JPH01301720A - High-transparent stretched film of polypropylene and production thereof - Google Patents

Abstract

PURPOSE:To obtain the subject industrially useful film excellent in transparency, by stretching a sheet with a specified ratio of X-ray diffraction intensity of beta-crystal in >=one direction. CONSTITUTION:To a high-crystalline polymer, e.g. a sorbitol-based nucleating agent is added and the resultant mixture is executed from a die and rapidly cooled to prepare a sheet with >=0.1 ratio of the height of a diffraction peak at 2theta=15.8 deg. belonging to beta-crystal to the sum total of the heights of diffraction peaks at 13.8 deg., 16.6 deg. and 18.3 deg. belonging to alpha-crystal in wide angle X-ray diffraction spectra (K-Cu ray is used). The resultant sheet is then stretched in >=one directions, thus obtaining the objective film.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a highly transparent stretched polypropylene film and a method for producing the same.Specifically, the present invention relates to a highly transparent stretched polypropylene film produced by stretching a sheet having specific properties, and a stretched polypropylene film produced by stretching a sheet having specific properties. Regarding the manufacturing method.

[Conventional technology]

Although polypropylene is a polymer with relatively excellent transparency, it is a crystalline polymer, and various degrees of transparency can be obtained depending on the molding conditions. A method of copolymerizing with other olefins such as ethylene to control the crystallinity or the size of spherulites for the purpose of further improving transparency;
Alternatively, there are known methods such as adding a nucleating agent to make the spherulites smaller, and increasing the cooling rate of the molded product to make the spherulites smaller. These methods have certain effects, and methods that control the size of spherulites are particularly useful.

(Problem B to be solved by the invention) A method of controlling the size of spherulites is useful, but
In the case of stretched films, even if the transparency of the original sheet is equally good, stretching produces a difference in transparency, and in some cases, the film may become extremely opaque.

An object of the present invention is to provide a highly transparent stretched polypropylene film that solves the above problems and a method for producing the same.

[Means for Solving the Problems] The present inventors conducted a rigorous analysis of the conventional films with differences in transparency, and found that the stretched films obtained had almost no difference in X-ray diffraction spectra. It has also been found that even if there is no difference in the size of the spherulites, the transparency may vary greatly, and this is due to the large difference in the smoothness of the stretched film surface.

As a result of intensive studies based on this discovery, the present inventors discovered that by stretching a sheet that satisfies specific conditions, a stretched film with extremely excellent transparency, which had not been previously known, could be obtained. completed.

That is, the present invention consists of a highly crystalline polypropylene that is a homopolymer of propylene or a copolymer with a small amount of other α-olefin, and has X-
Sorting in which the ratio of the intensity of the diffraction line attributed to the β crystal to the sum of the intensities of the diffraction lines attributed to the α crystal and the three products obtained by measurement with a line diffraction spectrum is 0.1 or less, at least one of them. This is a highly transparent stretched polypropylene film made by stretching the polypropylene. The present invention also relates to a suitable manufacturing method thereof, in which at least a sort obtained by extrusion molding a highly crystalline polypropylene, which is a propylene homopolymer or a copolymer with a small amount of other α-olefin, and taken out from a gooey. The ratio of the intensity of the diffraction line attributed to the β-crystal to the sum of the intensities of the diffraction lines attributed to the α-crystal and β-crystal obtained by measuring an X-ray diffraction spectrum on the surface is 0.1 or less. This is a method for producing a highly transparent stretched polypropylene film, which is characterized by stretching the sort obtained by cooling the polypropylene film.

The method for producing the film of the present invention will be shown below, and the film of the present invention will be explained in detail.

The stretched film of the present invention is characterized by the properties of the preceding sheet, and the sheet is characterized by the sum of the intensities of diffraction lines attributed to α crystals and β crystals obtained by measuring an X-ray diffraction spectrum at least on its surface. It is necessary that the ratio of the intensity of the diffraction line attributed to the β crystal is 0.1 or less. The smaller the ratio υ of the intensity of the diffraction line attributed to the β-crystal (hereinafter simply referred to as the ratio of the β-crystal), the better, more preferably 0.05 or less, and most preferably O.

There are various seeding methods for manufacturing such sheets, and there are no particular limitations. to do. To relatively rapidly cool the sheet that has been extruded from the goose when forming the sheet. Stretch from the thinnest sheet possible. By combining these conditions,
It is possible to reduce the ratio of the three items to 0.1 or less. The necessary conditions vary depending on the propylene used, but in the laboratory, it is possible to reduce the ratio of the three components to virtually zero by simply adding an additive that increases the crystallization temperature and cooling the sheet.
However, industrially, this can be achieved by using polypropylene added with a nucleating agent effective in forming α-crystals, and by molding the sheet under conditions that allow for relatively rapid cooling.

The polypropylene used in the present invention is not particularly limited as long as it has high crystallinity (not only propylene homopolymers but also statistical copolymers with ethylene, butene, hexene, etc. can be used, and propylene 1 is usually used as polypropylene. Against 0.
Those containing other olefins in a molar ratio of about 1 or less can be used. Further, as for the molecular weight, those having a melt flow rate of preferably about 0.1 to 10 as measured at 230'C can be used.

In the present invention, the proportion of β crystals was measured using a -Cu line according to the following definition. For example, when explaining the wide-angle X-ray diffraction spectrum of the sheet surface of Comparative Example 1 with reference to Fig. 2,
The 2θ value of wide-angle X-ray diffraction vector is approximately 13.8°,
The peaks at 16.6° and 18.3° are defined as α crystals, and the intensity is expressed by the peak height.

Similarly, a peak with a 2θ value of about 15.8° is defined as β crystal, and the intensity is similarly expressed by the peak height.

(TURIIERJORES et al. Makromol, Ch.
emie vol, 75+ 134 (1964). ).

[Example] The present invention will be further explained with reference to Examples below.

Example 1 Internal volume 0.97 containing 2.2 kg of steel balls with a diameter of 12 mm
A vibrating mill equipped with two N grinding pots was prepared, and 20 g of magnesium chloride, 4 mQ of tetranidoxin run, and 3 α,α,α-trichlorotoluene were added to each pot under a nitrogen atmosphere, and the mixture was ground for 40 hours. did.

Put 15 g of the co-pulverized product thus obtained into a 200 mff1 flask, add 80 m of titanium tetrachloride and 80 m of toluene.
1 and stirred at 100'C for 30 minutes. After that, the supernatant liquid was removed, 80 ml of titanium tetrachloride and 80 ml of toluene were added in the same manner, and the mixture was stirred at 100°C for 30 minutes.
The solid content obtained by removing the supernatant liquid was washed repeatedly with n-hexano to obtain a transition metal catalyst slurry. A portion of it was sampled and analyzed for titanium content, which was found to be 19%.

In a flask with an internal volume of 200 mff1, under a nitrogen atmosphere, 40 ml of toluene, 10.0 g of the above transition metal catalyst, 240 g of diethylaluminum chloride, 14 ml of methyl p-toluate, and 20 ml of methyl p-toluate were added and mixed. The catalyst slurry was placed in an autoclave with an internal volume of 3,001 cm containing sufficiently degassed n-hebutane 11, and after replacing the gas phase with propylene, hydrogen 2
ON, i! and then add propylene so that the pressure is 5 kg/cm gauge, the internal temperature is 70'c and the propylene charge is 50 kg.
It was polymerized until Next, unreacted propylene was purged, methanol 20β was added, and the mixture was stirred at 90° C., and the resulting slurry was purified by washing with water. Filter the slurry, separate the powder, 80°C160C16O
It was dried for 12 hours.

When the obtained powder was analyzed, it was found that the extraction residual rate of boiling K n -hebukun was 97.7%, and the intrinsic viscosity was 172 (hereinafter abbreviated as η) as measured with a tetralin solution at 135°C.

On the other hand, a master powder containing a polymer of allyltrimethylsilane was produced using the above transition metal catalyst. 3
In a flask of 00 precepts, 5 g of transition metal catalyst, 5 rrdl of diethylaluminum chloride, 10 precepts of allyltrimethylsilane, 10 m of l.luene! The slurry was then stirred at 60°C for 2 hours, and the slurry was placed in an autoclave with an internal volume of 31 cm.
In addition, 0.2NN of hydrogen and propylene were charged and the pressure was increased to 5.
kg/cf+ gauge, and then polymerization was carried out at a constant pressure at an internal temperature of 60°C until the amount of propylene charged was 500 g. A master powder containing 12,000 ppm of allyltolumethylsilane polymer was obtained by processing in the same manner as in the above method.

Next, a known antioxidant, the above-mentioned copolymer, and master powder were combined in an extruder to obtain a composition containing ioppm of allyltrimethylsilane polymer. This composition was extruded using an extruder with a diameter of 40 mm under the conditions of an extrusion temperature of 250°C and a sheet cooling temperature (chill roll surface temperature) of 80°C to a thickness of 5.
It was molded into a 50μ sheet. Next, 2 manufactured by TM Long Co.
A stretched film was obtained by stretching 5×7 times using an axial stretching machine at 155°C. The ratio of β crystals in this sheet and the physical properties of the film are shown in the table. In the table, transparency is expressed by haze and visual evaluation results.

Conforms to Hayes ASTRO01003.

Comparative Example 1 The same procedure as Example 1 was carried out except that the sheet thickness was 1300 μm. Evaluation results are not shown in the table.

Comparative Example 2 The same procedure as Example 1 was carried out except that the propylene homopolymer obtained in Example 1 was used and only an antioxidant was added. The results are shown in the table.

Example 2 Sheet cooling temperature (chill roll surface temperature) was 20°C,
The procedure was the same as in Example 1 except that the sheet thickness was 1300 μm. The results are shown in the table.

Example 3 The propylene homopolymer obtained in Example 1 was used as a nucleating agent in place of polyallyltrimethylsilane in 1.2.
Same as Example 1 except that 0.1 part by weight of 34-di(ethylhenzylidene) sorbitol was added to 100 parts by weight of polypropylene, the sheet cooling temperature (chill roll surface temperature) was 80°C, and the sheet thickness was 1300μ. I did the same. The results are shown in the table.

Example 4 The same procedure as in Example 3 was carried out except that 12.34-di(methylhenzylidene)sorbitol was used instead of 12.34-di(ethylhenzylidene)sorbitol.

The results are shown in the table.

The wide-angle X-ray diffraction spectrum of one side of the sheet used in manufacturing the stretched sheet of the present invention is shown in FIG. 1, but three items are not observed. For reference, the wide-angle X-ray diffraction vector of the surface not in contact with the roll of the sheet of Comparative Example 1 was
As shown in the figure, three items are frequently observed.

*Percentage of β crystals on the side of the sheet that does not touch the roll surface.

** Comparative example 2 under normal conditions is shown as a standard by △,
Those whose surfaces were flat and better were marked with a circle.

1? [Effects of the Invention] The stretched film of the present invention has extremely excellent transparency, can be used for various purposes, and is extremely industrially valuable.

[Brief explanation of the drawing]

FIG. 1 shows the wide-angle X-ray diffraction spectrum of one side of the sheet used in manufacturing the stretched sheet of the present invention, and FIG. Wide angle X-cotton diffraction spectrum is shown.

Claims (1)

[Scope of Claims] 1. Consisting of highly crystalline polypropylene which is a propylene homopolymer or a copolymer with a small amount of other α-olefin, at least the surface of the polypropylene is obtained by X-ray diffraction spectroscopy. Highly transparent polypropylene obtained by stretching a sheet in which the ratio of the intensity of the diffraction line attributed to the β crystal to the total intensity of the diffraction line attributed to the α crystal and β crystal is 0.1 or less in at least one direction. Stretched film. 2. A sheet of highly crystalline polypropylene, which is a homopolymer of propylene or a copolymer with a small amount of other α-olefin, is extruded and taken out from a die, and measured by X-ray diffraction spectrum at least on its surface. The sheet obtained by cooling is stretched so that the ratio of the intensity of the diffraction line attributed to the β crystal to the sum of the intensities of the diffraction lines attributed to the α crystal and β crystal obtained by the process is 0.1 or less. A method for producing a highly transparent stretched polypropylene film, characterized by: