JP2020184955A - Agricultural polyolefin-based resin film - Google Patents

Abstract

To provide an agricultural polyolefin-based resin film having excellent strength and flexibility.SOLUTION: There is provided an agricultural polyolefin-based resin film 1 which comprises an outer layer 2 composed of a resin material containing a linear low-density polyethylene (a) as a resin component, an inner layer 7 composed of a resin material containing a linear low-density polyethylene (c) as a resin component, and one or more intermediate layers composed of a resin material containing a linear low-density polyethylene (b) as a resin component which is provided between the outer layer 2 and the inner layer 7, wherein the density of the linear low-density polyethylene (b) is lower than the density of the linear low-density polyethylene (a) and the linear low-density polyethylene (c).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.

Generally, greenhouses, tunnels, etc. used in greenhouse cultivation, tunnel cultivation, etc. are made by coating a frame such as a metal pipe with a covering material such as a flexible resin film. The performance required for this coating material includes, for example, transparency, heat retention, and the like, and for example, a soft film made of vinyl chloride resin has been widely used as an excellent one in both of them.

However, in recent years, coating materials are rapidly being replaced from vinyl chloride resin films to polyolefin resin films. The polyolefin-based resin is a homopolymer or copolymer of an α-olefin (for example, ethylene or propylene) having a double bond at the end of the molecule. Specific examples thereof include low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer and the like.

The major reasons for replacing vinyl chloride resin film with polyolefin resin film are the lightness of the film, improvement of weather resistance, improvement of stain resistance by not containing plasticizer, improvement of heat retention by developing heat insulating agents, etc. As mentioned above, the polyolefin-based resin film has achieved performance comparable to that of the vinyl chloride resin film.

In addition to the above performance, the resin film as an agricultural coating material has good tear strength, impact resistance, tensile strength, etc., and has good moldability, high transparency, weather resistance, antifogging property, etc. It is required to be excellent. Therefore, an ethylene-vinyl acetate copolymer having excellent flexibility and an α-olefin copolymer resin having 4 to 40 carbon atoms produced by using a metallocene catalyst having excellent strength are used for the inner layer and the outer layer. A three-layer agricultural film using low-density polyethylene as an intermediate layer has been proposed (see, for example, Patent Document 1).

JP-A-11-254612

However, in the agricultural film described in Patent Document 1, although the above-mentioned copolymer resin having excellent strength is used for the inner layer and the outer layer, the intermediate layer occupying 80% of the thickness is an ethylene-vinyl acetate copolymer or Since it is composed of only low-density polyethylene, the strength of the film as a whole is not sufficient, and there is room for increasing the strength.

Here, as a method for increasing the strength of the entire film, for example, a method of reducing the usage ratio of ethylene-vinyl acetate copolymer or low-density polyethylene and increasing the usage ratio of the copolymer resin can be considered. If the ratio of the copolymer resin used is simply increased, the film becomes hard (inferior in flexibility), and as a result, the spreading workability is lowered (difficult to fasten with a spring).

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide an agricultural polyolefin resin film having excellent strength and flexibility.

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 containing linear low density polyethylene (a) as a resin component, and linear low density polyethylene (linear low density polyethylene) as a resin component. An inner layer made of a resin material containing c) and an intermediate layer provided between the outer layer and the inner layer and made of one or more layers of a resin material containing linear low-density polyethylene (b) as a resin component. The linear low-density polyethylene (b) is characterized in that the density is lower than that of the linear low-density polyethylene (a) and the linear low-density polyethylene (c).

According to the present invention, it becomes possible to provide an agricultural polyolefin resin film having excellent strength and flexibility.

It is sectional drawing which shows the 1st Embodiment of the polyolefin resin film for agriculture of this invention. It is sectional drawing which shows the 2nd Embodiment of the polyolefin resin film for agriculture of this invention.

Hereinafter, the agricultural polyolefin resin film according to the embodiment of the present invention will be described in detail with reference to the drawings. The following description of preferred embodiments is merely exemplary and is not intended to limit the present invention, its applications or its uses.

(First Embodiment)
(Agricultural polyolefin resin film)
As shown in FIG. 1, the agricultural polyolefin resin film 1 according to the present embodiment is a film having a five-layer structure including an outer layer 2, an intermediate layer 3 of three layers, and an inner layer 7.

<Outer layer>
The outer layer 2 is the outermost layer facing the side exposed to sunlight, that is, the outside of the facility when it is expanded in an agricultural facility. The outer layer 2 is a layer that prevents air for expanding the tubular molten resin from escaping from the inside when the agricultural polyolefin resin film 1 is manufactured by the inflation method. Further, since the outer layer 2 is a layer that protects the intermediate layer 3 without interfering with the function of the intermediate layer 3, it is made a layer having light transmission.

Here, the outer layer 2 is made of a resin material containing linear low-density polyethylene (LLDPE) (a), which is a polyolefin-based resin, as a main resin component in order to exhibit the above performance (strength, light transmittance). The layer may be a layer made of a resin material containing linear low-density polyethylene (a) alone as a resin component (in other words, the resin component is only linear low-density polyethylene (a)). ..

Examples of the linear low-density polyethylene (a) include linear low-density polyethylene produced by using a metallocene catalyst or a Ziegler catalyst. As this linear low-density polyethylene, a random copolymer of ethylene and α-olefin, a block copolymer, or the like can be used. Examples of the α-olefin include propylene, butene-1, 3-methylbutene-1, penten-1, 3-methylpentene-1, 4-methylpentene-1, hexene-1, octene-1, decene-1, and the like. Can be mentioned. The α-olefin may be used alone or in combination of two or more.

Further, the linear low-density polyethylene (a) preferably has a melt mass flow rate (MFR) of 0.2 g / 10 minutes or more. If the melt mass flow rate is 0.2 g / 10 minutes or more, it can be extruded without any problem without overload in the extruder.

The linear low-density polyethylene (a) preferably has a density of 0.912 g / cm ³ or more. As a result, the stickiness of the polyolefin-based resin film 1 for agriculture is suppressed, and dirt is less likely to adhere to the film 1. The upper limit of the density is 0.940 g / cm ³ or less from the viewpoint of improving transparency.

The resin material constituting the outer layer 2 is a polyolefin resin other than the linear low-density polyethylene (a) (for example, low-density polyethylene) and other known materials as long as the above performance required for the outer layer 2 is not impaired. It may contain additives and the like.

Examples of the additive include weather-resistant agents such as hindered amine-based light stabilizers and ultraviolet absorbers, antioxidants, lubricants, antistatic agents, colorants, and the like, and are examples of agricultural polyolefin resin films that can withstand long-term use. A weather resistant agent is preferable from the viewpoint of obtaining. Examples of the ultraviolet absorber include benzotriazole-based, benzophenone-based, and salicylic acid-based agents. The blending amount of the additive is, for example, 0.05 to 1 part by mass with respect to 100 parts by mass of the resin component of the outer layer 2.

The thickness of the outer layer 2 is preferably 10 to 40% of the thickness of the entire film from the viewpoint of improving the strength.

<Inner layer>
The inner layer 7 is the innermost layer facing the inside of the facility when it is spread over the agricultural facility. Similar to the outer layer 2, the inner layer 7 is a layer that prevents air for expanding the tubular molten resin from escaping from the inside when an agricultural polyolefin resin film is produced by an inflation method. Further, since the inner layer 7 is a layer that protects the intermediate layer 3 without interfering with the function of the intermediate layer 3, it is made a layer having light transmission.

Here, the inner layer 7 is made of a resin material containing linear low-density polyethylene (LLDPE) (c), which is a polyolefin-based resin, as a main resin component in order to exhibit the above performance (strength, light transmission). The layer may be a layer made of a resin material containing linear low-density polyethylene (c) alone as a resin component (in other words, the resin component is only linear low-density polyethylene (c)). ..

Examples of the linear low-density polyethylene (c) include linear low-density polyethylene produced by using a metallocene catalyst or a Ziegler catalyst. As the linear low-density polyethylene, the same as above can be used.

Further, the linear low-density polyethylene (c) preferably has a melt mass flow rate of 0.2 g / 10 minutes or more. If the melt mass flow rate is 0.2 g / 10 minutes or more, it can be extruded without any problem without overload in the extruder.

The linear low-density polyethylene (c) preferably has a density of 0.912 g / cm ³ or more. As a result, the stickiness of the polyolefin-based resin film 1 for agriculture is suppressed, and dirt is less likely to adhere to the film 1. The upper limit of the density is 0.940 g / cm ³ or less from the viewpoint of improving transparency.

The resin material constituting the inner layer 7 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 type, glycerin type, diglycerin type, etc.) and a fatty acid, or a condensate of these and 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 resin component of the inner layer 7.

Further, the resin material constituting the inner layer 7 may contain a fluorine-based surfactant or a silicone-based surfactant together with the antifogging agent in order to impart antifogging property to the polyolefin-based resin film 1 for agriculture. ..

Further, the resin material constituting the inner layer 7 may contain other polyolefin-based resin (low-density polyethylene or the like), other known additives and the like as long as the above performance required for the inner layer 7 is not impaired. Examples of the additive include the same as above. The blending amount of the additive is, for example, 0.05 to 1 part by mass with respect to 100 parts by mass of the resin component of the inner layer 7.

The thickness of the inner layer 7 is preferably 10 to 40% of the thickness of the entire film from the viewpoint of improving the strength.

<Middle layer>
The intermediate layer 3 is provided between the outer layer 2 and the inner layer 7. The intermediate layer 3 is composed of three layers including a first intermediate layer 4, a second intermediate layer 5, and a third intermediate layer 6 in order from the outer layer 2 side. The first intermediate layer 4, the second intermediate layer 5, and the third intermediate layer 6 are all non-foaming layers.

Here, at least one of the first intermediate layer 4, the second intermediate layer 5, and the third intermediate layer 6 is a linear low-density polyethylene which is a polyolefin-based resin as a main resin component in order to develop strength. (LLDPE) (b) is a layer made of a resin material containing (b).

More specifically, the layer made of the resin material containing the linear low-density polyethylene (b) contains the linear low-density polyethylene (b) alone as the resin component (in other words, the resin component is linear. It may be a layer made of a resin material (only the low-density polyethylene (b)), or a layer made of a resin material containing a linear low-density polyethylene (b) as a resin component and another polyolefin-based resin. May be good.

Examples of the linear low-density polyethylene (b) include linear low-density polyethylene produced by using a metallocene catalyst or a Ziegler catalyst. As the linear low-density polyethylene, the same as above can be used.

Further, the linear low-density polyethylene (b) preferably has a melt mass flow rate of 0.2 g / 10 minutes or more. If the melt mass flow rate is 0.2 g / 10 minutes or more, it can be extruded without any problem without overload in the extruder.

Also, linear low density polyethylene (b), from the viewpoint of improving the flexibility of the agricultural polyolefin resin film 1, that the density of 0.870 g / cm ³ or more 0.911 g / cm ³ or less.

Here, in the present embodiment, the density of the linear low-density polyethylene (b) is smaller than the density of the linear low-density polyethylene (a) and the linear low-density polyethylene (c). As a result, even if at least one of the intermediate layers is a layer made of a resin material containing linear low-density polyethylene (b) as a resin component, flexibility is maintained, and as a result, extension workability is also maintained. To.

The flexibility of the polyolefin-based resin film 1 for agriculture can be evaluated by low-temperature elongation. In order to obtain the agricultural polyolefin resin film 1 having excellent flexibility, the low temperature elongation is preferably 5% or more and 40% or less, and more preferably 5% or more and 15% or less. In addition, in this specification, a low temperature elongation means a value calculated by the method described in the following Examples.

Also, linear low density polyethylene (b) is preferably one density of 0.870 g / cm ³ or more 0.911 g / cm ³ or less, a density of 0.870 g / cm ³ or more 0.906 g / cm ³ or less Is more preferable. If the density of the linear low density polyethylene (b) is 0.870 g / cm ³ or more 0.911 g / cm ³ or less, it is possible to obtain the agricultural polyolefin resin film 1 that can withstand long-term use.

Whether or not the agricultural polyolefin resin film 1 can withstand long-term use is calculated from, for example, the tensile cutting strength after the accelerated weather resistance test by the sunshine weather meter (WOM) and the tensile cutting strength before and after the test. It can be evaluated by the residual growth rate and the like. In order to obtain an agricultural polyolefin resin film 1 that can withstand long-term use, the accelerated weather resistance test by Sunshine WOM has a tensile cutting strength of 30 N / mm ² or more after 3000 hours, and / or the accelerated weather resistance by the Sunshine WOM. It is preferable that the elongation residual rate before and after the sex test is 79% or more. In this specification, the tensile cutting strength and the elongation residual ratio refer to the values measured and calculated by the method described in the following Examples.

Other polyolefin-based resins include olefin-vinyl acetate copolymers and low-density polyethylene-based resins because they impart flexibility to the agricultural polyolefin-based resin film 1 to facilitate stretching work and impart stable antifogging properties. Density polyethylene (LDPE) is preferred, and ethylene-vinyl acetate copolymer (EVA) and low density polyethylene are more preferred. These other polyolefin-based resins may be used alone or in combination of two or more.

The ethylene-vinyl acetate copolymer preferably has a vinyl acetate content of 5 to 30% by mass, and more preferably a vinyl acetate content of 10 to 25% by mass. When the vinyl acetate content is 5% by mass or more, the flexibility is good. When the vinyl acetate content is 30% by mass or less, the film is elastic, supple and durable, so that it can be easily handled during stretching, and the obtained agricultural polyolefin resin film 1 has sufficient strength and is transparent. The sex is also good.

Examples of the low-density polyethylene include high-pressure low-density polyethylene and the like. The high-pressure low-density polyethylene preferably has a density of 0.935 g / cm ³ or less, it can be suitably used in 0.910 to 0.935 g / cm ^3.

When the resin component of the layer made of the resin material containing the linear low-density polyethylene (b) is 100 parts by mass, the content of the linear low-density polyethylene (b) is preferably 60 parts by mass or more. The upper limit is 100 parts by mass. When the content is 60 parts by mass or more, it is possible to obtain an agricultural polyolefin resin film 1 having excellent flexibility while maintaining strength.

Further, at least one of the first intermediate layer 4, the second intermediate layer 5, and the third intermediate layer 6 contains a low-density polyethylene or ethylene-vinyl acetate copolymer alone as a resin component (in other words, a resin component). May be a layer made of a resin material (only a low-density polyethylene or an ethylene-vinyl acetate copolymer), or a layer made of a resin material containing an ethylene-vinyl acetate copolymer alone as a resin component. Good. This imparts flexibility to the polyolefin-based resin film 1 for agriculture, and facilitates the stretching work of the film 1. Examples of the low-density polyethylene and ethylene-vinyl acetate copolymer include the same as above.

When the resin component of the intermediate layer 3 (all the resin components of the first intermediate layer 4, the second intermediate layer 5 and the third intermediate layer 6) is 100 parts by mass, the linear low-density polyethylene (b) is contained. From the viewpoint of improving the strength and transparency of the agricultural polyolefin resin film 1, the amount is preferably 10 parts by mass or more and 80 parts by mass or less, and more preferably 20 parts by mass or more and 70 parts by mass or less.

The structure of the intermediate layer 3 is not particularly limited, but is, for example, a linear low with the first intermediate layer 4 and the third intermediate layer 6 made of a resin material containing low density polyethylene or an ethylene-vinyl acetate copolymer alone. A three-layer structure with a second intermediate layer 5 made of a resin material containing density polyethylene (b); a first intermediate layer 4 and a third intermediate layer 6 made of a resin material containing linear low-density polyethylene (b), Examples thereof include a three-layer structure with a second intermediate layer 5 made of a resin material containing low-density polyethylene or an ethylene-vinyl acetate copolymer alone. From the viewpoint of improving the tear strength between the outer layer 2 and the inner layer 7 and the intermediate layer 3, the first intermediate layer 4 and the third intermediate layer 6 made of a resin material containing an ethylene-vinyl acetate copolymer alone are used. A three-layer structure with a second intermediate layer 5 made of a resin material containing linear low-density polyethylene (b) is preferable.

The resin material of each layer constituting the intermediate layer 3 may contain a heat insulating agent (far infrared ray absorbing agent) from the viewpoint of enhancing the heat retaining property. Examples of the heat insulating agent include hydrotalcite compounds, inorganic oxides, inorganic hydroxides and the like. The blending amount of the heat insulating agent is preferably 1 to 1 with respect to 100 parts by mass of the resin component of each layer constituting the intermediate layer 3 from the viewpoint of improving the heat retaining property while maintaining the strength of the polyolefin resin film 1 for agriculture. It is 20 parts by mass, more preferably 3 to 10 parts by mass.

Further, the resin material of each layer constituting the intermediate layer 3 may contain pigments such as titanium oxide pigment, carbon black pigment, and aluminum pigment as long as the above performance required for the intermediate layer 3 is not impaired.

In addition, each resin material constituting the intermediate layer 3 contains a polyolefin resin other than the linear low-density polyethylene (b), other known additives, and the like, as long as the above performance required for the intermediate layer 3 is not impaired. It may be included.

Examples of the additive include the same as above. The blending amount of the additive is not particularly limited, and is, for example, 0.05 to 1 part by mass with respect to 100 parts by mass of the resin component of each layer constituting the intermediate layer 3.

The thickness of the intermediate layer 3 (the total thickness of each layer constituting the intermediate layer 3) is preferably 10 to 80% of the thickness of the entire film from the viewpoint of improving flexibility. When the ratio is 10% or more, the flexibility of the film 1 is improved, so that the spreading workability is improved. Further, since the Elmendorf tear strength becomes large, the film 1 becomes difficult to tear. When the ratio is 80% or less, the tensile strength is improved, so that the film 1 is unlikely to become thin even if it is strongly pulled when the film 1 is stretched, and the film 1 that can withstand long-term use can be obtained.

In order to obtain an agricultural polyolefin resin film 1 having a strength that does not easily tear when stretched, the Ermendorf tear strength in the mechanical axis (longitudinal) direction (hereinafter referred to as “MD direction”) of the film is 20 N or more. It is preferable that the Ermendorf tear strength in the direction orthogonal to the MD direction (hereinafter, referred to as “TD direction”) is 35 N or more. In addition, in this specification, Elmendorf tear strength means a value measured by the method described in the following Examples.

(Production method)
The polyolefin-based resin film 1 for agriculture is preferably produced by an inflation method.

Specifically, the molten resin materials constituting the outer layer 2, the intermediate layer 3, and the inner layer 7 are co-extruded from the die into a tube shape, expanded from the inside by the pressure of air, and then cooled to be used for agriculture. Polyolefin-based resin film 1 for use can be produced.

Examples of the coextrusion method of the molten resin constituting each layer include a pre-die lamination method in which the molten resin is brought into contact with the front of the die, an in-die lamination method in which the molten resin is brought into contact with the inside of the die, and a plurality of concentric lips of the die. Examples thereof include a die outer lamination method in which the resin is brought into contact after being discharged.

The thickness of the obtained polyolefin-based resin film 1 for agriculture (total thickness of the outer layer 2, the intermediate layer 3, and the inner layer 7) is preferably 50 to 400 μm from the viewpoint of strength and handleability.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. FIG. 2 shows an agricultural polyolefin resin film 10 according to the second embodiment. Since the overall structure of the agricultural polyolefin resin film 10 other than the intermediate layer 30 is the same as that of the first embodiment, detailed description thereof will be omitted here. Further, the same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

In the present embodiment, the intermediate layer 30 is composed of one layer made of a resin material containing linear low-density polyethylene (b) as a resin component. In other words, as shown in FIG. 2, the agricultural polyolefin resin film 10 according to the present embodiment is a film having a three-layer structure including an outer layer 2, an intermediate layer 30 of one layer, and an inner layer 7.

<Middle layer>
The intermediate layer 30 is a layer that imparts heat retention and heat insulation to the agricultural polyolefin resin film 10.

The intermediate layer 30 is a layer made of a resin material containing linear low-density polyethylene (b) as a polyolefin-based resin.

More specifically, the layer made of the resin material containing the linear low-density polyethylene (b) contains the linear low-density polyethylene (b) alone as the resin component (in other words, the resin component is linear. The layer may be made of a resin material (only low density polyethylene (b)), or may be a layer made of a resin material containing linear low density polyethylene (b) as a resin component and another polyolefin resin. Good.

When the resin component of the intermediate layer 30 is 100 parts by mass, the content of the linear low-density polyethylene (b) is preferably 10 parts by mass or more from the viewpoint of improving the strength of the polyolefin-based resin film 10 for agriculture. It is 80 parts by mass or less, more preferably 60 parts by mass or more and 80 parts by mass or less.

The thickness of the intermediate layer 30 is preferably 10 to 80% of the thickness of the entire film from the viewpoint of improving flexibility.

(Production method)
The agricultural polyolefin resin film 10 according to the present embodiment can be produced by the same method as the method for producing the agricultural polyolefin resin film 1 of the first embodiment.

The thickness of the obtained polyolefin-based resin film 10 for agriculture is preferably 50 to 400 μm from the viewpoint of strength and handleability.

(Other embodiments)
The agricultural polyolefin resin films 1 and 10 of the present invention are not limited to those shown in the illustrated examples. For example, in each of the above embodiments, the intermediate layer is composed of three layers or one layer, but may be two layers or four or more layers. When the intermediate layer is composed of two or more layers, at least one of the intermediate layers may be composed of a layer made of a resin material containing linear low-density polyethylene (b) as a resin component.

In each of the above embodiments, the outer layer 2 and the inner layer 7 are light-transmitting layers, but may not be light-transmitting layers.

In the first embodiment, each layer constituting the intermediate layer 3 is a non-foaming layer, but at least one of the intermediate layers 3 may be a layer in which a resin material is foamed (foamed layer). Good. Further, in the second embodiment, the intermediate layer 30 is a non-foaming layer, but may be a foaming layer.

Further, in the agricultural polyolefin resin films 1 and 10 of the present invention, an antifogging coating film composed of a thermoplastic resin binder and an inorganic colloidal sol may be provided on the surface of the inner layer 7. As a result, stable antifogging properties can be imparted to the polyolefin-based resin films 1 and 10 for agriculture.

The agricultural polyolefin resin films 1 and 10 of the present invention may have a light-shielding property.

(Example 1)
<Preparation of resin material>
First, each resin component shown in Table 1 was blended in the blending ratio (parts by mass) shown in Table 1 to prepare a resin material having the composition shown in Example 1. In all layers, for 100 parts by mass of each resin component, 0.3 parts by mass of a hindered amine-based light stabilizer [BASF Japan Ltd., product name: Chinubin (registered trademark) 622, the same applies hereinafter] and a benzophenone-based 0.1 part by mass of an ultraviolet absorber [BASF Japan Ltd., product name: Kimasorb 81, the same applies hereinafter] was added. Further, with respect to 100 parts by mass of the resin component constituting each layer of the intermediate layer, hydrotalcite (Mg _0.67 Al _0.33 (OH) ₂ (CO ₃ ) _0.165 / 0.5H ₂ O) was used as a heat insulating agent. [Kyowa Chemical Industry Co., Ltd., trade name: Alchemizer (registered trademark) 1, average particle size 0.5 μm, the same applies hereinafter] 5 parts by mass was further added.

<Manufacturing of film>
Next, using a five-kind, five-layer inflation device, the die is concentric so that the outer layer, the first intermediate layer, the second intermediate layer, the third intermediate layer, and the inner layer are formed in this order from the outside. The resin material constituting each of the above layers was co-extruded from a plurality of lips in a molten state, and the resin material was expanded from the inside by the pressure of air. Then, the expanded resin material was cooled and wound up. As a result, the thickness of the outer layer and the inner layer: 30 μm each, the thickness of the first intermediate layer, the second intermediate layer and the third intermediate layer: 30 μm each, and the total thickness: 150 μm. A resin film was manufactured.

<Evaluation of film>
The performance of the light-shielding agricultural polyolefin resin film (hereinafter, also simply referred to as a film) obtained in Example 1 was evaluated based on the following method.

(Elmendorf tear 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 with the digital Elmendorf / tear tester. Two large and small values were excluded from the nine measured values, and the average value of the remaining five values was calculated and used as the Elmendorf tear strength. The above results are shown in Table 1.
(Evaluation criteria)
◯: The Elmendorf tear strength in the MD direction is 20 N or more, and the Elmendorf tear strength in the TD direction is 35 N or more (excellent in strength).
X: The Elmendorf tear strength in the MD direction is less than 20 N, and the Elmendorf tear strength in the TD direction is less than 35 N (insufficient strength).

(Low temperature elongation)
A cold resistance test was conducted according to JIS K 6732: 2006, the low temperature elongation of the film obtained in Example 1 was calculated, and the flexibility (cold resistance) of the film was evaluated based on the following evaluation criteria. The results are shown in Table 1. A low-temperature elongation tester [manufactured by Ueshima Seisakusho Co., Ltd., product name: vinyl cold resistance tester] was used as the device.
(Evaluation criteria)
◯: Low temperature elongation is 5% or more and 40% or less (excellent in flexibility).
X: Low temperature elongation is less than 5% or more than 40% (insufficient flexibility).

(Haze)
The haze of the film obtained in Example 1 was calculated according to JIS K 7136, and the transparency of the film was evaluated based on the following evaluation criteria. The results are shown in Table 1. As the device, a haze meter / haze meter [NDH2000 manufactured by Nippon Denshoku Kogyo Co., Ltd.] was used. The term "haze" as used herein refers to a percentage of the transmitted light passing through the test piece that deviates from the incident light by 0.44 rad (2.5 degrees) or more due to forward scattering.
(Evaluation criteria)
◯: Haze is 10% or less (excellent in transparency).
X: Haze exceeds 10% (insufficient transparency).

(Sticky)
The friction coefficient test of the film obtained in Example 1 was carried out according to JIS K 7125, the static friction force was measured, and the stickiness of the film was evaluated based on the following evaluation criteria. More specifically, the size of the test piece is 80 x 200 mm, a square sliding piece having a contact area of 40 cm ² (side length: 63 mm) is used, and the outer layer surfaces of the two test pieces are brought into contact with each other to generate static friction. Was measured. The results are shown in Table 1. A friction and wear tester [manufactured by Shinto Kagaku Co., Ltd., product number: HEIDON TYPE 40] was used as the apparatus.
(Evaluation criteria)
No stickiness: The static friction force is less than 2 kgf.
Sticky: The static friction force is 2 kgf or more.

(Examples 2 to 6 and 8)
An agricultural polyolefin resin film was produced in the same manner as in Example 1 above, except that the composition (part by mass) of the resin component was changed to the composition shown in Examples 2 to 6 and 8 shown in Table 1. Then, the film was evaluated. The results are shown in Table 1.

(Comparative Examples 3 to 5)
An agricultural polyolefin resin film was produced in the same manner as in Example 1 above, except that the composition (parts by mass) of the resin component was changed to the composition shown in Comparative Examples 3 to 5 shown in Table 2. The film was evaluated. The results are shown in Table 2.

(Example 7)
<Preparation of resin material>
First, each resin component shown in Table 1 was blended in the blending ratio (parts by mass) shown in Table 1 to prepare a resin material having the composition shown in Example 7. In all layers, 0.3 parts by mass of a hindered amine-based light stabilizer and 0.1 parts by mass of a benzophenone-based ultraviolet absorber were added to 100 parts by mass of each resin component. Further, 5 parts by mass of hydrotalcite was further added as a heat insulating agent to 100 parts by mass of the resin component of the intermediate layer.

<Manufacturing of film>
Next, using a three-kind, three-layer inflation device, each resin material is co-extruded from a plurality of concentric lips of the die in a molten state so as to form an outer layer, an intermediate layer, and an inner layer in order from the outside, and air is used. After expanding from the inside by the pressure of, it was cooled and wound up. As a result, three types of three-layer agricultural polyolefin resin films having an outer layer and an inner layer thickness of 30 μm each, an intermediate layer thickness of 90 μm, and a total thickness of 150 μm were produced.

<Evaluation of film>
The performance of the agricultural polyolefin resin film (hereinafter, also simply referred to as a film) obtained in Example 7 was evaluated in the same manner as in Example 1 described above. The results are shown in Table 1.

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

The resin components shown in Tables 1 and 2 are as follows.

LLDPE1: Linear low density polyethylene, MFR 0.9g / 10min, density 0.927g / cm ³ [manufactured by Japan Polyethylene Corporation, product number: UF621]
LLDPE2: Linear low-density polyethylene, MFR 1.0 g / 10 min, density 0.923 g / cm ³ [manufactured by Japan Polyethylene Corporation, product number: UF332]
LLDPE3: Linear low-density polyethylene, MFR 2.0 g / 10 min, density 0.908 g / cm ³ [manufactured by Prime Polymer Co., Ltd., product number: SP1022]
LLDPE4: Linear low density polyethylene, MFR 1.2g / 10min, density 0.903g / cm ³ [manufactured by Prime Polymer Co., Ltd., product number: SP0511]
LLDPE5: Linear low density polyethylene, MFR: 0.8 g / 10 min, density: 0.905 g / cm ³ [manufactured by Dow Chemical Co., Ltd., product number: ELITE AT6101]
LDPE: High-pressure method low-density polyethylene, MFR 0.7 g / 10 min, density 0.919 g / cm ³ [manufactured by NUC Co., Ltd., product number: NUC-8323]
EVA15: Ethylene-vinyl acetate copolymer having a vinyl acetate unit content of 15% by weight, MFR 1.1 g / 10 minutes, density 0.940 g / cm ³ [manufactured by NUC Co., Ltd., product number: NUC-8452D]

<Promoted weather resistance test by Sunshine WOM>
Accelerated weather resistance test and tensile test were performed in accordance with JIS K 6732. The details of the test method are as follows.

(Promoted weather resistance test)
Test pieces for accelerated weather resistance test were collected from the films obtained in Examples 1 to 3 and Comparative Examples 1 to 3. After that, using a sunshine carbon arc lamp type light resistance tester [manufactured by Suga Test Instruments Co., Ltd., product name: Sunshine Weather Meter S80] specified in JIS B 7753, the above test was performed in accordance with the conditions specified in JIS K 6732. One irradiated surface was irradiated for 3000 hours.

(Tensile test)
The test piece after the accelerated weather resistance test was punched out to prepare a test piece for a tensile test specified in JIS K 6732. The measurement width of this test piece was 5 mm, and the test piece was measured exactly 10 mm from the center to both ends and marked. The distance between the marked lines was set to 20 mm, and the test piece was accurately attached to a precision universal testing machine [manufactured by Shimadzu Corporation, product number: Autograph AG-500D]. The test speed was 200 ± 20 mm per minute, and the force at which the test piece was cut was defined as the tensile cutting strength, and whether or not the film could withstand long-term use was evaluated based on the following evaluation criteria. The results are shown in Table 3.
(Evaluation criteria)
◯: Tensile cutting strength is 30 N / mm ² or more (can withstand long-term use).
X: Tensile cutting strength is less than 30 N / mm ² (cannot withstand long-term use).

(Calculation of residual growth rate)
The elongation residual ratio was calculated by the following formula, and it was evaluated whether or not the film could withstand long-term use based on the following evaluation criteria. The results are shown in Table 3.

Residual elongation (%) = [Tensile cutting strength after 3000 hours of sunshine WOM (after the accelerated weather resistance test)] / [Tensile cutting strength before 3000 hours of sunshine WOM (before the accelerated weather resistance test)] × 100 (Equation) )
(Evaluation criteria)
◯: The residual rate of growth is 79% or more (it can withstand long-term use).
X: The residual rate of growth is less than 79% (cannot withstand long-term use).

As shown in Table 1, it can be seen that all of the agricultural polyolefin resin films of Examples 1 to 8 are superior in strength and flexibility to the films of Comparative Examples 1 to 5 shown in Table 2.

More specifically, as shown in Table 1, in an agricultural polyolefin resin film having a five-layer structure in which the second intermediate layer contains linear low-density polyethylene (b), Examples 1 to 3 and 6 and 8 are compared with Comparative Examples 4 and 5 because the density of the linear low-density polyethylene (b) is smaller than the density of the linear low-density polyethylene (a) and the linear low-density polyethylene (c). It can be seen that the strength and flexibility are excellent. Further, in Examples 1 to 3, 6 and 8, the outer layer and the inner layer contain linear low-density polyethylene (a) and linear low-density polyethylene (c) having a density of 0.912 g / cm ³ or more, respectively. Therefore, it can be seen that the stickiness of the film is suppressed as compared with Comparative Example 5.

In a five-layered agricultural polyolefin resin film in which the first intermediate layer and the third intermediate layer contain the linear low-density polyethylene (b), Examples 4 and 5 describe the linear low-density polyethylene (b). Since the density of b) is smaller than that of the linear low-density polyethylenes (a) and (c), it can be seen that the strength and flexibility are excellent as compared with Comparative Examples 3 and 4.

Further, Examples 1 to 6 and 8 are linear when the resin component of the intermediate layer 3 (all the resin components of the first intermediate layer, the second intermediate layer and the third intermediate layer) is 100 parts by mass. Since the content of the low-density polyethylene (b) is 10 parts by mass or more and 80 parts by mass or less, it can be seen that the transparency is also excellent as compared with Comparative Example 4.

In the three-layer structure of an agricultural polyolefin resin film, Example 7 has strength and flexibility as compared with Comparative Examples 1 and 2 because the intermediate layer contains linear low-density polyethylene (b). It turns out that it is excellent. Further, in Example 7, since the outer layer contains linear low-density polyethylene (a) having a density of 0.912 g / cm ³ or more, the stickiness of the film is suppressed as compared with Comparative Example 2. You can see that.

Further, as shown in Table 3, Examples 1 to 3 have a larger tensile cutting strength and elongation residual ratio after 3000 hours of the accelerated weather resistance test by Sunshine WOM as compared with Comparative Examples 1 to 3, and are long-term. It turns out that it can withstand use.

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

1,10 Agricultural polyolefin resin film 2 Outer layer 3,30 Intermediate layer 4 First intermediate layer 5 Second intermediate layer 6 Third intermediate layer 7 Inner layer

Claims (4)

An outer layer made of a resin material containing linear low-density polyethylene (a) as a resin component,
An inner layer made of a resin material containing linear low-density polyethylene (c) as a resin component,
An intermediate layer provided between the outer layer and the inner layer and made of a resin material containing one or more layers of linear low-density polyethylene (b) as a resin component is provided.
The density of the linear low-density polyethylene (b) is smaller than the densities of the linear low-density polyethylene (a) and the linear low-density polyethylene (c). the film. The first aspect of claim 1, wherein the content of the linear low-density polyethylene (b) is 10 parts by mass or more and 80 parts by mass or less when the resin component of the intermediate layer is 100 parts by mass. Agricultural polyolefin resin film. Agricultural polyolefin resin film according to claim 1 or claim 2, wherein the density of the linear low density polyethylene (b) is less than 0.870 g / cm ³ or more 0.911 g / cm ³ .. The agricultural polyolefin system according to any one of claims 1 to 3, wherein the tensile cutting strength after 3000 hours of the accelerated weather resistance test by a sunshine weather meter is 30 N / mm ² or more. Resin film.

Images