A method for synthesizing polyvinyl butyral resin
By using a deep eutectic solvent catalytic reaction medium and a microchannel reaction device, the problems of equipment corrosion and insufficient catalytic activity in traditional processes have been solved, enabling efficient and green synthesis of PVB resin and improving the uniformity and transparency of the product.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 四川东材新材料有限责任公司
- Filing Date
- 2026-01-13
- Publication Date
- 2026-06-02
AI Technical Summary
In existing technologies, strong protic acid catalysts cause problems such as equipment corrosion, numerous side reactions, acidic wastewater discharge, and complex processes, as well as insufficient catalytic activity and poor reusability of ion exchange resins.
A deep eutectic solvent catalyzes the reaction medium, weakening the hydrogen bond network between PVA molecular chains through hydrogen bonding, thereby improving swelling and exposing reactive sites. Combined with microenvironment acid-base regulation, a highly efficient condensation reaction between PVA and n-butyraldehyde is achieved. A microchannel reaction device is used for two-stage condensation.
It achieves efficient and green synthesis of PVB resin, with uniform particle size, excellent solubility and high transparency, avoiding equipment corrosion and wastewater discharge, and improving catalytic activity and production efficiency.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer synthesis technology, specifically a method for synthesizing polyvinyl butyral resin. Background Technology
[0002] Polyvinyl butyral (PVB) resin is an important chemical product, produced by the acetalization reaction of polyvinyl alcohol (PVA) and n-butyral under acid catalysis. Based on differences in molecular weight, the number of hydroxyl groups, acetal groups, and acetyl groups in the molecular structure, PVB resin can be widely used in various fields such as safety glass, inks, adhesives, and coatings.
[0003] Currently, the commonly used catalysts in the industrial production of PVB resin mainly include strong protic acids such as hydrochloric acid, sulfuric acid, and p-toluenesulfonic acid, or ion exchange resins. These catalysts catalyze the acetalization reaction of PVB with n-butyraldehyde to achieve product preparation. However, using strong protic acids as catalysts can easily cause equipment corrosion and may trigger numerous side reactions. Furthermore, neutralization and separation are required after the reaction, making the process relatively complex and generating acidic wastewater. While ion exchange resins can alleviate equipment corrosion problems to some extent, they suffer from insufficient catalytic activity and poor reusability in practical applications, affecting production efficiency and product stability.
[0004] Therefore, it is extremely important to provide a method for synthesizing polyvinyl butyral resin that can avoid the drawbacks of traditional processes such as equipment corrosion, wastewater discharge, and insufficient catalytic efficiency. Summary of the Invention
[0005] The purpose of this invention is to provide a method for synthesizing polyvinyl butyral resin, which solves the problems of equipment corrosion, numerous side reactions, acidic wastewater discharge and complex subsequent treatment caused by strong protic acid catalysis in traditional processes, and achieves efficient and green synthesis of PVB resin.
[0006] The objective of this invention is achieved through the following technical solution: A method for synthesizing polyvinyl butyral resin includes the following steps: S1. PVA powder is added to a deep eutectic solvent catalytic reaction medium and stirred until PVA is completely dissolved into a transparent solution to obtain a PVA-deep eutectic solvent solution; the deep eutectic solvent catalytic reaction medium is a eutectic mixture formed by the interaction of hydrogen bond donors and hydrogen bond acceptors through non-covalent bonds. S2. Under inert gas protection, the PVA-deep eutectic solvent solution and n-butyraldehyde are subjected to a condensation reaction. After the reaction is completed, the reaction solution is slowly poured into a large amount of deionized water, and a white solid is precipitated. After washing and drying, polyvinyl butyral resin is obtained.
[0007] This invention utilizes a deep eutectic solvent with specific composition and properties as a catalytic reaction medium. This medium exhibits dual advantages during the reaction: it not only weakens the hydrogen bond network between PVA molecular chains during PVA dissolution through hydrogen bonding, thereby improving the swelling performance of PVA and the exposure of reactive sites; but also precisely controls the acetalization reaction process through its microenvironmental acid-base regulation function—ensuring efficient condensation of PVA hydroxyl groups with n-butyraldehyde while inhibiting cross-linking side reactions caused by excessive acetalization. The resulting PVB resin possesses characteristics such as uniform particle size, excellent solubility, and high transparency.
[0008] As some possible implementation methods of this application, in step S1, the average degree of polymerization of PVA is 1500~3500 and the degree of hydrolysis is 88~100%.
[0009] As one possible implementation of this application, in step S1, the deep eutectic solvent catalytic reaction medium is prepared by heating and stirring at 90-100°C to form a uniform and transparent system. This temperature range can promote the full interaction between hydrogen bond donors and hydrogen bond acceptors, ensuring the formation of a structurally stable and uniformly performing catalytic medium, avoiding fluctuations in catalytic efficiency caused by uneven medium dispersion, and providing a reliable foundation for the subsequent efficient dissolution and acetalization reaction of PVA.
[0010] As one possible implementation method of this application, in step S1, the PVA dissolution temperature is 65~75℃. This temperature ensures that the PVA powder dissolves quickly and fully to form a transparent solution without damaging the catalytic structure and performance of the deep eutectic solvent. At the same time, it allows the PVA molecular chains to stretch appropriately, further increasing the exposure of reactive sites and creating favorable conditions for the subsequent uniform condensation with n-butyraldehyde, thus helping to ensure the uniformity of the product particle size.
[0011] As some possible implementations of this application, in step S1, the hydrogen bond acceptor is choline chloride, and the hydrogen bond donor is selected from one or more of glycerol, ethylene glycol, urea, and oxalic acid.
[0012] As one possible implementation of this application, in step S2, the molar ratio of PVA to n-butyraldehyde in the PVA-deep eutectic solvent solution is 1:(0.5~1).
[0013] As some possible implementations of this application, in step S2, the condensation reaction includes two stages, both in a microchannel reaction device; the first stage involves reacting the PVA-deep eutectic solvent solution and n-butyraldehyde at a constant temperature for 0.8-1.5 hours; the second stage involves uniformly heating to 75-95°C at a heating rate of 5-7 min / °C after the first stage of the reaction is completed, and then holding the temperature for 2-5 hours.
[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention utilizes a deep eutectic solvent catalytic reaction medium with specific composition and properties. This medium can achieve efficient catalysis without relying on strong protic acids, effectively avoiding the problems of equipment corrosion, increased side reactions, and acidic wastewater discharge that are easily caused by strong acid systems. It also eliminates complex neutralization and separation steps, simplifying the process flow. On the other hand, its catalytic activity is significantly better than that of traditional ion exchange resins, and it can stably exert its catalytic effect without frequent replacement, thus improving the shortcomings of the latter, such as insufficient activity and poor reusability.
[0015] Meanwhile, this catalytic reaction medium can weaken the hydrogen bond network between PVA molecular chains through hydrogen bonding, significantly improving the swelling capacity of PVA and the exposure of reactive sites. Furthermore, its unique microenvironment acid-base regulation capability controls the acetalization reaction process—ensuring efficient condensation of PVA hydroxyl groups with n-butyraldehyde, effectively improving reaction efficiency, while suppressing cross-linking side reactions caused by excessive acetalization. The resulting PVB resin exhibits uniform particle size, excellent ethanol solubility, high light transmittance, and outstanding bonding performance in practical applications, successfully achieving the goal of green, efficient, and high-quality synthesis of PVB resin. Detailed Implementation
[0016] Example 1 S1. Weigh out the appropriate mass of choline chloride and urea according to the molar ratio of choline chloride: urea = 1:2, mix the two together, heat to 93°C and stir until a homogeneous, colorless and transparent deep eutectic solvent is formed. 100g of polyvinyl alcohol 1799 was slowly added to 760ml of the prepared deep eutectic solvent and stirred continuously until the PVA was completely dissolved to form a transparent solution. Then the temperature was lowered to 70℃ to obtain the PVA-deep eutectic solvent solution. S2. Under inert gas protection, the above PVA-deep eutectic solvent solution and n-butyraldehyde (the molar ratio of PVA to n-butyraldehyde in the PVA-deep eutectic solvent solution is 1:0.5) are mixed through a microchannel reaction device, then heated to 60°C and kept at that temperature for 1 hour; the temperature is then increased to 80°C at a rate of 6 min / °C and kept at that temperature for 3 hours; after the reaction is completed, the reaction solution is slowly poured into a large amount of deionized water, and a white solid is precipitated. After repeated washing with deionized water, the solid is centrifuged and dried to obtain polyvinyl butyral resin.
[0017] The residual hydroxyl content in the resin was determined by titration, and the acetalization conversion rate was calculated to be 82%.
[0018] Example 2 S1. Weigh out the appropriate amounts of choline chloride and oxalic acid according to the molar ratio of choline chloride to oxalic acid = 1:2. Mix the two together and heat to 95°C while stirring until a homogeneous, colorless, and transparent deep eutectic solvent is formed. Slowly add 100g of polyvinyl alcohol 2488 to 880ml of the above deep eutectic solvent and continue stirring until the PVA is completely dissolved to form a transparent solution. Then cool to 70°C to obtain a PVA-deep eutectic solvent solution. S2. Under inert gas protection, the above PVA-deep eutectic solvent solution and n-butyraldehyde (the molar ratio of PVA to n-butyraldehyde in the PVA-deep eutectic solvent solution is 1:0.8) are mixed through a microchannel reaction device, and then heated to 65°C and kept at that temperature for 1 hour; the temperature is then increased to 80°C at a heating rate of 6 min / °C and kept at that temperature for 5 hours; after the reaction is completed, the reaction solution is slowly poured into a large amount of deionized water, and a white solid is precipitated. After repeated washing with deionized water, the solid is centrifuged and dried to obtain polyvinyl butyral resin.
[0019] The residual hydroxyl content in the resin was determined by titration, and the acetalization conversion rate was calculated to be 88%.
[0020] Example 3 S1. Weigh out the appropriate amounts of choline chloride and ethylene glycol according to the molar ratio of choline chloride: ethylene glycol = 1:2. Mix the two together and heat to 95°C while stirring until a homogeneous, colorless, and transparent deep eutectic solvent is formed. Separately, slowly add 100g of polyvinyl alcohol 3598 to 1650ml of the above deep eutectic solvent and continue stirring until the PVA is completely dissolved to form a transparent solution. Then cool to 70°C to obtain a PVA-deep eutectic solvent solution. S2. Under inert gas protection, the above PVA-deep eutectic solvent solution and n-butyraldehyde (the molar ratio of PVA to n-butyraldehyde in the PVA-deep eutectic solvent solution is 1:1) are mixed through a microchannel reaction device, and then heated to 70°C and kept at that temperature for 1 hour; the temperature is then increased to 90°C at a heating rate of 6 min / °C and kept at that temperature for 5 hours; after the reaction is completed, the reaction solution is slowly poured into a large amount of deionized water, and a white solid is precipitated. After repeated washing with deionized water, the solid is centrifuged and dried to obtain polyvinyl butyral resin.
[0021] The residual hydroxyl content in the resin was determined by titration, and the acetalization conversion rate was calculated to be 90%.
[0022] Comparative Example 1 S1. At room temperature, add 100g of polyvinyl alcohol and 900g of deionized water to a dissolving vessel, heat to 96℃ and stir to completely dissolve into a polyvinyl alcohol aqueous solution, then filter, cool to 45℃ and add n-butyraldehyde (the molar ratio of PVA to n-butyraldehyde is 1:0.8), and then stir mechanically to form a uniform emulsion. S2. The above emulsion was cooled to 15℃, and a certain amount of hydrochloric acid aqueous solution was added dropwise at a rate of 2s / drop while stirring. After the addition was complete, the reaction was maintained at this temperature for 1 hour. Then, the temperature was increased to 60℃ at a rate of 6min / ℃, and the reaction was maintained at this temperature for 3 hours. After the reaction was completed, NaOH solution was added to neutralize the reaction, and then the mixture was repeatedly washed with deionized water. Finally, the mixture was centrifuged and dried to obtain polyvinyl butyral resin. The content of residual hydroxyl groups in the resin was determined by titration, and the acetalization conversion rate was calculated to be 75%.
[0023] Comparative Example 2 S1. Select D001 type strong acid cation exchange resin, soak and activate it with 5wt% hydrochloric acid aqueous solution for 4h, stirring 3 times during the process, then wash it repeatedly with deionized water until the pH of the washing solution is 7, and dry it under vacuum at 80℃ for 6h to obtain pretreated ion exchange resin. S2. At room temperature, add 100g of polyvinyl alcohol 2488 and 900g of deionized water to a dissolving vessel, heat to 96℃ and stir to completely dissolve into a polyvinyl alcohol aqueous solution, filter and cool to 45℃, add n-butyraldehyde (the molar ratio of PVA to n-butyraldehyde is 1:0.8), and mechanically stir to form a uniform emulsion. S3. Add 5g of pretreated ion exchange resin to the above emulsion and react at 60℃ and 300r / min for 5h with stirring. After the reaction, filter to remove the ion exchange resin, slowly pour the reaction solution into a large amount of deionized water, and a white solid precipitates. After repeated washing with deionized water, centrifuge and dry to obtain polyvinyl butyral resin. The residual hydroxyl content in the resin is determined by titration, and the acetalization conversion rate is calculated to be 65%.
[0024] Experimental Example The relevant properties of the polyvinyl butyral resins prepared in Examples 1-3 and Comparative Examples 1-2 were tested, and are shown in Table 1.
[0025] Table 1: As can be seen from Table 1: The PVB resins prepared in Examples 1-3 of this invention exhibit superior performance in terms of appearance, solubility, and light transmittance. In terms of appearance, the products of the examples all show uniform particle size and shape, while the product of Comparative Example 1 shows significant differences in particle size and contains irregular lumps, indicating that the synthesis process of this invention helps improve the uniformity of the product's morphology. Regarding solubility, after dissolving the products of the examples in 5% ethanol solvent for 16 minutes, no visible gel particles were observed, indicating good solubility and uniform dispersion in ethanol; Comparative Example 1 showed some visible gel particles, reflecting insufficient dissolution. In terms of light transmittance, the products of the examples have a transmittance between 89.0% and 90.1%, higher than the 87.8% of Comparative Example 1, demonstrating that the products of this invention have superior transparency.
[0026] As can be seen from Table 1 and the conversion rates mentioned above: The PVB resins prepared in Examples 1-3 of this invention not only exhibit superior performance in terms of appearance, solubility, and light transmittance, but also show significantly better acetalization conversion rates than traditional catalytic systems.
[0027] In terms of appearance, the products of the embodiments all exhibit the characteristics of uniform particle size and shape, while the product of Comparative Example 1 has large differences in particle size and contains irregular lumps, and the product of Comparative Example 2 has uneven particle shape and contains a small amount of agglomerates, indicating that the synthesis process of the present invention helps to improve the morphological uniformity of the product. Regarding solubility, none of the products in the examples showed visible gel particles, indicating that they dissolved well in ethanol and were evenly dispersed. However, Comparative Example 1 showed some visible gel particles, and Comparative Example 2 showed a small amount of visible gel particles, both of which reflected insufficient dissolution. In terms of light transmittance, the light transmittance of the product in the example is between 89.0% and 90.1%, which is higher than that of Comparative Example 1 (87.8%) and Comparative Example 2 (86.6%), demonstrating that the product of the present invention has better transparency. In terms of conversion rate, the conversion rate of the products in the examples is between 82% and 90%, which is much higher than that of Comparative Example 2 (65%) and Comparative Example 1 (75%), highlighting the high efficiency of the catalytic system of the present invention. In summary, the dual advantages in performance and conversion rate demonstrated in Examples 1-3 are closely related to the process design of this invention, which employs a deep eutectic solvent catalytic reaction medium, a two-stage condensation reaction, and a microchannel reaction device. This process not only enhances the acetalization conversion rate through highly efficient catalytic characteristics, ensuring a complete reaction, but also makes the reaction stable and controllable, effectively reducing the occurrence of side reactions, ultimately leading to a simultaneous improvement in both the overall performance of PVB resin and reaction efficiency.
Claims
1. A method for synthesizing polyvinyl butyral resin, characterized in that, Includes the following steps: S1. PVA powder is added to a deep eutectic solvent catalytic reaction medium and stirred until PVA is completely dissolved into a transparent solution to obtain a PVA-deep eutectic solvent solution; the deep eutectic solvent catalytic reaction medium is a eutectic mixture formed by the interaction of hydrogen bond donors and hydrogen bond acceptors through non-covalent bonds. S2. Under inert gas protection, the PVA-deep eutectic solvent solution and n-butyraldehyde are subjected to a condensation reaction. After the reaction is completed, the reaction solution is slowly poured into a large amount of deionized water, and a white solid is precipitated. After washing and drying, polyvinyl butyral resin is obtained.
2. The method for synthesizing polyvinyl butyral resin according to claim 1, characterized in that, In step S1, the average degree of polymerization of PVA is 1500~3500, and the degree of hydrolysis is 88~100%.
3. The method for synthesizing polyvinyl butyral resin according to claim 1, characterized in that, In step S1, the deep eutectic solvent catalytic reaction medium is heated and stirred at 90~100℃ to form a uniform and transparent system.
4. The method for synthesizing polyvinyl butyral resin according to claim 1, characterized in that, In step S1, the PVA dissolution temperature is 65~75℃.
5. The method for synthesizing polyvinyl butyral resin according to claim 1, characterized in that, In step S1, the hydrogen bond acceptor is choline chloride, and the hydrogen bond donor is selected from one or more of glycerol, ethylene glycol, urea, and oxalic acid.
6. The method for synthesizing polyvinyl butyral resin according to claim 1, characterized in that, In step S2, the molar ratio of PVA to n-butyraldehyde in the PVA-deep eutectic solvent solution is 1:(0.5~1).
7. The method for synthesizing polyvinyl butyral resin according to claim 1, characterized in that, In step S2, the condensation reaction includes two stages, both in a microchannel reaction device; in the first stage, the PVA-deep eutectic solvent solution and n-butyraldehyde are kept at 50~75℃ for 0.8-1.5h; in the second stage, after the first stage of the reaction is completed, the temperature is uniformly increased to 75~95℃ at a heating rate of 5-7min / ℃, and kept at 75~95℃ for 2~5h.