One-pot preparation of poly(vinyl n-butyral) with controllable acetoxy content
By preparing PVB resin in a one-pot process and controlling the amount of alkaline solution used for saponification, combined with a catalyst and emulsifier, the problem of limited acetoxy group content was solved, enabling flexible control of acetoxy group content and simplification of the production process, thereby improving production efficiency and product competitiveness.
Patent Information
- Application Number
- CN202611073150.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-20
- Publication Date
- 2026-11-06
AI Technical Summary
In existing technologies, the acetoxy content of PVB resin is limited by the raw material PVA and is difficult to control flexibly. This limits the synthesis of PVB resins with other acetoxy contents and makes it impossible to prepare PVB resins with high alcoholysis degree. In addition, traditional methods require a multi-step separation process, which increases cost and complexity.
A one-pot preparation method is adopted, which improves the degree of alcoholysis by controlling the amount of alkaline solution used in the saponification reaction, and directly adds catalyst and emulsifier to carry out the acetalization reaction. This avoids the separation step of polyvinyl alcohol with a high degree of alcoholysis, achieves the control of acetoxy content, and simplifies the process.
It enables flexible control of acetoxy content, simplifies the production process, reduces costs, and improves production efficiency and product competitiveness.
Smart Images
Figure CN123042230A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of synthetic resin technology, and more specifically, to a one-pot method for preparing polyvinyl butyral with adjustable acetoxy content. Background Technology
[0002] Polyvinyl butyral (PVB) is a polymer compound containing three functional groups: hydroxyl, n-butyral, and acetoxy groups. The hydroxyl group structure gives PVB excellent adhesion and high tensile strength, while the six-membered ring structure of the n-butyral group enhances the strength and non-crystalline nature of the molecular chain, and the acetoxy group increases its water resistance. Due to its good adhesion, optical transparency, tensile strength, and water resistance, PVB is widely used in adhesives, coatings, photovoltaic encapsulation, and interlayer films in laminated glass. The properties of PVB resin are influenced by the ratio of these three functional groups; by adjusting the ratio, the properties of PVB resin can be modified, allowing for the development of PVB resin products with different applications and specifications.
[0003] Currently, PVB resin synthesis mainly employs one-step and precipitation methods. The one-step method uses vinyl acetate as a raw material, with alcoholysis and acetalization reactions occurring simultaneously, making it impossible to control the degree of alcoholysis. The precipitation method uses polyvinyl alcohol (PVA) as a raw material, but its degree of alcoholysis is limited by existing PVA grades on the market; common degrees of alcoholysis for PVA are 68%, 78%, and 88%. The degree of alcoholysis is the molar percentage of hydroxyl groups out of all substituents in polyvinyl alcohol. In PVA raw material product designations, the thousands and hundreds digits of the degree of polymerization are generally placed first, followed by the percentage of the degree of alcoholysis. For example, PVA-1799 refers to polyvinyl alcohol with a degree of polymerization of 1700 and a degree of alcoholysis of 99%.
[0004] The acetyloxy group content in PVB resin is influenced by the raw material PVA, resulting in a relatively uniform acetyloxy group content. This limits the synthesis of other PVB resins with specific acetyloxy group contents, making it impossible to directly prepare high-degree-of-hydrolysis PVB resin products from low-degree-of-hydrolysis polyvinyl alcohol. Generally, low-degree-of-hydrolysis polyvinyl alcohol needs to be first alkali-treated to obtain high-degree-of-hydrolysis polyvinyl alcohol, which is then separated and purified before undergoing butyralization to obtain high-degree-of-hydrolysis polyvinyl butyral resin. Furthermore, the selection of conventional polyvinyl alcohols is limited by grade restrictions, making it impossible to flexibly adjust the acetyloxy group content.
[0005] Therefore, developing a simple, stable, and tunable method for preparing PVB resin with acetoxy groups is an urgent technical problem to be solved. Summary of the Invention
[0006] The main objective of this invention is to provide a method for preparing polyvinyl alcohol n-butyral resin containing a fixed amount of acetoxy groups, thereby addressing the problem in existing technologies where the acetoxy group content in PVB resin is limited by the raw material PVA, making it difficult to control the acetoxy group content in the prepared PVB resin as needed. Furthermore, this one-pot method eliminates the need for separating highly hydrolyzed polyvinyl alcohol, significantly accelerating the reaction process. Reducing separation steps effectively lowers costs and enhances product competitiveness.
[0007] To achieve the above objectives, the present invention provides a one-pot method for preparing polyvinyl butyral with adjustable acetoxy content, comprising the following steps: Step 1: Dissolve low-hydrolyzed polyvinyl alcohol (PVA) with a degree of first hydrolysis in distilled water in a reaction vessel to obtain an aqueous solution of low-hydrolyzed PVA; Step 2: Add an alkaline solution with a concentration of 0.5~2 mol / L to the aqueous solution of low-hydrolyzed PVA and carry out a saponification reaction at 40~60℃ for 1~4 hours; Add acid to the solution after the saponification reaction to adjust the pH of the solution to neutral, to obtain a high-hydrolyzed PVA solution with a degree of second hydrolysis and cool it to room temperature; wherein, the amount of alkaline solution is controlled to be 0.08~1 times the molar number of acetoxy groups in the low-hydrolyzed PVA; the second degree of hydrolysis is greater than the first degree of hydrolysis; Step 3: At room temperature, a catalyst and emulsifier are added to the polyvinyl alcohol solution with high alcoholysis degree, and n-butyraldehyde is added dropwise at 15~25℃ and mixed well. The reaction is carried out for 1~2 hours, and then the temperature is raised to 50~60℃ and the reaction is carried out for 1~2 hours to obtain a reaction solution in which polyvinyl alcohol n-butyraldehyde resin is precipitated. Step 4: Adjust the pH of the reaction solution to neutral, filter it, and rinse the filter cake to obtain crude polyvinyl butyral product; wash the crude polyvinyl butyral product with distilled water, filter it, and dry it to obtain white powdered polyvinyl butyral resin.
[0008] Optionally, the low degree of alcoholysis polyvinyl alcohol is at least one of PVA-0574, PVA-0578, PVA-2078, PVA-0380, PVA-3280, PVA-3580, PVA-4880, PVA-0588, and PVA-1788.
[0009] Optionally, in step 1, dissolving low-hydrolyzability polyvinyl alcohol in distilled water in a reaction vessel to obtain an aqueous solution of low-hydrolyzability polyvinyl alcohol specifically includes: Add low-hydrolyzability polyvinyl alcohol to a reaction vessel, then add 8-12 times the mass of the low-hydrolyzability polyvinyl alcohol to distilled water, heat to 80-100 °C, and stir for 0.5-2 h to obtain an aqueous solution of the low-hydrolyzability polyvinyl alcohol.
[0010] Optionally, in step 3, the mass concentration of the catalyst is 10-30%, and the catalyst is one of hydrochloric acid, sulfuric acid, phosphoric acid, and hydroiodic acid.
[0011] Optionally, the emulsifier is a mixture of a first emulsifier and a second emulsifier, wherein the first emulsifier is one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium dodecyl sulfonate; The second emulsifier is one of Tween 20, Tween 40, Tween 60, Tween 80, Span 20, Span 60, Span 80, and Span 85; In the mixture, the mass ratio of the first emulsifier to the second emulsifier is 1:(1~3).
[0012] Optionally, in step 3, the mass ratio of the emulsifier to the low-hydrolyzability polyvinyl alcohol is (0.01~0.03):1.
[0013] Optionally, the mass ratio of the butyraldehyde to the low-hydrolysis polyvinyl alcohol is (0.5~0.75):1.
[0014] Optionally, in step 3, the heating rate to 50~60℃ is 0.1~0.2℃ / min.
[0015] Optionally, in step 4, the filter cake is rinsed with at least 3 times the volume of the reaction liquid using distilled water; The process of washing the crude polyvinyl butyral product with distilled water, followed by filtration and drying, specifically includes: washing with distilled water at 50-70°C for 3-5 times, each time using a volume at least equal to the volume of the reaction liquid; filtering and then drying in a vacuum drying oven at 40-60°C for 8-10 hours.
[0016] This invention discloses a one-pot method for preparing polyvinyl butyral with adjustable acetoxy content, comprising the following steps: Step 1: Dissolving low-hydrolysis degree polyvinyl alcohol (PHE) with a degree of first hydrolysis in distilled water in a reaction vessel to obtain an aqueous solution of low-hydrolysis degree polyvinyl alcohol; Step 2: Adding an alkaline solution with a concentration of 0.5~2 mol / L to the aqueous solution of low-hydrolysis degree polyvinyl alcohol and performing a saponification reaction at 40~60℃ for 1~4 h; Adding acid to the solution after the saponification reaction to adjust the pH of the solution to neutral, obtaining a high-hydrolysis degree polyvinyl alcohol solution with a degree of second hydrolysis and cooling to room temperature; wherein, the amount of alkaline solution is controlled to be the same as that of the low-hydrolysis degree polyvinyl alcohol. The number of acetoxy groups in the enol is 0.08 to 1 times; the second degree of alcoholysis is greater than the first degree of alcoholysis; Step 3: At room temperature, a catalyst and emulsifier are added to the high degree of alcoholysis polyvinyl alcohol solution, and n-butyraldehyde is added dropwise at 15 to 25°C and mixed well. The reaction is carried out for 1 to 2 hours, and then the temperature is raised to 50 to 60°C and the reaction is carried out for 1 to 2 hours to obtain a reaction solution in which polyvinyl alcohol n-butyraldehyde resin is precipitated; Step 4: The pH of the reaction solution is adjusted to neutral, filtered, and the filter cake is washed to obtain crude polyvinyl alcohol n-butyraldehyde product; the crude polyvinyl alcohol n-butyraldehyde product is washed with distilled water, filtered, and dried sequentially to obtain white powdered polyvinyl alcohol n-butyraldehyde resin. Therefore, using low-hydrolyzed polyvinyl alcohol as raw material, the degree of hydrolysis of the raw material polyvinyl alcohol is increased through saponification reaction, and the acetoxy content is adjusted by controlling the amount of alkali used in the saponification reaction; after the saponification reaction is completed, high-hydrolyzed polyvinyl alcohol is added directly to the emulsifier for acetalization reaction without separation, so that polyvinyl alcohol n-butyral resin with adjustable acetoxy content can be prepared in one pot. Attached Figure Description
[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a one-pot process flow chart of polyvinyl butyral with adjustable acetoxy content, which is an optional embodiment of the present invention. Figure 2 This is the 1H NMR spectrum of the polyvinyl butyral resin obtained in Example 1; Figure 3 This is the 1H NMR spectrum of the polyvinyl butyral resin obtained in Example 2. Detailed Implementation
[0018] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0019] like Figure 1 As shown, a one-pot method for preparing polyvinyl butyral with adjustable acetoxy group content includes the following steps: Step 1: Dissolve low-hydrolyzed polyvinyl alcohol (with a degree of first hydrolysis) in distilled water in a reaction vessel to obtain an aqueous solution of low-hydrolyzed polyvinyl alcohol. Step 2: Add an alkaline solution with a concentration of 0.5~2 mol / L to the aqueous solution of the low-hydrolyzability polyvinyl alcohol and carry out a saponification reaction at 40~60℃ for 1~4 hours; add acid to the solution after the saponification reaction to adjust the pH of the solution to neutral, to obtain a high-hydrolyzability polyvinyl alcohol solution with a second degree of hydrolysis, and cool it to room temperature; wherein, the amount of the alkaline solution is controlled to be 0.08~1 times the number of moles of acetoxy groups in the low-hydrolyzability polyvinyl alcohol; the second degree of hydrolysis is greater than the first degree of hydrolysis; Step 3: At room temperature, a catalyst and emulsifier are added to the polyvinyl alcohol solution with high alcoholysis degree, and n-butyraldehyde is added dropwise at 15~25℃ and mixed well. The reaction is carried out for 1~2 hours, and then the temperature is raised to 50~60℃ and the reaction is carried out for 1~2 hours to obtain a reaction solution in which polyvinyl alcohol n-butyraldehyde resin is precipitated. Step 4: Adjust the pH of the reaction solution to neutral, filter it, and rinse the filter cake to obtain crude polyvinyl butyral product; wash the crude polyvinyl butyral product with distilled water, filter it, and dry it to obtain white powdered polyvinyl butyral resin.
[0020] Specifically, step 1: In a reaction vessel, low-hydrolyzed polyvinyl alcohol with a degree of first hydrolysis and distilled water are mixed and stirred until they are completely dissolved to obtain a polyvinyl alcohol aqueous solution.
[0021] Step 2: Add a certain amount of alkaline solution to the polyvinyl alcohol aqueous solution and carry out a saponification reaction at 40-60℃ for 1-4 hours. After the reaction, add acid to the solution to adjust the pH to 6.5-7.5 to neutralize the residual alkali after the saponification reaction, obtaining a high degree of alcoholysis polyvinyl alcohol solution with a degree of alcoholysis of the second degree. Then cool to room temperature. The concentration of the alkaline solution is 0.5-2 mol / L, and the amount of alkaline solution used is 0.08-1 times the number of moles of acetoxy groups in the low degree of alcoholysis polyvinyl alcohol. With a fixed concentration of alkaline solution, the high degree of alcoholysis polyvinyl alcohol solution can be obtained by controlling the amount of alkaline solution used. The acid used to neutralize the residual alkali is one of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, with sulfuric acid being preferred in this invention. The alkaline solution is a sodium hydroxide or potassium hydroxide solution.
[0022] Step 3: At room temperature, add the catalyst and emulsifier to the high-hydrolysis degree polyvinyl alcohol aqueous solution obtained in Step 2. Add n-butyraldehyde dropwise to the system at a rate of 0.1-0.5 mL / min at 15-25℃. During the dropwise addition, the solution gradually becomes turbid and the viscosity gradually increases. When the acetalization reaches a certain degree, the viscosity of the solution drops sharply and turns into a white emulsion. After the n-butyraldehyde is completely added, raise the temperature to 20-25℃ and react for 1-2 hours, then raise the temperature to 50-60℃ and react for 1-2 hours. During the temperature rise, as the degree of acetalization further increases, PVB resin gradually precipitates, resulting in a reaction solution with polyvinyl alcohol n-butyraldehyde resin precipitated.
[0023] Step 4: Adjust the pH of the reaction solution obtained in Step 3 to 6.5-7.5. Then, perform solid-liquid separation on the neutralized reaction solution using vacuum filtration or pressure filtration. Collect the filter cake obtained from filtration and wash away unreacted raw materials, catalyst residues, and emulsifier impurities adhering to the surface of the filter cake with distilled water to obtain crude polyvinyl butyral product. To further remove trace impurities embedded inside the crude product, the crude product is boiled in distilled water to fully dissolve the impurities. After boiling and washing, it is filtered again and dried to constant weight to finally obtain a high-purity, stable white powder of polyvinyl butyral resin.
[0024] The method in this application uses low-hydrolyzed polyvinyl alcohol as raw material, increases the degree of hydrolysis of the raw material polyvinyl alcohol through saponification reaction, and adjusts the acetoxy content by controlling the amount of alkali used in the saponification reaction; after the saponification reaction is completed, high-hydrolyzed polyvinyl alcohol is added directly to the emulsifier for acetalization reaction without separation, and polyvinyl alcohol n-butyral resin with adjustable acetoxy content can be prepared in one pot.
[0025] In this example, sodium hydroxide solution is used as the alkaline solution. Low-degree-of-hydrolysis polyvinyl alcohol (PVA) undergoes saponification under suitable conditions when added to sodium hydroxide solution to produce high-degree-of-hydrolysis PVA. High-degree-of-hydrolysis PVA and n-butyraldehyde react in an acidic catalytic environment to produce PVA n-butyraldehyde resin. The synthetic route is as follows:
[0026] In the formula, a, b, a+n, bn, p, and q are all degrees of polymerization, and the relationships between the parameters are: a / (a+b)≤90, (a+n) / (a+b)>90; p / (p+q+bn)>90. It should also be noted that the high and low degrees of alcoholysis here are not strictly defined according to the hydroxyl content, but rather as relative relationships.
[0027] In one possible implementation, the low degree of alcoholysis polyvinyl alcohol is at least one of PVA-0574, PVA-0578, PVA-2078, PVA-0380, PVA-3280, PVA-3580, PVA-4880, PVA-0588, and PVA-1788.
[0028] Specifically, the low degree of alcoholysis polyvinyl alcohol is selected from at least one of PVA-0574, PVA-0578, PVA-2078, PVA-0380, PVA-3280, PVA-3580, PVA-4880, PVA-0588, and PVA-1788. These models are all standardized polyvinyl alcohol products produced in industrial mass production, and their degree of polymerization covers a wide range (from 300 to 4800). They can be flexibly selected according to the performance requirements of the target PVB resin to adapt to the preparation of products for different applications. The model number follows industry-standard coding. The first two (or three) digits represent the thousands and hundreds (or thousands, hundreds, and tens) digits of the degree of polymerization, and the last two digits represent the percentage of the degree of hydrolysis. For example, PVA-0574 represents a degree of polymerization of approximately 500 and a degree of hydrolysis of 74%, PVA-1788 represents a degree of polymerization of approximately 1700 and a degree of hydrolysis of 88%, and PVA-4880 represents a degree of polymerization of approximately 4800 and a degree of hydrolysis of 80%. The key parameters such as the degree of polymerization and degree of hydrolysis of each model are accurate and have strong batch stability. Using this as raw material can effectively avoid problems such as incomplete saponification reaction and uneven acetalization caused by fluctuations in raw material parameters, and ensure the controllability of the acetoxy content of the target PVB resin and the consistency of product performance. Meanwhile, these models are all commonly available products in the market, with readily available raw materials and controllable procurement costs. There is no need to customize special low-hydrolysis polyvinyl alcohol, which can significantly reduce production input. In addition, these models of polyvinyl alcohol have good water solubility and can be adapted to the dissolution process of 80~100℃ and stirring for 0.5~2h in step 1 of this invention, quickly forming a clear, transparent, and stable aqueous solution, laying the foundation for the uniformity of the subsequent saponification reaction. Moreover, the acetoxy groups on their molecular chains are evenly distributed, and the degree of saponification can be precisely adjusted by controlling the amount of alkaline solution in step 2, thereby achieving on-demand control of the acetoxy group content of the final PVB resin.
[0029] In one possible implementation, step 1 involves dissolving low-hydrolyzability polyvinyl alcohol in distilled water in a reaction vessel to obtain an aqueous solution of low-hydrolyzability polyvinyl alcohol, specifically including: Add low-hydrolyzability polyvinyl alcohol to a reaction vessel, then add 8-12 times the mass of the low-hydrolyzability polyvinyl alcohol to distilled water, heat to 80-100 °C, and stir for 0.5-2 h to obtain an aqueous solution of the low-hydrolyzability polyvinyl alcohol.
[0030] Specifically, after adding low-hydrolyzed polyvinyl alcohol (PVA) raw material to the reactor, add 8-12 times its mass of distilled water. This ratio provides sufficient solvent space for the full expansion of the PVA molecular chains, preventing the raw material from clumping and becoming difficult to dissolve due to insufficient water, while also preventing excessive water from diluting the system concentration and increasing the energy consumption and processing load of subsequent reactions. The system is then heated to 80-100°C. This temperature range effectively breaks the hydrogen bonds between PVA molecules, promoting rapid dispersion and dissolution in water, while avoiding the degradation of PVA molecular chains caused by prolonged high-temperature heating. Continuous stirring for 0.5-2 hours further accelerates the dissolution process, ensuring uniform distribution of PVA molecules in the water, ultimately forming a clear, transparent, and viscosity-stable low-hydrolyzed PVA aqueous solution.
[0031] In one possible implementation, in step 3, the mass concentration of the catalyst is 10-30%, and the catalyst is one of hydrochloric acid, sulfuric acid, phosphoric acid, and hydroiodic acid.
[0032] Specifically, a concentration range of 10-30% ensures sufficient hydrogen ion active sites for the acetalization reaction. This provides a suitable acidic catalytic environment for the condensation reaction of polyvinyl alcohol and n-butyraldehyde, accelerating the reaction process, while avoiding excessive acidity due to high concentrations, which could lead to polyvinyl alcohol chain degradation and increased side reactions. It also prevents insufficient catalytic efficiency and prolonged reaction time caused by low concentrations. Hydrochloric acid, sulfuric acid, phosphoric acid, and hydroiodic acid are all readily available industrial inorganic acid catalysts. Their catalytic performance is stable and easily neutralized and removed. Compared to other types of catalysts, they do not require complex separation processes, further simplifying the production process and ensuring the purity and performance stability of the final polyvinyl alcohol n-butyraldehyde resin.
[0033] In one possible implementation, the emulsifier is a mixture of a first emulsifier and a second emulsifier, wherein the first emulsifier is one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium dodecyl sulfonate. The second emulsifier is one of Tween 20, Tween 40, Tween 60, Tween 80, Span 20, Span 60, Span 80, and Span 85; In the mixture, the mass ratio of the first emulsifier to the second emulsifier is 1:(1~3).
[0034] Specifically, this application uses a combination of a first emulsifier and a second emulsifier, rather than a single emulsifier. The first emulsifier is selected from sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium dodecyl sulfonate. These are all anionic emulsifiers with good surface activity and emulsifying and dispersing capabilities. They can rapidly reduce the surface tension of the aqueous system, allowing the hydrophobic n-butyraldehyde to disperse quickly in a high-hydrolysis degree polyvinyl alcohol aqueous solution, forming an initially stable dispersion system. Furthermore, their anionic properties can weakly interact with the hydroxyl groups on the polyvinyl alcohol molecular chain, further enhancing dispersion stability. The second emulsifier is selected from the Tween series and Span series. These are all nonionic emulsifiers with a wide range of hydrophilic and hydrophobic properties and good compatibility. They can effectively compensate for the insufficient emulsifying stability of a single anionic emulsifier under pH changes (neutralization to neutral after saponification, acidic environment during acetalization catalysis). This compound system can improve the dispersion uniformity of n-butyraldehyde droplets, avoid droplet aggregation which could lead to excessively vigorous local acetalization reactions, and thus ensure the uniformity of the product's molecular chain structure and the uniform distribution of functional groups. The mass ratio of the first emulsifier to the second emulsifier is limited to 1:(1~3). If the proportion of the first emulsifier is too high, it can easily lead to over-emulsification of the system, making it difficult to completely remove residual emulsifiers in subsequent water washing and boiling processes, thus affecting the purity of the product. If the proportion of the second emulsifier is too high, it will reduce the emulsification and dispersion efficiency, resulting in uneven dispersion of n-butyraldehyde, triggering side reactions, and affecting the acetalization degree, water resistance, and adhesion properties of polyvinyl alcohol n-butyraldehyde resin. This compound system is suitable for the entire process of the one-pot preparation process of this application, without the need for additional adjustments to the emulsification system, which can further simplify the process steps, reduce production costs, and at the same time ensure the stability and consistency of product performance.
[0035] In this application, the nonionic emulsifier is preferably Tween 80.
[0036] In one possible implementation, in step 3, the mass ratio of the emulsifier to the low-hydrolyzability polyvinyl alcohol is (0.01~0.03):1.
[0037] Specifically, the mass ratio of emulsifier to the low-hydrolyzability polyvinyl alcohol is (0.01~0.03):1. Within this ratio range, the amount of emulsifier added can fully utilize the synergistic effect of the sodium dodecyl sulfate and Tween 80 compound system, effectively reducing the surface tension of the reaction system and allowing n-butyraldehyde to disperse into stable micro-droplets in the polyvinyl alcohol aqueous solution, ensuring a uniform and efficient acetalization reaction. It also avoids residue problems caused by excessive emulsifier addition. Excess emulsifier will adsorb onto the surface of the polyvinyl alcohol n-butyraldehyde particles, making it difficult to completely remove through subsequent washing and boiling processes. At the same time, a suitable low addition ratio can control production costs. Compared to a high addition ratio, it reduces raw material consumption while ensuring process stability, making it more suitable for large-scale production.
[0038] In one possible implementation, the mass ratio of n-butyraldehyde to the low-hydrolysis polyvinyl alcohol is (0.5~0.75):1.
[0039] Specifically, a suitable mass ratio of n-butyraldehyde to low-hydrolyzed polyvinyl alcohol ensures that the reaction proceeds fully to give the product ideal acetalization, water resistance, and bonding strength, while avoiding side reactions caused by excessive n-butyraldehyde or residues, or substandard product performance due to insufficient n-butyraldehyde.
[0040] In one possible implementation, in step 3, the heating rate to 50-60°C is 0.1-0.2°C / min.
[0041] Specifically, a temperature rise of 0.1℃ / min to 0.2℃ / min can ensure a uniform increase in the temperature of the reaction system, avoid local overheating that could trigger side reactions, and guarantee a stable and controllable acetalization reaction, thereby improving the performance consistency of polyvinyl butyral resin.
[0042] In one possible implementation, in step 4, the filter cake is rinsed with at least three times the volume of the reaction liquid using distilled water. The process of washing the crude polyvinyl butyral product with distilled water, followed by filtration and drying, specifically includes: washing with distilled water at 50-70°C for 3-5 times, each time using a volume at least equal to the volume of the reaction liquid; filtering and then drying in a vacuum drying oven at 40-60°C for 8-10 hours.
[0043] Specifically, the filter cake is rinsed with at least three times the volume of the reaction liquid using distilled water to thoroughly remove catalysts, emulsifiers, and unreacted small molecule impurities adhering to the filter cake surface. Subsequently, the crude product is boiled 3-5 times at 50-70°C with at least one volume of distilled water each time to further remove residual impurities embedded within the product particles. This temperature range also prevents high-temperature damage to the resin structure. Finally, the product is dried in a vacuum drying oven at 40-60°C for 8-10 hours to completely remove moisture and prevent thermal degradation of the resin caused by high-temperature drying, ultimately yielding a high-purity, stable, white powdered polyvinyl butyral resin.
[0044] The following examples will further illustrate this solution. Example
[0045] Add 100g of water to the reaction vessel, weigh 10.0g of polyvinyl alcohol 1788 and add it to the reaction vessel. Install a condenser and thermometer, and slowly heat to 95℃. Stir at 95℃ for 1 hour to completely dissolve the polyvinyl alcohol. After dissolution, stop heating and wait for the solution to cool to 60℃. Then add 6.1mL of sodium hydroxide solution (2mol / L) and saponify at this temperature for 3 hours. After the reaction is complete, add 5.6mL of sulfuric acid solution to neutralize. Dissolve 0.2g of the weighed emulsifier (sodium dodecyl sulfate / Tween 80 = 1 / 1). After the solution cools to 30℃, add it to the reaction vessel and stir until completely mixed. Then add 2mL of sulfuric acid solution and stir until homogeneous. After the solution cools to 20℃, maintain the solution temperature at 20℃ and add 7.9mL of n-butyraldehyde dropwise at a rate of 0.3mL / min. After the n-butyraldehyde is added, continue the reaction at 20℃ for 1 hour. After 1 hour, increase the temperature to 60℃ at a rate of 0.17℃ / min and react for another 1 hour. After the reaction is complete, adjust the pH of the reaction solution to neutral, filter the reaction solution, and wash the resulting filter cake with 300mL of water to obtain crude PVB product. Then boil and wash three times with 100mL of water at 50℃, filter, and dry in a vacuum drying oven at 60℃ for 8 hours to obtain polyvinyl alcohol n-butyraldehyde resin. The 1H NMR spectrum of the obtained polyvinyl alcohol n-butyraldehyde resin is shown below. Figure 2 As shown, the obtained product has a hydroxyl content of 19.34%, an acetal degree (mol) of 72.99%, and an acetoxy content of 7.66%. This example uses a raw material with a 12% acetoxy content to produce a product with a 7.6% acetoxy content in a one-step process. Conventional PVA raw materials with a 7-8% acetoxy content are not readily available or are too expensive, which is not conducive to industrial production applications. Example
[0046] The amount of sodium hydroxide solution used in Example 1 was changed to 8.8 mL, and the amount of sulfuric acid used for neutralization was changed to 7.9 mL. The amounts and steps of other reactants remained unchanged. The 1H NMR spectrum of the resulting polyvinyl butyral resin is shown below. Figure 3 As shown, the obtained product has a hydroxyl content of 24.09%, an acetal degree (mol) of 66.45%, and an acetoxy content of 4.65%. Example
[0047] The amount of sodium hydroxide solution used in Example 1 was changed to 9.8 mL, the amount of sulfuric acid used for neutralization was changed to 9.0 mL, and the amounts and steps of other reactants remained unchanged. The resulting product had a hydroxyl content of 25.67%, an acetal degree (mol) of 70.78%, and an acetoxy content of 3.55%. Example
[0048] The amount of sodium hydroxide solution used in Example 1 was changed to 3.7 mL, the amount of sulfuric acid used for neutralization was changed to 3.3 mL, and the amounts and steps of other reactants remained unchanged. The resulting product had a hydroxyl content of 20.09%, an acetal degree (mol) of 70.67%, and an acetoxy content of 9.24%. Example
[0049] The saponification reaction temperature in Example 1 was changed to 60°C, the reaction time was changed to 4 hours, and the amounts and steps of other reactants remained unchanged. The resulting product had a hydroxyl content of 22.23%, an acetal degree (mol) of 72.67%, and an acetoxy content of 6.10%.
[0050] The raw materials, reaction conditions, and product performance data for each of the above embodiments are shown in Table 1: Table 1. Raw material, reaction conditions, and product performance data for each embodiment. The data above shows that increasing the amount of alkali can reduce the acetoxy content, decreasing the amount of alkali can increase the acetoxy content, and increasing the saponification temperature and time can reduce the acetoxy content.
[0051] Example 1 describes a one-step process using raw materials with a 12% acetoxy content to obtain a product with an adjustable acetoxy content (3-9%). Conventional PVA raw materials with 3-9% acetoxy content are either difficult to obtain or too expensive, hindering industrial production applications. Previous reports all involved stepwise methods, requiring separation after converting high-acetyl PVA to low-acetyl PVA, followed by further reaction to obtain the desired PVB. The innovation of this method lies in its one-pot method for obtaining low-acetyl PVB from high-acetyl PVA without requiring separation and purification.
[0052] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A one-pot method for preparing polyvinyl butyral with adjustable acetoxy group content, characterized in that, Includes the following steps: Step 1: Dissolve low-hydrolyzed polyvinyl alcohol (with a degree of first hydrolysis) in distilled water in a reaction vessel to obtain an aqueous solution of low-hydrolyzed polyvinyl alcohol. Step 2: Add an alkaline solution with a concentration of 0.5~2 mol / L to the aqueous solution of the low-hydrolyzability polyvinyl alcohol and carry out a saponification reaction at 40~60℃ for 1~4 hours; add acid to the solution after the saponification reaction to adjust the pH of the solution to neutral, to obtain a high-hydrolyzability polyvinyl alcohol solution with a second degree of hydrolysis, and cool it to room temperature; wherein, the amount of the alkaline solution is controlled to be 0.08~1 times the number of moles of acetoxy groups in the low-hydrolyzability polyvinyl alcohol; the second degree of hydrolysis is greater than the first degree of hydrolysis; Step 3: At room temperature, a catalyst and emulsifier are added to the polyvinyl alcohol solution with high alcoholysis degree, and n-butyraldehyde is added dropwise at 15~25℃ and mixed well. The reaction is carried out for 1~2 hours, and then the temperature is raised to 50~60℃ and the reaction is carried out for 1~2 hours to obtain a reaction solution in which polyvinyl alcohol n-butyraldehyde resin is precipitated. Step 4: Adjust the pH of the reaction solution to neutral, filter it, and rinse the filter cake to obtain crude polyvinyl butyral product; wash the crude polyvinyl butyral product with distilled water, filter it, and dry it to obtain white powdered polyvinyl butyral resin.
2. The one-pot preparation method of polyvinyl butyral with adjustable acetoxy content according to claim 1, characterized in that, The low degree of alcoholysis polyvinyl alcohol is at least one of PVA-0574, PVA-0578, PVA-2078, PVA-0380, PVA-3280, PVA-3580, PVA-4880, PVA-0588, and PVA-1788.
3. The one-pot preparation method of polyvinyl butyral with adjustable acetoxy content according to claim 1, characterized in that, In step 1, low-hydrolyzability polyvinyl alcohol is dissolved in distilled water in a reaction vessel to obtain an aqueous solution of low-hydrolyzability polyvinyl alcohol, specifically including: Add low-hydrolyzability polyvinyl alcohol to a reaction vessel, then add 8-12 times the mass of the low-hydrolyzability polyvinyl alcohol to distilled water, heat to 80-100 °C, and stir for 0.5-2 h to obtain an aqueous solution of the low-hydrolyzability polyvinyl alcohol.
4. The one-pot preparation method of polyvinyl butyral with adjustable acetoxy content according to claim 1, characterized in that, In step 3, the mass concentration of the catalyst is 10-30%, and the catalyst is one of hydrochloric acid, sulfuric acid, phosphoric acid, and hydroiodic acid.
5. The one-pot preparation method of polyvinyl butyral with adjustable acetoxy content according to claim 1, characterized in that, The emulsifier is a mixture of a first emulsifier and a second emulsifier, wherein the first emulsifier is one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium dodecyl sulfonate. The second emulsifier is one of Tween 20, Tween 40, Tween 60, Tween 80, Span 20, Span 60, Span 80, and Span 85; In the mixture, the mass ratio of the first emulsifier to the second emulsifier is 1:(1~3).
6. The one-pot preparation method of polyvinyl butyral with adjustable acetoxy group content according to claim 5, characterized in that, In step 3, the mass ratio of the emulsifier to the low-hydrolyzability polyvinyl alcohol is (0.01~0.03):
1.
7. The one-pot preparation method of polyvinyl butyral with adjustable acetoxy content according to claim 1, characterized in that, The mass ratio of n-butyraldehyde to the low-hydrolysis polyvinyl alcohol is (0.5~0.75):
1.
8. The one-pot preparation method of polyvinyl butyral with adjustable acetoxy content according to claim 1, characterized in that, In step 3, the heating rate to 50~60℃ is 0.1~0.2℃ / min.
9. The one-pot preparation method of polyvinyl butyral with adjustable acetoxy content according to claim 1, characterized in that, In step 4, the filter cake is rinsed with distilled water at least 3 times the volume of the reaction liquid. The process of washing the crude polyvinyl butyral product with distilled water, followed by filtration and drying, specifically includes: washing with distilled water at 50-70°C for 3-5 times, each time using a volume at least equal to the volume of the reaction liquid; filtering and then drying in a vacuum drying oven at 40-60°C for 8-10 hours.