JP2020195332A - Polyolefin-based resin film for agriculture - Google Patents

Abstract

To provide a polyolefin-based resin film for agriculture which can apply an anti-fogging agent uniformly by suppressing formation of unevenness on a surface to which an anti-fogging agent is applied and can be used for a lining ceiling requiring high antifogging properties.SOLUTION: There is provided a polyolefin-based resin film for agriculture 1 which comprises an outer layer 2 composed of a resin material (a) containing a polyolefin-based resin, an inner layer 3 composed of a resin material (c) containing a polyolefin-based resin, intermediate layers 4 which are provided between the outer layer 2 and the inner layer 3 and are composed of a resin material (b) containing a polyolefin-based resin and an antifogging layer 8 provided on the surface of the inner layer 3 on the opposite side to the outer layer 2 side. At least one layer of the intermediate layers 4 is a foam layer in which the resin material (b) is foamed and the maximum height Rz of a surface 3a of the inner layer 3 on the opposite side to the outer layer 2 side is 95 μm or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to an agricultural polyolefin resin film used in agricultural facilities such as agricultural greenhouses and agricultural tunnels, and a method for producing the same.

In recent years, agricultural films made of olefin resins have been used, but in agricultural greenhouses and tunnels, the indoor air temperature and soil temperature that have risen due to sunlight during the day should not drop too much at night. , Agricultural films are required to retain heat.

For example, a polyolefin-based agricultural film (see Patent Document 1) containing a heat insulating agent containing a composite hydroxide condensed silicate as an active ingredient, or a cap film having a large number of cap-shaped protrusions and having excellent heat insulating properties. An agricultural film in which is laminated (see Patent Document 2) has been proposed.

Japanese Unexamined Patent Publication No. 2007-12001 Japanese Unexamined Patent Publication No. 2009-4560

Here, in order to give the agricultural polyolefin resin film an antifogging function, it is generally necessary to apply an antifogging agent to the agricultural polyolefin resin film, but in the above-mentioned conventional agricultural film, the antifogging agent is applied. It was difficult to apply the antifogging agent uniformly because the unevenness on the coated surface of the agent was large.

Further, instead of applying the antifogging agent, a method of kneading the antifogging agent into the film is conceivable, but in this case, since the drip-proofing agent applied to the inner surface of the film is a surfactant having a hydrophilic group, After the drip-proof agent is ejected onto the surface of the film and flows out due to moisture, the anti-fog property is lost and the anti-fog effect cannot be maintained for a long period of time. Therefore, it has been difficult to apply an agricultural polyolefin resin film to a lining ceiling that requires high anti-fog properties.

Therefore, the present invention has been made in view of the above problems, and by suppressing the formation of irregularities on the surface to which the antifogging agent is applied, the antifogging agent can be uniformly applied and high antifogging property. It is an object of the present invention to provide an agricultural polyolefin resin film that can be used for a lining ceiling that is required to be used.

In order to achieve the above object, the agricultural polyolefin resin film of the present invention has an outer layer made of a resin material (a) containing a polyolefin resin, an inner layer made of a resin material (c) containing a polyolefin resin, and an outer layer. An intermediate layer made of a resin material (b) containing a polyolefin-based resin, which is provided between the inner layer and one or more layers, and an antifogging layer provided on the surface of the inner layer opposite to the outer layer side. At least one of the intermediate layers is a foamed layer in which the resin material (b) is foamed, and the maximum height Rz of the surface of the inner layer opposite to the outer layer side is 95 μm or less. ..

According to the present invention, it is possible to provide an agricultural polyolefin resin film that can be uniformly applied with an antifogging agent and can be used for a lining ceiling that requires high antifogging property.

It is sectional drawing which shows the polyolefin resin film for agriculture which concerns on embodiment of this invention.

Hereinafter, the agricultural polyolefin resin film of the present invention will be specifically described. The present invention is not limited to the following embodiments, and can be appropriately modified and applied without changing the gist of the present invention.

<Agricultural polyolefin resin film>
As shown in FIG. 1, the agricultural polyolefin resin film 1 of the present invention includes an outer layer 2 which is a layer on the side where sunlight is incident and an inner layer 3 which is a layer opposite to the side where sunlight is incident. , The intermediate layer 4 provided between the outer layer 2 and the inner layer 3 and the anti-fog layer (anti-fog coating film) 8 provided on the surface of the inner layer 3 (the surface opposite to the outer layer 2 side) 3a. It has a multi-layer structure in which each of these layers is laminated.

From the viewpoint of strength and handleability, the thickness of the agricultural polyolefin resin film 1 is preferably 50 to 400 μm, more preferably 100 to 300 μm.

<Outer layer>
The outer layer 2 becomes the outermost layer facing the outside of the facility when it is extended to the agricultural facility. The outer layer 2 is a layer that reinforces the intermediate layer 3 that lacks strength due to the fact that various pigments are blended in a large amount and the resin material is foamed, and is an agricultural polyolefin resin film by the inflation method. Since it is a layer that prevents air for expanding the tubular molten resin from being released from the inside when manufacturing No. 1, it is made into a non-foaming layer.

Further, since the outer layer 2 is a layer that protects the various pigments of the intermediate layer 4 from deterioration without interfering with the functions (reflection, shading, etc.) of the intermediate layer 4, it is a layer having light transmission.

The outer layer 2 is a layer made of a resin material (a) containing a polyolefin-based resin, and the polyolefin-based resin is a linear low-density polyethylene from the viewpoint of improving the strength of the polyolefin-based resin film 1 for agriculture. Is preferable.

Further, as the outer layer 2, for example, linear low-density polyethylene is used as a main component, and high-pressure low-density polyethylene having a different melt mass flow rate (MRF) of about 0.5 to 2.0 g / 10 minutes is blended as a secondary component. The composition can be used. By blending resins having different melt mass flow rates of about 0.5 to 2.0 g / 10 minutes, the satinness of the multilayer film can be further increased.

The above melt mass flow rate can be obtained by measuring in accordance with the provisions of JIS K 7210: 1999.

Further, the resin material may contain other polyolefin-based resins, known additives, and the like as long as the strength, light transmission, and the like are not impaired.

The thickness of the outer layer 2 is preferably 10 to 40 μm, more preferably 15 to 30 μm. When the thickness is 10 μm or more, the dustproof effect is sufficient, and when the thickness is 40 μm or less, the light transmission is good.

<Inner layer>
When the inner layer 3 is installed in an agricultural facility, the inner layer 3 becomes the innermost layer facing the inside of the facility. The inner layer 3 is a layer that reinforces the intermediate layer 3 like the outer layer 2 described above, and is a non-foaming and light-transmitting layer.

The inner layer 3 is a layer made of a resin material (c) containing a polyolefin-based resin, and examples of the polyolefin-based resin include linear low-density polyethylene and low-density polyethylene. Of the polyolefin-based resin film 1 for agriculture. Linear low-density polyethylene is preferable from the viewpoint of improving the strength.

From the viewpoint of ensuring strength, the density of the polyolefin resin is preferably 0.900 to 0.930 g / cm ³ , and the melt mass flow rate (MRF) is preferably 0.5 to 3.0 g / 10 minutes.

When a conventional resin material containing an ethylene-vinyl acetate copolymer is used, unevenness is likely to be formed on the surface 3a of the inner layer 3 opposite to the outer layer 2 side, so that the antifogging layer is formed on the surface 3a. It becomes difficult to provide 8 and it is not preferable.

Further, other polyolefin-based resins, other known additives, and the like may be contained as long as the flexibility, transparency, and the like are not impaired.

For example, the resin material (c) forming the inner layer 3 may contain an anti-fog agent in order to impart anti-fog properties to the agricultural polyolefin resin film 1. Examples of the antifogging agent include a partial ester of a polyhydric alcohol (sorbitan-based, glycerin-based, diglycerin-based, etc.) and a fatty acid, or a condensate of these with an alkylene glycol.

The amount of the antifogging agent blended is preferably 1 to 5 parts by mass, more preferably 1.2 to 3 parts by mass with respect to 100 parts by mass of the polyolefin resin.

Further, the resin material (c) may contain a fluorine-based surfactant or a silicone-based surfactant together with the antifogging agent in order to impart antifog properties to the agricultural polyolefin resin film 1.

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

<Middle layer>
The intermediate layer 4 has a first intermediate layer 5, a second intermediate layer 6, and a third intermediate layer 7 in this order from the outer layer 2 side, and has heat retention and heat insulating properties with respect to the agricultural polyolefin resin film 1. From the viewpoint of imparting the above, at least one of these first to third intermediate layers 5 to 7 is composed of a foamed layer obtained by foaming a resin material (b) containing a polyolefin-based resin.

The first to third intermediate layers 5 to 7 are layers made of a resin material (b) containing a polyolefin-based resin such as linear low-density polyethylene or an ethylene-vinyl acetate copolymer, and have a film strength and handleability. From the viewpoint of flexibility, it is preferable to use an ethylene-vinyl acetate copolymer as the polyolefin resin.

The ethylene-vinyl acetate copolymer preferably has a vinyl acetate content of 5 to 30% by mass, more preferably 10 to 25% by mass. When the vinyl acetate content is 5% by mass or more, the adhesion to the antifogging layer described later is good. Further, when it is 30% by mass or less, the strength of the obtained film becomes sufficient and the transparency becomes good.

Further, as the ethylene-vinyl acetate copolymer, it is preferable to use one having a melt mass flow rate of 1.2 to 10 g / 10 minutes. If the melt mass flow rate is 1.2 g / 10 minutes or more, a low density polyethylene having a high melt mass flow rate can be used, and the molding speed can be increased, so that the film can be produced efficiently. Becomes possible. On the other hand, if the melt mass flow rate exceeds 10 g / 10 minutes, it becomes difficult to maintain the shape of the film, and the film forming property deteriorates.

When the first to third intermediate layers 5 to 7 are foamed, the resin material (b) containing the polyolefin-based resin is foamed with a foaming agent.

As the foaming agent, a known foaming agent for polyolefin resins may be used. For example, sodium hydrogencarbonate, azodicarbonamide, p, p'-oxybisbenzenesulfonylhydrazide, hydrazodicarboxylicamide, N, Examples thereof include N'-dinitrosopentamethylenetetramine. For example, commercially available products such as Policelen EV306G (manufactured by Sankyo Kasei Co., Ltd.), Cell Mike 3031T (manufactured by Eiwa Kasei Co., Ltd.), and Cell Mike MB1061-7 (manufactured by Eiwa Kasei Co., Ltd.) can be used.

The blending amount of the foaming agent is preferably 0.05 to 5 parts by mass, more preferably 0.3 to 3 parts by mass with respect to 100 parts by mass of the polyolefin resin.

From the viewpoint of further improving the smoothness of the surface 3a of the inner layer 3, at least one of the first intermediate layer 5 and the second intermediate layer 6 is a foamed layer in the agricultural polyolefin resin film 1 of the present invention. It is preferable that the layer on the inner layer 3 side of the intermediate layer 4 (that is, the third intermediate layer 7) is a non-foaming layer.

Further, the resin material (b) may contain other polyolefin-based resins, other known additives, and the like as long as the strength, handleability, and flexibility are not impaired.

The thickness of the intermediate layer 4 is preferably 30 to 100 μm, more preferably 40 to 80 μm. If the thickness of the intermediate layer 4 is 30 μm or more, sufficient physical properties such as tensile strength and elasticity of the polyolefin resin film 1 for agriculture can be obtained, and if it is 100 μm or less, sufficient light transmission can be obtained. it can. From the viewpoint of ensuring good physical properties of the agricultural polyolefin resin film 1, the thickness of the intermediate layer 4 is in the range of 50 to 80% when the total thickness of the agricultural polyolefin resin film 1 is 100%. Is preferable, and the range of 55 to 75% is more preferable.

<Anti-fog layer>
The antifogging layer 8 is for maintaining the surface state of the film (that is, preventing smoothing due to fogging (moisture)) and maintaining the scattering performance, and is an antifogging agent such as a thermoplastic resin binder and an inorganic colloid sol. It is composed of and.

The thermoplastic resin binder used for the antifogging layer 8 may be a thermoplastic resin that exhibits good adhesion to the inner layer 3, and there are no other restrictions. For example, acrylic resin, urethane resin, vinyl acetate resin, vinyl chloride-vinyl acetate resin, polyester resin and the like can be mentioned. In addition, these thermoplastic resin binders are usually used as an aqueous emulsion in which water or water and an aqueous solvent such as alcohol are dispersed.

Among the thermoplastic resin binders, an aqueous urethane resin, particularly an aqueous acrylic modified urethane resin is preferable. The aqueous acrylic modified urethane resin is preferably polyester-based anionic, for example, (a) a hydroxy group-containing acrylic compound is polymerized in the presence of (b) polyester-based anionic aqueous urethane resin. , (C) Can be produced by reacting with an active isocyanate compound.

On the other hand, examples of the inorganic colloidal sol used as another component of the antifogging layer 8 include colloidal silica particles and colloidal alumina particles. The colloidal silica particles may be spherical or have a large aspect ratio, for example, an elongated shape. As the spherical colloidal silica particles, colloidal silica particles having an average particle size of 5 to 90 nm, preferably 20 to 80 nm can be used. Further, as the elongated colloidal silica particles, the ratio D1 / D2 of the measured particle size (D1 millimicron) by the dynamic light scattering method and the measured particle size (D2 millimicron) by the nitrogen gas adsorption method is 5 or more. Therefore, it is possible to use a D1 having a D1 of 40 to 500 nm and a minor axis of 5 to 40 nm as observed by an electron microscope. Colloidal silica particles having such an elongated shape are known (Japanese Patent Laid-Open No. 4-65314) and can be obtained as a commercially available product.

In addition to the above, colloidal lithium silicate particles and the like can be used. On the other hand, as the colloidal alumina particles, those having an average particle size of 5 to 70 nm, preferably 20 to 60 nm are preferable. These inorganic colloidal sol may be used alone or in combination of two or more.

The ratio of the thermoplastic resin binder to the inorganic colloidal sol is preferably in the range of 1: 9 to 7: 3 in terms of solid content weight ratio. When the ratio of the thermoplastic resin binder to the inorganic colloidal sol is within this range, sufficient adhesive force between the antifogging layer 8 and the inner layer 3 can be obtained, and good antifogging properties can be exhibited.

In order to form the antifogging layer 8 on the surface 3a of the inner layer 3, the following method is preferably used. First, an aqueous emulsion composition (anti-fog agent) containing a thermoplastic resin binder and an inorganic colloid sol in a predetermined ratio is prepared, and the composition is used by a coating method using a gravure coater, a reverse roll coater, an air knife coater, or the like. Is applied to the surface 3a of the inner layer 3. Then, it may be dried with hot air at a temperature of about 50 to 150 ° C. to form a coating film having a film thickness of about 0.2 to 5 μm, preferably about 0.5 to 2 μm. When the film thickness is 0.2 μm or more, the antifogging effect is sufficiently exhibited, and when the film thickness is 5 μm or less, the light transmission is good.

At the time of forming the coating film, the aqueous emulsion composition may contain a silicone-based surfactant or a fluorine-based surfactant, if desired, for the purpose of improving the coatability. As the silicone-based surfactant, for example, a polyether-modified silicone oil is preferable, and as the fluorine-based surfactant, for example, a surfactant containing a fluoroalkyl group or a fluoroalkenyl group is used. The blending amount of these surfactants is usually selected in the range of 0.01 to 1% by mass with respect to the total amount of the aqueous emulsion composition.

In addition, various additive components such as emulsifiers, dispersants, stabilizers, and cross-linking agents that have been conventionally used can be contained as long as the object of the present invention is not impaired. Further, in order to enhance the weather resistance of the coating film, a hindered amine-based light stabilizer, an ultraviolet absorber, or the like can be contained. If a cross-linking agent is added, the effect of improving the water resistance of the coating film can be obtained. Examples of the cross-linking agent include epoxy-based and aziridine-based cross-linking agents.

Here, the present inventors examined the conditions for ensuring the smoothness of the surface 3a of the inner layer 3 in the polyolefin-based resin film 1 for agriculture, and found that the surface roughness (maximum height) of the surface 3a of the inner layer 3 was examined. It has been found that the applicability of the antifogging agent on the surface 3a can be improved by controlling Rz).

More specifically, by setting the maximum height Rz of the surface 3a of the inner layer 3 to 95 μm or less, the formation of irregularities on the surface 3a of the inner layer 3 can be suppressed, so that the antifogging agent is applied on the surface 3a. It becomes possible to apply evenly. As a result, it becomes easy to provide the antifogging layer 8 on the surface 3a of the inner layer 3.

Further, since the antifogging agent can be uniformly applied to the surface 3a of the inner layer 3, unlike the above-mentioned conventional technique, it is not necessary to knead the antifogging agent or apply the drip-proofing agent. As a result, the antifogging property of the polyolefin-based resin film 1 for agriculture is improved, and it can be used for a lining ceiling that requires high antifogging property.

In this specification, the "maximum height Rz" is measured in accordance with JIS B 0601: 2001, and is the height of the highest mountain and the depth of the deepest valley in the roughness curve. It means what is required as a sum.

Further, from the viewpoint of improving the heat retention of the polyolefin-based resin film 1 for agriculture, the porosity calculated by the following formula (1) is preferably 5% or more.

[Number 1]
Porosity [%] = 1- (ρ / ρ ₀ ) (1)
(Here, ρ is the apparent specific gravity including the pores, and ρ ₀ is the true specific gravity not including the pores.)

In addition, in this specification, "porosity" means the thing measured in accordance with JIS R 2205 (measurement method of apparent porosity, water absorption rate, specific gravity of refractory brick).

Further, the "apparent specific gravity including pores" and the "true specific gravity not including pores" are specific gravities measured in accordance with JIS K 7222, but the polyolefin-based resin film for agriculture of the present invention has a foamed layer. Does not appear on the outside and can be regarded as a closed pore, so the specific gravity measured according to the underwater replacement method of JIS K 7222 is used.

From the viewpoint of maintaining strength, the porosity is preferably 60% or less, more preferably 50% or less, and even more preferably 30% or less.

Further, in the polyolefin-based resin film 1 for agriculture, the breaking strength is 10 N or more and 30 N or less and the Elmendorf strength is 10 N or more and 38 N in the mechanical axis (longitudinal) direction (hereinafter referred to as “MD direction”) of the film. The following is preferable.

In the present specification, the "breaking strength" refers to the tensile cutting strength measured by the method described in the examples described later, and the "Elmendorf strength" is based on JIS K 7128-2. It refers to the tear strength measured by.

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

Specifically, first, the molten resin materials (a) to (c) forming the outer layer 2, the inner layer 3, and the intermediate layer 4 are co-extruded from the die into a tube shape and expanded from the inside by the pressure of air. After that, cool it. At this time, at least one of the molten resin materials (b) forming the first to third intermediate layers 5 to 7 needs to include the above-mentioned foam layer in advance.

The methods for coextruding the molten resins constituting each layer include a pre-die lamination method in which each molten resin is brought into contact with each other in front of the die, an in-die lamination method in which the molten resins are brought into contact with each other inside the die, and a plurality of concentric circles of the die. An example is a die outer lamination method in which the resin is contacted after being discharged from the lip.

Next, using a coating method using a gravure coater, a reverse roll coater, an air knife coater, or the like, the above-mentioned antifogging agent is applied to the surface 3a of the inner layer 3 and dried to prevent fogging on the surface 3a of the inner layer 3. The layer 8 can be formed to produce the agricultural polyolefin resin film 1 of the present invention.

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

The intermediate layer 4 preferably contains various pigments when light-shielding property is required, but may not contain various pigments when light-shielding property is not required.

Hereinafter, the present invention will be described based on examples. The present invention is not limited to these examples, and these examples can be modified or modified based on the gist of the present invention, and these examples are excluded from the scope of the present invention. is not.

The materials used to prepare the polyolefin-based resin film for agriculture are shown below.

(1) LLDPE: Linear low density polyethylene, density: 0.915 g / cm ³ , MFR: 2.0 g / 10 minutes (manufactured by Prime Polymer Co., Ltd., trade name: SP2020)
(2) EVA: Ethylene-vinyl acetate copolymer having a vinyl acetate unit content of 15% by mass, MFR: 1.1 g / 10 minutes (manufactured by NUC Co., Ltd., product name: NUC-8452D)
(3) Foaming agent 1: Azodicarbonamide (manufactured by Eiwa Kasei Co., Ltd., trade name: Polyslen EE405F)
(4) Foaming agent 2: Azodicarbonamide (manufactured by Eiwa Kasei Co., Ltd., trade name: Polyslen EE2275F)
(5) Foaming agent 3: Azodicarbonamide (manufactured by Sankyo Kasei Co., Ltd., trade name: cell microphone cell microphone MB1023)

(Example 1)
<Production of polyolefin-based resin film for agriculture>
First, each material shown in Table 1 was blended to prepare a resin material of Example 1 having the composition (parts by mass) shown in Table 1. Next, using a 5 type 5 layer inflation device, the resin material of the inner layer, the resin material of the first intermediate layer, the resin material of the second intermediate layer, the resin material of the third intermediate layer, and the resin material of the outer layer are used from the outside. The resin material is co-extruded from a plurality of concentric lips of the die in a molten state, expanded from the inside by the pressure of air, cooled, and wound up so that the thickness of the outer layer is 20 μm and the middle. A five-kind, five-layer film having a layer thickness of 100 to 170 μm and an inner layer thickness of 20 μm was prepared.

Next, a coating liquid (antifogging agent) for forming an antifogging layer consisting of 50 parts by mass of an acrylic resin emulsion, 50 parts by mass of an alumina sol, and 0.5 parts by mass of a polyether-modified silicone-based surfactant was prepared and prepared. The outer surface of the film (the surface of the inner layer opposite to the outer layer side) is coated with bar coater # 7 and dried at 50 ° C. for 5 minutes to obtain an antifogging layer having a thickness of 2 μm. Was formed to prepare an agricultural polyolefin resin film of this example.

<Measurement of surface roughness (maximum height Rz) of the inner layer surface>
According to JIS B 0601: 2001, the surface roughness (maximum height Rz) of the surface of the inner layer (the surface of the inner layer opposite to the outer layer side) before the antifogging layer was formed was measured. More specifically, the surface roughness was measured three times in a region of 2000 μm × 2756 μm using a shape analysis laser microscope (manufactured by KEYENCE, trade name: VK-X1000), and the average value was taken as Rz. The above results are shown in Table 1.

<Evaluation of coatability>
The state of the coated surface when the above-mentioned coating liquid for forming an antifogging layer was dried at 50 ° C. for 5 minutes was evaluated according to the following evaluation criteria. The above results are shown in Table 1.
The coated surface is dry and has excellent coatability: ○
The coated surface is not dry and the coatability is inferior: ×

<Measurement of porosity>
In accordance with JIS R 2205, the porosity of the produced polyolefin-based resin film for agriculture was measured using the above formula (1). More specifically, in accordance with JIS K 7222, an automatic hydrometer (manufactured by Toyo Seiki Co., Ltd., trade name: high) measures the apparent specific gravity ρ including pores and the true specific gravity ρ ₀ not containing pores by the underwater substitution method. The porosity was determined by measurement using the precision type D-H100). The above results are shown in Table 1.

<Measurement of breaking strength>
Using a precision universal testing machine (manufactured by Shimadzu Corporation, trade name: Autograph AG-500D), the breaking strength in the longitudinal direction of the produced polyolefin-based resin film for agriculture was measured. The measurement width of the test piece was 5 mm, a marked line was placed at a position exactly 10 mm from the center of the test piece toward both ends, the distance between the marked lines was 20 mm, and the test piece was accurately attached to the tensile tester. The test speed was 200 ± 20 mm / min, and the force at which the test piece was cut was defined as the tensile cutting strength (breaking strength in the longitudinal direction). The above results are shown in Table 1.

<Measurement of Elmendorf strength>
According to JIS K 6732, a test piece (MD direction: 76 mm, TD direction: 63 mm) for the Elmendorf tear strength test was collected from the film obtained in Example 1. Next, using a digital Elmendorf tear tester [Toyo Seiki Seisakusho Co., Ltd., product number: SA-WP], the Elmendorf tear strength test of the above test piece was performed in accordance with JIS K 7128-2, and the following The strength of the film was evaluated based on the evaluation criteria.

More specifically, nine of the above test pieces were collected, the test temperature was 23 ° C., and the test pieces were kept in the test place for 1 hour or more. Then, the tear strength of the test piece was measured using the digital Elmendorf / tear tester. In addition, 2 values each of large and small were excluded from the 9 measured values, and the average value of the remaining 5 values was calculated and used as the Elmendorf tear strength. The above results are shown in Table 1.

(Examples 2 to 8)
An agricultural polyolefin resin film was produced in the same manner as in Example 1 above, except that the composition of the resin material was changed to the composition (parts by mass) shown in Table 1.

Then, in the same manner as in Example 1 described above, the surface roughness (maximum height Rz) of the inner layer surface is measured, the coatability is evaluated, the porosity is measured, the breaking strength is measured, and the Ermendorf strength is measured. went. The above results are shown in Tables 1 to 3.

(Comparative Examples 1-2)
An agricultural polyolefin resin film was produced in the same manner as in Example 1 above, except that the composition of the resin material was changed to the composition (parts by mass) shown in Table 2.

Then, in the same manner as in Example 1 described above, the surface roughness (maximum height Rz) of the inner layer surface is measured, the coatability is evaluated, the porosity is measured, the breaking strength is measured, and the Ermendorf strength is measured. went. The above results are shown in Table 4.

As shown in Tables 1 to 3, in the films of Examples 1 to 8, the maximum height Rz of the surface of the inner layer (the surface coated with the antifogging agent) is 95 μm or less, and it is on the surface of the inner layer. Since the formation of unevenness is suppressed, it can be seen that the antifogging agent is excellent in coatability (that is, the antifogging agent can be applied uniformly).

Further, in the films of Examples 1 to 8, the porosity is 5% or more, so that the moisturizing property is excellent, and the breaking strength and the Elmendorf strength are both 10 N or more, so that the strength is also excellent. You can see that.

On the other hand, as shown in Table 4, in the films of Comparative Examples 1 and 2, the maximum height Rz of the surface of the inner layer (the surface coated with the antifogging agent) is larger than 95 μm, and the surface of the inner layer has large irregularities. It can be seen that the antifogging agent is inferior in coatability (that is, the antifogging agent cannot be applied uniformly). In particular, in Comparative Example 2, since the second intermediate layer and the third intermediate layer are foam layers and the inner layer is formed of a resin material containing an ethylene-vinyl acetate copolymer, an antifogging agent is applied. It can be seen that large irregularities are formed on the surface of the inner layer to be formed, and the coatability of the antifogging agent on the surface is inferior.

Further, in Comparative Example 2, it can be seen that the strength is inferior because both the breaking strength and the Elmendorf strength are less than 10N.

As described above, the present invention is suitable for agricultural polyolefin resin films.

1 Agricultural polyolefin resin film 2 Outer layer 3 Inner layer 3a The surface of the inner layer on the opposite side of the outer layer 4 Intermediate layer 5 First intermediate layer 6 Second intermediate layer 7 Third intermediate layer 8 Anti-fog layer

Claims (5)

An outer layer made of a resin material (a) containing a polyolefin resin,
An inner layer made of a resin material (c) containing a polyolefin resin,
An intermediate layer provided between the outer layer and the inner layer and made of one or more layers of a resin material (b) containing a polyolefin-based resin.
The inner layer is provided with an anti-fog layer provided on the surface opposite to the outer layer side.
At least one of the intermediate layers is a foamed layer obtained by foaming the resin material (b).
An agricultural polyolefin resin film having a maximum height Rz of 95 μm or less on the surface of the inner layer opposite to the outer layer side. The agricultural polyolefin resin film according to claim 1, wherein the porosity calculated by the following formula (1) is 5% or more.
Porosity [%] = 1- (ρ / ρ ₀ ) (1)
(Here, ρ is the apparent specific gravity including the pores, and ρ ₀ is the true specific gravity not including the pores.) The agricultural polyolefin resin film according to claim 1 or 2, wherein the breaking strength is 10 N or more and the Elmendorf strength is 10 N or more in the longitudinal direction. The agricultural polyolefin according to any one of claims 1 to 3, wherein at least one of the resin material (a) and the resin material (c) contains a linear low-density polyethylene resin. Based resin film. Any one of claims 1 to 4, wherein the intermediate layer is composed of two or more layers, and the inner layer side layer of the intermediate layer is a non-foamed layer made of the resin material (b). Agricultural polyolefin resin film according to the item.

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