Environment-friendly degradable plastic material and preparation method thereof

Abstract

The invention relates to the technical field of plastic materials, and particularly discloses an environment-friendly degradable plastic material and a preparation method thereof. The environment-friendly degradable plastic material is prepared from the following raw materials in percentage by mass: 85 to 95 percent of polylactic acid, 5 to 15 percent of modified poly (butylene adipate-co-terephthalate), 25 to 35 percent of plant fiber and 2.2 to 3.6 percent of water-resistant emulsion, and the water-resistant emulsion is boron water-resistant emulsion. The environment-friendly degradable plastic material has the advantage that the defect that the overall waterproof performance of environment-friendly degradable plastic is still insufficient can be overcome.

Description

Technical Field

[0001] The present application relates to the technical field of plastic materials, and more specifically, to an environmentally friendly degradable plastic material and a preparation method thereof. Background Art

[0002] Traditional plastics are derived from non-renewable fossil fuels such as petroleum and are widely used in various fields due to their low price and lightweight properties. However, due to the difficulty of degrading traditional plastic products, their large-scale use and improper waste disposal can lead to "white pollution", causing great harm to humans and the ecological environment. Bio-based plastics are a class of polymer materials derived from biomass resources. They constitute a sustainable plastic manufacturing option. These biomass resources, such as corn sugar, tubers, and cellulose, are converted through modern chemical or biological processes. This not only reduces dependence on fossil fuels, but also has relatively low carbon emissions throughout the life cycle. Typical biodegradable plastics include polylactic acid (PLA), which has excellent barrier properties, making it important for applications in areas such as food packaging.

[0003] Plant fibers are widely available, low in cost, low in density, biodegradable, and have good mechanical properties. Compounding them with polylactic acid to develop environmentally friendly materials has an enhancing effect and improves the overall performance of the material, meeting the requirements of a benign cycle of natural resources and promoting sustainable development. However, the natural hydrophilic hydroxyl groups on the surface of the cellulose fibrils in plant fibers are sensitive to moisture, causing the plant fibers to be unstable in water, which may reduce the overall waterproof performance of the plastic material. Summary of the Invention

[0004] In order to improve the defect that the overall waterproof performance of environmentally friendly degradable plastics is still insufficient, the present application provides an environmentally friendly degradable plastic material and a preparation method thereof.

[0005] This application provides an environmentally friendly degradable plastic material and a preparation method thereof, which adopts the following technical solutions: In a first aspect, an environmentally friendly degradable plastic material comprises the following raw materials by mass fraction: 85-95% polylactic acid, 5-15% modified polybutylene adipate terephthalate, 25-35% plant fiber, and 2.2-3.6% water-resistant emulsion, wherein the water-resistant emulsion is a boron-based water-resistant emulsion.

[0006] Since the main component of plant fiber is cellulose, its molecular chain contains a large number of hydroxyl groups, which can easily form hydrogen bonds with water molecules, causing the fiber to absorb water and swell. In addition, plant fiber has natural porosity, which increases the surface area in contact with water, further aggravating water absorption. After absorbing water, the interfacial bonding strength between the fiber and the plastic matrix decreases.

[0007] The boric acid ester in the boron-based water-repellent emulsion can undergo an esterification reaction with the hydroxyl groups in cellulose to form stable chemical bonds, thereby reducing the hydrophilicity of the hydroxyl groups. The chemical bonds of the boric acid ester are relatively stable in a humid environment, which can delay the hydrolysis process and maintain the waterproof effect for a long time. The water-repellent emulsion can be evenly dispersed in polylactic acid and modified polybutylene adipate terephthalate to form a continuous hydrophobic network, covering the surface and gaps of the plant fibers, thereby improving the overall water resistance of the plastic material.

[0008] Preferably, the water-resistant emulsion comprises the following raw materials: 55-59g stearic acid, 100-150ml deionized water, 18-24g diethanolamine, 4.8-9.5ml sodium hydroxide solution, 18-34g isopropyl alcohol, 5.8-6.6g boric acid, 90-120ml toluene water agent, 95-105g liquid rosin, 3-3.74ml potassium hydroxide and 20-30g Yinsong emulsifier.

[0009] Because the long carbon chain of stearic acid can form a hydrophobic layer through esterification or amidation reaction, it can effectively block water penetration, and can react with diethanolamine to form stearic acid diethanolamide, which can enhance the interfacial bonding with plant fibers and reduce fiber water absorption and swelling. It can also introduce polar amide groups to enhance hydrogen bonding with cellulose hydroxyl groups and enhance interfacial adhesion.

[0010] Preferably, the preparation method of the water-resistant emulsion is: Weigh 55-59g of stearic acid granules into a four-necked flask, add 100-150ml of deionized water and melt at 80-90°C, then add 18-24g of diethanolamine and 4.8-9.5ml of sodium hydroxide solution, and heat at 150-170°C for 5-7h to produce white solid stearic acid diethanolamide; Weigh 35-39.6 g of stearic acid diethanolamide, add 3-9 g of isopropyl alcohol and 5.8-6.6 g of boric acid, and add 30-50 ml of toluene with water, and heat at 110-130 ° C for 5-7 hours to obtain a borate ester / amide complex; Weigh 95-105g of melted liquid rosin into a four-necked flask, add 15-25g of isopropyl alcohol, 3-3.74ml of potassium hydroxide, and 60-70ml of toluene with water, and react at 150-170°C for 7-9h to produce isopropyl rosinate. Take 40-48g of borate ester / amide complex and 30-40g of isopropyl rosinate and react at 110-130°C until a yellow solid stabilizes to obtain a rosin / stearic acid borate complex; Weigh 75-85 g of rosin / stearate borate complex and emulsify it with 20-30 g of pine emulsifier to obtain a water-resistant emulsion.

[0011] Stearic acid and diethanolamine are reacted under alkaline conditions to generate stearic acid diethanolamide. Its molecule contains both a long hydrophobic carbon chain and a hydrophilic amide group, which can serve as an amphiphilic intermediate to enhance the subsequent interfacial bonding with plant fibers and reduce water absorption and swelling. Stearic acid diethanolamide reacts with boric acid to form a borate ester bond, which can significantly reduce hydrophilicity by chemically cross-linking and blocking the hydroxyl groups of plant fibers. Liquid rosin reacts with isopropyl alcohol to generate isopropyl rosinate. Its rosin acid structure is a rigid hydrophobic skeleton that can combine with flexible borate ester bonds to form a dense water-resistant layer to block water penetration.

[0012] Preferably, the modified polybutylene adipate-terephthalate comprises the following raw materials: 45-55 g polybutylene adipate-terephthalate, 0.05-0.1 g initiator and 0.5-1 g modified itaconic anhydride.

[0013] Since modified itaconic anhydride contains anhydride groups, it can combine with poly(butylene adipate terephthalate) chains to generate carboxylic acid groups, which is beneficial to enhance the polarity of poly(butylene adipate terephthalate) and thus improve its compatibility with polylactic acid and plant fibers.

[0014] Preferably, the preparation method of the modified polybutylene adipate-terephthalate is as follows: 45-55g of polybutylene adipate-terephthalate, 0.05-0.1g of initiator and 0.5-1g of modified itaconic anhydride are weighed and blended in an internal mixer at 170-190°C to obtain modified polybutylene adipate-terephthalate.

[0015] Preferably, the modified itaconic anhydride comprises the following raw materials: 9.5-10.1 g itaconic anhydride, 5-5.6 g diethylene glycol, 9-10.4 g calcium acetate, and 10-14 g zinc acetate.

[0016] Since the two hydroxyl groups in diethylene glycol can undergo esterification reaction with the anhydride groups of itaconic anhydride to form long chains or cross-linked networks, the molecular weight is increased and the thermal motion of the molecular chains is inhibited. The calcium ions in calcium acetate and the zinc ions in zinc acetate can form coordination bonds with the carboxylic acid groups to construct a rigid metal-organic framework, which is beneficial to improving the thermal stability of the plastic material.

[0017] Preferably, the preparation method of the modified itaconic anhydride is as follows: 9.5-10.1g of itaconic anhydride is weighed, an oil bath is preheated, and when the reaction temperature rises to 100-120°C, 5-5.6g of diethylene glycol is slowly added dropwise to obtain an intermediate product, 9-10.4g of calcium acetate and 10-14g of zinc acetate are weighed and dissolved in deionized water respectively, the intermediate product is placed in an oil bath at 110-130°C, and an aqueous solution of calcium acetate and an aqueous solution of zinc acetate are slowly added dropwise, and the reaction is stirred for 2-4h, followed by rotary evaporation to remove the deionized water, and reduced pressure distillation to remove the by-product acetic acid until no liquid is distilled out to obtain the modified itaconic anhydride.

[0018] In a second aspect, the present application provides a method for preparing an environmentally friendly degradable plastic material, which adopts the following technical solution: A method for preparing an environmentally friendly degradable plastic material comprises the following steps: S1: 85-95% by mass of polylactic acid and 5-15% by mass of modified polybutylene adipate-terephthalate are vacuum dried at 70-90° C. for 10-14 h, and then melt-blended to obtain a blend; S2: Add 25-35% by mass of plant fiber and 2.2-3.6% by mass of water-resistant emulsion to the above blend, and mix with a double-roll plastic mill at 130-150° C. for 3-7 minutes.

[0019] In summary, this application has the following beneficial effects: 1. Since the main component of plant fiber is cellulose, its molecular chain contains a large number of hydroxyl groups, which can easily form hydrogen bonds with water molecules, causing the fiber to absorb water and swell. In addition, plant fiber has natural porosity, which increases the surface area in contact with water, further aggravating water absorption. After absorbing water, the interfacial bonding force between the fiber and the plastic matrix decreases.

[0020] The boric acid ester in the boron-based water-repellent emulsion can undergo an esterification reaction with the hydroxyl groups in cellulose to form stable chemical bonds, thereby reducing the hydrophilicity of the hydroxyl groups. The chemical bonds of the boric acid ester are relatively stable in a humid environment, which can delay the hydrolysis process and maintain the waterproof effect for a long time. The water-repellent emulsion can be evenly dispersed in polylactic acid and modified polybutylene adipate terephthalate to form a continuous hydrophobic network, covering the surface and gaps of the plant fibers, thereby improving the overall water resistance of the plastic material.

[0021] 2. Since the long carbon chain of stearic acid can form a hydrophobic layer through esterification or amidation reaction, it can effectively block water penetration, and can react with diethanolamine to form stearic acid diethanolamide, which can enhance the interfacial bonding with plant fibers, reduce fiber water absorption and swelling, and can also introduce polar amide groups to enhance hydrogen bonding with cellulose hydroxyl groups and enhance interfacial adhesion.

[0022] 3. Stearic acid and diethanolamine are reacted under alkaline conditions to generate stearic acid diethanolamide. Its molecule contains both a long hydrophobic carbon chain and a hydrophilic amide group, which can serve as an amphiphilic intermediate to enhance the subsequent interfacial bonding with plant fibers and reduce water absorption and swelling. Stearic acid diethanolamide reacts with boric acid to generate borate bonds, which can significantly reduce hydrophilicity by chemically cross-linking and blocking the hydroxyl groups of plant fibers. Liquid rosin reacts with isopropyl alcohol to generate isopropyl rosinate. Its rosin acid structure is a rigid hydrophobic skeleton that can combine with flexible borate bonds to form a dense water-resistant layer to block water penetration. DETAILED DESCRIPTION

[0023] The present application is further described in detail below in conjunction with Examples 1 to 10 and Comparative Examples 1 and 2.

[0024] raw material Polylactic acid CAS: 31852-84-3; Ramie fiber Hunan Huasheng Dongting Hemp Industry Co., Ltd.; Stearic acid CAS: 57-11-4; Deionized water CAS: 7732-18-5; Diethanolamine CAS: 111-42-2; Sodium hydroxide CAS: 1310-73-2; Isopropyl alcohol CAS: 67-63-0; Boric acid CAS: 10043-35-3; Toluene CAS: 108-88-3; Rosin Weifang Huapu Chemical Co., Ltd.; Hydroxide Potassium CAS: 1310-58-3; Yinsong emulsifier Weifang Huapu Chemical Co., Ltd.; Polybutylene adipate-terephthalate Xinjiang Lanshan Tunhe Technology Co., Ltd.; Initiator 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane Shanghai Aladdin Biochemical Technology Co., Ltd.; Itaconic anhydride CAS: 2170-03-8; Diethylene glycol CAS: 110-99-6; Calcium acetate CAS: 62-54-4; Zinc acetate CAS: 557-34-6. Example 1

[0025] An environmentally friendly degradable plastic material comprises the following raw materials by mass: 90% polylactic acid, 10% modified polybutylene adipate terephthalate, 30% plant fiber and 2.9% water-resistant emulsion.

[0026] Specifically, the preparation method of the environmentally friendly degradable plastic material includes the following steps: S1: Weigh 9.8 g of itaconic anhydride, preheat an oil bath, and when the reaction temperature rises to 110°C, slowly add 5.3 g of diethylene glycol dropwise to obtain an intermediate product. Weigh 9.7 g of calcium acetate and 12 g of zinc acetate, respectively, and dissolve them in deionized water. Place the intermediate product in a 120°C oil bath, slowly add an aqueous solution of calcium acetate and an aqueous solution of zinc acetate dropwise, and stir to react for 3 h. Then, remove the deionized water by rotary evaporation, and remove the by-product acetic acid by vacuum distillation until no liquid is distilled out to obtain modified itaconic anhydride. S2: 50 g of poly(butylene adipate-terephthalate), 0.075 g of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, and 0.75 g of modified itaconic anhydride were weighed and blended in an internal mixer at 180° C. to obtain modified poly(butylene adipate-terephthalate); S3: Weigh 57 g of stearic acid granules into a four-necked flask, add 130 ml of deionized water and melt at 85°C. Then, add 21 g of diethanolamine and 7.15 ml of 5% sodium hydroxide solution, and heat at 160°C for 6 h to produce white solid stearic acid diethanolamide. S4: Weigh 37.3 g of stearic acid diethanolamide, add 6 g of isopropyl alcohol and 6.2 g of boric acid, and add 40 ml of toluene with water, and heat the mixture at 120°C for 6 h to obtain a borate / amide complex; S5: Weigh 100g of melted liquid rosin into a four-necked flask, add 20g of isopropyl alcohol, 3.37ml of 5% potassium hydroxide catalyst and 65ml of toluene water agent, and react at 160°C for 8h to produce isopropyl rosinate; S6: 44 g of the borate / amide complex and 35 g of isopropyl rosinate were reacted at 120° C. until a yellow solid stabilized to obtain a rosin / stearic acid borate complex; S7: Weigh 80 g of rosin / stearate borate complex and emulsify it with 25 g of Yinsong emulsifier to obtain a water-resistant emulsion; S8: 90% by mass of polylactic acid and 10% by mass of modified poly(butylene adipate terephthalate) were vacuum dried at 80° C. for 12 h, and then melt-blended to obtain a blend; S9: 30% by mass of plant fiber and 2.9% by mass of water-resistant emulsion were added to the above blend, and mixed with a double-roll plastic mill at 140° C. for 5 minutes to obtain an environmentally friendly biodegradable plastic material.

[0027] Example 2-Example 3 The difference from Example 1 is that the added mass fractions of the components of the environmentally friendly degradable plastic material are different, as shown in Table 1.

[0028] Table 1 Addition mass fraction of each component of the environmentally friendly degradable plastic material in Examples 1 to 3 (%) Example 1 Example 2 Example 3 polylactic acid 90 85 95 Modified polybutylene adipate terephthalate 10 15 5 plant fiber 30 35 25 Water-resistant emulsion 2.9 2.2 3.6 Example 4

[0029] The difference from Example 1 is that the modified poly(butylene adipate terephthalate) is replaced by poly(butylene adipate terephthalate) in an equal amount.

[0030] Example 5-Example 6 The difference from Example 1 is that the addition amounts of the various components of the modified polybutylene adipate-terephthalate are different, as shown in Table 2.

[0031] Table 2 Addition amount of each component of modified polybutylene adipate terephthalate in Examples 1 and 5-6 (g) Example 1 Example 5 Example 6 Polybutylene adipate-terephthalate 50 45 55 2,5-Dimethyl-2,5-bis(tert-butylperoxy)hexane 0.075 0.1 0.05 Modified itaconic anhydride 0.75 1 0.5 Example 7-Example 8 The difference from Example 1 is that the addition amounts of the various components of the modified itaconic anhydride are different, as shown in Table 3.

[0032] Table 3 Addition amount of each component of modified itaconic anhydride in Example 1 and Example 7-Example 8 (g) Example 1 Example 7 Example 8 Itaconic anhydride 9.8 10.1 9.5 Diethylene glycol 5.3 5 5.6 calcium acetate 9.7 9 10.4 Zinc acetate 12 14 10 Example 9-Example 10 The difference from Example 1 is that the addition amount of each component of the water-resistant emulsion is different, as shown in Table 4.

[0033] Table 4 Addition amount of each component of the water-resistant emulsion in Example 1 and Example 9-Example 10 Example 1 Example 9 Example 10 stearic acid 57g 55g 59g Deionized water 130ml 150ml 100ml Diethanolamine 21g 18g 24g Sodium hydroxide solution 7.15ml 4.8ml 9.5ml Isopropyl alcohol 26g 18g 34g Boric acid 6.2g 6.6g 5.8g Toluene water solution 105ml 90ml 120ml Liquid rosin 100g 105g 95g potassium hydroxide 3.37ml 3ml 3.74ml Yinsong emulsifier 25g 20g 30g Comparative Example 1 The difference from Example 1 is that no water-resistant emulsion is added.

[0034] Comparative Example 2 The difference from Example 1 is that the modified itaconic anhydride is replaced by an equal amount of itaconic anhydride.

[0035] Performance testing 1. Waterproof performance Three samples were taken from each of Examples 1 to 10 and Comparative Examples 1 and 2, respectively, and extruded into films. The water resistance of the samples was tested according to GB / T 1037-2021 "Plastic Film and Sheeting - Determination of Water Vapor Transmission Properties - Cup Weight Gain and Weight Loss Method"; The test data is shown in Table 5.

[0036] Table 5 Waterproof performance test results of Examples 1 to 10 and Comparative Examples 1 to 2 <![CDATA[Water vapor transmission rate g / (m 2 ·24 h) <!-- 5 -->]]> Example 1 12 Example 2 18 Example 3 15 Example 4 36 Example 5 14 Example 6 16 Example 7 13 Example 8 17 Example 9 20 Example 10 19 Comparative Example 1 68 Comparative Example 2 25 2. Thermal stability Three samples were taken from Examples 1 to 10 and Comparative Example 1, respectively, and pressed into thin sheets. The sheets were placed in a heat aging test chamber and heated at a constant temperature of 180°C. Samples were taken every 10 minutes to observe the color changes of the samples. The time it took for the samples to turn black was recorded as the static aging test change time, and the average value was taken.

[0037] The test data is shown in Table 6.

[0038] Table 6 Thermal stability test results of Examples 1-10 and Comparative Examples 1-2 Static aging test change time (min) Example 1 115 Example 2 100 Example 3 105 Example 4 50 Example 5 110 Example 6 112 Example 7 113 Example 8 111 Example 9 108 Example 10 106 Comparative Example 1 90 Comparative Example 2 60 Combining Example 1 and Comparative Example 1 with Tables 5 and 6, it can be seen that the water vapor transmission rate of Comparative Example 1 is significantly increased compared to Example 1, and the static aging test change time of Comparative Example 1 is shortened. This shows that, compared with not adding a water-repellent emulsion, the addition of a water-repellent emulsion affects the thermal stability of the plastic material and can effectively improve the waterproof performance of the plastic material.

[0039] The reason is that the boric acid ester in the boron-based water-repellent emulsion can undergo an esterification reaction with the hydroxyl groups in cellulose to form stable chemical bonds, thereby reducing the hydrophilicity of the hydroxyl groups. The chemical bonds of the boric acid ester are relatively stable in a humid environment, which can delay the hydrolysis process and maintain the waterproof effect for a long time. In addition, the water-repellent emulsion can be evenly dispersed in polylactic acid and modified polybutylene adipate terephthalate to form a continuous hydrophobic network, covering the surface and gaps of the plant fibers, thereby improving the overall water resistance of the plastic material.

[0040] Stearic acid reacts with diethanolamine under alkaline conditions to form stearic acid diethanolamide. Its molecule contains both a long hydrophobic carbon chain and a hydrophilic amide group, which can serve as an amphiphilic intermediate to enhance the subsequent interfacial bonding with plant fibers and reduce water absorption and swelling. Stearic acid diethanolamide reacts with boric acid to form a borate ester bond, which can significantly reduce hydrophilicity by chemically cross-linking and blocking the hydroxyl groups of plant fibers. Liquid rosin reacts with isopropyl alcohol to form isopropyl rosinate. Its rosin acid structure is a rigid hydrophobic skeleton that can combine with flexible borate ester bonds to form a dense water-resistant layer to block water penetration.

[0041] Combining Example 1 and Comparative Example 2 with Tables 5 and 6, it can be seen that the water vapor permeability of Comparative Example 2 is increased compared to Example 1, and the static aging test change time of Comparative Example 2 is significantly shortened. This shows that, compared with the addition of conventional itaconic anhydride, the addition of modified itaconic anhydride can effectively improve the waterproof performance and thermal stability of the plastic material.

[0042] The reason is that the two hydroxyl groups in diethylene glycol can undergo esterification reaction with the anhydride groups of itaconic anhydride to form long chains or cross-linked networks, increase the molecular weight, and inhibit the thermal motion of the molecular chains. The calcium ions in calcium acetate and the zinc ions in zinc acetate can form coordination bonds with the carboxylic acid groups to construct a rigid metal-organic framework, which is beneficial to improving the thermal stability of the plastic material.

[0043] Combining Example 1 and Example 2-Example 3 with Table 5 and Table 6, it can be seen that, relative to Example 1, the water vapor permeability of Example 2 and Example 3 is increased, and the static aging test change time of Example 2 and Example 3 is slightly shortened. This shows that the added mass fraction of each component of the environmentally friendly degradable plastic material affects the waterproof performance and thermal stability of the plastic material, and the added mass fraction of each component of the environmentally friendly degradable plastic material in Example 1 is optimal.

[0044] Combining Examples 1 and 4 with Tables 5 and 6, it can be seen that, relative to Example 1, the water vapor transmission rate of Example 4 is significantly increased, and the static aging test change time of Example 4 is significantly shortened. This indicates that, compared with the addition of conventional polybutylene adipate-terephthalate, the addition of modified polybutylene adipate-terephthalate can effectively improve the waterproof properties and thermal stability of the plastic material.

[0045] The reason is that modified itaconic anhydride contains anhydride groups, which can combine with poly(butylene adipate terephthalate) chains to generate carboxylic acid groups, which is beneficial to enhance the polarity of poly(butylene adipate terephthalate) and thus improve its compatibility with polylactic acid and plant fibers.

[0046] Combining Example 1 with Examples 5 and 6 and Tables 5 and 6, it can be seen that, relative to Example 1, the water vapor permeability of Examples 5 and 6 is increased, and the static aging test change time of Examples 5 and 6 is shortened. This indicates that the addition amount of each component of the modified poly(butylene adipate-terephthalate) affects the waterproof performance and thermal stability of the plastic material, and the addition amount of each component of the modified poly(butylene adipate-terephthalate) in Example 1 is optimal.

[0047] Combining Example 1 with Example 7-Example 8 and Table 5 and Table 6, it can be seen that, relative to Example 1, the water vapor permeability of Example 7 and Example 8 is increased, and the static aging test change time of Example 7 and Example 8 is shortened. This shows that the addition amount of each component of modified itaconic anhydride affects the waterproof performance and thermal stability of the plastic material, and the addition amount of each component of modified itaconic anhydride in Example 1 is optimal.

[0048] Combining Example 1 with Examples 9 and 10 and Tables 5 and 6, it can be seen that, relative to Example 1, the water vapor permeability of Examples 9 and 10 increased, and the static aging test change time of Examples 9 and 10 was shortened. This indicates that the amount of each component added in the water-repellent emulsion affects the waterproof properties of the plastic material, and that the amount of each component added in Example 1 is optimal.

[0049] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. An environmentally friendly degradable plastic material, characterized in that: The invention comprises the following raw materials by mass fraction: 85-95% of polylactic acid, 5-15% of modified polybutylene adipate-terephthalate, 25-35% of plant fiber and 2.2-3.6% of water-resistant emulsion, wherein the water-resistant emulsion is a boron-based water-resistant emulsion.

2. The environmentally friendly degradable plastic material according to claim 1, characterized in that: The water-resistant emulsion comprises the following raw materials: 55-59g stearic acid, 100-150ml deionized water, 18-24g diethanolamine, 4.8-9.5ml sodium hydroxide solution, 18-34g isopropyl alcohol, 5.8-6.6g boric acid, 90-120ml toluene with water, 95-105g liquid rosin, 3-3.74ml potassium hydroxide and 20-30g Yinsong emulsifier.

3. The environmentally friendly degradable plastic material according to claim 2, characterized in that: The preparation method of the water-resistant emulsion: Weigh 55-59g of stearic acid granules into a four-necked flask, add 100-150ml of deionized water and melt at 80-90°C, then add 18-24g of diethanolamine and 4.8-9.5ml of sodium hydroxide solution, and heat at 150-170°C for 5-7h to produce white solid stearic acid diethanolamide; Weigh 35-39.6 g of stearic acid diethanolamide, add 3-9 g of isopropyl alcohol and 5.8-6.6 g of boric acid, and add 30-50 ml of toluene with water, and heat at 110-130 ° C for 5-7 hours to obtain a borate ester / amide complex; Weigh 95-105g of melted liquid rosin into a four-necked flask, add 15-25g of isopropyl alcohol, 3-3.74ml of potassium hydroxide, and 60-70ml of toluene with water, and react at 150-170°C for 7-9h to produce isopropyl rosinate. Take 40-48g of borate ester / amide complex and 30-40g of isopropyl rosinate and react at 110-130°C until a yellow solid stabilizes to obtain a rosin / stearic acid borate complex; Weigh 75-85 g of rosin / stearate borate complex and emulsify it with 20-30 g of pine emulsifier to obtain a water-resistant emulsion.

4. The environmentally friendly degradable plastic material according to claim 1, characterized in that: The modified polybutylene adipate-terephthalate comprises the following raw materials: 45-55g polybutylene adipate-terephthalate, 0.05-0.1g initiator and 0.5-1g modified itaconic anhydride.

5. The environmentally friendly degradable plastic material according to claim 4, characterized in that: The modified polybutylene adipate-terephthalate is prepared by weighing 45-55g of polybutylene adipate-terephthalate, 0.05-0.1g of initiator and 0.5-1g of modified itaconic anhydride, and blending them in an internal mixer at 170-190°C to obtain the modified polybutylene adipate-terephthalate.

6. The environmentally friendly degradable plastic material according to claim 5, characterized in that: The modified itaconic anhydride comprises the following raw materials: 9.5-10.1 g itaconic anhydride, 5-5.6 g diethylene glycol, 9-10.4 g calcium acetate, 10-14 g zinc acetate.

7. The environmentally friendly degradable plastic material according to claim 6, characterized in that: The preparation method of the modified itaconic anhydride comprises the following steps: weighing 9.5-10.1 g of itaconic anhydride, preheating an oil bath, and slowly dripping 5-5.6 g of diethylene glycol when the reaction temperature rises to 100-120° C. to obtain an intermediate product; weighing 9-10.4 g of calcium acetate and 10-14 g of zinc acetate, respectively dissolving them in deionized water; placing the intermediate product in an oil bath at 110-130° C., slowly dripping an aqueous solution of calcium acetate and an aqueous solution of zinc acetate, stirring and reacting for 2-4 hours, then removing the deionized water by rotary evaporation, and removing the byproduct acetic acid by vacuum distillation until no liquid is distilled out to obtain the modified itaconic anhydride.

8. The method for preparing an environmentally friendly degradable plastic material according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: 85-95% by mass of polylactic acid and 5-15% by mass of modified polybutylene adipate-terephthalate are vacuum dried at 70-90° C. for 10-14 h, and then melt-blended to obtain a blend; S2: Add 25-35% by mass of plant fiber and 2.2-3.6% by mass of water-resistant emulsion to the above blend, and mix with a double-roll plastic mill at 130-150° C. for 3-7 minutes.