Degradable plastic, container made of the same and preparation method thereof

Abstract

The present invention discloses a degradable plastic, a container made from the plastic, and a preparation method thereof, belonging to the technical field of degradable plastic container processing. The preparation method of the degradable plastic comprises the following steps: mixing polybutylene terephthalate-adipate resin, starch, composite aerogel, modified corn straw fiber, a lubricant, and a plasticizer, stirring uniformly to obtain a mixture; and extruding and granulating the mixture to obtain a degradable plastic. The composite aerogel has gas barrier properties, improving the gas barrier properties of the polybutylene terephthalate-adipate plastic container. The composite aerogel also has high mechanical strength, preventing the leakage of modified ultrafine coal powder caused by the poor mechanical properties of the sericin aerogel, causing the modified ultrafine coal powder to migrate and precipitate in the plastic, affecting the degradation performance of the plastic.

Description

Technical Field

[0001] The present invention relates to the technical field of processing degradable plastic containers, in particular to degradable plastics, containers prepared using the plastics and a preparation method thereof. Background Art

[0002] Degradable plastics refer to plastics that meet the requirements of use, whose performance remains unchanged during the shelf life, and which can be degraded into environmentally friendly substances under natural environmental conditions after use. They include photodegradable plastics, biodegradable plastics, light / oxidation / biodegradable plastics, carbon dioxide-based biodegradable plastics, thermoplastic starch resin degradable plastics, etc. Degradable plastic containers are mainly used for plastic packaging of liquids or solids such as beverages, food, pickles, honey, dried fruits, and cooking oils; plastic containers are made of polyester, polyethylene, and polypropylene as raw materials, and after adding corresponding organic solvents, they are heated at high temperature and made through plastic molds by blow molding, extrusion blow molding, or injection molding. However, polyester, polyethylene, and polypropylene raw materials cannot be degraded and are likely to cause environmental pollution.

[0003] Plastic containers made from polybutylene terephthalate-adipate resin as raw material have good biodegradability, but polybutylene terephthalate-adipate resin has poor gas barrier properties and cannot meet the application requirements of plastic containers in beverages, food, pickles, honey, dried fruits, cooking oil and other fields. They can only be used as shopping bags, garbage bags, ground films and other film bag products without gas barrier requirements; coal powder is used as a photodegradation agent, and the oxygen-containing functional groups it contains produce free radicals under the action of ultraviolet light, which can trigger the breakage of polyvinyl alcohol molecular chains and complete efficient degradation. However, coal powder as an inorganic material has poor compatibility with organic polymer materials and is easy to precipitate, resulting in a decrease in degradation performance. Summary of the Invention

[0004] The present invention aims to provide a degradable plastic, a container made of the plastic, and a preparation method thereof. Ultrafine coal powder is surface-treated with hydrogen peroxide to introduce a larger number of oxygen-containing functional groups, thereby increasing the activity of the ultrafine coal powder and facilitating the synthesis of calcium phosphate oligomers in the pores and surface of the ultrafine coal powder. Nanosized calcium phosphate oligomers are synthesized on the surface and in the pores of the pretreated ultrafine coal powder to block the pores of the ultrafine coal powder and prevent the porous structure of the ultrafine coal powder from easily absorbing moisture. A composite aerogel is formed by mixing sericin powder, naringin, and modified ultrafine coal powder. The composite aerogel has high heat resistance and gas barrier properties. Porous carbon is adhered to the surface of polydopamine-modified corn straw fibers, allowing microorganisms to contact the corn straw fibers through the pores of the porous carbon and decompose the corn straw fibers. Furthermore, the excellent aspect ratio of corn straw fibers makes it possible to add them to the degradable plastic to prepare a plastic container having good mechanical properties.

[0005] The technical problems to be solved by the present invention are as follows: Polybutylene terephthalate-adipate resin has poor gas barrier properties and cannot meet the application requirements of plastic containers in the fields of beverages, food, pickles, honey, dried fruits, edible oils, etc.; coal powder is used as a photodegradation agent, and the oxygen-containing functional groups it contains generate free radicals under the action of ultraviolet light, which can trigger the breakage of polyvinyl alcohol molecular chains and achieve efficient degradation. However, as an inorganic material, coal powder has poor compatibility with organic polymer materials and is easily precipitated, resulting in a decrease in degradation performance.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The method for preparing degradable plastics comprises the following steps:

[0008] S1. Mix polybutylene terephthalate adipate resin, starch, composite aerogel, modified corn straw fiber, lubricant, and plasticizer, and stir evenly to obtain a mixture.

[0009] S2. The mixed material is extruded and granulated to obtain a biodegradable plastic.

[0010] Furthermore, the weight average molecular weight of the polybutylene terephthalate-adipate resin is 2.5×10 5 -3.5×10 5 g / mol.

[0011] Furthermore, the plasticizer is selected from one of epoxidized soybean oil, triethyl citrate, glycerol and polyethylene glycol.

[0012] Furthermore, the lubricant is selected from erucamide or ethylene bisstearamide.

[0013] Furthermore, a twin-screw extruder is used for extrusion, the temperature of the first melting section is 145-155°C, the temperature of the second melting section is 140-150°C, the temperature of the third melting section is 130-140°C, the screw speed is 80-100rpm, and the extrusion port temperature is 118-122°C.

[0014] Furthermore, the mass ratio of polybutylene terephthalate-adipate resin, starch, composite aerogel, modified corn straw fiber, lubricant, and plasticizer is (60-80):(30-40):(5-7):(4-6):(0.3-1):(3-5).

[0015] Furthermore, the starch is corn starch.

[0016] Furthermore, the composite aerogel is prepared by mixing modified ultrafine coal powder, sericin powder and naringin.

[0017] Furthermore, the modified ultrafine coal powder is prepared by subjecting the ultrafine coal powder to a surface treatment with hydrogen oxide and then reacting the surface with a calcium source and phosphoric acid.

[0018] Furthermore, the ultrafine coal powder has a particle size of 1-5 μm and a pore size of 100-300 nm.

[0019] Furthermore, the mass fraction of hydrogen peroxide is 10-15%.

[0020] Furthermore, the calcium source is selected from calcium chloride dihydrate or hydrated calcium nitrate.

[0021] Furthermore, the composite aerogel is specifically prepared by the following steps:

[0022] A1. After washing and drying the ultrafine coal powder, the washed ultrafine coal powder was added to a 10-15% mass fraction of hydrogen peroxide solution, stirred at 80 ° C for 3h, filtered, washed, and dried to obtain pretreated ultrafine coal powder;

[0023] A2. The pretreated ultrafine coal powder and a calcium source were added to ethanol and stirred. Triethylamine and phosphoric acid were then added. The mixture was stirred at 45°C for 5 h, centrifuged at 8000 rpm for 5 min, washed three times with ethanol and three times with deionized water, and dried in an oven at 60°C for 10 min to obtain modified ultrafine coal powder.

[0024] A3. Add sericin powder, modified ultrafine coal powder, and naringin to deionized water and heat at 45°C until the sericin powder is completely dissolved. Continue stirring and reacting for 30 minutes. Then, place the mixture in a freezer and freeze-dry at -20°C for 2 hours to obtain a composite aerogel.

[0025] Furthermore, during the above-mentioned reaction A1, hydrogen peroxide has strong oxidizing properties and can react with impurities on the surface of the coal powder to remove surface impurities. It also introduces more oxygen-containing functional groups, thereby increasing the activity of the coal powder, which is beneficial to the synthesis of calcium phosphate oligomers in the pores and surface of the ultrafine coal powder, thereby enhancing the degradation performance of the ultrafine coal powder on plastic containers.

[0026] Furthermore, during the above-mentioned reaction A2, the surface of the pretreated ultrafine coal powder contains a porous structure and has good adsorption properties. The oxygen-containing functional groups on its surface can combine with calcium ions in the calcium source, so that the calcium ions are adsorbed in the pores of the ultrafine coal powder, and the phosphate ions can form calcium phosphate complexes with the calcium ions through electrostatic bonding. Under the action of the catalyst triethylamine, the generated calcium phosphate complexes interact and arrange with each other to form nano-sized calcium phosphate oligomers, thereby realizing the synthesis of nano-sized calcium phosphate oligomers on the surface of the pretreated ultrafine coal powder.

[0027] Furthermore, during the above-mentioned reaction A3, the sericin powder is heated at 45°C to form a sericin solution. The hydroxyl and carboxyl groups contained in the sericin can combine with the oxygen-containing functional groups in naringin through chemical bonds to form a cross-linked network structure, and the phosphate and calcium ions contained on the surface of the modified ultrafine coal powder can also participate in the reaction to form a composite aerogel.

[0028] Furthermore, in step A1, the ratio of the washed ultrafine coal powder to the hydrogen peroxide solution is (5-7) g: (45-55) mL.

[0029] Furthermore, in step A2, the ratio of the amount of pretreated ultrafine coal powder, calcium source, ethanol, triethylamine and phosphoric acid is (2-4) g: (1-1.2) g: (55-65) mL: (0.1-0.3) g: (1-2) g.

[0030] Furthermore, in step A3, the ratio of sericin powder, modified ultrafine coal powder, naringin and deionized water is (7-9) g: (2-3) g: (2.2-2.4) g: (70-90) mL.

[0031] Furthermore, the sericin powder is specifically prepared by the following steps:

[0032] The silk cocoons were cut into blocks, placed in deionized water, and sterilized under high pressure at a temperature of 120-122° C. and a pressure of 0.05-0.15 MPa for 25-35 minutes, and the sericin solution was collected and freeze-dried to obtain sericin powder.

[0033] Among them, the cocoons are cut into blocks and sterilized under high temperature and pressure. The cell membranes of the bacteria in the cocoons are subjected to pressure, resulting in rupture of the cell membranes and leakage of substances inside the cells. High temperature can destroy the proteins and nucleic acids of the bacteria, causing them to lose their biological activity and replication ability. The bacteria, viruses and other microorganisms in the cocoons are killed under the action of high temperature and high pressure, achieving the purpose of sterilization, ensuring the purity of the sericin, and retaining its original structure and properties, providing high-quality raw materials for subsequent processing and application.

[0034] Furthermore, the ratio of silk cocoon to deionized water is (4-6) g: (45-55) mL.

[0035] Furthermore, the modified corn straw fiber is prepared by modifying the corn straw fiber with polydopamine and then mixing it with porous carbon.

[0036] Furthermore, the diameter of corn straw fiber is 20-50 μm, the length is 2-5 mm, the water absorption rate is 25-35%, and the density is 1.2-1.4 g / cm 3 .

[0037] Furthermore, the porous carbon has a pore size of 20-100 nm and a particle size of 0.2-5 μm.

[0038] Furthermore, the modified corn straw fiber is specifically prepared by the following steps:

[0039] B1. Add corn straw fiber to Tris-HCl buffer, stir evenly, add dopamine, stir for 4-6 hours, filter, wash with deionized water, and dry to obtain polydopamine-modified corn straw fiber.

[0040] B2. Add polydopamine-modified corn straw fiber and porous carbon to deionized water, stir evenly, let stand, filter, wash, and dry to obtain modified corn straw fiber.

[0041] Furthermore, during the above-mentioned reaction B1, in the Tris-HCl buffer, dopamine can self-polymerize on the surface of the corn straw fiber to form polydopamine, which makes the corn straw fiber have better adhesion and is conducive to the adhesion of porous carbon on the surface of the corn straw fiber.

[0042] Furthermore, during the above-mentioned B2 reaction process, the polydopamine layer on the surface of the polydopamine-modified corn straw fiber has good adhesion and contains a large amount of phenolic hydroxyl groups, thereby being able to adhere the porous carbon to the surface of the polydopamine-modified corn straw fiber.

[0043] Furthermore, in step B1, the ratio of corn straw fiber, Tris-HCl buffer and dopamine is (1-2) g: (50-60) mL: (0.5-0.9) g.

[0044] Furthermore, in step B2, the ratio of polydopamine-modified corn straw fiber, porous carbon and deionized water is (1-2) g: (0.6-0.8) g: (25-35) mL.

[0045] Furthermore, the container made of degradable plastic includes the following preparation steps:

[0046] The degradable plastic is added to the injection machine hopper, melted at 140-150°C, and injected into the tube blank mold. After being kept at 165-175°C for 20-30 minutes, it is cooled to room temperature and opened to obtain a degradable plastic container.

[0047] Furthermore, compared with the prior art, the present invention has the following beneficial effects:

[0048] (1) In the technical solution of the present invention, the ultrafine coal powder is a photodegradation agent with a macromolecular aromatic lamellar structure as the main body, and its outer edge is connected to some weak bonds and some oxygen-containing functional groups. The hydroxyl groups, phenolic hydroxyl groups, and weak bonds contained in the ultrafine coal powder are easily dissociated into free radicals under ultraviolet irradiation. In addition, in the presence of oxygen, the ultrafine coal powder can react with oxygen to generate peroxides and peroxy radicals, which are further decomposed to generate oxidative free radicals, which can participate in the degradation of polybutylene terephthalate-adipate plastic containers; the ultrafine coal powder is surface-treated with hydrogen peroxide, and hydrogen peroxide has strong oxidizing properties and can react with impurities on the surface of the coal powder to remove surface impurities, and introduce more oxygen-containing functional groups, thereby improving the activity of the ultrafine coal powder, facilitating the synthesis of calcium phosphate oligomers in the pores and surface of the ultrafine coal powder, and enhancing the degradation performance of the ultrafine coal powder on plastic containers.

[0049] (2) In the technical solution of the present invention, nano-sized calcium phosphate oligomers are synthesized on the surface and in the pores of the pretreated ultrafine coal powder. On the one hand, the pores of the ultrafine coal powder can be blocked to prevent the porous structure of the ultrafine coal powder from absorbing moisture easily, thereby affecting the performance of the degradable plastic container. On the other hand, the formed nano-sized calcium phosphate oligomers have high mechanical strength, which cooperates with the pretreated ultrafine coal powder to enhance the mechanical properties of the degradable plastic container.

[0050] (3) In the technical solution of the present invention, sericin powder, naringin, and modified ultrafine coal powder are mixed to form a composite aerogel. The formed composite aerogel has high heat resistance stability and gas barrier performance, which improves the gas barrier performance of polybutylene terephthalate-adipate plastic containers. The modified ultrafine coal powder and naringin are embedded in the composite aerogel, which increases the crosslinking density of the sericin composite aerogel and improves the mechanical strength. It avoids the poor mechanical properties of the sericin aerogel leading to leakage of the modified ultrafine coal powder and affects the gas barrier performance of the composite aerogel, so that the modified ultrafine coal powder migrates and precipitates in the plastic, affecting the degradation performance of the plastic. In addition, the formed composite aerogel has high heat resistance stability, which avoids the decomposition of sericin powder and naringin during the melting process of the plastic.

[0051] (4) In the technical solution of the present invention, porous carbon is adhered to the surface of polydopamine-modified corn straw fibers. On the one hand, the porous carbon can block the direct contact between the corn straw fibers and the external environment, reduce the corn straw fibers from absorbing moisture in the environment, and avoid the corn straw fibers from absorbing water and swelling, which leads to a decrease in the mechanical properties of the plastic container. The porous carbon is coated on the surface of the corn straw fibers, which increases the surface roughness of the corn straw fibers and increases the bonding force between the corn straw fibers and the plastic matrix. On the other hand, the porous structure of the porous carbon can be connected with the outside world, and microorganisms can contact the corn straw fibers through the pores of the porous carbon, and then decompose the corn straw fibers without affecting the degradation performance of the corn straw fibers. In addition, the excellent aspect ratio of the corn straw fibers is added to the degradable plastic, and the prepared plastic container has good mechanical properties. DETAILED DESCRIPTION

[0052] The technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0053] The raw materials used in the embodiments of the present invention are as follows:

[0054] Calcium chloride dihydrate, triethylamine, and phosphoric acid were purchased from Sinopharm Chemical Reagent Co., Ltd.; naringin (98% purity, purchased from Xi'an Zhanxun Biotechnology Co., Ltd.); Tris-HCl buffer (99% purity, purchased from Wuhan Desheng Biochemical Technology Co., Ltd.); and dopamine (purchased from Shanghai Myrrel Biochemical Technology Co., Ltd.).

[0055] The weight average molecular weight of polybutylene terephthalate adipate resin is 3×10 5 g / mol.

[0056] Ultrafine coal powder with a particle size of 3 μm and a pore size of 200 nm was purchased from Pingdingshan Zhurun Energy Co., Ltd.

[0057] The porous carbon had a pore size of 20-100 nm and a particle size of 0.2-5 μm and was purchased from Jinan Shengquan Group Co., Ltd.

[0058] The diameter of corn straw fiber is 35 μm, the length is 3 mm, the water absorption rate is 30%, and the density is 1.3 g / cm 3 .

[0059] The starch is corn starch.

[0060] Silkworm cocoons were purchased from Suzhou Huguangshanse Velvet Development Co., Ltd.

[0061] Sericin powder is specifically prepared by the following steps:

[0062] 5 g of silk cocoons were cut into blocks, placed in 55 mL of deionized water, and sterilized under high pressure at a temperature of 121°C and a pressure of 0.1 MPa for 30 min to dissolve the sericin. The sericin aqueous solution was collected and freeze-dried at -20°C for 30 min to obtain sericin powder.

[0063] Example 1 The composite aerogel is prepared by the following steps:

[0064] A1. Ultrafine coal powder was washed three times with water and dried in a 60°C oven for 10 minutes. Six grams of the washed ultrafine coal powder was added to 50 mL of a 13% hydrogen peroxide solution and stirred at 80°C for 3 hours. The mixture was filtered, washed three times with deionized water, and dried in a 70°C oven for 10 minutes to obtain pretreated ultrafine coal powder.

[0065] A2. 3 g of pretreated ultrafine coal powder and 1.1 g of calcium chloride dihydrate were added to 60 mL of ethanol and stirred for 30 minutes. Then, 0.2 g of triethylamine and 1.5 g of phosphoric acid were added. The mixture was stirred at 45°C for 5 hours, centrifuged at 8000 rpm for 5 minutes, filtered, washed three times with ethanol and three times with deionized water, and dried in an oven at 60°C for 10 minutes to obtain modified ultrafine coal powder.

[0066] A3. 8 g of sericin powder, 2.5 g of modified ultrafine coal powder, and 2.3 g of naringin were added to 80 mL of deionized water. The mixture was heated at 45°C until the sericin powder was completely dissolved. The mixture was stirred for 30 minutes and then freeze-dried at -20°C for 2 hours to obtain a composite aerogel.

[0067] Comparative Example 1 The difference between this comparative example and Example 1 is that the pretreated ultrafine coal powder is replaced by ultrafine coal powder, and the remaining steps and raw materials are synchronized with Example 1.

[0068] A1. 3 g of ultrafine coal powder and 1.1 g of calcium chloride dihydrate were added to 60 mL of ethanol and stirred for 30 minutes. Then, 0.2 g of triethylamine and 1.5 g of phosphoric acid were added. The mixture was stirred at 45°C for 5 hours, centrifuged at 8000 rpm for 5 minutes, filtered, washed three times with ethanol and three times with deionized water, and dried in an oven at 60°C for 10 minutes to obtain modified ultrafine coal powder.

[0069] A2. 8 g of sericin powder, 2.5 g of modified ultrafine coal powder, and 2.3 g of naringin were added to 80 mL of deionized water. The mixture was heated at 45°C until the sericin powder was completely dissolved. The mixture was stirred for 30 minutes and then freeze-dried at -20°C for 2 hours to obtain a composite aerogel.

[0070] Comparative Example 2 The difference between this comparative example and Example 1 is that the modified ultrafine coal powder is replaced by pretreated ultrafine coal powder, and the remaining steps and raw materials are the same as Example 1.

[0071] A1. Ultrafine coal powder was washed three times with water and dried in a 60°C oven for 10 minutes. Six grams of the washed ultrafine coal powder was added to 50 mL of a 13% hydrogen peroxide solution and stirred at 80°C for 3 hours. The mixture was filtered, washed three times with deionized water, and dried in a 70°C oven for 10 minutes to obtain pretreated ultrafine coal powder.

[0072] A2. 8 g of sericin powder, 2.5 g of pretreated ultrafine coal powder, and 2.3 g of naringin were added to 80 mL of deionized water. The mixture was heated at 45°C until the sericin powder was completely dissolved. After stirring for 30 minutes, the mixture was placed in a freezer and freeze-dried at -20°C for 2 hours to obtain a composite aerogel.

[0073] Comparative Example 3 The difference between this comparative example and Example 1 is that no naringin is added, and the remaining steps and raw materials are the same as Example 1.

[0074] A1. Ultrafine coal powder was washed three times with water and dried in a 60°C oven for 10 minutes. Six grams of the washed ultrafine coal powder was added to 50 mL of a 13% hydrogen peroxide solution and stirred at 80°C for 3 hours. The mixture was filtered, washed three times with deionized water, and dried in a 70°C oven for 10 minutes to obtain pretreated ultrafine coal powder.

[0075] A2. 3 g of pretreated ultrafine coal powder and 1.1 g of calcium chloride dihydrate were added to 60 mL of ethanol and stirred for 30 minutes. Then, 0.2 g of triethylamine and 1.5 g of phosphoric acid were added. The mixture was stirred at 45°C for 5 hours, centrifuged at 8000 rpm for 5 minutes, filtered, washed three times with ethanol and three times with deionized water, and dried in an oven at 60°C for 10 minutes to obtain modified ultrafine coal powder.

[0076] A3. Add 8 g of sericin powder and 2.5 g of modified ultrafine coal powder to 80 mL of deionized water. Heat at 45°C until the sericin powder is completely dissolved. Continue stirring for 30 minutes. Then, place in a freezer and freeze-dry at -20°C for 2 hours to obtain a composite aerogel.

[0077] Example 2 Modified corn straw fiber is prepared by the following steps:

[0078] B1. Add 1.5 g of corn straw fiber to 55 mL of Tris-HCl buffer and stir evenly. Add 0.7 g of dopamine and stir for 4 h. Filter, wash three times with deionized water, and dry in an oven at 70°C for 10 min to obtain polydopamine-modified corn straw fiber.

[0079] B2. Add 1.5 g of polydopamine-modified corn straw fiber and 0.7 g of porous carbon to 30 mL of deionized water, stir evenly, let stand for 10 min, filter, wash with deionized water three times, and dry in an oven at 70°C for 10 min to obtain modified corn straw fiber.

[0080] Comparative Example 4 The difference between this comparative example and Example 2 is that the polydopamine-modified corn straw fiber is replaced by corn straw fiber, and the remaining steps and raw materials are the same as Example 2.

[0081] 1.5 g corn straw fiber and 0.7 g porous carbon were added to 30 mL deionized water, stirred evenly, allowed to stand for 10 min, filtered, washed with deionized water three times, and dried in an oven at 70 °C for 10 min to obtain modified corn straw fiber.

[0082] Comparative Example 5 The difference between this comparative example and Example 2 is that porous carbon is not added, and the remaining steps and raw materials are the same as Example 2.

[0083] 1.5 g corn straw fiber was added to 55 mL Tris-HCl buffer and stirred evenly. 0.7 g dopamine was added and stirred for 4 h. The mixture was filtered, washed with deionized water three times, and dried in an oven at 70 °C for 10 min to obtain modified corn straw fiber.

[0084] Example 3 A method for preparing a degradable plastic container comprises the following steps:

[0085] S1. The polybutylene terephthalate-adipate resin, corn starch, the composite aerogel prepared in Example 1, the modified corn straw fiber prepared in Example 2, erucamide, and epoxy soybean oil were mixed and stirred to obtain a mixture.

[0086] S2. The mixed material is extruded and granulated to obtain a biodegradable plastic.

[0087] S3. Add the biodegradable plastic into the hopper of the injection machine, melt it at 140°C, and inject it into the tube mold. After keeping it at 165°C for 20 minutes, cool it to room temperature, and open the mold to obtain a biodegradable plastic container.

[0088] The mass ratio of polybutylene terephthalate-adipate resin, corn starch, the composite aerogel prepared in Example 1, the modified corn straw fiber prepared in Example 2, erucamide, and epoxy soybean oil is 60:30:5:4:0.3:3.

[0089] A twin-screw extruder was used for extrusion, with the temperature of the first melting section being 145°C, the temperature of the second melting section being 140°C, the temperature of the third melting section being 130°C, the screw speed being 80 rpm, and the extrusion port temperature being 118°C.

[0090] Example 4 A method for preparing a degradable plastic container comprises the following steps:

[0091] S1. The polybutylene terephthalate-adipate resin, corn starch, the composite aerogel prepared in Example 1, the modified corn straw fiber prepared in Example 2, ethylene bisstearamide, and triethyl citrate were mixed and stirred to obtain a mixture.

[0092] S2. The mixed material is extruded and granulated to obtain a biodegradable plastic.

[0093] S3. Add the biodegradable plastic into the hopper of the injection machine, melt it at 145°C, and inject it into the tube mold. After keeping it at 170°C for 25 minutes, cool it to room temperature, and open the mold to obtain a biodegradable plastic container.

[0094] The mass ratio of polybutylene terephthalate-adipate resin, corn starch, the composite aerogel prepared in Example 1, the modified corn straw fiber prepared in Example 2, ethylene bisstearamide, and triethyl citrate is 70:35:6:5:0.6:4.

[0095] A twin-screw extruder was used for extrusion, with the temperature of the first melting section being 150°C, the temperature of the second melting section being 145°C, the temperature of the third melting section being 135°C, the screw speed being 90 rpm, and the extrusion port temperature being 120°C.

[0096] Example 5 A method for preparing a degradable plastic container comprises the following steps:

[0097] S1. Mix polybutylene terephthalate adipate resin, corn starch, the composite aerogel prepared in Example 1, the modified corn straw fiber prepared in Example 2, erucamide, and glycerol, and stir evenly to obtain a mixture.

[0098] S2. The mixed material is extruded and granulated to obtain a biodegradable plastic.

[0099] S3. Add the biodegradable plastic into the hopper of the injection machine, melt it at 150°C, and inject it into the tube mold. After keeping it at 175°C for 30 minutes, cool it to room temperature, and open the mold to obtain a biodegradable plastic container.

[0100] The mass ratio of polybutylene terephthalate-adipate resin, corn starch, the composite aerogel prepared in Example 1, the modified corn straw fiber prepared in Example 1, erucamide, and glycerol is 80:40:7:6:1:5.

[0101] A twin-screw extruder was used for extrusion, with the temperature of the first melting section being 155°C, the temperature of the second melting section being 150°C, the temperature of the third melting section being 140°C, the screw speed being 100 rpm, and the extrusion port temperature being 122°C.

[0102] Comparative Example 6 The difference between this comparative example and Example 4 is that the composite aerogel prepared in Example 1 is replaced by the material prepared in Comparative Example 1, and the remaining steps are synchronized with Example 4.

[0103] Comparative Example 7 The difference between this comparative example and Example 4 is that the composite aerogel prepared in Example 1 is replaced by the material prepared in Comparative Example 2, and the remaining steps are synchronized with Example 4.

[0104] Comparative Example 8 The difference between this comparative example and Example 4 is that the composite aerogel prepared in Example 1 is replaced by the material prepared in Comparative Example 3, and the remaining steps are synchronized with Example 4.

[0105] Comparative Example 9 The difference between this comparative example and Example 4 is that the modified corn straw fiber prepared in Example 2 is replaced by the material prepared in Comparative Example 4, and the remaining steps are synchronized with Example 4.

[0106] Comparative Example 10 The difference between this comparative example and Example 4 is that the modified corn straw fiber prepared in Example 2 is replaced by the material prepared in Comparative Example 5, and the remaining steps are synchronized with Example 4.

[0107] The performance of the degradable plastic containers prepared in Examples 3-5 and Comparative Examples 6-10 was tested.

[0108] Tensile strength test: The tensile strength of the biodegradable plastic container prepared above was tested according to the standard GB / T 1040.1-2018 test method.

[0109] Elongation at break test: The elongation at break of the biodegradable plastic container prepared above was tested according to standard GB / T 1040.1-2018.

[0110] Degradability test: The biodegradable plastic container prepared above was dried at 90°C to constant weight. A 10 cm thick layer of soil was laid in a beaker, and the water activity was adjusted to 15%. The soil was evenly spaced and evenly buried. The beaker was irradiated with ultraviolet light (wavelength of 300 nm). After 15 days, the sample was removed, the surface was rinsed with water, and then dried at 90°C to constant weight. The weight loss rate was calculated.

[0111] Barrier property test: The barrier property of the biodegradable plastic container prepared above was tested in accordance with the national standard GB / T 31354-2014 "Oxygen permeability test method for packages and containers - Coulometric method". The test results are shown in Table 1 below:

[0112] Table 1

[0113]

[0114] As can be seen from the data in Table 1, in Comparative Example 6, the pretreated ultrafine coal powder is replaced with a composite aerogel prepared from ultrafine coal powder and added to a degradable plastic container, and its mechanical properties and degradability are reduced. This may be because the ultrafine coal powder is surface-treated with hydrogen oxide, which is conducive to the synthesis of calcium phosphate oligomers in the pores and surface of the ultrafine coal powder, thereby enhancing the degradation performance of the ultrafine coal powder on the plastic container. However, the surface of the ultrafine coal powder lacks oxygen-containing functional groups, and this effect cannot be achieved, so the mechanical properties and degradability are reduced.

[0115] In Comparative Example 7, the composite aerogel prepared by replacing the modified ultrafine coal powder with pretreated ultrafine coal powder was added to a degradable plastic container, and its mechanical properties decreased. This may be because nano-sized calcium phosphate oligomers were synthesized on the surface and in the pores of the pretreated ultrafine coal powder, which prevented the porous structure contained in the ultrafine coal powder from being easily hygroscopic, and the formed nano-sized calcium phosphate oligomers had higher mechanical strength. However, the pretreated ultrafine coal powder lacked nano-sized calcium phosphate oligomers and could not achieve this effect, so its mechanical properties decreased.

[0116] In Comparative Example 8, the composite aerogel prepared without the composite filler prepared with naringin was added to a degradable plastic container, and its mechanical properties, degradation properties, and barrier properties decreased. This may be because naringin was embedded in the composite aerogel, increasing the crosslinking density of the sericin composite aerogel and improving the mechanical strength. It also prevented the modified ultrafine coal powder from leaking out due to the poor mechanical properties of the sericin aerogel, causing migration and precipitation in the plastic, which would affect the degradation properties of the plastic. In the absence of naringin, this effect could not be achieved, resulting in a decrease in the mechanical properties and degradation properties.

[0117] In Comparative Example 9, modified corn straw fibers prepared by replacing polydopamine-modified corn straw fibers with corn straw fibers were added to a degradable plastic container, and its mechanical properties decreased. This may be because polydopamine was self-polymerized on the surface of the corn straw fibers, which gave the corn straw fibers better adhesion, facilitating the adhesion of porous carbon on the surface of the corn straw fibers. The porous carbon can block direct contact between the corn straw fibers and the external environment, reduce the corn straw fibers' absorption of moisture in the environment, and avoid the corn straw fibers' swelling due to water absorption, which leads to a decrease in the mechanical properties of the plastic container. Without polydopamine-modified corn straw fibers, this effect cannot be achieved, and therefore the mechanical properties decrease.

[0118] In Comparative Example 10, the modified corn straw fiber prepared without adding porous carbon was added to the biodegradable plastic container, and its mechanical properties decreased. This may be because the porous carbon adhered to the surface of the polydopamine-modified corn straw fiber, which can reduce the corn straw fiber's absorption of moisture from the environment, and the porous carbon was coated on the surface of the corn straw fiber, increasing the surface roughness of the corn straw fiber and increasing the bonding force between the corn straw fiber and the plastic matrix. Without porous carbon, this effect could not be achieved, and thus the mechanical properties decreased.

[0119] The data in Table 1 show that the degradable plastic containers prepared in Examples 3-5 meet the test performance requirements, while the degradable plastic containers prepared in Comparative Examples 5-8 do not meet the performance requirements, indicating that the degradable plastic containers prepared in the present invention have good mechanical properties, degradability and gas barrier properties.

[0120] Throughout the specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0121] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing degradable plastics, characterized in that: The following steps are involved: S1. The polybutylene terephthalate - adipate resin, starch, composite aerogel, modified corn straw fiber, lubricant, plasticizer are mixed and stirred to obtain a mixture; S2. The mixture is extruded and granulated to obtain a biodegradable plastic; The composite aerogel is prepared by mixing modified ultrafine coal powder, sericin powder and naringin; The modified ultrafine coal powder is prepared by reacting ultrafine coal powder with a calcium source and phosphoric acid after surface treatment with hydrogen oxide; The composite aerogel is specifically prepared by the following steps: A1. After washing and drying the ultrafine coal powder, the washed ultrafine coal powder was added to a 10-15% by mass hydrogen peroxide solution and stirred at 80°C for 3 hours. The mixture was filtered, washed, and dried to obtain pretreated ultrafine coal powder. A2. The pretreated ultrafine coal powder and a calcium source were added to ethanol and stirred. Triethylamine and phosphoric acid were then added. The mixture was stirred at 45°C for 5 h, centrifuged at 8000 rpm for 5 min, washed three times with ethanol and three times with deionized water, and dried in an oven at 60°C for 10 min to obtain modified ultrafine coal powder. A3. Sericin powder, modified ultrafine coal powder, and naringin were added to deionized water and heated at 45°C until the sericin powder was completely dissolved. The mixture was stirred for 30 minutes and then freeze-dried at -20°C for 2 hours to obtain a composite aerogel. The modified corn straw fiber is prepared by modifying corn straw fiber with polydopamine and then mixing the modified corn straw fiber with porous carbon.

2. The method for preparing the degradable plastic according to claim 1, wherein: The ultrafine coal powder has a particle size of 1-5 μm and a pore size of 100-300 nm; and the mass fraction of hydrogen peroxide is 10-15%.

3. The method for preparing the degradable plastic according to claim 1, wherein: The sericin powder is specifically prepared by the following steps: cutting silk cocoons into blocks, placing them in deionized water, sterilizing them under high pressure at a temperature of 120-122° C. and a pressure of 0.05-0.15 MPa for 25-35 minutes, collecting the sericin solution, and freeze-drying the sericin solution to obtain sericin powder.

4. The method for preparing a degradable plastic according to claim 1, wherein: The calcium source is selected from calcium chloride dihydrate or hydrated calcium nitrate.

5. The method for preparing the degradable plastic according to claim 1, characterized in that: The corn straw fiber has a diameter of 20-50 μm, a length of 2-5 mm, a water absorption rate of 25-35%, and a density of 1.2-1.4 g / cm3; the porous carbon has a pore size of 20-100 nm and a particle size of 0.2-5 μm.

6. The method for preparing a degradable plastic according to claim 1, wherein: The weight average molecular weight of the polybutylene terephthalate-adipate resin is 2.5×10 5 -3.5×10 5 g / mol.

7. The method for preparing a degradable plastic according to claim 1, wherein: The plasticizer is selected from one of epoxidized soybean oil, triethyl citrate, glycerol and polyethylene glycol; and the lubricant is selected from erucamide or ethylene bisstearamide.

8. The method for preparing a degradable plastic according to claim 1, wherein: The extrusion is carried out using a twin-screw extruder, with the temperature of the first melting section being 145-155°C, the temperature of the second melting section being 140-150°C, the temperature of the third melting section being 130-140°C, the screw speed being 80-100rpm, and the extrusion port temperature being 118-122°C.

9. A degradable plastic produced by the method for producing a degradable plastic according to any one of claims 1 to 8.

10. A container made of the degradable plastic obtained according to claim 9, characterized in that: The method comprises the following preparation steps: The degradable plastic is added to the injection machine hopper, melted at 140-150°C, and injected into the tube blank mold. After being kept at 165-175°C for 20-30 minutes, it is cooled to room temperature and opened to obtain a degradable plastic container.

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