A bio-based packaging material and its preparation method

Abstract

The present invention discloses a bio-based packaging material and a preparation method thereof, relating to the field of polymer materials. When preparing the bio-based packaging material of the present invention, a flame-retardant crosslinking agent is prepared by reacting 6-maleimido-1-hexanal with bis(3-aminopropyl)phenylphosphine; a modified chitosan is prepared by reacting N-(2-bromoethyl)maleimide with chitosan; zinc oxide is first reacted with [3-(trimethoxysilyl)propyl]succinic anhydride and then with the modified chitosan, and finally quaternized with methyl iodide to obtain modified zinc oxide; 2,5-furandicarboxylic acid and propylene glycol are reacted to obtain a furan copolyester; the flame-retardant crosslinking agent, the modified zinc oxide and the furan copolyester are subjected to mixing, molding and heat preservation to obtain the bio-based packaging material. The bio-based packaging material prepared by the present invention has good tensile properties, flame-retardant properties, antibacterial properties and recyclability.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, and specifically to a bio-based packaging material and a preparation method thereof. Background Art

[0002] Since the new century, the global economy and technology have developed rapidly. People's demands for a better life have increased successively, and the application of petroleum products has become more and more extensive. The polyester industry mainly sourced from petrochemical resources has been continuously developing, making polymer materials play a prominent role as extremely versatile and diverse structures in multifunctional polyester materials. They are not only available on an industrial scale but also meet the needs of daily life.

[0003] In the context of the serious white pollution problem caused by petroleum-based plastics, bio-based packaging plastics in the packaging industry have received extensive attention from scholars. The raw materials of bio-based packaging materials are partially or completely processed and polymerized from crops or trees in nature through biochemical or physical means, and bacteria convert these raw materials into various monomers required for polymer production through biological actions. Compared with petroleum-based packaging materials using petroleum and natural gas as raw materials, bio-based packaging materials are more environmentally friendly, such as polylactic acid, chitosan, and starch. 2,5-Furandicarboxylic acid is obtained from biomass resources such as cellulose or sugars, and the bio-based polyester material synthesized from 2,5-furandicarboxylic acid has excellent properties and broad development prospects. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of a bio-based packaging material to solve the problems existing in the prior art.

[0005] To solve the above technical problems, the present invention provides the following technical solutions:

[0006] A bio-based packaging material, wherein the bio-based packaging material is prepared by reacting 6-maleimido-1-hexanal with bis(3-aminopropyl)phenylphosphine to obtain a flame-retardant crosslinking agent; reacting N-(2-bromoethyl)maleimide with chitosan to obtain modified chitosan; first reacting zinc oxide with [3-(trimethoxysilyl)propyl]succinic anhydride and then with modified chitosan, and finally quaternizing with methyl iodide to obtain modified zinc oxide; reacting 2,5-furandicarboxylic acid with propylene glycol to obtain a furan copolyester; and obtaining the bio-based packaging material by mixing, molding, and heat preservation of the flame-retardant crosslinking agent, modified zinc oxide, and furan copolyester.

[0007] A preparation method of a bio-based packaging material, comprising the following preparation steps:

[0008] (1) Mix 6-maleimidyl-1-hexanal, bis(3-aminopropyl)phenylphosphine, and absolute ethanol at a mass ratio of 1:(0.5 - 0.7):(4 - 8), stir at 200 - 300 r / min at 75 - 85 °C for 1.5 - 2.5 h, perform suction filtration, wash the filter residue with absolute ethanol 3 - 5 times, and vacuum dry at 55 - 65 °C for 4 - 6 h to obtain a flame retardant crosslinking agent;

[0009] (2) Mix [3-(trimethoxysilyl)propyl]succinic anhydride, nano-zinc oxide, and absolute ethanol at a mass ratio of 1:(2 - 4):(15 - 25), stir at a rate of 200 - 300 r / min at 60 - 70 °C and heat in a water bath for 0.5 - 1.5 h, cool to room temperature, filter, wash the filter residue with absolute ethanol 3 - 5 times, and vacuum dry at 55 - 65 °C for 4 - 6 h to obtain initially modified zinc oxide;

[0010] (3) Mix the initially modified zinc oxide, modified chitosan, and N,N-dimethylformamide at a mass ratio of 1:

[0011] (1.2 - 1.4):(10 - 20), stir at 500 - 700 r / min at 75 - 85 °C for 8 - 10 h under a nitrogen atmosphere, cool to room temperature, add chloroform 2 - 3 times the mass of absolute ethanol, continue stirring for 25 - 35 min, filter, wash the filter residue with absolute ethanol 3 - 5 times, and vacuum dry at 55 - 65 °C for 4 - 6 h to obtain chitosan-modified zinc oxide; Mix chitosan-modified zinc oxide, iodomethane, sodium hydroxide, sodium iodide, and N-methyl-pyrrolidone at a mass ratio of 1:(0.4 - 0.6):(0.1 - 0.2):(0.04 - 0.06):(5 - 7), stir at 500 - 700 r / min at room temperature for 4 - 6 h, filter, wash the filter residue with deionized water and absolute ethanol 3 - 5 times respectively, and vacuum dry at 55 - 65 °C for 4 - 6 h to obtain modified zinc oxide;

[0012] (4) Mix 2,5-furandicarboxylic acid and propylene glycol at a molar ratio of 1:(1.5 - 1.7), add to a reaction kettle at 205 - 215 °C, add tetrabutyl titanate 0.002 - 0.004 times the mass of 2,5-furandicarboxylic acid, introduce nitrogen, stir at 500 - 700 r / min for 3 - 4 h, raise the temperature to 225 - 235 °C, slowly evacuate to 60 - 200 Pa, continue stirring, and discharge when the rod climbing effect occurs to obtain furan copolyester;

[0013] (5) Add furan copolyester, modified zinc oxide, and flame retardant crosslinking agent to a torque rheometer for internal mixing at a mass ratio of 1:(0.1 - 0.3):(0.1 - 0.3), then mold and press with a mold, and keep warm at 50 °C for 48 h to obtain a bio-based packaging material.

[0014] A preparation method of a bio-based packaging material according to claim 2, characterized in that the reaction process of the flame retardant crosslinking agent in step (1) is as follows:

[0015]

[0016] As an optimization, the preparation method of the modified chitosan in step (2) is: mixing N-(2-bromoethyl) maleimide, chitosan, triethylamine, and absolute ethanol according to a mass ratio of 1:(1-1.2):(0.2-0.4):(10-20), stirring at 300-500 r / min at 55-65 °C for 3-5 h, cooling to room temperature, filtering by suction, washing the filter residue with absolute ethanol 3-5 times, and vacuum drying at 55-65 °C for 4-6 h to obtain.

[0017] As an optimization, the chitosan in step (2) is chitosan with a deacetylation degree of 85%.

[0018] As an optimization, the zinc oxide in step (2) is industrial-grade zinc oxide.

[0019] As an optimization, the process parameters of the internal mixing in step (5) are: temperature 65-75 °C, time 10-20 min, and screw speed 100 r / min.

[0020] As an optimization, the process parameters of the molding in step (5) are: hot pressing temperature 125-135 °C, hot pressing time 30-40 min, pressure 7-10 MPa, and cold pressing time 10 min.

[0021] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0022] When preparing the bio-based packaging material of the present invention, 6-maleimidyl-1-hexanal and bis(3-aminopropyl)phenylphosphine are reacted to obtain a flame retardant crosslinking agent; N-(2-bromoethyl) maleimide and chitosan are reacted to obtain modified chitosan; zinc oxide is first reacted with [3-(trimethoxysilyl)propyl] succinic anhydride and then with modified chitosan, and finally quaternized with methyl iodide to obtain modified zinc oxide; 2,5-furandicarboxylic acid and propylene glycol are reacted to obtain furan copolyester; the flame retardant crosslinking agent, modified zinc oxide, and furan copolyester are mixed, molded, and heat-insulated to obtain the bio-based packaging material.

[0023] First, 6-maleimido-1-hexanal and bis(3-aminopropyl)phenylphosphine are used to prepare a flame-retardant crosslinking agent. Bis(3-aminopropyl)phenylphosphine introduces phosphorus elements into the bio-based packaging material, which can promote the formation of a dense carbon layer on the surface of the material during combustion. The dense carbon layer can block the transfer of heat and oxygen, reduce the internal combustion of the material, and thus improve the flame-retardant performance of the bio-based packaging material. 6-Maleimido-1-hexanal introduces a bismaleimide structure, which can undergo a thermoreversible Diels-Alder reaction with furan on the furan copolyester, chemically crosslink with the furan copolyester, effectively increase the crosslinking density, and thus improve the tensile properties of the bio-based packaging material. Moreover, the thermoreversible Diels-Alder reaction enables the bio-based packaging material to be remolded by melt molding after recycling to obtain a material with no obvious decline in mechanical properties, thus having recyclability.

[0024] Secondly, N-(2-bromoethyl)maleimide reacts with chitosan to prepare modified chitosan. Zinc oxide first reacts with [3-(trimethoxysilyl)propyl]succinic anhydride and then reacts with modified chitosan, and finally is quaternized with methyl iodide to obtain modified zinc oxide. The maleimide structure introduced on the modified chitosan can undergo a thermoreversible Diels-Alder reaction with furan on the furan copolyester, further improving the tensile properties and recyclability. Methyl iodide reacts with amino groups to generate quaternary ammonium salts, and the quaternary ammonium salts, as cationic antibacterial agents, have good contact antibacterial effects, improving the antibacterial properties of the bio-based packaging material. Moreover, zinc oxide can generate free radicals to damage the cell walls and cell membranes of bacteria, inhibit the growth and reproduction of bacteria, and further improve the antibacterial properties of the bio-based packaging material. Detailed implementation manners

[0025] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] Example 1:

[0027] A preparation method of a bio-based packaging material includes the following preparation steps:

[0028] (1) Mix 6-maleimido-1-hexanal, bis(3-aminopropyl)phenylphosphine, and absolute ethanol according to a mass ratio of 1:0.5:4, stir at 200 r / min at 75 °C for 1.5 h, perform suction filtration, wash the filter residue with absolute ethanol 3 times, and vacuum dry at 55 °C for 4 h to obtain a flame-retardant crosslinking agent;

[0029] (2) Mix N-(2-bromoethyl) maleimide, chitosan, triethylamine, and absolute ethanol in a mass ratio of 1:1:0.2:10, stir at 300 r / min at 55 °C for 3 h, cool to room temperature, filter, wash the filter cake with absolute ethanol three times, and vacuum dry at 55 °C for 4 h to obtain modified chitosan; Mix [3-(trimethoxysilyl)propyl] succinic anhydride, nano-zinc oxide, and absolute ethanol in a mass ratio of 1:2:15, stir at a rate of 200 r / min at 60 °C and heat in a water bath for 0.5 h, cool to room temperature, filter, wash the filter cake with absolute ethanol three times, and vacuum dry at 55 °C for 4 h to obtain initially modified zinc oxide;

[0030] (3) Mix initially modified zinc oxide, modified chitosan, and N,N-dimethylformamide in a mass ratio of 1:1.2:10, stir at 500 r / min at 75 °C for 8 h under a nitrogen atmosphere, cool to room temperature, add chloroform twice the mass of absolute ethanol, continue stirring for 25 min, filter, wash the filter cake with absolute ethanol three times, and vacuum dry at 55 °C for 4 h to obtain chitosan-modified zinc oxide; Mix chitosan-modified zinc oxide, iodomethane, sodium hydroxide, sodium iodide, and N-methyl-pyrrolidone in a mass ratio of 1:0.4:0.1:0.04:5, stir at 500 r / min at room temperature for 4 h, filter, wash the filter cake with deionized water and absolute ethanol three times respectively, and vacuum dry at 55 °C for 4 h to obtain modified zinc oxide;

[0031] (4) Mix 2,5-furandicarboxylic acid and propylene glycol in a molar ratio of 1:1.5, add to a reaction kettle at 205 °C, add tetrabutyl titanate 0.002 times the mass of 2,5-furandicarboxylic acid, introduce nitrogen, stir at 500 r / min for 3 h, raise the temperature to 225 °C, slowly evacuate to 60 Pa, continue stirring, and discharge when the rod climbing effect occurs to obtain furan copolyester;

[0032] (5) Add furan copolyester, modified zinc oxide, and flame retardant crosslinking agent to a torque rheometer for internal mixing in a mass ratio of 1:0.1:0.1, set the internal mixing process parameters as: temperature 65 °C, time 10 min, screw speed 100 r / min, then mold and press with a mold, set the molding parameters as: hot pressing temperature 125 °C, hot pressing time 30 min, pressure 7 MPa, cold pressing time 10 min, and keep warm at 50 °C for 48 h to obtain a bio-based packaging material.

[0033] Example 2:

[0034] A preparation method of a bio-based packaging material, comprising the following preparation steps:

[0035] (1) Mix 6-maleimido-1-hexanal, bis(3-aminopropyl)phenylphosphine, and absolute ethanol in a mass ratio of 1:0.6:6. Stir at 250 r / min for 2 h at 80 °C, then perform suction filtration. Wash the filter residue 4 times with absolute ethanol and vacuum dry at 60 °C for 5 h to obtain a flame retardant crosslinking agent.

[0036] (2) Mix N-(2-bromoethyl)maleimide, chitosan, triethylamine, and absolute ethanol in a mass ratio of 1:1.1:0.3:15. Stir at 400 r / min for 4 h at 60 °C, cool to room temperature, then perform suction filtration. Wash the filter residue 4 times with absolute ethanol and vacuum dry at 60 °C for 5 h to obtain modified chitosan. Mix [3-(trimethoxysilyl)propyl]succinic anhydride, nano-zinc oxide, and absolute ethanol in a mass ratio of 1:3:20. Stir at a rate of 250 r / min and heat in a water bath at 65 °C for 1 h, cool to room temperature, then filter. Wash the filter residue 4 times with absolute ethanol and vacuum dry at 60 °C for 5 h to obtain initially modified zinc oxide.

[0037] (3) Mix initially modified zinc oxide, modified chitosan, and N,N-dimethylformamide in a mass ratio of 1:1.3:15. Stir at 600 r / min for 9 h at 80 °C under a nitrogen atmosphere, cool to room temperature, add chloroform 2.5 times the mass of absolute ethanol, and continue stirring for 30 min. Then filter, wash the filter residue 4 times with absolute ethanol, and vacuum dry at 60 °C for 5 h to obtain chitosan-modified zinc oxide. Mix chitosan-modified zinc oxide, iodomethane, sodium hydroxide, sodium iodide, and N-methyl-pyrrolidone in a mass ratio of 1:0.5:0.15:0.05:6. Stir at 600 r / min for 5 h at room temperature, then filter. Wash the filter residue 4 times with deionized water and absolute ethanol respectively, and vacuum dry at 60 °C for 5 h to obtain modified zinc oxide.

[0038] (4) Mix 2,5-furandicarboxylic acid and propylene glycol in a molar ratio of 1:1.6, add them to a reaction kettle at 210 °C, add tetrabutyl titanate 0.003 times the mass of 2,5-furandicarboxylic acid, introduce nitrogen, stir at 600 r / min for 3.5 h, raise the temperature to 230 °C, slowly evacuate to 130 Pa, and continue stirring. Discharge the material when the rod climbing effect occurs to obtain furan copolyester.

[0039] (5) Add furan copolyester, modified zinc oxide, and flame retardant crosslinking agent to a torque rheometer for internal mixing in a mass ratio of 1:0.2:0.2. Set the internal mixing process parameters as follows: temperature 70 °C, time 15 min, screw speed 100 r / min. Then perform molding by die pressing, and set the die pressing parameters as follows: hot pressing temperature 130 °C, hot pressing time 35 min, pressure 8.5 MPa, cold pressing time 10 min, and keep warm at 50 °C for 48 h to obtain a bio-based packaging material.

[0040] Example 3:

[0041] A preparation method of a bio-based packaging material, comprising the following preparation steps:

[0042] (1) Mix 6-maleimidyl-1-hexanal, bis(3-aminopropyl)phenylphosphine, and absolute ethanol in a mass ratio of 1:0.7:8, stir at 300 r / min at 85 °C for 2.5 h, perform suction filtration, wash the filter residue with absolute ethanol 5 times, and vacuum dry at 65 °C for 6 h to obtain a flame retardant crosslinking agent;

[0043] (2) Mix N-(2-bromoethyl)maleimide, chitosan, triethylamine, and absolute ethanol in a mass ratio of 1:1.2:0.4:20, stir at 500 r / min at 65 °C for 5 h, cool to room temperature, perform suction filtration, wash the filter residue with absolute ethanol 5 times, and vacuum dry at 65 °C for 6 h to obtain modified chitosan; Mix [3-(trimethoxysilyl)propyl]succinic anhydride, nano-zinc oxide, and absolute ethanol in a mass ratio of 1:4:25, stir at a rate of 300 r / min at 70 °C and heat in a water bath for 1.5 h, cool to room temperature, filter, wash the filter residue with absolute ethanol 5 times, and vacuum dry at 65 °C for 6 h to obtain initially modified zinc oxide;

[0044] (3) Mix the initially modified zinc oxide, modified chitosan, and N,N-dimethylformamide in a mass ratio of 1:1.4:20, stir at 700 r / min at 85 °C in a nitrogen atmosphere for 10 h, cool to room temperature, add chloroform 3 times the mass of absolute ethanol, continue stirring for 35 min, filter, wash the filter residue with absolute ethanol 5 times, and vacuum dry at 65 °C for 6 h to obtain chitosan-modified zinc oxide; Mix chitosan-modified zinc oxide, iodomethane, sodium hydroxide, sodium iodide, and N-methyl-pyrrolidone in a mass ratio of 1:0.6:0.2:0.06:7, stir at 700 r / min at room temperature for 6 h, filter, wash the filter residue with deionized water and absolute ethanol 5 times respectively, and vacuum dry at 65 °C for 6 h to obtain modified zinc oxide;

[0045] (4) Mix 2,5-furandicarboxylic acid and propylene glycol in a molar ratio of 1:1.7 and add them to a reaction kettle at a temperature of 215 °C, add tetrabutyl titanate 0.004 times the mass of 2,5-furandicarboxylic acid, introduce nitrogen, stir at 700 r / min for 4 h, raise the temperature to 235 °C, slowly evacuate to 200 Pa, continue stirring, and discharge when the rod climbing effect occurs to obtain furan copolyester;

[0046] (5) Mix furan copolyester, modified zinc oxide, and flame retardant crosslinking agent in a mass ratio of 1:0.3:0.3 and conduct internal mixing in a torque rheometer. Set the internal mixing process parameters as follows: temperature 75°C, time 20 min, screw speed 100 r / min. Then, perform molding by die pressing. Set the die pressing parameters as follows: hot pressing temperature 135°C, hot pressing time 40 min, pressure 10 MPa, cold pressing time 10 min, and keep warm at 50°C for 48 h to obtain the bio-based packaging material.

[0047] Comparative Example 1:

[0048] A preparation method of a bio-based packaging material, comprising the following preparation steps:

[0049] (1) Mix N-(2-bromoethyl) maleimide, chitosan, triethylamine, and absolute ethanol in a mass ratio of 1:1.1:0.3:15, stir at 400 r / min at 60°C for 4 h, cool to room temperature, perform suction filtration, wash the filter residue with absolute ethanol 4 times, and vacuum dry at 60°C for 5 h to obtain modified chitosan; Mix [3-(trimethoxysilyl)propyl] succinic anhydride, nano zinc oxide, and absolute ethanol in a mass ratio of 1:3:20, stir at a rate of 250 r / min and perform water bath heating at 65°C for 1 h, cool to room temperature, filter, wash the filter residue with absolute ethanol 4 times, and vacuum dry at 60°C for 5 h to obtain initially modified zinc oxide;

[0050] (2) Mix the initially modified zinc oxide, modified chitosan, and N,N-dimethylformamide in a mass ratio of 1:1.3:15, stir at 600 r / min at 80°C for 9 h in a nitrogen atmosphere, cool to room temperature, add chloroform 2.5 times the mass of absolute ethanol, continue stirring for 30 min, filter, wash the filter residue with absolute ethanol 4 times, and vacuum dry at 60°C for 5 h to obtain chitosan-modified zinc oxide; Mix chitosan-modified zinc oxide, iodomethane, sodium hydroxide, sodium iodide, and N-methyl-pyrrolidone in a mass ratio of 1:0.5:0.15:0.05:6, stir at 600 r / min at room temperature for 5 h, filter, wash the filter residue with deionized water and absolute ethanol 4 times respectively, and vacuum dry at 60°C for 5 h to obtain modified zinc oxide;

[0051] (3) Mix 2,5-furandicarboxylic acid and propylene glycol in a molar ratio of 1:1.6 and add them to a reaction kettle at a temperature of 210°C. Add tetrabutyl titanate 0.003 times the mass of 2,5-furandicarboxylic acid, introduce nitrogen, stir at 600 r / min for 3.5 h, raise the temperature to 230°C, slowly evacuate to 130 Pa, continue stirring, and discharge when the rod climbing effect occurs to obtain furan copolyester;

[0052] (4) Add furan copolyester, modified zinc oxide, and bis(3-aminopropyl)phenylphosphine to a torque rheometer for internal mixing at a mass ratio of 1:0.2:0.1. Set the internal mixing process parameters as follows: temperature 70°C, time 15 min, screw speed 100 r / min. Then, perform molding using a mold, and set the molding parameters as follows: hot pressing temperature 130°C, hot pressing time 35 min, pressure 8.5 MPa, cold pressing time 10 min, and keep warm at 50°C for 48 h to obtain a bio-based packaging material.

[0053] Comparative Example 2:

[0054] A preparation method for a bio-based packaging material, comprising the following preparation steps:

[0055] (1) Mix N-(2-bromoethyl)maleimide, chitosan, triethylamine, and absolute ethanol at a mass ratio of 1:1.1:0.3:15, stir at 400 r / min at 60°C for 4 h, cool to room temperature, perform suction filtration, wash the filter residue with absolute ethanol 4 times, and vacuum dry at 60°C for 5 h to obtain modified chitosan; Mix [3-(trimethoxysilyl)propyl]succinic anhydride, nano-zinc oxide, and absolute ethanol at a mass ratio of 1:3:20, stir at a rate of 250 r / min and heat in a water bath at 65°C for 1 h, cool to room temperature, filter, wash the filter residue with absolute ethanol 4 times, and vacuum dry at 60°C for 5 h to obtain initially modified zinc oxide;

[0056] (2) Mix the initially modified zinc oxide, modified chitosan, and N,N-dimethylformamide at a mass ratio of 1:1.3:15, stir at 600 r / min at 80°C for 9 h in a nitrogen atmosphere, cool to room temperature, add chloroform 2.5 times the mass of absolute ethanol, continue stirring for 30 min, filter, wash the filter residue with absolute ethanol 4 times, and vacuum dry at 60°C for 5 h to obtain chitosan-modified zinc oxide; Mix chitosan-modified zinc oxide, iodomethane, sodium hydroxide, sodium iodide, and N-methyl-pyrrolidone at a mass ratio of 1:0.5:0.15:0.05:6, stir at 600 r / min at room temperature for 5 h, filter, wash the filter residue with deionized water and absolute ethanol 4 times respectively, and vacuum dry at 60°C for 5 h to obtain modified zinc oxide;

[0057] (3) Mix 2,5-furandicarboxylic acid and propylene glycol at a molar ratio of 1:1.6 and add them to a reaction kettle at a temperature of 210°C. Add tetrabutyl titanate 0.003 times the mass of 2,5-furandicarboxylic acid, introduce nitrogen, stir at 600 r / min for 3.5 h, raise the temperature to 230°C, slowly evacuate to 130 Pa, continue stirring, and discharge when the rod climbing effect occurs to obtain furan copolyester;

[0058] (4) Mix furan copolyester and modified zinc oxide in a mass ratio of 1:0.2 in a torque rheometer for internal mixing. Set the internal mixing process parameters as follows: temperature 70°C, time 15 min, screw speed 100 r / min. Then, use a mold for compression molding. Set the compression molding parameters as follows: hot pressing temperature 130°C, hot pressing time 35 min, pressure 8.5 MPa, cold pressing time 10 min, and keep warm at 50°C for 48 h to obtain the bio-based packaging material.

[0059] Comparative Example 3:

[0060] A preparation method of a bio-based packaging material, comprising the following preparation steps:

[0061] (1) Mix 6-maleimido-1-hexanal, bis(3-aminopropyl)phenylphosphine, and absolute ethanol in a mass ratio of 1:0.6:6, stir at 250 r / min at 80°C for 2 h, perform suction filtration, wash the filter residue with absolute ethanol 4 times, and vacuum dry at 60°C for 5 h to obtain the flame retardant crosslinking agent.

[0062] (2) Mix [3-(trimethoxysilyl)propyl]succinic anhydride, nano zinc oxide, and absolute ethanol in a mass ratio of 1:3:20, stir at a rate of 250 r / min at 65°C and heat in a water bath for 1 h, cool to room temperature, filter, wash the filter residue with absolute ethanol 4 times, and vacuum dry at 60°C for 5 h to obtain the preliminarily modified zinc oxide.

[0063] (3) Mix the preliminarily modified zinc oxide, chitosan, and N,N-dimethylformamide in a mass ratio of 1:1.3:15, stir at 600 r / min at 80°C in a nitrogen atmosphere for 9 h, cool to room temperature, add chloroform 2.5 times the mass of absolute ethanol, continue stirring for 30 min, filter, wash the filter residue with absolute ethanol 4 times, and vacuum dry at 60°C for 5 h to obtain chitosan-modified zinc oxide; mix chitosan-modified zinc oxide, iodomethane, sodium hydroxide, sodium iodide, and N-methyl-pyrrolidone in a mass ratio of 1:0.5:0.15:0.05:6, stir at 600 r / min at room temperature for 5 h, filter, wash the filter residue with deionized water and absolute ethanol 4 times respectively, and vacuum dry at 60°C for 5 h to obtain the modified zinc oxide.

[0064] (4) Mix 2,5-furandicarboxylic acid and propylene glycol in a molar ratio of 1:1.6 and add them to a reaction kettle at a temperature of 210°C. Add tetrabutyl titanate 0.003 times the mass of 2,5-furandicarboxylic acid, introduce nitrogen, stir at 600 r / min for 3.5 h, raise the temperature to 230°C, slowly evacuate to 130 Pa, continue stirring, and discharge when the rod climbing effect occurs to obtain furan copolyester.

[0065] (5) Add furan copolyester, modified zinc oxide, and flame retardant crosslinking agent to the internal mixer of the torque rheometer in a mass ratio of 1:0.2:0.2. Set the internal mixing process parameters as follows: temperature 70°C, time 15 min, screw speed 100 r / min. Then, use a mold for compression molding. Set the compression molding parameters as follows: hot pressing temperature 130°C, hot pressing time 35 min, pressure 8.5 MPa, cold pressing time 10 min, and keep warm at 50°C for 48 h to obtain the bio-based packaging material.

[0066] Comparative Example 4:

[0067] A preparation method of a bio-based packaging material, comprising the following preparation steps:

[0068] (1) Mix 6-maleimidyl-1-hexanal, bis(3-aminopropyl)phenylphosphine, and absolute ethanol in a mass ratio of 1:0.6:6, stir at 250 r / min at 80°C for 2 h, perform suction filtration, wash the filter residue with absolute ethanol 4 times, and vacuum dry at 60°C for 5 h to obtain the flame retardant crosslinking agent;

[0069] (2) Mix N-(2-bromoethyl)maleimide, chitosan, triethylamine, and absolute ethanol in a mass ratio of 1:1.1:0.3:15, stir at 400 r / min at 60°C for 4 h, cool to room temperature, perform suction filtration, wash the filter residue with absolute ethanol 4 times, and vacuum dry at 60°C for 5 h to obtain modified chitosan; Mix [3-(trimethoxysilyl)propyl]succinic anhydride, nano-zinc oxide, and absolute ethanol in a mass ratio of 1:3:20, stir at a rate of 250 r / min and heat in a water bath at 65°C for 1 h, cool to room temperature, filter, wash the filter residue with absolute ethanol 4 times, and vacuum dry at 60°C for 5 h to obtain initially modified zinc oxide;

[0070] (3) Mix the initially modified zinc oxide, modified chitosan, and N,N-dimethylformamide in a mass ratio of 1:1.3:15, stir at 600 r / min at 80°C for 9 h in a nitrogen atmosphere, cool to room temperature, add chloroform 2.5 times the mass of absolute ethanol, continue stirring for 30 min, filter, wash the filter residue with absolute ethanol 4 times, and vacuum dry at 60°C for 5 h to obtain chitosan-modified zinc oxide;

[0071] (4) Mix 2,5-furandicarboxylic acid and propylene glycol in a molar ratio of 1:1.6 and add them to a reaction kettle at a temperature of 210°C. Add tetrabutyl titanate 0.003 times the mass of 2,5-furandicarboxylic acid, introduce nitrogen, stir at 600 r / min for 3.5 h, raise the temperature to 230°C, slowly evacuate to 130 Pa, continue stirring, and discharge when the rod climbing effect occurs to obtain furan copolyester;

[0072] (5) Mix furan copolyester, chitosan-modified zinc oxide, and flame retardant crosslinker in a mass ratio of 1:0.2:0.2 and conduct internal mixing in a torque rheometer. Set the internal mixing process parameters as follows: temperature 70°C, time 15 min, screw speed 100 r / min. Then, perform molding by die pressing. Set the die pressing parameters as follows: hot pressing temperature 130°C, hot pressing time 35 min, pressure 8.5 MPa, cold pressing time 10 min, and keep warm at 50°C for 48 h to obtain the bio-based packaging material.

[0073] Comparative Example 5:

[0074] A preparation method of a bio-based packaging material, comprising the following preparation steps:

[0075] (1) Mix 6-maleimido-1-hexanal, bis(3-aminopropyl)phenylphosphine, and absolute ethanol in a mass ratio of 1:0.6:6, stir at 250 r / min at 80°C for 2 h, perform suction filtration, wash the filter residue with absolute ethanol 4 times, and vacuum dry at 60°C for 5 h to obtain the flame retardant crosslinker;

[0076] (2) Mix initially modified zinc oxide, modified chitosan, and N,N-dimethylformamide in a mass ratio of 1:1.3:15, stir at 600 r / min at 80°C for 9 h under a nitrogen atmosphere, cool to room temperature, add chloroform 2.5 times the mass of absolute ethanol, continue stirring for 30 min, filter, wash the filter residue with absolute ethanol 4 times, and vacuum dry at 60°C for 5 h to obtain chitosan-modified zinc oxide; Mix chitosan-modified zinc oxide, iodomethane, sodium hydroxide, sodium iodide, and N-methyl-pyrrolidone in a mass ratio of 1:0.5:0.15:0.05:6, stir at 600 r / min at room temperature for 5 h, filter, wash the filter residue with deionized water and absolute ethanol 4 times respectively, and vacuum dry at 60°C for 5 h to obtain modified zinc oxide;

[0077] (3) Mix 2,5-furandicarboxylic acid and propylene glycol in a molar ratio of 1:1.6, add them to a reaction kettle at a temperature of 210°C, add tetrabutyl titanate 0.003 times the mass of 2,5-furandicarboxylic acid, introduce nitrogen, stir at 600 r / min for 3.5 h, raise the temperature to 230°C, slowly evacuate to 130 Pa, continue stirring, and discharge the material when the rod climbing effect occurs to obtain furan copolyester;

[0078] (4) Mix furan copolyester and flame retardant crosslinker in a mass ratio of 1:0.2 and conduct internal mixing in a torque rheometer. Set the internal mixing process parameters as follows: temperature 70°C, time 15 min, screw speed 100 r / min. Then, perform molding by die pressing. Set the die pressing parameters as follows: hot pressing temperature 130°C, hot pressing time 35 min, pressure 8.5 MPa, cold pressing time 10 min, and keep warm at 50°C for 48 h to obtain the bio-based packaging material.

[0079] Test Example 1:

[0080] Tensile property test: The samples prepared in each example and comparative example were made into standard specimens with a specification of 75×4.3×1 mm. The specimens were placed in a drying dish for 48 h before testing to eliminate internal stress. A ZwickRoell Z020 universal material testing machine was used for tensile testing. The test speed was set at 20 mm / min, and the force sensor was 500 N. The breaking strength 1 was recorded. The results are shown in Table 1.

[0081] Recyclability test: The bio-based packaging materials in each example and comparative example were cut into small particles, and then repeatedly hot-pressed into square thin plates with a thickness of about 1 mm using a mold of 100×120×1 mm on a water-cooled electric vulcanizing molding machine (Gaotie Testing Instruments Co., Ltd.). The hot-pressing temperature was 130 °C, and the hot-pressing time was 30 min, followed by cold-pressing for 10 min to obtain square thin plates. The square thin plates were placed in a vacuum oven at a constant temperature of 50 °C under normal pressure for 48 h, and then cut according to the specification of 75×4.3×1 mm to obtain recycled test specimens. The recycled test specimens were placed in a drying dish for 48 h before testing to eliminate internal stress. A ZwickRoell Z020 universal material testing machine was used for tensile testing. The test speed was set at 20 mm / min, and the force sensor was 500 N. The breaking strength 2 was recorded. The results are shown in Table 1.

[0082] Table 1

[0083] Breaking strength 1 Breaking strength 2 Breaking strength 1 Breaking strength 2 Example 1 28.6 MPa 28.5 MPa Comparative example 1 22.7 MPa 18.7 MPa Example 2 28.9 MPa 29.0 MPa Comparative example 2 22.5 MPa 18.5 MPa Example 3 29.0 MPa 28.8 MPa Comparative example 3 25.1 MPa 22.3 MPa Comparative example 4 28.7 MPa 28.5 MPa Comparative example 5 25.5 MPa 22.5 MPa

[0084] From the comparison of the experimental data of Examples 1-3 and Comparative Examples 1-5 in Table 1, it can be found that the bio-based packaging materials prepared by the present invention have good tensile properties and recyclability.

[0085] By comparison, the breaking strength 1 of Examples 1-3 is greater than that of Comparative Examples 1 and 2, indicating that the bismaleimide on the flame retardant crosslinking agent can undergo a Diels-Alder reaction with the furan on the furan copolyester, chemically crosslink with the furan copolyester, effectively increase the crosslinking density, and thus improve the tensile properties of the bio-based packaging materials.

[0086] By comparison, the difference between the breaking strength 2 and the breaking strength 1 of Examples 1-3 is less than the difference between the breaking strength 2 and the breaking strength 1 of Comparative Examples 1, 2, 5, and 5, indicating that the thermoreversible Diels-Alder reaction between furan and maleimide enables the bio-based packaging materials to be remelted and molded after recycling, and materials with no obvious decrease in mechanical properties can be obtained, thus having recyclability.

[0087] Test Example 2:

[0088] Antibacterial performance test: The materials of each example and comparative example were crushed into powders with a particle size of less than 150 microns. Samples of the same mass were taken and tested for the antibacterial rate against Staphylococcus aureus according to the Quinn test method. The results are shown in Table 2.

[0089] Table 2

[0090] Bacteriostasis rate (%) Bacteriostasis rate (%) Example 1 99.1 Comparative example 1 99.2 Example 2 98.9 Comparative example 2 99.1 Example 3 99.4 Comparative example 3 98.9 Comparative example 4 43.5 Comparative example 5 11.7

[0091] From the comparison of the experimental data of Examples 1-3 and Comparative Examples 1-5 in Table 3, it can be found that the bio-based packaging material prepared by the present invention has good antibacterial performance.

[0092] By comparison, the antibacterial rates of Examples 1-3 are significantly greater than those of Comparative Example 4, indicating that after the amino group on the modified chitosan reacts with N-(2-bromoethyl) maleimide and is quaternized with methyl iodide to form a quaternary ammonium salt, the quaternary ammonium salt, as a cationic antibacterial agent, has a good contact antibacterial effect and improves the antibacterial performance of the bio-based packaging material; the antibacterial rates of Examples 1-3 are significantly greater than those of Comparative Example 5, indicating that the free radicals generated by zinc oxide can effectively damage the cell walls and cell membranes of bacteria, inhibit the growth and reproduction of bacteria, and thus improve the antibacterial performance of the material.

[0093] Test Example 3:

[0094] Flame retardant performance test: The bio-based packaging materials obtained in each example and test example were prepared into samples according to GB / T 2406 and the limiting oxygen index was tested. The results are shown in Table 3.

[0095] Table 3

[0096] Limiting oxygen index (%) Limiting oxygen index (%) Example 1 33.8 Comparative example 1 33.7 Example 2 34.1 Comparative example 2 21.6 Example 3 33.9 Comparative example 3 33.8 Comparative example 4 33.9 Comparative example 5 33.4

[0097] From the comparison of the experimental data of Examples 1-3 and Comparative Examples 1-5 in Table 3, it can be found that the bio-based packaging material prepared by the present invention has good flame retardant performance.

[0098] By comparison, the limiting oxygen index of Examples 1-3 is significantly greater than that of Comparative Example 2, indicating that bis(3-aminopropyl)phenylphosphine introduces phosphorus elements into the bio-based packaging material, which can promote the formation of a dense carbon layer on the surface of the material during combustion. The dense carbon layer can block the transfer of heat and oxygen, reduce the internal combustion of the material, and thus improve the flame retardant performance of the bio-based packaging material.

[0099] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and does not limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A bio-based packaging material, characterized in that, The bio-based packaging material is prepared by mixing, molding and heat preservation of a flame retardant crosslinking agent, modified zinc oxide and furan copolyester; The flame retardant crosslinking agent is prepared by reacting 6-maleimidyl-1-hexanal with bis(3-aminopropyl)phenylphosphine; The modified zinc oxide is prepared by first reacting N-(2-bromoethyl)maleimide with chitosan to obtain modified chitosan, then reacting zinc oxide with [3-(trimethoxysilyl)propyl]succinic anhydride and modified chitosan, and finally quaternizing with methyl iodide; The furan copolyester is prepared by reacting 2,5-furandicarboxylic acid with propylene glycol.

2. A preparation method of a bio-based packaging material, characterized in that, It includes the following preparation steps: (1) Mix 6-maleimidyl-1-hexanal, bis(3-aminopropyl)phenylphosphine and absolute ethanol according to the mass ratio of 1:(0.5-0.7):(4-8), stir at 200-300 r / min at 75-85 °C for 1.5-2.5 h, filter by suction, wash the filter residue with absolute ethanol for 3-5 times, and vacuum dry at 55-65 °C for 4-6 h to obtain the flame retardant crosslinking agent; (2) Mix [3-(trimethoxysilyl)propyl]succinic anhydride, nano-zinc oxide and absolute ethanol according to the mass ratio of 1:(2-4):(15-25), stir at a rate of 200-300 r / min at 60-70 °C and heat in a water bath for 0.5-1.5 h, cool to room temperature, filter, wash the filter residue with absolute ethanol for 3-5 times, and vacuum dry at 55-65 °C for 4-6 h to obtain the initially modified zinc oxide; (3) Mix N-(2-bromoethyl)maleimide, chitosan, triethylamine and absolute ethanol according to the mass ratio of 1:(1-1.2):(0.2-0.4):(10-20), stir at 300-500 r / min at 55-65 °C for 3-5 h, cool to room temperature, filter by suction, wash the filter residue with absolute ethanol for 3-5 times, and vacuum dry at 55-65 °C for 4-6 h to obtain modified chitosan; Mix the initially modified zinc oxide, modified chitosan and N,N-dimethylformamide according to the mass ratio of 1:(1.2-1.4):(10-20), under a nitrogen atmosphere, at 75-85 °C, stir at 500-700 r / min for 8-10 h, cool to room temperature, add chloroform 2-3 times the mass of absolute ethanol, continue to stir for 25-35 min, filter, wash the filter residue with absolute ethanol for 3-5 times, and vacuum dry at 55-65 °C for 4-6 h to obtain chitosan-modified zinc oxide; Mix chitosan-modified zinc oxide, methyl iodide, sodium hydroxide, sodium iodide and N-methyl-pyrrolidone according to the mass ratio of 1:(0.4-0.6):(0.1-0.2):(0.04-0.06):(5-7), stir at 500-700 r / min at room temperature for 4-6 h, filter, wash the filter residue with deionized water and absolute ethanol for 3-5 times respectively, and vacuum dry at 55-65 °C for 4-6 h to obtain the modified zinc oxide; (4) Mix 2,5-furandicarboxylic acid and propylene glycol at a molar ratio of 1:(1.5 - 1.7), add them to a reaction kettle at a temperature of 205 - 215 °C, add tetrabutyl titanate at 0.002 - 0.004 times the mass of 2,5-furandicarboxylic acid, introduce nitrogen, stir at 500 - 700 r / min for 3 - 4 h, raise the temperature to 225 - 235 °C, slowly evacuate to 60 - 200 Pa, continue stirring, and discharge when the rod climbing effect occurs to obtain the furan copolyester; (5) Add the furan copolyester, modified zinc oxide, and flame retardant crosslinking agent at a mass ratio of 1:(0.1 - 0.3):(0.1 - 0.3) to a torque rheometer for internal mixing, then mold and press with a mold, and keep warm at 50 °C for 48 h to obtain the bio-based packaging material.

3. The preparation method of a bio-based packaging material according to claim 2, characterized in that, (2) The reaction process of the flame retardant crosslinking agent described in step (1) is as follows:

4. The preparation method of a bio-based packaging material according to claim 2, characterized in that, (3) The chitosan described in step (3) is chitosan with a deacetylation degree of 85%.

5. The preparation method of a bio-based packaging material according to claim 2, characterized in that, (2) The zinc oxide described in step (2) is industrial grade zinc oxide.

6. The preparation method of a bio-based packaging material according to claim 2, wherein (5) The process parameters of the internal mixing are: temperature 65 - 75 °C, time 10 - 20 min, and screw speed 100 r / min.

7. The preparation method of a bio-based packaging material according to claim 2, wherein (5) The process parameters of the mold pressing are: hot pressing temperature 125 - 135 °C, hot pressing time 30 - 40 min, pressure 7 - 10 MPa, and cold pressing time 10 min.

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