Antibacterial mildew-proof bamboo powder biodegradable material, preparation method thereof and application of antibacterial mildew-proof bamboo powder biodegradable material in food packaging

Abstract

The invention discloses an antibacterial mildew-proof bamboo powder biodegradable material as well as a preparation method and application thereof in food packaging, and relates to the technical field of bamboo powder biodegradable materials. When the antibacterial and mildew-proof bamboo powder biodegradable material is prepared, firstly, polylactic acid reacts with 2-bromoisobutyryl bromide and then reacts with 4-vinylphenylboronic acid, and modified polylactic acid is obtained; secondly, the pretreated bamboo powder reacts with modified silicone oil and 3-thiopheneethanol and then reacts with DL-2-(3-thienyl)-glycine to obtain a modified bamboo powder precursor, and thiophene and thiophene-3, 4-diol are polymerized on the surface of the modified bamboo powder precursor to obtain modified bamboo powder; finally, the modified polylactic acid, the modified bamboo powder and poly (butylene succinate) are subjected to melt blending, shearing and granulation, and the antibacterial and mildew-proof bamboo powder biodegradable material is prepared. The antibacterial and mildew-proof bamboo powder biodegradable material prepared by the preparation method disclosed by the invention has good biodegradability, antibacterial property and antistatic property.

Description

Technical Field

[0001] The invention relates to the technical field of bamboo powder biodegradable materials, in particular to an antibacterial and mildew-proof bamboo powder biodegradable material and a preparation method thereof and application in food packaging. Background Art

[0002] In the field of food packaging, plastic packaging materials dominate the market due to their light weight, high strength, good processing performance and excellent barrier properties; however, the polymers used in plastic packaging materials, such as polyethylene, polypropylene, polyvinyl chloride and polystyrene, generally have poor degradation properties, which has a profound impact on the environment.

[0003] These polymers are difficult to decompose in the natural environment. This difficult-to-degrade property has led to the accumulation of large amounts of plastic waste in the environment, posing a serious threat to soil, water sources and ecosystems. In addition, the toxic gases released during the incineration of plastics can also pollute the atmospheric environment.

[0004] In response to these problems, biodegradable food packaging materials have emerged. This type of material is mainly made of natural polymer compounds or their derivatives, which can be decomposed by microorganisms and eventually converted into harmless substances such as carbon dioxide and water. Bamboo powder is a natural material that has light weight, high specific surface area, high strength and good biodegradability. Using bamboo powder as a raw material and combining it with other biodegradable polymers can produce BBM (bamboo powder-based biodegradable materials); this approach can reduce dependence on traditional composite materials, effectively reduce environmental burden, and produce composite materials with excellent performance in many aspects.

[0005] Food packaging materials with antibacterial properties can effectively inhibit the growth and reproduction of microorganisms, thereby maintaining the freshness and safety of food; antibacterial packaging materials have broad application prospects in the packaging of perishable foods such as meat, dairy products, fruits and vegetables; in addition, food packaging materials with antistatic properties have also attracted much attention; especially when packaging powdered, granular and other foods that are prone to static electricity, antistatic packaging materials are particularly important; they can ensure the integrity and sealing of the packaging and improve the safety and hygiene of food. Summary of the invention

[0006] The purpose of the present invention is to provide an antibacterial and mildew-proof bamboo powder biodegradable material and a preparation method thereof, so as to solve the problems existing in the prior art.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: an antibacterial and mildew-proof bamboo powder biodegradable material, which is prepared by melt blending and shear granulation of modified polylactic acid, modified bamboo powder and polybutylene succinate.

[0008] As an optimization, the modified polylactic acid is obtained by reacting polylactic acid with 2-bromoisobutyryl bromide and then with 4-vinylbenzeneboronic acid.

[0009] As an optimization, the modified bamboo powder is obtained by reacting bamboo powder with xylene diisocyanate, then reacting with modified silicone oil and 3-thiophene ethanol, and then reacting with DL-2-(3-thienyl)-glycine to obtain a modified bamboo powder precursor, and thiophene and thiophene-3,4-diol are polymerized on the surface of the modified bamboo powder precursor; the modified silicone oil is obtained by reacting hydroxy silicone oil and isophorone diisocyanate.

[0010] A method for preparing an antibacterial and mildew-proof bamboo powder biodegradable material comprises the following preparation steps: (1) polylactic acid, dichloromethane and triethylamine are mixed, and 2-bromoisobutyryl bromide is added to react to obtain pre-modified polylactic acid; pre-modified polylactic acid, copper bromide, toluene and hexamethyltriethylenetetramine are mixed, and stannous octoate and 4-vinylbenzene boronic acid are added to react to obtain modified polylactic acid; (2) reacting hydroxy silicone oil and isophorone diisocyanate to obtain modified silicone oil; (3) Pretreated bamboo powder, modified silicone oil, 3-methyl-1-phenyl-2-phosphocyclopentene-1-oxide, and N,N-dimethylformamide are mixed, and dibutyltin dilaurate and 3-thiopheneethanol are added to continue the reaction to obtain pre-modified bamboo powder; pre-modified bamboo powder, DL-2-(3-thienyl)-glycine, zinc trifluoromethanesulfonate, triethylamine, and tetrahydrofuran are reacted to obtain a modified bamboo powder precursor; (4) mixing a modified bamboo powder precursor, a hydrochloric acid solution, thiophene, thiophene-3,4-diol, and potassium persulfate to obtain modified bamboo powder; (5) The modified polylactic acid, the modified bamboo powder and polybutylene succinate are melt-blended and shear-granulated to obtain an antibacterial and anti-mildew bamboo powder biodegradable material.

[0011] As an optimization, the preparation method of the pre-modified polylactic acid in step (1) is as follows: weigh polylactic acid, dichloromethane, triethylamine, and 2-bromoisobutyryl bromide according to the mass ratio of (4.8-5.0): (20-30): (1.1-1.2): 1; in an anhydrous and oxygen-free argon atmosphere, mix the polylactic acid, dichloromethane, and triethylamine, add 2-bromoisobutyryl bromide at 0°C and react for 4 hours, then heat to room temperature and continue to react for 24 hours, evaporate under reduced pressure, purify the methanol solution, and vacuum dry at 35°C for 24 hours to obtain pre-modified polylactic acid, wherein the methanol solution temperature is 0°C and the mass fraction is 50%; the polylactic acid model is 4023D, which was purchased from Nature Works in the United States.

[0012] As an optimization, the preparation method of the modified polylactic acid in step (1) is as follows: pre-modified polylactic acid, copper bromide, toluene, hexamethyltriethylenetetramine, stannous octoate, and 4-vinylbenzeneboronic acid are weighed in a mass ratio of 1:0.05:(30-40):0.001:0.001:(10-12); under argon protection, the pre-modified polylactic acid, copper bromide, toluene, and hexamethyltriethylenetetramine are mixed for 10 minutes, stannous octoate and 4-vinylbenzeneboronic acid are added, and the mixture is reacted at 70°C for 24 hours, and then tetrahydrofuran (2-3 times the volume of toluene) is added, and alumina (0.1 times the mass of the pre-modified polylactic acid) is added and stirred for 3-5 minutes, and the filtrate is filtered and retained. Finally, the mixture is precipitated in ether at 0°C and vacuum dried at 45°C for 24 hours to obtain the modified polylactic acid. The alumina model is AM-21, which was purchased from Shanghai Hongzhuang Chemical Technology Co., Ltd.

[0013] As an optimization, the preparation method of the modified silicone oil in step (2) is as follows: hydroxy silicone oil and isophorone diisocyanate are weighed at a mass ratio of 0.8:1, and one third of the hydroxy silicone oil is added to the isophorone diisocyanate at a stirring speed of 500 r / min in a nitrogen atmosphere, and the heating is stopped after the temperature is raised to 50°C, and the remaining hydroxy silicone oil is added dropwise at a dropping rate of 1 mL / min at a stirring speed of 1000 r / min. After the addition is completed, the temperature is raised to 70°C and the reaction is carried out for 1 hour. After the reaction is completed, cyclohexanone in an amount of 0.1-0.2 times the mass of isophorone diisocyanate is added, and the temperature is lowered to room temperature to obtain the modified silicone oil.

[0014] As an optimization, the preparation method of the modified bamboo powder precursor in step (3) is as follows: under nitrogen protection, bamboo powder, dimethylbenzene diisocyanate, and toluene are mixed in a mass ratio of 1: (2-3): (40-50), reacted at 110°C for 3-4 hours, filtered after the reaction, and washed with toluene to obtain pretreated bamboo powder; pretreated bamboo powder, modified silicone oil, 3-methyl-1-phenyl-2-phosphopentene-1-oxide, and N,N-dimethylformamide are mixed in a mass ratio of 1: (1.5-2): (0.03-0.04): (30-40), heated to 150-160°C for reaction for 6-8 hours, cooled to 80°C, and pre-modified 0.01 times the mass of bamboo powder dibutyltin dilaurate and 10-12 times the mass of pre-modified bamboo powder 3-thiopheneethanol are reacted for 5-6 hours. After the reaction is completed, the mixture is filtered, washed with N,N-dimethylformamide and dried to obtain pre-modified bamboo powder; pre-modified bamboo powder, DL-2-(3-thienyl)-glycine, zinc trifluoromethanesulfonate, triethylamine and N,N-dimethylformamide are mixed in a mass ratio of 1: (2-3): 0.05: (1.1-1.2): (20-30), the mixture is heated to 90°C and reacted for 10 hours. After the reaction is completed, the mixture is filtered, washed with pure water and dried in a vacuum at 35°C to obtain a modified bamboo powder precursor; the mesh size of the bamboo powder is 300 mesh.

[0015] As an optimization, the preparation method of the modified bamboo powder in step (4) is: mixing the modified bamboo powder precursor, 0.04 mol / L hydrochloric acid solution, thiophene, thiophene-3,4-diol, and potassium persulfate in a mass ratio of 1: (100-110): (10-12): (5-7): (3-4), reacting at 30-40°C for 6-8h, washing with pure water after the reaction, and vacuum drying at 40°C to obtain the modified bamboo powder.

[0016] As an optimization, the preparation method of the antibacterial and mildew-proof bamboo powder biodegradable material in step (5) is: adding modified polylactic acid, modified bamboo powder, and polybutylene succinate in a mass ratio of 1: (0.8-0.9): (0.2-0.3) into a twin-screw extruder for melt blending and shear granulation to obtain the antibacterial and mildew-proof bamboo powder biodegradable material; wherein the temperatures of each heating zone of the twin-screw extruder are set to 155°C, 160°C, 170°C, 170°C, 175°C, and 170°C, respectively, and the extruder speed is 80rpm; the polybutylene succinate model is TH803S; it was purchased from Tunhe, Lanshan, Xinjiang.

[0017] The present invention also provides an application of the antibacterial and mildew-proof bamboo powder biodegradable material prepared according to the preparation method of the antibacterial and mildew-proof bamboo powder biodegradable material in food packaging.

[0018] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: the antibacterial and mildew-proof bamboo powder biodegradable material prepared by the present invention mainly comprises biodegradable polylactic acid and natural bamboo powder; firstly, polylactic acid is reacted with 2-bromoisobutyryl bromide, and then reacted with 4-vinylphenylboronic acid to obtain modified polylactic acid; secondly, bamboo powder is reacted with dimethylbenzene diisocyanate, and then reacted with modified silicone oil and 3-thiophene ethanol, and then reacted with DL-2-(3-thienyl)-glycine to obtain a modified bamboo powder precursor, thiophene and thiophene-3,4-diol are polymerized on the surface of the modified bamboo powder precursor to obtain modified bamboo powder, and the modified silicone oil is obtained by reacting hydroxy silicone oil and isophorone diisocyanate; finally, the modified polylactic acid, modified bamboo powder and polybutylene succinate are melt-blended and shear-granulated to obtain the antibacterial and mildew-proof bamboo powder biodegradable material.

[0019] Firstly, through the reaction of polylactic acid and 2-bromoisobutyryl bromide, polylactic acid becomes a macromolecular initiator that can initiate the polymerization grafting of 4-vinylphenylboronic acid, so that the side chain of polylactic acid has a phenylboronic acid structure; secondly, hydroxy silicone oil and isophorone diisocyanate are reacted to obtain silicone oil containing isocyanate functional groups, which can improve the hydrophobicity of bamboo powder, thereby improving its barrier properties; bamboo powder is reacted with xylene diisocyanate, and the hydroxyl groups on the surface of bamboo powder can react with the isocyanate functional groups, thereby grafting isocyanate groups on the surface of bamboo powder; the isocyanate groups on the surface of bamboo powder and the isocyanate groups on the modified silicone oil react under the catalysis. In the presence of a catalytic agent, condensation is performed to form a carbodiimide structure, and 3-thiophene ethanol blocks the excess isocyanate functional groups through hydroxyl groups; then it reacts with DL-2-(3-thienyl)-glycine, and glycine and the carbodiimide structure react with guanidine to form a cyclic guanidine salt derivative with antibacterial properties, thereby giving the material good antibacterial properties, and the thiophene functional group on 3-thiophene ethanol as a blocking agent, the thiophene functional group of DL-2-(3-thienyl)-glycine and thiophene, thiophene-3,4-diol are oxidized and polymerized to form a polythiophene structure with conductive properties, thereby giving the material good antistatic properties.

[0020] Finally, modified polylactic acid, modified bamboo powder and polybutylene succinate were melt blended and shear granulated to obtain antibacterial and mildew-proof bamboo powder biodegradable material. The phenylboronic acid structure on the modified polylactic acid and the multiple hydroxyl groups on the modified bamboo powder can be cross-linked by forming reversible borate bonds. The presence of the cross-linked structure can enhance the mechanical properties of the material. The reversible borate is structurally stable in an aqueous environment and under normal pH conditions, but is easily oxidized and hydrolyzed in a hydrogen peroxide environment and is also easily broken under alkaline conditions. The breaking of the borate bonds can destroy the cross-linked network in the material, thereby improving the degradation performance of the material. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0022] The hydroxy silicone oil in the following examples and comparative examples was purchased from Zaoyang Jinpeng Petrochemical Co., Ltd.; the mesh number of the bamboo powder was 300 mesh; the alumina model was AM-21, purchased from Shanghai Hongzhuang Chemical Technology Co., Ltd.; the polylactic acid model was 4023D, purchased from Nature Works, USA; the polybutylene succinate model was TH803S, purchased from Tunhe, Lanshan, Xinjiang.

[0023] Example 1 A method for preparing an antibacterial and mildew-proof bamboo powder biodegradable material, the method comprising the following preparation steps: (1) Polylactic acid, dichloromethane, triethylamine, and 2-bromoisobutyryl bromide were weighed in a mass ratio of 4.8:20:1.1:1; in an anhydrous and oxygen-free argon atmosphere, polylactic acid, dichloromethane, and triethylamine were mixed, 2-bromoisobutyryl bromide was added at 0°C for 4 hours, and then the temperature was raised to room temperature for further reaction for 24 hours. After vacuum rotary evaporation, the methanol solution was purified and vacuum dried at 35°C for 24 hours to obtain pre-modified polylactic acid, the methanol solution temperature was 0°C, and the mass fraction was 50%; polylactic acid was weighed in a mass ratio of 1:0.05:30:0.001:0.001:10 Take pre-modified polylactic acid, copper bromide, toluene, hexamethyltriethylenetetramine, stannous octoate, and 4-vinylbenzeneboronic acid; under argon protection, mix the pre-modified polylactic acid, copper bromide, toluene, and hexamethyltriethylenetetramine for 10 minutes, add stannous octoate and 4-vinylbenzeneboronic acid, react at 70°C for 24 hours, add tetrahydrofuran 3 times the volume of toluene, add alumina 0.1 times the mass of the pre-modified polylactic acid, stir for 5 minutes, filter and retain the filtrate, finally, precipitate in ether at 0°C, and vacuum dry at 45°C for 24 hours to obtain modified polylactic acid; (2) Weigh hydroxy silicone oil and isophorone diisocyanate at a mass ratio of 0.8:1, add one-third of the hydroxy silicone oil to isophorone diisocyanate under a nitrogen atmosphere at a stirring speed of 500 r / min, heat to 50°C and stop heating, add the remaining hydroxy silicone oil dropwise at a rate of 1 mL / min at a stirring speed of 1000 r / min, heat to 70°C after the addition is completed, react for 1 h, add cyclohexanone in an amount of 0.1 times the mass of isophorone diisocyanate after the reaction is completed, and cool to room temperature to obtain modified silicone oil; (3) Pretreated bamboo powder, modified silicone oil, 3-methyl-1-phenyl-2-phosphocyclopentene-1-oxide, and N,N-dimethylformamide were mixed in a mass ratio of 1:1.5:0.03:30, heated to 160°C for reaction for 8 hours, cooled to 80°C, and 0.01 times the mass of pre-modified bamboo powder and 12 times the mass of pre-modified bamboo powder were added. The reaction was continued for 6 hours. After the reaction was completed, the mixture was filtered, washed with N,N-dimethylformamide, and dried to obtain pre-modified bamboo powder; pre-modified bamboo powder, DL-2-(3-thienyl)-glycine, zinc trifluoromethanesulfonate, triethylamine, and N,N-dimethylformamide were mixed in a mass ratio of 1:2:0.05:1.1:20, heated to 90°C, and reacted for 10 hours. After the reaction was completed, the mixture was filtered and washed with pure water, and dried in a vacuum at 35°C to obtain a modified bamboo powder precursor; (4) mixing the modified bamboo powder precursor, 0.04 mol / L hydrochloric acid solution, thiophene, thiophene-3,4-diol, and potassium persulfate in a mass ratio of 1:100:10:5:3, reacting at 40°C for 8 h, washing with pure water after the reaction, and vacuum drying at 40°C to obtain modified bamboo powder; (5) Modified polylactic acid, modified bamboo powder and polybutylene succinate were added into a twin-screw extruder in a mass ratio of 1:0.8:0.2 for melt blending and shear granulation to obtain an antibacterial and mildew-proof bamboo powder biodegradable material; wherein the temperatures of each heating zone of the twin-screw extruder were set to 155°C, 160°C, 170°C, 170°C, 175°C and 170°C, respectively, and the extruder speed was 80 rpm.

[0024] Example 2 A method for preparing an antibacterial and mildew-proof bamboo powder biodegradable material, the method comprising the following preparation steps: (1) Polylactic acid, dichloromethane, triethylamine, and 2-bromoisobutyryl bromide were weighed in a mass ratio of 4.9:25:1.15:1; in an anhydrous and oxygen-free argon atmosphere, polylactic acid, dichloromethane, and triethylamine were mixed, 2-bromoisobutyryl bromide was added at 0°C for 4 hours, and then the temperature was raised to room temperature for further reaction for 24 hours. After vacuum rotary evaporation, the methanol solution was purified and vacuum dried at 35°C for 24 hours to obtain pre-modified polylactic acid, the methanol solution temperature was 0°C, and the mass fraction was 50%; the polylactic acid was weighed in a mass ratio of 1:0.05:35:0.001:0.001:11 Take pre-modified polylactic acid, copper bromide, toluene, hexamethyltriethylenetetramine, stannous octoate, and 4-vinylbenzeneboronic acid; under argon protection, mix the pre-modified polylactic acid, copper bromide, toluene, and hexamethyltriethylenetetramine for 10 minutes, add stannous octoate and 4-vinylbenzeneboronic acid, react at 70°C for 24 hours, add tetrahydrofuran 2.5 times the volume of toluene, add alumina 0.1 times the mass of the pre-modified polylactic acid, stir for 4 minutes, filter and retain the filtrate, finally, precipitate in ether at 0°C, and vacuum dry at 45°C for 24 hours to obtain modified polylactic acid; (2) Weigh hydroxy silicone oil and isophorone diisocyanate at a mass ratio of 0.8:1, add one-third of the hydroxy silicone oil to isophorone diisocyanate under a nitrogen atmosphere at a stirring speed of 500 r / min, heat to 50°C and stop heating, add the remaining hydroxy silicone oil dropwise at a rate of 1 mL / min at a stirring speed of 1000 r / min, heat to 70°C after the addition is completed, react for 1 h, add cyclohexanone in an amount of 0.15 times the mass of isophorone diisocyanate after the reaction is completed, and cool to room temperature to obtain modified silicone oil; (3) Pretreated bamboo powder, modified silicone oil, 3-methyl-1-phenyl-2-phosphocyclopentene-1-oxide, and N,N-dimethylformamide were mixed in a mass ratio of 1:1.7:0.035:35, heated to 155°C for reaction for 7 hours, cooled to 80°C, and 0.01 times the mass of pre-modified bamboo powder and 11 times the mass of pre-modified bamboo powder were added. The reaction was continued for 5.5 hours. After the reaction was completed, the mixture was filtered, washed with N,N-dimethylformamide, and dried to obtain pre-modified bamboo powder; pre-modified bamboo powder, DL-2-(3-thienyl)-glycine, zinc trifluoromethanesulfonate, triethylamine, and N,N-dimethylformamide were mixed in a mass ratio of 1:2.5:0.05:1.15:25, heated to 90°C, and reacted for 10 hours. After the reaction was completed, the mixture was filtered and washed with pure water, and dried in a vacuum at 35°C to obtain a modified bamboo powder precursor; (4) The modified bamboo powder precursor, 0.04 mol / L hydrochloric acid solution, thiophene, thiophene-3,4-diol, and potassium persulfate were mixed in a mass ratio of 1:105:11:6:3.5, reacted at 35°C for 7 hours, washed with pure water after the reaction, and vacuum dried at 40°C to obtain modified bamboo powder; (5) Modified polylactic acid, modified bamboo powder and polybutylene succinate were added into a twin-screw extruder in a mass ratio of 1:0.85:0.25 for melt blending and shear granulation to obtain an antibacterial and mildew-proof bamboo powder biodegradable material; wherein the temperatures of each heating zone of the twin-screw extruder were set to 155°C, 160°C, 170°C, 170°C, 175°C and 170°C, respectively, and the extruder speed was 80 rpm.

[0025] Example 3 A method for preparing an antibacterial and mildew-proof bamboo powder biodegradable material, the method comprising the following preparation steps: (1) Polylactic acid, dichloromethane, triethylamine, and 2-bromoisobutyryl bromide were weighed in a mass ratio of 5.0:30:1.2:1; in an anhydrous and oxygen-free argon atmosphere, polylactic acid, dichloromethane, and triethylamine were mixed, 2-bromoisobutyryl bromide was added at 0°C for 4 hours, and then the temperature was raised to room temperature for further reaction for 24 hours. After vacuum rotary evaporation, the methanol solution was purified and vacuum dried at 35°C for 24 hours to obtain pre-modified polylactic acid, the methanol solution temperature was 0°C, and the mass fraction was 50%; the polylactic acid was weighed in a mass ratio of 1:0.05:40:0.001:0.001:12 Take pre-modified polylactic acid, copper bromide, toluene, hexamethyltriethylenetetramine, stannous octoate, and 4-vinylbenzeneboronic acid; under argon protection, mix the pre-modified polylactic acid, copper bromide, toluene, and hexamethyltriethylenetetramine for 10 minutes, add stannous octoate and 4-vinylbenzeneboronic acid, react at 70°C for 24 hours, add tetrahydrofuran 3 times the volume of toluene, add alumina 0.1 times the mass of the pre-modified polylactic acid, stir for 3 minutes, filter and retain the filtrate, finally, precipitate in ether at 0°C, and vacuum dry at 45°C for 24 hours to obtain modified polylactic acid; (2) Weigh hydroxy silicone oil and isophorone diisocyanate at a mass ratio of 0.8:1, add one-third of the hydroxy silicone oil to isophorone diisocyanate under a nitrogen atmosphere at a stirring speed of 500 r / min, heat to 50°C and stop heating, add the remaining hydroxy silicone oil dropwise at a rate of 1 mL / min at a stirring speed of 1000 r / min, heat to 70°C after the addition is completed, react for 1 h, add cyclohexanone in an amount of 0.2 times the mass of isophorone diisocyanate after the reaction is completed, and cool to room temperature to obtain modified silicone oil; (3) Pretreated bamboo powder, modified silicone oil, 3-methyl-1-phenyl-2-phosphocyclopentene-1-oxide, and N,N-dimethylformamide were mixed in a mass ratio of 1:2:0.04:40, heated to 150°C for reaction for 6 hours, cooled to 80°C, and 0.01 times the mass of pre-modified bamboo powder and 12 times the mass of pre-modified bamboo powder were added. The reaction was continued for 5 hours. After the reaction was completed, the mixture was filtered, washed with N,N-dimethylformamide, and dried to obtain pre-modified bamboo powder; pre-modified bamboo powder, DL-2-(3-thienyl)-glycine, zinc trifluoromethanesulfonate, triethylamine, and N,N-dimethylformamide were mixed in a mass ratio of 1:3:0.05:1.2:30, heated to 90°C, and reacted for 10 hours. After the reaction was completed, the mixture was filtered and washed with pure water, and dried in a vacuum at 35°C to obtain a modified bamboo powder precursor; (4) mixing the modified bamboo powder precursor, 0.04 mol / L hydrochloric acid solution, thiophene, thiophene-3,4-diol, and potassium persulfate in a mass ratio of 1:110:12:7:4, reacting at 30°C for 6 h, washing with pure water after the reaction, and vacuum drying at 40°C to obtain modified bamboo powder; (5) Modified polylactic acid, modified bamboo powder and polybutylene succinate were added into a twin-screw extruder in a mass ratio of 1:0.9:0.3 for melt blending and shear granulation to obtain an antibacterial and mildew-proof bamboo powder biodegradable material; wherein the temperatures of each heating zone of the twin-screw extruder were set to 155°C, 160°C, 170°C, 170°C, 175°C and 170°C, respectively, and the extruder speed was 80 rpm.

[0026] Comparative Example 1: The preparation method of the antibacterial and mildew-proof bamboo powder biodegradable material of Comparative Example 1 differs from that of Example 2 in that step (4) is not included, and step (5) is modified as follows: modified polylactic acid, modified bamboo powder precursor, and polybutylene succinate are added into a twin-screw extruder in a mass ratio of 1:0.85:0.25 for melt blending and shear granulation to obtain the antibacterial and mildew-proof bamboo powder biodegradable material; wherein the temperatures of the heating zones of the twin-screw extruder are set to 155° C., 160° C., 170° C., 170° C., 175° C., and 170° C., respectively, and the extruder speed is 80 rpm.

[0027] Comparative Example 2: The preparation method of the antibacterial and mildew-proof bamboo powder biodegradable material of Comparative Example 2 differs from that of Example 2 in that steps (2) to (4) are not included, and step (5) is modified as follows: modified polylactic acid, bamboo powder, and polybutylene succinate are added into a twin-screw extruder in a mass ratio of 1:0.85:0.25 for melt blending and shear granulation to obtain the antibacterial and mildew-proof bamboo powder biodegradable material; wherein the temperatures of the heating zones of the twin-screw extruder are set to 155°C, 160°C, 170°C, 170°C, 175°C, and 170°C, respectively, and the extruder speed is 80 rpm.

[0028] Comparative Example 3: The preparation method of the antibacterial and mildew-proof bamboo powder biodegradable material of Comparative Example 3 differs from that of Example 2 in that step (1) is not included, and step (5) is modified as follows: polylactic acid, modified bamboo powder, and polybutylene succinate are added into a twin-screw extruder in a mass ratio of 1:0.85:0.25 for melt blending and shear granulation to obtain the antibacterial and mildew-proof bamboo powder biodegradable material; wherein the temperatures of the heating zones of the twin-screw extruder are set to 155° C., 160° C., 170° C., 170° C., 175° C., and 170° C., respectively, and the extruder speed is 80 rpm.

[0029] Test Example 1: Antibacterial performance test: Test method: The antibacterial and anti-mildew bamboo powder biodegradable materials prepared in the examples and comparative examples were tested for antibacterial properties by the film pasting method in accordance with the standard QB / T2591-2003. The results are shown in Table 1.

[0030]

[0031] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 3 in Table 1, it can be found that the antibacterial and mildew-proof bamboo powder biodegradable material prepared by the present invention has good antibacterial properties.

[0032] By comparison, the antibacterial rates of Examples 1 to 3 are greater than that of Comparative Example 1, indicating that the isocyanate groups on the surface of the bamboo powder and the isocyanate groups on the modified silicone oil condense in the presence of a catalyst to form a carbodiimide structure, which then reacts with DL-2-(3-thienyl)-glycine. The glycine and the carbodiimide structure react with guanidine to form a cyclic guanidine salt derivative with antibacterial properties, thereby giving the material good antibacterial properties.

[0033] Test Example 2: Antistatic performance test: Test method: The materials prepared in the examples and comparative examples were made into strips with a diameter of 2.5 cm and a thickness of 2 mm by an injection molding machine. The antistatic performance test was carried out in accordance with GB / T1410-2006. The test voltage was 100 V and the charging time was 30 s. Before the test, the strips were placed in a constant temperature and humidity chamber for 24 h. The temperature of the constant temperature and humidity chamber was 23°C and the relative humidity was 45%. The results are shown in Table 2.

[0034]

[0035] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 3 in Table 2, it can be found that the antibacterial and anti-mildew bamboo powder biodegradable material prepared by the present invention has good antistatic performance.

[0036] By comparison, the resistivity of Examples 1 to 3 is less than that of Comparative Examples 1 to 2, indicating that the isocyanate structures on the bamboo powder and the modified silicone oil are condensed in the presence of a catalyst to form a carbodiimide structure, and the 3-thiophene ethanol blocks the excess isocyanate functional groups through the hydroxyl group; and then reacts with DL-2-(3-thienyl)-glycine, and the glycine and the carbodiimide structure are reacted with guanidine to form a cyclic guanidine salt derivative, and the thiophene functional group on the 3-thiophene ethanol as a blocking agent, the thiophene functional group of DL-2-(3-thienyl)-glycine, and thiophene and thiophene-3,4-diol are oxidatively polymerized to form a polythiophene structure with conductive properties, thereby giving the material good antistatic properties.

[0037] Test Example 3: Mechanical properties test: Test method: The materials prepared in the examples and comparative examples were made into strips with a size of 62×10×2 mm by an injection molding machine. According to the standard GB / T1040.2-2006, the antibacterial and mildew-proof bamboo powder biodegradable materials prepared in the examples and comparative examples were subjected to a tensile performance test on a tensile testing machine at a tensile rate of 50 mm / min, and the tensile strength was recorded. The results are shown in Table 3.

[0038] Degradation performance test: Test method: The materials obtained in the examples and comparative examples were made into a 1cm 2 The square was weighed as M0, and placed in a sample bottle containing phosphate buffer solution (pH=9), and proteinase K (Genview) was added at a concentration of 0.1 mg / mL. The temperature was set to 70°C. After 10 days, it was taken out, washed with deionized water, and dried under vacuum to constant weight. The mass after drying was weighed as M1, and its mass loss rate was calculated according to the following formula: mass loss rate = ; The results are shown in Table 3.

[0039]

[0040] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 3 in Table 3, it can be found that the antibacterial and mildew-proof bamboo powder biodegradable material prepared by the present invention has good mechanical properties and degradability.

[0041] The tensile strength of Examples 1 to 3 is greater than that of Comparative Examples 1 to 3. Both the Examples and the Comparative Examples have a high mass loss rate. While the cross-linked network improves the mechanical properties of the material, the degradable properties of the material are not affected, indicating that after the reaction of polylactic acid and 2-bromoisobutyryl bromide, polylactic acid becomes a macromolecular initiator that can initiate the polymerization grafting of 4-vinylphenylboronic acid, so that the side chain of polylactic acid carries a phenylboronic acid structure; the phenylboronic acid structure on the modified polylactic acid and the multiple hydroxyls on the modified bamboo powder can be cross-linked by forming a reversible borate ester bond. The presence of the cross-linked structure can enhance the mechanical properties of the material, and the reversible borate ester is structurally stable in an aqueous environment and under normal pH conditions, but is easily oxidized and hydrolyzed in a hydrogen peroxide environment, and is also easily broken under alkaline conditions. The breaking of the borate ester bond can destroy the cross-linked network in the material, thereby improving the degradation performance of the material.

[0042] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and scope of the equivalent elements of the claims be included in the invention. Any marking in a claim should not be considered as limiting the claim to which it relates.

Claims

1. An antibacterial and mildew-proof bamboo powder biodegradable material, characterized in that: The antibacterial and mildew-proof bamboo powder biodegradable material is prepared by melt blending and shear granulation of modified polylactic acid, modified bamboo powder and polybutylene succinate; the modified polylactic acid is obtained by reacting polylactic acid with 2-bromoisobutyryl bromide and then with 4-vinylphenylboronic acid; the modified bamboo powder is obtained by reacting bamboo powder with dimethylbenzene diisocyanate, then with modified silicone oil and 3-thiophene ethanol, and then with DL-2-(3-thienyl)-glycine to obtain a modified bamboo powder precursor, and thiophene and thiophene-3,4-diol are polymerized on the surface of the modified bamboo powder precursor; the modified silicone oil is obtained by reacting hydroxy silicone oil with isophorone diisocyanate.

2. A method for preparing an antibacterial and mildew-proof bamboo powder biodegradable material, characterized in that: The method comprises the following preparation steps: (1) polylactic acid, dichloromethane and triethylamine are mixed, and 2-bromoisobutyryl bromide is added to react to obtain pre-modified polylactic acid; pre-modified polylactic acid, copper bromide, toluene and hexamethyltriethylenetetramine are mixed, and stannous octoate and 4-vinylbenzene boronic acid are added to react to obtain modified polylactic acid; (2) reacting hydroxy silicone oil and isophorone diisocyanate to obtain modified silicone oil; (3) Pretreated bamboo powder, modified silicone oil, 3-methyl-1-phenyl-2-phosphocyclopentene-1-oxide, and N,N-dimethylformamide are mixed, and dibutyltin dilaurate and 3-thiopheneethanol are added to continue the reaction to obtain pre-modified bamboo powder; pre-modified bamboo powder, DL-2-(3-thienyl)-glycine, zinc trifluoromethanesulfonate, triethylamine, and tetrahydrofuran are reacted to obtain a modified bamboo powder precursor; (4) mixing a modified bamboo powder precursor, a hydrochloric acid solution, thiophene, thiophene-3,4-diol, and potassium persulfate to obtain modified bamboo powder; (5) The modified polylactic acid, the modified bamboo powder and polybutylene succinate are melt-blended and shear-granulated to obtain an antibacterial and anti-mildew bamboo powder biodegradable material.

3. The method for preparing an antibacterial and mildew-proof bamboo powder biodegradable material according to claim 2, characterized in that: The preparation method of the pre-modified polylactic acid in step (1) is as follows: polylactic acid, dichloromethane, triethylamine and 2-bromoisobutyryl bromide are weighed in a mass ratio of (4.8-5.0): (20-30): (1.1-1.2): 1; in an anhydrous and oxygen-free argon atmosphere, polylactic acid, dichloromethane and triethylamine are mixed, 2-bromoisobutyryl bromide is added at 0°C for reaction for 4 hours, the temperature is raised to room temperature and the reaction is continued for 24 hours, and the methanol solution is purified by vacuum rotary evaporation and vacuum dried at 35°C for 24 hours to obtain pre-modified polylactic acid, wherein the methanol solution temperature is 0°C and the mass fraction is 50%.

4. The method for preparing an antibacterial and mildew-proof bamboo powder biodegradable material according to claim 2, characterized in that: The preparation method of the modified polylactic acid in step (1) is as follows: pre-modified polylactic acid, copper bromide, toluene, hexamethyltriethylenetetramine, stannous octoate, and 4-vinylbenzene boronic acid are weighed in a mass ratio of 1:0.05:(30-40):0.001:0.001:(10-12); under argon protection, the pre-modified polylactic acid, copper bromide, toluene, and hexamethyltriethylenetetramine are mixed for 10 minutes, stannous octoate and 4-vinylbenzene boronic acid are added, and the mixture is reacted at 70°C for 24 hours, and then tetrahydrofuran in an amount 2-3 times the volume of toluene is added, and alumina in an amount 0.1 times the mass of the pre-modified polylactic acid is added, and stirred for 3-5 minutes, and the filtrate is filtered and retained, and finally, the mixture is precipitated in ether at 0°C, and vacuum dried at 45°C for 24 hours to obtain the modified polylactic acid.

5. The method for preparing an antibacterial and mildew-proof bamboo powder biodegradable material according to claim 2, characterized in that: The preparation method of the modified silicone oil in step (2) is as follows: hydroxy silicone oil and isophorone diisocyanate are weighed in a mass ratio of 0.8:1, one third of the hydroxy silicone oil is added to the isophorone diisocyanate at a stirring speed of 500 r / min in a nitrogen atmosphere, the heating is stopped after the temperature is raised to 50°C, the remaining hydroxy silicone oil is added dropwise at a dropping rate of 1 mL / min at a stirring speed of 1000 r / min, after the addition is completed, the temperature is raised to 70°C for reaction for 1 hour, after the reaction is completed, cyclohexanone in an amount of 0.1-0.2 times the mass of isophorone diisocyanate is added, and the temperature is lowered to room temperature to obtain the modified silicone oil.

6. The method for preparing an antibacterial and mildew-proof bamboo powder biodegradable material according to claim 2, characterized in that: The preparation method of the modified bamboo powder precursor in step (3) is as follows: under nitrogen protection, bamboo powder, dimethylbenzene diisocyanate and toluene are mixed in a mass ratio of 1: (2-3): (40-50), reacted at 110° C. for 3-4 hours, filtered and washed with toluene after the reaction to obtain pretreated bamboo powder; pretreated bamboo powder, modified silicone oil, 3-methyl-1-phenyl-2-phosphopentene-1-oxide and N,N-dimethylformamide are mixed in a mass ratio of 1: (1.5-2): (0.03-0.04): (3 0-40) mixed, heated to 150-160 ℃ for reaction for 6-8h, cooled to 80 ℃, added dibutyltin dilaurate in an amount of 0.01 times the mass of the pre-modified bamboo powder and 3-thiopheneethanol in an amount of 10-12 times the mass of the pre-modified bamboo powder, and continued to react for 5-6h. After the reaction was completed, filtered, washed with N,N-dimethylformamide and dried to obtain pre-modified bamboo powder; pre-modified bamboo powder, DL-2-(3-thienyl)-glycine, zinc trifluoromethanesulfonate, triethylamine, N,N-dimethylformamide were added in a mass ratio of 1: (2-3): 0.05: (1.1-1.2): (20-30) were mixed, heated to 90°C and reacted for 10 hours. After the reaction was completed, the mixture was filtered and washed with pure water, and then vacuum dried at 35°C to obtain a modified bamboo powder precursor. The mesh size of the bamboo powder was 300 meshes.

7. The method for preparing an antibacterial and mildew-proof bamboo powder biodegradable material according to claim 2, characterized in that: The preparation method of the modified bamboo powder in step (4) is as follows: a modified bamboo powder precursor, a 0.04 mol / L hydrochloric acid solution, thiophene, thiophene-3,4-diol, and potassium persulfate are mixed in a mass ratio of 1: (100-110): (10-12): (5-7): (3-4), reacted at 30-40° C. for 6-8 hours, and after the reaction is completed, washed with pure water and vacuum dried at 40° C. to obtain the modified bamboo powder.

8. The method for preparing an antibacterial and mildew-proof bamboo powder biodegradable material according to claim 2, characterized in that: The preparation method of the antibacterial and mildew-proof bamboo powder biodegradable material in step (5) is as follows: modified polylactic acid, modified bamboo powder, and polybutylene succinate are added into a twin-screw extruder in a mass ratio of 1: (0.8-0.9): (0.2-0.3) for melt blending and shear granulation to obtain the antibacterial and mildew-proof bamboo powder biodegradable material; wherein the temperatures of each heating zone of the twin-screw extruder are respectively set to 155° C., 160° C., 170° C., 170° C., 175° C., and 170° C., and the extruder speed is 80 rpm.

9. Use of the antibacterial and mildew-proof bamboo powder biodegradable material prepared by the method for preparing the antibacterial and mildew-proof bamboo powder biodegradable material according to any one of claims 2 to 8 in food packaging.

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