JP7144508B2 - agricultural film - Google Patents

Description

FIELD OF THE DISCLOSURE The present disclosure relates to agricultural films.

In general, agricultural films are desired to have high light transmittance, but depending on the type of crop, it is desired to minimize the proportion of direct light and increase the proportion of scattered light. For example, in greenhouses for growing soft vegetables such as leaf tobacco and lettuce, it is essential to use an agricultural film with little direct light to prevent the leaves from sunburn. In addition, in a leaf tobacco drying greenhouse, it is essential to use an agricultural film that receives less direct light in order to prevent rapid drying or to prevent the formation of dull leaves or dull leaves. Therefore, satin-like films have been used as agricultural films.

As a satin type agricultural film, for example, Japanese Patent No. 3219319 discloses that at least one of the outermost layer and the innermost layer has a vinyl acetate content of 24 to 34% by weight and a melt flow rate (MFR) of 4 to 50 g/ A 10-minute ethylene-vinyl acetate copolymer (A) and a mixture of a low-density polyethylene (B) having an MFR of 0.04 to 2.0 g/10 minutes, and the mixing ratio of (A) and (B) is (A)/(B) = 35-90/65-10 (weight ratio), the average vinyl acetate content of the mixture is 12-22% by weight, and its MFR ratio (MFR of (A)/(B) MFR) = 10 to 100, a multi-layered structure comprising the mixture layer and another olefin resin layer, a total light transmittance of 80% or more, and a trans of 10% or less. is disclosed.

As shown in Japanese Patent No. 3219319, various attempts have been made to obtain agricultural films (plastic films) with various functionalities and satin-like surfaces.

The problem to be solved by one embodiment of the present disclosure is an agricultural film that has better mechanical properties while maintaining the total light transmittance and haze values within the allowable range compared to conventional agricultural films. is to provide

Note that the satin-like surface indicates a surface state having a plurality of indeterminate, fine spot-like irregularities like the skin of a pear, and having a rough texture.
The allowable range of the total light transmittance is 85% or more and less than 95%, and the allowable range of the haze value is 70% or more and less than 95%.

Means for solving the above problems include the following aspects.
<1>
The content of structural units derived from vinyl acetate is 12% by mass or more and 35% by mass or less, and the melt flow rate (MFR, JIS K7210-1999, 190°C, 2160g load) is 4g/10min or more and 100g/10min or less. an ethylene-vinyl acetate copolymer (A) of
and a polyolefin (B) containing at least one selected from the group consisting of high-density polyethylene and metallocene-catalyzed polyethylene,
Agricultural use having a mixture layer, wherein the content ratio [(A):(B)] of the ethylene-vinyl acetate copolymer (A) and the polyolefin (B) is 35:65 to 85:15 in mass ratio the film.
<2>
The agricultural film according to <1>, further comprising low-density polyethylene as the polyolefin (B).
<3>
The agricultural film according to <1> or <2>, wherein the average content of the structural unit derived from vinyl acetate is 9% by mass or more and less than 30% by mass when the resin component in the mixture layer is 100% by mass. .
<4>
The agricultural film according to any one of <1> to <3>, wherein the mixture layer is the outermost layer.
<5>
<1> to <4> wherein the ratio (MFR ^A /MFR ^B ) of the MFR ^A of the ethylene-vinyl acetate copolymer (A) and the MFR ^B of the polyolefin (B) is 10 or more and 100 or less. Agricultural film according to any one of.

According to one embodiment of the present disclosure, an agricultural film having excellent mechanical properties while maintaining the total light transmittance and haze values within acceptable ranges is provided.

An embodiment that is an example of the agricultural film of the present disclosure will be described below. The present disclosure is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the purpose of the present disclosure.

In the present disclosure, "~" in a numerical range means including the numbers before and after "~". In the numerical ranges described stepwise in this specification, the upper limit or lower limit described in a certain numerical range may be replaced with the upper limit or lower limit of another numerical range described stepwise. Moreover, in the numerical ranges described in this specification, the upper limit or lower limit described in a certain numerical range may be replaced with the values shown in the examples.
As used herein, the amount of each component in the composition refers to, when there are multiple substances corresponding to each component in the composition, unless otherwise specified, the constituent units of the multiple substances present in the composition means

[Agricultural film]
The agricultural film of the present disclosure has a vinyl acetate-derived structural unit content of 12% by mass or more and 35% by mass or less, and a melt flow rate (MFR, JIS K7210-1999, 190° C., 2160 g load) of 4 g/ An ethylene-vinyl acetate copolymer (A) of 10 minutes or more and 100 g/10 minutes or less, and a polyolefin (B) containing at least one selected from the group consisting of high-density polyethylene and metallocene-catalyzed polyethylene. , the content ratio [(A):(B)] of the ethylene-vinyl acetate copolymer (A) and the polyolefin (B) is 35:65 to 85:15 in mass ratio.

The agricultural film of the present disclosure has excellent total light transmittance and haze value as an agricultural film by blending the ethylene-vinyl acetate copolymer (A) having an MFR within the above range at a content ratio within the above range. It is thought that a new thing can be obtained.
In addition, for the polyolefin (B), at least one selected from the group consisting of high-density polyethylene and metallocene-catalyzed polyethylene is used, and the content ratio within the above range is used to improve the total light transmittance and haze. It is considered that excellent mechanical properties can be obtained while the values are kept within the allowable range.

Each component contained in the agricultural film of the present disclosure will be described in detail below.
Unless otherwise specified, the melt flow rate (MFR) in the present disclosure is a value [g/10 minutes] measured at 190° C. under a load of 2160 g according to Japanese Industrial Standards JIS K7210-1999.

[Mixture layer]
The agricultural film of the present disclosure has a mixture layer containing an ethylene/vinyl acetate copolymer (A) and a polyolefin (B).
The mixture layer may contain other polymers and additives as needed.

<Ethylene/vinyl acetate copolymer (A)>
The ethylene/vinyl acetate copolymer (A) used in the present disclosure contains at least a structural unit derived from ethylene and a structural unit derived from vinyl acetate, and may be a random copolymer or a block copolymer. or an alternating copolymer.
The ethylene/vinyl acetate copolymer (A) may further contain monomer units other than vinyl acetate and ethylene. In the present disclosure, the ethylene/vinyl acetate copolymer does not contain monomer units other than vinyl acetate and ethylene, and is composed of structural units derived from vinyl acetate and structural units derived from ethylene. preferable.

The ethylene/vinyl acetate copolymer (A) in the present disclosure contains specific amounts of structural units derived from ethylene and structural units derived from vinyl acetate, and optionally other monomers. It may be copolymerized.

In the ethylene/vinyl acetate copolymer (A) in the present disclosure, the content of structural units derived from vinyl acetate is 12% by mass or more and 35% by mass or less. When the content of structural units derived from vinyl acetate is 12% by mass or more and 35% by mass or less, the haze of the resulting film is favorable as an agricultural film.
From the viewpoint of haze value, the content of structural units derived from vinyl acetate is preferably in the range of 16% by mass or more and 30% by mass or less, more preferably 18% by mass or more and 25% by mass or less.

The content of structural units derived from ethylene is preferably 65% by mass or more and 88% by mass or less, more preferably 70% by mass or more and 84% by mass or less.
The content of structural units derived from other monomers may be 10% by mass or less, preferably 0% by mass.

The MFR of the ethylene/vinyl acetate copolymer (A) in the present disclosure is 4 g/10 min or more and 100 g/10 min or less, preferably 8 g/10 min or more and 60 g/10 min or less, and 10 g/10 min. It is more preferably 50 g/10 minutes or more, and even more preferably 12 g/10 minutes or more and 30 g/10 minutes or less.
When the MFR of the ethylene-vinyl acetate copolymer (A) is 4 g/10 min or more and 100 g/10 min or less, the resulting film has a haze value that is preferable as an agricultural film.

The ethylene/vinyl acetate copolymer (A) can be used singly or in combination of two or more different copolymerization ratios.
From the viewpoint of obtaining excellent mechanical strength, the content of the ethylene-vinyl acetate copolymer (A) contained in the mixture layer of the agricultural film of the present disclosure is 35% by mass or more and 85% by mass of the entire mixture layer. % or less is preferable.

<Polyolefin (B)>
Polyolefin (B) includes at least one selected from the group consisting of high-density polyethylene and metallocene-catalyzed polyethylene.
When the polyolefin (B) contains one of the above types, the agricultural film of the present disclosure has excellent mechanical properties.
The polyolefin (B) preferably contains high-density polyethylene from the viewpoint of obtaining excellent mechanical properties, particularly Grave tear strength and elongation at break.

Here, high-density polyethylene refers to polyethylene having a density of 935 kg/m ³ or more according to the old JIS K6748:1995, and is usually produced by a low-pressure method or a medium-pressure method. Low-pressure methods include the Ziegler method, and medium-pressure methods include the Phillips method.
Metallocene-catalyzed polyethylene is produced using a homogeneous catalyst such as a metallocene catalyst, and examples thereof include linear low-density polyethylene (LLDPE) produced using a metallocene catalyst.
The polyethylene may also be an ethylene/α-olefin copolymer obtained by copolymerizing ethylene and α-olefin.

Moreover, the polyolefin (B) may contain other polyolefins than the above.
Other polyolefins include low-density polyethylene such as high-pressure low-density polyethylene, ethylene/unsaturated carboxylic acid copolymers, ethylene/vinyl acetate copolymers, α-olefins other than ethylene copolymerized with ethylene (propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene, etc.) to reduce crystallinity or exhibit substantial crystallinity. Ethylene/α-olefin copolymer elastomer, polypropylene, propylene-based copolymer (copolymer of propylene and α-olefin other than propylene), polybutene, and other olefin-based (co)polymers, and these polymers A blend etc. can be mentioned.

The content of the polyolefin (B) contained in the mixture layer of the agricultural film of the present disclosure is 15% by mass or more and 65% by mass or less with respect to the entire mixture layer from the viewpoint of obtaining excellent mechanical strength. is preferred.
Here, the polyolefin (B) contained in the mixture layer may further contain low-density polyethylene as another polyolefin. Low-density polyethylene refers to polyethylene having a density of less than 930 kg/m ³ according to the old JIS K6748:1995, and is produced by a high-pressure method (bulk polymerization method). Also, low-density polyethylene in the present disclosure does not include linear low-density polyethylene (LLDPE).
At this time, the content of the low-density polyethylene is preferably less than 30% by mass, more preferably less than 20% by mass, with respect to the entire mixture layer, from the viewpoint of obtaining excellent mechanical properties. It is more preferably less than 15% by mass, and particularly preferably 0% by mass.

From the viewpoint of obtaining a satin-like film, the MFR of the polyolefin (B) in the present disclosure is preferably 5 g/10 min or less, more preferably 3 g/10 min or less, and 1.5 g/10 min. Minutes or less is more preferable. The lower limit is preferably 0.04 g/10 minutes or more.
The ratio of MFR ^A of the ethylene-vinyl acetate copolymer (A) to MFR ^B of the polyolefin (B) (MFR ^A /MFR ^B ) is preferably 10 or more and 100 or less, more preferably 10 or more and 80 or less, 10 or more and 60 or less are more preferable.

In the mixture layer of the agricultural film of the present disclosure, the content ratio [(A):(B)] of the ethylene/vinyl acetate copolymer (A) and the polyolefin (B) is 35:65 to 85:15 in mass ratio. is.
When the mass ratio of the ethylene/vinyl acetate copolymer (A) is within the above range, the obtained film has a preferable haze value and Grave tear strength.
Therefore, when the mass ratio of the ethylene/vinyl acetate copolymer (A) and the polyolefin (B) is within the above range, the agricultural film has excellent mechanical strength while maintaining the haze value within the allowable range. can be obtained.
The content ratio [(A):(B)] of the ethylene-vinyl acetate copolymer (A) and the polyolefin (B) is within the above range, while maintaining the haze value within the allowable range, and the mechanical strength is excellent. from the viewpoint of obtaining a film of , it is preferably 40:60 to 80:20, more preferably 45:55 to 75:25, and even more preferably 45:55 to 70:30.

<Other polymers>
The mixture layer may contain other polymers. Examples of other polymers include ethylene/(meth)acrylic acid copolymers and ionomers. The content of other polymers is preferably 30% by mass or less with respect to the entire agricultural film.

<Other additives>
The mixture layer may contain other additives.
Other additives include conventionally known chemical cross-linking agents, cross-linking auxiliaries, softening agents, fillers, antioxidants, heat stabilizers, weather stabilizers, acetic acid supplements, heat retaining agents, ultraviolet absorbers, and anti-fogging agents. , an anti-fogging agent, etc. are appropriately added. As the heat insulating material, a known material having a refractive index close to that of the mixture layer can be used. It is most preferable to use hydrotalcite as the heat-retaining agent because it has particularly good heat-retaining properties and does not adversely affect light transmittance.
The content of other additives is preferably 30% by mass or less with respect to the entire agricultural film.

<Mixture layer>
The mixture layer of the agricultural film of the present disclosure has an average content of structural units derived from vinyl acetate of 9% by mass or more and less than 30% by mass when the resin component in the mixture layer is 100% by mass. It is preferably 9% by mass or more and 25% by mass or less, and most preferably 10% by mass or more and 23% by mass or less.
When the average content of structural units derived from vinyl acetate in the resin component of the mixture layer is within the above range, stickiness can be suppressed and satin finish can be maintained.

The "average content of structural units derived from vinyl acetate" can be determined according to JIS-K7192:1999. In this method, the polymer is decomposed by heating it to 500°C or higher in an electric furnace, and the acetic acid derived from the resulting vinyl acetate is determined by neutralization titration. Even mixtures with various types of polyethylene can be determined as the average content of structural units derived from vinyl acetate.

From the viewpoint of film processability, the MFR of the mixture layer is preferably 2 g/10 minutes or more and 7 g/10 minutes or less, more preferably 2 g/10 minutes or more and 5 g/10 minutes or less. When the MFR of the mixture layer is within the above range, the film processability is excellent.
The total content of the ethylene/vinyl acetate copolymer (A) and the polyolefin (B) in the mixture layer is preferably 70% by mass or more, more preferably 80% by mass or more, and most preferably 90% by mass or more.

The thickness of the mixture layer is preferably 3 μm or more and 500 μm or less, more preferably 10 μm or more and 200 μm or less.

[Layers other than the mixture layer]
The agricultural film of the present disclosure may have layers other than the above-described mixture layer from the viewpoint of obtaining necessary properties such as mechanical strength, durability, and heat retention suitable for agricultural films.
Specific examples of layers other than the mixture layer include an olefin resin layer and a barrier resin layer using a barrier resin such as EVOH (ethylene-vinyl alcohol copolymer resin).

The mixture layer in the present disclosure is preferably the outermost layer from the viewpoint of suppressing excessive direct light to plants.

[Method for producing agricultural film]
Examples of the method for producing an agricultural film in the present disclosure include a method of forming a film by a known method after preparing a mixture containing the components described above.
A method for producing an agricultural film having a mixture layer alone will be described below. However, the method for producing an agricultural film in the present disclosure is not limited to the method below.

For example, the above mixture is prepared by dry blending or melt blending the above components. In the case of dry blending, each component is mixed at the stage of melt plasticization in a molding machine. In the case of melt blending, melt mixing may be performed using various extruders such as a single-screw or twin-screw extruder, various mixers such as a Banbury mixer, rolls, kneaders, and other blenders and mixers. There are no particular restrictions on the mixing order for melt blending.
After that, it is molded into a film by a known method such as an inflation method or a casting method.

EXAMPLES Hereinafter, the present embodiment will be described more specifically in detail with reference to Examples and Comparative Examples, but the present embodiment is not limited thereto. Also, "parts" and "%" are based on mass unless otherwise specified.

The details of the components used to produce the agricultural film are as follows.
<1. Ethylene-Vinyl Acetate Copolymer (EVA)>
(EVA-1):
Content of vinyl acetate structural unit (VA content): 28% by mass
MFR (JIS K7210-1999, 190°C, load 2160g) 15g/10min (EVA-2):
Content of vinyl acetate structural unit (VA content): 19% by mass
MFR (JIS K7210-1999, 190°C, load 2160g) 15g/10min (EVA-3):
Content of vinyl acetate structural unit (VA content): 19% by mass
MFR (JIS K7210-1999, 190°C, load 2160g) 2.5g/10min (EVA-4):
Content of vinyl acetate structural unit (VA content): 41% by mass
MFR (JIS K7210-1999, 190°C, load 2160g) 65g/10min (EVA-5):
Content of vinyl acetate structural unit (VA content): 10% by mass
MFR (JIS K7210-1999, 190°C, load 2160g) 9g/10min

<2. Polyolefin (PO)>
(PO-1):
Type: Low density polyethylene (LDPE)
Density: (JIS K7112-1999) ^920kg /m3
MFR: (JIS K7210-1999, 190°C, load 2160g) 0.15g/10min (PO-2):
Type: High density polyethylene (HDPE)
Density: (JIS K7112-1999) ^950kg /m3
MFR: (JIS K7210-1999, 190°C, load 2160g) 1.1g/10min (PO-3):
Type: High density polyethylene (HDPE)
Density: (JIS K7112-1999) ^940kg /m3
MFR: (JIS K7210-1999, 190°C, load 2160g) 0.45g/10min (PO-4):
Type: Linear low density polyethylene (mPE: metallocene catalyst polymerized polyethylene Density: (JIS K7112-1999) 923 kg/m ³
MFR (JIS K7210-1999, 190°C, load 2160g) 1.3g/10 minutes

[Example 1]
(Production of agricultural film)
The following ingredients were prepared.
<ingredient>
・EVA-1: 80 parts by mass ・PO-3: 20 parts by mass

-Preparation of mixture-
When the above components were melt-blended using a single-screw extruder (extruder screw diameter: 65 mm) under conditions of a die temperature of 180°C and a melting zone temperature of 180°C, stable granulation could be achieved.
Then, the content of vinyl acetate structural units (average content of structural units derived from vinyl acetate (unit: mass %); indicated as VA content in Table 1) and MFR of the mixture after melt blending were already determined. It was measured by the method described above. The results are shown in Table 1.
The notation "-" in Table 1 indicates that the corresponding component is not included.

-Molding-
The above melt-blended mixture is processed using a single layer inflation molding machine (caliber 150 mm, extruder screw diameter 50 mm), die temperature 180 ° C., melting zone temperature 180 ° C., LS (line speed) 5.0 m / min, BUR (blow A mixture layer was formed by molding into a tube under the conditions of up ratio) of 2.1 to obtain an agricultural film with a folded diameter of 520 mm and a thickness of 50 μm.

[evaluation]
The obtained agricultural film was evaluated for the following items. Results are shown in Table 2.

-Total light transmittance-
The total light transmittance of the obtained agricultural film was measured using a haze meter (manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS-K7136 (2000), and an index for evaluating the light transmittance of the agricultural film. and If the total light transmittance is 85% or more and less than 95%, there is no practical problem.

-Haze-
The haze of the obtained agricultural film was measured with a haze meter (manufactured by Suga Test Instruments Co., Ltd.) according to JIS-K7136 (2000), and used as an index for evaluating the degree of satin-like texture of the agricultural film. . If the haze is 70% or more and less than 95%, there is no practical problem.

- Stress at break -
The obtained agricultural film was measured according to JIS-K6760:1995, with the machine axis direction as the MD direction and the direction perpendicular to the machine axis direction as the TD direction. It was determined that a stress at break of 18 MPa or more (in the MD direction) was excellent.

-Elongation at break-
The obtained agricultural film was measured according to JIS-K6760:1995, with the machine axis direction as the MD direction and the direction perpendicular to the machine axis direction as the TD direction. An elongation at break of 400% or more was judged to be excellent in elongation at break.

-Grave Tear Strength-
The obtained agricultural film was measured according to JIS-K7128-3:1998, with the machine axis direction as the MD direction and the direction perpendicular to the machine axis direction as the TD direction.
Grave tear strength of 70 N/mm or more (MD direction) was judged to be excellent in Grave tear strength.

[Examples 2 to 8, Comparative Examples 1 to 7]
An agricultural film was produced in the same manner as in Example 1, except that the composition of the agricultural film was changed according to Table 1.
Similar to Example 1, Examples 2 to 8 could be stably granulated when preparing the mixture, but Comparative Example 3 was unstable in granulation.
Then, the obtained agricultural film was evaluated in the same manner as in Example 1. Results are shown in Table 2.

As can be seen from Tables 1 and 2, the agricultural films of this example maintained the values of total light transmittance and haze within the allowable range, and all of the stress at break, elongation at break, and Grave tear strength were was also excellent in terms of That is, the agricultural film of this example maintained the values of total light transmittance and haze within the allowable range, and was excellent in mechanical strength. On the other hand, the agricultural films of Comparative Examples were inferior to those of Examples in at least one of haze value and mechanical strength. For example, Comparative Example 7 had an acceptable haze value, but was inferior to those of Examples in mechanical strength such as stress at break, elongation at break, and Grave tear strength.

The disclosure of Japanese Patent Application No. 2018-051725 filed on March 19, 2018 is incorporated herein by reference in its entirety.
All publications, patent applications and technical standards mentioned herein are to the same extent as if each individual publication, patent application and technical standard were specifically and individually noted to be incorporated by reference. incorporated herein by reference.

Claims (5)

The content of structural units derived from vinyl acetate is 12% by mass or more and 35% by mass or less, and the melt flow rate (MFR, JIS K7210-1999, 190°C, 2160g load) is 4g/10min or more and 100g/10min or less. an ethylene-vinyl acetate copolymer (A) of
a polyolefin (B) comprising high density polyethylene ;
and the content ratio [(A):(B)] of the ethylene/vinyl acetate copolymer (A) and the polyolefin (B) is 35:65 to 85:15 in mass ratio,
having a mixture layer,
An agricultural film having a haze of 70% or more and less than 95% as measured according to JIS-K7136 (2000) . The agricultural film according to claim 1, further comprising low-density polyethylene as the polyolefin (B). 3. The agricultural film according to claim 1, wherein the average content of the structural unit derived from vinyl acetate is 9% by mass or more and less than 30% by mass when the resin component in the mixture layer is 100% by mass. . 4. The agricultural film according to any one of claims 1 to 3, wherein the mixture layer is the outermost layer. Claims 1 to 4, wherein the ratio (MFR ^A /MFR ^B ) of the MFR ^A of the ethylene-vinyl acetate copolymer (A) and the MFR ^B of the polyolefin (B) is 10 or more and 100 or less. The agricultural film according to any one of .