A bamboo powder bio-based degradable material for light aging-resistant agricultural mulch film and a preparation method thereof

Abstract

The invention discloses a bamboo powder bio-based degradable material for agricultural mulch film resistant to light aging and a preparation method thereof, and relates to the technical field of agricultural mulch film. When preparing the bamboo powder bio-based degradable material for agricultural mulch film resistant to light aging, the present invention reacts polylactic acid with 6-vinyl-2-naphthol and vinyltetramethyldisilane to obtain pre-modified polylactic acid; reacts pre-modified polylactic acid and 1,1-diphenyl-2-propynyl-1-ol to obtain modified polylactic acid; oxidizes bamboo powder with sodium periodate to obtain oxidized bamboo powder; polymerizes and grows 4,4'-diaminodiphenylamine and allyl phosphoric acid on oxidized bamboo powder to obtain modified bamboo powder; and extrudes the modified polylactic acid and modified bamboo powder after mixing to obtain the bamboo powder bio-based degradable material for agricultural mulch film resistant to light aging. The bamboo powder bio-based degradable material for agricultural mulch film resistant to light aging prepared by the present invention has excellent flame retardant, anti-aging and mechanical properties.

Description

Technical Field

[0001] The invention relates to the technical field of agricultural mulch films, and in particular to a bamboo powder bio-based degradable material for light aging resistant agricultural mulch films and a preparation method thereof. Background Art

[0002] Traditional agricultural films are petrochemical products, such as polyethylene and polyvinyl chloride, which have stable molecular structures and are not easily decomposed by light and microorganisms under natural conditions. Fragments of plastic mulch remain in the soil. If they accumulate over the years, they will cause certain damage to the soil structure and affect the absorption of water and nutrients by crops from the soil to a certain extent, which is not conducive to the activity of soil microorganisms. In addition, traditional agricultural films contain harmful residues such as phthalates and biphenols, which will pollute agricultural products and seriously endanger human health.

[0003] At present, the main methods to solve the pollution of plastic mulch in the world are to recycle the plastic mulch remaining in the soil, carry out centralized treatment, and develop biodegradable mulch. However, due to the influence of natural aging and wind and rain erosion, the mulch breaks down into fragments of different sizes, so it is very difficult and time-consuming to collect the residual film. Biodegradable mulch can be decomposed by microorganisms in farmland soil, effectively solving the problem of residual film pollution. Therefore, eco-friendly biodegradable mulch has emerged in the agricultural market and has become the development trend of agricultural mulch.

[0004] Bamboo powder is a natural material obtained by drying and crushing bamboo. Its main component is plant fiber. It has the advantages of light weight, large specific surface area, high strength and biodegradability. Using bamboo powder as a raw material and degradable polylactic acid to prepare BBM bamboo powder biodegradable materials can reduce the use of traditional petrochemical products; however, the BBM bamboo powder biodegradable materials prepared by the prior art have problems such as low mechanical properties and easy aging, which seriously limits the application of BBM bamboo powder biodegradable materials in agricultural mulch films. Summary of the invention

[0005] The object of the present invention is to provide a bamboo powder bio-based degradable material for agricultural mulch film with light aging resistance and a preparation method thereof, so as to solve the problems existing in the prior art.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: a light-resistant bamboo powder bio-based degradable material for agricultural mulch film, wherein the light-resistant bamboo powder bio-based degradable material for agricultural mulch film is prepared by reacting pre-modified polylactic acid and 1,1-diphenyl-2-propyn-1-ol to obtain modified polylactic acid; 4,4'-diaminodiphenylamine and allyl phosphoric acid are polymerized and grown on oxidized bamboo powder to obtain modified bamboo powder; the modified polylactic acid and the modified bamboo powder are mixed and extruded to obtain the light-resistant bamboo powder bio-based degradable material for agricultural mulch film; the pre-modified polylactic acid is obtained by reacting polylactic acid with 6-vinyl-2-naphthol and vinyltetramethyldisilane; the oxidized bamboo powder is obtained by oxidizing bamboo powder with sodium periodate.

[0007] A method for preparing a bamboo powder bio-based degradable material for a light-resistant agricultural mulch film, the method comprising the following preparation steps:

[0008] (1) Pre-modified polylactic acid, p-toluenesulfonic acid and dichloromethane were mixed evenly, stirred at 10-30°C and 300-500 r / min for 8-10 min, and under nitrogen protection, 1,1-diphenyl-2-propyn-1-ol (0.5-0.6 times the mass of pre-modified polylactic acid) was added dropwise at a uniform rate within 15 min, and the reaction was continued by stirring for 20-24 h. Under vacuum conditions, the mixture was dried at 50-60°C for 8-10 h to obtain modified polylactic acid;

[0009] (2) Mix oxidized bamboo powder, 4,4'-diaminodiphenylamine, dicyclohexylcarbodiimide and N,N-dimethylformamide evenly, add allyl phosphoric acid (1 times the molar amount of 4,4'-diaminodiphenylamine) dropwise at a constant speed within 5 minutes at 30-40°C and 300-500 r / min stirring conditions, raise the temperature to 70-80°C, continue stirring and reacting for 4-6 hours, filter, wash with anhydrous ethanol and deionized water for 3-5 times each, and dry at 50-60°C under vacuum conditions for 12-14 hours to obtain modified bamboo powder;

[0010] (3) The modified polylactic acid and the modified bamboo powder are mixed and placed in a hot melt machine. The mixture is stirred at 180-190°C and 300-500 r / min for 10-20 min. 0.001-0.003 of platinum (0)-1,3-diethene-1,1,3,3-tetramethyldisiloxane by weight of the modified polylactic acid is added. The mixture is stirred for 2-3 min. The mixture is then sent to a twin-screw extruder for extrusion molding. The extrusion temperature of the twin-screw extruder is set at 180-200°C, the extrusion pressure is set at 16-20 MPa, and the screw speed is set at 100-120 r / min. Thus, a bamboo powder biodegradable material for light-resistant agricultural mulch film is obtained.

[0011] As an optimization, the preparation method of the pre-modified polylactic acid in step (1) is as follows: polylactic acid, 6-vinyl-2-naphthol and vinyltetramethyldisilane are mixed in a mass ratio of 1: (0.2-0.3): (0.1-0.2), placed in an internal mixer, stirred at 175-185° C. and 400-600 r / min for 8-10 min, 0.03-0.05 times the mass of polylactic acid of diisopropyl peroxide is added, and the stirring reaction is continued for 20-30 min to obtain the pre-modified polylactic acid;

[0012] The reaction process is:

[0013] .

[0014] As an optimization, the molecular weight of the polylactic acid is 40,000 to 50,000.

[0015] As an optimization, the reaction process of the modified polylactic acid in step (1) is:

[0016] .

[0017] As an optimization, a naphthol pyran structure is generated during the reaction of the modified polylactic acid; the pyran ring in the naphthol pyran structure will break and open under the action of ultraviolet light, and the pyran ring will be regenerated after the ultraviolet light is removed. Through the reversible ring opening and closing reaction, the ultraviolet light energy is converted into heat energy and released. The mechanism is as follows:

[0018] .

[0019] As an optimization, the mass ratio of the pre-modified polylactic acid, p-toluenesulfonic acid and dichloromethane in step (1) is 1: (0.01-0.03): (10-12).

[0020] As an optimization, the mass ratio of the oxidized bamboo powder, 4,4'-diaminodiphenylamine, dicyclohexylcarbodiimide, and N,N-dimethylformamide in step (2) is 1: (0.4-0.6): (0.01-0.03): (10-12).

[0021] As an optimization, the preparation method of the oxidized bamboo powder in step (2) is as follows: in a light-proof condition, bamboo powder, sodium periodate and deionized water are uniformly mixed in a mass ratio of 1: (0.2-0.3): (8-10), stirred at 10-30°C and 300-500 r / min for 2-3 hours, ethylene glycol in an amount of 2-3 times the mass of sodium periodate is added, stirring is continued for 20-30 minutes, filtered, washed with anhydrous ethanol and deionized water for 3-5 times respectively, and dried at 50-60°C under vacuum conditions for 8-10 hours to obtain oxidized bamboo powder.

[0022] As an optimization, the particle size of the bamboo powder is 200 meshes.

[0023] As an optimization, the mass ratio of the modified polylactic acid to the modified bamboo powder in step (3) is 1:(0.1~0.14).

[0024] As an optimization, the process parameters of the extrusion molding in step (3) are: setting the extrusion temperature of the twin-screw extruder to 180-200°C, the extrusion pressure to 16-20 MPa, and the screw speed to 100-120 r / min.

[0025] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: when preparing the bamboo powder bio-based degradable material for agricultural mulch film resistant to light aging, the present invention reacts polylactic acid with 6-vinyl-2-naphthol and vinyltetramethyldisilane to obtain pre-modified polylactic acid; reacts the pre-modified polylactic acid and 1,1-diphenyl-2-propyn-1-ol to obtain modified polylactic acid; oxidizes bamboo powder with sodium periodate to obtain oxidized bamboo powder; polymerizes and grows 4,4'-diaminodiphenylamine and allyl phosphoric acid on the oxidized bamboo powder to obtain modified bamboo powder; and mixes the modified polylactic acid and the modified bamboo powder and extrude them to obtain the bamboo powder bio-based degradable material for agricultural mulch film resistant to light aging.

[0026] Firstly, polylactic acid is reacted with 6-vinyl-2-naphthol and vinyltetramethyldisilane to obtain pre-modified polylactic acid. The hydrogen atoms on the tertiary carbon on the polylactic acid molecular chain have certain activity. Under the action of the initiator, the hydrogen atoms on the tertiary carbon can be captured by free radical reaction, and the naphthol structure, Si-O bond and Si-H bond are introduced into the side chain of the polylactic acid molecule. The bond energy of the Si-O bond is greater than that of the CC bond, so compared with the CC bond, the Si-O bond needs to absorb more heat and its own vibration energy to resolve the energy of thermal decomposition of the polymer material, thereby giving the light-resistant agricultural mulch bamboo powder bio-based degradable material excellent flame retardant properties. The Si-H bond can A cross-linked network is formed by a hydrosilylation reaction with the carbon-carbon double bonds introduced on the modified bamboo powder, which inhibits the relative slip between the molecular chains and gives the bamboo powder bio-based degradable material for light-resistant agricultural mulch film excellent mechanical properties; the naphthol structure introduced on the pre-modified polylactic acid is reacted with 1,1-diphenyl-2-propyn-1-ol to obtain the modified polylactic acid; a naphthol pyran structure is generated on the side chain of the modified polylactic acid molecule, and the pyran ring in the naphthol pyran structure will break and open under the action of ultraviolet light. When the ultraviolet light is removed, the pyran ring will be regenerated to absorb the ultraviolet light energy, thereby giving the bamboo powder bio-based degradable material for light-resistant agricultural mulch film excellent anti-ultraviolet aging properties.

[0027] Secondly, part of the hydroxyl groups in the bamboo powder were oxidized with sodium periodate to obtain oxidized bamboo powder, and aldehyde groups were introduced into the bamboo powder; 4,4'-diaminodiphenylamine and allyl phosphoric acid were polymerized and grown on the oxidized bamboo powder to obtain modified bamboo powder; phosphorus element, carbon-carbon double bond and diaryl secondary amine structure were introduced into the modified bamboo powder; the introduction of phosphorus element can further improve the flame retardant properties of the bamboo powder bio-based degradable material for light-resistant agricultural mulch film; the carbon-carbon double bond introduced into the modified bamboo powder can undergo a silylation reaction with the Si-H bond introduced into the modified polylactic acid to form a cross-linked network, inhibit the relative slip between the molecular chains, and endow the bamboo powder bio-based degradable material for light-resistant agricultural mulch film with excellent mechanical properties; the introduction of diaryl secondary amine structure can capture the free radicals generated by the material during the thermal oxidative aging process, inhibit the generation and transfer of free radicals, and endow the bamboo powder bio-based degradable material for light-resistant agricultural mulch film with excellent anti-thermal oxidative aging properties. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] Example 1

[0030] A method for preparing a bamboo powder bio-based degradable material for a light-resistant agricultural mulch film, the method comprising the following preparation steps:

[0031] (1) Polylactic acid, 6-vinyl-2-naphthol and vinyltetramethyldisilane were mixed in a mass ratio of 1:0.2:0.1, placed in an internal mixer, stirred at 175°C and 400 r / min for 10 min, and diisopropyl peroxide (0.03 times the mass of polylactic acid) was added, and the mixture was stirred and reacted for 30 min to obtain pre-modified polylactic acid; pre-modified polylactic acid, p-toluenesulfonic acid and dichloromethane were mixed in a mass ratio of 1:0.01:10, stirred at 10°C and 300 r / min for 10 min, and under nitrogen protection, 1,1-diphenyl-2-propyn-1-ol (0.5 times the mass of pre-modified polylactic acid) was uniformly added dropwise within 15 min, and the mixture was stirred and reacted for 24 h. The mixture was dried at 50°C for 10 h under vacuum conditions to obtain modified polylactic acid;

[0032] (2) Under light-proof conditions, bamboo powder, sodium periodate, and deionized water were mixed in a mass ratio of 1:0.2:8, stirred at 10°C and 300 r / min for 3 h, ethylene glycol twice the mass of sodium periodate was added, stirring was continued for 30 min, filtered, washed with anhydrous ethanol and deionized water three times each, and dried at 50°C for 10 h under vacuum conditions to obtain oxidized bamboo powder; oxidized bamboo powder, 4,4'-diaminodiphenylamine, dicyclohexylcarbodiimide, and N,N-dimethylformamide were mixed in a mass ratio of 1:0.4:0.01:10, allyl phosphoric acid twice the molar amount of 4,4'-diaminodiphenylamine was added dropwise at a uniform rate within 5 min under 30°C and 300 r / min stirring conditions, the temperature was raised to 70°C, stirring was continued for 6 h, filtered, washed with anhydrous ethanol and deionized water three times each, and dried at 50°C for 14 h under vacuum conditions to obtain modified bamboo powder;

[0033] (3) The modified polylactic acid and modified bamboo powder were mixed in a mass ratio of 1:0.1, placed in a hot melt machine, stirred at 180°C and 300 r / min for 20 min, 0.001 mass of platinum (0)-1,3-diethene-1,1,3,3-tetramethyldisiloxane of the modified polylactic acid was added, and stirring was continued for 3 min. The mixture was then sent to a twin-screw extruder for extrusion molding. The extrusion temperature of the twin-screw extruder was set to 180°C, the extrusion pressure was set to 16 MPa, and the screw speed was set to 100 r / min to obtain a bamboo powder biodegradable material for light-resistant agricultural mulch film.

[0034] Example 2

[0035] A method for preparing a bamboo powder bio-based degradable material for a light-resistant agricultural mulch film, the method comprising the following preparation steps:

[0036] (1) Polylactic acid, 6-vinyl-2-naphthol and vinyltetramethyldisilane were mixed in a mass ratio of 1:0.25:0.15, placed in an internal mixer, stirred at 180°C and 500 r / min for 9 minutes, and diisopropyl peroxide (0.04 times the mass of the polylactic acid) was added, and the stirring reaction was continued for 25 minutes to obtain pre-modified polylactic acid; pre-modified polylactic acid, p-toluenesulfonic acid and dichloromethane were mixed in a mass ratio of 1:0.02:11, stirred at 20°C and 400 r / min for 9 minutes, and under nitrogen protection, 1,1-diphenyl-2-propyn-1-ol (0.55 times the mass of the pre-modified polylactic acid) was uniformly added dropwise within 15 minutes, and the stirring reaction was continued for 22 hours. Under vacuum conditions, it was dried at 55°C for 9 hours to obtain modified polylactic acid;

[0037] (2) In a light-proof condition, bamboo powder, sodium periodate and deionized water were mixed in a mass ratio of 1:0.25:9, stirred at 20°C and 400 r / min for 2.5 h, ethylene glycol (2.5 times the mass of sodium periodate) was added, and stirring was continued for 25 min. The mixture was filtered, washed with anhydrous ethanol and deionized water for 4 times each, and dried at 55°C for 9 h under vacuum conditions to obtain oxidized bamboo powder. The oxidized bamboo powder, 4,4'-diaminodiphenylamine, and diphenylamine were mixed. Cyclohexylcarbodiimide and N,N-dimethylformamide were mixed uniformly in a mass ratio of 1:0.5:0.02:11, and allyl phosphoric acid with a molar amount of 1 times that of 4,4'-diaminodiphenylamine was added dropwise at a uniform speed within 5 minutes at 35°C and 400 r / min stirring conditions, and the temperature was raised to 75°C, and the stirring reaction was continued for 5 hours, and the mixture was filtered, washed with anhydrous ethanol and deionized water for 4 times respectively, and dried at 55°C for 13 hours under vacuum conditions to obtain modified bamboo powder;

[0038] (3) The modified polylactic acid and modified bamboo powder were mixed in a mass ratio of 1:0.12, placed in a hot melt machine, stirred at 185°C and 400 r / min for 15 min, 0.002 mass of platinum (0)-1,3-diethene-1,1,3,3-tetramethyldisiloxane of the modified polylactic acid was added, and stirring was continued for 2.5 min. The mixture was then sent to a twin-screw extruder for extrusion molding. The extrusion temperature of the twin-screw extruder was set to 190°C, the extrusion pressure was set to 18 MPa, and the screw speed was set to 110 r / min to obtain a bamboo powder biodegradable material for light-resistant agricultural mulch film.

[0039] Example 3

[0040] A method for preparing a bamboo powder bio-based degradable material for a light-resistant agricultural mulch film, the method comprising the following preparation steps:

[0041] (1) Polylactic acid, 6-vinyl-2-naphthol and vinyltetramethyldisilane were mixed in a mass ratio of 1:0.3:0.2, placed in an internal mixer, stirred at 185°C and 600 r / min for 8 min, and diisopropyl peroxide (0.05 times the mass of polylactic acid) was added, and the mixture was stirred and reacted for 20 min to obtain pre-modified polylactic acid; pre-modified polylactic acid, p-toluenesulfonic acid and dichloromethane were mixed in a mass ratio of 1:0.03:12, stirred at 30°C and 500 r / min for 8 min, and under nitrogen protection, 1,1-diphenyl-2-propyn-1-ol (0.6 times the mass of pre-modified polylactic acid) was added dropwise at a uniform speed within 15 min, and the mixture was stirred and reacted for 20 h. The mixture was dried at 60°C under vacuum conditions for 8 h to obtain modified polylactic acid;

[0042] (2) Under light-proof conditions, bamboo powder, sodium periodate, and deionized water were mixed in a mass ratio of 1:0.3:10, stirred at 30°C and 500 r / min for 2 h, ethylene glycol was added in an amount 3 times the mass of sodium periodate, stirring was continued for 20 min, filtered, washed with anhydrous ethanol and deionized water 5 times each, and dried at 60°C for 8 h under vacuum conditions to obtain oxidized bamboo powder; oxidized bamboo powder, 4,4'-diaminodiphenylamine, dicyclohexylcarbodiimide, and N,N-dimethylformamide were mixed in a mass ratio of 1:0.6:0.03:12, allyl phosphoric acid in an amount 1 times the molar amount of 4,4'-diaminodiphenylamine was added dropwise at a uniform rate within 5 min under 40°C and 500 r / min stirring conditions, the temperature was raised to 80°C, stirring was continued for 4 h, filtered, washed with anhydrous ethanol and deionized water 5 times each, and dried at 60°C for 12 h under vacuum conditions to obtain modified bamboo powder;

[0043] (3) The modified polylactic acid and modified bamboo powder were mixed in a mass ratio of 1:0.14, placed in a hot melt machine, stirred at 190°C and 500 r / min for 10 min, 0.003 mass of platinum (0)-1,3-diethene-1,1,3,3-tetramethyldisiloxane of the modified polylactic acid was added, and stirring was continued for 2 min. The mixture was then sent to a twin-screw extruder for extrusion molding. The extrusion temperature of the twin-screw extruder was set to 200°C, the extrusion pressure was set to 20 MPa, and the screw speed was set to 120 r / min to obtain a bamboo powder biodegradable material for light-resistant agricultural mulch film.

[0044] Comparative Example 1

[0045] The preparation method of the bamboo powder bio-based degradable material for light aging resistant agricultural mulch film of Comparative Example 1 is different from that of Example 2 in that step (1) is modified as follows: polylactic acid and vinyltetramethyldisilane are mixed in a mass ratio of 1:0.15, placed in an internal mixer, stirred at 180° C. and 500 r / min for 9 min, diisopropyl peroxide (0.04 times the mass of polylactic acid) is added, and the reaction is continued with stirring for 25 min to obtain modified polylactic acid. The remaining steps are the same as those of Example 2.

[0046] Comparative Example 2

[0047] The preparation method of the bamboo powder bio-based degradable material for light aging resistant agricultural mulch film of Comparative Example 2 is different from that of Example 2 in that step (1) is different. Step (1) is modified as follows: polylactic acid and 6-vinyl-2-naphthol are mixed in a mass ratio of 1:0.25, placed in an internal mixer, stirred at 180°C and 500 r / min for 9 min, diisopropyl peroxide (0.04 times the mass of the polylactic acid) is added, and the stirring reaction is continued for 25 min to obtain pre-modified polylactic acid; pre-modified polylactic acid, p-toluenesulfonic acid, and dichloromethane are mixed in a mass ratio of 1:0.02:11, stirred at 20°C and 400 r / min for 9 min, and 1,1-diphenyl-2-propyn-1-ol (0.55 times the mass of the pre-modified polylactic acid) is uniformly added dropwise within 15 min under nitrogen protection, the stirring reaction is continued for 22 h, and the mixture is dried at 55°C under vacuum for 9 h to obtain modified polylactic acid. The remaining steps are the same as in Example 2.

[0048] Comparative Example 3

[0049] The preparation method of the bamboo powder bio-based degradable material for light-resistant agricultural mulch film of Comparative Example 3 is different from that of Example 2 only in that step (2) is not performed, and step (3) is modified as follows: the modified polylactic acid and bamboo powder are mixed in a mass ratio of 1:0.12, placed in a hot melt machine, stirred at 185°C and 400r / min for 15min, 0.002 mass of platinum (0)-1,3-diethene-1,1,3,3-tetramethyldisiloxane of the modified polylactic acid is added, stirring is continued for 2.5min, and then sent to a twin-screw extruder for extrusion molding, the extrusion temperature of the twin-screw extruder is set to 190°C, the extrusion pressure is 18MPa, and the screw speed is 110r / min, to obtain the bamboo powder bio-based degradable material for light-resistant agricultural mulch film. The remaining steps are the same as those of Example 2.

[0050] Test Example 1

[0051] Flame retardant performance test

[0052] Test method: The examples and comparative examples were prepared into standard specimens according to GB / T2406.2, and the limiting oxygen index of the standard specimens was tested. The results are shown in Table 1.

[0053]

[0054] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 3 in Table 1, it can be found that the light aging resistant bamboo powder bio-based degradable material for agricultural mulch film prepared by the present invention has good flame retardant properties.

[0055] By comparison, the limiting oxygen index of Examples 1 to 3 is greater than that of Comparative Example 2, indicating that the pre-modified polylactic acid is prepared by reacting polylactic acid with 6-vinyl-2-naphthol and vinyltetramethyldisilane, and the hydrogen atoms on the tertiary carbon on the polylactic acid molecular chain have certain activity, and can capture the hydrogen atoms on the tertiary carbon through free radical reaction under the action of the initiator, and introduce Si-O bonds on the side chains of the polylactic acid molecules; the bond energy of the Si-O bond is greater than that of the CC bond, so compared with the CC bond, the Si-O bond needs to absorb more heat and its own vibration energy to resolve the energy of thermal decomposition of the polymer material, thereby giving the light-resistant bamboo powder bio-based degradable material for agricultural mulch film excellent flame retardant properties.

[0056] By comparison, the limiting oxygen index of Examples 1 to 3 is greater than that of Comparative Example 3, indicating that part of the hydroxyl groups in the bamboo powder are oxidized with sodium periodate to obtain oxidized bamboo powder, and aldehyde groups are introduced into the bamboo powder; 4,4'-diaminodiphenylamine and allyl phosphoric acid are polymerized and grown on the oxidized bamboo powder to obtain modified bamboo powder; phosphorus element is introduced into the modified bamboo powder; and the introduction of phosphorus element can further improve the flame retardant properties of the bamboo powder bio-based degradable material for light-resistant agricultural mulch film.

[0057] Test Example 2

[0058] Testing of mechanical properties and anti-aging properties

[0059] Test method: The examples and comparative examples were prepared into standard specimens according to GB / T1040, and their tensile strength was tested. The examples and comparative examples were treated at a temperature of 100°C and an oxygen concentration of 32% under normal pressure for 72 hours, and their tensile strength was tested. The change rate of the tensile strength of the examples and comparative examples before and after the thermal oxygen aging treatment was calculated. The examples and comparative examples were irradiated with a xenon arc lamp for 72 hours, and the tensile strength of the examples and comparative examples after ultraviolet aging treatment was tested according to GB / T1040, and the change rate of the tensile strength of the examples and comparative examples before and after the ultraviolet aging treatment was calculated. The results are shown in Table 2.

[0060]

[0061] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 3 in Table 2, it can be found that the light-resistant bamboo powder bio-based degradable material for agricultural mulch film prepared by the present invention has good mechanical properties and anti-aging properties.

[0062] By comparison, the tensile strength of Examples 1 to 3 is greater than that of Comparative Example 2, indicating that the pre-modified polylactic acid is obtained by reacting polylactic acid with 6-vinyl-2-naphthol and vinyltetramethyldisilane, and the hydrogen atoms on the tertiary carbon on the polylactic acid molecular chain have certain activity. Under the action of the initiator, the hydrogen atoms on the tertiary carbon can be captured by free radical reaction to introduce Si-H bonds on the side chains of the polylactic acid molecules; the Si-H bonds can undergo a silylation reaction with the carbon-carbon double bonds introduced on the modified bamboo powder to form a cross-linked network, thereby inhibiting the relative slip between the molecular chains and giving the light-resistant bamboo powder bio-based degradable material for agricultural mulch film excellent mechanical properties.

[0063] By comparison, the tensile strength of Examples 1 to 3 is greater than that of Comparative Example 3, indicating that part of the hydroxyl groups in the bamboo powder are oxidized with sodium periodate to obtain oxidized bamboo powder, and aldehyde groups are introduced into the bamboo powder; 4,4'-diaminodiphenylamine and allyl phosphoric acid are polymerized and grown on the oxidized bamboo powder to obtain modified bamboo powder; carbon-carbon double bonds are introduced into the modified bamboo powder; the carbon-carbon double bonds introduced into the modified bamboo powder can undergo a silylation reaction with the Si-H bonds introduced into the modified polylactic acid to form a cross-linked network, thereby inhibiting the relative slip between the molecular chains and giving the light-resistant bamboo powder bio-based degradable material for agricultural mulch film excellent mechanical properties.

[0064] By comparison, the change rate of tensile strength before and after the thermal oxidative aging treatment of Examples 1 to 3 is less than the change rate of tensile strength before and after the thermal oxidative aging treatment of Comparative Example 3, indicating that part of the hydroxyl groups in the bamboo powder are oxidized with sodium periodate to obtain oxidized bamboo powder, and aldehyde groups are introduced into the bamboo powder; 4,4'-diaminodiphenylamine and allyl phosphoric acid are polymerized and grown on the oxidized bamboo powder to obtain modified bamboo powder; a diaryl secondary amine structure is introduced into the modified bamboo powder; the introduction of the diaryl secondary amine structure can capture the free radicals generated by the material during the thermal oxidative aging process, inhibit the generation and transfer of free radicals, and endow the light-resistant bamboo powder bio-based degradable material for agricultural mulch film with excellent thermal oxidative aging resistance.

[0065] By comparison, the change rate of tensile strength before and after ultraviolet aging treatment in Examples 1 to 3 is less than the change rate of tensile strength before and after ultraviolet aging treatment in Comparative Example 1, indicating that the pre-modified polylactic acid is obtained by reacting polylactic acid with 6-vinyl-2-naphthol and vinyltetramethyldisilane, and the hydrogen atoms on the tertiary carbon on the polylactic acid molecular chain have certain activity. Under the action of the initiator, the hydrogen atoms on the tertiary carbon can be captured by free radical reaction, and the naphthol structure is introduced into the side chain of the polylactic acid molecule; the naphthol structure introduced into the pre-modified polylactic acid is reacted with 1,1-diphenyl-2-propyn-1-ol to obtain the modified polylactic acid; a naphthol pyran structure is generated on the side chain of the modified polylactic acid molecule, and the pyran ring in the naphthol pyran structure will break and open under the action of ultraviolet light, and the pyran ring will be regenerated when the ultraviolet light is removed, so as to absorb ultraviolet light energy, thereby giving the light-resistant bamboo powder bio-based degradable material for agricultural mulch film excellent anti-ultraviolet aging performance.

[0066] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a bamboo powder bio-based degradable material for light aging resistant agricultural mulch film, characterized in that: The method for preparing the bamboo powder bio-based degradable material for light aging resistant agricultural mulch film comprises the following preparation steps: (1) Polylactic acid, 6-vinyl-2-naphthol and vinyltetramethyldisilane are mixed in a mass ratio of 1: (0.2-0.3): (0.1-0.2), placed in an internal mixer, stirred at 175-185°C and 400-600 r / min for 8-10 min, 0.03-0.05 times the mass of polylactic acid of diisopropyl peroxide is added, and the reaction is continued with stirring for 20-30 min to obtain pre-modified polylactic acid; Pre-modified polylactic acid, p-toluenesulfonic acid and dichloromethane were mixed evenly, stirred at 10-30°C and 300-500r / min for 8-10min, and under nitrogen protection, 1,1-diphenyl-2-propyn-1-ol (0.5-0.6 times the mass of pre-modified polylactic acid) was uniformly added dropwise within 15min, and the reaction was continued by stirring for 20-24h. Under vacuum conditions, the mixture was dried at 50-60°C for 8-10h to obtain modified polylactic acid. (2) In a light-proof condition, mix bamboo powder, sodium periodate and deionized water in a mass ratio of 1: (0.2-0.3): (8-10), stir at 10-30°C and 300-500 r / min for 2-3 h, add ethylene glycol in an amount 2-3 times the mass of sodium periodate, continue stirring for 20-30 min, filter, wash with anhydrous ethanol and deionized water for 3-5 times respectively, and dry at 50-60°C under vacuum for 8-10 h to obtain oxidized bamboo powder; 4,4'-diaminodiphenylamine, dicyclohexylcarbodiimide and N,N-dimethylformamide were uniformly mixed, and allyl phosphoric acid with a molar amount of 1 times of 4,4'-diaminodiphenylamine was uniformly added dropwise within 5 minutes at 30-40°C and 300-500r / min stirring conditions, and the temperature was raised to 70-80°C, and the stirring reaction was continued for 4-6 hours, and the mixture was filtered, and washed with anhydrous ethanol and deionized water for 3-5 times respectively, and dried at 50-60°C under vacuum conditions for 12-14 hours to obtain modified bamboo powder; (3) The modified polylactic acid and the modified bamboo powder are mixed and placed in a hot melt machine. The mixture is stirred at 180-190°C and 300-500 r / min for 10-20 min. 0.001-0.003 of platinum (0)-1,3-diethene-1,1,3,3-tetramethyldisiloxane by weight of the modified polylactic acid is added. The mixture is stirred for 2-3 min. The mixture is then sent to a twin-screw extruder for extrusion molding to obtain a bamboo powder biodegradable material for light-resistant agricultural mulch film.

2. The method for preparing a light-resistant bamboo powder biodegradable material for agricultural mulch film according to claim 1, characterized in that: The molecular weight of the polylactic acid in step (1) is 40,000 to 50,000.

3. The method for preparing a light-resistant bamboo powder bio-based degradable material for agricultural mulch film according to claim 1, characterized in that: The mass ratio of the pre-modified polylactic acid, p-toluenesulfonic acid and dichloromethane in step (1) is 1: (0.01-0.03): (10-12).

4. The method for preparing a light-resistant bamboo powder biodegradable material for agricultural mulch film according to claim 1, characterized in that: The mass ratio of the oxidized bamboo powder, 4,4'-diaminodiphenylamine, dicyclohexylcarbodiimide and N,N-dimethylformamide in step (2) is 1: (0.4-0.6): (0.01-0.03): (10-12).

5. The method for preparing a light-resistant bamboo powder bio-based degradable material for agricultural mulch film according to claim 1, characterized in that: The particle size of the bamboo powder in step (2) is 200 mesh.

6. The method for preparing a light-resistant bamboo powder biodegradable material for agricultural mulch film according to claim 1, characterized in that: In step (3), the mass ratio of the modified polylactic acid to the modified bamboo powder is 1:(0.1-0.14).

7. The method for preparing a light-resistant bamboo powder bio-based degradable material for agricultural mulch film according to claim 1, characterized in that: The process parameters of the extrusion molding in step (3) are as follows: the extrusion temperature of the twin-screw extruder is set to 180-200° C., the extrusion pressure is set to 16-20 MPa, and the screw speed is set to 100-120 r / min.

8. A light aging resistant bamboo powder bio-based degradable material for agricultural mulch film prepared according to the method for preparing a light aging resistant bamboo powder bio-based degradable material for agricultural mulch film according to any one of claims 1 to 7.

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