Preparation method of polylactic acid modified unsaturated resin

Abstract

The invention 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 1, adding propylene glycol, diethylene glycol, modified polylactic acid, maleic anhydride and phthalic anhydride into a container, and heating for reaction to obtain a mixture; and 2, mixing the mixture, a polymerization inhibitor and a modified initiator, diluting, and curing 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 invention belongs to the technical field of unsaturated resin preparation, and particularly relates to a method for preparing a polylactic acid-modified unsaturated resin. Background Art

[0002] With rising environmental awareness and strengthened regulations and policies, the unsaturated resin industry is gradually moving towards environmentally friendly products. These resins offer advantages such as low volatility, low toxicity, recyclability, and biodegradability, meeting the requirements of sustainable development. In the future, the unsaturated resin industry will place greater emphasis on the research and development and production of environmentally friendly products to meet market demand.

[0003] Polylactic acid (PLA) is a new biodegradable material made from starch, a renewable plant resource. The starch is saccharified to produce glucose, which is then fermented with a specific bacterial strain to produce high-purity lactic acid. Polylactic acid of a specific molecular weight is then synthesized through chemical synthesis. This material exhibits excellent biodegradability and is completely degraded by natural microorganisms, ultimately producing carbon dioxide and water, without polluting the environment. Polylactic acid-modified unsaturated resin is a new polymer material that combines the biodegradability of PLA with the excellent properties of unsaturated resin, offering broad application prospects in a variety of fields.

[0004] Patent CN118344568A discloses a lactic acid-based unsaturated polyester resin and a preparation method thereof. The preparation method comprises: performing a first dehydration condensation reaction and a second dehydration condensation reaction on lactic acid, a monobasic acid, and a first antioxidant at 125-215°C under an inert atmosphere; adding a dibasic acid or dibasic acid anhydride, a diol, and a second antioxidant, and performing a third dehydration condensation reaction at 180-205°C; adding a gas drying agent, a first polymerization inhibitor, and a catalyst, and performing a fourth dehydration condensation reaction and a fifth dehydration condensation reaction at 170-180°C; the gas drying agent is selected from allyl ethers and contains two hydroxyl groups; and mixing the fourth and fifth dehydration condensation reaction products, the second polymerization inhibitor, and a diluent to obtain the lactic acid-based unsaturated polyester resin. The obtained unsaturated polyester resin can be used in buttons for clothing and has good biodegradability. However, the light curing speed, temperature, and toughness of the resin prepared by this method still need to be improved. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing a polylactic acid modified unsaturated resin, which is used to solve the technical problems of poor light curing speed, temperature and toughness of unsaturated resins in the prior art.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for preparing a polylactic acid-modified unsaturated resin, comprising the following steps:

[0008] Step 1: adding propylene glycol, diethylene glycol, modified polylactic acid, maleic anhydride and phthalic anhydride into a container, heating and reacting to obtain a mixture;

[0009] Step 2: Mix the mixture, polymerization inhibitor and modified initiator, dilute and solidify to obtain polylactic acid modified unsaturated resin.

[0010] Preferably, in step 1, the usage 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 to a container containing dimethyl sulfoxide, stir to dissolve, then add N,N-carbonyldiimidazole. Heat and stir under a nitrogen atmosphere to react. After the reaction is complete, cool, filter, wash, and vacuum dry to obtain intermediate 1.

[0013] Q2: Mix intermediate 1 with polyetheramine, heat and stir to react. After the reaction is completed, cool, then add hexane, shake and let stand, collect the lower liquid, add chloroform to dilute, wash, dry, filter, rotary evaporate, and vacuum dry to obtain intermediate 2;

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

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

[0016]

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

[0018] Preferably, in Q1, the amount 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, the heating and stirring reaction temperature is 80-85°C, the reaction time is 2-3 h, and the reaction is washed with ethanol. The vacuum drying temperature is 30-35°C and the time is 2-4 h.

[0019] Preferably, in Q2, the ratio of the intermediate 1 to the polyetheramine is (0.7-3.3) g: (31.2-42.1) g, the heating and stirring reaction temperature is 40-42° C., the reaction time is 40-48 h, and the mixture is washed with saturated sodium chloride solution and deionized water, and dried with anhydrous sodium sulfate.

[0020] Preferably, in Q3, the usage 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, the stirring time at room temperature is 1-2 h, and the continued stirring time is 12-24 h.

[0021] Preferably, in the step three, 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-butylcatechol, trimethylhydroquinone, p-benzoquinone and 2,6-di-tert-butyl-p-cresol.

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

[0023] S1: Add bis(4-hydroxyphenyl)ketone and anhydrous potassium carbonate to N,N-dimethylformamide, heat and stir under a nitrogen atmosphere, then add 4-nitrophthalonitrile and stir, then add anhydrous potassium carbonate, continue heating and stirring, cool after stirring, pour into ice water and stir, precipitate, filter, wash, dry, and purify to obtain monomer A;

[0024] S2: Add 2-naphthol and anhydrous potassium carbonate to N,N-dimethylformamide, heat and stir under a nitrogen atmosphere, then add 4-nitrophthalonitrile and stir, then add anhydrous potassium carbonate, heat and continue stirring, after stirring, cool, add to ice water and stir, precipitate, filter, wash, dry, and recrystallize to obtain monomer B;

[0025] S3: Monomer A, monomer B and zinc acetate are added to a container containing n-pentanol, stirred under nitrogen protection, and then DBU is added and heated for reaction. After the reaction is completed, the mixture is cooled and anhydrous methanol is added to precipitate. The precipitate is vacuum filtered, washed, vacuum dried, and purified to obtain a modified initiator.

[0026] In the above process, the synthetic reaction formula of the modified initiator is as follows:

[0027]

[0028] The mass spectrometry analysis results of 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 of monomer B were: m / z: 270.08 (100.0%), 271.08 (20.2%), 272.09 (1.8%); the mass spectrometry analysis results of the modified initiator were: m / z: 234 6.69(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%),234 9.70(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%),235 0.68(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 amount 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 time for stirring 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 amount 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 usage 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 ° C, 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. The present 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, then uses bis(4-hydroxyphenyl)ketone, 4-nitrophthalonitrile, 2-naphthol and zinc acetate as main raw materials to prepare a modified initiator. The modified polylactic acid and the modified initiator are applied to the preparation process of unsaturated resin, thereby effectively shortening the curing time of the unsaturated resin and improving the toughness.

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

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

[0035] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

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

[0037] Q1: Add 12.5 g of 2-amino-4-hydroxy-6-methylpyrimidine to a container containing 525 mL of dimethyl sulfoxide, stir to dissolve, then add 17.1 g of N,N-carbonyldiimidazole. Heat and stir at 80°C under a nitrogen atmosphere for 2 h. After the reaction, cool, filter, wash with ethanol, and dry in vacuo at 35°C for 4 h to obtain intermediate 1.

[0038] Q2: 2 g of intermediate 1 was mixed with 36.15 g of polyetheramine, heated to 40°C with stirring for 48 h, cooled after the reaction, and then added with 5°C hexane. After shaking, the mixture was allowed to stand. The lower layer of liquid was collected and diluted with 20 mL of chloroform. The mixture was washed with saturated sodium chloride solution and deionized water, dried with anhydrous sodium sulfate, filtered, rotary evaporated, and vacuum dried to obtain intermediate 2.

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

[0040] This embodiment discloses a method for preparing a modified initiator, comprising 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, and heated with stirring for 30 min under a nitrogen atmosphere. 1.84 g of 4-nitrophthalonitrile was then added, and the mixture was 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 the stirring was completed, the mixture was cooled, poured into ice water, and stirred to separate the 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, and heated with stirring for 30 min under a nitrogen atmosphere. Subsequently, 1.83 g of 4-nitrophthalonitrile was added and stirred for 2 h. Subsequently, 1.02 g of anhydrous potassium carbonate was added, and heating and stirring were continued at 70°C for 36 h. After stirring, the mixture was cooled and added to ice water with stirring for 30 min. The precipitate was filtered, washed, dried, and recrystallized to obtain monomer B.

[0043] S3: 0.23 g of monomer A, 0.85 g of monomer B and 0.28 g of zinc acetate were added to a container containing 40 mL of n-pentanol, stirred under nitrogen for 45 min, then 2.25 mL of DBU was added, and the mixture was heated at 150°C for 48 h. After the reaction was completed, the mixture was cooled, anhydrous methanol was added, the precipitate was precipitated, vacuum filtered, washed, vacuum dried, and purified to obtain a modified initiator.

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

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

[0046] Step 2: 90.5 g of the mixture, 0.02 g of hydroquinone and 3.5 g of the modified initiator are mixed, diluted and cured to obtain a polylactic acid modified unsaturated resin.

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

[0048] Q1: Add 10 g of 2-amino-4-hydroxy-6-methylpyrimidine to a container containing 450 mL of dimethyl sulfoxide, stir to dissolve, then add 15.2 g of N,N-carbonyldiimidazole. Heat and stir at 80°C under a nitrogen atmosphere for 2 h. After the reaction, cool, filter, wash with ethanol, and dry in vacuo at 35°C for 4 h to obtain intermediate 1.

[0049] Q2: 0.7 g of intermediate 1 was mixed with 31.2 g of polyetheramine, heated at 40°C with stirring for 48 h. After the reaction, the mixture was cooled, and then 5°C hexane was added. The mixture was shaken and allowed to stand. The lower layer of liquid was collected and diluted with 20 mL of chloroform. The mixture was washed with saturated sodium chloride solution and deionized water, dried with anhydrous sodium sulfate, filtered, rotary evaporated, and vacuum dried to obtain intermediate 2.

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

[0051] This embodiment discloses a method for preparing a modified initiator, comprising 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, and heated with stirring 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 heating and stirring were continued at 85°C for 48 h. After the stirring was completed, the mixture was cooled, poured into ice water with stirring, and 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, and heated with stirring for 30 min under a nitrogen atmosphere. Subsequently, 1.56 g of 4-nitrophthalonitrile was added and stirred for 2 h. Subsequently, 1.02 g of anhydrous potassium carbonate was added, and heating and stirring were continued at 70°C for 36 h. After stirring, the mixture was cooled and added to ice water with stirring for 30 min. The precipitate was filtered, washed, dried, and recrystallized to obtain monomer B.

[0054] S3: 0.11 g of monomer A, 0.71 g of monomer B, and 0.21 g of zinc acetate were added to a container containing 35 mL of n-pentanol, stirred under nitrogen for 45 min, then 2 mL of DBU was added, and the mixture was heated at 150°C for 48 h. After the reaction was completed, the mixture was cooled, anhydrous methanol was added, the precipitate was precipitated, vacuum filtered, washed, vacuum dried, and purified to obtain a modified initiator.

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

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

[0057] Step 2: 85 g of the mixture, 0.01 g of hydroquinone and 2 g of the modified initiator are mixed, diluted and cured to obtain a polylactic acid modified unsaturated resin.

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

[0059] Q1: Add 15 g of 2-amino-4-hydroxy-6-methylpyrimidine to a container containing 600 mL of dimethyl sulfoxide, stir to dissolve, then add 19.1 g of N,N-carbonyldiimidazole. Heat and stir at 80°C under a nitrogen atmosphere for 2 h. After the reaction, cool, filter, wash with ethanol, and dry in vacuo at 35°C for 4 h to obtain intermediate 1.

[0060] Q2: 3.3 g of intermediate 1 was mixed with 42.1 g of polyetheramine, heated at 40°C with stirring for 48 h. After the reaction, the mixture was cooled, and then 5°C hexane was added. The mixture was shaken and allowed to stand. The lower layer of liquid was collected and diluted with 20 mL of chloroform. The mixture was washed with saturated sodium chloride solution and deionized water, dried with anhydrous sodium sulfate, filtered, rotary evaporated, and vacuum dried to obtain intermediate 2.

[0061] Q3: 25.7 g of polylactic acid was added to 1000 mL of N,N-dimethylformamide, followed by 0.62 g of EDC and 0.63 g of NHS. After stirring at room temperature for 2 h, 3.02 g of intermediate 2 was added and stirring was continued for 24 h. After stirring, precipitation was performed, filtration was performed, and vacuum drying was performed to obtain modified polylactic acid.

[0062] This embodiment discloses a method for preparing a modified initiator, comprising 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, and heated with stirring 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 heating and stirring were continued at 85°C for 48 h. After the stirring was completed, the mixture was cooled, poured into ice water with stirring, and 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, and heated with stirring for 30 min under a nitrogen atmosphere. Subsequently, 2.11 g of 4-nitrophthalonitrile was added and stirred for 2 h. Subsequently, 1.02 g of anhydrous potassium carbonate was added, and heating and stirring were continued at 70°C for 36 h. After stirring, the mixture was cooled and added to ice water with stirring for 30 min. The precipitate was filtered, washed, dried, and recrystallized to obtain monomer B.

[0065] S3: 0.36 g of monomer A, 1.08 g of monomer B and 0.36 g of zinc acetate were added to a container containing 45 mL of n-pentanol, stirred under nitrogen for 45 minutes, then 2.5 mL of DBU was added, and the mixture was heated at 150°C for 48 hours. After the reaction was completed, the mixture was cooled, anhydrous methanol was added, the precipitate was precipitated, vacuum filtered, washed, vacuum dried, and purified to obtain a modified initiator.

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

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

[0068] Step 2: 96 g of the mixture, 0.03 g of hydroquinone and 5 g of the modified initiator are mixed, diluted and cured to obtain a polylactic acid modified unsaturated resin.

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

[0070] Q1: Add 11 g of 2-amino-4-hydroxy-6-methylpyrimidine to a container containing 500 mL of dimethyl sulfoxide, stir to dissolve, then add 16.3 g of N,N-carbonyldiimidazole. Heat and stir at 80°C under a nitrogen atmosphere for 2 h. After the reaction, cool, filter, wash with ethanol, and dry in vacuo at 35°C for 4 h to obtain intermediate 1.

[0071] Q2: 1.4 g of intermediate 1 was mixed with 33.8 g of polyetheramine, heated to 40°C with stirring for 48 h, cooled, and then added with 5°C hexane. The mixture was shaken and allowed to stand. The lower layer of liquid was collected and diluted with 20 mL of chloroform. The mixture was washed with saturated sodium chloride solution and deionized water, dried with anhydrous sodium sulfate, filtered, rotary evaporated, and vacuum dried to obtain intermediate 2.

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

[0073] This embodiment discloses a method for preparing a modified initiator, comprising 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, and heated with stirring 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 heating and stirring were continued at 85°C for 48 h. After the stirring was completed, the mixture was cooled, poured into ice water with stirring, and 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, and heated with stirring for 30 min under a nitrogen atmosphere. Subsequently, 1.73 g of 4-nitrophthalonitrile was added and stirred for 2 h. Subsequently, 1.02 g of anhydrous potassium carbonate was added, and heating and stirring were continued at 70°C for 36 h. After stirring, the mixture was cooled, added to ice water, and stirred for 30 min. The precipitate was filtered, washed, dried, and recrystallized to obtain monomer B.

[0076] S3: 0.15 g of monomer A, 0.79 g of monomer B and 0.24 g of zinc acetate were added to a container containing 38 mL of n-pentanol, stirred under nitrogen for 45 min, then 2.1 mL of DBU was added, and the mixture was heated at 150°C for 48 h. After the reaction was completed, the mixture was cooled, anhydrous methanol was added, the precipitate was precipitated, vacuum filtered, washed, vacuum dried, and purified to obtain a modified initiator.

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

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

[0079] Step 2: 87 g of the mixture, 0.01 g of hydroquinone and 3 g of the modified initiator are mixed, diluted and cured to obtain a polylactic acid modified unsaturated resin.

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

[0081] Q1: Add 14 g of 2-amino-4-hydroxy-6-methylpyrimidine to a container containing 575 mL of dimethyl sulfoxide, stir to dissolve, then add 18.7 g of N,N-carbonyldiimidazole. Heat and stir at 80°C under a nitrogen atmosphere for 2 h. After the reaction, cool, filter, wash with ethanol, and dry in vacuo at 35°C for 4 h to obtain intermediate 1.

[0082] Q2: 2.8 g of intermediate 1 was mixed with 40.2 g of polyetheramine, heated at 40°C with stirring for 48 h. After the reaction, the mixture was cooled, and then 5°C hexane was added. The mixture was shaken and allowed to stand. The lower layer of liquid was collected and diluted with 20 mL of chloroform. The mixture was washed with saturated sodium chloride solution and deionized water, dried with anhydrous sodium sulfate, filtered, rotary evaporated, and vacuum dried to obtain intermediate 2.

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

[0084] This embodiment discloses a method for preparing a modified initiator, comprising 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, and heated with stirring for 30 min under a nitrogen atmosphere. 2.01 g of 4-nitrophthalonitrile was then added, and the mixture was 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 the stirring was completed, the mixture was cooled, poured into ice water, and stirred to separate the 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, and heated with stirring for 30 min under a nitrogen atmosphere. Subsequently, 2.05 g of 4-nitrophthalonitrile was added and stirred for 2 h. Subsequently, 1.02 g of anhydrous potassium carbonate was added, and heating and stirring were continued at 70°C for 36 h. After stirring, the mixture was cooled and added to ice water with stirring for 30 min. The precipitate was filtered, washed, dried, and recrystallized to obtain monomer B.

[0087] S3: 0.28 g of monomer A, 0.95 g of monomer B and 0.32 g of zinc acetate were added to a container containing 42 mL of n-pentanol, stirred under nitrogen for 45 min, then 2.4 mL of DBU was added, and the mixture was heated at 150°C for 48 h. After the reaction was completed, the mixture was cooled, anhydrous methanol was added, the precipitate was precipitated, vacuum filtered, washed, vacuum dried, and purified to obtain a modified initiator.

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

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

[0090] Step 2: 93 g of the mixture, 0.03 g of hydroquinone and 4 g of the modified initiator are mixed, diluted and cured to obtain a polylactic acid modified unsaturated resin.

[0091] Comparative Example 1: Compared with Example 1, in the process of preparing the polylactic acid-modified unsaturated resin in Comparative Example 1, polylactic acid is used instead of the modified polylactic acid, and other conditions remain unchanged.

[0092] Comparative Example 2: Compared with Example 1, in Comparative Example 2, during the preparation of the polylactic acid-modified unsaturated resin, no modified initiator was added, and 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 of the samples was tested according to GB / T 24148.7-2014, and the heat resistance of the samples was tested according to GB / T 1634.2-2019. The test results are shown in Table 1:

[0094] Table 1

[0095] project Tensile strength / MPa Curing time / s Deformation temperature / ℃ Example 1 148.42 36 145 Example 2 146.93 38 143 Example 3 147.12 41 142 Example 4 146.04 45 138 Example 5 145.64 42 140 Comparative Example 1 113.53 43 141 Comparative Example 2 145.81 216 116

[0096] The test results in Table 1 show that the unsaturated resins prepared in Examples 1-5 of the present invention have excellent toughness, heat resistance, and short curing times. A comparison between Comparative Example 1 and Examples 1-5 shows that the addition of modified polylactic acid can effectively improve the toughness of the unsaturated resin; a comparison between Comparative Example 2 and Examples 1-5 shows that the addition of 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 specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

[0098] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a polylactic acid modified unsaturated resin, characterized in that: The following steps are involved: Step 1: adding propylene glycol, diethylene glycol, modified polylactic acid, maleic anhydride and phthalic anhydride into a container, heating and reacting to obtain a mixture; Step 2: Mix the mixture, polymerization inhibitor and modified initiator, dilute and solidify to obtain polylactic acid modified unsaturated resin.

2. The method for preparing a polylactic acid modified unsaturated resin according to claim 1, wherein: In the step 1, the usage 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 a polylactic acid modified unsaturated resin according to claim 1, wherein: The preparation method of the modified polylactic acid comprises 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 to react. 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 completed, cool, then add hexane, shake and let stand, collect the lower liquid, add chloroform to dilute, 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, precipitate after stirring, filter, and vacuum dry to obtain modified polylactic acid.

4. The method for preparing a polylactic acid modified unsaturated resin according to claim 3, wherein: In the Q1, the usage 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.

5. The method for preparing a polylactic acid modified unsaturated resin according to claim 3, wherein: In the Q2, the usage ratio of the intermediate 1 and the polyetheramine is (0.7-3.3) g: (31.2-42.1) g.

6. The method for preparing a polylactic acid modified unsaturated resin according to claim 3, wherein: In Q3, the usage 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.

7. The method for preparing a polylactic acid modified unsaturated resin according to claim 1, wherein: In the step three, the usage 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, methyl hydroquinone, p-tert-butylcatechol, trimethyl hydroquinone, p-benzoquinone and 2,6-di-tert-butyl-p-cresol.

8. The method for preparing a polylactic acid modified unsaturated resin according to claim 1, wherein: The preparation method of the modified initiator comprises the following steps: S1: Add bis(4-hydroxyphenyl)ketone and anhydrous potassium carbonate to N,N-dimethylformamide, heat and stir under a nitrogen atmosphere, then add 4-nitrophthalonitrile and stir, then add anhydrous potassium carbonate, continue heating and stirring, cool after stirring, pour into ice water and stir, precipitate, filter, wash, dry, and purify to obtain monomer A; S2: Add 2-naphthol and anhydrous potassium carbonate to N,N-dimethylformamide, heat and stir under a nitrogen atmosphere, then add 4-nitrophthalonitrile and stir, then add anhydrous potassium carbonate, heat and continue stirring, after stirring, cool, add to ice water and stir, precipitate, filter, wash, dry, and recrystallize to obtain monomer B; S3: Monomer A, monomer B and zinc acetate are added to a container containing n-pentanol, stirred under nitrogen protection, and then DBU is added and heated for reaction. After the reaction is completed, the mixture is cooled and anhydrous methanol is added to precipitate. The precipitate is vacuum filtered, washed, vacuum dried, and purified to obtain a modified initiator.

9. The method for preparing a polylactic acid modified unsaturated resin according to claim 8, wherein: In S1, the usage 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 usage ratio of 2-naphthol, N,N-dimethylformamide and 4-nitrophthalonitrile is (1.21-2.38) g: (20-30) mL: (1.56-2.11) g.

10. The method for preparing a polylactic acid modified unsaturated resin according to claim 8, characterized in that: In the S3, the usage 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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