阅读说明：本技术 一种可生物降解的发泡聚丙烯及其制备方法 (Biodegradable foamed polypropylene and preparation method thereof ) 是由 陈奕镔 于 2021-07-13 设计创作，主要内容包括：本发明公开了一种可生物降解的发泡聚丙烯,具体涉及高分子材料技术领域,包括以下原料：聚丙烯树脂、淀粉、氢氧化钙、醋酸乙烯酯、分散剂、抗氧剂、发泡成核剂、光降解剂和增韧剂。本发明利用氢氧化钙和醋酸乙烯酯对淀粉进行改性,碱土金属氢氧化钙对淀粉进行初次改性使得淀粉的相容性增加,然后利用硝酸铈铵使醋酸乙烯酯和淀粉进行接枝共聚反应,极大地增加了接枝共聚后改性淀粉的相容性,使得淀粉与聚丙烯的混合效果更好,从而有效提高聚丙烯材料的生物降解速率,通过添加有光降解剂能够有效提高聚丙烯材料的光降解速率,同时利用生物降解和光降解对发泡聚丙烯材料进行处理,使得发泡聚丙烯材料的降解速率大大提高。(The invention discloses biodegradable foamed polypropylene, and particularly relates to the technical field of high polymer materials, wherein the biodegradable foamed polypropylene comprises the following raw materials: polypropylene resin, starch, calcium hydroxide, vinyl acetate, a dispersing agent, an antioxidant, a foaming nucleating agent, a photodegradation agent and a toughening agent. According to the invention, calcium hydroxide and vinyl acetate are utilized to modify starch, alkaline earth metal calcium hydroxide is utilized to primarily modify starch to increase the compatibility of starch, then ammonium ceric nitrate is utilized to carry out graft copolymerization reaction on vinyl acetate and starch, the compatibility of modified starch after graft copolymerization is greatly increased, the mixing effect of starch and polypropylene is better, so that the biodegradation rate of a polypropylene material is effectively improved, the photodegradation rate of the polypropylene material can be effectively improved by adding a photodegradation agent, and the degradation rate of the foamed polypropylene material is greatly improved by treating the foamed polypropylene material through biodegradation and photodegradation.)

1. A biodegradable foamed polypropylene characterized by: the feed comprises the following raw materials in parts by weight: 40-60 parts of polypropylene resin, 30-50 parts of starch, 1-5 parts of calcium hydroxide, 20-40 parts of vinyl acetate, 2-6 parts of dispersing agent, 1-5 parts of antioxidant, 1-3 parts of foaming nucleating agent, 1-5 parts of photodegradation agent and 4-10 parts of toughening agent.

2. The biodegradable expanded polypropylene according to claim 1, wherein: the feed comprises the following raw materials in parts by weight: 45-55 parts of polypropylene resin, 35-45 parts of starch, 2-4 parts of calcium hydroxide, 25-35 parts of vinyl acetate, 3-5 parts of dispersant, 2-4 parts of antioxidant, 2-3 parts of foaming nucleating agent, 2-4 parts of photodegradation agent and 6-8 parts of toughening agent.

3. The biodegradable expanded polypropylene according to claim 1, wherein: the feed comprises the following raw materials in parts by weight: 50 parts of polypropylene resin, 40 parts of starch, 3 parts of calcium hydroxide, 30 parts of vinyl acetate, 4 parts of dispersing agent, 3 parts of antioxidant, 2 parts of foaming nucleating agent, 3 parts of photodegradation agent and 7 parts of toughening agent.

4. The biodegradable expanded polypropylene according to claim 1, wherein: the starch is one of potato starch, sweet potato starch or corn starch, the dispersing agent is aluminum sulfate, the antioxidant is an alkyl monophenol antioxidant or an azacyclo-polyphenol antioxidant, the photodegradant is ferric stearate, the toughening agent is maleic anhydride grafted polypropylene or maleic anhydride grafted EVA, and the foaming nucleating agent is sodium bicarbonate.

5. The method for preparing biodegradable expanded polypropylene according to any one of claims 1 to 4, wherein: the preparation method comprises the following specific steps:

the method comprises the following steps: placing the weighed starch into a high-speed airflow pulverizer for pulverizing, placing the pulverized starch into a ball mill for grinding, placing the ground starch into a reaction container, adding deionized water and calcium hydroxide into the reaction container, stirring and mixing uniformly, adding vinyl acetate and a catalyst, continuously stirring for 3-5h, and placing a product into a centrifuge for dehydration after the reaction is finished to obtain modified starch;

step two: adding a dispersing agent, a foaming nucleating agent and a photodegradable agent into the modified starch in the step one, uniformly mixing in a high-speed mixer, and then putting in a double-screw extruder for extrusion and granulation to obtain modified starch master batches;

step three: drying the modified starch master batch obtained in the step two in a drying oven to ensure that the moisture content of the modified starch master batch is 5-15% for later use;

step four: and (3) uniformly mixing the modified starch master batch dried in the step three with polypropylene resin, an antioxidant and a toughening agent in a high-speed mixer, placing the mixture in a double-screw extruder for heating, melting, extruding and granulating after uniform mixing, heating and boosting the obtained particles, washing with water after heating and boosting, placing the particles in a dehydrator for dehydration, performing hot air blowing and drying after dehydration treatment, performing secondary screening on the dried polypropylene particles, and screening the foamed polypropylene particles with uniform length and size to obtain the biodegradable foamed polypropylene.

6. The method for preparing biodegradable foamed polypropylene according to claim 5, wherein: the gas consumption of the high-speed jet mill in the step I is 6m³The grinding time of the jet mill is 8-15min, the rotating speed of the ball mill is 800-.

7. The method for preparing biodegradable foamed polypropylene according to claim 5, wherein: the adding amount of the deionized water in the first step is 1.8-2.5 times of the weight of the ball-milled starch, the continuous stirring speed in the first step is 800r/min, the catalyst in the first step is ceric ammonium nitrate, and the water content of the modified starch after the centrifugal machine is dehydrated in the first step is 25-35%.

8. The method for preparing biodegradable foamed polypropylene according to claim 5, wherein: the extrusion granulation of the double-screw extruder in the second step comprises nine temperature zones which are sequentially arranged, wherein the temperature of the first zone is 185-minus 195 ℃, the temperature of the second zone and the temperature of the third zone are 200-minus 210 ℃, the temperature of the fourth zone to the seventh zone is 210-minus 220 ℃, the temperature of the eighth zone is 205-minus 215 ℃, the temperature of the ninth zone is 200-minus 210 ℃, the temperature of the head of the double-screw extruder is 195-minus 205 ℃, and the screw rotating speed of the double-screw extruder is 500-minus 600 r/min.

9. The method for preparing biodegradable foamed polypropylene according to claim 5, wherein: the drying temperature of the drying oven in the third step is 50-60 ℃.

10. The method for preparing biodegradable foamed polypropylene according to claim 5, wherein: in the fourth step, the temperature is 160-180 ℃ and the pressure is 0.3-0.4MPa when the pressure is increased by heating, and the temperature is 60-70 ℃ when the hot air blowing drying is carried out after the dehydration treatment is finished.

Technical Field

The invention relates to the technical field of high polymer materials, in particular to biodegradable foamed polypropylene and a preparation method thereof.

Background

Polypropylene (PP) has been widely used in various industries due to its advantages of good stability, excellent mechanical properties, low price, etc., but the material degrades very slowly in natural environment, so that the "white pollution" brought by the waste products causes little harm to the environment, which hinders the further development of PP. At present, two methods of incineration and landfill are mainly adopted when PP waste is treated, although the two treatment methods reduce white pollution to a certain extent, the problems of air pollution, soil pollution, water pollution and the like are brought along with the white pollution, and the symptom that the PP waste pollutes the environment cannot be eradicated.

Biodegradable plastics refer to a class of plastics that are degraded by the action of microorganisms such as bacteria, molds (fungi), and algae that exist in nature. The ideal biodegradable plastic is a high polymer material which has excellent service performance, can be completely decomposed by microorganisms in the environment after being discarded, and is finally degraded into carbon dioxide and water. Most pure polymers are not easily decomposed by microorganisms, and although the PP material can be biodegraded in the environment, the degradation time is very long, and the biodegradation performance of the PP can be improved by adding starch.

The existing biodegradable polypropylene material is prepared by mixing starch and polypropylene, and due to insufficient compatibility of the starch and the polypropylene material, the degradation rate of the polypropylene material is low, and the use requirements of people cannot be met.

Disclosure of Invention

In order to overcome the above-mentioned defects of the prior art, embodiments of the present invention provide a biodegradable foamed polypropylene and a preparation method thereof, and the problems to be solved by the present invention are: how to improve the degradation rate of the polypropylene material and reduce the pollution of the polypropylene material to the environment.

In order to achieve the purpose, the invention provides the following technical scheme: a biodegradable foamed polypropylene comprises the following raw materials in parts by weight: 40-60 parts of polypropylene resin, 30-50 parts of starch, 1-5 parts of calcium hydroxide, 20-40 parts of vinyl acetate, 2-6 parts of dispersing agent, 1-5 parts of antioxidant, 1-3 parts of foaming nucleating agent, 1-5 parts of photodegradation agent and 4-10 parts of toughening agent.

In a preferred embodiment, the feed comprises the following raw materials in parts by weight: 45-55 parts of polypropylene resin, 35-45 parts of starch, 2-4 parts of calcium hydroxide, 25-35 parts of vinyl acetate, 3-5 parts of dispersant, 2-4 parts of antioxidant, 2-3 parts of foaming nucleating agent, 2-4 parts of photodegradation agent and 6-8 parts of toughening agent.

In a preferred embodiment, the feed comprises the following raw materials in parts by weight: 50 parts of polypropylene resin, 40 parts of starch, 3 parts of calcium hydroxide, 30 parts of vinyl acetate, 4 parts of dispersing agent, 3 parts of antioxidant, 2 parts of foaming nucleating agent, 3 parts of photodegradation agent and 7 parts of toughening agent.

In a preferred embodiment, the starch is one of potato starch, sweet potato starch or corn starch, the dispersing agent is aluminum sulfate, the antioxidant is an alkyl monophenol antioxidant or an azacyclo-polyphenol antioxidant, the photodegradant is ferric stearate, the toughening agent is maleic anhydride grafted polypropylene or maleic anhydride grafted EVA, and the foaming nucleating agent is sodium bicarbonate.

The invention also provides a preparation method of the biodegradable foamed polypropylene, which comprises the following specific preparation steps:

the method comprises the following steps: placing the weighed starch into a high-speed airflow pulverizer for pulverizing, placing the pulverized starch into a ball mill for grinding, placing the ground starch into a reaction container, adding deionized water and calcium hydroxide into the reaction container, stirring and mixing uniformly, adding vinyl acetate and a catalyst, continuously stirring for 3-5h, and placing a product into a centrifuge for dehydration after the reaction is finished to obtain modified starch;

step two: adding a dispersing agent, a foaming nucleating agent and a photodegradable agent into the modified starch in the step one, uniformly mixing in a high-speed mixer, and then putting in a double-screw extruder for extrusion and granulation to obtain modified starch master batches;

step three: drying the modified starch master batch obtained in the step two in a drying oven to ensure that the moisture content of the modified starch master batch is 5-15% for later use;

step four: and (3) uniformly mixing the modified starch master batch dried in the step three with polypropylene resin, an antioxidant and a toughening agent in a high-speed mixer, placing the mixture in a double-screw extruder for heating, melting, extruding and granulating after uniform mixing, heating and boosting the obtained particles, washing with water after heating and boosting, placing the particles in a dehydrator for dehydration, performing hot air blowing and drying after dehydration treatment, performing secondary screening on the dried polypropylene particles, and screening the foamed polypropylene particles with uniform length and size to obtain the biodegradable foamed polypropylene.

In a preferred embodiment, the gas consumption of the high-speed jet mill in the first step is 6m³The grinding time of the jet mill is 8-15min, the rotating speed of the ball mill is 800-.

In a preferred embodiment, the deionized water added in the first step is 1.8-2.5 times of the weight of the ball-milled starch, the continuous stirring rate in the first step is 500-.

In a preferred embodiment, the extrusion granulation of the twin-screw extruder in the second step comprises nine temperature zones sequentially arranged, wherein the temperature of the first zone is 185-.

In a preferred embodiment, the drying temperature of the drying oven in step three is 50-60 ℃.

In a preferred embodiment, the temperature for heating and pressurizing in the fourth step is 160-180 ℃, the pressure is 0.3-0.4MPa, and the temperature for hot air blowing drying after the dehydration treatment is finished is 60-70 ℃.

The invention has the technical effects and advantages that:

1. the biodegradable foamed polypropylene prepared by the raw material formula of the invention utilizes calcium hydroxide and vinyl acetate to modify starch, alkaline earth metal calcium hydroxide to primarily modify the starch to increase the compatibility of the starch, then utilizes ammonium ceric nitrate to make vinyl acetate and the starch perform graft copolymerization reaction, greatly increases the compatibility of the modified starch after graft copolymerization, and ensures that the mixing effect of the starch and the polypropylene is better, thereby effectively improving the biodegradation rate of the polypropylene material, adopts aluminum sulfate as a dispersing agent to introduce hydrophobic ions into starch molecules, can reduce the hydrophilicity of hydroxyl groups in the starch molecules, has better compatibility effect when the starch and the polypropylene are mixed in an extruder, can effectively improve the photodegradation rate of the polypropylene material by adding a photodegradation agent, and simultaneously utilizes biodegradation and photodegradation to treat the foamed polypropylene material, the degradation rate of the foamed polypropylene material is greatly improved;

2. according to the invention, before starch modification, the starch is subjected to superfine grinding treatment by using a high-speed jet mill, and then is subjected to grinding treatment by using a ball mill, so that the starch can be micronized, the compatibility of the starch and a polypropylene material is improved, the starch is finally degraded into carbon dioxide and water in a natural environment, the problem of environmental pollution is solved, the cost of the foamed polypropylene material can be effectively reduced by using potato starch, sweet potato starch or corn starch and vinyl acetate with lower price, and the method can be widely popularized in the market.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1:

the invention provides biodegradable foamed polypropylene, which comprises the following raw materials in parts by weight: 40 parts of polypropylene resin, 30 parts of starch, 1 part of calcium hydroxide, 20 parts of vinyl acetate, 2 parts of dispersant, 1 part of antioxidant, 1 part of foaming nucleating agent, 1 part of photodegradation agent and 4 parts of toughening agent.

In a preferred embodiment, the starch is one of potato starch, sweet potato starch or corn starch, the dispersing agent is aluminum sulfate, the antioxidant is an alkyl monophenol antioxidant or an azacyclo-polyphenol antioxidant, the photodegradant is ferric stearate, the toughening agent is maleic anhydride grafted polypropylene or maleic anhydride grafted EVA, and the foaming nucleating agent is sodium bicarbonate.

The invention also provides a preparation method of the biodegradable foamed polypropylene, which comprises the following specific preparation steps:

the method comprises the following steps: placing the weighed starch into a high-speed airflow pulverizer for pulverizing, placing the pulverized starch into a ball mill for grinding, placing the ground starch into a reaction container, adding deionized water and calcium hydroxide into the reaction container, stirring and mixing uniformly, adding vinyl acetate and a catalyst, continuously stirring for 4 hours, and placing a product into a centrifuge for dehydration after the reaction is finished to obtain modified starch;

step two: adding a dispersing agent, a foaming nucleating agent and a photodegradable agent into the modified starch in the step one, uniformly mixing in a high-speed mixer, and then putting in a double-screw extruder for extrusion and granulation to obtain modified starch master batches;

step three: drying the modified starch master batch obtained in the step two in a drying oven to ensure that the moisture content of the modified starch master batch is 10% for later use;

step four: and (3) uniformly mixing the modified starch master batch dried in the step three with polypropylene resin, an antioxidant and a toughening agent in a high-speed mixer, placing the mixture in a double-screw extruder for heating, melting, extruding and granulating after uniform mixing, heating and boosting the obtained particles, washing with water after heating and boosting, placing the particles in a dehydrator for dehydration, performing hot air blowing and drying after dehydration treatment, performing secondary screening on the dried polypropylene particles, and screening the foamed polypropylene particles with uniform length and size to obtain the biodegradable foamed polypropylene.

In a preferred embodiment, the gas consumption of the high-speed jet mill in the first step is 6m³The grinding time of the jet mill is 12min, and the rotating speed of the ball millThe ball milling time is 30min and is 1000 r/min.

In a preferred embodiment, the deionized water is added in an amount of 2 times the weight of the ball-milled starch in the first step, the continuous stirring rate in the first step is 700r/min, the catalyst in the first step is ceric ammonium nitrate, and the modified starch after the centrifugal machine dehydration in the first step has a water content of 30%.

In a preferred embodiment, the extrusion granulation of the twin-screw extruder in the second step comprises nine temperature zones arranged in sequence, wherein the temperature of the first zone is 190 ℃, the temperature of the second zone and the temperature of the third zone are 205 ℃, the temperature of the fourth zone to the seventh zone is 215 ℃, the temperature of the eighth zone is 210 ℃, the temperature of the ninth zone is 205 ℃, the head temperature of the twin-screw extruder is 200 ℃, and the screw rotation speed of the twin-screw extruder is 550 r/min.

In a preferred embodiment, the drying temperature of the drying oven in step three is 55 ℃.

In a preferred embodiment, the temperature at the time of heating and pressurizing in the fourth step is 170 ℃ and the pressure is 0.35MPa, and the temperature at the time of hot air blast drying after completion of the dehydration treatment is 65 ℃.

Example 2:

different from the embodiment 1, the invention provides biodegradable foamed polypropylene, which comprises the following raw materials in parts by weight: 50 parts of polypropylene resin, 40 parts of starch, 3 parts of calcium hydroxide, 30 parts of vinyl acetate, 4 parts of dispersing agent, 3 parts of antioxidant, 2 parts of foaming nucleating agent, 3 parts of photodegradation agent and 7 parts of toughening agent.

Example 3:

different from the embodiments 1-2, the invention provides biodegradable foamed polypropylene, which comprises the following raw materials in parts by weight: 60 parts of polypropylene resin, 50 parts of starch, 5 parts of calcium hydroxide, 40 parts of vinyl acetate, 6 parts of dispersing agent, 5 parts of antioxidant, 3 parts of foaming nucleating agent, 5 parts of photodegradation agent and 10 parts of toughening agent.

Example 4:

the invention provides biodegradable foamed polypropylene, which comprises the following raw materials in parts by weight: 40 parts of polypropylene resin, 30 parts of starch, 20 parts of vinyl acetate, 2 parts of dispersant, 1 part of antioxidant, 1 part of foaming nucleating agent, 1 part of photodegradation agent and 4 parts of toughening agent.

In a preferred embodiment, the starch is one of potato starch, sweet potato starch or corn starch, the dispersing agent is aluminum sulfate, the antioxidant is an alkyl monophenol antioxidant or an azacyclo-polyphenol antioxidant, the photodegradant is ferric stearate, the toughening agent is maleic anhydride grafted polypropylene or maleic anhydride grafted EVA, and the foaming nucleating agent is sodium bicarbonate.

The invention also provides a preparation method of the biodegradable foamed polypropylene, which comprises the following specific preparation steps:

the method comprises the following steps: placing the weighed starch into a high-speed airflow pulverizer for pulverizing, placing the pulverized starch into a ball mill for grinding after the pulverizing is completed, placing the ground starch into a reaction container, adding deionized water into the reaction container, adding vinyl acetate and a catalyst after stirring and mixing uniformly, continuously stirring for 4 hours, and placing a product into a centrifuge for dehydration after the reaction is completed to obtain modified starch;

step two: adding a dispersing agent, a foaming nucleating agent and a photodegradable agent into the modified starch in the step one, uniformly mixing in a high-speed mixer, and then putting in a double-screw extruder for extrusion and granulation to obtain modified starch master batches;

step three: drying the modified starch master batch obtained in the step two in a drying oven to ensure that the moisture content of the modified starch master batch is 10% for later use;

step four: and (3) uniformly mixing the modified starch master batch dried in the step three with polypropylene resin, an antioxidant and a toughening agent in a high-speed mixer, placing the mixture in a double-screw extruder for heating, melting, extruding and granulating after uniform mixing, heating and boosting the obtained particles, washing with water after heating and boosting, placing the particles in a dehydrator for dehydration, performing hot air blowing and drying after dehydration treatment, performing secondary screening on the dried polypropylene particles, and screening the foamed polypropylene particles with uniform length and size to obtain the biodegradable foamed polypropylene.

In a preferred embodimentIn an embodiment, the gas consumption of the high-speed jet mill in the first step is 6m³And/min, wherein the crushing time of the jet mill is 12min, the rotating speed of the ball mill is 1000r/min, and the ball milling time is 30 min.

In a preferred embodiment, the deionized water is added in an amount of 2 times the weight of the ball-milled starch in the first step, the continuous stirring rate in the first step is 700r/min, the catalyst in the first step is ceric ammonium nitrate, and the modified starch after the centrifugal machine dehydration in the first step has a water content of 30%.

In a preferred embodiment, the extrusion granulation of the twin-screw extruder in the second step comprises nine temperature zones arranged in sequence, wherein the temperature of the first zone is 190 ℃, the temperature of the second zone and the temperature of the third zone are 205 ℃, the temperature of the fourth zone to the seventh zone is 215 ℃, the temperature of the eighth zone is 210 ℃, the temperature of the ninth zone is 205 ℃, the head temperature of the twin-screw extruder is 200 ℃, and the screw rotation speed of the twin-screw extruder is 550 r/min.

In a preferred embodiment, the drying temperature of the drying oven in step three is 55 ℃.

In a preferred embodiment, the temperature at the time of heating and pressurizing in the fourth step is 170 ℃ and the pressure is 0.35MPa, and the temperature at the time of hot air blast drying after completion of the dehydration treatment is 65 ℃.

Example 5:

a biodegradable foamed polypropylene comprises the following raw materials in parts by weight: 40 parts of polypropylene resin, 30 parts of starch, 1 part of calcium hydroxide, 20 parts of vinyl acetate, 2 parts of dispersant, 1 part of antioxidant, 1 part of foaming nucleating agent and 4 parts of toughening agent.

In a preferred embodiment, the starch is one of potato starch, sweet potato starch or corn starch, the dispersing agent is aluminum sulfate, the antioxidant is alkyl monophenol antioxidant or azacyclo-polyphenol antioxidant, the toughening agent is maleic anhydride grafted polypropylene or maleic anhydride grafted EVA, and the foam nucleating agent is sodium bicarbonate.

The invention also provides a preparation method of the biodegradable foamed polypropylene, which comprises the following specific preparation steps:

the method comprises the following steps: placing the weighed starch into a high-speed airflow pulverizer for pulverizing, placing the pulverized starch into a ball mill for grinding, placing the ground starch into a reaction container, adding deionized water and calcium hydroxide into the reaction container, stirring and mixing uniformly, adding vinyl acetate and a catalyst, continuously stirring for 4 hours, and placing a product into a centrifuge for dehydration after the reaction is finished to obtain modified starch;

step two: adding a dispersing agent and a foaming nucleating agent into the modified starch in the step one, uniformly mixing in a high-speed mixer, and then putting in a double-screw extruder for extrusion granulation to obtain modified starch master batches;

step three: drying the modified starch master batch obtained in the step two in a drying oven to ensure that the moisture content of the modified starch master batch is 10% for later use;

step four: and (3) uniformly mixing the modified starch master batch dried in the step three with polypropylene resin, an antioxidant and a toughening agent in a high-speed mixer, placing the mixture in a double-screw extruder for heating, melting, extruding and granulating after uniform mixing, heating and boosting the obtained particles, washing with water after heating and boosting, placing the particles in a dehydrator for dehydration, performing hot air blowing and drying after dehydration treatment, performing secondary screening on the dried polypropylene particles, and screening the foamed polypropylene particles with uniform length and size to obtain the biodegradable foamed polypropylene.

In a preferred embodiment, the gas consumption of the high-speed jet mill in the first step is 6m³And/min, wherein the crushing time of the jet mill is 12min, the rotating speed of the ball mill is 1000r/min, and the ball milling time is 30 min.

In a preferred embodiment, the deionized water is added in an amount of 2 times the weight of the ball-milled starch in the first step, the continuous stirring rate in the first step is 700r/min, the catalyst in the first step is ceric ammonium nitrate, and the modified starch after the centrifugal machine dehydration in the first step has a water content of 30%.

In a preferred embodiment, the extrusion granulation of the twin-screw extruder in the second step comprises nine temperature zones arranged in sequence, wherein the temperature of the first zone is 190 ℃, the temperature of the second zone and the temperature of the third zone are 205 ℃, the temperature of the fourth zone to the seventh zone is 215 ℃, the temperature of the eighth zone is 210 ℃, the temperature of the ninth zone is 205 ℃, the head temperature of the twin-screw extruder is 200 ℃, and the screw rotation speed of the twin-screw extruder is 550 r/min.

In a preferred embodiment, the drying temperature of the drying oven in step three is 55 ℃.

In a preferred embodiment, the temperature at the time of heating and pressurizing in the fourth step is 170 ℃ and the pressure is 0.35MPa, and the temperature at the time of hot air blast drying after completion of the dehydration treatment is 65 ℃.

The boards made of the biodegradable foamed polypropylene prepared in the above examples 1 to 5 were taken as an experimental group 1, an experimental group 2, an experimental group 3, an experimental group 4 and an experimental group 5, respectively, the boards made of 60% polypropylene and 40% starch were taken as a control group, and then the boards produced by the experimental group and the control group were tested for degradation rate, which was measured for biodegradation rate and photodegradation rate, the boards were buried in the same soil during biodegradation rate test, the degradation rates of the boards were tested after 60 days, 120 days and 180 days, respectively, the boards were degraded by exposure to the sun, wind, rain and microbial etching during photodegradation rate test, the degradation rates of the boards were tested after 90 days, 150 days and 180 days, respectively, and the test results are as shown in table one:

watch 1

As can be seen from the table I, compared with the plate produced by directly using polypropylene and starch, the plate produced by using the biodegradable foamed polypropylene of the invention has significantly improved biodegradation rate and photodegradation rate, and the plate produced by directly using polypropylene and starch is not suitable for photodegradation, the calcium hydroxide and the photodegradation rate in the ingredients are respectively removed in the examples 4 and 5, the biodegradation rate and the photodegradation rate in the example 4 are slightly reduced, while the photodegradation rate in the example 5 is obviously reduced, the starch is modified by using the calcium hydroxide and the vinyl acetate, the starch is primarily modified by using the alkaline earth metal calcium hydroxide so that the compatibility of the starch is increased, then the ammonium ceric nitrate is used for carrying out graft copolymerization on the vinyl acetate and the starch, the compatibility of the modified starch after graft copolymerization is greatly increased, the mixing effect of the starch and the polypropylene is better, and the biodegradation rate of the polypropylene material is effectively increased, the aluminum sulfate is used as a dispersing agent, so that hydrophobic ions can be introduced into starch molecules, the hydrophilicity of hydroxyl groups in the starch molecules can be reduced, the compatibility effect of the starch and polypropylene is better when the starch and the polypropylene are mixed in an extruder, the photodegradation rate of the polypropylene material can be effectively improved by adding the photodegradation agent, and meanwhile, the foamed polypropylene material is treated by means of biodegradation and photodegradation, so that the degradation rate of the foamed polypropylene material is greatly improved.

And finally: the above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that are within the spirit and principle of the present invention are intended to be included in the scope of the present invention.