CN113583368A

CN113583368A - Modified starch PVA (polyvinyl alcohol) -based composite film and preparation method thereof

Info

Publication number: CN113583368A
Application number: CN202110938818.8A
Authority: CN
Inventors: 顾程松; 张毅倩; 杨国栋
Original assignee: Anhui Dingyang Bio Based Materials Co ltd
Current assignee: Anhui Dingyang Bio Based Materials Co ltd
Priority date: 2021-08-16
Filing date: 2021-08-16
Publication date: 2021-11-02

Abstract

The invention relates to a modified starch PVA-based composite film, which belongs to the technical field of film preparation and comprises the following raw materials in parts by weight: 20-30 parts of polyvinyl alcohol, 20-30 parts of modified starch, 400 parts of deionized water, 600 parts of melamine, 5-8 parts of glyoxal aqueous solution and 5-10 parts of water; adding a starch solution, a polyvinyl alcohol solution and melamine into a reaction kettle, stirring for 20m & lti & gt n & lt/i & gt, adding a glyoxal aqueous solution, carrying out ultrasonic degassing, and pressing into a film by using a flat vulcanizing machine; the modified starch is obtained by polymerization reaction of an intermediate 5, an intermediate 7, N, N, N-trimethyl-3- (2-methyl allylamido) -1-propyl ammonium chloride and dodecafluoroheptyl methacrylate, the starch has a plasticizing effect, and has multiple functions after modification, so that the composite film has excellent mechanical properties, self-repairing property, antibacterial property, oxidation resistance and hydrophobic property.

Description

Modified starch PVA (polyvinyl alcohol) -based composite film and preparation method thereof

Technical Field

The invention belongs to the technical field of film preparation, and particularly relates to a modified starch PVA (polyvinyl alcohol) based composite film and a preparation method thereof.

Background

Polyvinyl alcohol is a water-soluble polymer with wide application, has unique performance, and is widely used for producing products such as coatings, emulsifiers, adhesives, textiles, paper processing agents, plastic films and the like. The PVA film has good strong adhesion, toughness and transparency, high adhesive film strength, oil resistance, corrosion resistance, solvent resistance and wear resistance, and has good gas barrier property and thermal stability, but the PVA film has soft mechanical property and poor water resistance, so that the application of the PVA film is greatly limited, and the use requirement of the PVA film in practical application cannot be met, therefore, the PVA film needs to be modified, the application properties of mechanics, water resistance and the like can be improved, and the functions of the PVA film can be widened.

Chinese patent CN106117618A discloses an agricultural mulching film and a preparation method thereof, the agricultural mulching film comprises a middle frame-net PBS copolymer film layer and an upper and a lower modified starch-polyvinyl alcohol film layers which can be completely degraded, the starch material modified by nano silicon dioxide and polyvinyl alcohol is used as a base material, the strength, the toughness and the waterproof performance are improved, but the water absorption rate is 20-23%, the starch material does not have antibacterial and antioxidant effects, is easy to age and limits the application of the starch material in other fields and the like, and therefore, the technical problem needing to be solved at present is to provide a modified starch PVA-based composite film.

Disclosure of Invention

The invention aims to provide a modified starch PVA-based composite film and a preparation method thereof, which aim to solve the technical problems in the background.

The purpose of the invention can be realized by the following technical scheme:

a modified starch PVA-based composite film comprises the following raw materials in parts by weight: 20-30 parts of polyvinyl alcohol, 20-30 parts of modified starch, 400 parts of deionized water, 600 parts of melamine, 5-8 parts of glyoxal aqueous solution and 5-10 parts of water;

the modified starch PVA-based composite film is prepared by the following steps:

the method comprises the following steps of firstly, dividing deionized water into two parts in equal amount, adding modified starch into one part, stirring and pasting for 30min at the temperature of 90 ℃ to obtain a starch solution, adding polyvinyl alcohol into the other part, and stirring for 30min at the temperature of 90 ℃ to obtain a polyvinyl alcohol solution;

secondly, adding the starch solution, the polyvinyl alcohol solution and the melamine into a reaction kettle, stirring and mixing for 20min at the temperature of 90 ℃, adding the glyoxal aqueous solution, cooling to 45 ℃, stirring and reacting for 5min, and then ultrasonically degassing the reaction product in an ultrasonic cleaning instrument for 30min to obtain a film forming solution;

and thirdly, pressing the film forming solution into a film by using a flat vulcanizing machine, wherein the mold pressing temperature is 95 ℃, and then drying the film in a 50 ℃ oven to constant weight to obtain the modified starch PVA-based composite film.

Further, an aqueous glyoxal solution was prepared from glyoxal and deionized water in a ratio of 3 g: 6mL of the mixture was mixed.

Further, the modified starch is prepared by the following steps:

step 1, adding a coupling agent KH-550 and 4-methoxyphenol into a three-neck flask, then dropwise adding hydroxyethyl acrylate, stirring and reacting at a rotation speed of 80-120r/min for 0.5h, heating to 40 ℃, stirring and reacting for 4-6h, extracting for 3-5 times by deionized water, and then performing rotary evaporation at 50 ℃ and-0.1 MPa to obtain an intermediate 1;

the reaction process is as follows:

step 2, adding the intermediate 1, tetrahydrofuran and sodium bromide into a three-neck flask, stirring for 5-8min, dropwise adding concentrated sulfuric acid, after dropwise adding, heating to 40-50 ℃, stirring for 1-2h, filtering, and distilling the filtrate under reduced pressure to obtain an intermediate 2;

the reaction process is as follows:

step 3, adding 4, 4-dihydroxy benzophenone and DMF into a three-neck flask, then dropwise adding a DMF solution of the intermediate 2, then adding anhydrous potassium carbonate, heating to 90 ℃, stirring and reacting for 20 hours under a nitrogen atmosphere, after the reaction is finished, filtering, pouring filtrate into ultrapure water, separating out a product, and drying in vacuum at 60 ℃ to constant weight to obtain an intermediate 3;

the reaction process is as follows:

step 4, adding the intermediate 3, DMF, isopropanol and glacial acetic acid into a round-bottom flask, stirring at the rotating speed of 60-80r/min for 30min, transferring to a photochemical reactor, irradiating for 6d at the wavelength of 350nm, transferring the mixed solution to ultrapure water after the irradiation is finished, separating out a product, performing vacuum filtration, and drying a filter cake at 70 ℃ to constant weight to obtain an intermediate 4;

the reaction process is as follows:

step 5, stirring the intermediate 4, tetrahydrofuran and glycidyl methacrylate for 5min, then dropwise adding triethylamine, after the dropwise adding is finished, stirring and reacting for 0.5-1h at the rotation speed of 100-200r/min, after the reaction is finished, adding a hydrochloric acid solution with the mass fraction of 7% to adjust the pH value to 7, separating liquid, and carrying out vacuum distillation on the organic phase until the weight is constant to obtain an intermediate 5;

the reaction process is as follows:

step 6, sequentially adding 2-tert-butylphenol, methyl acetoacetate and dodecyl mercaptan into a four-neck flask at normal temperature, stopping introducing nitrogen in a water bath at 0 ℃ under the protection of nitrogen when the reaction temperature is reduced to 5 ℃, starting introducing HCl gas for 2h, heating to room temperature, carrying out heat preservation reaction for 20h, carrying out reduced pressure degassing after the reaction is finished, degassing for 2-3h at 20-50 ℃, and carrying out reduced pressure distillation for 20min at 160 ℃ to obtain an intermediate 6;

the reaction process is as follows:

step 7, adding the intermediate 6, allyl alcohol, dibutyltin oxide and chlorobenzene into a reaction kettle, introducing nitrogen for protection, reacting for 8-10h at the temperature of 130-135 ℃, filtering after the reaction is finished, washing the filtrate with ultrapure water, extracting with ethyl acetate, and then distilling under reduced pressure until the weight is constant to obtain an intermediate 7;

the reaction process is as follows:

and step 8, adding corn starch and deionized water into a three-neck flask, stirring for 10min, introducing nitrogen, stirring for 30min at the rotation speed of 200 plus 300r/min, then adding ammonium persulfate and urea, continuously stirring for 5min, then adding an intermediate 5, an intermediate 7, N, N, N-trimethyl-3- (2-methylallylamido) -1-ammonium chloride and dodecafluoroheptyl methacrylate, stirring and reacting for 4h in a water bath at 50 ℃, washing reaction products twice by using acetone and absolute ethyl alcohol in sequence after the reaction is finished, drying in an oven at 60 ℃ to constant weight, grinding, extracting for 24h in a Soxhlet extractor by using DMF as an extracting agent, further extracting for 12h by using acetone as the extracting agent, and finally drying in an oven at 60 ℃ for 24h to obtain the modified starch.

Further, in the step 1, the dosage ratio of the coupling agent KH-550, the 4-methoxyphenol and the hydroxyethyl acrylate is 0.1 mol: 0.9-1.1 g: 0.21 mol.

Further, in the step 2, the using ratio of the intermediate 1, tetrahydrofuran, sodium bromide and concentrated sulfuric acid is 30 mmol: 60-67 mL: 30 mmol: 2-4mL, and the mass fraction of concentrated sulfuric acid is 95%.

Further, the ratio of the amount of 4, 4-dihydroxybenzophenone, DMF, the DMF solution of intermediate 2 and anhydrous potassium carbonate in step 3 was 50 mmol: 80-100 mL: 40mL of: 0.6-1.1g, DMF solution of intermediate 2 as 50 mmol: 20mL of the mixture was mixed.

Further, the amount ratio of the intermediate 3, DMF, isopropanol and glacial acetic acid in the step 4 is 5 g: 20mL of: 30mL of: 0.5-1 mL.

Further, in the step 5, the using ratio of the intermediate 4, tetrahydrofuran, glycidyl methacrylate and triethylamine is 50 mmol: 60-80 mL: 200 mmol: 1.5-2.4 mL.

Further, in step 6, the ratio of the amount of 2-tert-butylphenol, methyl acetoacetate and dodecyl mercaptan is 0.31 mol: 0.18-0.25 mol: 0.23-0.28 mol.

Further, in step 7, the ratio of the amount of the intermediate 6, allyl alcohol, dibutyltin oxide and chlorobenzene was 0.1 mol: 0.1 mol: 0.1-0.3 g: 68-72 mL.

Further, in step 8, the amount ratio of corn starch, deionized water, ammonium persulfate, urea, intermediate 5, intermediate 7, N-trimethyl-3- (2-methylallyl amido) -1-propylamine chloride to dodecafluoroheptyl methacrylate was 16 g: 100-120 mL: 0.25-0.34 g: 0.3 g: 1.2-1.4 g: 2-3 g: 1.1-1.3 g: 1.0 g.

The invention has the beneficial effects that:

the invention takes polyvinyl alcohol, modified starch, deionized water, melamine and glyoxal aqueous solution as raw materials to prepare a modified starch PVA-based composite film, takes melamine as a plasticizer, glyoxal aqueous solution as a cross-linking agent and modified starch as a functional additive to ensure that the composite film has excellent mechanical property, self-repairing property, antibacterial property, oxidation resistance and hydrophobic property, firstly takes coupling agent KH-550 and hydroxyethyl acrylate as substrates, obtains an intermediate 1 containing silicon-oxygen bonds and terminal hydroxyl groups through Michael addition reaction, then leads the intermediate 1 to generate halogen substitution reaction to obtain an intermediate 2, then takes 4, 4-dihydroxy benzophenone and the intermediate 2 as raw materials to obtain an intermediate 3 through substitution elimination reaction, takes the intermediate 3 as a substrate to obtain a functionalized aromatic sheet Na-alcohol monomer intermediate 4, and further leads the terminal hydroxyl group of the intermediate 4 to generate ring-opening reaction with the epoxy group of glycidyl methacrylate to obtain the modified starch PVA-based composite film Intermediate 5 containing a terminally unsaturated carbon-carbon double bond; 2-tert-butylphenol and methyl acetoacetate are taken as substrates to obtain an intermediate 6 with a semi-hindered phenol structure, then the intermediate 6 and allyl alcohol are subjected to ester exchange reaction under the catalytic action of dibutyltin oxide to obtain an intermediate 7 with an end unsaturated carbon-carbon double bond, finally corn starch is taken as a raw material, ammonium persulfate and urea are taken as initiators, the intermediate 5, the intermediate 7, N, N, N-trimethyl-3- (2-methyl allylamido) -1-ammonium chloride and dodecafluoro heptyl methacrylate are taken as unsaturated functional monomers, modified starch is obtained through polymerization reaction, the modified starch retains the plasticizing effect thereof and has good compatibility with polyvinyl alcohol, the intermediate 5 with a siloxane bond and an aromatic sheet pinacol structure is grafted in the starch, and the aromatic sheet pinacol is taken as a traditional free radical initiator, the central C-C bond can generate homolytic-combined equilibrium reaction under the condition of light/heat and can generate dynamic light reversible exchange reaction, the dynamic covalent bond on the crack interface can simultaneously generate fracture and structural reaction under single wavelength, and form covalent bond through cross reaction, thereby realizing the self-repairing purpose, N, N, N-trimethyl-3- (2-methyl allyl amido) -1-propyl ammonium chloride belongs to quaternary ammonium salt antibacterial agent and can endow modified starch with antibacterial property, the upper F-C chain of the methacrylic acid dodecafluoroheptyl ester can play a synergistic effect with silicon oxygen bond, as the bond energy is higher, the heat resistance of the composite film is improved, the free energy on the surface of the composite material can be reduced, the hydrophobicity of the material is improved, the intermediate 7 has two semi-hindered phenol structures and can capture free radicals, the oxidation resistance of the composite membrane is improved.

Detailed Description

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 only a part of the embodiments of the present invention, and not all of the 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 modified starch is prepared by the following steps:

step 1, adding 0.1mol of coupling agent KH-550 and 0.9g of 4-methoxyphenol into a three-neck flask, then dropwise adding 0.21mol of hydroxyethyl acrylate, stirring and reacting at the rotating speed of 80r/min for 0.5h, heating to 40 ℃, stirring and reacting for 4h, extracting for 3 times by deionized water, and then performing rotary evaporation at the temperature of 50 ℃ and the pressure of-0.1 MPa to obtain an intermediate 1;

step 2, adding 30mmol of the intermediate 1, 60mL of tetrahydrofuran and 30mmol of sodium bromide into a three-neck flask, stirring for 5min, dropwise adding 2mL of concentrated sulfuric acid, heating to 40 ℃ after dropwise adding, stirring for 1h, filtering, and distilling the filtrate under reduced pressure to obtain an intermediate 2;

step 3, adding 50mmol of 4, 4-dihydroxy benzophenone and 80mL of DMF into a three-neck flask, then dropwise adding 40mL of DMF solution of the intermediate 2, then adding 0.6g of anhydrous potassium carbonate, heating to 90 ℃, stirring under a nitrogen atmosphere for reaction for 20 hours, after the reaction is finished, filtering, pouring filtrate into ultrapure water, and separating out a product, and drying in vacuum at 60 ℃ to constant weight to obtain an intermediate 3;

step 4, adding 5g of the intermediate 3, 20mL of DMMF, 30mL of isopropanol and 0.5mL of glacial acetic acid into a round-bottom flask, stirring at the rotating speed of 60r/min for 30min, transferring to a photochemical reactor, irradiating for 6d at the wavelength of 350nm, transferring the mixed solution to ultrapure water after the irradiation is finished, after a product is separated out, performing vacuum filtration, and drying a filter cake at 70 ℃ to constant weight to obtain an intermediate 4;

step 5, stirring 50mmol of the intermediate 4, 60mL of tetrahydrofuran and 200mmol of glycidyl methacrylate for 5min, then dropwise adding 1.5mL of triethylamine, after dropwise adding, stirring and reacting for 0.5h at the rotating speed of 100r/min, after reaction, adding a hydrochloric acid solution with the mass fraction of 7% to adjust the pH value to 7, separating liquid, and carrying out vacuum distillation on the organic phase until the weight is constant to obtain an intermediate 5;

step 6, sequentially adding 0.31mol of 2-tert-butylphenol, 0.18mol of methyl acetoacetate and 0.23mol of dodecyl mercaptan into a four-neck flask at normal temperature, stopping introducing nitrogen in a 0 ℃ water bath under the protection of nitrogen when the reaction temperature is reduced to 5 ℃, starting introducing HCl gas, introducing the HCl gas for 2 hours, then heating to room temperature, reacting for 20 hours under heat preservation, degassing under reduced pressure at 20 ℃, degassing for 2 hours at 160 ℃, and distilling under reduced pressure for 20 minutes at 160 ℃ to obtain an intermediate 6;

step 7, adding 0.1mol of the intermediate 6, 0.1mol of allyl alcohol, 0.1g of dibutyltin oxide and 68mL of chlorobenzene into a reaction kettle, introducing nitrogen for protection, reacting for 8 hours at the temperature of 130 ℃, filtering after the reaction is finished, washing filtrate with ultrapure water, extracting with ethyl acetate, and then distilling under reduced pressure to constant weight to obtain an intermediate 7;

step 8, adding 16g of corn starch and 100mL of deionized water into a three-neck flask, stirring for 10min, introducing nitrogen, stirring for 30min at the rotation speed of 200r/min, then adding 0.25g of ammonium persulfate and 0.3g of urea, continuously stirring for 5min, then adding 1.2g of intermediate 5, 2g of intermediate 7, 1.1g of N, N, N-trimethyl-3- (2-methyl allylamido) -1-propylamine chloride and 1.0g of dodecafluoroheptyl methacrylate, stirring and reacting for 4h in a water bath at 50 ℃, after the reaction is finished, washing a reaction product twice by using acetone and absolute ethyl alcohol in sequence, drying to constant weight in a 60 ℃ oven, then crushing, selecting DMF as an extracting agent, placing in a Soxhlet extractor for extracting for 24h, further using acetone as an extracting agent, extracting again for 12h, and finally drying in an oven at 60 ℃ for 24h, modified starch is obtained.

Example 2

The modified starch is prepared by the following steps:

step 1, adding 0.1mol of coupling agent KH-550 and 1.1g of 4-methoxyphenol into a three-neck flask, then dropwise adding 0.21mol of hydroxyethyl acrylate, stirring and reacting at the rotating speed of 120r/min for 0.5h, heating to 40 ℃, stirring and reacting for 5h, extracting for 5 times by deionized water, and then performing rotary evaporation at the temperature of 50 ℃ and the pressure of-0.1 MPa to obtain an intermediate 1;

step 2, adding 30mmol of the intermediate 1, 67mL of tetrahydrofuran and 30mmol of sodium bromide into a three-neck flask, stirring for 8min, dropwise adding 4mL of concentrated sulfuric acid, heating to 50 ℃ after dropwise adding, stirring for 2h, filtering, and distilling the filtrate under reduced pressure to obtain an intermediate 2;

step 3, adding 50mmol of 4, 4-dihydroxy benzophenone and 100mL of DMF into a three-neck flask, then dropwise adding 40mL of DMF solution of the intermediate 2, then adding 1.1g of anhydrous potassium carbonate, heating to 90 ℃, stirring under a nitrogen atmosphere for reaction for 20 hours, after the reaction is finished, filtering, pouring filtrate into ultrapure water, and separating out a product, and drying in vacuum at 60 ℃ to constant weight to obtain an intermediate 3;

step 4, adding 5g of the intermediate 3, 20mL of DMMF, 30mL of isopropanol and 1mL of glacial acetic acid into a round-bottom flask, stirring at the rotating speed of 80r/min for 30min, transferring to a photochemical reactor, irradiating for 6d at the wavelength of 350nm, transferring the mixed solution to ultrapure water after the irradiation is finished, after a product is separated out, performing vacuum filtration, and drying a filter cake at 70 ℃ to constant weight to obtain an intermediate 4;

step 5, stirring 50mmol of the intermediate 4, 80mL of tetrahydrofuran and 200mmol of glycidyl methacrylate for 5min, then dropwise adding 2.4mL of triethylamine, stirring and reacting for 1h at the rotation speed of 200r/min after dropwise adding, adding a hydrochloric acid solution with the mass fraction of 7% after reaction to adjust the pH value to 7, separating liquid, and carrying out vacuum distillation on the organic phase until the weight is constant to obtain an intermediate 5;

step 6, sequentially adding 0.31mol of 2-tert-butylphenol, 0.25mol of methyl acetoacetate and 0.28mol of dodecyl mercaptan into a four-neck flask at normal temperature, stopping introducing nitrogen in a 0 ℃ water bath under the protection of nitrogen when the reaction temperature is reduced to 5 ℃, starting introducing HCl gas, introducing the HCl gas for 2 hours, then heating to room temperature, reacting for 20 hours under heat preservation, degassing under reduced pressure at 50 ℃ after the reaction is finished, degassing for 3 hours at 160 ℃, and distilling under reduced pressure for 20 minutes to obtain an intermediate 6;

step 7, adding 0.1mol of the intermediate 6, 0.1mol of allyl alcohol, 0.3g of dibutyltin oxide and 72mL of chlorobenzene into a reaction kettle, introducing nitrogen for protection, reacting for 10 hours at the temperature of 135 ℃, filtering after the reaction is finished, washing filtrate with ultrapure water, extracting with ethyl acetate, and then distilling under reduced pressure to constant weight to obtain an intermediate 7;

step 8, adding 16g of corn starch and 120mL of deionized water into a three-neck flask, stirring for 10min, introducing nitrogen, stirring for 30min at the rotation speed of 300r/min, then adding 0.34g of ammonium persulfate and 0.3g of urea, continuously stirring for 5min, then adding 1.4g of intermediate 5, 3g of intermediate 7, 1.3g of N, N, N-trimethyl-3- (2-methyl allylamido) -1-propylamine chloride and 1.0g of dodecafluoroheptyl methacrylate, stirring and reacting for 4h in a water bath at 50 ℃, after the reaction is finished, washing a reaction product twice by using acetone and absolute ethyl alcohol in sequence, drying to constant weight in a 60 ℃ oven, then crushing, selecting DMF as an extracting agent, placing in a Soxhlet extractor for extracting for 24h, further using acetone as an extracting agent, extracting again for 12h, and finally drying in an oven at 60 ℃ for 24h, modified starch is obtained.

Comparative example 1

This comparative example is corn starch sold by Suzhou Chang chemical technology Co., Ltd.

Example 3

A modified starch PVA-based composite film comprises the following raw materials in parts by weight: 20 parts of polyvinyl alcohol, 20 parts of modified starch in example 1, 400 parts of deionized water, 5 parts of melamine and 5 parts of glyoxal aqueous solution;

step one, dividing deionized water into two parts in equal amount, adding one part of the modified starch of example 1 into the two parts, stirring and gelatinizing the mixture at 90 ℃ for 30min to obtain a starch solution, adding the other part of the modified starch into polyvinyl alcohol, and stirring the mixture at 90 ℃ for 30min to obtain a polyvinyl alcohol solution;

Example 4

A modified starch PVA-based composite film comprises the following raw materials in parts by weight: 25 parts of polyvinyl alcohol, 25 parts of modified starch of example 1, 500 parts of deionized water, 7 parts of melamine and 8 parts of glyoxal aqueous solution;

Example 5

A modified starch PVA-based composite film comprises the following raw materials in parts by weight: 30 parts of polyvinyl alcohol, 30 parts of modified starch of example 2, 600 parts of deionized water, 8 parts of melamine and 10 parts of glyoxal aqueous solution;

step one, dividing deionized water into two parts in equal amount, adding one part of the modified starch of the embodiment 2 into the two parts, stirring and pasting the mixture for 30min at the temperature of 90 ℃ to obtain a starch solution, adding the other part of the modified starch into polyvinyl alcohol, and stirring the mixture for 30min at the temperature of 90 ℃ to obtain a polyvinyl alcohol solution;

Comparative example 2

The modified starch from example 3 was removed and the remaining raw materials and preparation were unchanged.

Comparative example 3

The modified starch of example 4 was replaced with the corn starch of comparative example 1.

Comparative example 4

The comparative example is nano SiO sold by Xian Qiyue biotechnology limited company₂Modified tapioca starch/PVA/chitosan film.

The films of examples 3-5 and comparative examples 2-4 were subjected to performance tests according to the following test criteria:

breaking strength and elongation at break: cutting each group of films into strip-shaped samples of 200mm multiplied by 10mm, placing the samples in a constant temperature and humidity chamber with the temperature of 25 ℃ and the relative humidity of 65% for balancing for 24h, measuring the breaking strength and the breaking elongation of the films according to GB/T1040.3-2006, measuring the stretching speed of 50mm/min, the clamping distance of the samples is 100mm, testing each sample for 10 times, and taking an average value after eliminating abnormal values;

antibacterial property: taking escherichia coli as a test strain, respectively crushing the films of the examples and the comparative examples, adding the crushed films into bacterial suspension, culturing for 24 hours at 35 ℃ and under the condition of relative humidity of 90%, observing and counting the number of colony groups, and testing the antibacterial performance of the composite antibacterial film, wherein the test standard refers to GB/T31402-2015;

hydrophobicity: measuring the contact angle between the water drop and the film by adopting a full-automatic water drop angle tester;

aging resistance: placing each group of films in an aging box at 110 ℃ for 20h, testing the elongation at break of the films, and calculating the ratio of the elongation at break of the films before the rest aging;

self-repairing: and (3) marking a crack with the width of about 20 mu m on the surface of the film sample by using a knife, treating for 10min under 365nm ultraviolet illumination, and observing the change condition before and after crack repair by using a super-depth-of-field three-dimensional microscope system.

The test results are shown in the following table:

as can be seen from the above table, the test results of the films of examples 3-5 are superior to those of comparative examples 2-4 in the processes of testing mechanical properties, antibacterial properties, hydrophobicity, aging resistance and self-repairing properties, which indicates that the composite film prepared by the invention has the characteristic of diversified functions and has great application value in the field of films.

In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The foregoing is illustrative and explanatory only and is not intended to be exhaustive or to limit the invention to the precise embodiments described, and various modifications, additions, and substitutions may be made by those skilled in the art without departing from the scope of the invention or exceeding the scope of the claims.

Claims

1. A modified starch PVA-based composite film is characterized in that: the feed comprises the following raw materials in parts by weight: 20-30 parts of polyvinyl alcohol, 20-30 parts of modified starch, 400 parts of deionized water, 600 parts of melamine, 5-8 parts of glyoxal aqueous solution and 5-10 parts of water;

wherein, the modified starch is prepared by the following steps:

step 1, adding coupling agents KH-550 and 4-methoxyphenol into a three-neck flask, dropwise adding hydroxyethyl acrylate, stirring and reacting for 0.5h, heating to 40 ℃, stirring and reacting for 4-6h, extracting by deionized water, and then performing rotary evaporation to obtain an intermediate 1;

step 2, adding the intermediate 1, tetrahydrofuran and sodium bromide into a three-neck flask, stirring for 5-8min, dropwise adding concentrated sulfuric acid, heating to 40-50 ℃, stirring for 1-2h, filtering, and distilling the filtrate under reduced pressure to obtain an intermediate 2;

step 3, adding 4, 4-dihydroxy benzophenone and DMF into a three-neck flask, dropwise adding a DMF solution of the intermediate 2, adding anhydrous potassium carbonate, heating to 90 ℃, stirring and reacting for 20 hours under a nitrogen atmosphere, filtering, pouring filtrate into ultrapure water, and drying a precipitated product to obtain an intermediate 3;

step 4, adding the intermediate 3, DMF, isopropanol and glacial acetic acid into a round-bottom flask, stirring for 30min, transferring to a photochemical reactor for illumination for 6d, transferring to ultrapure water after illumination is finished, and after a product is separated out, performing reduced pressure suction filtration and drying to obtain an intermediate 4;

step 5, stirring the intermediate 4, tetrahydrofuran and glycidyl methacrylate for 5min, then dropwise adding triethylamine, stirring for reacting for 0.5-1h, adding a hydrochloric acid solution to adjust the pH value to 7, separating liquid, and distilling under reduced pressure to obtain an intermediate 5;

step 6, sequentially adding 2-tert-butylphenol, methyl acetoacetate and dodecyl mercaptan into a four-neck flask at normal temperature, stopping introducing nitrogen when the reaction temperature is reduced to 5 ℃ in a water bath at 0 ℃ under the protection of nitrogen, starting introducing HCl gas for 2 hours, then heating to room temperature, carrying out heat preservation reaction for 20 hours, carrying out reduced pressure degassing and reduced pressure distillation to obtain an intermediate 6;

step 7, adding the intermediate 6, allyl alcohol, dibutyltin oxide and chlorobenzene into a reaction kettle, introducing nitrogen for protection, reacting for 8-10h at the temperature of 130-135 ℃, filtering, washing filtrate, extracting, and distilling under reduced pressure to obtain an intermediate 7;

and step 8, adding corn starch and deionized water into a three-neck flask, stirring for 10min, introducing nitrogen, stirring for 30min, adding ammonium persulfate and urea, continuing stirring for 5min, adding the intermediate 5, the intermediate 7, N, N, N-trimethyl-3- (2-methylallyl amido) -1-propylamine chloride and dodecafluoroheptyl methacrylate, stirring in a water bath at 50 ℃ for reaction for 4h, washing, drying and purifying to obtain the modified starch.

2. The modified starch PVA-based composite film according to claim 1, wherein the amount of the coupling agent KH-550, the 4-methoxyphenol and the hydroxyethyl acrylate in the step 1 is 0.1 mol: 0.9-1.1 g: 0.21mol, wherein the dosage ratio of the intermediate 1, tetrahydrofuran, sodium bromide and concentrated sulfuric acid in the step 2 is 30 mmol: 60-67 mL: 30 mmol: 2-4mL, and the mass fraction of concentrated sulfuric acid is 95%.

3. The modified starch PVA-based composite film according to claim 1, wherein the ratio of the amount of 4, 4-dihydroxybenzophenone in step 3 to DMF to the amount of intermediate 2 in DMF to the amount of anhydrous potassium carbonate is 50 mmol: 80-100 mL: 40mL of: 0.6-1.1g, DMF solution of intermediate 2 as 50 mmol: 20mL, wherein the dosage ratio of the intermediate 3, DMF, isopropanol and glacial acetic acid in the step 4 is 5 g: 20mL of: 30mL of: 0.5-1 mL.

4. The modified starch PVA-based composite film according to claim 1, wherein the amount ratio of the intermediate 4, tetrahydrofuran, glycidyl methacrylate and triethylamine in the step 5 is 50 mmol: 60-80 mL: 200 mmol: 1.5-2.4mL, and the using amount ratio of the 2-tert-butylphenol, the methyl acetoacetate and the dodecyl mercaptan in the step 6 is 0.31 mol: 0.18-0.25 mol: 0.23-0.28 mol.

5. The modified starch PVA based composite film according to claim 1, wherein the amount ratio of the intermediate 6, allyl alcohol, dibutyltin oxide and chlorobenzene in the step 7 is 0.1 mol: 0.1 mol: 0.1-0.3 g: 68-72mL, and the ratio of corn starch, deionized water, ammonium persulfate, urea, intermediate 5, intermediate 7, N, N, N-trimethyl-3- (2-methylallyl amido) -1-propanaminium chloride, and dodecafluoroheptyl methacrylate in step 8 was 16 g: 100-120 mL: 0.25-0.34 g: 0.3 g: 1.2-1.4 g: 2-3 g: 1.1-1.3 g: 1.0 g.

6. The preparation method of the modified starch PVA based composite film according to claim 1, characterized by comprising the following steps: