CN115322545B - Decrosslinked waste latex reinforced toughened polylactic acid composite material and preparation method thereof - Google Patents

Abstract

The invention discloses a method for preparing a crosslinked waste latex reinforced and toughened polylactic acid composite material, which comprises the following steps: adding expandable graphite and a stripping agent into water, putting them into a liquid-phase circulating high-speed shearing and grinding equipment for shearing, grinding and dispersing, Uniformly dispersing the stripping agent to obtain a dispersion of expandable graphite coated with the stripping agent; placing it in a microwave reactor, performing an expansion reaction assisted by microwave irradiation and ultrasonic vibration, and obtaining a fully stripped and uniformly dispersed graphene dispersion; The waste latex is added to the graphene dispersion liquid, placed in a microwave reactor, and the decrosslinking reaction of the latex is carried out; the decrosslinked latex is dried, mixed with polylactic acid, put into a melt blending equipment for melt blending, and obtained High-strength and high-toughness polylactic acid composite material. The invention can efficiently and controllably realize the decrosslinking reaction of the waste latex, thereby improving the melting processing performance of the waste latex, and significantly improving the comprehensive performance of the polylactic acid composite material such as strength, toughness and electrical conductivity.

Description

Decrosslinked waste latex reinforced toughened polylactic acid composite material and preparation method thereof

technical field

The invention relates to a high-efficiency decrosslinking of waste latex through a microwave-assisted reaction to obtain a reinforced and toughened polylactic acid composite material and a preparation method thereof, belonging to the technical field of solid waste resource utilization and high-performance polylactic acid.

Background technique

With the application of latex products in daily household, industrial and medical industries, a large amount of waste latex is disposed of in landfills every year. Due to its non-degradability, it is easy to become vectors (such as Aedes aegypti, dengue fever, favorable breeding grounds for Kungunya, Zika and yellow fever). It may also pollute groundwater sources due to harmful leachate components, which will cause serious pollution problems to the environment and cause a huge waste of resources.

The natural latex in the latex pillow is the liquid that flows out of the rubber tree when it is tapped. It is milky white, with a solid content of 30% to 40%, and an average rubber particle size of about 1.06 μm. Fresh natural latex contains 27%~41.3% rubber and 44%~70% water. At the same time, ammonia and other stabilizers are often added to prevent natural latex from solidifying due to the action of microorganisms and enzymes. It is also necessary to add zinc diethyldithiocarbamate, benzothiazole accelerator, sulfur-containing vulcanizer, silicate and zinc oxide during the foaming process.

In the molding process of latex pillows, the cross-linked structure formed during the vulcanization process makes it difficult to recycle them. In order to make them have higher added value, it is necessary to destroy their original three-dimensional cross-linked structure and restore their fluidity. . Some methods commonly used at present are: thermomechanical method, thermochemical method, mechanochemical method, biochemical method and physical method (microwave method and ultrasonic method). Microwave heating is an efficient and novel material processing technology, which has a wide range of applications in materials science, food processing, analytical chemistry and other fields. Since microwaves are electromagnetic waves, they propagate through materials, and the accompanying transmission process results in electricity consumption and heat dissipation. However, the microwave energy absorbed by the sample depends on its dielectric properties. The larger the dielectric constant and dielectric loss factor, the more microwave power the sample absorbs and the faster the heating. Therefore, the advantage of using microwave-induced carbonization to recover carbon or solid residues from waste is that compared with the high temperature of 700-900 °C in the waste carbonization process, the effect of carbonization (or pyrolysis) can be achieved at 400-600 °C. achieved at relatively moderate temperatures. In traditional heating methods, the heat source is located outside the carbon, and the heat generated by the heat source is transferred through conduction and radiation mechanisms. The surface is first heated and then transferred to the inside, while microwave heating provides volume heating to the inside and outside of the object at the same time with extremely high efficiency. At the same time, no chemicals are involved in the heating process, which is a green and efficient technology.

In order to solve the global problem of non-degradable latex waste and polluting the environment, it is urgent to develop microwave-assisted environmentally friendly treatment methods for efficient decrosslinking of waste latex, thereby improving the melt processability of latex and making it suitable for use in thermoplastic composites. be effectively applied.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the existing technical defects of waste latex being non-degradable and polluting the environment, to provide a method to solve the above-mentioned deficiencies in the existing material technology in the field of solid waste recycling, and to provide a product capable of efficiently decrosslinking waste latex An environmentally friendly synthesis method improves the melt processability of waste latex, thereby expanding its application in reinforced and toughened polylactic acid composites.

In order to solve the above-mentioned technical problems, a kind of preparation method of decrosslinking waste latex reinforced toughened polylactic acid composite material provided by the present invention comprises the following steps:

S1. Preparation of intercalation expandable graphite solution: add expandable graphite and stripping agent into water, stir evenly, put into liquid phase circulation high-speed shear grinding equipment to shear, grind and disperse, so that the stripping agent is evenly distributed on the surface of the graphite sheet and between the sheets , to obtain a dispersion in which the stripping agent evenly coats the expandable graphite;

S2. Prepare graphene dispersion: put the dispersion obtained in S1 into a microwave reactor, raise the temperature to 200~260°C under built-in ultrasonic vibration, and react for 2~10 minutes to fully expand the graphite flakes and peel them into graphene Nanosheets to obtain a dispersion containing homogeneously dispersed graphene;

S3. Preparation of decrosslinked latex: Put the waste latex into the graphene dispersion obtained in S2, put it into a microwave reactor, heat up to 150-220°C under stirring, and react for 30 seconds to 20 minutes to obtain decrosslinked latex. Linked latex;

S4. Preparation of polylactic acid composite material: dry the decrosslinked latex obtained in S3 until the water content is lower than 0.1%, mix it with polylactic acid evenly, put it into a melt blending device for melt blending, and obtain a polylactic acid composite material.

As an improvement, the fixed carbon content of the expandable graphite in the step S1 is 90% to 99.9%, the graphite sheet size is 5 μm to 1500 μm , and the mass fraction in the aqueous solution is 0.5% to 5%.

As an improvement, the stripping agent in the step S1 is polyvinylpyrrolidone, sodium dodecylbenzenesulfonate, sodium dodecylsulfate, sodium dodecylsulfonate, polyoxyethylene octylphenol ether-10 and octane At least one of the base phenol polyoxyethylene ethers, the mass fraction is 1/200~1/50 of the expandable graphite.

As an improvement, the liquid-phase circulating high-speed shearing and grinding equipment that provides grinding and dispersing in the step S1 is a shearing homogeneous emulsifier, a pipeline type shearing homogeneous emulsifier, a vacuum homogeneous emulsifier, a pin-type sand mill and At least one of the turbine sand mills, the energy consumption per unit mass of the grinding and dispersing process is 0.5~10 kWh/kg.

As an improvement, the output power of the microwave reactor in the step S2 is 200-5000 W, and the energy consumption per unit mass of the built-in ultrasonic oscillator is 1-20 kWh/kg.

As an improvement, the output power of the microwave reactor in the step S3 is 200-5000 W, and the mass ratio of graphene to latex is 1/1000-1/50.

As an improvement, the melt blending equipment in the step S4 is a high-speed mixer, an open mill, a turning mixer, a continuous mixer, a reciprocating screw extruder, a twin-screw extruder, and a single-screw extruder. At least one of kneader, Z-type kneader, screw kneader, vacuum kneader and horizontal twin-screw mixer, the processing temperature is 80~265 ℃, and the energy consumption per unit mass of the melt blending process is 0.1~5 kWh/ kg; the mass ratio of decrosslinked latex to polylactic acid is 1:19~1:1.

The present invention also provides a kind of decrosslinked waste latex reinforced and toughened polylactic acid composite material prepared according to the above method, and has good antistatic performance. The composite material is composed of polylactic acid, decrosslinked latex and graphene. The tensile strength is 50~70 MPa, the impact toughness is 8~30 kJ/m ² , the surface resistance is 1.0×10 ⁸ ~9.9×10 ¹² Ω, and the volume resistivity is 1.0×10 ⁷ ~9.9×10 ¹¹ Ω·m .

The beneficial effects of the present invention are: (1) The liquid phase circulation high-speed shear grinding technology can effectively grind the expandable graphite sheet, which ensures the uniform dispersion and coating of the stripping agent on the surface of the graphite sheet; (2) Microwave irradiation and ultrasonic vibration are used The combined technology forces the graphite sheet to expand at a high rate and at the same time forms a good peeling effect; (3) Add waste latex to the dispersion liquid in which the nanosheets are uniformly dispersed graphene, so that the graphene is evenly attached inside the latex, effectively improving the latex. (4) High shear rate melt blending process uniformly disperses the decrosslinked latex in the polylactic acid matrix and endows good processability. At the same time, fully exfoliates the graphene nano (5) The composite material has the characteristics of high strength, high toughness and antistatic, and the preparation method embodies the characteristics of environmental protection and low cost, which is beneficial to expand the use of decrosslinked waste latex in multifunctional Applications and developments in the field of composite materials. The production process adopted by the method is simple and convenient for large-scale and low-cost production, and the composite material product is multifunctional.

Description of drawings

Fig. 1 is the flow chart of the preparation method of decrosslinking waste latex reinforced toughened polylactic acid composite material of the present invention;

Fig. 2 is the digital photo of the sample of waste latex (a), decrosslinked latex (b) and high-strength and high-toughness polylactic acid composite material (c) in Example 1;

Fig. 3 is the scanning electron microscope image of decrosslinked latex reinforced toughened polylactic acid composite material in embodiment 1;

FIG. 4 is a scanning electron microscope image of the latex-filled polylactic acid composite material in Comparative Example 1.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings.

Example 1

A kind of preparation method of decrosslinking waste latex reinforced toughened polylactic acid composite material provided by the present invention comprises the following steps:

S11. Preparation of intercalated expandable graphite solution: add 0.5 parts by mass of expandable graphite and 0.01 parts by mass of exfoliating agent (sodium dodecylbenzenesulfonate) to 100 parts by mass of water, stir well, and then shear Cutting, grinding and dispersing, after the energy consumption per unit mass reaches 0.5 kWh/kg, a dispersion liquid in which the stripping agent is evenly coated with expandable graphite is obtained;

S12. Preparation of graphene dispersion: Put the dispersion obtained in S11 into a microwave reactor (output power 200 W), heat up to 200°C, and react for 10 minutes. The energy consumption per unit mass of the built-in ultrasonic oscillation reaches 1 kWh/kg , the graphite flakes are fully expanded and peeled off into graphene nano flakes to obtain a dispersion containing homogeneously dispersed graphene;

S13. Preparation of decrosslinked latex: put 500 parts by mass of waste latex into the graphene dispersion obtained in S12, put it into a microwave reactor (output power 200 W), raise the temperature to 150°C under stirring, and react for 20 minutes , to obtain the decrosslinked latex;

S14. Preparation of polylactic acid composite material: dry the decrosslinked latex obtained in S13 until the water content is lower than 0.1%, mix it with 500 parts by mass of polylactic acid, and put it into a reciprocating screw extruder for melt blending (processing temperature is 120 ~195℃), after the energy consumption per unit mass reaches 0.1 kWh/kg, a high-strength and high-toughness PLA composite material is obtained.

Example 2

A kind of preparation method of decrosslinking waste latex reinforced toughened polylactic acid composite material provided by the present invention comprises the following steps:

S21. Preparation of intercalated expandable graphite solution: add 5 parts by mass of expandable graphite and 0.025 parts by mass of stripping agent (polyoxyethylene octylphenol ether-10) to 100 parts by mass of water, stir evenly, and pass through a pin-type sand mill Machine shearing, grinding and dispersing, after the energy consumption per unit mass reaches 10 kWh/kg, a dispersion liquid in which the stripping agent is evenly coated with expandable graphite is obtained;

S22. Preparation of graphene dispersion: put the dispersion obtained in S21 into a microwave reactor (output power 5000W), raise the temperature to 260°C, and react for 2 minutes. The energy consumption per unit mass of the built-in ultrasonic oscillation reaches 20 kWh/kg. The graphite flakes are fully expanded and exfoliated into graphene nano flakes to obtain a dispersion containing homogeneously dispersed graphene;

S23. Preparation of decrosslinked latex: put 250 parts by mass of waste latex into the graphene dispersion obtained in S22, put it into a microwave reactor (output power 5000 W), raise the temperature to 220°C under stirring, and react for 30 seconds , to obtain the decrosslinked latex;

S24. Preparation of polylactic acid composite material: dry the decrosslinked latex obtained in S23 until the water content is lower than 0.1%, mix it with 250 parts by mass of polylactic acid, and put it into a rotary internal mixer for melt blending (processing temperature is 240~ 265 ℃), after the energy consumption per unit mass reaches 5 kWh/kg, a high-strength and high-toughness PLA composite material is obtained.

Example 3

A kind of preparation method of decrosslinking waste latex reinforced toughened polylactic acid composite material provided by the present invention comprises the following steps:

S31. Preparation of intercalated expandable graphite solution: add 1 mass part of expandable graphite and 0.01 mass part of stripping agent (polyvinylpyrrolidone) to 100 mass parts of water, stir evenly, and disperse by shearing and grinding with a turbo sand mill. After the energy consumption per unit mass reaches 2 kWh/kg, a dispersion liquid in which the stripping agent is evenly coated with expandable graphite is obtained;

S32. Preparation of graphene dispersion: put the dispersion obtained in S31 into a microwave reactor (output power 1000W), raise the temperature to 230°C, and react for 5 minutes. The energy consumption per unit mass of the built-in ultrasonic oscillation reaches 5 kWh/kg. The graphite flakes are fully expanded and exfoliated into graphene nano flakes to obtain a dispersion containing homogeneously dispersed graphene;

S33. Preparation of decrosslinked latex: Put 100 parts by mass of waste latex into the graphene dispersion obtained in S32, put it into a microwave reactor (output power 1000 W), heat up to 190°C under stirring, and react for 10 minutes , to obtain the decrosslinked latex;

S34. Preparation of polylactic acid composite material: dry the decrosslinked latex obtained in S33 until the water content is lower than 0.1%, mix it with 1000 parts by mass of polylactic acid, and put it into a high-speed mixer (temperature 80~100°C) and continuous banburying successively Melt blending is carried out in a machine (temperature 140~210°C), and after the energy consumption per unit mass reaches 1.5 kWh/kg, a high-strength and high-toughness polylactic acid composite material is obtained.

Example 4

A kind of preparation method of decrosslinking waste latex reinforced toughened polylactic acid composite material provided by the present invention comprises the following steps:

S41. Preparation of intercalated expandable graphite solution: add 2 parts by mass of expandable graphite and 0.03 parts by mass of stripping agent (sodium dodecylsulfonate) to 100 parts by mass of water, stir evenly, and pass through a pipeline type shear dispersion emulsifier Shear grinding and dispersion, after the energy consumption per unit mass reaches 5 kWh/kg, a dispersion liquid in which the exfoliant is evenly coated with expandable graphite is obtained;

S42. Preparation of graphene dispersion: put the dispersion obtained in S41 into a microwave reactor (output power 3000W), raise the temperature to 240°C, and react for 6 minutes. The energy consumption per unit mass of the built-in ultrasonic oscillation reaches 10 kWh/kg. The graphite flakes are fully expanded and exfoliated into graphene nano flakes to obtain a dispersion containing homogeneously dispersed graphene;

S43. Preparation of decrosslinked latex: put 500 parts by mass of waste latex into the graphene dispersion obtained in S42, put it into a microwave reactor (output power 2000 W), raise the temperature to 170°C under stirring, and react for 12 minutes , to obtain the decrosslinked latex;

S44. Preparation of polylactic acid composite material: dry the decrosslinked latex obtained in S43 until the water content is lower than 0.1%, mix it with 7000 parts by mass of polylactic acid, put it into a screw kneader (temperature 90~120°C) and single-screw extrusion Melt-blending in a machine (temperature 180-240°C), after the energy consumption per unit mass reaches 3 kWh/kg, a high-strength and high-toughness polylactic acid composite material is obtained.

Example 5

A kind of preparation method of decrosslinking waste latex reinforced toughened polylactic acid composite material provided by the present invention comprises the following steps:

S51. Preparation of intercalated expandable graphite solution: add 3 parts by mass of expandable graphite and 0.025 parts by mass of stripping agent (sodium lauryl sulfate) to 100 parts by mass of water, stir evenly, and then shear through a shear emulsification homogenizer Grinding and dispersing, after the energy consumption per unit mass reaches 8 kWh/kg, a dispersion liquid in which the stripping agent is evenly coated with expandable graphite is obtained;

S52. Preparation of graphene dispersion: put the dispersion obtained in S51 into a microwave reactor (output power 4000W), raise the temperature to 250°C, and react for 4 minutes. The energy consumption per unit mass of the built-in ultrasonic oscillation reaches 6 kWh/kg. The graphite flakes are fully expanded and exfoliated into graphene nano flakes to obtain a dispersion containing homogeneously dispersed graphene;

S53. Preparation of decrosslinked latex: put 2500 parts by mass of waste latex into the graphene dispersion obtained in S52, put it into a microwave reactor (output power 3500 W), raise the temperature to 195°C under stirring, and react for 7 minutes , to obtain the decrosslinked latex;

S54. Preparation of polylactic acid composite material: dry the decrosslinked latex obtained in S53 until the water content is lower than 0.1%, mix it with 25,000 parts by mass of polylactic acid, and put it into a continuous internal mixer for melt blending (processing temperature is 160~ 230°C), after the energy consumption per unit mass reaches 2.2 kWh/kg, a high-strength and high-toughness PLA composite material is obtained.

Comparative example 1 (do not decrosslink the waste latex)

Basically adopt the method of Example 1 to prepare the polylactic acid composite material, the difference is that this example does not carry out any treatment on the waste latex, but directly mixes 500 mass parts of waste latex and 500 mass parts of polylactic acid, and puts them into a reciprocating screw extruder. Melt blending is carried out in the machine (processing temperature is 120~195°C), and the polylactic acid composite material is obtained after the energy consumption per unit mass reaches 0.1 kWh/kg.

Comparative example 2 (without introducing graphene, direct microwave-assisted decrosslinking of waste latex)

The method of Example 2 is basically used to prepare decrosslinked waste latex and its filled polylactic acid composite material. The difference is that graphene nanosheets are not introduced in this example, and the waste latex is directly subjected to microwave-assisted decrosslinking reaction, that is, the Put 250 parts by mass of waste latex into a microwave reactor (output power 5000 W), raise the temperature to 220°C under stirring, and react for 30 seconds to obtain decrosslinked latex; dry the obtained decrosslinked latex and mix with 250 parts by mass of polymer The lactic acid was mixed evenly, and put into an overturning internal mixer for melt blending (the processing temperature was 240-265°C). After the energy consumption per unit mass reached 5 kWh/kg, the polylactic acid composite material was obtained.

Comparative example 3 (only introduce expandable graphite, cooperate with microwave-assisted decrosslinking waste latex)

The method of Example 3 is basically used to prepare decrosslinked waste latex and its filled polylactic acid composite material. The difference is that this example only uses expandable graphite to improve the dielectric properties of waste latex, that is, 1 mass part of expandable graphite and Add 100 parts by mass of waste latex to 100 parts by mass of water, stir evenly, put it into a microwave reactor (output power 1000 W), raise the temperature to 190 °C under stirring, and react for 10 minutes to obtain decrosslinked latex; The decrosslinked latex is dried, mixed evenly with 1000 parts by mass of polylactic acid, put into a high-speed mixer (temperature 80~100°C) and a continuous internal mixer (temperature 140~210°C) successively for melt blending, in the unit After the mass energy consumption reaches 1.5 kWh/kg, the polylactic acid composite material is obtained.

Structural characterization and performance testing:

The microscopic morphology of the quenched section of Example 1 and the microscopic morphology of the quenched section of Comparative Example 1 were observed by a field emission scanning electron microscope (SEM). The results are shown in Figure 3 and Figure 4;

The mechanical properties and electrical conductivity of the composite materials obtained in Examples 1-5 of the present invention and Comparative Examples 1-3 were tested, and the results are shown in Table 1. Its performance evaluation method and test standard are as follows: dry the extruded and granulated composite material at 100°C for 1 to 2 hours, and then use an injection molding machine equipped with a standard test sample mold to form test samples (each group of samples contains 5 tensile samples) tensile test specimens, 5 impact test specimens and 3 volume resistivity test plates).

Mechanical performance test: The obtained composite material is obtained by injection molding (the molding temperature is 160~220 ℃) to obtain tensile and impact specimens. According to the ASTM D638-2003 plastic tensile performance test standard of the American Society for Testing and Materials, the American Instron The company's universal tensile machine (model 5900) tests the tensile properties of composite materials; according to ASTM D256-1997 "Standard Test Method for Izod Impact Performance of Plastics" issued by the American Society for Testing Materials, the impact properties of composite materials are tested. test. At least 3 parallel test samples are guaranteed for each group, and the results are averaged.

Electrical performance test: According to the national standard GB/T 1410-2006 "Test method for volume resistivity and surface resistivity of solid insulating materials", the surface resistance and volume resistivity of composite materials are tested. At least 5 parallel samples were tested in each group, and the results were averaged.

Table 1. Test results of mechanical properties and electrical properties of composite materials

It is also of great significance that due to the introduction of fully exfoliated and uniformly dispersed graphene nanosheets, examples 1 to 5 also exhibit good antistatic properties, and the surface resistance is in the range of 1.0×10 ⁸ to 9.9×10 ¹² Ω , and the volume resistivity is in the range of 1.0×10 ⁷ ~9.9×10 ¹¹ Ω·m, which is a good antistatic material. In particular, the surface resistance of Example 2 is as low as 2×10 ⁸ Ω, and the volume resistivity is as low as 5×10 ⁷ Ω·m, indicating that a very small amount of graphene nanosheets in a uniformly dispersed state can ensure a better composite material. electrical properties. However, Comparative Examples 1-3 are all in an insulating state, and cannot be used as antistatic materials.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, some improvements can be made without departing from the principle of the present invention, and these improvements should also be regarded as the present invention. scope of protection.

Claims (10)

1. The preparation method of the uncrosslinked waste latex reinforced and toughened polylactic acid composite material is characterized by comprising the following steps of:

s1, preparing an intercalation expandable graphite solution: adding the expandable graphite and the stripping agent into water, stirring, and then placing the mixture into a liquid-phase circulating high-speed shearing and grinding device for shearing, grinding and dispersing to obtain a stripping agent coated expandable graphite dispersion liquid;

s2, preparing graphene dispersion liquid: placing the dispersion liquid obtained in the step S1 into a microwave reaction kettle, heating to 200-260 ℃ under ultrasonic oscillation, and reacting for 2-10 minutes to obtain graphene dispersion liquid;

s3, preparing a decrosslinked emulsion: placing the waste latex into the graphene dispersion liquid obtained in the step S2, placing the graphene dispersion liquid into a microwave reaction kettle, heating to 150-220 ℃, and reacting for 30 seconds-20 minutes to obtain the uncrosslinked latex;

s4, preparing a polylactic acid composite material: and (3) drying the uncrosslinked latex obtained in the step (S3), mixing with polylactic acid, and placing into a melt blending device for melt blending to obtain the polylactic acid composite material.

2. The method of manufacturing according to claim 1, characterized in that: the fixed carbon content of the expandable graphite in the step S1 is 90% -99.9%, and the size of the graphite flake is 5μm~1500 μm, the mass fraction of the m in the aqueous solution is 0.5% -5%.

3. The method of manufacturing according to claim 1, characterized in that: the stripping agent in the step S1 is at least one of polyvinylpyrrolidone, sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, sodium dodecyl sulfonate, polyoxyethylene octyl phenol ether-10 and octyl phenol polyoxyethylene ether, and the mass fraction of the stripping agent is 1/200-1/50 of that of the expandable graphite.

4. The method of manufacturing according to claim 1, characterized in that: the liquid-phase circulation high-speed shearing and grinding equipment in the step S1 is at least one of a shearing and emulsifying homogenizer, a pipeline shearing and dispersing emulsifier, a vacuum homogenizing and emulsifying machine, a rod pin type sand mill and a turbine type sand mill, and the unit mass energy consumption in the grinding and dispersing process is 0.5-10 kWh/kg.

5. The method of manufacturing according to claim 1, characterized in that: the output power of the microwave reaction kettle in the step S2 is 200-5000W, and the energy consumption per unit mass of ultrasonic vibration is 1-20 kWh/kg.

6. The method of manufacturing according to claim 1, characterized in that: and in the step S3, the output power of the microwave reaction kettle is 200-5000W, and the mass ratio of the graphene to the waste latex is 1/1000-1/50.

7. The method of manufacturing according to claim 1, characterized in that: in the step S4, the uncrosslinked latex obtained in the step S3 is dried until the moisture is lower than 0.1%.

8. The method of manufacturing according to claim 1, characterized in that: the melt blending equipment in the step S4 is at least one of an open mill, a turnover internal mixer, a continuous internal mixer, a reciprocating screw extruder, a double screw extruder, a single screw extruder, a Z-type kneader, a screw kneader and a vacuum kneader, the processing temperature is 80-265 ℃, the energy consumption per unit mass in the melt blending process is 0.1-5 kWh/kg, and the mass ratio of the uncrosslinked latex to the polylactic acid is 1:19-1:1.

9. A polylactic acid composite material obtained by the preparation method according to any one of claims 1 to 8.

10. The polylactic acid composite according to claim 9, wherein: the tensile strength of the polylactic acid composite material is 50-70 MPa, and the impact toughness is 8-30 kJ/m ² The surface resistance was 1.0X10 ⁸ ~9.9×10 ¹² Omega, volume resistivity of 1.0X10 ⁷ ~9.9×10 ¹¹ Ω·m。

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