Chemical degradation and separation method of unsaturated polyester resin waste

Abstract

The invention discloses a chemical degradation and separation method of unsaturated polyester resin waste, which comprises the following steps: crushing a raw material containing unsaturated polyester resin, mixing the raw material with glacial acetic acid, a catalyst and acetic anhydride for swelling, raising the temperature after swelling, and carrying out degradation reaction to obtain a degradation liquid; carrying out reduced pressure rectification on the degradation liquid in a rectifying tower to respectively obtain acetic acid and diethyl ester depolymerization products; mixing the tower bottom material with water, heating, fully dissolving, and filtering to obtain a depolymerization product styrene-maleic anhydride copolymer insoluble in a water phase; and cooling, crystallizing, filtering and washing the aqueous solution to obtain a degradation product phthalic acid, and evaporating the residual aqueous phase to remove water and recover to obtain the catalyst. In a catalytic reaction system, acetic anhydride is used as a dehydrating agent, trace water in the catalytic reaction system is removed, the integrity of the structure of a high-added-value diethyl ester degradation product is reserved, and side reactions of ester substances can be reduced or avoided in the degradation and separation process.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of organic solid waste chemical recycling, and particularly relates to a chemical degradation and separation method of unsaturated polyester resin waste. BACKGROUND

[0002] Unsaturated polyester resin is a thermosetting resin with three-dimensional network structure formed by condensation polymerization of unsaturated diacid (or anhydride) and saturated diol, and then curing and cross-linking with a vinyl monomer (such as styrene). The unsaturated polyester resin is cheap, simple to prepare, and has excellent mechanical properties, and is often used as a matrix resin material for resin buttons, artificial stone, cast artware, chemical storage tanks, pipes, and glass steel. In addition, wind turbine nacelle covers, wind power blades and other parts also contain a large amount of unsaturated polyester resin composites.

[0003] With the continuous development of the unsaturated polyester resin industry and the increasing amount of blade waste, a large amount of unsaturated polyester resin waste is generated. At present, the main recovery methods of unsaturated polyester resin and its composites include mechanical recovery, thermal recovery and chemical recovery. Mechanical recovery is to crush the unsaturated polyester resin and its composites for use as fillers. Thermal recovery is to pyrolyze the unsaturated polyester resin and its composites at high temperature to form pyrolysis gas, pyrolysis oil and other fuels for system heating. The above-mentioned recovery methods have low product added value, and are prone to cause problems such as dust, emission of small molecule toxic substances and environmental pollution.

[0004] Chemical recovery method is mainly through breaking the chemical bonds in the resin to recover high value-added degradation products and is widely concerned. The method for catalytic recovery of unsaturated polyester resin disclosed in the prior art is to add hot water in the separation process, and then separate diethyl ester compounds by using organic solvent extraction. Considering that the ester bond in the small molecule ester compound is active in chemical properties, the diethyl ester small molecule product is prone to hydrolysis in the separation process, which affects the yield of diethyl ester product, and the separation process is complex and not conducive to industrial production. SUMMARY

[0005] The present application provides a chemical degradation and separation method of unsaturated polyester resin waste, which at least solves the technical problem that the separation process is prone to decomposition of depolymerization products, and can obtain depolymerization products diethyl ester, phthalic acid and styrene-maleic anhydride copolymer with high purity.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is: A chemical degradation and separation method of unsaturated polyester resin waste, comprising: Step one, the raw material containing unsaturated polyester resin is crushed, and the raw material is mixed with glacial acetic acid, a catalyst and acetic anhydride to swell, the swelling temperature is 80-130 ℃, and the swelling time is 4-12 h; Step two, after swelling, the temperature is raised to perform a degradation reaction, the reaction temperature is 160-210 ℃, and the reaction time is 4-12 h, to obtain a degradation liquid; Step three, the degradation liquid is subjected to vacuum rectification in a rectification tower to obtain acetic acid and diethyl ester depolymerization products respectively; the tower bottom material is mixed with water and heated to be fully dissolved, filtered to obtain a water-insoluble depolymerization product styrene-maleic anhydride copolymer; the water solution is cooled to crystallize, filtered, washed with water to obtain a degradation product phthalic acid, and the remaining water phase is evaporated to remove water to recover the catalyst.

[0007] As a preferred embodiment, in step one, the catalyst is one or a combination of methanesulfonic acid, p-toluenesulfonic acid, benzene sulfonic acid and dodecyl benzene sulfonic acid.

[0008] As a preferred embodiment, in step one, the mass ratio of the raw material to glacial acetic acid, the catalyst and acetic anhydride is 1:2-10:0.1-3:0.05-0.5.

[0009] As a preferred embodiment, in step one, the swelling temperature is 90-100 ℃.

[0010] As a preferred embodiment, in step two, the reaction temperature is 180-190 ℃.

[0011] As a preferred embodiment, in step three, the overhead temperature of the rectification tower is 55-180 ℃, the bottom temperature is 120-270 ℃, and the vacuum degree at the top of the tower is 0.02 MPa-0.09 MPa.

[0012] As a preferred embodiment, in step three, the diethyl ester depolymerization product is any one or a combination of ethylene glycol diacetate, diethylene glycol diacetate, 1,2-propanediol diacetate and 1,3-propanediol diacetate.

[0013] As a preferred embodiment, in step three, when the tower bottom material is mixed with water and heated, the mass ratio of the two is 1:2-5, and the heating temperature is 80-130 ℃.

[0014] As a preferred embodiment, in step three, the temperature for cooling crystallization of the water solution is 4-20 ℃.

[0015] As a preferred embodiment, when the raw material is an unsaturated polyester resin composite material, solid-liquid separation is performed after the degradation reaction to obtain recovered fibers.

[0016] The application provides a chemical degradation and separation method of unsaturated polyester resin waste, and the overall concept is that acetic anhydride is used as a reactant and a dehydrating agent to participate in an acyl exchange reaction of the unsaturated polyester resin in a catalytic reaction system, trace water in the catalytic reaction system is removed, the integrity of a high-value-added diethyl ester degradation product structure is preserved, and side reactions of ester substances can be reduced or avoided in the degradation and separation process. The method can obtain diethyl ester, phthalic acid and styrene-maleic anhydride copolymer with high purity. In addition, the separation process is easy to industrialize, and the industrialization cost is low. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 HNMR spectrum of recovered acetic acid in Example 1 1 HNMR spectrum of recovered acetic acid in Example 1 Figure 2 HNMR spectrum of separated product phthalic acid in Example 1 1 HNMR spectrum of separated product phthalic acid in Example 1 Figure 3 HNMR spectrum of separated product styrene-maleic anhydride copolymer (SMA resin) in Example 1 1 HNMR spectrum of separated product styrene-maleic anhydride copolymer (SMA resin) in Example 1 Figure 4 HNMR spectrum of separated product diethyl ester in Example 1 1 HNMR spectrum of separated product diethyl ester in Example 1 DETAILED DESCRIPTION

[0018] The chemical degradation and separation method of unsaturated polyester resin waste provided by a typical embodiment of the application for preparing diethyl ester, phthalic acid and styrene-maleic anhydride copolymer mainly includes the following steps one to three.

[0019] In step one, raw materials containing unsaturated polyester resin are crushed, and the raw materials are mixed with glacial acetic acid, a catalyst and acetic anhydride to swell, the swelling temperature is 80-130 DEG C, and the swelling time is 4-12 h.

[0020] The above raw materials are mainly pure unsaturated polyester resin or unsaturated polyester resin composite. Glacial acetic acid is used as a solvent, the catalyst is selected from organic Bronsted acids, and acetic anhydride is used as a dehydrating agent.

[0021] The catalysts in the application are preferably one or a combination of methanesulfonic acid, p-toluenesulfonic acid, benzene sulfonic acid and dodecyl benzene sulfonic acid.

[0022] Diethyl ester degradation products cannot exist stably in Lewis acids, inorganic Bronsted acids and alkaline catalysts, but the integrity of the diethyl ester degradation product structure can be well preserved in organic Bronsted acids. In addition, the catalytic activity of organic Bronsted acids is higher, the amount used is less, and the organic Bronsted acids are environmentally friendly and more in line with the concept of green and sustainable development.

[0023] In the present application, acetic anhydride can not only be used as a reactant, but also as a dehydrating agent. When acetic anhydride is used as a reactant, acetic anhydride can undergo acyl exchange reaction with unsaturated polyester resin, which is conducive to the degradation reaction. On the other hand, in the catalytic reaction system, the presence of trace water will lead to the decomposition of diethyl ester degradation products. In order to not introduce new substances into the catalytic reaction system and reduce the subsequent separation steps and further reduce the separation cost, acetic anhydride is selected as a dehydrating agent. When the dehydrating agent acetic anhydride is added to the catalytic reaction system, on the one hand, trace water in the catalytic reaction system can be removed, the structural integrity of the high-value-added diethyl ester degradation product is maximized, and the yield of the ester product is improved; on the other hand, the acetic acid generated by the hydrolysis of acetic anhydride can strengthen the mass transfer process, which is conducive to the depolymerization reaction.

[0024] In step one, the swelling temperature is 80-130 ℃, such as 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃, 105 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃, 130 ℃, etc., and the swelling time is 4-12 h, such as 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, etc. If the swelling temperature is too low (< 80 ℃) or the swelling time is too short (< 4 h), the resin is in a thermally stable glass state, the polymer chain segment is frozen, the free volume is insufficient, the solvent diffusion coefficient is small, and the swelling rate is extremely low. If the swelling temperature is too high (> 130 ℃) or the swelling time is too long (> 12 h), it may lead to the volatilization of styrene, the depolymerization of the resin, the rapid rise of the solvent vapor pressure, the increase of the operation risk, and the secondary reaction (such as hydrogen bonding) between the solvent and the resin, which is difficult to desorb. Since the crosslinking monomer of the resin or the composite material described in the present application is styrene, the upper limit of the swelling temperature should be lower than the boiling point of styrene (145 ℃), and a safety margin of 15 ℃ should be reserved to prevent boiling. Therefore, the maximum swelling temperature is ≤ 130 ℃, which has a good swelling effect on the resin, is conducive to the entry of the catalyst and the solvent into the resin body, and can fully contact and react with specific chemical bonds.

[0025] In step one, the mass ratio of the raw material, glacial acetic acid, catalyst and acetic anhydride is preferably 1: (2-10): (0.1-3): (0.05-0.5) from the aspects of catalytic efficiency, energy consumption, cost and the like. If the content of the solvent glacial acetic acid is too low, the resin cannot be completely immersed, the swelling effect is poor, and the catalytic effect is reduced. If the content of the solvent glacial acetic acid is too high, the solvent is wasted, and the process cost of subsequent solvent recovery is high. If the content of the organic Bronsted acid catalyst is too low, the catalytic efficiency is low, and the resin cannot be completely degraded. If the content of the organic Bronsted acid catalyst is too high, the compatibility of the degradation products and the solvent is better, the energy consumption and cost of subsequent product separation are high. If the content of the dehydrating agent acetic anhydride is too low, trace water in the catalytic reaction system cannot be completely removed, and the high-value-added diethyl ester degradation product is easily decomposed. If the content of the dehydrating agent acetic anhydride is too high, the energy consumption and cost of the subsequent separation process are high.

[0026] In step two, the temperature is increased after swelling to perform the degradation reaction, the reaction temperature is 160-210 ℃, and the reaction time is 4-12 h to obtain a degradation liquid.

[0027] In this step, the reaction temperature is 160-210 ℃, for example, 160 ℃, 165 ℃, 170 ℃, 175 ℃, 180 ℃, 185 ℃, 190 ℃, 195 ℃, 200 ℃, 205 ℃, 210 ℃, and the reaction time is 4-12 h, for example, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h or the like.

[0028] When the reaction temperature is lower than 160 ℃ or the reaction time is less than 4 h, the degradation reaction basically does not occur. When the reaction temperature is higher than 210 ℃ or the reaction time is greater than 12 h, the chemical bonds in the resin are randomly broken, the product is complex, the depolymerization product is dark in color, needs to be decolorized, and the recovery cost is further increased.

[0029] It should be noted that if the raw material is an unsaturated polyester resin composite material, solid-liquid separation is needed after the degradation reaction to obtain recycled fibers. If the raw material is pure unsaturated polyester resin, this step does not need to be performed.

[0030] In step three, the degradation liquid is subjected to vacuum rectification in a rectification tower to obtain acetic acid and diethyl ester depolymerization products, and the diethyl ester depolymerization products are any one or a combination of ethylene glycol diacetate, diethylene glycol diacetate, 1,2-propanediol diacetate and 1,3-propanediol diacetate.

[0031] The bottom material is mixed with water, heated and fully dissolved, filtered to obtain the insoluble water phase depolymerization product styrene-maleic anhydride copolymer; the water solution is cooled and crystallized, filtered, washed with water to obtain the degradation product phthalic acid, and the remaining water phase is evaporated to remove water to obtain the catalyst.

[0032] If the overhead temperature of the rectifying tower is lower than 55 ℃, the solvent acetic acid is not fully vaporized, and part of the acetic acid remains in the tower bottom, which results in incomplete recovery of the solvent acetic acid. If the overhead temperature of the rectifying tower is higher than 180 ℃, part of the solvent acetic acid is entrained in the recovered diethyl ester degradation product, the purity of the diethyl ester degradation product is reduced, and the energy consumption is large. Therefore, the overhead temperature of the rectifying tower is selected to be 55-180 ℃.

[0033] If the tower bottom temperature is lower than 120 ℃, the solvent acetic acid is not fully vaporized, and the separation is insufficient. In order to compensate for the insufficient separation, the material circulation frequency is increased, and the comprehensive energy consumption is increased. If the tower bottom temperature is higher than 270 ℃, the product of the depolymerization product is dark, and the acid value is increased. Moreover, the steam consumption is increased by 15-20% per 10 ℃ increase in temperature, which results in a sharp increase in energy consumption and equipment damage. Therefore, the tower bottom temperature is selected to be 120-270 ℃.

[0034] In addition, if the overhead vacuum is too high, the solvent acetic acid and the diethyl ester depolymerization product are azeotroped, the purity is reduced, and the energy consumption (electricity consumption of the vacuum system) is increased. If the overhead vacuum is too low, the separation efficiency of the depolymerization product is reduced, and the steam consumption of the reboiler is increased. Therefore, the overhead vacuum is selected to be 0.02 MPa-0.09 MPa.

[0035] In this step, the mass ratio of the tower bottom material to water is preferably 1:2-5, and the heating temperature is preferably 80-130 ℃. Too little water is added, and the phthalic acid cannot be completely and sufficiently dissolved in water. Too much water is added, which results in a sharp increase in energy consumption in the process of recovering the catalyst. Hot water can increase the solubility of phthalic acid, and phthalic acid can be completely and thoroughly recovered (high yield).

[0036] In this step, the temperature for water solution cooling crystallization is 4-20 ℃. The solubility of phthalic acid in water is low at room temperature (i.e. 4-20 ℃). When the temperature exceeds 20 ℃, the solubility of phthalic acid increases sharply with the increase of the temperature. The energy consumption is low at this temperature, which is conducive to the realization of industrialization.

[0037] The technical solutions claimed in the present application are further described below through some examples. However, the examples are used to explain the embodiments of the present application, and do not exceed the scope of the subject matter of the present application, and the protection scope of the present application is not limited by the examples. Unless otherwise specified, the materials and reagents used in the present application can be obtained from commercial products in the art. Example 1

[0038] 1 g of crushed pure unsaturated polyester resin powder is mixed with 2 g of glacial acetic acid, 0.1 g of p-toluenesulfonic acid and 0.1 g of acetic anhydride to prepare a reaction system for swelling. The swelling temperature is 80 ℃, and the swelling time is 8 h.

[0039] After swelling is complete, the temperature is increased to carry out the degradation reaction. The reaction temperature is 180 °C and the reaction time is 12 h.

[0040] After the degradation reaction was completed, the degradation solution cooled to room temperature was subjected to vacuum distillation. The top temperature of the distillation column was 60℃, the bottom temperature was 180℃, and the vacuum degree at the top of the column was 0.085 MPa, to obtain acetic acid and diethyl ester degradation products, respectively.

[0041] The bottom material of the tower was mixed with water and heated to fully dissolve it. The mass ratio of the bottom material to water was 1:2, and the heating temperature was 80℃. After filtration, the styrene-maleic anhydride copolymer, which is insoluble in water, was obtained. The aqueous solution was cooled to 4℃ to crystallize, filtered, and washed with water to obtain the degradation product phthalic acid. The remaining aqueous phase was evaporated to remove water and recover p-toluenesulfonic acid.

[0042] The following were obtained: 0.47 g of styrene-maleic anhydride copolymer, 0.25 g of phthalic acid, 0.16 g of ethylene glycol diacetate, 0.10 g of diethylene glycol diacetate, and 0.15 g of 1,2-propanediol diacetate. 0.09 g of p-toluenesulfonic acid catalyst and 1.90 g of acetic acid were recovered, with a degradation rate of 100%. Example 2

[0043] 1g of pulverized pure unsaturated polyester resin powder was mixed with 10g of glacial acetic acid, 1g of methanesulfonic acid and 0.05g of acetic anhydride to prepare a reaction system for swelling. The swelling temperature was 130℃ and the swelling time was 4h.

[0044] After swelling is complete, the temperature is increased to carry out the degradation reaction. The reaction temperature is 210 °C and the reaction time is 4 h.

[0045] After the degradation reaction was completed, the degradation solution cooled to room temperature was subjected to vacuum distillation. The top temperature of the distillation column was 55℃, the bottom temperature was 120℃, and the vacuum degree at the top of the column was 0.09 MPa, to obtain acetic acid and diethyl ester degradation products, respectively.

[0046] The bottom material of the tower was mixed with water and heated to fully dissolve it. The mass ratio of the bottom material to water was 1:5, and the heating temperature was 130 °C. After filtration, the insoluble aqueous depolymerization product, styrene-maleic anhydride copolymer, was obtained. The aqueous solution was cooled to 20 °C to crystallize. After filtration and washing with water, the degradation product, phthalic acid, was obtained. The remaining aqueous phase was evaporated to remove water and recover methanesulfonic acid.

[0047] The following were obtained: 0.44 g of styrene-maleic anhydride copolymer, 0.21 g of phthalic acid, 0.16 g of ethylene glycol diacetate, 0.24 g of 1,2-propanediol diacetate, 0.92 g of methanesulfonic acid catalyst, and 9.80 g of acetic acid. The degradation rate was 100%. Example 3

[0048] 1 g of the unsaturated polyester resin composite material powder after crushing was mixed with 6 g of glacial acetic acid, 3 g of dodecylbenzenesulfonic acid and 0.5 g of acetic anhydride to prepare a reaction system for swelling, the swelling temperature was 100 ℃ and the swelling time was 12 h.

[0049] After the swelling was completed, the temperature was increased for degradation reaction, the reaction temperature was 160 ℃ and the reaction time was 12 h. After the reaction was completed, the degradation liquid cooled to room temperature was subjected to solid-liquid separation to obtain recovered fibers.

[0050] Then, the filtrate was subjected to vacuum rectification, the rectification column top temperature was 180 ℃, the column bottom temperature was 270 ℃ and the column top vacuum degree was 0.02 MPa, to obtain solvent acetic acid and diethyl ester degradation products, respectively.

[0051] The column bottom material was mixed with water and heated to be fully dissolved, the mass ratio of the column bottom material to water was 1:3, the heating temperature was 100 ℃, and after filtration, the water-insoluble depolymerization product styrene-maleic anhydride copolymer was obtained; the water solution was cooled at 10 ℃ to crystallize, and after filtration and water washing, the degradation product phthalic acid was obtained, and the remaining water phase was evaporated to remove water to obtain dodecylbenzenesulfonic acid.

[0052] Styrene-maleic anhydride copolymer 0.21 g, phthalic acid 0.12 g, ethylene glycol diacetate 0.07 g, 1,2-propanediol diacetate 0.08 g, 1,3-propanediol diacetate 0.08 g, recovered dodecylbenzenesulfonic acid catalyst 2.8 g, recovered acetic acid 5.85 g, recovered fibers 0.45 g, and degradation rate 90% were obtained. Example 4

[0053] 1 g of the unsaturated polyester resin composite material powder after crushing was mixed with 4 g of glacial acetic acid, 2 g of benzenesulfonic acid and 0.3 g of acetic anhydride to prepare a reaction system for swelling, the swelling temperature was 90 ℃ and the swelling time was 8 h.

[0054] After the swelling was completed, the temperature was increased for degradation reaction, the reaction temperature was 160 ℃ and the reaction time was 10 h. After the reaction was completed, the degradation liquid cooled to room temperature was subjected to solid-liquid separation to obtain recovered fibers.

[0055] Then, the filtrate was subjected to vacuum rectification, the rectification column top temperature was 120 ℃, the column bottom temperature was 200 ℃ and the column top vacuum degree was 0.085 MPa, to obtain solvent acetic acid and diethyl ester degradation products, respectively.

[0056] The bottom material was mixed with water and heated to fully dissolve, the mass ratio of the bottom material and water was 1:4, the heating temperature was 130 ℃, and after filtration, the insoluble depolymerization product styrene-maleic anhydride copolymer was obtained; the aqueous solution was cooled at 8 ℃ to crystallize, filtered, and washed with water to obtain the degradation product phthalic acid, and the remaining aqueous phase was evaporated to remove water to recover benzene sulfonic acid.

[0057] Styrene-maleic anhydride copolymer 0.15 g, phthalic acid 0.10 g, diethylene glycol diacetate 0.04 g, 1,2-propanediol diacetate 0.06 g, 1,3-propanediol diacetate 0.06 g, recovered benzene sulfonic acid catalyst 1.86 g, recovered acetic acid 3.86 g, and recovered fiber 0.53 g were obtained, and the degradation rate was 87.50%. Example 5

[0058] 1 g of crushed pure unsaturated polyester resin powder was mixed with 4 g of glacial acetic acid, 1.5 g of p-toluene sulfonic acid, and 0.3 g of acetic anhydride to prepare a reaction system for swelling, the swelling temperature was 90 ℃, and the swelling time was 6 h.

[0059] After swelling was completed, the temperature was raised for degradation reaction, the reaction temperature was 190 ℃, and the reaction time was 10 h.

[0060] After the reaction was completed, the cooled degradation liquid was subjected to vacuum rectification, the top temperature of the rectification column was 120 ℃, the bottom temperature was 180 ℃, and the vacuum degree at the top of the column was 0.06 MPa, and solvent acetic acid and diethyl ester degradation products were obtained, respectively.

[0061] The bottom material was mixed with water and heated to fully dissolve, the mass ratio of the bottom material and water was 1:3.5, the heating temperature was 100 ℃, and after filtration, the insoluble depolymerization product styrene-maleic anhydride copolymer was obtained; the aqueous solution was cooled at 4 ℃ to crystallize, filtered, and washed with water to obtain the degradation product phthalic acid, and the remaining aqueous phase was evaporated to remove water to recover p-toluene sulfonic acid.

[0062] Styrene-maleic anhydride copolymer 0.44 g, phthalic acid 0.26 g, ethylene glycol diacetate 0.18 g, diethylene glycol diacetate 0.15 g, recovered p-toluene sulfonic acid catalyst 1.44 g, and recovered acetic acid 3.88 g were obtained, and the degradation rate was 100%.

[0063] Comparative Example 1 The difference between this comparative example and Example 2 is that acetic anhydride is not added.

[0064] 1 g of crushed pure unsaturated polyester resin powder was mixed with 10 g of glacial acetic acid and 1 g of methane sulfonic acid to prepare a reaction system for swelling, the swelling temperature was 130 ℃, and the swelling time was 4 h.

[0065] After the swelling is completed, the temperature is raised to perform the degradation reaction, the reaction temperature is 210 ℃, and the reaction time is 4 h.

[0066] After the degradation reaction is completed, the degradation liquid cooled to room temperature is subjected to vacuum rectification, the rectification column top temperature is 55 ℃, the column bottom temperature is 120 ℃, and the column top vacuum degree is 0.09 MPa, and solvent acetic acid and diethyl ester degradation products are obtained respectively.

[0067] The bottom material is mixed with water and heated to be fully dissolved, the mass ratio of the bottom material to water is 1:5, the heating temperature is 130 ℃, and after filtration, the water-insoluble depolymerization product styrene-maleic anhydride copolymer is obtained; the water solution is cooled at 20 ℃ to crystallize, filtered, and washed with water to obtain the degradation product phthalic acid, and the remaining water phase is evaporated to remove water to obtain methane sulfonic acid.

[0068] Styrene-maleic anhydride copolymer 0.44 g, phthalic acid 0.21 g, ethylene glycol diacetate 0.10 g, 1,2-propanediol diacetate 0.12 g, recovered methane sulfonic acid catalyst 0.92 g, and recovered acetic acid 9.80 g are obtained, and the degradation rate is 100%.

[0069] Comparative Example 2 The difference between the present comparative example and Example 2 is that anhydrous calcium sulfate is used as the dehydrating agent.

[0070] 1 g of crushed pure unsaturated polyester resin powder is mixed with 10 g of glacial acetic acid, 1 g of methane sulfonic acid, and 0.5 g of anhydrous calcium sulfate to prepare a reaction system for swelling, the swelling temperature is 130 ℃, and the swelling time is 4 h.

[0071] After the swelling is completed, the temperature is raised to perform the degradation reaction, the reaction temperature is 210 ℃, and the reaction time is 4 h.

[0072] After the degradation reaction is completed, the degradation liquid cooled to room temperature is subjected to vacuum rectification, the rectification column top temperature is 55 ℃, the column bottom temperature is 120 ℃, and the column top vacuum degree is 0.09 MPa, and solvent acetic acid and diethyl ester degradation products are obtained respectively.

[0073] The bottom material is mixed with water and heated to be fully dissolved, the mass ratio of the bottom material to water is 1:5, the heating temperature is 130 ℃, and after filtration, the water-insoluble depolymerization product styrene-maleic anhydride copolymer and calcium sulfate are obtained; the filter residue is dissolved in THF, filtered, and dried to obtain calcium sulfate; the organic phase is subjected to recovered THF to obtain the depolymerization product styrene-maleic anhydride copolymer; the water solution is cooled at 20 ℃ to crystallize, filtered, and washed with water to obtain the degradation product phthalic acid, and the remaining water phase is evaporated to remove water to obtain methane sulfonic acid.

[0074] Styrene-maleic anhydride copolymer 0.44 g, phthalic acid 0.21 g, ethylene glycol diacetate 0.12 g, 1,2-propanediol diacetate 0.14 g, recycled methane sulfonic acid catalyst 0.92 g, recycled acetic acid 9.80 g, degradation rate 100%.

[0075] In the degradation system of unsaturated polyester resin, in order to maximize the structural integrity and yield of high value-added diacetate degradation products (such as 1,2-propanediol diacetate), it is necessary to strictly control the influence of trace water in the reaction system on the hydrolysis of ester products. With the basic degradation system composed of acetic acid and p-toluenesulfonic acid monohydrate as the reference, the introduction of dehydrating agent can effectively inhibit the hydrolysis of diacetate caused by the presence of trace water in the system. In the comparison of two dehydrating agents-acetic anhydride and anhydrous calcium sulfate, acetic anhydride shows better comprehensive performance.

[0076] Acetic anhydride not only acts as an efficient dehydrating agent to completely remove trace water in the system, ensuring the stability of diacetate structure, but also participates in the acyl exchange reaction as a reactant to promote the degradation process of unsaturated polyester resin. In addition, the acetic acid generated by its hydrolysis can further enhance the mass transfer efficiency of the reaction system, thereby promoting the forward progress of depolymerization reaction. In contrast, the water removal effect of anhydrous calcium sulfate is not good, resulting in a significant decrease in the yield of diacetate products (especially 1,2-propanediol diacetate and 1,3-propanediol diacetate), and its introduction makes the subsequent separation process complex and the cost increases. Therefore, from the perspective of improving product yield, avoiding the introduction of new impurities, and simplifying the post-processing process, the selection of acetic anhydride as a dehydrating agent is a better strategy to achieve efficient degradation of unsaturated polyester resin and ensure high retention rate of diacetate products.

[0077] The scope of protection of the present application is not limited to the above specific embodiments, and the present application can have various modifications and alterations for those skilled in the art, and any modification, improvement and equivalent replacement within the concept and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A method for chemical degradation and separation of unsaturated polyester resin waste, characterized by, The application relates to a method for preparing unsaturated polyester resin and a product thereof. Step one: raw materials containing unsaturated polyester resin are crushed, and the raw materials are mixed with glacial acetic acid, a catalyst and acetic anhydride to swell, the swelling temperature is 80-130 DEG C, and the swelling time is 4-12 h; Step two: after swelling, the temperature is increased to carry out a degradation reaction, the reaction temperature is 160-210 DEG C, and the reaction time is 4-12 h, so as to obtain a degradation liquid; Step three: the degradation liquid is subjected to vacuum rectification in a rectification tower to obtain acetic acid and diethyl ester depolymerization products; the tower bottom material is mixed with water, heated and fully dissolved, filtered to obtain a water-insoluble depolymerization product styrene-maleic anhydride copolymer; the water solution is cooled and crystallized, filtered and washed with water to obtain a degradation product phthalic acid, and the remaining water phase is evaporated to remove water to recover the catalyst.

2. The method of chemical degradation and separation of unsaturated polyester resin waste according to claim 1, characterized in that: In step one, the catalyst is one or a combination of the following: methane sulfonic acid, p-toluene sulfonic acid, benzene sulfonic acid and dodecyl benzene sulfonic acid.

3. The method of chemical degradation and separation of unsaturated polyester resin waste according to claim 2, characterized in that: In step one, the mass ratio of the raw materials, glacial acetic acid, the catalyst and acetic anhydride is 1:2-10:0.1-3:0.05-0.

5.

4. The method of chemical degradation and separation of unsaturated polyester resin waste according to claim 1, 2 or 3, characterized in that: In step one, the swelling temperature is 90-100 DEG C.

5. The method of chemical degradation and separation of unsaturated polyester resin waste according to claim 4, characterized in that: In step two, the reaction temperature is 180-190 DEG C.

6. The method of chemical degradation and separation of unsaturated polyester resin waste according to claim 1 or 5, characterized in that: In step three, the top temperature of the rectification tower is 55-180 DEG C, the bottom temperature is 120-270 DEG C, and the top vacuum degree is 0.02 MPa-0.09 MPa.

7. The method of chemical degradation and separation of unsaturated polyester resin waste according to claim 6, characterized by the fact that: In step three, the diethyl ester depolymerization product is any one or a combination of the following: ethylene glycol diacetate, diethylene glycol diacetate, 1,2-propylene glycol diacetate and 1,3-propylene glycol diacetate.

8. The method of chemical degradation and separation of unsaturated polyester resin waste according to claim 1 or 7, characterized by: In step three, when the tower bottom material is mixed with water and heated, the mass ratio of the two is 1:2-5, and the heating temperature is 80-130 DEG C.

9. The method of chemical degradation and separation of unsaturated polyester resin waste according to claim 8, characterized by the fact that: In step three, the temperature for cooling and crystallizing the water solution is 4-20 DEG C.

10. The method of chemical degradation and separation of unsaturated polyester resin waste according to claim 1 or 9, characterized in that: When the raw material is an unsaturated polyester resin composite material, a recycled fiber is obtained after solid-liquid separation after the degradation reaction.

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