JPH11115126A - Biaxially oriented polypropylene laminated film and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially oriented polypropylene laminated film having different orientations of a surface layer and an intermediate layer by easily manually tearing from an end of the film without notch, easily manually tearing even from a center of the film (easily manual tearability) and providing tearability (dispenser cuttability) by a cutting blalde of a dispenser (cutting jig) in application to tape with the both satisfactory and a method for manufacturing it. SOLUTION: This laminated film comprises surface layers (A) each formed of propylene (coopolymers, and an intermediate layer (B) made of syndiotactic polypropylene of three-layer ((A)/(B)/(A)) structure. In this case, a ratio (NA/NB) of double refractive index NA of the layer (A) to that NB of the layer (B) is 5.0 to 20, and both easily manual tearability and dispenser cuttability are satisfactory.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polypropylene laminated film, and more particularly, to a film which can be easily torn by hand from the edge of the film without notch and easily by hand from the center of the film. The present invention relates to a biaxially oriented polypropylene laminated film having excellent tearability (hereinafter abbreviated as dispenser cutability) by a cutting blade of a dispenser (cutting jig) for tape use, and a method for producing the same.

[0002]

2. Description of the Related Art In general, polypropylene is used for a wide variety of applications because of its low cost and excellent mechanical properties and appearance of molded articles. Although widely used in the film field, as a polypropylene film having good hand tearability and dispenser cut property, a uniaxially stretched film (for example, Japanese Utility Model Publication No. 50-16053) and a biaxially stretched film And a uniaxially stretched film (for example, Japanese Utility Model Publication No. 50-41271).
No.) or 25-35 watts of petroleum resin in polypropylene
t% added film (for example, JP-A-58-74774).
And a film using a relatively brittle resin or an amorphous resin for the intermediate layer.

[0003]

SUMMARY OF THE INVENTION A uniaxially stretched film (for example, Japanese Utility Model Publication No. 50-16053) or a laminated film of a biaxially stretched film and a uniaxially stretched film (for example, Japanese Utility Model Publication No. 50-16053) According to Japanese Patent Application Laid-Open No. 41271/1990), when a notch is made at the edge of the film, the film shows good tearability in one direction but does not show tearability in the other direction. Can not. In addition, petroleum resin is 25 to 35 wt% in polypropylene.
% (For example, JP-A-58-74774) shows good dispenser cut properties,
Easy tearability is not enough. Furthermore, in the case of a film using a relatively brittle resin such as a cyclic polyolefin resin or an amorphous resin such as a polystyrene resin for the intermediate layer, a different type of resin is used, although easy tearing and dispenser cutting properties are sufficient. Therefore, there are many problems in molding.

[0004] The present invention provides a biaxially oriented polypropylene laminated film using a syndiotactic polypropylene resin and having both good hand tearability and dispenser cutability, and a method for producing the same.

[0005]

Means for Solving the Problems As a result of repeated studies to solve the above problems, the present inventors have found that the surface layer (A) of the polypropylene resin is sufficiently oriented and the intermediate layer (B) The present invention has been found that, by adopting a film configuration in which the resin of (a) is not oriented as compared with the surface layer (A), a biaxially oriented polypropylene laminated film having both easy tearability and dispenser cut property can be obtained. It has been reached.

That is, the surface layer (A) and the intermediate layer (B) of the present invention have at least a three-layer structure of (A) / (B) / (A), and the surface layer (A) and the intermediate layer ( The biaxially stretched polypropylene laminated film having different orientations of B) and good tearability and dispenser cut property is essentially composed of a propylene (co) polymer in the surface layer (A) and an intermediate layer (B). Syndiotactic polypropylene or
A mixture of 60 to 100 parts by weight of syndiotactic polypropylene and 0 to 40 parts by weight of a propylene (co) polymer, the melting point of which is lower than the melting point of the propylene (co) polymer of the surface layer (A), and the syndiotactic of the intermediate layer (B). formed by stretching at a temperature above the melting point of isotactic polypropylene, the surface layer birefringence N _a and the intermediate layer (a) the ratio of the birefringence N _B of _{(B) (N a / N} B)
Is 5.0 or more and 20 or less. The thickness of all layers of the film is 10 to 100 μm, preferably 15 to 80 μm.
The thickness of each layer of the film is such that the intermediate layer (B) exceeds 50% of all layers, preferably 60% or more, and the total thickness of the surface layer (A) is at least 1 to 50 μm, preferably 2%.
４０40 μm.

Further, a film having the constitution as in the present invention, that is, a polypropylene (co) polymer for the surface layer (A), a syndiotactic polypropylene or a syndiotactic polypropylene or a polypropylene (co) for the intermediate layer (B)
Films having a constitution using a polymer mixture are described in, for example, JP-A-8-99393, JP-A-8-99394 and the like. a far as the good polypropylene heat-shrinkable laminated film sex, surface layer of the present invention birefringence N _a and the intermediate layer (a) the ratio of the birefringence N _B of _{(B) (N a / N} B) However, it is 5.0 or more and 20 or less, which is different from a biaxially stretched polypropylene laminated film having both good hand tearing property and good dispenser cutting property.

[0008] The difference from such a laminated film is that the conventional product is biaxially stretched at a temperature at which the conventional product can be oriented (for example, at a temperature of 95 to 105 ° C according to the example of JP-A-8-99394). While the orientation of the tic polypropylene is maintained, the product of the present invention is not more than the melting point of the polypropylene (co) polymer of the surface layer (A) and the intermediate layer (B).
It is presumed to be caused by lowering the degree of orientation of the syndiotactic polypropylene layer by performing transverse stretching or biaxial stretching at a temperature equal to or higher than the melting point of the syndiotactic polypropylene (130 to 160 ° C. according to the example of the present report). Is done.

The propylene (co) polymer used for the surface layer (A) in the present invention is a conventionally known crystalline propylene (co) polymer having a melting point of 135 to 165 ° C. Isotactic Index I. I. (Boiling n-heptane insoluble fraction) is 75% or more, preferably 80% to 99% of isotactic polypropylene or propylene.
It is composed of an ethylene copolymer or a propylene / ethylene / butene terpolymer. In addition, as long as the object of the present invention is not impaired, ethylene-vinyl acetate copolymer, ethylene-α-olefin copolymer, ionomer, polybutene, petroleum resin and the like can be used.

The propylene (co) polymer used for the surface layer (A) in the present invention does not necessarily have to be identical on both sides. That is, another propylene (co) polymer (C) different from (A) may be used, and the layer structure may be (A) / (B) / (C).

The intermediate layer (B) used in the present invention is a syndiotactic polypropylene having a melting point of 120 to 130 ° C., and a syndiotactic pentad fraction of 0.7 or more, preferably 0.75 or more. It is a mixture of 60 to 100 parts by weight of a syndiotactic polypropylene or a syndiotactic pentad fraction of 0.7 or more, preferably 0.75 or more, and 0 to 40 parts by weight of a propylene (co) polymer.

The syndiotactic polypropylene mentioned here is different from, for example, a syndiotactic polypropylene having a low syndiotacticity obtained by using a conventional catalyst comprising a vanadium compound, an ether compound and an organoaluminum compound. J. A.
First discovered by EWEN et al. (J. Am. Che
m. Soc. , 1988, 110, 6255-625.
6) A bridged transition metal compound having asymmetrical ligands can be obtained using a so-called metallocene-based catalyst and a catalyst comprising aluminoxane. The syndiotactic pentad fraction was measured by ¹³ C-NMR. ¹³ C-NMR
The syndiotactic pentad fraction can be measured by a known method described in, for example, JP-A-2-41303.

On the other hand, the propylene (co) polymer used for the intermediate layer (B) is essentially the same as the surface layer (A), but need not necessarily be the same.

In the propylene (co) polymer and syndiotactic propylene used in the present invention, additives such as heat stabilizers, lubricants, antistatic agents, antiblocking agents, ultraviolet absorbers, antifogging agents, etc. Can be added and used as long as the object of the present invention is not impaired.

The biaxially stretched polypropylene laminated film of the present invention can be obtained by a known stretching method such as tenter sequential biaxial stretching by coextrusion T-die method, tenter simultaneous biaxial stretching, and coextrusion inflation biaxial stretching. It can be manufactured using.

For example, when manufactured using a tenter sequential biaxial stretching method by a co-extrusion T-die method, the surface layer (A) is isotactic polypropylene having a melting point of 160 ° C., and the intermediate layer (B) is having a melting point of 127 ° C. A syndiotactic polypropylene having a syndiotactic pentad fraction of 0.7 or more is melted from each extruder, merged into three layers in a die, coextruded, and cooled to obtain an unstretched film. The unstretched film is longitudinally stretched to 3.0 to 6.0 with a roll heated at a temperature of 80 to 130C, preferably 90 to 120C.
, Preferably 4.0 to 5.0 times, and then using a tenter-type stretching machine, the melting point (160 ° C.) or less of the isotactic polypropylene of the surface layer (A) and the syndication of the intermediate layer (B). Melting point of tactic polypropylene (1
27 ° C.) or more, ie, 130 to 160 ° C., preferably 140 to 160 ° C., and stretches 5 to 12 times, preferably 8 to 10 times in the width direction, and 130 to 180 ° C., preferably 1 to 10 times.
Heat treatment is performed at 40 to 170 ° C. to obtain a biaxially stretched polypropylene laminated film having different orientations of the surface layer (A) and the intermediate layer (B). In this biaxially stretched polypropylene laminated film, the orientation of the surface layer (A) and the intermediate layer (B) are different, and the birefringence N _A of the surface layer (A) and the intermediate layer (B) are different.
The ratio of the value of the birefringence index N _B of (N _A / N _B) is 5.0 or more 20
When the content is below, both the easy tearing property and the dispenser cutting property are good. The ratio of the birefringence N _B of birefringence N _A and the intermediate layer of the surface layer (A) (B) (N A / N B) is 5.
If it is less than 0, it cannot be easily torn by hand,
Dispenser cut property also worsens.

The thickness of all layers of the film is 10 to 10
The thickness of each layer of the film is such that the intermediate layer (B) exceeds 50% of all layers, preferably 60% or more, and the total thickness of the surface layer (A) is at least 1%. It is 50 μm, preferably 2 to 40 μm.
When the thickness of the intermediate layer is 50% or less, it cannot be easily torn by hand, and the dispenser-cutting property also deteriorates. When the thickness (total) of (A) of the surface layer is 1 μm or less, the film sticks to the cooling roll, which causes a problem in moldability.

[0018]

The biaxially oriented polypropylene laminated film of the present invention uses the specific resin described in the text and satisfies the specific conditions, so that in the biaxially oriented polypropylene film, both easy tearing property and dispenser cut property are good. Can be produced.

[0019]

EXAMPLES The present invention will be described below in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

The methods for measuring and evaluating the physical properties of the film and the like used in the following Examples and Comparative Examples are as follows. 1) Easy tearing property: It was evaluated whether or not the film could be easily torn directly by hand in the longitudinal direction and the width direction of the film. The evaluation criteria were "○" for easily tearing without resistance, "△" for resistance but tearing, and "x" for no tearing.
And 2) Dispenser cutability: When a film is cut into a width of 15 mm and pulled in a direction perpendicular to the dispenser using a commercially available tape dispenser (cutting blade),
Those that could be cut easily without resistance were rated as “○”, those that had some resistance but could be cut were rated “△”, and those that had considerable resistance but could be cut were rated “x”. 3) Birefringence: The birefringence of each layer was measured using an automatic birefringence measuring device KOBRA-21DH manufactured by Oji Scientific Instruments. The birefringence of the surface layer was measured by molding a biaxially stretched film having only the surface layer under the same conditions. The birefringence of the intermediate layer was determined by changing the thickness of the surface layer since biaxially stretched film molding of the intermediate layer alone was impossible under the same conditions.
The birefringence of the axially stretched film was measured, and the thickness of the surface layer was set to 0.
Extrapolated to

Example 1 Isotactic polypropylene manufactured by Grand Polymer Co., Ltd. (melting point: 160 ° C., MFR: 2.4) was used for the surface layer.
g / 10 min), and 100% by weight of syndiotactic polypropylene manufactured by Mitsui Chemicals, Inc. (melting point: 1) in the intermediate layer.
27 ° C, syndiotacticity: 0.79, MFR:
2.6 g / 10 min, Mw / Mn: 2.0)
Melt at 230-250 ° C from each extruder, 3 in die
The layers are co-extruded and cooled on a cooling roll at 30 to 50 ° C. to obtain an unstretched film of three layers. This unstretched film is stretched 5.0 times in the longitudinal direction by a roll heated at a temperature of 100 ° C., then stretched 10 times in the width direction at 155 ° C., heat-treated at 170 ° C., and biaxially stretched polypropylene laminated A film was obtained. Regarding the thickness of each layer, the thickness of the surface layer (total) was 5 μm, and the thickness of the intermediate layer was 25 μm.
Table 1 shows the ratio of the easy tearing property, dispenser cut property and birefringence of this film.

Example 2 In Example 1, the resin of the surface layer was changed to a propylene / ethylene / butene ternary random copolymer manufactured by Grand Polymer Co., Ltd. (melting point: 137 ° C., MFR: 7.0 g / 10
min), 100 wt% of syndiotactic polypropylene manufactured by Mitsui Chemicals, Inc. (melting point: 127 ° C.,
Syndiotacticity: 0.79, MFR: 2.6 g
/ 10 min, Mw / Mn: 2.0), melted at 230 to 250 ° C. from each extruder, merged into three layers in a die, co-extruded, and cooled on a cooling roll at 30 to 50 ° C. A layer of unstretched film is obtained. 4. This unstretched film is rolled in a longitudinal direction with a roll heated at a temperature of 100 ° C.
The film was stretched 0 times, then stretched 10 times in the width direction at 135 ° C, and heat-treated at 140 ° C to obtain a biaxially stretched polypropylene laminated film. The thickness of each layer is the thickness of the surface layer (total)
Was 5 μm, and the thickness of the intermediate layer was 25 μm. Table 1 shows the ratio of the easy tearing property, dispenser cut property and birefringence of this film.

Example 3 Using the same resin as in Example 1, 230 to 25
It is melted at 0 ° C., merged into three layers in a die, co-extruded from an annular die, and a tubular unstretched film is obtained in cooling water at 30 ° C. This tubular unstretched film is
The film was stretched 5 times in the longitudinal direction and 5 times in the width direction at ℃ to obtain a biaxially stretched polypropylene laminated film. Regarding the thickness of each layer, the thickness of the surface layer (total) was 4 μm, and the thickness of the intermediate layer was 16 μm. Table 1 shows the ratio of the easy tearing property, dispenser cut property and birefringence of this film.

Example 4 The resin for the intermediate layer was syndiotactic polypropylene 80
Example 1 was repeated except that wt% and isotactic polypropylene were 20 wt%.

Comparative Example 1 Syndiotactic polypropylene 40 was used as the resin for the intermediate layer.
Example 1 was repeated except that wt% and isotactic polypropylene were 60 wt%.

Comparative Example 2 Syndiotactic polypropylene 20 was used as the resin for the intermediate layer.
Example 1 was repeated except that wt% and isotactic polypropylene were 80 wt%. .

Comparative Example 3 The resin for the intermediate layer was isotactic polypropylene 100
Example 1 was repeated, except that the wt% was used.

Comparative Example 4 In Example 1, the intermediate layer of the biaxially stretched polypropylene laminated film had 50% or less of all layers, that is, the thickness of each layer was
Example 1 was repeated except that the surface layer (total) was formed so as to have a thickness of 15 μm and the intermediate layer was formed so as to have a thickness of 15 μm.

[Table 1]

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Claims (4)

[Claims] The surface layer (A) is a propylene (co) polymer, and the intermediate layer (B) is at least (A) / (B) / (S) of a syndiotactic polypropylene having a syndiotactic pentad fraction of 0.70 or more. (a) a three-layered structure, the birefringence of the birefringence N _a and the intermediate layer of the surface layer (a) (B) N _B
The biaxially oriented polypropylene laminated film having a ratio (N _A / N _B ) of 5.0 or more and 20 or less and having good tearability and dispenser cut property. 2. The thickness of all layers is 10 to 100 μm, the thickness (total) of the surface layer (A) is 1.0 to 50 μm, and the thickness of the intermediate layer (B) is 50% of all layers. % Of the biaxially oriented polypropylene laminated film according to claim 1. 3. The surface layer (A) is a propylene (co) polymer, and the intermediate layer (B) is a syndiotactic polypropylene 60 having a syndiotactic pentad fraction of 0.70 or more.
The biaxially stretched polypropylene laminated film according to claim 1, comprising a mixture of １００100 parts by weight and 0-40 parts by weight of a propylene (co) polymer. 4. A laminate film having at least a three-layer structure of (A) / (B) / (A) is prepared by subjecting a laminated film having a melting point of the propylene (co) polymer of the surface layer (A) to not more than the melting point of the intermediate layer (B). The method for producing a laminated film according to any one of claims 1 to 3, wherein the laminated film is produced by stretching at a temperature equal to or higher than the melting point of tic polypropylene.