JP7018300B2 - Agricultural polyolefin multilayer film - Google Patents

Description

The present invention relates to an agricultural polyolefin-based multilayer film.

Currently, polyolefin-based films are used in packaging equipment, agricultural films, electric wire coating materials, and the like. Polyolefin-based films showing high strength have a wide range of uses, and even now, improvements and developments in film strength characteristics are in progress.
In particular, in agricultural films that are used for a long period of time, work such as winding the film occurs depending on the season and environment, and at that time, the metal part of the winder and the film or the films are rubbed against each other. .. In particular, there is a high demand for a film that is resistant to tearing while maintaining the transparency of the greenhouse required for taking in sunlight.

As a means for preventing the film from rubbing and tearing, it is effective to reduce the coefficient of friction on the film surface. As a film having a low coefficient of friction, a technique for reducing the coefficient of friction by using an additive called a lubricant has been conventionally known. However, there is a problem that the lubricant in these film volumes coagulates and solidifies with time, blooms on the film surface, and powders. The powdered lubricant acts as an external scatterer and impairs the transparency of the greenhouse. Further, since the elastic modulus of the film is lowered, even if the slip is good, it becomes a problem that the film is caught by an external action accompanied by deformation.

As a method that does not use additives, high-density polyethylene (HDPE), which exhibits low coefficient of friction characteristics, can be used as a single-layer film, but HDPE has high crystallinity and is specified by the stretch orientation during film formation. Since the tear strength in the direction of is low, the tear easily propagates. Further, since the crystalline phase and the amorphous phase having different refractive indexes are mixed, the transparency is low.

For example, Patent Document 1 discloses a technique for blending two types of polyethylene having different densities as a technique for preventing blocking during winding with respect to a surface protective film of an optical film.
Further, Patent Document 2 discloses a method of imparting unevenness as a method of reducing the rubbing noise between bags of a packaging film.
Further, Patent Document 3 discloses a technique for exhibiting a sealing property by adding a lubricant to a polyethylene sealant material.

Japanese Unexamined Patent Publication No. 2005-28619 Japanese Unexamined Patent Publication No. 2000-169598 Japanese Unexamined Patent Publication No. 2016-49727

However, Patent Document 1 has a problem that due to the nature of a protective film, it cannot develop sufficient strength to maintain its strength in a long-term use environment.
Further, Patent Document 2 has a problem that sufficient transparency cannot be obtained.
Further, Patent Document 3 has a problem that the transparency is lowered by long-term use due to the surface segregation of the lubricant component.

Further, as a method of reducing the friction coefficient without using an additive, there is also a method of using ultra-high molecular weight polyethylene (UHMWPE, ultra-high molecular weight PE) in a single film layer. However, in the case of UHMWPE, the melt viscosity is high due to the high molecular weight, and the processability at the time of film molding is poor. Furthermore, the present inventors have newly found that if agglomerates of ultra-high molecular weight chains remain, fish eyes may occur during molding, which may cause a problem of becoming a starting point of fracture.

Further, for example, in the case of processing a thin film having a thickness of 200 μm or less, it is difficult to obtain a film that secures sufficient transparency and is resistant to rubbing.

The present invention has been made in view of this point. Therefore, an object of the present invention is to provide an agricultural film that improves wear resistance and imparts breaking strength and tear strength of the film.

As a method for improving the wear resistance of an agricultural film and imparting breaking strength to the film, the present inventors use a layer to which an ultra-high molecular weight PE having a molecular weight of 400,000 or more is added as an outer layer or an inner layer of the agricultural film. I found. The present invention was reached based on this finding.

That is, the present invention is as follows.
(1)
It has at least an outer layer and an inner layer,
From an ultrahigh molecular weight polyethylene resin composition in which at least one of the outer layer and the inner layer contains an ultrahigh molecular weight polyethylene having a weight average molecular weight of 400,000 or more and a low density polyethylene and / or an ethylene-vinyl acetate copolymer. Naru,
The ultra-high molecular weight polyethylene resin composition contains 1 to 30% by mass of the ultra-high molecular weight polyethylene and 20% by mass or more of the low-density polyethylene and / or ethylene-vinyl acetate copolymer.
The low density polyethylene comprises a linear low density polyethylene,
Agricultural polyolefin-based multilayer film characterized by this.
(2)
The density of the low-density polyethylene is 0.910 g / cm ³ or more and less than 0.930 g / cm ³ .
The agricultural polyolefin-based multilayer film according to claim 1, wherein the ethylene-vinyl acetate copolymer has a density of 0.880 to 0.945 g / cm ³ .
(3)
The specific wear amount of the layer containing the ultra-high molecular weight polyethylene measured by a slip wear test conforming to JIS K7218A is 5 × 10 ^-6 mm ³ / Nm or less, according to (1) or (2) . Agricultural polyolefin-based multilayer film.
(4)
The agricultural polyolefin-based multilayer film according to any one of (1) to (3) , wherein the layer containing the ultra-high molecular weight polyethylene has a thickness of 10 to 100 μm.
(5)
The agricultural polyolefin-based multilayer film according to any one of (1) to (4) , wherein the total light transmittance measured according to JIS K 7631-1 under the condition of a thickness of 150 μm is 88% or more.
(6)
The agriculture according to any one of (1) to (5) , wherein an intermediate layer is further contained between the outer layer and the inner layer, and the outer layer and the inner layer contain ultra-high molecular weight polyethylene having a weight average molecular weight of 400,000 or more. Polyolefin-based multilayer film for.

According to the present invention, it is possible to provide an agricultural film having improved wear resistance and imparting breaking strength and tear strength of the film.

Hereinafter, embodiments for carrying out the present invention (hereinafter, simply referred to as “the present embodiment”) will be described in detail. The embodiments described below are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be appropriately modified and carried out within the scope of the gist thereof.

The agricultural polyolefin-based multilayer film of the present invention has at least an outer layer and an inner layer, and the outer layer and at least one of the inner layers contain ultra-high molecular weight polyethylene having a weight average molecular weight of 400,000 or more. The polyolefin-based multilayer film for agriculture of the present embodiment is preferably a laminated film having at least a three-layer structure, and forms a reinforcing layer having improved mechanical strength in either or both of the outer layer and the inner layer in the form of a vinyl house. However, the intermediate layer may be a film composed of a resin composition having a composition different from that of the outer layer and the inner layer.
In the present specification, the polyolefin-based multilayer film for agriculture may be simply referred to as "agricultural film". Further, the "outer layer" and the "inner layer" refer to a layer including one surface of the film and a layer including the other surface. Further, "polyolefin-based" means that at least one layer of the agricultural polyolefin-based multilayer film of the present embodiment contains a polyolefin-based resin, and the polyolefin-based resin is contained in all layers of the agricultural film of the present embodiment. It may be included. Examples of the polyolefin-based resin include polyethylene, polypropylene, and cycloolefin polymers described later.

According to the agricultural film of the present embodiment, it is possible to reduce the rubbing between the iron pipe and the film that occurs during the house stretching work and the mechanical damage due to the breakage when the film is folded. Further, in the agricultural film of the present embodiment, the breaking strength and the tear strength of the film can be improved by providing a layer containing ultra-high molecular weight polyethylene on the surface.

<Agricultural film>
The agricultural film of the present embodiment is formed by at least two layers, an outer layer and an inner layer. An intermediate layer may be further included between the outer layer and the inner layer. The intermediate layer may be a single layer or a plurality of layers.
The agricultural film of the present embodiment is a multilayer film having at least two layers, and may have a three-layer structure or a four-layer or more structure.
The agricultural film of the present embodiment further includes an intermediate layer between the outer layer and the inner layer from the viewpoint of absorbing heat rays of mid-infrared to far-infrared rays and exhibiting heat retention performance in the house, and the outer layer and the inner layer are heavy. A film containing ultra-high molecular weight polyethylene having an average molecular weight of 400,000 or more may be used.

The agricultural film of the present embodiment contains ultra-high molecular weight polyethylene having a weight average molecular weight of 400,000 or more in at least one of the outer layer and the inner layer. The agricultural film of the present embodiment may be a layer in which the outer layer or the inner layer contains an ultra-high molecular weight polyethylene having a weight average molecular weight of 400,000 or more, or the outer layer and the inner layer are ultra-high molecular weight polyethylene having a weight average molecular weight of 400,000 or more. It may be a layer containing.

In the agricultural film of the present embodiment, the ultra-high molecular weight PE resin composition contains other polyolefin-based resins (particularly polyethylene) in addition to the ultra-high molecular weight polyethylene having a weight average molecular weight of 400,000 or more from the viewpoint of improving processability. ), The content of the other polyolefin resin is more preferably 50% by mass or more, further preferably 70% by mass or more, and particularly preferably 80% by mass or more.
Further, by using a mixture of ultra-high molecular weight polyethylene having a weight average molecular weight of 400,000 or more and another polyolefin resin (particularly polyethylene), uniformity can be exhibited and fish eyes can be suppressed.

[Polyethylene-based resin composition forming a layer containing ultra-high molecular weight polyethylene having a weight average molecular weight of 400,000 or more]
A polyethylene-based resin composition (“ultra-high molecular weight polyethylene resin composition” or “ultra-high molecular weight polyethylene resin composition”) that forms a layer containing ultra-high molecular weight polyethylene having a weight average molecular weight of 400,000 or more (sometimes referred to as “ultra-high molecular weight PE layer”). (Sometimes referred to as "high molecular weight PE resin composition") contains ultra-high molecular weight polyethylene having a weight average molecular weight of 400,000 or more. Further, it preferably contains low density polyethylene having a density of 0.880 to 0.945 g / cm ³ and / or other polyolefin-based resin such as an ethylene-vinyl acetate copolymer.
Among them, the ultra-high molecular weight PE resin composition contains 20% by mass or more of low-density polyethylene having a density of 0.880 to 0.945 g / cm ³ and / or an ethylene-vinyl acetate copolymer, and has a weight average molecular weight. Those containing 1 to 30% by mass of an ultra-high molecular weight PE component of 400,000 or more are preferable.
In the present specification, the ultra-high molecular weight polyethylene contained in the ultra-high molecular weight PE resin composition may be referred to as "ultra-high molecular weight polyethylene component (A)" or "polyethylene component (A)".

The ultra-high molecular weight PE resin composition may contain other olefin-based resins in order to satisfactorily disperse the ultra-high molecular weight PE.

Hereinafter, the ultra-high molecular weight polyethylene component (A) and other olefin-based resins will be described in detail.

(Ultra High Molecular Weight Polyethylene Component (A))
By blending the ultra-high molecular weight polyethylene component (A) in a uniformly dispersed state, an ultra-high molecular weight PE resin composition capable of forming a layer having few terminal branches as adhesion points and a low specific wear amount can be obtained. be able to.

By containing ultra-high molecular weight polyethylene, it is possible to form a structure in which long-chain molecules of ultra-high molecular weight polyethylene are spread two-dimensionally when stretched in a specific direction, such as in the form of a film. It is possible to produce a film having improved tear strength and tensile breaking strength in both TD directions.

The ultra-high molecular weight polyethylene component (A) may be used alone or in combination of two or more. In particular, by blending two types of ultra-high molecular weight polyethylene, the crystallinity of polyethylene can be suppressed, and a transparent film having a low internal haze can be produced.

The ultra-high molecular weight polyethylene component (A) is not particularly limited, and examples thereof include a homopolymer of ethylene or a copolymer of ethylene and another monomer. The other monomer is not particularly limited, but is, for example, α-olefin such as propylene, butene-1, hexene-1, octene-1; vinyl compound such as vinyl acetate; acrylic acid, methacrylic acid, acrylic acid. Examples thereof include (meth) acrylic compounds such as esters and methacrylic acid esters. Among these, a homopolymer of ethylene, a copolymer of ethylene and another α-olefin, and a copolymer containing 90 mol% or more of an ethylene monomer unit is preferable.

When the weight average molecular weight of the ultra-high molecular weight polyethylene component (A) is 400,000 or more, a molded product having excellent high strength, wear resistance, self-lubricating property, hygiene property, chemical resistance and the like can be obtained.

The weight average molecular weight of the ultra-high molecular weight polyethylene component (A) is 400,000 or more, preferably 1 million or more, and more preferably 3 million or more. When the weight average molecular weight of the ultra-high molecular weight polyethylene component (A) is 400,000 or more, the wear resistance and slidability of the obtained molded product are further improved. Further, ultra-high molecular weight polyethylene having a weight average molecular weight of 1 million or more tends to be difficult to disperse under normal kneading conditions, but the ultra-high molecular weight PE resin composition described later contains ultra-high molecular weight polyethylene with good dispersibility. It will be a thing. On the other hand, when the weight average molecular weight of the ultra-high molecular weight polyethylene is less than 400,000, the molecular weight of the entire resin contained in the ultra-high molecular weight PE resin composition is too low, which is one of the original characteristics of the ultra-high molecular weight polyethylene. The characteristics such as wear resistance and slidability are deteriorated.
When the weight average molecular weight of the ultra-high molecular weight polyethylene component (A) is less than 4 million, the productivity in the production process of the ultra-high molecular weight polyethylene is further improved.
It is preferable that the weight average molecular weight of all kinds of ultra-high molecular weight polyethylene contained in the ultra-high molecular weight PE resin composition satisfies the above range.

The weight average molecular weight of the ultra-high molecular weight polyethylene component (A) can be adjusted by allowing hydrogen as a chain transfer agent in the polymerization system of the ultra-high molecular weight polyethylene, changing the polymerization temperature, or the like.

The weight average molecular weight of ultra-high molecular weight polyethylene was measured using PL-GPC220 manufactured by Agilent. Column: TSKgel GMH-H (20) HT (7.8 mml. D x 30 cm 2 pieces), calibration curve is polystyrene EasiCal PS. Measured at -1 (manufactured by Agilent).

The catalyst used in the production of ultra-high molecular weight polyethylene is not particularly limited, but a Ziegler-Natta catalyst is preferable.

(Other polyolefin resins)
As the other polyolefin-based resin contained in the ultra-high molecular weight PE resin composition, an ethylene resin (preferably polyethylene) having excellent transparency and mechanical strength can be preferably used. Examples of such an ethylene resin include high-pressure low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, and high-density polyethylene (HDPE). ) Etc. can be mentioned. The other polyolefin-based resin may be one type alone or a combination of two or more types, and among them, low-density polyethylene having a density of 0.880 to 0.945 g / cm ³ (for example, Among other olefinic resins, it has the lowest MFR and preferably contains low density polyethylene having a density of 0.880 to 0.945 g / cm ³ ) and / or an ethylene-vinyl acetate copolymer, and has a density of 0. It is more preferable to contain one of the low density polyethylene of 880 to 0.945 g / cm ³ or the ethylene-vinyl acetate copolymer, and further to contain the low density polyethylene having a density of 0.880 to 0.945 g / cm ³ . preferable.
The weight average molecular weight of other polyolefin resins may be less than 400,000.

LDPE has good molding processability, transparency, and is soft. However, since it is easily oriented, the tear strength, impact, and tensile strength are weak.
The LDPE is not particularly limited, and examples thereof include Suntech LD (manufactured by Asahi Kasei Co., Ltd.), UBE polyethylene (manufactured by Ube-Maruzen Polyethylene Co., Ltd.), Petrosen (manufactured by Tosoh Co., Ltd.) and the like. Among these, Suntech LD is preferable. The density of LDPE is 0.880 to 0.945 g / cm ³ , preferably 0.910 to 0.930 g / cm ³ from the viewpoint of achieving both transparency and rigidity, and 0.920 g / cm ³ It is more preferable to be around.

Among the low density polyethylenes, LLDPE is more preferable from the viewpoint of transparency and mechanical strength.
The LLDPE may be a homopolymer of ethylene, or may be a copolymer of ethylene and another α-olefin (ethylene-α-olefin copolymer). Further, those obtained by adding a modified resin to these copolymers may be used.
The density of LLDPE is 0.880 to 0.945 g / cm ³ , and more preferably 0.910 to 0.940 g / cm ³ from the viewpoint of achieving both transparency and rigidity.
LLDPE may be used alone or in combination of two or more. Among them, it is preferable to use two or more types of LLDPE, and it is more preferable to use two or more types of LLDPE having different MFRs. In two or more types of LLDPE having different MFRs, the difference between the lowest MFR and the highest MFR is preferably 1.0 deg / min or more, and more preferably 2.0 deg / min or more. Two or more types of LLDPEs having different MFRs include LLDPEs having a density of 0.880 to 0.945 g / cm ³ (preferably 0.910 to 0.940 g / cm ³ ) and LLDPEs having a density of 0.900 to 0. It may be in combination with LLDPE which is 940 g / cm ³ (preferably 0.91 to 0.935 g / cm ³ ).
Further, the LLDPE preferably contains LLDPE having a larger MFR than the polyethylene component (A) from the viewpoint of further improving the dispersibility of the polyethylene component (A).
Examples of LLDPE include Ube-Maruzen Polyethylene Co., Ltd.

Examples of the ethylene-α-olefin copolymer include a random copolymer of ethylene and at least one α-olefin monomer selected from α-olefins having 3 to 18 carbon atoms. Examples of the α-olefin include propylene, butene-1, pentene-1, 4-methyl-pentene-1, hexene-1, octene-1, decene-1, dodecene-1, and the like. Of these, hexene-1 is preferable.
The ethylene-α-olefin copolymer can be polymerized by a method such as living polymerization or chain polymerization.
The polymerization catalyst used for producing the ethylene-α-olefin copolymer is not particularly limited, and examples thereof include a multisite catalyst and a singlesite catalyst. A single-site system is preferable because it enhances the slipperiness of the film surface.
The content of the structural unit derived from ethylene in the ethylene-α-olefin copolymer is preferably 40 to 95% by mass, more preferably 50 to 90% by mass, and further, because it improves the sealing property and transparency. It is preferably 60 to 85% by mass.

The ethylene-vinyl acetate copolymer preferably has a content of structural units derived from vinyl acetate in the range of 3 to 25% by mass, more preferably 5 to 20% by mass.
When the content of the structural unit derived from vinyl acetate is 3% by mass or more, the adhesion to the dust-proof coating film and the anti-fog coating film provided on the ultra-high molecular weight PE layer is good. Further, when the content is 25% by mass or less, the strength of the obtained film is sufficient and the transparency is also good. When the vinyl acetate content is 5% by mass or more, the obtained film becomes hard and wrinkles and slacks are less likely to occur when the film is spread on the house, and when the vinyl acetate content is larger than 25% by mass, the melting point of the resin is reached. Because the film is low, the film slackens at high temperatures in the summer when the house is expanded, and it is liable to tear due to rubbing against the house structure due to fluttering in the wind, so it is not practical.
The density of the ethylene-vinyl acetate copolymer may be 0.880 to 0.945 g / cm ³ .

The HDPE is not particularly limited, and examples of commercially available products include Suntech HD (manufactured by Asahi Kasei Corporation), Novatec HD (manufactured by Japan Polyethylene Corporation), and Hi-Zex (manufactured by Prime Polymer Co., Ltd.). Of these, Suntech HD is preferred. The density of HDPE is preferably 0.950 to 0.980 g / cm ³ , and more preferably 0.960 to 0.970 g / cm ³ .

As the other olefin resin, the melt mass flow rate (MFR) is preferably 0.1 to 800 dl / min, more preferably 1 from the viewpoint of improving the dispersibility of the ultra-high molecular weight polyethylene component (A). It is about 700 deg / min, more preferably 5 to 600 deg / min. When the MFR is within the above range, the dispersibility of the ultra-high molecular weight polyethylene component (A) tends to be further improved.

(Content of ultra-high molecular weight polyethylene component (A))
The content of the ultra-high molecular weight polyethylene component (A) is preferably 1.0 to 50.0% by mass and 5 to 30% by mass with respect to 100% by mass of the ultra-high molecular weight PE resin composition. Is more preferable, and 7 to 20% by mass is further preferable. When the content of the ultra-high molecular weight polyethylene component (A) is 1.0 to 50.0% by mass, it is possible to achieve both breaking strength, tear strength, and processability into a film form.
The content of the ultra-high molecular weight polyethylene component (A) in the ultra-high molecular weight PE layer is preferably 1.0 to 50.0% by mass, more preferably 5 to 30% by mass, and 7 to 20%. It is more preferably by mass%. When the content of the ultra-high molecular weight polyethylene component (A) is 1.0 to 50.0% by mass, it is possible to achieve both breaking strength, tear strength, and processability into a film form.

(Contents of other polyolefin resins)
The content of the other polyolefin resin is preferably 50 to 99% by mass, more preferably 70 to 95% by mass, and further preferably 80 to 93 with respect to 100% by mass of the ultrahigh molecular weight PE resin composition. It is mass%. When the content of the other polyethylene-based resin is in the above range, the dispersibility of the polyethylene component (A) is improved and the breaking strength is excellent.
The content of the other polyolefin resin in the ultra-high molecular weight PE layer is preferably 50 to 99% by mass, more preferably 70 to 95% by mass, and further preferably 80 to 93% by mass. When the content of the other polyethylene-based resin is within the above range, the dispersibility of the polyethylene component (A) is improved, fish eyes can be suppressed, and the breaking strength is excellent.

When other polyolefin-based resins include low-density polyethylene having a density of 0.880 to 0.945 g / cm ³ and / or an ethylene-vinyl acetate copolymer, the density is 0.880 to 0.945 g / cm ³ . The total content of the low-density polyethylene and the ethylene-vinyl acetate copolymer is preferably 20 to 99% by mass, more preferably 20 to 95% by mass, based on 100% by mass of the ultra-high molecular weight PE resin composition. %, More preferably 20 to 93% by mass, still more preferably 25 to 75% by mass, still more preferably 50 to 75% by mass, and particularly preferably 30 to 70% by mass. When the content is in the above range, the ultra-high molecular weight PE resin composition is transparent and has good processability into a film.
The total content of the low-density polyethylene and the ethylene-vinyl acetate copolymer having a density of 0.880 to 0.945 g / cm ³ in the ultra-high molecular weight PE layer is preferably 20 to 99% by mass, more preferably 20 to 99% by mass. Is 20 to 95% by mass, more preferably 20 to 93% by mass, still more preferably 25 to 75% by mass, still more preferably 50 to 75% by mass, and particularly preferably 30 to 70% by mass. When the content is in the above range, the ultra-high molecular weight PE resin composition is transparent and has good processability into a film.

(Additive)
The ultra-high molecular weight PE resin composition includes, for example, a heat stabilizer, a stabilizer such as a weather resistant agent, a colorant such as a pigment and a dye, a cross-linking agent, a cross-linking aid, an antifogging agent, and a filler such as an organic and inorganic filler. , Other additives such as resins may be added as needed.
The content of the above additive is preferably 0.01 to 20% by mass, more preferably 0.1 to 10% by mass, based on 100% by mass of the ultra-high molecular weight PE resin composition.
The ultra-high molecular weight PE resin composition of the present embodiment preferably contains substantially no lubricant. Specifically, the content of the lubricant is higher than the total amount of the ultra-high molecular weight PE resin composition. It is preferably 0.01% by mass or less.

[Manufacturing method of ultra-high molecular weight PE resin composition]
The method for producing the ultra-high molecular weight PE resin composition is not particularly limited, but the method for producing the following example is preferable.

An example of the method for producing the ultra-high molecular weight PE resin composition is a first melting method in which the ultra-high molecular weight polyethylene component (A) and another polyolefin-based resin are melt-kneaded to obtain a high-concentration diluted ultra-high molecular weight polyethylene resin. A kneading step and a second melt-kneading step of melt-kneading the ultra-high molecular weight polyethylene resin high-concentration diluted product and another polyolefin resin once or multiple times to obtain an ultra-high molecular weight polyethylene resin composition intermediate. It has a third and subsequent melt-kneading steps of melt-kneading the ultra-high molecular weight polyethylene resin composition intermediate and another polyolefin-based resin to obtain an ultra-high molecular weight polyethylene resin composition.
In this way, a high-concentration diluted product of the ultra-high molecular weight polyethylene component (A) and another polyolefin resin is prepared, and the high-concentration diluted product is used as a low-density polyethylene having a density of 0.880 to 0.945 g / cm ³ . (For example, low density polyethylene having the lowest MFR among other olefin resins and a density of 0.880 to 0.945 g / cm ³ ) is further added and melt-kneaded. As a result, an ultra-high molecular weight polyethylene resin composition capable of forming an ultra-high molecular weight PE layer having excellent properties can be obtained.

(First melt-kneading step)
The first melt-kneading step is a step of melt-kneading the ultra-high molecular weight polyethylene component (A) and another polyolefin-based resin to obtain a high-concentration diluted product of the ultra-high molecular weight polyethylene-based resin composition.
The ultra-high molecular weight polyethylene component (A) and the other polyolefin-based resin may be used alone or in combination of two or more. Examples of other polyolefin-based resins used in the first melt-kneading step include HDPE, LLDPE (for example, LLDPE having the highest MFR among LLDPE contained in an ultra-high molecular weight polyethylene resin composition) and the like.

The melt-kneading means is not particularly limited, and examples thereof include known kneading means such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, and the like. According to the conventional idea, as a melt-kneading means, for example, a method of providing a kneading strengthening portion such as a damage, a pin, a kneading disc, and a reverse screw on a screw of an extruder to strengthen the shearing force and mechanically kneading. Is used. However, from the viewpoint of avoiding cutting of the ultra-high molecular weight polyethylene molecular chain due to excessively strengthening the shearing force, it is preferable to suppress the use of the screw provided with these shearing force strengthening portions to the extent that it does not become excessive. From this point of view, as the melt-kneading means, a kneading means including a full flight screw and a screw provided with a part for strengthening the shearing force is preferable.

In the first melt-kneading step, it is preferable that the ultra-high molecular weight polyethylene component (A) is stirred in a relatively high-viscosity atmosphere, whereby long-chain molecules that are difficult to move are expanded. From the viewpoint of improving the propulsive force for expanding the molecular chain of the ultra-high molecular weight polyethylene, the molecular weight of the other polyethylene-based resin used is preferably relatively low. The weight average molecular weight of the other polyolefin resin is preferably 1000 to 50,000. The weight average molecular weight can be measured by the same method as the above-mentioned ultra-high molecular weight PE. Further, from the viewpoint of improving the propulsive force for expanding the molecular chain of the ultra-high molecular weight polyethylene component (A), it is preferable that the viscosity of the entire system in the first melt-kneading step is high, and the temperature is adjusted so that the viscosity becomes high. It is preferable to do so.

The melt mass flow rate (MFR) of the other polyolefin resin used in the first melt-kneading step is preferably 0.1 to 800 dl / min, more preferably 1 to 700 dl / min, and further preferably 10 to 10 to min. It is 600 deg / min. When the MFR of the other polyolefin resin used in the first melt-kneading step is within the above range, the dispersibility of the ultra-high molecular weight polyethylene component (A) tends to be further improved.
In the present disclosure, the melt mass flow rate is a value measured at 200 ° C. and a load of 49 N in accordance with ISO 1133.

The amount of the ultra-high molecular weight polyethylene component (A) added in the first melt-kneading step is not particularly limited, but the total amount of the ultra-high molecular weight polyethylene component (A) and other polyolefin resins used in the first melt-kneading step is used. On the other hand, it is preferably 30 to 90% by mass, more preferably 40 to 80% by mass, and further preferably 50 to 70% by mass. When the amount of the ultra-high molecular weight polyethylene component (A) added in the first melt-kneading step is 30% by mass or more, the viscosity of the entire system becomes higher, and the driving force for expanding the molecular chain of the ultra-high molecular weight polyethylene. As a result, the size of the mass observed due to the difference in refractive index tends to be smaller, and the number thereof also tends to decrease. Further, when the amount of the ultra-high molecular weight polyethylene component (A) added in the first melt-kneading step is 90% by mass or less, the load on the kneading apparatus tends to be further reduced.

The temperature in the first melt-kneading step is preferably 150 to 260 ° C, more preferably 160 to 250 ° C, and even more preferably 170 to 240 ° C. When the temperature in the first melt-kneading step is 150 ° C. or higher, the mobility of the ultra-high molecular weight polyethylene component (A) can be increased, and the dispersion of the ultra-high molecular weight polyethylene component (A) tends to be promoted. It is in. Further, when the temperature in the first melt-kneading step is 260 ° C. or lower, the viscosity of the entire system is increased to promote the dispersion of the ultra-high molecular weight polyethylene component (A), and further, the ultra-high molecular weight polyethylene component (A). The decrease in molecular weight due to thermal decomposition can be further suppressed, and the resulting decrease in strength of the molded product tends to be further suppressed.

The kneading time in the first melt-kneading step varies depending on the kneading apparatus used, but is preferably 0.5 to 20 minutes, more preferably 1 to 10 minutes, still more preferably 2 to 8 minutes. .. When the kneading time in the first melt-kneading step is 0.5 minutes or more, the size of the agglomerates observed due to the difference in the refractive index tends to be smaller and the number thereof tends to decrease. Further, since the ultra-high molecular weight polyethylene is slow to move due to the huge size of the molecule, the kneading time in the first melt-kneading step is 0.5 minutes or more, so that the ultra-high molecular weight polyethylene tends to be more dispersed. Further, it is economically preferable that the kneading time in the first melt-kneading step is 20 minutes or less. The first melt-kneading step may be performed once or may be kneaded a plurality of times.

(Second melt-kneading step)
The second melt-kneading step is a step of melt-kneading the ultra-high molecular weight polyethylene high-concentration diluted product and another polyolefin resin to obtain an ultra-high molecular weight polyethylene resin composition intermediate. The second melt-kneading step may be performed once or may be performed a plurality of times. Further, the second melt-kneading may be performed by the same device as the first melt-kneading step, or may be performed by a different device.

The melt-kneading means is not particularly limited, but can be, for example, the same as in the first melt-kneading step.

The content of the ultra-high molecular weight polyethylene component (A) in the ultra-high molecular weight polyethylene resin composition intermediate obtained in the second melt-kneading step varies depending on the required physical properties of the target product, but is preferably 20 to 80. It is by mass, more preferably 30 to 70% by mass, and even more preferably 35 to 60% by mass. When the content of the ultra-high molecular weight polyethylene component (A) in the ultra-high molecular weight polyethylene resin composition intermediate obtained in the second melt-kneading step is 20% by mass or more, the viscosity of the entire system becomes higher. The propulsive force for expanding the molecular chain of ultra-high molecular weight polyethylene is improved, and as a result, the size of the agglomerates observed due to the difference in refractive index tends to be smaller, and the number thereof tends to be reduced. Further, since the amount of the ultra-high molecular weight polyethylene component (A) added in the second melt-kneading step is 80% by mass or less, the load on the kneading device can be further reduced, and therefore the discharge amount can be increased. It tends to improve economically as well.

The other polyolefin-based resin used in the second melt-kneading step may be the same as or different from the other polyolefin-based resin used in the first melt-kneading step.
Examples of other polyolefin-based resins used in the second melt-kneading step include HDPE and LLDPE (for example, LLDPE excluding LLDPE having the lowest MFR among LLDPE contained in an ultra-high molecular weight polyethylene resin composition). Can be mentioned.

The MFR of the other polyolefin resin used in the second melt-kneading step is preferably 0.1 to 800 deg / min, more preferably 0.5 to 500 deg / min, and further preferably 1 to 200 dl / min. Is. When the MFR of the other polyolefin resin used in the second melt-kneading step is 800 dl / min or less, the viscosity of the entire system in the second melt-kneading step is further improved, and the viscosity is further improved in the ultra-high molecular weight polyethylene high-concentration diluted product. There is a tendency to further promote the dispersion of the resin.

Further, it is preferable that the MFR of the other polyolefin-based resin used in the second melt-kneading step is the same as or lower than the MFR of the other polyolefin-based resin used in the first melt-kneading step. This makes it possible to increase the viscosity of the system in the second melt-kneading step, and as a result, there is a tendency to obtain small-sized or small-sized lumps observed due to the difference in refractive index. .. The MFR of the other polyolefin-based resin used in the second melt-kneading step is preferably 1 times or less, more preferably 0.5 times or less the MFR of the other polyolefin-based resin used in the first melt-kneading step. Yes, more preferably 0.3 times or less. Since the MFR of the other polyolefin-based resin used in the second melt-kneading step is 1 times or less the MFR of the other polyolefin-based resin used in the first melt-kneading step, the entire system of the second melt-kneading step is performed. There is a tendency that the viscosity of the resin is further improved and the dispersion of the resin in the ultra-high molecular weight polyethylene high-concentration diluted product can be further promoted.

The amount of the ultra-high molecular weight polyethylene high-concentration diluted product and other polyolefin-based resin added in the second melt-kneading step also depends on the content of the ultra-high molecular weight polyethylene component (A) in the ultra-high molecular weight polyethylene high-concentration diluted product. Differently, it can be appropriately determined in consideration of the final concentration of the ultra-high molecular weight polyethylene component (A) that can obtain the physical properties of the target film, the fluidity required for producing the target film, and the like.

The temperature at the time of melt-kneading in the second melt-kneading step is preferably 150 to 250 ° C., more preferably 150 to 240 ° C., and further preferably 150 to 230 ° C. When the temperature at the time of melt-kneading in the second melt-kneading step is 250 ° C. or lower, the viscosity of the entire system tends to be improved and the dispersion of the ultra-high molecular weight polyethylene high-concentration diluted product tends to be further improved. Further, since the temperature at the time of melt-kneading in the second melt-kneading step is 250 ° C. or lower, it is possible to suppress the decrease in molecular weight due to thermal decomposition of the ultra-high molecular weight polyethylene component (A), and the resulting film strength decrease. It tends to be more restrained. Further, when the temperature at the time of melt-kneading in the second melt-kneading step is 150 ° C. or higher, the mobility of the ultra-high molecular weight polyethylene component (A) can be increased, and the ultra-high molecular weight polyethylene component (A) can be easily moved. Dispersion tends to be promoted. The second melt-kneading step may be performed once or may be kneaded a plurality of times.
Other polyolefin-based resins for the second and subsequent kneading can be appropriately determined.

(Third melt-kneading step)
The third melt-kneading step is a low density of the polyethylene-based resin composition intermediate obtained in the second melt-kneading step and another polyolefin-based resin (preferably a density of 0.880 to 0.945 g / cm ³ ). Polyethylene (particularly, low-density polyethylene having the lowest MFR among the low-density polyethylene contained in the ultra-high molecular weight polyethylene resin composition and having a density of 0.880 to 0.945 g / cm ³ ) and / or both ethylene and vinyl acetate. This is a step of melt-kneading the polymer) to obtain an ultra-high molecular weight polyethylene resin composition.

The third melt-kneading may be performed by the same device as the first and second melt-kneading steps, or may be performed by different devices. The melt-kneading means is not particularly limited, but can be, for example, the same as in the first melt-kneading step.

The MFR of the other polyolefin resin used in the third melt-kneading step can be appropriately selected depending on the fluidity and strength required by the intended application.

The MFR of the other polyolefin resin used in the third melt-kneading step is preferably 0.1 to 800 dl / min, more preferably 0.5 to 500 dl / min, still more preferably 0.8 to 200 dl. / Min. Since the MFR of a part of the polyethylene component (A) or other polyolefin resin containing no UHMWPE used in the third melt-kneading step is 800 deg / min or less, the viscosity of the entire system in the third melt-kneading step becomes high. It tends to be further improved and the dispersion of the ultra-high molecular weight polyethylene resin composition intermediate can be further promoted.

The amount of the ultra-high molecular weight polyethylene resin composition intermediate and other polyolefin-based resin added in the third melt-kneading step depends on the content of the ultra-high molecular weight polyethylene component (A) in the ultra-high molecular weight polyethylene resin composition intermediate. Also different, it can be appropriately determined in consideration of the final concentration of the ultra-high molecular weight polyethylene component (A) that can obtain the physical properties of the target film, the fluidity required to produce the target film, and the like. ..

The temperature at the time of melt-kneading in the third melt-kneading step is preferably 150 to 260 ° C, more preferably 160 to 250 ° C, and further preferably 170 to 240 ° C. When the temperature at the time of melt-kneading in the third melt-kneading step is 260 ° C. or lower, the viscosity of the entire system tends to be improved and the dispersion of the polyethylene-based resin composition intermediate tends to be further improved. Further, since the temperature at the time of melt-kneading in the third melt-kneading step is 260 ° C. or lower, it is possible to suppress the decrease in molecular weight due to thermal decomposition of the ultra-high molecular weight polyethylene in the ultra-high molecular weight polyethylene component (A), resulting in the result. There is a tendency that the decrease in the strength of the film to be obtained can be further suppressed. Further, when the temperature at the time of melt-kneading in the third melt-kneading step is 150 ° C. or higher, the mobility of the ultra-high molecular weight polyethylene component (A) can be increased, and the ultra-high molecular weight polyethylene component (A) can be easily moved. Dispersion tends to be promoted.

In addition to this, it is also possible to provide a fourth and subsequent melt-kneading steps, if necessary. The fourth and subsequent melt-kneading steps can be performed under the same operations and conditions as the third melt-kneading step.

The first melt-kneading step and the second and third or fourth and subsequent melt-kneading steps may be performed in separate steps, or the second and subsequent melt-kneading steps may be performed on the apparatus for performing the first melt-kneading step. The first melt-kneading step and the second and subsequent melt-kneading steps may be continuously performed by connecting the devices for performing the above-mentioned The first melt-kneading step and the second and subsequent melt-kneading steps may be continuously performed by side-feeding. In either case, the temperature conditions and the like are set so that the above-mentioned ultra-high molecular weight polyethylene component (A), the ultra-high molecular weight polyethylene high-concentration diluted product, and the ultra-high molecular weight polyethylene-based resin composition intermediate are sufficiently dispersed in each step. It is preferable to melt and knead in consideration of this.

By using a processing aid or the like in the above kneading, the effect of lowering the apparent melt viscosity can be obtained. When the processing aid is not added, the operation is performed at a specific temperature under the torque limit condition of the device, whereas when the processing aid is added, the resin pressure at the time of extrusion decreases. , It is possible to operate at a lower temperature.
In particular, in the second kneading, it is desirable to knead at a low temperature as much as possible for the purpose of promoting the dispersion of the ultra-high molecular weight polyethylene component (A), and it is preferable to add these processing aids.
As the processing aid, a PVDF-based (3M Co., Ltd., Dynamar FX5920) or acrylic-modified PTFE-based (Mitsubishi Rayon Co., Ltd., Metabrene A3000) processing aid can be preferably used. At the time of use, it is preferable to add in the range of 0.01 to 1.0% by mass with respect to 100% by mass of the polyethylene-based resin composition in advance before the first melt-kneading step.

In order to prepare a laminated film having a three-layer structure composed of an outer layer, an intermediate layer and an inner layer, which is an example of the agricultural film of the present embodiment, first, pellets capable of forming each layer are prepared, and then a known method, for example, is used. , The film may be formed so that each layer has a predetermined thickness by a coextrusion inflation molding method or the like.

The thickness of the outer layer and the inner layer is preferably 1 to 150 μm, more preferably 10 to 100 μm, and further preferably 20 to 50 μm. The thicknesses of the outer layer and the inner layer may be the same or different. When the outer layer and / or the inner layer is an ultra-high molecular weight PE layer, the thickness of the layer is preferably 1 to 150 μm, more preferably 10 to 100 μm, and further preferably 20 to 50 μm.

In the agricultural film of the present embodiment, when the outer layer or the inner layer is not a super high molecular weight PE layer, the outer layer or the inner layer is a single or a plurality of other polyolefin-based resins (particularly, the density is 0.880 to 0.945 g / cm). ³ low density polyethylene (for example, low density polyethylene with the lowest MFR among other olefin resins and a density of 0.880 to 0.945 g / cm ³ ) and / or an ethylene-vinyl acetate copolymer). It is preferably a layer containing only, more preferably a layer composed of only a single or a plurality of other polyolefin-based resins, and further preferably a layer composed of only the above-mentioned polyethylene-vinyl acetate copolymer. When the outer layer or the inner layer is not an ultra-high molecular weight PE layer, the outer layer or the inner layer may contain the above-mentioned additive.
When the outer layer or the inner layer is not an ultra-high molecular weight PE layer, the content of the other polyolefin resin in the outer layer or the inner layer is preferably 50 to 100% by mass, more preferably 80 to 100% by mass. When the content of the other polyolefin resin is in the above range, the ultra-high molecular weight PE resin composition is transparent and has good processability into a film.

[Middle layer]
An intermediate layer provided between the inner layer and the outer layer of the agricultural film of the present embodiment will be described.
The number and composition of the intermediate layer are not particularly limited, but the ethylene-vinyl acetate copolymer has an infrared absorbing ability and can absorb radiant heat from the ground, so that the agricultural film should be provided with heat retention. Therefore, it can be suitably used. Further, other polyolefin-based resins (for example, low-density polyethylene having a density of 0.880 to 0.945 g / cm ³ (for example, the lowest MFR among other olefin-based resins and a density of 0.880 to 0.945 g). It is also possible to combine a heat insulating material with (such as low density polyethylene of / ^cm3 ) and / or an ethylene-vinyl acetate copolymer). The intermediate layer may further contain an anti-fog agent.
Examples of the material constituting the intermediate layer include the following.

(Ethylene-vinyl acetate copolymer)
The vinyl acetate content in the intermediate layer is preferably 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 anti-fog coating film is good. Further, when the content is 30% by mass or less, the strength of the obtained film is sufficient and the transparency is also good.
The ethylene-vinyl acetate copolymer preferably has a vinyl acetate content in the range of 3 to 25% by mass, more preferably 5 to 20% by mass. If the vinyl acetate content is smaller than this range, the obtained film becomes hard and wrinkles and slacks are likely to occur when the film is spread on the house, which adversely affects the anti-fog property and is not practical, and the vinyl acetate content is this. If it is larger than the range, the melting point of the resin is low, so that the film loosens under high temperature in summer when the house is expanded, and it is liable to be torn due to rubbing against the house structure due to fluttering in the wind, which is not practical.

(Insulation material)
The heat insulating material improves the heat retaining property of the film, and has a general formula [Al ₂ Li (OH) ₆ ] _n X · mH ₂ O (I).
A lithium aluminum compound represented by (X in the formula is an inorganic or organic anion, n is the valence of the anion X, m is a number of 3 or less), and the general formula M 2 ⁺ _1-x Al _x (OH) ₂ ( A ^p- ) _{x / p} · qH ₂ O (II)
(M ²⁺ represents a divalent metal ion selected from the group consisting of Mg ²⁺ , Ca ²⁺ and Zn ²⁺ , Ap − is a ^p- valent anion, and x and q are 0 <x <0.5, 0 ≦ q, respectively. Hydrotalsites and the like represented by) (which is a number satisfying ≦ 2) can be mentioned.
This heat insulating material can be blended in a proportion of 1 to 20 parts by mass, preferably 3 to 10 parts by mass with respect to 100 parts by mass of the resin component contained in the intermediate layer. If the blending amount is less than 1 part by mass, the effect of improving the heat retention property is not sufficiently exhibited, and if it exceeds 20 parts by mass, the mechanical properties such as the tensile strength and the tear strength of the film are lowered. Further, in the intermediate layer, the heat insulating material is blended uniformly with the resin component in a compatible manner, and the lithium aluminum compound is particularly preferable because of its high transparency.

In the lithium aluminum compound represented by the general formula (I), X is an inorganic or organic anion, and specific examples thereof are inorganic such as carbonate ion, sulfate ion, phosphate ion, phosphite ion, and metaphosphate ion. Examples thereof include organic anions such as anions, acetate ions, propionic acid ions, oxalate ions, adipates ions, benzoate ions, and phthalates ions.

In the hydrotalcites represented by the general formula (II), A is an inorganic or organic anion, and specific examples thereof include inorganic anions such as carbonate ion, sulfate ion, and phosphate ion, CH ₃ COO ⁻ , and C. ₆ Organic anions such as H4 ₍ OH) COO ⁻ can be mentioned.

The intermediate layer is a base material layer of an agricultural film, and the thickness thereof is usually selected in the range of 30 to 180 μm, preferably 50 to 130 μm. If this thickness is too thin, the mechanical properties of the obtained film will be insufficient, and if it is too thick, the light transmission will decrease. The thickness of the intermediate layer is preferably in the range of 50 to 80%, particularly preferably in the range of 55 to 75% with respect to the thickness of the entire film.

(Anti-fog agent)
In the agricultural film of the present embodiment, 1 to 10% by mass of an anti-fog agent may be added to the composition constituting the intermediate layer with respect to the total amount of the composition. If it is less than 1% by mass, the anti-fog effect is not sufficient, and if it exceeds 10% by mass, the film becomes opaque due to a large number of blowouts to the film surface, or foaming during film forming. Problems arise. The anti-fog agent may be added not only to the intermediate layer but also to the inner layer or the inner layer and the outer layer as needed.

（式中、Ｒ_１は炭素数が８～２２のアルキル基、アルケニル基またはアシル基、Ｒ_２およびＲ_３は互いに独立して水素原子または炭素数が８～２２のアシル基、ａおよびｂは互いに独立してａ＋ｂ＝２～２０となる１以上の整数、ｃは０または１～１０の整数、ｎは２または３を示す。） Examples of the anti-fog agent include nonionic surfactants, cationic surfactants, anionic surfactants, amphoteric surfactants, etc., as well as the degree of esterification of the anti-fog agent, the chain length of the alkyl group, and the alkylene oxide. Examples thereof include those obtained by changing the number of added moles or their purity. Examples of these are partial carboxylic acid esters of polyhydric alcohols such as sorbitan monolaurate, diglycerin sesquilaurate, and glycerin monoolate, and polyhydric alcohols such as polyoxyethylene sorbitan monolaurate and polyoxyethylene sorbitan monoolate. Examples thereof include polyoxyethylene derivatives of partially carboxylic acid esters, amines and fatty acid amides. Among them, a neutralized salt of the compound represented by the following formula (1) and their organic acid is preferably used.

(In the formula, R ₁ is an alkyl group having 8 to 22 carbon atoms, an alkenyl group or an acyl group, R ₂ and R ₃ are independent hydrogen atoms or acyl groups having 8 to 22 carbon atoms, and a and b are. An integer of 1 or more in which a + b = 2 to 20 independently of each other, c is an integer of 0 or 1 to 10, and n is 2 or 3).

<Agricultural film molding method>
The agricultural film of the present embodiment is obtained by extrusion molding the above ultra-high molecular weight PE resin composition. The extrusion molding method is not particularly limited, and examples thereof include T-die molding, inflation molding, hot press molding, and vacuum forming. Among them, inflation molding is preferable. The processing temperature is preferably 150 to 250 ° C, more preferably 160 to 230 ° C, and even more preferably 170 to 220 ° C.

Further, the agricultural film of the present embodiment may undergo a crosslinking reaction after film molding. By the cross-linking reaction, a polyethylene layer having a higher molecular weight can be obtained, and a film having improved slip wear characteristics can be obtained.

Hereinafter, the characteristics of the agricultural film of the present embodiment will be described.

(Specific wear amount of ultra-high molecular weight PE layer)
The coefficient of friction is a characteristic that governs the wear characteristics. The coefficient of friction is calculated by the maximum point at which a strain that dissociates the bound energy from the intramolecular force between substances and the adhesion due to the interatomic force is applied. In the case of a resin having viscoelasticity such as polyethylene, due to the viscous property of the resin, for a resin having a viscous property with a long relaxation time, the time to recover the strain due to deformation becomes long, and the movement of the center of gravity of the moving body is always. Since a negative load is applied in the opposite direction, the dynamic friction coefficient becomes large and the specific wear amount increases. Based on these findings, in order to reduce the amount of specific wear, it is preferable to blend ultra-high molecular weight polyethylene (UHMWPE) with few sites that serve as adhesion points.

The specific wear amount of the ultra-high molecular weight PE layer can be reduced by containing a predetermined amount of ultra-high molecular weight polyethylene. It can be suitably used as an outer layer of an agricultural film from the viewpoint of suppressing film deterioration due to wear due to dust and rubbing between films during winding work. Further, since rubbing during the winding operation also occurs in the inner layer and the outer layer, a reinforcing layer may be provided in the inner layer.

From this point of view, the specific wear amount of the ultra-high molecular weight PE layer carried out in accordance with the JIS K7218A method is preferably 5 × ^10-6 mm ³ / Nm or less ^, more preferably 3.6 × 10-. It is ⁶ mm ³ / Nm or less.
When there are a plurality of ultra-high molecular weight PE layers, the specific wear amount of at least one layer is preferably in the above range, and the specific wear amount of all layers is more preferably in the above range.
Test piece 30 × 30 × t = 0.15 mm
Mating material SUS304 ring (contact area 2 cm ² ) Roughness 0.1 μm Ra or less Speed 0.5 m / s Load 35 N Time 100 minutes Measuring device A & D Co., Ltd. Friction wear tester MODEL EMF-III-F

(Thickness of agricultural film)
The thickness of the agricultural film of the present embodiment is preferably 1 to 200 μm, more preferably 5 to 180 μm, and even more preferably 10 to 175 μm from the viewpoint of transparency.

(Breaking strength of agricultural film)
The tensile breaking strength of the agricultural film of the present embodiment is preferably 0.2 MPa or more, more preferably 0.26 MPa or more. When the tensile breaking strength is 0.2 MPa or more, it is preferable because it can be suitably used as an agricultural film.
In the present disclosure, the tensile breaking strength of the agricultural film is a value measured in accordance with JIS K7161.

(Tear strength of agricultural film)
The tear strength of the agricultural film of the present embodiment is preferably 170 N / mm or more, more preferably 200 N / mm or more. When the tear strength is 170 N / mm or more, it is preferable because it can be suitably used as an agricultural film.
In the present disclosure, the tensile breaking strength of the agricultural film is a value measured by the trouser tearing method based on JIS K7218-1.

(Total light transmittance of agricultural film)
The internal haze of the agricultural film of the present embodiment is preferably 45 or less, more preferably 35 or less, still more preferably 30 or less in a film having a thickness of 150 μm. When the internal haze is 45 or less, it can be suitably used as a transparent film.
The total light transmittance of the agricultural film of the present embodiment is preferably 88% or more, more preferably 90% or more.
The internal haze is a value excluding the haze derived from the surface structure such as unevenness, and is measured in accordance with JIS K7136. The total light transmittance is measured according to JIS K7631-1 under the condition of a thickness of 150 μm.

The agricultural film of the present embodiment can be used as a covering material for facility horticulture such as an agricultural house or an agricultural tunnel, and is particularly useful as a covering material for an agricultural house equipped with a winder.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples.

<Raw materials used in Examples and Comparative Examples>
The polyethylene used as the ultra-high molecular weight polyethylene component (A) in the production of the agricultural film is as follows.
UHMWPE1: Asahi Kasei Corporation, Sunfine (registered trademark) UH900 (density: 0.940 g / cm ³ , tensile modulus: 0.34 GPa, weight average molecular weight 3 million)

The polyethylene used as other polyolefin resins in the production of agricultural films is as follows.
LLDPE1: Made by Prime Polymer Co., Ltd., Evolu (registered trademark) SP4020 (density: 0.937 g / cm ³ , tensile modulus: 0.45 GPa) MFR 1.8 dl / min
-EVA1 UBE Polyethylene V115 manufactured by Ube-Maruzen Polyethylene Co., Ltd. (Density: 0.94 g / cm ³ , Tension modulus: 0.04 GPa) MFR 0.8 dl / min
-EVA2 UBE Polyethylene V106 manufactured by Ube-Maruzen Polyethylene Co., Ltd. (Density: 0.92 g / cm ³ , Tension modulus: 0.08 Gpa) MFR 0.4 dg / min
HDPE1: Asahi Kasei Corporation, Suntech (registered trademark) J300 (density: 0.961 g / cm ³ , tensile modulus: 0.68 GPa) MFR 42 deg / min
HDPE2: Asahi Kasei Corporation, Suntech (registered trademark) J240 (density: 0.966 g / cm ³ , tensile modulus: 0.7 GPa) MFR 5 dg / min
LLDPE2: manufactured by Ube Industries, Ltd., Umerit (registered trademark) 631J (density: 0.931 g / cm ³ , tensile modulus: 0.29 GPa) MFR 20 dg / min
LLDPE3: manufactured by Ube Industries, Ltd., Umerit (registered trademark) 2040FC (density: 0.919 g / cm ³ , tensile modulus: 0.21 GPa) MFR 5 dg / min

The heat insulating materials used in the production of agricultural films are as follows.
・ Insulation material 1 Kyowa Chemical Industry Co., Ltd. DHT-4A

(1) Measurement of breaking strength The breaking strength (MPa) of the films obtained in Examples and Comparative Examples is determined by Autograph AG-XPlus (manufactured by Shimadzu Corporation) with a sample width of 10 mm and a chuck distance of 50 mm. It was measured according to K7161. The measurement results are shown in Table 1.

(2) Measurement of trouser tear strength The tear strength (GPa) of the films obtained in Examples and Comparative Examples was measured by Autograph AG-XPlus (manufactured by Shimadzu Corporation) with a sample width of 10 mm and a chuck distance of 50 mm. It was measured according to JIS K7211-1. The measurement results are shown in Table 1.

(3) Measurement of total light transmittance The total light transmittance of the films obtained in Examples and Comparative Examples is JIS K using a film having a thickness of 150 μm using HAZEMETER NDH-5000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.). It was measured according to 7361-1. The measurement results are shown in Table 1.

(4) Measurement of specific wear amount The specific wear amount of the outer layer of the films obtained in Examples and Comparative Examples was measured under the following conditions according to JIS K7218A. In Example 4, when the specific wear amount of the inner layer was also measured, it was almost the same value as that of the outer layer.
Test piece 30 × 30 × t = 0.15 mm
Mating material SUS304 ring (contact area 2 cm ² ) Roughness 0.1 μm Ra or less Speed 0.5 m / s Load 35 N Time 100 minutes Measuring device A & D Co., Ltd. Friction wear tester MODEL EMF-III-F

[Example 1]
After mixing 55.5% by mass of UHMWPE1 and 44.5% by mass of HDPE1, the mixture was melt-kneaded with a TEM-18s twin-screw extruder (L / D = 50) manufactured by Toshiba Machine Co., Ltd. The kneading was carried out at a temperature of 215 ° C. and a screw rotation speed of 200 rotations, and the feeder was adjusted so that the discharge amount was about 1 to 2 kg / Hr to obtain an ultra-high molecular weight polyethylene resin high-concentration diluted product.
After mixing 66.7% by mass of the ultra-high molecular weight polyethylene resin high-concentration diluted product obtained above and 33.3% by mass of HDPE2, the mixture is charged into the above twin-screw extruder and subjected to the second melt-kneading. did. Kneading was performed at a temperature of 210 ° C. and a screw rotation speed of 200 rpm by adjusting the feeder so that the discharge rate was 1 to 2 kg / Hr to obtain pellets of the first intermediate of the ultra-high molecular weight polyethylene resin composition. rice field.
After mixing 81.1% by mass of the first intermediate of the ultra-high molecular weight polyethylene resin composition obtained above and HDPE1 of 18.9% by mass, the mixture is charged into the twin-screw extruder and second melt-kneaded. It was used for (the second time). The kneading was carried out at a temperature of 210 ° C. and a screw rotation speed of 200 rpm by adjusting the feeder so that the discharge amount was about 1 to 2 kg / Hr to obtain a second intermediate of the ultra-high molecular weight polyethylene resin composition. ..
After mixing 40% by mass of the second intermediate of the ultra-high molecular weight polyethylene resin composition obtained above and 60% by mass of LLDPE1, the mixture was charged into the twin-screw extruder and subjected to a third melt-kneading. The kneading was carried out at a temperature of 210 ° C. and a screw rotation speed of 200 rotations, and the feeder was adjusted so that the discharge amount was about 3 to 5 kg / Hr to obtain pellets of an ultra-high molecular weight polyethylene resin composition.
These pellets were supplied to an extruder of a multi-layer inflation molding machine to inflate the outer layer extruded at 10 kg / Hr from a 190 ° C. die, the intermediate layer extruded EVA1 at 30 Kg / Hr, and the inner layer extruded at 10 Kg / Hr for EVA2. An agricultural film having a thickness of 0.15 mm and a width of 100 cm was obtained.
Table 1 shows the compositions of the obtained ultra-high molecular weight polyethylene resin composition and the agricultural film, and the measurement results of each physical property.

[Example 2]
After mixing 55.5% by mass of UHMWPE1 and 44.5% by mass of LLDPE2, the mixture was melt-kneaded with a TEM-18ss twin-screw extruder (L / D = 50) manufactured by Toshiba Machine Co., Ltd. The kneading was carried out at a temperature of 215 ° C. and a screw rotation speed of 200 rotations, and the feeder was adjusted so that the discharge amount was about 1 to 2 kg / Hr to obtain an ultra-high molecular weight polyethylene resin high-concentration diluted product.
After mixing 66.7% by mass of the ultra-high molecular weight polyethylene resin high-concentration diluted product obtained above and 33.3% by mass of LLDPE3, the mixture is charged into the above twin-screw extruder and subjected to the second melt-kneading. did. The kneading was carried out at a temperature of 210 ° C. and a screw rotation speed of 200 rotations, and the feeder was adjusted so that the discharge amount was 1 to 2 kg / Hr to obtain a first intermediate of an ultra-high molecular weight polyethylene resin composition.
After mixing 81.1% by mass of the first intermediate of the ultra-high molecular weight polyethylene resin composition obtained above and 18.9% by mass of LLDPE2, the mixture is charged into the twin-screw extruder and second melt-kneaded. It was used for (the second time). The kneading was carried out at a temperature of 210 ° C. and a screw rotation speed of 200 rotations, and the feeder was adjusted so that the discharge amount was about 1 to 2 kg / Hr to obtain an ultra-high molecular weight polyethylene resin second intermediate.
After mixing 40% by mass of the second intermediate of the ultra-high molecular weight polyethylene resin composition obtained above and 60% by mass of LLDPE1, the mixture was charged into the twin-screw extruder and subjected to a third melt-kneading. The kneading was carried out at a temperature of 210 ° C. and a screw rotation speed of 200 rotations, and the feeder was adjusted so that the discharge amount was about 3 to 5 kg / Hr to obtain pellets of an ultra-high molecular weight polyethylene resin composition.
These pellets were supplied to an extruder of a multi-layer inflation molding machine to inflate the outer layer extruded at 10 kg / Hr from a 190 ° C. die, the intermediate layer extruded EVA1 at 30 Kg / Hr, and the inner layer extruded at 10 Kg / Hr for EVA2. An agricultural film having a thickness of 0.15 mm and a width of 100 cm was obtained.
Table 1 shows the compositions of the obtained ultra-high molecular weight polyethylene resin composition and the agricultural film, and the measurement results of each physical property.

[Example 3]
80% by mass of the second intermediate of the ultra-high molecular weight polyethylene resin composition obtained in the second kneading (second time) of Example 1 and 20% by mass of LLDPE1 were mixed, and then the twin-screw extruder was used. It was charged and subjected to a fourth melt-kneading. The kneading was carried out at a temperature of 210 ° C. and a screw rotation speed of 200 rotations, and the feeder was adjusted so that the discharge amount was about 1 to 2 kg / Hr to obtain pellets of an ultra-high molecular weight polyethylene resin composition.
These pellets were supplied to an extruder of a multi-layer inflation molding machine to inflate the outer layer extruded at 10 kg / Hr from a 190 ° C. die, the intermediate layer extruded EVA1 at 30 Kg / Hr, and the inner layer extruded at 10 Kg / Hr for EVA2. An agricultural film having a thickness of 0.15 mm and a width of 100 cm was obtained.
Table 1 shows the compositions of the obtained ultra-high molecular weight polyethylene resin composition and the agricultural film, and the measurement results of each physical property.

[Example 4]
The pellets of the ultra-high molecular weight polyethylene resin composition obtained in the third kneading of Example 1 were supplied to an extruder of a multilayer inflation molding machine, and an outer layer extruded from a die at 190 ° C. by 10 kg / Hr, EVA1 was 30 kg / g /. An intermediate layer extruded with Hr and an inner layer extruded with the same pellets as the outer layer at 10 kg / Hr were inflation-molded to obtain an agricultural film having a thickness of 0.15 mm and a width of 100 cm.
Table 1 shows the compositions of the obtained ultra-high molecular weight polyethylene resin composition and the agricultural film, and the measurement results of each physical property.

[Example 5]
After mixing 90% by mass of EVA1 and 10% by mass of the heat insulating material 1, the mixture was melt-kneaded with a TEM-18ss twin-screw extruder (L / D = 50) manufactured by Toshiba Machine Co., Ltd. The kneading was carried out at a temperature of 170 ° C. and a screw rotation speed of 200 rotations, and the feeder was adjusted so that the discharge amount was about 3 to 5 kg / Hr to obtain EVA1 pellets containing a heat insulating material.
The pellets of the ultra-high molecular weight polyethylene resin composition obtained in the third kneading of Example 1 were supplied to an extruder of a multilayer inflation molding machine, and an outer layer extruded from a die at 190 ° C. by 10 kg / Hr, EVA1 containing a heat insulating material. An intermediate layer in which pellets were extruded at 30 kg / Hr and an inner layer in which the same pellets as the outer layer were extruded at 10 kg / Hr were inflation-molded to obtain an agricultural film having a thickness of 0.15 mm and a width of 100 cm.
Table 1 shows the compositions of the obtained ultra-high molecular weight polyethylene resin composition and the agricultural film, and the measurement results of each physical property.

[Comparative Example 1]
LLDPE1 was supplied to an extruder of a multilayer inflation molding machine, and an outer layer extruded at 10 Kg / Hr from a 190 ° C. die, an intermediate layer extruded EVA1 at 30 Kg / Hr, and an inner layer extruded at 10 Kg / Hr from EVA2 were inflated. A polyolefin resin film having a thickness of 0.15 mm and a width of 100 cm was obtained.
Table 1 shows the compositions of the obtained polyethylene-based resin composition and film, and the measurement results of each physical property.

[Comparative Example 2]
After mixing 61.5% by mass HDPE1 and 38.5% by mass HDPE2, the mixture was melt-kneaded with a TEM-18ss twin-screw extruder (L / D = 50) manufactured by Toshiba Machine Co., Ltd. The kneading was carried out at a temperature of 205 ° C. and a screw rotation speed of 200 rotations, and the feeder was adjusted so that the discharge amount was about 3 to 5 kg / Hr to obtain a polyethylene-based resin composition intermediate.
After mixing 40% by mass of the polyethylene-based resin composition intermediate obtained above and 60% by mass of LLDPE1, the mixture was charged into the twin-screw extruder and subjected to a second melt-kneading. The kneading was carried out at a temperature of 210 ° C. and a screw rotation speed of 200 rotations, and the feeder was adjusted so that the discharge amount was about 3 to 5 kg / Hr to obtain pellets of a polyethylene-based resin composition.
These pellets were supplied to an extruder of a multi-layer inflation molding machine to inflate the outer layer extruded at 10 kg / Hr from a 190 ° C. die, the intermediate layer extruded EVA1 at 30 Kg / Hr, and the inner layer extruded at 10 Kg / Hr for EVA2. A polyolefin resin film having a thickness of 0.15 mm and a width of 100 cm was obtained.
Table 1 shows the compositions of the obtained polyethylene-based resin composition and film, and the measurement results of each physical property.

[Comparative Example 3]
LLDPE1 is supplied to an extruder of a multilayer inflation molding machine, and an outer layer extruded at 10 kg / Hr from a 190 ° C. die, an intermediate layer extruded EVA1 at 30 Kg / Hr, and an inner layer extruded at 10 Kg / Hr LLDPE1 are inflation-molded. A polyolefin resin film having a thickness of 0.15 mm and a width of 100 cm was obtained.
Table 1 shows the compositions of the obtained polyethylene-based resin composition and film, and the measurement results of each physical property.

The polyethylene-based agricultural film of the present invention can be widely used as a vinyl house, a mulch film, or the like.

Claims (6)

It has at least an outer layer and an inner layer,
From an ultrahigh molecular weight polyethylene resin composition in which at least one of the outer layer and the inner layer contains an ultrahigh molecular weight polyethylene having a weight average molecular weight of 400,000 or more and a low density polyethylene and / or an ethylene-vinyl acetate copolymer. Naru,
The ultra-high molecular weight polyethylene resin composition contains 1 to 30% by mass of the ultra-high molecular weight polyethylene and 20% by mass or more of the low-density polyethylene and / or ethylene-vinyl acetate copolymer.
The low density polyethylene comprises a linear low density polyethylene,
Agricultural polyolefin-based multilayer film characterized by this. The density of the low density polyethylene is 0.910 g / cm ³ Above 0.930 g / cm ³ Is less than
The density of the ethylene-vinyl acetate copolymer is 0.880 to 0.945 g / cm. ³ The agricultural polyolefin-based multilayer film according to claim 1. The agriculture according to claim 1 or 2 , wherein the specific wear amount of the layer containing the ultra-high molecular weight polyethylene measured by a slip wear test conforming to JIS K7218A is 5 × 10 ^-6 mm ³ / Nm or less. Polyolefin-based multilayer film for. The agricultural polyolefin-based multilayer film according to any one of claims 1 to 3 , wherein the layer containing the ultra-high molecular weight polyethylene has a thickness of 10 to 100 μm. The agricultural polyolefin-based multilayer film according to any one of claims 1 to 4 , wherein the total light transmittance measured according to JIS K 7631-1 under the condition of a thickness of 150 μm is 88% or more. The agriculture according to any one of claims 1 to 5 , further comprising an intermediate layer between the outer layer and the inner layer, and the outer layer and the inner layer containing ultra-high molecular weight polyethylene having a weight average molecular weight of 400,000 or more. Polyolefin-based multilayer film for.