High-tensile color-changing car cover and preparation method thereof

Abstract

The invention relates to a high-tensile color-changing automobile cover and a preparation method thereof, and relates to the technical field of automobile material processing. Preparation raw materials comprise the following components in parts by mass: 50 to 60 parts of hyperbranched polycarbonate polyol, 30 to 40 parts of isocyanate, 2 to 5 parts of a composite chain extender, 10 to 20 parts of modified epoxy resin, 10 to 20 parts of anti-ultraviolet modified spandex fiber, 1 to 3 parts of pigment, 0.5 to 1.5 parts of an antioxidant, 0.5 to 1 part of a lubricant and 15 to 25 parts of a solvent. The preparation method comprises the following steps: mixing and reacting the components to obtain a material; coating release paper with the material, heating, curing, cooling and rolling to obtain the high-tensile modified car cover. The high-tensile modified car cover has the effect of improving the tensile property and weather resistance of the car cover, and good performance and appearance of the high-tensile modified car cover can be kept for a long time.

Description

Technical Field

[0001] This application relates to the technical field of automotive material processing, and particularly to a high-stretch color-changing car wrap and its preparation method. Background Art

[0002] With the continuous increase in the number of automobiles in use and the continuous upgrading of consumers' aesthetic concepts, car owners' pursuit of vehicle appearance personalization has become increasingly strong. Traditional automotive painting for color change is not only cumbersome and costly in procedures, but also has poor reversibility. Once painted, it often requires a great deal of effort and money to change back to the original color. Against this background, color-changing car wraps have emerged, which can easily achieve diverse color transformations, meet car owners' ever-changing fashion tastes, and at the same time do not damage the original vehicle paint. Their detachable and replaceable characteristics have quickly won market favor and initiated a new trend in automotive appearance modification.

[0003] However, some existing color-changing car wraps have gradually revealed shortcomings in material performance during actual application. Especially in terms of tensile performance, when the car wrap needs to fit complex curved surfaces and arcs of the vehicle body, such as door handles, rearview mirrors, bumpers, etc., some ordinary color-changing car wraps are prone to wrinkles, cracks, or even poor fitting due to poor stretchability. This not only affects the aesthetics of the car wrap but may also reduce its protective effect on the vehicle paint, so improvement is needed. Summary of the Invention

[0004] In order to improve the tensile performance of the car wrap, this application provides a high-stretch color-changing car wrap and its preparation method.

[0005] A high-stretch color-changing car wrap and its preparation method provided by this application adopt the following technical solutions: In the first aspect, a high-stretch color-changing car wrap provided by this application adopts the following technical solutions: A high-stretch color-changing car wrap, the preparation raw materials of which include the following components in parts by mass: Hyperbranched polycarbonate polyol 50 - 60 parts Isocyanate 30 - 40 parts Compound chain extender 2 - 5 parts Modified epoxy resin 10 - 20 parts UV-resistant modified spandex fiber 10 - 20 parts Pigment 1 - 3 parts Antioxidant 0.5 - 1.5 parts Lubricant 0.5 - 1 part Solvent 15 - 25 parts.

[0006] The branched structure of hyperbranched polycarbonate polyol gives the material good flexibility and fluidity. Its hydroxyl group reacts with the isocyanate group of isocyanate to form a long-chain polyurethane structure, building a stable and elastic molecular network, improving the tensile properties of the car cover, and can effectively withstand external tensile force; the composite chain extender can adjust the molecular weight of the polymer, optimize the molecular chain length, and further enhance the tensile properties and elastic recovery properties; the modified epoxy resin can enhance the adhesion between the car cover and the car body, and its epoxy group is chemically bonded with other components, allowing the car cover to fit tightly, and also improving the overall hardness to protect the car paint from impact; the anti-UV modified spandex fiber has both good tensile properties and UV resistance, can absorb and scatter ultraviolet rays, reduce aging and fading of the car cover, and improve the weather resistance and tensile properties of the car cover.

[0007] Preferably, the raw materials for preparing the hyperbranched polycarbonate polyol include 1,6-hexanediol, propylene carbonate and pentaerythritol.

[0008] The flexible chain segment of 1,6-hexanediol improves the flexibility of the molecular chain. This flexibility enables the car cover to conform to the complex and changeable curved surface of the car body, improves the tensile performance, and effectively reduces the risk of rupture during tensile stress. The flexible chain segment also has a buffering capacity. When facing changes in external environmental factors such as temperature and humidity, it can relieve the internal stress of the material, reduce structural degradation caused by environmental impact, and help improve weather resistance. The cyclic carbonate structure of propylene carbonate gives the molecular chain moderate rigidity, which complements the flexibility of 1,6-hexanediol, making the car cover have good tensile properties while being structurally stable and not easy to deform. During long-term outdoor exposure, this structure can better resist erosion such as ultraviolet rays and oxidation, maintain stable material performance, and enhance weather resistance. Pentaerythritol, with its highly branched structure and multiple hydroxyl groups, promotes the polymerization reaction to efficiently construct a hyperbranched network, which can moderately increase the cross-linking density, thereby improving tensile properties. At the same time, the increase in cross-linking degree reduces the channels for the invasion of external environmental substances, reduces the damage to the internal structure of the material by ultraviolet rays, moisture, etc., and improves the weather resistance of high-stretch color-changing car covers.

[0009] Preferably, the mass ratio of 1,6-hexanediol, propylene carbonate and pentaerythritol is 1:0.2:(0.03-0.1).

[0010] The high-strength color-changing car cover prepared according to the above mass ratio has good weather resistance and tensile properties.

[0011] Preferably, the isocyanate comprises 3-isopropyl-dimethylbenzyl isocyanate.

[0012] The isopropyl group and benzyl group in the isocyanate provide steric hindrance effects. When undergoing a polymerization reaction with raw materials such as hyperbranched polycarbonate polyol, this steric hindrance can regulate the growth morphology of the polymer molecular chain, preventing the molecular chain from arranging too regularly and causing embrittlement of the material, making the formed polymer network structure more ductile, thereby enhancing the tensile properties of the car wrap; the benzene ring structure of 3-isopropyl-dimethylbenzyl isocyanate can play a barrier role, effectively reducing the impact of ultraviolet rays on the polymer molecular chain, reducing deterioration phenomena such as molecular chain breakage and cross-linking caused by photooxidation, maintaining the stability of the material chemical structure, and thus enhancing the weather resistance.

[0013] Preferably, the composite chain extender includes dimethylthiotoluenediamine and diethyltoluenediamine.

[0014] The sulfur atom in dimethylthiotoluenediamine has an electron cloud structure with strong polarizability and can participate in weak intermolecular interactions. During the reaction chain extension, this weak interaction makes the connection between molecular segments more flexible, endowing the car wrap material with better flexibility and effectively enhancing the tensile properties; at the same time, the sulfur atom also has antioxidant ability and can capture free radicals in the long-term outdoor environment, slowing down the oxidation degradation process caused by light, heat, etc., ensuring the stability of the material chemical structure, and enhancing the weather resistance of the car wrap; the ethyl group in the diethyltoluenediamine molecule introduces appropriate steric hindrance and flexibility to the molecular chain. During the chain extension reaction, it can optimize the stacking mode of the molecular chain, prevent the chain segments from aggregating too closely and causing embrittlement of the material, and further enhance the flexibility and tensile properties of the car wrap; the benzene ring conjugate system in the structure of diethyltoluenediamine can absorb and disperse ultraviolet energy, reducing the damage of ultraviolet rays to the polymer molecular chain, and synergistically acting with dimethylthiotoluenediamine to strengthen the weather resistance of the car wrap.

[0015] Preferably, the preparation raw materials of the modified epoxy resin include bisphenol A epoxy resin, terephthaloyl chloride, and p-phenylenediamine.

[0016] The rigid benzene ring structure in the bisphenol A epoxy resin molecule can enhance the strength of the car wrap. After the car wrap is formed, it can effectively increase the hardness of the material, enabling the car wrap to have sufficient resistance to maintain the surface integrity when facing external forces such as tree branch scratches and sandstone impacts during daily use, and avoiding scratches and damages easily, providing support for good tensile properties; at the same time, the benzene ring structure has a conjugate system and can absorb ultraviolet energy and disperse the energy through the delocalization of the electron cloud when exposed to the ultraviolet environment outdoors for a long time, reducing the direct damage of ultraviolet rays to the molecular chain and enhancing the weather resistance. The acyl chloride group of terephthaloyl chloride has high reactivity and can undergo chemical bonding with bisphenol A epoxy resin and p-phenylenediamine to form a more compact and regular cross-linked network structure, enhancing the mechanical strength of the material, improving the tensile strength of the car wrap, enabling it to better conform to the complex curved surface of the vehicle body during stretching, and evenly dispersing external forces when stressed to prevent the material from tearing due to local stress concentration; the tight cross-linked structure effectively blocks the intrusion of external moisture, oxygen and other corrosive substances, slowing down the aging process caused by oxidation, hydrolysis and other reactions inside the material, and effectively ensuring the durability of the car wrap in different environments and strengthening the weather resistance; The amino group of p-phenylenediamine has strong polarity. During the polymerization process with other raw materials, it can form intermolecular forces such as hydrogen bonds, further optimizing the interconnection between molecular chains. This not only increases the flexibility of the material, making the molecular chains of the car wrap easier to slide and stretch during stretching and improving the tensile performance, but also fills the tiny voids in the cross-linked network to a certain extent, and cooperates with the cross-linked structure to block the invasion of external environmental factors. The three work together to improve the tensile performance, weather resistance and stability of the car wrap.

[0017] Preferably, the raw materials for preparing the ultraviolet-resistant modified spandex fiber include a spandex fiber body, tetrabutyl titanate and N-cyclohexyl-γ-aminopropylmethyldimethoxysilane.

[0018] Spandex fiber has excellent tensile performance. Its unique molecular structure contains flexible chain segments, enabling the fiber to stretch and retract freely when stressed, improving the tensile performance of the car wrap; tetrabutyl titanate can hydrolyze to form titanium dioxide nanoparticles, which are evenly dispersed inside and on the surface of the spandex fiber. When the car wrap is exposed to outdoor ultraviolet light, the titanium dioxide nanoparticles can absorb and scatter ultraviolet light, effectively preventing ultraviolet light from penetrating the fiber and reaching the interior of the car wrap, reducing the damage of ultraviolet light to the fiber molecular chains and the entire car wrap material, thereby improving the weather resistance of the car wrap; the silane oxy groups in N-cyclohexyl-γ-aminopropylmethyldimethoxysilane hydrolyze to form silanol groups, and the silanol groups undergo a condensation reaction with the hydroxyl groups on the surface of the spandex fiber to form a tight organosilicon protective film, which can improve the compatibility of the spandex fiber and further improve the tensile performance of the car wrap; at the same time, the organosilicon protective film can effectively block external moisture, dust and other corrosive substances, slowing down the aging and deterioration process of the car wrap caused by a humid environment and pollutant attachment, and cooperating with the titanium dioxide particles to improve the weather resistance of the car wrap.

[0019] Preferably, the mass ratio of the spandex fiber body, tetrabutyl titanate and N-cyclohexyl-γ-aminopropylmethyldimethoxysilane is 1:0.4:(0.1 - 0.2).

[0020] Preferably, the ultraviolet-resistant modified spandex fiber is prepared by the following steps: The spandex fibers are cleaned and dried to obtain pretreated spandex fibers; tetrabutyl titanate is added to ethanol and stirred to obtain a tetrabutyl titanate solution; N-cyclohexyl-γ-aminopropylmethyldimethoxysilane is added to the tetrabutyl titanate solution, stirred, and the pH is adjusted to acidic to obtain a precursor solution; the pretreated spandex fibers are impregnated into the precursor solution, stirred, heated for reaction, centrifuged to obtain a product, washed and dried to obtain anti-ultraviolet modified spandex fibers.

[0021] The anti-ultraviolet modified spandex fibers prepared according to the above mass ratio and steps can effectively improve the tensile properties and weather resistance of the car wrap.

[0022] In a second aspect, the present application provides a method for preparing a highly stretchable color-changing car wrap, adopting the following technical solution: A method for preparing a highly stretchable color-changing car wrap, comprising the following steps: Hyperbranched polycarbonate polyol and isocyanate are mixed and stirred, heated for reaction, a composite chain extender is added, and stirred for reaction to obtain a prepolymer; modified epoxy resin is added to the prepolymer, heated and stirred for reaction to obtain a blend polymer; the pigment is dissolved in a solvent to obtain a pigment dispersion, and anti-ultraviolet modified spandex fibers and the pigment dispersion are added to the blend polymer, and stirred while adding to obtain a mixture; an antioxidant and a lubricant are added to the mixture, and stirred to obtain a material; the material is coated on a release paper, heated and cured, cooled and wound up to obtain a highly stretchable modified car wrap.

[0023] The highly stretchable modified car wrap prepared according to the above steps has good tensile properties, can conform to the complex and changeable curved surface of the vehicle body, effectively reduce the risk of cracking during the tensile force process, and at the same time has good weather resistance, and can maintain good appearance and performance for a long time in an outdoor environment.

[0024] In summary, the present application includes at least one of the following beneficial technical effects: 1. The branched structure of the hyperbranched polycarbonate polyol endows the material with good flexibility and fluidity. Its hydroxyl groups react with the isocyanate groups of the isocyanate to form a long-chain polyurethane structure, constructing a stable and elastic molecular network, improving the tensile properties of the car wrap, and being able to effectively bear external tensile forces; the composite chain extender can adjust the molecular weight of the polymer, optimize the molecular chain length, and further enhance the tensile properties and elastic recovery properties; the modified epoxy resin can enhance the adhesion between the car wrap and the vehicle body, and its epoxy groups are chemically bonded with other components, making the car wrap fit tightly, and also improving the overall hardness to protect the car paint from impact; the anti-ultraviolet modified spandex fibers have both good tensile characteristics and anti-ultraviolet ability, can absorb and scatter ultraviolet rays, reduce the aging and fading of the car wrap, and improve the weather resistance and tensile properties of the car wrap.

[0025] 2. The flexible chain segment of 1,6-hexanediol improves the flexibility of the molecular chain. This flexibility enables the car cover to conform to the complex and changeable curved surface of the car body, improves the tensile performance, and effectively reduces the risk of rupture during tensile stress. The flexible chain segment also has a buffering capacity. When facing changes in external environmental factors such as temperature and humidity, it can relieve the internal stress of the material, reduce structural degradation caused by environmental impact, and help improve weather resistance. The cyclic carbonate structure of propylene carbonate gives the molecular chain moderate rigidity, which complements the flexibility of 1,6-hexanediol, making the car cover have good tensile properties while being structurally stable and not easy to deform. During long-term outdoor exposure, this structure can better resist erosion such as ultraviolet rays and oxidation, maintain stable material performance, and enhance weather resistance. Pentaerythritol, with its highly branched structure and multiple hydroxyl groups, promotes the polymerization reaction to efficiently construct a hyperbranched network, which can moderately increase the cross-linking density, thereby improving tensile properties. At the same time, the increase in cross-linking degree reduces the channels for the invasion of external environmental substances, reduces the damage to the internal structure of the material by ultraviolet rays, moisture, etc., and improves the weather resistance of high-stretch color-changing car covers.

[0026] 3. Spandex fiber has excellent tensile properties. Its unique molecular structure contains flexible segments, which enable the fiber to stretch and retract freely when subjected to stress, thus improving the tensile properties of the car cover. Tetrabutyl titanate can be hydrolyzed to form titanium dioxide nanoparticles, which are evenly dispersed inside and on the surface of the spandex fiber. When the car cover is exposed to outdoor ultraviolet light, the titanium dioxide nanoparticles can absorb and scatter ultraviolet light, effectively preventing ultraviolet light from penetrating the fiber into the car cover, reducing the damage of ultraviolet light to the fiber molecular chain and the entire car cover material, thereby improving the weather resistance of the car cover. The silanol group in the N-cyclohexyl-γ-aminopropylmethyldimethoxysilane molecule is hydrolyzed to form a silanol group, which reacts with the hydroxyl group on the surface of the spandex fiber to form a tight silicone protective film, which can improve the compatibility of the spandex fiber and further improve the tensile properties of the car cover. At the same time, the silicone protective film can effectively block external corrosive substances such as water vapor and dust, slow down the aging and deterioration of the car cover caused by humid environment and the attachment of pollutants, and synergize with the titanium dioxide particles to improve the weather resistance of the car cover. DETAILED DESCRIPTION

[0027] The present application discloses a high-stretch color-changing car cover and a preparation method thereof. The raw materials used in the present application can be obtained from commercially available raw materials unless otherwise specified. The present application is further described in detail below in conjunction with the embodiments: Raw material description: 1,6 - hexanediol (CAS No.: 629 - 11 - 8), propylene carbonate (CAS No.: 108 - 32 - 7), pentaerythritol (CAS No.: 115 - 77 - 5), bisphenol A epoxy resin (CAS No.: 25085 - 99 - 8), terephthaloyl chloride (CAS No.: 100 - 20 - 9), p - phenylenediamine (CAS No.: 106 - 50 - 3), triethylamine (CAS No.: 121 - 44 - 8), the spandex fiber is conventional spandex, purchased from Yantai Tayho Advanced Materials Co., Ltd., tetrabutyl titanate (CAS No.: 5593 - 70 - 4), N - cyclohexyl - γ - aminopropylmethyldimethoxysilane (CAS No.: 120218 - 28 - 2), the isocyanate is 3 - isopropyl - dimethylbenzyl isocyanate (CAS No.: 2094 - 99 - 7), dimethylthiotoluenediamine (CAS No.: 106264 - 79 - 3), diethyltoluenediamine (CAS No.: 68479 - 98 - 1), the solvent is N,N - dimethylformamide (CAS No.: 68 - 12 - 2), the antioxidant is antioxidant 1010 (CAS No.: 6683 - 19 - 8), the lubricant is polydimethylsiloxane (CAS: 9016 - 00 - 6), methyl isocyanate (CAS No.: 624 - 83 - 9).

[0028] Example 1 Preparation of hyperbranched polycarbonate polyol Mix 81.3 g of 1,6 - hexanediol, 16.26 g of propylene carbonate and 2.44 g of pentaerythritol, under nitrogen protection, stir at a speed of 300 rpm for 15 min to obtain a mixed material; heat the mixed material to 160 °C, stir and react at a speed of 300 rpm for 6 h, after cooling to 30 °C, discharge to obtain hyperbranched polycarbonate polyol.

[0029] Preparation of modified epoxy resin Disperse 25 g of bisphenol A epoxy resin into 50 mL of N,N - dimethylformamide, stir at a stirring speed of 350 rpm at 70 °C until completely dissolved to obtain an epoxy resin solution; add 15 g of terephthaloyl chloride and 10 g of p - phenylenediamine to the epoxy resin solution, add them within 30 min, stir at a speed of 350 rpm while adding, after adding, add 2 g of triethylamine, stir and react at a speed of 350 rpm at 100 °C for 4 h, after cooling to below 30 °C, discharge to obtain modified epoxy resin.

[0030] Preparation of ultraviolet - resistant modified spandex fiber The spandex fibers were washed with ethanol and deionized water, and the washed spandex fibers were dried in a vacuum oven at 60 °C to obtain pretreated spandex fibers; 13.33 g of tetrabutyl titanate was added to 50 mL of absolute ethanol and stirred at a speed of 300 rpm for 15 min to obtain a tetrabutyl titanate solution; 3.33 g of N-cyclohexyl-γ-aminopropylmethyldimethoxysilane was added to the tetrabutyl titanate solution and stirred at a speed of 500 rpm for 30 min, and the pH was adjusted to 4 with glacial acetic acid to obtain a precursor solution; 33.34 g of pretreated spandex fibers were impregnated into the precursor solution, stirred at a speed of 200 rpm for 60 min, heated to 50 °C and reacted for 4 h, centrifuged to obtain the product, washed with absolute ethanol and deionized water, and vacuum dried at 60 °C to obtain ultraviolet-resistant modified spandex fibers.

[0031] Preparation of high-tensile color-changing car wrap 50 g of hyperbranched polycarbonate polyol and 30 g of isocyanate were mixed and stirred at a speed of 300 rpm for 30 min, heated to 60 °C and reacted for 1 h, 2 g of a composite chain extender was added, and the mass ratio of dimethylthiotoluenediamine to diethyltoluenediamine in the composite chain extender was 3:2, stirred and reacted at a speed of 500 rpm for 1 h to obtain a prepolymer; 10 g of modified epoxy resin was added to the prepolymer, heated to 65 °C and stirred and reacted at a speed of 500 rpm for 1 h to obtain a blend polymer; 1 g of pigment was dissolved in 15 g of solvent to obtain a pigment dispersion, 10 g of ultraviolet-resistant modified spandex fibers and the pigment dispersion were added to the blend polymer, the pigment dispersion was added within 1 h, and stirred at a speed of 500 rpm while adding to obtain a mixture; 0.5 g of antioxidant and 0.5 g of lubricant were added to the mixture and stirred at a speed of 500 rpm for 30 min to obtain a material; the material was coated on a release paper, cured at 80 °C for 5 h, cooled and wound up to obtain a high-tensile modified car wrap.

[0032] Example 2 Preparation of hyperbranched polycarbonate polyol 76.92 g of 1,6-hexanediol, 15.39 g of propylene carbonate and 7.69 g of pentaerythritol were mixed, and under nitrogen protection, stirred at a speed of 300 rpm for 15 min to obtain a mixed material; the mixed material was heated to 160 °C and stirred and reacted at a speed of 300 rpm for 6 h, and after cooling to 30 °C, discharged to obtain hyperbranched polycarbonate polyol.

[0033] Preparation of modified epoxy resin Disperse 25 g of bisphenol A epoxy resin into 50 mL of N,N-dimethylformamide, and stir at a stirring speed of 350 rpm at 70 °C until completely dissolved to obtain an epoxy resin solution; add 15 g of terephthaloyl chloride and 10 g of p-phenylenediamine to the epoxy resin solution, add them within 30 min, stir at a speed of 350 rpm while adding, after adding, add 2 g of triethylamine, stir and react at 100 °C at a speed of 350 rpm for 4 h, after cooling to below 30 °C, discharge to obtain a modified epoxy resin.

[0034] Preparation of anti-ultraviolet modified spandex fiber Wash the spandex fiber with ethanol and deionized water, and dry the washed spandex fiber in a vacuum oven at 60 °C to obtain a pretreated spandex fiber; add 12.5 g of tetrabutyl titanate to 50 mL of absolute ethanol, stir at a speed of 300 rpm for 15 min to obtain a tetrabutyl titanate solution; add 6.25 g of N-cyclohexyl-γ-aminopropylmethyldimethoxysilane to the tetrabutyl titanate solution, stir at a speed of 500 rpm for 30 min, and adjust the pH to 4 with glacial acetic acid to obtain a precursor solution; immerse 31.25 g of the pretreated spandex fiber into the precursor solution, stir and impregnate at a speed of 200 rpm for 60 min, heat up to 50 °C and react for 4 h, centrifuge to obtain the product, wash with absolute ethanol and deionized water, and dry in vacuum at 60 °C to obtain anti-ultraviolet modified spandex fiber.

[0035] Preparation of high-tensile color-changing car wrap Mix 60 g of hyperbranched polycarbonate polyol and 40 g of isocyanate, stir at a speed of 300 rpm for 30 min, heat up to 60 °C and react for 1 h, add 5 g of a composite chain extender, and the mass ratio of dimethylthiotoluenediamine to diethyltoluenediamine in the composite chain extender is 3:2, stir and react at a speed of 500 rpm for 1 h to obtain a prepolymer; add 20 g of the modified epoxy resin to the prepolymer, heat up to 65 °C and stir and react at a speed of 500 rpm for 1 h to obtain a blend polymer; dissolve 3 g of pigment in 25 g of solvent to obtain a pigment dispersion, add 20 g of anti-ultraviolet modified spandex fiber and the pigment dispersion to the blend polymer, add the pigment dispersion within 1 h, stir at a speed of 500 rpm while adding to obtain a mixture; add 1.5 g of antioxidant and 1 g of lubricant to the mixture, stir at a speed of 500 rpm for 30 min to obtain a material; coat the material on the release paper, cure at 80 °C for 5 h, cool and wind up to obtain a high-tensile modified car wrap.

[0036] Example 3 Preparation of hyperbranched polycarbonate polyol Mix 79.05 g of 1,6 - hexanediol, 15.81 g of propylene carbonate and 5.14 g of pentaerythritol. Under nitrogen protection, stir at a speed of 300 rpm for 15 min to obtain a mixed material. Heat the mixed material to 160 °C and stir - react at a speed of 300 rpm for 6 h. After cooling to 30 °C, discharge to obtain hyperbranched polycarbonate polyol.

[0037] Prepare modified epoxy resin Disperse 25 g of bisphenol A epoxy resin into 50 mL of N,N - dimethylformamide, stir at a speed of 350 rpm at 70 °C until completely dissolved to obtain an epoxy resin solution. Add 15 g of terephthaloyl chloride and 10 g of p - phenylenediamine to the epoxy resin solution, add them within 30 min, and stir at a speed of 350 rpm while adding. After adding, add 2 g of triethylamine and stir - react at a speed of 350 rpm at 100 °C for 4 h. After cooling to below 30 °C, discharge to obtain modified epoxy resin.

[0038] Prepare ultraviolet - resistant modified spandex fiber Clean the spandex fiber with ethanol and deionized water, and dry the cleaned spandex fiber in a vacuum oven at 60 °C to obtain pretreated spandex fiber. Add 12.9 g of tetrabutyl titanate to 50 mL of absolute ethanol, stir at a speed of 300 rpm for 15 min to obtain a tetrabutyl titanate solution. Add 4.84 g of N - cyclohexyl - γ - aminopropylmethyldimethoxysilane to the tetrabutyl titanate solution, stir at a speed of 500 rpm for 30 min, and adjust the pH to 4 with glacial acetic acid to obtain a precursor solution. Immerse 32.26 g of pretreated spandex fiber into the precursor solution, stir and immerse at a speed of 200 rpm for 60 min, heat up to 50 °C and heat - react for 4 h, centrifuge to obtain the product, wash with absolute ethanol and deionized water, and dry in a vacuum at 60 °C to obtain ultraviolet - resistant modified spandex fiber.

[0039] Prepare high - tensile color - changing car wrap Mix 55 g of hyperbranched polycarbonate polyol and 35 g of isocyanate, stir at a speed of 300 rpm for 30 min, heat up to 60 °C and react for 1 h, add 3.5 g of composite chain extender. The mass ratio of dimethylthiotoluenediamine to diethyltoluenediamine in the composite chain extender is 3:2. Stir and react at a speed of 500 rpm for 1 h to obtain a prepolymer; add 15 g of modified epoxy resin to the prepolymer, heat up to 65 °C and stir and react at a speed of 500 rpm for 1 h to obtain a blend polymer; dissolve 2 g of pigment in 20 g of solvent to obtain a pigment dispersion. Add 15 g of ultraviolet-resistant modified spandex fiber and the pigment dispersion to the blend polymer. The pigment dispersion is added within 1 h, and stir while adding at a speed of 500 rpm to obtain a mixture; add 1 g of antioxidant and 0.75 g of lubricant to the mixture, stir at a speed of 500 rpm for 30 min to obtain a material; coat the material on a release paper, cure at 80 °C for 5 h, cool and then wind up to obtain a high-tensile modified car wrap.

[0040] Example 4 Example 4 is based on Example 3. The difference between Example 4 and Example 3 is only that the dosage of 1,6-hexanediol in Example 4 is 82.64 g, the dosage of propylene carbonate is 16.53 g, and the dosage of pentaerythritol is 0.83 g.

[0041] Example 5 Example 5 is based on Example 3. The difference between Example 5 and Example 3 is only that the dosage of 1,6-hexanediol in Example 5 is 74.07 g, the dosage of propylene carbonate is 14.82 g, and the dosage of pentaerythritol is 11.11 g.

[0042] Example 6 Example 6 is based on Example 3. The difference between Example 6 and Example 3 is only that the isocyanate is replaced with methyl isocyanate in Example 6.

[0043] Example 7 Example 7 is based on Example 3. The difference between Example 7 and Example 3 is only that dimethylthiotoluenediamine is not added to the composite chain extender in Example 7.

[0044] Example 8 Example 8 is based on Example 3. The difference between Example 8 and Example 3 is only that diethyltoluenediamine is not added to the composite chain extender in Example 8.

[0045] Example 9 Example 9 is based on Example 3. The difference between Example 9 and Example 3 is only that the dosage of spandex fiber in Example 9 is 34.48 g, the dosage of tetrabutyl titanate is 13.79 g, and the dosage of N-cyclohexyl-γ-aminopropylmethyldimethoxysilane is 1.73 g.

[0046] Example 10 Example 10 is based on Example 3. The difference between Example 10 and Example 3 is only that the dosage of spandex fiber in Example 10 is 29.41 g, the dosage of tetrabutyl titanate is 11.76 g, and the dosage of N-cyclohexyl-γ-aminopropylmethyldimethoxysilane is 8.83 g.

[0047] Example 11 Example 11 is based on Example 3. The difference between Example 11 and Example 3 is only that N-cyclohexyl-γ-aminopropylmethyldimethoxysilane is not added when preparing the anti-ultraviolet modified spandex fiber in Example 11.

[0048] Comparative Example 1 Comparative Example 1 is based on Example 3. The difference between Comparative Example 1 and Example 3 is only that the modified epoxy resin is replaced with bisphenol A epoxy resin in Comparative Example 1.

[0049] Comparative Example 2 Comparative Example 2 is based on Example 3. The difference between Comparative Example 2 and Example 3 is only that the anti-ultraviolet modified spandex fiber is replaced with spandex fiber in Comparative Example 2.

[0050] Performance Detection Test (1) Select "GB1040-79 Plastics Tensile Test Method" and "GB / T 1865-2009 Paints and Varnishes - Artificial Weathering and Artificial Radiation Exposure (Filtered Xenon-Arc Radiation)" as the standards to test the tensile strength of the specimens before and after aging. Prepare three samples for each specimen, and take the average value after measurement. The test results are recorded in Table 1.

[0051] (2) Select "GB / T 37841-2019 Test Method for Puncture Resistance of Plastic Films and Sheets" as the standard. Prepare 5 specimens of 25 mm * 25 mm, select 4 points around the specimens to measure the thickness, calculate the average thickness, conduct a puncture experiment at a speed of 100 mm / min, calculate the puncture strength, and take the average value after measurement. The results are recorded in Table 1.

[0052] Table 1 Detection Results of Tensile Performance, Weather Resistance and Puncture Resistance of the Color-Changing Car Wrap As can be seen from Table 1, the tensile strength of Examples 1-3 is greater than 23.54 MPa, the tensile strength after aging is greater than 19.81 MPa, and the puncture strength is greater than 86.73 N / mm. Thus, it can be seen that the highly stretchable modified car wrap prepared in this application has good tensile properties, weather resistance, and puncture resistance.

[0053] As can be seen from Table 1, the only differences between Examples 4 and 5 and Example 3 are as follows: in Example 4, the mass ratio of 1,6-hexanediol, propylene carbonate, and pentaerythritol is 1:0.2:0.01; in Example 5, the mass ratio of 1,6-hexanediol, propylene carbonate, and pentaerythritol is 1:0.2:0.15. Compared with Example 3, the tensile properties, weather resistance, and puncture resistance of Examples 4 and 5 have decreased. This is because the optimal component ratio of the hyperbranched polycarbonate polyol has been disrupted. Excessive pentaerythritol will lead to over-crosslinking, while too little pentaerythritol will reduce the crosslinking density, both of which will affect the stability of the molecular structure inside the car wrap, resulting in a decrease in tensile properties, weather resistance, and puncture resistance.

[0054] As can be seen from Table 1, the only differences between Examples 6, 7, and 8 and Example 3 are as follows: in Example 6, the isocyanate is replaced with methyl isocyanate; in Example 7, dimethylthiotoluenediamine is not added to the composite chain extender; in Example 8, diethyltoluenediamine is not added to the composite chain extender. Compared with Example 3, the tensile properties, weather resistance, and puncture resistance of Examples 6, 7, and 8 have all decreased. This is because the synthetic components in the car wrap have been replaced. Methyl isocyanate lacks the regulatory effect of the steric hindrance of isopropyl and benzyl groups, resulting in a worse growth morphology of the molecular chain and a decrease in the anti-ultraviolet oxidation effect. Without adding dimethylthiotoluenediamine or diethyltoluenediamine, the lack of compound synergistic effect makes the tensile properties and weather resistance of the car wrap worse.

[0055] As can be seen from Table 1, the only differences between Examples 9, 10, and 11 and Example 3 are as follows: in Example 9, the mass ratio of spandex fiber, tetrabutyl titanate, and N-cyclohexyl-γ-aminopropylmethyldimethoxysilane is 1:0.4:0.05; in Example 10, the mass ratio of spandex fiber, tetrabutyl titanate, and N-cyclohexyl-γ-aminopropylmethyldimethoxysilane is 1:0.4:0.3; in Example 11, N-cyclohexyl-γ-aminopropylmethyldimethoxysilane is not added when preparing the anti-ultraviolet modified spandex fiber. Compared with Example 3, the tensile properties, weather resistance, and puncture resistance of Examples 9, 10, and 11 have decreased. This is because the optimal component ratio of the anti-ultraviolet modified spandex fiber synthesis components has been disrupted. Too much or too little N-cyclohexyl-γ-aminopropylmethyldimethoxysilane will affect the performance of the anti-ultraviolet modified spandex fiber. Excessive amounts will affect the interaction between the fiber and other components in the car wrap, while too little will result in limited protection effects. Without adding N-cyclohexyl-γ-aminopropylmethyldimethoxysilane, the performance will further decline.

[0056] As can be seen from Table 1, the difference between Comparative Example 1 and Example 3 is only that: in Comparative Example 1, the modified epoxy resin is replaced with bisphenol A epoxy resin. Compared with Example 3, the tensile properties, weather resistance and puncture resistance of Comparative Example 1 are significantly decreased; this is because the bisphenol A epoxy resin lacks modification treatment, the interaction between components decreases, and the stability decreases, resulting in a decrease in tensile properties, weather resistance and puncture resistance.

[0057] As can be seen from Table 1, the difference between Comparative Example 2 and Example 3 is only that: in Comparative Example 2, the anti-ultraviolet modified spandex fiber is replaced with spandex fiber. Compared with Example 3, the tensile properties, weather resistance and puncture resistance of Comparative Example 2 are significantly decreased; this is because the spandex fiber lacks modification treatment, the weather resistance decreases, and substances such as ultraviolet rays are more likely to have an adverse effect, and the car wrap is prone to aging, resulting in a significant decrease in tensile properties, weather resistance and puncture resistance.

[0058] This specific embodiment is only an explanation of the present application, and it is not a limitation of the present application. Through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of this application. The technical scope of this application is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A high-stretch color-changing car cover, characterized in that: The raw materials for preparation include the following components in parts by weight: Hyperbranched polycarbonate polyol 50-60 parts Isocyanate 30-40 parts 2-5 parts of composite chain extender Modified epoxy resin 10-20 parts 10-20 parts of UV-resistant modified spandex fiber 1-3 parts of pigment Antioxidant 0.5-1.5 parts Lubricant 0.5-1 part 15-25 parts of solvent.

2. The high-stretch color-changing car cover according to claim 1, characterized in that: The raw materials for preparing the hyperbranched polycarbonate polyol include 1,6-hexanediol, propylene carbonate and pentaerythritol.

3. The high-stretch color-changing car cover according to claim 2, characterized in that: The mass ratio of the 1,6-hexanediol, propylene carbonate and pentaerythritol is 1:0.2:(0.03-0.1).

4. The high-stretch color-changing car cover according to claim 1, characterized in that: The isocyanate includes 3-isopropyl-dimethylbenzyl isocyanate.

5. The high-stretch color-changing car cover according to claim 1, characterized in that: The composite chain extender includes dimethylthiotoluenediamine and diethyltoluenediamine.

6. The high-stretch color-changing car cover according to claim 1, characterized in that: The raw materials for preparing the modified epoxy resin include bisphenol A epoxy resin, terephthaloyl chloride and p-phenylenediamine.

7. The high-stretch color-changing car cover according to claim 1, characterized in that: The raw materials for preparing the anti-ultraviolet modified spandex fiber include spandex fiber body, tetrabutyl titanate and N-cyclohexyl-γ-aminopropylmethyldimethoxysilane.

8. The high-stretch color-changing car cover according to claim 7, characterized in that: The mass ratio of the spandex fiber body, tetrabutyl titanate and N-cyclohexyl-γ-aminopropylmethyldimethoxysilane is 1:0.4:(0.1-0.2).

9. The high-stretch color-changing car cover according to claim 8, characterized in that: The anti-ultraviolet modified spandex fiber is prepared by the following steps: The spandex fiber is cleaned and dried to obtain pretreated spandex fiber; tetrabutyl titanate is added to ethanol and stirred to obtain a tetrabutyl titanate solution; N-cyclohexyl-γ-aminopropylmethyldimethoxysilane is added to the tetrabutyl titanate solution, and after stirring, the pH is adjusted to acidic to obtain a precursor solution; The pretreated spandex fiber is immersed in the precursor solution, stirred and then heated to react, centrifuged to obtain a product, washed and then dried to obtain the anti-ultraviolet modified spandex fiber.

10. A method for preparing a high-stretch color-changing car cover as claimed in any one of claims 1 to 9, characterized in that: The following steps are involved: The hyperbranched polycarbonate polyol and isocyanate are mixed and stirred, heated to react, a composite chain extender is added, stirred to react, and a prepolymer is obtained; a modified epoxy resin is added to the prepolymer, heated to react with stirring, and a blended polymer is obtained; a pigment is dissolved in a solvent to obtain a pigment dispersion, and anti-ultraviolet modified spandex fiber and the pigment dispersion are added to the blended polymer, and stirred while adding to obtain a mixture; an antioxidant and a lubricant are added to the mixture, and stirred to obtain a material; the material is coated on a release paper, heated to cure, and rolled up after cooling to obtain a high-stretch modified car cover.

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