Polyvinyl alcohol for PVB (Polyvinyl Butyral) and preparation method thereof
By adding aqueous alcohol solution when the gel appears in the low-base alcoholization method, the problem of unbalanced supply and demand of PVB special polyvinyl alcohol product quality and market supply and demand is solved, and PVA resin production with high alcohol resolution and excellent product quality is achieved.
Patent Information
- Application Number
- CN202311036160.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-08-17
- Publication Date
- 2025-02-21
AI Technical Summary
In the prior art, the quality standards of PVB-specific polyvinyl alcohol products are strict, resulting in shortages. At the same time, domestic PVA production capacity is overcapacity and fierce market competition is difficult to meet PVB production needs.
Based on the low-base alcoholization method, polyvinyl alcohol with specific alcohol degree is obtained by adding aqueous alcohol solution when the gel appears, and polyvinyl alcohol with specific alcohol degree is further carried out to reduce the system viscosity, break the gel, and control the progress of the hydrolysis reaction. product.
It achieves a more uniform alcoholylation, better product quality, and a alcoholylation degree of between 97-99%, meeting the requirements of PVA resin for PVB, simplifying the process and improving economic benefits.
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Abstract
Description
Technical Field
[0001] The invention relates to the field of organic chemical synthesis, and in particular to a polyvinyl alcohol product for PVB and a preparation method thereof. Background Art
[0002] Polyvinyl butyral (PVB for short) is a condensation product of polyvinyl alcohol (PVA for short) and n-butyraldehyde under acid catalysis. PVB resin is widely used as the main interlayer material of safety glass due to its excellent adhesion and optical properties. It can also be used in coatings, adhesives, ceramic flower paper and other aspects. With the rapid development of the PVB industry, the prospects for the production of PVB film with PVB resin are promising, and the market is in short supply. However, as the raw material for the production of PVB resin for film, PVB special polyvinyl alcohol is in short supply. This is because there are certain requirements for the quality standards of PVB special polyvinyl alcohol products, and in different uses, there are strict requirements for the ash content, viscosity and molecular weight distribution of PVA. According to the survey, the PVA quality indicators applicable to PVB are shown in Table 1. On the other hand, the domestic PVA production capacity has been in excess, and the competition in the PVA industry is becoming increasingly severe. Most manufacturers only have conventional varieties such as 1788 and 1799, and it is difficult to gain a foothold in the increasingly fierce market competition. Therefore, the development of PVA that meets the requirements of PVB can not only meet the needs of PVB production, but also resolve the contradiction of PVA surplus.
[0003] Table 1 Quality indexes of polyvinyl alcohol applicable to PVB
[0004] project Quality indicators Analytical methods Alcoholysis degree (%) 97-99 GB / T 12010.2 Appendix D Viscosity, mPa·s 25-30 GB / T 12010.2 Appendix E Sodium hydroxide content (%) 0 GB / T 12010.7 Sodium acetate content (%) <1.2 GB / T 12010.2 Appendix B Volatile matter (%) <4 GB / T 12010.2 Appendix A Ash content (%) <0.4 GB / T 12010.2 Appendix C purity(%) >95 GB / T 12010.3
[0005] Polyvinyl alcohol is obtained by hydrolysis of polyvinyl acetate under the condition of acid or alkali as catalyst. The industrial preparation method usually uses methanol as solvent and adopts alkaline alcoholysis with sodium hydroxide as catalyst. The reaction rate is fast and the product quality is good. The alkaline catalyzed alcoholysis method is divided into two production processes: high alkaline method and low alkaline method. In the high alkaline alcoholysis method, 1-2% water is added to the methanol solution of polyvinyl acetate, and then sodium hydroxide aqueous solution is added. The main saponification reaction occurs. The content of sodium acetate in the product is high, and the product purity is not high. Only a single variety with high alcoholysis degree can be produced, and the recovery of alcoholysis waste liquid is complicated and energy consumption is high. In the low alkaline alcoholysis method, the methanol solution of polyvinyl acetate basically does not contain water. The alkali is added after being dissolved in alcohol. The amount of alkali added can be reduced to one-tenth of the high alkaline method. The main ester exchange reaction occurs, with fewer side reactions, and the sodium acetate content in the product is less than 2%.
[0006] In addition, during the alcoholysis of polyvinyl acetate, the solubility of polyvinyl alcohol generated is relatively high in water, but low in non-polar solvents such as alcohols. This means that when PVA is dissolved in an alcohol solvent, the interaction between its molecules is enhanced, and it is easy to form a hydrophobic region of the polymer. In this case, a gel state will be formed, which will make the system difficult to stir and cause the phenomenon of climbing poles. At this time, if the gel is not evenly broken up, the alcoholysis will be uneven, which will have an adverse effect on the performance and appearance of the product. For example, when making glue or other coatings, the gel will make the product uneven and the viscosity will change. In addition, PVA gel also has potential hazards to equipment. In pipes and filters, the gel may block the pipes or filters, causing equipment shutdown and affecting production efficiency. Therefore, in the process of alcoholysis to generate PVA, the hydrolysis reaction should be controlled to reduce the generation of gel. If the gel has been formed, it needs to be handled in time to avoid affecting the product and equipment. Summary of the invention
[0007] In view of the deficiencies in the above-mentioned prior art, the present invention provides a polyvinyl alcohol product for PVB and a preparation method thereof. The method provided by the present invention has a simple process and can obtain a polyvinyl alcohol product with a specific alcoholysis degree. On the basis of the low-alkali alcoholysis method, the present invention first adds an alcohol aqueous solution to the system when the gel appears to further perform an alcoholysis reaction. On the one hand, the addition of the alcohol aqueous solution can reduce the viscosity of the system, making the gel easier to break, and the alcoholysis more uniform, thereby obtaining a product of better quality. On the other hand, the addition of the alcohol aqueous solution consumes sodium hydroxide, thereby controlling the degree of hydrolysis reaction and obtaining the required alcoholysis degree; subsequently, after washing, filtering and drying with the alcohol aqueous solution, a PVA resin that meets the requirements is obtained.
[0008] The present invention first provides a method for preparing polyvinyl alcohol for PVB, comprising the following steps:
[0009] S1: Add a methanol solution of polyvinyl acetate into a reaction kettle, raise the temperature, and then drop a methanol solution of sodium hydroxide into the solution under stirring, and react in a closed manner until a gel appears;
[0010] S2: When the gel appears in step S1, add the alcohol aqueous solution to the reaction system and stir until the gel breaks up;
[0011] S3: Continue the reaction for 10 to 30 minutes, and the methanol liquid in the gel precipitates (specifically, when the gel appears, the methanol will be wrapped in the gel, and as the alcoholysis reaction proceeds, the methanol will gradually precipitate, and the reaction can be terminated after the methanol precipitates), and then terminate the reaction; filter to obtain wet PVA;
[0012] S4: without drying, add alcohol solution to wash, stir for 30 min, wash twice;
[0013] S5: Filter and dry to obtain a white solid PVA product.
[0014] Preferably, in step S1, the concentration of the polyvinyl acetate methanol solution is 20-30%.
[0015] Preferably, in step S1, the temperature after heating is 35-50°C.
[0016] Preferably, in step S1, the mass concentration of the sodium hydroxide methanol solution is 0.05-0.20.
[0017] Preferably, in step S1, the alkali molar ratio of sodium hydroxide to polyvinyl acetate is 0.005-0.03, wherein the alkali molar ratio is the molar ratio of the amount of sodium hydroxide entering the alcoholysis reaction to the amount of polyvinyl acetate.
[0018] Preferably, in step S1 or S2, the stirring rate is 150 to 300 rpm.
[0019] Preferably, in step S2 or S4, the alcohol in the alcohol aqueous solution is one or any combination of methanol, ethanol or isopropanol.
[0020] Preferably, in step S2 or S4, the alcohol in the alcohol aqueous solution is methanol.
[0021] Preferably, in step S2, the mass ratio of alcohol to water in the alcohol aqueous solution is 50:(1-4).
[0022] Preferably, in step S4, the mass ratio of alcohol to water in the alcohol aqueous solution is (5-20):1.
[0023] Preferably, in step S5, the drying is vacuum drying at a drying temperature of 50-60°C.
[0024] The present invention also provides polyvinyl alcohol for PVB prepared by the above-mentioned preparation method, wherein the alcoholysis degree of the polyvinyl alcohol is 97.0% to 99.0%, and the process index thereof meets the requirements of PVA resin for PVB.
[0025] Compared with the prior art, the technical effects of the present invention are as follows:
[0026] (1) The preparation method provided by the present invention is to use low-alkali sodium hydroxide as a catalyst for alcoholysis, and in particular, when gel appears in the alcoholysis reaction, a certain proportion of alcohol aqueous solution is added to the system to further carry out alcoholysis reaction. On the one hand, the addition of alcohol aqueous solution can reduce the viscosity of the system, make the gel easier to break, increase the swelling degree of PVA, make the alcoholysis more uniform, and obtain a granular product with more uniform alcoholysis and better quality. On the other hand, the addition of alcohol aqueous solution will consume sodium hydroxide, thereby controlling the degree of hydrolysis reaction. By changing the proportion of alcohol aqueous solution added, the alcoholysis degree is controlled to be maintained in a higher range to obtain the required alcoholysis degree; subsequently, after the product is washed and dried, the obtained PVA meets the process indicators of PVA resin material for PVB.
[0027] (2) The present invention, without changing the original equipment, obtains a PVA product that meets the requirements of PVA resin for PVB by changing the production process. This method is simple to operate, can more accurately control the alcoholysis degree of the reaction, and obtain a polyvinyl alcohol product with an alcoholysis degree between 97-99%. The gel is easier to break and the alcoholysis is more uniform. The obtained product has a more uniform alcoholysis degree, better quality, simpler operation, and higher economic benefits.
[0028] (3) The prior art prepares PVA with different alcoholysis degrees by adding water to the system or adding water to the methanol solution of the catalyst sodium hydroxide on the basis of the low-base alcoholysis method, and stopping the reaction by controlling the amount of water added and the reaction time, the purpose of which is to consume the catalyst sodium hydroxide and obtain PVA with different alcoholysis degrees. However, these two methods of adding water at the beginning of the reaction will reduce the reaction rate and accelerate the consumption of sodium hydroxide. Under the same reaction conditions, compared with the present invention, the alcoholysis degree is not high enough. In addition, in the present invention, the alcohol aqueous solution is added when the gel appears, and the alcoholysis degree is already in a higher range. At this time, the alcoholysis degree of PVA can be adjusted more accurately. DETAILED DESCRIPTION
[0029] The exemplary embodiments of the present invention are described in detail below. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to implement the present invention, it should be understood that other embodiments can be implemented and various changes can be made to the present invention without departing from the spirit and scope of the present invention. The principles and features of the present invention are described below in conjunction with specific embodiments, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention.
[0030] The technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. The test methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturer. Unless otherwise specified, all percentages and parts are by weight.
[0031] The experimental materials used in the following examples include:
[0032] Table 2 Experimental raw materials
[0033] name Specification source Polyvinyl acetate Superior products Shanghai Petrochemical Sodium hydroxide Analytical grade Shanghai Aladdin Biochemical Technology Co., Ltd. Deionized water Deionized Shanghai Aladdin Biochemical Technology Co., Ltd. Methanol Analytical grade Shanghai Aladdin Biochemical Technology Co., Ltd. Ethanol Analytical grade Shanghai Aladdin Biochemical Technology Co., Ltd.
[0034] The experimental instruments used in the following examples include:
[0035] Table 3 Experimental instruments
[0036]
[0037]
[0038] The technical scheme of the present invention is described in detail below in conjunction with the embodiments. The following embodiments are implemented on the premise of the technical scheme of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.
[0039] Example 1
[0040] Add 200 g of a 25% methanol solution of polyvinyl acetate to a 1L four-necked reactor, stir, heat to 40°C, stir at a rate of 300 rpm, and add a methanol solution of NaOH with a mass concentration of 0.1 and an alkali molar ratio of 0.02 through a dropping funnel, and then react in a closed environment at 40°C. When a gel appears, add 50 g of a methanol aqueous solution in which the weight of water is 1 g, stir at a rate of 300 rpm, and continue to react for 10 min. After the reaction is completed, filter to obtain a PVA wet product, then add 100 g of a methanol aqueous solution (methanol: water = 10:1) and stir for 30 min, wash twice, filter, and vacuum dry at 60°C for 12 h to obtain a white granular solid PVA product.
[0041] Example 2
[0042] Add 200 g of a 25% methanol solution of polyvinyl acetate to a 1L four-necked reactor, stir, heat to 40°C, stir at a rate of 300 rpm, add a methanol solution of NaOH with a mass concentration of 0.1 and an alkali molar ratio of 0.02 through a dropping funnel, and then react in a closed environment at 40°C. When gel appears, add 50 g of methanol aqueous solution, in which the weight of water is 2 g, stir at a rate of 300 rpm, and continue to react for 10 min. After the reaction is completed, filter to obtain a PVA wet product, then add 100 g of methanol aqueous solution (methanol: water = 10:1) and stir for 30 min, wash twice, filter, and vacuum dry at 60°C for 12 h to obtain a white granular solid PVA product.
[0043] Example 3
[0044] Add 200 g of a 25% methanol solution of polyvinyl acetate to a 1L four-necked reactor, stir, heat to 40°C, stir at a rate of 300 rpm, add a methanol solution of NaOH with a mass concentration of 0.1 and an alkali molar ratio of 0.02 through a dropping funnel, and then react in a closed environment at 40°C. When a gel appears, add 50 g of a methanol aqueous solution, in which the weight of water is 4 g, stir at a rate of 300 rpm, and continue to react for 10 min. After the reaction is completed, filter to obtain a PVA wet product, then add 100 g of a methanol aqueous solution (methanol: water = 10:1) and stir for 30 min, wash twice, filter, and vacuum dry at 60°C for 12 h to obtain a white granular solid PVA product.
[0045] Example 4
[0046] Add 200 g of a 30% methanol solution of polyvinyl acetate to a 1L four-necked reactor, stir, heat to 40°C, stir at a rate of 300 rpm, and add a methanol solution of NaOH with a mass concentration of 0.1 and an alkali molar ratio of 0.01 through a dropping funnel, and then react in a closed environment at 40°C. When a gel appears, add 50 g of a methanol aqueous solution in which the weight of water is 2 g, stir at a rate of 300 rpm, and continue to react for 20 min. After the reaction is completed, filter to obtain a PVA wet product, then add 100 g of a methanol aqueous solution (methanol: water = 10:1) and stir for 30 min, wash twice, filter, and vacuum dry at 60°C for 12 h to obtain a white granular solid PVA product.
[0047] Example 5
[0048] Add 200 g of a 28% methanol solution of polyvinyl acetate to a 1L four-necked reactor, stir, heat to 35°C, stir at a rate of 300 rpm, and drop a 0.1 mass concentration of NaOH in methanol using a dropping funnel, with an alkali molar ratio of 0.02. Then react in a closed environment at 35°C. When gel appears, add 50 g of ethanol aqueous solution, in which the weight of water is 2 g. Stir at a rate of 300 rpm and continue to react for 30 min. After the reaction is completed, filter to obtain a PVA wet product. Add 100 g of methanol aqueous solution (methanol: water = 10:1) and stir for 30 min. Wash twice, filter, and vacuum dry at 60°C for 12 h to obtain a white granular solid PVA product.
[0049] Example 6
[0050] Add 200 g of a 20% methanol solution of polyvinyl acetate to a 1L four-necked reactor, stir, heat to 45°C, stir at a rate of 150 rpm, add a 0.05 mass concentration of NaOH methanol solution with an alkali molar ratio of 0.005 through a dropping funnel, and then react in a closed environment at 45°C. When a gel appears, add 50 g of an ethanol aqueous solution, in which the weight of water is 1 g, stir at a rate of 150 rpm, and continue to react for 10 min. After the reaction is completed, filter to obtain a PVA wet product, then add 100 g of an ethanol aqueous solution (ethanol: water = 5:1) and stir for 30 min, wash twice, filter, and vacuum dry at 50°C for 12 h to obtain a white granular solid PVA product.
[0051] Example 7
[0052] Add 200 g of a 22% methanol solution of polyvinyl acetate to a 1L four-necked reactor, stir, heat to 50°C, stir at 200 rpm, add a methanol solution of NaOH with a mass concentration of 0.15 and an alkali molar ratio of 0.03 through a dropping funnel, and then react in a closed environment at 50°C. When a gel appears, add 50 g of an isopropanol aqueous solution, in which the weight of water is 4 g, stir at 200 rpm, and continue to react for 10 min. After the reaction is completed, filter to obtain a PVA wet product, then add 100 g of an isopropanol aqueous solution (isopropanol: water = 15:1) and stir for 30 min, wash twice, filter, and vacuum dry at 55°C for 12 h to obtain a white granular solid PVA product.
[0053] Add 200 g of a 25% methanol solution of polyvinyl acetate to a 1L four-necked reactor, stir, heat to 40°C, stir at 250 rpm, add a methanol solution of NaOH with a mass concentration of 0.20 and an alkali molar ratio of 0.01 through a dropping funnel, and then react in a closed environment at 40°C. When a gel appears, add 50 g of a methanol aqueous solution, in which the weight of water is 2 g, stir at 250 rpm, and continue to react for 10 min. After the reaction is completed, filter to obtain a PVA wet product, then add 100 g of a methanol aqueous solution (methanol: water = 20:1) and stir for 30 min, wash twice, filter, and vacuum dry at 50°C for 12 h to obtain a white granular solid PVA product.
[0054] Comparative Example 1
[0055] In a 1L four-necked reactor, add 200g of a 25% methanol solution of polyvinyl acetate and 50g of a methanol aqueous solution, of which the weight of water is 2g, and stir. Heat to 40°C, stir at a rate of 300 rpm, and add a methanol solution of NaOH with a mass concentration of 0.1 and an alkali molar ratio of 0.02 through a dropping funnel. Then react in a closed environment at 40°C and continue the reaction for 10min. After the reaction is completed, filter to obtain a PVA wet product, then add 100g of a methanol aqueous solution (methanol: water = 10:1) and stir for 30min, wash twice, filter, and vacuum dry at 60°C for 12h to obtain a white granular solid PVA product.
[0056] The performance test methods of the products obtained in each embodiment and comparative example are shown in Table 1, and the results are shown in Table 4:
[0057] Table 4 Test results of samples in various embodiments of the present invention
[0058]
[0059] As shown in the table above, compared with Comparative Example 1, the difference in experimental conditions between the embodiment and the comparative example 1 is that the alcohol-water solution is added before and after the gel appears. The alcohol-water solution is added before the reaction, and the initial reaction speed is accelerated, but the sodium hydroxide will be consumed, resulting in a decrease in the alcoholysis degree, and thus it does not meet the process indicators of PVA resin for PVB. When the alcohol-water solution is added when the gel appears, because most of the polyvinyl acetate has been alcoholyzed at this time, the added water has little effect on the alcoholysis degree, and it is easier to regulate the alcoholysis degree within a specific range. It can be seen from Examples 1-3 that when the gel appears, different amounts of water added will also result in different alcoholysis degrees, and as the water content increases, the alcoholysis degree first increases and then decreases, indicating that the amount of water added should be kept in a suitable range. Too much water will cause the sodium hydroxide to be consumed too quickly and the alcoholysis degree will decrease, and too little water will cause the alcoholysis rate to be slow and the alcoholysis is not sufficient. In addition, it can be seen from Examples 1, 4, and 5 that the alcoholysis time is extended and the alcoholysis degree will also increase.
[0060] The prior art prepares PVA with different alcoholysis degrees by adding water to the system or adding water to the methanol solution of the catalyst sodium hydroxide on the basis of the low-alkali alcoholysis method, and stopping the reaction by controlling the amount of water added and the reaction time, the purpose of which is to consume the catalyst sodium hydroxide and obtain PVA with different alcoholysis degrees. However, these two methods of adding water at the beginning of the reaction will reduce the reaction speed and accelerate the consumption of sodium hydroxide. Under the same reaction conditions, compared with the present invention, the alcoholysis degree is not high enough. In addition, in the present invention, an alcohol aqueous solution is added when the gel appears, and the alcoholysis degree is already in a higher range. At this time, the alcoholysis degree of PVA is adjusted more accurately.
[0061] When the gel appears, alcohol-water solution is added, and when the process conditions are changed to change the alcoholysis degree, the alcoholysis degree changes relatively little, and it is easier to accurately control, and a PVA product with an alcoholysis degree between 97-99% is obtained. After washing, filtering and drying, a PVA resin product for PVB that meets the requirements is obtained.
[0062] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.
Claims
1. A method for preparing polyvinyl alcohol for PVB, characterized in that: The following steps are involved: S1: Add a methanol solution of polyvinyl acetate into a reaction kettle, raise the temperature, and then drop a methanol solution of sodium hydroxide into the solution under stirring, and react in a closed manner until a gel appears; S2: When the gel appears in step S1, add the alcohol aqueous solution to the reaction system and stir until the gel breaks up; S3: Continue the reaction for 10 to 30 minutes, the methanol liquid in the gel precipitates, and the reaction is terminated; filter to obtain wet PVA; S4: without drying, add alcohol solution to wash, stir for 30 min, wash twice; S5: Filter and dry to obtain a white solid PVA product.
2. The method for preparing polyvinyl alcohol for PVB according to claim 1, characterized in that: In step S1, the concentration of the polyvinyl acetate methanol solution is 20-30%.
3. The method for preparing polyvinyl alcohol for PVB according to claim 1, characterized in that: In step S1, the temperature after heating is 35-50°C.
4. The method for preparing polyvinyl alcohol for PVB according to claim 1, characterized in that: In step S1, the mass concentration of the sodium hydroxide methanol solution is 0.05-0.
20.
5. The method for preparing polyvinyl alcohol for PVB according to claim 1, characterized in that: In step S1, the alkali mole ratio of sodium hydroxide to polyvinyl acetate is 0.005-0.03, wherein the alkali mole ratio is the mole ratio of the amount of sodium hydroxide entering the alcoholysis reaction to the amount of polyvinyl acetate.
6. The method for preparing polyvinyl alcohol for PVB according to claim 1, characterized in that: In step S1 or S2, the stirring rate is 150 to 300 rpm.
7. The method for preparing polyvinyl alcohol for PVB according to claim 1, characterized in that: In step S2 or S4, the alcohol in the alcohol aqueous solution is one or any combination of methanol, ethanol or isopropanol.
8. The method for preparing polyvinyl alcohol for PVB according to claim 1, characterized in that: In step S2 or S4, the alcohol in the alcohol aqueous solution is methanol.
9. The method for preparing polyvinyl alcohol for PVB according to claim 1, characterized in that: In step S2, the mass ratio of alcohol to water in the alcohol aqueous solution is 50:(1-4).
10. The method for preparing polyvinyl alcohol for PVB according to claim 1, characterized in that: In step S4, the mass ratio of alcohol to water in the alcohol aqueous solution is (5-20):
1.
11. The method for preparing polyvinyl alcohol for PVB according to claim 1, characterized in that: In step S5, the drying is vacuum drying at a drying temperature of 50-60°C.
12. Polyvinyl alcohol for PVB prepared according to any one of the preparation methods of claims 1 to 11, characterized in that: The alcoholysis degree of the polyvinyl alcohol is 97.0% to 99.0%, and its process index meets the requirements of PVA resin for PVB.