CN113789059A - ZnO-chitosan grafted polylactic acid mulching film - Google Patents

ZnO-chitosan grafted polylactic acid mulching film Download PDF

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CN113789059A
CN113789059A CN202111179150.XA CN202111179150A CN113789059A CN 113789059 A CN113789059 A CN 113789059A CN 202111179150 A CN202111179150 A CN 202111179150A CN 113789059 A CN113789059 A CN 113789059A
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甘德彬
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01G—HORTICULTURE; CULTIVATION OF VEGETABLES, FLOWERS, RICE, FRUIT, VINES, HOPS OR SEAWEED; FORESTRY; WATERING
    • A01G13/00—Protecting plants
    • A01G13/02—Protective coverings for plants; Coverings for the ground; Devices for laying-out or removing coverings
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    • C08K5/00—Use of organic ingredients
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    • C08K5/11—Esters; Ether-esters of acyclic polycarboxylic acids

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Abstract

The invention provides a ZnO-chitosan grafted polylactic acid mulching film, which relates to the technical field of mulching films and comprises the following raw materials in parts by weight: 40-50 parts of polylactic acid, 80-100 parts of ZnO-chitosan, 0.15-1.5 parts of lubricant, 2-3 parts of plasticizer, 0.15-1.5 parts of ultraviolet absorbent and 2-4 parts of pH regulator. According to the invention, chitosan is firstly grafted on the surface of ZnO to increase the dispersibility of ZnO in a polymer, then ZnO-chitosan is used for grafting polylactic acid, and ZnO-chitosan-polylactic acid is used as a base material to be mixed with other additives and the like to prepare the mulching film, so that the pulling-up property, the elongation at break and the impact strength of the mulching film are increased, and the biodegradability of the polylactic acid is not influenced.

Description

ZnO-chitosan grafted polylactic acid mulching film
Technical Field
The invention relates to the technical field of mulching films, in particular to a ZnO-chitosan grafted polylactic acid mulching film.
Background
Thin film materials refer to thin metal or organic layers with thicknesses ranging from a single atom to several millimeters. When a solid or liquid has a one-dimensional linear dimension that is much smaller than its other two-dimensional dimension, we refer to such a solid or liquid as a membrane. The film has good toughness, moisture resistance and heat sealing performance, and is widely applied. The film types include biaxially oriented polypropylene (BOPP), Low Density Polyethylene (LDPE), Polyester (PET), nylon (PA), cast polypropylene (CPP) and aluminized films. The film material has the same structure as the paper material, and the only difference is that the surface of the material needs to be processed.
The plastic product has the advantages of strong stability, small specific gravity, low production cost and the like, so that the using amount is large. In recent years, the plastic industry has been rapidly developed, and the use of a large number of plastic products, particularly disposable products, brings great convenience to human life. However, general plastics (PE, PP, PS, PVC) have high chemical stability, and are discarded in the environment for a long time, so that a large amount of solid plastic waste is accumulated in the environment and seriously harms the environment. The agricultural mulching film has the advantages of moisture preservation, heat preservation, insect resistance, weed growth inhibition, crop yield improvement and the like, so that the agricultural mulching film becomes an important production data of modern agriculture. However, the mulching film has the above-mentioned disadvantages of being difficult to degrade and easy to break, and thus imposes a great burden on the environment.
Polylactic acid is also called polylactide, is thermoplastic aliphatic polyester derived from renewable resources, has good biocompatibility, solvent resistance, mechanical property and processability, is non-toxic and free of pungent smell, has high yield and bright development prospect, is a novel green and friendly material, and is widely applied to the fields of packaging materials, biomedical materials and the like. However, polylactic acid has the disadvantages of hard and brittle texture, poor impact resistance, notch sensitivity, low notch impact strength and the like, so that the application of polylactic acid is greatly limited.
Disclosure of Invention
Technical problem to be solved
Aiming at the defects of the prior art, the invention provides the ZnO-chitosan grafted polylactic acid mulching film, the mulching film is prepared from polylactic acid, ZnO-chitosan, a lubricant, a plasticizer, an ultraviolet absorbent and a pH regulator, and the obtained mulching film has the advantages of good toughness, easy degradation and the like.
(II) technical scheme
In order to achieve the purpose, the invention is realized by the following technical scheme:
the ZnO-chitosan grafted polylactic acid mulching film comprises the following raw materials in parts by weight: 40-50 parts of polylactic acid, 80-100 parts of ZnO-chitosan, 0.15-1.5 parts of lubricant, 2-3 parts of plasticizer, 0.15-1.5 parts of ultraviolet absorbent and 2-4 parts of pH regulator.
Further, the lubricant is prepared by mixing one or more of liquid paraffin, stearate, oxidized polyethylene wax, glyceryl monostearate and white oil in any proportion.
Further, the plasticizer is one or more of polyethylene glycol, triethyl citrate and acetyl tri-n-butyl citrate which are mixed according to any proportion.
Further, the ultraviolet absorbent is prepared by mixing one or more of UV234, UV327, UV329 and UV531 in any proportion.
Further, the pH adjusting agent is trisodium phosphate.
Further, the preparation method of the ZnO-chitosan comprises the following steps:
(1) preparing modified nano zinc oxide: placing nano zinc oxide and gamma-glycidyl ether oxypropyl trimethoxy silane in absolute ethyl alcohol, stirring and dissolving under the protection of argon, refluxing for 5 hours at 70-75 ℃, filtering reaction liquid, and cleaning and drying obtained solid to obtain modified nano zinc oxide;
(2) preparation of phthaloyl chitosan: taking a proper amount of chitosan and phthalic anhydride, adding a proper amount of DMF solvent into a reaction kettle, mixing to completely dissolve phthalic anhydride, introducing nitrogen to remove oxygen, heating at 120 ℃ for 5 hours, carrying out ice-water precipitation separation on reactants, extracting, washing and purifying by hot ethanol, and carrying out vacuum drying at 40 ℃ to obtain phthaloylated chitosan;
(3) phthalic acylation chitosan grafting modified nano zinc oxide: adding phthaloyl chitosan and modified nano zinc oxide into a reaction kettle, adding a proper amount of dibutyltin dilaurate as a catalyst, wherein the weight ratio of phthaloyl chitosan: modified nano zinc oxide: the molar ratio of dibutyltin dilaurate is 1: (2-3): (0.01-0.02) and reacting for 5-12h at the temperature of 120-150 ℃ to obtain ZnO-phthaloyl chitosan;
(4) deprotection of the amino group of the phthaloyl chitosan: dissolving ZnO-phthaloyl chitosan in DMF, adding appropriate amount of hydrazine hydrate, and adding ZnO-phthaloyl chitosan: the molar ratio of hydrazine hydrate is 1: (1.1-1.2), reacting for 2 hours at 100 ℃ in nitrogen atmosphere, naturally cooling to room temperature, adding distilled water for precipitation and separation, washing with ethanol for multiple times, centrifuging, and vacuum-drying at room temperature to obtain the ZnO-chitosan.
Further, in the step (1) of the preparation method of ZnO-chitosan, the molar ratio of the nano zinc oxide to the gamma-glycidyl ether oxypropyl trimethoxysilane is 1: (1.1-1.2).
Further, in the step (2) of the preparation method of ZnO-chitosan, the molar ratio of chitosan to phthalic anhydride is 1: (3.2-3.6).
Further, the preparation method of the mulching film comprises the following steps:
(1) dissolving polylactic acid and 1, 6-hexanediol with the molar ratio of 5 (7-8) in toluene, reacting for 24-30h at the temperature of 150-;
(2) adding the esterified polylactic acid obtained in the step (1) and acetic anhydride into DMSO (dimethyl sulfoxide), reacting for 20-25h, wherein the molar ratio of the molar weight of hydroxyl in the esterified polylactic acid to the molar weight of the acetic anhydride is 1 (20-21), washing with absolute ethyl alcohol, filtering, centrifuging and drying to obtain hydroformylation polylactic acid;
(3) sequentially adding the hydroformylation polylactic acid and the ZnO-chitosan obtained in the step (2) into DMSO, stirring for 24-30h at 20-25 ℃, and performing centrifugal filtration to obtain polylactic acid grafted with ZnO-chitosan, namely ZnO-chitosan-polylactic acid;
(4) adding ZnO-chitosan-polylactic acid, a lubricant, a plasticizer, an ultraviolet absorbent and a pH regulator into a high-speed mixer in proportion, uniformly mixing to obtain a mixture, adding the mixture into a double-screw extruder, carrying out melt plasticizing and granulation to obtain granules, and adding the granules into a single-screw extruder to blow a film to obtain the mulching film.
(III) advantageous effects
The invention aims to overcome the problems in the prior art and provide a ZnO-chitosan grafted polylactic acid mulching film.
A large number of active hydroxyl groups exist on the surface of ZnO, the active groups and phthaloyl chitosan are subjected to a grafting reaction by a polymerization method, and the surface of nano ZnO particles is coated with the phthaloyl chitosan, so that the aim of modifying nano ZnO powder is fulfilled, and the dispersibility of the nano ZnO powder in polylactic acid is remarkably improved after the phthaloyl chitosan is grafted on the surface of the nano ZnO powder. And then the ZnO-phthaloyl chitosan is subjected to deprotection, so that the subsequent grafting of amino and polylactic acid of the chitosan is facilitated.
The ZnO-chitosan grafted polylactic acid has positive influence on the mechanical property of the prepared degradable film, nano ZnO particles are dispersed in the polylactic acid, occupy small holes in the polylactic acid structure, increase the cross-linking density of the polylactic acid, increase the tensile property of the polymer film, obviously increase the elongation at break and the impact strength of the blend, and cannot influence the biodegradable property of the polylactic acid. The chitosan is grafted on the polylactic acid, so that the visible light transmittance of the mulching film is increased, the visible light transmittance of the mulching film prepared by the method is over 96 percent, the hydrophilic property is improved, and the degradation rate is accelerated.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1:
the ZnO-chitosan grafted polylactic acid mulching film is characterized by comprising the following raw materials in parts by weight: 40 parts of polylactic acid, 80 parts of ZnO-chitosan, 0.15 part of liquid paraffin, 2 parts of acetyl tributyl citrate, 3270.15 parts of UV and 2 parts of trisodium phosphate.
The preparation method of the ZnO-chitosan comprises the following steps:
(1) preparing modified nano zinc oxide: placing nano zinc oxide and gamma-glycidoxypropyltrimethoxysilane into absolute ethyl alcohol, wherein the molar ratio of the nano zinc oxide to the gamma-glycidoxypropyltrimethoxysilane is 1: 1.1, stirring and dissolving under the protection of argon, refluxing for 5 hours at 70 ℃, filtering reaction liquid, and cleaning and drying obtained solid to obtain modified nano zinc oxide;
(2) preparation of phthaloyl chitosan: taking a proper amount of chitosan and phthalic anhydride in a reaction kettle, wherein the molar ratio of the chitosan to the phthalic anhydride is 1: 3.2, adding a proper amount of DMF solvent for mixing to completely dissolve phthalic anhydride, introducing nitrogen for removing oxygen, heating at 120 ℃ for 5 hours, precipitating and separating reactants by ice water, extracting, washing and purifying by hot ethanol, and drying in vacuum at 40 ℃ to obtain the phthaloylated chitosan;
(3) phthalic acylation chitosan grafting modified nano zinc oxide: adding phthaloyl chitosan and modified nano zinc oxide into a reaction kettle, adding a proper amount of dibutyltin dilaurate as a catalyst, wherein the weight ratio of phthaloyl chitosan: modified nano zinc oxide: the molar ratio of dibutyltin dilaurate is 1: 2: 0.01, reacting for 5 hours at 120 ℃ to obtain ZnO-phthaloyl chitosan;
(4) deprotection of the amino group of the phthaloyl chitosan: dissolving ZnO-phthaloyl chitosan in DMF, adding appropriate amount of hydrazine hydrate, and adding ZnO-phthaloyl chitosan: the molar ratio of hydrazine hydrate is 1: 1.1, reacting for 2 hours at 100 ℃ in nitrogen atmosphere, naturally cooling to room temperature, adding distilled water for precipitation and separation, washing with ethanol for multiple times, centrifuging, and drying in vacuum at room temperature to obtain ZnO-chitosan.
The preparation method of the mulching film comprises the following steps:
(1) dissolving polylactic acid and 1, 6-hexanediol with a molar ratio of 5:7 in toluene, reacting at 150 ℃ for 24h, distilling under reduced pressure, naturally cooling to room temperature, extracting with acetone, washing with water, and filtering to obtain a solid esterified polylactic acid;
(2) adding the esterified polylactic acid obtained in the step (1) and acetic anhydride into DMSO (dimethyl sulfoxide), reacting for 20 hours, wherein the molar ratio of the molar weight of hydroxyl in the esterified polylactic acid to the acetic anhydride is 1:20, washing with absolute ethyl alcohol, filtering, centrifuging and drying to obtain hydroformylation polylactic acid;
(3) sequentially adding the hydroformylation polylactic acid and ZnO-chitosan obtained in the step (2) into DMSO, stirring for 24h at 20 ℃, and performing centrifugal filtration to obtain polylactic acid grafted with ZnO-chitosan, namely ZnO-chitosan-polylactic acid;
(4) adding ZnO-chitosan-polylactic acid, liquid paraffin, acetyl tri-n-butyl citrate, UV327 and trisodium phosphate into a high-speed mixer according to a proportion, uniformly mixing to obtain a mixture, adding the mixture into a double-screw extruder, carrying out melt plasticizing and granulation to obtain granules, and adding the granules into a single-screw extruder to blow a film to obtain the mulching film.
Example 2:
the ZnO-chitosan grafted polylactic acid mulching film is characterized by comprising the following raw materials in parts by weight: 50 parts of polylactic acid, 100 parts of ZnO-chitosan, 1.5 parts of liquid paraffin, 3 parts of acetyl tributyl citrate, 3271.5 parts of UV and 4 parts of trisodium phosphate.
The preparation method of the ZnO-chitosan comprises the following steps:
(1) preparing modified nano zinc oxide: placing nano zinc oxide and gamma-glycidoxypropyltrimethoxysilane into absolute ethyl alcohol, wherein the molar ratio of the nano zinc oxide to the gamma-glycidoxypropyltrimethoxysilane is 1: 1.2, stirring and dissolving under the protection of argon, refluxing for 5 hours at 75 ℃, filtering reaction liquid, and cleaning and drying obtained solid to obtain modified nano zinc oxide;
(2) preparation of phthaloyl chitosan: taking a proper amount of chitosan and phthalic anhydride in a reaction kettle, wherein the molar ratio of the chitosan to the phthalic anhydride is 1: 3.6, adding a proper amount of DMF solvent for mixing to completely dissolve phthalic anhydride, introducing nitrogen for removing oxygen, heating at 120 ℃ for 5 hours, precipitating and separating reactants by ice water, extracting, washing and purifying by hot ethanol, and drying in vacuum at 40 ℃ to obtain the phthaloylated chitosan;
(3) phthalic acylation chitosan grafting modified nano zinc oxide: adding phthaloyl chitosan and modified nano zinc oxide into a reaction kettle, adding a proper amount of dibutyltin dilaurate as a catalyst, wherein the weight ratio of phthaloyl chitosan: modified nano zinc oxide: the molar ratio of dibutyltin dilaurate is 1: 3: 0.02, reacting for 12h at 150 ℃ to obtain ZnO-phthaloyl chitosan;
(4) deprotection of the amino group of the phthaloyl chitosan: dissolving ZnO-phthaloyl chitosan in DMF, adding appropriate amount of hydrazine hydrate, and adding ZnO-phthaloyl chitosan: the molar ratio of hydrazine hydrate is 1: 1.2, reacting for 2 hours at 100 ℃ in nitrogen atmosphere, naturally cooling to room temperature, adding distilled water for precipitation and separation, washing with ethanol for multiple times, centrifuging, and drying in vacuum at room temperature to obtain ZnO-chitosan;
the preparation method of the mulching film comprises the following steps:
(1) dissolving polylactic acid and 1, 6-hexanediol with a molar ratio of 5:8 in toluene, reacting at 200 ℃ for 30h, distilling under reduced pressure, naturally cooling to room temperature, extracting with acetone, washing with water, and filtering to obtain a solid esterified polylactic acid;
(2) adding the esterified polylactic acid obtained in the step (1) and acetic anhydride into DMSO (dimethyl sulfoxide), reacting for 25h, wherein the molar ratio of the molar weight of hydroxyl in the esterified polylactic acid to the acetic anhydride is 1:21, washing with absolute ethyl alcohol, filtering, centrifuging and drying to obtain hydroformylation polylactic acid;
(3) sequentially adding the hydroformylation polylactic acid and ZnO-chitosan obtained in the step (2) into DMSO, stirring for 30h at 25 ℃, and performing centrifugal filtration to obtain polylactic acid grafted with ZnO-chitosan, namely ZnO-chitosan-polylactic acid;
(4) adding ZnO-chitosan-polylactic acid, liquid paraffin, acetyl tri-n-butyl citrate, UV327 and trisodium phosphate into a high-speed mixer according to a proportion, uniformly mixing to obtain a mixture, adding the mixture into a double-screw extruder, carrying out melt plasticizing and granulation to obtain granules, and adding the granules into a single-screw extruder to blow a film to obtain the mulching film.
Example 3:
the ZnO-chitosan grafted polylactic acid mulching film is characterized by comprising the following raw materials in parts by weight: 40 parts of polylactic acid, 100 parts of ZnO-chitosan, 0.15 part of liquid paraffin, 3 parts of acetyl tributyl citrate, 3270.15 parts of UV and 4 parts of trisodium phosphate.
The preparation method of the ZnO-chitosan comprises the following steps:
(1) preparing modified nano zinc oxide: placing nano zinc oxide and gamma-glycidoxypropyltrimethoxysilane into absolute ethyl alcohol, wherein the molar ratio of the nano zinc oxide to the gamma-glycidoxypropyltrimethoxysilane is 1: 1.1, stirring and dissolving under the protection of argon, refluxing for 5 hours at 75 ℃, filtering reaction liquid, and cleaning and drying obtained solid to obtain modified nano zinc oxide;
(2) preparation of phthaloyl chitosan: taking a proper amount of chitosan and phthalic anhydride in a reaction kettle, wherein the molar ratio of the chitosan to the phthalic anhydride is 1: 3.2, adding a proper amount of DMF solvent for mixing to completely dissolve phthalic anhydride, introducing nitrogen for removing oxygen, heating at 120 ℃ for 5 hours, precipitating and separating reactants by ice water, extracting, washing and purifying by hot ethanol, and drying in vacuum at 40 ℃ to obtain the phthaloylated chitosan;
(3) phthalic acylation chitosan grafting modified nano zinc oxide: adding phthaloyl chitosan and modified nano zinc oxide into a reaction kettle, adding a proper amount of dibutyltin dilaurate as a catalyst, wherein the weight ratio of phthaloyl chitosan: modified nano zinc oxide: the molar ratio of dibutyltin dilaurate is 1: 3: 0.01, reacting for 5 hours at 150 ℃ to obtain ZnO-phthaloyl chitosan;
(4) deprotection of the amino group of the phthaloyl chitosan: dissolving ZnO-phthaloyl chitosan in DMF, adding appropriate amount of hydrazine hydrate, and adding ZnO-phthaloyl chitosan: the molar ratio of hydrazine hydrate is 1: 1.2, reacting for 2 hours at 100 ℃ in nitrogen atmosphere, naturally cooling to room temperature, adding distilled water for precipitation and separation, washing with ethanol for multiple times, centrifuging, and drying in vacuum at room temperature to obtain the ZnO-chitosan.
The preparation method of the mulching film comprises the following steps:
(1) dissolving polylactic acid and 1, 6-hexanediol with a molar ratio of 5:7 in toluene, reacting at 200 ℃ for 24 hours, distilling under reduced pressure, naturally cooling to room temperature, extracting with acetone, washing with water, and filtering to obtain a solid, namely esterified polylactic acid;
(2) adding the esterified polylactic acid obtained in the step (1) and acetic anhydride into DMSO (dimethyl sulfoxide), reacting for 25h, wherein the molar ratio of the molar weight of hydroxyl in the esterified polylactic acid to the acetic anhydride is 1:20, washing with absolute ethyl alcohol, filtering, centrifuging and drying to obtain hydroformylation polylactic acid;
(3) sequentially adding the hydroformylation polylactic acid and ZnO-chitosan obtained in the step (2) into DMSO, stirring for 24h at 25 ℃, and performing centrifugal filtration to obtain polylactic acid grafted with ZnO-chitosan, namely ZnO-chitosan-polylactic acid;
(4) adding ZnO-chitosan-polylactic acid, liquid paraffin, acetyl tri-n-butyl citrate, UV327 and trisodium phosphate into a high-speed mixer according to a proportion, uniformly mixing to obtain a mixture, adding the mixture into a double-screw extruder, carrying out melt plasticizing and granulation to obtain granules, and adding the granules into a single-screw extruder to blow a film to obtain the mulching film.
Example 4:
the ZnO-chitosan grafted polylactic acid mulching film is characterized by comprising the following raw materials in parts by weight: 50 parts of polylactic acid, 80 parts of ZnO-chitosan, 1.5 parts of liquid paraffin, 2 parts of acetyl tributyl citrate, UV 3271.5 parts and 2 parts of trisodium phosphate.
The preparation method of the ZnO-chitosan comprises the following steps:
(1) preparing modified nano zinc oxide: placing nano zinc oxide and gamma-glycidoxypropyltrimethoxysilane into absolute ethyl alcohol, wherein the molar ratio of the nano zinc oxide to the gamma-glycidoxypropyltrimethoxysilane is 1: 1.2, stirring and dissolving under the protection of argon, refluxing for 5 hours at 70 ℃, filtering reaction liquid, and cleaning and drying obtained solid to obtain modified nano zinc oxide;
(2) preparation of phthaloyl chitosan: taking a proper amount of chitosan and phthalic anhydride in a reaction kettle, wherein the molar ratio of the chitosan to the phthalic anhydride is 1: 3.2, adding a proper amount of DMF solvent for mixing to completely dissolve phthalic anhydride, introducing nitrogen for removing oxygen, heating at 120 ℃ for 5 hours, precipitating and separating reactants by ice water, extracting, washing and purifying by hot ethanol, and drying in vacuum at 40 ℃ to obtain the phthaloylated chitosan;
(3) phthalic acylation chitosan grafting modified nano zinc oxide: adding phthaloyl chitosan and modified nano zinc oxide into a reaction kettle, adding a proper amount of dibutyltin dilaurate as a catalyst, wherein the weight ratio of phthaloyl chitosan: modified nano zinc oxide: the molar ratio of dibutyltin dilaurate is 1: 2: 0.02, reacting for 12 hours at 120 ℃ to obtain ZnO-phthaloyl chitosan;
(4) deprotection of the amino group of the phthaloyl chitosan: dissolving ZnO-phthaloyl chitosan in DMF, adding appropriate amount of hydrazine hydrate, and adding ZnO-phthaloyl chitosan: the molar ratio of hydrazine hydrate is 1: 1.1, reacting for 2 hours at 100 ℃ in nitrogen atmosphere, naturally cooling to room temperature, adding distilled water for precipitation and separation, washing with ethanol for multiple times, centrifuging, and drying in vacuum at room temperature to obtain ZnO-chitosan.
The preparation method of the mulching film comprises the following steps:
(1) dissolving polylactic acid and 1, 6-hexanediol with a molar ratio of 5:8 in toluene, reacting at 150 ℃ for 30h, distilling under reduced pressure, naturally cooling to room temperature, extracting with acetone, washing with water, and filtering to obtain a solid esterified polylactic acid;
(2) adding the esterified polylactic acid obtained in the step (1) and acetic anhydride into DMSO (dimethyl sulfoxide), reacting for 20 hours, wherein the molar ratio of the molar weight of hydroxyl in the esterified polylactic acid to the acetic anhydride is 1:21, washing with absolute ethyl alcohol, filtering, centrifuging and drying to obtain hydroformylation polylactic acid;
(3) sequentially adding the hydroformylation polylactic acid and ZnO-chitosan obtained in the step (2) into DMSO, stirring for 30h at 20 ℃, and performing centrifugal filtration to obtain polylactic acid grafted with ZnO-chitosan, namely ZnO-chitosan-polylactic acid;
(4) adding ZnO-chitosan-polylactic acid, liquid paraffin, acetyl tri-n-butyl citrate, UV327 and trisodium phosphate into a high-speed mixer according to a proportion, uniformly mixing to obtain a mixture, adding the mixture into a double-screw extruder, carrying out melt plasticizing and granulation to obtain granules, and adding the granules into a single-screw extruder to blow a film to obtain the mulching film.
Example 5:
the ZnO-chitosan grafted polylactic acid mulching film is characterized by comprising the following raw materials in parts by weight: 45 parts of polylactic acid, 90 parts of ZnO-chitosan, 0.3 part of liquid paraffin, 2.5 parts of acetyl tributyl citrate, 3270.3 parts of UV and 3 parts of trisodium phosphate.
The preparation method of the ZnO-chitosan comprises the following steps:
(1) preparing modified nano zinc oxide: placing nano zinc oxide and gamma-glycidoxypropyltrimethoxysilane into absolute ethyl alcohol, wherein the molar ratio of the nano zinc oxide to the gamma-glycidoxypropyltrimethoxysilane is 1: 1.1, stirring and dissolving under the protection of argon, refluxing for 5 hours at 75 ℃, filtering reaction liquid, and cleaning and drying obtained solid to obtain modified nano zinc oxide;
(2) preparation of phthaloyl chitosan: taking a proper amount of chitosan and phthalic anhydride in a reaction kettle, wherein the molar ratio of the chitosan to the phthalic anhydride is 1: 3.5, adding a proper amount of DMF solvent for mixing to completely dissolve phthalic anhydride, introducing nitrogen for removing oxygen, heating at 120 ℃ for 5 hours, precipitating and separating reactants by ice water, extracting, washing and purifying by hot ethanol, and drying in vacuum at 40 ℃ to obtain the phthaloylated chitosan;
(3) phthalic acylation chitosan grafting modified nano zinc oxide: adding phthaloyl chitosan and modified nano zinc oxide into a reaction kettle, adding a proper amount of dibutyltin dilaurate as a catalyst, wherein the weight ratio of phthaloyl chitosan: modified nano zinc oxide: the molar ratio of dibutyltin dilaurate was 200: 500: 3, reacting for 10 hours at 140 ℃ to obtain ZnO-phthaloyl chitosan;
(4) deprotection of the amino group of the phthaloyl chitosan: dissolving ZnO-phthaloyl chitosan in DMF, adding appropriate amount of hydrazine hydrate, and adding ZnO-phthaloyl chitosan: the molar ratio of hydrazine hydrate is 1: 1.2, reacting for 2 hours at 100 ℃ in nitrogen atmosphere, naturally cooling to room temperature, adding distilled water for precipitation and separation, washing with ethanol for multiple times, centrifuging, and drying in vacuum at room temperature to obtain the ZnO-chitosan.
The preparation method of the mulching film comprises the following steps:
(1) dissolving polylactic acid and 1, 6-hexanediol with a molar ratio of 5:8 in toluene, reacting at 150 ℃ for 30h, distilling under reduced pressure, naturally cooling to room temperature, extracting with acetone, washing with water, and filtering to obtain a solid esterified polylactic acid;
(2) adding the esterified polylactic acid obtained in the step (1) and acetic anhydride into DMSO (dimethyl sulfoxide), reacting for 25h, wherein the molar ratio of the molar weight of hydroxyl in the esterified polylactic acid to the acetic anhydride is 1:21, washing with absolute ethyl alcohol, filtering, centrifuging and drying to obtain hydroformylation polylactic acid;
(3) sequentially adding the hydroformylation polylactic acid and ZnO-chitosan obtained in the step (2) into DMSO, stirring for 24h at 25 ℃, and performing centrifugal filtration to obtain polylactic acid grafted with ZnO-chitosan, namely ZnO-chitosan-polylactic acid;
(4) adding ZnO-chitosan-polylactic acid, liquid paraffin, acetyl tri-n-butyl citrate, UV327 and trisodium phosphate into a high-speed mixer according to a proportion, uniformly mixing to obtain a mixture, adding the mixture into a double-screw extruder, carrying out melt plasticizing and granulation to obtain granules, and adding the granules into a single-screw extruder to blow a film to obtain the mulching film.
Comparative example 1:
compared with the embodiment 5, the mulching film comprises the following raw materials in parts by weight: 135 parts of polylactic acid, 0.3 part of liquid paraffin, 2.5 parts of acetyl tributyl citrate, 3270.3 parts of UV and 3 parts of trisodium phosphate.
Adding polylactic acid, liquid paraffin, acetyl tributyl citrate, UV327 and trisodium phosphate into a high-speed mixer according to a proportion, uniformly mixing to obtain a mixture, adding the mixture into a double-screw extruder, carrying out melt plasticizing and granulation to obtain granules, and adding the granules into a single-screw extruder to blow a film to obtain the mulching film.
Content of the experiment
Composite foam insulation boards were produced according to the compositions and methods of examples 1-5 and comparative examples 1-3, respectively.
Measurement of tensile Strength and elongation at Break
According to the test conditions for films and sheets, part 3 of the national Standard "determination of tensile Properties of plastics" (GB \ T1040.3-2006): the dumbbell bars were 150mm in length and 10mm in narrow parallel width, and the results are shown in Table 1 at a tensile rate of 50mm/min at room temperature of 25 ℃.
Measurement of tear Strength
GB/T16578-.
(iii) artificially accelerated photoaging experiment
Using fluorescent ultraviolet lamp tube to emit lightAging test, irradiation intensity 0.68W/m2The temperature of the blackboard is 60 ℃, and the condensation temperature is 60 ℃; a single cycle process: illuminating for 3h, condensing for 3h, and blowing for 10 min; the circulation process is repeated continuously, and the total experiment time is 168 h; after aging, tensile strength, tear strength and elongation at break were measured and the results are shown in table 1.
Light transmission performance
The material to be tested is prepared into a square sample of 50mm multiplied by 50mm according to the specification in GB/T2410-2008 determination of light transmittance and haze of transparent plastic, and the result is shown in Table 2.
Degradation property
And (3) measuring the final aerobic biological decomposition capacity of the material to be measured under GB/T19277.1-2011 controlled composting conditions by adopting a method part 1 for measuring released carbon dioxide: the results of the tests specified in general methods "are shown in Table 2.
Table 1: tensile strength, elongation at break and aging Property test results
Figure 423413DEST_PATH_IMAGE002
Table 2: light transmittance and degradation test results
Figure 278236DEST_PATH_IMAGE004
As can be seen from tables 1-2, the mulching films prepared in examples 1-5 of the present invention are superior to comparative example 1 in not only tensile strength, elongation at break and aging resistance, but also excellent in light transmittance and biodegradability. Can meet the requirements of the industry and has better application prospect.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (9)

  1. The ZnO-chitosan grafted polylactic acid mulching film is characterized by comprising the following raw materials in parts by weight: 40-50 parts of polylactic acid, 80-100 parts of ZnO-chitosan, 0.15-1.5 parts of lubricant, 2-3 parts of plasticizer, 0.15-1.5 parts of ultraviolet absorbent and 2-4 parts of pH regulator.
  2. 2. The ZnO-chitosan grafted polylactic acid mulching film according to claim 1, wherein the lubricant is one or more of liquid paraffin, stearate, oxidized polyethylene wax, glyceryl monostearate and white oil which are mixed in any proportion.
  3. 3. The ZnO-chitosan grafted polylactic acid mulching film according to claim 1, wherein the plasticizer is one or more of polyethylene glycol, triethyl citrate and acetyl tri-n-butyl citrate, and is prepared by mixing the components in any proportion.
  4. 4. The ZnO-chitosan grafted polylactic acid mulching film according to claim 1, wherein the ultraviolet absorbent is prepared by mixing one or more of UV234, UV327, UV329 and UV531 in any proportion.
  5. 5. The ZnO-chitosan grafted polylactic acid mulching film according to claim 1, wherein the pH adjusting agent is trisodium phosphate.
  6. 6. The ZnO-chitosan grafted polylactic acid mulching film according to claim 1, wherein the preparation method of the ZnO-chitosan comprises the following steps:
    (1) preparing modified nano zinc oxide: placing nano zinc oxide and gamma-glycidyl ether oxypropyl trimethoxy silane in absolute ethyl alcohol, stirring and dissolving under the protection of argon, refluxing for 5 hours at 70-75 ℃, filtering reaction liquid, and cleaning and drying obtained solid to obtain modified nano zinc oxide;
    (2) preparation of phthaloyl chitosan: taking a proper amount of chitosan and phthalic anhydride, adding a proper amount of DMF solvent into a reaction kettle, mixing to completely dissolve phthalic anhydride, introducing nitrogen to remove oxygen, heating at 120 ℃ for 5 hours, carrying out ice-water precipitation separation on reactants, extracting, washing and purifying by hot ethanol, and carrying out vacuum drying at 40 ℃ to obtain phthaloylated chitosan;
    (3) phthalic acylation chitosan grafting modified nano zinc oxide: adding phthaloyl chitosan and modified nano zinc oxide into a reaction kettle, adding a proper amount of dibutyltin dilaurate as a catalyst, wherein the weight ratio of phthaloyl chitosan: modified nano zinc oxide: the molar ratio of dibutyltin dilaurate is 1: (2-3): (0.01-0.02) and reacting for 5-12h at the temperature of 120-150 ℃ to obtain ZnO-phthaloyl chitosan;
    (4) deprotection of the amino group of the phthaloyl chitosan: dissolving ZnO-phthaloyl chitosan in DMF, adding appropriate amount of hydrazine hydrate, and adding ZnO-phthaloyl chitosan: the molar ratio of hydrazine hydrate is 1: (1.1-1.2), reacting for 2 hours at 100 ℃ in nitrogen atmosphere, naturally cooling to room temperature, adding distilled water for precipitation and separation, washing with ethanol for multiple times, centrifuging, and vacuum-drying at room temperature to obtain the ZnO-chitosan.
  7. 7. The ZnO-chitosan grafted polylactic acid mulching film according to claim 6, wherein the molar ratio of the nano zinc oxide to the gamma-glycidoxypropyltrimethoxysilane in the step (1) is 1: (1.1-1.2).
  8. 8. The ZnO-chitosan grafted polylactic acid mulching film according to claim 6, wherein the molar ratio of the chitosan to the phthalic anhydride in the step (2) is 1: (3.2-3.6).
  9. 9. The ZnO-chitosan grafted polylactic acid mulching film according to claim 1, wherein the preparation method of the mulching film comprises the following steps:
    (1) dissolving polylactic acid and 1, 6-hexanediol with the molar ratio of 5 (7-8) in toluene, reacting for 24-30h at the temperature of 150-;
    (2) adding the esterified polylactic acid obtained in the step (1) and acetic anhydride into DMSO (dimethyl sulfoxide), reacting for 20-25h, wherein the molar ratio of the molar weight of hydroxyl in the esterified polylactic acid to the molar weight of the acetic anhydride is 1 (20-21), washing with absolute ethyl alcohol, filtering, centrifuging and drying to obtain hydroformylation polylactic acid;
    (3) sequentially adding the hydroformylation polylactic acid and the ZnO-chitosan obtained in the step (2) into DMSO, stirring for 24-30h at 20-25 ℃, and performing centrifugal filtration to obtain polylactic acid grafted with ZnO-chitosan, namely ZnO-chitosan-polylactic acid;
    (4) adding ZnO-chitosan-polylactic acid, a lubricant, a plasticizer, an ultraviolet absorbent and a pH regulator into a high-speed mixer in proportion, uniformly mixing to obtain a mixture, adding the mixture into a double-screw extruder, carrying out melt plasticizing and granulation to obtain granules, and adding the granules into a single-screw extruder to blow a film to obtain the mulching film.
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