Agricultural film

Abstract

This agricultural film is characterized by containing 0.10-4.0 mass% of inorganic fine particles that have an average primary particle size of 1.0-500 nm, and having a surface roughness Ra of 0.100 μm or less. With the present invention, it is possible to provide an agricultural film that has high light transmittance and scattering properties, and exhibits little decrease in light transmittance and scattering properties as a result of long-term use.

Description

Agricultural film

[0001] The present invention relates to an agricultural film, and more particularly to a light-transmissive agricultural film used as a covering material for tunnel cultivation, greenhouse cultivation, etc.

[0002] In recent years, tunnel cultivation and greenhouse cultivation using transparent synthetic resin films have been widely popularized in the cultivation of crops such as vegetables, fruit crops, and flowers.

[0003] In these tunnels or greenhouses for crop cultivation, in winter when the temperature is low, in addition to heat preservation, since sunlight is weak and the position of the sun is also low, it is necessary to allow sunlight to enter as much as possible and irradiate the crops.

[0004] In response to such problems, conventionally, attempts have been made to scatter light rays such as sunlight by a greenhouse covering material such as a film to reduce the shadow within the community of cultivated plants. By scattering light rays such as sunlight, light also easily enters the corners of the greenhouse and the lower parts of the crops, which is beneficial to the cultivation environment and the growth of the crops.

[0005] For example, Patent Document 1 discloses covering a greenhouse with a covering material using a film containing substances with different refractive indices of light as a light scattering method.

[0006] Further, Patent Document 2 discloses a matte polyolefin-based resin coating material characterized in that a film derived from a matte composition mainly composed of a thermoplastic resin binder and inorganic and / or organic particles is formed on at least one side of a polyolefin-based resin film.

[0007] Further, Patent Document 3 proposes an agricultural fluorine-containing laminated film having a thermoplastic resin layer on one surface of a fluorine-based resin layer, the surface of the thermoplastic resin layer having irregularities, and a water droplet layer provided on the surface having the irregularities.

[0008] JP-A-2000-139244 JP-A-11-137095 WO2018 / 016617

[0009] However, Patent Documents 1 and 3 had a problem in that, due to their uneven structure, when subjected to long-term stretching tests, fine dust and organic matter tended to adhere to and accumulate, causing a significant lack of light.

[0010] Furthermore, Patent Document 2 described a problem in which, when stretched for a long period, the adhesion between the polyolefin resin film and the acrylic resin coating deteriorated over time, and the acrylic resin layer gradually peeled off when exposed to the outdoors for a long period, resulting in poor durability.

[0011] Therefore, the present invention aims to provide an agricultural film that has high light transmittance and scattering properties and exhibits little decrease in light transmittance and scattering properties due to long-term use.

[0012] The above problems are solved by the present invention as follows. That is, the present invention (1) provides an agricultural film characterized by containing 0.10 to 4.0% by mass of inorganic fine particles having an average primary particle diameter of 1.0 to 500 nm, and having a surface roughness Ra of 0.100 μm or less.

[0013] Furthermore, the present invention (2) provides an agricultural film of the same type as (1), characterized in that the transmission intensity at an incident angle of 50° is 70.00 to 95.00.

[0014] Furthermore, the present invention (3) provides an agricultural film according to (1) or (2), characterized in that the haze is 23.0 or less.

[0015] Furthermore, the present invention (4) provides an agricultural film according to any of (1) to (4), characterized in that the inorganic fine particles are at least one selected from the group consisting of silicon dioxide, natural or synthetic silicates, natural or synthetic hydrotalcite compounds, aluminum oxide, calcium carbonate, and magnesium oxide.

[0016] According to the present invention, it is possible to provide an agricultural film that has high light transmittance and scattering properties and exhibits little decrease in light transmittance and scattering properties due to long-term use.

[0017] This figure shows the plots used in the cultivation tests for the examples and comparative examples.

[0018] The agricultural film of the present invention is characterized by containing 0.10 to 4.0% by mass of inorganic fine particles with a primary particle size of 1.0 to 500 nm, and having a surface roughness Ra of 0.100 μm or less.

[0019] The agricultural film of the present invention is a film-like molded article of a resin composition comprising a light-transmitting resin and inorganic fine particles dispersed in the resin. In other words, the agricultural film of the present invention is a film-like light-transmitting resin matrix in which inorganic fine particles are dispersed.

[0020] The light-transmitting resin (matrix) for the agricultural film of the present invention is not particularly limited, and a general-purpose plastic commonly used as an agricultural covering material can be used.

[0021] Examples of light-permeable resins include polysaccharides, polysaccharide ester derivatives, polyethylene, polypropylene, polystyrene, polymethylpentene, polybutene, butadiene styrene, polyvinyl chloride, polymethacrylic styrene, polysulfone, styrene-acrylonitrile resin, acrylonitrile-butadiene resin, acrylonitrile-butadiene-acrylic acid ester resin, acrylonitrile-butadiene-styrene resin, urea-formaldehyde resin, polyethylene terephthalate, polytrimethylene terephthalate, polymethyl methacrylate, polyphosphate Nylene ether, polyphenylene sulfide, polyphenylene sulfide, polyacrylonitrile, polychlorotrifluoroethylene, polyvinyl alcohol, polyvinylidene chloride, polyvinylidene fluoride, polycarbonate, polyamide, polyamide-imide, polyoxymethylene, polyacetal, polyformaldehyde, polybutylene terephthalate, polytetrafluoroethylene, ethyl vinyl acetate copolymer, ethylene tetrafluoroethylene copolymer, melamine resin, polyurea, polyurethane, epoxy resin, unsaturated polyester, poly Allyl sulfone, polyacrylate, hydroxybenzoate polyester, polyetherimide, polycyclohexylene dimethylene terephthalate, polyethylene naphthalate, polyester carbonate, aromatic polyester, aliphatic polyester, polylactic acid, lactic acid polyester, cellulose ester, polyhydroxybutyrate, polybutylene terephthalate, polybutylene adipate terephthalate, polybutylene succinate, polybutylene succinate adipate, hydroxybutyrate / 3-hydroxyhexanoic acid copolymer polyester, polyglycol Polyuric acid, polyethylene terephthalate, polyethylene terephthalate succinate, polytetramethylene adipate terephthalate, polyhydroxybutyric acid, cellulose acetate, cellulose nitrate, cellulose propionate, ethylcellulose, bacterial cellulose, furan-formaldehyde resin, melamine-formaldehyde resin, polyimide, chitosan, cellulose, starch, polycaprolactone, starch-based copolyester, esterified starch, polyhydroxyalkanoate, polybutylene succinate adipate, polybutylene adipate terephthalate,Examples include phenolic resins, silicones, polyethers, long-chain dicarboxylic acid copolymers, or any combination thereof.

[0022] Furthermore, examples of light-transmitting resins include UV- and other photocurable polymers, such as acrylic compounds, epoxy compounds, urethane compounds, and silicone compounds. Examples of acrylic compounds include unsubstituted alkyl-(meth)acrylates, such as methyl-acrylate, methyl-methacrylate, ethyl-acrylate, ethyl-methacrylate, butyl-acrylate, butyl-methacrylate, 2-ethylhexyl-acrylate, and 2-ethylhexyl-methacrylate; substituted alkyl-(meth)acrylates, such as hydroxyl-group, epoxy-group, or halogen-substituted alkyl-(meth)acrylates; cyclopentenyl (meth)acrylate, tetra-hydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, and polyethylene-glycol di-(meth)acrylate.

[0023] The weight-average molecular weight of the light-transmitting resin is not particularly limited, but is preferably 5,000 to 500,000, more preferably 10,000 to 300,000. In this invention, the weight-average molecular weight is the molecular weight on a styrene basis, measured by gel permeation chromatography (GPC).

[0024] The light transmittance of the light-transmitting resin is preferably 80 to 99, more preferably 85 to 95. Having the light transmittance of the light-transmitting resin within this range increases the light transmission of the agricultural film, thereby enhancing the effect of improving plant growth. In this invention, the light transmittance of the light-transmitting resin is measured according to a measurement method compliant with JIS K7136. A haze meter "NDH4000" (manufactured by Nippon Denshoku Industries Co., Ltd.) was used as the measuring instrument.

[0025] The agricultural film of the present invention contains inorganic fine particles. The inorganic fine particles are not particularly limited and include silicon oxide such as synthetic silica, quartz, silica gel, and diatomaceous earth; various natural or synthetic silicates such as talc, zeolite, feldspar, calcium silicate, and glass; natural or synthetic hydrotalcite compounds; and metal oxides such as aluminum oxide, calcium carbonate, and magnesium oxide. Among these, synthetic silica particles, silicon oxide such as quartz, silica gel, and diatomaceous earth; various natural or synthetic silicates, such as talc, zeolite, feldspar, calcium silicate, glass, and natural or synthetic hydrotalcite compounds, are preferred as inorganic fine particles because they have low hardness and therefore high dispersibility, while synthetic silica particles are particularly preferred because they have high uniformity of particle size. The inorganic fine particles may be one type or a combination of two or more types.

[0026] The average primary particle diameter of the inorganic fine particles is 1.0 to 500 nm, preferably 5.0 to 300 nm, and more preferably 10 to 200 nm. In agricultural films, inorganic fine particles exist in the form of aggregated particles, where several primary particles are aggregated. In the agricultural film of the present invention, the particle diameter of aggregated particles can be reduced by including inorganic fine particles with small primary particle diameters in a predetermined amount. Because the average primary particle diameter of the inorganic fine particles is within the above range, the light transmittance and scattering properties of the agricultural film are increased, thereby enhancing the effect of improving plant growth. Furthermore, since the particle diameter of aggregated inorganic fine particles (aggregates of primary particles) can be reduced, the surface roughness of the agricultural film can be reduced, making it less susceptible to dirt and dust, and reducing the decrease in light transmittance and scattering properties of the agricultural film due to long-term use. In addition, in the agricultural film of the present invention, the particle diameter of aggregated inorganic fine particles (aggregates of primary particles) can be reduced by using a dispersant, using surface-modified inorganic fine particles, etc., in addition to including inorganic fine particles with small primary particle diameters in a predetermined amount. On the other hand, if the average primary particle diameter of the inorganic microparticles exceeds the above range, the particle diameter of the aggregated inorganic microparticles becomes too large, resulting in excessively high surface roughness of the agricultural film. Conversely, if it falls below the above range, the handling of the inorganic microparticles becomes difficult, making manufacturing difficult.

[0027] In this invention, the average primary particle diameter of inorganic fine particles refers to the value measured by the gas adsorption method (BET method) described below. That is, first, the specific surface area S is measured using the inorganic fine particles to be measured by the gas adsorption method. For nearly spherical particles, the average primary particle diameter d (nm) is given by the following formula: Average primary particle diameter d (nm) = 6000 / (BET specific surface area S (nm) ２ / g) x true density (g / cm ３ It can be determined by the following formula. If the inorganic fine particles are silica particles, the true density of the silica particles is 2.2 g / cm³. ３ Therefore, the average primary particle diameter d (nm) of silica particles is given by the following formula: Average primary particle diameter (nm) of silica particles = 2727 / specific surface area (m²) ２ It is calculated by ( / g).

[0028] In the agricultural film of the present invention, the content of inorganic fine particles is 0.10 to 4.0% by mass, preferably 0.20 to 3.5% by mass, and more preferably 0.30 to 3.0% by mass. When the content of inorganic fine particles in the agricultural film is within the above range, the light transmittance and scattering properties of the agricultural film are increased, thereby enhancing the effect of improving plant growth. Furthermore, since the amount of aggregated inorganic fine particles does not become excessive, the surface roughness of the agricultural film can be reduced, making it less susceptible to dirt such as soil and dust, thus reducing the decrease in the light transmittance and scattering properties of the agricultural film due to long-term use. On the other hand, if the content of inorganic fine particles in the agricultural film is below the above range, the light scattering properties of the agricultural film are low, and the effect of improving plant growth is low. If it exceeds the above range, there are too many aggregated inorganic fine particles in the agricultural film, resulting in low light transmittance and excessive surface roughness, which leads to a large decrease in the light transmittance and scattering properties of the agricultural film due to long-term use.

[0029] The surface roughness Ra of the agricultural film of the present invention is 0.100 μm or less, preferably 0.095 μm or less, and more preferably 0.090 μm or less. When the particle size of aggregated inorganic fine particles contained in the agricultural film increases, the surface roughness Ra of the agricultural film increases. Therefore, a small surface roughness Ra of the agricultural film indicates that the particle size of aggregated inorganic fine particles contained in the agricultural film is small. As a result, when the surface roughness Ra of the agricultural film is within the above range, the particle size of aggregated inorganic fine particles (aggregates of primary particles) is small, and the light transmittance of the agricultural film is increased. Furthermore, when the surface roughness Ra of the agricultural film is within the above range, aggregated inorganic fine particles (aggregates of primary particles) with a particle size that can enhance light diffusion are dispersed in the agricultural film, and thus the light diffusion of the agricultural film is increased. Furthermore, if the surface roughness Ra of the agricultural film is within the above range, dirt such as soil and dust will not adhere easily, thus reducing the decrease in light transmittance and scattering properties of the agricultural film due to long-term use. In addition, there is no particular limit to the lower limit of the surface roughness Ra of the agricultural film of the present invention, but 0.001 μm or more is preferred.

[0030] In the present invention, the surface roughness Ra is expressed in μm units, obtained by (1) below when a reference length (L) is extracted from the roughness curve in the direction of the average line, the X-axis is taken in the direction of the average line of this extracted portion, the Y-axis is taken in the direction perpendicular to the X-axis, and the roughness curve is represented as Y = f(X).

[0031]

[0032] The transmittance intensity of the agricultural film of the present invention at an incident angle of 50° is preferably 70.00 to 95.00, more preferably 70.00 to 90.00. Having the transmittance intensity of the agricultural film at an incident angle of 50° within this range results in high light scattering, which is beneficial for crop growth.

[0033] The haze of the agricultural film of the present invention is preferably 23.0 or less, more preferably 20.0 or less. If there are many aggregated particles with a large particle size in the agricultural film, the haze will be large. In other words, a large haze in the agricultural film indicates that there are few aggregated particles with a large particle size. And if there are many aggregated particles with a large particle size, the light transmittance of the agricultural film will be low. Therefore, when the haze of the agricultural film is within the above range, the light transmittance of the agricultural film will be high. In this invention, the haze is measured by a measurement method in accordance with JIS K7361.

[0034] In the agricultural film of the present invention, the term "film" is not limited to its name, and any thin film is included in the agricultural film of the present invention. For example, it may include not only what is generally called a "film" (thickness of 250 μm or less), but also what is called a "sheet" (thickness of 250 μm or more) or what is called a "foil." In other words, there is no limit to the thickness of the agricultural film of the present invention. The thickness of the agricultural film of the present invention is preferably 50 to 250 μm, more preferably 75 to 200 μm.

[0035] The agricultural film of the present invention may optionally contain additives such as ultraviolet absorbers, anti-fading agents, various anionic, cationic, or nonionic surfactants, fluorescent whitening agents, pH adjusters such as sulfuric acid, phosphoric acid, acetic acid, citric acid, sodium hydroxide, potassium hydroxide, and potassium carbonate, defoaming agents, lubricants such as diethylene glycol, preservatives, antifungal agents, antistatic agents, matting agents, heat stabilizers, antioxidants, flame retardants, crystal nucleating agents, organic particles, viscosity reducers, lubricants, infrared absorbers, dyes, and pigments.

[0036] The agricultural film of the present invention may be single-layered or multi-layered. In the case of a multi-layered film, the composition (types and composition of contained components), thickness, etc., of each layer may be changed as appropriate.

[0037] The method for producing the agricultural film of the present invention is not particularly limited, and for example, one method is to melt-knead a predetermined amount of light-transmitting resin, a predetermined amount of inorganic fine particles, and additives as needed in a twin-screw kneader to produce pellets, and then use the obtained pellets to perform inflation molding to a predetermined thickness to obtain a film.

[0038] Conventional agricultural films have employed a method of increasing light diffusion by increasing the surface roughness of the film. Therefore, large inorganic particles were incorporated to achieve this increased surface roughness.

[0039] In contrast, the present inventors have found that by reducing the particle size of aggregated inorganic fine particles dispersed in an agricultural film and controlling their amount within a specific range, when light is incident on the agricultural film from an oblique direction, for example at an incident angle of 45 to 55°, the light diffusion is high and the light transmittance is not easily reduced due to the reflection of light by the inorganic fine particles. Therefore, the inventors have found that by setting the average primary particle diameter of the inorganic fine particles contained in the agricultural film to 1.0 to 500 nm, preferably 5 to 300 nm, more preferably 10 to 200 nm, and the inorganic fine particle content to 0.10 to 4.0 mass%, preferably 0.20 to 3.5 mass%, more preferably 0.30 to 3.0 mass%, the following can be achieved: (1) The amount of aggregated inorganic fine particles is not excessive, while the inorganic fine particles provide a light diffusion effect, so that when light is incident on the agricultural film from an oblique direction, for example at an incident angle of 45 to 55°, the light diffusion and light transmission can be increased; (2) As a result, the effect of improving plant growth is enhanced; (3) Furthermore, since the amount of aggregated inorganic fine particles is not excessive, the surface roughness Ra of the agricultural film is reduced, so that the decrease in light transmission and scattering of the agricultural film due to long-term use can be reduced. In this invention, a surface roughness Ra of the agricultural film being 0.100 μm or less, preferably 0.095 μm or less, and more preferably 0.900 μm or less, means that the size of aggregated inorganic fine particles is small.

[0040] Hereinafter, examples will be shown to specifically describe the present invention. However, the present invention is not limited to the examples shown below.

[0041] (Examples 1 to 4, Comparative Examples 1 to 2) Low-density polyethylene (manufactured by Tosoh Corporation: Petrothene 180) and the inorganic fine particles shown in Table 1 (inorganic fine particle 1 was used in Examples 1 to 3 and Comparative Example 2, and inorganic fine particle 2 was used in Example 4) were kneaded in a biaxial kneader to a predetermined content and formed into pellets. Using the pellets, inflation molding was performed to obtain a film with a thickness of 75 μm.

[0042] <Inorganic fine particles> (Inorganic fine particle 1) Silica particles (manufactured by Fuso Chemical Industry Co., Ltd., trade name HSP-6A), average primary particle diameter: 60 nm (Inorganic fine particle 2) Silica particles (manufactured by Fuso Chemical Industry Co., Ltd., trade name HSP-10A), average primary particle diameter: 100 nm

[0043] <Analysis> (Average primary particle diameter) The average primary particle diameter of the inorganic fine particles was measured by the gas adsorption method (BET method) described below. First, the specific surface area S by the gas adsorption method was measured using the inorganic fine particles to be measured. For particles that are approximately spherical, the average primary particle diameter d (nm) is given by the following formula: Average primary particle diameter d (nm) = 6000 / (BET specific surface area S (m ２ / g) × true density (g / cm ３ )). When the inorganic fine particles are silica particles, since the true density of the silica particles is 2.2 g / cm ３ , the average primary particle diameter d (nm) of the silica particles is given by the following formula: Average primary particle diameter of silica particles (nm) = 2727 / specific surface area (m ２ / g).

[0044] (Surface roughness Ra) For the surface roughness Ra, using a super-depth shape measurement microscope "VK-8510" (manufactured by Keyence Corporation), with an objective lens: 20 times and a measurement interval of 0.5 μm, a roughness curve Y = f(X) with a reference length (L) = 900 μm was measured along the longitudinal direction of the multilayer film, and the measurement was performed based on the following calculation formula (1) defined in JIS B 0601-2001 from the curve.

[0045]

[0046] (Haze) Measurement was performed according to the measurement method in accordance with JIS K7361. The film was cut into 5 cm squares, and the haze was measured in accordance with JIS K 7361 using the "NDH7000" manufactured by Nippon Denshoku Industries Co., Ltd.

[0047] (Transmittance intensity at an incident angle of 50°) This was calculated by measuring the relative transmittance when light rays were incident on the film surface at an angle of 50° using the "Automatic Variable Angle Photometer GP-200" manufactured by Murakami Color Research Institute Co., Ltd.

[0048] <Evaluation> (Open-field tunnel cultivation experiment) As shown in Figure 1, seeds were sown in open ground by making ridges. Tunnel supports were installed, and the same ridge was divided into sections and covered with film before the cultivation experiment was conducted. Comparative example 1 was set up as the control section, and examples 1 to 4 and comparative example 2 were set up as the test sections. Variety: Spinach Cultivation period: Late November to late January (Growing days: 57 days) Number of samples: 60 plants (20 plants x 3 locations / ridge) Random selection and fresh weight measurement: 60 plants were randomly selected, the root portion was cut off, and the weight of the above-ground part was measured. The average of these values ​​was taken as the average fresh weight.

[0049]

Claims

1. An agricultural film characterized by containing 0.10 to 4.0% by mass of inorganic fine particles with an average primary particle diameter of 1.0 to 500 nm, and having a surface roughness Ra of 0.100 μm or less.

2. The agricultural film according to claim 1, characterized in that the transmission intensity at an incident angle of 50° is 70.00 to 95.

00.

3. The agricultural film according to claim 1, characterized in that the haze is 23.0 or less.

4. The agricultural film according to claim 1, characterized in that the inorganic fine particles are at least one selected from the group consisting of silicon dioxide, natural or synthetic silicates, natural or synthetic hydrotalcite compounds, aluminum oxide, calcium carbonate, and magnesium oxide.

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