JP3726127B2 - Agricultural mulching film - Google Patents

Description

表１の結果に示した通り、ｌｏｏｆａｈ構造からなる本発明の実施例１の多孔性フィルムの方が、比較例１の多孔性フィルムと比較して膜厚が約１．７倍厚いのにもかかわらず、通気性、透湿性に優れ、機械的強度も高いものであることがわかる。
【００５４】
【発明の効果】
本発明の農業用マルチングフィルムはｌｏｏｆａｈ状構造をとることによって高い通気性、透湿性を得ることができると共に、機械的強度を向上することができる。
【図面の簡単な説明】
【図１】実施例１の農業用マルチングフィルムの電子顕微鏡写真[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an agricultural mulching film. More specifically, the present invention relates to a mulching film having an effect of preventing the weeds from growing without mechanically forming vent holes, air permeability, and moisture permeability.
[0002]
[Prior art]
Agricultural mulching film is intended to prevent weeds from growing by covering the soil around the hole for planting a crop or the trunk of a fruit tree. Conventional agricultural mulching film is made of black thermoplastic resin, so it has good light-shielding properties, but it has poor air permeability and moisture permeability. There was a problem of rotting.
[0003]
In order to solve such a problem, for example, as disclosed in Japanese Utility Model Laid-Open No. 49-95129, an agricultural mulching film having a hole for planting a crop and a large number of pores around the hole is known. It is.
[0004]
[Problems to be solved by the invention]
The mulching film described in Japanese Utility Model Laid-Open No. 49-95129 is improved in air permeability and moisture permeability by preventing formation of mud and corrosion of crops by providing pores using a mechanical perforation means after film formation. It has been done.
[0005]
However, although it is fine, it is mechanically formed and has a hole that can be visually checked, so rainwater enters and sunlight also reaches the soil surface through this hole, preventing weeds from breeding. The effect was not enough.
[0006]
Further, in an orchard or the like, an operator may lay on the ground and walk on the ground, and the mulching film is also required to have a strength that does not break in such a case. However, the conventional agricultural mulching film is made of a general thermoplastic resin film, and the strength itself is not so high. Further, since the hole has a mechanically formed hole, this hole is cracked by stress. As a result, the overall strength was not sufficient.
[0007]
The object of the present invention is to have water resistance capable of preventing intrusion of rainwater and to have uniform breathability and moisture permeability as a whole without mechanically providing pores, and can prevent crops from being stuffy or corroded. Another object is to provide an agricultural mulching film having sufficient strength.
[0008]
[Means for Solving the Problems]
The agricultural mulching film of the present invention is made of a film formed of a thermoplastic resin, and is formed of a three-dimensional network composed of stem fibrils extending in one direction of the film and branch fibrils connecting the stem fibrils. The branch fibrils are formed at a density higher than that of the trunk fibrils.
[0009]
The agricultural mulching film having such a structure has water resistance capable of preventing rainwater intrusion, uniform air permeability and moisture permeability capable of preventing stuffiness and corrosion of crops, and sufficient strength. Further, the agricultural mulching film having such a configuration is opaque as a whole and does not have mechanically formed through-holes, and therefore does not transmit light enough to grow weeds.
[0010]
Moreover, when the formation density of the branch fibril is higher than the formation density of the trunk fibril, an agricultural mulching film having an excellent balance of mechanical strength between the maximum heat shrinkage direction and the direction orthogonal thereto is obtained. Branch fibrils and trunk fibrils do not necessarily have to extend linearly. Further, the direction in which the trunk fibril extends can be confirmed by an electron micrograph and is determined by cutting the film, and is not particularly specified. “Extending in one direction” does not require that all the trunk fibrils extend in a specific direction linearly in parallel, and meanders in a specific direction with a certain degree of variation while meandering. Means that
[0011]
The formation density of each of the branch fibrils and the trunk fibrils is the number of fibrils existing in an area of 1 μm ² of the film, and is determined by observing the film surface with a scanning electron microscope. Specifically, the number of fibrils present in 5 × 5 μm is measured and determined. The hole structure of the agricultural mulching film of the present invention is referred to as a lofah structure.
[0012]
In the above-described agricultural mulching film, the average pore diameter d (μm) of the micropores determined by the bubble point method (ASTM F316-86) and the average of the micropores determined by the mercury intrusion method (JIS K1150) The pore radius r (μm) is the following formula 1.2 ≦ 2r / d ≦ 1.7
It is preferable that
[0013]
An agricultural mulching film having a value of 2r / d within the above range is particularly excellent in the balance of air permeability, moisture permeability and strength. In view of the strength of the film, the value of 2r / d is preferably 1.65 or less, and more preferably 1.60 or less.
[0014]
The film thickness Y of the agricultural mulching film comprising the porous film of the present invention is usually 1 to 200 μm, preferably 5 to 50 μm, more preferably 5 to 30 μm. If it is too thick, the air permeability and moisture permeability deteriorate, and if it is too thin, the physical strength becomes insufficient.
[0015]
In the above-described agricultural mulching film, the branch fibrils are preferably oriented in the maximum heat shrinkage direction of the film.
[0016]
When the branch fibrils are oriented in the maximum heat shrink direction of the film, the mechanical strength in the maximum heat shrink direction is increased.
[0017]
In the agricultural mulching film of the present invention, the fine pores preferably have an average pore diameter d of 0.06 to 3 μm. The agricultural mulching film of the present invention preferably has a Gurley value of 10 to 1000 seconds / 100 cc per 25 μm thickness. Moreover, it is preferable that the porosity is 40 to 80%.
[0018]
If the Gurley value is less than 10 seconds / 100 cc, the breathability or moisture permeability may be too low and the crop may be stuffy. If it exceeds 1000 seconds / 100 cc, rainwater tends to enter.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
The thermoplastic resin which is the main raw material of the porous film constituting the agricultural mulching film of the present invention is a homopolymer of olefins such as ethylene, propylene, butene, hexene or a copolymer of two or more olefins. Polyolefin resins, butadiene-styrene copolymers, polystyrene, styrene resins such as styrene-butadiene-styrene copolymers, styrene-isoprene-styrene copolymers, vinyl chloride resins, polyvinyl fluoride, polyvinylidene fluoride, etc. Vinyl fluoride resins, polyamide resins such as 6-nylon, 6,6-nylon, 12-nylon, saturated polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate, polyphenylene oxide, polyacetal, polyphenyle Sulfide, silicone resin, thermoplastic polyurethane resin, polyether ether ketone, polyetherimide, thermoplastic elastomers, and their crosslinked products, and the like.
[0020]
The thermoplastic resin constituting the agricultural mulching film of the present invention may be one type or a mixture of two or more types.
[0021]
As the thermoplastic resin, a polyolefin-based resin is more preferable because it is excellent in chemical resistance and does not generate dioxin even when incinerated.
[0022]
Such a polyolefin resin is mainly composed of a polymer of one kind of olefin or a copolymer of two or more kinds of olefins. Examples of the olefin that is a raw material for the polyolefin resin include ethylene, propylene, butene, and hexene. Specific examples of the polyolefin resin include polyethylene resins such as low density polyethylene, linear polyethylene (ethylene-α-olefin copolymer) and high density polyethylene, polypropylene resins such as polypropylene and ethylene-propylene copolymer, Examples thereof include poly (4-methylpentene-1), poly (butene-1), and ethylene-vinyl acetate copolymer.
[0023]
In particular, an agricultural mulching film in which a polyolefin resin contains a long molecular chain length polyolefin having a molecular chain length of 2850 nm or more is excellent in strength, and thus the film thickness can be reduced while maintaining mechanical strength. For this reason, air permeability and moisture permeability can be further improved, and an agricultural mulching film exhibiting the effects of the present invention can be obtained. From the viewpoint of the strength of the agricultural mulching film, the polyolefin resin preferably contains 1% by weight or more of a long molecular chain length polyolefin having a molecular chain length of 2850 nm or more, and preferably contains 10% by weight or more. More preferably, it is more preferably 20% by weight or more.
[0024]
The molecular chain length, weight average molecular chain length, molecular weight and weight average molecular weight of polyolefin are measured by GPC (gel permeation chromatography), and the mixing ratio (% by weight) of polyolefin in the specific molecular chain length range or specific molecular weight range is GPC. It can be obtained by integration of a molecular weight distribution curve obtained by measurement.
[0025]
Here, the molecular chain length of the polyolefin is a molecular chain length in terms of polystyrene measured by GPC (gel permeation chromatography), which will be described later, and more specifically is a parameter determined by the following procedure.
[0026]
That is, as a mobile phase for GPC measurement, a solvent capable of dissolving both an unknown sample to be measured and standard polystyrene having a known molecular weight is used. First, GPC measurement of a plurality of types of standard polystyrenes having different molecular weights is performed to determine the retention time of each standard polystyrene. The molecular chain length of each standard polystyrene is determined using the polystyrene Q factor, and thereby the molecular chain length of each standard polystyrene and the corresponding retention time are known. The molecular weight, molecular chain length, and Q factor of standard polystyrene have the following relationship.
[0027]
Molecular weight = molecular chain length × Q factor Next, GPC measurement of an unknown sample is performed to obtain a retention time-eluting component amount curve. In the standard polystyrene GPC measurement, when the molecular chain length of the standard polystyrene that was the holding time T is L, the “polystyrene converted molecular chain length” of the component that was the holding time T in the GPC measurement of the unknown sample is L. To do. Using this relationship, the polystyrene-reduced molecular chain length distribution of the unknown sample (relation between the polystyrene-reduced molecular chain length and the eluted component amount) is determined from the retention time-eluted component amount curve of the unknown sample.
[0028]
The agricultural mulching film of the present invention may contain a filler such as an inorganic filler or an organic filler.
[0029]
Furthermore, the agricultural mulching film of the present invention can be used to color stretching aids, stabilizers, antioxidants, ultraviolet absorbers, flame retardants, pigments, etc., such as fatty acid esters and low molecular weight polyolefin resins, as long as they do not interfere with the purpose of the present invention. You may contain additives, such as an agent.
[0030]
In the agricultural mulching film of the present invention, for example, when a polyolefin resin containing a long molecular chain length polyolefin having a molecular chain length of 2850 nm or more is used as a raw material, a resin raw material and an inorganic compound and / or a fine resin powder are strong. It can be manufactured by kneading using a twin-screw kneader designed as a segment so as to be kneaded, forming a film by a roll rolling method, and stretching the obtained raw film by a stretching machine.
[0031]
As an apparatus used for stretching, a known stretching apparatus can be used without limitation, and a clip tenter is exemplified as a suitable means.
[0032]
Examples of the fine powder of the inorganic compound include aluminum oxide and aluminum hydroxide having an average particle size of 0.1 to 1 μm, magnesium oxide and magnesium hydroxide, hydrotalcite, zinc oxide, iron oxide, titanium oxide, calcium carbonate, Examples include magnesium carbonate. In particular, it is suitable to obtain stable air permeability and moisture permeability by using calcium carbonate and magnesium carbonate and then dissolving and removing the mulching film for agriculture with acidic water after production.
[0033]
The thermoplastic resin constituting the agricultural mulching film of the present invention may be crosslinked by irradiation with radiation. An agricultural mulching film in which a thermoplastic resin is crosslinked is superior in heat resistance and strength to an agricultural mulching film made of a non-crosslinked thermoplastic resin.
[0034]
It is effective that the agricultural mulching film of the present invention is a thin film having a thickness of about 10 to 150 μm. In this case, it is also effective that the thermoplastic resin constituting the agricultural mulching film is cross-linked by radiation irradiation. Usually, when the agricultural mulching film is thinned, there is a problem that the film strength is lowered. In contrast, an agricultural mulching film according to the present invention having a film thickness of about 10 to 150 μm and a film in which a thermoplastic resin constituting the film is cross-linked by irradiation with radiation is aerated. It can be an agricultural mulching film having particularly stable properties and moisture permeability and high strength.
[0035]
The agricultural mulching film of the present invention, in which a thermoplastic resin is crosslinked, is obtained by further irradiating the agricultural mulching film of the present invention, which is produced using a non-crosslinked thermoplastic resin, with radiation. be able to.
[0036]
The type of radiation applied to the agricultural mulching film of the present invention for crosslinking is not particularly limited, but gamma rays, alpha rays, electron beams, etc. are preferably used, and the use of electron beams is preferred from the viewpoint of production speed and safety. Particularly preferred.
[0037]
As the radiation source, an electron beam accelerator having an acceleration voltage of 100 to 3000 kV is preferably used. If the accelerating voltage is less than 100 kV, the electron beam penetration depth is insufficient, and if it is greater than 3000 kV, the apparatus is too large and not preferable in terms of cost. Examples of the radiation irradiation device include an electron beam scanning type device such as a van de graff type and an electron beam fixed / conveyor moving type device such as an electron curtain type.
[0038]
The absorbed dose of radiation is preferably 0.1 to 100 Mrad, and more preferably 0.5 to 50 Mrad. When the absorbed dose is smaller than 0.1 Mrad, the effect of crosslinking the resin is not sufficient, and when it is larger than 100 Mrad, the strength is remarkably lowered, which is not preferable.
[0039]
The irradiation atmosphere when irradiating the agricultural mulching film of the present invention may be air, but an inert gas atmosphere such as nitrogen is preferable.
[0040]
Further, in the agricultural mulching film of the present invention, the pores of the porous film can be impregnated with other organic or inorganic compounds regardless of the presence or absence of irradiation. The compound to be impregnated can be appropriately selected according to the use of the porous film, and examples thereof include insecticides, agricultural chemicals, chemical fertilizers and the like.
[0041]
【Example】
EXAMPLES Hereinafter, examples will be shown to describe the present invention more specifically, but the present invention is not limited to these examples.
The physical properties of agricultural mulching films shown in Examples and Comparative Examples were measured by the following evaluation methods.
[0042]
[Evaluation methods]
(1) Gurley value (Breathability evaluation)
The Gurley value (second / 100 cc) of the film was measured with a B-type densometer (manufactured by Toyo Seiki) according to JIS P8117.
[0043]
(2) Average pore diameter Based on ASTM F316-86, the average pore diameter d (μm) was measured by Perm-Porometer (manufactured by PMI) by the bubble point method.
[0044]
(3) Average pore radius Based on JIS K1150, the average pore radius r (μm) was measured with Autopore III9420 (manufactured by MICROMERITICS) by mercury porosimetry. In determining the average pore radius, the pore radius distribution in the range of 0.0032 to 7.4 μm was measured.
[0045]
(4) Puncture strength A hole is opened when a metal needle having a diameter of 1 mm and a radius of curvature of the needle tip of 0.5 mm is pierced on a film fixed with a washer having a diameter of 12 mm at a speed of 200 mm / min. The maximum load was measured and used as the puncture strength.
[0046]
(5) Moisture permeability Based on the cup method specified in JIS Z 0208, the state of the water is adjusted for 1 hour in an atmosphere of 40 ° C. and 90% relative humidity, and the amount of water vapor permeated after 1 hour from the completion of the state adjustment is measured. And it converted into the quantity of the water vapor | steam permeate | transmitted per day per unit area of a film, and represented as moisture permeability.
[0047]
(6) Water pressure resistance Measured according to the hydrostatic pressure A method (low water pressure method) defined in JIS L 1092 and displayed in units of mm water column.
[0048]
[Manufacture of agricultural mulching film]
(Example 1)
Calcium carbonate star pigot 15A (manufactured by Shiraishi Calcium Co., Ltd., average particle size 0.15 μm) 30 vol% and polyethylene powder (Hi-Zex Million 340M, manufactured by Mitsui Chemicals, weight average molecular chain length 17000 nm, weight average molecular weight 3 million, melting point 136 ° C.) A twin-screw kneader with a segment designed to be able to knead 70% by weight of 70% by weight of polyethylene wax (High Wax 110P, Mitsui Chemicals, weight average molecular weight 1000, melting point 110 ° C.) 30% by weight. To obtain a resin composition. The content of polyethylene having a molecular chain length of 2850 nm or more in this resin composition was 27% by weight. By rolling this resin composition (roll temperature: 150 ° C.), an original film having a thickness of about 70 μm was produced.
[0049]
The obtained raw film was stretched about 5 times by a tenter stretching machine at a stretching temperature of 110 ° C. to obtain an agricultural mulching film comprising a porous film having a lofah structure. A scanning electron micrograph of the surface of the obtained agricultural mulching film is shown in FIG. A slightly thicker fiber oriented while meandering in the V direction in FIG. 1 is a trunk fibril, and branch fibrils are formed in a direction perpendicular to the V direction. As is clear from FIG. 1, the density of branch fibril formation is higher than that of trunk fibrils. Many fine holes are formed by the trunk fibrils and the branch fibrils. The branch fibrils were oriented in the maximum heat shrinkage direction.
[0050]
Table 1 shows measurement results of air permeability, moisture permeability, water pressure resistance, film thickness, average pore diameter d, average pore radius r and 2r / d, and piercing strength of the agricultural mulching film obtained in Example 1. It was shown in 1.
[0051]
(Example 2)
A raw film having a film thickness of 60 μm was prepared in the same manner as in Example 1 except that the calcium carbonate star piggot 15A used in Example 1 was changed to Piggot 10 (average particle size 0.1 μm, manufactured by Shiraishi Calcium Co., Ltd.).
The obtained raw film was stretched about 5 times by a tenter stretching machine at a stretching temperature of 110 ° C. to obtain an agricultural mulching film composed of a porous film having a lofah structure. The physical properties of this agricultural mulching film are shown in Table 1.
[0052]
(Comparative Example 1)
Table 1 shows the measurement results of air permeability, film thickness, average pore diameter d, average pore radius r and 2r / d, and piercing strength when a commercially available porous film is used as the porous membrane. . This porous film is obtained by subjecting a laminated film having a layer structure of polypropylene layer / polyethylene layer / polypropylene layer formed at a high draft ratio (take-off speed / extrusion speed) to crystallization heat treatment, and then stretching it at low temperature. The film is formed by stretching at a high temperature to peel off the crystal interface, and does not have a lofah structure.
[0053]
[Table 1]

As shown in the results of Table 1, the porous film of Example 1 of the present invention having a loofah structure is about 1.7 times thicker than the porous film of Comparative Example 1. Regardless, it can be seen that it has excellent breathability and moisture permeability and high mechanical strength.
[0054]
【The invention's effect】
The agricultural mulching film of the present invention can obtain a high air permeability and moisture permeability by taking a loofah-like structure, and can improve mechanical strength.
[Brief description of the drawings]
1 is an electron micrograph of an agricultural mulching film of Example 1. FIG.

Claims (5)

The film comprises a film formed of a thermoplastic resin, and has micropores formed by a three-dimensional network composed of trunk fibrils extending in one direction of the film and branch fibrils connecting the trunk fibrils, An agricultural mulching film having a fibril formation density higher than that of the trunk fibril. The average pore diameter d (μm) of the micropores determined by the bubble point method (ASTM F316-86) and the average pore radius r (μm) of the micropores determined by the mercury intrusion method (JIS K1150) The agricultural mulching film according to claim 1, which satisfies the following formula.
1.2 ≦ 2r / d ≦ 1.7 The agricultural mulching film according to claim 1 or 2, wherein the branch fibrils are oriented in the maximum heat shrink direction of the film. The agricultural mulching film according to any one of claims 1 to 3, wherein the micropores have an average pore diameter d of 0.06 to 3 µm. The agricultural mulching film according to any one of claims 1 to 4, wherein the thermoplastic resin is a polyolefin-based thermoplastic resin.

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