Full-biodegradable mulching film and preparation method thereof

Abstract

The invention discloses a full-biodegradable mulching film and a preparation method thereof. The full-biodegradable mulching film is prepared from the following raw materials in parts by weight: 15 parts of polylactic acid, 70 parts of poly (adipic acid) / butylene terephthalate, 10 parts of modified starch, 2 parts of talcum powder, 2 parts of a chain extender, 0.2 part of an antioxidant, 0.2 part of an anti-aging agent, 0.2 part of an ultraviolet light absorber and 0.4 part of a light stabilizer. The environment-friendly plastic film has the advantage of being environmentally friendly, and the problems that in the process that an existing plastic film is used as a mulching film, part of the plastic film is likely to be left in planting soil, the film is difficult to degrade by the soil, and the soil environment is polluted are solved.

Description

Technical Field

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

[0002] Fully biodegradable mulch is a plastic film that can be completely decomposed by microorganisms into carbon dioxide, water and biomass in the natural environment. This kind of mulch is often used in the agricultural field, covering the soil surface to promote crop growth, while reducing competition from weeds and maintaining soil moisture and temperature. Compared with traditional plastic mulch, it will not remain in the soil like traditional polyethylene mulch, thus avoiding the problem of soil pollution caused by long-term accumulation. Fully biodegradable mulch is made from renewable resources, such as corn starch or other plant materials, which helps reduce dependence on fossil fuels.

[0003] When existing plastic films are used as ground films, some of the plastic films are likely to remain in the planting soil. The soil has difficulty in degrading the films, which will cause pollution to the soil environment. Summary of the invention

[0004] The purpose of the present invention is to provide a fully biodegradable mulch film and a preparation method thereof, which has the advantage of being environmentally friendly and solves the problem that when existing plastic films are used as mulch films, part of the plastic films are easily left in the planting soil, making it difficult for the soil to degrade the films, thus causing pollution to the soil environment.

[0005] To achieve the above object, the present invention provides the following technical solution: a fully biodegradable mulch film, comprising the following raw materials in parts by weight:

[0006] 15 parts of polylactic acid, 70 parts of polybutylene adipate / terephthalate, 10 parts of modified starch, 2 parts of talc, 2 parts of chain extender, 0.2 parts of antioxidant, 0.2 parts of antioxidant, 0.2 parts of ultraviolet absorber, and 0.4 parts of light stabilizer.

[0007] 3. A method for preparing a fully biodegradable mulch film, comprising the following steps:

[0008] S1. Put the well-proportioned polylactic acid, polybutylene adipate / terephthalate, modified starch, talcum powder, chain extender, antioxidant, anti-aging agent, ultraviolet absorber and light stabilizer into a high-speed mixer, and mix the above materials in the high-speed mixer;

[0009] S2, putting the mixed raw materials into a granulator for heating and granulation;

[0010] S3, putting the prepared plastic particles into a film blowing device, the film blowing device heats and melts the plastic particles, the melted plastic is extruded through an annular die, and the extruded plastic bubble tube is expanded by a film blowing molding structure;

[0011] S4, using a traction roller to pull the cooled bubble tube downward, and then rolling and cutting it into a ground film;

[0012] S5. During the preparation of the ground film, the film blowing ratio and the traction ratio are adjusted according to the width and thickness of the ground film.

[0013] As a preferred method for preparing a fully biodegradable mulch film of the present invention, the time for the high-speed mixer in S1 to mix the materials is 50 minutes.

[0014] As a preferred method for preparing a fully biodegradable mulch film of the present invention, the heating temperature in S2 is 180-200°C.

[0015] As a preferred method for preparing a fully biodegradable ground film of the present invention, in the process of film blowing in S3, the film blowing temperature is 145-150°C, and the blowing ratio is 5. The blowing ratio is the ratio of the film bubble diameter to the die diameter, reflecting the degree of film bubble inflation.

[0016] As a preferred method for preparing a fully biodegradable ground film of the present invention, the cooling device cools down and shapes the expanded bubble tube in S3.

[0017] As a preferred method for preparing a fully biodegradable mulch film of the present invention, the pulling ratio during pulling in S4 is 7, and the pulling ratio of 7 means that the pulling speed is 7 times the extrusion speed. This high speed helps the longitudinal stretching of the film, thereby improving its mechanical properties.

[0018] As a preferred method for preparing a fully biodegradable mulch film of the present invention, the calculation formula of the inflation ratio is:

[0019]

[0020] d1 is the inner diameter of the annular die at the extruder die outlet;

[0021] d2 is the maximum diameter of the membrane bubble.

[0022] As a preferred method for preparing a fully biodegradable mulch film of the present invention, the calculation formula of the traction ratio is:

[0023]

[0024] B is the traction ratio;

[0025] U is the traction speed;

[0026] U0 is the extrusion speed.

[0027] As a preferred method for preparing a fully biodegradable mulch film of the present invention, the method further comprises the following steps:

[0028] S6. When a black ground film is required, 5% of carbon black material is added to the raw materials, and the carbon black is mixed with plastic particles to finally prepare a black ground film;

[0029] S7. When it is necessary to adjust the degradation cycle of the mulch film according to the growth cycle of crops, the proportion of antioxidants, antioxidants, UV absorbers and light stabilizers in the material is adjusted. When it is necessary to accelerate the degradation, the proportion of antioxidants, antioxidants, UV absorbers and light stabilizers is reduced. When it is necessary to slow down the degradation, the proportion of antioxidants, antioxidants, UV absorbers and light stabilizers is increased.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The present invention uses biodegradable materials such as polylactic acid, polyadipate / butylene terephthalate, etc., which can be decomposed into carbon dioxide, water and biomass by microorganisms in the natural environment and will not cause environmental pollution. Compared with traditional non-degradable plastic mulch, the mulch produced by this method can be naturally degraded after use, reducing plastic residues in farmland and protecting soil health. Covering the mulch helps to maintain soil moisture and temperature and inhibit weed growth, thereby increasing crop yield and quality. Since the mulch can degrade by itself, no manual recycling is required, which saves labor costs and improves agricultural production efficiency.

[0032] 2. The present invention ensures the uniformity and stability of the product by strictly controlling key parameters such as mixing time, heating temperature, film blowing temperature, blowing ratio and traction ratio. The appropriate traction ratio setting can not only ensure the consistency of film thickness, but also effectively improve its longitudinal tensile strength, making the ground film more durable. Some raw materials such as modified starch come from plants, which reduces dependence on fossil fuels and is in line with the concept of sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the preparation process of the present invention. DETAILED DESCRIPTION

[0034] Example 1

[0035] A fully biodegradable ground film, comprising the following raw materials in parts by weight:

[0036] 15 parts of polylactic acid, 70 parts of polybutylene adipate / terephthalate, 10 parts of modified starch, 2 parts of talc, 2 parts of chain extender, 0.2 parts of antioxidant, 0.2 parts of antioxidant, 0.2 parts of ultraviolet absorber, and 0.4 parts of light stabilizer.

[0037] Biodegradability is a fully biodegradable polymer derived from renewable resources such as corn starch, which helps reduce plastic pollution and can provide good tensile strength and modulus, increasing the overall mechanical strength of the mulch.

[0038] Polybutylene adipate / terephthalate can give the mulch better flexibility and ductility, making it less likely to break and more suitable for application in agricultural environments. Polybutylene adipate / terephthalate is a fully biodegradable polymer, ensuring that the product can decompose naturally after use.

[0039] Modified starch as a filler can reduce production costs and increase the biodegradation rate of materials. It can accelerate the degradation process of mulch in the soil and promote soil health.

[0040] As an inorganic filler, talcum powder can effectively improve the rigidity and surface smoothness of the ground film, and help improve melt fluidity and demolding performance, reducing possible problems in the production process.

[0041] Chain extenders can extend polymer chains, thereby increasing the molecular weight of the material, enhancing its physical and mechanical properties, and helping to improve the material's heat resistance and tear strength.

[0042] Antioxidants are used to prevent materials from aging or degradation due to oxidation during processing and use, protect the ground membrane from chemical changes caused by oxygen, and maintain its long-term performance stability.

[0043] Antioxidants can slow down the aging process of the mulch under the influence of factors such as light, oxygen and temperature, extend its service life, and help maintain the physical properties of the mulch, such as tensile strength and elasticity.

[0044] UV absorbers can absorb and convert UV energy to prevent it from directly damaging the mulch structure, enhance the mulch's ability to resist UV radiation under outdoor environmental conditions, and reduce degradation caused by UV radiation.

[0045] Light stabilizers work synergistically with UV absorbers to further improve the stability of the film to light and prevent light-induced aging.

[0046] Example 2

[0047] See also Figure 1 A method for preparing a fully biodegradable mulch film comprises the following steps:

[0048] S1. Put polylactic acid, polybutylene adipate / terephthalate, modified starch, talcum powder, chain extender, antioxidant, anti-aging agent, ultraviolet absorber and light stabilizer in a high-speed mixer, and mix the above materials in the high-speed mixer.

[0049] S2. Put the mixed raw materials into a granulator for heating and granulation.

[0050] S3. Put the prepared plastic particles into the film blowing equipment. The film blowing equipment heats and melts the plastic particles. The melted plastic is extruded through the annular die, and the extruded plastic bubble tube is expanded through the film blowing molding structure.

[0051] Furthermore, a cooling device is used to cool and shape the expanded bubble tube in S3.

[0052] S4. Use a traction roller to pull the cooled bubble tube downward, and then roll and cut it into a ground film.

[0053] S5. During the preparation of the ground film, the film blowing ratio and the traction ratio are adjusted according to the width and thickness of the ground film.

[0054] Furthermore, the time for the high-speed mixer in S1 to mix the materials is 50 minutes.

[0055] Furthermore, the heating temperature in S2 is 180-200°C.

[0056] Furthermore, in the process of film blowing in S3, the film blowing temperature is 145-150° C., and the blowing ratio is 5. The blowing ratio is the ratio of the film bubble diameter to the die diameter, reflecting the degree of film bubble inflation.

[0057] Furthermore, the pulling ratio during pulling in S4 is 7, which means that the pulling speed is 7 times the extrusion speed. This high speed helps to stretch the film in the longitudinal direction, thereby improving its mechanical properties.

[0058] Furthermore, the calculation formula of the blowing ratio is:

[0059]

[0060] d1 is the inner diameter of the annular die at the extruder die outlet;

[0061] d2 is the maximum diameter of the membrane bubble.

[0062] Furthermore, the calculation formula of the traction ratio is:

[0063]

[0064] B is the traction ratio;

[0065] U is the traction speed;

[0066] U0 is the extrusion speed.

[0067] The following steps are also included:

[0068] S6. When a black ground film is required, 5% of carbon black material is added to the raw materials, and the carbon black is mixed with plastic particles to finally prepare a black ground film;

[0069] S7. When it is necessary to adjust the degradation cycle of the mulch film according to the growth cycle of crops, the proportion of antioxidants, antioxidants, UV absorbers and light stabilizers in the material is adjusted. When it is necessary to accelerate the degradation, the proportion of antioxidants, antioxidants, UV absorbers and light stabilizers is reduced. When it is necessary to slow down the degradation, the proportion of antioxidants, antioxidants, UV absorbers and light stabilizers is increased.

[0070] The various raw materials are mixed for a long time by a high-speed mixer to ensure that the ingredients are fully and evenly dispersed, which helps to improve the mechanical properties and consistency of the final product. The appropriate mixing time can promote the chemical reaction between certain additives and the polymer matrix, further enhancing the material performance.

[0071] The granulation is carried out at a temperature of 180-200℃, so that the mixed raw materials are melted and solidified into granules, which is convenient for the subsequent film blowing process. The granulation temperature is accurately controlled to ensure the consistency of the quality of each plastic granule and avoid defects caused by too high or too low temperature.

[0072] The film blowing temperature is set at 145-150℃ to ensure that the plastic can be smoothly extruded and formed into a bubble tube through the annular die, while maintaining appropriate fluidity to adapt to the blowing process. Use cooling equipment to cool the expanded bubble tube to prevent the film from deforming during the cooling process and ensure its dimensional stability and thickness uniformity. Set the blowing ratio to 5, that is, the diameter of the bubble is 5 times the diameter of the die. This ratio can effectively control the transverse stretching of the film, thereby affecting its width and thickness distribution.

[0073] The traction ratio is set to 7, which achieves efficient longitudinal stretching of the film and improves its mechanical strength and toughness. The cooled bubble tube is pulled downward using a traction roller, and then rolled and cut to prepare a suitable ground film product for subsequent packaging and transportation.

[0074] According to the specific width and thickness requirements of the ground film, the film blowing ratio and traction ratio can be flexibly adjusted to ensure that the produced ground film meets the requirements of different application scenarios.

[0075] Furthermore, the annular mold includes a main structure, a flow channel system, a temperature control system, air holes, an air ring and a seal.

[0076] The main structure includes a die shell and a feed port. The die shell is made of high-strength metal, which is resistant to high temperatures and not easily deformed. A heating chamber is provided inside the die shell to accommodate the heating element. The feed port is located above or on the side of the die shell and is connected to the screw system of the extruder so that the molten plastic can smoothly enter the die shell.

[0077] The flow channel system includes a distribution flow channel and an annular gap. The distribution flow channel extends from the feed port to the annular gap and is responsible for evenly distributing the molten plastic around the entire circumference. The annular gap is the core part of the die head and determines the thickness of the final extruded film. The width of the annular gap can be adjusted as needed to adapt to the production of ground films with different thickness requirements.

[0078] The temperature control system includes a heating element and a cooling device. The heating element is installed in the heating cavity inside the die housing to maintain the appropriate processing temperature to prevent premature curing or thermal degradation of the plastic. The cooling device is used to adjust the die temperature to ensure stable temperature, especially in high-volume production.

[0079] The air hole is located below the die head and is used to inject air into the plastic bubble tube that has just been extruded to make it expand.

[0080] The air ring is set close to the air hole to provide cooling air to help quickly solidify the surface of the bubble tube while controlling its diameter. The air ring is divided into single layer or multi-layer to achieve a more refined cooling effect.

[0081] Seals are used to prevent leakage of molten plastic, especially when working under high pressure conditions, maintaining good sealing performance.

[0082] Furthermore, the blown film molding structure is a blowing system, which includes an air hole, a pressure regulator and a filter. The air hole is located below the annular die head and is used to inject compressed air into the bubble tube to expand it. The pressure regulator is used to accurately control the blowing pressure to ensure that the bubble tube expands evenly and stably. The filter ensures that the air entering the bubble tube is clean and free of impurities to avoid contaminating the film.

[0083] Furthermore, the basic structure of the traction roller is a roller body, a shaft and a bearing. The roller body is made of metal and the surface is specially treated to increase friction and prevent the film from slipping. The shaft supports the roller body and is connected to the drive system to ensure that the roller can rotate smoothly. The bearings are located at both ends of the shaft to reduce friction and support the rotational movement of the shaft.

[0084] The drive system includes a motor, a reducer and a transmission device. The motor provides the power source and is an AC servo motor or a stepper motor. The speed is precisely controlled to reduce the motor output speed and match the required traction speed. The transmission device transmits the power to the traction roller.

[0085] It also includes a tension control system, which includes a tension sensor and a controller. The tension sensor monitors the tension changes of the film during the traction process in real time. The controller adjusts the motor speed or applies additional tension according to the sensor feedback to maintain a constant tension level.

[0086] It also includes a guide roller and a clamping device. The guide roller helps guide the film into between the traction rollers to ensure that it is straight and wrinkle-free. The clamping device is an adjustable clamping wheel for increasing the contact pressure to ensure a good fit between the film and the roller surface.

[0087] During operation, the traction roller pulls the cooled bubble tube downward from the upper air ring, and the film is stretched longitudinally by the set traction ratio. This stretching not only helps to improve the mechanical strength of the film, but also improves its optical properties. The thickness of the film can be adjusted by precisely controlling the speed of the traction roller. A higher traction speed will result in a greater stretching, thus producing a thinner but stronger film. Conversely, a thicker and softer film will be obtained. The tension control system ensures that the film maintains appropriate tension throughout the traction process to avoid rupture due to over-tightening or wrinkling due to relaxation.

[0088] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A fully biodegradable mulch film, characterized in that: The invention comprises the following raw materials in parts by weight: 15 parts of polylactic acid, 70 parts of polybutylene adipate / terephthalate, 10 parts of modified starch, 2 parts of talc, 2 parts of chain extender, 0.2 parts of antioxidant, 0.2 parts of antioxidant, 0.2 parts of ultraviolet absorber, and 0.4 parts of light stabilizer.

2. A method for preparing a fully biodegradable mulch film, applicable to the fully biodegradable mulch film according to claim 1, characterized in that: The following steps are involved: S1. Put the well-proportioned polylactic acid, polybutylene adipate / terephthalate, modified starch, talcum powder, chain extender, antioxidant, anti-aging agent, ultraviolet absorber and light stabilizer into a high-speed mixer, and mix the above materials in the high-speed mixer; S2, putting the mixed raw materials into a granulator for heating and granulation; S3, putting the prepared plastic particles into a film blowing device, the film blowing device heats and melts the plastic particles, the melted plastic is extruded through an annular die, and the extruded plastic bubble tube is expanded by a film blowing molding structure; S4, using a traction roller to pull the cooled bubble tube downward, and then rolling and cutting it into a ground film; S5. During the preparation of the ground film, the film blowing ratio and the pulling ratio are adjusted according to the width and thickness of the ground film.

3. The method for preparing a fully biodegradable mulch film according to claim 2, characterized in that: The high-speed mixer in S1 mixes the materials for 50 minutes.

4. The method for preparing a fully biodegradable mulch film according to claim 3, characterized in that: The heating temperature in S2 is 180-200°C.

5. The method for preparing a fully biodegradable mulch film according to claim 4, characterized in that: In the process of film blowing in S3, the film blowing temperature is 145-150° C., and the blowing ratio is 5. The blowing ratio is the ratio of the film bubble diameter to the die diameter, reflecting the degree of film bubble inflation.

6. The method for preparing a fully biodegradable mulch film according to claim 5, characterized in that: Use cooling equipment to cool down and shape the expanded bubble tube in S3.

7. The method for preparing a fully biodegradable mulch film according to claim 6, characterized in that: The drawing ratio during drawing in S4 is 7, which means that the drawing speed is 7 times the extrusion speed. This high speed is conducive to the longitudinal stretching of the film, thereby improving its mechanical properties.

8. The method for preparing a fully biodegradable mulch film according to claim 7, characterized in that: The calculation formula of the blow-up ratio is: d1 is the inner diameter of the annular die at the extruder die outlet; d2 is the maximum diameter of the membrane bubble.

9. The method for preparing a fully biodegradable mulch film according to claim 8, characterized in that: The calculation formula of the traction ratio is: B is the traction ratio; U is the traction speed; U0 is the extrusion speed.

10. The method for preparing a fully biodegradable mulch film according to claim 9, characterized in that: The following steps are also included: S6. When a black ground film is required, 5% of carbon black material is added to the raw materials, and the carbon black is mixed with plastic particles to finally prepare a black ground film; S7. When it is necessary to adjust the degradation cycle of the mulch film according to the growth cycle of crops, the proportion of antioxidants, antioxidants, UV absorbers and light stabilizers in the material is adjusted. When it is necessary to accelerate the degradation, the proportion of antioxidants, antioxidants, UV absorbers and light stabilizers is reduced. When it is necessary to slow down the degradation, the proportion of antioxidants, antioxidants, UV absorbers and light stabilizers is increased.

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