A kind of mildew-proof fresh-keeping packaging bag and preparation method thereof

Abstract

The present invention relates to the technical field of packaging bags, and in particular to a mildew-proof and fresh-keeping packaging bag and a preparation method thereof. In order to improve the environmental performance of the packaging bag, the present invention uses PBAT material as a main substrate of the packaging bag, and adds a mildew-proof and antibacterial agent therein; the present invention uses chitosan oligosaccharide as a raw material, reacts it with dicyandiamide in an acidic environment, thereby introducing a guanidine structure into the chitosan oligosaccharide, and further prepares a halamine-containing hydantoin having a halamine structure, and mixes it with chitosan oligosaccharide under the crosslinking action of glutaraldehyde, thereby further introducing a halamine structure into the chitosan oligosaccharide, thereby enhancing the antibacterial breadth and strength of the mildew-proof and antibacterial agent prepared by the present application, thereby effectively preventing the PBAT packaging bag from being degraded by bacteria too early, resulting in a decrease in the mechanical properties of the product.

Description

Technical Field

[0001] The invention relates to the technical field of packaging bags, in particular to a mildew-proof and fresh-keeping packaging bag and a preparation method thereof. Background Art

[0002] Packaging bags are used to form a protective surface on the surface of products, thereby protecting the products inside from dust, oil and water. They are widely used in industrial production and daily life. At present, the mainstream packaging bags in my country are mostly made of polypropylene, polyethylene and other materials, which have high mechanical properties and excellent chemical stability, but their degradation performance is poor and they are easy to cause serious environmental pollution.

[0003] PBAT is a biodegradable polyester material that can be degraded in a relatively short period of time and has excellent processing properties. However, since PBAT is degradable and does not have antibacterial properties, its application is severely limited. Summary of the invention

[0004] The object of the present invention is to provide a mildew-proof and fresh-keeping packaging bag and a preparation method thereof, so as to solve the problems raised in the prior art.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for preparing a mildew-proof and fresh-keeping packaging bag, comprising the following steps:

[0006] S1. Preparation of antifungal and antibacterial agent;

[0007] S11. Disperse chitosan oligosaccharide in a hydrochloric acid solution, stir until dissolved at room temperature, add anhydrous ethanol, collect the filtered product by filtration, continue to wash with anhydrous ethanol for 3-5 times, dry to constant weight, disperse the obtained precipitate in deionized water, stir until completely dissolved, add dicyandiamide to the water, reflux in an oil bath at 120-125°C for 8-24h, filter, precipitate the filtrate with anhydrous ethanol, collect the precipitate again, dry, perform Soxhlet extraction with acetone for 12-24h, and dry to obtain a guanidino chitosan oligosaccharide intermediate;

[0008] S12. 5,5-dimethylhydantoin is dispersed in anhydrous ethanol, sodium hydroxide is added, and the mixture is stirred at room temperature for 30-45 minutes, and 3-bromomethylbenzyl alcohol is added dropwise thereto, and the mixture is cooled to 30-40°C, stirred for reaction for 8-24 hours, and then cooled to 0-5°C, filtered, and the filtrate is evaporated to collect the dry product, which is dispersed again in an ethanol aqueous solution, sodium hypochlorite is added, the mixture is heated to 35-40°C, and ultrasonic vibration is applied to the mixture for reaction for 45-90 minutes, and then the excess solvent is removed by rotary evaporation to obtain halogenated hydantoin;

[0009] S13. The halogenated hydantoin and guanidino chitosan oligosaccharide intermediates are dispersed in deionized water, stirred for 30-45 minutes, and 0.03-0.05% glutaraldehyde by volume of deionized water is added thereto, the temperature is raised to 45-50°C, ultrasonically shaken for 45-90 minutes, and then vacuum evaporated to constant weight to obtain an antifungal and antibacterial agent;

[0010] S2. Preparation of anti-mildew and fresh-keeping masterbatch;

[0011] After heating PBAT to 85-90°C and drying for 2-4h, mix it with antifungal and antibacterial agent and maleic anhydride, heat it to 150-155°C, mix evenly, add modified calcium carbonate, heat it to 160-165°C, blend and melt, and obtain antifungal and fresh-keeping masterbatch;

[0012] S3. Preparation of mildew-proof and fresh-keeping packaging bags;

[0013] Add the anti-mildew and antibacterial masterbatch into the film blowing machine, heat it to 165-175°C, extrude and blow the film after melting, and roll it up to obtain the anti-mildew and fresh-keeping packaging bag.

[0014] Furthermore, in step S11, the mass ratio of chitosan oligosaccharide to dicyandiamide is 10:(0.1-0.8);

[0015] Wherein, the molecular weight of the chitosan oligosaccharide is 1800-3000Da.

[0016] Furthermore, in step S12, the mass ratio of the 5,5-dimethylhydantoin, sodium hydroxide and 3-bromomethylbenzyl alcohol is 10:(2-3.4):(11-15.7).

[0017] Furthermore, in step S12, the mass ratio of 5,5-dimethylhydantoin to sodium hypochlorite is 10:(1-3).

[0018] Furthermore, in step S13, the mass ratio of halogenated hydantoin to guanidino chitosan oligosaccharide intermediate is (0.5-1):8.

[0019] Furthermore, in step S2, the mildew-proof and fresh-keeping masterbatch is composed of 75-82 parts of PBAT, 0.8-1.5 parts of maleic anhydride, 2-5 parts of mildew-proof and antibacterial agents, and 12-15 parts of modified calcium carbonate.

[0020] Furthermore, in step S2, the preparation method of the modified calcium carbonate is:

[0021] Calcium carbonate was dispersed in anhydrous ethanol, and after being dispersed by ultrasonic vibration for 15-20 minutes, ethyltriethoxysilane was added thereto, and the reaction was continued by stirring for 5-15 minutes, and then dried to constant weight to obtain modified calcium carbonate.

[0022] Furthermore, the mass ratio of calcium carbonate to ethyltriethoxysilane is 15:(1-2).

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] In order to improve the environmental performance of the packaging bag, the present invention uses PBAT material as the main base material of the packaging bag, and in order to improve the antibacterial and mildew-proof performance of the PBAT material, the present invention also prepares and adds mildew-proof and antibacterial agents;

[0025] The invention first uses chitosan oligosaccharide as a raw material, disperses it in hydrochloric acid, and then reacts it with dicyandiamide in an acidic environment, so that the nitrogen atom with arc electrons in the chitosan oligosaccharide attacks the cyano group in the dicyandiamide as a nucleophilic reagent, thereby introducing a guanidine group structure into the chitosan oligosaccharide. Compared with a simple chitosan oligosaccharide structure, the guanidine group has a stronger positive charge and can react with proteins in the cell membrane of bacteria and fungi, thereby affecting the normal physiological activities of microorganisms, causing leakage of cell contents, and thus inhibiting the growth of bacteria.

[0026] On this basis, the present invention further uses 5,5-dimethylhydantoin as a raw material, performs halogen amination treatment on it, and then cross-links it with chitosan oligosaccharide under the action of glutaraldehyde, thereby preparing an antifungal and antibacterial agent containing guanidine and halogenamine structures;

[0027] And unlike the antibacterial mechanism of guanidine, the antibacterial property of halamine is to release oxidized halogen into bacterial receptors, thereby oxidizing microbial cells, thereby effectively destroying various structures of sanitary cells, thereby improving antibacterial properties. Therefore, the introduction of halogenated hydantoin further enhances the antibacterial breadth and strength of the mildew and antibacterial agent prepared in this application, thereby effectively preventing PBAT from being degraded by bacteria prematurely, resulting in a decrease in the mechanical properties of the product. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The PBAT used in this application is ecoflex C1200 PBAT resin; the molecular weight of the chitosan oligosaccharide used is 2000Da;

[0030] Example 1. A method for preparing a mildew-proof and fresh-keeping packaging bag, comprising the following steps:

[0031] S1. Preparation of antifungal and antibacterial agent;

[0032] S11. Disperse 10 parts of chitosan oligosaccharide in a 0.8 mol / L hydrochloric acid solution by weight, stir until dissolved at room temperature, add anhydrous ethanol, collect the filtered product by filtration, continue to wash the precipitate with anhydrous ethanol for 3 times, dry to constant weight, disperse the obtained precipitate in deionized water, stir until completely dissolved, add 0.1 parts of dicyandiamide to the water, reflux in an oil bath at 120-125°C for 12h, filter, precipitate the filtrate with anhydrous ethanol, collect and dry the precipitate again, perform Soxhlet extraction with acetone for 24h, and dry to obtain guanidino chitosan oligosaccharide intermediate;

[0033] S12. Disperse 10 parts of 5,5-dimethylhydantoin in anhydrous ethanol by weight, add 2 parts of sodium hydroxide, stir and mix at room temperature for 30 minutes, then drop 11 parts of 3-bromomethylbenzyl alcohol thereto, cool to 30°C, stir and react for 12 hours, cool to 0-5°C, filter, and collect the dry product after rotary evaporation of the filtrate, and disperse it again in an ethanol aqueous solution with an ethanol concentration of 75wt%, add 1 part of sodium hypochlorite, heat to 35-40°C, mix and react under ultrasonic vibration for 90 minutes, and then rotary evaporate to remove excess solvent to obtain halogenated hydantoin;

[0034] S13. By weight, 0.5 parts of halogenated hydantoin and 8 parts of guanidino chitosan oligosaccharide intermediate were dispersed in deionized water, stirred for 45 minutes, and 0.03% glutaraldehyde by volume of deionized water was added thereto, the temperature was raised to 45 ° C, ultrasonically shaken for 90 minutes, and then vacuum evaporated to constant weight to obtain an antifungal and antibacterial agent;

[0035] S2. Preparation of anti-mildew and fresh-keeping masterbatch;

[0036] By weight, 80 parts of PBAT were heated to 85°C and dried for 2 hours, then mixed with 2 parts of mildew and antibacterial agent and 1 part of maleic anhydride, heated to 150°C, mixed evenly, and then 12 parts of modified calcium carbonate were added thereto, heated to 160-165°C, blended and melted, and extruded to obtain mildew and fresh-keeping masterbatch;

[0037] Wherein, the preparation method of the modified calcium carbonate is:

[0038] 15 parts of calcium carbonate were dispersed in anhydrous ethanol by weight, and then 1.5 parts of ethyltriethoxysilane were added thereto after ultrasonic dispersion for 15-20 minutes. After stirring and reacting for 15 minutes, the mixture was dried to constant weight to obtain modified calcium carbonate.

[0039] S3. Preparation of mildew-proof and fresh-keeping packaging bags;

[0040] The anti-mildew and antibacterial masterbatch is added into the film blowing machine, the temperature is raised to 168°C, the film is extruded and blown after melting, and the film is rolled up to obtain the anti-mildew and fresh-keeping packaging bag.

[0041] Comparative Example 2. A method for preparing a mildew-proof and fresh-keeping packaging bag, comprising the following steps:

[0042] Compared with Example 1, this embodiment increases the amount of dicyandiamide added in step S11;

[0043] S1. Preparation of antifungal and antibacterial agent;

[0044] S11. Disperse 10 parts of chitosan oligosaccharide in a 0.8 mol / L hydrochloric acid solution by weight, stir until dissolved at room temperature, add anhydrous ethanol, collect the filtered product by filtration, continue to wash the precipitate with anhydrous ethanol for 3 times, dry to constant weight, disperse the obtained precipitate in deionized water, stir until completely dissolved, add 0.8 parts of dicyandiamide to the water, reflux in an oil bath at 120-125°C for 12h, filter, precipitate the filtrate with anhydrous ethanol, collect and dry the precipitate again, perform Soxhlet extraction with acetone for 24h, and dry to obtain guanidino chitosan oligosaccharide intermediate;

[0045] S12. Disperse 10 parts of 5,5-dimethylhydantoin in anhydrous ethanol by weight, add 2 parts of sodium hydroxide, stir and mix at room temperature for 30 minutes, then drop 11 parts of 3-bromomethylbenzyl alcohol thereto, cool to 30°C, stir and react for 12 hours, cool to 0-5°C, filter, and collect the dry product after rotary evaporation of the filtrate, and disperse it again in an ethanol aqueous solution with an ethanol concentration of 75wt%, add 1 part of sodium hypochlorite, heat to 35-40°C, mix and react under ultrasonic vibration for 90 minutes, and then rotary evaporate to remove excess solvent to obtain halogenated hydantoin;

[0046] S13. By weight, 0.5 parts of halogenated hydantoin and 8 parts of guanidino chitosan oligosaccharide intermediate were dispersed in deionized water, stirred for 45 minutes, and 0.03% glutaraldehyde by volume of deionized water was added thereto, the temperature was raised to 45 ° C, ultrasonically shaken for 90 minutes, and then vacuum evaporated to constant weight to obtain an antifungal and antibacterial agent;

[0047] S2. Preparation of anti-mildew and fresh-keeping masterbatch;

[0048] By weight, 80 parts of PBAT were heated to 85°C and dried for 2 hours, then mixed with 2 parts of mildew and antibacterial agent and 1 part of maleic anhydride, heated to 150°C, mixed evenly, and then 12 parts of modified calcium carbonate were added thereto, heated to 160-165°C, blended and melted, and extruded to obtain mildew and fresh-keeping masterbatch;

[0049] Wherein, the preparation method of the modified calcium carbonate is:

[0050] 15 parts of calcium carbonate were dispersed in anhydrous ethanol by weight, and then 1.5 parts of ethyltriethoxysilane were added thereto after ultrasonic dispersion for 15-20 minutes. After stirring and reacting for 15 minutes, the mixture was dried to constant weight to obtain modified calcium carbonate.

[0051] S3. Preparation of mildew-proof and fresh-keeping packaging bags;

[0052] The anti-mildew and antibacterial masterbatch is added into the film blowing machine, the temperature is raised to 168°C, the film is extruded and blown after melting, and the film is rolled up to obtain the anti-mildew and fresh-keeping packaging bag.

[0053] Example 3. A method for preparing a mildew-proof and fresh-keeping packaging bag, comprising the following steps:

[0054] Compared with Example 1, this example increases the amount of 3-bromomethylbenzyl alcohol added in step S12;

[0055] S1. Preparation of antifungal and antibacterial agent;

[0056] S11. Disperse 10 parts of chitosan oligosaccharide in a 0.8 mol / L hydrochloric acid solution by weight, stir until dissolved at room temperature, add anhydrous ethanol, collect the filtered product by filtration, continue to wash the precipitate with anhydrous ethanol for 3 times, dry to constant weight, disperse the obtained precipitate in deionized water, stir until completely dissolved, add 0.1 parts of dicyandiamide to the water, reflux in an oil bath at 120-125°C for 12h, filter, precipitate the filtrate with anhydrous ethanol, collect and dry the precipitate again, perform Soxhlet extraction with acetone for 24h, and dry to obtain guanidino chitosan oligosaccharide intermediate;

[0057] S12. Disperse 10 parts of 5,5-dimethylhydantoin in anhydrous ethanol by weight, add 2 parts of sodium hydroxide, stir and mix at room temperature for 30 minutes, then drop 15.7 parts of 3-bromomethylbenzyl alcohol thereto, cool to 30°C, stir and react for 12 hours, cool to 0-5°C, filter, and collect the dry product after rotary evaporation of the filtrate, and disperse it again in an ethanol aqueous solution with an ethanol concentration of 75wt%, add 1 part of sodium hypochlorite, heat to 35-40°C, mix and react under ultrasonic vibration for 90 minutes, and then rotary evaporate to remove excess solvent to obtain halogenated hydantoin;

[0058] S13. By weight, 0.5 parts of halogenated hydantoin and 8 parts of guanidino chitosan oligosaccharide intermediate were dispersed in deionized water, stirred for 45 minutes, and 0.03% glutaraldehyde by volume of deionized water was added thereto, the temperature was raised to 45 ° C, ultrasonically shaken for 90 minutes, and then vacuum evaporated to constant weight to obtain an antifungal and antibacterial agent;

[0059] S2. Preparation of anti-mildew and fresh-keeping masterbatch;

[0060] By weight, 80 parts of PBAT were heated to 85°C and dried for 2 hours, then mixed with 2 parts of mildew and antibacterial agent and 1 part of maleic anhydride, heated to 150°C, mixed evenly, and then 12 parts of modified calcium carbonate were added thereto, heated to 160-165°C, blended and melted, and extruded to obtain mildew and fresh-keeping masterbatch;

[0061] Wherein, the preparation method of the modified calcium carbonate is:

[0062] 15 parts of calcium carbonate were dispersed in anhydrous ethanol by weight, and then 1.5 parts of ethyltriethoxysilane were added thereto after ultrasonic dispersion for 15-20 minutes. After stirring and reacting for 15 minutes, the mixture was dried to constant weight to obtain modified calcium carbonate.

[0063] S3. Preparation of mildew-proof and fresh-keeping packaging bags;

[0064] The anti-mildew and antibacterial masterbatch is added into the film blowing machine, the temperature is raised to 168°C, the film is extruded and blown after melting, and the film is rolled up to obtain the anti-mildew and fresh-keeping packaging bag.

[0065] Example 4. A method for preparing a mildew-proof and fresh-keeping packaging bag, comprising the following steps:

[0066] Compared with Example 1, this example increases the amount of halogenated hydantoin added in step S12;

[0067] S1. Preparation of antifungal and antibacterial agent;

[0068] S11. Disperse 10 parts of chitosan oligosaccharide in a 0.8 mol / L hydrochloric acid solution by weight, stir until dissolved at room temperature, add anhydrous ethanol, collect the filtered product by filtration, continue to wash the precipitate with anhydrous ethanol for 3 times, dry to constant weight, disperse the obtained precipitate in deionized water, stir until completely dissolved, add 0.1 parts of dicyandiamide to the water, reflux in an oil bath at 120-125°C for 12h, filter, precipitate the filtrate with anhydrous ethanol, collect and dry the precipitate again, perform Soxhlet extraction with acetone for 24h, and dry to obtain guanidino chitosan oligosaccharide intermediate;

[0069] S12. Disperse 10 parts of 5,5-dimethylhydantoin in anhydrous ethanol by weight, add 2 parts of sodium hydroxide, stir and mix at room temperature for 30 minutes, then drop 11 parts of 3-bromomethylbenzyl alcohol thereto, cool to 30°C, stir and react for 12 hours, cool to 0-5°C, filter, and collect the dry product after rotary evaporation of the filtrate, and disperse it again in an ethanol aqueous solution with an ethanol concentration of 75wt%, add 1 part of sodium hypochlorite, heat to 35-40°C, mix and react under ultrasonic vibration for 90 minutes, and then rotary evaporate to remove excess solvent to obtain halogenated hydantoin;

[0070] S13. By weight, 1 part of halogenated hydantoin and 8 parts of guanidino chitosan oligosaccharide intermediate were dispersed in deionized water, stirred for 45 minutes, and 0.03% glutaraldehyde by volume of deionized water was added thereto, the temperature was raised to 45 ° C, ultrasonically shaken for 90 minutes, and then vacuum evaporated to constant weight to obtain an antifungal and antibacterial agent;

[0071] S2. Preparation of anti-mildew and fresh-keeping masterbatch;

[0072] By weight, 80 parts of PBAT were heated to 85°C and dried for 2 hours, then mixed with 2 parts of mildew and antibacterial agent and 1 part of maleic anhydride, heated to 150°C, mixed evenly, and then 12 parts of modified calcium carbonate were added thereto, heated to 160-165°C, blended and melted, and extruded to obtain mildew and fresh-keeping masterbatch;

[0073] Wherein, the preparation method of the modified calcium carbonate is:

[0074] 15 parts of calcium carbonate were dispersed in anhydrous ethanol by weight, and then 1.5 parts of ethyltriethoxysilane were added thereto after ultrasonic dispersion for 15-20 minutes. After stirring and reacting for 15 minutes, the mixture was dried to constant weight to obtain modified calcium carbonate.

[0075] S3. Preparation of mildew-proof and fresh-keeping packaging bags;

[0076] The anti-mildew and antibacterial masterbatch is added into the film blowing machine, the temperature is raised to 168°C, the film is extruded and blown after melting, and the film is rolled up to obtain the anti-mildew and fresh-keeping packaging bag.

[0077] Example 5. A method for preparing a mildew-proof and fresh-keeping packaging bag, comprising the following steps:

[0078] Compared with Example 1, this embodiment increases the amount of antifungal and antibacterial agent added in step S2;

[0079] S1. Preparation of antifungal and antibacterial agent;

[0080] S11. Disperse 10 parts of chitosan oligosaccharide in a 0.8 mol / L hydrochloric acid solution by weight, stir until dissolved at room temperature, add anhydrous ethanol, collect the filtered product by filtration, continue to wash the precipitate with anhydrous ethanol for 3 times, dry to constant weight, disperse the obtained precipitate in deionized water, stir until completely dissolved, add 0.1 parts of dicyandiamide to the water, reflux in an oil bath at 120-125°C for 12h, filter, precipitate the filtrate with anhydrous ethanol, collect and dry the precipitate again, perform Soxhlet extraction with acetone for 24h, and dry to obtain guanidino chitosan oligosaccharide intermediate;

[0081] S12. Disperse 10 parts of 5,5-dimethylhydantoin in anhydrous ethanol by weight, add 2 parts of sodium hydroxide, stir and mix at room temperature for 30 minutes, then drop 11 parts of 3-bromomethylbenzyl alcohol thereto, cool to 30°C, stir and react for 12 hours, cool to 0-5°C, filter, and collect the dry product after rotary evaporation of the filtrate, and disperse it again in an ethanol aqueous solution with an ethanol concentration of 75wt%, add 1 part of sodium hypochlorite, heat to 35-40°C, mix and react under ultrasonic vibration for 90 minutes, and then rotary evaporate to remove excess solvent to obtain halogenated hydantoin;

[0082] S13. By weight, 0.5 parts of halogenated hydantoin and 8 parts of guanidino chitosan oligosaccharide intermediate were dispersed in deionized water, stirred for 45 minutes, and 0.03% glutaraldehyde by volume of deionized water was added thereto, the temperature was raised to 45 ° C, ultrasonically shaken for 90 minutes, and then vacuum evaporated to constant weight to obtain an antifungal and antibacterial agent;

[0083] S2. Preparation of anti-mildew and fresh-keeping masterbatch;

[0084] By weight, 80 parts of PBAT were heated to 85°C and dried for 2 hours, then mixed with 5 parts of mildew and antibacterial agent and 1 part of maleic anhydride, heated to 150°C, mixed evenly, and then 12 parts of modified calcium carbonate were added thereto, heated to 160-165°C, blended and melted, and extruded to obtain mildew-proof and fresh-keeping masterbatch;

[0085] Wherein, the preparation method of the modified calcium carbonate is:

[0086] 15 parts of calcium carbonate were dispersed in anhydrous ethanol by weight, and then 1.5 parts of ethyltriethoxysilane were added thereto after ultrasonic dispersion for 15-20 minutes. After stirring and reacting for 15 minutes, the mixture was dried to constant weight to obtain modified calcium carbonate.

[0087] S3. Preparation of mildew-proof and fresh-keeping packaging bags;

[0088] The anti-mildew and antibacterial masterbatch is added into the film blowing machine, the temperature is raised to 168°C, the film is extruded and blown after melting, and the film is rolled up to obtain the anti-mildew and fresh-keeping packaging bag.

[0089] Comparative Example 1. A method for preparing a mildew-proof and fresh-keeping packaging bag, comprising the following steps:

[0090] Compared with Example 1, no mildew and antibacterial agent was prepared in this comparative example;

[0091] S1. Preparation of anti-mildew and fresh-keeping masterbatch;

[0092] By weight, 80 parts of PBAT were heated to 85°C and dried for 2 hours, then mixed with 1 part of maleic anhydride, heated to 150°C, mixed evenly, and then 12 parts of modified calcium carbonate were added thereto, heated to 160-165°C, blended and melted, and extruded to obtain a mildew-proof and fresh-keeping masterbatch;

[0093] Wherein, the preparation method of the modified calcium carbonate is:

[0094] 15 parts of calcium carbonate were dispersed in anhydrous ethanol by weight, and then 1.5 parts of ethyltriethoxysilane were added thereto after ultrasonic dispersion for 15-20 minutes. After stirring and reacting for 15 minutes, the mixture was dried to constant weight to obtain modified calcium carbonate.

[0095] S2. Preparation of mildew-proof and fresh-keeping packaging bags;

[0096] The anti-mildew and antibacterial masterbatch is added into the film blowing machine, the temperature is raised to 168°C, the film is extruded and blown after melting, and the film is rolled up to obtain the anti-mildew and fresh-keeping packaging bag.

[0097] Detection: The mildew-proof and fresh-keeping packaging bags prepared in Examples 1-5 and Comparative Example 1 were prepared into samples with a single-layer film thickness of 6±0.2 μm, dried to constant weight, weighed M1, and buried in the soil. After 120 days, the samples were taken out, cleaned, and dried again to constant weight, and the weight after degradation was weighed M2 to test the degradation rate;

[0098] Degradation rate = (M1-M2) / M1×100%;

[0099] The breaking strength of the mildew-proof and fresh-keeping packaging bags prepared in Examples 1-5 and Comparative Example 1 was tested according to GB 1040.3-2006;

[0100] According to QB / T 2591-2003A, the antibacterial properties of the mildew-proof and fresh-keeping packaging bags prepared in Examples 1-5 and Comparative Example 1 were tested, and the tested bacteria were Staphylococcus aureus and Escherichia coli;

[0101] The mildew resistance levels of the mildew-proof fresh-keeping packaging bags prepared in Examples 1-5 and Comparative Example 1 were tested according to ASTM G21-96, and the tested fungus species was Aspergillus niger;

[0102] The standards for each level are: Level 0 - no growth; Level 1 - trace growth, the growth coverage area is less than 10%; Level 2 - the growth coverage area is greater than 10%;

[0103] The test results are shown in the table below;

[0104]

[0105] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A method for preparing a mildew-proof and fresh-keeping packaging bag, characterized in that: The following steps are involved: S1. Preparation of antifungal and antibacterial agent; S11. Disperse chitosan oligosaccharide in a hydrochloric acid solution, stir until dissolved at room temperature, add anhydrous ethanol, collect the filtered product by filtration, continue to wash with anhydrous ethanol for 3-5 times, dry to constant weight, disperse the obtained precipitate in deionized water, stir until completely dissolved, add dicyandiamide to the water, reflux in an oil bath at 120-125°C for 8-24h, filter, precipitate the filtrate with anhydrous ethanol, collect the precipitate again, dry, perform Soxhlet extraction with acetone for 12-24h, and dry to obtain a guanidino chitosan oligosaccharide intermediate; The mass ratio of chitosan oligosaccharide to dicyandiamide is 10:(0.1-0.8); wherein the molecular weight of chitosan oligosaccharide is 1800-3000Da; S12. 5,5-dimethylhydantoin is dispersed in anhydrous ethanol, sodium hydroxide is added, and the mixture is stirred at room temperature for 30-45 minutes, and 3-bromomethylbenzyl alcohol is added dropwise thereto, and the mixture is cooled to 30-40°C, stirred for reaction for 8-24 hours, and then cooled to 0-5°C, filtered, and the filtrate is evaporated to collect the dry product, which is dispersed again in an ethanol aqueous solution, sodium hypochlorite is added, the mixture is heated to 35-40°C, and ultrasonic vibration is applied to the mixture for reaction for 45-90 minutes, and then the excess solvent is removed by rotary evaporation to obtain halogenated hydantoin; The mass ratio of the 5,5-dimethylhydantoin, sodium hydroxide and 3-bromomethylbenzyl alcohol is 10:(2-3.4):(11-15.7); The mass ratio of 5,5-dimethylhydantoin to sodium hypochlorite is 10:(1-3); S13. The halogenated hydantoin and guanidino chitosan oligosaccharide intermediates are dispersed in deionized water, stirred for 30-45 minutes, and 0.03-0.05% glutaraldehyde by volume of deionized water is added thereto, the temperature is raised to 45-50°C, ultrasonically shaken for 45-90 minutes, and then vacuum evaporated to constant weight to obtain an antifungal and antibacterial agent; The mass ratio of the halogenated hydantoin and the guanidino chitosan oligosaccharide intermediate is (0.5-1):8; S2. Preparation of anti-mildew and fresh-keeping masterbatch; After heating PBAT to 85-90°C and drying for 2-4h, mix it with antifungal and antibacterial agent and maleic anhydride, heat it to 150-155°C, mix evenly, add modified calcium carbonate, heat it to 160-165°C, blend and melt, and obtain antifungal and fresh-keeping masterbatch; S3. Preparation of mildew-proof and fresh-keeping packaging bags; Add the anti-mildew and antibacterial masterbatch into the film blowing machine, heat it to 165-175°C, extrude and blow the film after melting, and roll it up to obtain the anti-mildew and fresh-keeping packaging bag.

2. The method for preparing a mildew-proof and fresh-keeping packaging bag according to claim 1, characterized in that: In step S2, the mildew-proof and fresh-keeping masterbatch is composed of 75-82 parts of PBAT, 0.8-1.5 parts of maleic anhydride, 2-5 parts of mildew-proof and antibacterial agent, and 12-15 parts of modified calcium carbonate.

3. The method for preparing a mildew-proof and fresh-keeping packaging bag according to claim 1, characterized in that: In step S2, the preparation method of the modified calcium carbonate is: Calcium carbonate was dispersed in anhydrous ethanol, and after being dispersed by ultrasonic vibration for 15-20 minutes, ethyltriethoxysilane was added thereto, and the reaction was continued by stirring for 5-15 minutes, and then dried to constant weight to obtain modified calcium carbonate.

4. The method for preparing a mildew-proof and fresh-keeping packaging bag according to claim 3, characterized in that: The mass ratio of calcium carbonate to ethyltriethoxysilane is 15:(1-2).

5. A mildew-proof and fresh-keeping packaging bag prepared by the preparation method according to any one of claims 1 to 4.

Images