JPH0789022A - Polypropylene laminated film - Google Patents

Abstract

PURPOSE:To inexpensively obtain excellent heat sealability and scratch resistance by laminating a propylene homopolymer whose syndiotactic pentad ratio is within a specific value range or a copolymer of propylene and a small amt. of other olefin to the single surface of a base material layer composed of isotactic polypropyelene. CONSTITUTION:A propylene homopolymer having a syndiotactic structure whose syndiotactic pentad ratio is within the range of 0.6-0.9 or a copolymer of propylene and a small amt. of olefin is laminated to at least the single surface of a base material layer composed of isotactic polyproplylene by a method laminating syndiotactic polypropylene and isotactic polypropylene by coextrusion and uniaxially or biaxially stretching the obtained laminate if necessary or a method extruding isotactic polypropylene and syndiotactic polypropylene in a molten state to laminate them.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene laminated film, and more particularly to a polypropylene laminated film excellent in heat sealability.

[0002]

2. Description of the Related Art Generally, isotactic polypropylene is used in a wide variety of applications because it is relatively inexpensive and has excellent rigidity, appearance of molded articles and moldability. For example, the propylene-ethylene copolymer film has been preferably used in the field of film, which is widely used, and particularly in the field where the heat sealing property of the film is important.

In order to improve the heat-sealing property, the copolymerization amount of ethylene in the propylene-ethylene copolymer used is increased, or in addition to ethylene, a higher α-olefin such as butene-1 is copolymerized. It has been known. Blending a higher α-olefin polymer or an amorphous olefin-based copolymer with these copolymers is also known as an effective means.

On the other hand, the existence of syndiotactic polypropylene has been known for a long time, but the conventional method of low-temperature polymerization with a catalyst composed of a vanadium compound, an ether and an organoaluminum has a poor syndiotacticity, resulting in syndiotacticity. It was hard to say that the characteristics of tic polypropylene were exhibited.

On the other hand, J. A. EWEN et al. Discovered that a catalyst composed of a transition metal catalyst component having an asymmetric ligand and an aluminoxane can also provide polypropylene with good tacticity such that the syndiotactic pentad fraction exceeds 0.7 ( J, Am.C
hem.Soc., 1988,110,6255-6256). Extruded sheets, films and inflation films made of this syndiotactic polypropylene and having excellent transparency have also been proposed (JP-A-3-81128 and JP-A-3-81130).
issue).

[0006]

If the copolymerization amount of ethylene is increased in order to improve the heat-sealing property of the above-mentioned propylene-ethylene copolymer having substantially isotactic structure, it is soluble in the polymerization medium. In the case of slurry polymerization, many components having no utility value are generated, and the yield of the target copolymer is lowered and the properties of the slurry are deteriorated, which makes handling difficult. Also in the gas phase polymerization, the fluidity of the polypropylene powder is deteriorated, and the handling becomes difficult. Therefore, the productivity is lowered and the manufacturing cost is increased.

In addition to ethylene, an expensive higher α-olefin is copolymerized, or an expensive amorphous olefin copolymer is blended to further improve the heat sealing property. This will increase the manufacturing cost. In addition, the scratch resistance, which is a characteristic of polypropylene films, is also impaired. Therefore, there has been a demand for a polypropylene film that is relatively inexpensive and has excellent heat sealability and scratch resistance without using a large amount of expensive higher α-olefin or amorphous olefin copolymer.

On the other hand, a film obtained by molding a propylene homopolymer having a substantially syndiotactic structure by, for example, a T-die extrusion molding method has heat sealability and transparency as compared with a film obtained from isotactic polypropylene. It has excellent properties, and its application is expected to develop, but the dimensional stability of the film is poor, and the film sticks to the cooling roll and the winding roll during film formation, or the wound film shrinks. There is a problem that the film cannot be practically formed because the films stick together and become difficult to peel off.

An object of the present invention is to solve the above problems and to provide a polypropylene film which is relatively inexpensive and which is excellent in heat sealability and scratch resistance.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a surface of a base material layer made of isotactic polypropylene has a syndiotactic polypropylene having a specific stereoregularity. It was found that a film which is relatively inexpensive and has excellent heat sealability, scratch resistance, and dimensional stability can be obtained by laminating the layers, and the present invention was completed. That is, the present invention comprises a homopolymer of propylene having a syndiotactic petad fraction in the range of 0.6 to 0.9, or a copolymer of propylene and a small amount of another olefin, which is isotactic polypropylene. It is a polypropylene laminated film laminated on at least one surface of a base material layer.

The catalyst for producing syndiotactic polypropylene in the present invention is, for example, JP-A-2-
41303, JP-A-2-41305, JP-A-2-2
74703, JP-A-2-274704, JP-A-3-
179005, JP-A-3-179006, JP-A-4
Examples of the catalyst include a bridged transition metal compound having asymmetric ligands and a cocatalyst as described in JP-A-69394, but even if the catalyst has a different structure, ¹³ C- Any polymer capable of producing polypropylene having a syndiotactic pentad fraction measured by NMR in the range of 0.6 to 0.9 can be used, and its polymerization method is not particularly limited, and solvent weight using an inert solvent is not limited. A conventional method, a bulk polymerization method in which an inert solvent is substantially absent, or a gas phase polymerization method can also be used.

The syndiotactic polypropylene used in the present invention is measured by ¹³ C-NMR. Syndiotactic pentad fraction 0.6
A comonomer other than propylene, for example, ethylene, 1-butene, 1-hexene, 1-
Copolymers containing a small amount of olefins such as decene, 1-hexadecene, cyclopentene, norbornene, and diene such as hexadiene, octadiene, decadiene, dicyclopentadiene, 5-ethylidene, and 2-norbornene may be used. Such a copolymer is a poly-α having good syndiotacticity as described above.
It can be obtained by copolymerizing propylene with small amounts of comonomers in the presence of known catalysts which give olefins.

The syndiotactic polypropylene used in the present invention has a syndiotactic pentad fraction determined by ¹³ C-NMR of 0.6 to 0.9. If the syndiotactic pentad fraction exceeds 0.9, the heat sealability becomes insufficient, while if it is less than 0.6, the scratch resistance and blocking resistance become insufficient.

The molecular weight of syndiotactic polypropylene is 0.1 to 10 dl / g, preferably 0.5 to 10 as an intrinsic viscosity measured in a tetralin solution at 135 ° C.
It is in the range of 5.0 dl / g.

If necessary, the syndiotactic polypropylene used in the present invention may contain other resins such as polyolefin copolymers, polyethylene, higher α-olefin polymers, mixtures thereof and additives such as anti-blocking agents. Agents, lubricants, crystal nucleating agents, ultraviolet absorbers, heat stabilizers, weather resistance stabilizers, radiation resistance agents, pigments, dyes and the like may be added.

As the isotactic polypropylene used as the base layer in the present invention, any of known propylene homopolymers, ethylene-propylene block copolymers and crystalline ethylene-propylene random copolymers which are commercially available. Among them, a crystalline ethylene-propylene copolymer or a propylene homopolymer can be used to obtain a polypropylene laminate having excellent transparency. Also,
In addition, for example, JP-A-61-130314 and JP-A-3
Isotactic polypropylene produced by using a catalyst containing a so-called metallocene compound as a main component as described in JP-A-13406 can also be used.

Although the monolayer film of syndiotactic polypropylene has poor dimensional stability, this problem can be solved by laminating it with the above isotactic polypropylene film.

The following methods are possible as a stacking method. (1) A method in which syndiotactic polypropylene and isotactic polypropylene are laminated by coextrusion and, if necessary, at least uniaxially or biaxially stretched. (2) A method in which syndiotactic polypropylene is extruded in a molten state and laminated on an isotactic polypropylene film which is a base material. In this case, the isotactic polypropylene film as the base material may be uniaxially stretched or biaxially stretched. (3) A method of laminating an isotactic polypropylene film and a syndiotactic polypropylene film, which are base materials, with an adhesive.

In particular, in the methods (1) and (2), the film sticks to a cooling roll or a winding roll during film formation, or the wound film shrinks, so that the films stick to each other and become difficult to peel off. It is preferable because it can solve the problem of

The syndiotactic polypropylene layer of the laminated film of the present invention has a thickness in the range of 1 to 100 μm, preferably 2 to 30 μm, and the isotactic polypropylene layer is 4 to 200 μm, preferably 10 to 60 μm.
It is in the range of μm.

[0021]

EXAMPLES In order to explain the present invention in more detail, the following examples are shown, but the present invention is not limited to these. In the examples, each measurement item was measured by the following method. (1) Melt Flow Index: ASTM D-123
Compliant with 8. (2) Haze: According to ASTM D-1003. (3) Heat-sealing temperature: Using a heat-gradient heat-sealing tester manufactured by Toyo Seiki Co., Ltd., heat-sealing the heat-sealing surfaces with each other at several temperatures. Heat sealed 2
A peel strength test is performed on each of the film test pieces to determine the peel strength at each temperature. Peel strength is 30 from the graph
The temperature at which the width became 0 g / 25 mm was determined and used as the heat sealing temperature. (4) Anti-blocking property: Two films cut into a predetermined size are overlapped, and a load of 20 g / cm ^{2 is} applied,
After leaving it in a thermostatic chamber at 50 ° C. for 24 hours, it was taken out from the thermostatic chamber and the contact area ratio of the film was visually determined. (5) Sliding property (tan θ): Based on ASTM D1894. (6) Heat shrinkage rate: Measured in accordance with JIS K-6782 by holding for 30 minutes in an atmosphere of 120 ° C. (7) Scratch resistance: Layers of syndiotactic polypropylene of the laminated film are laminated on each other,
After rubbing twice with a 2 kg iron block as a load,
The haze of the three samples was measured by the method (2), and the difference (Δhaze) from the haze of the three samples before rubbing was determined to determine.

Example 1 Melt Flow Index (hereinafter abbreviated as MFI)
Has an intrinsic viscosity (hereinafter, abbreviated as [η]) of 1, measured in a tetralin solution at 135 ° C. at 8.8 g / 10 min.
1 dl / g, Mw / Mn measured by GPC is 2.4, ¹³ C
40% of a propylene homopolymer having a syndiotactic structure with a syndiotactic pentad fraction of 0.79 measured by NMR (hereinafter abbreviated as SPP-1)
It was melted by an extruder of mmφ and supplied to a die outside-bonding type two-layer coextrusion die at a resin temperature of 230 ° C. On the other hand, with another 50 mmφ extruder, isotactic polypropylene (manufactured by Mitsui Toatsu Chemicals, Inc., FL-400: MFI 7.5 g / 10 mi
n) was melted and supplied to the die at a resin temperature of 230 ° C.
By the above method, the substrate 30μ without any problems in film formation,
SPP-1 layer (hereinafter abbreviated as heat seal layer)
A laminated film having a thickness of 10 μm was obtained. The physical properties of the film are shown in Table 1.

Example 2 Instead of SPP-1 in Example 1, MFI was 7.3 g /
10 min, [η] is 1.1 dl / g, and Mw / Mn is 2.
4. The same procedure as in Example 1 was carried out except that a propylene homopolymer having a syndiotactic pentad fraction of 0.65 (hereinafter abbreviated as SPP-2) was used, and there was no problem in film formation. A laminated film was obtained. The physical properties of the film are shown in Table 1.

Example 3 Instead of SPP-1 in Example 1, MFI was 10.3 g.
/ 10 min, [η] is 1.0 dl / g, Mw / Mn is 2.4, and syndiotactic pentad fraction is 0.85.
Was carried out in the same manner as in Example 1 except that the propylene homopolymer (hereinafter abbreviated as SPP-3) was used to obtain a laminated film without any problem in film formation. The physical properties of the film are shown in Table 1.

Comparative Example 1 Instead of SPP-1 in Example 1, a commercially available isotactic propylene-ethylene-butene-1 terpolymer (manufactured by Mitsui Toatsu Chemicals, Inc., TPFL-4831; MFI =) was used.
5.3g / 10min, ethylene unit content 3.7wt
%, Butene-1 unit content: 3.5 wt%) was performed in the same manner as in Example 1 to obtain a laminated film. The physical properties of the film are shown in Table 1.

Comparative Example 2 TPFL-4831 was added to 70 parts by weight of propylene.
Butene-1 copolymer (Mitsui Petrochemical Co., Ltd., M345
0) Mix 30 parts by weight with a Henschel mixer,
Melt kneading with a 5 mmφ extruder and pellets (hereinafter referred to as EP
Abbreviated as BC). Then, a laminated film was obtained in the same manner as in Example 1 except that EPBC was used instead of SPP-1. The physical properties of the film are shown in Table 1.

Comparative Example 3 Instead of SPP-1 in Example 1, MFI was 2.8 g /
10 min, [η] is 1.4 dl / g, and Mw / Mn is 2.
2. A laminated film was obtained in the same manner as in Example 1 except that a propylene homopolymer having a syndiopentad fraction of 0.93 (hereinafter abbreviated as SPP-4) was used. The physical properties of the film are shown in Table 1.

Comparative Example 4 Instead of SPP-1 in Example 1, MFI was 5.3 g /
10 min, [η] is 1.3 dl / g, and Mw / Mn is 2.
3. A laminated film was obtained in the same manner as in Example 1 except that a propylene homopolymer having a syndiopentad fraction of 0.55 (hereinafter abbreviated as SPP-5) was used. Adhesion of the film to the wiper roll was observed during film formation. Also, the wound film comrades were sticky. The physical properties of the film are shown in Table 1.

Comparative Example 5 In order to compare the film-forming property with that of the example, SPP-1 was melted and supplied to a die for a single-layer film at a resin temperature of 240 ° C. to obtain 40 μm.
m monolayer film was formed. Adhesion of the film to the cooling roll was observed during film formation. Also, the wound film comrades were sticky. The physical properties of the film are shown in Table 1.

[0030]

[Table 1]

[0031]

EFFECT OF THE INVENTION The polypropylene laminated film of the present invention has extremely good heat-sealing property, excellent dimensional stability and scratch resistance, and is industrially extremely valuable.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeo Inoue 1-6 Takasago, Takaishi-shi, Osaka Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] 1. A syndiotactic pentad fraction of 0.
A polypropylene laminated film obtained by laminating a homopolymer of propylene in the range of 6 to 0.9 or a copolymer of propylene and a small amount of another olefin on at least one surface of a base material layer made of isotactic polypropylene.