Bamboo powder-containing biodegradable plastic for food contact and preparation method thereof

Abstract

The invention discloses a bamboo powder-containing biodegradable plastic for food contact and a preparation method thereof, and relates to the technical field of bio-based materials. The bamboo powder-containing biodegradable plastic for food contact comprises chitosan starch and modified bamboo powder, the chitosan starch is prepared by adding composite chitosan and amino-terminated polyethylene glycol into oxidized corn starch, and the composite chitosan is prepared by grafting chlorogenic acid on the surface of chitosan and then coating succinic anhydride derivatives. The succinic anhydride derivative is prepared from dodecenyl succinic anhydride and 1, 4-butanediamine through a reaction, so that the plastic has the antibacterial property, and meanwhile, the mechanical property is enhanced; the modified bamboo powder is prepared by reacting bamboo powder with a carboxyl-terminated composition, and the carboxyl-terminated composition comprises carboxyl-terminated polylactic acid and carboxyl-terminated polyamide. The toughness of the plastic is enhanced, and the mechanical property of the plastic is further enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of bio-based materials, in particular to a biodegradable plastic containing bamboo powder for food contact and a preparation method thereof. Background Art

[0002] Biodegradable plastics containing bamboo powder for food contact use are a class of polymers that can completely degrade in biochemical or biological environments, ultimately converting into environmentally friendly polymers such as carbon dioxide and water. The degradation of biodegradable plastics containing bamboo powder for food contact use involves two main steps: microbial decomposition and hydrolysis. During degradation, microbial enzymes on the surface of the adhered material further break down the long polymer chains through reactions such as hydrolysis, ultimately reducing them to low-molecular-weight fragments.

[0003] Biodegradable plastics are environmentally friendly plastics that have developed rapidly in recent years and have excellent application properties. They are a type of plastic produced by the action of microorganisms (such as bacteria, molds, and fungi) and algae. This type of material can be widely used in the fields of catering, packaging, and film. After use, they are degraded into non-toxic and harmless small molecules in nature under appropriate conditions, which not only avoids the waste of plastic products but also achieves energy recycling. Among natural polymer materials, starch is the most widely used biodegradable material. However, the presence of hydrogen bonds between natural starch molecules leads to poor solubility and thermoplasticity, resulting in poor mechanical properties of starch plastic products, which affects their use. Therefore, the present invention studies and prepares a biodegradable plastic containing bamboo powder for food contact with high mechanical properties. Summary of the Invention

[0004] The object of the present invention is to provide a biodegradable plastic containing bamboo powder for food contact and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solution: a biodegradable plastic containing bamboo powder for food contact, comprising chitosan starch, modified bamboo powder, a plasticizer, a compatibilizer and deionized water.

[0006] Preferably, the chitosan starch is prepared by adding composite chitosan and amino-terminated polyethylene glycol to oxidized corn starch; the composite chitosan is prepared by grafting chlorogenic acid onto the surface of chitosan and then coating it with a succinic anhydride derivative; the succinic anhydride derivative is prepared by reacting dodecenylsuccinic anhydride with 1,4-butanediamine.

[0007] Preferably, the modified bamboo powder is prepared by reacting bamboo powder with a carboxyl-terminated composition; the carboxyl-terminated composition includes carboxyl-terminated polylactic acid and carboxyl-terminated polyamide.

[0008] Preferably, the toughening agent is one or a mixture of ethylene glycol, dimethyl sulfoxide and glycerol; and the compatibilizer is polyglycerol sebacate.

[0009] Preferably, a method for preparing a biodegradable plastic containing bamboo powder for food contact comprises the following specific steps:

[0010] S1. Chlorogenic acid, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride, ethanol, and deionized water were mixed in a mass ratio of 5:2-3:150-160:50, stirred evenly, and placed in an ice bath. N-hydroxysuccinimide (0.2-0.3 times the mass of chlorogenic acid) was added and stirred evenly. A chitosan solution (80-100 times the mass of chlorogenic acid) was added dropwise at a rate of 1-3 ml / min. The mass ratio of chitosan to 2-4% acetic acid solution was 1:40-50. After reacting for 40-50 minutes, the mixture was transferred to room temperature, and a succinic anhydride derivative (8-20 times the mass of chlorogenic acid) was added. The mixture was protected from light and reacted for 24 hours. The mixture was centrifuged and freeze-dried at -40--60°C to obtain a composite chitosan.

[0011] S2. The carboxyl-terminated polylactic acid and the carboxyl-terminated polyamide were mixed in a mass ratio of 1:4 to 6 and stirred to obtain a carboxyl-terminated composition; the bamboo powder, the carboxyl-terminated composition and dimethyl sulfoxide were mixed in a mass ratio of 1:0.2 to 0.4:50 and stirred, and then heated to 80 to 90 ° C., concentrated sulfuric acid of 0.2 to 0.4 times the mass of the bamboo powder was added dropwise at a rate of 1 to 3 ml / min, and the reaction was carried out for 6 to 8 hours, and the mixture was distilled under reduced pressure to obtain a modified bamboo powder;

[0012] S3. Oxidized corn starch, composite chitosan, amino-terminated polyethylene glycol, and deionized water were mixed in a mass ratio of 4-6:0.2:1:10-20, stirred evenly, heated to 70-80°C, adjusted the pH to 4.8-5.2 with aqueous ammonia, reacted for 3-5 hours, washed with deionized water 3-5 times, dried, and pulverized to obtain chitosan starch;

[0013] S4. Chitosan starch, modified bamboo powder, plasticizer, compatibilizer and deionized water are mixed in a mass ratio of 40-80:6-9:1-3:0.2-0.5:8, stirred evenly and then subjected to hot-melt extrusion blow molding into a plastic film through a single-screw extrusion film blowing machine at a processing temperature of 160-170°C. Finally, the mixture is cut, rolled and packaged to obtain a biodegradable plastic containing bamboo powder for food contact.

[0014] Preferably, in the above step S1, the preparation method of the succinic anhydride derivative is: dodecenylsuccinic anhydride, 1,4-butanediamine and dimethyl sulfoxide are mixed in a mass ratio of 1:2.2-2.5:10-20, heated to 48-52°C, refluxed for 4-6 hours, cooled to room temperature and precipitated with deionized water, filtered, recrystallized with a 50% mass fraction ethanol solution, and finally dried to obtain the succinic anhydride derivative.

[0015] Preferably, in the above step S2, the preparation method of the carboxyl-terminated polylactic acid is as follows: after heating and melting the lactide, adding stannous octoate in an amount of 0.03 to 0.05 times the mass of the lactide, stirring evenly, adding succinic anhydride in an amount of 1.13 to 1.15 times the mass of the lactide, adjusting the pressure to 0.08 to 0.09 MPa, heating to 130 to 132°C and reacting for 2 to 3 hours, continuing to heat to 150 to 152°C and reacting for 2 to 3 hours, and continuing to heat to 170 to 172°C and reacting for 2 to 3 hours to obtain the carboxyl-terminated polylactic acid.

[0016] Preferably, in the above step S2, the preparation method of the terminal carboxyl polyamide is: placing diethylenetriamine in an ice bath, adding a methanol solution of methyl acrylate with a mass fraction of 20-30% at a rate of 1-3 ml / min, reacting at room temperature for 6-8 hours, and then rotary evaporation, then heating to 110-130°C, reacting for 2-4 hours, cooling to 5-7°C, adding sodium hydroxide with a mass of 0.02-0.04 times that of diethylenetriamine and acrylic acid with a mass of 0.4-0.6 times that of diethylenetriamine, stirring evenly, heating to 70-80 hours, reacting for 12-14 hours, cooling to room temperature and adjusting the pH to 6.8-7.2 with triethylamine, rotary evaporation again, and vacuum drying at 80-90°C to obtain the terminal carboxyl polyamide.

[0017] Preferably, in the above step S3, the preparation method of the amino-terminated polyethylene glycol is: polyethylene glycol, phthalamide, triphenylphosphine and tetrahydrofuran are mixed in a mass ratio of 1:1 to 4:0.1:100, stirred evenly and placed in an ice bath to react for 1 to 2 hours, diethyl azodicarboxylate of equal mass to triphenylphosphine is added, and the reaction is continued for 1 to 2 hours, and then transferred to room temperature for reaction for 10 to 12 hours, anhydrous ethanol with a mass of 50 to 100 times that of the polyethylene glycol and hydrazine hydrate with a mass of 2 to 4 times that of the polyethylene glycol are added, and after standing for 2 to 4 hours, the mixture is extracted and concentrated with chloroform to obtain the amino-terminated polyethylene glycol.

[0018] Preferably, in the above step S3, the preparation method of oxidized corn starch is: corn starch and deionized water are mixed in a mass ratio of 1:1.8-2.2, stirred evenly, heated to 35-45°C, adjusted to pH 8.8-9.2 with sodium hydroxide, added with sodium hypochlorite in an amount of 0.2-0.4 times the mass of corn starch, reacted for 3-5 hours, terminated the reaction with sodium metabisulfite, and then adjusted to pH 6.8-7.2 with hydrochloric acid, washed with deionized water 3-5 times, dried and crushed to obtain oxidized corn starch.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The food contact biodegradable plastic containing bamboo powder prepared by the present invention comprises chitosan starch and modified bamboo powder;

[0021] Chitosan starch is prepared by adding composite chitosan and amino-terminated polyethylene glycol to oxidized corn starch. The composite chitosan is prepared by grafting chlorogenic acid onto the surface of chitosan and then coating it with a succinic anhydride derivative. The succinic anhydride derivative is prepared by reacting dodecenylsuccinic anhydride with 1,4-butanediamine. After grafting chlorogenic acid onto the surface of chitosan, it is reacted with a succinic anhydride derivative with double-terminal carboxyl groups to introduce a large number of carboxyl groups while enhancing its compatibility with starch. After adding composite chitosan to oxidized corn starch, it is cross-linked with amino-terminated polyethylene glycol to form a dense three-dimensional cross-linked spatial network structure, which tightly connects the oxidized corn starch and the composite chitosan, making the plastic antibacterial while enhancing its mechanical properties.

[0022] The modified bamboo powder is prepared by reacting bamboo powder with a carboxyl-terminated composition, wherein the carboxyl-terminated composition includes carboxyl-terminated polylactic acid and carboxyl-terminated polyamide. The carboxyl-terminated composition reacts with hydroxyl groups on the surface of the bamboo powder and is coated on the surface of the bamboo powder, thereby reducing the polarity of the bamboo powder surface and enhancing the compatibility of the bamboo powder with chitosan starch. Amino groups can also be introduced on the surface to introduce the modified bamboo powder into the three-dimensional cross-linked spatial network structure of the chitosan starch, and the modified bamboo powder is evenly dispersed in the plastic, thereby enhancing the toughness of the plastic while further enhancing the mechanical properties of the plastic. DETAILED DESCRIPTION

[0023] 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 embodiments described 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 efforts are within the scope of protection of the present invention.

[0024] In order to more clearly illustrate the method provided by the present invention, the following examples are used to describe in detail the various index testing methods of the biodegradable plastics containing bamboo powder for food contact prepared in the examples and comparative examples as follows:

[0025] Mechanical properties: The biodegradable plastics containing bamboo powder for food contact prepared in the examples and comparative examples were tested for elongation at break and toughness according to GB / T1040, where toughness is the integrated area of the strain curve.

[0026] Example 1

[0027] S1. Dodecenylsuccinic anhydride, 1,4-butanediamine, and dimethyl sulfoxide were mixed in a mass ratio of 1:2.2:10, heated to 48°C, refluxed for 4 hours, cooled to room temperature, and precipitated with deionized water. The mixture was filtered, recrystallized with a 50% ethanol solution, and finally dried to obtain a succinic anhydride derivative. Chlorogenic acid, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, ethanol, and deionized water were mixed in a mass ratio of 5:2:150:50. After stirring evenly, place in an ice bath, add N-hydroxysuccinimide with a mass of 0.2 times that of chlorogenic acid, stir evenly, and then add chitosan solution with a mass of 80 times that of chlorogenic acid at a rate of 1 ml / min. The mass ratio of chitosan to 2% acetic acid solution in the chitosan solution is 1:40. After reacting for 40 minutes, transfer to room temperature, add succinic anhydride derivative with a mass of 8 times that of chlorogenic acid, react in the dark for 24 hours, centrifuge and freeze-dry at -40°C to obtain composite chitosan:

[0028] S2. Place diethylenetriamine in an ice bath, add a methanol solution of 20% methyl acrylate (3 times the mass of diethylenetriamine) at a rate of 1 ml / min, react at room temperature for 6 hours, then evaporate, heat to 110°C, react for 2 hours, cool to 5°C, add sodium hydroxide (0.02 times the mass of diethylenetriamine) and acrylic acid (0.4 times the mass of diethylenetriamine), stir evenly, heat to 70 hours, react for 12 hours, cool to room temperature, adjust the pH to 6.8 with triethylamine, evaporate again, and dry in vacuo at 80°C to obtain a carboxyl-terminated polyamide; heat and melt lactide, add 0.03 times the mass of lactide, and add octanoic acid. After stirring evenly, add succinic anhydride 1.13 times the mass of lactide, adjust the pressure to 0.08MPa, heat to 130℃ and react for 2h, continue to heat to 150℃ and react for 2h, continue to heat to 170℃ and react for 2h to obtain carboxyl-terminated polylactic acid; mix the carboxyl-terminated polylactic acid and carboxyl-terminated polyamide in a mass ratio of 1:4 and stir evenly to obtain a carboxyl-terminated composition; mix bamboo powder, carboxyl-terminated composition and dimethyl sulfoxide in a mass ratio of 1:0.2:50 and stir evenly, heat to 80℃, add concentrated sulfuric acid 0.2 times the mass of bamboo powder dropwise at a rate of 1ml / min, react for 6h, and distill under reduced pressure to obtain modified bamboo powder;

[0029] S3. Corn starch and deionized water were mixed in a mass ratio of 1:1.8, stirred evenly, and heated to 35°C. The pH was adjusted to 8.8 with sodium hydroxide, and sodium hypochlorite (0.2 times the mass of corn starch) was added. After reacting for 3 hours, the reaction was terminated with sodium metabisulfite, and the pH was adjusted to 6.8 with hydrochloric acid. The mixture was washed three times with deionized water, dried, and crushed to obtain oxidized corn starch. Polyethylene glycol, phthalamide, triphenylphosphine, and tetrahydrofuran were mixed in a mass ratio of 1:1:0.1:100, stirred evenly, and placed in an ice bath for 1 hour. Triphenylphosphine was added. An equal mass of diethyl azodicarboxylate was added, and the reaction was continued for 1 hour, and then the mixture was transferred to room temperature for reaction for 10 hours. Anhydrous ethanol 50 times the mass of polyethylene glycol and hydrazine hydrate 2 times the mass of polyethylene glycol were added, and the mixture was allowed to stand for 2 hours, and then extracted and concentrated with chloroform to obtain amino-terminated polyethylene glycol. Oxidized corn starch, composite chitosan, amino-terminated polyethylene glycol and deionized water were mixed in a mass ratio of 4:0.2:1:10, stirred evenly, and then heated to 70°C. The pH was adjusted to 4.8 with ammonia water, and the mixture was reacted for 3 hours. The mixture was washed with deionized water 3 times, dried and crushed to obtain chitosan starch.

[0030] S4. Chitosan starch, modified bamboo powder, plasticizer ethylene glycol, a compatibilizer, and deionized water are mixed in a mass ratio of 40:6:1:0.2:8, stirred evenly, and then hot-melt extruded and blown into a plastic film using a single-screw extruder at a processing temperature of 160°C. Finally, the mixture is cut, rolled, and packaged to produce a biodegradable plastic containing bamboo powder for food contact.

[0031] Example 2

[0032] S1. Dodecenylsuccinic anhydride, 1,4-butanediamine, and dimethyl sulfoxide were mixed in a mass ratio of 1:2.4:15, heated to 50°C, refluxed for 5 h, cooled to room temperature, and precipitated with deionized water. The mixture was filtered, recrystallized with a 50% ethanol solution, and finally dried to obtain a succinic anhydride derivative. Chlorogenic acid, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, ethanol, and deionized water were mixed in a mass ratio of 5:2.5:15:50. After stirring evenly, place in an ice bath, add N-hydroxysuccinimide with a mass of 0.25 times that of chlorogenic acid, stir evenly, and then add chitosan solution with a mass of 90 times that of chlorogenic acid at 2 ml / min. The mass ratio of chitosan to 3% acetic acid solution in the chitosan solution is 1:45. After reacting for 45 minutes, transfer to room temperature, add succinic anhydride derivative with a mass of 15 times that of chlorogenic acid, react in the dark for 24 hours, centrifuge and freeze-dry at -50°C to obtain composite chitosan:

[0033] S2. Place diethylenetriamine in an ice bath, add a methanol solution of 25% methyl acrylate (4 times the mass of diethylenetriamine) at a rate of 1 to 3 ml / min, react at room temperature for 7 hours, then evaporate, heat to 120°C, react for 3 hours, cool to 6°C, add sodium hydroxide (0.03 times the mass of diethylenetriamine) and acrylic acid (0.5 times the mass of diethylenetriamine), stir evenly, heat to 75 hours, react for 13 hours, cool to room temperature, adjust the pH to 7 with triethylamine, evaporate again, and dry in vacuo at 85°C to obtain a carboxyl-terminated polyamide; heat and melt lactide, add stannous octoate (0.04 times the mass of lactide), stir, and obtain a polyamide. After uniformity, succinic anhydride (1.14 times the mass of lactide) was added, the pressure was adjusted to 0.085 MPa, the temperature was raised to 131°C for reaction for 2.5 hours, the temperature was further raised to 151°C for reaction for 2.5 hours, and the temperature was further raised to 171°C for reaction for 2.5 hours to obtain carboxyl-terminated polylactic acid; the carboxyl-terminated polylactic acid and the carboxyl-terminated polyamide were mixed in a mass ratio of 1:5 and stirred to obtain a carboxyl-terminated composition; bamboo powder, the carboxyl-terminated composition and dimethyl sulfoxide were mixed in a mass ratio of 1:0.3:50, stirred to obtain a mixture, the temperature was raised to 85°C, concentrated sulfuric acid (0.3 times the mass of bamboo powder) was added dropwise at a rate of 2 ml / min, the reaction was continued for 7 hours, and vacuum distillation was performed to obtain modified bamboo powder;

[0034] S3. Corn starch and deionized water were mixed in a mass ratio of 1:2, stirred evenly, and heated to 40°C. The pH was adjusted to 9 with sodium hydroxide, and sodium hypochlorite (0.4 times the mass of corn starch) was added. After reacting for 4 hours, the reaction was terminated with sodium metabisulfite, and the pH was adjusted to 7 with hydrochloric acid. The mixture was washed four times with deionized water, dried, and crushed to obtain oxidized corn starch. Polyethylene glycol, phthalamide, triphenylphosphine, and tetrahydrofuran were mixed in a mass ratio of 1:3:0.1:100, stirred evenly, and reacted in an ice bath for 1.5 hours. Triphenylphosphine and other mass ratios were added. The reaction was continued for 1.5 hours, and then the mixture was transferred to room temperature for 11 hours. Anhydrous ethanol 80 times the mass of polyethylene glycol and hydrazine hydrate 3 times the mass of polyethylene glycol were added. After standing for 3 hours, the mixture was extracted and concentrated with chloroform to obtain amino-terminated polyethylene glycol. Oxidized corn starch, composite chitosan, amino-terminated polyethylene glycol and deionized water were mixed in a mass ratio of 5:0.2:1:15, stirred evenly, and then heated to 75°C. The pH was adjusted to 5 with ammonia water, reacted for 4 hours, washed with deionized water 4 times, dried and crushed to obtain chitosan starch.

[0035] S4. Chitosan starch, modified bamboo powder, plasticizer glycerol, a compatibilizer, and deionized water were mixed in a mass ratio of 60:8:2:0.4:8, stirred evenly, and then hot-melt extruded and blown into a plastic film using a single-screw extruder at a processing temperature of 165°C. The film was finally cut, rolled, and packaged to produce a biodegradable plastic containing bamboo powder for food contact.

[0036] Example 3

[0037] S1. Dodecenylsuccinic anhydride, 1,4-butanediamine, and dimethyl sulfoxide were mixed in a mass ratio of 1:2.5:20, heated to 52°C, refluxed for 6 hours, cooled to room temperature, and precipitated with deionized water. The mixture was filtered, recrystallized with a 50% ethanol solution, and finally dried to obtain a succinic anhydride derivative. Chlorogenic acid, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, ethanol, and deionized water were mixed in a mass ratio of 5:3:160:50. , stir evenly and place in an ice bath, add N-hydroxysuccinimide with a mass of 0.3 times that of chlorogenic acid, stir evenly, and then add chitosan solution with a mass of 100 times that of chlorogenic acid at 3 ml / min, the mass ratio of chitosan to 4% acetic acid solution in the chitosan solution is 1:50, react for 50 minutes, transfer to room temperature, add succinic anhydride derivative with a mass of 20 times that of chlorogenic acid, react in the dark for 24 hours, centrifuge and freeze-dry at -60°C to obtain composite chitosan:

[0038] S2. Place diethylenetriamine in an ice bath, add a methanol solution of 30% methyl acrylate (5 times the mass of diethylenetriamine) at a rate of 1-3 ml / min, react at room temperature for 8 hours, then evaporate, heat to 130°C, react for 4 hours, cool to 7°C, add sodium hydroxide (0.04 times the mass of diethylenetriamine) and acrylic acid (0.6 times the mass of diethylenetriamine), stir evenly, heat to 80 hours, react for 14 hours, cool to room temperature, adjust the pH to 7.2 with triethylamine, evaporate again, and dry in vacuo at 90°C to obtain a carboxyl-terminated polyamide; heat and melt lactide, add octanoic acid (0.05 times the mass of lactide) After stirring evenly, add succinic anhydride 1.15 times the mass of lactide, adjust the pressure to 0.09MPa, heat to 132℃ and react for 3h, continue to heat to 152℃ and react for 3h, continue to heat to 172℃ and react for 3h to obtain carboxyl-terminated polylactic acid; mix the carboxyl-terminated polylactic acid and carboxyl-terminated polyamide in a mass ratio of 1:6 and stir evenly to obtain a carboxyl-terminated composition; mix bamboo powder, carboxyl-terminated composition and dimethyl sulfoxide in a mass ratio of 1:0.4:50 and stir evenly, heat to 90℃, add concentrated sulfuric acid 0.4 times the mass of bamboo powder dropwise at a rate of 3ml / min, react for 8h, and distill under reduced pressure to obtain modified bamboo powder;

[0039] S3. Corn starch and deionized water were mixed in a mass ratio of 1:2.2, stirred evenly, and heated to 45°C. The pH was adjusted to 9.2 with sodium hydroxide, and sodium hypochlorite (0.4 times the mass of the corn starch) was added. After reacting for 5 hours, the reaction was terminated with sodium metabisulfite, and the pH was adjusted to 7.2 with hydrochloric acid. The mixture was washed with deionized water five times, dried, and pulverized to obtain oxidized corn starch. Polyethylene glycol, phthalamide, triphenylphosphine, and tetrahydrofuran were mixed in a mass ratio of 1:4:0.1:100, stirred evenly, and reacted in an ice bath for 2 hours. Triphenylphosphine was added, etc. The reaction was continued for 1 to 2 hours, and then the mixture was transferred to room temperature for 12 hours. Anhydrous ethanol with a mass of 100 times that of the polyethylene glycol and hydrazine hydrate with a mass of 4 times that of the polyethylene glycol were added. After standing for 4 hours, the mixture was extracted and concentrated with chloroform to obtain amino-terminated polyethylene glycol. Oxidized corn starch, composite chitosan, amino-terminated polyethylene glycol and deionized water were mixed in a mass ratio of 6:0.2:1:20, stirred evenly, heated to 80°C, adjusted to pH 5.2 with ammonia water, reacted for 5 hours, washed with deionized water 5 times, dried and crushed to obtain chitosan starch.

[0040] S4. Chitosan starch, modified bamboo powder, plasticizer dimethyl sulfoxide, a compatibilizer, and deionized water were mixed in a mass ratio of 80:9:3:00.5:8, stirred evenly, and then hot-melt extruded and blown into a plastic film using a single-screw extruder at a processing temperature of 170°C. The film was finally cut, rolled, and packaged to produce a biodegradable plastic containing bamboo powder for food contact.

[0041] Comparative Example 1

[0042] The composition of Comparative Example 1 is the same as that of Example 2. The difference between the preparation method of the biodegradable plastic containing bamboo powder for food contact and Example 2 is that the composite chitosan is prepared by coating the surface of chitosan with a succinic anhydride derivative.

[0043] Comparative Example 2

[0044] The composition of Comparative Example 2 is the same as that of Example 2. The difference between the preparation method of the biodegradable plastic containing bamboo powder for food contact and Example 2 is that the composite chitosan is prepared by grafting chlorogenic acid on the surface of chitosan.

[0045] Comparative Example 3

[0046] The composition of Comparative Example 3 is the same as that of Example 2. The difference between the preparation method of the biodegradable plastic containing bamboo powder for food contact and Example 2 is that chitosan starch is prepared by adding chitosan and amino-terminated polyethylene glycol to oxidized corn starch.

[0047] Comparative Example 4

[0048] The composition of Comparative Example 4 is the same as that of Example 2. The preparation method of the biodegradable plastic containing bamboo powder for food contact differs from that of Example 2 in that the biodegradable plastic containing bamboo powder for food contact comprises oxidized corn starch, modified bamboo powder, plasticizer glycerin, a compatibilizer, and deionized water.

[0049] Comparative Example 5

[0050] The composition of Comparative Example 5 is the same as that of Example 2. The difference between the preparation method of the biodegradable plastic containing bamboo powder for food contact and Example 2 is that the carboxyl-terminated composition is only carboxyl-terminated polylactic acid.

[0051] Comparative Example 6

[0052] The composition of Comparative Example 6 is the same as that of Example 2. The difference between the preparation method of the biodegradable plastic containing bamboo powder for food contact and Example 2 is that the carboxyl-terminated composite material is only carboxyl-terminated polyamide.

[0053] Comparative Example 7

[0054] The composition of Comparative Example 7 is the same as that of Example 2. The preparation method of the biodegradable plastic containing bamboo powder for food contact differs from that of Example 2 in that the biodegradable plastic containing bamboo powder for food contact comprises chitosan starch, bamboo powder, plasticizer glycerin, a compatibilizer and deionized water.

[0055] Effect Examples

[0056] Table 1 below shows the performance analysis results of the biodegradable plastics containing bamboo powder for food contact prepared using Examples 1 to 3 of the present invention and Comparative Examples 1 to 7:

[0057] Table 1

[0058] Elongation at break (%) <![CDATA[Toughness (MJ / m 3 )]]> Example 1 175 147 Example 2 184 151 Example 3 180 149 Comparative Example 1 159 137 Comparative Example 2 153 139 Comparative Example 3 148 132 Comparative Example 4 147 138 Comparative Example 5 137 127 Comparative Example 6 140 128 Comparative Example 7 136 119

[0059] By comparing the experimental data of the examples and the comparative examples in Table 1, it can be clearly found that the biodegradable plastics containing bamboo powder for food contact prepared using Examples 1, 2, and 3 have higher mechanical properties and toughness.

[0060] From the comparison of the experimental data of Example 1, Example 2, Example 3 and Comparative Examples 1-4, it can be found that after chlorogenic acid is grafted onto the surface of chitosan, it is reacted with a succinic anhydride derivative with a double-terminal carboxyl group to introduce a large number of carboxyl groups while enhancing the compatibility with starch. After the composite chitosan is added to the oxidized corn starch, it is cross-linked with amino-terminated polyethylene glycol to form a dense three-dimensional cross-linked spatial network structure, so that the oxidized corn starch and the composite chitosan are tightly connected together, thereby enhancing the mechanical properties.

[0061] From the comparison of the experimental data of Example 1, Example 2, Example 3 and Comparative Examples 5-7, it can be found that the carboxyl-terminated composition reacts with the hydroxyl groups on the surface of the bamboo powder, coats the surface of the bamboo powder, reduces the polarity of the bamboo powder surface, enhances the compatibility of the bamboo powder with chitosan starch, and can also introduce amino groups on the surface, introduce the modified bamboo powder into the three-dimensional cross-linked spatial network structure of the chitosan starch, and uniformly disperse the modified bamboo powder in the plastic, thereby enhancing the toughness of the plastic while further enhancing the mechanical properties of the plastic.

[0062] Obviously, the above embodiments are merely examples for the purpose of clearly illustrating the embodiments of the present invention and are not intended to limit the embodiments of the present invention. Those skilled in the art will readily appreciate that other variations or modifications based on the above description are possible. It is not necessary and impossible to enumerate all embodiments here. However, such obvious variations or modifications arising from the spirit of the present invention remain within the scope of protection of the present invention.

Claims

1. A biodegradable plastic containing bamboo powder for food contact, characterized in that: The invention comprises chitosan starch, modified bamboo powder, plasticizer, compatibilizer and deionized water.

2. The biodegradable plastic containing bamboo powder for food contact according to claim 1, characterized in that: The chitosan starch is prepared by adding composite chitosan and amino-terminated polyethylene glycol to oxidized corn starch; the composite chitosan is prepared by grafting chlorogenic acid onto the surface of chitosan and then coating a succinic anhydride derivative; the succinic anhydride derivative is prepared by reacting dodecenylsuccinic anhydride with 1,4-butanediamine.

3. The biodegradable plastic containing bamboo powder for food contact according to claim 1, characterized in that: The modified bamboo powder is prepared by reacting bamboo powder with a carboxyl-terminated composition; the carboxyl-terminated composition comprises carboxyl-terminated polylactic acid and carboxyl-terminated polyamide.

4. The biodegradable plastic containing bamboo powder for food contact according to claim 1, characterized in that: The toughening agent is one or a mixture of ethylene glycol, dimethyl sulfoxide and glycerol; and the compatibilizer is polyglycerol sebacate.

5. The method for preparing a biodegradable plastic containing bamboo powder for food contact according to claim 1, characterized in that: The specific steps include: S1. Chlorogenic acid, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride, ethanol, and deionized water were mixed in a mass ratio of 5:2-3:150-160:50, stirred evenly, and placed in an ice bath. N-hydroxysuccinimide (0.2-0.3 times the mass of chlorogenic acid) was added and stirred evenly. A chitosan solution (80-100 times the mass of chlorogenic acid) was added dropwise at a rate of 1-3 ml / min. The mass ratio of chitosan to 2-4% acetic acid solution was 1:40-50. After reacting for 40-50 minutes, the mixture was transferred to room temperature, and a succinic anhydride derivative (8-20 times the mass of chlorogenic acid) was added. The mixture was protected from light and reacted for 24 hours. The mixture was centrifuged and freeze-dried at -40--60°C to obtain a composite chitosan. S2. The carboxyl-terminated polylactic acid and the carboxyl-terminated polyamide were mixed in a mass ratio of 1:4 to 6 and stirred to obtain a carboxyl-terminated composition; the bamboo powder, the carboxyl-terminated composition and dimethyl sulfoxide were mixed in a mass ratio of 1:0.2 to 0.4:50 and stirred, and then heated to 80 to 90 ° C., concentrated sulfuric acid of 0.2 to 0.4 times the mass of the bamboo powder was added dropwise at a rate of 1 to 3 ml / min, and the reaction was carried out for 6 to 8 hours, and the mixture was distilled under reduced pressure to obtain a modified bamboo powder; S3. Oxidized corn starch, composite chitosan, amino-terminated polyethylene glycol, and deionized water were mixed in a mass ratio of 4-6:0.2:1:10-20, stirred evenly, heated to 70-80°C, adjusted the pH to 4.8-5.2 with aqueous ammonia, reacted for 3-5 hours, washed with deionized water 3-5 times, dried, and pulverized to obtain chitosan starch; S4. Chitosan starch, modified bamboo powder, plasticizer, compatibilizer and deionized water are mixed in a mass ratio of 40-80:6-9:1-3:0.2-0.5:8, stirred evenly and then subjected to hot-melt extrusion blow molding into a plastic film through a single-screw extrusion film blowing machine at a processing temperature of 160-170°C. Finally, the mixture is cut, rolled and packaged to obtain a biodegradable plastic containing bamboo powder for food contact.

6. The method for preparing a biodegradable plastic containing bamboo powder for food contact according to claim 5, characterized in that: In the above step S1, the preparation method of the succinic anhydride derivative is: dodecenylsuccinic anhydride, 1,4-butanediamine and dimethyl sulfoxide are mixed in a mass ratio of 1:2.2-2.5:10-20, heated to 48-52°C, refluxed for 4-6 hours, cooled to room temperature and precipitated with deionized water, filtered, recrystallized with a 50% by mass ethanol solution, and finally dried to obtain the succinic anhydride derivative.

7. The method for preparing a biodegradable plastic containing bamboo powder for food contact according to claim 5, characterized in that: In the above step S2, the preparation method of the carboxyl-terminated polylactic acid is as follows: after heating and melting the lactide, adding stannous octoate in an amount of 0.03 to 0.05 times the mass of the lactide, stirring evenly, adding succinic anhydride in an amount of 1.13 to 1.15 times the mass of the lactide, adjusting the pressure to 0.08 to 0.09 MPa, heating to 130 to 132°C and reacting for 2 to 3 hours, continuing to heat to 150 to 152°C and reacting for 2 to 3 hours, and continuing to heat to 170 to 172°C and reacting for 2 to 3 hours to obtain the carboxyl-terminated polylactic acid.

8. The method for preparing a biodegradable plastic containing bamboo powder for food contact according to claim 5, characterized in that: In the above step S2, the preparation method of the terminal carboxyl polyamide is as follows: placing diethylenetriamine in an ice bath, adding a methanol solution of methyl acrylate with a mass fraction of 20-30% at a rate of 1-3 ml / min, reacting at room temperature for 6-8 hours, and then rotary evaporation, then heating to 110-130°C, reacting for 2-4 hours, cooling to 5-7°C, adding sodium hydroxide with a mass of 0.02-0.04 times that of diethylenetriamine and acrylic acid with a mass of 0.4-0.6 times that of diethylenetriamine, stirring evenly, heating to 70-80 hours, reacting for 12-14 hours, cooling to room temperature and adjusting the pH to 6.8-7.2 with triethylamine, rotary evaporation again, and vacuum drying at 80-90°C to obtain the terminal carboxyl polyamide.

9. The method for preparing a biodegradable plastic containing bamboo powder for food contact according to claim 5, characterized in that: In the above step S3, the preparation method of the amino-terminated polyethylene glycol is as follows: polyethylene glycol, phthalamide, triphenylphosphine and tetrahydrofuran are mixed in a mass ratio of 1:1 to 4:0.1:100, stirred evenly and placed in an ice bath to react for 1 to 2 hours, diethyl azodicarboxylate of equal mass to triphenylphosphine is added, and the reaction is continued for 1 to 2 hours, and then transferred to room temperature for reaction for 10 to 12 hours, anhydrous ethanol with a mass of 50 to 100 times that of the polyethylene glycol and hydrazine hydrate with a mass of 2 to 4 times that of the polyethylene glycol are added, and after standing for 2 to 4 hours, the mixture is extracted and concentrated with chloroform to obtain the amino-terminated polyethylene glycol.

10. The method for preparing a biodegradable plastic containing bamboo powder for food contact according to claim 5, characterized in that: In the above step S3, the preparation method of oxidized corn starch is as follows: corn starch and deionized water are mixed in a mass ratio of 1:1.8-2.2, stirred evenly, heated to 35-45°C, adjusted to pH 8.8-9.2 with sodium hydroxide, added with sodium hypochlorite in an amount of 0.2-0.4 times the mass of corn starch, reacted for 3-5 hours, terminated the reaction with sodium metabisulfite, and then adjusted to pH 6.8-7.2 with hydrochloric acid. The mixture is washed with deionized water 3-5 times, dried and crushed to obtain oxidized corn starch.