Preparation method of inorganic acid and organic acid synergistically catalyzing polyvinyl butyral synthesis

Abstract

The application discloses a synthesis method of polyvinyl butyral resin and belongs to the technical field of synthetic resin of high polymer materials. In view of the problems of difficulty in controlling the reaction process, easy degradation of polyvinyl main chain and insufficient product performance stability in the preparation of polyvinyl butyral by using single inorganic strong acid or single organic acid catalysis in the prior art, the application introduces an organic acid and inorganic acid synergistic catalytic system in the acetal reaction process, so that the two types of acids jointly play a catalytic role in the reaction system to synergistically control the acetal reaction process. By the technical scheme, the controllability of the reaction process is improved while the acetal reaction efficiency is ensured, which is conducive to inhibiting the acid degradation of the polyvinyl main chain and improving the structural uniformity and performance stability of the obtained polyvinyl butyral. The method of the application is suitable for industrial preparation of polyvinyl butyral, and the obtained product can be applied to the fields of laminated safety glass, functional glass, photovoltaic components and paint and the like.

Description

Technical Field

[0001] This invention belongs to the field of synthetic resin technology, and particularly emphasizes a method for synthesizing a high-acetal-degree polyvinyl butyral resin using a synergistic catalysis of inorganic and organic acids. Background Technology

[0002] Polyvinyl butyral (PVB) is a polymer material produced by the acetal reaction of polyvinyl alcohol (PVA) and butyraldehyde (BA) under acidic catalysis. Its molecular structure contains both butyraldehyde structural units and a certain proportion of hydroxyl functional groups, giving it excellent flexibility, adhesion, and optical transparency. Due to its structural characteristics, PVB has significant applications in industry, particularly in laminated safety glass. As an interlayer material in architectural and automotive glass, it effectively absorbs fragments when the glass breaks, significantly improving the safety performance of glass products. Furthermore, PVB can be used in photovoltaic module encapsulation, functional glass, coatings, adhesives, and electronic materials, playing a crucial role in improving product structural stability, impact resistance, and service life.

[0003] Currently, PVB is typically prepared using a precipitation method, which involves using polyvinyl alcohol (PVA) as a raw material and reacting it with butyraldehyde (BA) in the presence of an acid catalyst to undergo an acetal reaction. After the reaction is complete, the product undergoes steps such as water treatment and drying to obtain polyvinyl butyral resin. The type of acid catalyst and the reaction conditions have a significant impact on the acetal reaction process and the performance of the final product. In existing technologies, commonly used acid catalysts mainly fall into two categories: inorganic strong acids and organic acids. Inorganic strong acids (such as hydrochloric acid and sulfuric acid) have strong acidity and high reactivity, which can accelerate the acetal reaction rate, allowing the reaction to be completed in a shorter time. However, due to the strong acidity of inorganic strong acids, a localized strong acid environment is easily formed during the reaction. This not only makes it difficult to precisely control the acetal reaction process but also easily triggers acid degradation of the polyvinyl alcohol backbone, leading to agglomeration and a decrease in molecular weight, thus adversely affecting the mechanical properties, film-forming properties, and long-term stability of polyvinyl butyral. Meanwhile, strong inorganic acids are typically highly corrosive and volatile, adversely affecting production equipment and the operating environment. Furthermore, the presence of significant inorganic ion residues after the reaction increases energy consumption for subsequent washing and wastewater treatment. In contrast, organic acids (such as acetic acid, oxalic acid, and p-toluenesulfonic acid) are relatively weaker, which can mitigate the acetal reaction process to some extent, reducing the risk of polyvinyl alcohol (PVA) main chain degradation and improving the mildness of the reaction. However, using only organic acids as catalysts results in limited activation capacity, slow reaction rates, and long reaction times, making it difficult to further improve acetal conversion efficiency and hindering industrial production efficiency. Therefore, existing PVB preparation methods using single strong inorganic or single organic acids as catalysts have limitations in terms of reaction controllability, product performance stability, and industrial adaptability. To overcome these problems, there is an urgent need in this field to improve acid catalysis systems, ensuring acetal reaction efficiency while achieving a mild and controllable reaction process, and balancing product performance with environmental friendliness. Based on this, we explore a method for preparing polyvinyl butyral through the synergistic catalysis of inorganic strong acid and organic acid. By utilizing the complementary effects of the two types of acids in terms of reactivity and acid regulation, the acetal reaction process can be synergistically regulated, thereby improving the controllability of the reaction and enhancing the overall performance of the product. This has significant research significance and application value. Summary of the Invention

[0004] To address the shortcomings of existing processes, this invention provides a method for preparing polyvinyl butyral based on the synergistic catalysis of inorganic and organic acids. By leveraging the synergistic effect of the two types of acids in terms of reactivity and acidity regulation, the reaction process is made more stable and controllable while ensuring the smooth progress of the acetal reaction.

[0005] To achieve the objective of this invention, the method for preparing polyvinyl butyral based on the synergistic catalysis of inorganic and organic acids is implemented through the following technical solution: (1) Weigh 100 parts of polyvinyl alcohol and add it to a certain proportion of water. Stir and heat to 90-100℃ to completely dissolve it in water and prepare a polyvinyl alcohol aqueous solution with a mass concentration of 5-8%. (2) Cool the polyvinyl alcohol aqueous solution to 55-65℃, add 0.5-2 parts of surfactant, and then add 1-5 parts of inorganic acid and organic acid in overlapping time periods to completely dissolve them into a mixed aqueous solution. (3) After cooling the mixed aqueous solution to 5-20℃, add 40-90 parts of n-butyraldehyde dropwise over 0.5-1.5h; (4) Maintain the temperature at 5-20℃ and continue the reaction for 1-2 hours; (5) After slowly raising the temperature to 55-65℃, maintain the temperature at 55-65℃ and continue the reaction for 1-3 hours; (6) After the reaction is complete, filter the emulsion, wash it 3-5 times, and then dry it at 40-60℃ for 6-12 hours to obtain polyvinyl butyral resin.

[0006] In steps (2) and (3), the polyvinyl alcohol is one of PVA1799 and PVA2499; the surfactant is selected from any one or a mixture of at least two of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate or sodium dodecyl sulfate; the molar ratio of inorganic acid to organic acid is 1:(0.5-20); the inorganic acid is selected from any one or a mixture of at least two of hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid; and the organic acid is selected from any one or a mixture of at least two of p-toluenesulfonic acid, oxalic acid, maleic acid, and trichloroacetic acid.

[0007] In step (3), n-butyraldehyde should be added at a constant rate.

[0008] In step (5), the heating process should not be faster than about 1-2℃ / min.

[0009] In step (6), the water is washed 3-5 times in clean water at 50-60℃.

[0010] This invention utilizes the synergistic effect of inorganic and organic acids in terms of reactivity and acidity regulation to ensure the smooth progress of the acetal reaction while making the reaction process more stable and controllable. Compared with other inventions, this invention has the following beneficial technical effects: (1) This invention reduces the amount of inorganic acid in the reaction system, thereby inhibiting the acid degradation reaction of the polyvinyl alcohol backbone under strong acid conditions, which is beneficial to maintaining the molecular weight level and mechanical properties of polyvinyl butyral. (2) The present invention improves the uniformity of the acetal reaction on the polyvinyl alcohol molecular chain, reduces the occurrence of local over-acetalization or incomplete reaction, thereby improving the structural uniformity and performance consistency of the obtained polyvinyl butyral product. (3) The present invention improves the acetal reaction efficiency without significantly prolonging the reaction time, overcomes the problem of low reaction rate when organic acid is used alone for catalysis, and makes the preparation method more suitable for industrial continuous or semi-continuous production. (4) This invention reduces the amount of inorganic ions remaining in the system after the reaction, simplifies the subsequent neutralization and washing processes, reduces the burden of wastewater treatment, and thus improves the safety and environmental friendliness of the production environment.

[0011] The polyvinyl butyral resin obtained by this invention is a white powder with an adjustable acetal content ranging from 67% to 86%, a weight-average molecular weight of 17-30 wDa, a viscosity of 30-80 mPa·s in a 5% ethanol solution, and a concentration of 2.5 kg / m³. 3 The intrinsic viscosity in ethanol solution is 0.83-1.35 dL / g, and the glass transition temperature is 66-76℃. Detailed Implementation

[0012] To better explain the present invention, specific embodiments of the present invention will be described below with reference to specific examples.

[0013] This invention provides a method for the synthesis of polyvinyl butyral by the synergistic catalysis of inorganic and organic acids, the specific steps of which are as follows: (1) Weigh 100 parts of polyvinyl alcohol using a balance, pour the weighed polyvinyl alcohol into a three-necked flask, measure a certain amount of water, pour it into the three-necked flask, install a thermometer and reflux condenser, heat to 90-100℃, and stir to completely dissolve it. (2) Cool the polyvinyl alcohol aqueous solution obtained in (1) to 55-65℃, weigh 0.5-2 parts of surfactant and add it, stir to dissolve it completely, and then add 1-5 parts of inorganic acid and organic acid in an overlapping time period according to a molar ratio of 1:(0.5-20), and stir to dissolve it completely. (3) Continue cooling to 5-20℃. After the temperature stabilizes, slowly add 40-90 parts of n-butyraldehyde. The n-butyraldehyde is added slowly over 0.5-1.5 hours using an injection pump. (4) Continue the reaction at 5-20℃ for 1-2 hours; (5) After reacting at 5-20℃ for 1-2 hours, slowly raise the temperature to 55-65℃ within 30-50 minutes and continue the reaction at 55-65℃ for 1-3 hours. (6) After the reaction is complete, the resulting emulsion is filtered, washed 3-5 times, and then dried at 40-60℃ for 6-12h to obtain white powdered polyvinyl butyral resin.

[0014]

Example 1

[0015]

Example 2

[0016]

Example 3

[0017]

Example 4

[0018] Comparative Example 1 Weigh 5.0 g of polyvinyl alcohol (179 g) into a three-necked flask. Measure 80 ml of water using a graduated cylinder and add it to the flask. Install a condenser and thermometer, and slowly heat to 95°C. Stir at 95°C for 40 minutes to completely dissolve the polyvinyl butyral. Stop heating after dissolution and allow the solution to cool to 60°C. Then, add 0.03 g of weighed sodium dodecyl sulfonate to the flask at 60°C and stir until completely dissolved. Next, add 0.056 g of 38% hydrochloric acid to the reaction system and stir to mix. After the mixture was homogenized and cooled to 15°C, the heating was turned on to maintain the solution at 15°C. 5.0 ml of n-butyraldehyde was added at a rate of 3 ml / h. After the addition of n-butyraldehyde was complete, the reaction was continued at 15°C for 1 hour. After 1 hour, the temperature was slowly increased to 60°C, and the reaction was carried out at 60°C for 1.5 hours. After the reaction was completed, the resulting white emulsion was filtered and washed to obtain a white polyvinyl butyral powder. The filtered white polyvinyl butyral powder was dried at 50°C for 8 hours to obtain 7.2 g of the product polyvinyl butyral. The acetal degree of the obtained product was 76%, the weight-average molecular weight was 18 wDa, the viscosity was 56.73 mPa·s, the intrinsic viscosity was 1.00 dL / g, and the glass transition temperature was 71.2°C.

[0019] Comparative Example 2 Weigh 5.0 g of polyvinyl alcohol (PVA) into a three-necked flask. Measure 80 ml of water using a graduated cylinder and add it to the flask. Install a condenser and thermometer, and slowly heat to 95°C. Stir at 95°C for 40 minutes to completely dissolve the PVA butyral. After dissolution, stop heating and allow the solution to cool to 60°C. Then, add 0.03 g of weighed sodium dodecyl sulfonate to the flask at 60°C and stir until completely dissolved. Finally, add 0.250 g of... Toluenesulfonic acid was added to the reaction system and stirred until homogeneous. After the solution cooled to 15°C, heating was started to maintain the solution at 15°C. 5.0 ml of n-butyraldehyde was added at a rate of 3 ml / h. After the addition of n-butyraldehyde was complete, the reaction was continued at 15°C for 1 h. After 1 h, the temperature was slowly increased to 60°C and the reaction was carried out at 60°C for 1.5 h. After the reaction was completed, the resulting white emulsion was filtered and washed to obtain a white polyvinyl butyral powder. The filtered white polyvinyl butyral powder was dried at 50°C for 8 h to obtain 6.6 g of the product polyvinyl butyral. The obtained product had an acetal degree of 72%, a weight-average molecular weight of 14 wDa, a viscosity of 51.22 mPa·s, an intrinsic viscosity of 0.95 dL / g, and a glass transition temperature of 69.1°C.

[0020] Comparative Example 3 Weigh 5.0 g of polyvinyl alcohol (1799 g) into a three-necked flask. Measure 80 ml of water using a graduated cylinder and add it to the flask. Install a condenser and thermometer, and slowly heat to 95°C. Stir at 95°C for 40 minutes to completely dissolve the polyvinyl butyral. Stop heating after dissolution and allow the solution to cool to 60°C. Then, add 0.03 g of weighed sodium dodecyl sulfonate to the flask at 60°C and stir until completely dissolved. Next, add 0.131 g of oxalic acid to the reaction system and stir until well mixed. After the solution cooled to 15°C, heating was started to maintain the solution at 15°C. 5.0 ml of n-butyraldehyde was added at a rate of 3 ml / h. After the addition of n-butyraldehyde was complete, the reaction was continued at 15°C for 1 hour. After 1 hour, the temperature was slowly increased to 60°C, and the reaction was carried out at 60°C for 1.5 hours. After the reaction was completed, the resulting white emulsion was filtered and washed to obtain a white polyvinyl butyral powder. The filtered white polyvinyl butyral powder was dried at 50°C for 8 hours to obtain 6.4 g of the product polyvinyl butyral. The obtained product had an acetal degree of 71%, a weight-average molecular weight of 17 wDa, a viscosity of 55.26 mPa·s, an intrinsic viscosity of 1.13 dL / g, and a glass transition temperature of 70.3°C.

[0021] Comparative Example 4 Weigh 5.0 g of polyvinyl alcohol (179 g) into a three-necked flask. Measure 80 ml of water using a graduated cylinder and add it to the flask. Install a condenser and thermometer, and slowly heat to 95°C. Stir at 95°C for 40 minutes to completely dissolve the polyvinyl butyral. Stop heating after dissolution and allow the solution to cool to 60°C. Then, add 0.03 g of weighed sodium dodecyl sulfonate to the flask at 60°C and stir until completely dissolved. Next, add 0.168 g of maleic acid to the reaction system and stir until homogeneous. After the solution cooled to 15°C, heating was started to maintain the solution at 15°C. 5.0 ml of n-butyraldehyde was added at a rate of 3 ml / h. After the addition of n-butyraldehyde was complete, the reaction was continued at 15°C for 1 hour. After 1 hour, the temperature was slowly increased to 60°C, and the reaction was carried out at 60°C for 1.5 hours. After the reaction was completed, the resulting white emulsion was filtered and washed to obtain a white polyvinyl butyral powder. The filtered white polyvinyl butyral powder was dried at 50°C for 8 hours to obtain 6.7 g of the product polyvinyl butyral. The acetal degree of the obtained product was 72%, the weight-average molecular weight was 14 wDa, the viscosity was 49.5 mPa·s, the intrinsic viscosity was 0.99 dL / g, and the glass transition temperature was 68.17°C.

[0022] Comparative Example 5 Weigh 5.0 g of polyvinyl alcohol (1799 g) into a three-necked flask. Measure 80 ml of water using a graduated cylinder and add it to the flask. Install a condenser and thermometer, and slowly heat to 95°C. Stir at 95°C for 40 minutes to completely dissolve the polyvinyl butyral. Stop heating after dissolution and allow the solution to cool to 60°C. Then, add 0.03 g of weighed sodium dodecyl sulfonate to the flask at 60°C and stir until completely dissolved. Next, add 0.237 g of trichloroacetic acid to the reaction system and stir until homogeneous. After the solution cooled to 15°C, heating was started to maintain the solution at 15°C. 5.0 ml of n-butyraldehyde was added at a rate of 3 ml / h. After the addition of n-butyraldehyde was complete, the reaction was continued at 15°C for 1 hour. After 1 hour, the temperature was slowly increased to 60°C, and the reaction was carried out at 60°C for 1.5 hours. After the reaction was completed, the resulting white emulsion was filtered and washed to obtain a white polyvinyl butyral powder. The filtered white polyvinyl butyral powder was dried at 50°C for 8 hours to obtain 7.5 g of the product polyvinyl butyral. The obtained product had an acetal degree of 69%, a weight-average molecular weight of 15 wDa, a viscosity of 51.74 mPa·s, an intrinsic viscosity of 1.02 dL / g, and a glass transition temperature of 68.21°C.

Claims

1. A method for preparing polyvinyl butyral through the synergistic catalysis of inorganic and organic acids, characterized in that, The method introduces organic and inorganic acids during the acetal reaction stage, so that the organic and inorganic acids coexist in the reaction system during the acetal reaction, thereby synergistically regulating the acidity of the reaction system and obtaining polyvinyl butyral resin.

2. The method as described in claim 1, characterized in that, The method includes the following steps: (1) Weigh a certain amount of polyvinyl alcohol and add it to water, heat it to 90-100℃, stir it to completely dissolve it in water, and form a polyvinyl alcohol aqueous solution. (2) After dissolution, cool the polyvinyl alcohol aqueous solution to 55-65℃, add the surfactant, and then add the inorganic acid and organic acid in overlapping time periods to completely dissolve them into a mixed aqueous solution. (3) After cooling the mixed aqueous solution to 5-20℃, add n-butyraldehyde in a certain proportion; (4) Maintain the temperature at 5-20℃ and continue the reaction for 1-2 hours; (5) After slowly raising the temperature to 55-65℃, maintain the temperature at 55-65℃ and continue the reaction for 1-3 hours; (6) After the reaction is complete, the resulting emulsion is filtered, washed 3-5 times at 50-65℃, and then dried at 40-60℃ for 6-12 hours to obtain polyvinyl butyral resin.

3. The method according to claim 2, characterized in that... In step (1), the mass concentration of the polyvinyl butyral aqueous solution is 5-8%, and the dissolution process is completed within 0.5-1.5 hours.

4. The method according to claim 2, characterized in that... The mass ratios of each substance in steps (2) and (3) are as follows: based on 100 parts of polyvinyl alcohol, the amount of surfactant is 0.5-2 parts, the amount of inorganic acid and organic acid is 1-5 parts, the molar ratio of organic acid to inorganic acid is (0.5-20):1, and the amount of n-butyraldehyde is 40-90 parts. Preferably, the polyvinyl alcohol is selected from PVA1799 and PVA2499; Preferably, the surfactant is selected from any one or a mixture of at least two of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, or sodium dodecyl sulfate; Preferably, the inorganic acid is selected from any one or a mixture of at least two of hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid; Preferably, the organic acid is selected from any one or a mixture of at least two of p-toluenesulfonic acid, oxalic acid, maleic acid, and trichloroacetic acid.

5. The method according to claim 2, characterized in that... The reaction times in steps (4), (5), and (6) are 1-2h, 1-3h, and 0.5-1h respectively, when the temperatures are in a wide temperature range of 5-20℃, 55-65℃, and 50-65℃.

6. The method according to claim 2, characterized in that... The synergistic catalytic system maintains acetal reaction efficiency while reducing the amount of inorganic acid used, making the preparation method suitable for continuous or semi-continuous industrial production.