Additive-based modified PLA composite material and preparation method thereof

Abstract

The invention discloses an additive-based modified PLA composite material and a preparation method thereof, two ends of a modifier molecular chain are grafted with isocyanate groups, and then the modifier molecular chain reacts with terminal hydroxyl groups of polylactic acid to prepare a copolymer. The preparation method comprises the following steps: in a molten state, blending a nucleating agent, a modified filler and a copolymer according to a weight ratio of (0.2-1): (4-8): (100-120), cooling and curing, and irradiating with ultraviolet rays to obtain the composite material. The modifier is prepared by taking a chemically modified silicone oil chain segment containing hydrogen at the end as a macromolecular initiator through a lactide ring-opening polymerization process, and the toughness of the material can be remarkably enhanced. Hydroxyl and methoxyl are introduced to the nucleating agent molecules, so that the crystallization rate is increased, and the thermal deformation temperature is increased. According to the modified filler with the core-shell structure formed by a sol-gel technology, the silicon dioxide of the shell layer has a toughening effect, and the lamellar structure of the bentonite of the core layer can provide a nucleation surface and promote crystallization.

Description

Technical Field

[0001] This invention relates to the field of PLA composite material preparation technology, specifically to an additive-modified PLA composite material and its preparation method. Background Technology

[0002] The continued depletion of non-renewable resources such as petroleum and the severe exacerbation of "white pollution" have drawn widespread attention. Most waste plastics are difficult to degrade in nature, severely damaging the Earth's ecological system. Developing biodegradable materials to replace traditional plastics is one effective way to solve these problems. Polylactic acid (PLA) is a bio-based polyester synthesized from sustainable resources such as starch. Due to its excellent biodegradability and biocompatibility, it has been widely used in various fields, including fibers, biomedical materials, and packaging materials. However, PLA materials are brittle and have insufficient heat resistance. The purpose of this invention is to prepare a PLA composite material with high toughness and good heat resistance. Summary of the Invention

[0003] The purpose of this invention is to provide an additive-modified PLA composite material and its preparation method, which solves the problems of high brittleness and poor heat resistance of ordinary PLA materials at present.

[0004] The objective of this invention can be achieved through the following technical solutions: A method for preparing PLA composite materials based on additive modification specifically includes the following steps: Step S1: Mix the modifier and dimethylformamide evenly, and under the conditions of 110-120 r / min, 70-80℃ and nitrogen gas, stir and add dibutyltin dilaurate and diisocyanate, and react for 3-5 h. Then stir and add polylactic acid, and react for 4-6 h to obtain the copolymer. Step S2: The copolymer, fir powder and nucleating agent are melt-blended at 170-190℃ under nitrogen gas for 2-3 minutes. Modified filler and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide are added and melt-blended for 3-4 minutes. The mixture is then cooled and cured, and irradiated with ultraviolet light for 30-40 seconds to obtain the additive-modified PLA composite material.

[0005] Furthermore, in step S1, the molar ratio of the modifier, diisocyanate, and polylactic acid is 1:1.2:0.5, the amount of dibutyltin dilaurate is 3-5% of the mass of diisocyanate, the D-isomer content of polylactic acid is 0.3%, and the weight-average molecular weight is 200,000.

[0006] Furthermore, the weight ratio of the copolymer, fir powder, nucleating agent, modified filler and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide in step S2 is 100-120:3-5:0.2-1:4-8:0.1-0.2, and the moisture content of the fir powder is 35-40%.

[0007] Furthermore, the modifier is prepared by the following steps: Step A1: Mix the hydrogen-containing silicone oil, allyl glycidyl ether, and toluene evenly. Under the conditions of 90-100 r / min, 70-80℃, and nitrogen purging, stir and add a solution of isopropanol in chloroplatinic acid. React for 2-3 hours to obtain intermediate 1. Mix intermediate 1 and tetrahydrofuran evenly. Under the conditions of 100-120 r / min, 60-80℃, and nitrogen purging, stir and add hydroquinone and acrylamine. React for 4-5 hours to obtain intermediate 2. Step A2: Mix intermediate 2 and tetrahydrofuran evenly, stir and add 1-cyclohexyl-3-phenylurea and 7-methylhexacyclic dicyclic guanidine under nitrogen conditions of 90-100 r / min and 20-30℃, and react for 1-2 h. Add lactide and react for 3-5 h. Centrifuge and dry to obtain the modifier.

[0008] Further, the hydrogen content of the hydrogen-terminated silicone oil mentioned in step A1 is 0.05-0.07%, the viscosity at 25°C is 80-110 cs, the molar ratio of the silicon-hydrogen bonds on the hydrogen-terminated silicone oil to the carbon-carbon double bonds on the allyl glycidyl ether is 1:1.1, the amount of isopropanol solution of chloroplatinic acid is 0.1-0.5% of the mass of the hydrogen-terminated silicone oil, the mass ratio of chloroplatinic acid to isopropanol is 0.01:9, the molar ratio of intermediate 1 to acrylamine is 1:1.1, and the amount of hydroquinone is 3-5% of the amount of acrylamine.

[0009] Furthermore, in step A2, the molar ratio of intermediate 2 to lactide is 1:1.2, the amount of 1-cyclohexyl-3-phenylurea is 3-5% of the mass of lactide, and the amount of 7-methylhexacyclic bicyclic guanidine is 3-5% of the mass of intermediate 2.

[0010] Furthermore, the nucleating agent is prepared by the following steps: 4-Methoxybenzoylhydrazine and pyridine were mixed evenly, and succinic anhydride was added while stirring at a speed of 90-100 r / min and a temperature of 40-60℃. The mixture was reacted for 4-6 h to obtain intermediate 3. Intermediate 3, 1-hydroxybenzotriazole and dichloromethane were mixed evenly, and dicyclohexylcarbodiimide was added while stirring at a speed of 90-100 r / min and a temperature of 0-5℃. The mixture was reacted for 30-50 min, and then heated to 20-30℃. 2-hydroxyaniline and triethylamine were added while stirring. The mixture was reacted for 4-6 h to obtain the nucleating agent.

[0011] Furthermore, the molar ratio of 4-methoxybenzoylhydrazine to succinic anhydride is 1:1.2, and the molar ratio of intermediate 3, 1-hydroxybenzotriazole, dicyclohexylcarbodiimide and 2-hydroxyaniline is 1 mmol:1.2 mmol:1.1 mmol:1.1 mmol.

[0012] Furthermore, the modified filler is prepared by the following steps: Step B1: Mix aluminum chloride solution and ferric chloride solution evenly, stir and add sodium hydroxide solution at a speed of 100-110 r / min and a temperature of 60-70℃, and react for 3-4 hours to obtain a columnarizing agent. Disperse bentonite in deionized water, stir and add columnarizing agent at a speed of 100-120 r / min and a temperature of 60-80℃, and react for 2-4 hours to obtain a bentonite suspension. Aged the bentonite suspension for 12-24 hours, centrifuged and dried to obtain column-supported bentonite. Step B2: Disperse the pillared bentonite in a mixed solution of ethanol and deionized water. Stir and add ammonia water at a speed of 80-90 r / min and a temperature of 60-80℃ to adjust the pH to 9-10. Add tetraethyl orthosilicate and react for 6-8 h. Wash, centrifuge, and calcine at 400℃ for 2-3 h to obtain the pretreated filler. Disperse the pretreated filler in tetrahydrofuran. Stir and add 3-mercaptopropyltrimethoxysilane at a speed of 200-300 r / min, a temperature of 60-80℃, and a pH of 4-5 to obtain the modified filler.

[0013] Furthermore, in step B1, the molar concentrations of the aluminum chloride solution and ferric chloride solution are 0.1 mol / L, the molar concentration of the sodium hydroxide solution is 0.2 mol / L, the volume ratio of the aluminum chloride solution, ferric chloride solution, and sodium hydroxide solution is 10 mL:10 mL:22 mL, the molar ratio of aluminum ions, iron ions, and hydroxide ions in the columnarizing agent is 2.4:0.5:1, and the volume ratio of bentonite, deionized water, and columnarizing agent is 2 g:100 mL:3 mL.

[0014] Furthermore, in step B2, the ratio of pillar-supported bentonite to tetraethyl orthosilicate is 1g:1-2mL, and the amount of 3-mercaptopropyltrimethoxysilane is 3-5% of the mass of the pretreated filler.

[0015] The beneficial effects of this invention are as follows: The hydroxyl groups at both ends of the modifier molecular chain react with the isocyanate groups on excess diisocyanate under the action of a catalyst. After a period of reaction, polylactic acid is added, and the hydroxyl groups at one end of its molecular chain react with the excess isocyanate groups to generate urethane groups, thus obtaining a copolymer. When the copolymer and nucleating agent are melt-blended, the carbonyl groups on the copolymer act as hydrogen bond acceptors, and the amide groups on the nucleating agent act as hydrogen bond donors, forming a strong, directional adsorption between the nucleating agent and the copolymer molecular chain, thereby significantly promoting nucleation. 2,4,6-Trimethylbenzoyl-diphenylphosphine oxide acts as an initiator, and when irradiated with ultraviolet light, it promotes the reaction between the thiol groups on the modified filler and the carbon-carbon double bonds on the copolymer, thus obtaining an additive-modified PLA composite material.

[0016] Modifier: The active silane-hydrogen bonds on the hydrogen-terminated silicone oil react with the carbon-carbon double bonds on allyl glycidyl ether under platinum catalysis to prepare intermediate 1. The epoxy group on intermediate 1 reacts with the amino group on allylamine to generate a secondary amine and a hydroxyl structure, thus preparing intermediate 2. 7-Methylhexanedicyclic guanidine, as a strong organic base, can activate intermediate 2, abstracting the proton from its hydroxyl group to make it a highly nucleophilic alkoxy ion. 1-Cyclohexyl-3-phenylurea forms a strong hydrogen bond with the carbonyl oxygen on the lactide molecule through its NH group, making the carbonyl oxygen more susceptible to nucleophilic attack by the alkoxy ion, causing the lactide to undergo ring-opening polymerization, thus preparing the modifier.

[0017] Nucleating agent: The nucleophilic amino group on 4-methoxybenzoylhydrazine attacks the carbonyl carbon of succinic anhydride, causing the anhydride ring to open and generating a product containing both an amide bond and a carboxylic acid group, thus producing an intermediate. The carboxyl group on the intermediate is activated by 1-hydroxybenzotriazole and dicyclohexylcarbodiimide, which reacts with the amino group on 2-hydroxyaniline to produce the nucleating agent.

[0018] Modified filler: Aluminum chloride and ferric chloride dissolve in water to release metal cations. These cations combine with water molecules to form hydrated metal ions, which then undergo hydrolysis. Slowly adding sodium hydroxide increases the pH of the solution, promoting hydrolysis and initiating a reaction between the hydroxyl groups on the hydrated metal ions and water molecules on another hydrated metal ion, forming a hydroxyl bridge structure. As the bridging reaction continues, a polymeric hydroxyl cationic structure is generated, yielding a column-forming agent. Bentonite is dispersed in deionized water, and the column-forming agent is added. The polymeric hydroxyl metal cations in the column-forming agent exchange for interlayer cations in the bentonite, yielding column-supported bentonite. Under alkaline conditions, tetraethyl orthosilicate hydrolyzes, and the resulting silanol bonds graft onto the silicon-oxygen bonds on the column-supported bentonite, causing tetraethyl orthosilicate to condense on the surface of the column-supported bentonite to form a core-shell structure. After high-temperature calcination, the interlayer hydroxyl cationic clusters in the bentonite lose their hydroxyl groups and water, transforming into robust, nano-sized metal oxide clusters, yielding a pretreated filler. Under acidic conditions, the silanol bonds formed by the hydrolysis of 3-mercaptopropyltrimethoxysilane graft onto the siloxane bonds on the pretreated filler to form a modified filler.

[0019] The modifier molecule contains an ABA-type triblock polymer, where B is a hydrogen-terminated silicone oil molecular chain segment and A is a polylactic acid molecular chain segment formed by the ring-opening polymerization of lactide. The ultra-flexible hydrogen-terminated silicone oil segments are incompatible with the matrix, forming a microphase separation structure. When the material is subjected to external impact, these dispersed, soft silicone oil micro-regions become stress concentration points, triggering a large amount of energy dissipation, thereby preventing crack propagation and significantly improving toughness. Hydroxyl and methoxy groups are introduced into the designed amide nucleating agent. The nucleating agent molecule can simultaneously utilize the strong hydrogen bonds of hydroxyl groups and the dipole interactions of methoxy groups to bind with the polylactic acid molecular chain at multiple points, resulting in stronger binding force, better anchoring effect, and increased crystallization rate, thus increasing the heat distortion temperature. The bentonite modified with the columnar modifier has a regular lamellar structure, providing a good nucleation surface for material crystallization, further increasing the heat distortion temperature. The core-shell structure formed through sol-gel can induce crazes and shear bands in the material, significantly improving the impact strength and elongation at break, thereby increasing toughness. Detailed Implementation

[0020] 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.

[0021] Example 1: A method for preparing PLA composite material based on additive modification, specifically including the following steps: Step S1: Mix the modifier and dimethylformamide evenly, stir and add dibutyltin dilaurate and diisocyanate under the conditions of 110 r / min, 70℃ and nitrogen gas, and react for 3 h. Then stir and add polylactic acid and react for 4 h to obtain the copolymer. Step S2: The copolymer, fir powder and nucleating agent are melt-blended for 2 min at 170℃ under nitrogen gas. Modified filler and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide are added and melt-blended for 3 min. The mixture is then cooled and cured, and irradiated with ultraviolet light for 30 s to obtain the additive-modified PLA composite material.

[0022] In step S1, the molar ratio of the modifier, diisocyanate, and polylactic acid is 1:1.2:0.5, the amount of dibutyltin dilaurate is 3% of the mass of diisocyanate, the D-isomer content of polylactic acid is 0.3%, and the weight average molecular weight is 200,000.

[0023] The copolymer, fir powder, nucleating agent, modified filler and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide mentioned in step S2 are in a weight ratio of 100:3:0.2:4:0.1, and the moisture content of the fir powder is 35%.

[0024] The modifier is prepared by the following steps: Step A1: Hydrogen-containing silicone oil, allyl glycidyl ether, and toluene are mixed evenly. Under conditions of 90 r / min, 70°C, and nitrogen purging, the mixture is stirred and an isopropanol solution of chloroplatinic acid is added. The reaction is carried out for 2 hours to obtain intermediate 1. Intermediate 1 is mixed evenly with tetrahydrofuran. Under conditions of 100 r / min, 60°C, and nitrogen purging, the mixture is stirred and hydroquinone and acrylamine are added. The reaction is carried out for 4 hours to obtain intermediate 2. Step A2: Mix intermediate 2 and tetrahydrofuran evenly, stir and add 1-cyclohexyl-3-phenylurea and 7-methylhexacyclic dicyclic guanidine under nitrogen conditions of 90 r / min and 20℃, and react for 1 h. Add lactide and react for 3 h. Centrifuge and dry to obtain the modifier.

[0025] The hydrogen-containing silicone oil described in step A1 has a hydrogen content of 0.05% and a viscosity of 80 cs at 25°C. The molar ratio of the silicon-hydrogen bonds on the hydrogen-containing silicone oil to the carbon-carbon double bonds on the allyl glycidyl ether is 1:1.1. The amount of isopropanol solution of chloroplatinic acid used is 0.1% of the mass of the hydrogen-containing silicone oil. The mass ratio of chloroplatinic acid to isopropanol is 0.01:9. The molar ratio of intermediate 1 to acrylamine is 1:1.1. The amount of hydroquinone used is 3% of the amount of acrylamine used.

[0026] In step A2, the molar ratio of intermediate 2 to lactide is 1:1.2, the amount of lactide is 1 mol, the amount of 1-cyclohexyl-3-phenylurea is 3% of the mass of lactide, and the amount of 7-methylhexacyclic bicyclic guanidine is 3% of the mass of intermediate 2.

[0027] The nucleating agent is prepared by the following steps: 4-Methoxybenzoylhydrazine and pyridine were mixed evenly, and succinic anhydride was added under stirring at 90 r / min and 40 °C. The mixture was reacted for 4 h to obtain intermediate 3. Intermediate 3, 1-hydroxybenzotriazole and dichloromethane were mixed evenly, and dicyclohexylcarbodiimide was added under stirring at 90 r / min and 0 °C. The mixture was reacted for 30 min, then heated to 20 °C, and 2-hydroxyaniline and triethylamine were added under stirring. The mixture was reacted for 4 h to obtain nucleating agent.

[0028] The molar ratio of 4-methoxybenzoylhydrazine to succinic anhydride is 1:1.2, and the molar ratio of intermediate 3, 1-hydroxybenzotriazole, dicyclohexylcarbodiimide and 2-hydroxyaniline is 1 mmol:1.2 mmol:1.1 mmol:1.1 mmol.

[0029] The modified filler is prepared by the following steps: Step B1: Mix aluminum chloride solution and ferric chloride solution evenly, stir and add sodium hydroxide solution at 100 r / min and 60℃, and react for 3 h to obtain columnarizing agent. Disperse bentonite in deionized water, stir and add columnarizing agent at 100 r / min and 60℃, and react for 2 h to obtain bentonite suspension. Aged bentonite suspension for 12 h, centrifuged and dried to obtain columnar bentonite. Step B2: Disperse the pillared bentonite in a mixed solution of ethanol and deionized water. Stir and add ammonia water at 80 r / min and 60℃ to adjust the pH to 9. Add tetraethyl orthosilicate and react for 6 h. Wash, centrifuge, and calcine at 400℃ for 2 h to obtain the pretreated filler. Disperse the pretreated filler in tetrahydrofuran. Stir and add 3-mercaptopropyltrimethoxysilane at 200 r / min, 60℃, and pH 4 to obtain the modified filler.

[0030] In step B1, the molar concentrations of the aluminum chloride solution and ferric chloride solution are 0.1 mol / L, the molar concentration of the sodium hydroxide solution is 0.2 mol / L, the volume ratio of the aluminum chloride solution, ferric chloride solution, and sodium hydroxide solution is 10 mL:10 mL:22 mL, the molar ratio of aluminum ions, iron ions, and hydroxide ions in the columnar admixture is 2.4:0.5:1, and the volume ratio of bentonite, deionized water, and columnar admixture is 2 g:100 mL:3 mL.

[0031] In step B2, the ratio of pillar-supported bentonite to tetraethyl orthosilicate is 1 g: 1 mL, and the amount of 3-mercaptopropyltrimethoxysilane is 3% of the mass of the pretreated filler.

[0032] Example 2, a method for preparing PLA composite material based on additive modification, specifically includes the following steps: Step S1: Mix the modifier and dimethylformamide evenly, stir and add dibutyltin dilaurate and diisocyanate under the conditions of 115 r / min, 75℃ and nitrogen gas, and react for 4 h. Then stir and add polylactic acid and react for 5 h to obtain the copolymer. Step S2: The copolymer, fir powder and nucleating agent are melt-blended for 2 min at 180℃ under nitrogen gas. Modified filler and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide are added and melt-blended for 3 min. The mixture is then cooled and cured, and irradiated with ultraviolet light for 35 s to obtain the additive-modified PLA composite material.

[0033] In step S1, the molar ratio of the modifier, diisocyanate, and polylactic acid is 1:1.2:0.5, the amount of dibutyltin dilaurate is 4% of the mass of diisocyanate, the D-isomer content of polylactic acid is 0.3%, and the weight average molecular weight is 200,000.

[0034] The weight ratio of the copolymer, fir powder, nucleating agent, modified filler and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide in step S2 is 110:4:0.5:6:0.1, and the moisture content of the fir powder is 35%.

[0035] The modifier is prepared by the following steps: Step A1: Hydrogen-containing silicone oil, allyl glycidyl ether, and toluene are mixed evenly. Under the conditions of 95 r / min, 75℃, and nitrogen purging, the mixture is stirred and an isopropanol solution of chloroplatinic acid is added. The reaction is carried out for 2 hours to obtain intermediate 1. Intermediate 1 is mixed evenly with tetrahydrofuran. Under the conditions of 110 r / min, 70℃, and nitrogen purging, the mixture is stirred and hydroquinone and acrylamine are added. The reaction is carried out for 4 hours to obtain intermediate 2. Step A2: Mix intermediate 2 and tetrahydrofuran evenly, stir and add 1-cyclohexyl-3-phenylurea and 7-methylhexacyclic dicyclic guanidine under nitrogen conditions of 95 r / min and 25℃, and react for 1 h. Add lactide and react for 4 h. Centrifuge and dry to obtain the modifier.

[0036] The hydrogen-containing silicone oil mentioned in step A1 has a hydrogen content of 0.06% and a viscosity of 90 cs at 25°C. The molar ratio of the silicon-hydrogen bonds on the hydrogen-containing silicone oil to the carbon-carbon double bonds on the allyl glycidyl ether is 1:1.1. The amount of isopropanol solution of chloroplatinic acid used is 0.3% of the mass of the hydrogen-containing silicone oil. The mass ratio of chloroplatinic acid to isopropanol is 0.01:9. The molar ratio of intermediate 1 to acrylamine is 1:1.1. The amount of hydroquinone used is 4% of the amount of acrylamine used.

[0037] In step A2, the molar ratio of intermediate 2 to lactide is 1:1.2, the amount of lactide is 1.5 mol, the amount of 1-cyclohexyl-3-phenylurea is 4% of the mass of lactide, and the amount of 7-methylhexacyclic bicyclic guanidine is 4% of the mass of intermediate 2.

[0038] The nucleating agent is prepared by the following steps: 4-Methoxybenzoylhydrazine and pyridine were mixed evenly, and succinic anhydride was added under stirring at 95 r / min and 50 °C. The mixture was reacted for 5 h to obtain intermediate 3. Intermediate 3, 1-hydroxybenzotriazole and dichloromethane were mixed evenly, and dicyclohexylcarbodiimide was added under stirring at 95 r / min and 2 °C. The mixture was reacted for 40 min, and the temperature was raised to 25 °C. 2-hydroxyaniline and triethylamine were added under stirring. The mixture was reacted for 5 h to obtain nucleating agent.

[0039] The molar ratio of 4-methoxybenzoylhydrazine to succinic anhydride is 1:1.2, and the molar ratio of intermediate 3, 1-hydroxybenzotriazole, dicyclohexylcarbodiimide and 2-hydroxyaniline is 1 mmol:1.2 mmol:1.1 mmol:1.1 mmol.

[0040] The modified filler is prepared by the following steps: Step B1: Mix aluminum chloride solution and ferric chloride solution evenly, stir and add sodium hydroxide solution at 105 r / min and 65℃, and react for 3 h to obtain columnarizing agent. Disperse bentonite in deionized water, stir and add columnarizing agent at 110 r / min and 70℃, and react for 3 h to obtain bentonite suspension. Aged bentonite suspension for 16 h, centrifuged and dried to obtain columnar bentonite. Step B2: Disperse the pillared bentonite in a mixed solution of ethanol and deionized water. Stir and add ammonia water at 85 r / min and 70℃ to adjust the pH to 9. Add tetraethyl orthosilicate and react for 7 h. Wash, centrifuge, and calcine at 400℃ for 2 h to obtain the pretreated filler. Disperse the pretreated filler in tetrahydrofuran. Stir and add 3-mercaptopropyltrimethoxysilane at 200 r / min, 70℃, and pH 4 to obtain the modified filler.

[0041] In step B1, the molar concentrations of the aluminum chloride solution and ferric chloride solution are 0.1 mol / L, the molar concentration of the sodium hydroxide solution is 0.2 mol / L, the volume ratio of the aluminum chloride solution, ferric chloride solution, and sodium hydroxide solution is 10 mL:10 mL:22 mL, the molar ratio of aluminum ions, iron ions, and hydroxide ions in the columnar admixture is 2.4:0.5:1, and the volume ratio of bentonite, deionized water, and columnar admixture is 2 g:100 mL:3 mL.

[0042] In step B2, the ratio of pillar-supported bentonite to tetraethyl orthosilicate is 1 g: 1 mL, and the amount of 3-mercaptopropyltrimethoxysilane is 4% of the mass of the pretreated filler.

[0043] Example 3: A method for preparing PLA composite material based on additive modification, specifically including the following steps: Step S1: Mix the modifier and dimethylformamide evenly, stir and add dibutyltin dilaurate and diisocyanate under the conditions of 120 r / min, 80℃ and nitrogen gas, and react for 5 h. Then stir and add polylactic acid and react for 6 h to obtain the copolymer. Step S2: The copolymer, fir powder and nucleating agent are melt-blended for 3 min at 190℃ under nitrogen gas. Modified filler and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide are added and melt-blended for 4 min. The mixture is then cooled and cured, and irradiated with ultraviolet light for 40 s to obtain the additive-modified PLA composite material.

[0044] In step S1, the molar ratio of the modifier, diisocyanate, and polylactic acid is 1:1.2:0.5, the amount of dibutyltin dilaurate is 5% of the mass of diisocyanate, the D-isomer content of polylactic acid is 0.3%, and the weight average molecular weight is 200,000.

[0045] The copolymer, fir powder, nucleating agent, modified filler and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide mentioned in step S2 are in a weight ratio of 120:5:1:8:0.2, and the moisture content of the fir powder is 40%.

[0046] The modifier is prepared by the following steps: Step A1: Hydrogen-containing silicone oil, allyl glycidyl ether, and toluene are mixed evenly. Under the conditions of 100 r / min, 80℃, and nitrogen purging, the mixture is stirred and an isopropanol solution of chloroplatinic acid is added. The reaction is carried out for 3 hours to obtain intermediate 1. Intermediate 1 is mixed evenly with tetrahydrofuran. Under the conditions of 120 r / min, 80℃, and nitrogen purging, the mixture is stirred and hydroquinone and acrylamine are added. The reaction is carried out for 5 hours to obtain intermediate 2. Step A2: Mix intermediate 2 and tetrahydrofuran evenly, stir and add 1-cyclohexyl-3-phenylurea and 7-methylhexacyclic dicyclic guanidine under nitrogen conditions of 100 r / min, 30℃, and 2 h, add lactide and react for 5 h, centrifuge and dry to obtain the modifier.

[0047] The hydrogen-containing silicone oil described in step A1 has a hydrogen content of 0.07% and a viscosity of 110 cs at 25°C. The molar ratio of the silicon-hydrogen bonds on the hydrogen-containing silicone oil to the carbon-carbon double bonds on the allyl glycidyl ether is 1:1.1. The amount of isopropanol solution of chloroplatinic acid used is 0.5% of the mass of the hydrogen-containing silicone oil. The mass ratio of chloroplatinic acid to isopropanol is 0.01:9. The molar ratio of intermediate 1 to acrylamine is 1:1.1. The amount of hydroquinone used is 5% of the amount of acrylamine used.

[0048] In step A2, the molar ratio of intermediate 2 to lactide is 1:1.2, the amount of lactide is 2 mol, the amount of 1-cyclohexyl-3-phenylurea is 5% of the mass of lactide, and the amount of 7-methylhexacyclic bicyclic guanidine is 5% of the mass of intermediate 2.

[0049] The nucleating agent is prepared by the following steps: 4-Methoxybenzoylhydrazine and pyridine were mixed evenly, and succinic anhydride was added under stirring at 100 r / min and 60 °C. The mixture was reacted for 6 h to obtain intermediate 3. Intermediate 3, 1-hydroxybenzotriazole and dichloromethane were mixed evenly, and dicyclohexylcarbodiimide was added under stirring at 100 r / min and 5 °C. The mixture was reacted for 50 min, then heated to 30 °C, and 2-hydroxyaniline and triethylamine were added under stirring. The mixture was reacted for 6 h to obtain nucleating agent.

[0050] The molar ratio of 4-methoxybenzoylhydrazine to succinic anhydride is 1:1.2, and the molar ratio of intermediate 3, 1-hydroxybenzotriazole, dicyclohexylcarbodiimide and 2-hydroxyaniline is 1 mmol:1.2 mmol:1.1 mmol:1.1 mmol.

[0051] The modified filler is prepared by the following steps: Step B1: Mix aluminum chloride solution and ferric chloride solution evenly, stir and add sodium hydroxide solution at 110 r / min and 70℃, and react for 4 h to obtain columnarizing agent. Disperse bentonite in deionized water, stir and add columnarizing agent at 120 r / min and 80℃, and react for 4 h to obtain bentonite suspension. Aged bentonite suspension for 24 h, centrifuged and dried to obtain columnar bentonite. Step B2: Disperse the pillared bentonite in a mixed solution of ethanol and deionized water. Stir and add ammonia water at 90 r / min and 80 °C to adjust the pH to 10. Add tetraethyl orthosilicate and react for 8 h. Wash, centrifuge, and calcine at 400 °C for 3 h to obtain the pretreated filler. Disperse the pretreated filler in tetrahydrofuran. Stir and add 3-mercaptopropyltrimethoxysilane at 300 r / min, 80 °C, and pH 5 to obtain the modified filler.

[0052] In step B1, the molar concentrations of the aluminum chloride solution and ferric chloride solution are 0.1 mol / L, the molar concentration of the sodium hydroxide solution is 0.2 mol / L, the volume ratio of the aluminum chloride solution, ferric chloride solution, and sodium hydroxide solution is 10 mL:10 mL:22 mL, the molar ratio of aluminum ions, iron ions, and hydroxide ions in the columnar admixture is 2.4:0.5:1, and the volume ratio of bentonite, deionized water, and columnar admixture is 2 g:100 mL:3 mL.

[0053] In step B2, the ratio of pillar-supported bentonite to tetraethyl orthosilicate is 1 g: 2 mL, and the amount of 3-mercaptopropyltrimethoxysilane is 5% of the mass of the pretreated filler.

[0054] Comparative Example 1: Compared with Example 1, this comparative example uses intermediate 2 instead of the modifier, and the other steps are the same.

[0055] Comparative Example 2: This comparative example uses aniline instead of 2-hydroxyaniline, but the other steps are the same as in Example 1.

[0056] Comparative Example 3: This comparative example uses bentonite instead of pillar bentonite, but the other steps are the same as in Example 1.

[0057] The additive-modified PLA composite materials prepared in Examples 1-3 and Comparative Examples 1-3 were tested for heat distortion temperature according to GB / T1633-2000 "Determination of Vicat Softening Temperature of Thermoplastic Plastics". The test results are shown in Table 1. The test sample size was 10mm × 10mm × 4mm, the heat transfer medium was silicone oil, the heating rate was set to 120℃ / h, the applied load was 10N, and the maximum deformation of the sample was 1mm.

[0058] The additive-modified PLA composite materials prepared in Examples 1-3 and Comparative Examples 1-3 were tested for cantilever beam notched impact strength according to GB / T1843-2008 "Determination of Impact Strength of Plastic Cantilever Beams". The test results are shown in Table 1. The samples were prepared into rectangular strips of 80mm × 12.5mm × 3mm using a universal sample preparation machine, and V-notches were milled using a notching machine. The tests were conducted at room temperature.

[0059] The additive-modified PLA composites prepared in Examples 1-3 and Comparative Examples 1-3 were tested for tensile strength according to GB / T1040.1-2025 "Determination of Tensile Properties of Plastics". The test results are shown in Table 1. The samples were prepared into dumbbell-shaped strips with dimensions of 50mm × 4mm × 1mm using a dumbbell-shaped cutter. The tests were conducted at room temperature with a tensile rate set to 20mm / min.

[0060] Table 1 Table 1 shows that the tensile strength of the additive-modified PLA composites prepared in Examples 1-3 ranges from 68.4 to 77.1 MPa, and the notched impact strength ranges from 89.4 to 97.5 KJ / m. 2 The heat distortion temperature range is 128.5-136.5℃, indicating that the present invention has excellent heat resistance and toughening effect.

[0061] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing PLA composite materials based on additive modification, characterized in that: Specifically, the steps include the following: Step S1: Mix the modifier and dimethylformamide, add dibutyltin dilaurate and diisocyanate, and react. Stir and add polylactic acid, and react to obtain the copolymer. Step S2: The copolymer, fir powder and nucleating agent are melt-blended, modified filler and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide are added, melt-blended, cooled and cured, and irradiated with ultraviolet light to obtain the PLA composite material based on additive modification. In step S1, the molar ratio of the modifier, diisocyanate, and polylactic acid is 1:1.2:0.5, and the amount of dibutyltin dilaurate is 3-5% of the mass of diisocyanate. The weight ratio of the copolymer, cedar powder, nucleating agent, modified filler and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide mentioned in step S2 is 100-120:3-5:0.2-1:4-8:0.1-0.

2.

2. The preparation method of PLA composite material based on additive modification according to claim 1, characterized in that: The modifier is prepared by the following steps: Step A1: Hydrogen-terminated silicone oil, allyl glycidyl ether and toluene are mixed and stirred, and an isopropanol solution of chloroplatinic acid is added to react and intermediate 1 is obtained. Intermediate 1 and tetrahydrofuran are mixed and stirred, and hydroquinone and acrylamine are added to react and intermediate 2 is obtained. Step A2: Mix intermediate 2 and tetrahydrofuran, add 1-cyclohexyl-3-phenylurea and 7-methylhexacyclic dicyclic guanidine, and react. Add lactide and react again. Centrifuge and dry to obtain the modifier.

3. The method for preparing an additive-modified PLA composite material according to claim 2, characterized in that: In step A1, the molar ratio of the silane-hydrogen bond on the hydrogen-terminated silicone oil to the carbon-carbon double bond on the allyl glycidyl ether is 1:1.

1. The amount of isopropanol solution of chloroplatinic acid is 0.1-0.5% of the mass of the hydrogen-terminated silicone oil, the mass ratio of chloroplatinic acid to isopropanol is 0.01:9, the molar ratio of intermediate 1 to acrylamine is 1:1.1, and the amount of hydroquinone is 3-5% of the amount of acrylamine.

4. The preparation method of PLA composite material based on additive modification according to claim 2, characterized in that: In step A2, the molar ratio of intermediate 2 to lactide is 1:1.2, the amount of 1-cyclohexyl-3-phenylurea is 3-5% of the mass of lactide, and the amount of 7-methylhexacyclic bicyclic guanidine is 3-5% of the mass of intermediate 2.

5. The method for preparing an additive-modified PLA composite material according to claim 1, characterized in that: The nucleating agent is prepared by the following steps: 4-Methoxybenzoylhydrazine and pyridine were mixed and stirred, and succinic anhydride was added to react and obtain intermediate 3. Intermediate 3, 1-hydroxybenzotriazole and dichloromethane were mixed and stirred, and dicyclohexylcarbodiimide was added to react and the mixture was heated, stirred and 2-hydroxyaniline and triethylamine were added to react and obtain nucleating agent.

6. The method for preparing an additive-modified PLA composite material according to claim 5, characterized in that: The molar ratio of 4-methoxybenzoylhydrazine to succinic anhydride is 1:1.2, and the molar ratio of intermediate 3, 1-hydroxybenzotriazole, dicyclohexylcarbodiimide and 2-hydroxyaniline is 1 mmol:1.2 mmol:1.1 mmol:1.1 mmol.

7. The method for preparing an additive-modified PLA composite material according to claim 1, characterized in that: The modified filler is prepared by the following steps: Step B1: Mix aluminum chloride solution and ferric chloride solution, stir and add sodium hydroxide solution to react and obtain columnarizing agent. Disperse bentonite in deionized water, stir and add columnarizing agent to react and obtain bentonite suspension. Aged bentonite suspension, centrifuged and dried to obtain columnar bentonite. Step B2: Disperse the pillared bentonite in a mixed solution of ethanol and deionized water, stir and add ammonia water, adjust the pH, add tetraethyl orthosilicate, react, wash, centrifuge, calcine to obtain pretreated filler, disperse the pretreated filler in tetrahydrofuran, stir and add 3-mercaptopropyltrimethoxysilane, react to obtain modified filler.

8. The method for preparing an additive-modified PLA composite material according to claim 7, characterized in that: In step B1, the molar concentrations of the aluminum chloride solution and ferric chloride solution are 0.1 mol / L, the molar concentration of the sodium hydroxide solution is 0.2 mol / L, the volume ratio of the aluminum chloride solution, ferric chloride solution, and sodium hydroxide solution is 10 mL:10 mL:22 mL, the molar ratio of aluminum ions, iron ions, and hydroxide ions in the columnar admixture is 2.4:0.5:1, and the volume ratio of bentonite, deionized water, and columnar admixture is 2 g:100 mL:3 mL.

9. The method for preparing an additive-modified PLA composite material according to claim 7, characterized in that: In step B2, the ratio of pillar-supported bentonite to tetraethyl orthosilicate is 1g:1-2mL, and the amount of 3-mercaptopropyltrimethoxysilane is 3-5% of the mass of the pretreated filler.

10. A waterproof UV-curable coating, characterized in that: Prepared according to any one of the preparation methods described in claims 1-9.

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