JP2972324B2 - Film comprising linear low-density ethylene / α-olefin copolymer and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a film comprising a linear low-density ethylene / α-olefin copolymer.

Technical Background of the Invention A copolymer of ethylene and an α-olefin having 4 to 18 carbon atoms has a linear molecular structure, has a density of 0.940 g / cm ³ or less, and has a linear structure. Low density polyethylene (LLDPE)
Also known as Such a linear low-density ethylene / α-olefin copolymer is a high-density polyethylene (HD
Superior in transparency, impact resistance and creep resistance compared to PE), and also superior in impact resistance and creep resistance compared to high pressure method low density polyethylene (LDPE). , And lamination are widely used.

However, linear low-density polyethylene as a film material has a problem that it is inferior in flowability at the time of melting and inferior in moldability compared to high-density polyethylene and low-density polyethylene. That is, the linear low-density ethylene / α-olefin copolymer has a very high Newtonian property during flow, a large shear stress in a high shear rate region, tends to cause melt fracture during molding, is inferior in high-speed moldability, and is molded. There is a problem that the energy required for flow during processing is large.

Further, the linear low-density ethylene / α-olefin copolymer has extremely low resistance to melt elongation deformation, that is, melt tension (melt tension), so that the valve cannot be stably expanded during inflation molding. In addition, during lamination molding, there was a problem that it could not be uniformly spread on the laminate base material.
Further, in the case of a sheet (thick film having a thickness of 300 μm or more) or the like, there is a problem that the formability is deteriorated at the time of secondary processing in which vacuum and pressure forming is performed.

In order to solve such problems, a film is formed by blending 10 to 50% by weight of low-density polyethylene with a linear low-density ethylene / α-olefin copolymer. When low-density polyethylene is blended with low-density ethylene / α-olefin copolymer, fluidity or melt tension is somewhat improved, but the excellent physical properties inherent in linear low-density ethylene / α-olefin copolymer are obtained. A new problem has arisen that not only is spoiled, but the increase in compounding cost cannot be ignored.

An object of the present invention is to solve the problems associated with the prior art as described above, and is a novel straight chain having excellent transparency, impact resistance, creep resistance, and economic efficiency. It is an object of the present invention to provide a film comprising a low-density ethylene / α-olefin copolymer and a method for producing the same.

SUMMARY OF THE INVENTION A film comprising a linear low-density ethylene / α-olefin copolymer according to the present invention comprises: (a) a copolymer of ethylene and an α-olefin having 4 to 18 carbon atoms; ) A density of 0.900 to 0.940 g / cm ³ , (c) a shear rate γ _{240 KPa} (sec ⁻¹ ) under a shear stress of 240 KPa at 190 ° C., and a melt flow rate MFR (g / 10
) Satisfies the _relationship represented by the formula [I] logγ 240 _KPa ≧ 0.982 _log MFR + 2.272... [I], and (d) a melt tension (melt tension) MT at 190 ° C.
_The linear low-density ethylene / α-olefin that satisfies the relationship represented by the formula [II] logMT _{190 ° C} ≧ −log MFR + 0.477 ... [II] when the melt flow rate MFR (g / 10 minutes) at _{190 ° C.} The film is characterized in that the film has an impact strength Y (Kg-cm / cm) of at least 1000 kg-cm / cm.

Further, the method for producing a film comprising a linear low-density ethylene / α-olefin copolymer according to the present invention comprises: (a) a copolymer of ethylene and an α-olefin having 4 to 18 carbon atoms, (B) linear low-density ethylene / α-olefin copolymer particles having a density of 0.900 to 0.940 g / cm ³ at a temperature not lower than the β dispersion temperature and not higher than the α dispersion temperature;
After irradiating an electron beam with an absorbed dose of 2 to 10 Mrad, the copolymer particles are formed into a film to obtain a film.

According to the present invention, a film comprising a linear low-density ethylene / α-olefin copolymer excellent in transparency, impact resistance and creep resistance, and a method for producing the same are provided.

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the film comprising the linear low-density ethylene / α-olefin copolymer according to the present invention will be specifically described.

First, the linear low-density ethylene α- used in the present invention
The olefin copolymer will be described.

Such a linear low-density ethylene / α-olefin copolymer has the following properties (a) to (d).

(A) ethylene and C4 to C18, preferably C4
A copolymer with the α-olefin copolymer of No. 8 to No. 8.

The α-olefin having 4 to 18 carbon atoms includes butene-
1,4-methyl-pentene-1, pentene-1, hexene-1, octene-1 and the like are used. These α-
Olefins may be used alone or in combination.

In this linear low-density ethylene / α-olefin copolymer, the constitutional unit derived from ethylene is 93 to 99 mol%
Preferably 95-99 mol%, more preferably 96-98 mol%
And a structural unit derived from an α-olefin having 4 to 18 carbon atoms is 1 to 7 mol%, preferably 1 to 5 mol%.
More preferably it is present in an amount of 2-3 mol%.

(B) The density is 0.900 to 0.940 g / cm ³ , preferably 0.900 to 0.90 g / cm ³ .
930 g / cm ³ , more preferably.

The density was measured by pressing a linear low-density ethylene / α-olefin copolymer powder into a press sheet in accordance with the method for preparing compression-molded test specimens of ASTM symbol D1928-68 polyethylene, and using this as a density gradient method. Can be measured.

(C) The shear rate γ _{240 KPa} (sec ⁻¹ ) under shear stress of 240 KPa at 190 ° C. and the melt flow rate MFR (g / 10
) Satisfy the _relationship represented by the formula [I] logγ 240 _KPa ≧ 0.982 logMFR + 2.272... [I], preferably _logγ240KPa ≧ 0.982logMFR + 2.427.

The shear rate γ _{240 KPa} (sec ⁻¹ ) under shear stress of 240 KPa at 190 ° C. can be easily measured by a usual capillary type rheometer (for example, a thin tube type extrusion rheometer manufactured by Shimadzu Corporation). The operation and calculation procedure at this time are described in “Polymer Processin” by JMMckelvey.
g "Wiley, New York (1962).

(D) Melt tension MT at 190 ° C
_{190 ° C.} and the melt flow rate MFR (g / 10 minutes) are represented by the formula [II] logMT _{190 ° C.} ≧ −log MFR + 0.477... [II] preferably logMT _{190 ° C.} ≧ −log MFR + 0.699. To satisfy the relationship.

The melt tension at 190 ° C (melt tension) M
T _{190 ° C.} can be measured, for example, using a melt tension tester manufactured by Toyo Seiki as follows. That is, the linear low-density ethylene / α-olefin copolymer was heated to 190 ° C. in the same apparatus, and the linear low-density ethylene / α-olefin copolymer was heated at 0.75 c from a 2 mmφ nozzle.
The strand was extruded at 23 ° C. in an atmosphere of 23 ° C. at a rate of 25 to 60 m / min through an air gap of 90 cm, and the tension of the yarn was measured.
_{190 ℃} .

It is preferable that the above-mentioned linear low-density ethylene / α-olefin copolymer further has the following properties.

(E) In the measurement by the X-ray diffraction method, the crystallinity is 30 to
60%, preferably 40-50%.

(F) The melt flow rate is 0.5 to 30 g / 10 minutes.

The melt flow rate is a value measured according to ASTM D1238E.

(G) The melting point is 100 to 125 ° C, preferably 110 to 120 ° C.

(H) The molecular weight distribution is from 3 to 12, preferably from 5 to 7, expressed as Mw (weight average molecular weight) / Mn (number average molecular weight).

(G) The g value measured as described later is 0.90 or more, preferably 0.95 or more.

(V) The gel fraction is 1.0% or less, preferably 0.5% or less.

The linear low-density ethylene / α-olefin copolymer having the above-mentioned properties (A) to (D) is a conventional linear low-density ethylene / α-olefin copolymer having transparency, In addition to having impact resistance and creep resistance, it has excellent fluidity and large melt tension (melt tension) as compared with conventionally known linear low-density ethylene / α-olefin copolymers, and has good moldability. Is excellent.

The reason why the linear low-density ethylene / α-olefin copolymer used in the present invention has the above-mentioned excellent properties is not clear, but is considered as follows.

The reason that the conventionally known linear low-density ethylene / α-olefin copolymer has excellent impact resistance is considered to be due to the linear molecular structure and low density. Linear low-density ethylene-α-olefin copolymers have a long distribution of linear molecules and exhibit impact resistance by being entangled with adjacent molecules. Is considered inferior.

On the other hand, high-pressure low-density polyethylene has a molecular structure of Y
It has a long-chain branched structure, in which the molecules exist in a thread-like shape and are in contact with neighboring molecules at multiple points, but do not have strong entanglement between the molecules. Therefore, high-pressure low-density polyethylene is
It has excellent fluidity and high melt tension at the time of melting, but is not so excellent in impact strength.

On the other hand, the linear low-density ethylene / α-olefin copolymer used in the present invention has a linear molecular structure like the conventionally known linear low-density ethylene / α-olefin copolymer. And a new structure other than the Y-type long-chain branched structure of the high-pressure low-density polyethylene.

It is confirmed as follows that the linear low-density ethylene / α-olefin copolymer used in the present invention does not have a Y-type long-chain branched structure. Here, the long-chain branched structure means having a branched chain having 18 or more carbon atoms with respect to the main chain, and having a carbon number such as methyl, ethyl, propyl, butyl, isobutyl, and pentyl in the polymer main chain. Does not include a structure to which 17 or more short chain groups are bonded.

Incidentally, the degree of the long-chain branched structure of an ethylene-based polymer is generally evaluated by a g value. This g value is given by the equation Required from.

In the formula, [η] lin can be calculated from GPC data, assuming that the ethylene-based polymer is linear. That is, using the same parameters as used for the measurement of ▲ ▼ (weight average molecular weight) and ▲ ▼ (number average molecular weight), the Mark-Howink equation and GP
From the Wi value obtained in C, [η] lin can be obtained by the following equation.

[Η] _lin = ΣWiηi is where ηi = KMi ^d, Mi is checked against the elution time by standard GPC calibration methods (elution time). Also Wi
Is the simple fraction weight of the polymer with molecular weight i. K is 3.95 × 10 ⁴ , and the value of d is 0.7 to 9.

[Η] _br is actually replaced by [η] _obs .
[Η] _obs is 0.015 of the ethylene polymer at 140 ° C.
It can be determined using a wt% trichlorobenzene solution and an Ubbelohde viscometer according to a standard method. The details are described in J. Appl. Polymer Sci., 21, 3331 to 3343 (1977).

High-pressure low-density polyethylene (LDPE) has one carbon atom
It is known to have up to 30 long-chain branched structures per 000, and the g-value of this high-pressure low-density polyethylene is 0.8 or less, most often 0.6 or less. In contrast, the g value of the linear low density ethylene / α-olefin copolymer used in the present invention is 0.90 or more, preferably 0.95 or more, and such a linear low density ethylene / α-olefin The copolymer does not have a long-chain branched structure. This means
It is also confirmed from ¹³ C-NMR.

The film according to the present invention comprises the above-mentioned linear low-density ethylene / α-olefin copolymer.

Next, a method for producing a film comprising the linear low-density ethylene / α-olefin copolymer according to the present invention will be described.

First, the linear low-density ethylene α
-The method for producing the olefin copolymer will be described.

Such a linear low-density ethylene / α-olefin copolymer is (a) a copolymer of ethylene and an α-olefin having 4 to 18 carbon atoms, and (b) a density of 0.900 to 0.940. g / cm ³ linear low-density ethylene / α-olefin copolymer particles (powder) at a temperature above the β dispersion temperature and below the α dispersion temperature,
It is preferable to manufacture by irradiating an electron beam in an amount of 2 to 10 Mrad as an absorbed dose.

Such linear low-density ethylene / α-olefin copolymer particles can be produced by copolymerizing ethylene and α-olefin to a desired density using a transition metal catalyst.

Examples of the transition metal catalyst include a combination system of a transition metal catalyst component containing a titanium compound or a vanadium compound and an organoaluminum compound, and a chromium compound-supporting type highly active catalyst component. In particular, a catalyst system comprising a combination of a titanium catalyst component (A) activated by a magnesium compound and an organoaluminum compound catalyst component (B) can be suitably used.

As the titanium catalyst component (A) activated by a magnesium compound, for example, a magnesium compound, a solubilizing agent and a titanium compound are dissolved in a solid titanium catalyst component containing magnesium, titanium and halogen as essential components or a hydrocarbon solvent. Highly active titanium catalyst components such as a solution-type titanium catalyst component can be mentioned. The titanium in the titanium catalyst component (A) is usually tetravalent and / or trivalent. The solid catalyst component (A) is
Usually preferably the titanium content is from about 0.2 to about 18% by weight, more preferably from about 0.3 to about 15% by weight, and the halogen / titanium (molar ratio) is preferably from about 4 to about 300, more preferably about 5 to about 200. Further, its specific surface area is preferably about 10 cm ² / g or more, more preferably about 20 to about 1
000 cm ² / g, more preferably from about 40 to about 900 cm ² / g.

Such a solid highly active titanium catalyst component (A) is widely known, and is basically obtained by reacting a magnesium compound with a titanium compound to obtain a reactant having a large specific surface area, or A method of reacting a titanium compound with a magnesium compound having a large value is often used. For example, a co-milling method of a magnesium compound and a titanium compound, a thermal reaction between a magnesium compound and a titanium compound having a sufficiently increased specific surface area, a thermal reaction between an oxygen-containing magnesium compound and a titanium compound, and treatment with an electron donor A magnesium compound previously treated with an organoaluminum compound or a halogen-containing silicon compound, or without treatment,
A typical example is a method of reacting with a titanium compound.

There are various magnesium compounds used for producing the solid highly active titanium catalyst component (A).
For example, magnesium chloride, magnesium bromide, magnesium iodide, magnesium fluoride, magnesium hydroxide, magnesium oxide, magnesium hydroxyhalide, alkoxymagnesium, alkoxymagnesium halide, allyloxymagnesium, allyloxymagnesium halide, alkylmagnesium halide, or these Mixtures and the like can be exemplified. These may be made by any manufacturing method. The magnesium compound may also contain other metals, electron donors and the like.

The titanium compound used for the production of the solid highly active titanium catalyst component (A) is represented by Ti (OR) _4-m X _m (R is a hydrocarbon group, X is a halogen, 0 ≦ m ≦ 4). Can be exemplified. Examples of such titanium _{compounds, TiCl 4, TiBr 4, Ti} (OC 2 H 5) Cl 3, Ti (OC 2 H 5) 2 Cl 2 Ti (OC 6 H 5) 3 Cl, Ti (OC 2 H _{5) 4,} and the like.

Further, various titanium trihalides, such as titanium trichloride, obtained by reducing titanium tetrahalide with a reducing agent such as aluminum, titanium, hydrogen, and an organic aluminum compound can be exemplified. These titanium compounds can be used in combination of two or more kinds.

Representative methods for obtaining such a highly active titanium catalyst component (A) are described, for example, in JP-B-46-34092 and JP-B-46-3.
No. 4094, JP-B-46-34098, JP-B-47-41676
Japanese Patent Publication No. 47-46269, Japanese Patent Publication No. 50-32270, Japanese Patent Publication No. 53-1796, and the like.

As the organoaluminum compound catalyst component (B) which can be used together with the highly active catalyst component containing a titanium compound or a vanadium compound, a compound having at least one Al-C in a molecule can be used. ) General formula R ¹ _m Al (OR ² ) _n H _p X _q (where R ¹ and R ² are hydrocarbon groups containing usually 1 to 15, preferably 1 to 4 carbon atoms, and may be the same or different. X is a halogen, m is 0 <m ≦ 3, and n is 0 ≦ n <.
3, p is a number of 0 ≦ p <3, q is 0 ≦ q <3, moreover organic aluminum compound represented by a is) m + n + p + q = 3, (ii) the general formula M ¹ AlR ¹ ₄ (wherein M ¹ is Li, Na, or K, and R ¹ is the same as described above).

The following can be exemplified as the organoaluminum compound belonging to the above (i).

General formula R ¹ _m Al (OR ² _m Al (OR ₂ ) _3-m (where R ¹ and R ² are the same as above. M is preferably 1.5
≦ m ≦ 3), a general formula R ¹ _m AlX _3-m (where R ¹ is the same as above; X is a halogen, m is preferably 0 <m <3), and a general formula R ¹ _m AlX _3-m (where R ¹ is the same as above, m is preferably a number of 2 ≦ m <3), and a general formula R ¹ _m Al (OR ² ) _n X _q (where R ¹ and R ² is the same as above, X is halogen, 0 <
m ≦ 3, 0 ≦ n <3, 0 ≦ q <3, and m + n + q = 3).

As the aluminum compound belonging to (i), more specifically, trialkylaluminum such as triethylaluminum and tributylaluminum; trialkenylaluminum such as triisoprenylaluminum; dialkylaluminum alkoxide such as diethylaluminum ethoxide and dibutylaluminum butoxide , ethylaluminum sesquichloride ethoxide, in addition to alkylaluminum sesqui alkoxides such as butyl sesquichloride _{^{butoxide, R 1 2.5 Al (OR 2}} ) partially alkoxylated alkyl aluminum having an average composition represented by like _0.5, diethylaluminum Dialkylaluminum halides such as chloride, dibutylaluminum chloride, diethylaluminum bromide, ethyl alcohol Alkyl aluminum sesquihalogenides such as aluminum sesquichloride, butyl aluminum sesquichloride, ethyl aluminum sesquibromide, partially halogenated alkyls such as alkyl aluminum dihalogenides such as ethyl aluminum dichloride, propyl aluminum dichloride, butyl aluminum dibromide Partially hydrogenated alkylaluminium, such as aluminum, dialkylaluminum hydride such as diethylaluminum hydride, dibutylaluminum hydride, alkylaluminum dihydride such as ethylaluminum dihydride, propylaluminum dihydride, etc. Chloride, ethylaluminum ethoxypromide, etc. Partially include alkoxylated and halogenated alkylaluminum.

Examples of the compound similar to (i) include an organic aluminum compound in which two or more aluminum atoms are bonded via an oxygen atom or a nitrogen atom. As such a compound, for example, And the like. Examples of the compound belonging to (ii) include LiAl (C ₂ H ₅ ) ₄ and LiAl (C ₇ H ₁₅ ) ₄ . Among these, it is particularly preferable to use trialkyl aluminum and / or alkyl aluminum halide.

As the catalyst component, in addition to the transition metal catalyst, various halogen compounds, electron donors, and the like may be coexistent for the purpose of adjusting the molecular weight and molecular weight distribution of the polymer or for the purpose of improving the catalytic activity.

In the copolymerization of ethylene and α-olefin, reaction forms such as gas phase polymerization, solution polymerization, and suspension polymerization can be adopted. It is preferred to produce the particles.

Such linear low-density ethylene / α-olefin copolymer particles preferably have a maximum particle size of 3 mm or less, preferably 30 to 500 μm, and more preferably 60 to 180 μm. In addition, particles mean including forms such as powder, flakes, and granules.

The film according to the present invention is obtained by forming a film of the linear low-density ethylene / α-olefin copolymer particles as described above, and irradiating the copolymer particles with an electron beam prior to film formation. Is preferred.

Such irradiation is performed by applying an electron beam to the copolymer particles at a temperature equal to or higher than the β dispersion temperature and equal to or lower than the α dispersion temperature so that the absorbed dose is 2 to 10 Mrad.

Here, the β-dispersion temperature of the linear low-density ethylene / α-olefin copolymer particles refers to the molecular mobility of the entire molecular chain existing in a part other than the crystal part of the molecular chain in the copolymer. Means the temperature to be started. Therefore, below this temperature, most of the molecular chains other than the crystal part of the copolymer are in a glassy state.

The α-dispersion temperature means a temperature at which molecular mobility of a molecular chain in a crystal part of the copolymer starts. Therefore, above this temperature, the crystal part of the copolymer is in a softened state. That is, in the linear low-density ethylene / α-olefin copolymer used in the present invention, the electron beam is irradiated at the above-mentioned absorbed dose in a state where the crystal part is robust and the molecular motion other than the crystal part is active. However, it is important to modify parts other than the crystal part. The reason for this is not clear, but the crystal part is usually composed of molecular chains without defects such as the central part of the molecular chain, and conversely, other than the crystal part is composed of many defective parts such as molecular terminal parts. Therefore, it is considered that a portion having no defect is left as it is, and a portion containing many defective portions is modified by electron beam irradiation.

Usually, the α-dispersion temperature of the linear low-density polyethylene copolymer used in the present invention is about 80 ° C., and the β-dispersion temperature is in the range of −60 ° C. to + 40 ° C., depending on the type and amount of the comonomer. It is in.

Further, the molecular structure of the linear low-density polyethylene copolymer used in the present invention is characterized in that it has no long-chain branched structure, and in addition to the normal linear structure used in the present invention. The low-density polyethylene copolymer has substantially no amyl branched structure per 10,000 carbon atoms,
You have more than 2.0. The relationship between the amyl branched structure and the physical properties of the linear low-density polyethylene copolymer used in the present invention is not clear. The number of amyl branches can be measured by a conventional method by using ¹³ C-NMR.

The electron beam in this specification refers to an electron flow obtained by accelerating thermoelectrons in a vacuum, and generally means an electron flow irradiated from a commercially available electron beam irradiation device.

When electron beam irradiation is performed on the linear low-density ethylene / α-olefin copolymer particles at a temperature higher than the dispersion temperature, the linear low-density ethylene / α-olefin copolymer has a Y-type long-chain branched structure in the copolymer. May occur or a gel component may be generated.On the other hand, when the linear low-density ethylene / α-olefin copolymer particles are irradiated with an electron beam at a temperature lower than the β dispersion temperature, the The effect may not be fully exhibited.

The β-dispersion temperature and α-dispersion temperature of the linear low-density ethylene / α-olefin copolymer are determined by a known method using a press sheet for density measurement, for example, using a rheometer such as Leo Vibron manufactured by Orientec. Can be measured by

The linear low-density ethylene / α-olefin copolymer particles can be irradiated with an electron beam in air, nitrogen gas, carbon dioxide gas or the like.
In order to prevent gelation of the olefin copolymer particles, it is preferable to perform the reaction under an inert atmosphere such as nitrogen gas.

Electron beam irradiation on the linear low-density ethylene / α-olefin copolymer particles is performed so that the absorbed irradiation amount is 2 to 10 Mrad, but the linear low-density ethylene / α-olefin before electron beam irradiation is used. and MFR _b olefin copolymer particles, the ratio of the MFR _a post-electron beam irradiation linear low density ethylene · alpha-olefin copolymer particles preferably the following equation MFR _b / MFR _a ≧ 1.5 is MFR _b / It is particularly preferable to carry out the reaction so as to satisfy MFR _a ≧ 3.0.

Increasing the MFR _b / MFR _a is preferred in order to improve the melt tension of the copolymer, the irradiation dose increases, the film impact Y is remarkably lowered, the upper limit of the MFR _b / MFR _a is MFR _b / MFR _a ≦ 15, preferably MFR _b / MFR _a ≦ 10.

Linear low-density ethylene-α-irradiated with electron beam
The olefin copolymer particles may contain additives such as various stabilizers and pigments, but preferably, the linear low-density ethylene / α-olefin copolymer particles not containing these additives are subjected to electron beam irradiation. It is desirable to perform irradiation and then pelletize the linear low-density ethylene / α-olefin copolymer particles together with additives to obtain a product.

At this time, the linear low-density ethylene / α-olefin copolymer powder that has been subjected to the electron beam irradiation treatment is pelletized with a heat stabilizer as soon as possible after the treatment, and the residue of radicals generated by the electron beam irradiation is obtained. Is desirably stabilized. As the heat stabilizer used at this time,
Phenol-based heat stabilizers, phosphorus-based heat stabilizers, sulfur-based heat stabilizers, amine-based heat stabilizers and the like, in the case of the present invention, phenol-based heat stabilizers are preferred, and furthermore phenol-based heat stabilizers A combination system using a phosphorus-based heat stabilizer is particularly preferred. When the linear low-density ethylene / α-olefin copolymer powder that has been subjected to the electron beam irradiation treatment is left for a long time, cross-linking occurs due to the remaining active radicals. Causes generation. In particular, care must be taken when the electron beam treatment is performed in an atmosphere below the β dispersion temperature or in the vicinity of the β dispersion temperature. For this reason, the electron beam irradiation atmosphere temperature is higher than the β dispersion temperature by 20 ° C. or more. Is particularly preferred.

As described above, in the present invention, linear low-density ethylene
α-olefin copolymer particles, the β dispersion temperature or more,
And at a temperature equal to or lower than the α dispersion temperature, the absorbed dose of the electron beam is 2 to
Irradiation in an amount of 10 Mrad, the linear low-density ethylene-α-olefin copolymer obtained in this way has a lower crystallinity, crystal melting point, and gel fraction than those before electron beam irradiation. Little change in point.

The linear low-density ethylene α- used in the present invention
As can be seen from the fact that the g value is 0.90 or more, the olefin copolymer does not have a Y-type long-chain branched structure due to electron beam irradiation, and the impact resistance does not decrease.

Furthermore, the linear low-density ethylene / α-olefin copolymer used in the present invention is obtained by MFR by electron beam irradiation.
As can be seen from the decrease, the molecular weight distribution is widened by increasing the molecular weight, and the moldability is improved and the melt tension is also increased. This is thought to mean that the linear low-density ethylene / α-olefin copolymer used in the present invention has a novel short-chain branched structure caused by electron beam irradiation.

As described above, in the present invention, even if the conventionally known linear low-density ethylene / α-olefin copolymer is irradiated with electron beams to increase the molecular weight, no gel component is generated and the Y-type length is reduced. A linear chain in which a chain branching structure is not generated, and therefore, the moldability and the melt tension are improved without impairing the impact resistance and the like of the conventionally known linear low-density ethylene / α-olefin copolymer. Low density ethylene α-
It can be modified to an olefin copolymer.

If a large amount of gel is generated in the linear low-density ethylene / α-olefin copolymer, the flowability of the linear low-density ethylene / α-olefin copolymer is significantly reduced, and the blown film after molding is formed. In this case, fish eyes are generated, and lamination results in uneven bonding of films. Linear low-density ethylene α
The gel fraction in the olefin copolymer can be represented by the weight fraction of the insoluble residue after the linear low-density ethylene / α-olefin copolymer is treated in boiling para-xylene for 4 hours.

Heretofore, electron beam irradiation to a conventionally known linear low-density ethylene / α-olefin copolymer is widely performed. For example, JP-A-57-202327 discloses a sheet-like cross-linked polyethylene foam in which bubbles are trapped by irradiating a linear low-density ethylene / α-olefin copolymer with an electron beam to cross-link molecules. Is disclosed. However, in the polyethylene foam disclosed in this publication, the gel fraction has reached 10 to 60%, and the flow moldability of the linear low-density ethylene / α-olefin copolymer is substantially increased by electron beam irradiation. Has been lost to.

Japanese Patent Application Laid-Open No. 57-78420 discloses that an electron beam is applied to an ethylene-based polymer particle such as an ethylene / α-olefin copolymer at a temperature of at least 80 ° C. in a steam atmosphere at a temperature of at least 80 ° C.
A method for irradiating polyethylene, characterized in that the irradiation is performed in an amount of less than rad, is disclosed. However, according to this method, the irradiation amount and irradiation conditions of the electron beam on the linear low-density ethylene / α-olefin copolymer particles are different from those of the present invention. An ethylene / α-olefin copolymer cannot be obtained.

In the present invention, a film is produced by forming a film of a linear low-density ethylene / α-olefin copolymer irradiated with an electron beam as described above. The film according to the present invention can be produced by any of a melting method and a solution method. For example, when using the melting method, the calendar method,
Any method such as an inflation method or a T-die method can be adopted. When the solution method is employed, a dry method such as an endless belt method or a drum method can be employed, or a wet method can be employed. Particularly, in the present invention, it is preferable to produce a film by employing a melting method. Among these, it is preferable to manufacture a film by an inflation method, and in this case, it is particularly preferable to manufacture the film under the following conditions.

 The expansion ratio is 1.0 or more, preferably 1.5 or more, the whitening height is 10 cm or more, preferably 20 cm or more, the die temperature is 150 ° C to 250 ° C, and the die slip width is 0.5 to 5.0 mm.

(However, in the above description, the expansion ratio and the whitening height are obtained as follows.

Whitening height: distance from the upper surface of the die to the cooling and solidifying portion of the bubble resin) The film according to the present invention may be in any state of unstretched, uniaxially stretched, and biaxially stretched.

The thickness of the film comprising the linear low-density ethylene / α-olefin copolymer according to the present invention is not particularly limited, but is usually from 10 μm to 3 mm. Therefore, the “film” used in the present invention means not only a film used in a general sense but also a so-called sheet.

Impact strength Y of the film thus obtained
(Kg-cm / cm) is preferably at least 1000 kg-cm / cm, preferably 1500 kg-cm / cm, and more preferably 2000 kg-cm / cm.

The film impact strength is determined by the following method.

After the inflation film is formed, the film is allowed to stand at 23 ± 1 ° C. for 48 hours or more. After that, a portion having no scratches or orientation is cut out with a polariscope as a test piece with scissors of 100 × 100 mm using a sampling prototype.

Use a dial gauge to determine the minimum thickness as the film thickness. The energy required for breaking the test piece is measured using a film impact tester (manufactured by Toyo Seiki). At this time, the impact head spherical surface and the capacity are usually 1 inch × 15 kg · cm. The detailed measurement method follows the measurement procedure manual of a film impact tester manufactured by Toyo Seiki.

The film impact strength Y (Kg-cm / cm) is determined by the following equation.

Here, E is the energy required for breaking (Kg · cm), and D is the minimum thickness (cm) of the film. Calculate up to one integer from the above formula, measure 10 times, round the average by JIS, and signify 2
Calculate up to digits.

Such a film according to the present invention can be used alone, or can be used as a composite film by laminating it with another resin film or a metal thin film. Further, the film according to the present invention or the above-mentioned composite film is coated with a thin film forming material in which a pigment, a dye, a metal powder, a photosensitive material, a magnetic material, a magneto-optical material, etc. are dispersed in a binder, and the like. Characteristics can also be imparted.

Further, the linear low-density ethylene / α-olefin copolymer according to the present invention is also excellent in a molded article during blow molding.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 The composition ratio of ethylene and 4-methyl-pentene-1 was 9
A continuous gas-phase polymerization of a mixed gas of 7.5: 2.5 (molar ratio) was performed at 60 ° C. with a mixed catalyst of a highly active titanium catalyst component and an organoaluminum compound catalyst component. The obtained ethylene
The average particle size of the 4-methyl-pentene-1 copolymer powder is 150 μm, and the powder bulk density is 0.42 g / cm ³
Met. Powder melt flow rate is 30g / 10
Minutes. The density obtained from the press sheet is 0.920 g / c
m ³ , and the α-dispersion temperature determined by the dynamic viscoelasticity measurement device is 80
° C and β dispersion temperature were -10 ° C.

The electron beam irradiation treatment was performed as follows. Electron beam irradiator (Nisshin High Voltage: acceleration voltage 750KV)
The above-mentioned powder was uniformly drawn to a thickness of about 3 mm on the irradiation conveyor of Example 1 and continuously subjected to electron beam irradiation in a nitrogen atmosphere. At this time, the ambient temperature was 40 ° C. The absorbed radiation dose was adjusted by adjusting the filament current and irradiation time.

Immediately after irradiation, the powder is treated with Iragnox1010
(Musashino Geigy) and Antioxidant701 (Ethyl, Co
(made by RP Co., Ltd.) in an amount of 0.1% by weight with respect to the powder, and then uniformly kneaded at 190 ° C. with a screw-type extruder to stabilize residual radicals and pelletize. And Table 1 shows the results.

Next, using the stabilized pellets, a 50 μm thick film was formed at a die setting temperature of 190 ° C. using a 30 mmφ blown film molding machine manufactured by Modern Machinery. The film impact strength of the obtained film was measured. At this time, the stability of the valve at the time of forming the blown film and the fisheye level of the film were simultaneously determined.

In addition, in Tables 1-3, the ethylene / α-olefin copolymer having a melt flow rate reduced by the electron beam irradiation and having not been irradiated with the electron beam having a melt flow rate substantially equal to that of the ethylene / α-olefin copolymer is shown. (Polymerization method, composition and density are controlled by ethylene
(substantially the same as the α-olefin copolymer). According to the present invention, it can be seen that the ethylene / α-olefin copolymer subjected to electron beam irradiation has a remarkably increased melt tension of 240 kpa, which is an index of moldability, even when the melt flow rate is almost the same.

Example 2 Continuous gas phase polymerization of a mixed gas having a composition ratio of ethylene and pentene-1 of 97.3: 2.7 (molar ratio) was performed by the method described in Example 1 to obtain a powder of an ethylene / pentene-1 copolymer. I got The average particle size of the obtained powder is 180
And the powder bulk density was 0.45 g / cm ³ .
The melt flow rate of the powder was 22 g / 10 minutes. The density determined from the pressed sheet was 0.922 g / cm ³ , and the α dispersion temperature determined by the dynamic viscoelasticity measurement device was 75 ° C.
The dispersion temperature was 5 ° C.

The powder thus obtained was subjected to an electron beam irradiation treatment by the method described in Example 1, and after irradiation, the remaining radicals were similarly stabilized to obtain pellets. Next, a film was formed using the stabilized pellet in the same manner as in Example 1, and the film impact strength of the obtained film was measured.

 Table 2 shows the results.

Example 3 Continuous gas phase polymerization of a mixed gas having a composition ratio of ethylene and butene-1 of 96.0: 4.0 (molar ratio) was carried out by the method described in Example 1 to obtain a powder of ethylene / butene-1 copolymer. I got The average particle size of the obtained powder was 130, and the bulk density of the powder was 0.43 g / cm ³ .
The melt flow rate of the powder was 17 g / 10 minutes. The density obtained from the press sheet is 0.930 g / cm ³ , and the α dispersion temperature obtained by the dynamic viscoelasticity measurement device is 80 ° C.,
β dispersion temperature was 10 ° C.

The powder thus obtained was subjected to an electron beam irradiation treatment by the method described in Example 1, and after irradiation, the remaining radicals were similarly stabilized to obtain pellets. Next, a film was formed using the stabilized pellet in the same manner as in Example 1, and the film impact strength of the obtained film was measured.

 Table 3 shows the results.

Comparative Example 1 Using the ethylene-4-methyl-pentene-1 copolymer powder produced in Example 1, an electron beam treatment was performed by the following method. The above-mentioned powder was uniformly packed to a thickness of 3 mm in an irradiation conveyor of an electron beam irradiation device (manufactured by Nissin High Voltage: acceleration voltage 750 KV), and subjected to electron beam irradiation continuously in a nitrogen atmosphere. The ambient temperature was adjusted by changing the nitrogen stream temperature.

Irradiation treatment powder, when the number of aluminum branches was measured by ¹³ C-NMR, irradiation dose 3.75Mrad, 5.0Mrad, 6.5Mrad,
For each 10,000 carbon atoms for 7.6 Mrad,
4.34, 5.27, 5.67 and 6.10.

The above-mentioned copolymer was pelletized in the same manner as in Example 1 and further formed into a film, and the film impact strength of the obtained film was measured.

 The results are shown in Tables 4 and 5.

Continuation of front page (72) Inventor Koji Matsunaga 3 Chigusa Coast, Ichihara-shi, Chiba Mitsui Oil Chemical Industry Co., Ltd. (56) References JP-A-57-78420 (JP, A) JP-A-55-71724 (JP) , A) JP-A-54-103496 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08J 5/18 C08J 3/28 C08F 210/16 C08F 8/00

Claims (2)

(57) [Claims] (1) a copolymer of ethylene and an α-olefin having 4 to 18 carbon atoms, (b) a density of 0.900 to 0.940 g / cm ³ , and (c) 240 KPa at 190 ° C. Shear rate under shear stress γ _{240 KPa} (sec ^-1 ) and melt flow rate MFR (g / 10
) Satisfies the _relationship represented by the formula [I] logγ 240 _KPa ≧ 0.982 _log MFR + 2.272... [I], and (d) a melt tension (melt tension) MT at 190 ° C.
_The linear low-density ethylene / α-olefin that satisfies the relationship represented by the formula [II] logMT _{190 ° C} ≧ −log MFR + 0.477 ... [II] when the melt flow rate MFR (g / 10 minutes) at _{190 ° C.} A film comprising a linear low-density ethylene / α-olefin copolymer, comprising a polymer and having an impact strength Y (Kg-cm / cm) of the film of at least 1000 kg-cm / cm. 2. A copolymer of ethylene and an α-olefin having 4 to 18 carbon atoms, wherein: (b) a linear low-density ethylene copolymer having a density of 0.900 to 0.940 g / cm ^3. The α-olefin copolymer particles are irradiated with an electron beam at a temperature equal to or higher than the β dispersion temperature and equal to or lower than the α dispersion temperature, as an absorbed dose of 2 to 10 Mrad, and then the copolymer particles are formed into a film to form a film. A method for producing a film comprising a linear low-density ethylene / α-olefin copolymer.