An elastic substrate for automobile spray coating, a preparation method thereof, and applications thereof

Abstract

The invention relates to the field of automobile covers and discloses an elastic substrate for automobile spray-coated covers, a preparation method thereof, and an application thereof. The elastic substrate for automobile spray-coated covers comprises a polyurethane prepolymer, a modified polydimethylsiloxane, a photoinitiator, and an alcohol solvent. The polyurethane prepolymer uses polycarbonate diol, a modified fluorine-containing diol, isocyanate, 2,2-dihydroxymethylbutyric acid, and modified nano-silica as raw materials. The modified fluorine-containing diol and the modified nano-silica are connected to the polyurethane main chain. Pentaerythritol triacrylate is used as a capping agent and p-hydroxyanisole is used as a polymerization inhibitor. The polyurethane prepolymer and the mercapto-terminated modified polydimethylsiloxane are reacted under the action of the photoinitiator to form a heavily cross-linked network, thereby imparting excellent mechanical properties, antifouling properties, thermal stability, and flame retardancy to the elastic substrate.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile covers, and particularly relates to an elastic substrate for automobile spray-coated covers, a preparation method thereof, and applications thereof. Background Art

[0002] With the rapid development of the automotive industry, cars have become an indispensable means of transportation in people's daily lives, and this has led to wear and damage to the exterior of cars. To protect the car body, people often use car covers to protect the vehicle. Thermoplastic polyurethane is a high-performance elastomeric material with excellent mechanical properties, chemical resistance, weather resistance, and wear resistance. In the field of car covers, polyurethane materials are widely used to manufacture various types of car covers due to their unique performance advantages. Current car covers are mainly made of polyurethane particles into a film, which is then artificially heated and stretched and affixed to the car body. The artificial heating and stretching process causes stress in the polyurethane film, which makes it prone to edge collapse at the corners. To avoid stress-induced edge collapse of the polyurethane film, a spray coating process can be used to spray the car cover directly onto the car body, resulting in a more aesthetically pleasing invisible car cover.

[0003] The polyurethanes produced in the prior art using water as a dispersion system have the advantages of being environmentally friendly, low in toxicity, and safe. However, water is used as a solvent in aqueous polyurethane emulsions, and the latent heat of evaporation of water is higher than that of commonly used organic solvents. At the same solid content, the water in aqueous polyurethane evaporates more slowly than the solvent in solvent-based polyurethane, resulting in a long drying time, making it difficult to meet the fast-paced production requirements of modern production lines. In order to solve this problem, most research efforts at home and abroad have focused on increasing the solid content of aqueous polyurethane to reduce the water volatilization load, shorten film formation, and drying time. However, high solid content and low viscosity are always contradictory in the synthesis of aqueous polyurethanes with high solid content. Aqueous polyurethanes synthesized with high solid content are prone to gelation, which brings inconvenience to the production, storage, and use of the material. In addition, aqueous polyurethanes have poor chemical and solvent resistance, low hardness, and low surface gloss, which seriously affect the application of aqueous polyurethanes in the field of car cover materials.

[0004] The current car cover materials are still prone to scratches, scrapes, and wear, and their mechanical properties need to be further improved. In addition, due to the large number of polar groups in the polyurethane structure, its surface energy is extremely large, and it is easy to fall dust and stain dirt, causing its surface to be contaminated, affecting its appearance, resulting in poor application experience and limiting its promotion and application. The existing technology achieves the flame retardant effect of car covers by adding additional liquid or solid flame retardants. The added flame retardant is often added in large quantities. While ensuring the flame retardant performance, it has a significant adverse effect and decrease on the mechanical properties of the material itself. Moreover, the flame retardant is very likely to migrate on the surface of the material at high temperatures, resulting in a reduction in the flame retardant effect, which limits its large-scale production and application. Summary of the Invention

[0005] In order to address the deficiencies mentioned in the above-mentioned background technology, the purpose of the present invention is to provide an elastic substrate for automobile spray cover, a preparation method and application thereof, and to prepare the elastic substrate using polyurethane prepolymer, modified polydimethylsiloxane, a photoinitiator and an alcohol solvent to replace the existing aqueous solvent to increase the solvent volatilization rate during the preparation of the cover, while giving the elastic substrate excellent mechanical properties, anti-fouling properties, thermal stability and flame retardant properties.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] An elastic substrate for spray-coated car covers comprises the following components by weight: 55-70 parts of a polyurethane prepolymer, 5-10 parts of a modified polydimethylsiloxane, 1-3 parts of a photoinitiator, and 40-60 parts of an alcohol solvent; the modified polydimethylsiloxane is prepared by esterification of hydroxyl-terminated polydimethylsiloxane with 3-mercaptopropionic acid.

[0008] The polyurethane prepolymer comprises the following components in parts by weight: 40-55 parts of polycarbonate diol, 30-50 parts of isocyanate, 10-20 parts of modified fluorine-containing diol, 10-30 parts of 2,2-dihydroxymethylbutyric acid, 2-5 parts of modified nano-silica, 2-7 parts of catalyst, 10-25 parts of pentaerythritol triacrylate, 3-8 parts of p-hydroxyanisole, and 20-35 parts of solvent;

[0009] The modified fluorinated diol is prepared by an amidation reaction between pentafluorooctanoic acid and 2-amino-2-methyl-1,3-propanediol to form a terminal hydroxyl fluorinated diol, and then the terminal hydroxyl fluorinated diol is further subjected to a substitution reaction with phenylphosphoryl dichloride; the modified nano-silica is prepared by modifying nano-silica with isopropoxy tris(ethylenediamino-N-ethoxy) titanate.

[0010] Preferably, the preparation method of the modified polydimethylsiloxane comprises the following steps: taking hydroxyl-terminated polydimethylsiloxane, 3-mercaptopropionic acid and p-toluenesulfonic acid in a reactor, placing it at 110-125° C. and stirring for 7-8 hours, and vacuum dehydrating to prepare the modified polydimethylsiloxane.

[0011] Preferably, the preparation method of the modified fluorinated diol comprises the following steps:

[0012] (1) Pentafluorooctanoic acid and 2-amino-2-methyl-1,3-propanediol are dissolved in a mixed solution of dichloromethane and methanol, and then 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline is added to dissolve the mixture. The mixture is stirred in the dark for 8 to 12 hours. After the reaction is completed, the solvent is removed by rotary evaporation. The obtained solid is mixed with diethyl ether and ground, filtered, and washed to prepare a terminal hydroxyl fluorinated diol.

[0013] (2) Phenylphosphoryl dichloride and terminal hydroxyl fluorinated diol are added to a reactor containing tetrahydrofuran, and the mixture is stirred at room temperature for 5 to 7 hours. During the reaction, triethylamine is added in batches to remove the hydrogen chloride produced by the reaction. After the reaction is completed, the mixture is filtered, rotary evaporated, and dried to prepare a modified fluorinated diol.

[0014] Preferably, in step (2), the molar ratio of phenylphosphoryl dichloride to terminal hydroxyl fluorinated diol is 1:2 to 2.7.

[0015] Preferably, the preparation method of the modified nano-silica comprises the following steps: taking nano-silica into a reactor, adding toluene solvent and ultrasonically dispersing it evenly, then adding isopropoxy tris(ethylenediamino-N-ethoxy) titanate, placing it at 65-75°C and stirring it for 4-6 hours. After the reaction is completed, centrifugation, washing, and drying are carried out to prepare modified nano-silica.

[0016] Preferably, the method for preparing the polyurethane prepolymer comprises the following steps:

[0017] Polycarbonate diol and a catalyst are placed in a reactor, nitrogen is introduced into the reaction, the temperature is raised to 75-85°C, isocyanate is added and the reaction is carried out for 1-1.5 hours, and then modified fluorine-containing diol and 2,2-dihydroxymethylbutyric acid are added and the reaction is carried out for 2.5-3 hours. After the reaction is completed, the temperature is lowered to 25-40°C, modified nano-silica is added, and then pentaerythritol triacrylate, a catalyst, p-hydroxyanisole and a solvent are added to the reactor, and the reaction is continued at 55-70°C for 2-4 hours to prepare a polyurethane prepolymer.

[0018] Preferably, the photoinitiator is benzoin dimethyl ether; and the alcohol solvent is one or more combinations of ethanol, isopropanol, and n-propanol.

[0019] Preferably, the isocyanate is one of isophorone diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate; the catalyst is dibutyltin dilaurate; and the solvent is ethyl acetate.

[0020] The method for preparing the elastic substrate for automobile spray cover as described above comprises the following steps: uniformly mixing parts by weight of a polyurethane prepolymer, modified polydimethylsiloxane, a photoinitiator and an alcohol solvent to obtain the elastic substrate for automobile spray cover.

[0021] An application of the elastic substrate for automobile spray coating in the field of automobile films / covers.

[0022] Beneficial effects of the present invention:

[0023] The present invention uses polyurethane prepolymer, modified polydimethylsiloxane, photoinitiator and alcohol solvent to prepare elastic substrate. Alcohol solvent replaces existing water-based solvent to increase solvent volatilization rate in the process of car cover preparation, fast drying speed, and effectively improve the production efficiency of car cover. The modified polydimethylsiloxane is a mercapto-terminated modified polydimethylsiloxane prepared by esterification reaction of hydroxyl-terminated polydimethylsiloxane and 3-mercaptopropionic acid; the polyurethane prepolymer is composed of polycarbonate diol, modified fluorinated diol, isocyanate, 2,2-dihydroxy The invention is prepared from methylbutyric acid, modified nano-silica, pentaerythritol triacrylate and p-hydroxyanisole as raw materials, wherein the modified fluorinated diol is prepared by amidation reaction of pentafluorooctanoic acid and 2-amino-2-methyl-1,3-propanediol to generate a terminal hydroxyl fluorinated diol, and then the hydroxyl group in the terminal hydroxyl fluorinated diol structure is substituted with phenylphosphoryl dichloride to synthesize the terminal hydroxyl modified fluorinated diol, which can be used as a chain extender to be connected to the polyurethane main chain, thereby introducing phosphorus element to achieve the purpose of improving the flame retardancy of the substrate, and at the same time The introduction of organic fluorine into polyurethane can endow the substrate with extremely low surface free energy and excellent hydrophobicity, thereby enhancing the antifouling property and surface self-cleaning ability of the substrate; the modified nano-silica is prepared by modifying nano-silica with amino groups on the surface using isopropoxy tris(ethylenediamino-N-ethoxy) titanate, and the modified nano-silica is connected to the polyurethane main chain, thereby endowing the substrate with good thermal stability and mechanical properties; the present invention uses pentaerythritol triacrylate as a capping agent and p-hydroxyanisole as a polymerization inhibitor to synthesize a hyperbranched polyurethane prepolymer containing multiple vinyl endcappings, providing a large number of cross-linking sites, and then undergoes a thiol-ene click reaction with a thiol-endcapped modified polydimethylsiloxane under the action of a photoinitiator, and forms a heavily cross-linked network through alternating propagation and chain transfer reactions under ultraviolet curing, which is conducive to the formation of a hydrophobic surface and has a synergistic effect on flame retardant properties. At the same time, the thermal stability and mechanical stability of the substrate can be enhanced, and external forces applied can be dispersed along the network structure, thereby improving the mechanical properties of the substrate. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0025] Example 1 A method for preparing modified polydimethylsiloxane comprises the following steps:

[0026] 10 g of hydroxyl-terminated polydimethylsiloxane, 0.42 g of 3-mercaptopropionic acid and 0.12 g of p-toluenesulfonic acid were placed in a reactor, stirred and reacted at 120° C. for 8 h, and vacuum-dehydrated to prepare modified polydimethylsiloxane.

[0027] Example 2 A method for preparing a modified fluorinated diol comprises the following steps:

[0028] (1) 4.15 g of pentadecafluorooctanoic acid and 1.2 g of 2-amino-2-methyl-1,3-propanediol were dissolved in a mixed solution of 100 mL of dichloromethane and 50 mL of methanol, and then 4.98 g of 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline was added and dissolved. The mixed solution was stirred in the dark for 12 h. After the reaction was completed, the solvent was removed by rotary evaporation. The obtained solid was mixed with diethyl ether and ground, filtered, and washed to prepare a terminal hydroxyl fluorinated diol;

[0029] (2) 1 g of phenylphosphoryl dichloride and 6.4 g of terminal hydroxyl fluorinated diol were added to a reactor containing 100 mL of tetrahydrofuran and stirred at room temperature for 6 h. During the reaction, 1.1 g of triethylamine was added in batches to remove the hydrogen chloride produced by the reaction. After the reaction was completed, the modified fluorinated diol was prepared by filtration, rotary evaporation, and drying.

[0030] Example 3 A method for preparing modified nano-silica comprises the following steps:

[0031] Take 0.65g of nano-silica in a reactor, add 70mL of toluene solvent and ultrasonically disperse it evenly, then add 3.2g of isopropoxy tris(ethylenediamino-N-ethoxy) titanate, place it at 75℃ and stir to react for 5h. After the reaction is completed, centrifuge, wash and dry to prepare modified nano-silica.

[0032] Example 4 An elastic substrate for spray-coated car covers comprises the following components in parts by weight: 57 parts of a polyurethane prepolymer, 5 parts of the modified polydimethylsiloxane prepared in Example 1, 1 part of benzoin dimethyl ether as a photoinitiator, and 42 parts of isopropyl alcohol as an alcohol solvent;

[0033] The preparation method of the elastic substrate for automobile spray cover is as follows: parts by weight of polyurethane prepolymer, modified polydimethylsiloxane, photoinitiator and alcohol solvent are uniformly mixed to obtain the elastic substrate for automobile spray cover.

[0034] The preparation method of the polyurethane prepolymer comprises the following steps:

[0035] 42 parts of polycarbonate diol and 1 part of dibutyltin dilaurate were placed in a reactor, nitrogen was passed through the reaction, the temperature was raised to 80° C., 30 parts of isophorone diisocyanate were added and the reaction was carried out for 1 hour, then 10 parts of the modified fluorinated diol prepared in Example 2 and 11 parts of 2,2-dihydroxymethylbutyric acid were added and the reaction was carried out for 3 hours. After the reaction was completed, the temperature was lowered to 30° C., 2 parts of the modified nano-silica prepared in Example 3 were added, and then 10 parts of pentaerythritol triacrylate, 1 part of dibutyltin dilaurate, 3 parts of p-hydroxyanisole and 21 parts of ethyl acetate were added to the reactor, and the reaction was continued at 60° C. for 4 hours to prepare a polyurethane prepolymer.

[0036] Example 5 An elastic substrate for spray-coated car covers comprises the following components in parts by weight: 64 parts of a polyurethane prepolymer, 7 parts of the modified polydimethylsiloxane prepared in Example 1, 2 parts of benzoin dimethyl ether as a photoinitiator, and 52 parts of ethanol as an alcohol solvent;

[0037] The preparation method of the elastic substrate for automobile spray cover is as follows: parts by weight of polyurethane prepolymer, modified polydimethylsiloxane, photoinitiator and alcohol solvent are uniformly mixed to obtain the elastic substrate for automobile spray cover.

[0038] The preparation method of the polyurethane prepolymer comprises the following steps:

[0039] 47 parts of polycarbonate diol and 3 parts of dibutyltin dilaurate were placed in a reactor, nitrogen was passed through the reaction, the temperature was raised to 80° C., 41 parts of isophorone diisocyanate were added and the reaction was carried out for 1 hour, then 14 parts of the modified fluorine-containing diol prepared in Example 2 and 20 parts of 2,2-dihydroxymethylbutyric acid were added and the reaction was carried out for 3 hours. After the reaction was completed, the temperature was lowered to 30° C., 4 parts of the modified nano-silica prepared in Example 3 were added, and then 17 parts of pentaerythritol triacrylate, 2 parts of dibutyltin dilaurate, 5 parts of p-hydroxyanisole and 28 parts of ethyl acetate were added to the reactor, and the reaction was continued at 60° C. for 4 hours to prepare a polyurethane prepolymer.

[0040] Example 6 An elastic substrate for spray-coated car covers comprises the following components in parts by weight: 68 parts of a polyurethane prepolymer, 10 parts of the modified polydimethylsiloxane prepared in Example 1, 3 parts of benzoin dimethyl ether as a photoinitiator, and 55 parts of n-propanol as an alcohol solvent;

[0041] The preparation method of the elastic substrate for automobile spray cover is as follows: parts by weight of polyurethane prepolymer, modified polydimethylsiloxane, photoinitiator and alcohol solvent are uniformly mixed to obtain the elastic substrate for automobile spray cover.

[0042] The preparation method of the polyurethane prepolymer comprises the following steps:

[0043] 55 parts of polycarbonate diol and 4 parts of dibutyltin dilaurate were placed in a reactor, nitrogen was passed through the reaction, the temperature was raised to 80° C., 50 parts of isophorone diisocyanate were added and the reaction was carried out for 1 hour, then 18 parts of the modified fluorine-containing diol prepared in Example 2 and 30 parts of 2,2-dimethylolbutyric acid were added and the reaction was carried out for 3 hours. After the reaction was completed, the temperature was lowered to 30° C., 5 parts of the modified nano-silica prepared in Example 3 were added, and then 23 parts of pentaerythritol triacrylate, 2 parts of dibutyltin dilaurate, 7 parts of p-hydroxyanisole and 32 parts of ethyl acetate were added to the reactor, and the reaction was continued at 60° C. for 4 hours to prepare a polyurethane prepolymer.

[0044] Comparative Example 1: An elastic substrate for spray-coated car covers comprises the following components in parts by weight: 68 parts of a polyurethane prepolymer, 10 parts of a hydroxyl-terminated polydimethylsiloxane, 3 parts of a photoinitiator, benzoin dimethyl ether, and 55 parts of an alcohol solvent, n-propanol;

[0045] The preparation method of the elastic substrate for the automobile spray cover is as follows: parts by weight of a polyurethane prepolymer, hydroxyl-terminated polydimethylsiloxane, a photoinitiator and an alcohol solvent are uniformly mixed to obtain the elastic substrate for the automobile spray cover.

[0046] The preparation method of the polyurethane prepolymer is the same as that in Example 6.

[0047] Comparative Example 2: An elastic substrate for spray-coated car covers comprises the following components in parts by weight: 68 parts of a polyurethane prepolymer, 10 parts of the modified polydimethylsiloxane prepared in Example 1, 3 parts of benzoin dimethyl ether as a photoinitiator, and 55 parts of n-propanol as an alcohol solvent;

[0048] The preparation method of the elastic substrate for automobile spray cover is as follows: parts by weight of polyurethane prepolymer, modified polydimethylsiloxane, photoinitiator and alcohol solvent are uniformly mixed to obtain the elastic substrate for automobile spray cover.

[0049] The preparation method of the polyurethane prepolymer comprises the following steps:

[0050] 55 parts of polycarbonate diol and 4 parts of dibutyltin dilaurate were placed in a reactor, nitrogen was passed through the reaction, the temperature was raised to 80° C., 50 parts of isophorone diisocyanate were added and the reaction was carried out for 1 hour, then 18 parts of 1,4-butanediol and 30 parts of 2,2-dihydroxymethylbutyric acid were added and the reaction was carried out for 3 hours. After the reaction was completed, the temperature was lowered to 30° C., 5 parts of modified nano-silica prepared in Example 3 were added, and then 23 parts of pentaerythritol triacrylate, 2 parts of dibutyltin dilaurate, 7 parts of p-hydroxyanisole and 32 parts of ethyl acetate were added to the reactor, and the reaction was continued at 60° C. for 4 hours to prepare a polyurethane prepolymer.

[0051] Comparative Example 3: An elastic substrate for spray-coated car covers comprises the following components in parts by weight: 68 parts of a polyurethane prepolymer, 10 parts of the modified polydimethylsiloxane prepared in Example 1, 3 parts of benzoin dimethyl ether as a photoinitiator, and 55 parts of n-propanol as an alcohol solvent;

[0052] The preparation method of the elastic substrate for automobile spray cover is as follows: parts by weight of polyurethane prepolymer, modified polydimethylsiloxane, photoinitiator and alcohol solvent are uniformly mixed to obtain the elastic substrate for automobile spray cover.

[0053] The preparation method of the polyurethane prepolymer comprises the following steps:

[0054] 55 parts of polycarbonate diol and 4 parts of dibutyltin dilaurate were placed in a reactor, the reaction was purged with nitrogen, the temperature was raised to 80°C, 50 parts of isophorone diisocyanate were added and the reaction was carried out for 1 hour, then 18 parts of the modified fluorinated diol prepared in Example 2 and 30 parts of 2,2-dimethylolbutyric acid were added and the reaction was carried out for 3 hours, then 23 parts of pentaerythritol triacrylate, 2 parts of dibutyltin dilaurate, 7 parts of p-hydroxyanisole and 32 parts of ethyl acetate were added to the reactor, and the reaction was continued at 60°C for 4 hours to prepare a polyurethane prepolymer.

[0055] Performance testing

[0056] The elastic substrates prepared in Examples 4-6 and Comparative Examples 1-3 were sprayed onto the surface of an automobile body. After curing, the coatings were allowed to stand for 7 days before being peeled off and performance tests were conducted: tensile strength and elongation at break were measured according to GB / T 528-2009; tear strength was measured according to GB / T 529-2008; and Shore D hardness was measured according to GB / T 531-1999. Hydrophobicity was tested using a contact angle meter; thermal properties were tested using a thermogravimetric analyzer at a heating rate of 20°C / min over a temperature range from room temperature to 700°C; and flame retardancy was evaluated using the limiting oxygen index. The data results are shown in Table 1.

[0057] Table 1 Test results of sample performance

[0058]

[0059]

[0060] As can be seen from Table 1, the elastic substrate prepared by the embodiment of the present invention 4-6 possesses excellent mechanical property, thermal stability and flame retardant properties, and water contact angle is all greater than 150 °, with super-hydrophobic surface, antifouling ability is strong.Wherein in comparative example 1, hydroxyl-terminated polydimethylsiloxane is not modified, it records mechanical property, water contact angle, thermal decomposition temperature and limiting oxygen index and reduces compared with embodiment 4-6, reason is due to hydroxyl-terminated polydimethylsiloxane not being carried out mercapto-terminated modification, thus not forming a heavy cross-linked network with polyurethane prepolymer reaction, causing its various performance reductions; In comparative example 2, modified fluorinated diol is equivalently replaced with 1,4-butanediol, it records hydrophobic property and flame retardant properties and reduces compared with embodiment 4-6, reason is due to not introducing fluorine element and phosphorus element, in comparative example 3, modified nano silicon is not added, it records mechanical property and thermal decomposition temperature and declines significantly compared with embodiment 4-6, illustrating that the interpolation of modified nano silicon can promote mechanical property and the thermal stability of substrate.

[0061] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. An elastic substrate for automobile spray coating, characterized in that: The invention comprises the following components in parts by weight: 55-70 parts of polyurethane prepolymer, 5-10 parts of modified polydimethylsiloxane, 1-3 parts of photoinitiator, and 40-60 parts of alcohol solvent; the modified polydimethylsiloxane is prepared by esterification reaction of hydroxyl-terminated polydimethylsiloxane with 3-mercaptopropionic acid; The polyurethane prepolymer comprises the following components in parts by weight: 40-55 parts of polycarbonate diol, 30-50 parts of isocyanate, 10-20 parts of modified fluorine-containing diol, 10-30 parts of 2,2-dimethylolbutyric acid, 2-5 parts of modified nano-silica, 2-7 parts of catalyst, 10-25 parts of pentaerythritol triacrylate, 3-8 parts of p-hydroxyanisole, and 20-35 parts of solvent; The modified fluorinated diol is prepared by an amidation reaction between pentafluorooctanoic acid and 2-amino-2-methyl-1,3-propanediol to produce a terminal hydroxyl fluorinated diol, which is then further subjected to a substitution reaction between the terminal hydroxyl fluorinated diol and phenylphosphoryl dichloride; the modified nano-silica is prepared by modifying nano-silica with isopropoxy tris(ethylenediamino-N-ethoxy) titanate; The preparation method of the modified polydimethylsiloxane comprises the following steps: adding hydroxyl-terminated polydimethylsiloxane, 3-mercaptopropionic acid and p-toluenesulfonic acid into a reactor, stirring and reacting at 110-125° C. for 7-8 hours, and vacuum dehydrating to prepare the modified polydimethylsiloxane; The preparation method of the modified fluorinated diol comprises the following steps: (1) Pentafluorooctanoic acid and 2-amino-2-methyl-1,3-propanediol were dissolved in a mixed solution of dichloromethane and methanol, and then 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline was added to dissolve the mixture. The mixture was stirred in the dark for 8 to 12 hours. After the reaction was completed, the solvent was removed by rotary evaporation. The obtained solid was mixed with diethyl ether and ground, filtered, and washed to prepare a terminal hydroxyl fluorinated diol. (2) Phenylphosphoryl dichloride and terminal hydroxyl fluorinated diol were added to a reactor containing tetrahydrofuran and stirred at room temperature for 5 to 7 hours. During the reaction, triethylamine was added in batches to remove the hydrogen chloride produced by the reaction. After the reaction was completed, the modified fluorinated diol was prepared by filtration, rotary evaporation, and drying.

2. The elastic substrate for automobile spray cover according to claim 1, characterized in that: In the step (2), the molar ratio of phenylphosphoryl dichloride to the terminal hydroxyl fluorinated diol is 1:2-2.

7.

3. The elastic substrate for automobile spray cover according to claim 1, characterized in that: The preparation method of the modified nano-silica comprises the following steps: placing nano-silica in a reactor, adding a toluene solvent for ultrasonic dispersion, then adding isopropoxy tris(ethylenediamino-N-ethoxy) titanate, stirring and reacting at 65-75° C. for 4-6 hours, and after the reaction is completed, centrifuging, washing, and drying to prepare the modified nano-silica.

4. The elastic substrate for automobile spray cover according to claim 1, characterized in that: The preparation method of the polyurethane prepolymer comprises the following steps: Polycarbonate diol and a catalyst are placed in a reactor, nitrogen is introduced into the reaction, the temperature is raised to 75-85°C, isocyanate is added and the reaction is carried out for 1-1.5 hours, and then modified fluorinated diol and 2,2-dihydroxymethylbutyric acid are added and the reaction is carried out for 2.5-3 hours. After the reaction is completed, the temperature is lowered to 25-40°C, modified nano-silica is added, and then pentaerythritol triacrylate, a catalyst, p-hydroxyanisole and a solvent are added to the reactor, and the reaction is continued at 55-70°C for 2-4 hours to prepare a polyurethane prepolymer.

5. The elastic substrate for automobile spray cover according to claim 1, characterized in that: The photoinitiator is benzoin dimethyl ether; the alcohol solvent is one or more combinations of ethanol, isopropanol, and n-propanol.

6. The elastic substrate for automobile spray cover according to claim 1, characterized in that: The isocyanate is one of isophorone diisocyanate, hexamethylene diisocyanate and dicyclohexylmethane diisocyanate; the catalyst is dibutyltin dilaurate; and the solvent is ethyl acetate.

7. A method for preparing an elastic substrate for automobile spray cover according to any one of claims 1 to 6, characterized in that: The following steps are involved: Parts by weight of polyurethane prepolymer, modified polydimethylsiloxane, photoinitiator and alcohol solvent are uniformly mixed to obtain an elastic base material for automobile spray coating.

8. Use of the elastic substrate for automobile spray cover according to any one of claims 1 to 6 in the field of automobile film / cover.

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