Biodegradable mulch film for rapeseed and preparation method thereof

Abstract

The present invention relates to the technical field of biodegradable agricultural film production, and specifically to a biodegradable mulch film for rapeseed and a preparation method thereof, which comprises the following raw materials by weight: 15-25 parts of PLA, 50-60 parts of modified PBAT, 3-5 parts of PGA, 1-3 parts of plasticizer, 3-5 parts of modified carbon black, and 0.5-2 parts of water retaining agent. The biodegradable mulch film for rapeseed prepared by the present invention has suitable tensile strength and is suitable for dryland machine operation, and has good degradability and weed control properties.

Description

Technical Field

[0001] The invention relates to the technical field of biodegradable agricultural film production, and in particular to a biodegradable mulch film for rapeseed and a preparation method thereof. Background Art

[0002] Rapeseed is a winter crop. Mechanized film-mulching rapeseed has a good effect of heat preservation and moisture retention, which is conducive to the early maturity of rapeseed. Under the same planting density, the plant height and the number of siliques per plant of rapeseed planted with film mulching are better than those of rapeseed planted without film mulching, which is conducive to improving yield and quality. In addition, the film-mulching planting method can improve fertilizer efficiency, reduce the use of chemical fertilizers, and is conducive to improving soil quality and ecological environment. At the same time, the use of mechanized film-mulching rapeseed planting saves labor and has good economic value and sustainability. In addition, in order to reduce agricultural pollution, the mulch used in rapeseed mulching planting technology is preferably biodegradable mulch. Therefore, it is particularly important to develop a biodegradable mulch suitable for rapeseed mulching planting.

[0003] Patent CN106947157B discloses a degradable nano water-retaining mulch film, which is composed of nano-CaCO3, nano-TiO2, polyvinyl alcohol, polypropylene, polylactic acid, straw biomass charcoal, MP3005 water-retaining agent, EM expansion liquid, composite plasticizer, biodegradation accelerator, photoinitiator and starch adhesive. It can increase the degradation rate of the mulch film, and after degradation, it can effectively improve the soil structure and porosity, reduce soil acidity, increase microbial activity, and improve the soil's ability to retain water and fertilizer. However, the mulch film prepared by this invention is not ideal in inhibiting weeds.

[0004] Patent CN109135313B discloses a weed-inhibiting straw biomass-based degradable mulch film. The invention is obtained by processing the straw to obtain straw fibers, then mixing them evenly with other fillers, vacuum dehydrating, pressing, and drying them into shape. The mulch film can be applied to the field of rice seedling cultivation. The mulch film obtained by this method may not have sufficient mechanical strength, is not suitable for machine operations, and is not conducive to rapeseed film-covered cultivation.

[0005] Therefore, there is an urgent need in the market for a biodegradable mulch film for rapeseed with good weed control performance and suitable mechanical strength. Summary of the invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to obtain a biodegradable mulch film for rapeseed with good tensile strength suitable for dryland machinery operations, excellent weed control, heat preservation and good degradation performance.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] On the one hand, the present invention provides a biodegradable mulch film for rapeseed, which comprises the following raw materials, by weight: 15-25 parts of PLA, 50-60 parts of modified PBAT, 3-5 parts of PGA, 1-3 parts of plasticizer, 3-5 parts of modified carbon black, and 0.5-2 parts of water retaining agent.

[0009] The applicant has prepared a mulch film by blending modified PBAT, PLA and PGA, which not only has good biodegradability but also has suitable tensile strength suitable for machinery operations in dry land. In addition, by adding modified carbon black, the thermal insulation and biodegradability of the mulch film are further improved, the light transmittance of the mulch film is reduced, and the weed control property is improved, making it suitable for rapeseed cultivation.

[0010] In some embodiments, the method for preparing the modified PBAT comprises the following steps:

[0011] A1. Place 2-butene-1,4-dicarboxylic acid, 2-hydroxy-4-acryloxybenzophenone, allyl alcohol glycidyl ether and azobisisobutyronitrile in a reaction vessel, and react at 60-70° C. for 1-2 hours to obtain a prepolymer;

[0012] A2. Add the prepolymer obtained in step A1, terephthalic acid, adipic acid, butanediol, a catalyst and a stabilizer into a reaction vessel at a pressure of 70-80 kPa, react at 240-250° C. for 6-7 hours, discharge, granulate and dry to obtain modified PBAT.

[0013] Preferably, the catalyst is one or more of sulfuric acid, phosphoric acid, and triphenyl phosphate.

[0014] More preferably, the catalyst is triphenyl phosphate.

[0015] Preferably, the stabilizer is tetrabutyl titanate.

[0016] The present invention uses a prepolymer obtained by using 2-butene-1,4-dicarboxylic acid, 2-hydroxy-4-acryloxybenzophenone and allyl alcohol glycidyl ether to replace part of terephthalic acid and adipic acid, so that the obtained ground film has suitable tensile strength and is suitable for dry land machinery operation, and has good weed control function. The possible reason is that 2-hydroxy-4-acryloxybenzophenone has a structure of multiple benzene rings, which increases the mechanical properties of the ground film, and benzophenone has certain anti-ultraviolet performance, which can reduce the light transmittance of the ground film and is beneficial to inhibiting the growth of weeds; in addition, the hydroxyl and epoxy groups in the prepolymer can make PBAT produce a cross-linked structure, increase the stability of the ground film, and it is not easy to be corroded and broken by pesticides and degraded in advance. In addition, the olefin segment in the prepolymer increases its film-forming property and shortens the processing time.

[0017] In some embodiments, the mass ratio of the 2-butene-1,4-dicarboxylic acid, 2-hydroxy-4-acryloxybenzophenone, and allyl alcohol glycidyl ether is 1:(2-3):(0.08-0.12).

[0018] The present invention limits the mass ratio of 2-butene-1,4-dicarboxylic acid, 2-hydroxy-4-acryloxybenzophenone and allyl alcohol glycidyl ether to prevent the obtained ground film from being easily deformed and having uneven thickness after stretching, thereby reducing the weed control property and stability and affecting the operation of dryland machinery.

[0019] In some embodiments, the mass ratio of the prepolymer, terephthalic acid, adipic acid, and butanediol in step A2 is (25-30):1:(1-3):(4.5-5.5).

[0020] The present invention limits the mass ratio of prepolymer, terephthalic acid, adipic acid and butanediol, so that the obtained modified mulch film has suitable tensile strength and stability, and has good compatibility with PLA when the amount of PBAT is relatively large.

[0021] In some embodiments, the plasticizer is one or more of acetyl triethyl citrate, acetyl tributyl citrate, and butyric acid glyceride.

[0022] Preferably, the plasticizer is butyric acid glyceride.

[0023] In some embodiments, the method for preparing the modified carbon black comprises the following steps:

[0024] B1. Add carbon black into nitric acid solution, stir for 7-8h at 75-85°C, filter, wash and dry to obtain oxidized carbon black;

[0025] B2, adding the oxidized carbon black obtained in step B1 to dichloromethane, adding thionyl chloride at 35-45° C. under N2 protection, stirring for 0.8-1.2 h, and rotary evaporation to obtain acyl chloride carbon black;

[0026] B3, adding N,N-dimethylformamide to the acyl chloride carbon black obtained in step B2, dropping a 23-27wt% glucose solution in N,N-dimethylformamide, reacting at 70-80°C for 1.9-2.2h, filtering, washing, and drying to obtain glucose-modified carbon black;

[0027] B4. Add chloroform to the glucose-modified carbon black, 4-methoxycarbonyloxybenzoic acid and tetrabutyl titanate obtained in step B3, react at 70-80° C. for 5-6 hours, filter, wash and dry to obtain modified carbon black.

[0028] Preferably, the concentration of the nitric acid solution is 7.5-8.5 mol / L.

[0029] Further preferably, the concentration of the nitric acid solution is 8 mol / L.

[0030] In order to have excellent weed control and heat preservation properties, the film needs to be prepared in black, and some carbon black is often needed to be added. Carbon black has a porous structure, which may enhance the air permeability of the mulch film and promote the growth of weeds. The applicant modified the carbon black with glucose to enhance the weed control and degradability of the mulch film. On the one hand, it may be because glucose occupies the pores of carbon black, which reduces the air permeability of the mulch film. However, glucose has a large number of hydroxyl groups and is hydrophilic, which increases the water molecule channels of the mulch film and may increase the humidity under the film, which is conducive to the reproduction of weeds. The present invention uses 4-methoxycarbonyloxybenzoic acid to modify glucose-modified carbon black, so that the modified carbon black has hydrophobicity, reduces the water vapor permeability, inhibits weeds, and enhances the heat preservation effect. In addition, it may be due to the presence of 4-methoxycarbonyloxybenzoic acid on the pores of carbon black. The carbonyl group has a similar polarity to carbon dioxide, and carbon dioxide has good solubility and affinity on the mulch. In addition, since the black mulch has a lower light transmittance and heat absorption, the temperature inside the mulch is increased, and the carbon dioxide in the mulch is easier to penetrate, while oxygen is difficult to enter, which weakens the respiration of weeds, further improves the weed control performance and the thermal insulation of the mulch. In addition, the hydrophobicity of the modified carbon black can reduce the mulch sticking to the ground during planting and after rainy weather, avoid the deterioration of soil permeability, and affect the growth of rapeseed. In addition, since the modified PBAT and carbon black introduce benzene rings and cross-linked structures, they may not be completely degraded after the use cycle is completed, affecting the cultivation of the next crop. During the degradation process, glucose can provide nutrients for microorganisms in the soil, increase microbial activity, and accelerate the decomposition of the mulch.

[0031] In some embodiments, the mass ratio of the chlorinated carbon black to the N,N-dimethylformamide solution of glucose in step B3 is 1:(15-25).

[0032] The present invention limits the mass ratio of acyl chloride carbon black and glucose N,N-dimethylformamide solution, so that the pore structure of carbon black is occupied as much as possible, thereby reducing the air permeability.

[0033] In some embodiments, the mass ratio of glucose-modified carbon black to 4-methoxycarbonyloxybenzoic acid in step B4 is 1:(5-6).

[0034] The invention limits the mass ratio of glucose-modified carbon black and 4-methoxycarbonyloxybenzoic acid, so that the hydroxyl groups on the surface of glucose-modified carbon black are esterified as much as possible, thereby enhancing the hydrophobicity of the carbon black.

[0035] In some embodiments, the water retaining agent is sodium polyacrylate synthetic resin.

[0036] Another aspect of the present invention provides a method for preparing a biodegradable mulch film for rapeseed, comprising the following steps:

[0037] (1) PLA, modified PBAT and PGA are mixed and then heated at 100-110° C. for 3-5 hours to obtain a dehydrated mixture;

[0038] (2) adding the dehydrated mixture obtained in step (1) and the plasticizer, modified carbon black, and water-retaining agent into a high-speed mixer and mixing them uniformly to obtain a premix;

[0039] (3) putting the premix obtained in step (2) into a twin-screw extruder, and controlling the extrusion temperature at 170-190° C. to obtain a blown film masterbatch;

[0040] (4) The film blowing masterbatch obtained in step (3) is blown into a film by a film blowing machine, the screw temperature is controlled at 160-170° C., the die processing temperature is controlled at 170-180° C., and the film thickness is controlled at 0.008-0.01 mm to obtain a biodegradable mulch film for rapeseed.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The mulch film prepared by adding modified PBAT and modified carbon black in the present invention not only has good biodegradability, but also has suitable tensile strength suitable for machine operations in dry land, low light transmittance, improved weed control, and is suitable for rapeseed cultivation.

[0043] (2) The present invention uses a prepolymer obtained by using 2-butene-1,4-dicarboxylic acid, 2-hydroxy-4-acryloxybenzophenone, and allyl alcohol glycidyl ether to replace part of terephthalic acid and adipic acid, so that the obtained ground film has suitable tensile strength and low light transmittance. In addition, the modified PBAT produces a cross-linked structure, which increases the stability of the ground film and is not easily corroded and broken by pesticides, and degrades prematurely. In addition, the olefin segment increases its film-forming property and shortens the processing time.

[0044] (3) The present invention uses 4-methoxycarbonyloxybenzoic acid to further modify the glucose-modified carbon black, so that the modified carbon black has hydrophobicity, reduces the water vapor permeability, inhibits weeds, and enhances the thermal insulation effect. In addition, the hydrophobicity can reduce the adhesion of the ground film to the ground during the planting process and after rainy weather, avoid soil compaction and poor soil permeability, and affect the growth of rapeseed. In addition, during the degradation process, glucose can provide nutrients for microorganisms in the soil, increase microbial activity, and promote the degradation of the ground film. In addition, the viscosity of glucose can further improve its film formation and increase the uniformity of the film. DETAILED DESCRIPTION

[0045] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following embodiments are examples of the present invention and are only used to illustrate the present invention, but not to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0046] In the following embodiments and comparative examples, except for modified PBAT and modified carbon black, the other compounds and related reagents used can be purchased from the market, among which the model of PLA is LX175, purchased from Dongguan Feiou Plastic Raw Materials Co., Ltd.; the model of PGA is MXK0281, purchased from Hubei Xinyuhong Biomedicine Technology Co., Ltd.; the model of carbon black is S380c, purchased from Anyang Wangtai New Materials Co., Ltd.; sodium polyacrylate synthetic resin is purchased from Henan Tianchou Chemical Products Co., Ltd.

[0047] Preparation Example 1

[0048] The preparation method of modified PBAT-1 comprises the following steps:

[0049] A1. Put 100 g of 2-butene-1,4-dicarboxylic acid, 250 g of 2-hydroxy-4-acryloxybenzophenone, 10 g of allyl alcohol glycidyl ether, and 3.6 g of azobisisobutyronitrile into a reaction container, and react at 65° C. for 1.5 h to obtain a prepolymer;

[0050] A2. Add 27 g of the prepolymer obtained in step A1, 1 g of terephthalic acid, 2 g of adipic acid, 5 g of butanediol, 0.35 g of triphenyl phosphate and 0.2 g of tetrabutyl titanate into a reaction vessel, the pressure is 75 kPa, the reaction is carried out at 245 ° C for 6.5 h, the material is discharged, granulated and dried to obtain modified PBAT-1.

[0051] Preparation Example 2

[0052] The preparation method of modified PBAT-2 comprises the following steps:

[0053] A1. Put 100 g of 2-butene-1,4-dicarboxylic acid, 100 g of 2-hydroxy-4-acryloxybenzophenone, 10 g of allyl alcohol glycidyl ether, and 3.6 g of azobisisobutyronitrile into a reaction container, and react at 65° C. for 1.5 h to obtain a prepolymer;

[0054] A2. Add 27 g of the prepolymer obtained in step A1, 1 g of terephthalic acid, 2 g of adipic acid, 5 g of butanediol, 0.35 g of triphenyl phosphate and 0.2 g of tetrabutyl titanate into a reaction vessel, the pressure is 75 kPa, the reaction is carried out at 245 ° C for 6.5 h, the material is discharged, granulated and dried to obtain modified PBAT-2.

[0055] Preparation Example 3

[0056] The preparation method of modified PBAT-3 has the same specific steps as Preparation Example 1, except that the amount of allyl alcohol glycidyl ether added in step A1 is 15 g.

[0057] Preparation Example 4

[0058] The preparation method of modified PBAT-4 has the same specific steps as Preparation Example 1, except that the amount of prepolymer added in step A2 is 33 g.

[0059] Preparation Example 5

[0060] The preparation method of modified PBAT-5 has the same specific steps as Preparation Example 1, except that the amount of prepolymer added in step A2 is 22 g.

[0061] Preparation Example 6

[0062] The preparation method of PBAT comprises the following steps: adding 1 g of terephthalic acid, 2 g of adipic acid, 5 g of butanediol, 0.35 g of triphenyl phosphate, and 0.2 g of tetrabutyl titanate into a reaction container, the pressure is 75 kPa, reacting at 245° C. for 6.5 h, discharging, granulating, and drying to obtain PBAT.

[0063] Preparation Example 7

[0064] The preparation method of modified carbon black-1 comprises the following steps:

[0065] B1. Add 10 g of carbon black into 50 ml of 8 mol / L nitric acid solution, stir at 80° C. for 7.5 h, filter, wash and dry to obtain oxidized carbon black;

[0066] B2, add 3g of oxidized carbon black obtained in step B1 to 10ml of dichloromethane, add 5ml of thionyl chloride at 40°C under N2 protection, stir for 1h, and rotary evaporate to obtain acyl chloride carbon black;

[0067] B3, add 3g of acyl chloride carbon black obtained in step B2 to 20ml of N,N-dimethylformamide, add dropwise 60g of 25wt% glucose solution in N,N-dimethylformamide, react at 75°C for 2h, filter, wash and dry to obtain glucose-modified carbon black;

[0068] B4. Add 30 ml of chloroform to 1 g of glucose-modified carbon black obtained in step B3, 5.5 g of 4-methoxycarbonyloxybenzoic acid and 0.06 g of tetrabutyl titanate, react at 75° C. for 5.5 h, filter, wash and dry to obtain modified carbon black-1.

[0069] Preparation Example 8

[0070] The preparation method of modified carbon black-2 has the same specific steps as Preparation Example 7, except that the amount of glucose N,N-dimethylformamide solution added in step B3 is 85g.

[0071] Preparation Example 9

[0072] The preparation method of modified carbon black-3, the specific steps are the same as those of Preparation Example 7, the difference is that the amount of 4-methoxycarbonyloxybenzoic acid added in step B4 is 7.5g.

[0073] Example 1

[0074] A biodegradable mulch film for rapeseed comprises the following raw materials, measured in parts by weight: 20 parts of PLA, 155 parts of modified PBAT, 4 parts of PGA, 2 parts of butyric acid glyceride, 14 parts of modified carbon black, and 1 part of sodium polyacrylate synthetic resin.

[0075] The method for preparing the biodegradable mulch film for rapeseed in this embodiment comprises the following steps:

[0076] (1) PLA, modified PBAT-1 and PGA were mixed and then heated at 105° C. for 4 h to obtain a dehydrated mixture;

[0077] (2) adding the dehydrated mixture obtained in step (1), glyceryl butyrate, modified carbon black-1, and sodium polyacrylate synthetic resin into a high-speed mixer and mixing them uniformly to obtain a premix;

[0078] (3) putting the premix obtained in step (2) into a twin-screw extruder, and controlling the extrusion temperature at 180° C. to obtain a blown film masterbatch;

[0079] (4) The film blowing masterbatch obtained in step (3) is blown into a film by a film blowing machine, the screw temperature is controlled at 165° C., the die processing temperature is controlled at 175° C., and the film thickness is 0.009 mm, to obtain a biodegradable mulch film for rapeseed.

[0080] Example 2

[0081] A biodegradable mulch film for rapeseed comprises the following raw materials, measured in parts by weight: 15 parts of PLA, 150 parts of modified PBAT, 3 parts of PGA, 1 part of butyric acid glyceride, 13 parts of modified carbon black, and 0.5 parts of sodium polyacrylate synthetic resin.

[0082] The method for preparing the biodegradable mulch film for rapeseed in this embodiment comprises the following steps:

[0083] (1) PLA, modified PBAT-1 and PGA were mixed and then heated at 100° C. for 5 h to obtain a dehydrated mixture;

[0084] (2) adding the dehydrated mixture obtained in step (1), glyceryl butyrate, modified carbon black-1, and sodium polyacrylate synthetic resin into a high-speed mixer and mixing them uniformly to obtain a premix;

[0085] (3) putting the premix obtained in step (2) into a twin-screw extruder, and controlling the extrusion temperature at 170° C. to obtain a film blowing masterbatch;

[0086] (4) The film blowing masterbatch obtained in step (3) is blown into a film by a film blowing machine, the screw temperature is controlled at 160° C., the die processing temperature is controlled at 170° C., and the film thickness is 0.008 mm, to obtain a biodegradable mulch film for rapeseed.

[0087] Example 3

[0088] A biodegradable mulch film for rapeseed comprises the following raw materials, measured in parts by weight: 25 parts of PLA, 160 parts of modified PBAT, 5 parts of PGA, 3 parts of butyric acid glyceride, 15 parts of modified carbon black, and 2 parts of sodium polyacrylate synthetic resin.

[0089] The method for preparing the biodegradable mulch film for rapeseed in this embodiment comprises the following steps:

[0090] (1) PLA, modified PBAT-1 and PGA were mixed and then heated at 110° C. for 3 h to obtain a dehydrated mixture;

[0091] (2) adding the dehydrated mixture obtained in step (1), glyceryl butyrate, modified carbon black-1, and sodium polyacrylate synthetic resin into a high-speed mixer and mixing them uniformly to obtain a premix;

[0092] (3) putting the premix obtained in step (2) into a twin-screw extruder, and controlling the extrusion temperature at 190° C. to obtain a blown film masterbatch;

[0093] (4) The film blowing masterbatch obtained in step (3) is blown into a film by a film blowing machine, the screw temperature is controlled at 170° C., the die processing temperature is controlled at 180° C., and the film thickness is 0.01 mm, to obtain a biodegradable mulch film for rapeseed.

[0094] Example 4

[0095] A biodegradable mulch film for rapeseed and a preparation method thereof, wherein the specific implementation manner is the same as that of Example 1, except that an equal amount of modified PBAT-1 is replaced by modified PBAT-2.

[0096] Example 5

[0097] A biodegradable mulch film for rapeseed and a preparation method thereof, wherein the specific implementation manner is the same as that of Example 1, except that an equal amount of modified PBAT-1 is replaced by modified PBAT-3.

[0098] Example 6

[0099] A biodegradable mulch film for rapeseed and a preparation method thereof, wherein the specific implementation manner is the same as that of Example 1, except that an equal amount of modified PBAT-1 is replaced by modified PBAT-4.

[0100] Example 7

[0101] A biodegradable mulch film for rapeseed and a preparation method thereof, wherein the specific implementation manner is the same as that of Example 1, except that an equal amount of modified PBAT-1 is replaced by modified PBAT-5.

[0102] Example 8

[0103] A biodegradable mulch film for rapeseed and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified carbon black-1 is replaced by modified carbon black-2.

[0104] Example 9

[0105] A biodegradable mulch film for rapeseed and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified carbon black-1 is replaced by modified carbon black-3.

[0106] Comparative Example 1

[0107] A biodegradable mulch film for rapeseed and a preparation method thereof, wherein the specific implementation manner is the same as that of Example 1, except that an equal amount of modified PBAT-1 is replaced by PBAT.

[0108] Comparative Example 2

[0109] A biodegradable mulch film for rapeseed and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified carbon black-1 is replaced by carbon black.

[0110] Performance Testing

[0111] The biodegradable mulch films for rapeseed obtained in the above embodiments and comparative examples were tested:

[0112] (1) Mechanical properties: The tensile strength of the mulch film was tested in accordance with Part 3 of the national standard "Determination of tensile properties of plastics" (GB / T1040.3-2006). The conditions were: the dumbbell-shaped specimen was 150 mm in length, the narrow parallel width was 10 mm, the tensile speed was 200 mm / min, and the room temperature was 25°C.

[0113] (2) Degradability

[0114] The mulch films obtained in the examples and comparative examples were used for rapeseed planting in the Nanzhuangtou test field in Lishui District, Nanjing City. The mulch films with cracks less than 2 cm, cracks ≥ 2 cm and less than 20 cm, cracks > 20 cm, and the largest mulch film debris area ≤ 16 cm were recorded.2 And there is no time for resilience.

[0115] (3) Evaluation of weed control effect

[0116] A 1m thick layer of paving was laid in the Nanzhuangtou test field in Lishui District, Nanjing. 2 The mulch films obtained from the above embodiments and comparative examples were weighed four months later to obtain the fresh weight of weeds per unit area. The fresh weight of weeds per unit area in the same experimental field was used as the control group to calculate the weed inhibition rate, which was: weed inhibition rate = (fresh weight of weeds per unit area in the control group - fresh weight of weeds per unit area in the mulch film) / fresh weight of weeds per unit area in the control group × 100%.

[0117] (4) Thermal insulation performance

[0118] The soil temperature after 25 days of laying the mulch films obtained in the above embodiments and comparative examples and the soil temperature after 25 days of not laying the mulch films were tested at the same time point during rapeseed planting. The soil temperature after 25 days of not laying the mulch films was 7.8°C.

[0119] The test results are shown in Table 1:

[0120] Table 1

[0121]

[0122] It can be seen from the data in Table 1 that the biodegradable mulch film for rapeseed in Examples 1-3 of the present invention has good mechanical properties, degradation properties and weed control properties. From the comparison between Example 4 and Example 1, it can be seen that the amount of 2-hydroxy-4-acryloxybenzophenone in the modified PBAT-2 is reduced, the crosslinking degree of PBAT is reduced, and the transmittance is increased, resulting in a decrease in the mechanical properties and weed control properties of the mulch film; from the comparison between Example 5 and Example 1, it can be seen that the amount of allyl alcohol glycidyl ether in the modified PBAT-3 is increased, the crosslinking degree of PBAT is improved, and the degradation time is increased; from the comparison between Example 6 and Example 1, it can be seen that the amount of prepolymer in the modified PBAT-4 is increased, resulting in excessive mechanical properties and a decrease in the degradation time of the mulch film; from the comparison between Example 7 and Example 1, From the comparison of Example 1, it can be seen that the amount of prepolymer in the modified PBAT-5 is reduced, the mechanical properties of the mulch film are deteriorated, it is easy to be broken, and the weed control property is reduced; from the comparison of Example 8 and Example 1, it can be seen that the amount of N, N-dimethylformamide solution of glucose in the modified carbon black-2 is increased, which makes water molecules easier to penetrate and the weed control property of the mulch film is reduced; from the comparison of Example 9 and Example 1, it can be seen that the amount of 4-methoxycarbonyloxybenzoic acid in the modified carbon black-3 is increased, the hydrophilicity of the mulch film is increased, and the weed control property is reduced; from the comparison of Comparative Example 1 and Example 1, it can be seen that the mechanical properties and weed control property of the mulch film with the addition of unmodified PBAT are poor; from the comparison of Comparative Example 2 and Example 1, it can be seen that the thermal insulation performance and weed control property of the mulch film are both reduced.

[0123] The above implementation modes are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A biodegradable mulch film for rapeseed, characterized in that: In parts by weight, the following raw materials are included: PLA 15-25 parts, modified PBAT 50-60 parts, PGA 3-5 parts, plasticizer 1-3 parts, modified carbon black 3-5 parts, water retaining agent 0.5-2 parts; The preparation method of the modified PBAT comprises the following steps: A1. Place 2-butene-1,4-dicarboxylic acid, 2-hydroxy-4-acryloxybenzophenone, allyl alcohol glycidyl ether and azobisisobutyronitrile in a reaction vessel, and react at 60-70° C. for 1-2 hours to obtain a prepolymer; A2. Add the prepolymer obtained in step A1, terephthalic acid, adipic acid, butanediol, a catalyst and a stabilizer into a reaction vessel, the pressure is 70-80 kPa, react at 240-250° C. for 6-7 hours, discharge, granulate and dry to obtain modified PBAT; The mass ratio of the 2-butene-1,4-dicarboxylic acid, 2-hydroxy-4-acryloxybenzophenone, and allyl alcohol glycidyl ether is 1:(2-3):(0.08-0.12); In step A2, the mass ratio of prepolymer, terephthalic acid, adipic acid and butanediol is (25-30):1:(1-3):(4.5-5.5); The preparation method of the modified carbon black comprises the following steps: B1. Add carbon black into nitric acid solution, stir for 7-8h at 75-85°C, filter, wash and dry to obtain oxidized carbon black; B2, adding the oxidized carbon black obtained in step B1 to dichloromethane, adding thionyl chloride at 35-45° C. under N2 protection, stirring for 0.8-1.2 h, and rotary evaporation to obtain acyl chloride carbon black; B3, adding N,N-dimethylformamide to the acyl chloride carbon black obtained in step B2, dropping a 23-27wt% glucose solution in N,N-dimethylformamide, reacting at 70-80°C for 1.9-2.2h, filtering, washing, and drying to obtain glucose-modified carbon black; B4, adding chloroform to the glucose-modified carbon black, 4-methoxycarbonyloxybenzoic acid and tetrabutyl titanate obtained in step B3, reacting at 70-80° C. for 5-6 hours, filtering, washing and drying to obtain modified carbon black; The mass ratio of the acyl chloride carbon black and the glucose N,N-dimethylformamide solution in step B3 is 1:(15-25); In the step B4, the mass ratio of glucose-modified carbon black to 4-methoxycarbonyloxybenzoic acid is 1:(5-6).

2. The biodegradable mulch film for rapeseed according to claim 1, characterized in that: The plasticizer is one or more of triethyl acetyl citrate, tributyl acetyl citrate and glyceryl butyrate.

3. The biodegradable mulch film for rapeseed according to claim 1, characterized in that: The water retaining agent is sodium polyacrylate synthetic resin.

4. A method for preparing a biodegradable mulch film for rapeseed according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) PLA, modified PBAT and PGA are mixed and then heated at 100-110°C for 3-5 hours to obtain a dehydrated mixture; (2) adding the dehydrated mixture obtained in step (1) and the plasticizer, modified carbon black, and water retaining agent into a high-speed mixer and mixing them uniformly to obtain a premix; (3) feeding the premix obtained in step (2) into a twin-screw extruder, and controlling the extrusion temperature at 170-190° C. to obtain a blown film masterbatch; (4) The film blowing masterbatch obtained in step (3) is blown into a film by a film blowing machine, the screw temperature is controlled at 160-170°C, the die processing temperature is controlled at 170-180°C, and the film thickness is controlled at 0.008-0.01mm to obtain a biodegradable mulch film for rapeseed.

Images