Biodegradable mulching film for improving ground temperature and preparation method and application thereof

Abstract

The invention discloses a biodegradable mulching film for improving ground temperature as well as a preparation method and application thereof, and relates to the technical field of agricultural new materials. The material is prepared from the following components in parts by weight: 95-97 parts of one or more of copolyester toughened polylactic acid, a polylactic acid / gelatin / acetyl tributyl citrate blending material and a polylactic acid / poly (butylene adipate-co-terephthalate) resin material; and a thermal insulation material: 3-5 parts of one or more of a copper phosphate improved material and ammonium isopropoxide modified ammonium polyphosphate. The prepared degradable mulching film has the heat preservation characteristic, the soil temperature in the early stage of cultivation of winter-spring tomatoes in a solar greenhouse can be increased, and tomato plant growth is promoted; after the mulching film is used, the mulching film is turned over, and the thermal insulation material can be used as a microelement fertilizer required by plant production, so that the later yield and economic benefits are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of new agricultural materials, and more particularly to a biodegradable ground film for increasing ground temperature, and a preparation method and application thereof. Background Art

[0002] Film mulching technology plays multiple roles in modern agriculture. However, the widespread use of film has also produced a large amount of residual film, leading to serious "white pollution" and causing serious impacts on agricultural production and environmental safety. Since ordinary polyethylene film is difficult to degrade, the residue in the soil will cause damage to the soil structure, reduce air permeability and water permeability, thereby affecting the transportation of water and mineral elements, inhibiting the vitality of microorganisms and soil animals in the soil, and even hindering the normal growth of crops. Therefore, solving the problem of film degradation and pollution is a future development trend.

[0003] At present, the black polyethylene mulch commonly used in the production of winter and spring tomatoes in solar greenhouses has a slow early temperature increase and is difficult to degrade, which can easily damage the soil structure and affect the growth and yield of tomatoes. In addition, the mechanical properties of most mulch films on the market are poor, and they are prone to lateral and longitudinal elongation and fracture, resulting in holes in the mulch films, which in turn affects the early insulation effect. Tomatoes have certain differences in their growth requirements for temperature at different growth stages, and are particularly sensitive to temperature changes during the seedling stage and flowering and fruiting stages; during the seedling stage, too low a temperature will lead to slow seedling growth, while too high a temperature will cause the seedlings to grow too long, and the seedlings will be thin and slender, which is not conducive to the formation of later yields. Therefore, how to create a biodegradable mulch film that is degradable, environmentally friendly, has good early insulation effect and is suitable for tomato growth to replace traditional polyethylene mulch films is an urgent problem that relevant personnel in this field need to solve.

[0004] The relevant patents about biodegradable mulch include Chinese patents CN118063941A, CN117534944A, CN117264309A, etc. However, they lack thermal insulation or mechanical properties, and it is difficult to control the degradation rate to meet the effective accumulated temperature requirement of crop seedlings. Therefore, it is of great significance to develop a mulch with both thermal insulation and excellent mechanical properties to meet the needs of crop growth. Summary of the invention

[0005] In view of this, the present invention provides a biodegradable ground film for increasing ground temperature, and a preparation method and application thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A biodegradable ground film for increasing ground temperature, calculated by weight, is composed of the following components:

[0008] Degradable materials: one or more of toughened polylactic acid, polylactic acid / gelatin / acetyl tributyl citrate blended material, polylactic acid / polybutylene adipate terephthalate resin material, 95-97 parts;

[0009] Insulation material: one or more of copper phosphate modified material and ammonium isopropylate modified ammonium polyphosphate, 3-5 parts.

[0010] Further, the preparation of the toughened polylactic acid:

[0011] The polylactic acid and polyethylene glycol were dried at 60° C. under vacuum for 12 h, mixed in a mass ratio of 95:5, and the mixture was mixed at 170-180° C. for 10-13 min to obtain toughened polylactic acid.

[0012] Further, the preparation of the polylactic acid / gelatin / acetyl tributyl citrate blend material:

[0013] The polylactic acid and gelatin / acetyl tributyl citrate mixture was dried in a drying oven at 60°C for 9-12h, mixed at a mass ratio of 95:5, and added to a torque rheometer for melt mixing modification, with specific settings of: temperature 170-180°C, rotation speed 80rpm, reaction time 4-6min, and naturally cooled to room temperature to obtain a polylactic acid / gelatin / acetyl tributyl citrate blended material;

[0014] The mass ratio of gelatin to acetyl tributyl citrate in the gelatin / acetyl tributyl citrate mixture is 1:1.

[0015] Further, the preparation of the polylactic acid / polybutylene adipate terephthalate resin material:

[0016] The polylactic acid and polybutylene adipate terephthalate mixture was dried at 60°C in a drying oven for 9-12 hours, mixed at a mass ratio of 95:5, and added to a torque rheometer for melt mixing modification. The specific settings were: temperature 170-180°C, rotation speed 80rpm, reaction time 4-6min, and naturally cooled to room temperature to obtain a polylactic acid / polybutylene adipate terephthalate resin material.

[0017] Further, the preparation of the copper phosphate improved material:

[0018] Using copper oxide and ammonium dihydrogen phosphate as precursor materials, the precursor material and zirconium dioxide grinding media are ball-milled in ethanol for 20-24 hours to be homogenized, then dried at 80-90° C., and then sintered at 1000° C. for 3-4 hours, and then cooled to obtain a copper phosphate modified material;

[0019] The mass ratio of copper oxide to diammonium phosphate is 4:1;

[0020] The mass ratio of the precursor material to zirconium dioxide is 99:1.

[0021] Further, the preparation of the ammonium isopropanol modified ammonium polyphosphate:

[0022] 25 g of isopropanolamine and 25 g of ammonium polyphosphate were mixed, and then the mixture was dissolved in 300 mL of 75% ethanol and stirred in nitrogen at 80-90° C. for 8-10 hours; after the reaction was completed, the mixture was cooled to room temperature, filtered and separated, and washed three times with anhydrous ethanol; finally, the isopropanolamine-modified ammonium polyphosphate material was obtained after vacuum drying at 70-80° C.

[0023] A method for preparing a biodegradable ground film for increasing ground temperature comprises the following steps: adding a degradable material and a thermal insulation material into a high-speed mixer and mixing them for 1-10 minutes; adding the mixture into a twin-screw extruder with a feed rate of 100-200 g / min and a screw speed of 100-300 rpm; melt-blending and cooling the obtained resin and then granulating it into a composite masterbatch in a pelletizer; adding the composite masterbatch into a single-screw extruder for melt extrusion and blow molding into a film.

[0024] Furthermore, the temperature of the seven zones of the twin-screw extruder from the feed port to the extruder head is set to: (130-200) / (130-200) / (130-200) / (130-200) / (130-200) / (130-200) / (130-200)°C.

[0025] Furthermore, the head temperature of the single screw extruder is set to: (130-200) / (130-200) / (130-200) / (130-200) / (130-200)°C.

[0026] The invention discloses an application of a biodegradable mulch film for increasing ground temperature in tomato production in winter and spring.

[0027] It can be seen from the above technical solution that, compared with the prior art, the beneficial effects of the present invention are:

[0028] The present invention uses one or more of copolyester toughened polylactic acid, polylactic acid / gelatin / acetyl tributyl citrate blended material, polylactic acid / polybutylene adipate terephthalate resin material as the degradable material, and on this basis adds one or more of the thermal insulation material copper phosphate improved material and ammonium isopropyl alcohol modified ammonium polyphosphate, which not only solves the problem of non-degradable ground film in winter and spring tomato planting in solar greenhouses, but also solves the problem of low ground temperature in the early stage, and can also save labor and improve soil fertility. The thermal insulation material added to the ground film material can increase the absorbance of the ground film to infrared rays, enhance the thermal insulation performance of the ground film, and ensure the appropriate soil temperature in the tomato root zone in the early stage of winter and spring tomato planting; in the late planting period, as the ambient temperature rises, the thermal insulation agent slowly seeps out of the ground film and the ground film itself cracks, and the thermal insulation agent no longer has the thermal insulation effect; after the tomato vines are pulled, the ground film can be deeply turned into the ground for degradation and no longer needs to be recycled. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0030] Figure 1 The effects of different mulching treatments on soil temperature;

[0031] Figure 2 is the elongation at break of different mulch films;

[0032] Figure 3 It is the weight loss rate (degradation rate) of different mulch films after burial. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in 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 creative work are within the scope of protection of the present invention.

[0034] Example 1

[0035] Biodegradable mulch preparation steps:

[0036] 1) A method for preparing copolyester toughened polylactic acid, characterized in that it comprises the following steps:

[0037] After the polylactic acid was dried under vacuum at 60° C. for 12 h, the polylactic acid and polyethylene glycol were mixed in a mass ratio of 95:5, and the mixture was mixed at 180° C. for 13 min to obtain a copolyester toughened polylactic acid;

[0038] 2) Preparation method of copper phosphate improved material:

[0039] Copper oxide and diammonium phosphate (mass ratio 4:1) are used as precursor materials. The precursor material is ball-milled with zirconium dioxide (mass ratio 99:1) grinding media in ethanol for 20-24 hours to mix and homogenize, then dried at 80-90°C, and then sintered at 1000°C for 3-4 hours. After cooling, the copper phosphate improved material is obtained.

[0040] 3) mixing 97 parts of copolyester toughened polylactic acid and 3 parts of copper phosphate modified material to obtain a mixed solution;

[0041] 4) Preheat the mixed solution at 60°C for 10 min; stir the preheated materials with a high-speed stirrer at a speed of 200 rpm for 3 min; ensure that the test materials are completely mixed to obtain a uniform mixed solution;

[0042] 5) Add the mixed liquid of the degradable material and the thermal insulation material into a high-speed mixer and mix for 5 minutes, then add the mixture into a twin-screw extruder, with a feed rate of 150 g / min, a screw speed of 200 rpm, and the temperature of the seven zones from the feed port to the extruder head is set to 135 / 145 / 155 / 165 / 175 / 185 / 195°C. The obtained resin is melt blended, cooled, and then granulated into a pelletizer to obtain a composite masterbatch, and the composite masterbatch is added to a single-screw extruder for melt extrusion, and the temperature of the single-screw extruder head is set to 145 / 155 / 165 / 175 / 185°C. After the film blowing machine is used for blowing, a biodegradable mulch film is obtained, and the thickness is controlled at 10±1μm.

[0043] Example 2

[0044] Biodegradable mulch preparation steps:

[0045] 1) A method for preparing a polylactic acid / gelatin / acetyltributyl citrate blend material, characterized in that it comprises the following steps:

[0046] Polylactic acid and gelatin / acetyl tributyl citrate mixture (gelatin: acetyl tributyl citrate mass ratio 1:1) were dried in a drying oven at 60°C for 12 h, mixed at a mass ratio of 95:5, and added to a torque rheometer for melt mixing modification, with specific settings of: temperature 180°C, rotation speed 80 rpm, reaction time 6 min, and the mixture was naturally cooled to room temperature to obtain;

[0047] 2) The preparation method of the copper phosphate improved material is the same as that of Example 1;

[0048] 3) mixing 97 parts of polylactic acid / gelatin / acetyltributyl citrate blend material and 3 parts of copper phosphate modified material to obtain a mixed solution;

[0049] Steps 4)-5) are the same as in Example 1.

[0050] Example 3

[0051] Biodegradable mulch preparation steps:

[0052] 1) The degradable material adopts copolyester toughened polylactic acid and polylactic acid / polybutylene adipate terephthalate resin material;

[0053] The preparation method of copolyester toughened polylactic acid is the same as that of Example 1;

[0054] Preparation method of polylactic acid / polybutylene adipate terephthalate resin material:

[0055] Polylactic acid and polybutylene adipate terephthalate were dried in a drying oven at 60°C for 12 h, mixed at a mass ratio of 95:5, and added to a torque rheometer for melt mixing modification. The specific settings were: temperature 180°C, rotation speed 80 rpm, reaction time 6 min, and the mixture was naturally cooled to room temperature to obtain;

[0056] 2) The copper phosphate improved material is the same as that in Example 1;

[0057] 3) mixing 7 parts of copolyester toughened polylactic acid, 90 parts of polylactic acid / polybutylene adipate terephthalate resin material and 3 parts of copper phosphate modified material to obtain a mixed solution;

[0058] Step 4) is the same as in Example 1;

[0059] Step 5) A biodegradable mulch film is prepared, and the thickness is controlled at 12±1 μm, and the rest is the same as in Example 1.

[0060] Example 4

[0061] Biodegradable mulch preparation steps:

[0062] 1) The degradation material is made of polylactic acid / polybutylene adipate terephthalate resin material, and the preparation method is the same as that of Example 3;

[0063] 2) Preparation method of the ammonium isopropanol modified ammonium polyphosphate:

[0064] 25 g of isopropanolamine and 25 g of ammonium polyphosphate were mixed, and then the mixture was dissolved in 300 mL of 75% ethanol, and stirred in nitrogen at 80-90° C. for 8-10 hours; after the reaction was completed, the mixture was cooled to room temperature, filtered and separated, and washed three times with anhydrous ethanol; finally, the isopropanolamine modified ammonium polyphosphate material was obtained after vacuum drying at 70-80° C.;

[0065] 3) mixing 97 parts of polylactic acid / polybutylene adipate terephthalate resin material and 3 parts of ammonium isopropylammonium modified ammonium polyphosphate to obtain a mixed solution;

[0066] Steps 4)-5) are the same as in Example 3.

[0067] Yield test

[0068] Using '3690' tomatoes as the test material, a winter and spring tomato cultivation experiment in a solar greenhouse covered with biodegradable mulch was carried out in the solar greenhouse of the Horticultural Experiment Station of Shandong Agricultural University from February to July 2023. The experimental mulch was a biodegradable mulch with black masterbatch added. 10μm ordinary black mulch (PE) (Shandong Qingtian Plastic Industry Co., Ltd., production batch number: 3000105499) was used as the control (CK) to analyze and study the tomato quality, yield and degradation characteristics of the mulch, and the final data was obtained by taking the average value.

[0069] The specific process is: adopt a high ridge double-row planting mode, with a ridge bottom width of 0.6m, a top width of 0.5m, a height of 0.25m, a large row spacing of 1.0m, a small row spacing of 0.4m, and a plant spacing of 0.4m. Each treatment has 4 ridges, and a protective row is set on each side of the east and west. When the tomato seedlings grow to five leaves and one heart, they are transplanted. Before transplanting, microbial agents (diluted 500 times) are used to dip the roots. After the seedlings have grown, they are covered with film. When the 6th ear of flowers bloom, the tops are cut. After all the fruits are picked, the seedlings are pulled out. The following indicators are measured: soil temperature, water vapor permeability, tensile strength of the mulch film, and degradation performance of the mulch film.

[0070] The results show that the biodegradable mulch can achieve the purpose of early thermal insulation ( Figure 1 ), the maximum daily average soil temperature was 0.17℃ higher than that of black mulch (PE); the transverse and longitudinal elongation at break of mulch decreased ( Figure 2 ), the degradation rate is accelerated ( Figure 3 ), the tomato yield increased by 2.91%, and the difference was not significant (Table 1). Therefore, the present invention saves labor, achieves the purpose of early heat preservation, and realizes high-quality and efficient cultivation of winter and spring tomatoes in a solar greenhouse.

[0071] Table 1: Effects of different mulch coverings on tomato yield and economic benefits

[0072]

[0073] Note: Economic benefits are based on the price of 4 yuan / kg when winter and spring tomatoes are on the market. -1 calculate.

[0074] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A biodegradable ground film for increasing ground temperature. It is characterized in that Calculated by weight, it is composed of the following components: Degradable materials: one or more of toughened polylactic acid, polylactic acid / gelatin / acetyl tributyl citrate blended material, polylactic acid / polybutylene adipate terephthalate resin material, 95-97 parts; Insulation material: one or more of copper phosphate modified material and ammonium isopropylate modified ammonium polyphosphate, 3-5 parts.

2. The biodegradable mulch film according to claim 1, It is characterized in that Preparation of the toughened polylactic acid: The polylactic acid and polyethylene glycol were dried at 60° C. under vacuum for 12 h, mixed in a mass ratio of 95:5, and the mixture was mixed at 170-180° C. for 10-13 min to obtain toughened polylactic acid.

3. The biodegradable mulch film according to claim 1, It is characterized in that Preparation of the polylactic acid / gelatin / acetyl tributyl citrate blend material: The polylactic acid and gelatin / acetyl tributyl citrate mixture was dried in a drying oven at 60°C for 9-12h, mixed at a mass ratio of 95:5, and added to a torque rheometer for melt mixing modification, with specific settings of: temperature 170-180°C, rotation speed 80rpm, reaction time 4-6min, and naturally cooled to room temperature to obtain a polylactic acid / gelatin / acetyl tributyl citrate blended material; The mass ratio of gelatin to acetyl tributyl citrate in the gelatin / acetyl tributyl citrate mixture is 1:

1.

4. The biodegradable mulch film according to claim 1, It is characterized in that Preparation of the polylactic acid / polybutylene adipate terephthalate resin material: The polylactic acid and polybutylene adipate terephthalate mixture was dried at 60°C in a drying oven for 9-12 hours, mixed at a mass ratio of 95:5, and added to a torque rheometer for melt mixing modification. The specific settings were: temperature 170-180°C, rotation speed 80rpm, reaction time 4-6min, and naturally cooled to room temperature to obtain a polylactic acid / polybutylene adipate terephthalate resin material.

5. The biodegradable mulch film according to claim 1, It is characterized in that Preparation of the copper phosphate improved material: Using copper oxide and ammonium dihydrogen phosphate as precursor materials, the precursor material and zirconium dioxide grinding media are ball-milled in ethanol for 20-24 hours to be homogenized, then dried at 80-90° C., and then sintered at 1000° C. for 3-4 hours, and then cooled to obtain a copper phosphate modified material; The mass ratio of copper oxide to diammonium phosphate is 4:1; The mass ratio of the precursor material to zirconium dioxide is 99:

1.

6. The biodegradable mulch film according to claim 1, It is characterized in that Preparation of the ammonium isopropanol modified ammonium polyphosphate: 25 g of isopropanolamine and 25 g of ammonium polyphosphate were mixed, and then the mixture was dissolved in 300 mL of 75% ethanol and stirred in nitrogen at 80-90° C. for 8-10 hours; after the reaction was completed, the mixture was cooled to room temperature, filtered and separated, and washed three times with anhydrous ethanol; finally, the isopropanolamine-modified ammonium polyphosphate material was obtained after vacuum drying at 70-80° C.

7. The method for preparing the biodegradable mulch film according to claim 1, It is characterized in that The degradation material and the thermal insulation material are added into a high-speed mixer and mixed for 1-10 minutes. The mixture is added into a twin-screw extruder with a feed rate of 100-200 g / min and a screw speed of 100-300 rpm. The obtained resin is melt-blended and cooled and then granulated into a pelletizer to obtain a composite masterbatch. The composite masterbatch is added into a single-screw extruder for melt extrusion and blow molding into a film.

8. The preparation method according to claim 7, It is characterized in that The temperature of the seven zones from the feed port to the extruder head of the twin-screw extruder is set as: (130-200) / (130-200) / (130-200) / (130-200) / (130-200) / (130-200) / (130-200)°C.

9. The preparation method according to claim 7, It is characterized in that The head temperature of the single screw extruder is set to: (130-200) / (130-200) / (130-200) / (130-200) / (130-200)°C.

10. Use of the biodegradable mulch film for increasing ground temperature as claimed in claims 1 to 6 in tomato production in winter and spring.

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