EVA / nano-zinc oxide anti-ultraviolet vehicle cover and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to an EVA / nano-zinc oxide anti-ultraviolet car cover and a preparation method thereof. The invention aims to solve the problem that the mechanical strength and the ultraviolet resistance of the existing car cover are difficult to consider at the same time. Ethylene-vinyl acetate resin is used as a matrix, a silane coupling agent and hydroxyethyl methylacrylate surface modified and grafted composite nano-zinc oxide, maleic anhydride grafted EVA and a polyurethane modifier are subjected to melt blending, a TMPTA cross-linking agent is added, and the vehicle cover film is prepared through extrusion casting and ultraviolet curing. Wherein the polyurethane modifier is obtained by reacting polycaprolactone polyol with isophorone diisocyanate and adopting hydroxyethyl methylacrylate and 2, 2 '-methylenebis (6-tert-butyl-4-methylphenol) for end capping. The uvioresistant car cover prepared by the invention has excellent tensile strength, elongation at break, uvioresistant performance and adhesive force at the same time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, in particular to an EVA / nano zinc oxide anti-ultraviolet car cover and a preparation method thereof. BACKGROUND

[0002] Ethylene-vinyl acetate copolymer (EVA) is a low-cost thermoplastic elastomer with good flexibility and processability, and is the mainstream material for replacing TPU as a car cover. The car cover is a mainstream product for protecting the original car paint of a car, and can effectively resist scratches, corrosion and ultraviolet damage. However, the traditional EVA-based car cover film has obvious problems. First, the tensile strength and tear resistance of pure EVA material are insufficient, and it is difficult to meet the mechanical requirements as a protective film. Second, EVA itself has poor ultraviolet resistance, and is prone to yellowing, cracking and performance degradation under long-term sunlight, which seriously affects the service life.

[0003] In the prior art, inorganic fillers are added to shield ultraviolet rays. However, the surface energy of nano particles is high, and agglomeration occurs due to uneven dispersion in the non-polar EVA matrix, resulting in a decrease in the mechanical properties of the material. Or small molecule additives, including antioxidants and ultraviolet absorbers, can provide protection, but due to migration and volatilization, the durability of the anti-aging effect is not good. Some studies have also shown that by adding a crosslinking agent to form crosslinks in the material, the strength of EVA is improved, but the toughness of the material is significantly affected.

[0004] In summary, the prior art cannot solve the overall performance of the EVA-based car cover film through simple physical blending or single modification methods. Typically, methods to enhance mechanical properties may compromise anti-aging properties, and vice versa. In actual application, there is still a problem of difficult to balance mechanical properties and ultraviolet resistance, resulting in insufficient comprehensive performance in actual application and reducing the service life.

[0005] Therefore, an EVA / nano zinc oxide anti-ultraviolet car cover and a preparation method thereof are proposed. SUMMARY

[0006] The application aims to provide an EVA / nano-zinc oxide anti-ultraviolet car cover and a preparation method thereof. The application discloses an EVA / nano-zinc oxide anti-ultraviolet car cover and a preparation method thereof.

[0007] To achieve the above object, the application provides the following technical scheme. The application provides a preparation method of an EVA / nano-zinc oxide anti-ultraviolet car cover. The nano-zinc oxide is modified by methyl methacryloyloxypropyl trimethoxysilane and then grafted by hydroxyethyl methacrylate to obtain a composite nano material. The polyurethane prepolymer is obtained by polymerization of polycaprolactone polyol and isophorone diisocyanate, and then the polyurethane improver is obtained by one-end capping of hydroxyethyl methacrylate and two-end capping of 2,2'-methylene bis(6-tert-butyl-4-methylphenol). The car cover film is obtained by stepwise high-speed mixing, melt extrusion and ultraviolet curing of the ethylene-vinyl acetate resin, the composite nano material, the polyurethane improver and the auxiliary agent. The car cover film is coated with pressure-sensitive adhesive, dried by sectional temperature control, wound by compounding and matured to obtain the anti-ultraviolet car cover.

[0008] Preferably, the auxiliary agent comprises maleic anhydride grafted EVA, stearic acid amide, polyethylene wax, trimethylolpropane triacrylate, ultraviolet absorber and antioxidant; the antioxidant is obtained by mixing antioxidant 1010 and antioxidant 168 according to a mass ratio.

[0009] Preferably, the preparation of the composite nano material comprises the following steps. The dried raw material is obtained by vacuum drying the nano zinc oxide in a vacuum drying oven; 5-8 parts of KH570 are added to 10 ml of 95% ethanol aqueous solution, acetic acid is added to adjust the pH value to 4-5, and stirring treatment is performed for 40 min to obtain a silane solution; 100 parts of the dried raw material are ultrasonically dispersed in 95% ethanol aqueous solution to prepare a dispersion liquid with a mass concentration of 20%, the ultrasonic dispersion time is 30-60 min, the ultrasonic power is 200-400 W, the silane solution is slowly added under stirring, the temperature is raised to 70-80℃, and stirring reaction is performed for 2-3 h, followed by separation and centrifugation, washing with deionized water for 3 times, and vacuum drying at 60℃ for 10 h to obtain modified nano zinc oxide; 60 parts of the modified nano zinc oxide and 20 parts of hydroxyethyl methacrylate are added to a flask, 0.3 parts of azobisisobutyronitrile is added under nitrogen protection, the temperature is raised to 70-90℃, grafting reaction is performed for 4-6 h, separation and centrifugation are performed, washing with deionized water and anhydrous ethanol is alternated for 3 times, and vacuum drying is performed at 80℃ for 8 h to obtain a composite nano material.

[0010] Preferably, the preparation of the polyurethane modifier comprises the following steps: The polyurethane prepolymer is cooled to 60-70℃, 3 parts of hydroxyethyl methacrylate is slowly added, and one-time end-capping reaction is performed for 1-3 h, the reaction system is obtained by monitoring the decrease of the -NCO content to the theoretical value through the dibutylamine titration method; 5 parts of 2,2'-methylenebis(6-tert-butyl-4-methylphenol) is dissolved in 2 ml of acetone to obtain a mixed solution; the mixed solution is slowly added to the reaction system, the temperature is raised to 80-90℃, and two-time end-capping reaction is performed for 2-4 h, the disappearance of the -NCO characteristic absorption peak is detected by infrared, and acetone is removed by vacuum distillation to obtain the polyurethane modifier.

[0011] Preferably, the preparation of the polyurethane prepolymer comprises the following steps: The polycaprolactone polyol and isophorone diisocyanate are added to a vacuum drying oven, vacuum drying is performed at 100-110℃ for 2 h to remove water, the polycaprolactone polyol is added to a reaction kettle under nitrogen protection, the number average molecular weight of the polycaprolactone polyol is 1500-2500 g / mol, isophorone diisocyanate is slowly added under the condition of 500 rpm and the temperature of 70℃, dibutyltin dilaurate is added after the addition is completed, the temperature is raised to 90℃, and polymerization reaction is performed for 4 h, the -NCO content is monitored to the theoretical value by the titration method, and the polyurethane prepolymer is obtained; wherein the -NCO / OH molar ratio is 1.6-2.0, the molar amount of hydroxyethyl methacrylate is 50-70% of the excess -NCO groups in the prepolymer, the molar amount of 2,2'-methylenebis(6-tert-butyl-4-methylphenol) is 30-50% of the excess -NCO groups in the prepolymer, and the amount of dibutyltin dilaurate accounts for 0.01-0.05% of the total mass of the reactants.

[0012] Preferably, the preparation of the car film comprises the following steps: ethylene-vinyl acetate resin 90-100 parts by mass is added into a high-speed mixer, preheated and melted, and stirred and mixed; then composite nanomaterial 5-10 parts, maleic anhydride grafted EVA 5-15 parts, ultraviolet absorber 1.2 parts, antioxidant 1.6 parts, antioxidant 1010 mixed with antioxidant 168 at a mass ratio of 1:1, stearic acid amide 0.6 parts, polyethylene wax 0.3 parts, and polyurethane modifier 10-20 parts and TMPTA 5-10 parts are added into the mixture, and stirring and mixing are continued to obtain a base mixture; the base mixture is melted and extruded by a double-screw extruder; the temperature of each section of the extruder is set as follows: the feeding section is 120-140℃, the melting section is 140-160℃, the homogenizing section is 150-170℃, and the discharging section is 160-170℃; the screw rotation speed is 180-250r / min; the extruded particles are cooled by water and cut into granules to obtain polymer particles; the polymer particles are cast into a film by a single-screw extruder; the feeding area is 130-150℃, the compression area is 150-170℃, the metering area is 160-180℃, the die head is 160-180℃, the screw rotation speed is maintained at 80-120rpm, the melt is extruded through a T-shaped die head, and is cast onto a cooling roller with a smooth surface; the cooling roller temperature is 20-40℃; the film thickness is controlled at 120-200µm by matching the pulling speed with the extrusion speed; then ultraviolet curing treatment is performed; the irradiation energy is controlled at 400-600mJ / cm², and the irradiation time is 20-30min to obtain a car cover film.

[0013] Preferably, the car cover film is uniformly coated with an emulsion type acrylate pressure-sensitive adhesive on the surface of the car cover film by a coating device; the solid content of the acrylate pressure-sensitive adhesive is 50-60%, and the dry coating amount is 30-40g / m²; the temperature is controlled in stages for drying, including the following steps: the first stage temperature is 70-80℃, and the holding time is 10min; the second stage temperature is 80-90℃, and the holding time is 8min; the third stage temperature is 90-100℃, and the holding time is 3min; then the product is wound after being compounded with a PP release film, and is aged at 40-50℃ for 15-24h to fully develop the adhesive properties of the pressure-sensitive adhesive to obtain an ultraviolet resistant car cover.

[0014] The application also provides an EVA / nano zinc oxide ultraviolet resistant car cover, which comprises ethylene-vinyl acetate resin, composite nanomaterial, polyurethane modifier, trimethylolpropane triacrylate, auxiliary agent, and acrylate pressure-sensitive adhesive.

[0015] Compared with the prior art, the application has the following beneficial effects: 1、The present application builds a chemical-physical double network reinforced system through the synergistic effect of polyurethane modifier, composite nanomaterial, maleic anhydride grafted EVA and TMPTA, which combines the physical reinforcement of nanoparticles, the toughening of polyurethane and the high cohesive strength of three-dimensional crosslinked network, can effectively disperse stress and resist deformation, and ultimately greatly improves the tensile properties and tear strength of the car paint.

[0016] 2、The present application realizes excellent ultraviolet resistance through multi-mechanism synergistic effect, and builds a double protection through the physical shielding of nano zinc oxide and the chemical absorption of ultraviolet absorber, and the polyurethane modifier containing hindered phenol groups and the antioxidant can effectively capture free radicals, combined with the stable crosslinked network, slow down photo-oxidative aging, thereby long-acting protection of the car paint material.

[0017] 3、The present application comprehensively improves the adhesion performance of the car paint film through physical and chemical methods. The polyurethane modifier improves the surface polarity and improves the wettability of the pressure-sensitive adhesive, the crosslinked network formed by ultraviolet curing and the embedding of nanomaterials enhance the interfacial mechanical interlocking and cohesive strength, and the segmented drying and curing process ensures uniform glue layer and promotes molecular entanglement, significantly improving the adhesion. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The effect picture of the ultraviolet resistance test of the car paint prepared in examples 6-8, comparative examples 1-3, comparative examples 9-10 of the present application is shown. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0020] KH570 is methacryloyloxypropyltrimethoxysilane; TMPTA is trimethylolpropane triacrylate; maleic anhydride grafted EVA is maleic anhydride grafted ethylene-vinyl acetate.

[0021] Please refer to Figure 1 The present application provides an EVA / nano zinc oxide ultraviolet resistant car paint and a preparation method thereof, and the technical scheme is as follows:

[0022] Example 1 The nano zinc oxide is placed in a vacuum drying oven, dried at 100°C for 5h to obtain a dried raw material; 6 parts of KH570 are added into 10ml of 95% ethanol aqueous solution, acetic acid is added to adjust the pH value to 5, and stirring treatment is performed for 40min to obtain a silane solution; 100 parts of the dried raw material are ultrasonically dispersed in 95% ethanol aqueous solution to prepare a dispersion liquid with a mass concentration of 20%, the ultrasonic dispersion time is 40min, the ultrasonic power is 300W, the silane solution is slowly added under stirring, the temperature is raised to 70°C, and the modification reaction is performed for 2h; the modified nano zinc oxide is separated and centrifuged, washed with deionized water for 3 times, and vacuum dried at 60°C for 10h to obtain the modified nano zinc oxide; 60 parts of the modified nano zinc oxide and 20 parts of hydroxyethyl methacrylate are added into a flask under nitrogen protection, 0.3 parts of azobisisobutyronitrile is added, the temperature is raised to 80°C, and the grafting reaction is performed for 5h; the composite nano material is separated and centrifuged, washed with deionized water and anhydrous ethanol alternately for 3 times, and vacuum dried at 80°C for 8h to obtain the composite nano material; The polycaprolactone polyol and isophorone diisocyanate are added into a vacuum drying oven, dried at 110°C for 2h to remove water, and then 60 parts of the polycaprolactone polyol with an average molecular weight of 2000g / mol are added into a reaction kettle under nitrogen protection, 10 parts of isophorone diisocyanate are slowly added under the condition of 500rpm and a temperature of 70°C, and then dibutyl tin dilaurate is added, the temperature is raised to 90°C, and the polymerization reaction is performed for 4h to obtain a polyurethane prepolymer by monitoring the -NCO content to the theoretical value through titration; the polyurethane prepolymer is cooled to 65°C, 3 parts of hydroxyethyl methacrylate are slowly added, and a one-time end-capping reaction is performed for 2h to obtain a reaction system by monitoring the decrease of -NCO content to the theoretical value through di-n-butylamine titration; 5 parts of 2,2'-methylenebis(6-tert-butyl-4-methylphenol) are dissolved in 2ml of acetone to obtain a mixed solution; the mixed solution is slowly added into the reaction system, the temperature is raised to 90°C, a two-time end-capping reaction is performed for 3h, and the -NCO characteristic absorption peak disappears through infrared detection, and then acetone is removed by vacuum distillation to obtain a polyurethane modifier; The ethylene-vinyl acetate resin 95 parts by mass was added into a high-speed mixer, preheated and melted at 100°C, the stirring speed was 1000 r / min, and stirring was performed for 20 min; then the composite nanomaterial 8 parts, the maleic anhydride grafted EVA 12 parts, the UV-329 1.2 parts, the antioxidant 1010 0.8 parts, the antioxidant 168 0.8 parts, the stearic acid amide 0.6 parts, the polyethylene wax 0.3 parts were added, and the mixture was obtained by keeping stirring and mixing for 30 min; the polyurethane modifier 15 parts and the TMPTA 6 parts were added into the mixture, the stirring speed was kept at 600 rpm, and the mixing was continued for 20 min to obtain a base mixture; the base mixture was melt-extruded and granulated by a double-screw extruder, the extruded granules were water-cooled and cut into particles to obtain polymer particles; the polymer particles were cast into a film by a single-screw extruder, the melt was extruded through a T-shaped die head and cast onto a cooling roller with a smooth surface; then the film was subjected to ultraviolet light curing treatment, the irradiation energy was controlled at 500 mJ / cm2, and the irradiation time was 20 min to obtain a car film. The car film was uniformly coated with an emulsion type acrylate pressure-sensitive adhesive on the surface of the car film by a coating device, and was dried by controlling the temperature in sections, the first section was at 80°C for 10 min; the second section was at 90°C for 8 min; the third section was at 100°C for 3 min; then the product was wound by being combined with a PP release film, and was aged at 40°C for 20 h to obtain an ultraviolet resistant car film.

[0023] Example 2-5 refers to the preparation method and parameter conditions of Example 1, and the differences are shown in Table 1.

[0024] Table 1 Parameter changes of Examples 1-5

[0025] Comparative Example 1 refers to Example 1, except that no polyurethane modifier is added, and the other components remain unchanged.

[0026] Comparative Example 2 refers to Example 1, except that no composite nanomaterial is added, and the other components remain unchanged.

[0027] Comparative Example 3 refers to Example 1, except that no polyurethane modifier and no composite nanomaterial are added.

[0028] Comparative Example 4 refers to Example 1, except that no TMPTA is added, and the other components remain unchanged.

[0029] Comparative Example 5 refers to Example 1, except that no maleic anhydride grafted EVA is introduced, and the other components remain unchanged.

[0030] Comparative Example 6 refers to Example 1, except that the car film is not prepared by high-speed mixing in steps.

[0031] Comparative Example 7 Refer to Example 1, the difference is that no UV curing treatment, directly melt extrusion, cast film.

[0032] Experimental Example 1 Mechanical Property Test The anti-ultraviolet car clothes prepared from Example 1-5 and Comparative Example 1-7 were tested for mechanical properties, the tensile strength and elongation at break were tested according to GB / T1040.3-2006, dumbbell-shaped samples were prepared, the tensile speed was 50 mm / min; the tear strength was tested according to GB / T 16578.1-2008, pants-shaped samples were prepared, the tensile speed was 100 mm / min, and the test results are shown in Table 2.

[0033] Table 2 Test results of Example 1-5 and Comparative Example 1-7

[0034] From the results in Table 2, in the comparative examples, by changing the components and adjusting the process, the mechanical properties of the anti-ultraviolet car clothes obtained are obviously different from those of the examples; in Comparative Examples 1-3, no polyurethane modifier is introduced, the lack of polar groups, the lack of chemical crosslinking points during melt extrusion, the weakening of the intermolecular force, the material is more prone to breakage under stress, and the lack of flexible chain segments leads to a decrease in mechanical properties; the lack of physical enhancement of nanoparticles leads to significant stress concentration, and the lack of interfacial crosslinking effect of nanoparticles leads to a decrease in elongation at break due to limited molecular chain slip, and the comprehensive mechanical properties decrease; the lack of chemical crosslinking of polyurethane modifier and physical enhancement of nanoparticles leads to a significant decrease in the overall strength and toughness of the material; in Comparative Example 4, no TMPTA is added to provide multifunctional crosslinking, the crosslinking density is reduced, the material is prone to chain slip under stress, and the mechanical properties are significantly reduced; as shown in Comparative Example 5, maleic anhydride grafted EVA forms covalent bonds with the polar anhydride groups on the surface of the polyurethane modifier and the nanoparticles, improving the interfacial compatibility, avoiding phase separation caused by poor interfacial compatibility, and reducing the stress transfer efficiency; in addition, the lack of compatibility leads to agglomeration of nanoparticles, further reducing the mechanical properties; in Comparative Examples 6-7, the process change has a significant effect on the mechanical properties, the lack of stepwise high-speed mixing leads to uneven dispersion of the nanoparticles, crosslinking agents and other additives, resulting in agglomeration and stress concentration points, affecting the uniformity of the crosslinking reaction and reducing the overall mechanical properties; the lack of photocuring process and chemical crosslinking leads to a significant decrease in strength due to the reliance on physical entanglement, in addition, the linear molecular chain structure formed during the melting process leads to a significant decrease in elongation at break due to the easy breakage of the molecular chain, and the material exhibits plastic failure, further affecting the mechanical properties.

[0035] In summary, in the composite nanomaterial, the nano zinc oxide modified by silanization and grafted with HEMA has small particle size and large specific surface area, and can effectively disperse stress as a reinforcing filler, and the organic long chain on the surface also helps to combine with the matrix resin; in the polyurethane modifier, the flexible polycaprolactone segment and the rigid isocyanate segment in the molecular structure endow the material with excellent toughness and strength, and the HEMA group at the end provides a reaction site for subsequent crosslinking, and under the synergistic effect of TMPTA, crosslinking reaction occurs inside the material to form a three-dimensional network structure, which significantly improves the cohesive strength and deformation resistance of the material, thereby greatly improving the tensile strength and tear strength; the addition of maleic anhydride grafted EVA improves the compatibility of the nanofiller, the polyurethane modifier and the non-polar EVA matrix, further enhances the interface bonding and improves the overall mechanical properties; through the synergistic effect of the chemical crosslinking effect provided by the polyurethane modifier, the physical reinforcing effect of the composite nanomaterial, the improved compatibility of the maleic anhydride grafted EVA and the three-dimensional crosslinked structure formed by TMPTA, a chemical-physical double network reinforcing system is formed, which significantly improves the mechanical properties of the anti-ultraviolet car paint.

[0036] Example 6 is the same as Example 1; Examples 7-9 refer to the preparation method and parameter conditions of Example 1, and the differences are shown in Table 3.

[0037] Table 3 Parameter changes of Examples 6-9

[0038] Comparative Example 1 refers to Example 1, except that no polyurethane modifier is added, and the other components remain unchanged.

[0039] Comparative Example 2 refers to Example 1, except that no composite nanomaterial is added, and the other components remain unchanged.

[0040] Comparative Example 3 refers to Example 1, except that no polyurethane modifier and composite nanomaterial are added.

[0041] Comparative Example 8 refers to Example 1, except that 2,2'-methylenebis(6-tert-butyl-4-methylphenol) is not used for end capping treatment in the polyurethane modifier, and hydroxyethyl methacrylate is used.

[0042] Comparative Example 9 refers to Example 1, except that no hydroxyethyl methacrylate grafting reaction is used in the composite nanomaterial, only modified nano zinc oxide is used.

[0043] Comparative Example 10 refers to Example 1, except that no silane modification and hydroxyethyl methacrylate grafting are performed on the composite nanomaterial, and nano zinc oxide is directly added.

[0044] Comparative Example 11 Reference to Example 1, the difference is not to join the ultraviolet absorber, other remain unchanged.

[0045] Comparative Example 12 Reference to Example 1, the difference is not to join the antioxidant, other remain unchanged.

[0046] Comparative Example 13 Reference to Example 1, the difference is not to join the ultraviolet absorber, antioxidant, other remain unchanged.

[0047] Experimental Example 2 Anti-ultraviolet performance test The anti-ultraviolet performance of the anti-ultraviolet car paint prepared in Examples 6-9, Comparative Examples 1-3, Comparative Examples 8-13 is tested, the initial tensile strength of the car paint is tested according to GB / T 1040.3-2006, the car paint is subjected to ultraviolet aging treatment according to GB / T 16422.3-2014, the UVB-313 light source is used, the irradiance is 1.0 W / m², the blackboard temperature is 60℃, the irradiation time is 300h, the tensile strength after irradiation is tested, and the tensile strength retention rate is calculated. The test results are shown in Table 4; the anti-ultraviolet performance test results of the car paint prepared in Examples 6-8, Comparative Examples 1-3, Comparative Examples 9-10 of the present application are shown in Table 4. Figure 1

[0048] Table 4 Test results of Examples 6-9, Comparative Examples 1-3, Comparative Examples 8-13

[0049] ​From the results of Table 4, in the comparative examples, by adjusting the components in the anti-ultraviolet car cover, the anti-ultraviolet performance is obviously reduced compared with the examples; from the results of comparative examples 1-3, in combination with comparative example 8, the hindered phenol structure of 2,2'-methylenebis(6-tert-butyl-4-methylphenol) in the polyurethane improver can capture hydroxyl radicals and alkoxy radicals generated by ultraviolet aging, inhibit oxidative chain scission, in addition, the crosslinked network formed by it and EVA can physically hinder molecular chain movement and reduce photooxidation damage; the composite nano zinc oxide provides a physical shielding effect by using the effect of nanoparticle scattering and absorbing ultraviolet rays, in combination with comparative examples 9-10, by silane-modified nano zinc oxide, only relying on physical adsorption to combine with the car cover matrix, it is easy to fall off due to thermal expansion and contraction during ultraviolet aging, resulting in a decrease in the dispersion stability of nanoparticles; without modification and grafting treatment of nano zinc oxide, the hydrophilic groups on the surface of zinc oxide form phase separation with the EVA matrix, generating a large number of agglomerates and interface defects, accelerating the fracture caused by ultraviolet aging; by using the silane modification effect to improve the dispersion uniformity of nano zinc oxide, and the chemical crosslinking formed by the hydroxyethyl methacrylate grafting and the matrix, a stable chemical anchoring effect is formed, by the multi-mechanism synergistic effect of polyurethane improver and composite nano material, the anti-ultraviolet performance is improved; from the results of comparative examples 11-13, the introduction of benzotriazole ultraviolet absorber can absorb 280-400 nm ultraviolet light and convert it into heat energy, reducing the energy reaching the matrix, forming a synergistic effect with nano zinc oxide; by compounding antioxidant 1010 and antioxidant 168, the oxidation chain reaction and hydrogen peroxide decomposition can be terminated, forming a double antioxidant network with hindered phenol, through multiple actions, the anti-ultraviolet performance of the car cover is further improved.

[0050] In summary, as a kind of excellent inorganic UV shielding agent, nano zinc oxide can strongly absorb UVA and UVB band of ultraviolet, in addition its nano size effect can also enhance the UV shielding effect, by its silane modification, hydroxyethyl methacrylate grafting, improve its compatibility with EVA matrix;Introducing 2,2'-methylene bis (6-tert-butyl-4-methyl phenol) capped polyurethane modifier, 2,2'-methylene bis (6-tert-butyl-4-methyl phenol) can capture the free radicals generated in the process of photo-oxidative aging of polymer, terminate chain reaction, protect the polymer from degradation, in addition, using the polar group in polyurethane modifier, in ultraviolet curing form stable crosslinked network structure, not easy to occur by ultraviolet light induced chain scission and rearrangement, slow down the aging process;Finally benzotriazole ultraviolet absorber can efficiently absorb specific wavelength of ultraviolet, and convert it into harmless heat energy release, reduce the ultraviolet energy reaching the interior of the polymer;Using nano ZnO physical shielding of ultraviolet and ultraviolet absorber combined with the chemical absorption of ultraviolet, build the first line of defense;The hindered phenol structure on the polyurethane modifier and antioxidant synergistic effect, can more effectively capture different types of free radicals, inhibit the initiation and growth of oxidative degradation chain;Through the action of ultraviolet absorber on the material surface, while nano zinc oxide and antioxidant can provide protection in the whole material system, through the synergistic effect of multiple mechanisms to further improve the anti-ultraviolet performance of car clothes.

[0051] Example 10 is the same as example 1. Examples 11-14 refer to the preparation method and parameter conditions of example 1, the difference is shown in table 5.

[0052] Table 5 parameter changes of examples 10-14

[0053] Comparative example 1 refers to example 1, the difference is that no polyurethane modifier is added, and the rest of the components remain unchanged.

[0054] Comparative example 2 refers to example 1, the difference is that no composite nanomaterial is added, and the rest of the components remain unchanged.

[0055] Comparative example 3 refers to example 1, the difference is that no polyurethane modifier and composite nanomaterial are added.

[0056] Comparative example 4 refers to example 1, the difference is that no TMPTA is added, and the rest of the components remain unchanged.

[0057] Comparative example 9 refers to example 1, the difference is that no hydroxyethyl methacrylate grafting reaction is used in the composite nanomaterial, only modified nano zinc oxide is used.

[0058] Comparative Example 10 Refer to Example 1, the difference is that the composite nanomaterial is not modified by silane and grafted by hydroxyethyl methacrylate, and the nanometer zinc oxide is directly added.

[0059] Comparative Example 14 Refer to Example 1, the difference is that the polyurethane modifier is not terminated by hydroxyethyl methacrylate, but only terminated by 2,2'-methylene bis(6-tert-butyl-4-methylphenol).

[0060] Comparative Example 15 Refer to Example 1, the difference is that the segmented temperature control drying is not performed when coating the acrylate pressure-sensitive adhesive.

[0061] Comparative Example 16 Refer to Example 1, the difference is that the curing treatment is not performed.

[0062] Experimental Example 3 Adhesion Test The adhesion of the anti-ultraviolet car paint obtained in Examples 10-14, Comparative Examples 1-4, Comparative Examples 9-10, Comparative Examples 14-16 was tested, the adhesion of the car paint to the automobile substrate was determined by the crosshatch method according to GB / T 5210-2006, and the adhesion of the car paint film to the pressure-sensitive adhesive was determined by the 180° peeling method according to GB / T 7122-1996; the test results are shown in Table 6.

[0063] Table 6 Performance test of Examples 10-14, Comparative Examples 1-4, Comparative Examples 9-10, Comparative Examples 14-16

[0064] From the results of Table 6, it can be seen that in the comparative examples, by adjusting the components and changing the process, the adhesion of the anti-ultraviolet car cover obtained is significantly reduced compared to the examples; from the results of Comparative Examples 1-3, the polyurethane modifier contains hydroxyl and methacrylate groups, which can form hydrogen bonds and chemical crosslinking with the EVA matrix through maleic anhydride grafting, and at the same time, the compatibility with the acrylate is improved through the ester group to enhance the interface adsorption; without using, it only relies on van der Waals force to combine, and the adhesion is reduced; the methacrylate grafting group on the surface of the composite nano-zinc oxide forms a chemical bond through ultraviolet crosslinking under the action of TMPTA, enhancing the anchoring effect of the nano-particles with the matrix, indirectly improving the overall cohesive strength of the material; the absence of nano-particles leads to a decrease in the crosslinking density of the matrix, and in addition, the surface roughness of the matrix decreases due to the absence of nano-particles, and the mechanical biting effect of the adhesive layer is weakened, the adhesion with the pressure-sensitive adhesive layer is reduced, and in turn the adhesion with the substrate is reduced, and the grid is easy to fall off along the interface; in combination with Comparative Example 4, TMPTA as a multi-functional crosslinking agent, under ultraviolet light, initiates the formation of a three-dimensional crosslinking network of EVA matrix and polyurethane, nano-material surface double bonds, improving the cohesive strength, thereby improving the peel strength; in Comparative Examples 9-10, the surface of the unmodified nano-zinc oxide is hydrophilic, and the oil-wet EVA matrix forms a phase separation particle, and there are cavities and stress concentration points at the interface, and after the pressure-sensitive adhesive penetrates into the gap between the particles, it forms an invalid bond, the actual effective contact area is reduced, and the peel force is significantly reduced; in addition, the surface of the nano-zinc oxide modified only by silane is a methacryloyloxy group, but it does not introduce double bonds through grafting, and it cannot crosslink with the matrix TMPTA, forming a weak interface mainly by physical adsorption, and the adhesion is significantly reduced; in Comparative Example 14, the absence of methacrylate groups, the polyurethane modifier cannot crosslink with the EVA matrix and TMPTA, and the polyurethane is only bonded by hydrogen bonds, with weak bonding force with the overall matrix, resulting in reduced adhesion; from the results of Comparative Example 15, it can be seen that the segmented temperature control ensures that the pressure-sensitive adhesive solvent volatilizes gradually, avoiding the generation of bubbles caused by rapid drying, and the residual bubbles reduce the effective contact area between the adhesive layer and the car cover film, and the bubbles are easy to tear during griding, in addition, stress concentration occurs in the bubble area during peeling, and the peel force decreases; from the results of Comparative Example 16, it can be seen that the curing process allows the pressure-sensitive adhesive molecular chain to fully diffuse and entangle with the surface groups of the car cover film, and completes the post-crosslinking of the residual monomers, avoiding insufficient stretching of the molecular chain, resulting in low interface entanglement density and reduced adhesion.

[0065] In summary, the EVA matrix itself contains vinyl acetate groups, which have certain polarity, are beneficial to improve the surface energy and improve the wettability of the acrylate pressure-sensitive adhesive; the introduction of polyurethane modifier will change the surface polarity and surface energy of the film material, which is beneficial to the combination with the pressure-sensitive adhesive; under the action of TMPTA, the crosslinked network formed by ultraviolet curing makes the surface of the car film more dense and more resistant to solvents, reducing the risk of adhesion decline caused by swelling, deformation or degradation of the substrate; the polar groups of polyurethane modifier form a three-dimensional network structure with EVA matrix and composite nanomaterials under the synergistic action of TMPTA, improving the adhesion; in addition, the composite nanomaterials are embedded in the crosslinked network by grafting double bonds, enhancing the mechanical interlocking of the interface; through the process of sectional temperature control drying and curing, it ensures that the adhesive layer is uniform and dense, and promotes the full entanglement of molecular chains; by the synergistic effect of the three, the chemical crosslinking density and the interface molecular diffusion degree are improved, and the overall adhesion performance of the car film is improved by physical and chemical methods.

[0066] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A preparation method of EVA / nano-zinc oxide anti-ultraviolet car clothes, characterized in that, The preparation of the anti-ultraviolet car cover comprises the following steps: The nano zinc oxide and methyl methacryloxypropyl trimethoxysilane are modified to react; then the composite nanomaterial is obtained by grafting with hydroxyethyl methacrylate; The polycaprolactone polyol and isophorone diisocyanate are polymerized to obtain a polyurethane prepolymer; then the polyurethane modifier is obtained by one-end capping with hydroxyethyl methacrylate and two-end capping with 2,2'-methylene bis(6-tert-butyl-4-methylphenol); The ethylene-vinyl acetate resin, the composite nanomaterial, the polyurethane modifier and the auxiliary agent are mixed by stepwise high-speed mixing, melt-extruded and ultraviolet light-cured to obtain a car cover film; The car cover film is coated with pressure-sensitive adhesive, dried by sectional temperature control, wound by compounding and matured to obtain the anti-ultraviolet car cover.

2. The preparation method of the EVA / nano-zinc oxide anti-ultraviolet car cover according to claim 1, characterized in that, The auxiliary agent comprises maleic anhydride grafted EVA, stearic acid amide, polyethylene wax, trimethylolpropane triacrylate, ultraviolet absorber and antioxidant; the ultraviolet absorber is UV-329; and the antioxidant is obtained by mixing antioxidant 1010 and antioxidant 168 at a mass ratio.

3. The preparation method of the EVA / nano-zinc oxide anti-ultraviolet car cover according to claim 1, characterized in that, The preparation of the composite nanomaterial comprises the following steps: The nano zinc oxide is placed in a vacuum drying box to obtain dried raw materials; KH570 is added into 95% ethanol aqueous solution, acetic acid is added to adjust the pH value, and stirring treatment is performed to obtain a silane solution; the dried raw materials are ultrasonically dispersed in 95% ethanol aqueous solution to configure a dispersion liquid, the silane solution is slowly added under stirring conditions, modification reaction is performed, separation and centrifugation are performed, deionized water washing is performed, and vacuum drying is performed to obtain modified nano zinc oxide; the modified nano zinc oxide and the hydroxyethyl methacrylate are added into a flask, azobisisobutyronitrile is added under nitrogen protection conditions, grafting reaction is performed, separation and centrifugation are performed, deionized water and anhydrous ethanol are alternately washed, and vacuum drying is performed to obtain the composite nanomaterial.

4. The preparation method of the EVA / nano-zinc oxide anti-ultraviolet car cover according to claim 1, characterized in that, The preparation of the polyurethane modifier comprises the following steps: The hydroxyethyl methacrylate is added into the polyurethane prepolymer to obtain a reaction system by one-end capping reaction; the 2,2'-methylene bis(6-tert-butyl-4-methylphenol) is dissolved in acetone to obtain a mixed solution; the mixed solution is added into the reaction system to perform two-end capping reaction, and the polyurethane modifier is obtained by reduced pressure distillation.

5. The preparation method of the EVA / nano-zinc oxide anti-ultraviolet car cover according to claim 4, characterized in that, The preparation of the polyurethane prepolymer comprises the following steps: The polycaprolactone polyol and the isophorone diisocyanate are added into a vacuum drying box to perform vacuum drying; under nitrogen protection, the polycaprolactone polyol is added into a reaction kettle, the isophorone diisocyanate is added by stirring, dibutyltin dilaurate is added after dropwise addition is completed, and polymerization reaction is performed to obtain the polyurethane prepolymer.

6. The preparation method of the EVA / nano-zinc oxide anti-ultraviolet car cover according to claim 1, characterized in that, The preparation of the car cover film comprises the following steps: The ethylene-vinyl acetate resin is added into a high-speed mixer, the composite nanomaterial, the maleic anhydride grafted EVA, the ultraviolet absorber, the antioxidant, the stearic acid amide, the polyethylene wax, the polyurethane modifier and the TMPTA are added by stepwise high-speed mixing, and stirring and mixing are conducted to obtain a matrix mixture; the matrix mixture is melt-extruded and pelletized by a double-screw extruder; after water cooling and granulation, polymer particles are obtained; the polymer particles are cast into a film by a single-screw extruder; and then ultraviolet light curing treatment is conducted to obtain the car film.

7. The preparation method of the EVA / nano-zinc oxide anti-ultraviolet car cover according to claim 6, characterized in that, The stepwise high-speed mixing comprises the following steps: The ethylene-vinyl acetate resin is added into a high-speed mixer, preheating and melting, and the composite nanomaterial, the maleic anhydride grafted EVA, the ultraviolet absorber, the antioxidant, the stearic acid amide and the polyethylene wax are added during stirring and mixing to obtain a mixture; the polyurethane modifier and trimethylolpropane triacrylate are added into the mixture, and uniform mixing is conducted to obtain the matrix mixture.

8. The EVA / nano-zinc oxide anti-ultraviolet car coat prepared by the method of claim 1, characterized in that, The ultraviolet-resistant car film comprises ethylene-vinyl acetate resin, a composite nanomaterial, a polyurethane modifier, trimethylolpropane triacrylate, an additive and an acrylate pressure-sensitive adhesive.

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