Yellowing-resistant polyvinyl butyral resin as well as preparation method and application thereof

Abstract

The invention provides anti-yellowing polyvinyl butyral resin and a preparation method and application thereof, the preparation method comprises the following steps: (1) dissolving polyvinyl alcohol in deionized water, then adding strong acid, stirring, degassing the obtained mixed solution, and then supplementing the strong acid to obtain a polyvinyl alcohol aqueous solution to be reacted; and (2) mixing the polyvinyl alcohol aqueous solution with n-butyraldehyde, and reacting under an ultrasonic condition to obtain the anti-yellowing polyvinyl butyral resin. By adopting the preparation method provided by the invention to prepare the polyvinyl butyral resin, the yellowing resistance of the polyvinyl butyral resin can be remarkably improved, so that the yellowing resistance of the prepared PVB adhesive film is improved, and meanwhile, less waste solvent and waste water are generated.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and relates to a yellowing-resistant polyvinyl butyral resin, a preparation method thereof, and an application thereof. Background Art

[0002] Polyvinyl butyral (PVB) resin is a product obtained by condensing polyvinyl alcohol (PVA) and n-butyraldehyde under the catalysis of an acid. PVB resin is the main raw material for preparing PVB film. The PVB film prepared therefrom has high transparency, cold resistance, excellent impact resistance, and strong adhesion to materials such as glass and metal, and is widely used as an interlayer material for automotive and architectural safety glass.

[0003] When the PVB film is used as an interlayer material for automotive or architectural safety glass, due to long-term exposure to the natural environment, in order to keep the optical properties of the PVB laminated glass unaffected, higher requirements are imposed on its weather resistance. The performance of the PVB film depends on the quality stability of the PVB resin, and the weather resistance of the PVB film directly corresponds to the yellowing resistance of the PVB resin. Therefore, using a PVB resin with good yellowing resistance can greatly improve the optical properties and weather resistance of the PVB film.

[0004] The yellowing resistance of PVB resin is related to the characteristics of raw materials. According to different initial raw materials, there are mainly three methods for industrially producing PVB resin: one-step method, precipitation method, and dissolution method. The one-step method uses polyvinyl acetate (PVAc) as the raw material, and the hydrolysis and acetalization reactions of PVAc are carried out simultaneously. The PVB resin prepared by this method has uneven distribution of butyraldehyde groups and high impurity content. The dissolution method uses PVA as the raw material, and the solvent is methanol. The acetalization reaction is carried out in a PVA methanol suspension. This method requires a large amount of methanol solvent, has a high cost, and the degree of acetalization of the synthesized PVB resin is relatively low. The precipitation method uses PVA as the raw material, and the acetalization reaction occurs in an aqueous PVA solution to gradually precipitate PVB resin. Most enterprises still mainly use the precipitation method to produce PVB resin. When using methanol as the alkali hydrolysis solvent to prepare PVA from PVAc as the raw material, side reactions often occur, and the obtained PVA inevitably contains impurities such as methanol, methyl acetate, and sodium acetate. In the acetalization reaction, some of these impurities will continue to react with n-butyraldehyde and be wrapped in PVB particles, forming small molecules and oligomer impurities that are difficult to remove. The presence of these impurities makes the yellowing resistance of PVB resin poor, and the weather resistance of the PVB laminated glass prepared therefrom is poor, and yellowing, bubbling, or even delamination of the PVB laminated film easily occurs.

[0005] At present, CN115873148A uses an ethanol solution to wash PVA products repeatedly, reducing the content of impurities such as methanol and methyl acetate in the PVA raw material, which can be used to improve the yellowing resistance of PVB resin. CN116082540A improves the yellowing resistance of PVB resin by performing a devolatilization treatment on an aqueous PVA solution and adding an emulsifier and an ionic liquid antioxidant during the condensation reaction process. However, the above-mentioned schemes will generate a large amount of waste solvents and waste water.

[0006] Therefore, in the present invention, it is desired to develop a method for preparing a yellowing-resistant polyvinyl butyral resin, which can not only significantly improve the yellowing resistance of the polyvinyl butyral resin, but also has a simple method and generates less waste solvent and waste water. Summary of the Invention

[0007] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a yellowing-resistant polyvinyl butyral resin, its preparation method and application. The present invention adopts a more convenient synthetic process means to improve the yellowing resistance of PVB resin. Using this synthetic process, the yellowing resistance of the obtained PVB resin is significantly improved, and at the same time, less waste solvent and waste water are generated.

[0008] To achieve this purpose, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides a method for preparing a yellowing-resistant polyvinyl butyral resin, and the preparation method includes the following steps:

[0010] (1) Dissolve polyvinyl alcohol in deionized water, then add a strong acid, stir, perform a degassing treatment on the obtained mixture, and then add the strong acid again to obtain an aqueous polyvinyl alcohol solution to be reacted;

[0011] (2) Mix the aqueous polyvinyl alcohol solution and n-butyraldehyde, and react under ultrasonic conditions to obtain the yellowing-resistant polyvinyl butyral resin.

[0012] During the production of PVA, sodium acetate and some small alcohol molecules will remain. During the reaction process of PVA becoming PVB, the alcohol will continue to react with n-butyraldehyde, and together with part of the sodium acetate, it will be wrapped in the PVB particles. These encapsulated small molecules have a great influence on the yellowing resistance of PVB particles and PVB films, and need to be cleaned as much as possible. Although a large amount of water can be used to wash the PVB particles subsequently, it is still difficult to clean the small molecules encapsulated in the PVB particles, and a large amount of water resources is wasted.

[0013] After dissolving PVA in deionized water in the present invention, a certain amount of strong acid is added, and after stirring evenly, the PVA solution is degassed to remove most of the organic small molecule substances in the system and acetic acid hydrolyzed from vinyl acetate units remaining on the polymer chain after adding the strong acid; subsequently, n-butyraldehyde is added, and ultrasound is carried out during the reaction, which not only promotes the dispersion of the generated PVB resin, reduces sticking to the kettle wall, but also enhances the full contact reaction of n-butyraldehyde with alcohol hydroxyl groups, improves the conversion rate and acetal degree, and finally obtains a yellowing-resistant polyvinyl butyral resin; by using the preparation method provided by the present invention to prepare polyvinyl butyral resin, not only can the yellowing resistance of polyvinyl butyral resin be significantly improved, thereby improving the yellowing resistance of the prepared PVB film, but also less waste solvent and waste water are generated, and the raw material conversion rate is improved.

[0014] Preferably, the strong acid in step (1) includes any one or a combination of at least two of hydrochloric acid, perchloric acid, sulfuric acid, and nitric acid.

[0015] Preferably, the strong acid is added in the form of an aqueous solution of the strong acid.

[0016] Preferably, in step (1), based on the mass of polyvinyl alcohol being 50 parts, the amount of deionized water used is 300 - 700 parts, such as 300 parts, 350 parts, 400 parts, 450 parts, 500 parts, 550 parts, 600 parts, 650 parts, 700 parts, etc., and preferably 400 - 600 parts.

[0017] Preferably, in step (1), based on the mass of polyvinyl alcohol being 50 parts, the amount of the strong acid added for the first time is 0.25 - 5 parts, such as 0.25 parts, 0.5 parts, 0.8 parts, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, etc.

[0018] Preferably, in step (1), the mass ratio of the supplementary strong acid (converted to dry strong acid, for example, if concentrated hydrochloric acid is added, converted to dry HCl) to polyvinyl alcohol (dry polyvinyl alcohol) is (0.005 - 0.1):1, such as 0.005:1, 0.008:1, 0.01:1, 0.03:1, 0.05:1, 0.08:1, 0.1:1, etc.

[0019] Preferably, the specific operation of dissolving polyvinyl alcohol in deionized water in step (1) is: dissolving polyvinyl alcohol in deionized water at a temperature of 90 - 100 °C (such as 90 °C, 92 °C, 94 °C, 96 °C, 98 °C, 100 °C, etc.) to obtain a uniform and clear aqueous solution of polyvinyl alcohol.

[0020] Preferably, when adding strong acid in step (1), the temperature of the system is controlled at 20 - 60 °C, such as 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, etc., preferably 30 - 40 °C, and more preferably 30 °C.

[0021] Preferably, the stirring time in step (1) is 20 - 60 min, such as 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, etc.

[0022] Preferably, the stirring rate in step (1) is 100 - 300 rpm, such as 100 rpm, 120 rpm, 140 rpm, 150 rpm, 160 rpm, 180 rpm, 200 rpm, 220 rpm, 240 rpm, 250 rpm, 260 rpm, 280 rpm, 300 rpm, etc.

[0023] Preferably, the degassing temperature in step (1) is 80 - 90 °C, such as 80 °C, 82 °C, 84 °C, 85 °C, 86 °C, 88 °C, 90 °C, etc.

[0024] Preferably, the mass ratio of the polyvinyl alcohol to the n - butyraldehyde is (1.2 - 2):1, such as 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, etc.

[0025] Preferably, when mixing the polyvinyl alcohol aqueous solution and n - butyraldehyde in step (2), the temperature of the polyvinyl alcohol aqueous solution is controlled at 0 - 30 °C, such as 0 °C, 5 °C, 10 °C, 15 °C, 20 °C, 25 °C, 30 °C, etc.

[0026] Preferably, mixing the polyvinyl alcohol aqueous solution and n - butyraldehyde in step (2) specifically means: while stirring the polyvinyl alcohol aqueous solution, dropping n - butyraldehyde into the polyvinyl alcohol aqueous solution, and simultaneously performing ultrasonic treatment on the system.

[0027] Preferably, the frequency of the ultrasonic wave for ultrasonic treatment is 20 KHZ - 100 KHZ, preferably 40 KHZ; the ultrasonic power is 0.05 KW - 5 KW / kg of potentially generated solid PVB, preferably 0.25 KW / kg of potentially generated solid PVB.

[0028] Preferably, the dropping includes dropping through an input pump.

[0029] Preferably, the dropping of n - butyraldehyde is controlled to be completed within 20 - 40 min (such as 20 min, 25 min, 30 min, 35 min, 40 min, etc.).

[0030] Preferably, the reaction in step (2) specifically includes: first reacting at 0 - 30°C (such as 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, etc.) for 10 - 20 min (such as 10 min, 15 min, 20 min, etc.), then heating up to 25 - 35°C (such as 25°C, 28°C, 30°C, 32°C, 33°C, 35°C, etc.) at a rate of 10 - 15°C / h (such as 10°C / h, 11°C / h, 12°C / h, 13°C / h, 14°C / h, 15°C / h, etc.). After the system temperature reaches 25 - 35°C (such as 25°C, 28°C, 30°C, 32°C, 33°C, 35°C, etc.), heat up to the curing temperature of 55 - 65°C (such as 55°C, 58°C, 60°C, 62°C, 63°C, 65°C, etc.) at a rate of 25 - 35°C / h (such as 25°C / h, 28°C / h, 30°C / h, 32°C / h, 33°C / h, 35°C / h, etc.), and keep the temperature for 1 - 3 h (such as 1 h, 1.5 h, 2 h, 2.5 h, 3 h, etc.) for the reaction.

[0031] Preferably, there is also a purification step after the reaction in step (2).

[0032] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0033] (1) Dissolve polyvinyl alcohol in deionized water at 90 - 100°C, cool down to 20 - 60°C, then add a strong acid aqueous solution, stir at a rate of 100 - 300 rpm for 20 - 60 min, perform degassing treatment on the obtained mixed solution at 80 - 90°C, and then add more strong acid to obtain the polyvinyl alcohol aqueous solution to be reacted.

[0034] (2) Cool down the polyvinyl alcohol aqueous solution to 0 - 30°C. While stirring the polyvinyl alcohol aqueous solution, dropwise add n - butyraldehyde thereto through an input pump, and at the same time perform ultrasonic treatment on the system, and control the dropping of n - butyraldehyde to be completed within 20 - 40 min. The system first reacts at 0 - 30°C for 10 - 20 min under ultrasonic conditions, then heats up to 25 - 35°C at a rate of 10 - 15°C / h. After the system temperature reaches 25 - 35°C, heat up to the curing temperature of 55 - 65°C at a rate of 25 - 35°C / h, keep the temperature for 1 - 3 h for the reaction, and then purify to obtain the yellowing - resistant polyvinyl butyral resin.

[0035] In the second aspect, the present invention provides a yellowing - resistant polyvinyl butyral resin, and the yellowing - resistant polyvinyl butyral resin is prepared by using the preparation method as described in the first aspect.

[0036] In a third aspect, the present invention provides an application of the yellowing-resistant polyvinyl butyral resin as described in the second aspect in architectural glass, automotive glass, and photovoltaic encapsulation materials.

[0037] Compared with the prior art, the present invention has at least the following beneficial effects:

[0038] After dissolving PVA in deionized water in the present invention, a certain amount of strong acid is added. After stirring evenly, the PVA solution is degassed to remove most of the organic small molecule substances in the system and acetic acid hydrolyzed from the vinyl acetate units remaining on the polymer chain after adding the strong acid; subsequently, n-butyraldehyde is added, and ultrasonic waves are applied during the reaction process, which not only promotes the dispersion of the generated PVB resin, reduces sticking to the kettle wall, but also enhances the full contact reaction of n-butyraldehyde with alcohol hydroxyl groups, improves the conversion rate and acetal degree, and finally obtains a yellowing-resistant polyvinyl butyral resin; by using the preparation method provided by the present invention to prepare polyvinyl butyral resin, the yellowing resistance of the polyvinyl butyral resin can be significantly improved, thereby improving the yellowing resistance of the prepared PVB film, while producing less waste solvent and waste water, and improving the raw material conversion rate. Specific Embodiments

[0039] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0040] Example 1

[0041] In this example, a preparation method of a yellowing-resistant polyvinyl butyral resin is provided, and the preparation method includes the following steps:

[0042] (1) Dissolve 50 g of PVA1799 (Chuanwei brand) in 500 mL of deionized water at 95 °C to obtain a PVA solution; cool the PVA solution to 50 °C, add 5 mL of concentrated hydrochloric acid (mass fraction 36%-38%), keep warm and stir for 30 min, the stirring rate is 200 rpm, degas the obtained mixture, the degassing temperature is 80 °C, volatilize 150 mL of water (containing a small amount of hydrolysis products), then add 150 ml of water, and add hydrochloric acid. Among them, the added hydrochloric acid is converted into dry-state HCl (hydrogen chloride), and the mass ratio of dry-state HCl (hydrogen chloride) to dry-state PVA is 0.023:1 to obtain an aqueous PVA solution to be reacted;

[0043] (2) Cool the PVA aqueous solution system to 10 °C, with a stirring rate of 200 rpm. Dropwise add 35 g of n-butyraldehyde through an input pump. At the same time, ultrasonicate the reaction system (20 W / 40 KHZ). Control the addition of n-butyraldehyde to be completed within 30 min. Under ultrasonic conditions, this system first reacts at a low temperature of 10 °C for 15 min, and then is heated to 30 °C at a rate of 12 °C / h. After the system temperature exceeds 30 °C, it is heated to the curing temperature of 60 °C at a rate of 30 °C / h and kept at this temperature for reaction for 2 h;

[0044] (3) After the reaction is completed, first cool the system to 45 °C and then perform suction filtration to obtain the crude product; then mix the crude product with 1 wt.% NaOH aqueous solution, stir magnetically for 30 min and then perform suction filtration again; then mix the powder obtained by suction filtration with 1000 mL of pure water, stir magnetically at 45 °C for 15 min and then perform suction filtration again. Repeat this step 5 times. Finally, obtain the PVB resin powder after drying in a vacuum oven.

[0045] Example 2

[0046] In this example, a method for preparing a yellowing-resistant polyvinyl butyral resin is provided. The preparation method includes the following steps:

[0047] (1) Dissolve 50 g of PVA1799 (Chuanwei brand) in 400 mL of deionized water at 90 °C to obtain a PVA solution; cool the PVA solution to 40 °C, add 5 mL of concentrated hydrochloric acid (mass fraction 36%-38%), keep warm and stir for 20 min, with a stirring rate of 150 rpm. Perform degassing treatment on the obtained mixture. The degassing treatment temperature is 85 °C. Add 200 ml of water to the initial liquid level and add hydrochloric acid. Among them, convert the added hydrochloric acid into dry-state HCl (hydrogen chloride). The mass ratio of dry-state HCl (hydrogen chloride) to dry-state PVA is 0.023:1 to obtain the PVA aqueous solution to be reacted;

[0048] (2) Cool the PVA aqueous solution system to 5 °C, with a stirring rate of 200 rpm. Dropwise add 35 g of n-butyraldehyde through an input pump. At the same time, ultrasonicate the reaction system. Control the addition of n-butyraldehyde to be completed within 20 min. Under ultrasonic conditions, this system first reacts at a low temperature of 5 °C for 20 min, and then is heated to 35 °C at a rate of 15 °C / h. After the system temperature exceeds 35 °C, it is heated to the curing temperature of 65 °C at a rate of 35 °C / h and kept at this temperature for reaction for 1 h;

[0049] (3) After the reaction is completed, first cool the system to 45 °C and then perform suction filtration to obtain the crude product; then mix the crude product with a 1 wt.% aqueous NaOH solution, stir magnetically for 30 min and then perform suction filtration again; then mix the powder obtained by suction filtration with 1000 mL of pure water, stir magnetically at 45 °C for 15 min and then perform suction filtration again, repeat this step 5 times, and finally obtain the PVB resin powder after drying in a vacuum oven.

[0050] Comparative Example 1

[0051] In this comparative example, a method for preparing polyvinyl butyral resin is provided, and the preparation method includes the following steps:

[0052] (1) Dissolve 50 g of PVA1799 (Chuanwei brand) in 500 mL of deionized water at 95 °C to obtain a PVA solution; cool the PVA solution to 50 °C, add hydrochloric acid until the mass ratio of dry HCl (hydrogen chloride) to dry PVA is about 0.023:1, keep warm and stir for 30 min, and the stirring rate is 200 rpm to obtain a PVA / hydrochloric acid mixed aqueous solution;

[0053] (2) Cool the PVA / hydrochloric acid mixed aqueous solution system to 10 °C, and the stirring rate is 200 rpm. Dropwise add 35 g of n-butyraldehyde through an input pump, and at the same time perform ultrasonic treatment on the reaction system, control the n-butyraldehyde to be added dropwise within 30 min. The system first reacts at a low temperature of 10 °C for 15 min under ultrasonic conditions, and then heats up to 30 °C at a rate of 12 °C / h. After the system temperature exceeds 30 °C, heat up to the curing temperature of 60 °C at a rate of 30 °C / h, and keep warm and react for 2 h;

[0054] (3) After the reaction is completed, first cool the system to 45 °C and then perform suction filtration to obtain the crude product; then mix the crude product with a 1 wt.% aqueous NaOH solution, stir magnetically for 30 min and then perform suction filtration again; then mix the powder obtained by suction filtration with 1000 mL of pure water, stir magnetically at 45 °C for 15 min and then perform suction filtration again, repeat this step 5 times, and finally obtain the PVB resin powder after drying in a vacuum oven.

[0055] Comparative Example 2

[0056] In this comparative example, a method for preparing polyvinyl butyral resin is provided, and the preparation method includes the following steps:

[0057] (1) Dissolve 50 g of PVA1799 (Chuanwei brand) in 500 mL of deionized water at 95 °C to obtain a PVA solution; cool the PVA solution to 50 °C, add hydrochloric acid until the mass ratio of dry-state HCl (hydrogen chloride) to dry-state PVA is about 0.023:1, keep it warm and stir for 30 min, with a stirring rate of 200 rpm, conduct degassing treatment on the obtained mixture, and the degassing treatment temperature is 80 °C to obtain an aqueous PVA solution;

[0058] (2) Cool the aqueous PVA solution system to 10 °C, with a stirring rate of 200 rpm, dropwise add 35 g of n-butyraldehyde through an input pump, control the addition of n-butyraldehyde to be completed within 30 min, the system first reacts at a low temperature of 10 °C for 15 min, and then heats up to 30 °C at a rate of 12 °C / h. After the system temperature exceeds 30 °C, heat it up to the curing temperature of 60 °C at a rate of 30 °C / h, and keep it warm and react for 2 h;

[0059] (3) After the reaction is completed, first cool the system to 45 °C and then perform suction filtration to obtain a crude product; then mix the crude product with a 1 wt.% NaOH aqueous solution, stir magnetically for 30 min and then perform suction filtration again; then mix the powder obtained by suction filtration with 1000 mL of pure water, stir magnetically at 45 °C for 15 min and then perform suction filtration again. Repeat this step 5 times, and finally obtain PVB resin powder after drying in a vacuum oven.

[0060] Comparative Example 3

[0061] In this comparative example, a preparation method of polyvinyl butyral resin is provided, and the preparation method includes the following steps:

[0062] (1) Dissolve 50 g of PVA1799 (Chuanwei brand) in 500 mL of deionized water at 95 °C to obtain a PVA solution;

[0063] (2) Cool the PVA solution system to 10 °C, with a stirring rate of 200 rpm, dropwise add 35 g of n-butyraldehyde through an input pump, and add hydrochloric acid until the mass ratio of dry-state HCl (hydrogen chloride) to dry-state PVA is about 0.023:1. At the same time, perform ultrasonic treatment on the reaction system, control the addition of n-butyraldehyde to be completed within 30 min, the system first reacts at a low temperature of 10 °C for 15 min under ultrasonic conditions, and then heats up to 30 °C at a rate of 12 °C / h. After the system temperature exceeds 30 °C, heat it up to the curing temperature of 60 °C at a rate of 30 °C / h, and keep it warm and react for 2 h;

[0064] (3) After the reaction is completed, first cool the system to 45 °C and then perform suction filtration to obtain the crude product; then mix the crude product with 1 wt.% NaOH aqueous solution, stir magnetically for 30 min and then perform suction filtration; then mix the powder obtained by suction filtration with 1000 mL of pure water, stir magnetically at 45 °C for 15 min and then perform suction filtration. Repeat this step 5 times. Finally, obtain the PVB resin powder after drying in a vacuum oven.

[0065] Perform performance tests on the polyvinyl butyral resins provided in the examples and comparative examples. The test methods are as follows:

[0066] (1) Acetal degree test: Adopt the hydroxylamine hydrochloride method. Take 0.3 g (accurate to 0.0001 g) of PVB resin and 30 mL of ethanol, add them to a three-necked flask, heat to reflux, and then add an aqueous solution of hydroxylamine hydrochloride (15 mL, 20 wt%) to the above solution. React continuously at the reflux temperature (about 357.15 K) for 3 h. Finally, cool the obtained solution to room temperature and perform potentiometric titration with a NaOH standard solution (0.5 mol / L). The mass acetal degree (w BA ) is calculated according to the following formula:

[0067]

[0068] In the formula, m is the mass of the PVB resin sample taken, g;

[0069] C NaOH is the concentration of the NaOH standard solution, mol / L;

[0070] V is the volume of the NaOH standard solution consumed in the titration of the experimental group, mL;

[0071] V0 is the volume of the NaOH standard solution consumed in the titration of the blank group, mL.

[0072] (2) GPC test: Use a gel permeation chromatograph (waters Alliance). Weigh 1 - 2 mg of PVB sample and dissolve it in 1 mL of THF. After filtering with a 0.45 μm filter membrane, place it in an injection bottle and inject it using a gel permeation chromatograph to obtain the PVB molecular weight and molecular weight distribution range, and observe whether there is a small molecule tailing phenomenon;

[0073] (3) Yellowing index test: Use a spectrophotometer (HunterLab Ultrascan VIS). According to the ASTM D1003 standard, analyze using a D65 light source and a 10° observation angle. In the RSIN mode, use a C light source and a 2° TTRAN test, and use a forced-air oven to heat the sample.

[0074] The performance test results are shown in Table 1.

[0075] Table 1

[0076]

[0077] As can be seen from Table 1, the polyvinyl butyral resins obtained by using the preparation method provided in the embodiments of the present invention all have excellent yellowing resistance (yellow index after 150°C / 3h: 17.5 - 19.3).

[0078] Compared with Example 1, the polyvinyl butyral resin oligomer provided in Comparative Example 1 has more trailing, and the yellowing resistance performance decreases; the polyvinyl butyral resin provided in Comparative Example 2 has no small molecule trailing, but the yellowing resistance performance also decreases; the polyvinyl butyral resin provided in Comparative Example 3 has a decrease in acetal degree and conversion rate, and at the same time there are oligomers, and the yellowing resistance performance decreases significantly.

[0079] The applicant declares that the present invention uses the above embodiments to illustrate the yellowing-resistant polyvinyl butyral resin and its preparation method and application of the present invention, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent substitution of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing yellowing-resistant polyvinyl butyral resin, characterized in that: The preparation method comprises the following steps: (1) dissolving polyvinyl alcohol in deionized water, then adding a strong acid, stirring, degassing the obtained mixed solution, and then adding a strong acid to obtain a polyvinyl alcohol aqueous solution to be reacted; (2) The polyvinyl alcohol aqueous solution and n-butyraldehyde are mixed and reacted under ultrasonic conditions to obtain the yellowing-resistant polyvinyl butyral resin.

2. The preparation method according to claim 1, characterized in that: The strong acid in step (1) includes any one of hydrochloric acid, perchloric acid, sulfuric acid, and nitric acid, or a combination of at least two thereof; Preferably, the strong acid is added in the form of a strong acid aqueous solution.

3. The preparation method according to claim 1 or 2, characterized in that: In step (1), based on 50 parts by mass of polyvinyl alcohol, the amount of deionized water used is 300-700 parts; Preferably, in step (1), based on 50 parts by mass of polyvinyl alcohol, the amount of the strong acid added for the first time is 0.25-5 parts; Preferably, in step (1), the mass ratio of the added strong acid to the polyvinyl alcohol is (0.005-0.1):

1.

4. The preparation method according to any one of claims 1 to 3, characterized in that The step (1) of dissolving polyvinyl alcohol in deionized water specifically comprises: dissolving polyvinyl alcohol in deionized water at 90-100° C.; Preferably, when adding the strong acid in step (1), the system temperature is controlled to be 20-60°C.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The stirring time in step (1) is 20-60 min; Preferably, the stirring rate in step (1) is 100-300 rpm; Preferably, the degassing temperature in step (1) is 80-90°C; Preferably, the mass ratio of the polyvinyl alcohol to the n-butyraldehyde is (1.2-2):

1.

6. The preparation method according to any one of claims 1 to 5, characterized in that: When the polyvinyl alcohol aqueous solution and n-butyraldehyde are mixed in step (2), the temperature of the polyvinyl alcohol aqueous solution is controlled to be 0-30° C.; Preferably, the step (2) of mixing the polyvinyl alcohol aqueous solution and n-butyraldehyde comprises: adding n-butyraldehyde dropwise to the polyvinyl alcohol aqueous solution while stirring the polyvinyl alcohol aqueous solution, and simultaneously subjecting the system to ultrasound; Preferably, the dripping comprises dripping through an input pump; Preferably, the dropwise addition of n-butyraldehyde is controlled to be completed within 20-40 minutes.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The reaction in step (2) specifically comprises: first reacting at 0-30°C for 10-20 minutes, then heating to 25-35°C at a rate of 10-15°C / h, and after the system temperature reaches 25-35°C, heating to a aging temperature of 55-65°C at a rate of 25-35°C / h, and keeping the temperature for reaction for 1-3 hours; Preferably, the reaction in step (2) is followed by a purification step.

8. A preparation method according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: (1) dissolving polyvinyl alcohol in deionized water at 90-100° C., cooling to 20-60° C., then adding a strong acid aqueous solution, stirring at a rate of 100-300 rpm for 20-60 min, degassing the obtained mixed solution at 80-90° C., and then adding a strong acid to obtain a polyvinyl alcohol aqueous solution to be reacted; (2) cooling the polyvinyl alcohol aqueous solution to 0-30° C., while stirring the polyvinyl alcohol aqueous solution, adding n-butyraldehyde thereto through an input pump, and simultaneously subjecting the system to ultrasonic treatment to control the n-butyraldehyde to be added within 20-40 min. The system is first reacted at 0-30° C. for 10-20 min under ultrasonic conditions, and then heated to 25-35° C. at a rate of 10-15° C. / h. After the system temperature reaches 25-35° C., it is heated to a aging temperature of 55-65° C. at a rate of 25-35° C. / h. The reaction is carried out at this temperature for 1-3 h, and then purified to obtain the yellowing-resistant polyvinyl alcohol butyral resin.

9. A yellowing-resistant polyvinyl butyral resin, characterized in that: The yellowing-resistant polyvinyl butyral resin is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the yellowing-resistant polyvinyl butyral resin according to claim 9 in architectural glass, automotive glass, and photovoltaic packaging materials.

Images