Method for continuously synthesizing polyvinyl acetal resin and adhesive film
The method of continuously synthesizing polyvinyl acetal resin from vinyl acetate solves the problems of high production cost and low efficiency, and realizes the efficient production of high-purity resin, which is suitable for laminated glass and photovoltaic module packaging film.
Patent Information
- Application Number
- CN202510836374.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-21
- Publication Date
- 2025-09-09
AI Technical Summary
In the prior art, the production cost of polyvinyl butyral is high and the production efficiency is low, and the purity of PVB synthesized by the existing one-step method is low.
Polyvinyl acetal resin is continuously synthesized from vinyl acetate through polymerization, alcoholysis and condensation reactions in independent reaction systems. The same alcohol solvent is used and the reaction conditions are controlled to improve purity and efficiency.
It reduces energy consumption and improves production efficiency. The polyvinyl acetal resin produced has high purity and is suitable for manufacturing laminated glass, photovoltaic module packaging film, etc.
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Figure CN120607653A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of resin synthesis, and in particular to a method for continuously synthesizing polyvinyl acetal resin and a film thereof. Background Art
[0002] Polyvinyl butyral (PVB) molecules contain long side chains, resulting in high tensile and impact strength. Its functional groups provide strong adhesion to materials such as glass and metal, making it widely used in the manufacture of laminated glass. Polyvinyl butyral is formed by the acid-catalyzed condensation of polyvinyl alcohol and butyraldehyde. Polyvinyl alcohol, in turn, is formed by the alcoholysis of polyvinyl acetate, which in turn is formed by the polymerization of vinyl acetate. These three reactions proceed independently, and the products of each reaction must undergo washing, drying, and other steps, and all require strict storage conditions. This increases the manufacturing cost and efficiency of polyvinyl butyral.
[0003] In order to reduce costs and improve production efficiency, the existing technology (paper "Difficulties of One-Step Synthesis of PVB Resin", Journal: Anhui Science and Technology, 2014 (11), authors: Hu Anning, Chen Jianxu) discloses the use of polyvinyl acetate (PVAC) to first undergo alcoholysis to produce PVA, and then react with butyraldehyde to produce PVB; the entire reaction process is carried out in one reaction system, and there are problems such as low purity of the prepared PVB.
[0004] In order to solve the above problems, it is currently urgent to invent a method for continuously synthesizing polyvinyl acetal resin and a film to reduce the manufacturing cost of PVB and improve the production efficiency of PVB. Summary of the Invention
[0005] A first aspect of the present invention provides a method for continuously synthesizing polyvinyl acetal resin. The first purpose is to continuously synthesize polyvinyl acetal resin and reduce production costs.
[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions.
[0007] A method for continuously synthesizing polyvinyl acetal resin using vinyl acetate comprises the following steps: S1: Polymerization reaction, vinyl acetate is polymerized under warm conditions to obtain a first product, the first product comprising more than 97 wt% of polyvinyl acetate and less than 3 wt% of an alcohol solvent, and the viscosity of the first product is 25-32 mPa·s; S2: alcoholysis reaction, performing alcoholysis on the first product obtained in S1 under alkaline conditions to obtain a second product, wherein the second product comprises 35 wt % to 50 wt % of polyvinyl alcohol and 50 wt % to 65 wt % of an alcohol solvent; S3: condensation reaction, condensing the second product obtained in S2 with an aldehyde substance under acidic conditions to obtain a polyvinyl acetal resin; The alcohol solvent in step S1 and the alcohol solvent in step S2 are the same alcohol solvent. Preferably, the alcohol solvent in step S1 and the alcohol solvent in step S2 are methanol.
[0008] According to the above-mentioned method for continuously synthesizing polyvinyl acetal resin, the polymerization reaction comprises the following steps: S11: dissolving vinyl acetate to obtain vinyl acetate solution; S12: initiating polymerization, adding an initiator to the vinyl acetate solution to initiate polymerization of vinyl acetate; S13: Recovery: Recover unreacted vinyl acetate using a methanol distillation process to obtain a first product.
[0009] According to the above-described method for continuously synthesizing polyvinyl acetal resin, the alcoholysis reaction comprises: S21: a primary alcoholysis, wherein the alcoholysis rate of the primary alcoholysis is greater than 90%; S22: secondary alcoholysis, wherein the alcoholysis rate of the secondary alcoholysis is greater than 99.5%; Wherein, the secondary alcoholysis is configured as the alcoholysis of the polyvinyl acetate remaining after the primary alcoholysis and the purification of polyvinyl alcohol, and the second product is obtained after the secondary alcoholysis.
[0010] According to the above-mentioned method for continuously synthesizing polyvinyl acetal resin, the condensation reaction includes: S31: dissolving the second product: dissolving the second product in water at a dissolution temperature of 40°C-55°C, recovering methanol after the dissolution is complete to obtain a third product, wherein the third product is an 8wt%-12wt% polyvinyl alcohol aqueous solution, and adding hydrochloric acid to the third product until the pH value of the solution reaches 1.0-2.5; S32: Polymerization of polyvinyl alcohol: add aldehydes and hydrochloric acid to the solution with a pH of 1.0-2.5 in S31, and keep the temperature at 70-75°C for 1.5-2.5 hours; S33: Post-treatment: neutralization, washing, dehydration and drying to obtain polyvinyl acetal resin powder.
[0011] According to the above-mentioned method for continuously synthesizing polyvinyl acetal resin, the hydroxyl content of the polyvinyl acetal resin powder is 17wt%-18wt%, and the melt index of the polyvinyl acetal resin powder is 8g / 10min-11g / 10min.
[0012] According to the above-described method for continuously synthesizing polyvinyl acetal resin, the second product is dried to obtain polyvinyl alcohol powder with a particle size of 1.0 mm to 1.3 mm. The second product also includes less than 1 wt % of methyl acetate, sodium acetate, sodium chloride and sodium hydroxide.
[0013] According to the above-mentioned method for continuously synthesizing polyvinyl acetal resin, the first product further includes less than 1 wt % of citral, acetaldehyde and acetic acid.
[0014] According to the above-mentioned method for continuously synthesizing polyvinyl acetal resin, In S11, vinyl acetate is dissolved in methanol at 20°C-35°C to obtain a vinyl acetate methanol solution; In S12, the reaction temperature for initiating the reaction is 60°C-67°C, and the reaction time is 4h-6h; In S13, the distillation temperature of the methanol distillation process is 1°C-3°C lower than the reaction temperature of the initiation reaction in S12.
[0015] According to the above-described method for continuous synthesis of polyvinyl acetal resin, in S21, the reaction temperature of the primary alcoholysis is 30°C-40°C, and the reaction temperature of the secondary alcoholysis is 64°C-65°C.
[0016] A second aspect of the present invention provides an adhesive film comprising a polyvinyl acetal resin prepared by the above-described method for continuous synthesis of a polyvinyl acetal resin and a plasticizer, wherein the plasticizer is present in an amount of 10-100 parts by weight per 100 parts by weight of the polyvinyl acetal resin. The adhesive film provided by the present invention is used to manufacture laminated glass for automobiles, laminated glass for buildings, and encapsulation films for photovoltaic modules.
[0017] Compared with the prior art, the present invention has the following technical effects: The present invention provides a method for continuously synthesizing a polyvinyl acetal resin and a film, wherein vinyl acetate is used to continuously synthesize the polyvinyl acetal resin, and the polyvinyl acetal resin is continuously prepared through polymerization reaction, alcoholysis reaction and condensation reaction. The product obtained in each reaction step does not need to be dried, thereby reducing energy consumption and improving production efficiency.
[0018] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0020] Figure 1 The present invention shows a process flow chart of a method for continuously synthesizing polyvinyl acetal resin. DETAILED DESCRIPTION
[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without carrying out creative work are within the scope of protection of the present invention.
[0022] Technologies, methods and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, such technologies, methods and equipment should be considered part of the authorization specification.
[0023] In the description of the present invention, it should be understood that the use of terms such as "first" and "second" to define components, etc., is merely for the purpose of distinguishing the corresponding components, etc., and unless otherwise stated, these terms have no special meaning and therefore should not be construed as limiting the scope of protection of the present invention. In the description of the present invention, "wt%" means weight percentage, and unless otherwise stated, "wt%" means weight percentage.
[0024] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0025] See also Figure 1 A method for continuously synthesizing polyvinyl acetal resin using vinyl acetate comprises the following steps: S1: Polymerization reaction, wherein vinyl acetate is polymerized under warm conditions to obtain a first product, wherein the first product comprises at least 97 wt% (weight percentage, the same below) of polyvinyl acetate and at most 3 wt% (weight percentage, the same below) of an alcohol solvent, and the viscosity of the first product is 25 mPa·s to 32 mPa·s; S2: alcoholysis reaction, performing alcoholysis on the first product obtained in S1 under alkaline conditions to obtain a second product, wherein the second product comprises 35 wt % to 50 wt % of polyvinyl alcohol and 50 wt % to 65 wt % of an alcohol solvent; S3: condensation reaction, condensing the second product obtained in S2 with an aldehyde substance under acidic conditions to obtain a polyvinyl acetal resin; The alcohol solvent in step S1 and the alcohol solvent in step S2 are the same alcohol solvent.
[0026] Specifically, steps S1, S2, and S3 are performed sequentially, and each step is performed in a separate reaction system. It is understood that step S1 is performed in the first reaction system, step S2 is performed in the second reaction system, and step S3 is performed in the third reaction system. The products of each step are transported between the first, second, and third reaction systems via a transport device (e.g., a solution is transported through a vacuum pump). Exemplarily, both the first and second products are transported to the second or third reaction system via a screw vacuum pump. The first product includes not only polyvinyl acetate produced by the polymerization reaction but also a portion of the solvent added during the polymerization reaction (exemplarily, methanol). To meet the requirements of the subsequent synthesis of polyvinyl acetal resin, the viscosity of the first product must be between 25 and 32 mPa·s, and this viscosity also facilitates the transport of the first product. At this viscosity, the first product comprises at least 97 wt% polyvinyl acetate and 3 wt% to 1 wt% of an alcohol solvent (in the present invention, methanol is generally used as the alcohol solvent, unless otherwise stated). From improving synthesis efficiency, reducing the occurrence of side reactions, the time interval between step S1, step S2 and step S3 is not easy to be too long, and the time interval needs to be controlled within 1h. The time interval is under the demand condition that the reaction product is transported from the previous reaction system to the next reaction system, and the shorter the time interval, the better. The above-mentioned warm condition refers to the condition that the reaction temperature is below 50 ° C. Preferably, the warm condition refers to the reaction temperature below 40 ° C.
[0027] In a specific embodiment, the polymerization reaction comprises the following steps: S11: dissolving vinyl acetate to obtain vinyl acetate solution; S12: initiating polymerization, adding an initiator to the vinyl acetate solution to initiate polymerization of vinyl acetate; S13: Recovery: Recover unreacted vinyl acetate using a methanol distillation process to obtain a first product.
[0028] Specifically, in S13, a methanol distillation process is used to remove unreacted vinyl acetate solution from the reaction using methanol vapor for recovery. It should be noted that the dissolution of vinyl acetate in S11, the initiation of polymerization of vinyl acetate in S12, and the recovery in S13 are each carried out in separate reaction vessels. Exemplarily, S11 and S12 are each carried out in two reactors equipped with stirring devices, with the reaction product being transported between the two reactors equipped with stirring devices via a vacuum pump. S13 is carried out in a reactor equipped with a stirring device and a distillation recovery device.
[0029] In a specific embodiment, the alcoholysis reaction comprises: S21: a primary alcoholysis, wherein the alcoholysis rate of the primary alcoholysis is greater than 90%; S22: secondary alcoholysis, wherein the alcoholysis rate of the secondary alcoholysis is greater than 99.5%; Wherein, the secondary alcoholysis is configured as the alcoholysis of the polyvinyl acetate remaining after the primary alcoholysis and the purification of polyvinyl alcohol, and the second product is obtained after the secondary alcoholysis.
[0030] Specifically, the primary alcoholysis is the main alcoholysis process, and most of the polyvinyl acetate undergoes alcoholysis to produce polyvinyl alcohol. The remaining polyvinyl acetate further undergoes alcoholysis during the recovery of the alcohol solvent. It can be understood that the role of the secondary alcoholysis is to alcoholyze the remaining vinyl acetate and recover the alcohol solvent. During the secondary alcoholysis process, the alcohol solvent is not completely recovered. The remaining alcohol solvent and the generated polyvinyl alcohol enter the condensation reaction in step S3 as the second product. The secondary alcoholysis is based on the alcoholysis rate of polyvinyl acetate being greater than or equal to 99.5%. At this time, the polyvinyl alcohol generated can meet the requirements of the subsequent condensation reaction with aldehyde substances, and the content of the remaining methanol also meets the subsequent needs. It should be noted that the primary alcoholysis in S21 and the secondary alcoholysis in S22 are respectively carried out in two independent reactors (in the present invention, unless otherwise stated, the reactor is generally equipped with a stirring device), and the materials are transported between the two reactors by a vacuum pump.
[0031] In a specific embodiment, the condensation reaction comprises: S31: dissolving the second product: dissolving the second product in water at a dissolution temperature of 40°C-55°C, recovering methanol after the dissolution is complete to obtain a third product, wherein the third product is an 8wt%-12wt% polyvinyl alcohol aqueous solution, and adding hydrochloric acid to the third product until the pH value of the solution reaches 1.0-2.5; S32: Polymerization of polyvinyl alcohol: add aldehydes and hydrochloric acid to the solution with a pH of 1.0-2.5 in S31, and keep the temperature at 70-75°C for 1.5-2.5 hours; S33: Post-treatment: neutralization, washing, dehydration and drying to obtain polyvinyl acetal resin powder.
[0032] Specifically, the second product includes polyvinyl alcohol and methanol. Polyvinyl alcohol can be completely dissolved in water at about 50°C (generally 45°C-55°C) under the action of methanol.
[0033] In a specific embodiment, the hydroxyl content of the polyvinyl acetal resin powder is 17 wt %-18 wt %, and the melt index of the polyvinyl acetal resin powder is 8 g / 10 min-11 g / 10 min.
[0034] In a specific embodiment, the second product, after drying, yields a polyvinyl alcohol powder having a particle size of 1.0 mm to 1.3 mm. The second product also includes less than 1 wt % of methyl acetate, sodium acetate, sodium chloride, and sodium hydroxide. Specifically, methyl acetate, sodium acetate, sodium chloride, and sodium hydroxide are unavoidable impurities generated during the reaction. By adjusting process parameters, the inventors have been able to control the impurity content to 1 wt %. Furthermore, when the impurity content is below 1 wt %, it does not affect subsequent reactions or the properties of the target product (polyvinyl acetal resin).
[0035] In a specific embodiment, the first product further comprises less than 1 wt % of citral, acetaldehyde, and acetic acid. It should be noted that citral, acetaldehyde, and acetic acid are unavoidable impurities generated during the reaction. By adjusting the process parameters, the inventors have been able to control the impurity content to 1 wt %. Furthermore, when the impurity content is below 1 wt %, it will not affect subsequent reactions or the properties of the target product (polyvinyl acetal resin).
[0036] In a specific embodiment, In S11, vinyl acetate is dissolved in methanol at 20°C-35°C to obtain a vinyl acetate methanol solution; In S12, the reaction temperature for initiating the reaction is 60°C-67°C, and the reaction time is 4h-6h; In S13, the distillation temperature of the methanol distillation process is 1°C-3°C lower than the reaction temperature of the initiation reaction in S12.
[0037] In a specific embodiment, in S21, the reaction temperature of the primary alcoholysis is 30°C-40°C, and the reaction temperature of the secondary alcoholysis is 64°C-65°C.
[0038] A second aspect of the present invention provides an adhesive film comprising a polyvinyl acetal resin prepared by the above-described method for continuous synthesis of a polyvinyl acetal resin and a plasticizer, wherein the plasticizer is present in an amount of 10-100 parts by weight per 100 parts by weight of the polyvinyl acetal resin. The adhesive film provided by the present invention is used to manufacture laminated glass for automobiles, laminated glass for buildings, and encapsulation films for photovoltaic modules.
[0039] The technical solution of the present invention is described below using the continuous synthesis of polyvinyl butyral (PVB) resin. Example
[0040] S11: Add 9000 g of vinyl acetate and 2340 g of methanol to the first mixing reactor, heat to 25°C (it should be noted that the heating temperature is not strictly required to be 25°C, and can be around 25°C, such as 24°C, 26°C, 27°C, 28°C, 29°C, 30°C, etc.), and stir at a speed of 200 r / min for 300 min until the vinyl acetate is completely dissolved; wherein the purity of vinyl acetate is 99.99%, and the purity of methanol is 99.99%.
[0041] S12: Transfer the solution in the first mixing reactor (unless otherwise stated, the solution or material transfer in the present invention is generally transported by a screw vacuum pump, the difference lies in the model and power of the screw vacuum pump) to the polymerization reactor, add 4.05 g of initiator (illustratively, in this embodiment, the initiator is azobisisobutyronitrile) into the polymerization reactor, the reaction temperature is 61°C, the stirring speed is 250 r / min, and the reaction time is 5 h.
[0042] S13: The solution in the polymerization reactor (the solution at this time contains methanol, citric acid, polyvinyl acetate, acetaldehyde, acetic acid, and vinyl acetate) is transferred to a first recovery reactor. The first recovery reactor is equipped with a distillation device (a distillation process using methanol distillation is used to use methanol vapor to remove the unreacted vinyl acetate solution in the reaction to the recovery device). After the distillation is completed, a methanol solution of polyvinyl acetate is obtained, i.e., the first product. At this time, the first product includes 97.6wt% polyvinyl acetate and 1.8wt% methanol, and the remainder is unavoidable impurities.
[0043] S21: The first product S was transferred to a first alcoholysis reactor. 836 g of sodium hydroxide and 23.5 kg of methanol were added to the first alcoholysis reactor. The reaction temperature was 35°C, the reaction time was 25 min, and the stirring speed was 300-500 rpm. Testing revealed an alcoholysis rate of 98.4% for the polyvinyl acetate.
[0044] S22: The product after alcoholysis in S21 is transferred to a second recovery reactor equipped with a distillation device for heating. When the temperature reaches 64°C, recovery begins. During this process, the polyvinyl acetate that was not alcoholysed in step S21 will continue to alcoholyze, and methanol will be distilled and recovered. After distillation, polyvinyl alcohol with a purity of 40% is obtained, and the polyvinyl alcohol contains 58% methanol, which is the second product. A small amount of the second product is dried and then tested. The size of the PVA is 1.18-1.25mm (more than 80% of the PVA size falls within this range). It can be understood that the second product is dried for the purpose of measuring the particle size of the PVA resin powder. It is not necessary to dry the second product in the continuous synthesis of polyvinyl butyral.
[0045] S31: The second mixture is transferred to a second mixing reactor, and 20L of water is added to the second mixing reactor. The dissolution temperature is 50±2°C and the stirring speed is 250r / min. After 30 minutes, the polyvinyl alcohol is completely dissolved. After complete dissolution, the methanol is subsequently recovered through a sieve plate column; after the methanol is completely discharged, hydrochloric acid is added until the pH value of the solution is 1.3.
[0046] S32: The product obtained in S31 is transferred to a condensation reactor, and the condensation reaction process is as follows: 1.42 kg of butyraldehyde is added at 17 ° C, 382 g of hydrochloric acid is added at 13 ° C, T7.78 g is accelerated, the phase change temperature is raised to 72 ° C, and the temperature is kept for two hours; specifically, in order to prevent the added materials from affecting each other, butyraldehyde is added to reactor one, the temperature of reactor one is maintained at 17 ° C, and then transferred to reactor two and hydrochloric acid is added, the temperature of reactor two is maintained at 13 ° C, a vacuum pump is used to transfer materials between reactor one and reactor two, and during the material transfer process, the material temperature drops by 2 ° C -3 ° C, and the material temperature can be lowered by lengthening the distance of the conveying pipeline, etc. The materials in reactor two are mixed evenly and then transferred to reactor three.
[0047] S33: Post-processing: The insulated PVB resin powder was washed 8-9 times with water at 50°C, filtered, and dried to obtain PVB resin powder. Testing of the PVB resin powder revealed a viscosity of 82 mPa·s, a hydroxyl content of 17.4 wt%, and a melt index of 9.3 g / 10 min.
[0048] It is understandable that during the continuous synthesis of polyvinyl acetal resin, processes at different temperatures are carried out in different reaction vessels (an exemplary reaction vessel is a reactor) to avoid repeated heating or cooling of a reactor, which increases its energy consumption.
[0049] The hydroxyl content and melt index are tested according to the provisions of standard HG / T6047-2022.
[0050] The viscosity was tested using a Tu-1 cup viscometer.
[0051] Tu-1 cup viscosity: Weigh 15g of PVB resin powder sample and 135g of anhydrous ethanol, mix thoroughly, and pour into the Tu-1 cup for measurement. Wipe the viscometer cup clean with gauze and solvent, dry it, and inspect it under a light to ensure that key parts, such as the Tu-1 viscometer nozzle, are clean. Stir the sample to be tested for viscosity. Adjust the sample temperature to 20±1°C. Place the Tu-1 viscometer in a water bath, insert the stopper, and introduce the sample into the viscometer. Adjust the leveling screw to ensure the liquid level is aligned with the scale. Close the lid and insert the thermometer. Allow to stand for a moment to allow any bubbles in the sample to escape. Place a 50mL measuring cup under the viscometer nozzle. When the sample temperature reaches the standard described in step 2, quickly remove the stopper and start a stopwatch. Stop the stopwatch immediately when the sample volume in the cup reaches the 50mL mark. The time required for 50mL of sample to flow into the cup is the sample outflow time. The average of three measurements is used as the measurement result. The difference between the three measurements should not exceed 3% of the average. Example
[0052] A film comprises 100 parts by weight of the polyvinyl butyral resin of Example 1, 50 parts by weight of a plasticizer, and necessary additives, wherein the additives include one or more of an antioxidant, an ultraviolet absorber, an infrared absorber, a dye, a flame retardant, a heat insulating agent, an adhesion regulator, and the like. The content of the additives is selectively configured by those skilled in the art according to the prior art and is not described in detail here. In this Example 2, the additive is an antioxidant, and the content of the antioxidant is 0.2 parts by weight.
[0053] Examples of the plasticizer include organic ester plasticizers such as monobasic organic acid esters and polybasic organic acid esters, and organic phosphate plasticizers such as organic phosphate plasticizers and organic phosphite plasticizers. Among these, organic ester plasticizers are preferred. The plasticizer is preferably a liquid plasticizer. In this embodiment, the plasticizer is triethylene glycol di-2-ethylhexanoate (3GO).
[0054] Examples of the antioxidant include pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), n-octadecanol β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and isooctyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate. In this embodiment, the antioxidant is pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.
[0055] Examples of the ultraviolet absorber include benzotriazole ultraviolet absorbers such as UV-P, UV-326, UV-327, and UV-531, triazine ultraviolet absorbers, and salicylate ultraviolet absorbers.
[0056] The method for producing the adhesive film is not particularly limited. In the case of a single-layer adhesive film, the method for producing the adhesive film may include extruding the resin composition using an extruder. In the case of a multilayer adhesive film, the method for producing the adhesive film may include laminating the obtained layers after forming each layer using each resin composition for forming each layer; and laminating the obtained layers by co-extruding each resin composition for forming each layer using an extruder. For suitability for continuous production, a method of producing by extrusion molding is preferred.
[0057] The method for manufacturing the adhesive film is explained by taking the manufacture of a single-layer film as an example.
[0058] Step 1: Pour the polyvinyl butyral resin and antioxidant into a mixing machine in proportion and stir and mix them for a period of not less than 20 minutes; Step 2: Add the stirred material to the inlet of the screw extruder, and at the same time inject a preset proportion of liquid plasticizer into the screw extruder through a vacuum pump. The temperature of each section of the extruder is 130°C to 220°C, and the extrusion time is 5 to 10 minutes; Step 3: The extruded film is pressed by an embossing roller, cooled, and rolled up to form an intermediate film; Step 4: Packaging after inspection.
[0059] The above description is merely an exemplary embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A method for continuously synthesizing polyvinyl acetal resin, characterized in that: The continuous synthesis of polyvinyl acetal resin using vinyl acetate comprises the following steps: S1: Polymerization reaction, vinyl acetate is polymerized under warm conditions to obtain the first product; S2: alcoholysis reaction, performing alcoholysis on the first product obtained in S1 under alkaline conditions to obtain a second product, wherein the second product comprises 35 wt % to 50 wt % of polyvinyl alcohol and 50 wt % to 65 wt % of an alcohol solvent; S3: condensation reaction, condensing the second product obtained in S2 with an aldehyde substance under acidic conditions to obtain a polyvinyl acetal resin; The alcohol solvent in step S1 and the alcohol solvent in step S2 are the same alcohol solvent.
2. The method for continuously synthesizing polyvinyl acetal resin according to claim 1, wherein: The polymerization reaction comprises the following steps: S11: dissolving vinyl acetate to obtain vinyl acetate solution; S12: initiating polymerization, adding an initiator to the vinyl acetate solution to initiate polymerization of vinyl acetate; S13: Recovery: Recovering unreacted vinyl acetate using a methanol distillation process to obtain a first product; The first product comprises more than 97 wt % of polyvinyl acetate and less than 3 wt % of an alcohol solvent, and the viscosity of the first product is 25-32 mPa·s.
3. The method for continuously synthesizing polyvinyl acetal resin according to claim 1, wherein: The alcoholysis reaction comprises: S21: a primary alcoholysis, wherein the alcoholysis rate of the primary alcoholysis is greater than 90%; S22: secondary alcoholysis, wherein the alcoholysis rate of the secondary alcoholysis is greater than 99.5%; Wherein, the secondary alcoholysis is configured as the alcoholysis of the polyvinyl acetate remaining after the primary alcoholysis and the purification of polyvinyl alcohol, and the second product is obtained after the secondary alcoholysis.
4. The method for continuously synthesizing polyvinyl acetal resin according to claim 1, wherein: The condensation reaction comprises: S31: dissolving the second product: dissolving the second product in water at a dissolution temperature of 40°C-55°C, recovering methanol after the dissolution is complete to obtain a third product, wherein the third product is an 8wt%-12wt% polyvinyl alcohol aqueous solution, and adding hydrochloric acid to the third product until the pH value of the solution reaches 1.0-2.5; S32: Condensation of polyvinyl alcohol: add aldehydes and hydrochloric acid to the solution with a pH of 1.0-2.5 in S31, and keep the temperature at 70-75°C for 1.5-2.5 hours; S33: Post-treatment: neutralization, washing, dehydration and drying to obtain polyvinyl acetal resin powder.
5. The method for continuously synthesizing polyvinyl acetal resin according to claim 4, characterized in that: The hydroxyl content of the polyvinyl acetal resin powder is 17 wt %-18 wt %, and the melt index of the polyvinyl acetal resin powder is 8 g / 10 min-11 g / 10 min.
6. The method for continuously synthesizing polyvinyl acetal resin according to claim 3, characterized in that: After drying, the second product obtains polyvinyl alcohol powder with a particle size of 1.0 mm to 1.3 mm. The second product also includes less than 1 wt % of methyl acetate, sodium acetate, sodium chloride and sodium hydroxide.
7. The method for continuously synthesizing polyvinyl acetal resin according to claim 2, characterized in that: The first product also includes less than 1 wt % of citral, acetaldehyde and acetic acid.
8. The method for continuously synthesizing polyvinyl acetal resin according to claim 2, wherein: In S11, vinyl acetate is dissolved in methanol at 20°C-35°C to obtain a vinyl acetate methanol solution; In S12, the reaction temperature for initiating the reaction is 60°C-67°C, and the reaction time is 4h-6h; In S13, the distillation temperature of the methanol distillation process is 1°C-3°C lower than the reaction temperature of the initiation reaction in S12.
9. The method for continuously synthesizing polyvinyl acetal resin according to claim 3, wherein: In S21, the reaction temperature of the primary alcoholysis is 30°C-40°C, and the reaction temperature of the secondary alcoholysis is 64°C-65°C.
10. A film, characterized in that: The invention comprises a polyvinyl acetal resin prepared by the method for continuously synthesizing a polyvinyl acetal resin according to any one of claims 1 to 9 and a plasticizer, wherein the plasticizer is in an amount of 10 to 100 parts by weight relative to 100 parts by weight of the polyvinyl acetal resin.