1. A biodegradable PVC plastic is characterized in that: the composite degradation aid comprises PVC resin, a plasticizer, a biodegradation agent and a composite degradation aid, wherein the composite degradation aid consists of a succinate degradation aid and a castor oil-based degradation aid, and the mass ratio of the succinate degradation aid to the castor oil-based degradation aid is 1: (1-5);

the synthesis method of the castor oil-based degradation assistant agent comprises the following steps: taking the molar ratio as (2-4): 1, mixing furfuryl alcohol and castor oil fatty acid, stirring at 50-70 ℃ for 30-60min, adding immobilized lipase, and reacting for 4-6 hours under a vacuum condition.

2. Biodegradable PVC plastic according to claim 1, characterized in that: the synthesis method of the succinate co-reducing agent comprises the following steps: taking the molar ratio as (1-3): 1: (8-10) n-butanol, succinic acid and H₂SO₄Mixing, stirring at 100-120 deg.C for 20-40min, introducing nitrogen, and reacting for 80-100 min.

3. Biodegradable PVC plastic according to claim 1, characterized in that: the plasticizer is at least one of dioctyl terephthalate, diisooctyl adipate, dibutoxybutyl adipate and citric acid ester.

4. Biodegradable PVC-plastic according to claim 1, characterized in that said biodegradable agent is selected from at least one of starch, cellulose, chitosan.

5. The biodegradable PVC plastic according to claim 1, wherein the raw material further comprises at least one of lubricant, stabilizer and filler.

6. The biodegradable PVC plastic according to claim 5, wherein the raw materials comprise, in parts by weight: 100 parts of PVC resin, 10-20 parts of plasticizer, 2-5 parts of lubricant, 1-2 parts of stabilizer, 5-10 parts of filler, 1-2 parts of biodegradation agent and 40-50 parts of composite degradation promoter.

7. Biodegradable PVC plastic according to claim 5, characterized in that the stabilizer is selected from at least one of calcium stearate, zinc stearate, styrene-methacrylate copolymer, cadmium stearate.

8. Biodegradable PVC-plastic according to claim 5, characterized in that said lubricant is selected from at least one of epoxidized soybean oil, epoxidized fatty acid methyl ester, dioctyl adipate.

9. The method for preparing biodegradable PVC plastic according to any one of claims 1 to 8, characterized in that it comprises the following steps:

(1) mixing: mixing the raw materials at the temperature of 110-120 ℃ to obtain a mixture;

(2) banburying: banburying the mixture for 3-5min, and kneading the mixture into blocks to obtain a banburying material;

(3) open mixing: carrying out secondary rolling mill open milling on the internal mixing material, wherein the temperature of the secondary rolling mill is respectively 160-170 ℃ and 165-175 ℃, so as to obtain a plasticized molten material;

(4) extrusion and filtration: extruding and filtering the plasticized melt material, wherein the extrusion temperature is 170-180 ℃, and the size of a filter screen is 100-200 meshes to obtain an extruded and filtered material;

(5) and (3) calendering and forming: sequentially carrying out four-time roller calendering molding on the extruded and filtered material, wherein the four-time molding temperature is respectively 180-fold 190 ℃, 180-fold 185 ℃, 175-fold 180 ℃ and 170-fold 175 ℃, and obtaining a semi-finished product;

(6) post-processing: and (3) taking and cooling the semi-finished product to obtain the biodegradable PVC plastic.

10. Use of biodegradable PVC plastic according to any one of claims 1 to 8 in plastic articles.

Background

With the development of science and technology in modern society, the use of plastics gradually deepens into various industries such as agriculture, medical treatment, toys and the like. Most of the plastics currently used are produced from petrochemical products, of which about 75% are petroleum-based plastics and about 20% of recycled plastics are mostly recycled from petroleum-based plastics. Although petroleum-based plastics have good physicochemical properties, the petroleum-based plastics are difficult to degrade, and cause great white pollution to the ecological environment. At present, the plastic waste treatment method mainly comprises three methods of high-temperature incineration, landfill and recycling. The incineration treatment of the wastes can release a large amount of harmful gases to generate secondary pollution. The landfill needs to occupy a large amount of arable land area, the shortage crisis of land resources can be aggravated, the recycling is difficult for separating difficult disposable plastic products, mulching films and the like, both from the economic aspect and the practical aspect, and the environmental pollution brought by the plastic film treatment and the more and more attention paid to the ecological environment by people are needed to be developed so as to improve the ecological pollution brought by the degradable plastic.

Degradable plastics, also called "environmentally degradable plastics", refer to a class of materials whose products have various properties meeting the use requirements, and whose properties are not changed during the storage period, and which can be degraded under natural environmental conditions after use to be harmless to the environment. Polyvinyl chloride (PVC) plastics are produced by adding certain amounts of plasticizers to modify their thermal and mechanical properties, the most common plasticizers being petroleum-based phthalates. However, petroleum-based phthalates migrate from the polymer matrix during processing, adversely affecting the environment, and have some toxicity. Meanwhile, due to high volatility and easy leachability, when the biodegradable plastic is used for degradable plastics, petroleum-based phthalate can be diffused to the environment when the degradable plastics are degraded under natural environmental conditions, and health and environmental problems are brought to people. In addition, the continuous decrease of petroleum and the rising of petroleum price both lead the price of petroleum-based phthalate to rise, thereby increasing the cost of polyvinyl chloride plastics.

Disclosure of Invention

The invention provides a biodegradable PVC plastic, a preparation method and application thereof, which aim to solve one or more technical problems in the prior art and at least provide a beneficial choice or creation condition.

In order to overcome the technical problems, the technical scheme adopted by the invention is as follows:

the biodegradable PVC plastic comprises PVC resin, a plasticizer, a biodegradation agent and a composite degradation aid, wherein the composite degradation aid consists of a succinate degradation aid and a castor oil-based degradation aid, and the mass ratio of the succinate degradation aid to the castor oil-based degradation aid is 1: (1-5);

the synthesis method of the castor oil-based degradation assistant agent comprises the following steps: taking the molar ratio as (2-4): 1, mixing furfuryl alcohol and castor oil fatty acid, stirring at 50-70 ℃ for 30-60min, adding immobilized lipase, and reacting for 4-6 hours under a vacuum condition.

The PVC resin is used as the matrix of the biodegradable plastic, the external load bearing performance is good, the environment is not damaged, and the defect of poor load bearing performance of the biodegradable agent can be overcome after the PVC is fused with the biodegradable agent, so that the mechanical property of a plastic product is ensured. Meanwhile, the castor oil contains hydroxyl, double bonds and glyceride bonds, and the castor oil-based degradation promoter is added into the PVC resin matrix, so that the flexibility and the processing performance of the matrix are enhanced, and the castor oil-based degradation promoter can be completely biodegraded. The succinate landing assistant can be self-decomposed after entering the environment, and cannot generate stable metabolites like the traditional phthalate, so that the succinate landing assistant has good biodegradability. And the succinate co-reducing agent and the castor oil-based co-reducing agent are nontoxic and are environment-friendly biodegradation aids. Researches find that the biodegradation performance of the PVC plastic can be further improved by adopting the compound use of the succinate degradation aid and the castor oil-based degradation aid and controlling the mass ratio of the succinate degradation aid and the castor oil-based degradation aid.

The castor oil based degradation assistant agent is prepared by taking furfuryl alcohol and castor oil fatty acid as raw materials and carrying out catalytic esterification reaction and synthesis on the raw materials by lipase. The furfuryl alcohol is a biological source molecule which is easy to polymerize under an acidic condition, has good thermal stability, and can endow plastics with excellent mechanical strength and thermodynamic property by the castor oil-based degradation promoter after the furfuryl alcohol and castor oil fatty acid are synthesized, and the mechanical strength and the thermodynamic property are equivalent to those of petroleum-based plasticized plastics. Meanwhile, due to the existence of aromatic rings in the furfuryl alcohol, ester bonds between free hydroxyl groups in the castor oil fatty acid and the furfuryl alcohol can effectively endow the castor oil-based degradation assistant with the molecular plasticizing property.

The invention adopts an enzyme catalysis method to synthesize the castor oil-based degradation aid, the reaction can be carried out in a completely solvent-free environment, and the safety of production and use is ensured. The immobilized lipase is prepared by adopting candida lipase and carrying out adsorption immobilization by using macroporous acrylic resin with the water content of 2% and the particle size of 450 mu m as a carrier, and the immobilized lipase is favorable for improving the stability of the lipase.

As a further improvement of the above scheme, the synthesis method of the succinate co-reducing agent comprises the following steps: taking the molar ratio as (1-3): 1: (8-10) n-butanol, succinic acid and H₂SO₄Mixing, stirring at 100-120 deg.C for 20-40min, introducing nitrogen, and reacting for 80-100 min.

Specifically, the succinic acid-based degradation assistant takes reproducible succinic acid and n-butyl alcohol as raw materials, adopts a solvent-free process, and only utilizes nitrogen to remove moisture in the esterification reaction. The succinic acid-based degradation assistant agent can be completely degraded into carbon dioxide and water in soil, does not contain halogen elements, benzene rings and other elements which are easy to generate toxic gas during degradation, and can effectively reduce the damage to the environment in the degradation process of plastics.

As a further improvement of the scheme, the plasticizer is selected from at least one of dioctyl terephthalate, diisooctyl adipate, dibutoxybutyl adipate and citric acid ester. Specifically, the plasticizer is selected from nontoxic and easily degradable raw materials which can ensure the mechanical property of the plastic, and the phthalate plasticizer which cannot be chemically combined with the plastic and finally migrates into the environment to influence the health and the environment is not adopted.

As a further improvement of the above scheme, the biodegradation agent is selected from at least one of starch, cellulose, chitosan and chitosan. Specifically, the biodegradation agent is selected from high molecular materials which can be biodegraded under the action of natural microorganisms such as bacteria, mould, algae and the like, and after the biodegradation agent is added into the PVC plastic, the plastic can be degraded under the action of soil microorganisms and enzymes.

As a preferable embodiment of the scheme, the biodegradable starch needs to be modified before use, and a specific modification method comprises the following steps:

dissolving an organic dispersant in purified water, respectively adding styrene, a cross-linking agent, an initiator, a pore-forming agent and a water-soluble monomer, uniformly stirring, then adding an inorganic dispersant, heating and shaping to obtain pre-microspheres, and continuing to perform suspension polymerization reaction on the pre-microspheres to obtain porous resin microspheres;

drying starch at 50-80 deg.C, pulverizing to obtain starch granule;

adding the starch particles into a coupling agent and an alcoholic solution for dispersion, adding the porous resin microspheres for dispersion, and drying to obtain the starch particle-loaded resin microspheres;

adding CaCl into the resin microspheres loaded with the starch particles₂And stirring the solution, and adding a sodium alginate solution to prepare the modified starch.

Specifically, all components of the starch can be biodegraded, a certain amount of the auxiliary agent added into the plastic system can be biodegraded therewith, and no pollution is caused to the environment, but the natural starch also has a series of defects of high water absorption, high viscosity, insufficient thermal stability, difficult processing control and the like, so that the natural starch needs to be modified before use.

Further, under the action of mechanical stirring, a dispersing agent and a pore-forming agent, a hydrophobic monomer styrene dissolved with an initiator and a crosslinking agent and a water-soluble monomer are dissolved, wherein the pore-forming agent exists in a monomer oil ball in a small droplet state to form pores in the resin, the monomer is dispersed into oil droplet droplets, and is suspended in water to perform suspension polymerization reaction and crosslinked into microspheres, so that the adsorption resin microspheres are prepared, and the prepared adsorption resin microspheres have a porous structure and the average pore diameter of the microspheres is 10-20 mu m.

As a preferred embodiment of the above adsorbent resin microsphere, wherein: the water-soluble monomer is methacryloyloxyethyl phosphorylcholine, the organic dispersant is gelatin, the inorganic dispersant is calcium phosphate, the cross-linking agent is divinylbenzene, the initiator is benzoyl peroxide, and the pore-forming agent is toluene.

Furthermore, the starch is dried at 50-80 ℃ and then crushed, and the experimental result shows that the starch has the best mechanical property at the heating temperature of 72 ℃, but when the temperature is higher than 80 ℃, the starch generates a molten system, so that the viscosity is increased, the rheological property is poor, and the processing property is reduced; when the temperature is lower than 50 ℃, the starch cannot be dried sufficiently, and the mechanical properties cannot reach a better value. Meanwhile, the particle size of the starch particles after heating and crushing needs to be controlled to be matched with the aperture of 10-20 mu m of the adsorption resin microspheres.

Further, adding the starch particles into a titanate coupling agent and an alcohol solution for uniform dispersion, adding the porous resin microspheres, performing ultrasonic dispersion treatment to enable the starch particles to be adsorbed in the porous structure of the adsorption resin microspheres, and heating to 50-80 ℃ for drying to obtain the starch particle-loaded resin microspheres.

Further, the starch-loaded particles are micronizedAdding 10-60% of CaCl into the resin microspheres₂Stirring in the solution to make the surface of the resin microsphere loaded with starch microparticles adhere with a large amount of Ca²⁺Then sodium alginate and Ca with the mass volume concentration of 0.1-5 g/L are added²⁺Cross-linking reaction with sodium alginate, alpha-L-guluronic acid (G) and Ca in sodium alginate solution²⁺Bonding and gelatinizing to form a structure-shaped microcapsule, and fixing the starch granules in the microcapsule.

After the starch is modified, the technical problems of natural starch can be effectively solved, the starch is prevented from being adhered to the wall of a mixer during processing, and the stability of the material is improved; improve the thermal stability of the starch and reduce the influence of high-temperature processing on the starch. Meanwhile, the main component of the microcapsule for fixedly sealing the starch granules is biodegradable sodium alginate, so that the biodegradability of the starch is not influenced after the starch is modified.

As a further improvement of the above scheme, the raw materials further comprise at least one of a lubricant, a stabilizer and a filler.

As a further improvement of the scheme, the raw materials comprise the following components in parts by weight: 100 parts of PVC resin, 10-20 parts of plasticizer, 2-5 parts of lubricant, 1-2 parts of stabilizer, 5-10 parts of filler, 1-2 parts of biodegradation agent and 40-50 parts of composite degradation promoter. Specifically, by designing the formula composition of each raw material of the biodegradable PVC plastic, each composition has the function and is synergistic with other components, so that the PVC plastic can meet the requirement of service performance, the performance is unchanged within a storage period, and the PVC plastic is degraded into a nontoxic and harmless substance under natural conditions after use.

As a further improvement of the scheme, the stabilizer is at least one selected from calcium stearate, zinc stearate, styrene-methacrylate copolymer and cadmium stearate. The stabilizers can prevent or relieve the decomposition of matrix resin in the high-temperature plasticizing process, weaken the action of light and oxygen in the environment to the matrix resin in the use process of the product, and enable the matrix resin to generate chemical changes so as to change the performance of the product and shorten the service life of the product.

As a further improvement of the above aspect, the lubricant is at least one selected from the group consisting of epoxidized soybean oil, epoxidized fatty acid methyl ester, and dioctyl adipate. These lubricants can prevent the adhesion of the material to the barrel during processing, inhibit frictional heat generation, prevent thermal deterioration of the material, improve fluidity during extrusion molding, improve the adhesion of the material to the barrel and the die, prevent and reduce the residues, and contribute to the improvement of the appearance and gloss of the plastic film.

As a further improvement of the above aspect, the filler is selected from activated calcium carbonate and/or kaolin. These fillers can increase the stability, hardness and rigidity of plastic articles, improve the processability of plastics, increase the heat resistance of plastic articles and reduce the cost of plastic articles.

The invention also provides a technical scheme that the preparation method of the biodegradable PVC plastic comprises the following steps:

(1) mixing: mixing the raw materials at the temperature of 110-120 ℃ to obtain a mixture;

(2) banburying: banburying the mixture for 3-5min, and kneading the mixture into blocks to obtain a banburying material;

(3) open mixing: carrying out secondary rolling mill open milling on the internal mixing material, wherein the temperature of the secondary rolling mill is respectively 160-170 ℃ and 165-175 ℃, so as to obtain a plasticized molten material;

(4) extrusion and filtration: extruding and filtering the plasticized melt material, wherein the extrusion temperature is 170-;

(5) and (3) calendering and forming: sequentially carrying out four-time roller calendering molding on the extruded and filtered material, wherein the four-time molding temperature is respectively 180-fold 190 ℃, 180-fold 185 ℃, 175-fold 180 ℃ and 170-fold 175 ℃, and obtaining a semi-finished product;

(6) post-processing: and (3) taking and cooling the semi-finished product to obtain the biodegradable PVC plastic.

As a specific embodiment of the preparation method, the preparation method of the biodegradable PVC plastic comprises the following steps:

(1) mixing: the raw materials are uniformly mixed by a mixer for 20-30 seconds at a low speed, then for 480 seconds at a high speed, and the mixing temperature is controlled at 110-120 ℃ to obtain a mixture.

(2) Banburying: and (3) feeding the mixture into an internal mixer through a material conveying pipeline, kneading the mixture by a single-screw extruder in the internal mixer to knead the powdery material into blocks, wherein the internal mixing time is 3-5 minutes, and the internal mixing current is 100-120A, so as to obtain the internal mixing material.

(3) Open mixing: and (3) carrying out secondary rolling and milling on the blocky internal mixing material, wherein the temperature of the first group of rolling turbines is 160-year-old 170 ℃, the blocky internal mixing material is subjected to preliminary plasticization by the first group of rolling turbines and then enters the second group of rolling turbines through a conveying belt for further plasticization, and the temperature of the second group of rolling turbines is 165-year-old 175 ℃, so that plasticized melting material is obtained.

(4) Extrusion and filtration: and conveying the plasticized melt material to an extrusion filter, wherein the temperature of the extrusion filter is 170-180 ℃, the size of a filter screen is 100-200 meshes, and the extruded filter material is obtained and used for filtering impurities.

(5) And (3) calendering and forming: and conveying the extruded and filtered material to a calendering host machine, wherein the calendering host machine is a four-roller calendering machine, the temperature of the calendering machine is 190 ℃ for the first round, 185 ℃ for the second round, 175 ℃ for the third round and 180 ℃ for the fourth round, 175 ℃ for the fourth round, obtaining a semi-finished product, further improving the plasticizing performance of the product through the temperature difference and the speed difference of the four rollers, and determining the thickness of the product through the gap between the third round and the fourth round.

(6) Post-processing: and (3) carrying out drawing, embossing and cooling on the semi-finished product for post-processing to obtain the biodegradable PVC plastic.

The invention also provides a technical scheme that the biodegradable PVC plastic can be widely applied to the fields of food, medicine, chemical industry and the like.

The technical scheme provided by the embodiment of the application at least has the following technical effects or advantages:

according to the invention, the biodegradation agent is added into the PVC resin matrix, and the mechanical property of the PVC plastic is ensured while the degradability of the PVC plastic is improved through the fusion of the PVC and the biodegradation agent. And simultaneously, a nontoxic and easily degradable composite degradation aid is added, the composite degradation aid consists of a succinate degradation aid and a castor oil-based degradation aid, and the mechanical property and the biodegradation property of the PVC plastic are further improved by compounding the two degradation aids and controlling the mass ratio of the two degradation aids.

The castor oil-based degradation assistant agent is prepared by taking furfuryl alcohol and castor oil fatty acid as raw materials and synthesizing through lipase catalytic esterification reaction, the synthesized castor oil-based degradation assistant agent endows PVC plastics with excellent mechanical strength, thermal stability, plasticizing property and degradability, and the reaction is carried out in a completely solvent-free environment, so that the production and use safety is guaranteed.

Detailed Description

The present invention is described in detail below by way of examples to facilitate understanding of the present invention by those skilled in the art, and it is to be specifically noted that the examples are provided only for the purpose of further illustrating the present invention and are not to be construed as limiting the scope of the present invention.

Example 1

A biodegradable PVC plastic comprises the following raw materials in parts by weight: 100 parts of PVC resin, 10 parts of plasticizer dioctyl terephthalate, 2 parts of lubricant epoxidized soybean oil, 1 part of stabilizer calcium stearate, 5 parts of filler activated calcium carbonate, 1 part of biodegradation agent starch and 40 parts of composite degradation aid. Wherein: the composite degradation aid consists of a succinate degradation aid and a castor oil-based degradation aid, wherein the mass ratio of the succinate degradation aid to the castor oil-based degradation aid is 1: 1.

the synthesis method of the castor oil-based degradation assistant agent comprises the following steps: taking the molar ratio as 3: 1, mixing furfuryl alcohol and castor oil fatty acid, stirring for 50min at 60 ℃, adding immobilized lipase, and reacting for 5 hours under a vacuum condition. Wherein: the immobilized lipase is prepared by adopting candida lipase and adsorbing and immobilizing the candida lipase by using macroporous acrylic resin with the water content of 2 percent and the particle size of 450 mu m as a carrier.

The synthesis method of the succinate co-reducing agent comprises the following steps: taking the molar ratio as 2: 1: n-butanol, succinic acid and H of 9₂SO₄Mixing, stirring at 110 deg.C for 30min, introducing nitrogen, and reacting for 90 min.

A preparation method of biodegradable PVC plastic comprises the following steps:

(1) mixing: mixing the raw materials at 110 ℃ to obtain a mixture;

(2) banburying: banburying the mixture for 3min, and kneading into blocks to obtain a banburying material;

(3) open mixing: carrying out secondary rolling mill open milling on the internal mixing material, wherein the temperature of a secondary rolling mill is 160 ℃ and 165 ℃ respectively, and obtaining plasticized melting material;

(4) extrusion and filtration: extruding and filtering the plasticized melt material, wherein the extrusion temperature is 170 ℃, and the size of a filter screen is 100 meshes to obtain an extruded and filtered material;

(5) and (3) calendering and forming: sequentially carrying out four-time roller calendering molding on the extruded and filtered material, wherein the four-time molding temperature is 180 ℃, 175 ℃ and 170 ℃ respectively, and obtaining a semi-finished product;

(6) post-processing: and (3) taking and cooling the semi-finished product to obtain the biodegradable PVC plastic.

Example 2

A biodegradable PVC plastic comprises the following raw materials in parts by weight: 100 parts of PVC resin, 15 parts of isooctyl adipate serving as a plasticizer, 3 parts of epoxy fatty acid methyl ester serving as a lubricant, 1 part of zinc stearate serving as a stabilizer, 6 parts of active calcium carbonate serving as a filling material, 1 part of cellulose serving as a biodegradation agent and 45 parts of a composite degradation assistant agent. Wherein: the composite degradation aid consists of a succinate degradation aid and a castor oil-based degradation aid, wherein the mass ratio of the succinate degradation aid to the castor oil-based degradation aid is 1: 1.

the synthesis method of the castor oil-based degradation assistant agent comprises the following steps: taking the molar ratio as 2: 1, mixing furfuryl alcohol and castor oil fatty acid, stirring at 50 ℃ for 40min, adding immobilized lipase, and reacting for 5 hours under a vacuum condition. Wherein: the immobilized lipase is prepared by adopting candida lipase and adsorbing and immobilizing the candida lipase by using macroporous acrylic resin with the water content of 2 percent and the particle size of 450 mu m as a carrier.

The synthesis method of the succinate co-reducing agent comprises the following steps: taking the molar ratio of 1: 1: 8 n-butanol, succinic acid and H₂SO₄Mixing, stirring at 100 deg.C for 20min, introducing nitrogen, and reacting for 80 min.

A preparation method of biodegradable PVC plastic comprises the following steps:

(1) mixing: mixing the raw materials at 110 ℃ to obtain a mixture;

(2) banburying: banburying the mixture for 4min, and kneading the mixture into blocks to obtain a banburying material;

(3) open mixing: carrying out secondary rolling mill open milling on the internal mixing material, wherein the temperature of a secondary rolling mill is 165 ℃ and 170 ℃ respectively, so as to obtain a plasticized melt material;

(4) extrusion and filtration: extruding and filtering the plasticized melt material, wherein the extrusion temperature is 170 ℃, and the size of a filter screen is 120 meshes to obtain an extruded and filtered material;

(5) and (3) calendering and forming: sequentially carrying out four-time roller calendering molding on the extruded and filtered material, wherein the four-time molding temperature is 185 ℃, 180 ℃ and 175 ℃ respectively, and obtaining a semi-finished product;

(6) post-processing: and (3) taking and cooling the semi-finished product to obtain the biodegradable PVC plastic.

Example 3

A biodegradable PVC plastic comprises the following raw materials in parts by weight: 100 parts of PVC resin, 5 parts of plasticizer dioctyl terephthalate and 5 parts of adipic acid isooctyl ester, 2 parts of lubricant epoxidized soybean oil, 1 part of stabilizer calcium stearate, 5 parts of filler activated calcium carbonate, 1 part of biodegradation agent starch and 40 parts of composite degradation aid. Wherein: the composite degradation aid consists of a succinate degradation aid and a castor oil-based degradation aid, wherein the mass ratio of the succinate degradation aid to the castor oil-based degradation aid is 1: 2.

the synthesis method of the castor oil-based degradation assistant agent comprises the following steps: taking the molar ratio as 4: 1, mixing furfuryl alcohol and castor oil fatty acid, stirring for 50min at 60 ℃, adding immobilized lipase, and reacting for 5 hours under a vacuum condition. Wherein: the immobilized lipase is prepared by adopting candida lipase and adsorbing and immobilizing the candida lipase by using macroporous acrylic resin with the water content of 2 percent and the particle size of 450 mu m as a carrier.

The synthesis method of the succinate co-reducing agent comprises the following steps: taking the molar ratio as 2: 1: 10 of n-butanol, succinic acid and H₂SO₄Mixing, stirring at 100 deg.C for 40min, introducing nitrogen, and reacting for 80 min.

A preparation method of biodegradable PVC plastic comprises the following steps:

(1) mixing: mixing the raw materials at 120 ℃ to obtain a mixture;

(2) banburying: banburying the mixture for 5min, and kneading the mixture into blocks to obtain a banburying material;

(3) open mixing: carrying out secondary rolling mill open milling on the internal mixing material, wherein the temperature of a secondary rolling mill is 170 ℃ and 175 ℃ respectively, so as to obtain a plasticized molten material;

(4) extrusion and filtration: extruding and filtering the plasticized melt material, wherein the extrusion temperature is 175 ℃, and the size of a filter screen is 200 meshes to obtain an extruded and filtered material;

(5) and (3) calendering and forming: sequentially carrying out four-time roller calendering molding on the extruded and filtered material, wherein the four-time molding temperature is 190 ℃, 185 ℃, 180 ℃ and 175 ℃ respectively, and obtaining a semi-finished product;

(6) post-processing: and (3) taking and cooling the semi-finished product to obtain the biodegradable PVC plastic.

Example 4

A biodegradable PVC plastic comprises the following raw materials in parts by weight: 100 parts of PVC resin, 20 parts of dibutoxybutyl adipate as a plasticizer, 5 parts of dioctyl adipate as a lubricant, 2 parts of cadmium stearate as a stabilizer, 10 parts of kaolin as a filler, 1 part of chitosan as a biodegradation agent and 50 parts of a composite degradation assistant agent. Wherein: the composite degradation aid consists of a succinate degradation aid and a castor oil-based degradation aid, wherein the mass ratio of the succinate degradation aid to the castor oil-based degradation aid is 1: 4.

the synthesis method of the castor oil-based degradation assistant agent comprises the following steps: taking the molar ratio as 3: 1, mixing furfuryl alcohol and castor oil fatty acid, stirring at 70 ℃ for 30min, adding immobilized lipase, and reacting for 4 hours under a vacuum condition. Wherein: the immobilized lipase is prepared by adopting candida lipase and adsorbing and immobilizing the candida lipase by using macroporous acrylic resin with the water content of 2 percent and the particle size of 450 mu m as a carrier.

The synthesis method of the succinate co-reducing agent comprises the following steps: taking the molar ratio as 3: 1: 8 n-butanol, succinic acid and H₂SO₄Mixing, stirring at 120 deg.C for 20min, introducing nitrogen, and reacting for 80 min.

A preparation method of biodegradable PVC plastic comprises the following steps:

(1) mixing: mixing the raw materials at 110 ℃ to obtain a mixture;

(2) banburying: banburying the mixture for 4min, and kneading the mixture into blocks to obtain a banburying material;

(3) open mixing: carrying out secondary rolling mill open milling on the internal mixing material, wherein the temperature of the secondary rolling mill is 160 ℃ and 175 ℃ respectively, so as to obtain plasticized melting material;

(4) extrusion and filtration: extruding and filtering the plasticized melt material, wherein the extrusion temperature is 175 ℃, and the size of a filter screen is 100 meshes to obtain an extruded and filtered material;

(5) and (3) calendering and forming: sequentially carrying out four-time roller calendering molding on the extruded and filtered material, wherein the four-time molding temperature is 180 ℃, 185 ℃, 175 ℃ and 175 ℃ respectively, and obtaining a semi-finished product;

(6) post-processing: and (3) taking and cooling the semi-finished product to obtain the biodegradable PVC plastic.

Example 5

A biodegradable PVC plastic comprises the following raw materials in parts by weight: 100 parts of PVC resin, 15 parts of plasticizer citrate, 4 parts of lubricant epoxidized soybean oil, 1.5 parts of stabilizer styrene-methacrylate copolymer, 8 parts of filler active calcium carbonate, 1.5 parts of biodegradation agent poly glucosamine and 42 parts of composite degradation assistant. Wherein: the composite degradation aid consists of a succinate degradation aid and a castor oil-based degradation aid, wherein the mass ratio of the succinate degradation aid to the castor oil-based degradation aid is 1: 5.

the synthesis method of the castor oil-based degradation assistant agent comprises the following steps: taking the molar ratio as 4: 1, mixing furfuryl alcohol and castor oil fatty acid, stirring at 60 ℃ for 40min, adding immobilized lipase, and reacting under a vacuum condition for 6 hours to obtain the product. Wherein: the immobilized lipase is prepared by adopting candida lipase and adsorbing and immobilizing the candida lipase by using macroporous acrylic resin with the water content of 2 percent and the particle size of 450 mu m as a carrier.

The synthesis method of the succinate co-reducing agent comprises the following steps: taking the molar ratio as 2: 1: 10 of n-butanol, succinic acid and H₂SO₄Mixing, stirring at 100 deg.C for 30min, introducing nitrogen, and reacting for 90 min.

A preparation method of biodegradable PVC plastic comprises the following steps:

(1) mixing: mixing the raw materials at 120 ℃ to obtain a mixture;

(2) banburying: banburying the mixture for 5min, and kneading the mixture into blocks to obtain a banburying material;

(3) open mixing: carrying out secondary rolling mill open milling on the internal mixing material, wherein the temperature of the secondary rolling mill is 160 ℃ and 170 ℃ respectively, and obtaining plasticized melting material;

(4) extrusion and filtration: extruding and filtering the plasticized melt material, wherein the extrusion temperature is 180 ℃, and the size of a filter screen is 200 meshes to obtain an extruded and filtered material;

(5) and (3) calendering and forming: sequentially carrying out four-time roller calendering molding on the extruded and filtered material, wherein the four-time molding temperature is 180 ℃, 185 ℃, 175 ℃ and 170 ℃ respectively, and obtaining a semi-finished product;

(6) post-processing: and (3) taking and cooling the semi-finished product to obtain the biodegradable PVC plastic.

Example 6

A biodegradable PVC plastic comprises the following raw materials in parts by weight: 100 parts of PVC resin, 15 parts of plasticizer citrate, 4 parts of lubricant epoxidized soybean oil, 2 parts of stabilizer calcium stearate, 6 parts of filler active calcium carbonate, 2 parts of biodegradation agent starch and 45 parts of composite degradation promoter. Wherein: the composite degradation aid consists of a succinate degradation aid and a castor oil-based degradation aid, wherein the mass ratio of the succinate degradation aid to the castor oil-based degradation aid is 1: 3.

the synthesis method of the castor oil-based degradation assistant agent comprises the following steps: taking the molar ratio as 3: 1, mixing furfuryl alcohol and castor oil fatty acid, stirring at 60 ℃ for 40min, adding immobilized lipase, and reacting under a vacuum condition for 6 hours to obtain the product. Wherein: the immobilized lipase is prepared by adopting candida lipase and adsorbing and immobilizing the candida lipase by using macroporous acrylic resin with the water content of 2 percent and the particle size of 450 mu m as a carrier.

The synthesis method of the succinate co-reducing agent comprises the following steps: taking the molar ratio as 2: 1: n-butanol, succinic acid and H of 9₂SO₄Mixing, stirring at 110 deg.C for 30min, introducing nitrogen, and reacting for 90 min.

A preparation method of biodegradable PVC plastic comprises the following steps:

(1) mixing: mixing the raw materials at 120 ℃ to obtain a mixture;

(2) banburying: banburying the mixture for 4min, and kneading the mixture into blocks to obtain a banburying material;

(3) open mixing: carrying out secondary rolling mill open milling on the internal mixing material, wherein the temperature of a secondary rolling mill is 165 ℃ and 170 ℃ respectively, so as to obtain a plasticized melt material;

(4) extrusion and filtration: extruding and filtering the plasticized melt material, wherein the extrusion temperature is 180 ℃, and the size of a filter screen is 200 meshes to obtain an extruded and filtered material;

(5) and (3) calendering and forming: sequentially carrying out four-time roller calendering molding on the extruded and filtered material, wherein the four-time molding temperature is 180 ℃, 185 ℃, 180 ℃ and 175 ℃ respectively, and obtaining a semi-finished product;

(6) post-processing: and (3) taking and cooling the semi-finished product to obtain the biodegradable PVC plastic.

Example 7

A biodegradable PVC plastic comprises the following raw materials in parts by weight: 100 parts of PVC resin, 15 parts of plasticizer citrate, 4 parts of lubricant epoxidized soybean oil, 2 parts of stabilizer calcium stearate, 6 parts of filler active calcium carbonate, 2 parts of biodegradable modified starch and 45 parts of composite degradation promoter. Wherein: the composite degradation aid consists of a succinate degradation aid and a castor oil-based degradation aid, wherein the mass ratio of the succinate degradation aid to the castor oil-based degradation aid is 1: 3.

the method for modifying starch comprises the following steps:

dissolving organic dispersant gelatin in purified water, respectively adding styrene, cross-linking agent divinylbenzene, initiator benzoyl peroxide, pore-forming agent toluene peroxide, isooctane and water-soluble monomer methacryloyloxyethyl phosphorylcholine, uniformly stirring, adding inorganic dispersant calcium phosphate, heating to 70 ℃, shaping for 4 hours to obtain pre-microspheres, and continuing to perform suspension polymerization reaction at 80 ℃ for 20 hours to obtain the porous resin microspheres with the average pore diameter of 20 microns. Wherein: the raw materials comprise, by weight, 5 parts of gelatin, 45 parts of styrene, 55 parts of divinylbenzene, 2 parts of benzoyl peroxide, 175 parts of toluene, 20 parts of isooctane, 6 parts of vinyl pyrrolidone and 0.6 part of calcium phosphate.

Drying starch at 72 deg.C, pulverizing to obtain starch granule with average particle diameter less than 20 μm;

adding the starch particles into coupling agent titanate and alcoholic solution for dispersion, adding the porous resin microspheres and performing ultrasonic dispersion treatment to make the starch particles adsorbed in the porous structure of the adsorption resin microspheres, and then heating to 60 ℃ for drying to obtain the resin microspheres loaded with the starch particles, wherein: the components of each raw material comprise 15 parts of starch particles, 2 parts of coupling agent titanate, 58 parts of alcoholic solution and 25 parts of porous resin microspheres by weight;

adding the resin microspheres loaded with the starch particles into CaCl with the mass concentration of 40%₂Stirring in the solution to make the surface of the resin microsphere loaded with starch microparticles adhere with a large amount of Ca²⁺Then adding sodium alginate with the mass volume concentration of 3g/L to form a structure-shaped microcapsule, and fixedly encapsulating starch granules in the microcapsule to obtain the modified starch.

The synthetic methods of the castor oil-based co-reducing agent and the succinate co-reducing agent and the preparation method of the biodegradable PVC plastic of the embodiment are the same as those of the embodiment 6.

Comparative example 1

A biodegradable PVC plastic comprises the following raw materials in parts by weight: 100 parts of PVC resin, 50 parts of plasticizer dioctyl terephthalate, 2 parts of lubricant epoxidized soybean oil, 1 part of stabilizer calcium stearate, 5 parts of filler activated calcium carbonate and 1 part of starch serving as a biodegradation agent.

Compared with the raw material composition of the biodegradable PVC plastic in the example 1, the biodegradable PVC plastic does not contain the composite degradation assistant, and the dosage of the dioctyl terephthalate is increased to make up for the dosage of the composite degradation assistant.

The biodegradable PVC plastic of this comparative example was prepared in the same manner as in example 6.

Comparative example 2

A biodegradable PVC plastic comprises the following raw materials in parts by weight: 100 parts of PVC resin, 10 parts of plasticizer dioctyl terephthalate, 2 parts of lubricant epoxidized soybean oil, 1 part of stabilizer calcium stearate, 5 parts of filler activated calcium carbonate, 1 part of biodegradation agent starch and 40 parts of composite degradation aid. Wherein: the composite degradation aid consists of a succinate degradation aid and a castor oil-based degradation aid, wherein the mass ratio of the succinate degradation aid to the castor oil-based degradation aid is 2: 1.

compared with the raw material composition of the biodegradable PVC plastic of the comparative example 1, the mass ratio of only the succinate co-reducing agent to the castor oil-based co-reducing agent is different.

The synthetic methods of the castor oil-based co-reducing agent and the succinate co-reducing agent of the comparative example and the preparation method of the biodegradable PVC plastic are the same as those of example 1.

Comparative example 3

A biodegradable PVC plastic comprises the following raw materials in parts by weight: 100 parts of PVC resin, 10 parts of plasticizer dioctyl terephthalate, 2 parts of lubricant epoxidized soybean oil, 1 part of stabilizer calcium stearate, 5 parts of filler activated calcium carbonate, 1 part of biodegradation agent starch and 40 parts of composite degradation aid. Wherein: the composite degradation aid consists of a succinate degradation aid and a castor oil-based degradation aid, wherein the mass ratio of the succinate degradation aid to the castor oil-based degradation aid is 1: 6.

compared with the raw material composition of the biodegradable PVC plastic of the comparative example 1, the mass ratio of only the succinate co-reducing agent to the castor oil-based co-reducing agent is different.

The synthetic methods of the castor oil-based co-reducing agent and the succinate co-reducing agent of the comparative example and the preparation method of the biodegradable PVC plastic are the same as those of example 1.

Comparative example 4

A biodegradable PVC plastic comprises the following raw materials in parts by weight: 100 parts of PVC resin, 10 parts of plasticizer dioctyl terephthalate, 2 parts of lubricant epoxidized soybean oil, 1 part of stabilizer calcium stearate, 5 parts of filler activated calcium carbonate, 1 part of biodegradation agent starch and 40 parts of castor oil-based degradation aid.

Compared with the raw material composition of the biodegradable PVC plastic of the example 1, the degradation assistant agent of the biodegradable PVC plastic is a single castor oil-based degradation assistant agent.

The synthetic method of the castor oil-based degradation assistant and the preparation method of the biodegradable PVC plastic of the comparative example are the same as those of example 1.

Comparative example 5

A biodegradable PVC plastic comprises the following raw materials in parts by weight: 100 parts of PVC resin, 10 parts of plasticizer dioctyl terephthalate, 2 parts of lubricant epoxidized soybean oil, 1 part of stabilizer calcium stearate, 5 parts of filler activated calcium carbonate, 1 part of biodegradation agent starch and 40 parts of succinate degradation aid.

Compared with the raw material composition of the biodegradable PVC plastic of the example 1, the biodegradable PVC plastic of the comparative example has the advantage that the degradation promoter is a single succinate degradation promoter.

The synthesis method of the succinate co-reducing agent and the preparation method of the biodegradable PVC plastic of the comparative example are the same as those of the example 1.

Comparative example 6

This comparative example differs from example 1 in that: during the synthesis process of the castor oil-based degradation promoter, candida lipase is directly used as a catalyst.

Comparative example 7

This comparative example differs from example 1 in that: in the synthesis process of the castor oil-based degradation assistant, the molar ratio of furfuryl alcohol to castor oil fatty acid is 1: 1.

comparative example 8

This comparative example differs from example 1 in that: in the synthesis process of the castor oil-based degradation assistant, the molar ratio of furfuryl alcohol to castor oil fatty acid is 5: 1.

performance testing

The biodegradable PVC plastics prepared in examples 1 to 7 and comparative examples 1 to 8 were subjected to mechanical property (modulus of elasticity, tensile strength, elongation at break) and biodegradability (compost degradation) tests, and the test results thereof are shown in table 1 below.

TABLE 1 comparison of Performance parameters for various examples and comparative examples

From the test results of table 1, it can be seen that: the biodegradable PVC plastics prepared in the embodiments 1-7 of the invention have good mechanical property and biodegradability, wherein: compared with example 6, the modified starch adopted in example 7 has obviously improved mechanical properties and biodegradability. Comparative examples 1 to 8 the biodegradable PVC plastics obtained were inferior to examples 1 to 7 in mechanical properties or biodegradability for the following reasons, such as no addition of a composite co-reducing agent, a ratio of two co-reducing agents out of the range of the present invention, and a difference in the method of using a single co-reducing agent or a synthetic castor oil based co-reducing agent, wherein: the comparative example 1 has a significant reduction in biodegradability compared to example 1 due to the absence of the addition of the composite degradation aid, and thus it is further demonstrated that the composite degradation aid is advantageous in promoting biodegradability of PVC plastics.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are intended to be within the scope of the invention.