JPH10292075A - Polypropylene resin composition for heat-resistant biaxially oriented matte film and biaxially oriented film prepared therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polypropylene resin compsn. which, when formed into a film, gives a biaxially oriented matte film having a sufficient roughness and a good heat resistance. SOLUTION: This compsn. comprises 60-90 wt.% propylene homopolymer (A) and 40-10 wt.% high-density polyethylene (B), and the melt viscosity (measured at 230 deg.C at a shear rate of 100 sec-1) of ingredient B is higher than that of ingredient A by at least 500 Pa.s.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a polypropylene resin composition and a biaxially stretched film thereof. Specifically, a biaxially stretched polypropylene resin composition capable of forming a mat having a high heat resistance by biaxially stretching, and having good heat resistance obtained by stretching the polypropylene resin composition About the film.

[0002]

2. Description of the Related Art Since polypropylene has excellent stretching properties, it can be formed into a uniform thin film, and is utilized widely in various fields by utilizing its excellent properties.

[0003] Biaxially stretched polypropylene films are usually used for applications that take advantage of their original transparency or gloss. On the other hand, matte films having a roughened surface such as a print laminate on printed matter are also used. It is increasingly being used.

As a method for producing such a matte film, there has been proposed a method based on a mixture of a propylene copolymer and high-density polyethylene as disclosed in JP-A-5-162266.

[0005]

Heretofore, in the production of a matte film, a copolymer of monomers such as propylene and ethylene has been used as a base polypropylene in order to obtain a sufficiently roughened film. Using
A mixture of this copolymer and high density polyethylene was used. However, the method using a mixture of a propylene copolymer and a high-density polyethylene has problems such as insufficient heat resistance when formed into a film, and the heat applied during print lamination reduces the roughness of the film.
Insufficient heat resistance is presumed to be due to the use of a propylene copolymer as a base, but in this case, using a propylene homopolymer alone to improve heat resistance does not provide a sufficient rough surface. . Generally, it is industrially preferable that the heat resistance of the film is high and the roughness of the film surface does not change with the heat history.

[0006]

Means for Solving the Problems The present inventors diligently searched for a polypropylene resin composition which has solved the above problems and has high heat resistance when formed into a stretched film, and completed the present invention.

That is, the present invention relates to (A) 60 to 90 parts by weight of a propylene homopolymer, and (B) a high density polyethylene 40
-10 parts by weight of the mixture, the shear rate measured at 230 ° C being 100 / sec. The melt viscosity difference between (A) and (B) (melt viscosity of (B) −melt viscosity of (A)) is 5
00Pa · sec. The heat-resistant matte biaxially stretched polypropylene resin composition described above.

[0008] The present invention is also a heat-resistant matt biaxially stretched film characterized in that the above-mentioned polypropylene resin composition is laminated on at least one surface of a polypropylene base layer.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention has been made by searching for and finding a resin composition which has an excellent rough surface state when formed into a film and which has good heat resistance.
The present invention relates to a polypropylene resin composition in which the problem that the film roughness is reduced by the heat applied during print lamination is solved. That is, it is a composition obtained by mixing a propylene homopolymer and a high-density polyethylene at a specific mixing ratio, and is a polypropylene resin composition in which a difference in melt viscosity of each component is equal to or more than a certain value. It is.

As the homopolymer of propylene as the component (A) used in the present invention, those obtained by industrially polymerizing olefins or those widely available in the market can be used without any problems. Above all, those having a relatively high stereoregularity are preferable, and the melting point (hereinafter, referred to as Tm) measured at a temperature of 10 ° C./min using a differential scanning calorimeter (DSC) is 155 ° C. to 160 ° C. Some are used. As long as it is within this melting point range, it may contain a small amount of another olefin (for example, ethylene of 1.0% or less). Particularly preferred is a homopolymer of propylene. The molecular weight is 230 ° C, 2.16 kg
Melt flow index measured by load (hereinafter, MI
It is written. ) Is preferably selected from those having 0.3 to 10.0 g / 10 minutes.

As the high-density polyethylene used in the present invention, those available on the market can be used, having a density of 0.940 to 0.965 g / cm ³ and a melt flow index measured at 190 ° C. of 0.1. 02-0.5
g / 10 min.

In the present invention, the amount of the component (A) used is 60 to 90 parts by weight. If the amount is less than 60 parts by weight, the roughness of the film becomes too large, and the heat resistance is lowered, which is not preferable. . On the other hand, if it exceeds 90 parts by weight, it is not preferable because sufficient roughness cannot be obtained when the film is formed. Therefore, the amount of the remaining component (B) used is 40 to 10 parts by weight.

In the present invention, what is important is a shear rate of 100 / sec. The melt viscosity difference between the component (A) and the component (B) at 500 Pa · sec. That is all. When the melt viscosity difference is 500 Pa · sec.
If it is less than 1, the roughness of the film is rapidly reduced, which is not preferable. The melt viscosity difference is 3000 Pa · s
ec. It is particularly preferred that: Melt viscosity difference is 3
000 Pa · sec. When the ratio exceeds the above range, what is called fish eyes based on high-density polyethylene when formed into a film becomes noticeable, which is not preferable.

Here, the melt viscosity of the resin was measured using a conical disk-type rheometer (MR-500 manufactured by Rheology Co., Ltd., cone angle 5 de).
g, disk diameter 20 mm) and the measurement temperature is 150 to 250.
° C, measurement angular frequency 0.1-100 rad / sec. , Measured within a linear range of 1 to 10%.

The polypropylene resin composition of the present invention may contain, if necessary, additives usually added to polypropylene, such as an antioxidant, an antistatic agent, a lubricant, an ultraviolet absorber, a coloring agent, and a hydrochloric acid scavenger. Of course, it is possible.

The respective components of the polypropylene resin composition of the present invention are mixed at 180-300
The mixture is heated and melted in the range of ° C. to form pellets, and usually formed into a biaxially stretched film after lamination on a polypropylene base layer.It is determined whether or not the polypropylene resin composition for the surface layer of this stretched film has specific characteristics. is important.

When the polypropylene resin composition of the present invention is actually used for a matting film, the above-mentioned polypropylene resin composition is usually laminated on at least one surface of a polypropylene base layer and then biaxially stretched to obtain a desired film. .

As the polypropylene base layer, a general propylene homopolymer or a copolymer of propylene can be used without any problem. However, it is preferable that the surface layer has higher heat resistance than the polypropylene used in the polypropylene resin composition of the present invention. Preferably, it is usually preferable to be a propylene homopolymer.

The method for forming the biaxially stretched film of the present invention is not particularly limited, but a usual method for producing a stretched film of a laminate of polypropylene can be used.

In the above method, for example, a laminated sheet is prepared by a two-layer T-die film forming machine so that the base layer is made of polypropylene and the surface layer is made of the polypropylene resin composition of the present invention. There is a method of obtaining.

In the present invention, since a propylene homopolymer is used, it is important to set the temperature slightly higher during stretching than in the case of using a propylene copolymer. When the composition of the present invention is stretched, if it is forcibly stretched at a relatively low temperature, sufficient roughness may not be developed, and the preferred stretching temperature is 5 ° C. lower than the melting point of the polypropylene used. ℃ higher temperature.

Specifically, a laminated sheet having a base layer thickness of 400 μm and a surface layer (rough surface layer) of 100 μm is prepared at 250 ° C. using a 20 mmφ two-layer T-die film forming machine. After preheating the sheet thus obtained at 160 ° C. for 30 seconds,
A method of sequentially stretching the film 7 times in the machine direction and 7 times in the transverse direction at a deformation rate of 300% / sec at 0 ° C. to obtain a film having a thickness of 10 μm can be exemplified. It is common to do it.

[0023]

The present invention will be further described with reference to the following examples.

In the following examples, the degree of surface roughening was determined by measuring the haze (according to ASTM-D1003). The measurement of the change in roughness during lamination of the film was performed by the following method.

Dry lamination with a biaxially stretched polypropylene film is performed at a linear pressure of 3 kg / cm at 110 ° C., 117 ° C. and 125 ° C., and the haze is measured. The difference between the haze value and the haze value before lamination is used as an index of the change in roughness.

Example 1 A propylene homopolymer having an MI of 1.5 g / 10 min and a Tm of 157.0 ° C. (FO, manufactured by Mitsui Toatsu Chemicals, Inc.) 7
A high-density polyethylene (manufactured by Mitsui Petrochemical Co., Ltd., Hyzex 8200) having a melt flow index measured at 190 ° C. of 0.03 g / 10 minutes with respect to 5 parts by weight.
B) 25 parts by weight of BHT.
10 parts by weight, 0.10 parts by weight of Irganox-H1010 (trade name, Ciba Geigy) and 0.10 parts by weight of calcium stearate as a hydrochloric acid scavenger are mixed, and then pelletized at 200 ° C. using a 30 mmφ twin screw extruder. It has become. The shear rate of each of the propylene homopolymer and the high-density polyethylene measured at 230 ° C was 100 / s.
ec. Melt viscosity at 720 Pa · s, 2510 P
a · s, and the melt viscosity difference was 1790 Pa · s.

The resulting pellet had an MI of 0.85 g / 1.
Tm was 130.2 ° C and 157.5 ° C.

Then, using the pellets as a surface layer material and a polypropylene homopolymer (PJS, manufactured by Mitsui Toatsu Chemicals, Inc.) with an MI of 1.5 g / 10 min as a base layer material, a two-layer T-die film of 20 mmφ was formed. A laminated sheet having a base layer thickness of 400 μm and a surface layer (rough surface layer) of 100 μm was prepared at 250 ° C. using a machine. After pre-heating the obtained sheet at 160 ° C. for 30 seconds using a TM Long Co. biaxial stretching machine,
Deformation rate 300% / sec at 0 ° C 7 times in vertical direction, 7 times in horizontal direction
Double stretching was performed to obtain a film having a thickness of 10 μm.

The total haze of the film obtained by the above method is 5
The internal haze was 6.8% and the internal haze was 1.5%.

The obtained film and the biaxially oriented polypropylene film were subjected to dry lamination at a linear pressure of 3 kg / cm at 110 ° C., 117 ° C. and 125 ° C., and the total haze value was measured to be 54.7%. , 52.
8% and 53.1%. It can be seen that the difference in haze value before and after lamination does not increase even when the temperature during lamination is increased, and the change in roughness is small, that is, the heat resistance is excellent.

Example 2 The procedure was the same as in Example 1 except that Hi-Zex 5000H manufactured by Mitsui Petrochemical Co., Ltd. having a melt flow index measured at 190 ° C. of 0.11 g / 10 minutes was used as high-density polyethylene. In addition, the shear rate of 100 / sec. Has a melt viscosity of 720
Pa · s, 1450 Pa · s, and the melt viscosity difference is 73
It was 0 Pa · s.

The resulting pellet had an MI of 1.10 g / 1.
It was 0 minutes and the Tm was 130.5 ° C, 157.3 ° C. The total haze of the obtained film was 54.7%, and the internal haze was 1.8%.

The total haze after dry lamination at 110 ° C., 117 ° C. and 125 ° C. was 53.5.
%, 52.6% and 52.9%, and the difference between the haze values before and after lamination did not increase even when the temperature during lamination was increased, the change in roughness was small, and the heat resistance was excellent.

Example 3 JH manufactured by Mitsui Toatsu Chemicals, Inc. having a MI of 7.8 g / 10 min and a Tm of 159.0 ° C. as a propylene homopolymer.
H, and the same procedure as in Example 1 except that HISEX 5000H manufactured by Mitsui Petrochemical Co., Ltd. was used as the high-density polyethylene. The shear rate of each of the propylene homopolymer and the high-density polyethylene measured at 230 ° C. was 100 / sec. Melt viscosity at 349 Pa.
s, 1450 Pa · s, and the melt viscosity difference is 1101 P
a · s.

The resulting pellet had an MI of 6.6 g / 10
And the Tm was 129.6 ° C and 159.1 ° C. The total haze of the obtained film was 50.2%, and the internal haze was 1.2%.

The total haze after dry lamination at 110 ° C., 117 ° C. and 125 ° C. was 48.0.
%, 46.9%, and 46.5%, and the difference in haze value before and after lamination did not increase even when the temperature during lamination was increased, the change in roughness was small, and the heat resistance was excellent.

COMPARATIVE EXAMPLE 1 A propylene homopolymer having an MI of 0.31 g / 10 min and a Tm of 160.0 ° C. manufactured by Mitsui Toatsu Chemicals, Inc.
Example 1 was carried out in exactly the same manner as in Example 1 except that B was used and HIZEX 5000H manufactured by Mitsui Petrochemical Co., Ltd. was used as high density polyethylene. The shear rate of each of the propylene homopolymer and the high-density polyethylene measured at 230 ° C. was 100 / sec. The melt viscosity at
s, 1450 Pa · s, and the melt viscosity difference is 340 Pa
-It was s.

The resulting pellet had an MI of 0.54 g / 1.
It was 0 minutes, and Tm was 130.1 ° C and 160.2 ° C. The total haze of the obtained film was 8.2%, the internal haze was 1.3%, and the film was very low in roughness.

Comparative Example 2 MI was 8.0 g / 10 instead of propylene homopolymer.
In the same manner as in Example 1 except that an ethylene-propylene random copolymer having a Tm of 153.9 ° C. and an ethylene content of 1.5% was used. Note that each of the ethylene-propylene random copolymer and the high-density polyethylene was 23
Shear rate 100 / sec. Was 349 Pa · s and 2510 Pa · s, and the difference in melt viscosity was 2161 Pa · s.

The resulting pellet had an MI of 5.4 g / 10
And the Tm was 130.0 ° C. and 154.8 ° C. The total haze of the obtained film was 52.0%,
The internal haze was 1.1%.

The total haze after dry lamination at 110 ° C., 117 ° C. and 125 ° C. was 50.0.
%, 47.3%, and 45.1%, and the difference between the haze values before and after lamination increased as the temperature during lamination increased, and the change in roughness increased. This indicates that the heat resistance is poor.

Comparative Example 3 MI instead of propylene homopolymer was 8.0 g / 10
The procedure was exactly the same as in Example 1 except that an ethylene-propylene random copolymer having a Tm of 147.3 ° C. and an ethylene content of 2.9% was used. Note that each of the ethylene-propylene random copolymer and the high-density polyethylene was 23
Shear rate 100 / sec. Was 320 Pa · s and 2510 Pa · s, and the difference in melt viscosity was 2190 Pa · s.

The resulting pellet had an MI of 5.8 g / 10
And Tm was 130.0 ° C. and 152.0 ° C. The total haze of the obtained film was 56.6%, and the internal haze was 1.1%.

The total haze value after dry lamination at 110 ° C., 117 ° C. and 125 ° C. was 53.1.
%, 49.3%, and 45.3%, and the difference between the haze values before and after lamination increased as the temperature during lamination increased, and the change in roughness increased. This indicates that the heat resistance is poor.

[0045]

EFFECT OF THE INVENTION By using the polypropylene resin composition of the present invention, it is possible to obtain a mat-stretched film having good heat resistance, which is extremely valuable industrially.

 ────────────────────────────────────────────────── ─── Continued from the front page (72) Inventor Tadashi Asanuma 1-6-6 Takasago, Takaishi-shi, Osaka Mitsui Toatsu Chemicals Co., Ltd.

Claims (2)

[Claims] 1. A propylene homopolymer (A)
Parts by weight, (B) a mixture of 40 to 10 parts by weight of high density polyethylene, having a shear rate of 100 measured at 230 ° C.
/ Sec. The melt viscosity difference between (A) and (B) (melt viscosity of (B) −melt viscosity of (A)) is 500 Pa
-Sec. The heat-resistant matt biaxially stretched polypropylene resin composition as described above. 2. A heat-resistant matt biaxially stretched film comprising the polypropylene resin composition according to claim 1 laminated on at least one surface of a polypropylene base layer.