Polyolefin resin film for agricultural use

Abstract

To provide an agricultural polyolefin resin film which can promote growth of a plant to improve productivity in even a plant with high height by thinning a shadow of a house aggregate and a shadow of a plant.SOLUTION: An agricultural polyolefin resin film 1 is configured so that an inner layer 3 on an opposite side of a side where sunlight enters, contains as a resin component, ethylene-vinyl acerate copolymer and low density polyethylene, the inner layer has whole light transmittance of 80% or greater, and if a transmitted light amount when an incident light angle measured by a gonio-photometer is 45° is A[%], and if a transmitted light amount when an incident light angle is 0°is B[%], 0%<A<20% is satisfied and a relationship of 1.7≤B / A is satisfied.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polyolefin resin film for agricultural use used in agricultural facilities such as agricultural greenhouses and agricultural tunnels, and a method for producing the same. [Background technology]

[0002] As for satin-finish agricultural films, for example, agricultural vinyl chloride resin films are produced by the calendar method or T-die method, and the surface is formed into a satin-finish by an embossing roll. Such films have high light transmittance and also high light diffusion properties, so when used for agricultural purposes, they are used in applications that require the prevention of leaf scorch caused by direct sunlight and the diffusion of light inside agricultural greenhouses and tunnels.

[0003] Meanwhile, agricultural films made of olefin-based resins have been improved in recent years and are increasingly being used. For example, instead of the above-mentioned embossing, a method has been proposed in which a composition made of two or more different resins with low compatibility is used. More specifically, a film molded from a composition made of polypropylene resin, saponified ethylene-vinyl acetate copolymer, and modified polyolefin resin (see Patent Document 1) has been proposed, as well as an agricultural satin film in which resin layers made of a specific saponified ethylene-vinyl acetate copolymer and an ionomer are laminated on both sides of an ethylene-vinyl acetate copolymer layer (see Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-60838 [Patent Document 2] Japanese Patent Application Publication No. 11-318228 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the agricultural light-scattering films described in Patent Documents 1 and 2 above, the scattering angle of the scattered light is small, and shadows remain in the greenhouse. Therefore, when cultivating tall crops (such as tomatoes, eggplants, cucumbers, peppers, etc.), as the crops grow, light does not reach the lower leaves. Even when cultivating in groups, there is a disadvantage that the photosynthesis efficiency of an individual plant deteriorates.

[0006] In addition, a method of adding an inorganic substance to increase the scattering property can be considered. However, in this method, since the total light transmittance decreases, burning is likely to occur during molding processing, and gels are generated, resulting in defective products. Also, when the amount of the inorganic substance added is increased, there is a problem that the inorganic substance drops off frequently during film molding processing, and the increased effect cannot be obtained.

[0007] Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide an agricultural polyolefin resin film that can promote plant growth and improve productivity even in tall crops by reducing the greenhouse frame shadow and plant shadow.

Means for Solving the Problems

[0008] In order to achieve the above object, the agricultural polyolefin resin film of the present invention has a layer on the side opposite to the side where sunlight enters, containing an ethylene-vinyl acetate copolymer and low-density polyethylene as resin components, having a total light transmittance of 80% or more, and when the transmitted light amount at an incident light angle of 45° measured by a goniophotometer is A [%] and the transmitted light amount at an incident light angle of 0° is B [%], 0% < A < 20% and a relationship of 1.7 ≦ B / A holds.

Effects of the Invention

[0009] According to the present invention, it becomes possible to reduce the greenhouse frame shadow and plant shadow, so that it is possible to promote plant growth and improve productivity even in tall crops.

Brief Description of the Drawings

[0010] [Figure 1] 1 is a cross-sectional view showing an agricultural polyolefin resin film according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing a modified example of an agricultural polyolefin resin film according to the present invention. [Figure 3] FIG. 1 is a diagram for explaining an evaluation method based on photosynthetically active photon flux density in Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0011] The agricultural polyolefin resin film of the present invention will be specifically described below. Note that the present invention is not limited to the following embodiments and can be appropriately modified and applied within the scope of the present invention.

[0012] <Polyolefin resin film for agricultural use> As shown in Figure 1, the agricultural polyolefin resin film 1 of the present invention has an outer layer 2 which is the layer on the side where sunlight is incident, an inner layer 3 which is the layer on the opposite side to the side where sunlight is incident, and an intermediate layer 4 provided between the outer layer 2 and the inner layer 3, and has a multilayer structure in which these layers are laminated together.

[0013] <Outer layer> The outer layer 2 is the outermost layer facing the outside of the agricultural facility when the film is installed in the facility. This outer layer 2 is a layer that reinforces the intermediate layer 3, which contains a large amount of various pigments and is made of foamed resin material and therefore lacks strength, and is also a layer that prevents air from escaping from the inside to expand the tubular molten resin when the agricultural polyolefin resin film 1 is manufactured by the inflation method. Therefore, the outer layer 2 is made a non-foamed layer.

[0014] Furthermore, the outer layer 2 is a layer that protects the various pigments in the intermediate layer 4 from deterioration without interfering with the functions (reflection, light blocking, etc.) of the intermediate layer 4, and therefore is made a light-transmitting layer.

[0015] The outer layer 2 is made of a resin material containing a polyolefin resin, and linear low-density polyethylene is preferred as the polyolefin resin from the viewpoint of ease of molding. Furthermore, linear low-density polyethylene produced using a metallocene catalyst or a Ziegler catalyst is preferred from the viewpoint of strength.

[0016] Furthermore, for example, a composition containing linear low-density polyethylene as the main component and high-pressure low-density polyethylenes with melt mass-flow rates (MFRs) differing by approximately 0.5 to 2.0 g / 10 min as minor components can be used for the outer layer 2. By blending resins with melt mass-flow rates differing by approximately 0.5 to 2.0 g / 10 min, the matte finish of the multilayer film can be further improved.

[0017] The melt mass flow rate can be obtained by measuring in accordance with the standard of JIS K7210:1999.

[0018] The resin material may also contain other polyolefin resins and known additives, etc., to the extent that the strength, light transmittance, etc. are not impaired.

[0019] The thickness of the outer layer 2 is preferably 10 to 40 μm, more preferably 15 to 30 μm. If the thickness is 10 μm or more, the dustproof effect is sufficient, and if it is 40 μm or less, the light transmittance is good.

[0020] <Inner layer> When the sheet is laid out in an agricultural facility, the inner layer 3 becomes the innermost layer facing the inside of the facility. Like the outer layer 2 described above, the inner layer 3 reinforces the intermediate layer 3 and is a non-foamed, light-transmitting layer.

[0021] The inner layer 3 is a layer made of a resin material containing a polyolefin-based resin, and as the polyolefin-based resin, a resin containing an ethylene-vinyl acetate copolymer and low-density polyethylene is used.

[0022] The ethylene-vinyl acetate copolymer preferably has a vinyl acetate content of 5 to 30% by mass, more preferably 10 to 25% by mass. A vinyl acetate content of 5% by mass or more improves adhesion to the anti-fogging coating film described below. Furthermore, a vinyl acetate content of 30% by mass or less improves the strength and transparency of the resulting film.

[0023] Furthermore, it is preferable to use an ethylene-vinyl acetate copolymer with a melt mass flow rate of 1.2 to 10 g / 10 min. If the melt mass flow rate is 1.2 g / 10 min or more, a low-density polyethylene with a high melt mass flow rate can be used, and the molding speed can be increased, making it possible to produce the film efficiently. On the other hand, if the melt mass flow rate exceeds 10 g / 10 min, it becomes difficult for the film to maintain its shape, and film formability deteriorates.

[0024] Furthermore, when the resin component of the inner layer 3 is taken as 100 parts by mass, the content of the ethylene-vinyl acetate copolymer is preferably 60 parts by mass or more, more preferably 70 parts by mass or more, and even more preferably 80 parts by mass or more. If the content of the ethylene-vinyl acetate copolymer is 60 parts by mass or more, irregularities are more likely to be formed on the surface of the inner layer 3, thereby improving light scattering properties.

[0025] Low-density polyethylene includes, for example, polyethylene having a density of 0.935 g / cm 3 or less, preferably 0.910 to 0.935 g / cm 3 The linear low-density polyethylene may be produced using, for example, a metallocene catalyst or a single-site catalyst, and may be a random copolymer or a block copolymer of ethylene and an α-olefin such as propylene, butene-1, 3-methylbutene-1, pentene-1, 3-methylpentene-1, 4-methylpentene-1, hexene-1, octene-1, or decene-1. The α-olefin may be used alone or in combination of two or more.

[0026] Furthermore, it is preferable to use a low-density polyethylene having a melt mass flow rate of 0.2 g / 10 min or more. If the melt mass flow rate is 0.2 g / 10 min or more, there is no overload in the extruder and extrusion can be performed without any problems.

[0027] Furthermore, other polyolefin resins and other known additives may be contained within the range that does not impair flexibility, transparency, etc.

[0028] For example, from the viewpoint of improving scattering properties, an inorganic substance can be added. From the viewpoint of suppressing a decrease in light transmittance, it is preferable to use, as the inorganic substance, calcium carbonate, natural mica such as muscovite, phlogopite, biotite, or synthetic mica.

[0029] The content of the inorganic substance is preferably 5 parts by mass or less, relative to 100 parts by mass of the resin component of the inner layer 3. This is because, if the content exceeds 5 parts by mass, problems such as discoloration or gel formation during molding or a decrease in the tear strength of the film may generally occur.

[0030] Furthermore, when using an inorganic substance having a substantially spherical shape, it is preferable that the average particle size is 1 μm or more, because if it is less than 1 μm, there may be a problem in that the light scattering property is reduced.

[0031] The term "average particle size" used herein refers to the 50% particle size (D50), which can be measured as the volume-average particle size using a laser diffraction / scattering particle size distribution analyzer (Microtrac (registered trademark) particle size distribution analyzer MT3200, manufactured by Nikkiso Co., Ltd.) or the like.

[0032] The resin material forming the inner layer 3 may contain an antifogging agent to impart antifogging properties to the agricultural polyolefin resin film 1. Examples of antifogging agents include partial esters of polyhydric alcohols (sorbitan, glycerin, diglycerin, etc.) with fatty acids, and condensates of these with alkylene glycols.

[0033] The amount of the antifogging agent to be added is preferably 1 to 5 parts by mass, more preferably 1.2 to 3 parts by mass, per 100 parts by mass of the polyolefin resin.

[0034] The thickness of the inner layer 3 is preferably 10 to 40 μm, and more preferably 15 to 30 μm.

[0035] <Middle class> The intermediate layer 4 includes, in order from the outer layer 2 side, a first intermediate layer 5, a second intermediate layer 6, and a third intermediate layer .

[0036] (First middle class) When the agricultural facility is installed, the first intermediate layer 5 serves as a layer that reflects sunlight from outside the facility. The first intermediate layer 5 is a layer that provides heat retention and heat insulation properties to the agricultural polyolefin resin film 1, and is therefore made into a foam layer.

[0037] The first intermediate layer 5 is a layer formed by foaming a resin material containing a polyolefin resin and a titanium oxide pigment with a foaming agent. From the viewpoint of strength, the polyolefin resin is preferably a linear low-density polyethylene produced using a metallocene catalyst or a Ziegler catalyst.

[0038] The amount of titanium oxide pigment to be blended is preferably 25 to 80 parts by mass, more preferably 30 to 50 parts by mass, per 100 parts by mass of the polyolefin resin.

[0039] The resin material may contain other polyolefin resins, other known additives, etc., to the extent that the strength and light transmittance are not impaired.

[0040] (Second middle class) When the agricultural facility is installed, the second intermediate layer 6 serves as a layer that blocks sunlight from outside the facility. Like the first intermediate layer 5, the second intermediate layer 6 is a layer that provides heat retention and heat insulation properties to the agricultural polyolefin resin film 1, and is therefore made a foam layer.

[0041] The second intermediate layer 6 is a layer formed by foaming a resin material containing a polyolefin resin, titanium oxide pigment, and carbon black pigment with a foaming agent. From the viewpoint of strength, the polyolefin resin is preferably linear low-density polyethylene produced using a metallocene catalyst or a Ziegler catalyst.

[0042] The amount of titanium oxide pigment to be blended is preferably 3 to 30 parts by mass, more preferably 4 to 15 parts by mass, per 100 parts by mass of the polyolefin resin.

[0043] The amount of carbon black pigment to be added is preferably 3 to 30 parts by mass, more preferably 4 to 15 parts by mass, per 100 parts by mass of the polyolefin resin.

[0044] The resin material may contain other polyolefin resins, other known additives, etc., to the extent that the strength and light transmittance are not impaired.

[0045] (Third middle class) When the agricultural facility is installed, the third intermediate layer 7 serves as a layer that reflects illumination light from inside the facility. The third intermediate layer 7 is a layer that provides heat retention and heat insulation properties to the agricultural polyolefin resin film 1, and is therefore made into a foam layer.

[0046] The third intermediate layer 7 is a layer formed by foaming a resin material containing a polyolefin resin and an aluminum pigment or a titanium oxide pigment with a foaming agent. As the polyolefin resin, an olefin-vinyl acetate copolymer having a vinyl acetate unit ratio of 5 to 28 mass % is preferred, and an ethylene-vinyl acetate copolymer is more preferred, from the viewpoints of imparting flexibility to the agricultural polyolefin resin film 1 to facilitate spreading, imparting stable anti-fogging properties, and providing good pigment dispersion.

[0047] The amount of the aluminum pigment to be added is preferably 3 to 20 parts by mass, more preferably 4 to 15 parts by mass, per 100 parts by mass of the polyolefin resin.

[0048] The amount of titanium oxide pigment to be blended is preferably 25 to 80 parts by mass, more preferably 30 to 50 parts by mass, per 100 parts by mass of the polyolefin resin.

[0049] The resin material forming the third intermediate 7 may contain the above-mentioned antifogging agent to impart antifogging properties to the agricultural polyolefin resin film 1. The amount of the antifogging agent blended is preferably 1 to 5 parts by mass, more preferably 1.2 to 3 parts by mass, per 100 parts by mass of the polyolefin resin.

[0050] The resin material may also contain a fluorine-based surfactant or a silicone-based surfactant in addition to the antifogging agent in order to impart antifogging properties to the agricultural polyolefin-based resin film 1.

[0051] The resin material may contain other polyolefin resins (such as low-density polyethylene), other known additives, and the like, as long as the flexibility and anti-fogging properties are not impaired.

[0052] Here, the inventors investigated the conditions under which light would be distributed throughout the greenhouse while maintaining high total light transmittance in the agricultural polyolefin resin film 1, and found that by controlling the amount of transmitted light at a specified incident light angle measured with a goniophotometer (a variable angle photometer) that can measure the scattering angle distribution of transmitted light that has passed through the agricultural polyolefin resin film 1, it is possible to reduce the shadow of the greenhouse aggregates and the shadow of the plants, thereby promoting plant growth.

[0053] More specifically, as a means of evaluating the amount of light transmitted through the agricultural polyolefin resin film 1 into the greenhouse, a goniophotometer equipped with a device that can change the angle of the sample (agricultural polyolefin resin film 1) is used to measure the amount of transmitted light when the incident light angle is 0° and 45° relative to the incident surface of the agricultural polyolefin resin film 1.

[0054] Here, the "amount of transmitted light" refers to the ratio of the amount of light in the straight-ahead direction of the incident light transmitted through the installed sample, when the maximum value of the amount of light in the state where no sample is installed (blank) is set to 100%.

[0055] In the present invention, when the amount of transmitted light at an incident light angle of 45° is A [%], it is characterized in that 0% < A < 20%. Since the ratio of the direct light component is small and the ratio of the scattered light is large when 0% < A < 20% for the amount of transmitted light A, the ratio of the penumbra of the shadow of plants and structures becomes large, and it becomes possible to make the shadow lighter. The range of the amount of transmitted light A is preferably 6% or more and 16% or less.

[0056] Further, in the present invention, when the amount of transmitted light at an incident light angle of 0° is B [%], it is characterized in that the relationship of 1.7 ≤ B / A holds. And since 1.7 ≤ B / A, particularly, the larger B / A is, the more the scattering characteristics differ depending on the film incident angle. Due to the different scattering characteristics of each part of the house with the film extended, light from more directions hits the plants, and it becomes possible to make the shadow lighter. The range of B / A is preferably 2.1 or more and 2.7 or less.

[0057] Also, from the viewpoint of reducing particularly strong direct light incident on the film at 0° and preventing disorders such as leaf burns, the amount of transmitted light B is preferably less than 35%.

[0058] Thus, in the present invention, by setting the amount of transmitted light A at an incident light angle of 45° and the amount of transmitted light B at an incident light angle of 0° within the above ranges, it becomes possible to make the shadow of the greenhouse aggregate and the shadow of plants lighter. Therefore, it is possible to promote the growth of plants and improve the productivity even in tall crops.

[0059] From the viewpoint of taking in a large amount of light into the greenhouse, in the present invention, the total light transmittance of the agricultural polyolefin resin film 1 is set to 80% or more.

[0060] The term "total light transmittance" used herein refers to the ratio of transmitted light to parallel incident light, and refers to light transmittance including a diffuse component.

[0061] <Manufacturing method> The agricultural polyolefin resin film 1 of the present invention is preferably produced by an inflation method.

[0062] Specifically, the molten resin materials forming the outer layer 2, inner layer 3, and intermediate layer 4 are co-extruded into a tubular shape from a die, expanded from the inside by air pressure, and then cooled to produce the agricultural polyolefin resin film 1 of the present invention.

[0063] Methods for co-extrusion of the molten resins that make up each layer include a pre-die lamination method in which the molten resins come into contact with each other before the die, an in-die lamination method in which the molten resins come into contact with each other inside the die, and an out-die lamination method in which the molten resins come into contact with each other after being discharged from multiple concentric lips of the die.

[0064] <Other forms> The agricultural polyolefin resin film of the present invention is not limited to the illustrated examples. For example, in the agricultural polyolefin resin film 1 of the above embodiment, the intermediate layer 4 is three layers, but the intermediate layer 4 may be one or more layers, may be two layers, or may be four or more layers.

[0065] Furthermore, for example, when the intermediate layer 4 has two or more layers, at least one of the layers must be a foam layer. From the viewpoint of heat retention and heat insulation, it is preferable that all of the intermediate layers 4 are foam layers. When light-blocking properties are required, the intermediate layer 4 preferably contains various pigments, but when light-blocking properties are not required, it is not necessary to contain various pigments.

[0066] Furthermore, in the agricultural polyolefin resin film 1 of the above embodiment, the intermediate layer 4 is a foamed layer, but it may be a non-foamed layer like the outer layer 2 and the inner layer 3.

[0067] In addition, in the agricultural polyolefin resin film 1 of the present invention, an anti-fog coating film 8 consisting of a thermoplastic resin binder and an anti-fog agent such as an inorganic colloidal sol may be provided on the surface 3a (surface opposite to the side where sunlight enters) of the inner layer 3, as shown in Fig. 2. By providing such an anti-fog coating film 8, the surface condition of the film can be maintained (i.e., smoothing due to fogging (moisture) can be prevented) and scattering performance can be maintained.

[0068] The thermoplastic resin binder used in the anti-fog coating film 8 is not particularly limited as long as it exhibits good adhesion to the inner layer 3. Examples include acrylic resins, urethane resins, vinyl acetate resins, vinyl chloride-vinyl acetate resins, and polyester resins. These thermoplastic resin binders are usually dispersed in water or an aqueous solvent such as water and alcohol and used as an aqueous emulsion.

[0069] Among thermoplastic resin binders, aqueous urethane resins, particularly aqueous acrylic-modified urethane resins, are preferred. The aqueous acrylic-modified urethane resin is preferably a polyester-based anionic one, which can be produced, for example, by polymerizing (ii) a hydroxyl-containing acrylic compound in the presence of (i) a polyester-based anionic aqueous urethane resin, followed by reacting (iii) an active isocyanate compound.

[0070] On the other hand, examples of inorganic colloidal sols used as other components of the anti-fogging coating film 8 include colloidal silica particles and colloidal alumina particles. Colloidal silica particles may be spherical or have a large aspect ratio, such as elongated shapes. Spherical colloidal silica particles may have an average particle size of 5 to 90 nm, preferably 20 to 80 nm. Elongated colloidal silica particles may have a ratio D1 / D2 (D1 millimicrons) of particle diameter measured by dynamic light scattering to D2 millimicrons (D2 millimicrons) measured by nitrogen gas adsorption) of 5 or more, with D1 being 40 to 500 nm and a minor axis of 5 to 40 nm as measured by electron microscopy. Such elongated colloidal silica particles are known (see Japanese Patent Laid-Open Publication No. 4-65314) and are commercially available.

[0071] In addition to the above, colloidal lithium silicate particles can also be used. On the other hand, colloidal alumina particles having an average particle size of 5 to 70 nm, preferably 20 to 60 nm, are suitable. These inorganic colloidal sols may be used alone or in combination of two or more.

[0072] The ratio of the thermoplastic resin binder to the inorganic colloid sol, in terms of solids weight ratio, is preferably in the range of 1:9 to 7:3. When the ratio of the thermoplastic resin binder to the inorganic colloid sol is in this range, sufficient adhesion between the anti-fogging coating film 8 and the inner layer can be obtained, and good anti-fogging properties can be exhibited.

[0073] The following method is preferably used to form the anti-fog coating film 8 on the surface of the inner layer 3. First, an aqueous emulsion composition containing a thermoplastic resin binder and an inorganic colloidal sol in a predetermined ratio is prepared, and the composition is applied to the surface 3a of the inner layer 3 using a coating method such as a gravure coater, reverse roll coater, or air knife coater. This is then dried with hot air at a temperature of about 50 to 150°C to form a coating film with a thickness of 0.2 to 5 μm, preferably about 0.5 to 2 μm. A thickness of 0.2 μm or more ensures sufficient anti-fog effect, while a thickness of 5 μm or less provides good light transmittance.

[0074] In forming a coating film, the aqueous emulsion composition may contain a silicone surfactant or a fluorine surfactant to improve coating properties, as desired. Examples of silicone surfactants include polyether-modified silicone oils, and examples of fluorine surfactants include surfactants containing a fluoroalkyl group or a fluoroalkenyl group. The amount of these surfactants added is typically selected from the range of 0.01 to 1% by mass based on the total amount of the aqueous emulsion composition.

[0075] Furthermore, various additives such as conventionally used emulsifiers, dispersants, stabilizers, and crosslinking agents can be added within the scope of the present invention. Furthermore, hindered amine-based light stabilizers and ultraviolet absorbers can be added to improve the weather resistance of the coating film. The incorporation of a crosslinking agent can particularly improve the water resistance of the coating film. Examples of crosslinking agents include epoxy-based and aziridine-based agents. [Example]

[0076] The present invention will be described below based on examples. However, the present invention is not limited to these examples, and these examples can be modified or changed based on the spirit of the present invention, and such modifications are not excluded from the scope of the present invention.

[0077] The materials used to prepare the agricultural polyolefin resin film are listed below. (1) EVA15: Ethylene-vinyl acetate copolymer with a vinyl acetate unit content of 15% by mass, MFR 1.1 g / 10 min (manufactured by NUC Corporation, product name: NUC-8452D) (2) EVA18: Ethylene-vinyl acetate copolymer with a vinyl acetate unit content of 18% by weight, MFR 0.9 g / 10 min (NUC Corporation, trade name: NUC-3765) (3) LDPE-1: High-pressure low-density polyethylene, density 0.922 g / cm 3 , MFR 0.2g / 10min (NUC, product name: DFDJ-6776) (4) LDPE-2: High-pressure low-density polyethylene, density 0.923 g / cm 3 , MFR 0.8g / 10min (NUC Corporation, product name: NUC-8505) (5) LL: Linear low-density polyethylene, density 0.915 g / cm 3 , MFR 2.0 g / 10 min (Prime Polymer Co., Ltd., product name: SP2020) (6) Mica: manufactured by Repco Co., Ltd., product name: M-XF (7) Calcium carbonate: manufactured by Maruo Calcium Co., Ltd. (average particle size 2.2 μm) (8) Coloring agent: PO-0107 White, manufactured by Nikko Vicks Co., Ltd. (9) Foaming agent: manufactured by Eiwa Chemical Industry Co., Ltd., product name: Celbon (10) Anti-fogging agent: non-ionic surfactant (polyoxyethylene ether)

[0078] Example 1 <Preparation of single-layer polyolefin resin film for agricultural use> First, the materials shown in Table 1 were blended to prepare a resin material of Example 1 having the composition (parts by mass) shown in Table 1. Next, using an inflation device, the resin material was extruded in a molten state from the lip of a die and expanded from the inside by air pressure, and then cooled and wound up to produce a 100 μm thick agricultural polyolefin resin film.

[0079] <Measurement of total light transmittance> The total light transmittance (%) of the prepared film was measured using a spectrophotometer (manufactured by Nippon Denshoku Industries Co., Ltd., trade name: NDH-2000 model) in accordance with JIS K 7361-1. The results are shown in Table 1.

[0080] <Measurement of transmitted light amount> The prepared film was placed in the sample holder of a commercially available goniophotometer GP200 (a three-dimensional variable angle photometer manufactured by Murakami Color Research Institute), and the amount of transmitted light was measured when the incident light angle was 0° and 45° relative to the surface of the prepared film. The maximum amount of light when no prepared film was installed (blank) was taken as 100%, and the transmitted light amount was calculated as the ratio of the amount of incident light transmitted in the straight direction through the installed film. The measurement light from the goniophotometer was attenuated using filters (ND1 + ND10). The results are shown in Table 1.

[0081] <Evaluation by photosynthetic photon flux density> First, a cubic frame 10 having a length, width, and height of 30 cm was fabricated using a 30 cm long steel material, as shown in Fig. 3. Next, as shown in Fig. 3, a cylindrical rod 11 having a diameter of 25 cm and a length of 30 cm was fixed with tape on the center line of the top surface of this frame 10. The rod 11 was fixed so that its longitudinal direction was parallel to the direction of the sun and horizontal to the ground.

[0082] Next, in Konan City, Shiga Prefecture, this frame 10 was placed outdoors between 1:00 PM and 2:00 PM on October 9, 2018, and the photosynthetically active photon flux density of the central portion C of the shadow of the rod-shaped body 11 fixed to the frame 10 was measured using a photon meter (manufactured by Fujiwara Seisakusho Co., Ltd., product name: MQ200) as shown in Figure 3. In addition, this frame 10 was prepared with the agricultural polyolefin resin film stretched over it, and placed outdoors, and under the same conditions, the photosynthetically active photon flux density of the central portion C of the shadow of the rod-shaped body 11 fixed to the frame 10 was measured.

[0083] The term "photosynthetically effective photon flux density" used here refers to the number of photons in the wavelength range of 400 nm to 700 nm that are effective for photosynthesis among the photons that pass through a unit area in a unit time.

[0084] Then, the photosynthetic photon flux density of the central part C of the shadow of the frame where the film is not stretched is defined as D1 [μmol m -2 s -1 ], and the photosynthetic photon flux density of the central part C of the shaded area of ​​the frame with the film stretched out is D2 [μmol m -2 s -1 When the ratio D2 / D1 was 2.00 or more, the shaded areas were judged to be able to improve the productivity of crop cultivation. The results are shown in Table 1.

[0085] (Examples 2 to 5, Comparative Examples 1 to 5) A polyolefin resin film for agricultural use was produced in the same manner as in Example 1 above, except that the composition of the resin component was changed to the composition (parts by mass) shown in Table 1.

[0086] Then, the total light transmittance was measured, the amount of transmitted light was measured, and evaluation was performed based on the photosynthetically active photon flux density in the same manner as in Example 1. The results are shown in Table 1.

[0087] [Table 1]

[0088] Example 6 First, the materials shown in Table 2 were blended to prepare the resin material of Example 5 having the composition (parts by mass) shown in Table 2. Next, using a three-type, three-layer inflation device, the resin materials were co-extruded in a molten state from multiple concentric lips of a die so that from the outside, the resin material for the inner layer, the resin material for the middle layer, and the resin material for the outer layer were formed. The extrusion was expanded from the inside by air pressure, and then cooled and wound up to produce a three-type, three-layer agricultural polyolefin resin film with an outer layer thickness of 20 μm, a middle layer thickness of 65 μm, and an inner layer thickness of 15 μm.

[0089] Next, a coating liquid for forming an anti-fogging coating film was prepared, consisting of 50 parts by mass of an acrylic resin emulsion, 50 parts by mass of alumina sol, and 0.5 parts by mass of a polyether-modified silicone surfactant. This was applied to the outer surface (i.e., the surface of the inner layer) of the agricultural polyolefin resin film using a gravure coater (gravure roll: 160 mesh), and dried at 120°C to form an anti-fogging coating film 2 μm thick.

[0090] Then, the total light transmittance, the amount of transmitted light, and the photosynthetically active photon flux density were measured in the same manner as in Example 1. The results are shown in Table 2.

[0091] (Comparative Example 6) A three-kind, three-layer agricultural polyolefin resin film was produced in the same manner as in Example 5 above, except that the composition of the resin components was changed to the composition (parts by mass) shown in Table 2.

[0092] Then, the total light transmittance, the amount of transmitted light, and the photosynthetically active photon flux density were measured in the same manner as in Example 1. The results are shown in Table 2.

[0093] (Comparative Example 7) A three-kind, three-layer agricultural polyolefin resin film was produced in the same manner as in Example 5 above, except that the resin component composition was changed to the composition (parts by mass) shown in Table 2.

[0094] Next, a coating liquid for forming an anti-fogging coating film was prepared, consisting of 50 parts by mass of an acrylic resin emulsion, 50 parts by mass of alumina sol, and 0.5 parts by mass of a polyether-modified silicone surfactant. This was applied to the outer surface (i.e., the surface of the inner layer) of the agricultural polyolefin resin film using a gravure coater (gravure roll: 160 mesh), and dried at 120°C to form an anti-fogging coating film 2 μm thick.

[0095] Then, the total light transmittance, the amount of transmitted light, and the photosynthetically active photon flux density were measured in the same manner as in Example 1. The results are shown in Table 2.

[0096] [Table 2]

[0097] <Evaluation based on crop growth status> At a test site in Ishibe Town, Koka District, Shiga Prefecture, the film of Example 6 described above was spread in a greenhouse (length 9.0 m x width 3.8 m x height 2.5 m), and cherry tomatoes were grown as tall crops from July to December 2018. The results are shown in Table 3.

[0098] [Table 3]

[0099] As shown in Table 1, the D2 / D1 ratio for the films of Examples 1 to 5 is 2.00 or more, and inside the frame 10 in which these films are extended, the shadow of the rod-shaped body 11 is faint and there are many photons in the wavelength range of 400 nm to 700 nm that are effective for photosynthesis, which shows that the productivity of crop cultivation can be improved.

[0100] Similarly, as shown in Table 2, the film of Example 6 had a D2 / D1 ratio of 2.00 or more, and as shown in Table 3, the yield of cherry tomatoes grown in a greenhouse in which the film of Example 5 was spread was very high, indicating that the film of Example 6 can improve tomato productivity. [Industrial Applicability]

[0101] As described above, the present invention is suitable for agricultural polyolefin resin films. [Explanation of symbols]

[0102] 1. Polyolefin resin film for agricultural use 2 outer layer 3. Inner layer (agricultural polyolefin resin film) 4. Middle class 5. First Middle Class 6. The second middle class 7. The third middle class 8 Anti-fog coating 10 Frame 11 Rod-shaped body C. The central part of the shadow of the rod-shaped body

Claims

1. A polyolefin-based resin film for agricultural use, the layer on the side opposite to the side on which sunlight is incident containing, as resin components, an ethylene-vinyl acetate copolymer and a low-density polyethylene, the ethylene-vinyl acetate copolymer has a melt mass flow rate of 0.9 to 1.1 g / 10 min; The total light transmittance is 80% or more, An agricultural polyolefin resin film characterized in that, when the amount of transmitted light measured with a goniophotometer at an incident light angle of 45° is A [%] and the amount of transmitted light at an incident light angle of 0° is B [%], the relationship is 0% < A < 20% and the relationship B / A satisfies 1.7 ≦ B / A.

2. 2. The agricultural polyolefin resin film according to claim 1, wherein the transmitted light amount B is less than 35%.

3. The agricultural polyolefin resin film according to claim 1, characterized in that the content of the ethylene-vinyl acetate copolymer is 60 parts by mass or more when the resin component of the layer is 100 parts by mass.

4. The agricultural polyolefin resin film according to any one of claims 1 to 3, characterized in that the resin component of the layer contains an inorganic substance having an average particle diameter of 1 μm or more, and the content of the inorganic substance is 5 parts by mass or less when the resin component of the layer is 100 parts by mass.

5. The agricultural polyolefin resin film according to any one of claims 1 to 4, characterized in that it has a multilayer structure further comprising another layer laminated on the layer and made of another resin material containing a polyolefin resin.

6. The agricultural polyolefin resin film according to any one of claims 1 to 5, characterized in that an anti-fogging coating film comprising a thermoplastic resin binder and an anti-fogging agent is provided on the surface of the layer opposite to the side on which sunlight is incident.

7. The agricultural polyolefin resin film described in claim 1, characterized in that when a cylindrical rod-shaped body with a diameter of 25 cm and a length of 30 cm is fixed on the center line of the top surface of a cubic frame body with length, width, and height of 30 cm and the longitudinal direction of the rod-shaped body is parallel to the direction of the sun and horizontal to the ground, and the frame body is installed outdoors, the photosynthetically effective photon flux density of the central part of the shadow of the rod-shaped body in the frame body on which the agricultural polyolefin resin film described in claim 1 is not stretched is D 1 [μmol m -2 s -1 ], and the photosynthetically effective photon flux density of the central part of the shadow of the rod-shaped body in the frame body on which the agricultural polyolefin resin film described in claim 1 is stretched is D 2 [μmol m -2 s -1 )], D 2 / D 1 is 2.00 or more.

8. A polyolefin resin film for agricultural use containing an ethylene-vinyl acetate copolymer and a low-density polyethylene as resin components, the ethylene-vinyl acetate copolymer has a melt mass flow rate of 0.9 to 1.1 g / 10 min; The total light transmittance is 80% or more, An agricultural polyolefin resin film characterized in that, when the amount of transmitted light measured with a goniophotometer at an incident light angle of 45° is A [%] and the amount of transmitted light at an incident light angle of 0° is B [%], the relationship is 0% < A < 20% and the relationship B / A satisfies 1.7 ≦ B / A.

9. The agricultural polyolefin resin film described in claim 8, characterized in that when a cylindrical rod-shaped body with a diameter of 25 cm and a length of 30 cm is fixed on the center line of the top surface of a cubic frame body with length, width, and height of 30 cm and the longitudinal direction of the rod-shaped body is parallel to the direction of the sun and horizontal to the ground, and the frame body is set outdoors, the photosynthetically effective photon flux density of the central part of the shadow of the rod-shaped body in the frame body on which the agricultural polyolefin resin film described in claim 8 is not stretched is D 1 [μmol m -2 s -1 ], and the photosynthetically effective photon flux density of the central part of the shadow of the rod-shaped body in the frame body on which the agricultural polyolefin resin film described in claim 8 is stretched is D 2 [μmol m -2 s -1 )], D 2 / D 1 is 2.00 or more.

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