Biodegradable foaming material, preparation method and equipment thereof

Abstract

The invention discloses a biodegradable foaming material, a preparation method and equipment thereof, relates to the technical field of foaming materials, and aims to solve the problems that an existing native starch material is poor in tensile strength, the biodegradable effect of the native starch material is easily affected after the native starch material is colored, and the performance of the material is easily damaged due to the fact that all mixed materials are mixed at a time in the preparation process. The problems that the foaming effect is affected and even damaged due to the fact that the foaming effect is affected and even damaged due to the fact that a one-by-one mixing and conveying mode is adopted, conveying modes and methods under different mixtures are different, conveying is inconvenient, the quality of the mixtures is prone to being affected in the conveying process, and cost expenditure is increased are solved. Comprising the following components in percentage by weight: 30-35% of polylactic acid; 10%-25% of starch; 10%-15% of fibers; 5%-15% of tea leaf residues; 1%-5% of pigment; 1%-5% of a reaction accelerator; and 1%-5% of a plasticizer.

Description

Technical Field

[0001] The invention relates to the technical field of foaming materials, in particular to a biodegradable foaming material, a preparation method and equipment thereof. Background Art

[0002] Nowadays, plastics are widely favored by people for their excellent properties such as light weight, waterproof, corrosion resistance, and high strength. However, with the rapid development of the fossil plastic industry, the environmental pollution caused by its difficulty in degradation affects economic development. Therefore, the use of some degradable materials to partially replace and then completely replace plastics has become a hot topic in today's materials research. Starch, as a natural high molecular polymer, is completely biodegradable and plays an important role in the development of biodegradable materials.

[0003] Although starch materials are biodegradable, their degradation efficiency still needs to be improved, and after being colored, their biodegradation effect is easily affected. Therefore, physical, chemical or biochemical methods are needed to change the structure, physical and chemical properties of biodegradable foaming materials to produce specific performance and uses.

[0004] In the preparation process of biodegradable foaming materials, the raw materials of the foaming materials need to be mixed and prepared. Since there are many materials in the foaming material, mixing all the mixed materials at once is likely to destroy the material properties, affecting or even destroying the foaming effect. If the method of mixing and conveying them one by one is adopted, the conveying method and method for different mixtures are different, which is inconvenient to convey, and the quality of the mixture is easily affected during transportation, thereby increasing the cost. For this reason, we provide a biodegradable foaming material, a preparation method and an equipment thereof. Summary of the invention

[0005] The object of the present invention is to provide a biodegradable foaming material, a preparation method and an apparatus thereof, so as to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a biodegradable foam material, comprising the following components in weight percentage:

[0007] Polylactic acid 30%-35%;

[0008] Starch 10%-25%;

[0009] Fiber 10%-15%;

[0010] Tea residue 5%~15%

[0011] Pigment 1% to 5%;

[0012] Reaction accelerator 1% to 5%;

[0013] Plasticizer 1%~5%.

[0014] Preferably, the starch is one or more of corn starch, sweet potato starch, potato starch, cassava starch, and wheat starch, and the weight content of amylose in the starch is 10% to 20%.

[0015] Preferably, the reaction accelerator is a coupling agent, and the coupling agent is one or both of a silane compound and an isocyanate compound.

[0016] Preferably, the plasticizer is one or a mixture of glycerol, sorbitol, acetyl citrate, polyethylene wax.

[0017] Preferably, the fibers are bamboo fibers and cotton fibers, mixed in a ratio of 3:1.

[0018] Preferably, the colorant is a plant extract pigment, the plant is tea leaves or petals, and the color is indigo or litmus yellow.

[0019] Preferably, the method for preparing the biodegradable foam material comprises the following steps:

[0020] Step 1: pre-mix the fiber, starch, reaction accelerator, and polylactic acid through a mixing device at a speed of 800-1200 r / min for 30-60 minutes;

[0021] Step 2: Add corresponding percentage of plasticizer and colorant during the mixing process for secondary mixing, and mix again at 1200-1500r / min for 60-90 minutes. During the mixing process, nitrogen is injected inside and mixed into the material by mechanical stirring to make the material expand and foam:

[0022] Step 3: Feed the foaming material into a twin-screw extruder at 120-170°C and a rotation speed of 300-600 rpm for 40-60 minutes, melt blend and draw into strips, feed the drawn material into a pelletizer at a rotation speed of 130 r / min, and form particles with a particle size of less than 100 microns through a pelletizer;

[0023] Step 4: The obtained granular material is sent to a drying device at a drying temperature of 50°C-80°C for 60-120 minutes to obtain a biodegradable foaming material.

[0024] Preferably, a mixing device for biodegradable foaming material is applied to the preparation method of the biodegradable foaming material: the mixing device comprises a tank body, a first motor is installed at a middle position above the tank body, a first transmission shaft is arranged at the output end of the first motor, a plurality of annularly distributed driven frames are arranged on the outer wall of the first transmission shaft, and the driven frames are provided with upper and lower layers; linear modules are installed on both sides of the outer wall of the driven frame, through holes are arranged between the linear modules, a mixing groove is arranged at the bottom of the tank body, and the outer wall of the first transmission shaft near the bottom A plurality of bottom stirring blades are arranged on the wall, and the bottom stirring blades are located inside the mixing tank, a discharge pipe is installed on one side of the mixing tank, and one end of the discharge pipe extends to the outside of the tank body, the linear module includes a screw motor and a ball screw, a screw slider is installed on the outer wall of the ball screw, a material receiving and mixing box is installed between the screw sliders, a second motor is installed on one side of the material receiving and mixing box, a second transmission shaft is arranged at the output end of the second motor, a plurality of rotating blades are arranged on the outer wall of the second transmission shaft, and the output end of the second motor is connected to the rotating blades through the second transmission shaft.

[0025] Preferably, a feeding layer is installed on both sides of the first motor, and the feeding layer includes an annular guide rail, a guide rail slider is arranged on the outer wall of the annular guide rail, an electric telescopic rod is installed on the outer wall of the guide rail slider, an electromagnet is installed at the telescopic end of the electric telescopic rod, a driven slide rail is arranged in an annular shape inside the annular guide rail, a driven slider is installed inside the driven slide rail, and the driven slider is magnetically connected to the electromagnet, and a feeding cavity is arranged at the middle position of the annular guide rail, and the feeding cavity is connected to the tank body.

[0026] Preferably, a raw material tank is installed above the driven slider, a first control valve is installed at the lower end of the raw material tank, a second control valve is installed below the material receiving and mixing box, and feeding pipes are installed on the outer walls on both sides of the tank body, and one end of the feeding pipe extends into the tank body.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention improves the tensile strength of the biodegradable foaming material by using polylactic acid, starch, fiber, tea residue, colorant, reaction accelerator and plasticizer, wherein polylactic acid has good biodegradability, and in addition, it also has good mechanical properties and physical properties. On this basis, bamboo fiber and cotton fiber are added, and the fiber structure has good biodegradability, and the degradation efficiency is increased compared with pure starch biodegradable materials. The colorant is a plant extract pigment, and the plant is tea and petals. The color is indigo and litmus yellow. All these materials are biodegradable materials, which can be decomposed in nature and will not pollute the environment. Tea residue contains tea polyphenols, and its main components such as catechins can significantly improve the disintegration value of starch, reduce the regeneration value, reduce the hot paste stability of starch and inhibit the regeneration of starch, thereby affecting the degradation rate of starch.

[0029] 2. The present invention drives the first transmission shaft and the driven frame to rotate by the first motor, and by adjusting the position of each driven frame, the material receiving and mixing boxes at different driven frames can be moved to different feeding layers for feeding operations, and can also drive the materials in the material receiving and mixing boxes to rotate and mix. At the same time, the bottom stirring blade performs the final mixing and preparation operation on the mixture, so that its functionality is enhanced;

[0030] The screw motor and the ball screw drive the screw slider to move linearly, and the position of the material receiving and mixing box is adjusted by moving. On the one hand, it is convenient to carry out upper and lower material receiving operations, and on the other hand, it can be aligned or staggered with the material receiving and mixing boxes at different levels by moving. When the upper and lower levels are aligned, the mixture in the upper material receiving and mixing box can be dropped into the next level for secondary mixing. When staggered, it can be directly dropped into the mixing tank at the bottom, which is convenient for users to adjust and use according to needs; the second motor drives the second transmission shaft and the rotating blade to rotate, and the materials in the material receiving and mixing box are mixed by rotation. After pre-mixing, the overall foaming and mixing are carried out to improve the quality of the finished product;

[0031] The annular guide rail and the guide rail slider are used to drive the electric telescopic rod to move in a circular manner. The position of the electric telescopic rod is adjusted by the circular movement, so that the electric telescopic rod can be moved to different raw material tanks for combination. After the electric telescopic rod moves to the required raw material tank, the electric telescopic rod is turned on to extend, and the electromagnet is turned on to make the electromagnet adsorbed on the driven slider. The electric telescopic rod extends forward to drive the driven slider to move on the driven slide rail, so that the raw material tank is driven to the unloading chamber for unloading operation. Through this structure, different raw materials can be adjusted and switched according to needs for unloading operation. Different raw materials can be matched with the rotation of the first transmission shaft below, and can fall into different material receiving and mixing boxes for mixed preparation, thereby improving preparation flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1It is a schematic diagram of the overall structure of the present invention;

[0033] Figure 2 It is a schematic diagram of the structure of the driven frame of the present invention;

[0034] Figure 3 It is a schematic diagram of the feeding layer structure of the present invention;

[0035] In the figure: 1. tank body; 2. first motor; 3. first transmission shaft; 4. driven frame; 5. linear module; 6. screw motor; 7. ball screw; 8. screw slider; 9. material receiving and mixing box; 10. second motor; 11. second transmission shaft; 12. rotating blade; 13. through hole; 14. feeding pipe; 15. mixing trough; 16. bottom stirring blade; 17. discharge pipe; 18. feeding layer; 19. annular guide rail; 20. guide rail slider; 21. electric telescopic rod; 22. electromagnet; 23. driven slide rail; 24. driven slider; 25. raw material tank; 26. feeding chamber; 27. first control valve; 28. second control valve. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0037] See also Figure 1-3 , an embodiment provided by the present invention: a biodegradable foaming material, comprising the following components in weight percentage:

[0038] Polylactic acid 30%-35%;

[0039] Starch 10%-25%;

[0040] Fiber 10%-15%;

[0041] Tea residue 5%~15%

[0042] Pigment 1% to 5%;

[0043] Reaction accelerator 1% to 5%;

[0044] Plasticizer 1%~5%.

[0045] Furthermore, the starch is one or more of corn starch, sweet potato starch, potato starch, cassava starch, and wheat starch, and the weight content of amylose in the starch is 10% to 20%;

[0046] Compared with traditional plastics, starch-based biodegradable materials can be degraded by the natural environment and will not cause environmental pollution. Starch-based biodegradable materials can also reduce the consumption of fossil energy because they are made from renewable plants.

[0047] High-amylose starch is a starch modified by chemical or enzymatic methods. The content of linear regions in its molecular structure is higher than that of traditional starch. Therefore, it is also called high-amylose starch. For environmental protection, amylose starch is used to replace polystyrene to produce degradable plastics. It has excellent transparency, flexibility, tensile strength, and water insolubility, which is of far-reaching significance for solving white pollution and protecting the environment.

[0048] Furthermore, the reaction accelerator is a coupling agent, and the coupling agent is one or both of a silane compound and an isocyanate compound;

[0049] Coupling agents are used to enhance the strength and hardness of plastics while improving their heat resistance and weather resistance.

[0050] Furthermore, the plasticizer is one or a mixture of glycerol, sorbitol, acetyl citrate, polyethylene wax;

[0051] Plasticizers are used to change the structure of polymers and make the plasticized materials soft. Changing the rheological properties of polymers helps the dispersion of liquid and solid additives, and is more effective for fillers, dyes and other liquid additives that are easily soluble in plasticizers.

[0052] Furthermore, the fiber is a mixture of bamboo fiber and cotton fiber in a ratio of 3:1;

[0053] Bamboo fiber has good air permeability and moisture absorption, and can quickly absorb and evaporate moisture. In addition, bamboo fiber contains natural antibacterial substances that can effectively inhibit the growth of bacteria and fungi. It is biodegradable and pollution-free to the environment. Cotton fiber is also biodegradable, has little impact on the environment, and has high color fastness. After dyeing, cotton fiber has bright colors, high saturation, and is not easy to fade.

[0054] Furthermore, the colorant is a plant extract pigment, the plant is tea leaves and petals, and the color is indigo and litmus yellow;

[0055] The pigments are made based on plant extracts and are naturally degradable substances, so they can be decomposed in nature without polluting the environment.

[0056] Furthermore, a method for preparing a biodegradable foam material comprises the following steps:

[0057] Step 1: pre-mix tea residues, fiber, starch, reaction accelerator, and polylactic acid through a mixing device at a speed of 800-1200 r / min for 30-60 minutes;

[0058] Step 2: Add corresponding percentage of plasticizer, reaction accelerator and colorant during the mixing process for secondary mixing, and mix again at 1200-1500r / min for 60-90 minutes. During the mixing process, nitrogen is injected inside and mixed into the material by mechanical stirring to make the material expand and foam:

[0059] In this embodiment, an environmentally friendly bio-based plasticizer is selected, such as dioctyl succinate (DOA) and vinyl ester plasticizer (such as EVA). The amount of plasticizer added usually depends on the required softness and processing conditions. Considering biodegradability, it is added in a lower range, such as 2%. For 100 kg of the mixture, 2 kg of plasticizer can be added.

[0060] The reaction accelerator may be a catalyst or a crosslinking agent, such as an organic peroxide or a metal acid salt. Taking safety and environmental protection factors into consideration, the commonly used addition amount of the selected accelerator is 3%, that is, for 100 kg of material, 3 kg of the reaction accelerator is added.

[0061] The specific amount of colorant added depends on the required color intensity and hiding power of the colorant. For medium-intensity colors, choose to add 1%. For 100 kg of mixture, 1 kg of colorant will be added. Be careful to ensure that the type of colorant is compatible with biodegradable materials and will not affect the biodegradability of the entire system.

[0062] Tea residues contain tea polyphenols and catechins. Tea polyphenols are a natural polyphenol compound with multiple biological activities such as antioxidant and antibacterial properties. The combination of tea polyphenols and starch can not only improve the antioxidant and antibacterial properties of the material, but also improve the degradation properties of starch-based materials. The main components of tea polyphenols, such as catechins, can significantly increase the disintegration value of starch, reduce the regeneration value, reduce the hot paste stability of starch and inhibit starch regeneration, thereby affecting the degradation rate of starch. In addition, tea residues can also be replaced with tea stems.

[0063] Step 3: Feed the foaming material into a twin-screw extruder at 120-170°C and a rotation speed of 300-600 rpm for 40-60 minutes, melt blend and draw into strips, feed the drawn material into a pelletizer at a rotation speed of 130 r / min, and form particles with a particle size of less than 100 microns through a pelletizer;

[0064] Step 4: The obtained granular material is sent to a drying device at a drying temperature of 50°C-80°C for 60-120 minutes to obtain a biodegradable foaming material.

[0065] In the above preparation method, the mixing process is realized based on a mixing device. Through the mixing method and the mixing device, the efficiency of the mixing process of the biodegradable foaming material in the preparation process can be improved, and during the mixing process, the ratio between each raw material and ingredient can be adjusted as needed, and classified and staggered transportation can be carried out.

[0066] Sample 1;

[0067] Polylactic acid 35%;

[0068] Starch 25%;

[0069] Fiber 15%;

[0070] Tea dregs 10%;

[0071] Pigment 5%;

[0072] Reaction accelerator 5%;

[0073] Plasticizer 5%.

[0074] Sample 2

[0075] Polylactic acid 35%;

[0076] Starch 20%;

[0077] Fiber 15%;

[0078] Tea residue 15%;

[0079] Pigment 5%;

[0080] Reaction accelerator 5%;

[0081] Plasticizer 5%.

[0082] Sample 3;

[0083] Polylactic acid 35%;

[0084] Starch 25%;

[0085] Fiber 10%;

[0086] Tea residue 15%;

[0087] Pigment 5%;

[0088] Reaction accelerator 5%;

[0089] Plasticizer 5%;

[0090] Comparative Example Sample 4:

[0091] Polylactic acid 35%;

[0092] Starch 35%;

[0093] Fiber 15%

[0094] Pigment 5%;

[0095] Reaction accelerator 5%;

[0096] Plasticizer 5%.

[0097] Biodegradation performance test:

[0098] The degradable material prepared in the above steps is made into samples of the same standard size and weight;

[0099] The above standard splines were tested for various properties using the following standard methods. The test results are shown in Table 1 below:

[0100] Place the prepared sample in the test soil under the same regional environment, pre-dig a 1-meter hole in the test soil, bury the sample in the hole, add a sample mark on the side of the hole, and fill the hole;

[0101] Take every 25 days as an observation period and record the weight change of the sample in the soil;

[0102] The weight change rate is (weight before the test - weight measured during the observation period) / weight before the test × 100%;

[0103] Table 1

[0104] cycle First cycle Second cycle Third cycle Sample 1 67.3 46.3 30.5 Sample 2 63.5 41.7 26.1 Sample 3 58.2 36.8 21.6 Comparative Example 4 72.4 56.8 41.1

[0105] It can be seen from Table 1 that after the third cycle, the weight change of the sample is basically in the 30% range, while the weight change of the comparative example is 40% in the third week for the biodegradable material without adding tea residue. Obviously, the biodegradation efficiency of the sample with tea residue added is higher.

[0106] By changing the amount of tea residue, fiber and starch as a control while keeping the polylactic acid unchanged, it can be concluded that the biodegradable material with added fiber, tea residue and starch has better biodegradability than the biodegradable material with high-grade starch or pure starch in the ratio under this field.

[0107] The mixing device includes a tank body 1, a first motor 2 is installed at the middle position above the tank body 1, a first transmission shaft 3 is provided at the output end of the first motor 2, a plurality of driven frames 4 distributed in an annular shape are provided on the outer wall of the first transmission shaft 3, and the driven frames 4 are provided with multiple layers up and down; linear modules 5 are installed on both sides of the outer wall of the driven frame 4, through holes 13 are provided between the linear modules 5, a mixing tank 15 is provided at the bottom of the tank body 1, a plurality of bottom stirring blades 16 are provided on the outer wall of the first transmission shaft 3 near the bottom, and the bottom stirring blades 16 are located inside the mixing tank 15, a discharge pipe 17 is installed on one side of the mixing tank 15, and one end of the discharge pipe 17 extends to the outside of the tank body 1;

[0108] The first transmission shaft 3 and the driven frame 4 are driven to rotate by the first motor 2. By adjusting the position of each driven frame 4, the material receiving and mixing boxes 9 at different driven frames 4 can be moved to different feeding layers 18 for feeding operations, and the materials in the material receiving and mixing boxes 9 can be driven to rotate and mix. At the same time, the mixture is finally mixed and prepared by the bottom stirring blades 16 to enhance its functionality.

[0109] Further, the linear module 5 includes a screw motor 6 and a ball screw 7, a screw slider 8 is installed on the outer wall of the ball screw 7, a material receiving and mixing box 9 is installed between the screw sliders 8, a second motor 10 is installed on one side of the material receiving and mixing box 9, a second transmission shaft 11 is provided at the output end of the second motor 10, a plurality of rotor blades 12 are provided on the outer wall of the second transmission shaft 11, and the output end of the second motor 10 is transmission-connected to the rotor blades 12 via the second transmission shaft 11;

[0110] The screw motor 6 and the ball screw 7 drive the screw slider 8 to move linearly, and the position of the material receiving and mixing box 9 is adjusted by movement. On the one hand, it is convenient to carry out upper and lower material receiving operations, and on the other hand, it can be aligned or staggered with the material receiving and mixing boxes 9 at different levels by movement. When the upper and lower levels are aligned, the mixture in the upper material receiving and mixing box 9 can be dropped into the next level for secondary mixing. When staggered, it can directly drop into the mixing trough 15 at the bottom, which is convenient for users to adjust and use according to needs; the second motor 10 drives the second transmission shaft 11 and the rotor 12 to rotate, and the materials in the material receiving and mixing box 9 are mixed by rotation. After pre-mixing, the overall foaming and mixing are carried out to improve the quality of the finished product.

[0111] Further, a feeding layer 18 is installed on both sides of the first motor 2, and the feeding layer 18 includes an annular guide rail 19, a guide rail slider 20 is arranged on the outer wall of the annular guide rail 19, an electric telescopic rod 21 is installed on the outer wall of the guide rail slider 20, and an electromagnet 22 is installed at the telescopic end of the electric telescopic rod 21, and a driven slide rail 23 is annularly distributed inside the annular guide rail 19, and a driven slider 24 is installed inside the driven slide rail 23, and the driven slider 24 is magnetically connected to the electromagnet 22, and a material discharge cavity 26 is arranged at the middle position of the annular guide rail 19, and the material discharge cavity 26 is connected to the tank body 1;

[0112] The annular guide rail 19 and the guide rail slider 20 are used to drive the electric telescopic rod 21 to move in a circular manner. The position of the electric telescopic rod 21 is adjusted by the circular movement, so that the electric telescopic rod 21 can be moved to different raw material tanks 25 for combination. After the electric telescopic rod 21 moves to the required raw material tank 25, the electric telescopic rod 21 is turned on to extend, and the electromagnet 22 is turned on to make the electromagnet 22 adsorbed on the driven slider 24. The electric telescopic rod 21 extends forward, driving the driven slider 24 to move on the driven slide rail 23, so that the raw material tank 25 is driven to the unloading chamber 26 for unloading operation. Through this structure, different raw materials can be adjusted and switched according to needs for unloading operation. Different raw materials can be matched with the rotation of the first transmission shaft 3 below, and can fall into different material receiving and mixing boxes 9 for mixed preparation, thereby improving preparation flexibility.

[0113] Furthermore, a raw material tank 25 is installed above the driven slider 24, a first control valve 27 is installed at the lower end of the raw material tank 25, a second control valve 28 is installed below the material receiving and mixing box 9, and a feeding pipe 14 is installed on the outer walls of both sides of the tank body 1, and one end of the feeding pipe 14 extends into the tank body 1;

[0114] The first control valve 27 is used to control the opening and closing state of the raw material tank 25; the second control valve 28 is used to control the opening and closing state of the material receiving and mixing box 9 to facilitate the feeding operation; the feeding pipe 14 is used for secondary feeding during premixing.

[0115] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A biodegradable foam material, characterized in that: The composition includes the following weight percentages: Polylactic acid 30%-35%; Starch 10%-25%; Fiber 10%-15%; Tea residue 5%~15% Pigment 1% to 5%; Reaction accelerator 1% to 5%; Plasticizer 1%~5%.

2. The biodegradable foam material according to claim 1, characterized in that: The starch is one or more of corn starch, sweet potato starch, potato starch, cassava starch and wheat starch, and the weight content of amylose in the starch is 10% to 20%.

3. The biodegradable foam material according to claim 2, characterized in that: The reaction accelerator is a coupling agent, and the coupling agent is one or both of a silane compound and an isocyanate compound.

4. The biodegradable foam material according to claim 3, characterized in that: The plasticizer is one or a mixture of glycerol, sorbitol, acetyl citrate, and polyethylene wax.

5. The biodegradable foam material according to claim 4, characterized in that: The fibers are bamboo fibers and cotton fibers, which are mixed in a ratio of 3:

1.

6. The biodegradable foam material according to claim 5, characterized in that: The colorant is a plant extract pigment, the plants are tea leaves and petals, and the colors are indigo and litmus yellow.

7. A method for preparing a biodegradable foam material, used for preparing a biodegradable foam material according to claim 6, characterized in that: The following steps are involved: Step 1: pre-mix tea residues, fiber, starch, reaction accelerator, and polylactic acid through a mixing device at a speed of 800-1200 r / min for 30-60 minutes; Step 2: Add corresponding percentage of plasticizer and colorant during the mixing process for secondary mixing, and mix again at 1200-1500r / min for 60-90 minutes. During the mixing process, nitrogen is injected inside and mixed into the material by mechanical stirring to make the material expand and foam: Step 3: Feed the foaming material into a twin-screw extruder at 120-170°C and a rotation speed of 300-600 rpm for 40-60 minutes, melt blend and draw into strips, feed the drawn material into a pelletizer at a rotation speed of 130 r / min, and form particles with a particle size of less than 100 microns through a pelletizer; Step 4: The obtained granular material is sent to a drying device at a drying temperature of 50°C-80°C for 60-120 minutes to obtain a biodegradable foaming material.

8. A mixing device for biodegradable foaming material, applied to the method for preparing a biodegradable foaming material as claimed in claim 7, characterized in that: The mixing device comprises a tank body (1), a first motor (2) is installed at a middle position above the tank body (1), a first transmission shaft (3) is arranged at the output end of the first motor (2), a plurality of driven frames (4) distributed in an annular shape are arranged on the outer wall of the first transmission shaft (3), and the driven frames (4) are provided with upper and lower layers; linear modules (5) are installed on both sides of the outer wall of the driven frame (4), through holes (13) are arranged between the linear modules (5), a mixing groove (15) is arranged at the bottom of the tank body (1), a plurality of bottom stirring blades (16) are arranged on the outer wall of the first transmission shaft (3) near the bottom, and the bottom stirring blades (16) are located inside the mixing groove (15). A discharge pipe (17) is installed on one side of the mixing tank (15), and one end of the discharge pipe (17) extends to the outside of the tank body (1); the linear module (5) includes a screw motor (6) and a ball screw (7), a screw slider (8) is installed on the outer wall of the ball screw (7), a material receiving and mixing box (9) is installed between the screw sliders (8), a second motor (10) is installed on one side of the material receiving and mixing box (9), a second transmission shaft (11) is provided at the output end of the second motor (10), a plurality of rotating blades (12) are provided on the outer wall of the second transmission shaft (11), and the output end of the second motor (10) is transmission-connected to the rotating blades (12) via the second transmission shaft (11).

9. A mixing device for biodegradable foaming materials according to claim 8, characterized in that: A feeding layer (18) is installed on both sides of the first motor (2), and the feeding layer (18) includes an annular guide rail (19), a guide rail slider (20) is arranged on the outer wall of the annular guide rail (19), an electric telescopic rod (21) is installed on the outer wall of the guide rail slider (20), and an electromagnet (22) is installed at the telescopic end of the electric telescopic rod (21), a driven slide rail (23) is arranged in an annular shape inside the annular guide rail (19), a driven slider (24) is installed inside the driven slide rail (23), and the driven slider (24) is magnetically connected to the electromagnet (22), and a material discharge cavity (26) is arranged at the middle position of the annular guide rail (19), and the material discharge cavity (26) is connected to the tank body (1).

10. A mixing device for biodegradable foaming materials according to claim 9, characterized in that: A raw material tank (25) is installed above the driven slider (24), a first control valve (27) is installed at the lower end of the raw material tank (25), a second control valve (28) is installed below the material receiving and mixing box (9), and feeding pipes (14) are installed on the outer walls of both sides of the tank body (1), and one end of the feeding pipe (14) extends into the tank body (1).

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