to prepare a modified silane coupling agent. Subsequently, the silanol groups in the modified silane coupling agent undergo a condensation reaction with the hydroxyl groups on the surface of halloysite nanotubes to prepare modified halloysite nanotubes, thereby tightly binding hindered phenol antioxidants to the surface of halloysite nanotubes through strong chemical bonds. Moreover, due to the tubular structure of halloysite nanotubes, the hindered phenol antioxidants can be slowly released, thereby restricting the migration phenomenon of the hindered phenol antioxidants in the substrate and achieving long-term heat and oxygen aging resistance performance. At the same time, thiazole monomers with antibacterial activity, amide groups, and urethane groups with good heat resistance are introduced onto the surface of halloysite nanotubes, improving the antibacterial and heat resistance properties of the protective film. Additionally, after the surface of halloysite nanotubes is modified with the modified silane coupling agent, the halloysite nanotubes are relatively uniformly dispersed in the substrate, which is beneficial to the full play of the properties of halloysite nanotubes. In addition, the present invention uses the sol-gel method to coat the silicon dioxide particles generated by the hydrolysis of tetraethyl orthosilicate under the catalysis of ammonia water on the core of polyacrylic acid to prepare modified silicon dioxide with a core-shell structure, avoiding direct contact between particles and reducing the generation of agglomeration phenomena. Moreover, the silicon dioxide shell layer in the modified silicon dioxide provides surface hardness, and the polyacrylic acid core absorbs impact energy, which is beneficial to improving the flexibility of the protective film and enhancing the tensile performance while maintaining the wear resistance of the protective film. Detailed Embodiments

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0034] Example 1 A preparation method of an isocyanated antioxidant component includes the following steps:

[0035] (1) Take 5 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, 0.2 g of 4-dimethylaminopyridine, and 40 mL of dichloromethane in a reactor, place it at 0 °C under a nitrogen atmosphere, stir to dissolve, and then add a mixed solution of 4.1 g of 1-ethyl-3(3-dimethylpropylamine)carbodiimide and 40 mL of dichloromethane, stir for 2 h, and then take 2.7 g of N-hydroxymethylacrylamide dissolved in 10 mL of dichloromethane and add it to the reactor, react at 20 °C for 4 h. After the reaction is completed, filter, rotary evaporate, and purify to prepare a double-bond grafted antioxidant component;

[0036] (2) Take 7.3 g of the double-bond grafted antioxidant component (Mr = 361.5) and 3.1 g of 2-mercaptoethanol in a reactor, add 50 mL of toluene solvent, heat up to 50 °C, add a mixed solution of 0.08 g of triethylamine and 10 mL of toluene, stir and react for 6 h. After the reaction is completed, it is purified by rotary evaporation under reduced pressure to remove the unreacted substances, and the hydroxylated antioxidant component is prepared;

[0037] (3) Take 4.4 g of the hydroxylated antioxidant component (Mr = 439.6), 2.2 g of isophorone diisocyanate and 40 mL of toluene in a reactor, then add a mixed solution of 0.63 g of dibutyltin dilaurate and 10 mL of toluene, place it at 65 °C and stir and react for 5 h. After the reaction is completed, it is rotary evaporated, washed and dried to prepare the isocyanated antioxidant component.

[0038] Example 2 A preparation method of a modified benzothiazole monomer includes the following steps:

[0039] ① Take 3 g of 2-aminobenzothiazole and 2.4 g of triethylamine in a reactor, add 50 mL of dichloromethane solvent, and under the condition of an ice-water bath, dropwise add a mixed solution of 4.4 g of bromoacetyl bromide and 15 mL of dichloromethane, stir and react for 0.5 h. After the reaction is completed, it is purified by rotary evaporation under reduced pressure to prepare the benzothiazole monomer-containing;

[0040] ② Take 2.7 g of the benzothiazole monomer-containing, 1.7 g of 3,5-dihydroxybenzylamine and 1.6 g of sodium carbonate in a reactor, add 50 mL of a mixed solvent of N,N-dimethylformamide and tetrahydrofuran with a volume ratio of 1:1, place it at 65 °C and react for 3 h. After the reaction is completed, it is rotary evaporated, washed, dried and purified to prepare the modified benzothiazole monomer.

[0041] Example 3 A preparation method of modified halloysite nanotubes includes the following steps:

[0042] A. Take 6.6 g of the isocyanated antioxidant component prepared in Example 1 (Mr = 661.9), 3.3 g of the modified benzothiazole monomer prepared in Example 2 (Mr = 329.3) and 50 mL of toluene in a reactor, then add a mixed solution of 0.63 g of dibutyltin dilaurate and 10 mL of toluene, place it at 50 °C and stir and react for 12 h. After the reaction is completed, it is rotary evaporated, washed and dried to prepare the functional additive;

[0043] B. Take 5 g of the functional additive (Mr = 991.2), 1.2 g of 3-chloropropyltrimethoxysilane, 0.6 g of triethylamine and 50 mL of tetrahydrofuran in a reactor, place it in a nitrogen atmosphere at 80 °C and stir and react for 6 h. After the reaction is completed, it is filtered, washed and dried to prepare the modified silane coupling agent;

[0044] C. Take 5 g of halloysite nanotubes and ultrasonically disperse them in a mixed solution of 90 mL of absolute ethanol and 10 mL of deionized water. Then add 4.2 g of modified silane coupling agent, place it under stirring reaction at 70 °C for 4 h. After the reaction is completed, centrifuge, wash, and dry to prepare modified halloysite nanotubes.

[0045] Example 4 A preparation method of modified silica includes the following steps:

[0046] Take 0.24 g of polyacrylic acid (Mw = 5000), dissolve it in 4.5 mL of ammonia water, add 90 mL of absolute ethanol and mix. Then, under magnetic stirring, add a total of 1.8 mL of tetraethyl orthosilicate in five batches at 1 h intervals. After reacting for 10 h, adjust the pH value of the system to 6 with acetic acid. Place the obtained mixed sol under stirring reaction at 60 °C for 1 h. After the reaction is completed, cool it in ice water and ultrasonically disperse it for 20 min to prepare modified silica.

[0047] Example 5 A high-transparency TPE protective film for a liquid crystal light guide plate includes the following components by weight: 47 parts of SEBS elastomer, 8.5 parts of polypropylene, 5 parts of the modified halloysite nanotubes prepared in Example 3, 2 parts of the modified silica prepared in Example 4, 1.5 parts of lubricant stearic acid, and 6 parts of plasticizer dibutyl phthalate.

[0048] The preparation method of the above high-transparency TPE protective film for a liquid crystal light guide plate includes the following steps:

[0049] S1. Weigh each component according to the weight parts. Add the SEBS elastomer, polypropylene, modified halloysite nanotubes, modified silica, lubricant, and plasticizer into a mixer, place it at 60 °C and mix for 10 min to obtain a premix.

[0050] S2. Extrude and pelletize the premix in a twin-screw extruder at 195 °C to obtain a mixed material.

[0051] S3. Blow-mold the mixed material to prepare a high-transparency TPE protective film for a liquid crystal light guide plate.

[0052] Example 6 A high-transparency TPE protective film for a liquid crystal light guide plate includes the following components by weight: 51 parts of SEBS elastomer, 10 parts of polypropylene, 7 parts of the modified halloysite nanotubes prepared in Example 3, 4 parts of the modified silica prepared in Example 4, 3 parts of lubricant polyethylene wax, and 8 parts of plasticizer diisononyl phthalate.

[0053] The preparation method of the above high-transparency TPE protective film for a liquid crystal light guide plate is the same as that of Example 5.

[0054] Example 7 A high-transparency TPE protective film for liquid crystal light guide plates, comprising the following components in parts by weight: 58 parts of SEBS elastomer, 12 parts of polypropylene, 9 parts of modified halloysite nanotubes prepared in Example 3, 5 parts of modified silica prepared in Example 4, 4.5 parts of lubricant polyethylene wax oxide, and 12 parts of plasticizer tributyl citrate.

[0055] The preparation method of the above high-transparency TPE protective film for liquid crystal light guide plates is the same as that in Example 5.

[0056] Comparative Example 1 A preparation method of modified halloysite nanotubes comprises the following steps:

[0057] (1) Take 5 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid, 0.2 g of 4-dimethylaminopyridine and 40 mL of dichloromethane in a reactor, place it at 0 °C under a nitrogen atmosphere, stir and dissolve, then add a mixed solution of 4.1 g of 1-ethyl-3(3-dimethylpropylamine) carbodiimide and 40 mL of dichloromethane, stir for 2 h, and then take 2.7 g of N-hydroxymethylacrylamide dissolved in 10 mL of dichloromethane and add it to the reactor, react at 20 °C for 4 h, and after the reaction is completed, filter, rotary evaporate and purify to prepare a double-bond grafted antioxidant component;

[0058] (2) Take 7.3 g of double-bond grafted antioxidant component (Mr = 361.5) and 3.1 g of 2-mercaptoethanol in a reactor, add 50 mL of toluene solvent, heat up to 50 °C, add a mixed solution of 0.08 g of triethylamine and 10 mL of toluene, stir and react for 6 h, and after the reaction is completed, carry out vacuum rotary evaporation and purification to remove unreacted substances to prepare a hydroxylated antioxidant component;

[0059] (3) Take 2.2 g of hydroxylated antioxidant component (Mr = 439.6), 1.2 g of 3-chloropropyltrimethoxysilane, 0.6 g of triethylamine and 50 mL of tetrahydrofuran in a reactor, place it in a nitrogen atmosphere and stir and react at 80 °C for 6 h, and after the reaction is completed, carry out suction filtration, washing and drying to prepare a modified silane coupling agent;

[0060] (4) Take 5 g of halloysite nanotubes, ultrasonically disperse them in a mixed solution of 90 mL of absolute ethanol and 10 mL of deionized water, then add 4.2 g of modified silane coupling agent, place it at 70 °C and stir and react for 4 h, and after the reaction is completed, carry out centrifugation, washing and drying to prepare modified halloysite nanotubes.

[0061] Comparative Example 2 A high-transparency TPE protective film for liquid crystal light guide plates, comprising the following components in parts by weight: 58 parts of SEBS elastomer, 12 parts of polypropylene, 9 parts of modified halloysite nanotubes prepared in Comparative Example 1, 5 parts of modified silica prepared in Example 4, 4.5 parts of lubricant polyethylene wax oxide, and 12 parts of plasticizer tributyl citrate.

[0062] The preparation method of the above high-transparency TPE protective film for liquid crystal light guide plate is the same as that in Example 5.

[0063] Comparative Example 3 A high-transparency TPE protective film for liquid crystal light guide plate, comprising the following components in parts by weight: 58 parts of SEBS elastomer, 12 parts of polypropylene, 9 parts of halloysite nanotubes, 5 parts of modified silica prepared in Example 4, 4.5 parts of lubricant polyethylene wax oxide, 12 parts of plasticizer tributyl citrate, and 2 parts of antioxidant 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid.

[0064] The preparation method of the above high-transparency TPE protective film for liquid crystal light guide plate is the same as that in Example 5.

[0065] Comparative Example 4 A high-transparency TPE protective film for liquid crystal light guide plate, comprising the following components in parts by weight: 58 parts of SEBS elastomer, 12 parts of polypropylene, 9 parts of modified halloysite nanotubes prepared in Example 1, 5 parts of silica, 4.5 parts of lubricant polyethylene wax oxide, and 12 parts of plasticizer tributyl citrate.

[0066] The preparation method of the above high-transparency TPE protective film for liquid crystal light guide plate is the same as that in Example 5.

[0067] Performance testing

[0068] Perform performance testing on the high-transparency TPE protective films for liquid crystal light guide plates prepared in Examples 5-7 and Comparative Examples 2-4:

[0069] a. Conduct tensile property testing on the samples according to GB / T 528-2008; place the samples in a TGA-103 thermogravimetric analyzer, under nitrogen protection, with a heating rate of 5 °C / min, raise the temperature from room temperature to 800 °C, record the initial decomposition temperature of the material, and evaluate the heat resistance of the samples; use the plate count method to detect the antibacterial effect of the samples on Escherichia coli and Staphylococcus aureus. Add the activated bacterial solution to a test tube and dilute it until the total number of bacterial colonies is 10 6 CFU / mL. Add the film material to the bacterial solution, place it in a constant temperature incubator, shake and culture it at 37 °C for 24 h. Then take the diluted bacterial solution and coat it on an agar medium, put it into a constant temperature incubator, and observe the number of colonies in each petri dish after culturing at 37 °C for 24 h. Calculate the antibacterial rate = (R0 - R1) / R0 using the number of colonies, where R0 is the number of colonies without the film material and R1 is the number of colonies with the film material. The data results are shown in Table 1.

[0070] Table 1 Test results of sample performance

[0071]

[0072] As can be seen from the data in Table 1, the protective films prepared in Examples 5-7 of the present invention have high tensile strength, are not easily broken, and have excellent heat resistance and antibacterial properties. Among them, the modified halloysite nanotubes added in Comparative Example 2 were not grafted with modified benzothiazole monomers and isophorone diisocyanate was not introduced. The measured initial thermal decomposition temperature, antibacterial rate against Escherichia coli, and antibacterial rate against Staphylococcus aureus were lower than those in Examples 5-7. The reason is that amide groups and urethane groups with good heat resistance were not introduced on the surface of the halloysite nanotubes, resulting in a decrease in the initial thermal decomposition temperature, and thiazole monomers with antibacterial activity were not introduced, resulting in a decrease in the antibacterial effect. In Comparative Example 3, the halloysite nanotubes were not modified, and the measured tensile strength, heat resistance, and antibacterial effect were lower than those in Examples 5-7. The possible reason is that the agglomeration of the halloysite nanotubes led to a decrease in the tensile strength, and it shows that modifying the halloysite nanotubes can, to a certain extent, modify the heat resistance and antibacterial properties of the protective film. In Comparative Example 4, the silica was not modified, and the measured tensile strength was lower than that in Examples 5-7, indicating that the modified silica with a core-shell structure can improve the tensile properties of the protective film.

[0073] b. Place the specimen in an air thermal aging test chamber for high-temperature thermal oxygen aging at 100 °C. The aging cycle is divided into four test cycles of 3, 6, 12, and 24 days. Take 5 samples for each cycle, and test the oxidation induction time of each sample to evaluate the heat-resistant oxygen aging performance of the protective film. The data results are shown in Table 2.

[0074] Table 2 Detection results of the heat-resistant oxygen aging performance of the specimen

[0075]

[0076] As can be seen from the data in Table 2, the protective films prepared in Examples 5-7 of the present invention have a longer oxidation induction time, and after 24 days of thermal oxygen aging process, they still maintain a longer oxidation induction time, having excellent heat-resistant oxygen aging performance. Among them, in Comparative Example 3, the halloysite nanotubes and antioxidant 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid were directly mixed, and the measured oxidation induction time was significantly shorter than that in Examples 5-7. The reason is that antioxidant components were not grafted on the surface of the halloysite nanotubes, resulting in poor long-term heat-resistant oxygen aging performance.

[0077] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0078] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification is only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed.

Claims

1. A high-transparency TPE protective film for a liquid crystal light guide plate, characterized in that It comprises the following components in parts by weight: 45-60 parts of SEBS elastomer, 8-12 parts of polypropylene, 5-10 parts of modified halloysite nanotubes, 2-5 parts of modified silica, 1-5 parts of lubricant, and 5-15 parts of plasticizer; The modified halloysite nanotubes are prepared by grafting a modified silane coupling agent formed by the substitution reaction of a functional additive and 3-chloropropyltrimethoxysilane onto the surface of halloysite nanotubes; wherein the functional additive is prepared by grafting an isocyanated antioxidant component and a modified benzothiazole monomer through a chemical reaction; The isocyanated antioxidant component is prepared by first performing an esterification reaction of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid and N-hydroxymethylacrylamide, then performing a thiol-ene click reaction with 2-mercaptoethanol to obtain a hydroxylated antioxidant component, and then reacting isophorone diisocyanate with the hydroxylated antioxidant component; the modified benzothiazole monomer is prepared by first performing a substitution reaction of 2-aminobenzothiazole and bromoacetyl bromide, and then further performing a substitution reaction with 3,5-dihydroxybenzylamine; The modified silica is prepared by using the sol-gel method to coat silica particles formed by the hydrolysis of tetraethyl orthosilicate on a polyacrylic acid core.

2. The high-transparency TPE protective film for a liquid crystal light guide plate according to claim 1, wherein The lubricant is one or a combination of stearic acid, polyethylene wax, oxidized polyethylene wax, and paraffin wax; the plasticizer is one or a combination of dibutyl phthalate, diisononyl phthalate, tributyl citrate, and acetyl tributyl citrate.

3. The high-transparency TPE protective film for a liquid crystal light guide plate according to claim 1, wherein The preparation method of the modified halloysite nanotubes comprises the following steps: A. Take the isocyanated antioxidant component, the modified benzothiazole monomer, and toluene in a reactor, then add a mixed solution of dibutyltin dilaurate and toluene, place it at 45-55 °C and stir for reaction for 10-12 h. After the reaction is completed, perform rotary evaporation, washing, and drying to prepare the functional additive; B. Take the functional additive, 3-chloropropyltrimethoxysilane, triethylamine, and tetrahydrofuran in a reactor, place it in a nitrogen atmosphere at 70-85 °C and stir for reaction for 5-8 h. After the reaction is completed, perform suction filtration, washing, and drying to prepare the modified silane coupling agent; C. Take halloysite nanotubes and ultrasonically disperse them in a mixed solution of absolute ethanol and deionized water, then add the modified silane coupling agent, place it at 60-75 °C and stir for reaction for 3-6 h. After the reaction is completed, perform centrifugation, washing, and drying to prepare the modified halloysite nanotubes.

4. The high-transparency TPE protective film for a liquid crystal light guide plate according to claim 3, characterized in that, The preparation method of the isocyanated antioxidant component in step A comprises the following steps: (1) Take 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid, 4-dimethylaminopyridine, and dichloromethane in a reactor, place it at 0-4 °C and in a nitrogen atmosphere, stir to dissolve, then add a mixed solution of 1-ethyl-3(3-dimethylpropylamine) carbodiimide and dichloromethane, stir for 1.5-2 h, then take N-hydroxymethylacrylamide dissolved in dichloromethane and add it to the reactor, place it at 18-22 °C and react for 3-4 h. After the reaction is completed, perform filtration, rotary evaporation, and purification to prepare the double-bond grafted antioxidant component; (2) Take the double-bond grafted antioxidant component and 2-mercaptoethanol in a reactor, add toluene solvent, heat up to 45-55 °C, add the mixed solution of triethylamine and toluene, stir and react for 4-6 h. After the reaction is completed, it is purified by rotary evaporation under reduced pressure to remove the unreacted substances, and the hydroxylated antioxidant component is prepared; (3) Take the hydroxylated antioxidant component, isophorone diisocyanate and toluene in a reactor, then add the mixed solution of dibutyltin dilaurate and toluene, place it at 55-65 °C and stir and react for 4-6 h. After the reaction is completed, it is subjected to rotary evaporation, washing and drying to prepare the isocyanated antioxidant component.

5. The high-transparency TPE protective film for a liquid crystal light guide plate according to claim 4, wherein, In the step (1), the molar ratio of 3-(3,5-ditert-butyl-4-hydroxyphenyl) propionic acid to N-hydroxymethylacrylamide is 1:1-1.5; in the step (2), the molar ratio of the double-bond grafted antioxidant component to 2-mercaptoethanol is 1:1.5-2.

6. The high-transparency TPE protective film for a liquid crystal light guide plate according to claim 4, wherein In the step (3), the molar ratio of the hydroxylated antioxidant component to isophorone diisocyanate is 1-1.1:

1.

7. The high-transparency TPE protective film for a liquid crystal light guide plate according to claim 1, wherein The preparation method of the modified benzothiazole monomer in the step A includes the following steps: ① Take 2-aminobenzothiazole and triethylamine in a reactor, add dichloromethane solvent, under the condition of ice-water bath, dropwise add the mixed solution of bromoacetyl bromide and dichloromethane, stir and react for 0.5-1 h. After the reaction is completed, it is purified by rotary evaporation under reduced pressure to prepare the benzothiazole-containing monomer; ② Take the benzothiazole-containing monomer, 3,5-dihydroxybenzylamine and sodium carbonate in a reactor, add the mixed solvent of N,N-dimethylformamide and tetrahydrofuran, place it at 55-70 °C and react for 2-3 h. After the reaction is completed, it is subjected to rotary evaporation, washing, drying and purification to prepare the modified benzothiazole monomer.

8. The high-transparency TPE protective film for a liquid crystal light guide plate according to claim 7, wherein, In the step ①, the molar ratio of 2-aminobenzothiazole to bromoacetyl bromide is 1:1-1.2; in the step ②, the molar ratio of the benzothiazole-containing monomer to 3,5-dihydroxybenzylamine is 1:1-1.

2.

9. The high-transparency TPE protective film for a liquid crystal light guide plate according to claim 1, wherein, The preparation method of the modified silica includes the following steps: Dissolve polyacrylic acid in ammonia water, add anhydrous ethanol and mix, then add tetraethyl orthosilicate in batches under magnetic stirring. After reacting for 8-10 h, adjust the pH value of the system to 5.5-6 with acetic acid. Place the obtained mixed sol at 55-65 °C and stir and react for 0.5-1 h. After the reaction is completed, cool it in ice water and ultrasonically disperse it for 15-20 min to prepare the modified silica.

10. A method for preparing a high-transparency tpe protective film for a liquid crystal light guide plate according to any one of claims 1 to 9, characterized in that, It includes the following steps: S1. Weigh each component by weight, add SEBS elastomer, polypropylene, modified halloysite nanotubes, modified silica, lubricant and plasticizer into a mixer, place it at 50-65 °C and mix for 8-12 min to obtain a premix; S2. Extrude and pelletize the premix in a twin-screw extruder at 185-220 °C to obtain a mixture; S3. Blow-mold the mixture to prepare a high-transparency tpe protective film for a liquid crystal light guide plate.

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