JP6614013B2 - Biaxially stretched multilayer film - Google Patents

Description

  The present invention relates to a polypropylene film having excellent gas permeability. More specifically, oxygen and carbon dioxide gas are suitably permeated and have excellent flexibility, transparency, transparency, glossiness, low elongation, good handleability, and low molecular weight components. The present invention relates to a polypropylene film having a good blocking property because of less stickiness.

Conventionally, when a polypropylene film is used as a packaging material, since the gas permeability is not sufficient, the polypropylene film has been perforated to impart gas permeability (Patent Document 1). However, in such a perforated film, contaminants may enter from the outside through the holes.
Then, the polypropylene-type film which permeate | transmits water vapor | steam, oxygen, and ethylene suitably without making a hole and the packaging material using the same are shown (patent document 2, 3, 4). However, the polypropylene-based films obtained in these documents are manufactured using Ziegler catalysts, and since there are many low molecular weight components, the low molecular weight components migrate to the surface over time, and the product is processed. They were not satisfied with the deterioration of blocking properties under long-term storage, transparency, and transparency.
Patent Documents 5 and 6 disclose a gas permeable film excellent in transparency and gas permeability, which is a gas permeable film containing a polypropylene copolymer and suitable for freshness-keeping packaging of fruits and vegetables and flowers. However, ethylene-octene resin is essential, and the composition differs from that of the present invention.
Patent Documents 7 and 8 are propylene resin compositions for packaging materials having specific properties, and are composed of propylene resin compositions for packaging materials excellent in rigidity, transparency, impact resistance, and blocking resistance. Although a film has been presented, the film uses an unstretched film, and has the disadvantages that the film itself is easy to stretch and handling properties are poor.

JP 2012-144278 A International Publication No. 99/051665 JP 2002-302580 A JP 2001-354784 A JP 2008-133350 A JP 2006-299229 A JP 2009-185238 A JP 2009-7457 A

The conventional polypropylene-based stretched flexible film still has transparency, transparency, gloss, flexibility, heat resistance, high gas permeability, and low elongation properties, yet still satisfies all of the anti-blocking performance. It has not been.
Therefore, the object of the present invention is to have flexibility while maintaining the characteristics of a polypropylene-based resin that is excellent in film appearance such as transparency, transparency, and glossiness and has high heat resistance, and further has gas permeability. Polypropylene-based biaxially-stretched flexible film that is a polypropylene-based film that suitably permeates oxygen and carbon dioxide, has excellent low elongation properties, has little stickiness and bleed-out, has good blocking resistance, and is easy to handle Is to develop.

Conventionally, in order to improve gas permeability, it has been known to incorporate a low molecular weight component. This is because by blending a low molecular weight component, gas can permeate through the low crystal part, and a film having excellent gas permeability tends to be obtained, and the flexibility tends to be improved. However, when such a low molecular weight component is blended in this way, stickiness occurs due to surface bleeding of the low molecular weight component over time, and transparency and blocking properties deteriorate. Further, the more flexible the film is, the higher the elongation becomes, and the secondary workability and handling properties deteriorate.
Therefore, as a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that a film produced using a propylene random copolymer having a specific composition is transparent, transparent, glossy, gas It has permeability, and more specifically, it has been found that the oxygen and carbon dioxide gas is suitably permeated and has excellent flexibility, while the low blocking property and the handling property by low elongation are improved. It came to complete.

That is, according to the first invention of the present invention, the laminated film composed of the upper layer (X) / intermediate layer (Y) / lower layer (Z) satisfies the following requirements (a) to (d). A featured biaxially oriented multilayer film is provided.
(I) The intermediate layer (Y) is composed of the following metallocene propylene-ethylene random copolymer (A1) 8 to 60% by weight, metallocene propylene-ethylene random copolymer (A2) 16 to 80% by weight, and propylene homopolymer. It is comprised from the propylene-type resin composition (C) which consists of 100 weight% of combined (B) 0-60 weight% in total.
(A1): Metallocene propylene-ethylene random copolymer having an ethylene content of 1.5 to 3% by weight.
(A2): A metallocene propylene-ethylene random copolymer containing 8 to 10% more ethylene than (A1).
(B): A propylene homopolymer having a melt flow rate (MFR: 2.16 kg load, 230 ° C.) in the range of 1 to 10 g / 10 min.
(B) The upper layer (X) and the lower layer (Z) are each independently a propylene having a melting point (Tp) determined by a differential scanning calorimeter (DSC) in accordance with JIS K 7122 (1987) of 135 ° C. or less. -It is comprised from an alpha olefin random copolymer (D).
(C) The oxygen permeability of the laminated film is 3000 to 8000 cc / m ² · 24 Hr · atm (based on JIS K 7126-A).
(D) Carbon dioxide gas permeability of the laminated film is 8000 to 40000 cc / m ² · 24 Hr · atm (based on JIS K 7126-A).

  Moreover, according to the second invention of the present invention, in the first invention, the transparency (Haze) of the laminated film measured in accordance with JIS K7105 (1981) is 5% or less. A biaxially oriented multilayer film is provided.

  Furthermore, according to the third invention of the present invention, in the first invention, the tensile elastic modulus of the laminated film measured according to JIS K7127 (1999) is 200 to 1200 MPa in the machine direction (MD), A biaxially stretched multilayer film is provided, characterized in that the direction (TD) is 400 to 2000 MPa.

  Furthermore, according to the fourth invention of the present invention, in the first invention, the tensile breaking elongation of the laminated film measured according to JIS K7127 (1999) is 150% or less in the transverse direction (TD). There is provided a biaxially oriented multilayer film characterized in that

  Furthermore, according to the fifth invention of the present invention, in the first invention, the blocking resistance of the laminated film after 7 days after 40 ° C. measured according to ASTM D-1893 is 6N or less. A biaxially stretched multilayer film is provided.

  Furthermore, according to the fifth aspect of the present invention, in the first aspect, the propylene-α-olefin random copolymer (D) is a propylene-ethylene random copolymer, propylene-ethylene-1-butene random. A biaxially stretched multilayer film comprising a copolymer or a mixture obtained by mixing them in an arbitrary ratio is provided.

The biaxially stretched multilayer film in the present invention has flexibility while maintaining the characteristics of a polypropylene-based resin that is excellent in film appearance such as transparency, transparency, and gloss, and has high heat resistance, and has low elongation characteristics. More specifically, it has the advantage of improved handling due to less adhesion due to stickiness and bleed-out while suitably transmitting oxygen and carbon dioxide gas and having excellent flexibility. Have
In the conventional film, when the blocking strength is large or the elongation is large, the mill roll tends to wrinkle when the product film is wound, or the films stick to each other at the time of use and tend to be unwound well. However, the biaxially stretched multilayer film of the present invention has a roughened surface, and since it is a metallocene polypropylene, there are few low molecular weight components, so there are few low molecular weight components that migrate to the surface over time. Blocking that occurs when superposed can be suppressed, and stable processability at the time of film formation and the rolled form of the product can be improved.
Furthermore, the biaxially stretched multilayer film of the present invention is a biaxially stretched multilayer film that does not require drilling as in the case of conventional films, and has the characteristics that it is flexible but has low elongation. When compared with a stretchable film such as a stretched film, the handleability is good and the film is rich in secondary workability in the subsequent process.
In addition, the low molecular weight component blended to give high gas permeability is a metallocene polypropylene, so there is no component that hinders transparency, and there are few components that migrate to the surface. It has blocking resistance while having properties and gloss.

As described above, the biaxially stretched multilayer film of the present invention satisfies the following requirements (a) to (d) in the laminated film composed of the upper layer (X) / intermediate layer (Y) / lower layer (Z). This is a biaxially stretched multilayer film.
(I) The intermediate layer (Y) is composed of the following metallocene propylene-ethylene random copolymer (A1) 8 to 60% by weight, metallocene propylene-ethylene random copolymer (A2) 16 to 80% by weight, and propylene homopolymer. It is comprised from the propylene-type resin composition (C) which consists of 100 weight% of combined (B) 0-60 weight% in total.
(A1): Metallocene propylene-ethylene random copolymer having an ethylene content of 1.5 to 3% by weight.
(A2): A metallocene propylene-ethylene random copolymer containing 8 to 10% more ethylene than (A1).
(B): A propylene homopolymer having a melt flow rate (MFR: 2.16 kg load, 230 ° C.) in the range of 1 to 10 g / 10 min.
(B) The upper layer (X) and the lower layer (Z) are each independently a propylene having a melting point (Tp) determined by a differential scanning calorimeter (DSC) in accordance with JIS K 7122 (1987) of 135 ° C. or less. -It is comprised from an alpha olefin random copolymer (D).
(C) The oxygen permeability of the laminated film is 3000 to 8000 cc / m ² · 24 Hr · atm (based on JIS K 7126-A).
(D) Carbon dioxide gas permeability of the laminated film is 8000 to 40000 cc / m ² · 24 Hr · atm (based on JIS K 7126-A).

  Hereinafter, the constituent components, the characteristics of the laminated film, the production method and the like will be described in detail.

1. Constituent Component of Intermediate Layer (Y) The intermediate layer (Y) constituting the biaxially stretched multilayer film of the present invention is composed of a propylene-based resin composition (C). The propylene resin composition (C) is composed of the following metallocene propylene-ethylene random copolymer (A1) 8 to 60% by weight, metallocene propylene-ethylene random copolymer (A2) 16 to 80% by weight, and Propylene homopolymer (B) consists of 0 to 60% by weight and 100% by weight in total. Here, the propylene homopolymer (B) is a propylene homopolymer having (B): melt flow rate (MFR: 2.16 kg load, 230 ° C.) in the range of 1 to 10 g / 10 min, preferably 2 It is -8g / 10min, More preferably, it is 3-6g / 10min.

Preferred examples of the biaxially stretched multilayer relating to the requirement (a) above regarding the constitution of the intermediate layer (Y) include the following.
The metallocene propylene-ethylene random copolymer (A1) is 8 to 60% by weight, preferably 8 to 40% by weight, and more preferably 8 to 32% by weight. If (A1) is 8% by weight or more, the gas permeability is lowered, but the handling property and blocking property are improved without becoming too flexible, and the practicality is improved. Moreover, if it is 40 weight% or less, crystallinity will fall and desired gas permeability will be acquired. Further, the metallocene propylene-ethylene random copolymer (A2) is 16 to 80% by weight, preferably 20 to 80% by weight, and more preferably 40 to 80% by weight.
When (A2) is 16% by weight or more, the low crystal component increases and the crystallinity decreases, so that desired gas permeability is obtained, and in addition, transparency and transparency are improved. Moreover, if it is 80 weight% or less, handling property and blocking property will become favorable without becoming too flexible, and practicality will improve.
Although it is 0 to 60 weight% of propylene homopolymer (B), Preferably it is 0 to 40 weight%, More preferably, it is 0 to 20 weight%. If a propylene homopolymer (B) is 60 weight% or less, a low crystal component will increase and transparency and gas permeability will improve.

(A1) is a metallocene propylene-ethylene random copolymer having an ethylene content of 1.5 to 3% by weight, preferably 1.5 to 2.5% by weight, more preferably 1.5 to 2%. % By weight. When the ethylene content of the propylene-ethylene random copolymer (A1) is 1.5% by weight or more, the crystallinity of the film is lowered and the gas permeability is improved. Further, if the ethylene content of the propylene-ethylene random copolymer (A1) is 3% by weight or less, the melting point rises, so it is necessary to set the temperature in the transverse stretching furnace high, and propylene laminated on both surface layers. -Since the melting point difference with the ethylene random copolymer (D) is small, the laminated propylene-ethylene random copolymer (D) is melted and stretched in a liquid phase, and thus uneven stretching occurs. The appearance of the film is improved.

(A2) is a metallocene propylene-ethylene random copolymer containing 8 to 10% more ethylene than (A1), and preferably contains 9 to 10% more ethylene. Moreover, if the ethylene component of the propylene-ethylene random copolymer (A2) contains 8% by weight or more of ethylene than (A1), the crystallinity in the film constituent component is lowered, and thus the gas permeability is reduced. improves. If the ethylene component of the propylene-ethylene random copolymer (A2) contains 10% by weight or less of ethylene from (A1), the compatibility with the polypropylene matrix is improved, and the transparency is improved.

The metallocene propylene-ethylene random copolymer in the intermediate layer (Y) can be obtained by successively polymerizing the components (A1) and (A2) by sequential polymerization.
In addition, as a method of continuously polymerizing the component (A1) and the component (A2) by multistage polymerization, a plurality of polymerization vessels are used, for example, the component (A1) is produced in the first stage, and the two stages. An example of the method for producing the component (A2) with the eyes is illustrated. This continuous polymerization method is preferable compared to the melt mixing method in that a metallocene propylene-ethylene random copolymer in which the component (A2) is uniformly dispersed in the component (A1) is obtained, and the quality can be stabilized. The method for continuously polymerizing by the multistage polymerization method is not particularly limited, and a known method can be adopted.
Below, the method to manufacture a preferable metallocene propylene-ethylene random copolymer is demonstrated.

(1) Production of metallocene propylene-ethylene random copolymer (A) in intermediate layer (Y) Metallocene propylene-ethylene random copolymer (A1) and (A2) in intermediate layer (Y) of the present invention The method for producing these together may be referred to as “propylene-ethylene random copolymer (A)”) requires the use of a metallocene catalyst. It is well known to those skilled in the art that stickiness and bleedout deteriorate when the molecular weight and crystallinity distribution are wide in the propylene-ethylene random copolymer, but also in the propylene-ethylene random copolymer used in the present invention, In order to suppress stickiness and bleed-out, and to achieve less fisheye in film forming, it is necessary to polymerize using a metallocene catalyst that can narrow the molecular weight and crystallinity distribution. -It is clear from the comparison between Examples and Comparative Examples described later that an excellent propylene-ethylene random copolymer used in the present invention cannot be obtained with a Natta-based catalyst.

Here, the type of the metallocene-based catalyst is not particularly limited as long as it can produce a copolymer having the above-mentioned performance. However, in order to satisfy the requirements of the present invention, for example, the following components It is preferable to use a metallocene catalyst composed of (x) and (y) and, if necessary, the component (z) used.
Component (x): At least one metallocene transition metal compound selected from transition metal compounds represented by the following general formula (1) Component (y): At least selected from the following (y-1) to (y-4) 1 type of solid component (y-1) particulate carrier on which an organoaluminoxy compound is supported (y-2) an ionic compound capable of reacting with component (x) to convert component (x) into a cation Or a particulate carrier on which a Lewis acid is supported (y-3) a solid acid particulate (y-4) an ion-exchange layered silicate component (z): an organoaluminum compound

Ingredient (x):
As the component (x), at least one metallocene transition metal compound selected from transition metal compounds represented by the following general formula (1) can be used.
^{_{Q (C 5 H 4-a}} -aR 1) (C 5 H 4-b -bR 2) MeXY ... (1)
[Wherein Q represents a divalent linking group that bridges two conjugated five-membered ring ligands, Me represents a metal atom selected from titanium, zirconium, or hafnium, and X and Y represent Independently, that is, they may be the same or different and each represents a hydrogen atom, a halogen atom, a hydrocarbon group, an alkoxy group, an amino group, a nitrogen-containing hydrocarbon group, a phosphorus-containing hydrocarbon group or a silicon-containing hydrocarbon group. R ¹ and R ² are a hydrogen atom, a hydrocarbon group, a halogenated hydrocarbon group, a silicon-containing hydrocarbon group, a nitrogen-containing hydrocarbon group, an oxygen-containing hydrocarbon group, a boron-containing hydrocarbon group, or a phosphorus-containing hydrocarbon group. Show. a and b are the number of substituents. ]

Specifically, Q represents a divalent linking group that bridges two conjugated five-membered ring ligands. For example, a divalent hydrocarbon group, a silylene group, an oligosilylene group, or a hydrocarbon group as a substituent. Examples thereof include a germylene group having a silylene group, an oligosilylene group or a hydrocarbon group as a substituent. Among these, preferred is a silylene group having a divalent hydrocarbon group and a hydrocarbon group as a substituent.
X and Y represent a hydrogen atom, a halogen atom, a hydrocarbon group, an alkoxy group, an amino group, a nitrogen-containing hydrocarbon group, a phosphorus-containing hydrocarbon group, or a silicon-containing hydrocarbon group. Among these, hydrogen is preferable Atoms, chlorine atoms, methyl, isobutyl, phenyl, dimethylamide, diethylamide groups and the like can be exemplified. X and Y may be independent, that is, may be the same or different.
R ¹ and R ² are a hydrogen atom, a hydrocarbon group, a halogenated hydrocarbon group, a silicon-containing hydrocarbon group, a nitrogen-containing hydrocarbon group, an oxygen-containing hydrocarbon group, a boron-containing hydrocarbon group, or a phosphorus-containing hydrocarbon group. Represent. Specific examples of the hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a phenyl group, a naphthyl group, a butenyl group, and a butadienyl group. In addition, halogenated hydrocarbon group, silicon-containing hydrocarbon group, nitrogen-containing hydrocarbon group, oxygen-containing hydrocarbon group, boron-containing hydrocarbon group or phosphorus-containing hydrocarbon group include methoxy group, ethoxy group, phenoxy group, trimethylsilyl group. Typical examples include a group, a diethylamino group, a diphenylamino group, a pyrazolyl group, an indolyl group, a dimethylphosphino group, a diphenylphosphino group, a diphenylboron group, and a dimethoxyboron group. In these, it is preferable that it is a C1-C20 hydrocarbon group, and it is especially preferable that they are a methyl group, an ethyl group, a propyl group, and a butyl group. By the way, adjacent R ¹ and R ² may combine to form a ring, on which a hydrocarbon group, halogenated hydrocarbon group, silicon-containing hydrocarbon group, nitrogen-containing hydrocarbon group, oxygen-containing You may have a substituent which consists of a hydrocarbon group, a boron containing hydrocarbon group, or a phosphorus containing hydrocarbon group.
Me is a metal atom selected from titanium, zirconium or hafnium, preferably zirconium or hafnium.

  Among the components (x) described above, the propylene-ethylene random copolymer (A) used in the present invention is preferably crosslinked with a silylene group, a germylene group or an alkylene group having a hydrocarbon substituent. A transition metal compound comprising a ligand having a substituted cyclopentadienyl group, a substituted indenyl group, a substituted fluorenyl group, a substituted azulenyl group, particularly preferably a silylene group having a hydrocarbon substituent or a germylene group. It is a transition metal compound comprising a ligand having a bridged 2,4-position substituted indenyl group and 2,4-position substituted azulenyl group.

Non-limiting specific examples include dimethylsilylene bis (2-methyl-4-phenylindenyl) zirconium dichloride, diphenylsilylene bis (2-methyl-4-phenylindenyl) zirconium dichloride, dimethylsilylene bis (2-methyl). Benzoindenyl) zirconium dichloride, dimethylsilylenebis {2-isopropyl-4- (3,5-diisopropylphenyl) indenyl} zirconium dichloride, dimethylsilylenebis (2-propyl-4-phenanthrylindenyl) zirconium dichloride, dimethyl Silylene bis (2-methyl-4-phenylazurenyl) zirconium dichloride, dimethylsilylene bis {2-methyl-4- (4-chlorophenyl) azurenyl} zirconium dichloride, dimethylsilylene bi (2-Ethyl-4-phenylazurenyl) zirconium dichloride, dimethylsilylenebis (2-isopropyl-4-phenylazurenyl) zirconium dichloride, dimethylsilylenebis {2-ethyl-4- (2-fluorobiphenyl) azurenyl} zirconium Dichloride, dimethylsilylenebis {2-ethyl-4- (4-t-butyl-3-chlorophenyl) azurenyl} zirconium dichloride, and the like can be given.
A compound in which the silylene group of the compounds of these specific examples is replaced with a germylene group and zirconium is replaced with hafnium is also exemplified as a suitable compound. In addition, since the catalyst component is not an important element of the present invention, it avoids complicated listing and is limited to a representative example, but it is obvious that the effective range of the present invention is not limited thereby. That is.

Ingredient (y):
As the component (y), at least one solid component selected from the components (y-1) to (y-4) described above is used. Each of these components is a known component, and can be appropriately selected from known technologies and used. Specific examples and manufacturing methods thereof are described in detail in JP-A No. 2002-284808, JP-A No. 2002-53609, JP-A No. 2002-69116, JP-A No. 2003-105015, and the like.
Here, as the particulate carrier used for the component (y-1) and the component (y-2), inorganic oxides such as silica, alumina, magnesia, silica alumina, silica magnesia, magnesium chloride, magnesium oxychloride, chloride Examples thereof include inorganic halides such as aluminum and lanthanum chloride, and porous organic carriers such as polypropylene, polyethylene, polystyrene, styrene divinyl benzene copolymer, and acrylic acid copolymer.

Further, as a non-limiting specific example of the component (y), as the component (y-1), a fine particle carrier on which methylalumoxane, isobutylalumoxane, methylisobutylalumoxane, aluminum butylboronate tetraisobutyl, etc. are supported As component (y-2), triphenylborane, tris (3,5-difluorophenyl) borane, tris (pentafluorophenyl) borane, triphenylcarbonium tetrakis (pentafluorophenyl) borate, N, N-dimethyl Particulate carrier carrying anilinium tetrakis (pentafluorophenyl) borate, etc. as component (y-3), alumina, silica alumina, magnesium chloride, etc. as component (y-4), montmorillonite, zakonite, beidellite , Nontronic , Saponite, hectorite, stevensite, bentonite, smectite group such as taeniolite, vermiculite, and the like mica group. These may form a mixed layer.
Particularly preferred among the above components (y) is the ion-exchange layered silicate of component (y-4), and more preferred are chemical treatments such as acid treatment, alkali treatment, salt treatment, and organic matter treatment. It is an ion exchange layered silicate applied.

Component (z):
Examples of organoaluminum compounds used as component (z) as needed include trialkylaluminum such as trimethylaluminum, triethylaluminum, tripropylaluminum, triisobutylaluminum represented by the following general formula or diethylaluminum monochloride, diethylaluminum Halogen or alkoxy-containing alkylaluminum such as monomethoxide. In addition, aluminoxanes such as methylaluminoxane can also be used. Of these, trialkylaluminum is particularly preferred.
AlR _a X _3-a
(In the formula, R represents a hydrocarbon group having 1 to 20 carbon atoms, X is a hydrogen atom, a halogen or an alkoxy group, and a is a number of 0 <a ≦ 3.)

The catalyst is formed by bringing the component (x), the component (y) and, if necessary, the component (z) into contact with each other. Although the contact method is not specifically limited, Contact can be made in the following order. Moreover, this contact may be performed not only at the time of catalyst preparation but also at the time of prepolymerization with olefin or at the time of polymerization of olefin.
(I) The component (x) is contacted with the component (y).
(Ii) After contacting the component (x) and the component (y), the component (z) is added.
(Iii) Component (x) and component (z) are contacted, and then component (y) is added.
(Iv) Component (x) is added after contacting component (y) and component (z).
(V) contacting the three components simultaneously.

The amount of components (x), (y) and (z) used in the present invention is arbitrary. For example, the amount of component (x) used relative to component (y) is preferably in the range of 0.1 to 1,000 μmol, particularly preferably 0.5 to 500 μmol, relative to 1 g of component (y). The amount of component (z) used relative to component (y) is preferably such that the amount of transition metal is 0.001 to 100 μmol, particularly preferably 0.005 to 50 μmol, relative to 1 g of component (z). Therefore, the amount of the component (z) to the component (x) is preferably in the range of 10 ⁻⁵ to 50, particularly preferably 10 ^{−4 to} 5 in terms of the molar ratio of the transition metal.

The catalyst used in the present invention is preferably subjected to a prepolymerization treatment consisting of a small amount of polymerization by contacting an olefin in advance. The olefin to be used is not particularly limited, but ethylene, propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-butene, vinylcycloalkane, styrene and the like can be used. It is possible to use, and it is particularly preferable to use propylene. The olefin can be supplied by any method, such as a supply method for maintaining the olefin at a constant speed or in a constant pressure state, a combination thereof, or a stepwise change. The prepolymerization temperature and time are not particularly limited, but are preferably in the range of −20 ° C. to 100 ° C. and 5 minutes to 24 hours, respectively. The amount of prepolymerization is preferably 0.01 to 100, more preferably 0.1 to 50 with respect to the component (y). After completion of the prepolymerization, the catalyst can be used as it is, depending on the usage form of the catalyst, but may be dried if necessary.
Further, a polymer such as polyethylene, polypropylene or polystyrene, or an inorganic oxide solid such as silica or titania can be allowed to coexist during or after the contact of the above components.

In the production of the propylene-ethylene random copolymer (A) used in the present invention, a crystalline propylene-ethylene random copolymer component (A1) and a low crystalline or amorphous propylene- Although it is a preferred embodiment that the ethylene random copolymer component (A2) is sequentially polymerized, it is not limited to these, and a melt mixing method by melt-mixing the component (A1) and the component (A2) individually polymerized may be used. .
When the propylene-ethylene random copolymer is a random copolymer obtained by simply copolymerizing ethylene with propylene, if the ethylene content is low, the flexibility and impact resistance are not sufficient, so that these physical properties can be improved. When the ethylene content is increased, the heat resistance is extremely deteriorated and the production may be difficult, and it is difficult to satisfy all the required qualities.
Therefore, in the present invention, the propylene-ethylene random copolymer (A) is a random copolymer obtained by sequentially polymerizing components having different ethylene contents in the first step and the second step, thereby balancing flexibility and heat resistance. Therefore, this is a preferred embodiment.
Further, in the present invention, since a copolymer having a low molecular weight and easily sticking alone may be used as the component (A2), the component (A1) was polymerized in order to prevent problems such as adhesion to the reactor. It is desirable to use a method of polymerizing component (A2) later.

(I) Sequential Polymerization When the propylene-ethylene random copolymer (A) used in the present invention is produced, the crystalline propylene-ethylene random copolymer component (A1) and the low crystalline or amorphous propylene- Sequential polymerization of the ethylene random copolymer component (A2) is a preferred embodiment for the reasons described above.
When performing sequential polymerization, either a batch method or a continuous method can be used, but it is generally desirable to use a continuous method from the viewpoint of productivity.
In the case of the batch method, it is possible to polymerize the component (A1) and the component (A2) individually using a single reactor by changing the polymerization conditions with time. As long as the effects of the present invention are not impaired, a plurality of reactors may be connected in parallel.
In the case of the continuous method, it is necessary to use a production facility in which two or more reactors are connected in series because it is necessary to individually polymerize the component (A1) and the component (A2), but the effect of the present invention is not impaired. As long as each of the component (A1) and the component (A2) is used, a plurality of reactors may be connected in series and / or in parallel.

(Ii) Polymerization process As the polymerization process (polymerization method), any polymerization method such as a slurry method, a bulk method, and a gas phase method can be used. Although supercritical conditions can be used as intermediate conditions between the bulk method and the gas phase method, they are substantially the same as the gas phase method, and are therefore included in the gas phase method without particular distinction.
Since the low crystalline or amorphous propylene-ethylene random copolymer component (A2) is easily soluble in organic solvents such as hydrocarbons and liquefied propylene, it is desirable to use a gas phase method for the production of the component (A2). .
For the production of the crystalline propylene-ethylene random copolymer component (A1), there is no particular problem even if any process is used, but in the case of producing the component (A1) having relatively low crystallinity, the adhesion In order to avoid such problems, it is desirable to use a gas phase method.
Therefore, using a continuous method, first, the crystalline propylene-ethylene random copolymer component (A1) is polymerized by the bulk method or the gas phase method, and subsequently the low crystalline or amorphous propylene-ethylene random copolymer elastomer. It is most desirable to polymerize component (A2) by a gas phase method.

(Iii) Other polymerization conditions The polymerization temperature can be used without any particular problem as long as it is within a commonly used temperature range. Specifically, a range of 0 ° C. to 200 ° C., more preferably 40 ° C. to 100 ° C. can be used. Further, the polymerization pressure varies depending on the process to be selected, but can be used without any problem as long as it is in a pressure range which is usually used. Specifically, a range of greater than 0 to 200 MPa, more preferably 0.1 MPa to 50 MPa can be used. At this time, an inert gas such as nitrogen can be coexisted.
In the case where the sequential polymerization of the component (A1) in the first step and the component (A2) in the second step is performed, it is desirable to add a polymerization inhibitor into the system in the second step. In the case of producing a propylene-ethylene random copolymer, the addition of a polymerization inhibitor to the reactor for carrying out the second step ethylene-propylene random copolymer, the particle properties (fluidity, etc.) of the resulting powder, gel, etc. Product quality can be improved. Various technical studies have been made on this technique, and examples thereof include Japanese Patent Publication Nos. 63-54296, 7-25960, and 2003-2939. It is desirable to apply the method to the present invention.

Here, a method for measuring the index of the propylene-ethylene random copolymer (A) will be described.
(A1) Ethylene content in component ([E] _A1 ), ethylene content in component (A2) ([E] _A2 ), and proportion of component (A1) constituting propylene-ethylene random copolymer (A) The measurement of the ratio of (W (A1)) and (A2) component (W (A2)) can be specified by the material balance at the time of manufacture (material balance), but in order to specify these more accurately It is desirable to use the following analysis:
(I) Identification of W (A1) and W (A2) by temperature-temperature elution fractionation (TREF) The technique for evaluating the crystalline distribution of a propylene-ethylene random copolymer by TREF is well known to those skilled in the art. Yes, for example, detailed measurement methods are shown in the following documents.
G. Glockner, J. et al. Appl. Polym. Sci. : Appl. Polym. Symp. 45, 1-24 (1990)
L. Wild, Adv. Polym. Sci. 98, 1-47 (1990)
J. et al. B. P. Soares, A .; E. Hamielec, Polymer; 36, 8, 1639-1654 (1995)

The propylene-ethylene random copolymer (A) used in the present invention has a large difference in crystallinity between the components (A1) and (A2), and each of the propylene-ethylene random copolymers (A) is produced using a metallocene catalyst. Since the crystallinity distribution is narrow, there are very few intermediate components between the two, and both can be accurately discriminated by TREF.
As a specific method, in the TREF elution curve (plot of elution amount versus temperature), components (A1) and (A2) show their elution peaks at T (A1) and T (A2), respectively, due to the difference in crystallinity. Since the difference is sufficiently large, separation is possible at an intermediate temperature T (C) (= {T (A1) + T (A2)} / 2).
In addition, the lower limit of the TREF measurement temperature is −15 ° C. in the apparatus used for this measurement, but when the crystallinity of the component (A2) is very low or an amorphous component, There may be no peak in the temperature range. (In this case, the concentration of the component (A2) dissolved in the solvent is detected at the measurement temperature lower limit (ie, −15 ° C.).)
At this time, T (A2) is considered to exist below the lower limit of the measurement temperature, but the value cannot be measured. In such a case, T (A2) is the lower limit of the measurement temperature − It is defined as 15 ° C.
Here, if the integrated amount of the component eluted by T (C) is defined as W (A2) wt%, and the integrated amount of the component eluted at T (C) or higher is defined as W (A1) wt%, W (A2) Corresponds almost to the amount of the low-crystalline or amorphous component (A2), and the integrated amount W (A1) of the component eluting at T (C) or higher is the component with relatively high crystallinity ( Almost corresponds to the amount of A1). The above-mentioned various temperatures and amounts can be calculated from the elution amount curve obtained by TREF.

(Ii) TREF measurement method In the present invention, the TREF is specifically measured as follows.
A sample is dissolved in o-dichlorobenzene (0.5 mg / mL, containing BHT) at 140 ° C. to obtain a solution. This is introduced into a 140 ° C. TREF column, cooled to 100 ° C. at a rate of 8 ° C./min, subsequently cooled to −15 ° C. at a rate of 4 ° C./min, and held for 60 minutes. Thereafter, o-dichlorobenzene (0.5 mg / mL, containing BHT) as a solvent is allowed to flow through the column at a flow rate of 1 mL / min, and 10 components dissolved in o-dichlorobenzene at −15 ° C. in the TREF column. Then, the column is linearly heated to 140 ° C. at a heating rate of 100 ° C./hour to obtain an elution curve.

(Iii) Specificity of ethylene content [E] _A1 and [E] _A2 in each component (a) Separation of component (A1) and component (A2) Based on T (C) determined by the above TREF measurement, Using a temperature-separating column separation method using a preparative type separation apparatus, the soluble component (A2) in T (C) and the insoluble component (A1) in T (C) are separated, and the ethylene content of each component is determined by NMR. .
The temperature rising column fractionation method refers to a measurement method disclosed in, for example, Macromolecules, 21 314 to 319 (1988). Specifically, the following method is used in the present invention.

(B) Fractionation conditions A cylindrical column having a diameter of 50 mm and a height of 500 mm is filled with a glass bead carrier (80 to 100 mesh) and maintained at 140 ° C. Next, 200 mL of the o-dichlorobenzene solution (10 mg / mL) of the sample dissolved at 140 ° C. is introduced into the column. Thereafter, the temperature of the column is cooled to 0 ° C. at a rate of temperature decrease of 10 ° C./hour. After holding at 0 ° C. for 1 hour, the column temperature is heated to T (C) at a heating rate of 10 ° C./hour and held for 1 hour. Note that the temperature control accuracy of the column through a series of operations is ± 1 ° C.
Next, while maintaining the column temperature at T (C), 800 mL of o (dichlorobenzene) of T (C) is allowed to flow at a flow rate of 20 mL / min, whereby components soluble in T (C) existing in the column are obtained. Elute and collect.
Next, the column temperature is increased to 140 ° C. at a rate of temperature increase of 10 ° C./min, left at 140 ° C. for 1 hour, and then 800 mL of a 140 ° C. solvent (o-dichlorobenzene) is flowed at a flow rate of 20 mL / min. , And eluting and recovering insoluble components at T (C).
The solution containing the polymer obtained by fractionation is concentrated to 20 mL using an evaporator and then precipitated in 5 times the amount of methanol. The precipitated polymer is recovered by filtration and then dried overnight in a vacuum dryer.

^(C) 13 C-NMR according to the measurement the fractionated by components obtained ethylene content (A1) (A2) an ethylene content of each by complete proton decoupling method, ¹³ C-NMR measured according to the following conditions Obtained by analyzing the spectrum.
[ ¹³ C-NMR measurement conditions for ethylene content measurement]
Model: GSX-400 manufactured by JEOL Ltd. or equivalent device (carbon nuclear resonance frequency of 100 MHz or more)
Solvent: o-dichlorobenzene / heavy benzene = 4/1 (volume ratio)
Concentration: 100 mg / mL
Temperature: 130 ° C
Pulse angle: 90 °
Pulse interval: 15 seconds Integration count: 5,000 times or more

Spectral assignment may be performed with reference to Macromolecules, 17 1950 (1984), for example. The attribution of spectra measured under the above conditions is as shown in Table 1 below. In Table 1, symbols such as S _αα represent Carman et al. (Macromolecules, 10 536 (1977)), P represents a methyl carbon, S represents a methylene carbon, and T represents a methine carbon.

Hereinafter, when “P” is a propylene unit in a copolymer chain and “E” is an ethylene unit, six types of triads of PPP, PPE, EPE, PEP, PEE, and EEE may exist in the chain. . As described in Macromolecules, 15 1150 (1982), the concentration of these triads and the peak intensity of the spectrum are linked by the following relational expressions (1) to (6).
[PPP] = k × I (T _ββ ) (1)
[PPE] = k × I (T _βδ ) (2)
[EPE] = k × I (T _δδ ) (3)
[PEP] = k × I (S _ββ ) (4)
[PEE] = k × I (S _βδ ) (5)
[EEE] = k × {I (S _δδ ) / 2 + I (S _γδ ) / 4} (6)
Here, [] indicates the fraction of triads, for example, [PPP] is the fraction of PPP triads in all triads. Therefore,
[PPP] + [PPE] + [EPE] + [PEP] + [PEE] + [EEE] = 1 (7)
It is. Further, k is a constant, I indicates the spectral intensity, and for example, I (T _ββ ) means the intensity of the peak at 28.7 ppm attributed to T _ββ .
By using the relational expressions (1) to (7) above, the fraction of each triad is obtained, and the ethylene content is obtained from the following expression.
Ethylene content (mol%) = ([PEP] + [PEE] + [EEE]) × 100

  In addition, when a propylene-ethylene random copolymer (A) is manufactured using a metallocene catalyst, a small amount of propylene heterogeneous bonds (2,1-bonds and / or 1,3-bonds) are generated, thereby The fine peaks in Table 2 are produced.

In order to obtain an accurate ethylene content, it is necessary to include the peaks derived from these heterogeneous bonds in the calculation, but it is difficult to completely separate and identify the peaks derived from the heterogeneous bonds. Since the amount of ethylene is small, the ethylene content should be determined using the relational expressions (1) to (7), as in the analysis of the copolymer produced with a Ziegler catalyst that does not substantially contain heterogeneous bonds. And
The conversion of the ethylene content from mol% to wt% is performed using the following formula.
Ethylene content (% by weight) = (28 × X / 100) / {28 × X / 100 + 42 × (1−X / 100)} × 100
Here, X is the ethylene content in mol%.

The ethylene content [E] _W of the entire propylene-ethylene random copolymer is calculated from the respective ethylene contents [E] _A1 , [E] _A2 and TREF measured from the components (A1) and (A2). From the weight ratios W (A1) and W (A2)% by weight of each component, the following formula is used.
[E] _W = {[E] _A1 × W (A1) + [E] _A2 × W (A2) / 100 (% by weight)

(2) Propylene homopolymer (B)
In the present invention, the propylene homopolymer (B) used for the intermediate layer (Y) has a melt flow rate (MFR) in the range of 1 to 10 g / 10 min, preferably 2 to 8 g / 10 min, more preferably. Can exemplify a propylene homopolymer in the range of 3 to 6 g / 10 min, and may be a mixture of two or more.
Here, the melt flow rate (MFR) is JIS K7210 (1999) “Method of testing plastic-thermoplastic plastic melt mass flow rate (MFR) and melt volume flow rate (MVR)”, condition M (230 ° C. , 2.16 kg load load).
As a specific method for adjusting the MFR to the above range, a method of changing the amount of hydrogen added during polymerization can be mentioned. Since hydrogen acts as a chain transfer agent in the polymerization of propylene, if the amount of hydrogen added is increased, the MFR increases. Conversely, if the amount added is decreased, the MFR can be decreased. The value of MFR relative to the hydrogen concentration inside the polymerization tank varies depending on the catalyst used and other polymerization conditions, but the relationship between the hydrogen concentration and MFR is determined in advance according to the catalyst type and other polymerization conditions, and the desired MFR value is determined. It is very easy for those skilled in the art to adjust the hydrogen concentration so as to obtain a value.

  The propylene homopolymer (B) can be obtained by using a highly stereoregular polymerization catalyst. As the highly stereoregular polymerization catalyst, a titanium compound prepared using titanium chloride, alkoxy titanium or the like as a starting material is used. So-called Ziegler-Natta catalysts or Kaminsky catalysts using metallocene compounds can be used. For example, as the propylene homopolymer (B) used in the present invention, a commercially available product can be used, and specifically, Novatec PP FL203D (trade name) manufactured by Nippon Polypro Co., Ltd. is exemplified.

2. Constituent components of upper layer (X) and lower layer (Z) (1) Propylene-α-olefin random copolymer (D)
In the present invention, the propylene-α-olefin random copolymer (D) used for the upper layer (X) and the lower layer (Z) is a differential based on the method described in JIS K7122 (1987) “Method for measuring the transition heat of plastic”. The melting point measured by scanning calorimetry (DSC method) is 135 ° C. or lower. When the temperature is 135 ° C. or lower, the crystallinity is lowered, and thus transparency and gas permeability are improved.
On the other hand, a propylene-α-olefin random copolymer having a melting point of 120 ° C. or higher is preferably 120 to 135 ° C. because it is easy to produce. Further, the heat of fusion is preferably 80 kJ / kg or less, more preferably 70 kJ / kg or less. The propylene-α-olefin random copolymer (D) having a heat of fusion of 80 kJ / kg or less has improved gas permeability and sufficient gas permeability performance is obtained. Here, the melting point and the heat of fusion are values measured by a differential scanning calorimetry (DSC method) based on the method described in JIS K7122 (1987).

  The propylene-α-olefin random copolymer (D) used in the present invention preferably contains propylene units in the range of 85 to 99.9% by weight, more preferably in the range of 90 to 99.9% by weight. It is desirable to include. The propylene-α-olefin random copolymer (D) having a propylene unit of 85% by weight or more is easy to produce and practically preferable.

  Examples of the α-olefin include ethylene or an α-olefin having 4 to 18 carbon atoms. Specific examples of the α-olefin having 4 to 18 carbon atoms include 1-butene, 1-pentene, 1-hexene, Examples include 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene, 3-methyl-1-pentene, and the like, and one or more of these can be used. From the viewpoint of production cost, ethylene, 1-butene or a combination thereof is most preferable. Therefore, the propylene-α-olefin random copolymer (D) used in the present invention is a propylene-ethylene random copolymer or a propylene-ethylene-1 butene random copolymer, and they are mixed at an arbitrary ratio. It may be a mixture. Further, the propylene-α-olefin random copolymer (D) used in the present invention can be obtained by using a highly stereoregular polymerization catalyst. Examples of the highly stereoregular polymerization catalyst include titanium chloride and alkoxy titanium. A so-called Ziegler-Natta catalyst using a titanium compound prepared using as a starting material or a Kaminsky catalyst using a metallocene compound can be used.

The propylene-α-olefin random copolymer (D) is blended with an antiblocking agent as necessary in order to prevent adhesion between films. As such an antiblocking agent, a known inorganic antiblocking agent, organic antiblocking agent, or the like can be used.

3. Other components In the upper layer (Y) / intermediate layer (X) / lower layer (Z) constituting the laminated film used in the present invention, an antioxidant, a neutralizing agent, etc., which are used for ordinary polyolefin film materials, respectively. Additives may be blended.

  Antioxidants include tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane, 2,6-di-t-butyl-4-methylphenol, Phenolic compounds such as n-octadecyl-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate and tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate Antioxidant, or tris (2,4-di-t-butylphenyl) phosphite, tris (nonylphenyl) phosphite, distearyl pentaerythritol diphosphite, tetrakis (2,4-di-t-butylphenyl) Examples thereof include phosphorus-based antioxidants such as -4,4'-biphenylene-diphosphonite.

  Examples of the neutralizing agent include metal salts of higher fatty acids such as calcium stearate and hydrotalcites.

  The amount of these additives is preferably about 0.01 to 3% by weight in each layer. Moreover, the method of mix | blending these additives is not specifically limited, For example, it can mix | blend by a well-known method, such as using a mixer with a high-speed stirrer, such as a Henschel mixer (brand name). Furthermore, after mixing various compounds constituting each layer, it may be pelletized using a single screw extruder or a twin screw extruder.

4). Production and Physical Properties of Biaxially Stretched Multilayer Film The biaxially stretched multilayer film of the present invention is a laminated film of at least 3 layers constituted in the order of upper layer (X) / intermediate layer (Y) / lower layer (Z). In addition, another layer may be included between the upper layer (X) and the intermediate layer (Y) and between the intermediate layer (Y) and the lower layer (Z) as long as the effects of the present invention are not hindered. Absent.

The production method of the laminated film is a sheet formed by an ordinary T-die method or an inflation method so as to be configured in the order of upper layer (X) / intermediate layer (Y) / lower layer (Z), and a sheet formed by these methods Obtained by biaxial stretching. As the biaxial stretching method, a sequential biaxial stretching method by a tenter method is preferable.
The stretching ratio of the biaxially stretched multilayer film of the present invention is preferably 3 to 7 times and 4 to 10 times in the machine direction (MD) and the transverse direction (TD), respectively 4 to 6 times and 4 to 9 times. Further preferred.

  The thickness of the biaxially stretched multilayer film of the present invention is preferably 20 to 80 μm, more preferably 25 to 50 μm, from the viewpoints of gas permeability, flexibility, transparency, and moldability. If the thickness of the film is 20 μm or more, the elastic modulus is improved and the handling tends to be good. On the other hand, when the thickness of the film is 80 μm or less, the gas permeability is improved and the desired permeability can be obtained.

  Furthermore, the ratio of the upper layer (X) / intermediate layer (Y) / lower layer (Z) to the thickness of the entire film is 20 to 5% / from the viewpoints of adhesiveness, flexibility, transparency, molding processability, and cost. It is preferably 60 to 90% / 20 to 5%, and more preferably 15 to 10% / 70 to 80% / 15 to 10%, respectively.

Biaxially oriented multilayer films of the present invention, in conformity with JIS K 7126-A, preferably permeability of oxygen is ^{3000~8000cc / m 2 · 24Hr · atm} , more preferably 6000~8000cc / m ² · 24Hr · The permeability of atm and carbon dioxide is preferably 8000 to 40000 cc / m ² · 24 Hr · atm, more preferably 15000 to 40000 cc / m ² · 24 Hr · atm. Unlike the general biaxially stretched film, the desired gas permeability can be obtained when the permeability of the film is equal to or higher than the respective lower limit values. On the other hand, when the transparency of the film is less than or equal to the respective upper limit values, the film can be prevented from being greatly softened, so that the film has good handling properties and blocking properties.

  The biaxially stretched multilayer film of the present invention has a transparency (Haze) of preferably 5% or less, and more preferably 3% or less. Here, the haze value is a value measured according to the method described in JIS K7105 (1981).

  The tensile elastic modulus of the biaxially stretched multilayer film of the present invention is preferably 200 to 1200 MPa and 400 to 2000 MPa in the machine direction (MD) and transverse direction (TD), respectively, more preferably 400 to 1000 MPa and 600 to 1500 MPa, respectively. When the elastic modulus of the film is equal to or higher than the respective lower limit values, flexibility tends to decrease and blocking tends to be difficult. On the other hand, when the elastic modulus of the film is equal to or less than the respective upper limit value, the crystal component is reduced and gas permeability tends to be improved. Here, the elastic modulus is a value measured according to JIS K7127 (2000).

The tensile elongation at break of the biaxially stretched multilayer film of the present invention is preferably 150% or less in the transverse direction (TD), more preferably 100% or less. When the elongation of the film is not more than the respective upper limit values, the elongation becomes small, and the secondary workability such as bag making and handling at the time of handling are improved.
Here, the elongation at break is a value measured according to JIS K7127 (1999).

The biaxially stretched multilayer film of the present invention can suppress blocking that occurs when the upper layer and the lower layer are overlapped, and preferably has a blocking resistance of 6 N or less, more preferably 5 N or less after 40 ° C.-7 days. It is. When the blocking resistance is 6N or less, wrinkles are not generated on the mill roll when the product film is wound, and the films are not adhered to each other at the time of use and cannot be unwound well.
Furthermore, when the products after bag making are stacked and stored for a long time, the products stick to each other and the product bag is not damaged during transportation or handling.
Here, the blocking resistance is a value measured according to the method described in ASTM D-1893.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited by these.
In addition, the physical-property value of the film used by the Example of this invention and a comparative example was measured by the method shown below, and the sample used was as follows.

1. Test method (1) MFR [unit: g / 10 min]:
MFR conforms to JIS K7210 (1999) “Method of testing plastic-thermoplastic melt mass flow rate (MFR) and melt volume flow rate (MVR)”, condition M (230 ° C., 2.16 kg load). And measured.
(2) Tensile modulus [unit: MPa]:
Measured in accordance with the method described in JIS K7127 (1999) “Plastics—Testing Method for Tensile Properties—Part 3: Test Conditions for Films and Sheets”. If the value of the elastic modulus (Young's modulus) is small, it is flexible.
(3) Tensile elongation at break Measured according to the method described in JIS K7127 (1999). The lower the value, the better the elongation.
(4) Transparency (Haze) [unit:%]:
Measured according to the method described in JIS K7105 (1981) “Testing method for optical properties of plastic”. If the value of the adhesive strength is decreased, the haze is decreased and the transparency is high.
(5) Translucency (LSI): [Unit:%]
The LSI of the biaxially stretched film was measured using an LSI meter (N207) manufactured by Toyo Seiki Seisakusho.
LSI measures the amount of light scattering at a small angle and is a measure of the transparency of a film that matches the visual feeling. The higher the value, the worse the transparency, and the lower the value, the better the transparency.
The smaller the LSI value (unit:%), the better the transparency, that is, the contents look clearer.
(6) Glossiness: Glossiness [Unit:%]
The measurement was performed according to the method described in ASTM D 523. The higher the number, the better the gloss. (7) Oxygen permeability: [Unit: cc / m ² · 24Hr · atm]
Measurement was performed according to JIS K 7126A. A higher numerical value indicates higher oxygen permeability.
(8) Carbon dioxide gas permeability: [Unit: cc / m ² · 24Hr · atm]
Measurement was performed according to JIS K 7126A. A higher numerical value indicates higher carbon dioxide permeability.
(9) Thickness: [Unit: μm]
The thickness was evaluated according to JIS B7503: 2011.
(10) Blocking resistance: [unit: N]
Two films to be measured are prepared, and the surfaces subjected to the corona treatment are overlapped with each other at 2 cm (width) × 2 cm (length). ,. The conditions are the conditions of 40 ° C. and 1 kg / 4 cm ² load, and left in the Tabai gear oven for 7 days. . Then, the peeling load is measured with a shopper tensile tester. It can be said that the lighter the peeling load, the better the blocking.

2. Resin used Various materials used in Examples and Comparative Examples are shown below.
The propylene-ethylene random copolymer (A) is shown by the following (A-1) to (A-3).
(1) A-1 (propylene-ethylene random copolymer):
(A) Multistage polymer of 56% by weight of (A1) component having an ethylene content of 2% by weight and 44% by weight of (A2) component having an ethylene content of 12% by weight: MFR _Whole ; 7.2 g / 10 min (polymerization) As an example, details of the manufacturing will be described later.).
(2) A-2 (propylene-ethylene random copolymer):
(A) Multistage polymer of (A1) component 25% by weight of ethylene content 2% by weight and (A2) component 75% by weight of ethylene content 12% by weight: MFRWhole; 7.2 g / 10 min (polymerization example) Details of the manufacturing will be described later.)
(3) A-3 (propylene resin composition):
Multistage polymer of 65% by weight of (A1) component having an ethylene content of 0.8% by weight and 35% by weight of (A2) component having an ethylene content of 20% by weight: MFR _Whole ; 5.5 g / 10 minutes (polymerization example) Details of the manufacturing will be described later.)

(7) B (Propylene homopolymer (B)):
NOVATEC PP FL203D (trade name) manufactured by Nippon Polypro Co., Ltd., which is a propylene homopolymer having a heat of fusion of 101 kJ / kg, a melting point of 161 ° C., MFR; 3.0 g / 10 min.
(8) D (propylene polymer (D)):
-Wintech WFX4TA (trade name) manufactured by Nippon Polypro Co., Ltd., which is a metallocene propylene-ethylene random copolymer having a melting heat of 62 kJ / kg and a melting point of 125 ° C.

[Polymerization Example 1] (Production of A-1):
(1) Preparation of olefin polymerization catalyst component (1-1) Chemical treatment of silicate:
To a 10-liter glass separable flask with a stirring blade, 3.75 liters of distilled water was added slowly followed by 2.5 kg of concentrated sulfuric acid (96%). At 50 ° C., 1 kg of montmorillonite (Menzawa Chemical Industry Co., Ltd. Benclay SL (trade name); average particle size = 50 μm) was dispersed, heated to 90 ° C., and maintained at that temperature for 6.5 hours. After cooling to 50 ° C., the slurry was filtered under reduced pressure to recover the cake. 7 liters of distilled water was added to this cake to reslurry it, and then filtered. This washing operation was performed until the pH of the washing liquid (filtrate) exceeded 3.5. The collected cake was dried at 110 ° C. overnight under a nitrogen atmosphere. The mass after drying was 707 g. The chemically treated silicate was dried in a kiln dryer.

(1-2) Preparation of catalyst:
200 g of the dry silicate obtained above was introduced into a glass reactor with an internal volume of 3 liters, and 1160 ml of mixed heptane and 840 ml of a heptane solution of triethylaluminum (0.60 M) were added and stirred at room temperature. . After 1 hour, the mixture was washed with mixed heptane, and the silicate slurry was adjusted to 2.0 liters.
Next, 9.6 ml of a heptane solution of triisobutylaluminum (0.71 M / L) was added to the prepared silicate slurry and reacted at 25 ° C. for 1 hour. In parallel, [(r) -dichloro [1,1′-dimethylsilylenebis {2-methyl-4- (4-chlorophenyl) -4H-azurenyl}] zirconium] (the synthesis is disclosed in JP-A-10-226712) 33.1 ml of a triisobutylaluminum heptane solution (0.71 M) was added to 2180 mg (3 mmol) and 870 ml of mixed heptane, and the mixture reacted at room temperature for 1 hour was added to a silicate slurry. Added and stirred for 1 hour.

(2) Preactivation treatment of olefin polymerization catalyst component 2.1 liters of n-heptane was introduced into a stirring autoclave having an internal volume of 10 liters that had been sufficiently substituted with nitrogen and maintained at 40 ° C. The previously prepared silicate / metallocene complex slurry was introduced therein. When the temperature was stabilized at 40 ° C., propylene was supplied at a rate of 100 g / hour to maintain the temperature. After 4 hours, the supply of propylene was stopped and maintained for another 2 hours. After completion of the prepolymerization, the remaining monomer was purged, stirring was stopped and the mixture was allowed to stand for about 10 minutes, and then about 3 liters of the supernatant was decanted.
Subsequently, 9.5 ml of a heptane solution of triisobutylaluminum (0.71 M / L) and 5.6 liters of mixed heptane were added, and the mixture was stirred at 40 ° C. for 30 minutes and allowed to stand for 10 minutes. Removed liters. This operation was further repeated 3 times. When the component analysis of the final supernatant was performed, the concentration of the organoaluminum component was 1.23 mmol / L and the Zr concentration was 8.6 × 10 ⁻⁶ g / L, and the abundance in the supernatant with respect to the amount charged. Was 0.016%. Subsequently, 17.0 ml of a heptane solution of triisobutylaluminum (0.71 M / L) was added, followed by drying at 45 ° C. under reduced pressure. By this operation, a prepolymerized catalyst containing 2.1 g of polypropylene per 1 g of catalyst was obtained.

(3) First polymerization step 35 kg of seed polymer was introduced into a horizontal polymerization vessel 1 (L / D = 6, internal volume 100 L) having stirring blades, and then nitrogen gas was allowed to flow for 3 hours. Thereafter, the temperature was raised while introducing propylene, ethylene and hydrogen so as to have the molar ratio and pressure shown in Table 3, and when the polymerization conditions were satisfied, the prepolymerized catalyst was 0.47 g / hr, organic Triisobutylaluminum was supplied as an aluminum compound so as to be constant at 15 mmol / hr. The mixed gas of ethylene / propylene shown in Table 3 was continuously supplied while maintaining the reaction temperature of 75 ° C., the reaction pressure of 1.8 MPaG, and the stirring speed of 35 rpm, and the hydrogen concentration in the gas phase of the reactor is shown in Table 3. Hydrogen gas and ethylene gas are continuously supplied to maintain the hydrogen / propylene molar ratio and the ethylene / propylene molar ratio to adjust the molecular weight (MFR) of the produced polymer, that is, the propylene-ethylene random copolymer component (A1). did.
The heat of reaction was removed by the heat of vaporization of the supplied raw material propylene. The unreacted gas discharged from the polymerization vessel was cooled and condensed outside the reactor system through a pipe and refluxed to the polymerization vessel. The ethylene-propylene random copolymer component (A1) obtained by the main polymerization is continuously withdrawn from the polymerization vessel through a pipe so that the retained level of the polymer is 50% by volume of the reaction volume. The polymerization vessel was fed. At this time, a part of the ethylene-propylene random copolymer component (A1) was intermittently extracted from the pipe to obtain a sample for determining MFR, ethylene content, and activity (polymer yield per unit mass of catalyst).

(4) Second polymerization step Propylene-ethylene random copolymer component (A1) from the first polymerization step and mixing of propylene and ethylene in a horizontal polymerization vessel 10 (L / D = 6, internal volume 100 L) having a stirring blade Gas was intermittently supplied to carry out copolymerization of propylene and ethylene. The reaction conditions were a stirring speed of 18 rpm, a reaction temperature of 70 ° C., a reaction pressure of 1.7 MPaG, and the hydrogen concentration in the gas phase of the reactor was maintained at the hydrogen / propylene molar ratio and the ethylene / propylene molar ratio shown in Table 3. Then, hydrogen gas and ethylene gas were continuously supplied to adjust the molecular weight (MFR) of the produced polymer, that is, the propylene-ethylene random copolymer component (A2). Oxygen gas was supplied as a polymerization activity inhibitor for adjusting the polymerization amount of the propylene-ethylene random copolymer component (A2).
The heat of reaction was removed by the heat of vaporization of the supplied raw material propylene. The unreacted gas discharged from the polymerization vessel was cooled and condensed outside the reactor system through a pipe and refluxed to the second polymerization step.
The propylene-ethylene random copolymer (A) obtained in the second polymerization step was continuously extracted from the polymerization vessel so that the retained level of the polymer was 50% by volume of the reaction volume. At this time, a part of the propylene-ethylene random copolymer (A) was intermittently extracted from the pipe to obtain a sample for determining MFR, ethylene content, and activity (polymer yield per unit mass of catalyst). Table 3 shows measurement results of various physical properties of the propylene-ethylene random copolymer component obtained in the first polymerization step and the second polymerization step.

[Polymerization Example 2] (Production of A-2)
In Polymerization Example 1, the amount of catalyst supplied in the first polymerization step, the molar ratio of propylene and ethylene and hydrogen and propylene, the molar ratio of propylene and ethylene and hydrogen and ethylene in the second polymerization step, and the polymerization temperature at each stage are shown in Table 3. A sample of a propylene random copolymer was obtained in the same manner except that the conditions were changed. Table 3 shows measurement results of various physical properties of the propylene-ethylene random copolymer component obtained in the first polymerization step and the second polymerization step.

[Polymerization Example 3] (Production of A-3)
(1) Preparation of Olefin Polymerization Catalyst Component In a stainless steel reactor substituted with nitrogen, 360 ml of titanium tetrachloride and 240 ml of toluene were charged to form a mixed solution. Then, a suspension formed by using 120 g of diethoxymagnesium having an average particle size of 42 μm, 500 ml of toluene and 43.2 ml of phthalic acid-di-n-butyl is added to the liquid mixture kept at a liquid temperature of 10 ° C. did. Then, it heated up over 10 minutes from 10 degreeC-90 degreeC, and was made to react, stirring for 2 hours. After the reaction is complete
The obtained solid product was washed four times with 1000 ml of toluene at 90 ° C., 360 ml of titanium tetrachloride and 800 ml of toluene were newly added, the temperature was raised to 112 ° C., and the reaction was allowed to stir for 2 hours. After completion of the reaction, the reaction product was washed 10 times with 1000 ml of n-heptane at 40 ° C. to obtain an olefin polymerization catalyst component.
The average particle diameter of the obtained olefin polymerization catalyst component was 42 μm, and the analytical values (by atomic absorption method) were Mg: 18.9 wt%, Ti: 2.2 wt%, Cl: 61.6 wt% Met.

(2) Preactivation treatment of olefin polymerization catalyst component After replacing a stainless steel reactor with an inner volume of 20 liters with inclined blades with nitrogen gas, 17.7 liters of hexane, 100.6 mmol of triethylaluminum, 15.1 mmol of diisopropyldimethoxysilane After adding 120.4 g of the olefin polymerization catalyst component prepared by the above method at room temperature, the mixture was heated to 30 ° C. Next, 240.8 g of propylene was supplied over 3 hours with stirring, and a preliminary activation treatment was performed. As a result of the analysis, 1.9 g of propylene was reacted per 1 g of the olefin polymerization catalyst component.

(3) First polymerization step 0.4 g / hr of an olefin polymerization catalyst component preactivated by the above method in a horizontal polymerization vessel (L / D = 6, internal volume 100 liters) having a stirring blade, organoaluminum compound As triethylaluminum and diisopropyldimethoxysilane as an organosilicon compound were continuously supplied at a molar ratio of Al / Mg molar ratio of 6 and Al / Si molar ratio of 6. A mixed gas of ethylene-propylene is continuously supplied while maintaining the conditions of a reaction temperature of 60 ° C., a reaction pressure of 2.1 MPa, and a stirring speed of 35 rpm, and the ethylene / propylene molar ratio in the gas phase of the reactor is 0.005, hydrogen / Hydrogen gas is continuously supplied from a circulation pipe so as to maintain a propylene molar ratio of 0.007, the molecular weight of the ethylene-propylene random copolymer component (A1) as a produced polymer is controlled, and the melt flow rate is controlled. It was adjusted.
The heat of reaction was removed by the heat of vaporization of the supplied raw material propylene. The unreacted gas discharged from the polymerization vessel was cooled and condensed outside the reactor system through a pipe and refluxed to the polymerization vessel. The ethylene-propylene random copolymer component (A1) obtained by the main polymerization is continuously withdrawn from the polymerization vessel through a pipe so that the retained level of the polymer is 50% by volume of the reaction volume. The polymerization vessel was fed. At this time, a part of the ethylene-propylene random copolymer component (A1) was intermittently extracted from the pipe to obtain a melt flow rate, an ethylene content, and a polymer yield per unit weight of the catalyst. The ethylene content was measured by infrared absorption spectrum analysis. The polymer yield per unit weight of the catalyst was measured by inductively coupled plasma emission spectroscopy analysis of Mg content in the polymer.

(4) Second polymerization step In a horizontal polymerization vessel (L / D = 6, internal volume 100 liters) having stirring blades, ethylene-propylene random copolymer component (A1) and ethylene-propylene-1 from the first polymerization step -Butene mixed gas was continuously supplied to carry out copolymerization of propylene, ethylene and 1-butene. The reaction conditions were a stirring speed of 25 rpm, a temperature of 55 ° C., a pressure of 1.9 MPa, and a gas phase gas composition of hydrogen / ethylene molar ratio of 0.62, ethylene / propylene molar ratio of 0.14, and 1-butene / propylene molar ratio. Adjusted to 0.06. In order to adjust the polymerization amount of the ethylene-propylene-1-butene random copolymer component (A2), carbon monoxide as a polymerization activity inhibitor and the ethylene-propylene-1-butene random copolymer component (A2) Hydrogen gas was supplied to adjust the molecular weight.
The heat of reaction was removed by the heat of vaporization of the supplied raw material propylene. The unreacted gas discharged from the polymerization reactor was cooled and condensed outside the reactor system through a pipe and refluxed to the second polymerization step.
The propylene-based resin composition (A) obtained in the second polymerization step was continuously extracted from the polymerization vessel so that the retained level of the polymer was 50% by volume of the reaction volume. The production rate of the propylene-based resin composition (A) was 8 to 15 kg / hr.
The extracted propylene-based resin composition (A-3) removes unreacted monomers, and partly measures the melt flow rate, measures the ethylene polymer unit and 1-butene polymer unit content by infrared absorption spectrum analysis, In addition, it was used for measuring the content of the ethylene-propylene-1-butene random copolymer component (A2).
Table 3 shows the polymerization conditions and physical properties of the propylene-based resin composition (A-3).

[Sample preparation]
Using the components shown in Tables 4 and 5 and blending them in the proportions described in Tables 4 and 5, an intermediate layer extruder (diameter 60 mm) or two surface layer extruders (diameter 30 mm) of a multilayer film molding machine Were extruded from a T die at 250 ° C. and cooled with a cooling roll at 30 ° C. to obtain a raw sheet.
In addition, about A-1, with respect to 100 weight part, tetrakis [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane 0.15 as an antioxidant. After mixing 0.10 parts by weight of calcium stearate as a part by weight and a neutralizing agent and mixing uniformly using a Henschel mixer (trade name), the resulting mixture is melt-kneaded with an extruder and pelletized Used.

Next, the obtained original fabric sheet was stretched 5 times in the machine direction (MD) with a heating roll at 100 ° C., and subsequently stretched 8 times in the transverse direction (TD) in a tenter oven to produce a film.
The obtained film was adjusted to a predetermined test piece, and HAZE, gloss, LSI, Young's modulus, tensile elongation, gas permeability, and blocking were measured and evaluated according to a predetermined test method.
The results are shown below.

[Examples 1 to 8]
A film was produced in the same manner as the above method except that the component ratio and the film thickness shown in Table 4 were used.
Table 4 shows the measurement results of the obtained film.

[Comparative Examples 1-4]
A film was produced in the same manner as the above method except that the component ratio and the film thickness shown in Table 5 were used.
Table 5 shows the measurement results of the obtained film.

(1) When the results of Examples 1 to 8 and Comparative Examples 1 to 4 described in Tables 4 and 5 are compared, the following becomes clear.
Examples 1 to 8 are biaxially stretched multilayer films in which the metallocene-based propylene monoethylene random copolymer of the present invention (first invention) is prepared for the intermediate layer (Y) within the scope of the claims. However, in this case, it has flexibility while maintaining the characteristics of the polypropylene resin such as excellent transparency, transparency, glossiness, and high heat resistance, and oxygen and carbon dioxide are preferable. It can be seen that it has a low elongation characteristic and a blocking property.

(2) On the other hand, Comparative Examples 1-4 are the cases where resin is prepared for the intermediate layer (Y) outside the scope of the present invention (first invention). In the case of Comparative Example 1, since it is a product using a Ziegler-based propylene-ethylene random copolymer, transparency, transparency and gloss are poor, and low crystal components are small, so that oxygen gas and carbon dioxide gas are present. It turns out that the permeability of is also bad.
Further, Comparative Examples 2 to 4 are those using a Ziegler-based propylene monoethylene random copolymer and increasing the blending amount. However, although flexibility and gas permeability are improved, transparency and transparency are improved. Further, it can be seen that the gloss and blocking properties tend to be remarkably deteriorated.
From the above, the biaxially stretched multilayer film of the present invention has flexibility while maintaining the characteristics of a polypropylene-based resin that is excellent in film appearance such as transparency, transparency, and gloss, and has high heat resistance, It is a film that suitably permeates oxygen and carbon dioxide, has excellent low elongation characteristics, and excellent blocking properties.

Since the biaxially stretched multilayer film of the present invention has the excellent characteristics as described above, it is not only used as a substitute for a gas permeable film that is generally used at present, but also for applications that require higher physical properties. Also, it can be suitably used.
In addition, the biaxially stretched multilayer film of the present invention uses a specific propylene-ethylene random copolymer and uses a metallocene catalyst, so there are few low molecular weight components, such as optical properties and blocking properties. A clean material that improves performance.
And even if a specific propylene-ethylene random copolymer passes through a biaxial stretching process, it maintains the flexibility substantially equivalent to an unstretched film, and has blocking resistance while having transparency, transparency, and glossiness. And a film having high thickness and thin accuracy which is a characteristic of a biaxially stretched film can be obtained.
Furthermore, since it is compatible with a significant reduction in elongation by biaxial stretching, it has excellent handling properties and therefore has excellent secondary workability.
In addition, it is suitable for the productivity of wide products, can be manufactured at low cost, and in the case of an unrolled film that does not have a stretching process, the fine fisheye that cannot be removed disappears by stretching, so the appearance of the film is not impaired. It can be set as a biaxially stretched multilayer film.

Claims (5)

A laminated film composed of an upper layer (X) / intermediate layer (Y) / lower layer (Z), which satisfies the following requirements (a) to ( e ): A biaxially stretched multilayer film.
(I) The intermediate layer (Y) is composed of the following metallocene propylene-ethylene random copolymer (A1) 8 to 60% by weight, metallocene propylene-ethylene random copolymer (A2) 16 to 80% by weight, and propylene homopolymer. It is comprised from the propylene-type resin composition (C) which consists of 100 weight% of combined (B) 0-60 weight% in total.
(A1): Metallocene propylene-ethylene random copolymer having an ethylene content of 1.5 to 3% by weight.
(A2): A metallocene propylene-ethylene random copolymer containing 8 to 10% more ethylene than (A1).
(B): A propylene homopolymer having a melt flow rate (MFR: 2.16 kg load, 230 ° C.) in the range of 1 to 10 g / 10 min.
(B) The upper layer (X) and the lower layer (Z) are each independently a propylene having a melting point (Tp) determined by a differential scanning calorimeter (DSC) in accordance with JIS K 7122 (1987) of 135 ° C. or less. -It is comprised from an alpha olefin random copolymer (D).
(C) The oxygen permeability of the laminated film is 3000 to 8000 cc / m ² · 24 Hr · atm (based on JIS K 7126-A).
(D) Carbon dioxide gas permeability of the laminated film is 8000 to 40000 cc / m ² · 24 Hr · atm (based on JIS K 7126-A).
(E) The tensile elastic modulus of the laminated film measured according to JIS K7127 (1999) is 200 to 1200 MPa in the machine direction (MD) and 400 to 2000 MPa in the transverse direction (TD). The biaxially stretched multilayer film according to claim 1, wherein the transparency (Haze) of the laminated film measured in accordance with JIS K7105 (1981) is 5% or less. 2. The biaxially stretched multilayer film according to claim 1, wherein the tensile breaking elongation of the laminated film measured according to JIS K7127 (1999) is 150% or less in the transverse direction (TD). The biaxially stretched multilayer film according to claim 1, wherein the laminated film has a blocking resistance of 6 N or less after 7 days at 40 ° C. measured in accordance with ASTM D-1893. The propylene-α-olefin random copolymer (D) is composed of a propylene-ethylene random copolymer, a propylene-ethylene-1-butene random copolymer, or a mixture obtained by mixing them in an arbitrary ratio. 2. The biaxially stretched multilayer film according to 1.