TWI889324B - Method for preparing unsaturated polyester resin, unsaturated polyester resin prepared thereof and unsaturated polyester cured product - Google Patents

Abstract

The present disclosure provides a method for preparing unsaturated polyester resin, which includes an alcoholysis step, an etherification step, a polycondensation step and a dilution step. The alcoholysis step is for mixing a polycarbonate, a glycol compound and an organic alkaline catalyst to obtain a first mixture. The etherification step is for adding a carbonate compound to the first mixture to obtain a second mixture. The polycondensation step is for reducing the temperature of the second mixture, and adding a dianhydride monomer or a diacid monomer to the second mixture to obtain a third mixture. The dilution step is for adding a styrene monomer or an acrylic monomer to the third mixture and diluting to a solid content to obtain an unsaturated polyester resin. Thus, in the present disclosure, the waste polycarbonate is converted into the unsaturated polyester resin by the alcoholysis step and the etherification step, and the reaction time of the process is short, which is favorable for the industrial production.

Description

Preparation method of unsaturated polyester resin, unsaturated polyester resin prepared therefrom and unsaturated polyester cured product

The present invention relates to a method for preparing an unsaturated polyester resin, in particular to a method for preparing an unsaturated polyester resin from polycarbonate, the unsaturated polyester resin prepared therefrom and an unsaturated polyester cured product.

Unsaturated Polyester Resin (UPR) is a polymer formed by the esterification reaction of dibasic acid and diol followed by condensation reaction with anhydride and dehydration. This polymer can form a cross-linked network structure at room temperature after being diluted with monomers containing free radicals and added with peroxide. The biggest advantage of unsaturated polyester resin is that it is very easy to mix with fillers and can be cured at room temperature and pressure. After curing, it has good mechanical strength, weather resistance, water resistance and chemical resistance, and can be widely used in injection and hand lay-up processes.

Previous technology has revealed that recycled waste PET is reacted with propylene glycol, ethylene glycol, diethylene glycol and a catalyst at 210 ^° C for 6 hours. After the reaction is completed, the temperature is lowered to 160 ^° C and maleic anhydride is added, and then the temperature is raised to 210 ^° C for another 6 hours. After the reaction is completed, an inhibitor and a diluent are added to obtain an environmentally friendly unsaturated polyester resin, in which recycled PET accounts for about 18-25%. However, the overall reaction time is as long as more than 12 hours, which requires a huge amount of electricity.

In view of this, how to use recycled polymer materials to prepare unsaturated polyester resins so that the production time is shortened to achieve the benefit of carbon reduction, and the unsaturated polyester resins produced still have excellent mechanical strength, has become the goal of relevant industries.

One object of the present invention is to provide a method for preparing an unsaturated polyester resin and the unsaturated polyester resin prepared, wherein polycarbonate is converted into diol by the principle of alcoholysis, and then the diol is reacted with anhydride for dehydration to form the unsaturated polyester resin.

Another object of the present invention is to provide an unsaturated polyester cured product, which is obtained by curing unsaturated polyester resin. The cured product has good mechanical properties and heat resistance.

One embodiment of the present invention provides a method for preparing an unsaturated polyester resin, comprising an alcoholysis step, an etherification step, a polycondensation step, and a dilution step. The alcoholysis step is to mix a polycarbonate, a diol compound, and an organic alkaline catalyst and heat them to an alcoholysis temperature to obtain a first mixture. The etherification step is to add a carbonate compound to the first mixture and keep the temperature at an etherification temperature to obtain a second mixture. The polycondensation step is to cool the second mixture and add a diacid anhydride monomer or a diacid monomer, and then heat it to a polycondensation temperature to react to obtain a third mixture. The dilution step is to cool the third mixture to a dilution temperature, then add a styrene monomer or an acrylic monomer and dilute to a solid content to obtain an unsaturated polyester resin.

According to the preparation method of the unsaturated polyester resin described in the preceding paragraph, the diol compound may have a structure as shown in formula (I): Formula (I), Wherein, R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen or an alkyl group having 1 to 6 carbon atoms.

According to the preparation method of the unsaturated polyester resin described in the preceding paragraph, the organic alkaline catalyst can be 1,8-diazabicyclo[5.4.0]undec-7-ene, imidazole compounds, triethylamine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, pyridine compounds or a combination thereof.

According to the preparation method of the unsaturated polyester resin described in the preceding paragraph, the molar ratio of the polycarbonate to the diol compound can be 1:1 to 1:2.

According to the preparation method of the unsaturated polyester resin described in the preceding paragraph, the amount of the organic alkaline catalyst added can be 0.2 mol% to 1 mol% of the diol compound content.

According to the preparation method of the unsaturated polyester resin described in the previous paragraph, the alcoholysis temperature can be 130 ^° C to 190 ^° C.

According to the preparation method of the unsaturated polyester resin described in the preceding paragraph, the carbonate compound may have a structure as shown in formula (II): Formula (II), Wherein, R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen or an alkyl group having 1 to 6 carbon atoms.

According to the preparation method of the unsaturated polyester resin described in the preceding paragraph, the molar ratio of the carbonate compound to the polycarbonate can be 1.5:1 to 0.8:1.

According to the preparation method of the unsaturated polyester resin described in the previous paragraph, the etherification temperature can be 130 ^° C to 190 ^° C.

According to the preparation method of the unsaturated polyester resin described in the preceding paragraph, the dianhydride monomer can be maleic anhydride, itaconic anhydride, phthalic anhydride or a combination thereof.

According to the preparation method of the unsaturated polyester resin described in the preceding paragraph, the diacid monomer can be maleic acid, fumaric acid, itaconic acid, terephthalic acid, isophthalic acid or a combination thereof.

According to the preparation method of the unsaturated polyester resin described in the preceding paragraph, the molar ratio of the dianhydride monomer or the diacid monomer to the polycarbonate can be 1:1 to 2:1.

According to the preparation method of the unsaturated polyester resin described in the preceding paragraph, the polycondensation temperature may be 170 ^° C to 230 ^° C.

According to the preparation method of the unsaturated polyester resin described in the previous paragraph, the dilution temperature can be 40 ^° C to 100 ^° C.

According to the preparation method of the unsaturated polyester resin described in the previous paragraph, the solid content can be 30 weight percent to 80 weight percent.

Another embodiment of the present invention provides an unsaturated polyester resin, which is prepared by the above-mentioned preparation method of the unsaturated polyester resin.

Another embodiment of the present invention provides an unsaturated polyester cured product, which is obtained by subjecting the unsaturated polyester resin to a curing reaction.

Thus, the present invention utilizes the principle of alcoholysis to convert polycarbonate into diol, then reacts the diol with anhydride to dehydrate to form an unsaturated polyester resin, and solidifies the unsaturated polyester resin. The obtained solid has good mechanical properties and heat resistance, which can meet the application requirements of composite materials and achieve the goal of recycling waste.

The following will discuss various embodiments of the present invention in more detail. However, this embodiment can be an application of various inventive concepts and can be specifically implemented in various different specific scopes. The specific embodiment is for illustrative purposes only and is not limited to the scope of the disclosure.

＜Preparation method of unsaturated polyester resin＞

Please refer to FIG. 1, which is a flow chart showing the steps of a method 100 for preparing an unsaturated polyester resin according to an embodiment of the present invention. In FIG. 1, the method 100 for preparing an unsaturated polyester resin includes steps 110, 120, 130, and 140.

Step 110 is to perform an alcoholysis step, which is to mix a polycarbonate, a diol compound and an organic alkaline catalyst and heat them to an alcoholysis temperature to obtain a first mixture. Specifically, the diol compound has a structure as shown in formula (I): Formula (I), Wherein, R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen or an alkyl group having 1 to 6 carbon atoms, and the organic alkaline catalyst can be 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), an imidazole compound, triethylamine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), a pyridine compound or a combination thereof. Specifically, the molar ratio of polycarbonate to diol compound can be 1:1 to 1:2, preferably 1:1 to 1:1.5, the amount of organic alkaline catalyst added can be 0.2 mol% to 1 mol% of the diol compound content, preferably 0.4 mol% to 0.8 mol%, and the alcoholysis temperature can be 130 ^° C to 190 ^° C, preferably 150 ^° C to 180 ^° C.

The chemical reaction formula for the alcoholysis step of the present invention is shown in Table 1 below. Table 1

Step 120 is an etherification step, which is to add a carbonate compound to the first mixture and keep the temperature at an etherification temperature to obtain a second mixture. Specifically, the carbonate compound has a structure as shown in formula (II): Formula (II), Wherein, R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen or an alkyl group having 1 to 6 carbon atoms. Specifically, the molar ratio of the carbonate compound to the polycarbonate may be 1.5:1 to 0.8:1, preferably 1.2:1 to 1:1, and the etherification temperature may be 130 ^° C to 190 ^° C, preferably 170 ^° C to 190 ^° C.

The chemical reaction formula for the etherification step of the present invention is shown in Table 2 below. Table 2

Step 130 is to perform a polycondensation step, which is to cool the second mixture and add a dianhydride monomer or a dian acid monomer, and then heat it to a polycondensation temperature for reaction to obtain a third mixture. Specifically, the dianhydride monomer can be maleic anhydride, itaconic anhydride, phthalic anhydride or a combination thereof, and the dian acid monomer can be maleic acid, fumaric acid, itaconic acid, terephthalic acid, isophthalic acid or a combination thereof. Specifically, the molar ratio of the dianhydride monomer or the dian acid monomer to the polycarbonate can be 1:1 to 2:1, preferably 1.4:1 to 1.7:1, and the polycondensation temperature can be 170 ^° C to 230 ^° C, preferably 180 ^° C to 220 ^° C.

The chemical reaction formula for the polycondensation step of the present invention is shown in Table 3 below. Table 3

Step 140 is a dilution step, which is to cool the third mixture to a dilution temperature, add a styrene monomer or an acrylic monomer and dilute to a solid content to obtain an unsaturated polyester resin. Specifically, the dilution temperature can be 40 ^° C to 100 ^° C, preferably 40 ^° C to 70 ^° C, and the solid content can be 30 weight percent to 80 weight percent, preferably 40 weight percent to 65 weight percent.

The present invention further provides an unsaturated polyester resin, which is prepared according to the above-mentioned preparation method 100 of the unsaturated polyester resin. The polycarbonate is converted into diol by the principle of alcoholysis, and the diol is then reacted with anhydride for dehydration to form the unsaturated polyester resin. The temperature required for this preparation process is lower than that of the traditional unsaturated polyester resin, and the process time is shorter.

＜Unsaturated polyester cured product＞

The present invention further provides an unsaturated polyester cured product, which is obtained by subjecting the unsaturated polyester resin to a curing reaction, and the curing reaction is briefly described below with reference to FIG. 2, wherein FIG. 2 shows a step flow chart of a method 200 for preparing an unsaturated polyester cured product according to another embodiment of the present invention. In FIG. 2, the method 200 for preparing an unsaturated polyester cured product includes step 210 and step 220.

Step 210 is a mixing step, which is to mix the aforementioned unsaturated polyester resin with a free radical initiator, and to form a latent curing composition by adding a free radical accelerator and a free radical inhibitor, wherein the free radical accelerator and the free radical inhibitor can be used to adjust the reactivity of the free radical initiator at room temperature, so that the unsaturated polyester resin can be cured at room temperature, but retain a certain degree of latency to facilitate operation.

Step 220 is a curing step, which is to pour the aforementioned curing composition into the mold, place it at room temperature for curing, and then place it in an oven for heating for post-curing to ensure that the unsaturated polyester resin can be completely cured.

The present invention is further illustrated by the following specific embodiments, which are used to facilitate those skilled in the art to which the present invention belongs, so that the present invention can be fully utilized and practiced without excessive interpretation. These embodiments should not be regarded as limiting the scope of the present invention, but are used to illustrate the materials and methods for implementing the present invention.

＜Example/Comparative Example＞

＜Preparation of unsaturated polyester resin＞

The preparation method of Example 1 is to add 400.24 grams (1.57 mole, calculated by repeating unit molecular weight) of polycarbonate pellets (purchased from Chi Mei Industrial, product code PC-122) and 146.55 grams (2.36 mole) of ethylene glycol (EG) into an integrated reaction tank, heat to 160 ^° C and stir, add 1.44 grams (0.4 mol% of EG) of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) after the temperature stabilizes, then heat to 180 ^° C and keep the temperature for 2.5 hours, then add 166.33 grams (1.89 mole) of ethylene carbonate (EC) and continue to react at 180 ^° C for 2.5 hours. After the reaction is completed, the temperature is lowered to 120 ^° C and a distillation device is set up. 231.52 g (2.36 mole) of maleic anhydride (MA) is added, and the initial acid value is measured to be 170 mgKOH/g. The temperature is then raised to 180 ^° C~215 ^° C for reaction and water is distilled out. When the acid value drops to 30 mgKOH/g, the temperature is lowered to 80 ^° C. Finally, 602.07 g of styrene monomer (SM) is added and diluted to a solid content of 55% to obtain the unsaturated polyester resin of Example 1, which is dark orange-red.

The preparation method of Example 2 is the same as that of Example 1, except that the polycarbonate pellets in Example 1 are replaced with discarded polycarbonate pellets (purchased from Yide Co., Ltd., product code YT-15), and 735.86 grams of styrene monomer (SM) are diluted to a solid content of 50% to obtain the unsaturated polyester resin of Example 2, which is dark orange-red in color.

The preparation method of Example 3 is to add 400.24 grams (1.57 mole) of polycarbonate pellets and 96.70 grams (1.57 mole) of ethylene glycol (EG) into an integrated reaction tank, heat it to 160 ^° C and stir it, add 0.96 grams (0.4 mol% of EG) of DBU after the temperature stabilizes, then heat it to 180 ^° C and keep it at this temperature for 2.5 hours, then add 138.61 grams (1.57 mole) of ethylene carbonate (EC) and continue to react at 180 ^° C for 2.5 hours. After the reaction is completed, the temperature is lowered to 120 ^° C and a distillation device is set up. 231.52 g (2.36 mole) of maleic anhydride (MA) is added, and the initial acid value is measured to be 182 mgKOH/g. The temperature is then raised to 180 ^° C~215 ^° C for reaction and water is distilled out. When the acid value drops to 30 mgKOH/g, the temperature is lowered to 80 ^° C. Finally, 700.65 g of styrene monomer (SM) is added and diluted to a solid content of 50% to obtain the unsaturated polyester resin of Example 3, which is dark orange-red.

The preparation method of Example 4 is the same as that of Example 3, except that the amount of maleic anhydride (MA) in Example 3 is changed to 153.95 g (1.57 mole), and 623.08 g of styrene monomer (SM) is diluted to a solid content of 50% to obtain the unsaturated polyester resin of Example 4, which is khaki in color.

The preparation method of Example 5 is to add 400.24 grams (1.57 mole) of waste polycarbonate fragments (purchased from Jiuxuan Technology Co., Ltd., product code RPC-Y) and 179.65 grams (2.36 mole) of 1,2-propylene glycol (PG) into an integrated reaction tank, heat it to 160 ^° C and stir it, add 2.88 grams (0.8 mol% of PG) of DBU after the temperature stabilizes, then heat it to 180 ^° C and keep the temperature for 9.5 hours, then add 192.83 grams (1.89 mole) of propylene carbonate (PC) and continue to react at 180 ^° C for 9 hours. After the reaction is completed, the temperature is lowered to 120 ^° C and a distillation device is set up. 231.52 g (2.36 mole) of maleic anhydride (MA) is added, and the initial acid value is measured to be 146.6 mgKOH/g. The temperature is then raised to 180 ^° C~215 ^° C for reaction and water is distilled out. When the acid value drops to 30 mgKOH/g, the temperature is lowered to 80 ^° C. Finally, 981.18 g of styrene monomer (SM) is added and diluted to a solid content of 45% to obtain the unsaturated polyester resin of Example 5, which is dark brown.

The preparation method of Example 6 is to add 400.24 grams (1.57 mole) of polycarbonate pellets and 194.90 grams (3.14 mole) of ethylene glycol (EG) into an integrated reaction tank, heat it to 160 ^° C and stir it, add 1.91 grams (0.4 mol% of EG) of DBU after the temperature stabilizes, then heat it to 180 ^° C and keep it at this temperature for 2.5 hours, then add 138.61 grams (1.57 mole) of ethylene carbonate (EC) and continue to react at 180 ^° C for 2.5 hours. After the reaction is completed, the temperature is lowered to 120 ^° C and a distillation device is set up. 307.91 g (3.14 mole) of maleic anhydride (MA) is added, and the initial acid value is measured to be 195 mgKOH/g. The temperature is then raised to 180 ^° C~215 ^° C for reaction and water is distilled out. When the acid value drops to 30 mgKOH/g, the temperature is lowered to 80 ^° C. Finally, 846.98 g of styrene monomer (SM) is added and diluted to a solid content of 50% to obtain the unsaturated polyester resin of Example 6, which is dark orange-red.

The preparation method of Comparative Example 1 is to add 150 grams (0.59 mole) of polycarbonate pellets and 72.23 grams (1.18 mole) of ethylene glycol (EG) into an integrated reaction tank, heat it to 160 ^° C and stir it, add 0.72 grams (0.4 mol% of EG) of DBU after the temperature stabilizes, and then heat it to 180 ^° C and keep the temperature for 2.5 hours. After the reaction is completed, the temperature is lowered to 120 ^° C and a distillation device is set up. 86.77 grams (0.88 mole) of maleic anhydride (MA) is added, and the initial acid value is measured to be 175 mgKOH/g. The temperature is then raised to 180 ^° C~215 ^° C for reaction and water is distilled out. When the acid value drops to 30 mgKOH/g, the temperature is lowered to 80 ^° C. Finally, 272.42 grams of styrene monomer (SM) is added and diluted to a solid content of 50% to obtain the unsaturated polyester resin of Comparative Example 1, which is opaque coffee color.

The preparation method of Comparative Example 2 is to add 400.24 grams (1.57 mole) of polycarbonate pellets and 146.55 grams (2.36 mole) of ethylene glycol (EG) into an integrated reaction tank, heat it to 160 ^° C and stir it, add 1.44 grams (0.4 mol% of EG) of DBU after the temperature stabilizes, then heat it to 180 ^° C and keep it at this temperature for 2.5 hours. After the reaction is completed, the temperature is lowered to 120 ^° C and a distillation device is set up. 231.52 grams (2.36 moles) of maleic anhydride (MA) is added, and the initial acid value is measured to be 186 mgKOH/g. The temperature is then raised to 180 ^° C~215 ^° C for reaction and water is distilled out. When the acid value drops to 30 mgKOH/g, the temperature is lowered to 80 ^° C. Finally, 666.55 grams of styrene monomer (SM) is added and diluted to a solid content of 50% to obtain the unsaturated polyester resin of Comparative Example 2, which is dark orange-red.

The preparation method of Comparative Example 3 is to add 400.24 grams (1.57 mole) of polycarbonate pellets and 179.65 grams (2.36 mole) of propylene glycol (PG) into an integrated reaction tank, heat it to 160 ^° C and stir it, add 1.44 grams (0.4 mol% of PG) of DBU after the temperature stabilizes, then heat it to 180 ^° C and keep it at this temperature for 2.5 hours. After the reaction is completed, the temperature is lowered to 120 ^° C and a distillation device is set up. 231.52 grams (2.36 moles) of maleic anhydride (MA) is added, and the initial acid value is measured to be 178 mgKOH/g. The temperature is then raised to 180 ^° C~215 ^° C for reaction and water is distilled out. When the acid value drops to 30 mgKOH/g, the temperature is lowered to 80 ^° C. Finally, 699.65 grams of styrene monomer (SM) is added and diluted to a solid content of 50% to obtain the unsaturated polyester resin of Comparative Example 3, which is dark orange-red.

The preparation method of Comparative Example 4 is to add 400.24 grams (1.57 mole) of waste polycarbonate fragments and 250.55 grams (2.36 mole) of diethylene glycol (DEG) into an integrated reaction tank, heat it to 160 ^o C and stir it, add 1.44 grams (0.4 mol% of DEG) of DBU after the temperature stabilizes, then heat it to 180 ^o C and keep it at this temperature for 2 hours, then add 166.33 grams (1.89 mole) of ethylene carbonate (EC) and continue to react at 180 ^o C for 1.5 hours. After the reaction is completed, the temperature is lowered to 120 ^° C and a distillation device is set up. 231.52 grams (2.36 moles) of maleic anhydride (MA) is added, and the initial acid value is measured to be 139.2 mgKOH/g. The temperature is then raised to 180 ^° C~215 ^° C for reaction and water is distilled out. When the acid value drops to 30 mgKOH/g, the temperature is lowered to 80 ^° C. Finally, 743.86 grams of styrene monomer (SM) is added and diluted to a solid content of 55% to obtain the unsaturated polyester resin of Comparative Example 4, which is dark brown.

＜Preparation of unsaturated polyester cured products＞

The preparation method of Examples 7 to 12 is to add 1.6 g of cobalt octoate and 1.5 g of 2,5-dihydroxytoluene to 400 g of the unsaturated polyester resin of Examples 1 to 6, respectively, and then add 4.8 g of butanone peroxide to form a curing composition. Then, the mixed curing composition is poured into a mold and molded at room temperature for one day, and then put into an oven at 105 ^° C for 2 hours to obtain the unsaturated polyester cured products of Examples 7 to 12.

The preparation method of Comparative Examples 5 to 7 is to add 1.6 g of cobalt octoate and 1.5 g of 2,5-dihydroxytoluene to 400 g of the unsaturated polyester resins of Comparative Examples 1 to 3, respectively, and then add 4.8 g of butanone peroxide to form a curing composition. It is found that the mixed curing composition cannot be cured at room temperature, so no cured product can be obtained.

The preparation method of Comparative Example 8 is to add 1.6 grams of cobalt octoate to 400 grams of the unsaturated polyester resin of Comparative Example 4. However, heat release begins during the mixing process, and gelatinization occurs before the addition of peroxide, so it cannot be smoothly molded.

＜Evaluation of mechanical and thermal properties＞

The unsaturated polyester cured products of Examples 7 to 12 were cut and subjected to the measurement of mechanical properties related to tension (ASTM D638), bending (ASTM D790) and thermal strain (ASTM D648) according to the standards of the American Society for Testing and Materials (ASTM). The glass transition temperature (T _g ) was measured by differential scanning calorimetry (DSC) at a heating rate of 10 ^° C/min. The measurement results are shown in Table 1 below. Table 1 Embodiment 7 Embodiment 8 Embodiment 9 Tensile strength(MPa) 75.33 75.93 67.72 Tensile modulus(GPa) 3265 3205 3270 Elongation(%) 3.81 4.12 2.76 Bending strength (MPa) 128.1 137.5 102.2 Bending modulus(GPa) 3405 3316 3596 Heat deformation temperature ( ^o C) 100.1 104.6 96.8 Glass transition temperature ( ^o C) 113.7 111.5 102.26 Embodiment 10 Embodiment 11 Embodiment 12 Tensile strength(MPa) 84.43 53.07 53.9 Tensile modulus(GPa) 3470 3160 3065 Elongation(%) 4.85 2.18 2.59 Bending strength (MPa) 166.5 135.88 86.3 Bending modulus(GPa) 4050 3460 2850 Heat deformation temperature ( ^o C) 112.0 109.8 60 Glass transition temperature ( ^o C) 118.12 117.4 71.4

From the results in Table 1, it can be seen that the unsaturated polyester resins of Examples 1 to 6 of the present invention can all be processed and molded smoothly. In Example 2, the raw material polycarbonate is replaced with waste polycarbonate to obtain an unsaturated polyester product with similar properties, which shows that the preparation method of the present invention has considerable feasibility in the reuse of waste polycarbonate. In addition, when the amounts of diol compounds, carbonate compounds and dianhydride monomers in the process are adjusted in Examples 3 to 5, the physical properties after curing are still maintained at a certain level, and when the amounts of diol compounds and dianhydride monomers in Example 6 are adjusted to twice the molar ratio of polycarbonate, the physical properties are poor, but it is still acceptable in the current composite material industry.

In addition, no carbonate compound was added in the preparation process of Comparative Examples 1 to 3, and the results of Comparative Examples 5 to 7 of the curing thereof show that the absence of carbonate compound in the preparation process will cause the unsaturated polyester resin obtained to not gelatinize during the curing process, which illustrates the importance of adding carbonate compound co-reaction in the synthesis formula. Furthermore, compared with Examples 1 to 6, Comparative Example 4 replaces the diol compound with longer chain diethylene glycol (DEG) in the preparation process, and the unsaturated polyester resin obtained quickly gelatinizes during the molding process and is difficult to operate. Therefore, if polycarbonate is to be prepared into unsaturated polyester resin for re-application, the alcoholysis step and the etherification step are key influencing factors. In addition, the alcoholysis step and the etherification step in the preparation method of the unsaturated polyester resin of the present invention only need to use a small amount of organic base as a catalyst and use a carbonate compound to complete the alcoholysis and etherification, and there will be no problem of deamination. The formed monomer does not need to be purified or solvent to continue to prepare the unsaturated polyester resin. In the prior art, the diol compound needs to be purified and dissolved in a solvent before continuing to prepare the unsaturated polyester resin.

In summary, the present invention can recycle waste polycarbonate into unsaturated polyester resin. Compared with the traditional unsaturated polyester resin process, the temperature required for the preparation process is lower and the process time is shorter. The obtained solidified product also has excellent mechanical strength. Under the current trend of reducing carbon emissions in the environment, not only the carbon emissions generated by chemicals in raw materials are reduced, but also the shortening of time and lowering of temperature in the process also greatly reduce the carbon emissions generated by electricity consumption, achieving a double benefit in reducing carbon emissions.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined in the attached patent application.

100: Preparation method of unsaturated polyester resin 200: Preparation method of unsaturated polyester cured product 110,120,130,140,210,220: Steps

In order to make the above and other purposes, features, advantages and embodiments of the present invention more clearly understandable, the attached drawings are described as follows: Figure 1 is a step flow chart of a method for preparing an unsaturated polyester resin according to one embodiment of the present invention; and Figure 2 is a step flow chart of a method for preparing an unsaturated polyester solid according to another embodiment of the present invention.

100: Preparation method of unsaturated polyester resin

110,120,130,140: Steps

Claims (17)

A method for preparing an unsaturated polyester resin comprises: performing an alcoholysis step, wherein a polycarbonate, a diol compound and an organic alkaline catalyst are mixed and heated to an alcoholysis temperature to obtain a first mixture; performing an etherification step, wherein a carbonate compound is added to the first mixture and the temperature is maintained at an etherification temperature to obtain a second mixture; performing a polycondensation step, wherein the second mixture is cooled and a dicarboxylic acid anhydride monomer or a dicarboxylic acid monomer is added, and the temperature is raised to a polycondensation temperature for reaction to obtain a third mixture; and performing a dilution step, wherein the third mixture is cooled to a dilution temperature, a styrene monomer or an acrylic monomer is added, and the mixture is diluted to a solid content to obtain an unsaturated polyester resin. The method for preparing an unsaturated polyester resin as described in claim 1, wherein the diol compound has a structure as shown in formula (I): Formula (I); Wherein, R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen or an alkyl group having 1 to 6 carbon atoms. A method for preparing an unsaturated polyester resin as described in claim 1, wherein the organic alkaline catalyst is 1,8-diazabicyclo[5.4.0]undec-7-ene, an imidazole compound, triethylamine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, a pyridine compound or a combination thereof. A method for preparing an unsaturated polyester resin as described in claim 1, wherein the molar ratio of the polycarbonate to the diol compound is 1:1 to 1:2. The method for preparing an unsaturated polyester resin as described in claim 1, wherein the amount of the organic alkaline catalyst added is 0.2 mol% to 1 mol% of the diol compound content. The method for preparing an unsaturated polyester resin as described in claim 1, wherein the alcoholysis temperature is 130 ^° C to 190 ^° C. The method for preparing an unsaturated polyester resin as described in claim 1, wherein the carbonate compound has a structure as shown in formula (II): Formula (II); Wherein, R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen or an alkyl group having 1 to 6 carbon atoms. A method for preparing an unsaturated polyester resin as described in claim 1, wherein the molar ratio of the carbonate compound to the polycarbonate is 1.5:1 to 0.8:1. The method for preparing an unsaturated polyester resin as described in claim 1, wherein the etherification temperature is 130 ^° C to 190 ^° C. The method for preparing an unsaturated polyester resin as described in claim 1, wherein the dianhydride monomer is maleic anhydride, itaconic anhydride, phthalic anhydride or a combination thereof. The method for preparing an unsaturated polyester resin as described in claim 1, wherein the diacid monomer is maleic acid, fumaric acid, itaconic acid, terephthalic acid, isophthalic acid or a combination thereof. The method for preparing an unsaturated polyester resin as described in claim 1, wherein the molar ratio of the dianhydride monomer or the diacid monomer to the polycarbonate is 1:1 to 2:1. A method for preparing an unsaturated polyester resin as described in claim 1, wherein the condensation temperature is 170 ^° C to 230 ^° C. A method for preparing an unsaturated polyester resin as described in claim 1, wherein the dilution temperature is 40 ^° C to 100 ^° C. A method for preparing an unsaturated polyester resin as described in claim 1, wherein the solid content is 30 weight percent to 80 weight percent. An unsaturated polyester resin recycled from waste polycarbonate is prepared by the method for preparing an unsaturated polyester resin as described in any one of claims 1 to 15. An unsaturated polyester cured product is obtained by subjecting the unsaturated polyester resin recycled from waste polycarbonate as described in claim 16 to a curing reaction.

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