High refractive index polyvinyl acetal resin powder and interlayer film and method for producing the same

Abstract

The application belongs to the technical field of photovoltaic materials, and relates to a high-refractive polyvinyl acetal resin powder, a structural formula of which is shown in the following formula: wherein z represents the number of polyvinyl mercapto acetal in the high-refractive polyvinyl acetal resin powder; x represents the number of hydroxyl groups in the high-refractive polyvinyl acetal resin powder; n represents the number of ester groups in the high-refractive polyvinyl acetal resin powder; y represents the number of polyvinyl acetal groups in the high-refractive polyvinyl acetal resin powder; x+2y+2z+n=the polymerization degree of raw material PVA; the R group is selected from one or more of a methyl group, a hydrogen, a propyl group, a phenyl group and a butyl group; and the R1 group is selected from one or more of an aliphatic group or an aromatic group with 6 or more carbon atoms. The application further provides a preparation method of the high-refractive polyvinyl acetal resin powder, an intermediate film and a preparation method of the intermediate film. The high-refractive polyvinyl acetal resin powder, the intermediate film and the preparation method of the application can obtain a high-refractive polyvinyl acetal intermediate film with excellent light transmittance and clear imaging.

Description

Technical Field

[0001] This invention belongs to the technical field of photovoltaic materials, and relates to a high refractive index polyvinyl acetal resin powder and an intermediate film and their preparation method. Background Technology

[0002] Automotive windshields are typically composed of two layers of glass interlayered with a polyvinyl butyral (PVB) film. The PVB film, used in the windshield interlayer, firmly binds the glass fragments together when the glass breaks upon impact, keeping the shards intact and preventing injury from broken glass. Therefore, the use of PVB film in automotive windshields is a mandatory requirement for safety glass. Besides automotive glass, PVB film is also widely used in ship glass and high-rise building glass, becoming the preferred safety glass.

[0003] Generally, the refractive index of normal glass is 1.500. Traditional polyvinyl butyral has a refractive index of 1.488–1.490, triethylene glycol di(2-ethylhexanoate) plasticizer has a refractive index of 1.440–1.450, and the refractive index of the PVB interlayer is 1.480–1.490. The interface between these materials with different refractive indices causes light reflection, and optical losses reduce the light transmittance of the film, limiting its applications. If the refractive index of the PVB interlayer is equal to or close to the geometric mean of the refractive index of the laminated glass, the reflectance is zero, and the light transmittance of the material can reach its maximum.

[0004] Traditional PVB interlayer films use triethylene glycol di(2-ethylhexanoate) plasticizer, which has limited compatibility with PVB. Increasing the content of triethylene glycol di(2-ethylhexanoate) helps improve compatibility with resin powder, but increasing the content of this monoester will reduce the refractive index of the film material, resulting in reduced light transmittance, unclear imaging, and limited application areas. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a high-refractive-index polyvinyl acetal resin powder and an intermediate film, as well as a method for preparing the same, which can produce a high-refractive-index polyvinyl acetal intermediate film with excellent light transmittance and clear imaging.

[0006] The objective of this invention is achieved through the following technical solution: High refractive index polyvinyl alcohol acetal resin powder, the structural formula of which is shown below: , Where z represents the number of polyvinyl acetals in the high-refractive-index polyvinyl acetal resin powder. x represents the number of hydroxyl groups in the high-refractive-index polyvinyl acetal resin powder; n represents the number of ester groups in the high-refractive-index polyvinyl acetal resin powder; y represents the number of polyvinyl acetal groups in the high-refractive-index polyvinyl acetal resin powder; x + 2y + 2z + n = Degree of polymerization of raw material PVA (polyvinyl alcohol); The R group is selected from one or more of methyl, hydrogen, propyl, phenyl, and butyl groups; The R1 group is selected from one or more aliphatic or aromatic groups with more than 6 Cs.

[0007] This invention also provides a method for preparing high-refractive-index polyvinyl acetal resin powder, using PVA, mercaptoaldehyde, and aldehyde solution as raw materials, and carrying out the following reaction under acid catalysis: , The thiol aldehyde is selected from one or more of aliphatic thiol aldehydes or aromatic thiol aldehydes with more than 6 carbon atoms. The aldehyde solution is selected from one or more of formaldehyde, acetaldehyde, glutaraldehyde, benzaldehyde, and butyraldehyde. Formaldehyde is a formaldehyde solution (37-40 wt.%), and acetaldehyde is an acetaldehyde solution (40 wt.%). Preferably, it is acetaldehyde (40 wt.%) or butyraldehyde.

[0008] In the above-described method for preparing high-refractive-index polyvinyl acetal resin powder, the reaction includes the following steps: (1) PVA is dissolved in water and prepared into a solution at 90-100℃. The temperature is lowered and the temperature inside the reactor is reduced to 20-40℃. Hydrochloric acid solution is added and the temperature is further lowered. When the temperature inside the reactor is reduced to 10-18℃, aldehyde solution is added dropwise. After the viscosity of the solution decreases, the reaction is carried out for 1 hour. (2) Add mercaptoaldehyde compounds to the above solution. After the solution precipitates, heat it to 60-70℃ in a gradient. After the product precipitates, keep it warm for 3 hours. Wash it with distilled water until the pH is neutral. Centrifuge and dry the material in a 65℃ oven to obtain high refractive index polyvinyl acetal resin powder.

[0009] In the above-described method for preparing high-refractive-index polyvinyl acetal resin powder, the degree of polymerization of the PVA is selected from one or more of 1000, 1700, 2000, 2400, or 2600. Preferably, the degree of polymerization of the PVA is 1700 or 2600.

[0010] In the above-described method for preparing high-refractive-index polyvinyl acetal resin powder, the mercaptoaldehyde is selected from one or more of 4-mercaptobenzaldehyde, 2-mercaptobenzaldehyde, and 3-mercapto-2-methyl-pentanal. 4-mercaptobenzaldehyde is preferred.

[0011] In the above-mentioned method for preparing high refractive index polyvinyl acetal resin powder, the mass fraction of PVA is 5-20 wt.% of the PVA aqueous solution system, preferably 10-15 wt.%; the amount of hydrochloric acid solution added is 0.5-0.9 wt.% of the entire solution system, the concentration of the hydrochloric acid solution is 30-35 wt.%, and the amount added is calculated as HCl; The amount of aldehyde solution added is 0.3-0.4 times the amount of PVA added, by mass. The amount of mercaptoaldehyde added is 0.2-0.4 times the amount of PVA added, by mass.

[0012] This invention also provides a method for preparing a high-refractive-index polyvinyl acetal interlayer film, wherein the interlayer film production process includes: (1) Ingredients: By weight, take 100 parts of the high refractive index polyvinyl alcohol acetal resin powder as described in claim 1, 30-40 parts of the plasticizer composition, 0.1-2 parts of the antioxidant and 0.1-3 parts of the UV absorber, and stir evenly to form the raw material; (2) Plasticization: The raw material in (1) is heated and plasticized by a twin-screw extruder; (3) Extrusion molding: The film material is extruded through a T-die.

[0013] In the above-described method for preparing a high-refractive-index polyvinyl acetal interlayer, the antioxidant is composed of hindered phenolic antioxidants and phosphite antioxidants. The hindered phenolic antioxidant is one or more of 1010, 1076, 1098, 245, and BHT (butylated hydroxytoluene), and the phosphite antioxidant is one or more of 168, 618, 619, and 626. Preferably, 1010 and 168 are used.

[0014] In the above-mentioned method for preparing high-refractive-index polyvinyl acetal interlayer, the UV absorber is selected from one or more of UV1577, UVP, UV326, UV329, UV531, UV770, UV5411, UV327, and UV6603, preferably UV326 and UV329.

[0015] In the above-mentioned method for preparing a high-refractive-index polyvinyl acetal interlayer, the plasticizer composition is a combination of triethylene glycol di(2-ethylhexanoate) (hereinafter referred to as 3GO) and other plasticizers; The other plasticizers are selected from 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, 3,4-epoxycyclohexylcarboxylic acid 3',4'-epoxycyclohexylmethyl ester, 6-methyl-3',4'-epoxycyclohexylcarboxylic acid 6'-methyl-3',4'-epoxycyclohexylmethyl ester, 3,4-epoxy-1-methyl-6-acetoxymethylcyclohexane carbonate, bis(3,4-epoxycyclohexylmethyl)adipate, glycidyl laurate, glycidyl tert-carbonate, glycidyl 2-ethylhexanoate, glycidyl hexanoate, diglycidyl succinate, diglycidyl adipic acid, diglycidyl sebacate, dihexyl succinate, diheptyl succinate, and di(2-ethylhexyl) succinate. The plasticizer comprises one or a mixture of several of the following: ester, dipentyl adipate, dihexyl adipate, diheptyl adipate, dicyclohexyl adipate, di(diethylene glycol monoethyl ether) adipate, di(diethylene glycol monobutyl ether) adipate, di(triethylene glycol monobutyl ether) adipate, dihexyl sebacate, diheptyl sebacate, di(2-ethylhexyl) sebacate, diethylene glycol di(2-ethylhexanoate), triethylene glycol dihexanoate, triethylene glycol diheptyl ester, triethylene glycol di(2-ethylhexanoate), and tetraethylene glycol diheptyl ester. Preferably, the other plasticizer is 3,4'-epoxycyclohexylformic acid methyl ester (hereinafter referred to as 2021P).

[0016] The high refractive index polyvinyl acetal resin powder and its intermediate film provided by this invention are used in automotive safety glass lamination and photovoltaic module encapsulation.

[0017] The principle behind this invention for increasing the refractive index is as follows: the refractive index contribution of hydrocarbon groups with the same number of carbon atoms is in the order of branched chain < straight chain < benzene ring. Halogens and sulfur atoms have relatively large molar refractive indices; aromatic rings contribute significantly to increasing the molecular refractive index. Because sulfur atoms have d-orbitals in their outer shell, their outermost two pairs of electrons are easily polarized, resulting in sulfur atoms possessing both a high molar refractive index and low molecular dispersion, which can improve the optical properties of the resin. Therefore, introducing sulfur atoms or benzene rings into the structure of polyvinyl butyral can significantly increase the refractive index of the product.

[0018] The advantages of this invention over the prior art are as follows: This invention proposes a method for preparing high-refractive-index polyvinyl acetal resin powder and its interlayer. The method utilizes a mercaptoaldehyde reaction with the hydroxyl groups in PVA to introduce sulfur atoms or benzene rings with higher molar refractive index into the polyvinyl acetal molecule, thereby increasing the refractive index of the resin powder. By employing triethylene glycol di(2-ethylhexanoate) and other plasticizers, the monoester content is reduced, improving the compatibility between the plasticizer and the resin powder, and increasing the refractive index of the interlayer to approach that of glass. This results in a high-refractive-index polyvinyl acetal interlayer with excellent light transmittance and clear imaging, suitable for photovoltaic module encapsulation and automotive HUD applications. The high-refractive-index polyvinyl acetal resin powder provided by this invention has a refractive index of 1.490–1.540; the high-refractive-index polyvinyl acetal interlayer provided has a refractive index of 1.490–1.520, representing a significant improvement over existing products. Detailed Implementation

[0019] The present invention will be further described below through specific embodiments, but this is not a limitation of the present invention. Those skilled in the art can make various modifications or improvements based on the basic idea of ​​the present invention, but as long as they do not depart from the basic idea of ​​the present invention, they are all within the scope of the present invention.

[0020] Unless otherwise specified, all raw materials and reagents used in the embodiments of this invention are commercially available.

[0021] In the embodiments, the refractive index and transmittance were detected using the following methods.

[0022] Fabrication of the intermediate membrane for transmittance testing Prepare two PET films (TORAYZ Co., Ltd. "Lumirror T60", 15cm long × 15cm wide × 100μm thick) and two cleaned and dried transparent float glass sheets (15cm long × 15cm wide × 2.5mm thick). Insert the two PET films between the two glass sheets, and further insert the obtained intermediate film inside to obtain a laminate. The resulting laminate has a glass sheet / PET film / intermediate film / PET film / glass sheet structure. Place the resulting laminate in a bag and degas it under vacuum at room temperature (23°C) with a reduced pressure of 933.2 hPa. Then, to maintain the degassing state, heat the vacuum bag to 100°C and maintain the temperature for 20 minutes. Next, cool the vacuum bag naturally until the temperature drops to 30°C, then release the pressure to atmospheric pressure.

[0023] Using an autoclave, at 135°C and 1.2 MPa, the laminated glass pre-pressed by the above vacuum bag method was kept for 20 minutes, and the surface was smoothed by passing it through a PET film to obtain the intermediate film.

[0024] Detection methods Refractive index evaluation method (Test environment) Temperature 25℃, relative humidity around 50%.

[0025] (Test Method) Unscrew the closing knobs of the measuring prism and auxiliary prism to ensure the frosted bevel of the auxiliary prism is horizontal. If the prism surface is not clean, add a small amount of acetone and gently wipe the surface in one direction with lens paper (do not wipe back and forth). After the surface is clean and dry, place the resin powder or intermediate film on the frosted surface of the auxiliary prism, quickly close the auxiliary prism, and tighten the closing knob. Rotate the microscope tube to make it vertical, adjust the reflecting mirror to allow the incident light to enter the prism, and simultaneously adjust the focus of the eyepiece to make the crosshairs in the eyepiece clear and bright. Adjust the achromatic compensator to make the colored light band in the eyepiece disappear. Then adjust the reading screw so that the interface between the bright and dark areas coincides exactly with the intersection of the crosshairs. Read the refractive index value on the dial from the reading telescope. Read to three decimal places. To ensure accurate readings, the sample should generally be measured three times, with each measurement differing by no more than 0.002, and then the average value should be taken.

[0026] The Shanghai Optics 2WAJ monocular Abbe refractometer was selected as the testing instrument. Transmittance Evaluation Method (Test environment) Temperature 25℃, relative humidity around 50%.

[0027] (Test Method) The interlayer film was placed under the above test environment for 24 hours. After the laser source and photodetector were powered on, without the test object placed on the loading device, the blank signal of the laser beam that did not pass through the test object, as measured by the photodetector, was obtained. The laser beam that did not pass through the test object refers to the laser beam emitted by the laser source, which, after being reflected by the reflective lens to the attenuator, and then transmitted to the photodetector at a specified wavelength. The high-refractive-index polyvinyl acetal interlayer film was cut to a suitable size, placed on the loading device, and a laser beam of 380nm to 1100nm was selected. The average transmittance measured by the photodetector was obtained. Generally, the sample should be measured three times to obtain the average value.

[0028] As the testing instrument, the "Cary 5000 Series UV-VIS-NIR Spectrophotometer" manufactured by Agilent Technologies was selected.

[0029] Comparative Example 1 Preparation of polyvinyl butyral resin powder PVA (degree of polymerization 1700) is dissolved in water and prepared into a 10 wt.% solution at 90-100℃. The solution is then cooled down to 25℃, and hydrochloric acid solution is added at a rate of 0.5 wt.% of the total solution. The solution is then cooled further until the temperature inside the reactor drops to 12-18℃, at a rate of 0.4 PVA. After the product precipitates, the reaction is maintained at this temperature for 1 hour. The temperature is then gradually increased to 70℃ and maintained for another hour.

[0030] After the product has finished its heat preservation process, add liquid alkali to adjust the pH to neutral, and wash the product with water until the conductivity is less than 20 μS / cm.

[0031] After centrifugation, the product is placed in a drying oven and dried at 65°C to obtain polyvinyl butyral resin powder.

[0032] Preparation of polyvinyl butyral interlayer: (1) Ingredients: 100 parts of polyvinyl butyral, 30 parts of plasticizer, 1 part of antioxidant and 2 parts of UV absorber are mixed evenly to form raw materials.

[0033] (2) Plasticizing: The raw material in (1) is heated and plasticized by a twin-screw extruder at a temperature of 165-170℃.

[0034] (3) Extrusion molding: Extruding a film material with a thickness of 0.76 mm through a T-die.

[0035] The antioxidants are 1010 and 168, the UV absorber is UV326, and the plasticizer is 3GO.

[0036] Comparative Example 2 Preparation of polyvinyl butyral resin powder PVA (degree of polymerization 1700) is dissolved in water and prepared into a 10 wt.% solution at 90-100℃. The solution is then cooled down to 25℃, and hydrochloric acid solution is added at a rate of 0.5 wt.% of the total solution. The solution is then cooled further until the temperature inside the reactor drops to 12-18℃, at a rate of 0.4 PVA. After the product precipitates, the reaction is maintained at this temperature for 1 hour. The temperature is then gradually increased to 70℃ and maintained for another hour.

[0037] After the product has finished its heat preservation process, add liquid alkali to adjust the pH to neutral, and wash the product with water until the conductivity is less than 20 μS / cm.

[0038] After centrifugation, the product is placed in a drying oven and dried at 65°C to obtain polyvinyl butyral resin powder.

[0039] A method for preparing a polyvinyl butyral interlayer film, comprising the following production steps: (1) Ingredients: 100 parts of polyvinyl butyral, 30 parts of plasticizer, 1 part of antioxidant and 2 parts of UV absorber are mixed evenly to form raw materials.

[0040] (2) Plasticizing: The raw material in (1) is heated and plasticized by a twin-screw extruder at a temperature of 160-170℃.

[0041] (3) Extrusion molding: Extruding a film material with a thickness of 0.76 mm through a T-die.

[0042] The antioxidants are 1010 and 168, the UV absorber is UV326, and the plasticizer is 2021P.

[0043] Example 1 Preparation of high refractive index polyvinyl alcohol acetal resin powder PVA (degree of polymerization 1700) is dissolved in water and prepared into a 15wt.% solution at 90-100℃. The solution is then cooled down until the temperature inside the reactor drops to 27℃. Hydrochloric acid solution is then added, with the amount added being 0.5wt.% of the entire solution system. The temperature is further cooled down until the temperature inside the reactor drops to 12-14℃. Then, 0.3% butyraldehyde solution of PVA is added dropwise. After the viscosity of the solution decreases, the reaction is carried out for 1 hour.

[0044] Add 0.3 PVA of 4-mercaptobenzaldehyde to the above solution. After the solution precipitates, heat it to 70°C in a gradient manner. After the product precipitates, keep it at this temperature for 3 hours. Wash it with distilled water until the pH is neutral. Centrifuge the mixture and dry it in a 65°C oven to obtain high refractive index polyvinyl acetal resin powder.

[0045] The synthesis route and product structure of the high refractive index polyvinyl acetal resin powder in this embodiment are as follows:

[0046] Preparation of high refractive index polyvinyl acetal interlayer (1) Ingredients: 100 parts of the above high refractive index polyvinyl alcohol acetal resin powder, 30 parts of plasticizer composition, 1 part of antioxidant and 2 parts of UV absorber are mixed evenly to form raw materials.

[0047] (2) Plasticizing: The raw material in (1) is heated and plasticized by a twin-screw extruder at a temperature of 160-170℃.

[0048] (3) Extrusion molding: Extruding a film material with a thickness of 0.76 mm through a T-die.

[0049] The antioxidants are 1010 and 168, the UV absorber is UV326, and the plasticizer composition is 3GO and 2021P.

[0050] The plasticizer composition, based on 100 parts by weight of the composition, includes 15 parts by weight of 2021P and 85 parts by weight of 3GO.

[0051] Example 2 Preparation of high refractive index polyvinyl alcohol acetal resin powder PVA (degree of polymerization 2600) is dissolved in water and prepared into a 15wt.% solution at 90-100℃. The solution is then cooled down to 25℃, and hydrochloric acid solution is added at a rate of 0.6wt.% of the total solution. The solution is then cooled further until the temperature inside the reactor drops to 10-14℃. Finally, acetaldehyde (40wt.%) solution of 0.4% PVA is added dropwise. After the viscosity of the solution decreases, the reaction is carried out for 1 hour.

[0052] Add 0.4% PVA of 3-mercapto-2-methyl-pentanal to the above solution. After the solution precipitates, heat it to 70°C in a gradient manner. After the product precipitates, keep it at this temperature for 3 hours. Wash it with distilled water until the pH is neutral. Centrifuge the mixture and dry it in a 65°C oven to obtain high refractive index polyvinyl acetal resin powder.

[0053] In this embodiment, the synthesis route and product structure of high refractive index polyvinyl acetal resin powder are as follows:

[0054] Preparation of high refractive index polyvinyl acetal interlayer (1) Ingredients: 100 parts of the above high refractive index polyvinyl alcohol acetal resin powder, 35 parts of plasticizer composition, 1 part of antioxidant and 2 parts of UV absorber are mixed evenly to form raw materials.

[0055] (2) Plasticizing: The raw material in (1) is heated and plasticized by a twin-screw extruder at a temperature of 165-175℃.

[0056] (3) Extrusion molding: Extruding a film material with a thickness of 0.76 mm through a T-die.

[0057] The antioxidants are 1010 and 168, the UV absorber is UV329, and the plasticizer composition is 3GO and 2021P.

[0058] The plasticizer composition, based on 100 parts by weight of the composition, includes 80 parts by weight of 2021P and 20 parts by weight of 3GO.

[0059] Example 3 Preparation of high refractive index polyvinyl alcohol acetal resin powder PVA (degree of polymerization 1700) is dissolved in water and prepared into a 12wt.% solution at 90-100℃. The solution is then cooled down to 25℃, and hydrochloric acid solution is added at a rate of 0.6wt.% of the total solution. The solution is then cooled further until the temperature inside the reactor drops to 12-16℃, and 0.3% butyraldehyde solution of PVA is added dropwise. After the viscosity of the solution decreases, the reaction is carried out for 1 hour.

[0060] Add 0.4 PVA of 2-mercaptobenzaldehyde to the above solution. After the solution precipitates, heat it to 70°C in a gradient manner. After the product precipitates, keep it at this temperature for 3 hours. Wash it with distilled water until the pH is neutral. Centrifuge the mixture and dry it in a 65°C oven to obtain high refractive index polyvinyl acetal resin powder.

[0061] The synthesis route and product structure of the high refractive index polyvinyl acetal resin powder in this embodiment are as follows:

[0062] Preparation of high refractive index polyvinyl acetal interlayer (1) Ingredients: 100 parts of the above high refractive index polyvinyl alcohol acetal resin powder, 40 parts of plasticizer composition, 2 parts of antioxidant and 3 parts of UV absorber are mixed evenly to form raw materials.

[0063] (2) Plasticizing: The raw material in (1) is heated and plasticized by a twin-screw extruder at a temperature of 160-170℃.

[0064] (3) Extrusion molding: Extruding a film material with a thickness of 0.76 mm through a T-die.

[0065] The antioxidants are 168 and 1010, the UV absorber is UV329, and the plasticizer composition is 3GO and 2021P.

[0066] The plasticizer composition, based on 100 parts by weight of the composition, includes 20 parts by weight of 2021P and 80 parts by weight of 3GO.

[0067] Example 4 Preparation of high refractive index polyvinyl alcohol acetal resin powder PVA (degree of polymerization 1700) is dissolved in water and prepared into a 15wt.% solution at 90-100℃. The solution is then cooled down until the temperature inside the reactor drops to 25℃. Hydrochloric acid solution is then added, with the amount added being 0.5wt.% of the total system. The temperature is further cooled until the temperature inside the reactor drops to 11-13℃. Then, acetaldehyde (40wt.%) solution of 0.3% PVA is added dropwise. After the viscosity of the solution decreases, the reaction is carried out for 1 hour.

[0068] Add 0.2 PVA of 4-mercaptobenzaldehyde to the above solution. After the solution precipitates, heat it to 70°C in a gradient manner. After the product precipitates, keep it at this temperature for 3 hours. Wash it with distilled water until the pH is neutral. Centrifuge the mixture and dry it in a 65°C oven to obtain high refractive index polyvinyl acetal resin powder.

[0069] The synthesis route and product structure of the high refractive index polyvinyl acetal resin powder in this embodiment are as follows:

[0070] Preparation of high refractive index polyvinyl acetal interlayer (1) Ingredients: 100 parts of the above high refractive index polyvinyl alcohol acetal resin powder, 40 parts of plasticizer composition, 2 parts of antioxidant and 3 parts of ultraviolet absorber are mixed evenly to form raw materials.

[0071] (2) Plasticizing: The raw material in (1) is heated and plasticized by a twin-screw extruder at a temperature of 165-175℃.

[0072] (3) Extrusion molding: Extruding a film material with a thickness of 0.76 mm through a T-die.

[0073] The antioxidants are 168 and 1010, the UV absorber is UV329, and the plasticizer composition is 3GO and 2021P.

[0074] The plasticizer composition, based on 100 parts by weight of the composition, includes 20 parts by weight of 2021P and 80 parts by weight of 3GO.

[0075] Example 5 Preparation of high refractive index polyvinyl alcohol acetal resin powder PVA (degree of polymerization 2600) is dissolved in water and prepared into a 12wt.% solution at 90-100℃. The solution is then cooled down to 25℃, and hydrochloric acid solution is added at a rate of 0.5wt.% of the total solution. The solution is then cooled further until the temperature inside the reactor drops to 13-15℃. At this point, acetaldehyde (40wt.%) solution of 0.4% PVA is added dropwise. After the viscosity of the solution decreases, the reaction is carried out for 1 hour.

[0076] Add 0.3 PVA of 4-mercaptobenzaldehyde to the above solution. After the solution precipitates, heat it to 70°C in a gradient manner. After the product precipitates, keep it at this temperature for 3 hours. Wash it with distilled water until the pH is neutral. Centrifuge the mixture and dry it in a 65°C oven to obtain high refractive index polyvinyl acetal resin powder.

[0077] The synthesis route and product structure of the high refractive index polyvinyl acetal resin powder in this embodiment are as follows:

[0078] Preparation of high refractive index polyvinyl acetal interlayer (1) Ingredients: 100 parts of the above high refractive index polyvinyl alcohol acetal resin powder, 35 parts of plasticizer composition, 2 parts of antioxidant and 3 parts of UV absorber are mixed evenly to form raw materials.

[0079] (2) Plasticizing: The raw material in (1) is heated and plasticized by a twin-screw extruder at a temperature of 160-170℃.

[0080] (3) Extrusion molding: Extruding a film material with a thickness of 0.76 mm through a T-die.

[0081] The antioxidants are 168 and 1010, the UV absorber is UV329, and the plasticizer composition is 3GO and 2021P.

[0082] The plasticizer composition, based on 100 parts by weight of the composition, includes 15 parts by weight of 2021P and 85 parts by weight of 3GO.

[0083] Example 6 Preparation of high refractive index polyvinyl alcohol acetal resin powder PVA (degree of polymerization 1700) is dissolved in water and prepared into a 15wt.% solution at 90-100℃. The solution is then cooled down until the temperature inside the reactor drops to 25℃. Hydrochloric acid solution is then added, with the amount added being 0.5wt.% of the entire solution system. The temperature is further cooled down until the temperature inside the reactor drops to 11-13℃. Then, 0.4% butyraldehyde solution of PVA is added dropwise. After the viscosity of the solution decreases, the reaction is carried out for 1 hour.

[0084] Add 0.4% PVA of 3-mercapto-2-methylpentanal to the above solution. After the solution precipitates, heat it to 70°C in a gradient manner. After the product precipitates, keep it at this temperature for 3 hours. Wash it with distilled water until the pH is neutral. Centrifuge the mixture and dry it in a 65°C oven to obtain high-refractive-index polyvinyl acetal resin powder.

[0085] The synthesis route and product structure of the high refractive index polyvinyl acetal resin powder in this embodiment are as follows:

[0086] Preparation of high refractive index polyvinyl acetal interlayer (1) Ingredients: 100 parts of the above high refractive index polyvinyl alcohol acetal resin powder, 35 parts of plasticizer composition, 2 parts of antioxidant and 3 parts of UV absorber are mixed evenly to form raw materials.

[0087] (2) Plasticizing: The raw material in (1) is heated and plasticized by a twin-screw extruder at a temperature of 160-170℃.

[0088] (3) Extrusion molding: Extruding a film material with a thickness of 0.76 mm through a T-die.

[0089] The antioxidants are 168 and 1010, the UV absorber is UV326, and the plasticizer composition is 3GO and 2021P.

[0090] The plasticizer composition, based on 100 parts by weight of the composition, includes 20 parts by weight of 2021P and 80 parts by weight of 3GO.

[0091] Example 7 Preparation of high refractive index polyvinyl alcohol acetal resin powder PVA (degree of polymerization 1700) is dissolved in water and prepared into a 14wt.% solution at 90-100℃. The solution is then cooled down to 25℃, and hydrochloric acid solution is added at a rate of 0.9wt.% of the total solution. The solution is then cooled further until the temperature inside the reactor drops to 12-14℃, and 0.3% butyraldehyde solution of PVA is added dropwise. After the viscosity of the solution decreases, the reaction is carried out for 1 hour.

[0092] Add 0.3 PVA of 4-mercaptobenzaldehyde to the above solution. After the solution precipitates, heat it to 70°C in a gradient manner. After the product precipitates, keep it at this temperature for 3 hours. Wash it with distilled water until the pH is neutral. Centrifuge the mixture and dry it in a 65°C oven to obtain high refractive index polyvinyl acetal resin powder.

[0093] The synthesis route and product structure of the high refractive index polyvinyl acetal resin powder in this embodiment are as follows:

[0094] Preparation of high refractive index polyvinyl acetal interlayer (1) Ingredients: 100 parts of the above high refractive index polyvinyl alcohol acetal resin powder, 30 parts of plasticizer composition, 1 part of antioxidant and 2 parts of UV absorber are mixed evenly to form raw materials.

[0095] (2) Plasticizing: The raw material in (1) is heated and plasticized by a twin-screw extruder at a temperature of 160-170℃.

[0096] (3) Extrusion molding: Extruding a film material with a thickness of 0.76 mm through a T-die.

[0097] The antioxidants are 1010 and 168, the UV absorber is UV326, and the plasticizer composition is 3GO and 2021P.

[0098] The plasticizer composition, based on 100 parts by weight of the composition, includes 85 parts by weight of 2021P and 15 parts by weight of 3GO.

[0099] The refractive index of the polyvinyl acetal resin powder, the refractive index of the polyvinyl acetal intermediate film, and the transmittance were tested in the comparative examples and embodiments described above.

[0100] The experimental results are shown in Table 1. Details and results are presented.

[0101]

[0102] As can be seen from the above results, the high refractive index polyvinyl acetal resin powder provided by the present invention utilizes the acetal reaction between mercaptoaldehyde and hydroxyl groups in PVA to introduce sulfur atoms or benzene rings with higher molar refractive index into the molecular structure of polyvinyl acetal, thereby increasing the refractive index of the resin powder to 1.490 to 1.540, which is higher than the refractive index of 1.488 in the comparative example.

[0103] Using high-refractive-index polyvinyl acetal resin powder as raw material, and employing triethylene glycol di(2-ethylhexanoate) and 3,4-epoxycyclohexylformic acid 3',4'-epoxycyclohexylmethyl ester as plasticizers, the refractive index of the interlayer is improved to 1.490-1.520, which is close to the refractive index of glass. This allows for the production of high-refractive-index polyvinyl acetal interlayers with excellent light transmittance and clear imaging.

Claims

1. A high-refractive-index polyvinyl acetal resin powder, characterized in that, The structural formula is as follows: ； Where z represents the number of polyvinyl acetals in the high-refractive-index polyvinyl acetal resin powder. x represents the number of hydroxyl groups in the high-refractive-index polyvinyl acetal resin powder; n represents the number of ester groups in the high-refractive-index polyvinyl acetal resin powder; y represents the number of polyvinyl acetal groups in the high-refractive-index polyvinyl acetal resin powder; x + 2y + 2z + n = degree of polymerization of the raw material PVA; The R group is selected from one or more of methyl, hydrogen, propyl, phenyl, and butyl groups; The R1 group is selected from one or more aliphatic or aromatic groups with more than 6 Cs.

2. The method for preparing high refractive index polyvinyl acetal resin powder as described in claim 1, characterized in that, Using PVA, mercaptoaldehyde, and aldehyde solution as raw materials, the following reaction is carried out under acid catalysis: ， The thiol aldehyde is selected from one or more of aliphatic thiol aldehydes or aromatic thiol aldehydes with more than 6 carbon atoms. The aldehyde solution is selected from one or more of formaldehyde, acetaldehyde, glutaraldehyde, benzaldehyde, and butyraldehyde.

3. The method for preparing high refractive index polyvinyl acetal resin powder according to claim 2, characterized in that, The reaction includes the following steps: (1) PVA is dissolved in water and prepared into a solution at 90-100℃. The temperature is lowered and the temperature inside the reactor is reduced to 20-40℃. Hydrochloric acid solution is added and the temperature is further lowered. When the temperature inside the reactor is reduced to 10-18℃, aldehyde solution is added dropwise. After the viscosity of the solution decreases, the reaction is carried out for 1 hour. (2) Add mercaptoaldehyde compounds to the above solution. After the solution precipitates, heat it to 60-70℃ in a gradient. After the product precipitates, keep it warm for 3 hours. Wash it with distilled water until the pH is neutral. Centrifuge and dry the material in a 65℃ oven to obtain high refractive index polyvinyl acetal resin powder.

4. The method for preparing high refractive index polyvinyl acetal resin powder according to claim 2, characterized in that, The degree of polymerization of the PVA is selected from one or more of 1000, 1700, 2000, 2400 or 2600.

5. The method for preparing high refractive index polyvinyl acetal resin powder according to claim 2, characterized in that, The mercaptoaldehyde is selected from one or more of 4-mercaptobenzaldehyde, 2-mercaptobenzaldehyde, and 3-mercapto-2-methyl-pentanal.

6. The method for preparing high refractive index polyvinyl acetal resin powder according to claim 2, characterized in that, The mass fraction of PVA in the PVA aqueous solution system is 5-20 wt.%. The concentration of the hydrochloric acid solution is 30-35 wt.%, and the amount added, calculated as HCl, is 0.5-0.9 wt.% of the total solution system. The amount of aldehyde added, by weight, is 0.3-0.4 times the amount of PVA added; The amount of mercaptoaldehyde added is 0.2-0.4 times the amount of PVA added, by mass.

7. A method for preparing a high-refractive-index polyvinyl acetal interlayer, characterized in that, The intermediate film production process includes the following steps: (1) Ingredients: By weight, take 100 parts of the high refractive index polyvinyl alcohol acetal resin powder as described in claim 1, 30-40 parts of the plasticizer composition, 0.1-2 parts of the antioxidant and 0.1-3 parts of the UV absorber, and stir evenly to form the raw material; (2) Plasticization: The raw material in (1) is heated and plasticized by a twin-screw extruder; (3) Extrusion molding: The film material is extruded through a T-die.

8. The method for preparing a high-refractive-index polyvinyl acetal interlayer according to claim 7, characterized in that, The antioxidant is composed of hindered phenolic antioxidants and phosphite antioxidants. The hindered phenolic antioxidants are one or more of 1010, 1076, 1098, 245, and BHT, and the phosphite antioxidants are one or more of 168, 618, 619, and 626.

9. The method for preparing a high-refractive-index polyvinyl acetal interlayer according to claim 7, characterized in that, The plasticizer composition is a combination of triethylene glycol di(2-ethylhexanoate) and other plasticizers; The other plasticizers are selected from 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, 3,4-epoxycyclohexylcarboxylic acid 3',4'-epoxycyclohexylmethyl ester, 6-methyl-3',4'-epoxycyclohexylcarboxylic acid 6'-methyl-3',4'-epoxycyclohexylmethyl ester, 3,4-epoxy-1-methyl-6-acetoxymethylcyclohexane carbonate, bis(3,4-epoxycyclohexylmethyl)adipate, glycidyl laurate, glycidyl tert-carbonate, glycidyl 2-ethylhexanoate, glycidyl hexanoate, diglycidyl succinate, diglycidyl adipic acid, diglycidyl sebacate, dihexyl succinate, diheptyl succinate, and di(2-ethylhexyl) succinate. The following are one or a mixture of esters, dipentyl adipate, dihexyl adipate, diheptyl adipate, dicyclohexyl adipate, di(diethylene glycol monoethyl ether) adipate, di(diethylene glycol monobutyl ether) adipate, di(triethylene glycol monobutyl ether) adipate, dihexyl sebacate, diheptyl sebacate, di(2-ethylhexyl) sebacate, diethylene glycol di(2-ethylhexanoate), triethylene glycol dihexanoate, triethylene glycol diheptyl ester, triethylene glycol di(2-ethylhexanoate), and tetraethylene glycol diheptyl ester.

10. The method for preparing a high-refractive-index polyvinyl acetal interlayer according to claim 9, characterized in that, The other plasticizer is 3,4'-epoxycyclohexylcarboxylic acid 3',4'-epoxycyclohexylmethyl ester.

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