Composite solid catalyst, its preparation method and application, and polyvinyl butyral and its synthesis method

Abstract

The present application relates to the technical field of high polymer material preparation, and particularly relates to a composite solid catalyst, a preparation method and application thereof, and polyvinyl butyral and a synthesis method thereof.The composite solid catalyst provided by the present application has a reuse frequency of 8-12 times, which is much higher than that of the existing solid catalyst, and the activity retention rate reaches more than 80%, thereby greatly reducing the consumption cost of the solid catalyst.The present application utilizes the composite solid catalyst, and then uses polyvinyl alcohol and n-butyl aldehyde as raw materials to synthesize polyvinyl butyral in a supercritical CO2-ethanol mixed medium through a three-stage pressurization method.The present application solves the problems of poor catalytic stability, low reaction efficiency and single product performance in the traditional method through the synergistic catalysis of the composite catalyst and the mass transfer optimization of the segmented pressurization process.

Description

Technical Field

[0001] This invention relates to the field of polymer material preparation technology, and in particular to a composite solid catalyst, its preparation method and application, and polyvinyl butyral and its synthesis method. Background Technology

[0002] Polyvinyl butyral (PVB) is widely used in interlayer films of laminated glass, metal treatment primers or adhesives due to its excellent film-forming properties, transparency, impact energy absorption and adhesion to glass. In recent years, its application in the field of electronic materials has also been expanding.

[0003] Traditional methods for preparing polyvinyl butyral rely on liquid acid catalysts such as hydrochloric acid, resulting in the presence of impurities such as residual halogen ions and basic ions in the product. This necessitates cumbersome neutralization and washing steps, which not only increases production costs but also makes it difficult to meet the purity requirements of high-end fields such as electronic materials.

[0004] US Patent 2007 / 0293651A1 discloses a method for preparing polyvinyl butyral using a solid catalyst under pressure, eliminating the dependence on liquid acid catalysts and achieving a butyralization degree of over 70 mol% in the prepared product. However, this preparation method still has significant shortcomings, such as limited catalyst performance: the solid catalysts used, such as acidic alumina or polystyrene sulfonic acid resin, exhibit significant catalytic activity degradation after 3-5 repeated uses under high pressure and high temperature conditions, with residual activity not exceeding 60%, increasing the cost of industrial production.

[0005] Therefore, developing a method for preparing polyvinyl butyral with high catalytic stability is an urgent problem to be solved in this field. Summary of the Invention

[0006] In view of this, the present invention provides a composite solid catalyst, its preparation method and application, as well as polyvinyl butyral and its synthesis method. The composite solid catalyst provided by the present invention has high stability and can be reused 8 to 12 times.

[0007] This invention provides a composite solid catalyst, comprising a support and an active component and a co-catalyst supported on the surface of the support; the support comprises ZSM-5 molecular sieve; the active component comprises sulfonated styrene-divinylbenzene copolymer; and the co-catalyst comprises Sn. 4+ .

[0008] Preferably, the sulfonated styrene-divinylbenzene copolymer is a styrene-divinylbenzene crosslinked copolymer with sulfonic acid groups (-SO3H) as active sites, and is a macroporous strong acid cation exchange resin; the degree of sulfonation (exchange capacity) of the sulfonated styrene-divinylbenzene copolymer is 4~5 mmol / g.

[0009] Preferably, the mass ratio of the support to the active component is 1:0.3~0.8; and the mass ratio of the support to the co-catalyst is 1:0.05~0.15.

[0010] The present invention also provides a method for preparing the composite solid catalyst described above, comprising the following steps: (1) The carrier is immersed in the active component solution and ultrasonically dispersed to obtain the active component carrier; (2) The active component support is doped with a cocatalyst compound to obtain the composite solid catalyst.

[0011] The present invention also provides the application of the composite solid catalyst described in the above-described scheme or the composite solid catalyst obtained by the preparation method described in the above-described scheme in the preparation of polyvinyl butyral.

[0012] This invention also provides a method for synthesizing polyvinyl butyral, comprising the following steps: Polyvinyl alcohol (PVA), supercritical CO2-ethanol mixed medium, n-butyraldehyde, pH adjuster and composite solid catalyst are mixed to obtain a mixture, and then the mixture is subjected to a staged pressurized reaction to obtain polyvinyl butyral; the composite solid catalyst is the composite solid catalyst described in the above scheme or the composite solid catalyst obtained by the preparation method described in the above scheme.

[0013] Preferably, the equipment for the segmented pressurized reaction includes a high-pressure reaction device with a built-in spiral baffle; the high-pressure reaction device with a built-in spiral baffle includes a raw material storage tank, a pressurization pump, a preheating section, a reaction section, a cooling section, and a product collection tank connected in sequence; the reaction section is a catalyst column with a built-in spiral baffle, and a detachable catalyst fixed bed is provided inside the catalyst column, with a composite solid catalyst filled in the detachable catalyst fixed bed.

[0014] Preferably, the segmented pressurized reaction includes a first-stage preheating, a second-stage reaction, and a third-stage maturation performed sequentially; the first-stage preheating temperature is 80~100 degrees Celsius, the pressure is 0.1~0.3 MPa, and the holding time is 10~20 minutes; the second-stage reaction temperature is 110~130 degrees Celsius, the pressure is 4~6 MPa, and the holding time is 20~40 minutes; the third-stage maturation temperature is 80~90 degrees Celsius, the pressure is 1~2 MPa, and the holding time is 5~10 minutes.

[0015] Preferably, the step after the staged pressurized reaction further includes post-processing of the obtained product; the post-processing further includes regenerating the obtained composite solid catalyst; the regeneration is a heat treatment, the temperature of which is 100~110 degrees Celsius and the holding time is 2~3 hours.

[0016] The present invention also provides polyvinyl butyral obtained by the above-described synthesis method, with a degree of butyralization of 85-92 mol%, a hydroxyl retention rate of 10-15%, a haze of not more than 0.1%, and a thermal decomposition temperature of not less than 150 degrees Celsius.

[0017] This invention provides a composite solid catalyst. Existing solid catalysts suffer from poor stability, specifically exhibiting poor reusability and rapid catalytic activity decay. The composite solid catalyst provided by this invention can be reused 8-12 times, far exceeding the existing solid catalysts (3-5 times), with an activity retention rate exceeding 80%, significantly reducing the consumption cost of solid catalysts.

[0018] This invention also provides a method for preparing the composite solid catalyst described above. The preparation method provided by this invention has simple steps, is easy to operate, and has stable processes, meeting the requirements of industrial production.

[0019] The present invention also provides the application of the composite solid catalyst described in the above-described scheme or the composite solid catalyst obtained by the preparation method described in the above-described scheme in the preparation of polyvinyl butyral.

[0020] This invention also provides a method for synthesizing polyvinyl butyral. Traditional methods for preparing polyvinyl butyral suffer from insufficient mass transfer, limited mass transfer efficiency of n-butyraldehyde, and the encapsulation of hydroxyl groups after precipitation in the later stages of the reaction, resulting in limited improvement in the degree of butyralization and poor uniformity. Furthermore, the hydroxyl retention rate and temperature resistance of polyvinyl butyral are poor, making it unsuitable for high-end applications. In addition, in continuous production, polyvinyl butyral easily deposits on the catalyst column surface, leading to channel blockage and low reaction efficiency. This invention utilizes the aforementioned composite solid catalyst to mediate segmented pressurization for the synthesis of polyvinyl butyral. This invention uses a composite solid catalyst, with polyvinyl alcohol and n-butyraldehyde as raw materials, to synthesize polyvinyl butyral in a supercritical CO2-ethanol mixed medium via a segmented (preheating, reaction, and aging) pressurization method. This invention addresses the problems of poor catalytic stability, low reaction efficiency, and limited product performance in traditional methods by combining the synergistic catalytic effect of composite catalysts with optimized mass transfer in a staged pressurized process. For example, it improves reaction efficiency and production continuity: the total reaction time of the staged pressurized reaction is 35-70 minutes, a reduction of 10-20% compared to existing methods; the mass transfer advantages of supercritical media and the use of baffles solve the problem of solid catalyst column blockage, increasing continuous production efficiency by over 40%. The synthesis method provided by this invention uses readily available raw materials, is environmentally friendly, and has high industrial feasibility, demonstrating significant economic and application value.

[0021] This invention also provides polyvinyl butyral obtained by the synthesis method described above. The polyvinyl butyral synthesized by this invention exhibits comprehensively optimized properties, with a degree of butyralization of 85-92 mol%, higher than the upper limit of existing methods (88 mol%), a hydroxyl retention rate of 10-15%, suitable for the bonding requirements of polyvinyl butyral to glass, a haze not exceeding 0.1%, and a thermal decomposition temperature above 150 degrees Celsius, meeting the requirements of high-end applications for transparency and temperature resistance. The polyvinyl butyral synthesized by this invention is particularly suitable for high-end laminated glass, electronic packaging materials, or medical adhesives, where high transparency, adhesion, and temperature resistance are required. Detailed Implementation

[0022] This invention provides a composite solid catalyst, comprising a support and an active component and a co-catalyst supported on the surface of the support; the support comprises ZSM-5 molecular sieve; the active component comprises sulfonated styrene-divinylbenzene copolymer; and the co-catalyst comprises Sn. 4+ .

[0023] In this invention, the ZSM-5 molecular sieve is preferably a porous ZSM-5 molecular sieve; the specific surface area of ​​the porous ZSM-5 molecular sieve is preferably 350~450 m². 2 / g, more preferably 370~420m 2 / g, further preferably 390~400m 2 / g, with a pore size preferably 10~30nm, more preferably 15~25nm, and even more preferably 20nm.

[0024] In this invention, the sulfonated styrene-divinylbenzene copolymer refers to a styrene-divinylbenzene crosslinked copolymer with sulfonic acid groups as active sites, which is a macroporous strong acid cation exchange resin.

[0025] In this invention, the degree of sulfonation of the sulfonated styrene-divinylbenzene copolymer is preferably 4~5 mmol / g, more preferably 4.5 mmol / g.

[0026] In this invention, the mass ratio of the carrier to the active component is preferably 1:0.3 to 0.8, more preferably 1:0.4 to 0.7, and even more preferably 1:0.5 to 0.6.

[0027] In this invention, the mass ratio of the support to the co-catalyst is preferably 1:0.05~0.15, more preferably 1:0.07~0.12, and even more preferably 1:0.09~0.11.

[0028] The composite solid catalyst provided by this invention comprises a ternary composite system of "support-active component-co-catalyst": ZSM-5 molecular sieve is used as the support, whose high specific surface area and excellent mechanical stability can support the active component and prevent the composite solid catalyst structure from collapsing during high-pressure reactions; sulfonated styrene-divinylbenzene copolymer is used as the active component, providing sufficient acidic sites to catalyze the butyralization reaction of n-butyraldehyde and polyvinyl alcohol; Sn 4+ The co-catalyst can promote the nucleophilic addition reaction of the aldehyde group in n-butyraldehyde, forming a synergistic catalytic effect with the active component, thereby improving the reaction efficiency and selectivity.

[0029] The present invention also provides a method for preparing the composite solid catalyst described above, comprising the following steps: (1) The carrier is immersed in the active component solution and ultrasonically dispersed to obtain the active component carrier; (2) The active component support is doped with a cocatalyst compound to obtain the composite solid catalyst.

[0030] In this invention, a carrier is impregnated in an active component solution and ultrasonically dispersed to obtain an active component carrier. In this invention, the impregnation temperature is preferably room temperature (20~38 degrees Celsius).

[0031] In this invention, the concentration of the active component solution is preferably 10-30 wt%, more preferably 15-25 wt%, and even more preferably 20 wt%.

[0032] In this invention, the ultrasonic dispersion power is preferably 150~200W, more preferably 170~180W, and the ultrasonic dispersion time is preferably 1~2 hours, more preferably 1.5 hours.

[0033] In this invention, the ultrasonic dispersion process preferably includes drying and cooling the resulting product; the drying temperature is preferably 100-120 degrees Celsius, more preferably 110 degrees Celsius, and the heat preservation time is preferably 4-6 hours, more preferably 4.5-5.5 hours, and even more preferably 5 hours.

[0034] In this invention, the cooling is preferably natural cooling; the final cooling temperature is preferably room temperature.

[0035] After obtaining the active component support, the present invention dops the active component support with a cocatalyst compound to obtain the composite solid catalyst.

[0036] In this invention, the co-catalyst compound is preferably a Sn salt; the Sn salt preferably includes one or more of SnCl4 and Sn(SO4)2.

[0037] In this invention, the doping method is preferably an equal-volume impregnation method or a grinding method; the doping preferably includes the following steps: impregnating the active component support in a cocatalyst compound solution followed by heat treatment.

[0038] In this invention, the solvent of the cocatalyst compound solution is preferably water or a C1-C4 alcohol; the C1-C4 alcohol preferably includes one or more of methanol, ethanol, propanol and butanol; the butanol preferably includes one or more of n-butanol and isobutanol.

[0039] In this invention, the Sn of the co-catalyst compound solution 4+ The concentration is preferably 0.05~0.2 mol / L, more preferably 0.08~0.16 mol / L, and even more preferably 0.1~0.12 mol / L.

[0040] In this invention, the immersion temperature is preferably 25~60℃, more preferably 35~50℃, and the immersion time is preferably 2~6 hours, more preferably 3~4 hours; the immersion is preferably carried out under stirring conditions; the stirring rate is preferably 100~300 rpm, more preferably 200 rpm.

[0041] In this invention, the impregnation process preferably includes drying the resulting product; the drying temperature is preferably 80~120℃, more preferably 100~110℃, and the heat preservation time is preferably 2~4 hours, more preferably 3 hours.

[0042] In this invention, the heat treatment temperature is preferably 150~250℃, more preferably 180~220℃, and the holding time is preferably 2~4 hours, more preferably 3 hours; the heat treatment is preferably carried out in a protective atmosphere or air; the protective atmosphere is preferably nitrogen.

[0043] In this invention, the grinding method preferably includes the following steps: grinding the active component support and the co-catalyst compound together.

[0044] In this invention, the grinding is preferably carried out at room temperature; the grinding speed is preferably 200-400 rpm, more preferably 300 rpm, and the grinding time is preferably 30-90 minutes, more preferably 45-60 minutes; the grinding is preferably ball milling; the ball milling equipment preferably includes a ball mill; the ball-to-material mass ratio is preferably 5-15:1, more preferably 7-12:1, and even more preferably 10:1. The solid powder obtained after grinding in this invention can be used directly or dried before use to remove any adsorbed moisture.

[0045] In this invention, the drying temperature is preferably 50~80℃, more preferably 60~70℃, and the heat preservation time is preferably 2~4 hours, more preferably 3 hours.

[0046] The present invention also provides the application of the composite solid catalyst described in the above-described scheme or the composite solid catalyst obtained by the preparation method described in the above-described scheme in the preparation of polyvinyl butyral.

[0047] This invention also provides a method for synthesizing polyvinyl butyral, comprising the following steps: Polyvinyl alcohol, supercritical CO2-ethanol mixed medium, n-butyraldehyde, pH adjuster and composite solid catalyst are mixed (denoted as the first mixture) to obtain a mixture. The mixture is then subjected to a staged pressurized reaction to obtain the polyvinyl butyraldehyde. The composite solid catalyst is the composite solid catalyst described in the above scheme or the composite solid catalyst obtained by the preparation method described in the above scheme.

[0048] In this invention, the degree of saponification of the polyvinyl alcohol is preferably 95-99%, more preferably 96-98%, and even more preferably 97%, and the degree of polymerization is preferably 300-800, more preferably 400-500.

[0049] In this invention, the volume ratio of CO2 to ethanol in the supercritical CO2-ethanol mixed medium is preferably 1:0.4~0.6, more preferably 1:0.5.

[0050] This invention uses a supercritical CO2-ethanol mixed medium to replace the traditional water or alcohol single medium. Supercritical CO2 has both the high diffusivity of a gas and the high solubility of a liquid, which can significantly improve the dispersion uniformity of n-butyraldehyde in the reaction system and solve the problem of limited mass transfer after polyvinyl butyral precipitation. Ethanol can further improve the solubility of n-butyraldehyde and optimize the reaction environment.

[0051] In this invention, the content of supercritical CO2-ethanol mixed medium in the mixture is preferably 60-90 wt%, more preferably 70-80 wt%, and even more preferably 75 wt%.

[0052] In this invention, the molar ratio of n-butyraldehyde to polyvinyl alcohol is preferably 1:1.2~2, more preferably 1:1.4~1.8, and even more preferably 1:1.5.

[0053] In this invention, the pH adjuster is preferably a solid acid or a volatile organic acid; the solid acid is preferably a hydrogen-form strong acid cation exchange resin; the hydrogen-form strong acid cation exchange resin is preferably a styrene-divinylbenzene copolymer-based dry resin with a macroporous structure and sulfonic acid groups (-SO3H) as active sites; the degree of crosslinking of the hydrogen-form strong acid cation exchange resin is preferably 8-20%, more preferably 12-15%; the exchange capacity (degree of sulfonation) of the hydrogen-form strong acid cation exchange resin is preferably 4.0-5.0 mmol / g, the average pore size is preferably not less than 20 nm, and the thermal decomposition onset temperature (T590, the temperature at which 5% weight loss occurs) is preferably higher than 280°C; the volatile organic acid preferably includes one or more of formic acid and acetic acid. This invention uses the above-mentioned pH adjuster, which can be separated from the system together with the composite solid catalyst in the post-treatment.

[0054] In this invention, the amount of the pH adjuster is preferably such that the hydrogen ion concentration in the mixture is 1 × 10⁻⁶. -5 ~5×10 -4 M is the standard, and more preferably 1×10 -5 ~3×10 -4 M; The content of pH adjuster in the mixture is preferably 0.1~2wt%, more preferably 0.5~1.5wt%, and even more preferably 1wt%.

[0055] In this invention, the content of the composite solid catalyst in the mixture is preferably 5-15 wt%, more preferably 7-12 wt%, and even more preferably 10 wt%.

[0056] In this invention, the first mixing is preferably stirred. This invention obtains a mixture in the form of a suspension through stirring.

[0057] In this invention, the equipment for the segmented pressurized reaction preferably includes a high-pressure reaction device with a built-in spiral baffle; the high-pressure reaction device with a built-in spiral baffle preferably includes a raw material storage tank, a pressurizing pump, a preheating section, a reaction section, a cooling section, and a product collection tank connected in sequence; the reaction section is a catalyst column with a built-in spiral baffle, and a detachable catalyst fixed bed is provided inside the catalyst column, with a composite solid catalyst filling the detachable catalyst fixed bed; the spiral baffle is preferably disposed on the inner wall of the reaction section; the pitch of the spiral baffle is preferably 5~15mm, the helix angle is preferably 10~30°, and the plate thickness is preferably 0.5~2mm; the spiral baffle is preferably disposed along the entire axial length of the reaction section or in segments; the material of the spiral baffle is preferably a corrosion-resistant metal, specifically preferably 316L stainless steel. The spiral baffle can guide the supercritical CO2-ethanol mixed medium to form spiral turbulence, enhance the mass transfer process between n-butyraldehyde and polyvinyl alcohol, and prevent the product from depositing on the surface of the catalyst fixed bed. Therefore, this invention improves the continuous reaction apparatus by incorporating a metallic spiral baffle within the catalyst column, thereby enhancing the turbulence of the reaction system and reducing the deposition of polyvinyl butyral on the catalyst surface. The material used in this invention meets the requirements for corrosion resistance and mechanical strength under supercritical CO2-ethanol mixed media and staged pressurized reaction conditions.

[0058] In this invention, the preheating section, reaction section, and cooling section are preferably each controlled by an independent temperature control jacket; the pressurization pump is preferably adjusted by a segmented pressure controller; and a ceramic membrane filter is preferably installed at the outlet of the catalyst column. This invention achieves real-time separation of the product and the catalyst by installing a ceramic membrane filter at the outlet of the catalyst column. The catalyst can be recycled after simple regeneration, improving production continuity.

[0059] In this invention, the segmented pressurized reaction preferably includes a first stage of preheating, a second stage of reaction, and a third stage of ripening, performed sequentially.

[0060] In this invention, the temperature of the first stage of preheating is preferably 80-100 degrees Celsius, more preferably 90 degrees Celsius, the pressure is preferably 0.1-0.3 MPa, more preferably 0.2 MPa, and the heat preservation time is preferably 10-20 minutes, more preferably 15 minutes.

[0061] In this invention, the temperature of the second stage reaction is preferably 110-130 degrees Celsius, more preferably 120 degrees Celsius, the pressure is preferably 4-6 MPa, more preferably 5 MPa, and the holding time is preferably 20-40 minutes, more preferably 30 minutes.

[0062] In this invention, the temperature of the third stage of curing is preferably 80-90 degrees Celsius, more preferably 85 degrees Celsius, the pressure is preferably 1-2 MPa, more preferably 1.5 MPa, and the holding time is preferably 5-10 minutes, more preferably 8 minutes.

[0063] This invention employs a staged pressurized reaction. The first stage involves preheating under low pressure (0.1~0.3 MPa) and medium temperature (80~100 degrees Celsius) to allow the supercritical medium to fully dissolve polyvinyl alcohol and n-butyraldehyde, ensuring thorough contact between the raw materials and the surface of the composite solid catalyst and preventing uneven localized reactions. The second stage, under high pressure (4~6 MPa) and suitable temperature (110~130 degrees Celsius), promotes the penetration of n-butyraldehyde into the molecular chain of polyvinyl alcohol, accelerating the butyralization reaction and increasing the degree of butyralization. The third stage, under medium-low pressure (1~2 MPa) and low temperature (80~90 degrees Celsius), matures the polyvinyl butyral, preventing excessive cross-linking that could increase brittleness, while simultaneously allowing unreacted hydroxyl groups to fully react, thus improving the overall performance of polyvinyl butyral.

[0064] In this invention, the staged pressurized reaction preferably includes post-processing of the resulting product; the post-processing preferably includes sequentially performing cooling, depressurization, separation of composite solid catalyst, precipitation, washing and drying.

[0065] In this invention, the final temperature of the cooling is preferably 60-80 degrees Celsius.

[0066] In this invention, the method for separating the composite solid catalyst is preferably filtration; the filtration is preferably ceramic membrane filtration; the filtration equipment preferably includes an integrated ceramic membrane filter and a staged pressurized reaction system; the ceramic membrane used for the ceramic membrane filtration is preferably made of α-alumina (α-Al2O3) or zirconium oxide (ZrO2); the average pore size of the ceramic membrane used for the ceramic membrane filtration is preferably 0.1~0.5μm, more preferably 0.3μm; the ceramic membrane used for the ceramic membrane filtration is preferably a multilayer composite membrane with an asymmetric structure (including a support body arranged sequentially, ... The transition layer and the surface separation layer); the pore size of the support is preferably 10~20μm; the pore size of the transition layer is preferably 1~5μm; the pore size of the surface separation layer is preferably 0.1~0.5μm; the ceramic membrane element used for ceramic membrane filtration is preferably a tubular structure with 19 or 37 channels, the inner diameter of a single channel is preferably 3~4mm, the outer diameter is preferably 25~40mm, and the length is preferably 800~1200mm; the number of membrane elements is preferably one or more; when the number of membrane elements is two or more, the membrane elements are preferably assembled in parallel.

[0067] This invention utilizes the aforementioned membrane material, which exhibits excellent chemical stability and mechanical strength in a supercritical CO2-ethanol mixed medium. The membrane pore size ensures effective retention of composite solid catalyst particles with a diameter greater than 1 μm (retention rate ≥99.9%), while allowing the reaction solution containing dissolved polyvinyl butyral (PVB) products to permeate smoothly, preventing rapid clogging of the membrane channels. The membrane structure maximizes permeate flux while maintaining membrane strength. Multiple membrane elements can be assembled in parallel to meet processing capacity requirements.

[0068] In this invention, the filtration temperature is preferably 80~100℃, more preferably 90℃; the filtration is preferably carried out under system back pressure conditions; the cross-flow velocity at the membrane surface is preferably 2~4 m / s, more preferably 3 m / s, and the transmembrane pressure difference (TMP) is preferably 0.2~0.5 MPa, more preferably 0.3~0.4 MPa. By employing the above conditions, this invention can achieve stable filtration with high flux and low pressure drop, and effectively reduce concentration polarization and membrane fouling.

[0069] Through the above-mentioned filtration, the present invention achieves online continuous separation of products and in-situ retention and recovery of catalysts, providing key guarantees for catalyst recycling and continuous operation of the process.

[0070] In this invention, the precipitation is preferably carried out in water; the water is preferably deionized water; the precipitation temperature is preferably 10-30 degrees Celsius, more preferably 15-25 degrees Celsius, and the precipitation time is preferably 1-3 hours, more preferably 1.5-2 hours.

[0071] In this invention, the precipitation preferably includes the following steps: injecting the separated liquid into water while stirring.

[0072] In this invention, the stirring speed is preferably 100-300 rpm, more preferably 200 rpm. By slowly and in a thin stream injecting the separated liquid into water under stirring conditions, this invention prevents excessively high local concentrations within the system from causing agglomeration.

[0073] In this invention, the washing is preferably performed 3 to 4 times; the washing water is preferably deionized water; the temperature of the deionized water is preferably 60 to 80 degrees Celsius, more preferably 70 degrees Celsius; and the target state of the washing is preferably that the pH value of the filtrate is in the range of 6.5 to 7.5.

[0074] In this invention, the drying temperature is preferably 80-100 degrees Celsius, more preferably 85-95 degrees Celsius, the vacuum degree is preferably -0.08 to -0.095 MPa (gauge pressure, i.e., absolute pressure of 0.02-0.005 MPa), more preferably -0.09 to -0.095 MPa, and the holding time is based on drying the material to constant weight, preferably 6-10 hours, more preferably 8 hours. In this invention, the post-treatment preferably includes regenerating the obtained composite solid catalyst; the regeneration is preferably heat treatment; the heat treatment temperature is preferably 100-110 degrees Celsius, more preferably 100 degrees Celsius, and the holding time is preferably 2-3 hours, more preferably 2 hours.

[0075] The preparation method provided by this invention also has environmental and cost advantages: supercritical CO2 can be recycled and reused (recovery rate not less than 90%), no neutralization treatment is required, and wastewater discharge is reduced; the amount of n-butyraldehyde used is reduced by 20-30% compared with existing methods, and the raw material cost is further reduced.

[0076] The present invention also provides polyvinyl butyral obtained by the above-described synthesis method, with a degree of butyralization of 85-92 mol%, a hydroxyl retention rate of 10-15%, a haze of not more than 0.1%, and a thermal decomposition temperature of not less than 150 degrees Celsius.

[0077] In this invention, the number-average molecular weight of the polyvinyl butyral is preferably 5 × 10⁻⁶. 4 ~1.2×10 5 .

[0078] To further illustrate the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments thereof.

[0079] Example 1 This embodiment prepares a composite solid catalyst and polyvinyl butyral, and the specific steps are as follows: (1) Preparation of composite solid catalyst: 10g of porous ZSM-5 molecular sieve support was immersed in 20mL of 20wt% sulfonated styrene-divinylbenzene copolymer-based dry resin (with sulfonic acid groups as active sites, crosslinking degree of 15%, exchange capacity of 4.5mmol / g, macroporous structure, average pore size of 20nm, and thermal decomposition initiation temperature of 290℃). The mixture was ultrasonically dispersed at 180W for 1.5 hours, dried at 110℃ for 5 hours, and after cooling, 1g of SnCl4 was added as a co-catalyst compound. The dried active component support and co-catalyst compound were placed in a ball mill with a ball-to-material mass ratio of 10:1 and a ball milling speed of 300rpm. The mixture was ball milled together at room temperature for 60 minutes. After ball milling, the mixture was dried at 60℃ for 3 hours to obtain a composite solid catalyst (mass ratio of support, active component and co-catalyst of 1:0.4:0.1). (2) Preparation of the reaction system: 44g of 10wt% polyvinyl alcohol aqueous solution (saponification degree 99%, polymerization degree 500) was mixed with 200g of supercritical CO2-ethanol (volume ratio 1:0.5) mixed medium, and 13.2g of n-butyraldehyde (molar ratio of 1:1.5 to polyvinyl alcohol) was added to adjust the hydrogen ion concentration of the system to 2×10 -4 M, add 6g of composite solid catalyst, stir evenly to form a suspension, and obtain the reaction system; (3) Segmented pressurized reaction: The suspension is passed into a high-pressure reaction device with a built-in spiral baffle (the spiral baffle is set on the inner wall of the reaction section, the pitch of the spiral baffle is 10mm, the helix angle is 20°, and the plate thickness is 1mm; the spiral baffle is set along the entire axial length of the reaction section). The first stage is preheated for 15 minutes at 0.2MPa and 90 degrees Celsius; the second stage is reacted for 30 minutes at 5MPa and 120 degrees Celsius; the third stage is matured for 8 minutes at 1.5MPa and 85 degrees Celsius. (4) Post-treatment: Cool down to 70 degrees Celsius, depressurize, and separate the composite solid catalyst by filtration through a ceramic membrane. The ceramic membrane used for filtration is made of zirconium oxide and includes a support with a pore size of 15 μm, a transition layer with a pore size of 3 μm, and a surface separation layer with a pore size of 0.5 μm arranged in sequence. The membrane element is a 37-channel tubular structure with an inner diameter of 3.5 mm, an outer diameter of 30 mm, and a length of 1000 mm per channel. Filtration is carried out at 90 degrees Celsius and under system back pressure. The cross-flow velocity on the membrane surface is 3 m / s, and the transmembrane pressure difference is 0.4 MPa. The filtrate is precipitated in deionized water. The separated liquid is injected into deionized water while stirring (200 rpm) and precipitated at 25 degrees Celsius for 2 hours. It is washed 4 times with deionized water at 70 degrees Celsius. The pH value of the filtrate is 7. It is dried at 90 degrees Celsius under vacuum (gauge pressure -0.09 MPa) for 7 hours to obtain polyvinyl butyral.

[0080] Example 2 (Preparation of composite solid catalysts by impregnation method and their applications) This embodiment uses an equal-volume impregnation method to prepare a composite solid catalyst, which is then used to synthesize polyvinyl butyral. The specific steps are as follows: (1) Preparation of composite solid catalysts: Take 10g of porous ZSM-5 molecular sieve carrier (same as in Example 1), immerse it in 20mL of 20wt% sulfonated styrene-divinylbenzene copolymer solution (same as in Example 1), ultrasonically disperse at 180W for 1.5 hours, dry at 110 degrees Celsius for 5 hours, and cool to obtain the active component carrier.

[0081] 10 mL of a 0.1 mol / L SnCl4 aqueous solution was prepared as the impregnation solution. The active component support was immersed in the prepared impregnation solution using an equal-volume impregnation method, and the mixture was stirred at 40°C and 200 rpm for 4 hours. Subsequently, it was dried at 100°C for 3 hours, and then heat-treated in air at 200°C for 3 hours to obtain a composite solid catalyst (mass ratio of support, active component, and co-catalyst was 1:0.4:0.1).

[0082] (2) Synthesis of polyvinyl butyral: The steps and conditions for preparing the reaction system, staged pressurized reaction, and post-treatment are the same as in Example 1, except that the composite solid catalyst is replaced with the composite solid catalyst prepared in step (1) of this example. (3) Preliminary test of the cycle performance of the composite solid catalyst: The composite solid catalyst recovered after the reaction was regenerated by heat treatment at 100 degrees Celsius for 2 hours and then reused once (i.e., used a total of 2 times) to preliminarily examine its stability.

[0083] Example 3 This embodiment tests the reusability of the composite solid catalyst. The test method is as follows: Using the composite solid catalyst prepared in Example 1, the reaction system preparation, staged pressurized reaction and post-treatment steps of Example 1 were repeated. The composite solid catalyst separated after each reaction was regenerated by drying at 100 degrees Celsius for 2 hours. The catalyst was used 12 times in a row, and the degree of polyvinyl butyralization and catalyst activity retention rate were recorded for each reaction.

[0084] Comparative Example 1 This comparative example uses the single catalyst and single pressurization method disclosed in US Patent US 2007 / 0293651A1, and the specific steps are as follows: Preparation of the reaction system: Add 11g of n-butyraldehyde and 5.5g of polystyrene sulfonic acid solid catalyst (AMBERLYST 15JWET) to 44g of a 10wt% polyvinyl alcohol aqueous solution (saponification degree 99%, polymerization degree 500), stir until homogeneous, and the hydrogen ion concentration of the system is 10. -4 M, to obtain a mixture; Pressure reaction: The resulting mixture was placed in an autoclave, nitrogen gas was introduced to 8 MPa, and the reaction was carried out at 100 degrees Celsius for 30 minutes; Post-processing: Cool to 80 degrees Celsius, depressurize, recover the product, precipitate, wash, and dry to obtain polyvinyl butyral.

[0085] Comparative Example 2 This comparative example uses the single catalyst disclosed in US Patent 2007 / 0293651A1 and the staged pressurized reaction of Example 1 of this invention. The specific steps are as follows: Reaction system preparation: Same as Comparative Example 1; Segmented pressurized reaction: The obtained mixture is passed into a high-pressure reaction device with a built-in spiral baffle for segmented pressurized reaction (parameters are the same as in Example 1). Post-processing: Same as in Example 1.

[0086] Comparative Example 3 This comparative example uses the composite solid catalyst prepared in Example 1 and employs an atmospheric pressure process. The specific steps are as follows: Reaction system preparation: Same as in Example 1; Atmospheric pressure reaction: The resulting suspension was placed in a three-necked flask and refluxed at 100 degrees Celsius for 180 minutes; Post-processing: Same as in Example 1.

[0087] Test Example 1 This test example evaluates the performance of polyvinyl butyral prepared in Examples 1-3 and Comparative Examples 1-3, as follows: Butyral degree: The prepared polyvinyl butyral was dissolved in deuterated dimethyl sulfoxide (DMSO-d6), and the solution was prepared using... 1 The degree of butyralization was calculated by integrating the characteristic peaks using an ¹H-NMR spectrometer. Hydroxyl retention rate: The retention rate was calculated by determining the content of residual hydroxyl groups in polyvinyl butyral using the acetylation titration method. Haze: The haze of polyvinyl butyral film (thickness 0.2 mm) was measured using a haze meter in accordance with GB / T 2410-2008 standard. Thermal decomposition temperature: Thermogravimetric analysis (TGA) was used to heat the temperature from room temperature to 500 degrees Celsius at a rate of 10℃ / min under a nitrogen atmosphere. The temperature at which the mass loss was 5% was recorded as the thermal decomposition temperature. Catalyst activity retention rate: The ratio of the degree of butyralization after repeated use to the baseline value is calculated based on the degree of butyralization at the time of first use. Molecular weight: Polyvinyl butyral was dissolved in tetrahydrofuran (THF) to prepare a 0.2 wt% solution. The number-average molecular weight (M) was determined by gel permeation chromatography (GPC). n ) and weight-average molecular weight (M w The performance test results for this test case are shown in Table 1: Table 1 Performance test results of Examples 1-3 and Comparative Examples 1-3

[0088] As shown in Table 1, regarding the synergistic effect of the composite solid catalyst and the staged pressurized reaction: the degree of butyralization in Example 1 (grinding method) and Example 2 (impregnation method) (90.5 mol% and 89.2 mol%, respectively) was significantly higher than that in Comparative Example 1 and Comparative Example 2, indicating that the synergistic catalytic effect of the composite solid catalyst of the present invention complements the mass transfer optimization of staged pressurization, and can promote the butyralization reaction more efficiently; the thermal decomposition temperatures of Example 1 and Example 2 (158.6 degrees Celsius and 157.1 degrees Celsius, respectively) were much higher than those in Comparative Example 1 and Comparative Example 2, proving that the composite solid catalyst and the staged pressurized reaction can reduce resin degradation and improve the thermal stability of the product.

[0089] Regarding the reusability of the catalyst: In Example 3, the composite solid catalyst retained an activity of 80.2% after 12 consecutive uses, while the single catalysts in Comparative Examples 1 and 2 retained only 58.3% and 62.5% of their activity after 5 uses, respectively. This indicates that the structural stability and regeneration performance of the composite solid catalyst of this invention are significantly superior to existing catalysts. The initial performance of the composite solid catalyst in Example 2 (impregnation method) was comparable to that of Example 1 (grinding method), further demonstrating that highly active composite solid catalysts can be obtained through different preparation methods.

[0090] Regarding the necessity of staged pressurization: Comparative Example 3 uses an atmospheric pressure process, and the degree of polyvinyl butyralization is only 52.7 mol%, which is much lower than that of Example 1 and Example 2. Moreover, the reaction time is as long as 180 minutes, which proves that pressurization is the key to solving the problem of limited mass transfer after polyvinyl butyral precipitation and improving reaction efficiency. The staged pressurization reaction of the present invention has the best effect.

[0091] Regarding the product's applicability: The haze of Examples 1 and 2 was 0.08% and 0.09%, respectively, both lower than that of the comparative example. The hydroxyl retention rate was 12.8%, which ensured transparency while also meeting the bonding requirements with glass, making it suitable for high-end laminated glass and electronic packaging materials. However, the hydroxyl retention rate of Comparative Example 1 was too low (9.5%), and the haze of Comparative Example 3 was too high (0.23%), both of which had limitations in application.

[0092] The embodiments of the present invention have been described above; however, these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. All other embodiments obtained by those skilled in the art based on the above embodiments of the present invention without inventive effort are within the protection scope of the present invention.

Claims

1. A composite solid catalyst, characterized in that, Includes a support and active components and cocatalysts supported on the surface of the support; The carrier includes ZSM-5 molecular sieve; The active component includes sulfonated styrene-divinylbenzene copolymer; The co-catalyst includes Sn 4+ .

2. The composite solid catalyst according to claim 1, characterized in that, The sulfonated styrene-divinylbenzene copolymer is a styrene-divinylbenzene crosslinked copolymer with sulfonic acid groups as active sites, and is a macroporous strong acid cation exchange resin; The degree of sulfonation of the sulfonated styrene-divinylbenzene copolymer is 4~5 mmol / g.

3. The composite solid catalyst according to claim 1, characterized in that, The mass ratio of the carrier to the active component is 1:0.3~0.8; The mass ratio of the support to the co-catalyst is 1:0.05~0.

15.

4. The method for preparing the composite solid catalyst according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) The carrier is immersed in the active component solution and ultrasonically dispersed to obtain the active component carrier; (2) The active component support is doped with a cocatalyst compound to obtain the composite solid catalyst.

5. The application of the composite solid catalyst according to any one of claims 1 to 3 or the composite solid catalyst obtained by the preparation method according to claim 4 in the preparation of polyvinyl butyral.

6. A method for synthesizing polyvinyl butyral, characterized in that, Includes the following steps: Polyvinyl alcohol, supercritical CO2-ethanol mixed medium, n-butyraldehyde, pH adjuster and composite solid catalyst are mixed to obtain a mixture, and then the mixture is subjected to a staged pressurized reaction to obtain polyvinyl butyraldehyde; the composite solid catalyst is the composite solid catalyst according to any one of claims 1 to 3 or the composite solid catalyst obtained by the preparation method of claim 4.

7. The synthesis method according to claim 6, characterized in that, The equipment for the segmented pressurized reaction includes a high-pressure reaction device with a built-in spiral baffle. The high-pressure reaction device with built-in spiral baffles includes a raw material storage tank, a pressurizing pump, a preheating section, a reaction section, a cooling section, and a product collection tank connected in sequence. The reaction section is a catalyst column with a built-in spiral baffle. A detachable catalyst fixed bed is set inside the catalyst column, and the composite solid catalyst is filled in the detachable catalyst fixed bed.

8. The synthesis method according to claim 6, characterized in that, The segmented pressurized reaction includes a first-stage preheating, a second-stage reaction, and a third-stage ripening, performed sequentially. The temperature for the first stage of preheating is 80~100 degrees Celsius, the pressure is 0.1~0.3 MPa, and the holding time is 10~20 minutes; The temperature of the second stage reaction is 110~130 degrees Celsius, the pressure is 4~6 MPa, and the holding time is 20~40 minutes; The third stage of curing is carried out at a temperature of 80-90 degrees Celsius, a pressure of 1-2 MPa, and a holding time of 5-10 minutes.

9. The synthesis method according to claim 6 or 8, characterized in that, The segmented pressurized reaction also includes post-processing of the resulting product; The post-processing also includes regenerating the obtained composite solid catalyst; The regeneration is a heat treatment, the temperature of which is 100-110 degrees Celsius and the holding time is 2-3 hours.

10. The polyvinyl butyral obtained by the synthesis method according to any one of claims 6 to 9, characterized in that, The degree of butyralization is 85-92 mol%, the hydroxyl retention rate is 10-15%, the haze is not higher than 0.1%, and the thermal decomposition temperature is not lower than 150 degrees Celsius.

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