JP2000188966A - Multilayered film for agriculture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film for agriculture, excellent in strength, transparency, heat retaining properties, and persistency of defogging properties, and further excellent in secondary processability such as heat-sealing properties and drawing processability. SOLUTION: This film for agriculture has at least three layers of an outer layer, a middle layer, and an inner layer. The outer layer of the film consists of a mixture of a branched low-density polyethylene produced by a high-pressure and radical method, and >=45% linear low density polyethylene. The middle layer consists of a composition comprising 100 pts.wt. composition obtained by mixing 5-60 wt.% ethylene-α-olefin copolymerized resin obtained by the copolymerization using a metallocene catalyst, and having the following characteristics (a) to (c), with 95-40 wt.% ethylene-vinyl acetate copolymerized resin in which the content of the vinyl acetate is >=10 wt.%, and 1-20 pts.wt. inorganic compound containing at least one atom of Mg, Ca, Al, Si and Li: (a) 0.1-10 g/10 min melt flow rate; (b) 0.88-0.915 g/cm3 density; and (c) 1.5-3.5 molecular weight distribution (Mw/Mn). The inner layer consists of a composition consisting essentially of the ethylene-vinyl acetate copolymerized resin in which the content of the vinyl acetate is 1-10 wt.%, and containing an anti-fogging agent in the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an agricultural film. More specifically, the present invention relates to an agricultural polyolefin resin multilayer film having high strength and excellent secondary workability such as heat sealability and drawability.

[0002]

2. Description of the Related Art In recent years, in order to increase marketability and productivity of agricultural crops by semi-forcing or suppressing cultivation, agricultural vinyl chloride films, polyethylene, ethylene-vinyl acetate copolymers, and polyolefin resins have been used. BACKGROUND ART So-called house cultivation and tunnel cultivation, in which useful plants are cultivated under coating with agricultural covering materials such as films, are mainly performed. Above all, films composed mainly of polyolefin resins have stable chemical structures, so their mechanical properties hardly change even after long-term use, and they generate little toxic gas even when incinerated. Due to its low cost, it is becoming popular.

[0003]

Now, such agricultural crop houses are increasing in size year by year, and the film area for covering the houses is also increasing. Normally, the film is shipped from a molding factory in a roll form, and after being subjected to an inselling operation and a releasing operation for connecting the film at a processing plant, the film is packed and shipped to the user. Generally, the inscribing of the film is performed using a heat sealing machine. If the film has curling properties, it becomes difficult to perform heat sealing and the workability is reduced. Also, if the film is bulky, it will be difficult to pack it.
In order to perform packing with less bulk, drawing of a film is often performed. In this case, the more flexible the film, the easier the drawing process is, and conversely, the harder, so-called stiff film is more difficult to process. Therefore, flexibility is also required for a film mainly composed of the above-mentioned polyolefin resin. Further, on the user side, when a film is spread on a large house, a high-strength film that does not break even when a considerably large force is applied is required.

[0004] As described above, a film having high strength and satisfying the above-mentioned performance excellent in suitability for secondary processing is demanded. However, at present, the development of such a film cannot be said to be sufficiently advanced. For example, Japanese Patent Publication No. 63-65026 proposes a method of laminating a linear polyethylene as a substrate layer, but it has not been satisfactory. Then, in recent years, for example,
Japanese Patent Application Laid-Open No. 276542/1997 and Japanese Patent Application Laid-Open No. 9-52332 propose a method of laminating, as a substrate layer, a new linear polyethylene obtained by copolymerizing ethylene and an α-olefin using a metallocene catalyst. I have. Films produced by these methods have improved transparency and strength, but are not sufficiently flexible.

[0005]

That is, the gist of the present invention is that the outer layer of the laminated film comprises a mixture of a branched low-density polyethylene and a linear low-density polyethylene produced by a high-pressure radical method, A layer comprising a composition in which the proportion of the branched low-density polyethylene in the mixture is 45% by weight or more, wherein the intermediate layer has the following properties (a) to (c) obtained by copolymerization with a metallocene catalyst. Ethylene-
α-olefin copolymer resin 5 to 60% by weight,

[0006]

(A) Melt flow rate 0.1 to 10 g / 10 min (b) Density 0.88 to 0.915 g / cm ³ (c) Molecular weight distribution (weight average molecular weight / number average molecular weight) 1.5 to 3.5

And an ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 10% by weight or more is 95 to 40% by weight.
Is mixed with 100 parts by weight of Mg, Ca, A
1 to 20 parts by weight of an inorganic compound containing at least one atom of l, Si, and Li, wherein the inner layer has a vinyl acetate content of 1 to 10% by weight.
An agricultural multi-layer film mainly comprising a vinyl acetate copolymer resin and having at least three layers, which are layers composed of a composition containing an antifogging agent in the resin.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The agricultural polyolefin resin laminated film of the present invention,
An outer layer, an intermediate layer, and an inner layer.When the film of the present invention is actually stretched and used, the outer surface of a house or a tunnel is the outer layer, the inner surface is the inner layer, and the intermediate layer is the inner layer. It is called an intermediate layer.

[0009]Film outer layer The outer layer of the present invention comprises a branched low-pressure layer produced by a high-pressure method
Mixture of high density polyethylene and linear low density polyethylene
And the proportion of branched low density polyethylene in the mixture
Is 45% by weight or more. In the present invention
High pressure radical used as one component of outer layer
The branched polyethylene produced by the
Force 1000-3500kg / cm ^Two, Reaction temperature 200 ~
Reaction of ethylene monomer with catalyst in the range of 350 ° C
And a density of 0.
91 to 0.93 g / cm^ThreeMeans Melt flow
Rate (MFR: measured based on JIS K6760)
Is preferably in the range of 0.3 to 3 g / 10 min.
No. Extrusion during film formation if MFR is less than 0.3
It is not preferable because processability and high-speed moldability deteriorate. Ma
In addition, if it is 3 or more, the tube in inflation molding
If the end of the film becomes uneven
It is not preferable because molding stability is lacking.

The linear low-density polyethylene used as the other mixed component constituting the outer layer in the present invention is commonly called L-LDPE, and is composed of ethylene and propylene, butene-1, hexene-1, It is a copolymer with an α-olefin such as 4-methylpentene-1 and octene. The copolymer is produced by copolymerizing in a liquid phase or a gas phase in the presence of a Ziegler catalyst, a chromium oxide catalyst, a molybdenum oxide catalyst, a metallocene catalyst and the like. Particularly preferred linear ethylene-α-olefin copolymers are described in JP-A-6-9724 and JP-A-6-136.
In the presence of a so-called metallocene-based olefin polymerization catalyst containing a metallocene catalyst component described in JP-A-195-195, JP-A-6-136196, JP-A-6-207057, etc., ethylene and C 3 -C 12 are present. Α
-It is prepared by copolymerizing an olefin so that the resulting copolymer has a density of 0.880 to 0.940 g / cm3 and a melt flow rate (MFR) of 0.3 to ³ g / 10 minutes. .

The composition used for the outer layer according to the present invention comprises 45 to 100% by weight, preferably 50 to 90% by weight, of the branched low-density polyethylene produced by the high-pressure radical method described above.
And a linear low-density polyethylene in the range of 55 to 0% by weight, preferably 50 to 10% by weight. If the content of the branched polyethylene is less than 45% by weight, the curl properties of the film are large and the heat sealing workability in the secondary processing is poor, which is not preferable.

The thickness of the outer layer of the laminated film of the present invention is preferably 5 to 50 μm. When the outer layer is less than 5 μm, the strength is substantially insufficient, so that it is not suitable as a film. It is preferable that a weathering stabilizer and an antioxidant are added to the resin constituting the outer layer from the viewpoint of maintaining weather resistance and heat resistance. The weather stabilizer is roughly classified into a light stabilizer and an ultraviolet absorber. As the light stabilizer, for example, a hindered amine light stabilizer is preferably used. As the ultraviolet absorber, a benzophenone-based ultraviolet absorber, a benzotriazole-based ultraviolet absorber, and a salicylic acid-based ultraviolet absorber are preferably used.

Film Intermediate Layer The composition used in the intermediate layer of the present invention comprises an ethylene-α-olefin copolymer resin having the following characteristics (a) to (c) obtained by copolymerization with the above-mentioned metallocene catalyst. 5-6
0% by weight and

[0014]

(A) Melt flow rate 0.1 to 10 g / 10 min (b) Density 0.88 to 0.915 g / cm ³ (c) Molecular weight distribution (weight average molecular weight / number average molecular weight) 1.5 to 3.5

Mg, Ca, A are added to 100 parts by weight of a resin composition containing 95 to 40% by weight of an ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 10% by weight or more.
and 1 to 20 parts by weight of an inorganic compound containing at least one atom of 1, Si, and Li. Particularly preferred mixing ratios of the ethylene-α-olefin copolymer resin and the ethylene-vinyl acetate copolymer resin are 10 to 50, respectively.
% By weight, 90 to 50% by weight. The ethylene-α-olefin copolymer obtained by copolymerization with the metallocene catalyst used as one component constituting the intermediate layer in the present invention has the following physical properties.

Melt flow rate (MFR) MFR measured according to JIS-K7210 is 0.01
It shows a value of from 10 to 10 g / 10 min, preferably from 0.1 to 5 g / 10 min. If the MFR is larger than this range, the film will meander during molding and will not be stable. In addition, the MFR
If the pressure is less than this range, the resin pressure at the time of molding increases and a load is applied to the molding machine. Therefore, it is necessary to reduce the production amount and suppress the increase in pressure, which is not practical.

[0017]density The density measured by JIS-K7112 is 0.880
~ 0.915 g / cm ^ThreeIt shows the value of. The density
Is greater than this range, the film becomes harder and
Is reduced. If the density is smaller than this range,
The fat pellet itself becomes more sticky and blocksin
And the practicability is poor.

Molecular weight distribution gel permeation chromatography (GPC)
Molecular weight distribution (weight average molecular weight / number average molecular weight) determined by (1) is 1.5 to 3.5, preferably 1.5 to 3.
It indicates a value of 0. If the molecular weight distribution is larger than this range, the mechanical strength decreases, which is not preferable. If the molecular weight distribution is smaller than this range, the film will meander during molding and will not be stable. The vinyl acetate content in the ethylene-vinyl acetate copolymer resin used as one component constituting the intermediate layer in the present invention is 10% by weight or more, preferably 12% by weight.
Not less than 30% by weight. When an ethylene-vinyl acetate copolymer resin having a vinyl acetate content in this range is used as the intermediate layer, an agricultural film excellent in flexibility and heat retention can be obtained. In the intermediate layer of the present invention, Mg,
An inorganic compound containing at least one atom of Ca, Al, Si and Li is blended. For example, inorganic oxides, inorganic hydroxides, hydrotalcites and the like containing at least one atom of Mg, Ca, Al, Si and Li effective as a heat insulator. Specifically, SiO ₂ ,
Inorganic oxides such as Al ₂ O ₃ , MgO, CaO; Al
Inorganic hydroxides such as (OH) ₃ , Mg (OH) ₂ , Ca (OH) ₂ ;

[0019]

## EQU4 ## M 2 ⁺ _{1 -x} Al _x (OH) ₂ (A ^n- ) _{x / n} ^* mH ₂ O

[Wherein, M²⁺Is Mg, Ca or Zn
A divalent metal ion, An^-Is Cl ^-, Br^-,
I^-, NO_Three ^2-, ClO^Four-, SO_Four ^2-, CO_Two ^Two-, Si
O_Three ^2-, HPO_Four ^2-, HBO_Three ^2-, PO_Four ^2-Etc. Anio
Where x is a numerical value satisfying the condition 0 <x <0.5
And m is a numerical value satisfying the condition of 0 ≦ m ≦ 2.
Of inorganic composite compounds represented by the formula
Rotalsites and the like. Among these, c
Idrotalcites are preferred, especially represented by the above formula
A fired product of an inorganic composite compound is preferred. Inorganic as above
Compounds may be used alone or in combination of two or more.
Can be.

The average particle size of the inorganic compound is preferably 10 μm or less, particularly preferably 5 μm or less. When the average particle size of the inorganic compound is within the above range, a laminated film having good transparency can be obtained. The content of the inorganic compound is preferably 1 to 20 parts by weight per 100 parts by weight of the resin. 1
If the amount is less than 10 parts by weight, the heat retention is insufficient.
If the amount is more than parts by weight, transparency is undesirably reduced. The composition used for the intermediate layer of the present invention is an ethylene-α-olefin copolymer resin obtained by copolymerization with a metallocene catalyst, an ethylene-vinyl acetate copolymer resin, an inorganic compound, and if necessary, an antifogging agent, A weather stabilizer, an antioxidant and the like may be contained.

As the antifogging agent to be added to the intermediate layer of the present invention, general antifogging agents which are usually blended in agricultural films can be used. Specifically, for example, lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene nonyl phenyl ether, polyethylene glycol monopalmitate, polyethylene glycol monostearate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate , Glycerin monolaurate, glycerin monopalmitate, glycerin monostearate, glycerin monooleate, pentaerythritol monolaurate, sorbitan monopalmitate, sorbitan monobehenate,
Sorbitan distearate, diglycerin monooleate, triglycerindiolate, sodium lauryl sulfate, sodium dodecylbenzenesulfonate,
Sodium butylnaphthalenesulfonate, acetyltrimethylammonium chloride, alkyldimethylbenzylammonium chloride, dodecylamine hydrochloride,
Lauryl lauramide ethyl phosphate, triethylacetylammonium iodide, oleylaminodiethylamine hydrochloride, basic pyridinium salt of dodecylpyridinium sulfate and the like. Among them, preferred are non-ionic fatty acids having 14 to 22 carbon atoms and esters of polyhydric alcohols such as sorbitan, sorbitol, glycerin, polyglycerin and propylene glycol or alkylene oxide adducts thereof. Surfactants and the like. These surfactants can be used alone or in combination of two or more.
The content is 0.1 to 5 per 100 parts by weight of the resin.
Part by weight, especially 0.3 to 3 parts by weight is preferred. If the amount is less than 0.1 part by weight, sufficient anti-fogging property cannot be obtained, and if it exceeds 5 parts by weight, a large amount of blowout to the film surface is caused and transparency is impaired, which is not preferable.

Inner Layer of Film The inner layer of the present invention is composed of a composition mainly composed of an ethylene-vinyl acetate copolymer resin having a vinyl acetate content in the range of 1 to 10% by weight and containing an antifogging agent. The preferred range of the vinyl acetate content in the ethylene-vinyl acetate copolymer resin is 2 to 8% by weight. When an ethylene-vinyl acetate copolymer resin having a vinyl acetate content in this range is used as the inner layer, an agricultural film having excellent flexibility can be obtained. Not only one kind of resin constituting the inner layer,
If the final average vinyl acetate content is in the range of 1 to 10% by weight, it is possible to mix two or more ethylene-vinyl acetate copolymer resins or to mix and use other types of resins. is there. As the antifogging agent to be added to the inner layer, the same antifogging agent added to the intermediate layer can be used. These antifogging agents can be used alone or in combination of two or more. The content of the antifogging agent is preferably 0.1 to 5 parts by weight per 100 parts by weight of the resin. More preferably, it is 0.3 to 3 parts by weight. Content is 0.1
If the amount is less than parts by weight, sufficient antifogging property cannot be obtained. On the other hand, if the content is 5 parts by weight or more, a large amount of gas is ejected to the film surface, and transparency is impaired.

Each layer of the agricultural polyolefin resin laminated film of the present invention may contain wax, antioxidant, antistatic agent, light stabilizer, ultraviolet absorber, lubricant, antiblocking agent, antifogging agent, if necessary. A heat insulator and the like can be added. Further, the outer layer surface of the agricultural polyolefin resin laminated film of the present invention can take a form of transparent, semi-matte, or matt depending on the purpose of use.

The agricultural polyolefin resin laminated film of the present invention is prepared by weighing the required amount of the polyolefin resin used in each layer and each additive, and using a ribbon blender, a Banbury mixer, a super mixer, other compounding machines and mixers. Mix. Then, the obtained composition can be prepared by laminating the outer layer, the intermediate layer and the inner layer by a method known per se, for example, a method such as a coextrusion inflation method or a coextrusion T-die method. The thickness of all the layers is preferably in the range of 0.05 to 0.2 mm in consideration of strength, performance, production cost and the like. The thickness of the outer layer is preferably 5 to 50 μm.
If it is less than μm, the strength is substantially insufficient, so that it is not suitable as a film. The thickness of each layer can be arbitrarily selected as long as the intermediate layer is thicker than the outer layer, preferably 2 to 4 times the outer layer, and the inner layer is in the same range as the outer layer.

[0026]

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.
It is not limited to the following example. (Examples 1-4, Comparative Examples 1-4)

(1) Preparation of Multilayer Film As a three-layer blown film forming apparatus, a die having a diameter of 100 mmφ is used as a three-layer die, and two extruders each using a screw having a diameter of 30 mmφ for the inner and outer layers, and a middle layer having a diameter of 30 mmφ. Assuming that a screw having a diameter of 40 mm was used, the temperature of the outer layer extruder was 180 ° C.
At 0 ° C., a die temperature of 180 ° C., a blow ratio of 2.0, a take-up speed of 5 m / min, and a thickness of 0.10 mm, a three-layer laminated film composed of the components shown in Tables 1 and 2 was obtained. The following evaluation tests were performed on each of the obtained films.

(1) Tensile Elongation at Tensile Break The tensile elongation at break in the machine and transverse directions of each film was measured by a tensile test (based on JIS K6783).

(2) Transparency The parallel light transmittance of each film at a wavelength of 555 mm was measured by a spectrophotometer, and the value was shown.

(3) Heat insulation In a field in Isshi-gun, Mie Prefecture, the height is 1 m, the width is 2 m, and the depth is 2
m on each pipe house, and 15
The temperature difference between the inside and outside of the house having a height of cm was measured every hour from 7:00 in the morning to 6:00 in the next morning, and the average value was calculated. Measurement is H9
It was implemented from December 20 to December 21. The larger the temperature difference, the better the heat retention.

(4) Antifogging Persistence The antifogging durability was evaluated using a pipe house on which each film in the same field was spread. In the evaluation method, the state of water droplets adhering to the inside surface of the house was visually observed over time. The evaluation criteria are as follows (test started on December 1, H9). ◎… Film surface (facing inside the house, the same applies hereinafter)
Water droplets adhering to each other are united and spread in the form of a thin film, and the area of the thin film portion extends over 2/3 or more of the film surface. …: Coalescence of water droplets adhering to the film surface is observed, but the area of the thin film portion is less than 2/3 or 1/2 or more of the film surface. Δ: Coalescence of water droplets adhering to the film surface is recognized, but the shape of the thin film portion is not recognized. ×: No coalescence of water droplets adhering to the film surface is observed.

(5) Film curl property The curl property of each film during heat sealing was evaluated according to the following criteria. …: Good heat sealing workability without curling. X: The film was curled toward the inner surface side, resulting in poor heat sealing workability. (6) Drawing Workability Using a drawing machine, the drawing workability of each film was evaluated based on the following criteria. ○: Less bulkiness before and after drawing, good workability and good packing. ×: The workability and packing property were large before and after drawing.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

[Table 4]

From the results of the above Examples and Comparative Examples, Comparative Example 1 in which the amount of branched low-density polyethylene in the mixture of the outer layer was small, and that of the ethylene-α-olefin copolymer resin in the mixture of the intermediate layer were large. In Comparative Example 2, which was too much, or in Comparative Example 3, in which the intermediate layer was composed of only the ethylene-vinyl acetate copolymer resin and the inner layer was not composed mainly of the ethylene-vinyl acetate copolymer resin, In the case of Comparative Example 4, which is a mixture of linear low-density polyethylene, it is required as an agricultural film. Properties, namely strength,
Transparency, heat retention, antifogging persistence, heat sealing properties, while showing poor results in any of the drawability, in the examples according to the present invention, these properties are generally excellent, It can be seen that a practical agricultural film can be obtained.

[0038]

The agricultural polyolefin film of the present invention is excellent in all basic performances such as strength, transparency, heat retention and anti-fogging durability, and has two properties such as heat sealability and drawability. It has excellent secondary processability, and its utility as an agricultural film is extremely high.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) C08L 23/00 C08L 23/00 F term (reference) 2B024 DB01 2B029 EB02 EC02 EC03 EC20 4F071 AA15 AA18 AA19 AA28 AA81 AA82 AA88 AB17 AB18 AB26 AC06 AC10 AC13 AH01 BB06 BB09 BC01 4F100 AA17B AA18B AA19B AA21B AK06A AK62B AK62C AK63A AK68B AL05A AL05B BA03 BA07 BA10A BA10C CA10C GB01 JA06B JA07B JA13B JJ02 JK01 DE02 J02JK01 DE02 J02JK01 DE02 J0201

Claims (2)

[Claims] 1. The film outer layer comprises a mixture of a branched low-density polyethylene and a linear low-density polyethylene produced by a high-pressure radical method, wherein the proportion of the branched low-density polyethylene in the mixture is 45% by weight or more. 5 to 60% by weight of an ethylene-α-olefin copolymer resin having the following characteristics (a) to (c) obtained by copolymerizing with a metallocene catalyst, (1) Melt flow rate: 0.1 to 10 g / 10 min (b) Density: 0.88 to 0.915 g / cm ³ (c) Molecular weight distribution (weight average molecular weight / number average molecular weight) 1.5 to 3. 5 and ethylene having a vinyl acetate content of 10% by weight or more.
Mg, Ca, Al, Si, L are added to 100 parts by weight of a composition obtained by mixing 95 to 40% by weight of a vinyl acetate copolymer resin.
a layer comprising a composition comprising 1 to 20 parts by weight of an inorganic compound containing at least one atom of i, wherein the inner layer of the film mainly comprises an ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 1 to 10% by weight. A multilayer film for agricultural use, comprising at least three layers, which are layers made of a composition containing an antifogging agent in a resin. 2. The method according to claim 1, wherein the linear low-density polyethylene in the outer layer comprises ethylene and α-C 3-12 in the presence of a metallocene catalyst.
The polyolefin resin film for agricultural use according to claim 1, which is a linear low-density polyethylene obtained by copolymerizing an olefin.