JP2671223B2 - Highly transparent propylene polymer film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a highly transparent propylene polymer film. More specifically, it relates to a propylene polymer film containing a specific 3-methylbutene-1 polymer and having excellent optical properties.

[Prior art and its problems] Propylene polymer films are excellent in optical properties such as transparency and luster, mechanical properties such as tensile strength and rigidity, and moisture resistance, and are inexpensive and therefore food packaging and fiber. Used in a wide range of packaging and other applications. However, depending on the application, these properties are not sufficiently satisfied. Above all, there is a problem with the optical properties, so that the field of use is greatly restricted.

Therefore, various attempts have been made to improve the optical properties of the propylene polymer film,
For example, it is known that the addition of an aluminum salt of an aromatic carboxylic acid, dibenzylidene sorbitol, substituted dibenzylidene sorbitol, etc. serves as the generator of crystal nuclei (hereinafter referred to as "agent") to alleviate the above problems. Has been. However, all of these agents are low molecular weight substances and have problems of odor and bleeding, and also contaminate the chill roll at the time of molding, and also deteriorate thermal stability, resulting in difficulty in long-term operation. .

On the other hand, several methods of using a polymer compound as the agent have been proposed as methods for improving the drawbacks of these agents. For example, JP-A-60-139731 proposes a method of using a vinylcycloalkane polymer having 6 or more carbon atoms as the polymer agent. This method gives relatively good results, but vinyl cycloalkanes are expensive, and since the boiling point is high, a stringent washing operation is required in the monomer removal step. There are some problems in producing the propylene polymer it contains.

Since 3-methylbutene-1 is cheaper than vinylcycloalkane and has a low boiling point and is easy to handle, some attempts have been made to improve transparency by using a polymer of 3-methylbutene-1 as a polymer. However, the current situation is that the expected effects have not been obtained.

For example, in JP-A-61-21144, 3-methylbutene-1
A propylene homopolymer containing a polymer at 12 ppm by weight,
The transparency of the 0.5 mm sheet obtained by melt extrusion was evaluated, but the transparency improving effect was hardly recognized as compared with the sheet containing no 3-methylbutene-1 polymer.

Further, in Japanese Patent Laid-Open No. 139731/1985, the same 3-methylbutene-
1 mm of propylene polymer containing 200 ppm by weight of 1 polymer
There is a description about the permeability of the press sheet, but this is also 3
Almost no improvement effect is recognized as compared with those containing no methylbutene-1 polymer.

In addition, JP-A-61-151204, JP-A-62-27511 and JP-A-63-69809 also disclose a propylene polymer containing a 3-methylbutene-1 polymer. The purpose is to improve rigidity, and nothing is said about improvement in transparency.

The present inventors have conducted intensive studies in view of the current situation as described above, and as a result, determined that the content of 3-methylbutene-1 polymer in the propylene polymer was specific and selected appropriate molding conditions. Thus, a propylene polymer film or sheet having excellent transparency was obtained, thereby achieving the present invention.

That is, the gist of the present invention is to prepare a propylene polymer composition containing 0.003 to 0.5% by weight of a 3-methylbutene-1 polymer having a melting point of more than 303 ° C. and a crystallization rate of 2 to 50 seconds from a T-die in a molten state. This is a highly transparent propylene polymer film obtained by cooling and solidifying with a chill roll at a temperature of 40 to 100 ° C. after extrusion.

In the present invention, the higher the crystallinity of the 3-methylbutene-1 polymer used, the greater the effect of improving the optical properties. The melting point or heat of fusion measured by a differential scanning calorimeter is used as one of the measures of the degree of crystallinity.

The melting point of the 3-methylbutene-1 polymer used in the present invention is higher than 303 ° C, and the heat of fusion is preferably 15 cal / g or more, more preferably, the melting point of the 3-methylbutene-1 polymer is higher than 305 ° C. The heat of fusion is more than 16 cal / g.

The 3-methylbutene-1 polymer of the present invention may be a copolymer with another α-olefin having 2 to 18 carbon atoms as long as the above conditions are satisfied.

As a catalyst system used for obtaining such a 3-methylbutene-1 polymer, a Ziegler-Natta catalyst that gives a polymer having a particularly high stereoregularity is used.

Examples of such a catalyst include, for example, JP-B Nos. 54-27871, 55-8451, 55-8452, and 55-8003.
And JP-A-55-39165 and JP-A-55-14054.

For example, the aluminum content is 0.15 or less in the atomic ratio of aluminum to titanium, and a solid titanium trichloride catalyst complex containing a complexing agent and organic aluminum or further as a third component ether, ester, amine,
A catalyst system consisting of an electron donating compound such as an amide is preferably used. In addition, a titanium compound-supporting titanium catalyst can be favorably used.

The amount of 3-methylbutene-1 polymer in the propylene polymer is preferably 0.003 to 0.5% by weight, more preferably 0.003 to 0.5% by weight.
It is 005 to 03% by weight. If the content of the 3-methylbutene-1 polymer is too small, the effect of improving the crystallization rate, which will be described later, will be insufficient, and the transparency will decrease. On the other hand, when the content of the 3-methylbutene-1 polymer is too large, fish eyes are generated, the 3-methylbutene-1 polymer itself or the transparency is lowered due to the crystallization rate becoming too fast, and the cost is increased. Such problems are not so preferable.

By setting the content of the 3-methylbutene-1 polymer in the above range, the crystallization rate of the propylene polymer is 2 to
It will be in the range of 50 seconds. When the crystallization speed is 2 seconds or less, the crystallization speed is too high, and the adhesion of the propylene polymer film to the chill roll is deteriorated, and the transparency is reduced.
When the crystallization speed is 50 seconds or more, spherulites grow, and the transparency also decreases.

The method for producing a propylene polymer composition containing a 3-methylbutene-1 polymer used in the present invention includes the following: 1) polymerizing 3-methylbutene-1 using a Ziegler-Natta catalyst or the like to obtain a 3-methylbutene-1 polymer; In the presence of propylene homopolymerization or propylene and other α
-Copolymerization with olefins.

2) Propylene is homopolymerized or copolymerized with another α-olefin using a Ziegler-Natta catalyst or the like, followed by polymerization of 3-methylbutene-1 in the presence of a propylene polymer.

3) A polymer to be a masterbatch is produced by the method of 1) or 2), and propylene alone or a copolymer of propylene and another α-olefin is mixed.

4) Separately polymerized, a method of mixing a polymer of 3-methylbutene-1 and propylene alone or a copolymer of propylene and another α-olefin, and the like, may be used. Method 3) is the most preferred method.

That is, in the method of polymerizing propylene after the polymerization of 3-methylbutene-1 by the method of 1), the activity or the stereoregularity may decrease during the polymerization of propylene, and the method of 2) Then, after polymerizing a large amount of propylene, a small amount of 3-methylbutene-1 will be polymerized,
The switching of monomers is tight.

In addition, since it is necessary to make a polymer containing a polymer in 3-methylbutene-1 for each grade of polypropylene, in the case of continuously producing each grade with a continuous polymerization brand, 3-methylbutene-1 polymer There are many problems of contamination with grades that do not need to include.

On the other hand, the above-mentioned problem does not occur in a method in which a propylene polymer masterbatch containing a relatively large amount of the 3-methylbutene-1 polymer is produced and mixed with a propylene polymer produced by a usual method.

In the case of the 3) method, the content of the 3-methylbutene-1 polymer in the propylene polymer composition containing the 3-methylbutene-1 polymer produced in the method 1) or 2) is not particularly limited, but is 70% by weight. The following is preferred, and more preferably
50% by weight or less.

As a mixing method of the 3) method and the 4) method, a general method such as an extruder, a Brabender kneader, or a roll may be used.

Upon mixing, it is desirable to knead at a temperature in a range that does not cause melting of the 3-methylbutene-1 polymer.

Various additives generally added to the propylene polymer composition, for example, antioxidants, lubricants, antistatic agents, antiblocking agents, known fillers such as silica and the like can be appropriately added.

The film or sheet according to the present invention is used in an extruder
It is molded by the T-die molding method with a die attached.

In the T-die molding of the present invention, a chill roll is provided in front of the T-die, and the temperature of the chill roll is 40 to 100 ° C, preferably 50 to 70 ° C. If the chill roll temperature is too low, the rigidity of the film during molding becomes high, the adhesion to the roll becomes poor, and the transparency decreases. On the other hand, if the roll temperature is too high, the crystallization progresses rapidly and the transparency is lowered.

The film may be further stretched in at least a uniaxial direction. The thickness of the film or sheet here is preferably about 5 μm to 3 mm.

The highly transparent polypropylene film obtained by the present invention is particularly suitable for food packaging film because of its excellent optical properties and odorless property.

[Examples] Examples will be shown below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Physical properties in the following examples were measured according to the following methods.

1) Melt Flow Index (MFI) The measurement was performed according to ASTM D-1238 (230 ° C 2.1 kg).

2) Haze Measurement was performed according to ASTM D-1003.

3) Crystallization temperature (Tc) Measurement was carried out with a DSC2C type differential scanning calorimeter manufactured by Perkin / Elmer at a temperature rising / falling speed of 10 ° C / min.

4) Crystallization rate The sample was melted twice using the same differential scanning calorimeter as in 3) under the conditions shown in Table 1 below.
After holding for 40 minutes, the temperature is lowered to 396 で K at 40 ° C / minute,
And the time until the peak of the crystallization peak is reached is measured.

o Catalyst production example At room temperature, 515 ml of purified toluene was put into an autoclave with a volume of 1 which was sufficiently replaced with nitrogen, and 65.1 g (0.5 mol) of n-butyl ether and 94.9 g (0.5 m of titanium tetrachloride) were added under stirring.
ol) and diethyl aluminum chloride 28.6g (0.24m
ol) was added to give a brown homogeneous solution. Then, the temperature was raised to 30 ° C. After a lapse of 30 minutes, the temperature was raised to 40 ° C. and maintained at 40 ° C. for 2 hours. Then 32g of titanium tetrachloride (0.17m
ol) and 15.5 g of tridecyl methacrylate (0.058mo
l) was added and the temperature was raised to 98 ° C. After maintaining at 98 ° C. for 2 hours, a granular purple solid was separated and washed with toluene to obtain solid titanium trichloride.

o Resin Production Example-1 (Production of Propylene Polymer Masterbatch Containing 3-Methylbutene-1 Polymer) 1.2 mmol of diethylaluminum chloride was added at room temperature under an argon seal to the induction stirring autoclave of 2 sufficiently replaced with purified argon. Then, 700 cc of liquid 3-methylbutene-1 was charged.

Then, the temperature was raised to 70 ° C., 91 mg of the solid catalyst component obtained in the catalyst production example was added, and 3-methylbutene-1 was polymerized for 1 hour. Then, after purging all of 3-methylbutene-1, 3 mmol of diethylaluminum chloride and 0.12 mmol of methyl methacrylate were added to make H ₂ 0.5 kg / cm ^2, and 700 g of propylene was further added to homopolymerize propylene for 30 minutes. After that, propylene was purged and the catalyst was removed with an isobutanol / normal hexane mixed solvent to obtain 271 g of a propylene polymer composition including a 3-methylbutene-1 polymer.

Under the same polymerization conditions, the amount of 3-methylbutene-1 polymer obtained from the experiment in which propylene polymerization was not performed was
It was 10.8 g.

This 3-methylbutene-1 polymer had a melting point of 311 ° C. and a heat of fusion of 20 cal / g.

The content of 3-methylbutene-1 polymer in the propylene polymer composition calculated from the yield of the above 3-methylbutene-1 polymer was 4.0% by weight.

The MFI of this polymer was 0.27 g / 10 minutes, the melting point was 163.4 ° C, and the crystallization temperature was 126.6 ° C.

o Resin Production Example-2 1.27 parts by weight of the polymer obtained in Resin Production Example-1 and 0.1 part by weight of calcium stearate as a stabilizer, BHT
(2,6-Geta-tert-butyl hydroxytoluene)
0.2 parts by weight, Isoganox 1010 {antioxidant manufactured by Ciba Geigy, tetrakis [methylene-3- (3 ', 5-di-
t-butyl-4-hydroxyphenyl) propionate] methane} 0.08 parts by weight of propylene homopolymer 1220FP (MFI: 1.9 g / 10 minutes, melting point: 161.3 ° C., manufactured by Mitsubishi Kasei Co., Ltd.)
Crystallization temperature: 108.6 ° C., crystallization speed: 180 seconds) 100 parts by weight was added and mixed with a Henschel mixer, and then granulated into pellets with a 50 mmφ extruder. The content of 3-methylbutene-1 polymer in this resin composition was 0.05% by weight, MFI was 1.7 g / 10 minutes, melting point was 162.2 ° C, crystallization temperature was 118.7 ° C, and crystallization rate was 10 seconds.

o Resin Production Example-3 The procedure of resin production example-2 was repeated except that the amount of the polymer obtained in resin production example-1 was changed to 0.63 parts by weight. The content of 3-methylbutene-1 polymer in the obtained resin composition was 0.02.
5% by weight, MFI was 1.7 g / 10 minutes, melting point was 162.7 ° C, crystallization temperature was 118.2 ° C, and crystallization rate was 14 seconds.

o Resin Production Example-4 The procedure of Resin Production Example-2 was repeated except that the amount of the polymer obtained in Resin Production Example-1 was changed to 0.127 parts by weight. The content of 3-methylbutene-1 polymer in the obtained resin composition was 0.
005% by weight, MFI was 1.7 g / 10 minutes, melting point was 162.7 ° C, crystallization temperature was 117.5 ° C, and crystallization rate was 35 seconds.

o Resin Production Example-5 Except that in Resin Production Example-1, the amount of catalyst, cocatalyst, and methyl methacrylate was doubled, the polymerization time of 3-methylbutene-1 was quadrupled, and the polymerization time of propylene was 30 minutes. Was polymerized in the same manner as in Resin Production Example-1.

432 g of propylene polymer containing 3-methylbutene-1 polymer was obtained. The amount of 3-methylbutene-1 polymer produced when propylene was not polymerized was 64.8 g, from which the content of 3-methylbutene-1 polymer in the propylene polymer composition was estimated to be 15.0% by weight. .

The melting point of this 3-methylbutene-1 polymer was similar to that of Resin Production Example-1.

0.33 parts by weight of this 3-methylbutene-1 polymer-containing propylene polymer composition and the above-mentioned propylene homopolymer
The above additives were added to 100 parts by weight of 1220FP, and the mixture was mixed with a Henshur mixer, and then granulated into pellets with a 50 mmφ extruder. The MFI of this resin was 1.7 g / 10 minutes, the melting point was 162 ° C., the crystallization temperature was 118.3 ° C., and the crystallization rate was 12 seconds.

The content of the 3-methylbutene-1 polymer was 0.05% by weight.

o Resin manufacture example-6 It carried out like resin manufacture example-2 except having used 0.025 weight part of the polymer obtained in resin manufacture example-1. The content of 3-methylbutene-1 polymer in the obtained resin composition is
0.001% by weight, MFI was 1.8 g / 10 min, melting point was 161.5 ° C, crystallization temperature was 111.2 ° C, and crystallization rate was 175 seconds.

Example-1 The pellets obtained in Resin Production Example-2 were melt extruded at a molding temperature of 270 ° C. and an extrusion rate of 12 kg / hour in a 30 mmφT die molding machine, and cooled and solidified in a chill roll at 50 ° C. to a thickness of 0.1. A film of mm was obtained. The haze of this film was measured and found to be 7.5%.

Example-2 The film obtained in Example-1 was stretched 6 times in the machine direction at a stretching temperature of 160 ° C with a Miyoshi oven stretching machine to obtain a film having a thickness of 17µ. The haze of this film was measured and found to be 2.9%.

Example-3 A film having a thickness of 0.1 mm was obtained in the same manner as in Example-1 except that the chill roll temperature was set to 60 ° C using the pellets obtained in Resin Production Example-3. The haze of this film is 7.7
%Met.

Example-4 A film having a thickness of 17 μm was obtained in the same manner as in Example-2 using the film obtained in Example-3. The haze of this film was measured and found to be 3.0%.

Example-5 Example using the pellets obtained in Resin Production Example-4
A film having a thickness of 0.1 mm was obtained in the same manner as in 1. The haze of this film was 10.0%.

Example-6 A film having a thickness of 17 μm was obtained in the same manner as in Example-2 using the film obtained in Example-5. The haze of this film was measured and found to be 3.3%.

Example-7 Example using the pellets obtained in Resin Production Example-5
A film having a thickness of 0.15 mm was obtained in the same manner as in 1. The haze of this film was 15.0%.

Comparative Example-1 Using polypropylene 1220FP pellets manufactured by Mitsubishi Kasei Co., Ltd., a film having a thickness of 0.1 mm and a film having a thickness of 0.15 mm were obtained in the same manner as in Example-1. The haze of these films is 16.1% each.
(0.1 mm) and 25.0% (0.15 mm).

Comparative Example-2 A film having a thickness of 17 µ was obtained in the same manner as in Example-2 using the 0.1 mm film obtained in Comparative Example-1. The haze of this film was 3.8%.

Comparative Example-3 A film having a thickness of 0.1 mm was obtained in the same manner as in Example-1 except that the temperature of the chill roll in Example-1 was 20 ° C. The haze of the film was 18%.

If the molding conditions are thus selected incorrectly, the transparency of the film obtained using the composition of the present invention will decrease.

Comparative Example-4 Practical example using the pellets obtained in Resin Production Example-6
A film having a thickness of 0.1 mm was obtained in the same manner as in 1. The haze of this film was 15.8%.

The haze measurement results of Examples 1 to 7 and Comparative Examples 1 to 4 are shown in Table-2.

[Effects of the Invention] The film of the present invention is excellent in transparency and has a great practical effect as a film for various packaging materials and other uses.

Claims (3)

(57) [Claims] (1) 3-methylbutene having a melting point exceeding 303 ° C.
Crystallization rate of 2 containing 0.003 to 0.5% by weight of 1 polymer
A highly transparent propylene polymer film obtained by extruding a propylene polymer composition for 50 seconds from a T-die in a molten state, and then cooling and solidifying with a chill roll at a temperature of 40 to 100 ° C. 2. The propylene polymer as claimed in claim 1, wherein the propylene polymer composition containing a 3-methylbutene-1 polymer is polymerized in the presence of the 3-methylbutene-1 polymer. And a propylene polymer obtained by mixing the propylene polymer and the propylene polymer. 3. The film according to claim 1, wherein the propylene polymer composition containing a 3-methylbutene-1 polymer is a 3-methylbutene-1 polymer polymerized in the presence of a propylene polymer. And a propylene polymer obtained by mixing the propylene polymer and the propylene polymer.