Degradable master batch for soil improvement as well as preparation method and application of degradable master batch

Abstract

The invention discloses a degradable master batch for soil improvement as well as a preparation method and application thereof, and belongs to the technical field of high polymer materials. The degradable master batch is prepared from the following raw materials in parts by weight: 20-30 parts of modified bamboo fiber powder; 20 to 30 parts of polyethylene; 3-5 parts of a compatilizer; 1-3 parts of a cross-linking agent; 1-2 parts of a lubricant; 1 to 10 parts of soybean oil; the modified bamboo fiber powder is obtained by dipping bamboo fiber powder in citric acid modified calcium bentonite; the compatilizer is a tricarboxylic acid substance; the raw materials are easy to obtain, the composition is simple, the cost is low, the prepared plastic product can directly enter soil to be degraded after being discarded, and the degraded decomposer can also achieve the effects of improving the water-retaining property and the air permeability of the soil, reducing fertilizer loss, slowly releasing nutrients and improving the soil environment after entering the soil.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials, and particularly relates to a degradable master batch for soil improvement and a preparation method and application thereof. BACKGROUND

[0002] At present, most of the plastic products used in various industries such as agricultural films, shopping bags, packaging bags, films, pipes, plates, food packaging, household appliances and the like are produced by using high molecular polymers as main materials or fillers.

[0003] Polyethylene (PE) is one of the most widely used plastic films and packaging materials at present, which has good flexibility and tensile property, can be made into thin and tough film, is suitable for packaging irregular-shaped articles, can maintain good toughness at low temperature and is not easy to be brittle, is suitable for packaging frozen food, has good resistance to common chemicals such as water, acid, alkali and salt, is not easy to be corroded, and is suitable for packaging liquid or slightly corrosive articles. In addition, the molecular structure of PE is dense, the barrier property to water vapor is strong, the moisture absorption of the packaged articles can be effectively prevented, and the film with different thicknesses can be made through blowing, casting or hot pressing process, the production efficiency is high, and the cost is low.

[0004] However, the traditional PE is extremely difficult to degrade in the natural environment, and is easy to cause white pollution after being discarded. Although some degradable PE materials have been disclosed in the prior art, the cost of these materials is high and the degradation conditions are harsh, and a specific temperature, humidity and microbial environment are required.

[0005] For example, Chinese Patent CN 110105652 A discloses a photodegradable PE film and a preparation method thereof, wherein the photodegradable PE film is prepared from raw materials including the following components in mass percentage: high-pressure low-density low-density polyethylene (LDPE) 55-80%, linear low-density low-density polyethylene (LDPE) 19-42%, photosensitive master batch 0.01-3%, and the preparation adopts a film blowing process and the processing temperature is not more than 175 DEG C; the photosensitive master batch includes 0.1-5wt% diatomite, 20-25wt% stearate and 70-79wt% low-density polyethylene (LDPE) alcohol. The photodegradable PE film disclosed in the patent needs to be exposed to light environment to realize degradation, and the environmental requirement is relatively strict.

[0006] Chinese patent CN110551334A discloses a kind of full biodegradable PE material and its preparation method, and application, and preparation raw material includes: PE 70~92 parts, biodegradable agent 0.5~10 parts, organic resin 1~5 parts and auxiliary agent 2~15 parts by weight, the biodegradable agent includes biological expansion agent, glutamic acid composition and biological enzyme, the weight ratio of the biological expansion agent, the glutamic acid composition and the biological enzyme is 0.01~5:0.1~10:1, the glutamic acid composition contains glutamic acid, glutaric acid and polylactic acid, the auxiliary agent at least includes opening agent, slip agent and antistatic agent. The full biodegradable PE material provided by this patent needs to rely on glutamic acid composition and biological enzyme to attract microorganisms in soil to adhere to full biodegradable PE material to realize its biodegradation. However, the cost of glutamic acid composition and biological enzyme is relatively high, and the economic benefit of such full biodegradable PE material is poor.

[0007] Chinese patent CN113683873 A discloses a kind of full biodegradable PE material and its preparation process, including the following components by weight: degradation resin 60-100 parts, plasticizer 1-5 parts, dispersing agent 2-12 parts, antioxidant 0.5-1.5 parts and ultraviolet absorber 0.3-0.6 parts;The degradation resin is prepared by the following steps: A1: lactic acid, zinc powder is added to a three-necked flask, stirring gradually, until no distillate is evaporated, the distillate is collected and cooled to form a solid, the solid is washed, recrystallized, and then dried to constant weight, to obtain intermediate 1;A2: intermediate 1, glycerol and stannous octoate solution are added to a three-necked flask, nitrogen is introduced for protection, stirring gradually, then constant temperature stirring reaction, then cooling and continuing constant temperature stirring reaction, after the reaction is completed, the reaction product is cooled to form a solid, then the solid is added to chloroform, then reprecipitated with methanol, filtered, and the filter cake is dried to constant weight to obtain intermediate 2;A3: intermediate 2, pentaerythritol and deionized water are added to a three-necked flask, nitrogen is introduced for protection, constant temperature stirring reaction, then heating and continuing stirring reaction, after the reaction is completed, the reaction product is rotary evaporated, dried to obtain intermediate 3;A4: lignin, formaldehyde solution and sodium hydroxide solution are added to a three-necked flask for constant temperature stirring reaction, after the reaction is completed, the reaction product is cooled to room temperature, then hydrochloric acid solution is added dropwise to form a precipitate, filtered, the filter cake is washed to neutral, then dried to constant weight to obtain intermediate 4;

[0008] A5: Intermediate 4, dimethyl sulfoxide is added to a four-necked flask and stirred, then 1-methylimidazole is added dropwise while stirring, after the dropwise addition is completed, maleic anhydride is added, then the temperature is raised while stirring, then constant temperature stirring reaction is continued, after the reaction is completed, the reaction product is cooled to room temperature, the pH of the reaction product is adjusted, filtration is performed, the filter cake is washed, then oven dried to constant weight to obtain intermediate 5; A6: Intermediate 3, intermediate 5, p-toluenesulfonic acid and tetrahydrofuran are added to a three-necked flask, nitrogen is introduced for protection, constant temperature stirring reaction is performed, after the reaction is completed, the reaction product is cooled to room temperature, the reaction product is added to petroleum ether, filtration is performed, the filter cake is washed, then oven dried to constant weight to obtain a degradation resin. The degradation resin in the patent needs to be prepared by a complex process, and the implementation difficulty is large. SUMMARY

[0009] To solve the above technical problems, the application provides a degradable master batch for soil improvement and a preparation method and application thereof, raw materials of which are easy to obtain, composition is simple, and cost is low, plastic products prepared therefrom can directly enter soil for degradation after damage and reach the service life, and decomposition products after degradation can also play a role in improving soil water retention and air permeability, reducing fertilizer loss, slow-release nutrients and improving soil environment.

[0010] To achieve the above object, the technical scheme adopted by the application is as follows:

[0011] The application provides a degradable master batch for soil improvement, which is prepared from the following raw materials by weight:

[0012] Modified bamboo fiber powder: 20-30 parts;

[0013] Polyethylene: 20-30 parts;

[0014] Compatibility agent: 3-5 parts;

[0015] Crosslinking agent: 1-3 parts;

[0016] Lubricating oil: 1-2 parts;

[0017] Soybean oil: 1-10 parts;

[0018] The modified bamboo fiber powder is obtained by impregnating bamboo fiber powder with calcium-based bentonite modified by citric acid. The calcium-based bentonite has a neutral pH value of 6-7 after modification, so it can be more fully impregnated with bamboo fiber powder. The modified calcium-based bentonite has higher density and higher bonding density with bamboo fiber, has stronger adsorption to carbon-based substances and fertilizers in soil, can effectively reduce the loss of carbon and fertilizers in soil, and the sodium-based bentonite has much lower density and adsorption than the calcium-based bentonite.

[0019] The compatibilizer is a tricarboxylic acid substance.

[0020] The polyethylene is any one or more of LDPE, HDPE, LLDPE.

[0021] Further, the preparation method of the modified bamboo fiber powder comprises the following steps:

[0022] (1) uniformly dispersing calcium bentonite in a dimethylformamide solution, then adding citric acid, keeping at 140-160℃ under nitrogen for 8-12h, and obtaining the citric acid modified calcium bentonite through filtering, washing and drying;

[0023] (2) uniformly dispersing bamboo fiber fine powder in deionized water, adding the citric acid modified calcium bentonite and a dispersant, mixing and dipping, and then drying to obtain the modified bamboo fiber powder through ultrasonic treatment.

[0024] In step (1), the mass ratio of the calcium bentonite to the citric acid is 1-7:1.

[0025] In step (1), the particle size of the calcium bentonite is 20-45nm, and the smaller the particle size, the better the dispersibility in the bamboo fiber.

[0026] In step (2), the mass ratio of the bamboo fiber fine powder, the citric acid modified calcium bentonite and the dispersant is 20-25:15-20:0.85-1.

[0027] In step (2), the dispersant is disodium ethylenediaminetetraacetate, which has the effects of antioxidation, corrosion prevention and stabilization of product structure and texture.

[0028] In step (2), the mixing and dipping time is 0.5-1.5h, and the ultrasonic treatment condition is 50-100kHz frequency and 8-10min.

[0029] In step (2), the ultrasonic treatment condition is 50-100kHz frequency and 8-10min.

[0030] The particle size of the modified bamboo fiber powder is more than 600 mesh, and such particle size has better dispersibility in PE.

[0031] The compatibilizer is any one or more of citric acid, isocitric acid, aconitic acid, agaric acid and tricarboxylic acid.

[0032] The crosslinking agent is any one or more of phthalic anhydride, maleic anhydride and pyromellitic anhydride.

[0033] The lubricant is any one or more of fatty acid esters, fatty acid amides, low-density polyethylene (LDPE) wax and methyl silicone oil.

[0034] The application further provides a preparation method of the degradable master batch for soil improvement, which comprises the following steps: sequentially feeding modified bamboo fiber powder, polyethylene, a compatibilizer, a crosslinking agent, a lubricant and soybean oil into a continuous internal mixer through a vacuum feeder, stirring and mixing at 90-110 DEG C for 30-40 min, and then performing melt extrusion and granulation, so that the degradable master batch for soil improvement is obtained.

[0035] The temperature of the melt extrusion and granulation is 130-180 DEG C.

[0036] The application further provides application of the degradable master batch for soil improvement in preparation of easily degradable plastic products.

[0037] The degradable master batch for soil improvement provided by the application takes modified bamboo fiber powder and polyethylene as main raw materials, the use of a large amount of modified bamboo fiber powder greatly reduces the production cost of the polyethylene master batch while ensuring the strength of the master batch product, and the biomass component contained in the modified bamboo fiber powder can generate a large amount of microorganisms after contacting the soil, and these microorganisms can biodegrade the plastic product made of the degradable master batch, after biodegradation, the calcium-based bentonite modified by citric acid contained in the plastic product made of the degradable master batch can enter the soil, which can effectively improve the water retention and air permeability of the soil, especially for sandy soil, and can reduce the loss of fertilizer in the soil, release nutrients, and achieve the effect of improving the soil environment.

[0038] The degradable master batch for soil improvement provided by the application solves the following problems:

[0039] 1. Compatibility problem of bamboo fiber powder and polyethylene: bamboo fiber has polarity and hydrophilicity, while polyethylene belongs to plastic and has non-polarity and hydrophobicity, due to the above differences, the bamboo fiber cannot be chemically compatible with the polyethylene, the interface adhesion of the bamboo fiber and the polyethylene is poor, and the performance of the bamboo fiber polyethylene composite material is low. To solve this problem, the calcium-based bentonite is first modified by citric acid, and then the calcium-based bentonite modified by citric acid and the bamboo fiber are immersed in deionized water, so that the interface compatibility of the bamboo fiber and the polyethylene is greatly improved.

[0040] Citric acid is a polycarboxylic organic acid, and contains three carboxyl groups and one hydroxyl group in the molecular structure, and has a tridentate or polydentate chelating structure. The carboxyl group of citric acid dissociates H + to form a negatively charged carboxyl ion, which can chelate with Ca 2+A chelation reaction occurs, forming a stable cyclic chelate, calcium citrate. This process consumes free Ca. 2 + This weakens the electrostatic attraction between calcium-based bentonite particles, making it easier to separate the originally agglomerated particles. Furthermore, when citric acid or its chelates are adsorbed on the surface of bentonite particles, the multiple polar groups and carbon chains in its molecular chain extend into the solution, forming a three-dimensional barrier that prevents calcium-based bentonite from agglomerating. This greatly improves the dispersibility of calcium-based bentonite in solution, enabling it to better fill the micropores and grooves on the surface of bamboo fiber. This reduces the void defects in bamboo fiber during the composite process with PE. In conjunction with the use of compatibilizers, it significantly enhances the interfacial compatibility between bamboo fiber and polyethylene.

[0041] The compatibilizer in this invention is a tricarboxylic acid (TCA) compound. TCA has a similar chemical structure to maleic anhydride-grafted polyethylene (MPPE). Although its effect on improving the adhesion between ordinary bamboo fiber and polyethylene is slightly inferior to that of MPPE, by modifying the bamboo fiber with an appropriate amount of citric acid-modified calcium bentonite, the modified bamboo fiber becomes more sensitive to the coupling effect of TCA, thus achieving a coupling effect comparable to or even superior to that of MPPE. This is because the interaction between the TCA and the hydroxyl groups of the modified bamboo fiber provides a better interfacial region. Furthermore, the TCA also has secondary interactions with the modified bamboo fiber; its hydrogen bonds promote the formation of a hydrophobic coating on the modified bamboo fiber, thereby significantly enhancing the interfacial compatibility between bamboo fiber and polyethylene, ultimately improving the tensile strength and elastic modulus of the products produced from this degradation masterbatch.

[0042] 2. The impact of bamboo fiber powder incorporation on polyethylene performance: Direct mixing of bamboo fiber powder and polyethylene results in poor interfacial compatibility, with a greater impact on PE performance due to the increased amount of bamboo fiber powder added. This invention addresses this issue by impregnating bamboo fiber powder with citric acid-modified calcium-based bentonite, combined with a compatibilizer, significantly improving the interfacial compatibility between bamboo fiber and polyethylene. Furthermore, the use of a crosslinking agent ensures the tensile strength and elastic modulus of the soil-modified degradation masterbatch products.

[0043] 3. Processing Issues: To improve the flowability of the raw material mixture, a lubricant is used in conjunction with a tricarboxylic acid compatibilizer to improve the two-phase separation state in the composite material, and soybean oil is used in conjunction to further improve the flowability of the composite material during preparation. Soybean oil, as a plasticizer, can reduce the melt viscosity of the polymer material, improve its flowability, making the material easier to flow and fill molds during processing, thereby improving production efficiency and product quality. In addition, soybean oil can reduce friction and energy consumption during processing, reduce equipment wear, and extend equipment life. Through interaction with the polymer matrix, soybean oil can form a tighter intermolecular structure, thereby enhancing the tensile strength and impact toughness of the material. This enhancing effect is particularly significant at low temperatures, helping to improve the material's crack resistance and durability. Antioxidant components in soybean oil, such as vitamin E, can capture free radicals and inhibit oxidation reactions, thereby delaying the aging process of the material. Soybean oil is a renewable resource with a relatively low price; its use can partially replace traditional petroleum-based plasticizers and antioxidants without compromising material performance, thus reducing production costs.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] This invention provides a biodegradable masterbatch for soil improvement, using locally produced bamboo as raw material to obtain bamboo fiber powder. The raw material is readily available and inexpensive. The bamboo fiber is modified with citric acid-modified calcium-based bentonite. The modified bamboo fiber contains biomass degradation and modified calcium-based bentonite components, giving the biodegradable masterbatch for soil improvement both the biodegradability of plastic products and soil-improving properties. The degradation effect is thorough, and it exhibits good mechanical properties, thermal stability, and physical properties. The citric acid-modified calcium-based bentonite modification of bamboo fiber overcomes the uneven distribution and agglomeration issues that occur when increasing the amount of bamboo fiber used, significantly enhancing the interfacial compatibility between bamboo fiber and polyethylene, and ensuring the mechanical properties of this composite material. Its unique citric acid-modified calcium-based bentonite component can also effectively improve soil water retention and aeration, making it particularly suitable for sandy soils. Furthermore, it can reduce fertilizer loss and slow-release nutrients in the soil, achieving the effect of improving the soil environment.

[0046] The biodegradable masterbatch or its products for soil improvement provided by this invention do not produce black smoke when burned, and the powder formed after combustion is easily soluble in water.

[0047] The biodegradable masterbatch or its products for soil improvement provided by this invention are easy to store, do not require protection from light, and do not deteriorate after long-term storage. Detailed Implementation

[0048] In this invention, unless otherwise specified, all parts are in units of weight, and the equipment and raw materials used can be purchased from the market.

[0049] The bamboo was harvested in Chizhou, Anhui Province. It was 2 years old, air-dried, and had a moisture content of 8-10%.

[0050] The average particle size of calcium-based bentonite is 20–45 nm.

[0051] The manufacturers and grades of LDPE granules, HDPE granules, and LLDPE granules are Lanzhou Petrochemical 1810D, Sinopec Tianjin Petrochemical BF7000, and Zhejiang Petrochemical DFDC-7050, respectively.

[0052] The present invention will now be described in detail with reference to the embodiments.

[0053] Example 1

[0054] A biodegradable masterbatch for soil amendment is prepared from the following components in parts by weight:

[0055] Modified bamboo fiber powder: 30 parts;

[0056] LDPE granules: 25 parts;

[0057] Compatibilizer: 3 parts;

[0058] Crosslinking agent: 2 parts;

[0059] Lubricating oil: 1 part;

[0060] Soybean oil: 4 parts;

[0061] The compatibilizer is citric acid; the crosslinking agent is phthalic anhydride; and the lubricant is methyl silicone oil.

[0062] The preparation method of modified bamboo fiber powder is as follows:

[0063] (1) Add 35 parts by weight of calcium-based bentonite to 140 parts by weight of dimethylformamide and mix well. Then add 5 parts by weight of citric acid to the above solution and keep it at 150°C for 10 hours under nitrogen. After the end, filter, wash with deionized water and vacuum dry to obtain citric acid modified calcium-based bentonite powder.

[0064] (2) After crushing the bamboo, grind it into fine bamboo fiber powder with a particle size of 600 mesh or more using a grinder. Add 30 parts by weight of fine bamboo fiber powder to 150 parts of distilled water, heat to 25°C, stir at 450 r / min for 30 min, then add 35 parts by weight of citric acid modified calcium bentonite powder and 1 part by weight of disodium ethylenediaminetetraacetate dispersant, mix and impregnate for 1 hour, sonicate at 55 kHz for 8 min, and dry to obtain modified bamboo fiber powder.

[0065] The method for preparing the biodegradable masterbatch for soil improvement is as follows: LDPE granules, modified bamboo fiber powder, compatibilizer, crosslinking agent, lubricant, and soybean oil are fed into a continuous mixer in sequence through a vacuum feeder, heated to 100°C, and stirred for 35 minutes. The mixture is then discharged into a high-pressure extruder and heated to 150°C by two or three screws for extrusion granulation, thus obtaining the biodegradable masterbatch for soil improvement.

[0066] Example 2

[0067] A biodegradable masterbatch for soil amendment is prepared from the following components in parts by weight:

[0068] Modified bamboo fiber powder: 25 parts;

[0069] HDPE granules: 25 parts;

[0070] Compatibilizer: 5 parts;

[0071] Crosslinking agent: 3 parts;

[0072] Lubricating oil: 2 parts;

[0073] Soybean oil: 10 parts;

[0074] Wherein, the compatibilizer is triformic acid; the crosslinking agent is maleic anhydride; and the lubricant is fatty acid amide.

[0075] The preparation method of modified bamboo fiber powder is as follows:

[0076] (1) Add 35 parts by weight of calcium-based bentonite to 140 parts by weight of dimethylformamide and mix well. Then add 7 parts by weight of citric acid to the above solution and keep it at 150°C for 10 hours under nitrogen. After the end, filter, wash with deionized water and vacuum dry to obtain citric acid modified calcium-based bentonite powder.

[0077] (2) After crushing the bamboo, grind it into fine bamboo fiber powder with a particle size of 600 mesh or more using a grinder. Add 25 parts by weight of fine bamboo fiber powder to 100 parts of distilled water, heat to 30°C, stir at 550 r / min for 25 min, then add 30 parts by weight of citric acid modified calcium bentonite powder and 0.85 parts by weight of disodium ethylenediaminetetraacetate dispersant, mix and impregnate for 1 hour, sonicate at 50 kHz for 10 min, and dry to obtain modified bamboo fiber powder.

[0078] The method for preparing the biodegradable masterbatch for soil improvement is as follows: HDPE granules, modified bamboo fiber powder, compatibilizer, crosslinking agent, lubricant and soybean oil in the prescribed amounts are sequentially fed into a continuous mixer via a vacuum feeder, heated to 110°C, stirred and mixed for 30 minutes, and discharged into a high-pressure extruder and heated to 160°C by 2 or 3 screws for extrusion granulation, thereby obtaining the biodegradable masterbatch for soil improvement.

[0079] Example 3

[0080] A biodegradable masterbatch for soil amendment is prepared from the following components in parts by weight:

[0081] Modified bamboo fiber powder: 30 parts;

[0082] LDPE granules: 10 parts;

[0083] HDPE granules: 15 parts;

[0084] Compatibilizer: 4 parts;

[0085] Crosslinking agent: 3 parts;

[0086] Lubricating oil: 2 parts;

[0087] Soybean oil: 4 parts;

[0088] The compatibilizer is agaric acid; the crosslinking agent is pyromellitic anhydride; and the lubricant is low-density polyethylene wax.

[0089] The preparation method of modified bamboo fiber powder is as follows:

[0090] (1) Add 32 parts by weight of calcium-based bentonite to 160 parts by weight of dimethylformamide and mix well. Then add 5 parts by weight of citric acid to the above solution and keep it at 150°C for 10 hours under nitrogen. After the end, filter, wash with deionized water and vacuum dry to obtain citric acid modified calcium-based bentonite powder.

[0091] (2) After crushing the bamboo, grind it into fine bamboo fiber powder with a particle size of 600 mesh or more using a grinder. Add 30 parts by weight of fine bamboo fiber powder to 150 parts by weight of distilled water, heat to 30°C, stir at 550 r / min for 25 min, then add 32 parts by weight of citric acid modified calcium bentonite powder and 1 part by weight of disodium ethylenediaminetetraacetate dispersant, mix and impregnate for 1 hour, sonicate at 55 kHz for 8 min, and dry to obtain modified bamboo fiber powder.

[0092] The method for preparing the biodegradable masterbatch for soil improvement is as follows: LDPE granules, HDPE granules, modified bamboo fiber powder, compatibilizer, crosslinking agent, lubricant, and soybean oil are fed into a continuous mixer via a vacuum feeder and heated to 90°C. The mixture is stirred and mixed for 40 minutes, then discharged into a high-pressure extruder and heated to 130°C by two or three screws for extrusion granulation, thus obtaining the biodegradable masterbatch for soil improvement.

[0093] Example 4

[0094] A biodegradable masterbatch for soil amendment is prepared from the following components in parts by weight:

[0095] Modified bamboo fiber powder: 25 parts;

[0096] LDPE granules: 10 parts;

[0097] LLDPE granules: 15 parts;

[0098] Compatibilizer: 4 parts;

[0099] Crosslinking agent: 3 parts;

[0100] Lubricating oil: 3 parts;

[0101] Soybean oil: 5 parts;

[0102] The compatibilizer is agaric acid; the crosslinking agent is pyromellitic anhydride; and the lubricant is low-density polyethylene wax.

[0103] The preparation method of modified bamboo fiber powder is as follows:

[0104] (1) Add 30 parts by weight of calcium-based bentonite to 120 parts by weight of dimethylformamide and mix well. Then add 10 parts by weight of citric acid to the above solution and keep it at 150°C for 10 hours under nitrogen. After the end, filter, wash with deionized water and vacuum dry to obtain citric acid modified calcium-based bentonite powder.

[0105] (2) After crushing the bamboo, grind it into fine bamboo fiber powder with a particle size of 600 mesh or more using a grinder. Add 30 parts by weight of fine bamboo fiber powder to 120 parts by weight of distilled water, heat to 25°C, stir at 500 r / min for 25 min, then add 30 parts by weight of citric acid modified calcium bentonite powder and 1 part by weight of disodium ethylenediaminetetraacetate dispersant, mix and impregnate for 1 hour, sonicate at 55 kHz for 8 min, and dry to obtain modified bamboo fiber powder.

[0106] The method for preparing the biodegradable masterbatch for soil improvement is as follows: LDPE granules, LLDPE granules, modified bamboo fiber powder, compatibilizer, crosslinking agent, lubricant, and soybean oil are fed into a continuous mixer via a vacuum feeder and heated to 110°C. After mixing for 30 minutes, the mixture is discharged into a high-pressure extruder and then extruded and granulated by heating to 140°C using two or three screws to obtain the biodegradable masterbatch for soil improvement.

[0107] Comparative Example 1

[0108] Everything else is the same as in Example 1, except that the compatibilizer used therein is acrylic acid.

[0109] Comparative Example 2

[0110] The rest is the same as in Example 1, except that the preparation method of the modified bamboo fiber powder is as follows:

[0111] (1) Add 35 parts by weight of calcium-based bentonite to 150 parts by weight of deionized water and mix well. Then add 5 parts by weight of silane coupling agent KH-560. Stir at 130°C for 10 hours. After the stirring is completed, filter, wash with deionized water and vacuum dry to obtain calcium-based bentonite powder modified by silane coupling agent.

[0112] (2) After crushing the bamboo, grind it into fine bamboo fiber powder with a particle size of 600 mesh or more using a grinder. Add 30 parts by weight of fine bamboo fiber powder to 150 parts by weight of distilled water, heat to 25°C, stir at 450 r / min for 30 min, then add 35 parts by weight of calcium-based bentonite powder modified with silane coupling agent and 1 part by weight of disodium ethylenediaminetetraacetate dispersant, mix and impregnate for 1 hour, sonicate at 55 kHz for 8 min, and dry to obtain modified bamboo fiber powder.

[0113] Comparative Example 3

[0114] The rest is the same as in Example 1, except that all the soybean oil in the raw materials is replaced with an equal amount of methyl silicone oil.

[0115] Comparative Example 4

[0116] The rest is the same as in Example 1, except that the compatibilizer is changed to maleic anhydride-grafted low-density polyethylene; and the modified bamboo fiber powder is changed to bamboo fiber powder with a mesh size of 600 or higher.

[0117] Test Example 1

[0118] The masterbatches in each embodiment and comparative example were hot-pressed into a 15-micrometer thick film in a hot press, and then cut into standard strips of 20mm × 20mm for later use.

[0119] Tensile tests, bending tests, impact tests, and soil degradability tests were performed on the above samples. The tensile tests were performed in accordance with GB / T1040.1-2018 standard, with a tensile speed of 10 mm / min; the bending tests were performed in accordance with GB / T 9341-2008 standard, with a bending speed of 5 mm / min; and the impact tests were performed in accordance with GB / T1843-2008 standard.

[0120] The soil degradation test procedure is as follows: First, the initial weight of the sample is recorded. Then, the sample is placed in moist, loose soil. The sample is periodically removed to observe changes in morphology and weight. The sample is allowed to degrade under natural conditions for 90 days. After that, the sample is removed, washed, dried, and weighed. The degradation performance of the sample is evaluated based on the weight loss rate. The weight loss rate is calculated with the difference in weight before and after the initial weight as the numerator and the initial weight as the denominator. The test results are shown in Table 1.

[0121] Table 1 Test Results

[0122]

[0123] As can be seen from Table 1, the components in this invention have a significant synergistic effect. Even with the amount of modified bamboo fiber powder being almost equal to that of polyethylene, the biodegradable masterbatch product still has good comprehensive performance. This shows that the interface of the modified bamboo fiber provided by this invention can combine more hydroxyl groups, form more hydrogen bonds and covalent bonds, reduce stress concentration, and improve the strength of the composite material.

[0124] In Comparative Example 1, the performance and degradability of the masterbatch product deteriorated because the compatibilizer used was not a tricarboxylic acid substance. This shows that tricarboxylic acid substances are more effective as compatibilizers.

[0125] In Comparative Example 2, although the bamboo fiber powder was also modified with calcium-based bentonite, the performance of the masterbatch product deteriorated because the modification of the calcium-based bentonite was carried out with silane coupling agent instead of citric acid. This indicates that the bamboo fiber powder modified by this method has poor compatibility with PE.

[0126] In Comparative Example 3, after replacing all the soybean oil in the raw materials with an equal amount of methyl silicone oil, the performance of the masterbatch product deteriorated, indicating that the synergistic use of lubricant and soybean oil has a better effect.

[0127] In Comparative Example 4, although biodegradable masterbatches could still be prepared by changing the compatibilizer to maleic anhydride-grafted low-density polyethylene and the modified bamboo fiber powder to bamboo fiber powder of 600 mesh or higher, the performance of the masterbatch products was poor. This shows that while maleic anhydride-grafted low-density polyethylene can improve the compatibility between bamboo fiber powder and PE, the effect is still not as good as when tricarboxylic acid-modified calcium-based bentonite is used as a compatibilizer to impregnate and modify bamboo fiber, resulting in better compatibility between the modified bamboo fiber powder and PE.

[0128] Test Example 2

[0129] The standard samples prepared in each embodiment of Test Example 1 were incinerated, and it was observed that no black smoke was produced after incineration, and the powder residue formed after incineration was soluble in water.

[0130] The above detailed description of a biodegradable masterbatch for soil improvement, its preparation method, and its application, with reference to the embodiments, is illustrative rather than limiting. Several embodiments may be listed within the defined scope. Therefore, variations and modifications without departing from the overall concept of the present invention should be within the protection scope of the present invention.

Claims

1. A biodegradable masterbatch for soil improvement, characterized in that, The biodegradable masterbatch for soil improvement is prepared from the following raw materials in parts by weight: Modified bamboo fiber powder: 20-30 parts; Polyethylene: 20-30 parts; Compatibilizer: 3-5 parts; Crosslinking agent: 1-3 parts; Lubricant: 1-2 parts; Soybean oil: 1-10 parts; The modified bamboo fiber powder is obtained by impregnating bamboo fiber powder with citric acid-modified calcium-based bentonite. The compatibilizer is a tricarboxylic acid substance.

2. The biodegradable masterbatch for soil improvement according to claim 1, characterized in that, The preparation method of the modified bamboo fiber powder includes the following steps: (1) Calcium-based bentonite was uniformly dispersed in dimethylformamide solution, and then citric acid was added. The mixture was kept at 140-160℃ for 8-12 hours under nitrogen conditions. After filtration, washing and drying, citric acid-modified calcium-based bentonite was obtained. (2) The bamboo fiber powder is evenly dispersed in deionized water, and citric acid modified calcium bentonite and dispersant are added. After mixing and impregnation, the mixture is ultrasonically treated and dried to obtain modified bamboo fiber powder.

3. The biodegradable masterbatch for soil improvement according to claim 2, characterized in that, In step (1), the mass ratio of calcium-based bentonite to citric acid is 1 to 7:

1.

4. The biodegradable masterbatch for soil improvement according to claim 2, characterized in that, In step (2), the mass ratio of bamboo fiber powder, citric acid modified calcium bentonite, and dispersant is 20-25:15-20:0.85-1.

5. The biodegradable masterbatch for soil improvement according to claim 2 or 4, characterized in that, The dispersant is disodium ethylenediaminetetraacetate.

6. The biodegradable masterbatch for soil improvement according to claim 2, characterized in that, In step (2), the mixing and impregnation time is 0.5 to 1.5 hours; the ultrasonic treatment conditions are ultrasonic treatment at a frequency of 50 to 55 kHz for 8 to 10 minutes.

7. The biodegradable masterbatch for soil improvement according to any one of claims 1-4, characterized in that, The polyethylene is any one or more of LDPE, HDPE, and LLDPE; the modified bamboo fiber powder has a particle size of 600 mesh or larger; the compatibilizer is any one or more of citric acid, isocitric acid, aconitic acid, agaric acid, and tricarboxylic acid; the crosslinking agent is any one or more of phthalic anhydride, maleic anhydride, and pyromellitic anhydride; and the lubricant is any one or more of fatty acid esters, fatty acid amides, polyethylene wax, and methyl silicone oil.

8. A method for preparing a biodegradable masterbatch for soil improvement as described in any one of claims 1-7, characterized in that, The preparation method includes the following steps: parts by weight of modified bamboo fiber powder, polyethylene, compatibilizer, crosslinking agent, lubricant, and soybean oil are sequentially fed into a continuous mixer via a vacuum feeder, heated to 90-110°C and stirred for 30-40 minutes, and then melt-extruded and granulated to obtain the biodegradable masterbatch for soil improvement.

9. The preparation method according to claim 8, characterized in that, The temperature of the melt extrusion granulation is 130–180°C.

10. The use of a biodegradable masterbatch for soil improvement as described in any one of claims 1-7 in the preparation of biodegradable plastic products.

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