CN114561032B - Biodegradable packaging film and preparation method thereof - Google Patents
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Abstract
The invention discloses a biodegradable packaging film and a preparation method thereof, wherein the biodegradable packaging film is prepared by using components such as polyvinyl alcohol, corn starch, graphene oxide, cellulose and the like to prepare a film casting solution, so that the biodegradable packaging film is obtained, has excellent barrier property, is environment-friendly, and can be widely applied to the fields of food preservation, transportation packaging and the like. According to the scheme, graphene oxide and cellulose are introduced, the layered structure of the graphene oxide can effectively block permeation of water vapor and oxygen, the cellulose fills and crosslinks the inside of the starch film so as to improve compactness of the film, and the cellulose and the graphene oxide are mutually matched, so that the product has excellent barrier property and water resistance.
Description
Technical Field
The invention relates to the technical field of packaging films, in particular to a biodegradable packaging film and a preparation method thereof.
Background
Plastic packaging materials have been widely popularized and applied in various fields of people's life and production because of their light weight, low cost and excellent processability. After the 50 s of the 20 th century, plastic packaging materials are rapidly developed and changed in the aspects of raw material utilization, research, development, production, application and the like, and become a hot topic of attention of researchers.
When the existing packaging film is prepared, the principle of green environmental protection is followed, the existing research and development personnel begin to prepare by taking degradable components such as starch, polyvinyl alcohol and the like as film raw materials, and meanwhile, particles such as graphene oxide and the like are doped for enhancement, but the actual research and development show that the performance of the film is improved obviously only by adding the graphene oxide, and the actual requirements of people cannot be met.
In order to solve the problem, a biodegradable packaging film and a preparation method thereof are disclosed, so as to obtain the packaging film with excellent performance.
Disclosure of Invention
The invention aims to provide a biodegradable packaging film and a preparation method thereof, which are used for solving the problems in the background technology.
In order to solve the technical problems, the invention provides the following technical scheme:
a method for preparing a biodegradable packaging film, comprising the steps of:
(1) Mixing sulfhydryl graphene and deionized water, and performing ultrasonic dispersion for 40-50min to obtain graphene dispersion; adding alkynyl starch and a photoinitiator into the graphene dispersion liquid, stirring for 20-30min, and irradiating with ultraviolet light for 30-40min to obtain a solution A;
(2) Uniformly mixing polyvinyl alcohol and deionized water to obtain a polyvinyl alcohol aqueous solution; uniformly mixing epoxidized starch, corn starch and deionized water to obtain a starch solution; mixing a polyvinyl alcohol aqueous solution and a starch solution, adding the solution A, cellulose and a cross-linking agent, and stirring for 1-2h to obtain a casting solution;
and taking casting film liquid, casting to form a film, and drying to obtain the packaging film.
In the more optimized scheme, in the step (1), the preparation steps of the sulfhydrylation graphene are as follows: adding hydrobromic acid into graphene oxide and thiourea in a nitrogen environment, uniformly mixing, heating to 60-65 ℃, carrying out reflux reaction for 10-12h, cooling to 20-25 ℃, carrying out ice water bath reaction for 20-30min, adding sodium hydroxide, stirring for reaction for 6-8h, regulating pH to 2-3 by sulfuric acid after stirring, collecting a product, and carrying out vacuum drying to obtain the mercapto graphene.
In an optimized scheme, the mass ratio of the graphene oxide to the thiourea is 1: (8-10).
In a more optimized scheme, the cross-linking agent is glutaraldehyde; the raw materials of each component in the step (2) comprise: 50-60 parts of polyvinyl alcohol, 10-15 parts of epoxidized starch, 10-15 parts of corn starch, 8-10 parts of solution A, 4-6 parts of cellulose and 5-7 parts of cross-linking agent by weight;
the mass concentration of the polyvinyl alcohol aqueous solution is 7-9%, and the mass concentration of the starch solution is 3-5%.
In the more optimized scheme, in the step (2), the drying is carried out under the irradiation of ultraviolet light.
In a more optimized scheme, in the step (1), the preparation steps of the alkynyl starch are as follows: adding carboxymethyl starch, propargylamine and sodium cyanoborohydride into acetic acid-sodium acetate buffer solution, stirring and mixing uniformly, stirring and reacting for 4-5d in water bath at 50-55 ℃, dialyzing and removing impurities after the reaction is finished, and freeze-drying to obtain alkynyl starch.
In the more optimized scheme, in the step (2), the preparation steps of the epoxidized starch are as follows: mixing corn starch and ethyl acetate, adding epichlorohydrin and pyridine, stirring uniformly, stirring and reacting for 2-2.5h in an oil bath at 60-65 ℃, filtering and washing after the reaction is finished, and vacuum drying to obtain the epoxidized starch.
In an optimized scheme, the addition amount of the epichlorohydrin is 30-35% of the mass of the corn starch; the addition amount of pyridine is 10-12% of the mass of corn starch.
In a more optimized scheme, in the step (1), the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-acetone, and the ultraviolet wavelength is 365nm.
More optimized scheme, the packaging film is prepared according to the preparation method of the biodegradable packaging film.
Compared with the prior art, the invention has the following beneficial effects:
the invention discloses a biodegradable packaging film and a preparation method thereof, wherein the biodegradable packaging film is prepared by using components such as polyvinyl alcohol, corn starch, graphene oxide, cellulose and the like to prepare a film casting solution, so that the biodegradable packaging film is obtained, has excellent barrier property, is environment-friendly, and can be widely applied to the fields of food preservation, transportation packaging and the like. According to the scheme, graphene oxide and cellulose are introduced, the layered structure of the graphene oxide can effectively block permeation of water vapor and oxygen, the cellulose fills and crosslinks the inside of the starch film so as to improve compactness of the film, and the cellulose and the graphene oxide are mutually matched, so that the product has excellent barrier property and water resistance.
In practical research and development, the simple graphene oxide is less obvious in performance improvement of a film layer and cannot meet the practical requirements of people, so that on the basis of an existing scheme, the graphene oxide is subjected to sulfhydrylation modification, hydroxyl groups of the graphene oxide are grafted with thiourea in a reaction manner to generate sulfhydrylation graphene, alkynyl starch is introduced into the scheme, compatibility between the graphene oxide and other starch components is improved through thiol-alkyne click reaction, and crosslinking between the graphene oxide and other starch components is improved, so that the barrier performance of the graphene oxide is more excellent, and the water resistance of the film layer is improved.
From the above, the graphene oxide in the solution casting system has excellent compatibility, and the reason is that: (1) introducing alkynyl starch; (2) the mass ratio of the oxidized graphene to the thiourea defines the introduction of the epoxidized starch.
The specific statement is: in the scheme, alkynyl starch is grafted on the surface of graphene oxide, so that the compatibility of the graphene oxide with components such as corn starch, epoxidized starch, polyvinyl alcohol and the like is improved, and the graphene oxide is uniformly dispersed into a film casting solution; meanwhile, the scheme limits that the mass ratio of graphene oxide to thiourea is 1: (8-10), in the surface sulfhydrylation process of the graphene oxide, because the binding energy of hydroxyl is smaller than that of epoxy, thiourea can react with the hydroxyl firstly and then react with the epoxy in a ring-opening way during the reaction, so that the scheme is used for further improving the compatibility of the epoxidized starch and the graphene oxide, the addition amount of the thiourea is limited during the reaction, so that the graphene oxide is ensured to contain enough epoxy, and the existence of the epoxy and the alkynyl starch can lead the compatibility of the graphene oxide in a scheme system to be more excellent.
Here, mention should be made in advance of: the corn starch, the epoxidized starch, the alkynyl starch and the polyvinyl alcohol are used as main materials of the casting solution, and the formula is a specific creative scheme independently developed by the applicant, and is characterized in that: on one hand, the crosslinking degree of the film layer under the formula is improved, the compactness of the film layer is better, and the comprehensive performance is more excellent; on the other hand, when the film layer is actually processed and applied, the surface of the film layer is coated and impregnated with an epoxy resin film layer after the packaging film layer is prepared, the scheme is generally that epoxy resin, a curing agent and a solvent are mixed, the solvent comprises but is not limited to acetone, the starch film layer is impregnated for a period of time after the mixing, and then the starch film with the epoxy resin film layer is finally obtained after heating and curing, so that the water resistance of the film layer is further improved.
However, in actual operation, the epoxy resin film layer can be selected according to actual needs to be coated, and whether the epoxy resin film layer is coated or not generally needs to be selected according to the needs of downstream manufacturers and the application direction of the film layer. Based on the application environment, the epoxy starch is introduced into the starch film layer, so that the epoxy resin film layer can have more excellent adhesion and impregnation performance with the starch film layer, and the epoxy resin film layer can achieve more excellent effects; it is emphasized that the formulations disclosed herein are presently undisclosed and inventive.
Since the direction of coating the epoxy resin film layer of the enterprise needs to be declared by the subsequent patent, and the biodegradable packaging film is mainly related to the patent, the coating of the epoxy resin film layer is not related to the patent, and is not described herein, but only a simple principle is stated.
On the basis of the scheme, when the film layer is processed, the sulfhydryl graphene and the alkynyl starch are combined under the action of the photoinitiator, the ultraviolet irradiation time is short, and the reaction is incomplete, so that after the film is formed by subsequent casting, ultraviolet is introduced for irradiation in the drying and curing process, and unreacted complete groups are further reacted; the purpose of the subsection reaction is to enable the film layers to be more tightly crosslinked, and the density of the film layers is improved, so that the barrier property and the water resistance of the film layers are improved.
The invention discloses a biodegradable packaging film and a preparation method thereof.
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the following examples, carboxymethyl starch is prepared by: mixing high amylose starch, sodium hydroxide and absolute ethyl alcohol, stirring for 1h at 50 ℃, heating to 65 ℃, adding chloroacetic acid, continuously stirring for 3.5h, adjusting pH to be neutral after the reaction is finished, washing, and drying in vacuum to obtain carboxymethyl starch; the mass ratio of the high amylose starch to the chloroacetic acid is 6:5, a step of; the mass ratio of the high amylose starch to the sodium hydroxide is 4:3.
example 1:
a method for preparing a biodegradable packaging film, comprising the steps of:
(1) Adding hydrobromic acid into graphene oxide and thiourea in a nitrogen environment, uniformly mixing, heating to 60 ℃, carrying out reflux reaction for 12h, cooling to 20 ℃, carrying out ice water bath reaction for 20min, adding sodium hydroxide, stirring for reaction for 6h, regulating pH to 3 by sulfuric acid after stirring, collecting a product, and carrying out vacuum drying to obtain the mercapto graphene. The mass ratio of the graphene oxide to the thiourea is 1:8, 8; the dosage of the thiourea and the hydrobromic acid is 1g:15mL.
(2) Adding carboxymethyl starch, propargylamine and sodium cyanoborohydride into acetic acid-sodium acetate buffer solution (pH is 5), stirring and mixing uniformly to obtain mixed solution, stirring and reacting for 5d at 50 ℃ in water bath, dialyzing and removing impurities after the reaction is finished, and freeze-drying to obtain the alkynyl starch. The molar ratio of carboxymethyl starch, propargylamine and sodium cyanoborohydride is 1:100:100.
(3) Mixing sulfhydryl graphene with deionized water, and performing ultrasonic dispersion for 40min to obtain 40g/L graphene dispersion; adding alkynyl starch and a photoinitiator into the graphene dispersion liquid, stirring for 20min, and irradiating with ultraviolet light for 30min to obtain a solution A; the mass ratio of the sulfhydryl graphene to the alkynyl starch is 3:1, wherein the dosage of the photoinitiator is 1 weight percent of the sulfhydryl graphene. The photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-acetone, and the ultraviolet wavelength is 365nm.
(4) Mixing corn starch and ethyl acetate, adding epichlorohydrin and pyridine, stirring uniformly at 400r/min, stirring at 60 ℃ in an oil bath for 2.5h, filtering, washing after the reaction is finished, and drying in vacuum to obtain the epoxidized starch. The addition amount of the epoxy chloropropane is 30% of the mass of the corn starch; the addition amount of pyridine is 10% of the mass of corn starch.
Taking 50 parts of polyvinyl alcohol and deionized water, and uniformly mixing to obtain a polyvinyl alcohol aqueous solution with the mass concentration of 8%; uniformly mixing 10 parts of epoxidized starch, 10 parts of corn starch and deionized water to obtain a starch solution with the mass concentration of 4%; mixing a polyvinyl alcohol aqueous solution and a starch solution, adding 8 parts of solution A, 4 parts of cellulose and 5 parts of cross-linking agent, and stirring at 600r/min for 2 hours to obtain a casting solution;
and taking casting film liquid, casting to form a film, and drying to obtain the packaging film. The drying is carried out under the irradiation of ultraviolet light with the wavelength of 365nm.
Example 2:
a method for preparing a biodegradable packaging film, comprising the steps of:
(1) Adding hydrobromic acid into graphene oxide and thiourea in a nitrogen environment, uniformly mixing, heating to 64 ℃, carrying out reflux reaction for 11h, cooling to 25 ℃, carrying out ice water bath reaction for 25min, adding sodium hydroxide, stirring for 7h, regulating pH to 3 by sulfuric acid after stirring, collecting a product, and carrying out vacuum drying to obtain the mercapto graphene. The mass ratio of the graphene oxide to the thiourea is 1:9, a step of performing the process; the dosage of the thiourea and the hydrobromic acid is 1g:15mL.
(2) Adding carboxymethyl starch, propargylamine and sodium cyanoborohydride into acetic acid-sodium acetate buffer solution (pH is 5), stirring and mixing uniformly to obtain mixed solution, stirring and reacting for 5d at 52 ℃ in water bath, dialyzing and removing impurities after the reaction is finished, and freeze-drying to obtain the alkynyl starch. The molar ratio of carboxymethyl starch, propargylamine and sodium cyanoborohydride is 1:100:100.
(3) Mixing sulfhydryl graphene with deionized water, and performing ultrasonic dispersion for 45min to obtain 40g/L graphene dispersion; adding alkynyl starch and a photoinitiator into the graphene dispersion liquid, stirring for 25min, and irradiating with ultraviolet light for 40min to obtain a solution A; the mass ratio of the sulfhydryl graphene to the alkynyl starch is 3:1, wherein the dosage of the photoinitiator is 1 weight percent of the sulfhydryl graphene. The photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-acetone, and the ultraviolet wavelength is 365nm.
(4) Mixing corn starch and ethyl acetate, adding epichlorohydrin and pyridine, stirring uniformly at 430r/min, stirring in an oil bath at 65 ℃ for reaction for 2.5h, filtering, washing after the reaction is finished, and drying in vacuum to obtain the epoxidized starch. The addition amount of the epoxy chloropropane is 30% of the mass of the corn starch; the addition amount of pyridine is 10% of the mass of corn starch.
Taking 55 parts of polyvinyl alcohol and deionized water, and uniformly mixing to obtain a polyvinyl alcohol aqueous solution with the mass concentration of 8%; taking 14 parts of epoxidized starch, 13 parts of corn starch and deionized water, and uniformly mixing to obtain a starch solution with the mass concentration of 4%; mixing a polyvinyl alcohol aqueous solution and a starch solution, adding 9 parts of solution A, 5 parts of cellulose and 6 parts of cross-linking agent, and stirring at a rotating speed of 700r/min for 1.5 hours to obtain a casting film solution;
and taking casting film liquid, casting to form a film, and drying to obtain the packaging film. The drying is carried out under the irradiation of ultraviolet light with the wavelength of 365nm.
Example 3:
a method for preparing a biodegradable packaging film, comprising the steps of:
(1) Adding hydrobromic acid into graphene oxide and thiourea in a nitrogen environment, uniformly mixing, heating to 65 ℃, carrying out reflux reaction for 10 hours, cooling to 25 ℃, carrying out ice water bath reaction for 30 minutes, adding sodium hydroxide, stirring for reaction for 8 hours, regulating pH to 3 by sulfuric acid after stirring, collecting a product, and carrying out vacuum drying to obtain the mercapto graphene. The mass ratio of the graphene oxide to the thiourea is 1:10; the dosage of the thiourea and the hydrobromic acid is 1g:15mL.
(2) Adding carboxymethyl starch, propargylamine and sodium cyanoborohydride into acetic acid-sodium acetate buffer solution (pH is 5), stirring and mixing uniformly to obtain mixed solution, stirring and reacting for 4d at 55 ℃ in water bath, dialyzing and removing impurities after the reaction is finished, and freeze-drying to obtain the alkynyl starch. The molar ratio of carboxymethyl starch, propargylamine and sodium cyanoborohydride is 1:100:100.
(3) Mixing sulfhydryl graphene with deionized water, and performing ultrasonic dispersion for 50min to obtain 40g/L graphene dispersion; adding alkynyl starch and a photoinitiator into the graphene dispersion liquid, stirring for 30min, and irradiating with ultraviolet light for 40min to obtain a solution A; the mass ratio of the sulfhydryl graphene to the alkynyl starch is 3:1, wherein the dosage of the photoinitiator is 1 weight percent of the sulfhydryl graphene. The photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-acetone, and the ultraviolet wavelength is 365nm.
(4) Mixing corn starch and ethyl acetate, adding epichlorohydrin and pyridine, stirring uniformly at a rotating speed of 450r/min, stirring in an oil bath at 65 ℃ for reaction for 2 hours, filtering and washing after the reaction is finished, and vacuum drying to obtain the epoxidized starch. The addition amount of the epoxy chloropropane is 30% of the mass of the corn starch; the addition amount of pyridine is 10% of the mass of corn starch.
Taking 60 parts of polyvinyl alcohol and deionized water, and uniformly mixing to obtain a polyvinyl alcohol aqueous solution with the mass concentration of 8%; uniformly mixing 15 parts of epoxidized starch, 15 parts of corn starch and deionized water to obtain a starch solution with the mass concentration of 4%; mixing a polyvinyl alcohol aqueous solution and a starch solution, adding 10 parts of solution A, 6 parts of cellulose and 7 parts of cross-linking agent, and stirring at a speed of 800r/min for 1h to obtain a casting solution;
and taking casting film liquid, casting to form a film, and drying to obtain the packaging film. The drying is carried out under the irradiation of ultraviolet light with the wavelength of 365nm.
Comparative example 1:
a method for preparing a biodegradable packaging film, comprising the steps of:
(1) Adding hydrobromic acid into graphene oxide and thiourea in a nitrogen environment, uniformly mixing, heating to 64 ℃, carrying out reflux reaction for 11h, cooling to 25 ℃, carrying out ice water bath reaction for 25min, adding sodium hydroxide, stirring for 7h, regulating pH to 3 by sulfuric acid after stirring, collecting a product, and carrying out vacuum drying to obtain the mercapto graphene. The mass ratio of the graphene oxide to the thiourea is 1:12; the dosage of the thiourea and the hydrobromic acid is 1g:15mL.
(2) Adding carboxymethyl starch, propargylamine and sodium cyanoborohydride into acetic acid-sodium acetate buffer solution (pH is 5), stirring and mixing uniformly to obtain mixed solution, stirring and reacting for 5d at 52 ℃ in water bath, dialyzing and removing impurities after the reaction is finished, and freeze-drying to obtain the alkynyl starch. The molar ratio of carboxymethyl starch, propargylamine and sodium cyanoborohydride is 1:100:100.
(3) Mixing sulfhydryl graphene with deionized water, and performing ultrasonic dispersion for 45min to obtain 40g/L graphene dispersion; adding alkynyl starch and a photoinitiator into the graphene dispersion liquid, stirring for 25min, and irradiating with ultraviolet light for 40min to obtain a solution A; the mass ratio of the sulfhydryl graphene to the alkynyl starch is 3:1, wherein the dosage of the photoinitiator is 1 weight percent of the sulfhydryl graphene. The photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-acetone, and the ultraviolet wavelength is 365nm.
(4) Mixing corn starch and ethyl acetate, adding epichlorohydrin and pyridine, stirring uniformly at 430r/min, stirring in an oil bath at 65 ℃ for reaction for 2.5h, filtering, washing after the reaction is finished, and drying in vacuum to obtain the epoxidized starch. The addition amount of the epoxy chloropropane is 30% of the mass of the corn starch; the addition amount of pyridine is 10% of the mass of corn starch.
Taking 55 parts of polyvinyl alcohol and deionized water, and uniformly mixing to obtain a polyvinyl alcohol aqueous solution with the mass concentration of 8%; taking 14 parts of epoxidized starch, 13 parts of corn starch and deionized water, and uniformly mixing to obtain a starch solution with the mass concentration of 4%; mixing a polyvinyl alcohol aqueous solution and a starch solution, adding 9 parts of solution A, 5 parts of cellulose and 6 parts of cross-linking agent, and stirring at a rotating speed of 700r/min for 1.5 hours to obtain a casting film solution;
and taking casting film liquid, casting to form a film, and drying to obtain the packaging film. The drying is carried out under the irradiation of ultraviolet light with the wavelength of 365nm.
With example 2 as a control, the mass ratio of graphene oxide to thiourea was adjusted to 1 in comparative example 1:12.
comparative example 2:
a method for preparing a biodegradable packaging film, comprising the steps of:
(1) Adding hydrobromic acid into graphene oxide and thiourea in a nitrogen environment, uniformly mixing, heating to 64 ℃, carrying out reflux reaction for 11h, cooling to 25 ℃, carrying out ice water bath reaction for 25min, adding sodium hydroxide, stirring for 7h, regulating pH to 3 by sulfuric acid after stirring, collecting a product, and carrying out vacuum drying to obtain the mercapto graphene. The mass ratio of the graphene oxide to the thiourea is 1:9, a step of performing the process; the dosage of the thiourea and the hydrobromic acid is 1g:15mL.
(2) Adding carboxymethyl starch, propargylamine and sodium cyanoborohydride into acetic acid-sodium acetate buffer solution (pH is 5), stirring and mixing uniformly to obtain mixed solution, stirring and reacting for 5d at 52 ℃ in water bath, dialyzing and removing impurities after the reaction is finished, and freeze-drying to obtain the alkynyl starch. The molar ratio of carboxymethyl starch, propargylamine and sodium cyanoborohydride is 1:100:100.
(3) Mixing sulfhydryl graphene with deionized water, and performing ultrasonic dispersion for 45min to obtain 40g/L graphene dispersion; adding alkynyl starch and a photoinitiator into the graphene dispersion liquid, stirring for 25min, and irradiating with ultraviolet light for 40min to obtain a solution A; the mass ratio of the sulfhydryl graphene to the alkynyl starch is 3:1, wherein the dosage of the photoinitiator is 1 weight percent of the sulfhydryl graphene. The photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-acetone, and the ultraviolet wavelength is 365nm.
(4) Mixing corn starch and ethyl acetate, adding epichlorohydrin and pyridine, stirring uniformly at 430r/min, stirring in an oil bath at 65 ℃ for reaction for 2.5h, filtering, washing after the reaction is finished, and drying in vacuum to obtain the epoxidized starch. The addition amount of the epoxy chloropropane is 30% of the mass of the corn starch; the addition amount of pyridine is 10% of the mass of corn starch.
Taking 55 parts of polyvinyl alcohol and deionized water, and uniformly mixing to obtain a polyvinyl alcohol aqueous solution with the mass concentration of 8%; taking 14 parts of epoxidized starch, 13 parts of corn starch and deionized water, and uniformly mixing to obtain a starch solution with the mass concentration of 4%; mixing a polyvinyl alcohol aqueous solution and a starch solution, adding 9 parts of solution A, 5 parts of cellulose and 6 parts of cross-linking agent, and stirring at a rotating speed of 700r/min for 1.5 hours to obtain a casting film solution;
and taking casting film liquid, casting to form a film, and drying to obtain the packaging film. The drying is carried out under the irradiation of ultraviolet light with the wavelength of 365nm.
With example 2 as a control, the drying in comparative example 2 was not performed under ultraviolet light irradiation.
Comparative example 3:
a method for preparing a biodegradable packaging film, comprising the steps of:
(1) Mixing corn starch and ethyl acetate, adding epichlorohydrin and pyridine, stirring uniformly at 430r/min, stirring in an oil bath at 65 ℃ for reaction for 2.5h, filtering, washing after the reaction is finished, and drying in vacuum to obtain the epoxidized starch. The addition amount of the epoxy chloropropane is 30% of the mass of the corn starch; the addition amount of pyridine is 10% of the mass of corn starch.
Taking 55 parts of polyvinyl alcohol and deionized water, and uniformly mixing to obtain a polyvinyl alcohol aqueous solution with the mass concentration of 8%; taking 14 parts of epoxidized starch, 13 parts of corn starch and deionized water, and uniformly mixing to obtain a starch solution with the mass concentration of 4%; mixing a polyvinyl alcohol aqueous solution and a starch solution, adding 5 parts of cellulose and 6 parts of cross-linking agent, and stirring at a rotating speed of 700r/min for 1.5 hours to obtain a casting solution;
and taking casting film liquid, casting to form a film, and drying to obtain the packaging film.
In comparative example 3, with example 2 as a control, mercapto graphene and alkynylated starch were not introduced.
Comparative example 4:
a method for preparing a biodegradable packaging film, comprising the steps of:
(1) Mixing graphene oxide with deionized water, and performing ultrasonic dispersion for 45min to obtain 40g/L graphene dispersion;
(2) Mixing corn starch and ethyl acetate, adding epichlorohydrin and pyridine, stirring uniformly at 430r/min, stirring in an oil bath at 65 ℃ for reaction for 2.5h, filtering, washing after the reaction is finished, and drying in vacuum to obtain the epoxidized starch. The addition amount of the epoxy chloropropane is 30% of the mass of the corn starch; the addition amount of pyridine is 10% of the mass of corn starch.
Taking 55 parts of polyvinyl alcohol and deionized water, and uniformly mixing to obtain a polyvinyl alcohol aqueous solution with the mass concentration of 8%; taking 14 parts of epoxidized starch, 13 parts of corn starch and deionized water, and uniformly mixing to obtain a starch solution with the mass concentration of 4%; mixing a polyvinyl alcohol aqueous solution and a starch solution, adding 9 parts of graphene dispersion liquid, 5 parts of cellulose and 6 parts of cross-linking agent, and stirring at a rotating speed of 700r/min for 1.5 hours to obtain a casting film liquid;
and taking casting film liquid, casting to form a film, and drying to obtain the packaging film.
With example 2 as a control, no alkynylated starch was introduced and only conventional graphene oxide was introduced in comparative example 4.
Detection experiment:
1. samples of the packaging films prepared in examples 1 to 3 and comparative examples 1 to 4 were taken, and the tensile strength of the samples was measured.
2. The packaging film samples prepared in examples 1-3 and comparative examples 1-4 were taken, the diameter of the sample was 72mm, the sample was dried at 50 ℃, weighed after drying, immersed in distilled water at 25 ℃ for 24 hours, taken out, wiped to dry, weighed and recorded, and the water absorption was calculated according to the front and rear weights.
3. Samples of the packaging films prepared in examples 1 to 3 and comparative examples 1 to 4 were taken, the diameter of the samples was 72mm, the water vapor transmission rate was measured at a relative humidity of 90%, the temperature was 30℃and the average value was recorded for 5 times.
4. The samples of the packaging films prepared in examples 1-3 and comparative examples 1-4 were taken and subjected to soil degradation under natural conditions for 30d, and the weight loss rate was calculated.
| Project | Example 1 | Example 2 | Example 3 | Comparative example 1 |
| Tensile Strength (MPa) | 41.8 | 43.1 | 42.4 | 39.2 |
| Water absorption (%) | 15％ | 14％ | 15％ | 17％ |
| Water vapor transmission rate (10) -11 ×g/m×s×Pa) | 3.12 | 2.98 | 3.05 | 3.73 |
| Weight loss ratio (%) | ＞80％ | ＞80％ | ＞80％ | / |
| Project | Comparative example 2 | Comparative example 3 | Comparative example 4 | |
| Tensile Strength (MPa) | 38.5 | 33.8 | 36.2 | |
| Water absorption (%) | 18％ | 27％ | 22％ | |
| Water vapor transmission rate (10) -11 ×g/m×s×Pa) | 3.98 | 6.29 | 4.52 |
Conclusion: the biodegradable packaging film prepared by the invention can be naturally degraded after being used, is environment-friendly, and has excellent barrier property and water resistance.
Finally, it should be noted that: the foregoing description is only a preferred embodiment of the present invention, and the present invention is not limited thereto, but it is to be understood that modifications and equivalents of some of the technical features described in the foregoing embodiments may be made by those skilled in the art, although the present invention has been described in detail with reference to the foregoing embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. A method for preparing a biodegradable packaging film, which is characterized in that: the method comprises the following steps:
(1) Mixing sulfhydryl graphene and deionized water, and performing ultrasonic dispersion for 40-50min to obtain graphene dispersion; adding alkynyl starch and a photoinitiator into the graphene dispersion liquid, stirring for 20-30min, and irradiating with ultraviolet light for 30-40min to obtain a solution A;
(2) Uniformly mixing polyvinyl alcohol and deionized water to obtain a polyvinyl alcohol aqueous solution; uniformly mixing epoxidized starch, corn starch and deionized water to obtain a starch solution; mixing a polyvinyl alcohol aqueous solution and a starch solution, adding the solution A, cellulose and a cross-linking agent, and stirring for 1-2h to obtain a casting solution;
taking casting film liquid, casting to form a film, and drying to obtain a packaging film;
in the step (1), the preparation steps of the sulfhydrylation graphene are as follows: adding hydrobromic acid into graphene oxide and thiourea in a nitrogen environment, uniformly mixing, heating to 60-65 ℃, carrying out reflux reaction for 10-12h, cooling to 20-25 ℃, carrying out ice water bath reaction for 20-30min, adding sodium hydroxide, stirring for reaction for 6-8h, regulating pH to 2-3 with sulfuric acid after stirring, collecting a product, and carrying out vacuum drying to obtain mercapto graphene; the mass ratio of the graphene oxide to the thiourea is 1: (8-10);
the preparation method of the alkynyl starch comprises the following steps: adding carboxymethyl starch, propargylamine and sodium cyanoborohydride into acetic acid-sodium acetate buffer solution, stirring and mixing uniformly, stirring and reacting for 4-5d in water bath at 50-55 ℃, dialyzing and removing impurities after the reaction is finished, and freeze-drying to obtain alkynyl starch;
in the step (2), the drying is carried out under the irradiation of ultraviolet light; the preparation method of the epoxidized starch comprises the following steps: mixing corn starch and ethyl acetate, adding epichlorohydrin and pyridine, stirring uniformly, stirring and reacting for 2-2.5h in an oil bath at 60-65 ℃, filtering and washing after the reaction is finished, and vacuum drying to obtain the epoxidized starch.
2. The method for producing a biodegradable packaging film according to claim 1, characterized in that: the cross-linking agent is glutaraldehyde; the raw materials of each component in the step (2) comprise: 50-60 parts of polyvinyl alcohol, 10-15 parts of epoxidized starch, 10-15 parts of corn starch, 8-10 parts of solution A, 4-6 parts of cellulose and 5-7 parts of cross-linking agent by weight;
the mass concentration of the polyvinyl alcohol aqueous solution is 7-9%, and the mass concentration of the starch solution is 3-5%.
3. A method of producing a biodegradable packaging film according to claim 2, characterized in that: the addition amount of the epoxy chloropropane is 30-35% of the mass of the corn starch; the addition amount of pyridine is 10-12% of the mass of corn starch.
4. The method for producing a biodegradable packaging film according to claim 1, characterized in that: in the step (1), the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-acetone, and the ultraviolet wavelength is 365nm.
5. A packaging film produced by the method for producing a biodegradable packaging film according to any one of claims 1 to 4.
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