A method for preparing a polylactic acid-modified unsaturated resin

Abstract

The application discloses a preparation method of polylactic acid modified unsaturated resin and belongs to the technical field of unsaturated resin preparation. The preparation method of the polylactic acid modified unsaturated resin comprises the following steps: step one, adding propylene glycol, diethylene glycol, modified polylactic acid, maleic anhydride and phthalic anhydride into a container, heating and reacting to obtain a mixture; step two, mixing, diluting, and curing the mixture, a polymerization inhibitor and a modified initiator to obtain the polylactic acid modified unsaturated resin. The unsaturated resin prepared by the method has excellent curing speed and toughness.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of unsaturated resin preparation, and particularly relates to a preparation method of polylactic acid modified unsaturated resin. BACKGROUND

[0002] With the improvement of environmental awareness and the strengthening of regulatory policies, the unsaturated resin industry is gradually developing towards environmentally friendly products. Environmentally friendly unsaturated resins have the advantages of low volatility, low toxicity, recyclability, and biodegradability, and meet the requirements of sustainable development. In the future, the unsaturated resin industry will pay more attention to the research and development and production of environmentally friendly products to meet the market demand for environmentally friendly products.

[0003] Polylactic acid is a new type of biodegradable material made from renewable plant resources. Starch raw materials are obtained by saccharification to obtain glucose, and then high-purity lactic acid is produced by fermentation of glucose and certain strains. Then, a certain molecular weight of polylactic acid is synthesized by chemical synthesis method. It has good biodegradability and can be completely degraded by microorganisms in nature after use, finally generating carbon dioxide and water without polluting the environment. Polylactic acid modified unsaturated resin is a new type of polymer material, which combines the biodegradability of polylactic acid and the excellent performance of unsaturated resin, making it have wide application prospects in many fields.

[0004] Patent CN118344568A discloses a lactic acid type unsaturated polyester resin and a preparation method thereof. The preparation method comprises: under an inert atmosphere, carrying out first and second dehydration condensation reactions on lactic acid, monobasic acid and first antioxidant at 125-215 DEG C; adding dibasic acid or dibasic anhydride, dibasic alcohol and second antioxidant, and carrying out third dehydration condensation reaction at 180-205 DEG C; adding air-drying agent, first polymerization inhibitor and catalyst to carry out fourth and fifth dehydration condensation reactions at 170-180 DEG C; the air-drying agent is selected from allyl ether and contains two hydroxyl groups; mixing the fourth and fifth dehydration condensation reaction products, second polymerization inhibitor and diluent to obtain the lactic acid type unsaturated polyester resin. The obtained unsaturated polyester resin can be used in the buttons of clothing and has good biodegradability. However, the light curing speed, temperature and toughness of the resin prepared by the method still have room for improvement. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of polylactic acid modified unsaturated resin, which solves the technical problems of poor light curing speed, temperature and toughness of unsaturated resin in the prior art.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] The application provides a preparation method of polylactic acid modified unsaturated resin, comprising the following steps:

[0008] Step one: add propylene glycol, diethylene glycol, modified polylactic acid, maleic anhydride and phthalic anhydride into a container, heat and react to obtain a mixture;

[0009] Step two: mix, dilute, and solidify the mixture, a polymerization inhibitor and a modified initiator to obtain the polylactic acid modified unsaturated resin.

[0010] Preferably, in step one, the amount ratio of propylene glycol, diethylene glycol, modified polylactic acid, maleic anhydride and phthalic anhydride is (10-22) g:(12-28) g:(3-8) g:(18-22) g:(26-34) g.

[0011] Preferably, the preparation method of the modified polylactic acid comprises the following steps:

[0012] Q1: add 2-amino-4-hydroxy-6-methylpyrimidine into a container containing dimethyl sulfoxide, stir and dissolve, then add N,N-carbonyldiimidazole, heat and stir under nitrogen atmosphere, cool after reaction, filter, wash, and vacuum dry to obtain intermediate 1;

[0013] Q2: mix intermediate 1 with polyether amine, heat and stir, cool after reaction, then add hexane, shake, stand, collect the lower liquid, dilute with chloroform, wash, dry, filter, rotary evaporate, and vacuum dry to obtain intermediate 2;

[0014] Q3: add polylactic acid into N,N-dimethylformamide, then add EDC and NHS, stir at room temperature, then add intermediate 2, continue to stir, precipitate after stirring, filter, and vacuum dry to obtain the modified polylactic acid.

[0015] In the above process, the synthesis reaction formula of intermediate 2 is as follows:

[0016]

[0017] The mass spectrum analysis result of intermediate 1 is: m / z: 219.08 (100.0%), 220.08 (9.9%), 220.07 (1.8%), 221.08 (1.0%).

[0018] As preferred, in the Q1, the ratio of 2-amino-4-hydroxy-6-methyl pyrimidine, dimethyl sulfoxide and N,N-carbonyl diimidazole is (10-15) g:(450-600) mL:(15.2-19.1) g, the reaction temperature is 80-85°C, the reaction time is 2-3h, the washing is performed by ethanol, and the vacuum drying temperature is 30-35°C, and the time is 2-4h.

[0019] As preferred, in the Q2, the ratio of intermediate 1 and polyether amine is (0.7-3.3) g:(31.2-42.1) g, the reaction temperature is 40-42°C, the reaction time is 40-48h, the washing is performed by saturated sodium chloride solution and deionized water, and the drying is performed by anhydrous sodium sulfate.

[0020] As preferred, in the Q3, the ratio of polylactic acid, N,N-dimethyl formamide, EDC, NHS and intermediate 2 is (22.3-25.7) g:(800-1000) mL:(0.45-0.62) g:(0.51-0.63) g:(2.45-3.02) g, the stirring time is 1-2h at room temperature, and the continuous stirring time is 12-24h.

[0021] As preferred, in the step two, the ratio of the mixture, the polymerization inhibitor and the modified initiator is (85-96) g:(0.01-0.03) g:(2-5) g, and the polymerization inhibitor is composed of one or more of hydroquinone, methylhydroquinone, p-tert-butyl hydroquinone, trimethylhydroquinone, p-benzoquinone and 2,6-di-tert-butyl-p-cresol.

[0022] As preferred, the preparation method of the modified initiator comprises the following steps:

[0023] S1: Bis(4-hydroxyphenyl) ketone and anhydrous potassium carbonate are added into N,N-dimethyl formamide, heated and stirred under nitrogen atmosphere, then 4-nitrophthalonitrile is added for stirring, followed by adding anhydrous potassium carbonate, continuously heating and stirring, after stirring, cooling, stirring in ice water, precipitating, suction filtration, washing, drying, purification, and monomer A is obtained;

[0024] S2: 2-naphthol and anhydrous potassium carbonate are added into N,N-dimethyl formamide, heated and stirred under nitrogen atmosphere, then 4-nitrophthalonitrile is added for stirring, followed by adding anhydrous potassium carbonate, continuously heating and stirring, after stirring, cooling, stirring in ice water, precipitating, suction filtration, washing, drying, recrystallization, and monomer B is obtained;

[0025] S3: Add monomer A, monomer B and zinc acetate to a container containing n-pentanol, stir under nitrogen protection, then add DBU, heat to react, after the reaction is complete, cool, add anhydrous methanol, precipitate, vacuum filter, wash, vacuum dry, and purify to obtain the modified initiator.

[0026] The synthesis reaction formula for the modified initiator in the above process is as follows:

[0027]

[0028] The mass spectrometry analysis results for monomer A were: m / z: 466.11 (100.0%), 467.11 (31.6%), 468.11 (5.9%), 467.10 (1.5%); the mass spectrometry analysis results for monomer B were: m / z: 270.08 (100.0%), 271.08 (20.2%), 272.09 (1.8%); the mass spectrometry analysis results for the modified initiator were: m / z: 2346.69 (100.0%), 2345.69 (82.6%), 2347.69 (75.5%), 2348.69 (65.3%), 2343.69 (63.1%), 2344.70 (49.0%), 2344.69 (48.2%). 2347.70 (39.0%), 2342.69 (38.8%), 2349.69 (38.7%), 2349.70 (34.3%), 2350.69 (29.6%), 2351.69 (26.6%), 2345.70 (26.4%), 2348.70 (19.2%), 2348.68 (17.5%), 2350.70 (14.6%), 2346.70 (13.0%), 2346.68 (12.8%), 2352.69 (11.1%), 2350.68 (8.1%), 2351.70 (6.5%), 2353.69 (5.8%) 2352.70 (5.5%), 2349.68 (3.7%), 2347.71 (3.5%), 2353.70 (2.5%), 2347.68 (2.5%), 2354.70 (2.4%), 2350.71 (1.6%), 2352.68 (1.0%).

[0029] Preferably, in S1, the ratio of bis(4-hydroxyphenyl) ketone, N,N-dimethylformamide, and 4-nitrophthalonitrile is (0.92-1.22) g : (20-30) mL : (1.54-2.15) g, the heating and stirring time is 30-45 min, the stirring time after adding 4-nitrophthalonitrile is 2-3 h, the heating and stirring temperature is 80-85 °C, and the stirring time is 40-48 h; in S2, the ratio of 2-naphthol, N,N-dimethylformamide, and 4-nitrophthalonitrile is (1.21-2.38) g : (20-30) mL : (1.56-2.11) g, the heating and stirring time is 30-45 min, the stirring time is 2-3 h, the heating and stirring temperature is 70-80 °C, and the stirring time is 30-40 h.

[0030] Preferably, in S3, the ratio of monomer A, monomer B, zinc acetate, n-pentanol and DBU is (0.11-0.35) g : (0.71-1.08) g : (0.21-0.36) g : (35-45) mL : (2-2.5) mL, the stirring time is 30-45 min, the heating reaction temperature is 140-155℃, and the reaction time is 40-50 h.

[0031] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0032] 1. This invention first uses 2-amino-4-hydroxy-6-methylpyrimidine, N,N-carbonyldiimidazole, polyetheramine, and polylactic acid as main raw materials to prepare modified polylactic acid. Subsequently, a modified initiator is prepared using bis(4-hydroxyphenyl) ketone, 4-nitrophthalonitrile, 2-naphthol, and zinc acetate as main raw materials. Applying the modified polylactic acid and the modified initiator to the preparation process of unsaturated resin effectively shortens the curing time of the unsaturated resin and improves its toughness.

[0033] 2. The modified polylactic acid prepared in this invention is used to modify unsaturated resin. The flexible segments contained therein can improve the toughness of the unsaturated resin. The hydrogen bond network formed can break and dissipate energy under external force, and restore the structure after recombination, thereby improving the toughness of the unsaturated resin. At the same time, the presence of hydrogen bonds can also endow the unsaturated resin with self-healing ability.

[0034] 3. The modified initiator prepared in this invention is applied to the preparation process of unsaturated resin, which can effectively shorten its curing time and heat resistance. The conjugated macrocyclic structure and zinc metal center contained in the modified initiator form a highly efficient photosensitive group, thereby realizing the curing of unsaturated resin. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1: This example discloses a method for preparing modified polylactic acid, including the following steps:

[0037] Q1: 12.5g of 2-amino-4-hydroxy-6-methylpyrimidine was added to a container containing 525mL of dimethyl sulfoxide. After stirring and dissolving, 17.1g of N,N-carbonyldiimidazole was added. The mixture was heated and stirred at 80°C for 2h under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled, filtered, washed with ethanol, and dried under vacuum at 35°C for 4h to obtain intermediate 1.

[0038] Q2: Mix 2g of intermediate 1 with 36.15g of polyetheramine, heat and stir at 40°C for 48h. After the reaction is complete, cool, then add hexane at 5°C, shake and let stand, collect the lower liquid, add 20mL of chloroform for dilution, wash with saturated sodium chloride solution and deionized water, dry with anhydrous sodium sulfate, filter, rotary evaporate, and vacuum dry to obtain intermediate 2;

[0039] Q3: Add 24.1g of polylactic acid to 900mL of N,N-dimethylformamide, then add 0.53g of EDC and 0.57g of NHS. Stir at room temperature for 2h, then add 2.73g of intermediate 2 and continue stirring for 24h. After stirring, precipitate, filter, and vacuum dry to obtain modified polylactic acid.

[0040] This embodiment discloses a method for preparing a modified initiator, including the following steps:

[0041] S1: 1.02 g of bis(4-hydroxyphenyl) ketone and 2.02 g of anhydrous potassium carbonate were added to 25 mL of N,N-dimethylformamide. The mixture was heated and stirred for 30 min under a nitrogen atmosphere. Then, 1.84 g of 4-nitrophthalonitrile was added and stirred for 3 h. Subsequently, 2.01 g of anhydrous potassium carbonate was added, and the mixture was heated at 85 °C and stirred for 48 h. After stirring, the mixture was cooled, poured into ice water and stirred to precipitate. The precipitate was filtered, washed, dried, and purified to obtain monomer A.

[0042] S2: 1.75 g of 2-naphthol and 1.02 g of anhydrous potassium carbonate were added to 25 mL of N,N-dimethylformamide. The mixture was heated and stirred for 30 min under a nitrogen atmosphere. Then, 1.83 g of 4-nitrophthalonitrile was added and stirred for 2 h. Then, 1.02 g of anhydrous potassium carbonate was added and the mixture was heated at 70 °C and stirred for 36 h. After stirring, the mixture was cooled and added to ice water and stirred for 30 min. The precipitate was precipitated, filtered, washed, dried, and recrystallized to obtain monomer B.

[0043] S3: Add 0.23g monomer A, 0.85g monomer B and 0.28g zinc acetate to a container containing 40mL n-pentanol, stir for 45min under nitrogen protection, then add 2.25mL DBU, heat at 150℃ for 48h. After the reaction is complete, cool, add anhydrous methanol, precipitate, vacuum filter, wash, vacuum dry, and purify to obtain the modified initiator.

[0044] This embodiment discloses a method for preparing polylactic acid modified unsaturated resin, including the following steps:

[0045] Step 1: Add 16g propylene glycol, 20g diethylene glycol, 5.5g modified polylactic acid, 20g maleic anhydride and 30g phthalic anhydride to a container, heat and react to obtain a mixture;

[0046] Step 2: Mix 90.5g of the mixture, 0.02g of hydroquinone and 3.5g of the modifying initiator, dilute and cure to obtain polylactic acid modified unsaturated resin.

[0047] Example 2: This example discloses a method for preparing modified polylactic acid, including the following steps:

[0048] Q1: 10g of 2-amino-4-hydroxy-6-methylpyrimidine was added to a container containing 450mL of dimethyl sulfoxide. After stirring and dissolving, 15.2g of N,N-carbonyldiimidazole was added. The mixture was heated and stirred at 80℃ for 2h under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled, filtered, washed with ethanol, and dried under vacuum at 35℃ for 4h to obtain intermediate 1.

[0049] Q2: Mix 0.7g of intermediate 1 with 31.2g of polyetheramine, heat and stir at 40°C for 48h. After the reaction is complete, cool, then add hexane at 5°C, shake and let stand, collect the lower liquid, add 20mL of chloroform for dilution, wash with saturated sodium chloride solution and deionized water, dry with anhydrous sodium sulfate, filter, rotary evaporate, and vacuum dry to obtain intermediate 2;

[0050] Q3: Add 22.3g of polylactic acid to 800mL of N,N-dimethylformamide, then add 0.45g of EDC and 0.51g of NHS. Stir at room temperature for 2h, then add 2.45g of intermediate 2 and continue stirring for 24h. After stirring, precipitate, filter, and vacuum dry to obtain modified polylactic acid.

[0051] This embodiment discloses a method for preparing a modified initiator, including the following steps:

[0052] S1: 0.92 g of bis(4-hydroxyphenyl) ketone and 2.02 g of anhydrous potassium carbonate were added to 20 mL of N,N-dimethylformamide. The mixture was heated and stirred for 30 min under a nitrogen atmosphere. Then, 1.54 g of 4-nitrophthalonitrile was added and stirred for 3 h. Subsequently, 2.01 g of anhydrous potassium carbonate was added, and the mixture was heated at 85 °C and stirred for 48 h. After stirring, the mixture was cooled, poured into ice water and stirred to precipitate. The precipitate was filtered, washed, dried, and purified to obtain monomer A.

[0053] S2: 1.21 g of 2-naphthol and 1.02 g of anhydrous potassium carbonate were added to 20 mL of N,N-dimethylformamide. The mixture was heated and stirred for 30 min under a nitrogen atmosphere. Then, 1.56 g of 4-nitrophthalonitrile was added and stirred for 2 h. Then, 1.02 g of anhydrous potassium carbonate was added and the mixture was heated at 70 °C and stirred for 36 h. After stirring, the mixture was cooled and added to ice water and stirred for 30 min. The precipitate was precipitated, filtered, washed, dried, and recrystallized to obtain monomer B.

[0054] S3: Add 0.11g monomer A, 0.71g monomer B and 0.21g zinc acetate to a container containing 35mL n-pentanol, stir for 45min under nitrogen protection, then add 2mL DBU, heat at 150℃ for 48h. After the reaction is complete, cool, add anhydrous methanol, precipitate, vacuum filter, wash, vacuum dry, and purify to obtain the modified initiator.

[0055] This embodiment discloses a method for preparing polylactic acid modified unsaturated resin, including the following steps:

[0056] Step 1: Add 10g propylene glycol, 12g diethylene glycol, 3g modified polylactic acid, 18g maleic anhydride and 26g phthalic anhydride to a container, heat and react to obtain a mixture;

[0057] Step 2: Mix 85g of the mixture, 0.01g of hydroquinone and 2g of the modifying initiator, dilute and cure to obtain polylactic acid modified unsaturated resin.

[0058] Example 3: This example discloses a method for preparing modified polylactic acid, including the following steps:

[0059] Q1: 15g of 2-amino-4-hydroxy-6-methylpyrimidine was added to a container containing 600mL of dimethyl sulfoxide. After stirring and dissolving, 19.1g of N,N-carbonyldiimidazole was added. The mixture was heated and stirred at 80℃ for 2h under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled, filtered, washed with ethanol, and dried under vacuum at 35℃ for 4h to obtain intermediate 1.

[0060] Q2: Mix 3.3g of intermediate 1 with 42.1g of polyetheramine, heat and stir at 40°C for 48h. After the reaction is complete, cool, then add hexane at 5°C, shake and let stand, collect the lower liquid, add 20mL of chloroform for dilution, wash with saturated sodium chloride solution and deionized water, dry with anhydrous sodium sulfate, filter, rotary evaporate, and vacuum dry to obtain intermediate 2;

[0061] Q3: Add 25.7g of polylactic acid to 1000mL of N,N-dimethylformamide, then add 0.62g of EDC and 0.63g of NHS. Stir at room temperature for 2h, then add 3.02g of intermediate 2 and continue stirring for 24h. After stirring, precipitate, filter, and vacuum dry to obtain modified polylactic acid.

[0062] This embodiment discloses a method for preparing a modified initiator, including the following steps:

[0063] S1: 1.22 g of bis(4-hydroxyphenyl) ketone and 2.02 g of anhydrous potassium carbonate were added to 30 mL of N,N-dimethylformamide. The mixture was heated and stirred for 30 min under a nitrogen atmosphere. Then, 2.15 g of 4-nitrophthalonitrile was added and stirred for 3 h. Subsequently, 2.01 g of anhydrous potassium carbonate was added, and the mixture was heated at 85 °C and stirred for 48 h. After stirring, the mixture was cooled, poured into ice water and stirred to precipitate. The precipitate was filtered, washed, dried, and purified to obtain monomer A.

[0064] S2: 2.38 g of 2-naphthol and 1.02 g of anhydrous potassium carbonate were added to 30 mL of N,N-dimethylformamide. The mixture was heated and stirred for 30 min under a nitrogen atmosphere. Then, 2.11 g of 4-nitrophthalonitrile was added and stirred for 2 h. Then, 1.02 g of anhydrous potassium carbonate was added and the mixture was heated at 70 °C and stirred for 36 h. After stirring, the mixture was cooled and added to ice water and stirred for 30 min. The precipitate was precipitated, filtered, washed, dried, and recrystallized to obtain monomer B.

[0065] S3: Add 0.36g monomer A, 1.08g monomer B and 0.36g zinc acetate to a container containing 45mL n-pentanol, stir for 45min under nitrogen protection, then add 2.5mL DBU, heat at 150℃ for 48h. After the reaction is complete, cool, add anhydrous methanol, precipitate, vacuum filter, wash, vacuum dry, and purify to obtain the modified initiator.

[0066] This embodiment discloses a method for preparing polylactic acid modified unsaturated resin, including the following steps:

[0067] Step 1: Add 22g propylene glycol, 28g diethylene glycol, 8g modified polylactic acid, 22g maleic anhydride and 34g phthalic anhydride to a container, heat and react to obtain a mixture;

[0068] Step 2: Mix 96g of the mixture, 0.03g of hydroquinone and 5g of the modifying initiator, dilute and cure to obtain polylactic acid modified unsaturated resin.

[0069] Example 4: This example discloses a method for preparing modified polylactic acid, including the following steps:

[0070] Q1: 11g of 2-amino-4-hydroxy-6-methylpyrimidine was added to a container containing 500mL of dimethyl sulfoxide. After stirring and dissolving, 16.3g of N,N-carbonyldiimidazole was added. The mixture was heated and stirred at 80℃ for 2h under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled, filtered, washed with ethanol, and dried under vacuum at 35℃ for 4h to obtain intermediate 1.

[0071] Q2: Mix 1.4g of intermediate 1 with 33.8g of polyetheramine, heat and stir at 40°C for 48h. After the reaction is complete, cool, then add hexane at 5°C, shake and let stand, collect the lower liquid, add 20mL of chloroform for dilution, wash with saturated sodium chloride solution and deionized water, dry with anhydrous sodium sulfate, filter, rotary evaporate, and vacuum dry to obtain intermediate 2;

[0072] Q3: Add 23.1g of polylactic acid to 850mL of N,N-dimethylformamide, then add 0.48g of EDC and 0.54g of NHS. Stir at room temperature for 2h, then add 2.58g of intermediate 2 and continue stirring for 24h. After stirring, precipitate, filter, and vacuum dry to obtain modified polylactic acid.

[0073] This embodiment discloses a method for preparing a modified initiator, including the following steps:

[0074] S1: 0.97 g of bis(4-hydroxyphenyl) ketone and 2.02 g of anhydrous potassium carbonate were added to 22 mL of N,N-dimethylformamide. The mixture was heated and stirred for 30 min under a nitrogen atmosphere. Then, 1.69 g of 4-nitrophthalonitrile was added and stirred for 3 h. Subsequently, 2.01 g of anhydrous potassium carbonate was added, and the mixture was heated at 85 °C and stirred for 48 h. After stirring, the mixture was cooled, poured into ice water and stirred to precipitate. The precipitate was filtered, washed, dried, and purified to obtain monomer A.

[0075] S2: 1.47 g of 2-naphthol and 1.02 g of anhydrous potassium carbonate were added to 28 mL of N,N-dimethylformamide. The mixture was heated and stirred for 30 min under a nitrogen atmosphere. Then, 1.73 g of 4-nitrophthalonitrile was added and stirred for 2 h. Then, 1.02 g of anhydrous potassium carbonate was added and the mixture was heated at 70 °C and stirred for 36 h. After stirring, the mixture was cooled and added to ice water and stirred for 30 min. The precipitate was precipitated, filtered, washed, dried, and recrystallized to obtain monomer B.

[0076] S3: Add 0.15g monomer A, 0.79g monomer B and 0.24g zinc acetate to a container containing 38mL n-pentanol, stir for 45min under nitrogen protection, then add 2.1mL DBU, heat at 150℃ for 48h. After the reaction is complete, cool, add anhydrous methanol, precipitate, vacuum filter, wash, vacuum dry, and purify to obtain the modified initiator.

[0077] This embodiment discloses a method for preparing polylactic acid modified unsaturated resin, including the following steps:

[0078] Step 1: Add 14g propylene glycol, 24g diethylene glycol, 6g modified polylactic acid, 19g maleic anhydride and 28g phthalic anhydride to a container, heat and react to obtain a mixture;

[0079] Step 2: Mix 87g of the mixture, 0.01g of hydroquinone and 3g of the modifying initiator, dilute and cure to obtain polylactic acid modified unsaturated resin.

[0080] Example 5: This example discloses a method for preparing modified polylactic acid, including the following steps:

[0081] Q1: 14g of 2-amino-4-hydroxy-6-methylpyrimidine was added to a container containing 575mL of dimethyl sulfoxide. After stirring and dissolving, 18.7g of N,N-carbonyldiimidazole was added. The mixture was heated and stirred at 80°C for 2h under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled, filtered, washed with ethanol, and dried under vacuum at 35°C for 4h to obtain intermediate 1.

[0082] Q2: Mix 2.8g of intermediate 1 with 40.2g of polyetheramine, heat and stir at 40℃ for 48h. After the reaction is complete, cool, then add hexane at 5℃, shake and let stand, collect the lower liquid, add 20mL of chloroform for dilution, wash with saturated sodium chloride solution and deionized water, dry with anhydrous sodium sulfate, filter, rotary evaporate, and vacuum dry to obtain intermediate 2;

[0083] Q3: Add 24.8g of polylactic acid to 950mL of N,N-dimethylformamide, then add 0.57g of EDC and 0.59g of NHS. Stir at room temperature for 2h, then add 2.91g of intermediate 2 and continue stirring for 24h. After stirring, precipitate, filter, and vacuum dry to obtain modified polylactic acid.

[0084] This embodiment discloses a method for preparing a modified initiator, including the following steps:

[0085] S1: 1.07 g of bis(4-hydroxyphenyl) ketone and 2.02 g of anhydrous potassium carbonate were added to 28 mL of N,N-dimethylformamide. The mixture was heated and stirred for 30 min under a nitrogen atmosphere. Then, 2.01 g of 4-nitrophthalonitrile was added and stirred for 3 h. Subsequently, 2.01 g of anhydrous potassium carbonate was added, and the mixture was heated at 85 °C and stirred for 48 h. After stirring, the mixture was cooled, poured into ice water and stirred to precipitate. The precipitate was filtered, washed, dried, and purified to obtain monomer A.

[0086] S2: 2.05 g of 2-naphthol and 1.02 g of anhydrous potassium carbonate were added to 22 mL of N,N-dimethylformamide. The mixture was heated and stirred for 30 min under a nitrogen atmosphere. Then, 2.05 g of 4-nitrophthalonitrile was added and stirred for 2 h. Then, 1.02 g of anhydrous potassium carbonate was added and the mixture was heated at 70 °C and stirred for 36 h. After stirring, the mixture was cooled and added to ice water and stirred for 30 min. The precipitate was precipitated, filtered, washed, dried, and recrystallized to obtain monomer B.

[0087] S3: Add 0.28g monomer A, 0.95g monomer B and 0.32g zinc acetate to a container containing 42mL n-pentanol, stir for 45min under nitrogen protection, then add 2.4mL DBU, heat at 150℃ for 48h. After the reaction is complete, cool, add anhydrous methanol, precipitate, vacuum filter, wash, vacuum dry, and purify to obtain the modified initiator.

[0088] This embodiment discloses a method for preparing polylactic acid modified unsaturated resin, including the following steps:

[0089] Step 1: Add 20g propylene glycol, 16g diethylene glycol, 7g modified polylactic acid, 21g maleic anhydride and 32g phthalic anhydride to a container, heat and react to obtain a mixture;

[0090] Step 2: Mix 93g of the mixture, 0.03g of hydroquinone and 4g of the modifying initiator, dilute and cure to obtain polylactic acid modified unsaturated resin.

[0091] Comparative Example 1: Compared with Example 1, in the preparation of polylactic acid modified unsaturated resin, polylactic acid was used instead of modified polylactic acid in Comparative Example 1, while other conditions remained unchanged.

[0092] Comparative Example 2: Compared with Example 1, Comparative Example 2 did not add a modifying initiator during the preparation of polylactic acid modified unsaturated resin, and all other conditions remained unchanged.

[0093] Experimental Example: The properties of the polylactic acid modified unsaturated resins prepared in Examples 1-5 and Comparative Examples 1-2 were tested. The toughness of the samples was tested according to GB / T 2567-2021, the curing time was tested according to GB / T 24148.7-2014, and the heat resistance was tested according to GB / T 1634.2-2019. The test results are shown in Table 1.

[0094] Table 1

[0095]

[0096] As shown in Table 1, the unsaturated resins prepared in Examples 1-5 of this invention exhibit excellent toughness, heat resistance, and short curing time. A comparison between Comparative Example 1 and Examples 1-5 shows that adding modified polylactic acid can effectively improve the toughness of the unsaturated resin; a comparison between Comparative Example 2 and Examples 1-5 shows that adding a modified initiator can effectively improve the heat resistance of the unsaturated resin and shorten the curing time.

[0097] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0098] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing polylactic acid modified unsaturated resin, characterized in that, Includes the following steps: Step 1: Add propylene glycol, diethylene glycol, modified polylactic acid, maleic anhydride and phthalic anhydride to a container, heat and react to obtain a mixture; Step 2: Mix the mixture, polymerization inhibitor and modified initiator, dilute and cure to obtain polylactic acid modified unsaturated resin; The method for preparing the modified polylactic acid includes the following steps: Q1: Add 2-amino-4-hydroxy-6-methylpyrimidine to a container containing dimethyl sulfoxide, stir to dissolve, then add N,N-carbonyldiimidazole, heat and stir under a nitrogen atmosphere, after the reaction is complete, cool, filter, wash, and vacuum dry to obtain intermediate 1; Q2: Mix intermediate 1 with polyetheramine, heat and stir to react. After the reaction is complete, cool, then add hexane, shake and let stand, collect the lower liquid, add chloroform for dilution, wash, dry, filter, rotary evaporate, and vacuum dry to obtain intermediate 2. Q3: Add polylactic acid to N,N-dimethylformamide, then add EDC and NHS, stir at room temperature, add intermediate 2, continue stirring, after stirring is completed, precipitate, filter, vacuum dry to obtain modified polylactic acid; The method for preparing the modified initiator includes the following steps: S1: Bis(4-hydroxyphenyl) ketone and anhydrous potassium carbonate were added to N,N-dimethylformamide. The mixture was heated and stirred under a nitrogen atmosphere. Then, 4-nitrophthalonitrile was added and stirred. Subsequently, anhydrous potassium carbonate was added, and the mixture was heated and stirred. After stirring, the mixture was cooled and poured into ice water and stirred to precipitate the precipitate. The precipitate was filtered, washed, dried, and purified to obtain monomer A. S2: 2-Naphthol and anhydrous potassium carbonate were added to N,N-dimethylformamide and heated and stirred under a nitrogen atmosphere. Then 4-nitrophthalonitrile was added and stirred. Anhydrous potassium carbonate was then added and heated and stirred continuously. After stirring, the mixture was cooled and added to ice water and stirred to precipitate. The precipitate was filtered, washed, dried, and recrystallized to obtain monomer B. S3: Add monomer A, monomer B and zinc acetate to a container containing n-pentanol, stir under nitrogen protection, then add DBU, heat to react, after the reaction is complete, cool, add anhydrous methanol, precipitate, vacuum filter, wash, vacuum dry, and purify to obtain the modified initiator.

2. The method for preparing polylactic acid modified unsaturated resin according to claim 1, characterized in that, In step one, the ratio of propylene glycol, diethylene glycol, modified polylactic acid, maleic anhydride and phthalic anhydride is (10-22) g: (12-28) g: (3-8) g: (18-22) g: (26-34) g.

3. The method for preparing polylactic acid modified unsaturated resin according to claim 1, characterized in that, In Q1, the ratio of 2-amino-4-hydroxy-6-methylpyrimidine, dimethyl sulfoxide and N,N-carbonyldiimidazole is (10-15) g : (450-600) mL : (15.2-19.1) g.

4. The method for preparing a polylactic acid-modified unsaturated resin according to claim 1, characterized in that, In Q2, the ratio of intermediate 1 to polyetheramine is (0.7-3.3) g : (31.2-42.1) g.

5. The method for preparing a polylactic acid modified unsaturated resin according to claim 1, characterized in that, In Q3, the ratio of polylactic acid, N,N-dimethylformamide, EDC, NHS and intermediate 2 is (22.3-25.7) g : (800-1000) mL : (0.45-0.62) g : (0.51-0.63) g : (2.45-3.02) g.

6. The method for preparing a polylactic acid-modified unsaturated resin according to claim 1, characterized in that, In step two, the ratio of the mixture, the polymerization inhibitor, and the modified initiator is (85-96) g: (0.01-0.03) g: (2-5) g. The polymerization inhibitor is composed of one or more of hydroquinone, methyl hydroquinone, p-tert-butylcatechol, trimethyl hydroquinone, p-benzoquinone, and 2,6-di-tert-butyl-p-cresol.

7. The method for preparing a polylactic acid modified unsaturated resin according to claim 1, characterized in that, In S1, the ratio of bis(4-hydroxyphenyl) ketone, N,N-dimethylformamide, and 4-nitrophthalonitrile is (0.92-1.22) g : (20-30) mL : (1.54-2.15) g; in S2, the ratio of 2-naphthol, N,N-dimethylformamide, and 4-nitrophthalonitrile is (1.21-2.38) g : (20-30) mL : (1.56-2.11) g.

8. The method for preparing a polylactic acid-modified unsaturated resin according to claim 1, characterized in that, In S3, the ratio of monomer A, monomer B, zinc acetate, n-pentanol and DBU is (0.11-0.35) g : (0.71-1.08) g : (0.21-0.36) g : (35-45) mL : (2-2.5) mL.

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