JPH08283427A - Agricultural covering film - Google Patents

Abstract

PURPOSE: To obtain an agricultural covering film 5-30μm thick excellent in adhesiveness to soil i.e., flexibility and in such properties as weatherability, tensile properties, tear properties, impact resistance and stiffness. CONSTITUTION: This agricultural covering film 5-30μm thick is made from such a straight-chain ethylene-α-olefin copolymer as to be capable of giving a film 10μm thick having a dirt impact strength of >=110g and Young's modulus in both MD and TD directions of 2.5×10<3> kg/cm<2> . The copolymer is obtained from ethylene and a 3-12C α-olefin. This agricultural covering film is excellent in balance between impact resistance and stiffness and also in flexibility and heat resistance, as compared with conventional films.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD OF THE INVENTION The present invention relates to agricultural coating films commonly referred to as mulch films.

[0002]

TECHNICAL BACKGROUND OF THE INVENTION In mulch cultivation, mulch films are used for the purpose of increasing soil temperature, retaining soil moisture, preventing soil consolidation, preventing nutrient runoff, and weed overgrowth.

As such a mulch film, a film made of high-pressure low-density polyethylene, a film made of a blend of high-pressure low-density polyethylene and ethylene / α-olefin random copolymer rubber (JP-A-56)
-116735), and further a film comprising an ethylene / α-olefin random copolymer (linear polyethylene) (JP-A-63-6038, JP-A-57).
-28114, JP-A-63-63731, etc.) are known.

However, the above-mentioned mulch film made of the high-pressure low-density polyethylene has a low physical strength and needs to have a thickness of 20 μm or more. For example, when an blown film is formed with a blow ratio of 2 or more and the thickness of the film is smaller than 20 μm, the tear strength is low and the film tends to tear during laying or removal of the film. On the other hand, when the thickness of the film is 20 μm or more, the Young's modulus of the film is high and the film feels stiff and hard and not supple, so that it is difficult to adhere to the soil surface such as ridges. This makes it easier to form an air layer in.
As a result, weeds are prone to overgrowth, and film flapping due to wind and rain causes damage to the growth.

Moreover, the mulch film made of high-pressure low-density polyethylene does not have sufficient heat resistance, and when used as a so-called perforated mulch, the holes are enlarged and the ability as a covering material is lost. There is a problem of going.

Further, in the mulch film composed of the blend of the above-mentioned high-pressure low-density polyethylene and ethylene / α-olefin copolymer rubber, long-run moldability and weather resistance are low, and strength, transparency, gloss, etc. The appearance is also unsatisfactory.

Ethylene / α-olefin random copolymers (linear polyethylene) described in JP-A-63-6038, JP-A-57-28114, and JP-A-63-63731. Has a considerably improved strength, but when the film becomes a thin film having a thickness of about 13 μm or less, problems such as stretching and tearing of the film occur when it is accidentally stepped on during the multi-film coating operation.
In particular, the denser the ethylene / α-olefin random copolymer, the more easily the film tends to be stretched and broken.

Therefore, compared with the conventional film, 1
A straight-chain polyethylene (straight chain ethylene / α-olefin copolymer capable of forming a thin film excellent in flexibility and heat resistance as well as having a good balance of impact resistance and rigidity even in a thin film of about 3 μm or less ) Is desired to appear.

[0009]

SUMMARY OF THE INVENTION The present invention is intended to solve the problems associated with the prior art as described above, and has impact resistance and rigidity even in a thin film having a thickness of about 13 μm or less as compared with the conventional film. It is an object of the present invention to provide an agricultural coating film made of a linear ethylene / α-olefin copolymer capable of forming a thin film having excellent balance and excellent flexibility and heat resistance.

[0010]

SUMMARY OF THE INVENTION The agricultural coating film according to the present invention has a dart impact strength of 110 g or more and a tensile Young's modulus of 2.5 in both MD and TD when a film having a thickness of 10 μm is formed. × 10 ³ kg
/ Cm ² or more, which can form a film having a thickness of linear ethylene / α-olefin copolymer of 5
-30 μm film, and the linear ethylene / α-
The olefin copolymer is ethylene and has 3 to 12 carbon atoms.
It is characterized in that it is composed of α-olefin.

The linear ethylene / α-olefin copolymer has a density (d) of 0.900 to 0.945 g / cm 3.
³ , the melt flow rate (MFR) is 0.1 to 2
It is preferably 0 g / 10 minutes and the molecular weight distribution (Mw / Mn) determined by the GPC method is 1.5 to 3.5.

Examples of the linear ethylene / α-olefin copolymer include ethylene / 1-butene copolymer, ethylene / 1-hexene copolymer, ethylene-4-methyl-1-pentene copolymer, or Ethylene / 1-octene copolymers are preferred.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The agricultural coating film according to the present invention will be specifically described below. Linear Ethylene / α-Olefin Copolymer The linear ethylene / α-olefin copolymer used in the present invention comprises ethylene and an α-olefin having 3 to 12 carbon atoms.

Specific examples of the α-olefin having 3 to 12 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene,
Examples include 1-decene and 1-dodecene.

In the present invention, ethylene / 1-butene copolymer, ethylene / 1-hexene copolymer, ethylene / 4-
Methylpentene-1 copolymer and ethylene / 1-octene copolymer are preferably used.

Linear ethylene / α-used in the present invention
The olefin copolymer usually has an ethylene content of 95 to 99.
The content of α-olefin as a comonomer is usually 1 to 5 mol%, preferably 2 to 4 mol%.

The composition of the linear ethylene / α-olefin copolymer is usually about 200 mg of the linear ethylene / α-olefin copolymer uniformly dissolved in 1 ml of hexachlorobutadiene in a 10 mmφ sample tube. ¹³ C- of sample
NMR spectrum, measurement temperature 120 ℃, measurement frequency 2
It is determined by measurement under the measurement conditions of 5.05 MHz, spectrum width 1500 Hz, pulse repetition time 4.2 sec., And pulse width 6 μsec.

Linear ethylene / α-used in the present invention
The olefin copolymer preferably has a density of 0.900 to
0.945 g / cm ³ , more preferably 0.910
0.940 g / cm ³ , particularly preferably 0.920 to
It is in the range of 0.940 g / cm ³ . The above density is JI
It is a value measured at a temperature of 23 ± 0.1 ° C. according to the D method of SK 7112.

Further, the melt flow rate (MFR; ASTM of this linear ethylene / α-olefin copolymer is
D 1238, 190 ° C., load 2.16 kg) is preferably 0.1 to 20 g / 10 minutes, more preferably 0.
2 to 10 g / 10 minutes, particularly preferably 0.5 to 5 g / 1
It is in the range of 0 minutes.

Linear ethylene / α-used in the present invention
The olefin copolymer preferably has a molecular weight distribution (Mw / Mn: Mw = weight average molecular weight, Mn = number average molecular weight) measured by GPC of 1.5 to 3.5, more preferably 1.7 to 3.0. Is in the range.

The molecular weight distribution (Mw / Mn) was measured as follows using GPC-150C manufactured by Millipore. The separation column is TSK GNH HT,
The column size is 72 mm in diameter and 600 mm in length,
The column temperature was 140 ° C, O-dichlorobenzene (Wako Pure Chemical Industries) as a mobile phase, and BHT as an antioxidant.
(Takeda Pharmaceutical Co., Ltd.) 0.025% by weight was used, the sample was moved at 1.0 ml / min, the sample concentration was 0.1% by weight, the sample injection amount was 500 microliters, and a differential refractometer was used as a detector. Standard polystyrene has a molecular weight of Mw <10
00 and Mw> 4 × 10 ⁶ were manufactured by Tosoh Corporation, and 1000 <Mw <4 × 10 ⁶ were manufactured by Pressure Chemicals.

In the present invention, among the linear ethylene / α-olefin copolymers having the above characteristics,
Dirt impact strength is 110g or more, preferably 12
0 g or more, and both the MD and TD tensile Young's modulus are 2.5 × 10 ³ kg / cm ² or more,
A linear ethylene / α-olefin copolymer capable of forming a film having a thickness of 2.8 × 10 ³ kg / cm ² or more and a thickness of 10 μm is preferably used.

The dirt impact strength is JIS Z
1707 is a value measured according to the Dart Impact Impact Test, and Young's modulus is a value measured according to the JIS Z 1702 Tensile Strength Test.

In the present invention, the above-mentioned linear ethylene
The α-olefin copolymer can be used alone or in combination of two or more kinds. The linear ethylene / α-olefin copolymer as described above can maintain sufficient strength even when formed into a thin film, and moreover, the linear ethylene / α-olefin copolymer It is possible to form a film with a small decrease in strength even if the density is relatively high.

[Preparation of Linear Ethylene / α-Olefin Copolymer] The linear ethylene / α-olefin copolymer used in the present invention is described in, for example, JP-A-6-9724 and JP-A-6-136195. Japanese Patent Laid-Open No. 6-136
Ethylene and an α-olefin having 3 to 12 carbon atoms in the presence of a so-called metallocene-based olefin polymerization catalyst containing the metallocene catalyst component (a) described in JP-A No. 196, JP-A-6-207057 and the like. And the density of the obtained copolymer is 0.900 to 0.945 g / cm ³
It can be prepared by copolymerizing so that

Such a metallocene catalyst usually contains at least one ligand having a cyclopentadienyl skeleton.
A metallocene catalyst component (a) consisting of a transition metal compound of Group IVB of the Periodic Table, an organoaluminum oxy compound catalyst component (b), and optionally a fine particle carrier (c), an organoaluminum compound catalyst component (d) ), An ionized ionic compound catalyst component (e).

The metallocene catalyst component (a) preferably used in the present invention is a transition metal compound of Group IVB of the periodic table having at least one ligand having a cyclopentadienyl skeleton. Examples of such transition metal compounds include transition metal compounds represented by the following general formula [I].

ML ¹ _x ... [I] In the formula, x is the valence of the transition metal atom M. M is a transition metal atom selected from Group IVB of the periodic table, specifically zirconium, titanium or hafnium. Of these, zirconium is preferable.

L ¹ is a ligand that coordinates to the transition metal atom M, and at least one of these ligands L ¹
Is a ligand having a cyclopentadienyl skeleton.
Specific examples of the ligand L ¹ having a cyclopentadienyl skeleton coordinated to the transition metal atom M as described above include:
Cyclopentadienyl group, methylcyclopentadienyl group, dimethylcyclopentadienyl group, trimethylcyclopentadienyl group, tetramethylcyclopentadienyl group, pentamethylcyclopentadienyl group, methylethylcyclopentadienyl group , An alkyl-substituted cyclopentadienyl group such as a hexylcyclopentadienyl group, an indenyl group, a 4,5,6,7-tetrahydroindenyl group, and a fluorenyl group. These groups are
It may be substituted with a halogen atom, a trialkylsilyl group or the like.

When the compound represented by the general formula [I] contains two or more groups having a cyclopentadienyl skeleton, the groups having two cyclopentadienyl skeletons among them are ethylene, propylene, etc. An alkylene group of
They may be bonded via a substituted alkylene group such as isopropylidene diphenylmethylene, a silylene group or a dimethylsilylene group, a substituted silylene group such as a diphenylsilylene group, a methylphenylsilylene group and the like.

The ligand L ¹ other than the ligand having a cyclopentadienyl skeleton is a hydrocarbon group having 1 to 12 carbon atoms; an alkoxy group such as a methoxy group; an aryloxy group such as a phenoxy group; a trimethylsilyl group, A trialkylsilyl group such as a triphenylsilyl group; SO ₃ R (R is a hydrocarbon group having 1 to 8 carbon atoms which may have a substituent such as halogen), a halogen atom or a hydrogen atom.

Examples of the hydrocarbon group having 1 to 12 carbon atoms include an alkyl group such as a methyl group, a cycloalkyl group such as a cyclopentyl group, an aryl group such as a phenyl group, and an aralkyl group such as a benzyl group.

Specific examples of the ligand represented by SO ₃ R include a P-toluenesulfonato group, a methanesulfonato group, and a trifluoromethanesulfonato group. Aluminoxane is preferably used as the organoaluminum oxy compound catalyst component (b). Specifically, the repeating unit represented by the formula: -Al (R) O- [wherein R is an alkyl group] is usually about 3 to 50 methylaluminoxane, ethylaluminoxane, methylethylaluminoxane. Etc. are used.

Such an aluminoxane can be prepared by a conventionally known method. The fine particle carrier (c), which is optionally used in the preparation of the olefin polymerization catalyst, is an inorganic or organic compound and has a particle size of usually about 10 to 300 μm, preferably 20 to 2
It is a solid in the form of granules or fine particles of 00 μm.

The inorganic carrier is preferably a porous oxide, and specifically, SiO ₂ , Al ₂ O ₃ , MgO, Zr.
O ₂ , TiO ₂ , B ₂ O ₃ , CaO, ZnO, BaO, S
Examples thereof include nO _{2 and the} like, or a mixture thereof. The inorganic oxide contains a small amount of a carbonate such as Na ₂ CO _3, a sulfate such as Al ₂ (SO ₄ ) ₃ , a nitrate such as KNO ₃ , and an oxide such as Li ₂ O. It doesn't matter.

The properties of such a carrier differ depending on the type and production method, but the carrier preferably used in the present invention has a specific surface area of 50 to 1000 m ² / g, preferably 1.
0 to 700 m ² / g and a pore volume of 0.3 to 2.
It is preferably 5 cm ³ / g.

This carrier may contain 100 to 100, if necessary.
It is used by firing at 0 ° C, preferably 150 to 700 ° C. The organic compound used as the fine particle carrier may be a (co) polymer produced mainly from an α-olefin having 2 to 14 carbon atoms such as ethylene or 4-methyl-1-pentene, or vinylcyclohexane. An example is a (co) polymer produced mainly from styrene.

Specific examples of the organoaluminum compound catalyst component (d) used in the preparation of the olefin polymerization catalyst include trialkyl aluminum such as trimethyl aluminum, alkenyl aluminum such as isoprenyl aluminum, and dimethyl aluminum. Examples thereof include dialkylaluminum halides such as chloride, alkylaluminum sesquihalides such as methylaluminum sesquichloride, alkylaluminum dihalides such as methylaluminum dichloride, and alkylaluminum hydrides such as diethylaluminum hydride.

Examples of the ionizable ionic compound catalyst component (e) include triphenylboron, MgCl ₂ , Al ₂ O ₃ and Si described in USP-547718.
Lewis acids such as O ₂ —Al ₂ O ₃ ; ionic compounds such as triphenylcarbenium tetrakis (pentafluorophenyl) borate; carborane compounds such as dodecaborane and bis n-butylammonium (1-carbedodeca) borate.

Linear ethylene / α-used in the present invention
The olefin copolymer is a metallocene catalyst component (a) as described above, and an organoaluminum oxy compound catalyst component (b), if necessary, a fine particle carrier (c), an organoaluminum compound catalyst component (d), an ionized ion. In the presence of an olefin polymerization catalyst containing a reactive compound catalyst component (e), ethylene and an α-olefin having 3 to 12 carbon atoms are mixed under various conditions in a gas phase or in a slurry or solution liquid phase. It can be obtained by copolymerization.

In the slurry polymerization method or the solution polymerization method, an inert hydrocarbon may be used as the solvent, or the olefin itself may be used as the solvent. When carrying out the polymerization, the metallocene-based olefin polymerization catalyst as described above generally has a concentration of transition metal atoms in the polymerization reaction system of usually 10 ^−8.
-10 ^-3 gram atom / liter, preferably 10 ^{-7 -1}
It is preferably used in an amount of ^0-4 gram atom / liter.

Further, in the polymerization, in addition to the organoaluminum oxy compound catalyst component (b) and the organoaluminum compound catalyst component (c) supported on the carrier, the organoaluminum oxy compound catalyst component (b) not further supported is added. And / or the organoaluminum compound catalyst component (c) may be used. In this case, the aluminum atom (Al) derived from the unsupported organoaluminum oxy compound catalyst component (b) and / or the organoaluminum compound catalyst component (c) and the transition metal atom (a) derived from the metallocene catalyst component (a) ( M) atomic ratio [Al
/ M] is in the range of 5 to 300, preferably 10 to 200, and more preferably 15 to 150.

The polymerization temperature in the slurry polymerization method is usually -50 to 100 ° C, preferably 0 to 90 ° C, and the polymerization temperature in the solution polymerization method is usually -50 to 50 ° C.
It is in the range of 0 ° C, preferably 0 to 400 ° C. The polymerization temperature in the gas phase polymerization method is usually 0 to 120 ° C, preferably 20 to 100 ° C.

The polymerization pressure is usually atmospheric pressure to 100 kg /
It is under a pressure condition of cm ² , preferably ² to 50 kg / cm ² , and the polymerization can be carried out by any of batch system, semi-continuous system and continuous system.

In the present invention, the above linear ethylene
When preparing the α-olefin copolymer, if necessary
(1) multi-stage polymerization, (2) multi-stage polymerization of liquid phase and gas phase, or (3)
Means such as performing prepolymerization in the liquid phase and then conducting polymerization in the gas phase can be adopted.

Other Film Components In addition to the above-mentioned linear ethylene / α-olefin copolymer, an antioxidant, a UV absorber, a lubricant, a slip agent, and the like may be used as components for forming the agricultural coating film according to the present invention. Various compounding agents such as an anti-blocking agent, a drip agent, an antistatic agent, a colorant, and carbon black can be used within a range that does not impair the object of the present invention.

Further, with respect to 100 parts by weight of the linear ethylene / α-olefin copolymer used in the present invention, polyethylene other than this linear ethylene / α-olefin copolymer (for example, high-pressure low-density polyethylene) , Medium density polyethylene, high density polyethylene, etc.), ethylene / vinyl acetate copolymer, and ethylene / α-olefin copolymer rubber in an amount of 30 parts by weight or less. By compounding, the film moldability and the strength and flexibility of the film can be improved.

Agricultural coating film The agricultural coating film according to the present invention comprises a linear ethylene / α-olefin copolymer as described above, and, if necessary, a conventionally known antioxidant, ultraviolet absorber, or lubricant. , Slip agent, anti-blocking agent, drip agent, antistatic agent,
It comprises various additives such as colorants, carbon black, high-pressure low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene / vinyl acetate copolymer, ethylene / α-olefin copolymer rubber, and the like.

The thickness of the agricultural coating film of the present invention is in the range of 5 to 30 μm, preferably 7 to 20 μm. The dirt impact strength [DI (g)] of the agricultural coating film according to the present invention is 100 ≦ D when the thickness is 5 μm or more and 10 μm or less.
I ≦ 250 When the thickness is more than 10 μm and 20 μm or less, 250
<DI ≦ 450 When the thickness is more than 20 μm and 30 μm or less, 450
<DI ≦ 1100.

Since the agricultural covering film according to the present invention has the dirt impact strength in the above range, it is possible to extremely effectively prevent damages during the construction of the film. Preparation of Film The agricultural coating film according to the present invention as described above can be prepared from the above-mentioned linear ethylene / α-olefin copolymer by film formation by, for example, the inflation method or the T-die method.

Film formation by the inflation method is carried out by extruding a linear ethylene / α-olefin copolymer through a slit die and expanding it by a predetermined air flow. The resin temperature at the time of extruding the linear ethylene / α-olefin copolymer is from 190 to
The temperature is preferably 250 ° C.

[0052]

EFFECTS OF THE INVENTION According to the present invention, it is excellent in adhesion to soil, that is, flexibility, and has various properties such as weather resistance, tensile property, tear property, impact resistance, rigidity, etc. A coated film is obtained.

This agricultural coating film is excellent in the balance between impact resistance and rigidity, as well as flexibility and heat resistance, even in a thin film having a thickness of about 13 μm or less, as compared with the conventional film.

Therefore, the agricultural coating film according to the present invention having the above-mentioned effects is mainly used as a multi-film which is required to have an effect of increasing the soil temperature, such as open-field cultivation, tunnel cultivation, house semi-forced cultivation, and non-processing. It is effectively used for prop cultivation and early digging cultivation.

The agricultural coating film according to the present invention has almost no directivity in tensile Young's modulus and has sufficient strength. Therefore, when it is used as a mulch film, for example, it is easily caught by unevenness or protrusions on the ridge surface. It will not be torn.

Further, since the agricultural coating film according to the present invention has a sufficient dirt impact strength, it is possible to very effectively prevent damages and the like during the construction of the film. Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

The tensile strength at break, elongation at break, tensile Young's modulus and dirt impact strength of the films in Examples and Reference Examples were determined according to the following test methods. (1) Tensile Breaking Point Strength, Tensile Breaking Point Elongation and Tensile Young's Modulus Tensile breaking point strength, tensile breaking point elongation and tensile Young's modulus are in accordance with JIS Z 1702 tensile strength test, and are films under the following conditions. MD direction and TD direction of
It was determined by performing a tensile test using a crosshead moving speed constant type tensile tester (manufactured by Instron).

[Test Conditions] Sample: Dumbbell prescribed in JIS Z 1702 Atmospheric temperature: 23 ° C. Pulling speed: 500 mm (2) Dirt impact strength Dirt impact strength was measured by performing an impact test in accordance with JIS Z 1707. I asked.

[0059]

Example 1 [Preparation of Catalyst for Olefin Polymerization] 6.3 kg of silica dried at 250 ° C. for 10 hours was suspended in 100 liter of toluene and then cooled to 0 ° C. Then, a toluene solution of methylaluminoxane (Al; 0.96 mol /
41 liters) was added dropwise in 1 hour. On this occasion,
The temperature in the system was kept at 0 ° C. Subsequently, the mixture was reacted at 0 ° C for 60 minutes, then heated to 95 ° C over 1.5 hours, and reacted at that temperature for 4 hours. Then, the temperature was lowered to 60 ° C., and the supernatant was removed by the decantation method.

The solid component thus obtained was washed twice with toluene and then resuspended in 125 liters of toluene. To this system, a solution of bis (n-butylcyclopentadienyl) zirconium dichloride in toluene (Zr; 4
2.7 mmol / liter) 15 liters at 30 ° C.
The mixture was added dropwise over 0 minutes, and further reacted at 30 ° C. for 2 hours.
Then, the supernatant was removed, and the solid catalyst was washed twice with hexane to obtain a solid catalyst containing 6.2 mg of zirconium per 1 g. [Preparation of Prepolymerization Catalyst] To 300 liters of hexane containing 14 mol of triisobutylaluminum, 8.5 kg of the solid catalyst obtained above was added, and ethylene was prepolymerized at 35 ° C. for 7 hours to obtain a solid. 1g catalyst
A prepolymerization catalyst was obtained in which 3 g of polyethylene was prepolymerized. [Preparation of Linear Ethylene / 1-Hexene Copolymer] Copolymerization of ethylene and 1-hexene was carried out using a continuous fluidized bed gas phase polymerization apparatus in the presence of the prepolymerization catalyst.

The linear ethylene.
The 1-hexene copolymer has a density of 0.922 g / cm ³ and a melt flow rate of 2.2 g / 10 minutes,
The 1-hexene content was 2.7 mol% and the Mw / Mn was 3.4. [Film Molding] The linear ethylene / α-olefin copolymer obtained as described above was molded by an air-cooled inflation method under the following molding conditions to give a thickness of 10 μm.
m, 15 μm and 30 μm films were obtained. [Molding conditions] Molding machine: Air-cooled inflation film molding machine equipped with an extruder having a die diameter of 50 mmφ Molding temperature: 200 ° C. Blow ratio: 2.4 For the film obtained as described above, the above-mentioned tensile breaking strength, Tensile elongation at break, Young's modulus in tension, and dirt impact strength were determined.

A thickness of 10 μm obtained as described above,
Films of 15 μm and 30 μm were applied as mulch films, but both films had high dirt impact strength, so there was no damage during film application.

The results are shown in Table 1.

[0064]

Example 2 Copolymerization of ethylene and 1-hexene was carried out using a continuous fluidized bed gas phase polymerization apparatus in the presence of the prepolymerization catalyst of Example 1 above.

The linear ethylene
The 1-hexene copolymer has a density of 0.931 g / cm ³ and a melt flow rate of 2.3 g / 10 minutes,
The 1-hexene content was 1.0 mol% and the Mw / Mn was 3.3.

Films with thicknesses of 10 μm, 15 μm and 30 μm were obtained in the same manner as in Example 1 from the linear ethylene / 1-hexene copolymer obtained as described above. The tensile strength at break, elongation at tensile break, Young's modulus in tension, and dirt impact strength of the obtained film were determined.

The thickness of 10 μm obtained as described above,
Films of 15 μm and 30 μm were applied as mulch films, but both films had high dirt impact strength, so there was no damage during film application.

The results are shown in Table 1.

[0069]

Reference Example 1 [Preparation of catalyst for olefin polymerization] 10 mol of commercially available anhydrous magnesium chloride was suspended in 50 liters of dehydrated and purified hexane in a nitrogen stream, and ethanol 60 was added with stirring.
After mol was added dropwise over 1 hour, the mixture was reacted at room temperature for 1 hour.

Then, 27 mol of diethylaluminum chloride was added dropwise to this reaction solution at room temperature, and the mixture was stirred for 1 hour. Subsequently, after adding 100 mol of titanium tetrachloride, the temperature of the system was raised to 70 ° C. and the reaction was carried out while stirring for 3 hours.
The produced solid part was separated by decantation, washed repeatedly with purified hexane, and made into a hexane suspension. [Preparation of linear low-density polyethylene resin] Copolymerization of ethylene and 4-methyl-1-pentene was carried out using a 200-liter continuous polymerization reactor in the presence of the catalyst obtained as described above. It was

The linear ethylene
4-methyl-1-pentene copolymer has a density of 0.921 g
/ Cm ³ , and the melt flow rate is 2.2 g / 10
Minutes, the 4-methyl-1-pentene content was 3.8 mol% and the Mw / Mn was 3.7.

Films having thicknesses of 10 μm, 15 μm and 30 μm were obtained in the same manner as in Example 1 from the linear ethylene-4-methyl-1-pentene copolymer obtained as described above.

With respect to the obtained film, the above-mentioned tensile strength at break, tensile elongation at break, Young's modulus in tension and dirt impact strength were determined. The films having a thickness of 10 μm, 15 μm and 30 μm obtained as described above were applied as a mulch film, and all the films had a low dirt impact strength, so that damage was observed during the film application.

The results are shown in Table 1.

[0075]

[Reference Example 2] [Preparation of linear low-density polyethylene resin] Using a continuous fluidized bed gas phase polymerization apparatus in the presence of the catalyst described in Reference Example 1 above, ethylene and 4-methyl-1-pentene were added. Was copolymerized.

The linear ethylene
4-methyl-1-pentene copolymer has a density of 0.931 g
/ Cm ³ , and the melt flow rate is 2.1 g / 10
Minutes, the 4-methyl-1-pentene content was 1.5 mol% and the Mw / Mn was 2.6.

Films having thicknesses of 10 μm, 15 μm and 30 μm were obtained from the linear ethylene-4-methyl-1-pentene copolymer obtained as described above in the same manner as in Example 1.

With respect to the obtained film, the above-mentioned tensile strength at break, tensile elongation at break, Young's modulus in tension and dirt impact strength were determined. The films having a thickness of 10 μm, 15 μm and 30 μm obtained as described above were applied as a mulch film, and all the films had a low dirt impact strength, so that damage was observed during the film application.

The results are shown in Table 1.

[0080]

[Table 1]

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Claims (5)

[Claims] 1. When a film having a thickness of 10 μm is formed, the dart impact strength is 110 g or more, and the tensile Young's modulus in both MD and TD is 2.5 × 10 ³ kg / cm ² or more. A film having a thickness of 5 to 30 μm, which comprises a linear ethylene / α-olefin copolymer capable of forming a film, wherein the linear ethylene / α-olefin copolymer is ethylene and has from 3 to 10 carbon atoms. An agricultural coating film comprising 12 α-olefins. 2. The dirt impact strength [DI (g)] is 100 ≦ D when the thickness is 5 μm or more and 10 μm or less.
I ≦ 250 When the thickness is more than 10 μm and 20 μm or less, 250
<DI ≦ 450 When the thickness is more than 20 μm and 30 μm or less, 450
The agricultural coating film according to claim 1, which is in a range represented by <DI ≦ 1100. 3. The linear ethylene / α-olefin copolymer has a density (d) of 0.900 to 0.945 g / cm 3.
³ , the melt flow rate (MFR) is 0.1 to 2
It is 0 g / 10 minutes, and the molecular weight distribution (Mw / Mn) calculated | required by GPC method is 1.5-3.5, The covering film for agriculture of Claim 1 or 2 characterized by the above-mentioned. 4. The linear ethylene / α-olefin copolymer is an ethylene / 1-butene copolymer, an ethylene / 1-hexene copolymer, an ethylene-4-methyl-1-pentene copolymer, Alternatively, the covering film for agriculture according to any one of claims 1 to 3, which is an ethylene / 1-octene copolymer. 5. The ethylene / α-olefin copolymer obtained by copolymerizing ethylene and an α-olefin having 3 to 12 carbon atoms in the presence of a metallocene catalyst. It is a polymer, The agricultural film in any one of Claims 1-4.