KR102271630B1 - A method for manufacturing agricultural covering material - Google Patents

Abstract

One aspect of the present invention comprises the steps of: (a) preparing a composition comprising a polyolefin-based resin and carbon nanotubes; (b) mixing a polyolefin-based resin with the product of step (a); and (c) manufacturing the agricultural coating material by molding the product of step (b), wherein the content of the carbon nanotubes in the composition of step (a) is 5 to 30% by weight, of the agricultural coating material A manufacturing method is provided.

Description

A method of manufacturing a covering material for agriculture {A METHOD FOR MANUFACTURING AGRICULTURAL COVERING MATERIAL}

The present invention relates to a method for manufacturing a covering material for agriculture.

Mulching farming method is to block the growth of weeds by covering the top surface of the soil with materials that cover the surface of the soil, such as rice straw, barley straw, grass, film, etc., when growing crops, prevent diseases and pests, and reduce the use of pesticides. It refers to an agricultural method performed for the purpose of preventing soil erosion and maintaining soil moisture.

In general, the mulching farming method using a film is the most widely used, and the mulching film can be divided into a transparent film, a black film, and a green film. The transparent film has excellent geothermal synergistic effect, the weed suppression effect is not large, and the black film has excellent weed suppression effect unlike the transparent film, but the geothermal synergistic effect is insignificant. As described above, the green film developed by supplementing the problems of the transparent film and the black film is excellent in the effect of increasing temperature and suppressing weeds.

The green film is a film manufactured by adjusting the light transmittance of the film to about 20% by adding a green pigment during the manufacturing process. As described above, when the light transmittance of the film is adjusted to about 20%, an appropriate level of temperature increase effect can be realized and the occurrence of weeds can be suppressed. However, in the case of a green film, the added green pigment is easily decomposed by sunlight, which causes deterioration of mechanical properties such as tearing of the film during use. In order to solve this problem, an excessive amount of a stabilizer is added, but as the exposure time to sunlight increases, the effect of preventing deterioration of mechanical properties becomes insignificant, and as the stabilizer is added, environmental problems and the cost of the film increase. Occurs.

Therefore, there is a demand for the development of a method for producing a coating material for agricultural use with excellent mechanical properties while realizing light transmittance that can maximize crop productivity by replacing green pigments.

The present invention is to solve the problems of the prior art described above, an object of the present invention is to provide a method of manufacturing a covering material for agricultural use excellent in light transmittance and mechanical properties, including carbon nanotubes.

One aspect of the present invention comprises the steps of: (a) preparing a composition comprising a polyolefin-based resin and carbon nanotubes; (b) mixing a polyolefin-based resin with the product of step (a); and (c) manufacturing the agricultural coating material by molding the product of step (b), wherein the content of the carbon nanotubes in the composition of step (a) is 5 to 30% by weight, of the agricultural coating material A manufacturing method is provided.

In one embodiment, the polyolefin-based resin is one selected from the group consisting of polypropylene, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene vinyl acetate, ethylene butyl acrylate, ethylene ethyl acrylate, and combinations of two or more thereof. can

In one embodiment, the carbon nanotube may be a multi-walled carbon nanotube having 20 or less walls.

In one embodiment, the carbon nanotubes may be bundled carbon nanotubes composed of a plurality of carbon nanotubes.

In one embodiment, the carbon purity of the carbon nanotubes may be 95% or more.

In one embodiment,

The content of the carbon nanotubes in the product of step (b) may be 0.35 to 0.65 wt%.

In one embodiment, the step (a) may be performed in a twin-screw extruder of 200 ~ 250 ℃.

In one embodiment, the step (b) may be performed in a twin-screw extruder of 180 ~ 250 ℃.

In one embodiment, the step (c) may be performed in a single-screw extruder of 180 ~ 250 ℃.

In one embodiment, the agricultural covering material of step (c) may be manufactured by blow molding.

In one embodiment, the agricultural covering material may have a light transmittance of 15 to 25%.

In one embodiment, the thickness of the agricultural covering material may be 0.02 ~ 0.04 mm.

The method of manufacturing an agricultural coating material according to an aspect of the present invention comprises the step of preparing a composition comprising a polyolefin-based resin and carbon nanotubes, and diluting the composition with a polyolefin-based resin and molding the composition in a film form. Since the transmittance can be adjusted to around 20%, the effect of increasing the temperature and suppressing weeds during crop cultivation can be improved. In addition, the agricultural covering material of the present invention can improve the cultivation efficiency of crops by stably maintaining mechanical properties such as tensile strength and elongation even when exposed to sunlight for a long time.

It should be understood that the effects of the present invention are not limited to the above-described effects, and include all effects that can be inferred from the configuration of the invention described in the detailed description or claims of the present invention.

1 is a method of manufacturing a covering material for agriculture according to an embodiment of the present invention.

Hereinafter, the present invention will be described with reference to the accompanying drawings. However, the present invention may be embodied in several different forms, and thus is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the specification, when a part is "connected" with another part, this includes not only the case where it is "directly connected" but also the case where it is "indirectly connected" with another member interposed therebetween. . In addition, when a part "includes" a certain component, this means that other components may be further provided without excluding other components unless otherwise stated.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Referring to Figure 1, an aspect of the present invention comprises the steps of (a) preparing a composition comprising a polyolefin-based resin and carbon nanotubes; (b) mixing a polyolefin-based resin with the product of step (a); and (c) manufacturing the agricultural coating material by molding the product of step (b), wherein the content of the carbon nanotubes in the composition of step (a) is 5 to 30% by weight, of the agricultural coating material A manufacturing method is provided.

In general, agricultural coating materials are manufactured in the form of a film and can be divided into a transparent film, a black film, and a green film according to the color. The transparent film has an excellent geothermal synergistic effect, but the weed suppression effect is insignificant.

In order to solve such a problem, the green film manufactured including the green pigment has the light transmittance adjusted to an appropriate range, so that the temperature increase effect and the weed suppression effect can be realized at the same time. However, the green pigment added during the manufacture of the green film decreases the stability as the exposure time to sunlight increases and is easy to decompose. Accordingly, the mechanical properties of the green film may decrease and tearing may occur during use. When other stabilizers for improving the stability of the pigment are added in excess, the cost of the film may increase.

According to an embodiment of the present invention, it is possible to manufacture a covering material for agriculture comprising a polyolefin-based resin and carbon nanotubes.

First, in step (a), a composition including a polyolefin-based resin and carbon nanotubes may be prepared.

The polyolefin-based resin may be one selected from the group consisting of polypropylene, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene vinyl acetate, ethylene butyl acrylate, ethylene ethyl acrylate, and a combination of two or more thereof, preferably It may be low-density polyethylene, but is not limited thereto.

The carbon nanotube is a material in which one carbon is combined with another carbon atom in a hexagonal honeycomb pattern by rolling carbon atoms in one dimension to form a tube, and the diameter of the tube is a material of an extremely small area at the nanometer level. The carbon nanotube has excellent mechanical properties, electrical selectivity, high-efficiency hydrogen storage, and the like.

Methods for synthesizing the carbon nanotubes include arc-discharge, pyrolysis, laser vaporization, plasma chemical vapor deposition, and thermal chemical vapor deposition. ), but all carbon nanotubes manufactured without limitation in the synthesis method may be used.

The carbon nanotube is a hollow tube in which a plurality of single wall carbon nanotube, double wall carbon nanotube, and truncated graphene are stacked according to the number of walls. of carbon nanofibers (cup-stacked carbon nanofiber), and may be one selected from the group consisting of a mixture of two or more thereof, and preferably, may be a multi-walled carbon nanotube having excellent manufacturing easiness and economy, and more Preferably, it may be a multi-walled carbon nanotube having 20 or less walls.

In addition, the carbon nanotubes may be bundled carbon nanotubes composed of a plurality of carbon nanotubes. The bundled carbon nanotubes have an average outer diameter of 5 to 30 μm, and a plurality of single-stranded multi-walled carbon nanotubes having an average inner diameter of 40% or more of the average outer diameter, preferably 40 to 90%, are mutually aggregated into a bundle It can exist in the form of a bundle. The outer diameter means the diameter of the carbon nanotube cross-section including the graphite layer constituting the wall of the carbon nanotube, and the inner diameter means the diameter of the hollow cross-section excluding the graphite layer. In addition, the carbon purity of the carbon nanotubes may be 95% or more. When the carbon purity of the carbon nanotube is 95% or more, when the light transmittance of the agricultural covering material is controlled to a required level, the mechanical properties are excellent and a thinner agricultural covering material can be manufactured.

As used herein, the term “bundle” refers to a bundle or rope form in which a plurality of carbon nanotubes are arranged side by side or entangled with each other. When present, it is also referred to as “non-bundled”.

The content of carbon nanotubes in the product of step (a) produced by mixing the polyolefin-based resin and carbon nanotubes may be 5 to 30% by weight. If the content of the carbon nanotube is less than 5% by weight, the light transmittance is increased more than necessary, so that the weed suppression effect of the agricultural covering may be reduced, and if it exceeds 30% by weight, the dispersibility of the carbon nanotube is poor and the agricultural covering uniformity and mechanical properties may be deteriorated.

On the other hand, the step (a) may be performed in a twin-screw extruder of 200 ~ 250 ℃. In general, the kneading process using an extruder may be performed in a single screw extruder or a twin screw extruder. As used herein, the terms "single-screw extruder" and "twin-screw extruder" refer to a screw-type extruder having one and two screws, respectively. In order to suppress the damage of the carbon nanotubes in step (a), it is preferable to use a twin-screw extruder, and the polyolefin-based resin is introduced into the extruder side, and the carbon nanotubes are side feeder using a side feeder. It is preferable to supply and knead.

The temperature for performing step (a) may be 200 ~ 250 ℃, if it is less than 200 ℃, the dispersibility of the carbon nanotubes is lowered, the light transmittance of the final product may rise more than necessary, and if it exceeds 250 ℃, the The polyolefin-based resin may be degraded.

On the other hand, the length: diameter ratio of the extruder may be 25 to 50: 1. The "length:diameter ratio" of the extruder means the ratio of the length (L) to the diameter (diameter, D) of the screw, which is one of the factors determining the extrusion performance of the extruder. In general, the larger the value of the “length:diameter ratio” of the screw, the better the kneading effect and product quality, and the reduction of the deviation of the extrusion amount. However, depending on the type and nature of the material injected into the extruder, the length:diameter ratio may vary. can be adjusted differently.

If the ratio of the length of the extruder to the diameter is less than 25: 1, the kneading effect of the required level cannot be realized, and if it exceeds 50: 1, the size of the extruder and the capacity of the driving motor are affected, thereby reducing the process efficiency.

In addition, the driving speed of the extruder may be 50 to 500 rpm. The driving speed of the extruder means the rotation speed of the screw provided in the extruder, and if the driving speed of the extruder is less than 50 rpm, the required level of kneading effect cannot be realized, and if it exceeds 500 rpm, the rotation of the motor compared to the number of rotations of the screw Due to the remarkably large number, excessive load may be applied to the motor and reduction gear to cause damage.

On the other hand, the product of step (a) may be prepared in the form of a masterbatch, it may be prepared including a high content of carbon nanotubes. In general, in the case of directly mixing a powdery functional material for imparting a special function to the resin, accurate mixing may be difficult, and physical properties may be deteriorated due to poor kneading and dispersion. Therefore, if the masterbatch is used, the mixing ratio can be precisely adjusted, the dispersibility can be improved, and the workability can be improved by preventing the scattering of the powder material during the operation.

The step (b) may include mixing the polyolefin-based resin with the product of (a). The polyolefin-based resin of step (b) may be the same as or different from the polyolefin-based resin of step (a), and the type and effect thereof are as described above.

In step (b), by mixing the polyolefin-based resin with the product of (a), it may include a step of diluting the high content of carbon nanotubes contained in the product of (a). As described above, when a functional material is directly mixed to impart a special function to the resin, its physical properties may be deteriorated due to accurate mixing, kneading, and poor dispersion. In the present invention, (a) polyolefin-based resin and carbon nanotube After preparing the masterbatch by first blending (b) the masterbatch by further blending a polyolefin-based resin to dilute the masterbatch, it is possible to prepare a product with a high concentration compared to processability, dispersibility and content.

Accordingly, the content of the carbon nanotubes in the product of step (b) may be 0.35 to 0.65 wt%, and if the content of the carbon nanotubes is less than 0.35 wt%, the light transmittance of the agricultural coating material as a final product is excessively increased If it is more than 0.65% by weight, the light transmittance may be lower than the appropriate range.

The mixing in step (b) may be a melt compounding method, an in-situ polymerization method, or a solution mixing method, but preferably using an extruder under high temperature and high shear force. Since carbon nanotubes can be uniformly dispersed in the resin, it may be a melt mixing method capable of increasing the capacity and reducing manufacturing costs.

In step (c), the product of step (b) may be molded to prepare an agricultural covering material, and the molding may be blow molding.

In one embodiment, the agricultural covering material of step (c) may be manufactured by blow molding, preferably by film blowing. The product of step (b) is put into the extruder and extruded in a cylindrical shape using a ring die installed at the end of the extruder, and air or gas is injected therein to expand it to form a thin film.

The step (b) may be performed in a twin-screw extruder at 180 to 250° C., and the step (c) may be performed in a single-screw extruder at 180 to 250° C. The twin screw extruder and the single screw extruder are as described above. same. The temperature for performing the steps (b) and (c) may be 180 ~ 250 ℃, if the temperature is less than 180 ℃ the dispersibility of the carbon nanotube is lowered, the light transmittance of the agricultural covering material rises more than necessary or for agriculture The uniformity of the covering material may be reduced, and if it exceeds 250° C., the agricultural covering material prepared by excessively softening the product of step (b) may be excessively contracted, or mechanical properties may be reduced.

When steps (a) and (b) are performed in a twin-screw extruder, damage to the carbon nanotubes is suppressed and a product in which the carbon nanotubes are uniformly dispersed can be prepared. When steps (a) and (b) are performed in a twin-screw extruder, even if the step (c) is performed in a single-screw extruder, damage to the carbon nanotubes can be minimized.

The agricultural covering material prepared according to the steps (a) to (c) may have a light transmittance of 15 to 25%. The light transmittance should be adjusted to about 20% in order for the agricultural covering material to improve productivity by simultaneously implementing the geothermal increase effect and the weed suppression effect in crop cultivation. Agricultural coating material of the present invention by including carbon nanotubes in the polyolefin-based resin, it is possible to adjust the light transmittance, preferably the light transmittance may be 15 to 25%. If the light transmittance is less than 15%, the geothermal synergistic effect may be reduced, and if it exceeds 25%, the weed suppression effect may be reduced.

On the other hand, the thickness of the agricultural covering material may be 0.02 ~ 0.04 mm. If the thickness of the agricultural covering material is less than 0.02 mm, mechanical properties may be reduced, and if it exceeds 0.04 mm, the production cost of the agricultural covering material may increase.

Hereinafter, embodiments of the present invention will be described in detail.

Example 1

Multi-walled carbon nanotubes (MWCNT) were put into the side feeder of the twin-screw extruder, and the low-density polyethylene resin was put into the main hopper at a feed rate of 15 kg/hr, followed by a kneading speed of 350 rpm and a processing temperature of 200 A product having a carbon nanotube content of 20% by weight was prepared by melt-kneading under °C.

The prepared product and the low-density polyethylene resin were put into a twin-screw extruder at an input rate of 15 kg/hr, and melt-kneaded at a kneading rate of 350 rpm and a processing temperature of 200° C. to prepare a product having a carbon nanotube content of 0.5% by weight.

The prepared product was put into a single screw extruder to prepare a covering material for agriculture of 0.03 mm.

Example 2

Multi-walled carbon nanotubes (MWCNT) were put into the side feeder of the twin-screw extruder, and the low-density polyethylene resin was put into the main hopper at a feed rate of 15 kg/hr, followed by a kneading speed of 300 rpm and a processing temperature of 200 A product having a carbon nanotube content of 15% by weight was prepared by melt-kneading at ℃.

The prepared product and the low-density polyethylene resin were put into a twin-screw extruder at an input rate of 15 kg/hr, and melt-kneaded at a kneading rate of 300 rpm and a processing temperature of 200° C. to prepare a product having a carbon nanotube content of 0.4% by weight.

The prepared product was put into a single-screw extruder to prepare an agricultural covering material of 0.02 mm.

Example 3

Multi-walled carbon nanotubes (MWCNT) were put into the side feeder of the twin-screw extruder, and the low-density polyethylene resin was put into the main hopper at a feed rate of 15 kg/hr, followed by a kneading speed of 350 rpm and a processing temperature of 200 A product having a carbon nanotube content of 25% by weight was prepared by melt-kneading under °C.

The prepared product and the low-density polyethylene resin were put into a twin-screw extruder at an input rate of 15 kg/hr, and melt-kneaded at a kneading speed of 350 rpm and a processing temperature of 200° C. to prepare a product having a carbon nanotube content of 0.6% by weight.

The prepared product was put into a single-screw extruder to prepare a covering material for agriculture of 0.04 mm.

Comparative Example 1

Multi-walled carbon nanotubes (MWCNT) were put into the side feeder of the twin-screw extruder, and the low-density polyethylene resin was put into the main hopper at a feed rate of 15 kg/hr, followed by a kneading speed of 350 rpm and a processing temperature of 200 A product having a carbon nanotube content of 5% by weight was prepared by melt-kneading under °C.

The prepared product and the low-density polyethylene resin were put into a twin-screw extruder at an input rate of 15 kg/hr, and melt-kneaded at a kneading speed of 350 rpm and a processing temperature of 200° C. to prepare a product having a carbon nanotube content of 0.2% by weight.

The prepared product was put into a single screw extruder to prepare a covering material for agriculture of 0.03 mm.

Comparative Example 2

Multi-walled carbon nanotubes (MWCNT) were put into the side feeder of the twin-screw extruder, and low-density polyethylene resin was put into the main hopper at a feed rate of 15 kg/hr, followed by a kneading speed of 400 rpm and a processing temperature of 200 A product having a carbon nanotube content of 50% by weight was prepared by melt-kneading under °C.

The prepared product and the low-density polyethylene resin were put into a twin-screw extruder at an input rate of 15 kg/hr, and melt-kneaded at a kneading speed of 400 rpm and a processing temperature of 200° C. to prepare a product having a carbon nanotube content of 0.8% by weight.

The prepared product was put into a single-screw extruder to prepare a covering material for agriculture of 0.04 mm.

Comparative Example 3

Multi-walled carbon nanotubes (MWCNT) were put into the side feeder of the twin-screw extruder, and low-density polyethylene resin was put into the main hopper at a feed rate of 15 kg/hr, followed by a kneading speed of 400 rpm and a processing temperature of 200 A product having a carbon nanotube content of 0.5% by weight was prepared by melt-kneading at °C.

The prepared product was put into a single screw extruder to prepare a covering material for agriculture of 0.03 mm.

Comparative Example 4

An agricultural coating material was prepared in the same manner as in Comparative Example 3, except that the carbon nanotube was replaced with a green pigment.

Comparative Example 5

An agricultural covering was prepared in the same manner as in Example 1, except that the thickness of the agricultural covering was adjusted to 0.01 mm.

Comparative Example 6

An agricultural covering was prepared in the same manner as in Example 1, except that the thickness of the agricultural covering was adjusted to 0.1 mm.

Experimental Example 1: Evaluation of light transmittance of agricultural coverings

In order to evaluate the light transmittance for the agricultural coating materials prepared in Examples and Comparative Examples, it was measured with a light transmittance meter (TC1800 visible light transmittance meter), and the results are shown in Table 1 below.

division CNT content (wt%) Film thickness (mm) Light transmittance (%) Example 1 0.5 0.03 19.7 Example 2 0.4 0.02 18.5 Example 3 0.6 0.04 20.3 Comparative Example 1 0.2 0.03 31.5 Comparative Example 2 0.8 0.04 5.2 Comparative Example 3 0.5 0.03 12.7 Comparative Example 4 - 0.03 17.4 Comparative Example 5 0.5 0.01 18.7 Comparative Example 6 0.5 0.1 10.8

Referring to Table 1 above, the agricultural covering material prepared according to the example had a light transmittance measured in the range of 18 to 21%, indicating the light transmittance in the optimal range, and when applied to the cultivation of crops as a final product, the geothermal synergistic effect and It can be expected that the weed suppression effect can be realized at the same time, so that the productivity of crops can be improved. On the other hand, when the content of carbon nanotubes is insignificant (Comparative Example 1) or excessively added (Comparative Example 2), light It was found that the transmittance was excessively high or too low, out of the optimal range, and was unsuitable for application to agricultural cladding, and also the primary mixing process of step (a) and the secondary mixing process of step (b) were omitted, that is, masterbatch In the case of manufacturing an agricultural covering material by omitting the manufacturing process (Comparative Example 3), the dispersibility of carbon nanotubes was lowered and the light transmittance was lower than the optimum range, and the green pigment used in the production of the conventional agricultural covering material was added. When prepared (Comparative Example 4), it did not reach the level of carbon nanotubes, but exhibited a light transmittance of almost the same level.

In addition, when the thickness of the agricultural covering material is excessively thick (Comparative Example 6), sunlight is blocked more than necessary, indicating that the light transmittance is poor.

Experimental Example 2: Evaluation of mechanical properties of agricultural coverings

In order to evaluate the mechanical properties of agricultural coverings according to Examples and Comparative Examples of the present invention, tensile strength and elongation were measured with a UTM measuring device. In order to measure the change in physical properties over time, after the initial measurement, exposure to sunlight for 250 h was re-measured, and the results are shown in Table 2 below.

Examples 1 to 3, Comparative Example 4 using a conventional green pigment, and Comparative Example 5 having a film thickness of 0.01 mm were used as test subjects.

division Tensile strength (N/㎠) Elongation (%) Early Sun exposure 250h Early Sun exposure 250h Example 1 33 24 620 452 Example 2 30 23 613 449 Example 3 34 24 622 454 Comparative Example 4 27 15 341 260 Comparative Example 5 20 15 320 280

Referring to Table 2, the initial tensile strength of Examples 1 to 3 and Comparative Example 4 was 20 to 34 N/cm 2 , respectively, indicating similar strength, but the strength measured again after exposure to sunlight was compared with Examples 1 to 3 Example 4 showed a significant difference, and the re-measured strength of Examples 1 to 3 was remarkably superior to those of Comparative Examples 4 and 5. As a result of the initial measurement and re-measurement of the elongation, it was shown that the Example was excellent. In particular, Comparative Example 4 using the green pigment showed that mechanical properties were remarkably deteriorated with time and exposure to sunlight. In the case of Comparative Example 5 including carbon nanotubes but the thickness of the covering material was thin, the thickness itself was confirmed as a factor of deterioration of physical properties rather than the difference in sunlight exposure. Those of ordinary skill in the art will understand that the present invention can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. For example, each component described as a single type may be implemented in a dispersed form, and likewise components described as distributed may be implemented in a combined form.

The scope of the present invention is indicated by the following claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention.

Claims (12)

(a) preparing a composition comprising a polyolefin-based resin and carbon nanotubes;
(b) mixing a polyolefin-based resin with the product of step (a); and
(c) forming the product of step (b) to prepare an agricultural covering;
The content of the carbon nanotubes in the composition of step (a) is 5 to 30% by weight,
The content of the carbon nanotubes in the product of step (b) is 0.35 to 0.65 wt%,
The agricultural covering material has a light transmittance of 15 to 25% in the visible light region,
The thickness of the agricultural covering material is 0.02 ~ 0.04 mm,
The initial tensile strength of the agricultural covering material is 30N/cm2 or more,
The carbon nanotube is a bundled carbon nanotube composed of a plurality of carbon nanotubes having 20 or less walls, and has an average outer diameter of 5 to 30 μm, an average inner diameter of 40% or more of the average outer diameter, and a carbon purity 95% or more, the manufacturing method of the covering material for agriculture. According to claim 1,
The polyolefin-based resin is one selected from the group consisting of polypropylene, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene vinyl acetate, ethylene butyl acrylate, ethylene ethyl acrylate, and a combination of two or more thereof. . delete delete delete delete According to claim 1,
The step (a) is carried out in a twin-screw extruder of 200 ~ 250 ℃, a method of manufacturing a covering material for agriculture. According to claim 1,
The step (b) is carried out in a twin-screw extruder of 180 ~ 250 ℃, the manufacturing method of the covering material for agriculture. According to claim 1,
The step (c) is carried out in a single screw extruder of 180 ~ 250 ℃, the manufacturing method of the covering material for agriculture. According to claim 1,
The agricultural covering material of step (c) is manufactured by blow molding, the method of manufacturing an agricultural covering material. delete delete

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