Heat-insulating and yellowing-resistant TPU film for vehicle windows and preparation method thereof

Abstract

The present invention relates to the field of TPU films, and specifically to a heat-insulating and yellowing-resistant TPU film for car windows and a preparation method thereof. The present invention aims to solve the problem that cars are prone to temperature rise through infrared radiation exchange and heat exchange between inside and outside the car, especially in hot summer weather, when the heat exchange between inside and outside the car is more obvious. Cesium tungsten bronze is loaded with microcrystalline cellulose, which is then doped into silica aerogel. After calcination, a heat-insulating agent having both infrared light shielding and heat exchange reduction effects is obtained, and the heat-insulating agent is applied to a car window heat-insulating film to obtain a heat-insulating and yellowing-resistant TPU film for car windows.

Description

Technical Field

[0001] The invention relates to the field of TPU films, in particular to a heat-insulating and yellowing-resistant TPU film for vehicle windows and a preparation method thereof. Background Art

[0002] The correct use of polyurethane materials can meet the high-performance requirements of automobiles in terms of power, comfort, appearance, interior softening, lightweight, and service life. It is an indispensable and important material in modern automobile manufacturing. In addition to using common foamed polyurethane materials to make parts, automobiles also use a large number of non-foamed polyurethane materials, such as thermoplastic polyurethane elastomers, polyurethane potting materials, polyurethane coatings, and polyurethane adhesives. The application of these new materials has greatly improved the driving safety and riding comfort of automobiles. In daily automobile use, solar radiation is an important problem that needs to be solved urgently, especially infrared rays that give people a strong sense of heat. It can greatly increase the temperature inside the car and give people an extremely uncomfortable driving experience. In order to improve the driving comfort of the car, it is very necessary to improve the anti-infrared performance of the car windows.

[0003] In order to block the excess solar energy from the car environment, there are generally two ideas. One is to reflect the solar energy. The other is to convert the solar energy into heat energy, block it on the car glass, and dissipate the heat energy into the air through the air flow outside the car. Therefore, the car glass film has developed in two directions, namely metal films with good heat reflection ability and ceramic films with strong heat absorption. Ceramic film is developed on the basis of the previous generation of "heat absorption product-organic heat absorption film". Organic heat absorption film can also achieve good heat insulation effect in a short time, but because organic materials are easy to fade and easily decompose and fission under sunlight and fail, the overall performance is not good. Using inorganic materials instead of organic materials to convert solar radiation energy into heat energy on glass has always been one of the main directions of heat insulation film research, but it is restricted by the development of material technology. It was not until recent years that there was a breakthrough and the current ceramic film was produced.

[0004] However, whether it is a metal film or a ceramic film, its technical requirements are relatively high, the processing is difficult, and the materials used are mostly precious metals, which are expensive and difficult to popularize. Therefore, it is a good idea to use polyurethane materials as carriers and add nanoparticles with heat-insulating properties to produce an organic film with excellent heat-insulating properties. However, it is necessary to solve the problem that organic polyurethane heat-absorbing films are easy to yellow and decompose and fission under sunlight, resulting in poor performance.

[0005] Tungsten bronze (MxWO3, M is Na + , K + , Rb + , Cs + and NH4 +) has been reported in recent years as the most promising heat shielding material. It has high visible light transmittance and can shield near-infrared light with a wavelength greater than 1000nm, thus having more excellent near-infrared shielding performance.

[0006] CN 102746781 B discloses a fully shielded infrared and ultraviolet polyurethane nano transparent heat-insulating coating and a preparation method thereof. The coating comprises 40%-80% polyurethane resin, 5%-30% nano ATO dispersion, 1%-10% nano LaB6 dispersion, 1%-15% nano WO3 dispersion, 0.5%-3% auxiliary agent and 5%-20% solvent. The preparation method comprises: dropping nano ATO dispersion, nano LaB6 dispersion and nano WO3 dispersion into polyurethane resin component A in sequence according to the weight ratio of the formula, stirring and dispersing for 15min-30min, then adding leveling agent, defoaming agent, adhesion promoter, solvent and curing agent B according to the formula ratio, stirring to obtain a fully shielded nano transparent heat-insulating coating. The disadvantage is that the organic polyurethane heat-absorbing film is easy to yellow and decompose and fission under sunlight. Summary of the invention

[0007] In view of the defects of the prior art, the present invention provides a heat-insulating and yellowing-resistant TPU film for vehicle windows and a preparation method thereof.

[0008] A heat-insulating and yellowing-resistant TPU film for vehicle windows is composed of the following raw materials, measured by mass: 4-6 parts of sodium silicate, 70-80 parts of water-based polyurethane, 1-2 parts of starch, 6-10 parts of heat-insulating agent, 0.5-1 part of potassium stearate, 5-10 parts of ethylene glycol, 5-10 parts of butanone, and 5-10 parts of water.

[0009] The sodium silicate is liquid sodium silicate, and the SiO2 / Na2O molar ratio is 2.6-2.9.

[0010] The starch is one or a mixture of two or more of acetylated distarch adipate, amylose, and cross-linked starch; preferably, the starch is acetylated distarch adipate.

[0011] The preparation method of the thermal insulation agent comprises the following steps:

[0012] S1: tetraethyl orthosilicate, anhydrous ethanol and water are mixed in a mass ratio of (1-2): (5-6): (6-8), stirred at 80-100 r / min, and the pH is adjusted to 2.0-3.0 with 0.5-1 mol / L hydrochloric acid, and then stirred at 80-100 r / min at 35-45° C. for 1.5-3 h, and then kept at a constant temperature of 35-45° C. for 8-14 h to obtain a hydrolyzate;

[0013] S2: Mix 9-11 parts of the hydrolyzate obtained in step S1 and 0.4-0.8 parts of microcrystalline cellulose loaded with cesium tungsten bronze by weight, adjust the pH value to 8-9 with 0.01-0.03 mol / L ammonia water, stir and react at a speed of 4000-6000 r / min for 10-20 min to obtain a modified SiO2 wet gel;

[0014] S3: Mix the modified SiO2 wet gel obtained in step S2 and acetone at a bath ratio of 1 g: (5-10) mL, let stand for 20-30 hours, filter out the precipitate, and dry it at 70-90° C. for 12-24 hours to obtain a modified SiO2 aerogel;

[0015] S4: In a nitrogen atmosphere, the modified SiO2 aerogel obtained in step S3 is carbonized at 280-300°C for 2-4 hours, and then crushed to less than 50 μm to obtain the thermal insulation agent.

[0016] The preparation method of the cesium tungsten bronze-loaded microcrystalline cellulose comprises the following steps:

[0017] Ammonium metatungstate, thiourea, oleylamine, CsCl, microcrystalline cellulose and water are mixed in a mass ratio of 2.74: (0.7-1.4): (0.5-1): (1.2-1.3): (1-2): (8-10), stirred at a speed of 80-100 r / min, and the pH is adjusted to 3-4 with 0.5-1 mol / L hydrochloric acid, and then placed at 180-220° C. and a pressure of 1-3 MPa for reaction for 12-24 hours. After cooling to room temperature, the mixture is filtered, washed and dried to obtain the microcrystalline cellulose loaded with cesium tungsten bronze.

[0018] A method for preparing a heat-insulating and yellowing-resistant TPU film for vehicle windows comprises the following steps:

[0019] (1) mixing a heat insulating agent, ethylene glycol, butanone, potassium stearate and water, and stirring at a speed of 100-140 r / min for 2-4 min to obtain a solution A;

[0020] (2) adding starch to the solution A in step (1), stirring at a speed of 400-800 r / min for 3-5 min to obtain a solution B;

[0021] (3) adding sodium silicate and aqueous polyurethane to the solution B obtained in step (2), stirring at a speed of 60-80 r / min for 10-15 min to obtain a TPU sol;

[0022] (4) Spraying 500-1000 μm of the TPU sol obtained in step (3) into the mold, drying at 30-40° C. for 8-12 h, reducing the thickness to 100-200 μm, and obtaining the heat-insulating and yellowing-resistant TPU film for vehicle windows.

[0023] Preferably, the method for preparing the heat-insulating and yellowing-resistant TPU film for vehicle windows comprises the following steps:

[0024] (1) Mix 6-10 parts of heat insulating agent, 5-10 parts of ethylene glycol, 5-10 parts of butanone, 0.5-1 part of potassium stearate, and 5-10 parts of water by mass, and stir at a speed of 100-140 r / min for 2-4 minutes to obtain solution A;

[0025] (2) adding 1-2 parts by mass of starch to the solution A in step (1), stirring at a speed of 400-800 r / min for 3-5 min to obtain a solution B;

[0026] (3) adding 4-6 parts by mass of sodium silicate and 70-80 parts by mass of aqueous polyurethane to the solution B obtained in step (2), stirring at a speed of 60-80 r / min for 10-15 min to obtain a TPU sol;

[0027] (4) pouring the TPU sol obtained in step (3) into a mold and drying it at 30-40° C. for 8-12 hours to obtain the heat-insulating and yellowing-resistant TPU film for vehicle windows.

[0028] The present invention uses waterborne polyurethane as a substrate, which has high transparency and cohesiveness, and has strong adhesion to vehicle window glass, but it is easy to decompose and is not resistant to yellowing. Therefore, the present invention adopts acetylated distarch adipate and sodium silicate to make up for the defect in its performance. Starch can improve the thermal stability of polyurethane, but due to the poor solubility of ordinary starch, it cannot be fully mixed with polyurethane, which will cause the transparency of the film to be reduced, while acetylated distarch adipate can have good solubility in a mixed solution of butanone, ethanol and water, and the transparency of the film formed after it is mixed with waterborne polyurethane is still above 97%. The addition of sodium silicate can form a more stable Si-O-Si with polyurethane, thereby reducing the high temperature decomposition and ultraviolet decomposition of polyurethane. In addition, sodium silicate can greatly improve the strength of polyurethane after hardening, and improve its bonding strength.

[0029] As we all know, there are many factors that cause the temperature inside the car to rise. In addition to the temperature rise caused by infrared light, heat exchange inside and outside the car is also an extremely important factor, especially in the hot summer. The dual effects of heat exchange and infrared light make the temperature inside the car extremely high, and the car window is not only the main location of infrared light irradiation, but also the main location of heat exchange. Therefore, when preparing a thermal insulation film for the car window, we should not only consider the absorption and reflection of infrared light, but also make certain treatments to prevent heat exchange. The thermal insulation of silica aerogel is mainly due to the fact that its pore size is smaller than the mean free path of air molecules (70nm). The gas molecules are confined in the pores, and the intermolecular interaction force is mainly the probability of collision with the pore wall, which greatly limits the thermal conductivity of the gas. That is, SiO2 aerogel can greatly limit convective heat transfer. Therefore, the thermal insulation ability of silica aerogel is very excellent. However, silica aerogel has little effect on blocking infrared radiation. In radiation heat transfer, objects transfer energy through electromagnetic waves. As the temperature rises, the radiation heat transfer increases rapidly. While cesium tungsten bronze has outstanding absorption and shielding effects on infrared light, its ability to prevent heat exchange is poor. Therefore, using silica aerogel or cesium tungsten bronze alone is difficult to prevent the temperature inside the car from rising in strong light and high temperature environments, which does not meet the requirements of actual use in life.

[0030] Therefore, the present invention further adopts cesium tungsten bronze doped aerogel. Due to the reduction of the amount of cesium tungsten bronze, its infrared light shielding effect becomes worse, but its overall thermal insulation performance is improved, which shows that the idea of ​​the present invention is correct. However, due to the poor dispersibility of cesium tungsten bronze nanoparticles, it is difficult to disperse them more evenly in the silica aerogel, which will cause them to be unevenly distributed in the film, resulting in a weakened local infrared shielding effect. In order to improve the dispersibility of cesium tungsten bronze and reduce its usage to reduce costs, the present invention uses microcrystalline cellulose as a carrier. Since microcrystalline cellulose has a large surface area, it is easy to load cesium tungsten bronze. At the same time, due to its large particle size, its dispersibility is also good, and it can be more evenly dispersed in the silica aerogel, greatly improving the distribution rate of cesium tungsten bronze in the crushed aerogel particles, thereby improving the dispersibility of cesium tungsten bronze. Further, the present invention carbonizes the microcrystalline cellulose by high-temperature carbonization. The carbonized microcrystalline cellulose and cesium tungsten bronze work synergistically, which can better improve the infrared light shielding effect of the film, thereby reducing the usage of cesium tungsten bronze and reducing costs. Cesium tungsten bronze is used to load microcrystalline cellulose, which is then doped with aerogel and applied to the heat-insulating and yellowing-resistant TPU film for car windows. This not only improves its infrared light shielding performance, but also further reduces its heat exchange capacity, making it more suitable for practical use.

[0031] In addition, due to its structural characteristics, cesium tungsten bronze has not only near-infrared shielding properties, but also a variety of physical and chemical properties, such as photochromism, photocatalysis, adsorption, etc. It has a certain degree of promoting effect on the aging of polyurethane, which shortens the service life of the heat-insulating and yellowing-resistant TPU film for vehicle windows prepared by the present invention. However, silica aerogel does not have this defect. Therefore, the present invention dopes cesium tungsten bronze into silica aerogel to reduce the decomposition of cesium tungsten bronze. The present invention believes that this is because the Si-O-Si bond is strong and cesium tungsten bronze cannot catalytically decompose. The use of silica aerogel can effectively prevent the promoting effect of cesium tungsten bronze on the aging of polyurethane. The cesium tungsten bronze is loaded with microcrystalline cellulose and then doped with aerogel. The color difference of the heat-insulating and yellowing-resistant TPU film for car windows is further reduced. The present invention believes that this is because cesium tungsten bronze is easy to agglomerate and has poor dispersion in silica aerogel. After being crushed, part of the cesium tungsten bronze is not wrapped by silica aerogel, which promotes the decomposition of polyurethane. After microcrystalline cellulose is loaded with cesium tungsten bronze, its dispersion is good and the silica aerogel is completely wrapped, which reduces the exposure rate of cesium tungsten bronze, thereby improving the film's resistance to ultraviolet aging.

[0032] Beneficial effects of the present invention

[0033] The present invention aims to solve the problem that the temperature of a car easily rises through infrared radiation exchange and heat exchange between the inside and outside of the car, especially in hot summer weather, when the heat exchange effect between the inside and outside of the car is more obvious. Cesium tungsten bronze is loaded with microcrystalline cellulose, which is then doped into silica aerogel. After calcination, a heat-insulating agent with both infrared light shielding and heat exchange reducing effects is obtained. The heat-insulating agent is applied to a car window heat-insulating film to obtain a heat-insulating and yellowing-resistant TPU film for car windows. DETAILED DESCRIPTION

[0034] Waterborne polyurethane, model: AH-1502E, Anhui Anda Huatai New Materials Co., Ltd.

[0035] Potassium stearate, CAS No.: 593-39-3, Hebei Lihua Biotechnology Co., Ltd.

[0036] Liquid sodium silicate, CAS No.: 1344-09-8, SiO2 / Na2O molar ratio is 2.7, Shenyang Ketuo Chemical Co., Ltd.

[0037] Acetylated distarch adipate, CAS number: 68130-14-3.

[0038] Microcrystalline cellulose, product number: S14009, Shanghai Yuanye Biotechnology Co., Ltd.

[0039] Example 1

[0040] A method for preparing a heat-insulating and yellowing-resistant TPU film for vehicle windows comprises the following steps:

[0041] (1) By weight, 8 parts of heat insulating agent, 6 parts of ethylene glycol, 8 parts of butanone, 0.7 parts of potassium stearate, and 8 parts of water were mixed and stirred at a speed of 120 r / min for 3 minutes to obtain solution A;

[0042] (2) adding 1.6 parts of starch by mass to the solution A in step (1), stirring at a speed of 600 r / min for 4 min to obtain a solution B;

[0043] (3) adding 5 parts by mass of sodium silicate and 75 parts by mass of aqueous polyurethane to the solution B obtained in step (2), stirring at a speed of 70 r / min for 15 min to obtain a TPU sol;

[0044] (4) Spray 500 μm of the TPU sol obtained in step (3) into the mold, and dry it at 40° C. for 12 h until the thickness is reduced to 100 μm, thereby obtaining the heat-insulating and yellowing-resistant TPU film for vehicle windows.

[0045] The sodium silicate is liquid sodium silicate, and the SiO2 / Na2O molar ratio is 2.7.

[0046] The starch is acetylated distarch adipate.

[0047] The preparation method of the thermal insulation agent comprises the following steps:

[0048] S1: Tetraethyl orthosilicate, anhydrous ethanol and water are mixed in a mass ratio of 1:5:7, stirred at 80 r / min, and the pH is adjusted to 3.0 with 0.6 mol / L hydrochloric acid, and then stirred at 80 r / min at 40°C for 2 h, and then kept at a constant temperature of 40°C for 12 h to obtain a hydrolyzate;

[0049] S2, by mass, adjusting the pH value of 10 parts of the hydrolyzate obtained in step S1 to 8 with 0.02 mol / L ammonia water, stirring at 6000 r / min for 10 min to obtain a modified SiO2 wet gel;

[0050] S3: Mix the modified SiO2 wet gel obtained in step S2 and acetone in a bath ratio of 1 g:5 mL, let stand for 24 hours, filter out the precipitate, dry it at 80° C. for 24 hours, and then crush it to less than 50 μm to obtain the thermal insulation agent.

[0051] Example 2

[0052] A method for preparing a heat-insulating and yellowing-resistant TPU film for vehicle windows comprises the following steps:

[0053] (1) By weight, 8 parts of heat insulating agent, 6 parts of ethylene glycol, 8 parts of butanone, 0.7 parts of potassium stearate, and 8 parts of water were mixed and stirred at a speed of 120 r / min for 3 minutes to obtain solution A;

[0054] (2) adding 1.6 parts of starch by mass to the solution A in step (1), stirring at a speed of 600 r / min for 4 min to obtain a solution B;

[0055] (3) adding 5 parts by mass of sodium silicate and 75 parts by mass of aqueous polyurethane to the solution B obtained in step (2), stirring at a speed of 70 r / min for 15 min to obtain a TPU sol;

[0056] (4) Spray 500 μm of the TPU sol obtained in step (3) into the mold, and dry it at 40° C. for 12 h until the thickness is reduced to 100 μm, thereby obtaining the heat-insulating and yellowing-resistant TPU film for vehicle windows.

[0057] The sodium silicate is liquid sodium silicate, and the SiO2 / Na2O molar ratio is 2.7.

[0058] The starch is acetylated distarch adipate.

[0059] The preparation method of the thermal insulation agent comprises the following steps:

[0060] Ammonium metatungstate, thiourea, oleylamine, CsCl and water are mixed in a mass ratio of 2.74:0.74:0.62:1.23:9, stirred at a speed of 80 r / min, and the pH is adjusted to 3 with 0.5 mol / L hydrochloric acid, and then placed at 200° C. and a pressure of 2 MPa for reaction for 12 hours. After cooling to room temperature, the mixture is filtered, washed and dried to obtain the thermal insulation agent.

[0061] Example 3

[0062] A method for preparing a heat-insulating and yellowing-resistant TPU film for vehicle windows comprises the following steps:

[0063] (1) By weight, 8 parts of heat insulating agent, 6 parts of ethylene glycol, 8 parts of butanone, 0.7 parts of potassium stearate, and 8 parts of water were mixed and stirred at a speed of 120 r / min for 3 minutes to obtain solution A;

[0064] (2) adding 1.6 parts of starch by mass to the solution A in step (1), stirring at a speed of 600 r / min for 4 min to obtain a solution B;

[0065] (3) adding 5 parts by mass of sodium silicate and 75 parts by mass of aqueous polyurethane to the solution B obtained in step (2), stirring at a speed of 70 r / min for 15 min to obtain a TPU sol;

[0066] (4) Spray 500 μm of the TPU sol obtained in step (3) into the mold, and dry it at 40° C. for 12 h until the thickness is reduced to 100 μm, thereby obtaining the heat-insulating and yellowing-resistant TPU film for vehicle windows.

[0067] The sodium silicate is liquid sodium silicate, and the SiO2 / Na2O molar ratio is 2.7.

[0068] The starch is acetylated distarch adipate.

[0069] The preparation method of the thermal insulation agent comprises the following steps:

[0070] S1: Tetraethyl orthosilicate, anhydrous ethanol and water are mixed in a mass ratio of 1:5:7, stirred at 80 r / min, and the pH is adjusted to 3.0 with 0.6 mol / L hydrochloric acid, and then stirred at 80 r / min at 40°C for 2 h, and then kept at a constant temperature of 40°C for 12 h to obtain a hydrolyzate;

[0071] S2: 10 parts by mass of the hydrolyzate obtained in step S1 and 0.6 parts by mass of cesium tungsten bronze are mixed, and the pH value is adjusted to 8 with 0.02 mol / L ammonia water, and the reaction is stirred at a speed of 6000 r / min for 10 minutes to obtain a modified SiO2 wet gel;

[0072] S3: Mix the modified SiO2 wet gel obtained in step S2 and acetone in a bath ratio of 1 g:5 mL, let stand for 24 hours, filter out the precipitate, dry it at 80° C. for 24 hours, and then crush it to less than 50 μm to obtain the thermal insulation agent.

[0073] The preparation method of cesium tungsten bronze comprises the following steps:

[0074] Ammonium metatungstate, thiourea, oleylamine, CsCl and water are mixed in a mass ratio of 2.74:0.74:0.62:1.23:9, stirred at a speed of 80 r / min, and the pH is adjusted to 3 with 0.5 mol / L hydrochloric acid, and then placed at 200° C. and a pressure of 2 MPa for reaction for 12 hours. After cooling to room temperature, the mixture is filtered, washed and dried to obtain the cesium tungsten bronze-loaded microcrystalline cellulose.

[0075] Example 4

[0076] A method for preparing a heat-insulating and yellowing-resistant TPU film for vehicle windows comprises the following steps:

[0077] (1) By weight, 8 parts of heat insulating agent, 6 parts of ethylene glycol, 8 parts of butanone, 0.7 parts of potassium stearate, and 8 parts of water were mixed and stirred at a speed of 120 r / min for 3 minutes to obtain solution A;

[0078] (2) adding 1.6 parts of starch by mass to the solution A in step (1), stirring at a speed of 600 r / min for 4 min to obtain a solution B;

[0079] (3) adding 5 parts by mass of sodium silicate and 75 parts by mass of aqueous polyurethane to the solution B obtained in step (2), stirring at a speed of 70 r / min for 15 min to obtain a TPU sol;

[0080] (4) Spray 500 μm of the TPU sol obtained in step (3) into the mold, and dry it at 40° C. for 12 h until the thickness is reduced to 100 μm, thereby obtaining the heat-insulating and yellowing-resistant TPU film for vehicle windows.

[0081] The sodium silicate is liquid sodium silicate, and the SiO2 / Na2O molar ratio is 2.7.

[0082] The starch is acetylated distarch adipate.

[0083] The preparation method of the thermal insulation agent comprises the following steps:

[0084] S1: Tetraethyl orthosilicate, anhydrous ethanol and water are mixed in a mass ratio of 1:5:7, stirred at 80 r / min, and the pH is adjusted to 3.0 with 0.6 mol / L hydrochloric acid, and then stirred at 80 r / min at 40°C for 2 h, and then kept at a constant temperature of 40°C for 12 h to obtain a hydrolyzate;

[0085] S2: 10 parts by mass of the hydrolyzate obtained in step S1 and 0.6 parts of microcrystalline cellulose loaded with cesium tungsten bronze are mixed, and the pH value is adjusted to 8 with 0.02 mol / L ammonia water, and the reaction is stirred at a speed of 6000 r / min for 10 minutes to obtain a modified SiO2 wet gel;

[0086] S3: Mix the modified SiO2 wet gel obtained in step S2 and acetone at a bath ratio of 1 g:5 mL, let stand for 24 hours, filter out the precipitate, and dry it at 80° C. for 24 hours to obtain a modified SiO2 aerogel;

[0087] S4: In a nitrogen atmosphere, the modified SiO2 aerogel obtained in step S3 is carbonized at 290°C for 3 hours, and then crushed to less than 50 μm to obtain the thermal insulation agent.

[0088] The preparation method of the cesium tungsten bronze-loaded microcrystalline cellulose comprises the following steps:

[0089] Ammonium metatungstate, thiourea, oleylamine, CsCl, microcrystalline cellulose and water are mixed in a mass ratio of 2.74:0.74:0.62:1.23:1.4:9, stirred at a speed of 80 r / min, and the pH is adjusted to 3 with 0.5 mol / L hydrochloric acid, and then placed at 200° C. and a pressure of 2 MPa for reaction for 12 hours. After cooling to room temperature, the cesium tungsten bronze-loaded microcrystalline cellulose is obtained by filtering, washing and drying.

[0090] Example 5

[0091] A method for preparing a heat-insulating and yellowing-resistant TPU film for vehicle windows comprises the following steps:

[0092] (1) By weight, 8 parts of heat insulating agent, 6 parts of ethylene glycol, 8 parts of butanone, 0.7 parts of potassium stearate, and 8 parts of water were mixed and stirred at a speed of 120 r / min for 3 minutes to obtain solution A;

[0093] (2) adding 1.6 parts of starch by mass to the solution A in step (1), stirring at a speed of 600 r / min for 4 min to obtain a solution B;

[0094] (3) adding 5 parts by mass of sodium silicate and 75 parts by mass of aqueous polyurethane to the solution B obtained in step (2), stirring at a speed of 70 r / min for 15 min to obtain a TPU sol;

[0095] (4) Spray 500 μm of the TPU sol obtained in step (3) into the mold, and dry it at 40° C. for 12 h until the thickness is reduced to 100 μm, thereby obtaining the heat-insulating and yellowing-resistant TPU film for vehicle windows.

[0096] The sodium silicate is liquid sodium silicate, and the SiO2 / Na2O molar ratio is 2.7.

[0097] The starch is acetylated distarch adipate.

[0098] The preparation method of the thermal insulation agent comprises the following steps:

[0099] S1: Tetraethyl orthosilicate, anhydrous ethanol and water are mixed in a mass ratio of 1:5:7, stirred at 80 r / min, and the pH is adjusted to 3.0 with 0.6 mol / L hydrochloric acid, and then stirred at 80 r / min at 40°C for 2 h, and then kept at a constant temperature of 40°C for 12 h to obtain a hydrolyzate;

[0100] S2: 10 parts by mass of the hydrolyzate obtained in step S1 and 0.6 parts by mass of microcrystalline cellulose are mixed, and the pH value is adjusted to 8 with 0.02 mol / L ammonia water, and the mixture is stirred at 6000 r / min for 10 min to obtain a modified SiO2 wet gel;

[0101] S3: Mix the modified SiO2 wet gel obtained in step S2 and acetone at a bath ratio of 1 g:5 mL, let stand for 24 hours, filter out the precipitate, and dry it at 80° C. for 24 hours to obtain a modified SiO2 aerogel;

[0102] S4: In a nitrogen atmosphere, the modified SiO2 aerogel obtained in step S3 is carbonized at 290°C for 3 hours, and then crushed to less than 50 μm to obtain the thermal insulation agent.

[0103] Comparative Example 1

[0104] A method for preparing a heat-insulating and yellowing-resistant TPU film for vehicle windows comprises the following steps:

[0105] (1) Mix 6 parts of ethylene glycol, 8 parts of butanone, 0.7 parts of potassium stearate, and 8 parts of water, by mass, and stir at 120 r / min for 3 min to obtain solution A;

[0106] (2) adding 1.6 parts of starch by mass to the solution A in step (1), stirring at a speed of 600 r / min for 4 min to obtain a solution B;

[0107] (3) adding 5 parts by mass of sodium silicate and 75 parts by mass of aqueous polyurethane to the solution B obtained in step (2), stirring at a speed of 70 r / min for 15 min to obtain a TPU sol;

[0108] (4) Spray 500 μm of the TPU sol obtained in step (3) into the mold, and dry it at 40° C. for 12 h until the thickness is reduced to 100 μm, thereby obtaining the heat-insulating and yellowing-resistant TPU film for vehicle windows.

[0109] The sodium silicate is liquid sodium silicate, and the SiO2 / Na2O molar ratio is 2.7.

[0110] The starch is acetylated distarch adipate.

[0111] Test Example 1

[0112] The thermal insulation temperature difference test is carried out in accordance with Appendix A of GB / T 29501-2013 "Thermal insulation coated glass"

[0113] The sample is a flat glass of 380 mm*380 mm*6 mm, with the exposed surface being covered with the heat-insulating and yellowing-resistant TPU films for vehicle windows prepared in various embodiments of the present invention and comparative examples, and the film thickness is 100 μm.

[0114] The comparison sample is flat glass.

[0115] Xenon lamp is used as light source, and the irradiation intensity is 1000W / m 2 , the ambient temperature is 23℃.

[0116] First, place the test box in a 23℃ environment and keep the temperature inside the box at 23℃. Then seal the boxes with the sample and the comparison sample respectively, raise the ambient temperature to 40℃, irradiate with a xenon lamp, and test the temperature inside the box after 2.5 hours.

[0117] Insulation temperature difference = comparison sample box temperature at 2.5h - sample box temperature at 2.5h

[0118] Ambient temperature difference = 2.5h, sample box temperature -40℃

[0119] Table 1: Thermal insulation temperature difference test results

[0120]

[0121]

[0122] It can be seen from Table 1 that the thermal insulation temperature difference of the heat-insulating and yellowing-resistant TPU film for car windows prepared in Example 1 is lower than that of Example 2, which indicates that the infrared light absorption rate of the heat-insulating and yellowing-resistant TPU film for car windows prepared in Example 1 is lower than that of Example 2, and the ambient temperature difference of Example 1 is lower than that of Example 2, which indicates that the thermal insulation performance of the heat-insulating and yellowing-resistant TPU film for car windows prepared in Example 1 is better than that of Example 2. As is known to all, there are many factors that cause the temperature inside the car to rise. In addition to the temperature rise caused by infrared light, the heat exchange inside and outside the car is also an extremely important factor, especially in the hot summer. The dual effects of heat exchange and infrared light make the temperature inside the car extremely high, and the car window is both the main location of infrared light irradiation and the main location of heat exchange. Therefore, the preparation of the heat insulation film for car windows cannot only consider the absorption and reflection of infrared light, but also should be treated in a certain way to prevent heat exchange. Silica aerogel has excellent thermal insulation ability, but its absorption and reflection effects on infrared light are not very good; while cesium tungsten bronze has outstanding absorption and shielding effects on infrared light, but its ability to prevent heat exchange is poor. Therefore, using silica aerogel or cesium tungsten bronze alone is difficult to prevent the temperature inside the car from rising in strong light and high temperature environments. The ambient temperature difference is only -1.9 and -0.3, which is almost no difference.

[0123] In Example 3, cesium tungsten bronze doped aerogel is used. Due to the reduction in the amount of cesium tungsten bronze, its infrared light shielding effect becomes worse. However, its overall thermal insulation performance is improved. The ambient temperature difference is -7.2, and the heating rate in the box is significantly slowed down, which shows that the idea of ​​the present invention is correct. However, due to the poor dispersibility of cesium tungsten bronze nanoparticles, it is difficult to disperse them evenly in the silica aerogel, which will cause them to be unevenly distributed in the film, resulting in a weakened local infrared shielding effect. In order to improve the dispersibility of cesium tungsten bronze and reduce its usage, the present invention uses microcrystalline cellulose as a carrier in Example 4. Since microcrystalline cellulose has a large surface area, it is easy to load cesium tungsten bronze. At the same time, due to its large particle size, its dispersibility is also good, and it can be dispersed more evenly in the silica aerogel, greatly improving the distribution rate of cesium tungsten bronze in the crushed aerogel particles, thereby improving the dispersibility of cesium tungsten bronze. Further, the present invention carbonizes microcrystalline cellulose by high-temperature carbonization. The carbonized microcrystalline cellulose and cesium tungsten bronze work synergistically, which can better improve the infrared light shielding effect of the film, thereby reducing the usage of cesium tungsten bronze and reducing costs. In Example 4, cesium tungsten bronze is used to load microcrystalline cellulose, which is then doped with aerogel and applied to the heat-insulating and yellowing-resistant TPU film for vehicle windows, which not only improves its infrared light shielding performance, but also further reduces its heat exchange capacity, which is more in line with practical use. In Example 5, microcrystalline cellulose is used alone to dope aerogel, and its heat insulation performance is worse than that of Example 4.

[0124] Test Example 2

[0125] UV aging test

[0126] The UV intensity is 400μW / cm 2 The test was conducted for 120 hours in an environment with a relative humidity of 2%, and the color difference and yellowness index tests were conducted on the heat-insulating and yellowing-resistant TPU films for vehicle windows prepared in each embodiment and comparative example before and after ultraviolet irradiation.

[0127] Color difference and yellow index test

[0128] As aging progresses, the polyurethane film will turn yellow. The yellowing of the film is an important indicator of polyurethane aging. The degree of film aging is measured by changes in color difference and yellowness index. In this experiment, a CR-10 colorimeter was used to test the changes in yellowness index and color difference of the heat-insulating and yellowing-resistant TPU films for vehicle windows prepared in various embodiments and comparative examples during exposure.

[0129] Test method: Place a smooth white marble plate on the platform, turn on the CR-10 colorimeter, first calibrate the instrument, then you can test the color difference and yellow index of the film. In order to reflect the change in color difference, a copy of the original sample is reserved for each group of samples and stored in a dryer. Then place the original sample on a standard flat white plate, press the test button of the colorimeter, lift it up and put it back to its original position, press the test button, record the data that appears on the screen, measure each film 3 times and take the average value. If there is a large difference between the three groups of data, re-measure.

[0130] Table 2: UV aging color difference

[0131] Chromatic Aberration Example 1 0.57 Example 2 1.72 Example 3 0.84 Example 4 0.62

[0132] As can be seen from Table 2, Example 2 uses cesium tungsten bronze alone as a heat-insulating agent, and after being irradiated with ultraviolet light, the color change is the largest. This is because cesium tungsten bronze, due to its structural characteristics, has a variety of physical and chemical properties in addition to near-infrared shielding properties, such as photochromism, photocatalysis, adsorption, etc. It has a certain degree of promoting effect on the aging of polyurethane, which shortens the service life of the heat-insulating and yellowing-resistant TPU film for vehicle windows prepared by the present invention. However, Example 1 does not have this defect when using silica aerogel alone, and it can be clearly seen from the data of Example 3 that doping cesium tungsten bronze into silica aerogel can reduce the decomposition of cesium tungsten bronze. The present invention believes that this is because the Si-O-Si bond is strong and cesium tungsten bronze cannot catalytically decompose. The use of silica aerogel can effectively prevent the promotion of cesium tungsten bronze on the aging of polyurethane. Example 4 Cesium tungsten bronze is loaded with microcrystalline cellulose and then doped with aerogel. The color difference of the heat-insulating and yellowing-resistant TPU film for car windows is further reduced. The present invention believes that this is because cesium tungsten bronze is easy to agglomerate and has poor dispersibility in silica aerogel. After being crushed, part of the cesium tungsten bronze is not wrapped by silica aerogel, which promotes the decomposition of polyurethane. After microcrystalline cellulose is loaded with cesium tungsten bronze, its dispersibility is good, and the silica aerogel is completely wrapped, which reduces the exposure rate of cesium tungsten bronze, thereby improving the film's resistance to ultraviolet aging.

Claims

1. A method for preparing a heat-insulating and yellowing-resistant TPU film for vehicle windows, characterized in that: The following steps are involved: (1) Mix 6-10 parts of heat insulating agent, 5-10 parts of ethylene glycol, 5-10 parts of butanone, 0.5-1 part of potassium stearate, and 5-10 parts of water by mass, and stir at a speed of 100-140 r / min for 2-4 minutes to obtain solution A; (2) adding 1-2 parts by mass of starch to the solution A in step (1), stirring at a speed of 400-800 r / min for 3-5 min to obtain a solution B; (3) adding 4-6 parts by mass of sodium silicate and 70-80 parts by mass of aqueous polyurethane to the solution B obtained in step (2), stirring at a speed of 60-80 r / min for 10-15 min to obtain a TPU sol; (4) pouring the TPU sol obtained in step (3) into a mold and drying at 30-40° C. for 8-12 h to obtain the heat-insulating and yellowing-resistant TPU film for vehicle windows; The starch is one or a mixture of two or more of acetylated distarch adipate, amylose, and cross-linked starch; The preparation method of the thermal insulation agent comprises the following steps: S1: tetraethyl orthosilicate, anhydrous ethanol and water are mixed, stirred at 80-100 r / min, and the pH is adjusted to 2.0-3.0 with hydrochloric acid, and then stirred at 80-100 r / min at 35-45°C for 1.5-3h, and then kept at a constant temperature of 35-45°C for 8-14h to obtain a hydrolyzate; S2: Mix 9-11 parts of the hydrolyzate obtained in step S1 and 0.4-0.8 parts of microcrystalline cellulose loaded with cesium tungsten bronze by weight, adjust the pH value to 8-9 with aqueous ammonia, stir and react at a speed of 4000-6000 r / min for 10-20 minutes to obtain a modified SiO2 wet gel; S3: Mix the modified SiO2 wet gel obtained in step S2 and acetone at a bath ratio of 1 g: (5-10) mL, let stand for 20-30 hours, filter out the precipitate, and dry it at 70-90° C. for 12-24 hours to obtain a modified SiO2 aerogel; S4: In a nitrogen atmosphere, the modified SiO2 aerogel obtained in step S3 is carbonized at 280-300°C for 2-4 hours, and then crushed to less than 50 μm to obtain the thermal insulation agent.

2. The method for preparing the heat-insulating and yellowing-resistant TPU film for vehicle windows according to claim 1, characterized in that: The sodium silicate is liquid sodium silicate, and the SiO2 / Na2O molar ratio is 2.6-2.

9.

3. The method for preparing the heat-insulating and yellowing-resistant TPU film for vehicle windows according to claim 1, characterized in that: In step S1, the mass ratio of tetraethyl orthosilicate, anhydrous ethanol and water is (1-2): (5-6): (6-8).

4. The method for preparing the heat-insulating and yellowing-resistant TPU film for vehicle windows according to claim 1, characterized in that: The concentration of hydrochloric acid in step S1 is 0.5-1 mol / L.

5. The method for preparing the heat-insulating and yellowing-resistant TPU film for vehicle windows according to claim 1, characterized in that: The concentration of the ammonia water in step S2 is 0.01-0.03 mol / L.

6. A heat-insulating and yellowing-resistant TPU film for vehicle windows, characterized in that: The film is prepared by the method for preparing the heat-insulating and yellowing-resistant TPU film for vehicle windows according to any one of claims 1 to 5.

Images