CN113980364B - Thermoplastic starch resin and application thereof in food packaging material - Google Patents
Thermoplastic starch resin and application thereof in food packaging material Download PDFInfo
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Abstract
The invention discloses a thermoplastic starch resin and application thereof in food packaging materials, wherein raw materials such as modified starch, polylactic acid, protein polyamide, glycerol monothioglycolate, triisocaprylic glyceride and the like are put into a double-screw extruder to be extruded and granulated to obtain the thermoplastic starch resin.
Description
Technical Field
The invention relates to the technical field of biodegradable materials, in particular to thermoplastic starch resin and application thereof in food packaging materials.
Background
At present, most of disposable articles used in daily biochemistry are plastics processed by petroleum and derivatives thereof, and although the plastics have the advantage of low price, all of the petroleum-based plastics belong to environmentally harmful products which are difficult to naturally degrade.
In recent years, the use amount of environmentally harmful petroleum-based plastic products is increasing, so that harmful phenomena such as white pollution and the like are caused, the problem of extremely serious environmental pollution is caused, and the balance of ecological environment is seriously influenced. In this context, degradable plastic articles are beginning to appear in the human field of vision.
However, the naturally degradable plastic products on the market at present often have various problems including low degradation efficiency, harsh degradation conditions, poor mechanical strength, complicated production process, high cost, secondary pollution in the production process and the like.
In the prior art, it is common to use petroleum-based plastic polyolefin material as a base material to prepare a naturally degradable plastic product, or use natural high molecular substances including polylactic acid and the like to prepare a plastic product with significant natural degradation capability. However, the degradable plastic products using polylactic acid as matrix obtained by the prior art often show poor mechanical strength and their degradation performance is not satisfactory.
Patent CN112457534A provides a biodegradable thermoplastic starch resin for food packaging material and a preparation method thereof, which uses modified starch mixed solution, ethylene acrylate polymer, natural fiber and antioxidant as raw materials, but the degradation rate and mechanical strength of the resin cannot meet the market demand, and the production process is complicated.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a thermoplastic starch resin and application thereof in food packaging materials.
In order to solve the technical problems, the invention adopts the technical scheme that:
the preparation method of the thermoplastic starch resin comprises the following steps: and (2) adding modified starch, polylactic acid, protein polyamide, sorbitol, diethylene glycol ether, glycerol monothioglycolate and triisocaprylic glyceride into a high-speed mixer, stirring, and then adding into a double-screw extruder for extrusion granulation to obtain the thermoplastic starch resin.
The sulfur element in the glycerol monothioglycolate can form hydrogen bonds with sulfur atoms in the protein polyamide, so that the bonding strength between the protein polyamide and the polylactic acid and the modified starch is enhanced, and the mechanical strength of the thermoplastic starch resin is improved.
As a preferred technical scheme, the preparation method of the thermoplastic starch resin comprises the following steps: 24-27 parts of modified starch, 13-17 parts of polylactic acid, 12-15 parts of protein polyamide, 3-4.5 parts of sorbitol, 5-6.5 parts of diethylene glycol ether, 0.7-1.2 parts of glycerol monothioglycolate and 0.5-1.2 parts of triisocaprylic glyceride are put into a high-speed mixer, stirred for 15-20min at the temperature of 175-.
The preparation method of the modified starch comprises the following steps: putting the mixed starch into a steam explosion machine for steam explosion treatment; mixing with oxalic acid water solution, and oscillating; and then centrifugally dewatering and drying under reduced pressure to obtain the modified starch.
In the technical scheme of the invention, the steam molecules permeating into the mixed starch are instantaneously released by utilizing a steam explosion means, so that the internal energy of the steam is converted into mechanical energy and acts between the molecules of the mixed starch, and the aim of decomposing the mixed starch, including acid-like hydrolysis, hydrogen bond destruction and structural rearrangement, is fulfilled by using less energy; in addition, the problem of secondary pollution possibly caused by chemical treatment is avoided, and the high-efficiency pretreatment sufficiency is obtained.
The internal hydrogen bonds, amorphous areas and partial crystalline areas of the mixed starch subjected to steam explosion treatment are destroyed, and at the moment, the mobility of molecular chains in the mixed starch is enhanced under the reduction action of oxalic acid, so that starch molecules are changed to an ordered structure in a kinetic angle, good adhesive performance is brought to the mixed starch, and the polylactic acid and the protein polyamide connected with the mixed starch have stronger adhesive strength and high elastic modulus.
As a preferred technical scheme, the preparation method of the modified starch comprises the following steps: putting the mixed starch into a steam explosion machine, and keeping the pressure at 3.3-3.5MPa for 100-115 seconds; mixing with oxalic acid water solution with temperature of 65-70 deg.C and concentration of 0.5-1.2mol/L at bath ratio of 1kg (3.2-4) L, and oscillating for 15-20 min; then performing centrifugal dehydration for 4-6min at 10000-. The oscillation process parameters are as follows: the amplitude of the convolution was 2-3mm and the oscillation speed was 600-700 rpm.
The mixed starch is at least two of corn starch, tapioca starch and maltodextrin. As a preferable technical scheme, the mixed starch is a mixture of corn starch, tapioca starch and maltodextrin in a mass ratio of (6-10) to (2-5) to (1-5).
The corn starch, the cassava starch and the maltodextrin can be mixed with high molecular materials including polylactic acid to achieve the purpose of improving the biodegradability of the materials, and can also obviously enhance the mechanical strength of the matrix materials including impact resistance, bending resistance and the like, thereby reducing the production cost of the environment-friendly degradable materials to the minimum.
The preparation method of the protein polyamide comprises the following steps:
mixing the compound protein, the modified polyamide and tetrahydrofuran, heating, oscillating, cooling and standing, filtering to obtain a precipitate I, and drying the precipitate I by hot air to obtain the protein polyamide.
Tetrahydrofuran is used as a solvent, the compound protein and the denatured polyamide are dissolved, the contact probability of reactants is increased by an oscillation means so as to increase the reaction rate, and then carbon dioxide is used as a medium for hot air drying to dry the reaction product, so that the protein polyamide is obtained.
As a preferred technical scheme, the preparation method of the protein polyamide comprises the following steps:
mixing the compound protein, the modified polyamide and the tetrahydrofuran according to the mass ratio of (4-6) to (8-11) to (90-120) at 20-30 ℃, heating to 43-45 ℃, oscillating at the oscillating speed of 400-600rpm and the convolution amplitude of 2-3mm for 25-40min, then cooling to 3-5 ℃, standing for 18-25h at the temperature, filtering to obtain a precipitate I, drying the precipitate I for 70-85min by using carbon dioxide hot air with the temperature of 43-45 ℃ and the air flow of 100-120mL/s to obtain the protein polyamide.
The compound protein is at least two of hydrolyzed keratin, soybean protein and zein. As a preferable technical scheme, the compound protein is a mixture of hydrolyzed keratin, soybean protein and zein in a mass ratio of (1-5) to (1-8) to (5-15).
The peptide main chain of the zein has hydrogen bond action of hydroxyl and imino to form alpha-spirochete, and the zein has lower surface energy and unique film forming property. The hydrolyzed keratin contains more cystine, so the disulfide bond content is higher, the hydrolyzed keratin can play a strong crosslinking role in a protein peptide chain by being compounded with the soybean protein and the zein, the chemical stability of the protein polyamide is enhanced, the protein polyamide is resistant to acid corrosion, light aging and the like, and the thermoplastic starch resin has higher mechanical strength and is shown to be impact resistant, bending resistant and the like, so the service life of a food package prepared from the starch resin is prolonged.
The preparation method of the modified polyamide comprises the following steps:
z1, dissolving a denaturant in a compound solvent and homogenizing to obtain a denaturant liquid;
z2, mixing and stirring the denatured liquid and polyamide, filtering to obtain a precipitate A, and drying the precipitate A by using carbon dioxide hot air to obtain an intermediate product A;
z3, putting the intermediate product A, 1, 2-cyclohexanediamine tetraacetic acid and polyacrylonitrile into a double-screw extruder for extrusion and granulation to obtain the modified polyamide.
Polyacrylonitrile has good weather resistance and sunlight resistance, and the service reliability and the service life of the modified polyamide can be enhanced by using the polyacrylonitrile for preparing the modified polyamide. The nitrogen atoms forming carbon-nitrogen bonds in polyacrylonitrile and the oxygen atoms in the carboxyl groups positioned at specific sites in the 1, 2-cyclohexanediaminetetraacetic acid can be in hydrogen bond connection with each other, so that the structural stability of the modified polyamide molecules can be enhanced, and the mechanical strength of the thermoplastic starch resin doped with the modified polyamide molecules can be improved macroscopically.
As a preferable technical scheme, the preparation method of the modified polyamide comprises the following steps:
z1 at 20-30 ℃, dissolving the denaturant in the compound solvent according to the bath ratio of 1g (9-11) mL, and homogenizing at 7000-8000rpm for 1-3min to obtain denaturant liquid;
z2 mixing the polyamide and the denaturing solution at a bath ratio of 1g (7-9) mL, stirring at the rotation speed of 200-260rpm for 15-20min, filtering to obtain a precipitate A, and drying the precipitate A70-85min by using carbon dioxide hot air with the temperature of 42-45 ℃ and the air flow rate of 100-120mL/s to obtain an intermediate product A;
z3 the intermediate product A, 1, 2-cyclohexanediaminetetraacetic acid and polyacrylonitrile are mixed according to the mass ratio of (10.5-13): (1.2-2.3): 2.5-3.3) and then put into a double-screw extruder with the temperature of 110-.
The denaturant is at least one of 2-amino-5-guanidino valeric acid and L-2-amino-3-methyl valeric acid. As a preferable technical scheme, the denaturant is a mixture of 2-amino-5-guanidino valeric acid and L-2-amino-3-methyl valeric acid in a mass ratio of (1-2) to (1-2). As a more preferable technical scheme, the denaturant is a mixture of 2-amino-5-guanidino valeric acid and L-2-amino-3-methyl valeric acid in a mass ratio of 1: 1.
The amino groups of both 2-amino-5-guanidinopentanoic acid and L-2-amino-3-methylpentanoic acid are located at specific positions so that they have specific charge attraction to each other, which makes it possible to enhance the chemical activity of the polyamide after incorporation into the polyamide molecule, resulting in a denatured polyamide which reacts more readily with the built protein.
The compound solvent is a mixture of ethyl acetate, tetrahydrofuran and water. As a preferable technical scheme, the compound solvent is a mixture of ethyl acetate, tetrahydrofuran and water in a mass ratio of (1-2) to (1-2).
The compound solvent prepared from ethyl acetate, tetrahydrofuran and water has good dissolution and solubilization effects on 1, 2-cyclohexanediamine tetraacetic acid, polyacrylonitrile and a denaturant.
The invention has the beneficial effects that:
1. the invention provides a thermoplastic starch resin, a preparation method thereof and application thereof in food packaging materials, wherein modified starch, polylactic acid, protein polyamide, glycerol monothioglycolate, triisocaprylic glyceride and the like are used as raw materials, and the protein polyamide prepared by the technical scheme of the invention is adopted, so that very good degradation efficiency and very strong mechanical property are obtained.
2. The protein polyamide obtained by using hydrolyzed keratin, soybean protein, zein, modified polyamide and the like as raw materials has a strong degradation effect and can enhance the mechanical strength of the thermoplastic starch resin.
3. Modified polyamide and a preparation method thereof are provided, the polyamide is modified by raw materials such as 1, 2-cyclohexanediamine tetraacetic acid, polyacrylonitrile and the like, and the obtained modified polyamide can be used for enhancing the degradation capability and the mechanical strength of the thermoplastic starch resin.
Detailed Description
The above summary of the present invention is described in further detail below with reference to specific embodiments, but it should not be understood that the scope of the above subject matter of the present invention is limited to the following examples.
Introduction of some raw materials in this application:
polylactic acid, co-engineering plastification technology (shanghai) ltd, brand: FY801-804, melt flow rate: 5g/10min, CAS: 31852-84-3.
Diethylene glycol ether, CAS: 111-46-6, larsson chemical ltd, suzhou.
Glycerol monothioglycolate, CAS: 30618-84-9, Shanghai Yien chemical technology, Inc.
Triisooctanoic acid glycerol ester, CAS: 7360-38-5, Wuhan Hua Zhi scientific Biotech Co.
Corn starch, bio-technology limited, guang blue, Anhui, implements the standard: GB 12309-: YMDF 001.
Tapioca starch, eastern skimmia food ltd, performance standard: GB/T29343-: 0251.
maltodextrin, DE value: 12, performing the standard: GB/T20884-2007, Jinan Qianji chemical industry Co., Ltd., Cat number: 022.
hydrolyzed keratin, CAS: 69430-36-0, available from seian exhibition Biotechnology Ltd, type: AS-1, source: the animal fur is hydrolyzed, and the molecular weight is as follows: 0.6kDa, purity: 98%, pH: 5.7.
soy protein, CAS: 9010-10-0, Jiangsu Bai Yao Biotech limited, molecular weight: 24kDa, protein content: 90 percent.
Zein, CAS: 9010-66-6, molecular weight: 26kDa, Merrel chemical technology, Inc. of Shanghai.
2-amino-5-guanidinopentanoic acid, vicker biotechnology limited, Sichuan, CAS: 74-79-3.
L-2-amino-3-methylpentanoic acid, biologies (shanghai) ltd, CAS: 73-32-5.
Polyamide, shandong changlio new materials limited, CAS: 63428-84-2, trade name: PA 6666A, a Vydyne series nylon 66 resin produced by Kono, USA.
1, 2-cyclohexanediaminetetraacetic acid, CAS: 482-54-2, Wande chemical Co., Ltd, Hubei.
Polyacrylonitrile, CAS: 25014-41-9, molecular weight: 15 million, Puyang, Puhan Hao chemical Co.
Example 1
The preparation method of the thermoplastic starch resin comprises the following steps: 26 parts by weight of modified starch, 15 parts by weight of polylactic acid, 13 parts by weight of protein polyamide, 4.5 parts by weight of sorbitol, 6 parts by weight of diethylene glycol ether, 1 part by weight of glycerol monothioglycolate and 1 part by weight of glycerol triisooctanoate are put into a high-speed mixer, stirred at 185 ℃ for 20min at the rotation speed of 800rpm, and then put into a twin-screw extruder with the temperature of 180 ℃ and the screw rotation speed of 130rpm for extrusion granulation, so as to obtain the thermoplastic starch resin.
The preparation method of the modified starch comprises the following steps: putting the mixed starch into a steam explosion machine, and maintaining the pressure for 100s at the pressure of 3.5 MPa; mixing with oxalic acid water solution at 70 deg.C and concentration of 1mol/L at bath ratio of 1kg:3.5L, and oscillating for 20 min; and then centrifugally dewatering at 12000rpm for 5min, and drying under reduced pressure at 65 ℃ and 50kPa for 5h to obtain the modified starch. The oscillation process parameters are as follows: the amplitude of the convolution was 3mm and the oscillation speed was 700 rpm. The mixed starch is a mixture of corn starch, cassava starch and maltodextrin in a mass ratio of 7:3: 1.
The preparation method of the protein polyamide comprises the following steps:
mixing the compound protein, the modified polyamide and the tetrahydrofuran at a mass ratio of 4.5:9.2:100 at 25 ℃, heating to 45 ℃, oscillating at an oscillation speed of 600rpm and a convolution amplitude of 3mm for 30min, then cooling to 5 ℃, standing for 20h at the temperature, filtering to obtain a precipitate I, drying the precipitate I for 80min by using carbon dioxide hot air at a temperature of 45 ℃ and an air flow rate of 120mL/s to obtain the protein polyamide. The compound protein is a mixture of hydrolyzed keratin, soybean protein and zein in a mass ratio of 3:7: 12.
The preparation method of the modified polyamide comprises the following steps:
z1 at 25 deg.C, dissolving denaturant in a mixed solvent at a bath ratio of 1g:9mL, and homogenizing at 8000rpm for 2min to obtain denaturant solution; the denaturant is a mixture of 2-amino-5-guanidino valeric acid and L-2-amino-3-methyl valeric acid in a mass ratio of 1: 1; the compound solvent is a mixture of ethyl acetate, tetrahydrofuran and water in a mass ratio of 1:1: 1;
z2 mixing the polyamide and the denatured liquid at a bath ratio of 1g:7mL, stirring at a rotation speed of 260rpm for 15min, filtering to obtain a precipitate A, and drying the precipitate A for 80min by using carbon dioxide hot air with the temperature of 45 ℃ and the air flow rate of 120mL/s to obtain an intermediate product A;
z3 mixing the intermediate product A with 1, 2-cyclohexanediamine tetraacetic acid and polyacrylonitrile according to the mass ratio of 12:2:3, and then putting the mixture into a double-screw extruder with the temperature of 120 ℃ and the screw rotation speed of 150rpm for extrusion and granulation to obtain the modified polyamide.
Example 2
The preparation method of the thermoplastic starch resin comprises the following steps: 26 parts by weight of modified starch, 15 parts by weight of polylactic acid, 13 parts by weight of protein polyamide, 4.5 parts by weight of sorbitol, 6 parts by weight of diethylene glycol ether, 1 part by weight of glycerol monothioglycolate and 1 part by weight of glycerol triisooctanoate are put into a high-speed mixer, stirred at 185 ℃ for 20min at the rotation speed of 800rpm, and then put into a twin-screw extruder with the temperature of 180 ℃ and the screw rotation speed of 130rpm for extrusion granulation, so as to obtain the thermoplastic starch resin.
The preparation method of the modified starch comprises the following steps: putting the mixed starch into a steam explosion machine, and maintaining the pressure for 100s at the pressure of 3.5 MPa; mixing with oxalic acid water solution at 70 deg.C and concentration of 1mol/L at bath ratio of 1kg:3.5L, and oscillating for 20 min; and then centrifugally dewatering at 12000rpm for 5min, and drying under reduced pressure at 65 ℃ and 50kPa for 5h to obtain the modified starch. The oscillation process parameters are as follows: the amplitude of the convolution was 3mm and the oscillation speed was 700 rpm. The mixed starch is a mixture of corn starch, cassava starch and maltodextrin in a mass ratio of 7:3: 1.
The preparation method of the protein polyamide comprises the following steps:
mixing the compound protein, the modified polyamide and the tetrahydrofuran at a mass ratio of 4.5:9.2:100 at 25 ℃, heating to 45 ℃, oscillating at an oscillation speed of 600rpm and a convolution amplitude of 3mm for 30min, then cooling to 5 ℃, standing for 20h at the temperature, filtering to obtain a precipitate I, drying the precipitate I for 80min by using carbon dioxide hot air at a temperature of 45 ℃ and an air flow rate of 120mL/s to obtain the protein polyamide. The compound protein is a mixture of hydrolyzed keratin, soybean protein and zein in a mass ratio of 3:7: 12.
The preparation method of the modified polyamide comprises the following steps:
z1 at 25 deg.C, dissolving denaturant in a mixed solvent at a bath ratio of 1g:9mL, and homogenizing at 8000rpm for 2min to obtain denaturant solution; the denaturant is 2-amino-5-guanidino valeric acid; the compound solvent is a mixture of ethyl acetate, tetrahydrofuran and water in a mass ratio of 1:1: 1;
z2 mixing the polyamide and the denatured liquid at a bath ratio of 1g:7mL, stirring at a rotation speed of 260rpm for 15min, filtering to obtain a precipitate A, and drying the precipitate A for 80min by using carbon dioxide hot air with the temperature of 45 ℃ and the air flow rate of 120mL/s to obtain an intermediate product A;
z3 mixing the intermediate product A with 1, 2-cyclohexanediamine tetraacetic acid and polyacrylonitrile according to the mass ratio of 12:2:3, and then putting the mixture into a double-screw extruder with the temperature of 120 ℃ and the screw rotation speed of 150rpm for extrusion and granulation to obtain the modified polyamide.
Example 3
The preparation method of the thermoplastic starch resin comprises the following steps: 26 parts by weight of modified starch, 15 parts by weight of polylactic acid, 13 parts by weight of protein polyamide, 4.5 parts by weight of sorbitol, 6 parts by weight of diethylene glycol ether, 1 part by weight of glycerol monothioglycolate and 1 part by weight of glycerol triisooctanoate are put into a high-speed mixer, stirred at 185 ℃ for 20min at the rotation speed of 800rpm, and then put into a twin-screw extruder with the temperature of 180 ℃ and the screw rotation speed of 130rpm for extrusion granulation, so as to obtain the thermoplastic starch resin.
The preparation method of the modified starch comprises the following steps: putting the mixed starch into a steam explosion machine, and maintaining the pressure for 100s at the pressure of 3.5 MPa; mixing with oxalic acid water solution at 70 deg.C and concentration of 1mol/L at bath ratio of 1kg:3.5L, and oscillating for 20 min; and then centrifugally dewatering at 12000rpm for 5min, and drying under reduced pressure at 65 ℃ and 50kPa for 5h to obtain the modified starch. The oscillation process parameters are as follows: the amplitude of the convolution was 3mm and the oscillation speed was 700 rpm. The mixed starch is a mixture of corn starch, cassava starch and maltodextrin in a mass ratio of 7:3: 1.
The preparation method of the protein polyamide comprises the following steps:
mixing the compound protein, the modified polyamide and the tetrahydrofuran at a mass ratio of 4.5:9.2:100 at 25 ℃, heating to 45 ℃, oscillating at an oscillation speed of 600rpm and a convolution amplitude of 3mm for 30min, then cooling to 5 ℃, standing for 20h at the temperature, filtering to obtain a precipitate I, drying the precipitate I for 80min by using carbon dioxide hot air at a temperature of 45 ℃ and an air flow rate of 120mL/s to obtain the protein polyamide. The compound protein is a mixture of hydrolyzed keratin, soybean protein and zein in a mass ratio of 3:7: 12.
The preparation method of the modified polyamide comprises the following steps:
z1 at 25 deg.C, dissolving denaturant in a mixed solvent at a bath ratio of 1g:9mL, and homogenizing at 8000rpm for 2min to obtain denaturant solution; the denaturant is L-2-amino-3-methyl valeric acid; the compound solvent is a mixture of ethyl acetate, tetrahydrofuran and water in a mass ratio of 1:1: 1;
z2 mixing the polyamide and the denatured liquid at a bath ratio of 1g:7mL, stirring at a rotation speed of 260rpm for 15min, filtering to obtain a precipitate A, and drying the precipitate A for 80min by using carbon dioxide hot air with the temperature of 45 ℃ and the air flow rate of 120mL/s to obtain an intermediate product A;
z3 mixing the intermediate product A with 1, 2-cyclohexanediamine tetraacetic acid and polyacrylonitrile according to the mass ratio of 12:2:3, and then putting the mixture into a double-screw extruder with the temperature of 120 ℃ and the screw rotation speed of 150rpm for extrusion and granulation to obtain the modified polyamide.
Example 4
The preparation method of the thermoplastic starch resin comprises the following steps: 26 parts by weight of modified starch, 15 parts by weight of polylactic acid, 13 parts by weight of protein polyamide, 4.5 parts by weight of sorbitol, 6 parts by weight of diethylene glycol ether, 1 part by weight of glycerol monothioglycolate and 1 part by weight of glycerol triisooctanoate are put into a high-speed mixer, stirred at 185 ℃ for 20min at the rotation speed of 800rpm, and then put into a twin-screw extruder with the temperature of 180 ℃ and the screw rotation speed of 130rpm for extrusion granulation, so as to obtain the thermoplastic starch resin.
The preparation method of the modified starch comprises the following steps: putting the mixed starch into a steam explosion machine, and maintaining the pressure for 100s at the pressure of 3.5 MPa; mixing with oxalic acid water solution at 70 deg.C and concentration of 1mol/L at bath ratio of 1kg:3.5L, and oscillating for 20 min; and then centrifugally dewatering at 12000rpm for 5min, and drying under reduced pressure at 65 ℃ and 50kPa for 5h to obtain the modified starch. The oscillation process parameters are as follows: the amplitude of the convolution was 3mm and the oscillation speed was 700 rpm. The mixed starch is a mixture of corn starch, cassava starch and maltodextrin in a mass ratio of 7:3: 1.
The preparation method of the protein polyamide comprises the following steps:
mixing the compound protein, the modified polyamide and the tetrahydrofuran at a mass ratio of 4.5:9.2:100 at 25 ℃, heating to 45 ℃, oscillating at an oscillation speed of 600rpm and a convolution amplitude of 3mm for 30min, then cooling to 5 ℃, standing for 20h at the temperature, filtering to obtain a precipitate I, drying the precipitate I for 80min by using carbon dioxide hot air at a temperature of 45 ℃ and an air flow rate of 120mL/s to obtain the protein polyamide. The compound protein is a mixture of hydrolyzed keratin, soybean protein and zein in a mass ratio of 3:7: 12.
The preparation method of the modified polyamide comprises the following steps:
z1 at 25 deg.C, dissolving denaturant in a mixed solvent at a bath ratio of 1g:9mL, and homogenizing at 8000rpm for 2min to obtain denaturant solution; the denaturant is a mixture of 2-amino-5-guanidino valeric acid and L-2-amino-3-methyl valeric acid in a mass ratio of 1: 1; the compound solvent is a mixture of ethyl acetate, tetrahydrofuran and water in a mass ratio of 1:1: 1;
z2 mixing the polyamide and the denatured liquid at a bath ratio of 1g:7mL, stirring at a rotation speed of 260rpm for 15min, filtering to obtain a precipitate A, and drying the precipitate A for 80min by using carbon dioxide hot air with the temperature of 45 ℃ and the air flow rate of 120mL/s to obtain an intermediate product A;
z3 mixing the intermediate product A and polyacrylonitrile according to the mass ratio of 12:3, and then putting the mixture into a double-screw extruder with the temperature of 120 ℃ and the screw rotating speed of 150rpm for extrusion and granulation to obtain the modified polyamide.
Example 5
The preparation method of the thermoplastic starch resin comprises the following steps: 26 parts by weight of modified starch, 15 parts by weight of polylactic acid, 13 parts by weight of protein polyamide, 4.5 parts by weight of sorbitol, 6 parts by weight of diethylene glycol ether, 1 part by weight of glycerol monothioglycolate and 1 part by weight of glycerol triisooctanoate are put into a high-speed mixer, stirred at 185 ℃ for 20min at the rotation speed of 800rpm, and then put into a twin-screw extruder with the temperature of 180 ℃ and the screw rotation speed of 130rpm for extrusion granulation, so as to obtain the thermoplastic starch resin.
The preparation method of the modified starch comprises the following steps: putting the mixed starch into a steam explosion machine, and maintaining the pressure for 100s at the pressure of 3.5 MPa; mixing with oxalic acid water solution at 70 deg.C and concentration of 1mol/L at bath ratio of 1kg:3.5L, and oscillating for 20 min; and then centrifugally dewatering at 12000rpm for 5min, and drying under reduced pressure at 65 ℃ and 50kPa for 5h to obtain the modified starch. The oscillation process parameters are as follows: the amplitude of the convolution was 3mm and the oscillation speed was 700 rpm. The mixed starch is a mixture of corn starch, cassava starch and maltodextrin in a mass ratio of 7:3: 1.
The preparation method of the protein polyamide comprises the following steps:
mixing the compound protein, the modified polyamide and the tetrahydrofuran at a mass ratio of 4.5:9.2:100 at 25 ℃, heating to 45 ℃, oscillating at an oscillation speed of 600rpm and a convolution amplitude of 3mm for 30min, then cooling to 5 ℃, standing for 20h at the temperature, filtering to obtain a precipitate I, drying the precipitate I for 80min by using carbon dioxide hot air at a temperature of 45 ℃ and an air flow rate of 120mL/s to obtain the protein polyamide. The compound protein is a mixture of hydrolyzed keratin, soybean protein and zein in a mass ratio of 3:7: 12.
The preparation method of the modified polyamide comprises the following steps:
z1 at 25 deg.C, dissolving denaturant in a mixed solvent at a bath ratio of 1g:9mL, and homogenizing at 8000rpm for 2min to obtain denaturant solution; the denaturant is a mixture of 2-amino-5-guanidino valeric acid and L-2-amino-3-methyl valeric acid in a mass ratio of 1: 1; the compound solvent is a mixture of ethyl acetate, tetrahydrofuran and water in a mass ratio of 1:1: 1;
z2 mixing the polyamide and the denatured liquid at a bath ratio of 1g:7mL, stirring at a rotation speed of 260rpm for 15min, filtering to obtain a precipitate A, and drying the precipitate A for 80min by using carbon dioxide hot air with the temperature of 45 ℃ and the air flow rate of 120mL/s to obtain an intermediate product A;
z3 mixing the intermediate product A and 1, 2-cyclohexanediamine tetraacetic acid according to the mass ratio of 12:2, and then putting the mixture into a double-screw extruder with the temperature of 120 ℃ and the screw rotation speed of 150rpm for extrusion and granulation to obtain the modified polyamide.
Example 6
The preparation method of the thermoplastic starch resin comprises the following steps: 26 parts by weight of modified starch, 15 parts by weight of polylactic acid, 13 parts by weight of polyamide, 4.5 parts by weight of sorbitol, 6 parts by weight of diethylene glycol ether, 1 part by weight of glyceryl monothioglycolate and 1 part by weight of glyceryl triisooctanoate are put into a high-speed mixer, stirred at 185 ℃ at the rotation speed of 800rpm for 20min, and then put into a twin-screw extruder at the temperature of 180 ℃ and the screw rotation speed of 130rpm for extrusion granulation, thereby obtaining the thermoplastic starch resin.
The preparation method of the modified starch comprises the following steps: putting the mixed starch into a steam explosion machine, and maintaining the pressure for 100s at the pressure of 3.5 MPa; mixing with oxalic acid water solution at 70 deg.C and concentration of 1mol/L at bath ratio of 1kg:3.5L, and oscillating for 20 min; and then centrifugally dewatering at 12000rpm for 5min, and drying under reduced pressure at 65 ℃ and 50kPa for 5h to obtain the modified starch. The oscillation process parameters are as follows: the amplitude of the convolution was 3mm and the oscillation speed was 700 rpm. The mixed starch is a mixture of corn starch, cassava starch and maltodextrin in a mass ratio of 7:3: 1.
Example 7
The preparation method of the thermoplastic starch resin comprises the following steps: 26 parts by weight of modified starch, 15 parts by weight of polylactic acid, 13 parts by weight of protein polyamide, 4.5 parts by weight of sorbitol, 6 parts by weight of diethylene glycol ether, 1 part by weight of glycerol monothioglycolate and 1 part by weight of glycerol triisooctanoate are put into a high-speed mixer, stirred at 185 ℃ for 20min at the rotation speed of 800rpm, and then put into a twin-screw extruder with the temperature of 180 ℃ and the screw rotation speed of 130rpm for extrusion granulation, so as to obtain the thermoplastic starch resin.
The preparation method of the modified starch comprises the following steps: putting the mixed starch into a steam explosion machine, and maintaining the pressure for 100s at the pressure of 3.5 MPa; mixing with oxalic acid water solution at 70 deg.C and concentration of 1mol/L at bath ratio of 1kg:3.5L, and oscillating for 20 min; and then centrifugally dewatering at 12000rpm for 5min, and drying under reduced pressure at 65 ℃ and 50kPa for 5h to obtain the modified starch. The oscillation process parameters are as follows: the amplitude of the convolution was 3mm and the oscillation speed was 700 rpm. The mixed starch is a mixture of corn starch, cassava starch and maltodextrin in a mass ratio of 7:3: 1.
The preparation method of the protein polyamide comprises the following steps:
mixing the compound protein, the polyamide and the tetrahydrofuran at a mass ratio of 4.5:9.2:100 at 25 ℃, heating to 45 ℃, oscillating at an oscillation speed of 600rpm and a convolution amplitude of 3mm for 30min, then cooling to 5 ℃, standing for 20h at the temperature, filtering to obtain a precipitate I, drying the precipitate I for 80min by using carbon dioxide hot air at a temperature of 45 ℃ and an air flow rate of 120mL/s to obtain the protein polyamide. The compound protein is a mixture of hydrolyzed keratin, soybean protein and zein in a mass ratio of 3:7: 12.
Example 8
The preparation method of the thermoplastic starch resin comprises the following steps: 26 parts by weight of modified starch, 15 parts by weight of polylactic acid, 13 parts by weight of protein polyamide, 4.5 parts by weight of sorbitol, 6 parts by weight of diethylene glycol ether, 1 part by weight of glycerol monothioglycolate and 1 part by weight of glycerol triisooctanoate are put into a high-speed mixer, stirred at 185 ℃ for 20min at the rotation speed of 800rpm, and then put into a twin-screw extruder with the temperature of 180 ℃ and the screw rotation speed of 130rpm for extrusion granulation, so as to obtain the thermoplastic starch resin.
The preparation method of the modified starch comprises the following steps: putting the mixed starch into a steam explosion machine, and maintaining the pressure for 100s at the pressure of 3.5 MPa; mixing with oxalic acid water solution at 70 deg.C and concentration of 1mol/L at bath ratio of 1kg:3.5L, and oscillating for 20 min; and then centrifugally dewatering at 12000rpm for 5min, and drying under reduced pressure at 65 ℃ and 50kPa for 5h to obtain the modified starch. The oscillation process parameters are as follows: the amplitude of the convolution was 3mm and the oscillation speed was 700 rpm. The mixed starch is a mixture of corn starch, cassava starch and maltodextrin in a mass ratio of 7:3: 1.
The preparation method of the protein polyamide comprises the following steps:
mixing the compound protein, the modified polyamide and the tetrahydrofuran at a mass ratio of 4.5:9.2:100 at 25 ℃, heating to 45 ℃, oscillating at an oscillation speed of 600rpm and a convolution amplitude of 3mm for 30min, then cooling to 5 ℃, standing for 20h at the temperature, filtering to obtain a precipitate I, drying the precipitate I for 80min by using carbon dioxide hot air at a temperature of 45 ℃ and an air flow rate of 120mL/s to obtain the protein polyamide. The compound protein is a mixture of hydrolyzed keratin and zein in a mass ratio of 3: 12.
The preparation method of the modified polyamide comprises the following steps:
z1 at 25 deg.C, dissolving denaturant in a mixed solvent at a bath ratio of 1g:9mL, and homogenizing at 8000rpm for 2min to obtain denaturant solution; the denaturant is a mixture of 2-amino-5-guanidino valeric acid and L-2-amino-3-methyl valeric acid in a mass ratio of 1: 1; the compound solvent is a mixture of ethyl acetate, tetrahydrofuran and water in a mass ratio of 1:1: 1;
z2 mixing the polyamide and the denatured liquid at a bath ratio of 1g:7mL, stirring at a rotation speed of 260rpm for 15min, filtering to obtain a precipitate A, and drying the precipitate A for 80min by using carbon dioxide hot air with the temperature of 45 ℃ and the air flow rate of 120mL/s to obtain an intermediate product A;
z3 mixing the intermediate product A with 1, 2-cyclohexanediamine tetraacetic acid and polyacrylonitrile according to the mass ratio of 12:2:3, and then putting the mixture into a double-screw extruder with the temperature of 120 ℃ and the screw rotation speed of 150rpm for extrusion and granulation to obtain the modified polyamide.
Example 9
The preparation method of the thermoplastic starch resin comprises the following steps: 26 parts by weight of mixed starch, 15 parts by weight of polylactic acid, 13 parts by weight of protein polyamide, 4.5 parts by weight of sorbitol, 6 parts by weight of diethylene glycol ether, 1 part by weight of glycerol monothioglycolate and 1 part by weight of glycerol triisooctanoate are put into a high-speed mixer, stirred at 185 ℃ for 20min at 800rpm, and then put into a twin-screw extruder with the temperature of 180 ℃ and the screw rotation speed of 130rpm for extrusion granulation, thereby obtaining the thermoplastic starch resin.
The mixed starch is a mixture of corn starch, cassava starch and maltodextrin in a mass ratio of 7:3: 1.
The preparation method of the protein polyamide comprises the following steps:
mixing the compound protein, the modified polyamide and the tetrahydrofuran at a mass ratio of 4.5:9.2:100 at 25 ℃, heating to 45 ℃, oscillating at an oscillation speed of 600rpm and a convolution amplitude of 3mm for 30min, then cooling to 5 ℃, standing for 20h at the temperature, filtering to obtain a precipitate I, drying the precipitate I for 80min by using carbon dioxide hot air at a temperature of 45 ℃ and an air flow rate of 120mL/s to obtain the protein polyamide. The compound protein is a mixture of hydrolyzed keratin, soybean protein and zein in a mass ratio of 3:7: 12.
The preparation method of the modified polyamide comprises the following steps:
z1 at 25 deg.C, dissolving denaturant in a mixed solvent at a bath ratio of 1g:9mL, and homogenizing at 8000rpm for 2min to obtain denaturant solution; the denaturant is a mixture of 2-amino-5-guanidino valeric acid and L-2-amino-3-methyl valeric acid in a mass ratio of 1: 1; the compound solvent is a mixture of ethyl acetate, tetrahydrofuran and water in a mass ratio of 1:1: 1;
z2 mixing the polyamide and the denatured liquid at a bath ratio of 1g:7mL, stirring at a rotation speed of 260rpm for 15min, filtering to obtain a precipitate A, and drying the precipitate A for 80min by using carbon dioxide hot air with the temperature of 45 ℃ and the air flow rate of 120mL/s to obtain an intermediate product A;
z3 mixing the intermediate product A with 1, 2-cyclohexanediamine tetraacetic acid and polyacrylonitrile according to the mass ratio of 12:2:3, and then putting the mixture into a double-screw extruder with the temperature of 120 ℃ and the screw rotation speed of 150rpm for extrusion and granulation to obtain the modified polyamide.
Example 10
The preparation method of the thermoplastic starch resin comprises the following steps: 26 parts by weight of modified starch, 15 parts by weight of polylactic acid, 13 parts by weight of protein polyamide, 4.5 parts by weight of sorbitol, 6 parts by weight of diethylene glycol ether, 1 part by weight of glycerol monothioglycolate and 1 part by weight of glycerol triisooctanoate are put into a high-speed mixer, stirred at 185 ℃ for 20min at the rotation speed of 800rpm, and then put into a twin-screw extruder with the temperature of 180 ℃ and the screw rotation speed of 130rpm for extrusion granulation, so as to obtain the thermoplastic starch resin.
The preparation method of the modified starch comprises the following steps: mixing the mixed starch with oxalic acid water solution with temperature of 70 deg.C and concentration of 1mol/L at bath ratio of 1kg:3.5L, and oscillating for 20 min; and then centrifugally dewatering at 12000rpm for 5min, and drying under reduced pressure at 65 ℃ and 50kPa for 5h to obtain the modified starch. The oscillation process parameters are as follows: the amplitude of the convolution was 3mm and the oscillation speed was 700 rpm. The mixed starch is a mixture of corn starch, cassava starch and maltodextrin in a mass ratio of 7:3: 1.
The preparation method of the protein polyamide comprises the following steps:
mixing the compound protein, the modified polyamide and the tetrahydrofuran at a mass ratio of 4.5:9.2:100 at 25 ℃, heating to 45 ℃, oscillating at an oscillation speed of 600rpm and a convolution amplitude of 3mm for 30min, then cooling to 5 ℃, standing for 20h at the temperature, filtering to obtain a precipitate I, drying the precipitate I for 80min by using carbon dioxide hot air at a temperature of 45 ℃ and an air flow rate of 120mL/s to obtain the protein polyamide. The compound protein is a mixture of hydrolyzed keratin, soybean protein and zein in a mass ratio of 3:7: 12.
The preparation method of the modified polyamide comprises the following steps:
z1 at 25 deg.C, dissolving denaturant in a mixed solvent at a bath ratio of 1g:9mL, and homogenizing at 8000rpm for 2min to obtain denaturant solution; the denaturant is a mixture of 2-amino-5-guanidino valeric acid and L-2-amino-3-methyl valeric acid in a mass ratio of 1: 1; the compound solvent is a mixture of ethyl acetate, tetrahydrofuran and water in a mass ratio of 1:1: 1;
z2 mixing the polyamide and the denatured liquid at a bath ratio of 1g:7mL, stirring at a rotation speed of 260rpm for 15min, filtering to obtain a precipitate A, and drying the precipitate A for 80min by using carbon dioxide hot air with the temperature of 45 ℃ and the air flow rate of 120mL/s to obtain an intermediate product A;
z3 mixing the intermediate product A with 1, 2-cyclohexanediamine tetraacetic acid and polyacrylonitrile according to the mass ratio of 12:2:3, and then putting the mixture into a double-screw extruder with the temperature of 120 ℃ and the screw rotation speed of 150rpm for extrusion and granulation to obtain the modified polyamide.
Example 11
The preparation method of the thermoplastic starch resin comprises the following steps: the thermoplastic starch resin is obtained by putting 26 parts by weight of modified starch, 15 parts by weight of polylactic acid, 13 parts by weight of protein polyamide, 4.5 parts by weight of sorbitol, 6 parts by weight of diethylene glycol ether and 2 parts by weight of tri-isooctanoic acid glyceride into a high-speed mixer, stirring at 185 ℃ at 800rpm for 20min, and then putting into a double-screw extruder with the temperature of 180 ℃ and the screw rotation speed of 130rpm for extrusion granulation.
The preparation method of the modified starch comprises the following steps: putting the mixed starch into a steam explosion machine, and maintaining the pressure for 100s at the pressure of 3.5 MPa; mixing with oxalic acid water solution at 70 deg.C and concentration of 1mol/L at bath ratio of 1kg:3.5L, and oscillating for 20 min; and then centrifugally dewatering at 12000rpm for 5min, and drying under reduced pressure at 65 ℃ and 50kPa for 5h to obtain the modified starch. The oscillation process parameters are as follows: the amplitude of the convolution was 3mm and the oscillation speed was 700 rpm. The mixed starch is a mixture of corn starch, cassava starch and maltodextrin in a mass ratio of 7:3: 1.
The preparation method of the protein polyamide comprises the following steps:
mixing the compound protein, the modified polyamide and the tetrahydrofuran at a mass ratio of 4.5:9.2:100 at 25 ℃, heating to 45 ℃, oscillating at an oscillation speed of 600rpm and a convolution amplitude of 3mm for 30min, then cooling to 5 ℃, standing for 20h at the temperature, filtering to obtain a precipitate I, drying the precipitate I for 80min by using carbon dioxide hot air at a temperature of 45 ℃ and an air flow rate of 120mL/s to obtain the protein polyamide. The compound protein is a mixture of hydrolyzed keratin, soybean protein and zein in a mass ratio of 3:7: 12.
The preparation method of the modified polyamide comprises the following steps:
z1 at 25 deg.C, dissolving denaturant in a mixed solvent at a bath ratio of 1g:9mL, and homogenizing at 8000rpm for 2min to obtain denaturant solution; the denaturant is a mixture of 2-amino-5-guanidino valeric acid and L-2-amino-3-methyl valeric acid in a mass ratio of 1: 1; the compound solvent is a mixture of ethyl acetate, tetrahydrofuran and water in a mass ratio of 1:1: 1;
z2 mixing the polyamide and the denatured liquid at a bath ratio of 1g:7mL, stirring at a rotation speed of 260rpm for 15min, filtering to obtain a precipitate A, and drying the precipitate A for 80min by using carbon dioxide hot air with the temperature of 45 ℃ and the air flow rate of 120mL/s to obtain an intermediate product A;
z3 mixing the intermediate product A with 1, 2-cyclohexanediamine tetraacetic acid and polyacrylonitrile according to the mass ratio of 12:2:3, and then putting the mixture into a double-screw extruder with the temperature of 120 ℃ and the screw rotation speed of 150rpm for extrusion and granulation to obtain the modified polyamide.
Example 12
The preparation method of the thermoplastic starch resin comprises the following steps: and (2) putting 26 parts by weight of modified starch, 15 parts by weight of polylactic acid, 13 parts by weight of protein polyamide, 4.5 parts by weight of sorbitol, 6 parts by weight of diethylene glycol ether and 2 parts by weight of glycerol monothioglycolate into a high-speed mixer, stirring at 185 ℃ at the rotating speed of 800rpm for 20min, and then putting into a double-screw extruder with the temperature of 180 ℃ and the screw rotating speed of 130rpm for extrusion granulation to obtain the thermoplastic starch resin.
The preparation method of the modified starch comprises the following steps: putting the mixed starch into a steam explosion machine, and maintaining the pressure for 100s at the pressure of 3.5 MPa; mixing with oxalic acid water solution at 70 deg.C and concentration of 1mol/L at bath ratio of 1kg:3.5L, and oscillating for 20 min; and then centrifugally dewatering at 12000rpm for 5min, and drying under reduced pressure at 65 ℃ and 50kPa for 5h to obtain the modified starch. The oscillation process parameters are as follows: the amplitude of the convolution was 3mm and the oscillation speed was 700 rpm. The mixed starch is a mixture of corn starch, cassava starch and maltodextrin in a mass ratio of 7:3: 1.
The preparation method of the protein polyamide comprises the following steps:
mixing the compound protein, the modified polyamide and the tetrahydrofuran at a mass ratio of 4.5:9.2:100 at 25 ℃, heating to 45 ℃, oscillating at an oscillation speed of 600rpm and a convolution amplitude of 3mm for 30min, then cooling to 5 ℃, standing for 20h at the temperature, filtering to obtain a precipitate I, drying the precipitate I for 80min by using carbon dioxide hot air at a temperature of 45 ℃ and an air flow rate of 120mL/s to obtain the protein polyamide. The compound protein is a mixture of hydrolyzed keratin, soybean protein and zein in a mass ratio of 3:7: 12.
The preparation method of the modified polyamide comprises the following steps:
z1 at 25 deg.C, dissolving denaturant in a mixed solvent at a bath ratio of 1g:9mL, and homogenizing at 8000rpm for 2min to obtain denaturant solution; the denaturant is a mixture of 2-amino-5-guanidino valeric acid and L-2-amino-3-methyl valeric acid in a mass ratio of 1: 1; the compound solvent is a mixture of ethyl acetate, tetrahydrofuran and water in a mass ratio of 1:1: 1;
z2 mixing the polyamide and the denatured liquid at a bath ratio of 1g:7mL, stirring at a rotation speed of 260rpm for 15min, filtering to obtain a precipitate A, and drying the precipitate A for 80min by using carbon dioxide hot air with the temperature of 45 ℃ and the air flow rate of 120mL/s to obtain an intermediate product A;
z3 mixing the intermediate product A with 1, 2-cyclohexanediamine tetraacetic acid and polyacrylonitrile according to the mass ratio of 12:2:3, and then putting the mixture into a double-screw extruder with the temperature of 120 ℃ and the screw rotation speed of 150rpm for extrusion and granulation to obtain the modified polyamide.
Test example 1
And (3) testing the disintegration of the compost: the degree of disintegration under defined composting pilot conditions of the thermoplastic starch resins obtained from the examples of the invention was determined in accordance with GB/T19811-2005-determination of the degree of disintegration of plastic materials under defined composting pilot conditions.
The method comprises the following steps of (1) adopting a mixture of fresh fruit and vegetable mixed waste and wood chips in a mass ratio of 2:1 as test biomass waste; the particle size of the wood chips was 25 mm. The carbon-nitrogen ratio (C: N) of the fresh mixture of biomass waste/filler was 25.
The test results are shown in table 1.
TABLE 1 degree of disintegration of thermoplastic starch resins
The modified protein polyamide prepared by the specific method of the invention uses the modified polyamide which is grafted with the groups of 2-amino-5-guanidino valeric acid and L-2-amino-3-methyl valeric acid, so that the energy state of the branched chain of the protein polyamide is converted into an energy state which is more sensitive to visible light, the modified protein polyamide is easy to absorb photons of visible light and further transits to an excited state, and the disintegration performance of the material in a high energy state is enhanced.
Test example 2
And (3) testing the impact resistance: according to GB/T9639.1-2008 "test method for impact resistance of Plastic films and sheets part 1 of the free Dart method: method A of the Cascade method "measures the impact resistance of the thermoplastic starch resins obtained from the examples of the present invention.
The thermoplastic starch resins obtained in the examples of the present invention were extruded and stretched in a conventional manner to give film-like specimens having a thickness of 0.8 mm. A weight of 30mm diameter was used. A rubber gasket with the thickness of 3mm, the Shore hardness A of 55, the inner diameter of 125mm and the outer diameter of 150mm is adopted. The falling height of the dart was 0.66 m. The head of the dart is provided with a round handle with the diameter of 6.5mm and the length of 120 mm; the dart head has a diameter of 38mm and is made of polished aluminum. Prior to the test, the sample was conditioned for 50 hours at a temperature of 23 ℃ and a relative humidity of 50%.
The test results are shown in table 2.
TABLE 2 impact Damage quality of thermoplastic starch resins
Tetrahydrofuran is used as a solvent, the compound protein and the denatured polyamide are dissolved, the contact probability of reactants is increased by an oscillation means so as to increase the reaction rate, and then carbon dioxide is used as a medium for hot air drying to dry the reaction product, so that the protein polyamide is obtained. The peptide main chain of the zein has hydrogen bond action of hydroxyl and imino to form alpha-spirochete, and the zein has lower surface energy and unique film forming property. The hydrolyzed keratin contains more cystine, so the disulfide bond content is higher, the hydrolyzed keratin can play a strong crosslinking role in a protein peptide chain by being compounded with the soybean protein and the zein, the chemical stability of the protein polyamide is enhanced, the protein polyamide is resistant to acid corrosion, light aging and the like, and the thermoplastic starch resin has higher mechanical strength and is shown to be impact resistant, bending resistant and the like, so the service life of a food package prepared from the starch resin is prolonged. The amino groups of both 2-amino-5-guanidinopentanoic acid and L-2-amino-3-methylpentanoic acid are located at specific positions so that they have specific charge attraction to each other, which makes it possible to obtain a denatured polyamide which is more reactive with the built protein after incorporation into the polyamide molecule. Polyacrylonitrile has good weather resistance and sunlight resistance, and the service reliability and the service life of the modified polyamide can be enhanced by using the polyacrylonitrile for preparing the modified polyamide. The nitrogen atoms forming carbon-nitrogen bonds in polyacrylonitrile and the oxygen atoms in the carboxyl groups positioned at specific sites in the 1, 2-cyclohexanediaminetetraacetic acid can be in hydrogen bond connection with each other, so that the structural stability of the modified polyamide molecules can be enhanced, and the mechanical strength of the thermoplastic starch resin doped with the modified polyamide molecules can be improved macroscopically. The sulfur element in the glycerol monothioglycolate can form hydrogen bonds with sulfur atoms in the protein polyamide, so that the bonding strength between the protein polyamide and the polylactic acid and the modified starch is enhanced, and the mechanical strength of the thermoplastic starch resin is improved. The three ester bonds in the triisocaprylic glyceride and the medium-long carbon chain structure with the branched chain can enhance the compatibility between the protein polyamide and the modified starch and the polylactic acid, thereby improving the weather resistance, the mechanical strength and the service life of the thermoplastic starch resin.
The phenomenon of agglomeration and enrichment easily occurs among raw materials due to the difference of molecular polarity of the common starch directly added into the polylactic acid-protein polyamide system, so that internal stress is generated, and the material has cracking damage tendency in the long-term transportation, storage and use processes. In the technical scheme of the invention, the steam molecules permeating into the mixed starch are instantaneously released by utilizing a steam explosion means, so that the internal energy of the steam is converted into mechanical energy and acts between the molecules of the mixed starch, and the aim of decomposing the mixed starch, including acid-like hydrolysis, hydrogen bond destruction and structural rearrangement, is fulfilled by using less energy; in addition, the problem of secondary pollution possibly caused by chemical treatment is avoided, and the high-efficiency pretreatment sufficiency is obtained. The internal hydrogen bonds, amorphous areas and partial crystalline areas of the mixed starch subjected to steam explosion treatment are destroyed, and at the moment, the mobility of molecular chains in the mixed starch is enhanced under the reduction action of oxalic acid, so that starch molecules are changed to an ordered structure in a kinetic angle, good adhesive performance is brought to the mixed starch, and the polylactic acid and the protein polyamide connected with the mixed starch have stronger adhesive strength and high elastic modulus. The corn starch, the cassava starch and the maltodextrin can be mixed with high molecular materials including polylactic acid to achieve the purpose of improving the biodegradability of the materials, and can also obviously enhance the mechanical strength of the matrix materials including impact resistance, bending resistance and the like, thereby reducing the production cost of the environment-friendly degradable materials to the minimum.
The direct use of polyamide in the resin formulation may provide a degree of mechanical strength enhancement, but not as effective as the protein polyamide obtained by the particular process of the present invention. The molecular structure of the protein polyamide is in a spatial, three-dimensional, compact and dense arrangement, so that the protein polyamide has higher elastic modulus, and the elastic modulus of the whole resin can be improved by dispersing the protein polyamide in the resin formula, so that the mechanical strength of the material is improved.
In the preparation of protein polyamide, if polyamide is directly adopted, the problem that the reaction efficiency between polyamide and the compound protein is too low exists, and the compatibility between the common polyamide and the resin formula is low due to the molecular configuration of the common polyamide, which is characterized in that the mechanical strength of the material is low. And the amino groups of the 2-amino-5-guanidino valeric acid and the L-2-amino-3-methyl valeric acid are positioned at specific positions, so that the amino groups have specific charge attraction force among the amino groups, the molecular configuration of the polyamide is influenced to a certain extent, the modified polyamide which is easier to react with the compound protein can be obtained after the modified polyamide is inserted into the polyamide molecule, and meanwhile, the compatibility between the protein polyamide and the resin formula is enhanced, and the mechanical strength of the material is enhanced.
Claims (3)
1. A method for preparing thermoplastic starch resin is characterized by comprising the following steps: putting 24-27 parts by weight of modified starch, 13-17 parts by weight of polylactic acid, 12-15 parts by weight of protein polyamide, 3-4.5 parts by weight of sorbitol, 5-6.5 parts by weight of diethylene glycol ether, 0.7-1.2 parts by weight of glycerol monothioglycolate and 0.5-1.2 parts by weight of triisocaprylic glyceride into a high-speed mixer, stirring, and then putting into a double-screw extruder for extrusion and granulation to obtain the thermoplastic starch resin;
the preparation method of the modified starch comprises the following steps: putting the mixed starch into a steam explosion machine, and keeping the pressure at 3.3-3.5MPa for 100-115 seconds; mixing with oxalic acid aqueous solution with the temperature of 65-70 ℃ and the concentration of 0.5-1.2mol/L at the bath ratio of 1kg (3.2-4) L, and oscillating for 15-20min, wherein the oscillation speed is 600-700rpm, and the convolution amplitude is 2-3 mm; then centrifugally dewatering and drying under reduced pressure to obtain the modified starch; the mixed starch is a mixture of corn starch, cassava starch and maltodextrin;
the preparation method of the protein polyamide comprises the following steps:
mixing the compound protein, the modified polyamide and the tetrahydrofuran in a mass ratio of (4-6) to (8-11) to (90-120) at 20-30 ℃, heating to 43-45 ℃, oscillating for 25-40min, wherein the oscillating speed is 400-600rpm, the convolution amplitude is 2-3mm, then cooling to 3-5 ℃, standing for 18-25h, filtering to obtain a precipitate I, and drying the precipitate I by hot air to obtain the protein polyamide; the compound protein is a mixture of hydrolyzed keratin, soybean protein and zein;
the preparation method of the modified polyamide comprises the following steps:
z1 at 20-30 ℃, dissolving the denaturant in the compound solvent according to the bath ratio of 1g (9-11) mL, and homogenizing at 7000-8000rpm for 1-3min to obtain denaturant liquid;
z2 mixing polyamide and the denaturation liquid at a bath ratio of 1g (7-9) mL, stirring at the rotating speed of 200-260rpm for 15-20min, filtering to obtain a precipitate A, and drying the precipitate A by using carbon dioxide hot air to obtain an intermediate product A;
z3, mixing the intermediate product A with 1, 2-cyclohexanediamine tetraacetic acid and polyacrylonitrile according to the mass ratio of (10.5-13) to (1.2-2.3) to (2.5-3.3), and then putting the mixture into a double-screw extruder for extrusion and granulation to obtain the modified polyamide;
the denaturant is a mixture of 2-amino-5-guanidino valeric acid and L-2-amino-3-methyl valeric acid; the compound solvent is a mixture of ethyl acetate, tetrahydrofuran and water.
2. A thermoplastic starch resin characterized by: the method for preparing the thermoplastic starch resin according to claim 1.
3. Use of the thermoplastic starch resin according to claim 2 in food packaging materials.
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