JPH0820093A - Polypropylene resin film - Google Patents

Abstract

PURPOSE:To provide a polypropylene resin film having uniform thickness, transparency corresponding to that of a film molded by a conventional T-die cast molding method and excellent impact strength. CONSTITUTION:A polypropylene resin film is molded by a three-layer co- extrusion air cooling inflation method and has a center layer mainly composed of a polypropylene resin (A) and an outer layer mainly composed of a polypropylene resin (B). The wt. average mol.wt. of the polypropylene resins (A), (B) is within a range of 80,000-400,000 and the elution amt. at specific temp. thereof due to a cross fractionation method is within a specific range of a total polypropylene amt.

Description

Detailed Description of the Invention

[0001]

The present invention has excellent transparency and gloss, which are widely used for packaging foods, clothing, sundries, etc.,
Moreover, the present invention relates to a polypropylene resin film having excellent impact resistance and the like.

[0002]

2. Description of the Related Art Polypropylene film, which is widely used for packaging foods, clothing, sundries, etc. and has excellent transparency and luster, has been conventionally formed by a T-die casting method or a downward water-cooled inflation method. . However, the T-die cast method has a drawback that the production cost is increased because the equipment is large, and the downward water-cooled inflation method is usually suitable for forming a small width of 800 mm or less, and it is difficult to form a wide film. .

When a polypropylene film is formed by an upward air-cooling inflation method which is widely used in the polyethylene film forming method, there is a drawback that a film having a uniform thickness cannot be obtained due to unstable bubbles, or There is a drawback that the film becomes cloudy and a film having excellent transparency cannot be obtained.

Further, in general, polypropylene films are not suitable for packaging heavy goods because of their poor impact resistance.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks, and an object of the present invention is to obtain a film having a stable and uniform thickness and to obtain a film having a conventional T -To provide a polypropylene resin film having transparency comparable to that of a film formed by a die-cast molding method and excellent impact strength.

[0006]

In the polypropylene resin film of the present invention, the center layer has a weight average molecular weight of 80,00.
A polypropylene resin in the range of 0 to 400,000, the elution amount at 0 ° C or less by the cross fractionation method is 30 to 55% by weight of the total polypropylene resin amount, and the elution amount at 0 ° C or more and 80 ° C or less. The elution amount is 20 to 40% by weight of the total polypropylene resin amount, and the elution amount at 80 ° C to 100 ° C is 1 to 15% by weight of the total polypropylene resin system,
Mainly composed of polypropylene resin (A) having a composition in the range of 10 to 35% by weight of the total polypropylene resin amount above 100 ° C. and 125 ° C. or less, provided on both sides of the central layer thereof. The outer layer is a polypropylene resin having a weight average molecular weight in the range of 80,000 to 400,000, and the elution amount by the cross fractionation method at 0 ° C. or higher and 20 ° C. or lower is 0 of the total polypropylene resin amount.
10 to 10% by weight, the elution amount at 20 ° C. to 70 ° C. is 5 to 20% by weight of the total polypropylene resin amount, and the elution amount at 70 ° C. to 110 ° C. is 80% of the total polypropylene resin amount. It is mainly composed of a polypropylene resin (B) having a composition within the range of ˜100% by weight, and is molded by a three-layer co-extrusion air-cooling inflation method, whereby the above object is achieved.

The present invention will be described in detail below.

In the present invention, the weight average molecular weight of the polypropylene resin is, for example, high temperature GPC manufactured by WATERS.
It can be measured at (150 CV).

The polypropylene resins (A) and (B) used in the present invention have a weight average molecular weight of 80,000 to
400,000, preferably 150,000 to 3
It is 50,000. If the weight average molecular weight is less than 80,000, the strength of the film is insufficient and impact resistance is poor, and if it exceeds 400,000, cloudiness of the film tends to occur.

The amount of resin eluted by the cross fractionation method used in the present invention is measured as follows.

The polypropylene resin is first heated at 140 ° C. or at a temperature at which the polypropylene resin is completely dissolved.
It is dissolved in dichlorobenzene, cooled at a constant rate, and a thin polymer layer is formed on the surface of an inert carrier prepared in advance in order of increasing crystallinity and increasing molecular weight. Next, the temperature of the generated polymer layer is continuously or stepwise increased, the concentrations of the components eluted in sequence are detected, and the composition distribution (crystallinity distribution) is measured <temperature rising elution fractionation>. At the same time, the molecular weight and molecular weight distribution of the component are measured by high temperature GPC. For example, the temperature rising elution fractionation (TRE
F = Temperature Rising Elut
ion Fractionation part and high temperature GP
C (SEC = Size Exclusion Chro
cross-fractionation chromatograph <CFC-T150A having a system including
Type: manufactured by Mitsubishi Petrochemical Co., Ltd. can be used.

The polypropylene resin (A) used in the present invention has an elution amount by the above cross fractionation method at 0 ° C. or lower of 30 to 55% by weight based on the total polypropylene resin (A) amount.
Is.

Further, by the cross fractionation method above 80 ° C. above 80 ° C.
Elution amount of resin below ℃ is all polypropylene resin (A)
20-40% by weight of the amount.

Further, by the cross fractionation method above 80 ° C. 1
The amount of resin eluted at 00 ° C. or lower is 1 to 15% by weight of the total amount of polypropylene resin (A).

Finally, the above-mentioned cross fractionation method at 100 ° C.
The resin elution amount at temperatures above 125 ° C. is 10 to 35% by weight based on the total polypropylene resin (A) amount.

In the polypropylene resin (B) used in the present invention, the resin elution amount at 0 ° C. or higher and 20 ° C. or lower by the above cross fractionation method is 0 of the total polypropylene resin (B) amount.
10 to 10% by weight.

Further, by the cross fractionation method, the temperature exceeds 20 ° C. 7
The resin elution amount at 0 ° C or lower is 5 to 20% by weight of the total polypropylene resin (B) amount.

Finally, the resin elution amount by the cross fractionation method at a temperature higher than 70 ° C. and lower than 110 ° C. is 80 to 100% by weight of the total amount of the polypropylene resin (B).

In the polypropylene resin used in the present invention, the elution amount and the weight average molecular weight in each temperature range being within the above ranges improve the impact resistance of the film and make the film excellent in transparency. It is very important in gaining.

The polypropylene resin is produced, for example, by the following multistage polymerization method.

First, as the first step, polymerization is carried out in the presence of a titanium compound catalyst and an aluminum compound catalyst using a propylene monomer and, if necessary, an ethylene monomer or an α-olefin monomer to obtain a first polypropylene resin. . The first polypropylene-based resin may be a propylene homopolymer, a propylene-ethylene copolymer, a propylene-α-olefin copolymer, or the like.

In the second step, the above-mentioned first polypropylene resin containing the titanium compound catalyst and the aluminum compound catalyst and an olefin monomer (for example, ethylene, propylene, or α-olefin) are used.
And are copolymerized to obtain a second polyolefin resin. The second polyolefin resin obtained by this two-step reaction is a propylene-ethylene copolymer or a propylene-α-olefin copolymer, or an ethylene-α
-It can be an olefin copolymer.

Similarly, a multi-step copolymerization reaction can be carried out depending on the purpose. The feature of this production method is that the polymerization is not completed in one step, but multi-step polymerization of two or more steps is performed. This allows multiple types of polymers to be built up in succession, producing blend-type copolymers at the molecular level, which is quite different from conventional polymer blends.

As a manufacturing method as described above, for example, there is a method described in Japanese Patent Laid-Open No. 4-224809. In this method, as a titanium compound, for example, titanium trichloride and magnesium chloride are co-ground, and this is orthotitanic acid n
A spherical solid titanium catalyst having an average particle diameter of 15 μm obtained by treatment with —butyl, 2-ethyl-1-hexanol, ethyl p-toluate, silicon tetrachloride, diisobutyl phthalate, etc. is used.

In this method, a silicon compound as an electron donor, especially diphenyldimethoxysilane, is added to the polymerization tank, and ethyl iodide is further added. further,
Japanese Unexamined Patent Publication (Kokai) No. 3-977747 discloses that a titanium compound obtained by treating an adduct of magnesium chloride and an alcohol with titanium tetrachloride and an electron donor is used. In addition to these methods, for example, Japanese Patent Laid-Open No.
-96912, 4-96907, 3-
No. 174410, No. 2-170803, No. 2
-170802, 3-205439, 4-153203, and JP 61-4255.
No. 3, for example, describes such a manufacturing method.

In producing the polypropylene resin for forming the polypropylene resin film of the present invention, any known method as described above can be used. Examples of actual resins obtained by such a production method include "PER" manufactured by Tokuyama Soda Co., Ltd. and "Cataloy" manufactured by Highmont Co., Ltd. Any of these can be used in the present invention.

Stabilizers such as antioxidants and ultraviolet absorbers can be added to the polypropylene resin used in the present invention. In applications where transparency is not required, precipitated barium sulfate, talc, calcium carbonate, Fillers such as mica and titanium oxide, colorants and the like can be added.

In the present invention, the above polypropylene resins (A) and (B) are melt-extruded into a sheet by a three-layer coextrusion air-cooling inflation method to obtain a film. The obtained film has a three-layer structure in which outer layers are respectively laminated on both sides of the central layer, and the thickness of the polypropylene resin film is 10 to 120 μm, preferably 30 to 100 μ from the viewpoint of strength and moldability.
m is suitable. The thickness of the central layer is preferably 40 to 90% of the total thickness, and the thickness of the outer layer is 30 to 90% of the total thickness.
5% is preferable.

[0029]

The polypropylene resin (A) is used to form the center layer of the film, and the outer layers laminated on both sides of the center layer are made of the polypropylene resin (B), and a normal upward three-layer air-cooled inflation facility is used. A film having a stable and uniform thickness can be obtained by molding a film having a three-layer structure, and a film having transparency comparable to that of the film formed by the T-die cast molding method and excellent impact strength. Obtainable.

[0030]

EXAMPLES The present invention will be specifically described below based on examples.

Example 1 As a polypropylene resin for forming the central layer, a weight average molecular weight of 250,000,
The elution amount by the cross fractionation method at 0 ° C or less is 44% by weight of the total polypropylene resin amount, and the elution amount at 0 ° C to 80 ° C is 29% by weight, 80% or less of the total polypropylene resin amount.
Polypropylene resin having a composition in which the amount of elution above 100 ° C and below 100 ° C is 4% by weight of the total amount of polypropylene resin, and the amount of elution above 100 ° C and below 125 ° C is 24% by weight of the total amount of polypropylene resin ( A-1) was used.

As the polypropylene resin forming the outer layers laminated on both sides of the central layer, a weight average molecular weight of 260,
000, the elution amount of 0 ° C. or more and 20 ° C. or less by the cross fractionation method is 3% by weight of the total polypropylene resin amount, and the elution amount of 20 ° C. or more and 70 ° C. or less is 16% by weight of the total polypropylene resin amount, 70 A polypropylene resin (B-1) having a composition of 81% by weight or more of the elution amount of 110 ° C. or less above 110 ° C. was used.

The above resins were extruded by the usual three-layer coextrusion air-cooling inflation method so that the central layer had a thickness of 50 μm and the outer layers had a thickness of 10 μm to obtain a polypropylene resin film having a three-layer structure. .

The results of measuring the physical properties of the obtained resin film are shown in Table 1.

The physical properties shown in Table 1 were measured according to the following methods.

Tensile strength: Measured at room temperature (23 ° C.) according to JIS K6301.

DDI (dirt drop impact strength, height 800 mm) impact strength value: measured according to JIS Z1702.

Haze value: Measured according to JIS K 7105.

Comparative Example 1 Polypropylene resin (A-
A 70 μm thick polypropylene resin film having a single-layer structure was obtained in the same manner as in Example 1 except that only 1) was used.

The physical properties of the obtained resin film were evaluated in the same manner as in Example 1. Table 1 shows the results.

(Comparative Example 2) Polypropylene resin (B-
A 70 μm thick polypropylene resin film having a single-layer structure was obtained in the same manner as in Example 1 except that only 1) was used.

The physical properties of the obtained resin film were evaluated in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 3 A polypropylene resin film having a single layer structure and a thickness of 70 μm was prepared in the same manner as in Example 1 except that only a random type copolymerized polypropylene resin (C) having an ethylene content of 2.5% by weight was used. Got

Since the thickness of the obtained film was not uniform, its physical properties could not be measured.

(Comparative Example 4) A film having a thickness of 70 μm was prepared in the same manner as in Example 1 except that only a random type copolymerized polypropylene resin (C) having an ethylene content of 2.5% by weight was used and the molding was carried out by the T-die casting method. A polypropylene resin film having a single layer structure was obtained.

The physical properties of the obtained resin film were evaluated in the same manner as in Example 1. Table 1 shows the results.

[0047]

[Table 1]

[0048]

According to the present invention, the center layer of the film is formed of the polypropylene resin (A), the outer layers laminated on both sides of the center layer are formed of the polypropylene resin (B), and the normal upward direction is obtained. A three-layer film was formed using a three-layer air-cooled inflation equipment, so that a film having a stable and uniform thickness was obtained, and the transparency was excellent and comparable to the film formed by the T-die casting method. A film having impact strength can be obtained.

That is, as in the conventional case, when only the polypropylene resin (A) is used, a film having a uniform thickness and excellent in impact resistance can be obtained, but the film becomes cloudy and transparency cannot be obtained. . Further, when only the polypropylene resin (B) is used, a film having a uniform thickness and relatively good transparency can be obtained, but the impact resistance is poor. When only the random type copolymerized polypropylene resin (C) is used, a film having a uniform thickness cannot be obtained.

On the other hand, according to the present invention, as described above, a film excellent in both transparency and impact resistance can be obtained.

The obtained polypropylene resin film is excellent in transparency and gloss, and is also excellent in impact resistance, so that it can be suitably used for packaging foods, clothing, sundries and the like.

Claims (1)

[Claims] 1. The center layer has a weight average molecular weight of from 80,000 to
Polypropylene resin in the range of 400,000, the elution amount at 0 ° C or less by the cross fractionation method is 30 to 55% by weight of the total polypropylene resin, and the elution amount at 0 ° C or more and 80 ° C or less. Is the total polypropylene resin amount of 2
0 to 40% by weight, and the elution amount at temperatures above 80 ° C and below 100 ° C is 1 to 15% by weight of the total polypropylene resin system, 10
Mainly composed of polypropylene resin (A) having a composition in the range of 10 to 35% by weight of the total amount of polypropylene resin above 0 ° C. and 125 ° C. or less, provided on both sides of the central layer. The outer layer is a polypropylene resin having a weight average molecular weight in the range of 80,000 to 400,000, and the temperature is 0 ° C. or more by a cross fractionation method.
Elution amount below ℃ is 0 to 1 of total polypropylene resin amount
0% by weight, the elution amount at 20 ° C. to 70 ° C. is 5 to 20% by weight of the total polypropylene resin amount, and the elution amount at 70 ° C. to 110 ° C. is 80 to the total polypropylene resin amount. A polypropylene resin film mainly composed of a polypropylene resin (B) having a composition within a range of 100% by weight and formed by a three-layer coextrusion air-cooled inflation method.