CN111944288A - Modified PLA material for biodegradable mulching film and preparation method thereof - Google Patents
Modified PLA material for biodegradable mulching film and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a modified PLA material for a biodegradable mulching film and a preparation method thereof. The mulching film obtained by blow molding the modified PLA material prepared by the invention has the advantages of high tensile strength, good flexibility, high transmittance and the like, and also has excellent ultraviolet aging resistance, excellent hydrolysis resistance, excellent heat preservation and soil moisture preservation performance, good mulching film opening performance, can effectively save film laying time, can be completely degraded into carbon dioxide and water under the action of microorganisms, and cannot generate pollution.
Description
Technical Field
The invention relates to the technical field of film products, in particular to a modified PLA material for a biodegradable mulching film and a preparation method thereof.
Background
In recent years, new material synthesis technology has been adoptedThe development of biodegradable mulching films is receiving wide attention from both academic and industrial fields. The biodegradable mulching film is degraded by microorganisms in soil under natural environment to generate non-toxic small molecules (CO)2And H2O), a plastic mulching film which does not cause harm to the ecological environment. The existing research shows that the biodegradable mulching film has the functions of warming, preserving soil moisture, inhibiting weeds and the like similar to the traditional PE mulching film, and can thoroughly solve the residue problem after the mulching film is used, so the biodegradable mulching film is expected to replace the PE mulching film and is widely applied to the field of crop planting.
The degradable mulching film is a novel mulching film which is exposed to natural environment and is degraded under the combined action of light, heat, water, oxygen, pollutants, microorganisms, insects, wind, sand, rain, mechanical force and the like. The existing degradable mulching film is mainly produced in a large scale by using a photodegradable mulching film and a biodegradable mulching film, the cost of the photodegradable mulching film is low, and the degradation time is difficult to control.
Polylactic acid (PLA) is a polymer obtained by polymerizing lactic acid as a main raw material, and has sufficient raw material sources and can be regenerated. The production process of PLA has no pollution, and the product can be biodegraded to realize the circulation in nature, so the PLA is an ideal green polymer material. In addition, polylactic acid also has some characteristics which are not possessed by other biodegradable materials, such as high strength, high transparency, good weather resistance and the like, and the prepared film has good glossiness and transparency. Although PLA has the above-mentioned excellent properties, its use in the field of film products such as mulching films is limited due to its great brittleness.
Disclosure of Invention
The invention aims to solve the defects in the prior art, and provides a modified PLA material for a biodegradable mulching film and a preparation method thereof.
One of the purposes of the invention is to provide a modified PLA material for a biodegradable mulching film, which comprises the following raw materials in percentage by weight: 45-65% of PLA, 15-25% of PCL, 10-20% of PHBV, 3-8% of modified nano-cellulose, 5-12% of modified halloysite nanotube, 0.05-0.5% of chain extender, 0.02-1% of ultraviolet absorber, 0.5-1% of coconut shell extract, 0.02-1% of light stabilizer and 0.02-1% of opening agent.
Further, the modified nano-cellulose is obtained by modifying nano-cellulose with a composite coupling agent, and the nano-cellulose is prepared by taking ramie waste as a raw material and performing mechanical crushing, alkali liquor cooking, low-grade fiber removal, bleaching, decomposition treatment, ultrasonic dispersion and centrifugal classification, wherein the weight part ratio of the composite silane coupling agent to the nano-cellulose is 0.2-0.8: 12 to 15.
Further, the composite silane coupling agent is prepared by the following steps: under the protection of protective gas, slowly adding vinyl trimethoxy silane and gamma-methacryloxypropyl trimethoxy silane into distilled water, stirring for 0.3-0.6 h, heating to 65-70 ℃ for reaction for 0.8-1.5 h, then removing low-boiling-point substances in vacuum, continuously heating to 115-130 ℃ until no substances are removed, and cooling to room temperature to obtain the composite silane coupling agent.
Further, the modified halloysite nanotube is prepared by the following steps: adding an acetic acid solution of chitosan into a water solution of polyvinyl alcohol, adding butanediol, stirring at 40-50 ℃ in a water bath, then adding an alkali liquor to adjust the pH value to 10-11, stirring, then adding a titanate coupling agent, heating, stirring, then adding an acid liquor to adjust the pH value to 7-8, carrying out reduced pressure distillation, drying and cooling to obtain modified polyvinyl alcohol, dissolving the obtained modified polyvinyl alcohol into dimethylformamide, then adding halloysite nanotubes, stirring and mixing to obtain a mixed solution, then adding the mixed solution into an aluminum trichloride solution, and carrying out reaction for 8-20 hours at the temperature of 55-75 ℃ to obtain the modified halloysite nanotubes.
Further, the concentration of polyvinyl alcohol in the mixed solution is 5-15 wt%, and the weight ratio of the halloysite nanotube to the polyvinyl alcohol is 1: 5 to 15.
Further, the PLA is poly-D-lactic acid or poly-DL-lactic acid with the weight-average molecular weight of 300000-400000, the molecular weight distribution of 1.25-2.0 and the crystallinity of 40-55%; the ultraviolet absorbent is 2-hydroxy-4-n-octoxy benzophenone; the light stabilizer is a polymer of succinic acid and 4-hydroxy-2, 2,6, 6-tetramethyl-1-piperidinol; the opening agent is one or the combination of more than two of talcum powder, calcium carbonate, erucamide and oleamide; the chain extender is one or the combination of more than two of epoxy chain extenders, 2- (1, 3-phenylene) -bisoxazoline or copolymers obtained by copolymerizing glycidyl methacrylate, methyl methacrylate and styrene.
Further, the weight ratio of PLA, PCL and PHBV is 55-60: 20-25: 12 to 15.
The invention also aims to provide a preparation method of the modified PLA material for the biodegradable mulching film, which comprises the following steps: PLA, PCL, PHBV, modified nano-cellulose and modified halloysite nanotubes are dried in vacuum at the temperature of 75-95 ℃ according to the weight parts, then added into a high-speed stirrer together with a chain extender, an ultraviolet absorbent, a coconut shell extract, a light stabilizer and an opening agent for mixing, and finally the obtained mixture is placed into a double-screw extruder for extrusion and granulation to obtain the modified PLA material.
Further, the parameters of the twin-screw extruder are set as follows: the temperature of the feeding section is 130-140 ℃, the temperature of the compression section is 140-155 ℃, the temperature of the homogenization section is 155-175 ℃, and the temperature of the mouth mold is 165-180 ℃.
The invention also aims to provide a biodegradable mulching film, which contains the PLA modified material.
Compared with the prior art, the invention has the following beneficial effects:
(1) according to the invention, the modified halloysite nanotube is used, the polyvinyl alcohol is grafted on the surface of the halloysite nanotube, the polyvinyl alcohol and the halloysite nanotube are combined by chemical bonds rather than simple physical action, the stress transfer efficiency between the halloysite nanotube and a polyvinyl alcohol matrix is greatly improved, and a large amount of hydroxyl groups are introduced on the surface of the halloysite nanotube, so that on one hand, the dispersibility of the halloysite nanotube is improved, the halloysite nanotube is more favorable for blending modification with various polymers PLA, PBAT and PCL, on the other hand, the finally prepared modified PLA material is toughened and enhanced, and meanwhile, the processing performance is also improved;
(2) according to the invention, the ramie waste is utilized and prepared into the nano-cellulose with high mechanical property and good biocompatibility, so that the problems of influence and harm of the existing ramie waste on ecological environment are solved, and meanwhile, the ramie waste is modified by adopting the composite silane coupling agent and then is compositely modified with various polymers PLA, PBAT and PCL, so that the mechanical property of the modified PLA material can be improved;
(3) in the modified PLA material provided by the invention, PBAT and PCL in a certain proportion are added into a PLA base material for blending modification, and a chain extender is used for compatibilization of each polymer, so that the prepared material retains the advantages of high strength and high transmittance of PLA after blow molding film forming, and meanwhile, the toughness is greatly improved; the blend of PLA, PBAT and PCL is compounded with modified nano-cellulose, modified halloysite nanotubes, a chain extender, an ultraviolet absorbent, a coconut shell extract, a light stabilizer and an opening agent, and the prepared mulching film is granulated and blown to form a film, and has the advantages of high tensile strength, good flexibility, high transmittance and the like, excellent ultraviolet aging resistance, excellent hydrolysis resistance, excellent heat preservation and soil moisture preservation performance and good opening property of the mulching film, can effectively save the film laying time, can be completely degraded into carbon dioxide and water under the action of microorganisms, cannot generate pollution, and accordingly the application range of the PLA biodegradable mulching film is widened.
Detailed Description
The present invention will be further illustrated with reference to the following specific examples.
Example 1
A modified PLA material for a biodegradable mulching film comprises the following raw materials in percentage by weight: 60% of PLA, 20% of PCL, 10% of PHBV, 3% of modified nanocellulose, 6% of modified halloysite nanotube, 0.1% of ADR-4370S, 0.05% of a polymer of succinic acid and 4-hydroxy-2, 2,6, 6-tetramethyl-1-piperidinol, 0.5% of coconut shell extract, 0.05% of a polymer of succinic acid and 4-hydroxy-2, 2,6, 6-tetramethyl-1-piperidinol and 0.08% of talcum powder; the preparation method comprises the following steps: vacuum drying the PLA, the PCL, the PHBV, the modified nano-cellulose and the modified halloysite nanotube at the temperature of 95 ℃ according to the weight percent, then adding the dried substances, a chain extender, an ultraviolet absorbent, a coconut shell extract, a light stabilizer and erucamide into a high-speed stirrer for mixing, finally placing the obtained mixture into a double-screw extruder for extrusion granulation, and crushing to obtain a modified PLA material;
the preparation method of the modified halloysite nanotube comprises the following steps: adding chitosan powder into acetic acid solution, and stirring at the rotation speed of 170r/min for 25min at normal temperature to obtain chitosan solution; adding polyvinyl alcohol into deionized water, and stirring at a rotating speed of 220r/min for 40min under a water bath condition of 80 ℃ to obtain a polyvinyl alcohol solution; dropping a chitosan solution into a polyvinyl alcohol solution, adding butanediol, stirring at the speed of 280r/min for 1.5h under the condition of a water bath at 50 ℃, then adding a sodium hydroxide solution, adjusting the pH value to 11, stirring, adding a composite silane coupling agent (prepared by the following steps of slowly adding vinyl trimethoxy silane and gamma-methacryloxypropyl trimethoxy silane into distilled water under the protection of protective gas, stirring for 0.6h, heating to 70 ℃, reacting for 1.0h, removing low-boiling-point substances in vacuum, continuously heating to 120 ℃, cooling to room temperature until no substances are removed to obtain the composite silane coupling agent), heating to 90 ℃, stirring for 1h, adding hydrochloric acid to adjust the pH value to 7, and carrying out reduced pressure distillation to obtain a reaction solution; drying the reaction solution in an oven at 100 ℃ for 6h, and cooling at normal temperature to obtain modified polyvinyl alcohol; dissolving the obtained modified polyvinyl alcohol in dimethylformamide, adding a halloysite nanotube, stirring and mixing for 30min to obtain a mixed solution, wherein the concentration of the polyvinyl alcohol is 12 wt%, then adding the mixed solution into an aluminum trichloride solution, and reacting at 75 ℃ for 18h to obtain the modified halloysite nanotube, wherein the weight percentage ratio of the halloysite nanotube to the polyvinyl alcohol is 1: 10;
the preparation method of the coconut shell extract comprises the following steps: taking dried coconut shells, crushing the dried coconut shells to 80 meshes, adding 80% ethanol with the volume fraction of 8 times the mass of the coconut shells, carrying out reflux extraction for 8 hours, filtering while hot, removing filter residues, and concentrating the filtrate under reduced pressure to obtain an extract; adsorbing the obtained extract with macroporous resin column, eluting with 70% ethanol, collecting eluate with 5 times of column volume, concentrating under reduced pressure, and vacuum drying to obtain coconut shell extract.
Example 2
A modified PLA material for a biodegradable mulching film comprises the following raw materials in percentage by weight: 60% of PLA, 20% of PCL, 12% of PHBV, 8% of modified nanocellulose, 10% of modified halloysite nanotube, 0.5% of chain extender, 0.5% of polymer of succinic acid and 4-hydroxy-2, 2,6, 6-tetramethyl-1-piperidinol, 1% of coconut shell extract, 0.02% of polymer of succinic acid and 4-hydroxy-2, 2,6, 6-tetramethyl-1-piperidinol and 0.02% of opening agent;
the preparation method of the modified halloysite nanotubes and coconut shell extract is the same as that of example 1.
Example 3
A modified PLA material for a biodegradable mulching film comprises the following raw materials in percentage by weight: 50% of PLA, 20% of PCL, 20% of PHBV, 5% of modified nanocellulose, 5% of modified halloysite nanotube, 0.1% of chain extender, 0.08% of ultraviolet absorber, 0.8% of coconut shell extract, 0.04% of light stabilizer and 0.05% of opening agent;
wherein the modified halloysite nanotubes and coconut shell extract were prepared as in example 1.
Example 4
A modified PLA material for a biodegradable mulching film comprises the following raw materials in percentage by weight: 45% of PLA, 25% of PCL, 15% of PHBV, 3% of modified nano-cellulose, 12% of modified halloysite nanotube, 0.05% of chain extender, 0.02% of ultraviolet absorber, 0.8% of coconut shell extract, 0.05% of light stabilizer and 0.02% of opening agent;
wherein the modified halloysite nanotubes and coconut shell extract were prepared as in example 1.
Example 5
A modified PLA material for a biodegradable mulching film comprises the following raw materials in percentage by weight: 55% of PLA, 25% of PCL, 12% of PHBV, 8% of modified nano-cellulose, 5% of modified halloysite nanotube, 0.8% of chain extender, 0.08% of ultraviolet absorber, 0.8% of coconut shell extract, 0.1% of light stabilizer and 0.1% of opening agent;
wherein the modified halloysite nanotubes and coconut shell extract were prepared as in example 1.
Comparative example 1
The procedure was as in example 1 except that modified halloysite nanotubes were not added.
Comparative example 2
The procedure is as in example 1 except that unmodified halloysite nanotubes are added.
Comparative example 3
Is a commercial biodegradable mulching film.
Drying the PLA materials (granules) prepared in the examples 1-5 and the comparative examples 1-2 for 5 hours to enable the water content of the granules to be lower than 0.05%, and obtaining dried extruded material particles; and carrying out blow molding on the extruded material particles in a film blowing machine to form a film, so as to obtain the biodegradable mulching film.
The performance of the mulching films prepared in examples 1 to 5 and comparative examples 1 to 2 and comparative example 3 (a commercially available mulching film) was measured according to the following test standards: the melt index is tested according to the standard of the A method in GB/T3682-2000; the transverse tensile strength and the elongation at break are tested according to the GB/T1040-2006 standard; the water permeability is tested according to the GB/T1037-1988 standard; the ultraviolet light aging is tested according to the GB/T16422-2006 standard. The test results are shown in table 1; and detecting the biological decomposition rate of the mulching film according to GB/T19277. The detection data are specifically seen in table 1 below:
TABLE 1
From table 1, it can be obtained: compared with the commercially available biodegradable mulching film, the biodegradable mulching film prepared from the (modified PLA material) granules prepared in the embodiments 1-5 has excellent tensile strength, water permeability and ultraviolet light aging resistance, and can realize full biodegradation.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (10)
1. The modified PLA material for the biodegradable mulching film is characterized by comprising the following raw materials in percentage by weight: 45-65% of PLA, 15-25% of PCL, 10-20% of PHBV, 3-8% of modified nano-cellulose, 5-12% of modified halloysite nanotube, 0.05-0.5% of chain extender, 0.02-1% of ultraviolet absorber, 0.5-1% of coconut shell extract, 0.02-1% of light stabilizer and 0.02-1% of opening agent.
2. The modified PLA material for the biodegradable mulch film as claimed in claim 1, wherein the modified nanocellulose is obtained by modifying nanocellulose with a composite coupling agent, and the nanocellulose is prepared by using ramie waste as a raw material and performing mechanical crushing, alkali liquor cooking, low-grade fiber removal, bleaching, decomposition treatment, ultrasonic dispersion and centrifugal classification, wherein the weight ratio of the composite silane coupling agent to the nanocellulose is 0.5-1: 12 to 15.
3. The modified PLA material for the biodegradable mulch film as claimed in claim 2, wherein the composite silane coupling agent is prepared by the following steps: under the protection of protective gas, slowly adding vinyl trimethoxy silane and gamma-methacryloxypropyl trimethoxy silane into distilled water, stirring for 0.3-0.6 h, heating to 65-70 ℃ for reaction for 0.8-1.5 h, then removing low-boiling-point substances in vacuum, continuously heating to 115-130 ℃ until no substances are removed, and cooling to room temperature to obtain the composite silane coupling agent.
4. The modified PLA material for the biodegradable mulch film according to claim 1, wherein the modified halloysite nanotubes are prepared by the following steps: adding an acetic acid solution of chitosan into a water solution of polyvinyl alcohol, adding butanediol, stirring at 40-50 ℃ in a water bath, then adding an alkali liquor to adjust the pH value to 10-11, stirring, then adding a titanate coupling agent, heating, stirring, then adding an acid liquor to adjust the pH value to 7-8, carrying out reduced pressure distillation, drying and cooling to obtain modified polyvinyl alcohol, dissolving the obtained modified polyvinyl alcohol into dimethylformamide, then adding halloysite nanotubes, stirring and mixing to obtain a mixed solution, then adding the mixed solution into an aluminum trichloride solution, and carrying out reaction for 8-20 hours at the temperature of 55-75 ℃ to obtain the modified halloysite nanotubes.
5. The modified PLA material for the biodegradable mulch film as claimed in claim 4, wherein the concentration of the polyvinyl alcohol in the mixed solution is 5-15 wt%, and the weight ratio of the halloysite nanotubes to the polyvinyl alcohol is 1: 5 to 12.
6. The modified PLA material for the biodegradable mulch film as claimed in claim 1, wherein the PLA is poly-D-lactic acid or poly-DL-lactic acid with a weight average molecular weight of 300000-400000, a molecular weight distribution of 1.25-2.0 and a crystallinity of 40-55%; the ultraviolet absorbent is 2-hydroxy-4-n-octoxy benzophenone; the light stabilizer is a polymer of succinic acid and 4-hydroxy-2, 2,6, 6-tetramethyl-1-piperidinol; the opening agent is one or the combination of more than two of talcum powder, calcium carbonate, erucamide and oleamide; the chain extender is one or the combination of more than two of epoxy chain extenders, 2- (1, 3-phenylene) -bisoxazoline or copolymers obtained by copolymerizing glycidyl methacrylate, methyl methacrylate and styrene.
7. The modified PLA material for the biodegradable mulch film according to claim 1, wherein the weight ratio of PLA, PCL and PHBV is 55-60: 20-25: 12 to 15.
8. A method for preparing the modified PLA material for the biodegradable mulch film according to any one of claims 1-7, comprising the steps of: PLA, PCL, PHBV, modified nano-cellulose and modified halloysite nanotubes are dried in vacuum at the temperature of 75-95 ℃ according to the weight parts, then added into a high-speed stirrer together with a chain extender, an ultraviolet absorbent, a coconut shell extract, a light stabilizer and an opening agent for mixing, and finally the obtained mixture is placed into a double-screw extruder for extrusion and granulation to obtain the modified PLA material.
9. The method for preparing the modified PLA material for the biodegradable mulch film according to claim 8, wherein the parameters of the twin-screw extruder are set as follows: the temperature of the feeding section is 130-140 ℃, the temperature of the compression section is 140-155 ℃, the temperature of the homogenization section is 155-175 ℃, and the temperature of the mouth mold is 165-180 ℃.
10. A biodegradable mulch film, characterized in that the biodegradable mulch film comprises the PLA modified material according to any one of claims 1 to 3.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116285245A (en) * | 2023-02-28 | 2023-06-23 | 山东道恩高分子材料股份有限公司 | Ultraviolet aging-resistant and hydrolysis-resistant PBAT material and preparation method thereof |
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2020
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116285245A (en) * | 2023-02-28 | 2023-06-23 | 山东道恩高分子材料股份有限公司 | Ultraviolet aging-resistant and hydrolysis-resistant PBAT material and preparation method thereof |
| CN116285245B (en) * | 2023-02-28 | 2024-04-16 | 山东道恩高分子材料股份有限公司 | Ultraviolet aging-resistant and hydrolysis-resistant PBAT material and preparation method thereof |
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