JP3070824B2 - Biaxially stretched film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a biaxially stretched film. More specifically, the present invention relates to a biaxially stretched film substantially made of isotactic polypropylene and obtained by polymerizing propylene using a metallocene catalyst and having excellent rigidity and gloss.

[0002]

2. Description of the Related Art Isotactic polypropylene produced using a conventional Ziegler-Natta catalyst has excellent mechanical properties, chemical resistance, etc., and is extremely useful in terms of balance with economy. Is widely used in each molding field. However, the performance of such known biaxially stretched films made of ordinary polypropylene is limited, and improvement of the film performance, particularly gloss and rigidity, is strongly desired to solve the problem. Although there is a method of using polypropylene having a wide molecular weight distribution to improve the rigidity, in this case, although the rigidity is improved, a new problem such as a decrease in gloss and stretchability arises.

On the other hand, in recent years, it has been known that isotactic polypropylene can be obtained by polymerizing propylene using a catalyst comprising a combination of a metallocene and an aluminoxane different from a conventional catalyst system.

For example, propylene is polymerized using a catalyst comprising a silicon-bridged metallocene having a specific structure and an aluminoxane to obtain a highly stereoregular polypropylene having a narrow molecular weight distribution (JP-A-3-12406,
JP-A-3-12407, CHEMISTRY LETTERS, pp.
1853-1856, 1989). The polypropylene obtained by the method has a narrow molecular weight distribution, a high stereoregularity, a high melting point and a high rigidity as compared with polypropylene obtained from a conventional metallocene catalyst, but the polymerization of propylene Is carried out in the absence of hydrogen, a double bond is present at one end of the polymer, and depending on the conditions of use, the chemical stability may be impaired, and an improvement has been desired.

[0005]

As described above, the biaxially stretched film made of polypropylene obtained by the conventional method has a problem of improving gloss and rigidity.

[0006] The present inventors have solved the above-mentioned problems of the known art and have intensively studied the invention of a biaxially stretched film having improved gloss and rigidity. As a result, when a specific polypropylene obtained by using a metallocene catalyst is used as a biaxially stretched film, a biaxially stretched film having extremely high gloss and high rigidity is obtained even though the polypropylene has a narrow molecular weight distribution. This led to the present invention.

[0007] As is apparent from the above description, an object of the present invention is to provide a biaxially stretched film having a very high gloss and a high rigidity, comprising a specific polypropylene obtained by a specific production method.

The present invention relates to the following compounds (A) and (B)
Or consist of the following compounds (A), (B) and (C)
Polymerization of propylene or propylene and
Α-olefins other than propylene having 2 to 12 carbon atoms
Number average of weight average molecular weight (Mw) obtained by copolymerization
The ratio (Mw / Mn) to the molecular weight (Mn) is 1.5 to
3.8 and a melting point of 150-168 ° C
Consisting essentially of tic polypropylene, gloss 1
20% or more and Young's modulus 1900N / mm ² or more
Stretched at least 4 times in the longitudinal and transverse directions
Is a biaxially stretched film. Compound (A): general formula _{Q (C 5 H 4-m} R 1 m) (C 5 H 4-n R
² _n ) a transition metal compound represented by MXY [wherein (C ₅ H)
_4-m R ¹ m) and _{(C 5 H 4-n R} 2 n) is substituted cyclopenta
A dienyl group; m and n are integers of 1 to 3;
R ¹ and R ² are a hydrocarbon group having 1 to 20 carbon atoms, containing silicon.
A hydrocarbon group or two on a cyclopentadienyl ring
May be substituted with a hydrocarbon by bonding to a carbon atom of
Hydrocarbon groups forming one or more hydrocarbon rings (but only
And substitutes for branched C ₄ -C ₁₀ alkyl and C ₁ -C ₆ alkyl
5- to 7-membered cycloalkyl which may be possessed as a base
Excluding C ₆ -C ₁₅ aryl or arylalkyl.
And may be the same or different. Q is
_{(C 5 H 4-m R} 1 m) and a _{(C 5 H 4-n R} 2 n) crosslinking Surui
The shift is also a divalent hydrocarbon group, unsubstituted silylene group, or
It is a hydrocarbon-substituted silylene group. M is titanium, zirconi
Or a transition metal that is hafnium, X and
Y may be the same or different, and hydrogen, halogen or
Represents a hydrocarbon group. Compound (B) :( B-1) an aluminoxane, (B-2)
Reacts with the transition metal compound (A) to form an ionic complex
From the formed ionic compound and (B-3) Lewis acid
One or more selected compounds Compound (C): organoaluminum compound

The configuration and effect of the present invention will be described in detail below. In the present invention, polypropylene is a propylene homopolymer or an α-olefin having 2 to 12 carbon atoms other than propylene and propylene, for example, ethylene, propylene, butene, pentene, hexene, octene, 4-
It means a random copolymer or a block copolymer with one or more kinds such as methyl-1-pentene and the like, in which propylene polymerization units are 50% by weight or more. Next, a method for producing the polypropylene used for the biaxially stretched film of the present invention will be described. The specific metallocene catalyst used in the production of the polypropylene used in the biaxially stretched film of the present invention is a catalyst comprising the following compounds (A) and (B) or (A), (B) and (C). (Hereinafter, a catalyst composed of the following compounds (A) and (B) or (A), (B) and (C) may be abbreviated as a metallocene catalyst used in the present invention.) Compound (A): π electron Transition metal compound having at least one conjugated ligand Compound (B): (B-1) aluminoxane, (B-2)
An ionic compound which forms an ionic complex by reacting with the transition metal compound (A), and (B-3) one or more compounds selected from Lewis acids Compound (C): an organoaluminum compound

The compound (A) is usually called a metallocene and has a π-electron conjugated ligand, ie, η-cyclopentadienyl structure, η-benzene structure, η-cycloheptatrienyl structure, or η-cyclooctaene. A transition metal complex in which at least one or more ligands having a tetraene structure are coordinated with a transition metal.

The metallocene used in the present invention is one of
General formula _{Q (C 5 H 4-m} R 1 m) represented by _{(C 5 H 4-n R} 2 n) MXY
Transition metal compound [wherein (C ₅ H _4-m R ¹ _m ) and
(C ₅ H _4-n R ² _n ) represents a substituted cyclopentadienyl group
And m and n are integers of 1 to 3. R ¹ and R ² are
A hydrocarbon group having 1 to 20 carbon atoms, a silicon-containing hydrocarbon group,
Or two carbon atoms on the cyclopentadienyl ring
One or more carbons optionally combined with hydrocarbons
Hydrocarbon group forming a hydrocarbon ring (provided that branched C ₄ -
Having C ₁₀ alkyl or C ₁ -C ₆ alkyl as a substituent
5- to 7-membered cycloalkyl, C ₆ -C ₁₅ which may be present
Aryl or arylalkyl),
They may be the same or different. Q is _{(C 5 H 4-m R} 1 m)
And either divalent _{(C 5 H 4-n R} 2 n) crosslinking the charcoal
Hydrogenated, unsubstituted silylene, or hydrocarbon substituted silylene
It is a len group. M is titanium, zirconium or hafni
X and Y are the same or different.
Represents a hydrogen, halogen or hydrocarbon group
You. ].

More preferably, in the above general formula, R
¹ and R ² are an alkyl group having 1 to 20 carbon atoms (however,
Branched C ₄ -C ₁₀ alkyl and C ₁ -C ₆ alkyl as substituents
5- to 7-membered cycloalkyl, which you may have
Or an arylalkyl), which is the same or
It may be different. Q is a dialkylsilylene group and M
Indicates a transition metal that is zirconium or hafnium
And X and Y may be the same or different;
Or chiral transition metal compounds that are hydrocarbon groups
Can be.

Specific examples of such a compound (A) include dimethylsilylene (3-t-butylcyclopentadienyl) (fluorenyl) zirconium dichloride and dimethylsilylene (3-t-butylcyclopentadienyl)
(Fluorenyl) hafnium dichloride, rac-ethylenebis (indenyl) zirconium dimethyl, ra
c-ethylenebis (indenyl) zirconium dichloride, rac-dimethylsilylenebis (indenyl) zirconium dimethyl, rac-dimethylsilylenebis (indenyl) zirconium dichloride, rac-ethylenebis (tetrahydroindenyl) zirconium dimethyl, rac-ethylenebis (tetrahydro Indenyl) zirconium dichloride, rac-dimethylsilylenebis (tetrahydroindenyl) zirconium dimethyl, rac-dimethylsilylenebis (tetrahydroindenyl) zirconium dichloride, rac-dimethylsilylenebis (2-methyl-4,5,6,7- Tetrahydroindenyl) zirconium dichloride, rac
-Dimethylsilylenebis (2-methyl-4,5,6,7
-Tetrahydroindenyl) zirconium dimethyl, r
ac-ethylenebis (2-methyl-4,5,6,7-tetrahydroindenyl) hafnium dichloride, ra
c-dimethylsilylenebis (2-methyl-4-phenylindenyl) zirconium dichloride, rac-dimethylsilylenebis (2-methyl-4-phenylindenyl) zirconium dimethyl, rac-dimethylsilylenebis (2-methyl-4- Phenylindenyl) hafnium dichloride, dimethylsilylene (2,4-dimethylcyclopentadienyl) (3 ′, 5′-dimethylcyclopentadienyl) titanium dichloride, dimethylsilylene (2,4-dimethylcyclopentadienyl)
(3 ', 5'-dimethylcyclopentadienyl) zirconium dichloride, dimethylsilylene (2,4-dimethylcyclopentadienyl) (3', 5'-dimethylcyclopentadienyl) zirconium dimethyl, dimethylsilylene (2, 4-dimethylcyclopentadienyl)
(3 ′, 5′-dimethylcyclopentadienyl) hafnium dichloride, dimethylsilylene (2,4-dimethylcyclopentadienyl) (3 ′, 5′-dimethylcyclopentadienyl) hafnium dimethyl, dimethylsilylene (2 3,5-trimethylcyclopentadienyl)
(2 ′, 4 ′, 5′-trimethylcyclopentadienyl) titanium dichloride, dimethylsilylene (2
3,5-trimethylcyclopentadienyl) (2 ′,
4 ', 5'-trimethylcyclopentadienyl) zirconium dichloride, dimethylsilylene (2,3,5-
Trimethylcyclopentadienyl) (2 ′, 4 ′, 5 ′
-Trimethylcyclopentadienyl) zirconium dimethyl, dimethylsilylene (2,3,5-trimethylcyclopentadienyl) (2 ', 4', 5'-trimethylcyclopentadienyl) hafnium dichloride, dimethylsilylene (2,3 , 5-trimethylcyclopentadienyl) (2 ', 4', 5'-trimethylcyclopentadienyl) hafnium dimethyl.

Among these compounds (A), particularly preferred are dimethylsilylene (2,4-dimethylcyclopentadienyl) (3 ', 5'-dimethylcyclopentadienyl) zirconium dichloride, dimethylsilylene (2, 4-dimethylcyclopentadienyl) (3 ′,
5′-dimethylcyclopentadienyl) zirconium dimethyl, dimethylsilylene (2,4-dimethylcyclopentadienyl) (3 ′, 5′-dimethylcyclopentadienyl) hafnium dichloride, dimethylsilylene (2,4-dimethylcyclo) Pentadienyl) (3 ',
5'-dimethylcyclopentadienyl) hafnium dimethyl, dimethylsilylene (2,3,5-trimethylcyclopentadienyl) (2 ', 4', 5'-trimethylcyclopentadienyl) zirconium dichloride, dimethylsilylene (2 , 3,5-Trimethylcyclopentadienyl) (2 ', 4', 5'-trimethylcyclopentadienyl) zirconium dimethyl, dimethylsilylene (2,3,5-trimethylcyclopentadienyl)
(2 ′, 4 ′, 5′-trimethylcyclopentadienyl) hafnium dichloride, dimethylsilylene (2,
3,5-trimethylcyclopentadienyl) (2 ′,
4 ', 5'-trimethylcyclopentadienyl) hafnium dimethyl.

In the above compound (A), a meso-form compound (A) having a non-chiral structure may be by-produced during the synthesis of a chiral metallocene. It does not need to be a metallocene and may be mixed with a meso form. However, when using a mixture with the meso form, depending on the mixing amount of the meso form and the propylene polymerization activity, an atactic polypropylene polymerized from the meso form so that the obtained polypropylene satisfies the above-mentioned essential requirements. May need to be removed by a known method such as solvent extraction.

The transition metal compound (A) can be used as a catalyst by combining it with the compound (B) as it is and, if necessary, further with the compound (C).
It is also possible to use it by supporting it on a particulate carrier. Such a particulate carrier is an inorganic or organic compound having a particle size of 5 to 300 μm, preferably 10 to 300 μm.
Granular or spherical fine particle solids of up to 200 μm are used.

Among these, as the inorganic compound used for the carrier, SiO ₂ , Al ₂ O ₃ , MgO, TiO ₂ , ZnO and the like or a mixture thereof, for example, SiO ₂ -Al
₂ O ₃ , SiO ₂ -MgO, SiO ₂ -TiO ₂ , SiO _2-
Al ₂ O ₃ -MgO and the like. In these, S
Those containing iO ₂ or Al ₂ O ₃ as a main component are preferred.

The organic compounds used for the carrier include ethylene, propylene, 1-butene and 4-methyl-
Examples thereof include a polymer or copolymer of an α-olefin having 2 to 12 carbon atoms such as 1-pentene, and a polymer or copolymer of styrene or a styrene derivative.

The compound (B) used in combination with the transition metal compound (A) which is a metallocene as a catalyst component used in the production of the polypropylene used in the biaxially stretched film of the present invention includes (B-1) aluminoxane, (B-2) And (B-3) at least one compound selected from the Lewis acids, which reacts with the transition metal compound (A) to form an ionic complex.

Among them, (B-1) aluminoxane is
An organoaluminum compound represented by the following general formula [1] or [2].

Embedded image

Embedded image Here, R ³ is a hydrocarbon group having 1 to 6, preferably 1 to 4 carbon atoms, and specifically, a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, a pentyl group, a hexyl group and the like. An alkyl group, an allyl group, a 2-methylallyl group,
Examples include an alkenyl group such as a propenyl group, an isopropenyl group, a 2-methyl-1-propenyl group, a butenyl group, a cycloalkyl group such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group, and an aryl group. Among these, an alkyl group is particularly preferred, and each R ³ may be the same or different. P is an integer of 4 to 30, preferably 6 to 30,
Particularly preferably, it is 8 to 30.

The above aluminoxane can be adjusted under various known conditions. Specifically, the following method can be exemplified. (1) A method in which a trialkylaluminum is directly reacted with water using an organic solvent such as toluene or ether. (2) salts having trialkylaluminum and water of crystallization,
For example, a method of reacting with copper sulfate hydrate and aluminum sulfate hydrate. (3) A method of reacting trialkylaluminum with water impregnated in silica gel or the like. (4) Trimethyl aluminum and triisobutyl aluminum are mixed, toluene,
A method of directly reacting with water using an organic solvent such as ether. (5) A method in which trimethylaluminum and triisobutylaluminum are mixed and reacted with a salt having water of crystallization, for example, copper sulfate hydrate or aluminum sulfate hydrate. (6) A method in which silica gel or the like is impregnated with water, triisobutylaluminum is reacted, and trimethylaluminum is further reacted.

(B-2) an ionic compound which forms an ionic complex by reacting with the transition metal compound (A) (hereinafter sometimes referred to as “compound (B-2)”); (B-3) As a Lewis acid, Japanese Unexamined Patent Publication No.
JP-A-501950, JP-A-1-502036, JP-A-3-179005, JP-A-3-179
No. 006, JP-A-3-207703, JP-A-3-207704, and the like, and ionic compounds and Lewis acids.

The ionic compound (B-
2) is a salt of a cationic compound and an anionic compound. The anion has the effect of stabilizing the transition metal cation species by reacting with the transition metal compound (A) to cationize the transition metal compound (A) and forming an ion pair. Examples of such anions include an organic boron compound anion and an organic aluminum compound anion. Examples of the cation include a metal cation, an organic metal cation, a carbonium cation, a tripium cation, an oxonium cation, a sulfonium cation, a phosphonium cation, and an ammonium cation.

Of these, an ionic compound containing a boron atom as an anion is preferable. Specifically, triethylammonium tetrakis (pentafluorophenyl) borate and triethylammonium tetrakis (pentafluorophenyl) borate are preferred.
n-butylammonium, triphenylammonium tetrakis (pentafluorophenyl) borate, methylanilium tetrakis (pentafluorophenyl) borate, dimethylanilium tetrakis (pentafluorophenyl) borate, trimethylanilium tetrakis (pentafluorophenyl) borate, etc. No.

As the (B-3) Lewis acid, a boron atom-containing Lewis acid is preferable, and a compound represented by the following general formula can be used. BR ⁴ R ⁵ R ⁶ (wherein R ⁴ , R ⁵ and R ⁶ are each independently a phenyl group which may have a substituent such as a fluorine atom, a methyl group, a trifluorophenyl group, or Represents a fluorine atom.)

Specific examples of the compound represented by the above general formula include tri (n-butyl) boron, triphenylboron, and tris [3,5-bis (trifluoromethyl) phenyl].
Boron, tris [(4-fluoromethyl) phenyl] boron, tris (3,5-difluorophenyl) boron, tris (2,4,6-trifluorophenyl) boron, tris (pentafluorophenyl) boron and the like. And tris (pentafluorophenyl) boron are particularly preferred.

Here, the ratio of the transition metal compound (A) to the compound (B) is (B-1) as the compound (B).
When an aluminoxane is used, the Al atom in the (B-1) aluminoxane is 1 to 50,000 mol, preferably 10 to 30,000 mol, per 1 mol of the transition metal atom in the transition metal compound (A). Particularly preferably 50 to
The range is 20,000 mol.

The compound (B) may be a compound (B-
When the Lewis acid 2) or (B-3) is used, the compound (B-2) or (B-3) Lewis acid is used in an amount of 0.01 to 1 mol per transition metal atom in the transition metal compound (A). 2,
000 mol, preferably 0.1 to 500 mol.

Any one or more of the above compounds (B) can be used.

Further, as the organoaluminum compound which is the compound (C) optionally used as one component of the polymerization catalyst according to the present invention, a compound represented by the following general formula can be used. ^{_{AlR 7 t R 8 t 'X}} 3- (t + t') ( ^{wherein, R 7, R 8, R} 6 is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group, a hydrocarbon group such as an aryl group or An alkoxy group, X represents a halogen atom, and t and t 'each represent an arbitrary number of 0 <t + t' ≦ 3), and each independently represents a substituent such as a fluorine atom, a methyl group, and a trifluorophenyl group. And a phenyl group which may have a fluorine atom or a fluorine atom. )

Specific examples of the compound represented by the above general formula include trialkylaluminums such as trimethylaluminum, triethylaluminum, triisopropylaluminum, triisobutylaluminum, tri-n-butylaluminum, dimethylaluminum chloride, and dimethylaluminum. Bromide, diethylaluminum chloride, dialkylaluminum halide such as diisopropylaluminum chloride, methylaluminum sesquichloride, ethylaluminum sesquichloride, ethylaluminum sesquibromide,
Examples thereof include alkyl aluminum sesquihalides such as isopropyl aluminum sesquichloride, and one or more kinds thereof can be used.

Here, the amount of the organoaluminum compound used as the compound (C) is such that the Al atom in the (C) organoaluminum compound is 0 to 10 per mol of the transition metal atom in the transition metal compound (A). 000 mol, preferably 0
The range is 5,000 mol, particularly preferably 0 to 3,000 mol.

Compound (A) thus combined,
The polypropylene used for the biaxially stretched film of the present invention can be obtained by polymerizing propylene using the compound (B) and, if necessary, a specific catalyst comprising the compound (C). Propylene polymerization process can be used, aliphatic hydrocarbons such as butane, pentane, hexane, heptane, isooctane, alicyclic hydrocarbons such as cyclopentane, cyclohexane and methylcyclohexane, and aromatics such as toluene, xylene and ethylbenzene Slurry polymerization method to polymerize propylene in an inert solvent such as hydrocarbon, gasoline fraction or hydrogenated diesel oil fraction, bulk polymerization using propylene itself as a solvent, and propylene polymerization in gas phase Gas phase polymerization methods can be used.

In the polymerization of propylene, the above-mentioned specific catalyst may be prepared by mixing a compound (A), a compound (B), and a compound (C) in an inert solvent in advance and supplying the mixture to the polymerization reaction system. Alternatively, compound (A), compound (B) and compound (C) may be separately supplied to the polymerization reaction system. Furthermore, prior to the main polymerization of propylene, a small amount of an α-olefin, specifically a compound, is added to a catalyst obtained by combining the compound (A), the compound (B) and, if necessary, the compound (C) in an inert solvent. (A) Per mol of the transition metal in (A), about 1 g to 10 kg of an α-olefin are polymerized and reacted to obtain a pre-activated catalyst, and then the main polymerization of propylene can be carried out. It is effective to obtain and is within the scope of the present invention.

As the α-olefin which can be used for the above preactivation, an α-olefin having 2 to 12 carbon atoms is preferably used. Specifically, ethylene, propylene, butene, pentene, hexene, octene, 4-octene, Methyl-1-
Pentene, etc., particularly ethylene, propylene, 4
-Methyl-1-pentene is preferably used.

Thus, the prepared specific catalyst used in the present invention or the preactivated specific catalyst is prepared by converting the propylene or propylene with an α-olefin other than propylene having 2 to 12 carbon atoms by the polymerization method described above. The polymerization conditions for the propylene polymerization are the same as those for propylene polymerization using a known Ziegler catalyst. That is, the polymerization temperature is -50.
At a temperature of ~ 150 ° C, preferably -10-100 ° C,
The polymerization pressure is from atmospheric pressure to 7 MPa, preferably 0.2 MPa
In general, the reaction is carried out at 5 MPa in the presence of hydrogen for about 1 minute to 20 hours. The amount of hydrogen is suitably from 0.1 kPa to 5 MPa, preferably from 1 kPa to 3 MPa, as a hydrogen partial pressure in the gas phase in the polymerization vessel.

After completion of the polymerization of propylene, the polypropylene according to the present invention is obtained, if necessary, through known post-treatment steps such as a catalyst deactivation treatment step, a catalyst residue removal step, and a drying step. Must have the two requirements described below. Unless these requirements are satisfied, the object of the present invention cannot be achieved.

The requirement is that the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 1.5.
-3.8 and a melting point of 150-168 ° C.

The ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the above requirements is based on the measurement result of gel permeation chromatography (GPC) according to the following method. calculate.
That is, an o-dichlorobenzene solution having a polymer concentration of 0.05% by weight was used, and the column was a mixed polystyrene gel column (for example, PSKgel GMH6- manufactured by Tosoh Corporation).
HT) and measurement at 135 ° C. As the measuring device, for example, the ratio (Mw) of the above-mentioned weight average molecular weight (Mw) to the number average molecular weight (Mn) is used.
/ Mn) is a measure of the molecular weight distribution and the ratio (Mw / M
When n) is large, the molecular weight distribution is wide, and when n is small, the molecular weight distribution is narrow.

The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) in the present invention ranges from 1.5 to 3.8, preferably from 1.5 to 3.
5 When the ratio (Mw / Mn) exceeds 3.8, the resulting biaxially stretched film has reduced gloss and also has poor stretchability during molding. It is outside the scope of the present invention since it has not been obtained under conditions.

The melting point, which is another requirement, is determined by raising the temperature of the polypropylene from room temperature to 230 ° C. under a heating condition of 30 ° C./min using a DSC7 differential scanning calorimeter manufactured by Perkin Elmer. After holding at the same temperature for 10 minutes,
After the temperature was lowered to −20 ° C. at 20 ° C./min and maintained at the same temperature for 10 minutes, the temperature at which the peak at the time of melting was raised under the temperature increasing condition of 20 ° C./min was defined as the melting point.

The above range of the melting point in the present invention is 1
50-168 ° C, preferably 153-168 ° C,
Most preferably, it is 155 to 168 ° C. Melting point 150
When the temperature is lower than 0 ° C, the Young's modulus of the obtained biaxially stretched film is reduced, and the temperature exceeding 168 ° C is not obtained under ordinary polymerization conditions, and thus is out of the scope of the present invention.

The polypropylene thus obtained for use in the present invention may contain, if necessary, an antioxidant, an ultraviolet absorber, an antistatic agent, a nucleating agent, a lubricant, a flame retardant, an antiblocking agent, a coloring agent, an inorganic or organic material. After blending various additives such as fillers, and further various synthetic resins, the mixture was usually melted and kneaded at 190 to 350 ° C. for about 20 seconds to 30 minutes using a melt kneader, and further cut into granules. In a pellet state, it is provided as a biaxially stretched film molding material.

The biaxially stretched film of the present invention is obtained by a known biaxially stretched film production method using the specific polypropylene obtained by the above method. However, the object of the present invention cannot be achieved unless the physical properties of the obtained film satisfy the following two requirements. The requirements are that the gloss is 120% or more and the Young's modulus is 1900 N / mm ² or more.
Requirements.

The gloss to achieve the object of the present invention is 120%.
Above, particularly preferably 123% or more. The upper limit is not specified, but at present, it is substantially 140
About 160% is considered to be the limit of the present invention. In addition, the glossiness of the biaxially stretched film may be different between the front and back of the film depending on the manufacturing method, but the lower glossiness in the present invention means that the value is 120% or more. .

The Young's modulus for achieving the object of the present invention is 1
900 N / mm ² or more, particularly preferably 2,000 or more N
/ Mm ² or more. Although the upper limit is not particularly specified, at present, it is substantially 6000 to 7000 N / mm.
^{About 2} is considered the limit of the present invention. The Young's modulus of the biaxially stretched film may be different in the longitudinal (MD) and transverse (TD) directions of the film depending on the manufacturing method.
The lower value of the Young's modulus in the present invention is 1900 N /
mm ² or more. In the case of the present invention,
The Young's modulus is achieved by stretching at least four times in the longitudinal and transverse directions.

The glossiness of the biaxially stretched film, which is the above requirement, was measured according to the method described in ASTM D523. The Young's modulus of the biaxially stretched film, which is the above requirement, was measured in accordance with the method described in ASTM D882.

The biaxially stretched film of the present invention thus obtained may contain an antioxidant, an ultraviolet absorber, an antistatic agent, a nucleating agent, a lubricant, a flame retardant, an antiblocking agent, if necessary, as described above. Colorants, various additives such as inorganic or organic fillers, and further various synthetic resins may be compounded, but substantially using the specific catalyst used in the present invention described above propylene or propylene And a polypropylene having specific properties obtained by polymerizing α-olefin having 2 to 12 carbon atoms other than propylene.
The term "consisting essentially of" is used to mean that it contains the above-mentioned substances, which are added and blended as necessary, and at least 70% by weight or more, preferably 80% by weight or more in the molded article.
As described above, it is more preferable that the specific polypropylene used in the present invention, which satisfies the specific requirements, is obtained by the above-mentioned method at a ratio of 90% by weight or more.

[0049]

Next, the present invention will be described specifically with reference to examples. Definitions of terms used in Examples and Comparative Examples and measurement methods are as follows. (1) MFR: (Melt flow rate), JIS K7
210 Melt flowability of resin under condition 14 in Table 1. (Unit: g / 10 min) (2) Ratio of weight average molecular weight to number average molecular weight: (M
w / Mn), which was measured by the method described above. (3) Melting point: (Tm), measured by the method described above.
(Unit: ° C.) (4) Glossiness: Measured by the method described above. (unit:
%) (5) Young's modulus: measured by the method described above. (unit:
N / mm ² )

Example 1 (1) Production of Polypropylene A stainless steel polymerization vessel equipped with a stirrer blade and having an internal volume of 100 dm ^{3 and having} a stirrer was replaced with nitrogen gas. Then, 50 dm of n-hexane and toluene of methylaluminoxane were introduced into the polymerization vessel. Solution (manufactured by Tosoh Akzo, trade name: MMAO, concentration:
2 mol / dm ³ ) as 7.6 mmol in terms of Al atom,
Chiral dimethylsilylene (2,3,3)
5-trimethylcyclopentadienyl) (2 ′, 4 ′,
1.48 mmol of 5'-trimethylcyclopentadienyl) hafnium dichloride and dimethylsilylene (2,3,5-trimethylcyclopentadienyl) (2 ', 3', 5'-trimethylcyclopentadienyl) which is a meso form A mixture of 0.05 mmol of hafnium dichloride was added at 20 ° C. together with 1 dm ³ of toluene. Subsequently, the temperature in the polymerization vessel was set to 27 ° C., and hydrogen was supplied so that the hydrogen partial pressure in the gas phase portion in the polymerization vessel became 0.01 MPa. Then, the pressure in the polymerization vessel was maintained at 0.4 MPa. Propylene was continuously supplied into the polymerization vessel for 4 hours to polymerize propylene. During the polymerization, the temperature in the polymerization vessel was set at 27 ° C.
Kept. After the completion of the polymerization, unreacted propylene was discharged from the polymerization vessel, and then ³ dm ³ of 2-propanol was charged into the polymerization vessel and stirred at 30 ° C. for 10 minutes to deactivate the catalyst. Subsequently, an aqueous solution of hydrogen chloride (concentration: 12 mol / dm ³ )
0.2 dm ³ 0 and 8 dm ³ of methanol are added and 60
Treated at 30 ° C for 30 minutes. After the treatment, the stirring was stopped, the aqueous phase was removed from the lower part of the polymerization vessel, and the same operations were repeated by adding the same amount of aqueous hydrogen chloride solution and methanol. Then
Aqueous sodium hydroxide solution (concentration: 5 mol / dm ³ )
0.02 dm ³ , water 2 dm ³ , and methanol 2 dm
^{3 was} added and stirred at 30 ° C. for 10 minutes. After the treatment, the stirring was stopped and the aqueous phase was removed from the lower part of the polymerization vessel. Then, 8 dm ³ of water was further added, the mixture was stirred at 30 ° C. for 10 minutes, and the operation of removing the aqueous phase was repeated twice. The slurry was taken out of the polymerization vessel, filtered and dried to obtain 5.0 kg of polypropylene used in the present invention.

(2) Production of Biaxially Stretched Film Tetrakis [methylene-3- (3′-5′-di-tert-butyl-4′-hydroxyphenyl) propionate] methane was added to 100 parts by weight of the obtained polypropylene. 0.05 parts by weight and 0.07 parts by weight of calcium stearate are mixed,
The mixture was screwed with a screw diameter of 40 mm and an extrusion temperature of 230.
Polypropylene pellets were obtained using a single-screw extrusion granulator set to ° C. The polypropylene pellet was extruded at 250 ° C. using a T-die type film forming machine having a screw diameter of 40 mm, and a 820 μm thick sheet was formed with a cooling roll at 25 ° C. Subsequently, the obtained sheet was heated at 158 ° C for 9 hours.
Heated for 0 seconds and stretched at a stretching speed of 5 using a batch-type biaxial stretching machine.
The film was stretched 4.2 times in the machine direction and 8.2 times in the transverse direction at m / min to obtain a biaxially stretched film having a thickness of 23 μm. Table 1 shows the evaluation results of the films measured according to the method described above.

Comparative Example 1 (1) Production of Polypropylene In Example 1 (1), the catalyst was replaced by metallocene and methylaluminoxane, and
The magnesium chloride-supported titanium catalyst component obtained by the same method as in Example 1 in JP-A No. 2 is 3.3 in terms of Ti.
mmol, 100 mmol of triethylaluminum,
And a catalyst obtained by combining 10 mmol of diisopropyldimethoxysilane as the third component of the catalyst. The hydrogen partial pressure before the start of polymerization was 0.02 MPa, and the polymerization temperature was 70.
Propylene was polymerized in the same manner except that the temperature was changed to ° C to obtain polypropylene.

(2) Production of Biaxially Stretched Film A biaxially stretched film was obtained from the polypropylene obtained in (1) in the same manner as in (2) of Example 1 and evaluated.

COMPARATIVE EXAMPLE 2 (1) Production of Polypropylene In Comparative Example 1, (1), the hydrogen pressure was set to 0.002MP.
A polypropylene was obtained in the same manner except that a was used.

(2) Production of Biaxially Stretched Film Tetrakis [methylene-3- (3′-5′-di-tert-butyl-4′-hydroxyphenyl) propionate] methane was added to 100 parts by weight of the obtained polypropylene. 0.05 parts by weight, 0.07 parts by weight of calcium stearate, and 0.05 parts by weight t of 1,3-bis- (t-butylperoxy-isopropyl) benzene, which is an organic peroxide, are mixed. With a screw diameter of 40 mm and an extrusion temperature of 2
Polypropylene pellets were obtained using a single-screw extrusion granulator set at 30 ° C. For the polypropylene pellets, a biaxially stretched film was obtained in the same manner as in (2) of Example 1, and the film was evaluated.

Comparative Example 3 (1) Production of Polypropylene In Example (1) of Example 1, 1.32 mmol of chiral rac-ethylenebis (indenyl) hafnium dichloride as metallocene and meso-ethylenebis (indenyl) hafnium meso-form were used. Dichloride 0.1
Propylene polymerization and post-treatment were performed in the same manner except that a 5 mmol mixture was used, and the hydrogen partial pressure before the start of polymerization was set to 0.04 MPa, to obtain polypropylene.

(2) Production of Biaxially Stretched Film A polypropylene pellet was obtained from the obtained polypropylene in the same manner as in (1) of Example 1, and then a biaxially oriented film was produced and evaluated. Physical properties of the obtained polypropylene were measured in the same manner as in Example 1.
When a biaxially stretched film was produced in the same manner as in Example 3, the sheet was sagged downward in the heating step of the sheet, so that stretching was impossible and the film could not be formed.

Example 2 (1) Production of Polypropylene A stainless steel polymerization apparatus equipped with a stirrer blade and having an inner volume of 100 dm ^{3 and having} a stirrer was replaced with nitrogen gas, and then a toluene solution of methylaluminoxane (trade name: manufactured by Tosoh Akzo Co., Ltd.)
MMAO, concentration: 2 mol / dm ³ ) was 11 mol in terms of Al atom, and the hydrogen partial pressure in the polymerization vessel was 0.2 at 20 ° C.
Hydrogen was charged into the polymerization reactor so that the pressure became 03 MPa, and then 30 kg of liquefied propylene was supplied. Then, a toluene solution of methylaluminoxane (trade name: M, manufactured by Tosoh Akzo Co., Ltd.)
MAO, concentration: 2 mol / dm ³ ) in terms of Al atom
1 mol, chiral dimethylsilylene as metallocene (2,3,5-trimethylcyclopentadienyl)
(2 ′, 4 ′, 5′-trimethylcyclopentadienyl) zirconium dichloride (0.033 mmol) and meso-form dimethylsilylene (2,3,5-trimethylcyclopentadienyl) (2 ′, 3 ′, 5 ′) A mixture of 0.002 mmol of -trimethylcyclopentadienyl) zirconium dichloride was injected into the polymerization vessel together with 0.1 dm ³ of toluene at 20 ° C. by pressurizing with nitrogen to start polymerization of propylene. During the polymerization, ethylene was continuously fed into the polymerization vessel at 4 g / Hr, and the temperature in the polymerization vessel was kept at 30 g / Hr.
C. After 4 hours from the start of the polymerization, ³ dm ³ of 2-propanol was injected into the polymerization vessel to terminate the polymerization at 30 ° C. for 5 minutes, and then unreacted propylene was discharged from the polymerization vessel to the outside of the system. Subsequently, 50 dm ³ of n-hexane was charged into the polymerization vessel, and thereafter, the same post-treatment as in (1) of Example 1 was performed to obtain a polypropylene containing 0.2% by weight of ethylene polymerization units.

(2) Production of Biaxially Stretched Film A polypropylene pellet was obtained from the obtained polypropylene in the same manner as in (1) of Example 1, and then a biaxially oriented film was produced and evaluated.

Examples 1 and 2 and Comparative Examples 1 to 3
Table 1 shows the physical properties of polypropylene and the evaluation results of the biaxially stretched film.

[0061]

[Table 1]

[0062]

As is clear from the above-described embodiment,
The biaxially stretched film of the present invention is excellent in gloss and rigidity, and has a performance not available in a biaxially stretched film made of polypropylene obtained by a conventional method. It is possible to use a stretched film.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI B29L 7:00 C08L 23:00 (56) References JP-A-4-211694 (JP, A) JP-A-6-239915 (JP) JP-A-2-139220 (JP, A) JP-A-60-76515 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 5/18 C08F 4/642 C08F 10/06 B29C 55/12

Claims (1)

(57) [Claims] 1. Polymerization of propylene or propylene and a compound having 2 carbon atoms by using a catalyst comprising the following compounds (A) and (B) or the following compounds (A), (B) and (C):
And a number average molecular weight (Mw) of weight average molecular weight (Mw) obtained by copolymerizing α-olefins other than propylene
n) consisting essentially of isotactic polypropylene having a ratio (Mw / Mn) of 1.5 to 3.8 and a melting point of 150 to 168 ° C., a gloss of at least 120% and a Young's modulus of 1900 N / mm. Less than ²
A biaxially stretched film stretched at least four times in the machine and transverse directions . Compound (A): general formula _{Q (C 5 H 4-m} R 1 m) (C 5 H 4-n R
² _n ) a transition metal compound represented by MXY [wherein (C ₅ H)
_4-m R ¹ m) and _{(C 5 H 4-n R} 2 n) represent a substituted cyclopentadienyl group, m and n are an integer of 1 to 3.
R ¹ and R ² are each a hydrocarbon group having 1 to 20 carbon atoms, a silicon-containing hydrocarbon group, or one which may be substituted with a hydrocarbon by bonding to two carbon atoms on a cyclopentadienyl ring. The hydrocarbon groups forming the above hydrocarbon rings (only
And substitutes for branched C ₄ -C ₁₀ alkyl and C ₁ -C ₆ alkyl
5- to 7-membered cycloalkyl which may be possessed as a base
Excluding C ₆ -C ₁₅ aryl or arylalkyl.
And may be the same or different. Q is a divalent hydrocarbon group, an unsubstituted silylene group or a hydrocarbon-substituted silylene group, each of which crosslinks (C ₅ H _4-m R ¹ _m ) and (C ₅ H _4-n R ² _n ). is there. M represents a transition metal that is titanium, zirconium or hafnium, and X and Y may be the same or different and represent a hydrogen, halogen or hydrocarbon group. Compound (B): (B-1) aluminoxane, (B-2)
An ionic compound which forms an ionic complex by reacting with the transition metal compound (A), and (B-3) one or more compounds selected from Lewis acids Compound (C): an organoaluminum compound