Anaerobic degradation compound yeast agent, production method and anaerobic biodegradable plastic

Abstract

The invention discloses a compound yeast agent for anaerobic degradation of biodegradable plastics. The compound yeast agent comprises the following components in percentage by mass: 0.5-3% of fenpropathrin, 1-6% of nitrite, 1-4% of ammonium molybdate, 5-10% of PLA, 5-10% of nano starch, 3-6% of nano calcium carbonate, 1-5% of carbamide and the balance of a biodegradable resin carrier. The production method comprises the following steps: 1, dispersion treatment; 2, centralization processing; 3, carrying out structured treatment; 4, carrying out carrier implantation treatment; and 5, plasticizing and granulating. The compound yeast agent is added into the plastic, and the addition amount is 1-5%, so that the anaerobic degradation plastic is formed. According to the invention, anaerobic degradation can be regulated and controlled, and more importantly, anaerobic degradation also realizes that the degradable plastic disclosed by the invention is in a normal use condition, the plastic cannot be degraded quickly in light and oxygen environments, the aging property of the plastic is equivalent to that of a resin matrix of the plastic, and the physical and mechanical properties are ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of biodegradable plastics, and particularly relates to a composite yeast agent for anaerobic biodegradable plastics. By adding it to plastics, the microbial degradation environment in a natural anaerobic environment is changed, and the complete biodegradation of polymers such as PP and PE is achieved. Background Art

[0002] Petroleum-based synthetic resins mainly include polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyurethane (PUR), as well as petroleum-based plastics such as PA (polyamide, nylon), ABS (acrylonitrile–butadiene–styrene copolymer) engineering plastics, and EPS expanded polystyrene plastics. These synthetic resins are made into plastics with different properties by adding some additives and have been widely used in all aspects of life. Due to their large molecular weight and hydrophobicity, the resin monomers are often combined through very strong and stable covalent bonds such as C-C bonds, and have high crystallinity, so they are very difficult to degrade under natural conditions. With the rapid development of the petroleum industry and the extensive application of synthetic plastics, the "white pollution" caused by a large number of discarded synthetic plastics has become a global problem.

[0003] The development of degradable plastics has gone through three stages: The first-generation degradable plastics are starch-modified plastics. During the monomer polymerization process, additives such as modified starch are added. Utilizing the biodegradable property of starch, the modified plastics are cracked into tiny plastic fragments in the environment. However, since high-molecular polymers such as PE are still very difficult to degrade, starch-modified plastics are also called "bio-destructive plastics" (incomplete degradation type). The second-generation degradable plastics are photo-oxidative degradable plastics. By constructing photosensitive groups in the main chain of plastic molecules, they absorb light energy (mainly ultraviolet light) to initiate photo-oxidation, and degrade high-molecular polymers into low-molecular-weight compounds. Industrialized ones include ethylene-CO copolymers (such as ECO) and ethylene-vinyl ketone copolymers. Photo-oxidative degradation has very strict requirements for degradation conditions such as temperature and light intensity, and its development is slow. The first-generation starch-modified plastics and the second-generation photo-thermal degradable plastics actually both crack plastics into tiny fragments, i.e., microplastics. Since these tiny fragments are macromolecules with difficult-to-degrade C-C chains, the first and second generations of degradable plastics are not completely degraded. Scientists' research shows that the presence of microplastics in the environment is even more harmful to humans than white pollution, and many evidences reveal that the occurrence of many diseases is related to microplastics.

[0004] The third-generation degradable plastics, namely completely biodegradable plastics, are formed by the dehydration polymerization of organic acids and alcohols. Their common feature is the introduction of ester groups into the molecular chain. Through various enzymes released by microorganisms, such as esterase, depolymerase, and dehydratase, they bind to specific receptors on the plastic surface and catalyze the hydrolysis or oxidation of the ester groups contained in the polymer, breaking down the macromolecules into fatty acids or lipid substances with a molecular weight less than 500. These oligomers or their degradation products will enter the microorganisms and ultimately be metabolized and decomposed by the microorganisms into water and carbon dioxide. Currently, such completely degradable plastics include polylactic acid (PLA), polyhydroxyalkanoates (PHA), poly-3-hydroxybutyrate (PHB), polybutylene succinate (PBS), poly(butylene adipate-co-terephthalate) (PBAT), etc. Their common feature is that they are all aliphatic polyesters. However, due to cost and performance limitations (such as poor water resistance), such degradable plastics only account for a very small proportion in practical applications.

[0005] Based on the different characteristics of the mechanical properties and degradability of resins such as PP and PE and the third-generation degradable plastics, mixing the third-generation degradable plastics such as PLA and PBAT with PE, PP, etc. has also become an option. For example, a method for preparing a degradable polyethylene mulch film material disclosed in CN109824962A is to mix modified polyethylene, modified meat and bone meal, modified polylactic acid, and modified straw in a mass ratio of 45:32 - 50:28 - 35:29 - 37, and then extrude and pelletize through high-speed mixing to make the mulch film. The modified polylactic acid is the main component that endows the mulch film with degradability, and the meat and bone meal, potassium silicate, urea, and ammonium lignosulfonate form organic and inorganic composite nutrient components to improve the overall degradation performance of the plastic. However, the content of its modified polyethylene is below 33%, and the degradation rate is tested according to the ISO846 standard (a method for measuring the deterioration of plastics by measuring the mass change of specimens, and its purpose is not to determine the biodegradability of plastics). The degradation rate of Example 1 can reach 83.1%. An environmentally friendly ECO biodegradable plasticizer for eating plastics and its production method disclosed in CN111138760A uses 30 - 50 parts of polypropylene, 20 - 30 parts of biodegradable material polycaprolactone, 10 - 15 parts of photo-degradable material stearic acid amide, 5 - 10 parts of erucic acid amide, and stearic acid and palmitic acid. Among them, stearic acid and palmitic acid promote the growth of microorganisms. It is a degradable plastic that combines photo-degradation and biodegradation. This ECO biodegradable plasticizer for eating plastics is added to the product at an addition amount of 1 - 5%. It is claimed that it can be completely degraded in 6 - 12 months under natural environmental conditions. However, this document does not provide detection methods and data. Therefore, based on different understandings of complete degradation at different times, it is impossible to determine whether it is true complete degradation or degradation into microplastics. The degradable plastic disclosed in CN102875853A is made by mixing 25 - 33% of superfine starch, 10 - 18% of superfine plant powder, 15 - 45% of synthetic degradable resins such as polylactic acid, 10 - 22% of synthetic resin, and various additives, and then extruding to make degradable particles. Among them, the modified superfine starch and superfine plant powder are used as the main biodegradable components, and polylactic acid is also a biodegradable plastic. The content of the biodegradable components is as high as more than 45%. It is claimed that the mass loss rate is ≥20% after being filled in the soil for 30 days under natural conditions, and it can be degraded into powder after being discarded outdoors for 90 days. However, the detection method is not disclosed. Therefore, it is not clear whether the weight loss is caused by deterioration or decomposition into methane or carbon dioxide. The common feature of the above-mentioned degradable plastics is that the content of polyethylene or polypropylene only accounts for 10 - 33%. They are still mainly based on degradable materials, and it is still uncertain whether their weight loss or degradation includes the degradation of PP and PE, or only the degradation of the biodegradable components therein. Moreover, with a low content of PP and PE and a high content of biodegradable components, the cost is still relatively high, and the comprehensive performance is difficult to reach the same performance as polyethylene and polypropylene plastics, so their use is restricted.

[0006] In recent years, scientists have isolated several strains from different ecological environments such as soil, landfill sites, the ocean, and the guts of insects that can grow using PE or PP as the sole carbon source. These microorganisms show biodegradation effects on resins such as PE and PP that were previously considered non-degradable. Such microorganisms include bacteria of the genus Pseudomonas AKS2, Rhodococcus C208, Bacillus sphaericus, Bacillus cereus, Pseudomonas sp., and Arthrobacter sp., Kocuria palustris M16, Bacillus pumilus M27, and Bacillus subtilis H1584, etc. Some monooxygenases, peroxidases, and laccases have been found to have the ability to oxidatively degrade PE, but the degradation mechanism and process are still under study. In addition, some researchers have used infrared spectroscopy to detect the functional groups and structures of PE films buried in soil for 100 days. A weak peak appeared at a wavelength of 1733 cm-1, indicating that carbonyl groups had appeared on the PE film due to oxidation, and it is a consensus that carbonyl groups are related to the degradation of plastics. These studies have revealed that PE has biodegradation potential in the natural environment, rather than being non-degradable as traditionally thought. Therefore, someone proposed the idea of adding such microorganisms to plastics, but no industrial products have emerged. The reason is that industrial plastic products are not mixed with microorganisms like in the laboratory, but go through a melting and extrusion process, and the melting temperature is sufficient to inactivate these microorganisms.

[0007] In addition, in order to ensure that plastic products do not deteriorate in performance due to natural degradation during normal use, the controllability of degradation must be considered. Otherwise, while solving the problem of white pollution, due to the shortening of the product service life, the consumption of plastic products will inevitably increase, thus increasing the harm of microplastics that have not been truly degraded to the environment and biological health, which is a negative factor.

[0008] As a plastic product processing enterprise, the applicant has, in the past fifteen years, cooperated with East China University of Science and Technology, China University of Petroleum, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Nanyang Technological University in Singapore and other units to solve the problem of white pollution. The applicant has been committed to the research on the microbial degradation conditions and environment of PE, PP, etc. in the soil environment, as well as the industrial research of such technologies and the drafting of industry standards, and has achieved certain results, thus obtaining the present invention. Summary of the Invention

[0009] Aiming at the problem of the difficult degradation of high molecular polymer plastics such as PE and PP in the soil environment, the purpose of the present invention is to provide an anaerobic degradation composite yeast agent for degrading plastics and a production method. The present invention can change the ecological environment for degrading plastics in the natural environment, improve the anaerobic degradation process and performance of plastics in the natural environment, and maintain the cost and performance advantages of the plastic base material with a small addition amount.

[0010] To achieve the first object of the present invention, the present invention provides an anaerobic degradation composite yeast agent for biodegradable plastics, comprising components in the following mass percentages:

[0011]

[0012] Further, in a preferred embodiment, it further contains nano-aerosil with a mass percentage of 7-12%. The particle size of the nano-aerosil does not exceed 100 nm, the specific surface area per gram is 200 square meters, and it is hydrophilic. In the present invention, the hydrophilicity and high specific surface area mainly function to cause microbial aggregation, and of course, it can also simultaneously act as a filler for enhancing and toughening.

[0013] Further, in a preferred embodiment, it further contains ferrous sulfate and / or ferrous gluconate with a mass percentage of 3-10% as nutrient agents required by microorganisms.

[0014] The nitrite can be one of sodium nitrite, potassium nitrite, calcium nitrite, ammonium nitrite, etc., or a mixture of several of them.

[0015] The biodegradable resin carrier can be one or a mixture of several of existing biodegradable resins such as PBAT, PHA, PLA, PHB, etc.

[0016] The nano-starch is mung bean starch modified by soaking in weak acid or weak alkaline sodium chloride solution and then drying.

[0017] As the most preferred embodiment, the composite yeast agent of the present invention comprises components in the following mass percentages:

[0018]

[0019]

[0020] To achieve the second object of the present invention, a production method of the above composite yeast agent is also provided, and its steps are as follows:

[0021] (1) Dispersibility treatment: Grind PLA into nanoscale, add nano-starch and mix evenly, and then add titanate and anhydrous ethanol for grinding treatment;

[0022] (2) Centralization treatment: First, mix carbamide with the material treated by the dispersion treatment in step (1), then add white oil and mix evenly, and then add aerosil for uniform mixing to carry out centralization protection;

[0023] (3) Structured processing: Fenvalerate, nitrite, and ammonium molybdate are respectively ground into nano-scale powders, then a part of the biodegradable resin carrier powder is added and ground and mixed evenly; then nano-calcium carbonate is added and mixed evenly to construct the material structure;

[0024] (4) Carrier implantation: The materials obtained from the centralized processing in step (2) and the structured processing in step (3) are added with the remaining biodegradable resin carrier with a particle size less than 10 microns and plastic additives, and mixed evenly;

[0025] (5) Plasticization and granulation: The mixture in step (4) is extruded and granulated.

[0026] Preferably, in step (1), the grinding of PLA is carried out under cryogenic conditions at -10 to -5 °C. Low temperature helps to weaken the van der Waals force between the molecules of the PLA material and increase brittleness, thus making it easier to grind.

[0027] Preferably, in step (2), the carbamide is first dehumidified with dry air at 12 to 15 °C and then mixed with the materials obtained from the dispersion treatment in step (1) in a dry environment at 20 to 22 °C to avoid the absorption of moisture, dissolution, and decomposition of the carbamide.

[0028] Preferably, in step (3), trace elements such as manganese, zinc, cobalt, copper, molybdenum, nickel, and selenium required for the growth of microorganisms can also be added.

[0029] In this application, the role of nano-starch is different from that of the modified starch in starch-based biodegradable plastics. The starch used in starch-based biodegradable plastics is modified. Through modification, first, the glass transition temperature of the starch is reduced to achieve the transformation from the crystalline state to the amorphous state to achieve thermoplasticity. Second, the hydrophilic starch is modified to be hydrophobic to enhance the compatibility with resins such as PLA. Both the starch and PLA in this application are used as attractants for anaerobic microorganisms and become nutrients and adsorption centers for microorganisms in nature (soil, water). It is necessary to maintain the hydrophilicity and high specific surface area of the nano-starch. Therefore, in this application, the nano-starch without the qualifier "modified" refers to starch that has not undergone conventional hydrophobic modification and plasticization modification to distinguish it from the modified starch in starch-based biodegradable plastics in the prior art.

[0030] Preferably, the nano-starch is mung bean starch modified by soaking in a weak acid or weak alkaline sodium chloride (2 - 5% wt) solution. Here, the modification is not the traditional hydrophobic and compatibilizing modification. Specifically, it is soaked in a weak acid (pH 6 - 7) or weak alkaline (pH 7 - 8) sodium chloride (2 - 5% wt) solution for 3 - 5 days and then dried to make the properties of the mung beans tend to be mild and balance the balanced development of anaerobic microorganisms.

[0031] PLA and nano-starch are treated with titanate and absolute ethanol to increase the binding (affinity) performance with other polar materials.

[0032] In the present invention, the carbamide provides a nitrogen source and energy for the growth of microorganisms. Importantly, the decomposed ammonia can adjust the environmental pH value to maintain the microbial diversity.

[0033] Nano calcium carbonate is used as an inorganic nano filler in plastics to improve the physical and mechanical properties and processing properties of plastics. Similarly, due to the functional groups and charges on the surface of nano calcium carbonate, it not only easily agglomerates, but also is difficult to disperse when mixed with resin due to its strong hydrophilicity. Therefore, nano calcium carbonate used as a filler in conventional plastics needs to be pretreated, such as being treated with coupling agents, polymer coating, or organic surface treatment. In this application, mainly taking advantage of the hydrophilicity and high specific surface area of nano calcium carbonate, in the soil and water environment, the dissolved calcium ions provide essential elements for the life activities of microorganisms, promoting the growth and metabolism of microorganisms during the initial implantation and enrichment stages of microorganisms. Since calcium carbonate is insoluble, and due to the control of the dosage and the isolation effect of the resin, the ion release is slow and it will not effectively inhibit anaerobic microorganisms.

[0034] Since the composite yeast of this application is pre-made into particles and added to PP, PE, etc. to form degradable plastics at a dosage of no more than 5% (wt) to form a microbial-induced active center, nano starch and nano calcium carbonate are not pretreated to maintain their hydrophilicity and a certain degree of agglomeration. However, in order not to affect the processability and physical and mechanical properties of the degradable plastics, a certain amount and type of plastic auxiliaries such as dispersants and compatibilizers are still required, and the carrier also uses a biodegradable resin.

[0035] The present invention also provides an anaerobic biodegradable plastic, which contains 1-5% by mass of the aforementioned composite yeast agent in a synthetic resin substrate.

[0036] The synthetic resin substrate is one or a mixture of more than one of PE, PP, PVC, PUR, PET, PLA, PHA, PHB, PBAT, PBS, PA, ABS, PS, and EPS resins.

[0037] The composite yeast agent of the present invention is added to a synthetic resin substrate to form an anaerobic biodegradable plastic. When the plastic is discarded into the environment, such as buried in the soil, deposited in water bodies, the composite yeast dispersed in the plastic products absorbs moisture in the environment and adsorbs microorganisms. While providing the nutrients and energy required for the growth and metabolism of microorganisms, an appropriate amount of fenpropathrin and nitrite can inhibit the growth and metabolism of miscellaneous bacteria, and promote the growth of degradable microorganisms such as Pseudomonas and Bacillus. In particular, ammonium molybdate has a promoting effect on the microorganisms in the process of acid production and gas production. By forming an ecological environment favorable for anaerobic degradation microorganisms, the anaerobic microbial degradation activity can be improved, and the complete biodegradation of difficult-to-degrade plastics such as PP and PE in the natural environment can be achieved. Moreover, the composite yeast agent is made into an additive masterbatch, which is easy to control the addition amount according to the needs of the degradation cycle length, so as to achieve controllable anaerobic degradation. More importantly, anaerobic degradation also realizes that the degradable plastic of the present invention will not accelerate degradation under normal use conditions, and its aging performance is equivalent to that of the resin matrix of the plastic, ensuring the physical and mechanical properties. Detailed implementation mode

[0038] The following further describes the present invention in detail with reference to examples.

[0039] The following further illustrates the present invention with specific examples to help understand the content of the present invention.

[0040] I. Examples of composite yeast agent

[0041] The components and component contents of Examples 1-6 of the composite yeast agent are shown in Table 1

[0042] Table 1 Components and mass percentage contents of the composite yeast agent in Examples 1-6

[0043]

[0044]

[0045] The preparation methods of the above Examples 1-6 are divided into five steps, namely: 1. Dispersibility treatment; 2. Centralization treatment; 3. Structuring treatment; 4. Carrier implantation treatment; 5. Plasticizing granulation, specifically.

[0046] 1. Dispersibility treatment

[0047] 1) Grind PLA particles into nanoscale at -10 to -5 °C; soak nano mung bean starch in sodium chloride (2-5% wt) with pH 6.5 for 3-5 days, dry it, add it to the nano PLA powder, and then uniformly mix and grind for 5 minutes to obtain a nano composite material;

[0048] 2) Add titanate with a particle size less than 5 microns to the above nano composite material, and stir and disperse it evenly in a high-speed mixer;

[0049] 3) Add absolute ethanol and grind at a high speed three times at a low temperature of -10 to -5 °C for 3 minutes each time, with a 1-hour interval between each time, to conduct a pretreatment chemical reaction; form a dispersive treatment material.

[0050] 2. Centralization treatment

[0051] 1) Dehumidify urea with dry air at a temperature of 12 - 15 °C for 2 hours;

[0052] 2) Mix the dehumidified urea and the dispersive treatment material obtained above at a low speed for 25 - 30 minutes in a dry environment at 20 - 22 °C; then add a small amount of white oil and mix evenly for 5 minutes;

[0053] 3) Add fumed silica and mix evenly at a medium speed in a clockwise direction for 10 minutes at 18 - 20 °C to conduct centralization protection.

[0054] 3. Structuring treatment

[0055] 1) Accelerator protection treatment: Grind fenpropathrin, nitrite, ferrous sulfate, ferrous gluconate, etc. into nano-scale powders at a low temperature (-10 to -5 °C) respectively; then mix evenly in proportion and add them to the powder of PBAT resin substrate, and grind and mix evenly at a low temperature for 30 minutes;

[0056] 2) Add nano-calcium carbonate and mix evenly at a high speed three times at room temperature for 2 minutes each time, with a 30-minute interval between each mixing, to structure the material structure;

[0057] 4. Carrier implantation

[0058] 1) Add the above-mentioned structured mixed material, a small amount of PBAT carrier powder with a particle size less than 10 microns, and related plasticizers and compatibilizer additives, and mix evenly at a high speed at a low temperature for 10 minutes;

[0059] 2) Add the filler and mix evenly at a low speed at room temperature for 30 minutes;

[0060] 3) Add the remaining PBAT powder and mix evenly at a high speed at a low temperature for 15 minutes;

[0061] 5. Plasticizing and pelletizing

[0062] 1) The preheating temperature of the twin-screw extruder is 190 - 230 °C, and the rotation speed is 135 - 230 r / min. Conduct extrusion pelletizing to obtain a composite yeast agent.

[0063] II. Degradation experiment

[0064] The components and contents of Comparative Examples 1 - 3 are shown in Table 2

[0065] Table 2 Components and mass percentage contents of Comparative Examples 1 - 3

[0066]

[0067]

[0068] The preparation methods of Comparative Examples 1-3 refer to Examples 1-6. For the components not included, the corresponding steps need to be omitted in the preparation method, and the comparative composite additives of Comparative Examples 1-3 are obtained.

[0069] For Comparative Example 4, according to the components and mass percentages of Comparative Example 1, but the preparation method is that after mixing all components, directly plasticize and granulate to obtain the composite additive of Comparative Example 4.

[0070] Add the composite yeast agents of Examples 1-6 to HDPE, and according to the blown film process, form a biodegradable plastic film containing 3% of the composite yeast agent. Add the composite additives of Comparative Examples 1-4 to HDPE in the same way to form a plastic film containing 3% of the composite additive.

[0071] 1. Anaerobic degradation detection

[0072] According to "Determination of the ultimate anaerobic biodegradability of plastics under high-solid composting conditions - Method for analyzing and measuring the evolved biogas" (GBT33797-2017 or ASTM D5511), detect the degradation rates of the degradable plastic films of Examples 1-6 and Comparative Examples 1-4. This method is used to determine the decomposition rate of anaerobic decomposition, that is, the percentage of the carbon content in the test material and the carbon dioxide and methane converted after its degradation is used as the degradation rate. The measurement results are shown in Table 2 below:

[0073] Table 2 Anaerobic degradation rates of different materials (%)

[0074] Number of days 30 60 90 120 150 Example 1 1.4％ 3.7％ 7.5％ 11.3％ 15.2％ Example 2 1.2％ 2.8％ 3.7％ 5.2％ 6.9％ Example 3 1.1％ 2.9％ 3.8％ 5.4％ 7.2％ Example 4 1.0％ 2.4％ 3.2％ 4.1％ 5.2％ Example 5 1.1％ 2.7％ 3.6％ 4.7％ 6.6％ Example 6 1.3％ 3.2％ 5.8％ 8.6％ 10.1％ Comparative Example 1 1.1％ 2.0％ 2.6％ 2.7％ 2.8％ Comparative Example 2 1.2％ 2.2％ 2.9％ 3.6％ 4.4％ Comparative Example 3 1.1％ 2.1％ 2.7％ 2.9％ 3.2％ Comparative Example 4 0.7％ 1.5％ 2.1％ 2.6％ 3.0％

[0075] It can be seen from Table 2 that the degradation rates of Comparative Examples 1-4 are basically the degradable PLA and starch contents. The degradation rates of Examples 1-6 under anaerobic conditions at 150 days are significantly better than those of Comparative Examples 1-4, and are significantly higher than the addition amount of the composite yeast in the plastic samples, indicating that obvious degradation of HDPE has occurred. Among Examples 1-6, the degradation rate of Example 1 reaches 15.2% at 150 days, with the highest degradation efficiency. The degradation rate of Example 4 is the lowest, indicating that nano-aerosil has a promoting effect on degradation. The degradation rate of Example 6 is lower than that of Example 1 but significantly higher than that of Examples 2-5, and ferrous gluconate is better than ferrous sulfate.

[0076] 2. Apparent detection of anaerobic degradation

[0077] After 150 days of degradation, the plastics of Example 1 and Comparative Example 1 were taken out, cleaned, dried with hot air at 60 °C, weighed, and the weight change before and after degradation was compared to calculate the weight loss rate. The weight loss rate of Example 1 was 14.6%, and the weight loss rate of Comparative Example 1 was 2.7%. The appearance of the plastics was inspected. The plastic film of Example 1 was apparently intact without holes, while the plastic film of Comparative Example 1 had micropores, indicating that the degradation of Example 1 occurred on the entire surface of the plastic film rather than local deterioration. In Comparative Example 1, only the biodegradable components such as PLA and PBAT were degraded locally, and HDPE was not degraded.

[0078] 3. Aerobic degradation detection

[0079] The anaerobic degradation plastic film of Example 1 was tested for the degradation rate under aerobic conditions according to GB / T 19277.1-2011 Determination of the ultimate aerobic biodegradability of materials under controlled composting conditions - Method by measuring the evolved carbon dioxide. Obviously, the degradation rate after 90 days was 2.6%, which was significantly lower than the anaerobic degradation rate, proving that under aerobic conditions, only PBAT and PLA, which are inherently biodegradable materials, were degraded, and HDPE was not degraded. Such an effect is beneficial to maintaining the durability of the properties of degradable plastics under normal use.

[0080] 4. Detection of the effect of different yeast agent addition amounts on the mechanical properties of plastic films

[0081] As the addition amount of yeast increases, the degradation rate of plastic products will increase. However, it will also have an adverse effect on the mechanical properties of plastic products, especially plastic film products such as packaging bags. To determine the reasonable addition amount of the yeast agent, the yeast agent in Example 1 was added to HDPE and blown into plastic films. The addition amounts were 1%, 3%, 5%, and 7% by mass percentage, and their tensile strengths were measured according to GB / T1040.1-2018. The results are shown in Table 3.

[0082] Table 3 Mechanical properties of HDPE 60-micron films with different yeast agent addition amounts

[0083] Yeast agent content 1％ 3％ 5％ 7％ Transverse tensile strength 16.1 16.7 17.4 11.6 Longitudinal tensile strength 13.5 14.1 14.4 10.2

[0084] As can be seen from Table 3, after the addition amount exceeds 5%, the mechanical properties of the plastic deteriorate significantly. Therefore, in the present invention, 1-5% is taken.

[0085] Those of ordinary skill in the art can understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An anaerobic degradation composite yeast agent for biodegradable plastics, comprising components with the following mass percentages:

2. The composite yeast agent according to claim 1, characterized in that: It also contains nano-aerosil with a mass percentage of 7-12%.

3. The composite yeast agent according to claim 1, characterized in that: It also contains ferrous sulfate and / or ferrous gluconate with a mass percentage of 3-10%.

4. The composite yeast agent according to claim 1, characterized in that: The nitrite is one or a mixture of several of sodium nitrite, potassium nitrite, calcium nitrite, ammonium nitrite, etc.

5. The composite yeast agent according to claim 1, characterized in that The biodegradable resin carrier is one or a mixture of several of PBAT, PHA, PLA, and PHB.

6. The composite yeast agent according to claim 1, characterized in that: The nano-starch is mung bean starch modified by soaking in a weak acid or weak alkaline sodium chloride solution and then drying.

7. The composite yeast agent according to claim 1, characterized in that, It includes components with the following mass percentages:

8. A production method of the composite yeast agent according to any one of claims 1-7, the steps are as follows: (1) Dispersibility treatment: Grind PLA into nanoscale, add nano starch and mix evenly, then add titanate and anhydrous ethanol for grinding treatment; (2) Centralization treatment: First, mix carbamide with the material treated by step (1) of dispersion treatment, then add white oil and mix evenly, and then add fumed silica and mix evenly for centralization protection; (3) Structuring treatment: Grind fenpropathrin, nitrite, and ammonium molybdate into nanoscale powders respectively, then add biodegradable resin carrier powders and grind and mix evenly; then add nano calcium carbonate and mix evenly to construct the material structure; (4) Carrier implantation: Add the materials treated by step (2) of centralization treatment and step (3) of structuring treatment, add biodegradable resin carriers with a particle size less than 10 microns and plastic additives, and mix evenly; (5) Plasticizing and pelletizing: Extrude and pelletize the mixture in step (4).

9. The production method according to claim 8, characterized in that: In step (1), the grinding of PLA is carried out by cryogenic grinding under the condition of -10 to -5°C.

10. The production method according to claim 8, characterized in that: In step (2), the carbamide needs to be dehumidified with dry air at 12 to 15°C first, and then mixed with the material dispersed in step (1) in a dry environment at 20 to 22°C.

11. The production method according to claim 8, characterized in that: In step (3), trace elements are also added.

12. An anaerobic biodegradable plastic, which is added with 1-5% by mass of the composite yeast agent according to any one of claims 1-7 in a synthetic resin substrate.

13. The anaerobic biodegradable plastic according to claim 12, wherein The synthetic resin substrate is one or a mixture of several of PE, PP, PVC, PUR, PET, PLA, PHA, PHB, PBAT, PBS, PA, ABS, PS, and EPS resins.

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