JP2837199B2 - Isotactic polypropylene molded article and method for producing the same - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to substantially isotactic polypropylene moldings and a method for producing the same. Specifically, the present invention relates to a molded article having excellent transparency obtained by molding isotactic polypropylene or a copolymer having high tacticity and a molding method thereof.

(Prior art)

J, A, EWEN J.Am.Chem.S. that isotactic polypropylene with a very narrow molecular weight distribution can be produced by using a homogeneous catalyst having a specific structure.
oc., vo1106 6355 (1984), W. Kaminsky et al. Angew. Chem., vo.
124 507 (1985) and the like, it is reported that polypropylene having relatively good tacticity can be obtained.

[Problems to be solved by the invention]

However, these polymers have relatively poor impact resistance due to their narrow molecular weight distribution, and have exceptional properties compared to conventional isotactic polypropylene except for their relatively low melting points. There was nothing.

[Means for solving the problem]

The present inventors diligently searched for the characteristics of the isotactic polypropylene having a narrow molecular weight distribution and found that a specific molded product was extremely excellent in transparency, and completed the present invention.

That is, the present invention has an isotactic pentad fraction of 0.
A copolymer of propylene having a substantially isotactic structure of 8 or more and a small amount of another olefin, and a polymer having a weight-average molecular weight to number-average molecular weight ratio of 1.5 to 3.5 was heat-melted. Thereafter, by gradually cooling at a rate of 100 ° C./min or less, the melting point measured by raising the temperature at a rate of 10 ° C./min by the differential scanning calorimetry is substantially observed as two peaks, and observed by X-ray diffraction measurement. The isotactic polypropylene molding having good transparency, characterized in that a diffraction line is observed at 2θ of 20 ° in the diffraction spectrum. The present invention is also a method suitable for producing the above-mentioned molded product, wherein a copolymer of propylene having an isotactic pentad fraction of 0.8 or more and having a substantially isotactic structure and a small amount of another olefin is provided. Isotactic polypropylene molding with good transparency, characterized in that a polymer having a ratio of weight average molecular weight to number average molecular weight of 1.5 to 3.5 is heated and melt molded and then gradually cooled at 100 ° C / min or less. It is a method of manufacturing a product.

Examples of the catalyst used for producing isotactic polypropylene having a narrow molecular weight distribution in the present invention include the compounds described in the above-mentioned literatures.After that, various improvements have been made and many patents have been filed, and those methods have been used. Available. Basically, a catalyst system in which the isotactic pentad fraction of the polymer obtained when performing propylene homopolymerization is 0.8 or more, usually a relatively large,
A transition metal catalyst having a symmetric ligand is used, and usually an aluminoxane is used in combination. However, a catalyst system using a phenylboron-based compound discovered as a counter anion may be used. Specifically, ethylene-bis (4,5,6,7-tetrahydroindenylfluorenyl) described in the above literature
Zirconium dichloride, ethylene-bis (4,5,6,7-
Tetrahydroindenylfluorenyl) hafnium dichloride and the like; and aluminoxanes are represented by the general formula: (Wherein R is a hydrocarbon residue having 1 to 3 carbon atoms). Examples thereof include methylaluminoxane wherein R is a methyl group and n is 5 or more, preferably 10 or more. . The use ratio of the aluminoxane to the transition metal catalyst is 10 to 100,000,000 times, usually 50 to 5000 times. There are no particular restrictions on the polymerization conditions,
A solvent polymerization method using an inert medium, a bulk polymerization method substantially free of an inert medium, and a gas phase polymerization method can also be used. In general, the polymerization is carried out at a temperature of -100 to 200 ° C. and at a pressure of normal pressure to 100 kg / cm ² . Preferably, it is -100 to 100 ° C and normal pressure to 50 kg / cm ² .

Examples of the other olefin used in the copolymerization include ethylene and α-olefins having 4 to 20 carbon atoms. Specific examples include butene-1, pentene-1, hexene-1, octene-1, and 4-methylpentene. 1 and the like. The ratio of polymerization to propylene is usually 0.1 to 2
If it is polymerized under the condition that about 0 wt% of another olefin is copolymerized, if it is more than 20 wt%, the rigidity of the molded product decreases, which is not preferable. If it is less than 0.1 wt%, the transparency of the molded product is poor, which is not preferable.

In consideration of impact resistance, the comonomer content is 0.5 wt%
It is preferable that it is above. The conditions for the copolymerization are not particularly limited, and known ordinary conditions can be employed. The polymerization is carried out substantially in a single-stage polymerization, and the polymer thus synthesized has a narrow molecular weight distribution and a ratio of the weight average molecular weight to the number average molecular weight measured by gel permeation chromatography at 135 ° C. (hereinafter referred to as MW / MN) is usually 1.5
About 3.5, which is suitable for producing the molded article of the present invention. The preferred molecular weight is generally about 0.5 to 3.0 dl / g as the intrinsic viscosity measured with a 135 ° C. tetralin solution.

The isotactic polypropylene is then heated and melted and formed into a specific shape. There is no limitation on the molding method as long as it can be gradually cooled after molding, and an extrusion molding method or an injection molding method can be employed.

What is important in the present invention is from the molten state of the molded product.
100 ° C./min or less, preferably slowly cooling at a rate of 80 ° C./min or less, and the melting point when the molded product is heated at 10 ° C./min by differential scanning calorimetry and measured. Is substantially two peaks. Also, the molded product is Cu-K
A major feature of the diffraction spectrum observed by X-ray diffraction measurement using α-rays is that diffraction rays are observed at 2θ of 20 °. Here, it is of course possible to use a crystallization nucleating agent.

〔Example〕

 Hereinafter, the present invention will be described with reference to Examples.

Example 1 Ethylene-bis (4,5,6,4) obtained by lithiation of ethylene-bisindene synthesized according to a conventional method, reaction with zirconium tetrachloride, hydrogenation and recrystallization.
Using 0.2 g of 7-tetrahydroindenyl) zirconium dichloride and 30 g of methylaluminoxane manufactured by Toyo Akzo Co., Ltd. (degree of polymerization 16.1), 80 l of toluene was added in an autoclave having a 200 l internal volume, and ethylene was added at a polymerization pressure of 3 kg / cm ² -G. Was polymerized at 20 ° C. for 2 hours while inserting at a rate of 100 g / h, then decalcified with methanol and methyl acetoacetate, washed with an aqueous hydrochloric acid solution, and filtered to obtain 6.1 kg of isotactic polypropylene. According to ¹³ C-NMR, the ratio of the peak intensity observed at 20.7 ppm to the peak intensity of all methyl groups according to ¹³ C-NMR is 0.91, and the intrinsic viscosity measured at 135 ° C. tetralin solution is 1.24 dl / g, 1,2 MW / MN measured with 2,4-trichlorobenzene was 2.4. The ethylene content was 2.8% by weight. A known stabilizer was added to the polypropylene, granulated with an extruder, melt-pressed at 240 ° C. to form a 1 mm sheet, and then gradually cooled while fixed to the press. At this time, the temperature drop rate was measured by a sensor inserted at the center of the sheet and found to be 45 ° C./min.
The following physical properties of this sheet were measured.

Flexural rigidity: kg / cm ² ASTM D-747 (23 ° C) Tensile yield strength: kg / cm ² ASTM D-638 (23 ° C) Elongation at break:% ASTM D-638 (23 ° C) Izod (with notch) ) Impact strength: kg · cm / cm ASTM D-638 (23 ° C, -10 ° C) Haze:% According to ASTM D1003.

The flexural rigidity, tensile yield strength, elongation at break, and Izod impact strength are 9800, 300, 680, 2.5, and 2.0, respectively.
The haze was 18.

According to the X-ray diffraction spectrum, a diffraction line was observed at a position of 20 ° as 2θ.

Comparative Example 1 In Example 1, the press sheet was cooled by taking out the sheet, putting it into press sheet water, and rapidly cooling it.
Except for cooling, the same molding was performed and the physical properties were measured.The flexural rigidity, tensile yield strength, elongation at break, and Izod impact strength were 1050, 305, 420, 2.3, and 2.0, respectively, and the haze was 50. Was. According to the X-ray diffraction spectrum, 2θ
No diffraction line was observed at a position of 20 °.

Comparative Example 2 Commercially available copolymer of propylene and ethylene, ethylene content 2.8 wt%, ratio of peak intensity observed at 20.7 ppm by ¹³ C-NMR to peak intensity of all methyl groups is 0.94, intrinsic viscosity 1.38 dl / g The procedure was the same as in Example 1 except that a polymer having a MW / MN of 5.0 was used. Flexural rigidity, tensile yield strength, elongation at break, Izod impact strength are 9750, 310, 660, respectively
3.1 and 2.0, and haze was 71.

Example 2 The hexene content was 4 w in the presence of hexene-1 during the polymerization.
Thus, t% of the copolymer was obtained. According to ¹³ C-NMR, this copolymer is
The peak intensity at 20.7 ppm was 0.82 of the total peak intensity of the methyl group in the propylene unit, which was substantially isotactic, and the MW / MN was 2,2. This copolymer was molded in the same manner as in Example 1 and the physical properties were measured.
The tensile yield strength, elongation at break, and Izod impact strength were 8,900, 288, 773, 3.8, and 2.4, respectively, and the haze was 15.

Comparative Example 3 In Example 2, the press sheet was cooled at 140 ° C./min.
And the other conditions were the same except that the flexural rigidity, tensile yield strength, elongation at break, and Izod impact strength were 860 respectively.
0, 265, 755, 3.9, 2.3, and haze was 57.

〔The invention's effect〕

The molded product of the present invention has extremely good transparency and excellent physical properties, and is extremely valuable industrially.

[Brief description of the drawings]

FIG. 1 shows the melting behavior of the polymer obtained by analyzing the molded products of Example 2 and Comparative Example 3 by differential scanning calorimetry.
Corresponds to Example 2 and (b) corresponds to Comparative Example 3. Second
The figure shows the X-ray diffraction spectrum of the molded product of Example 2, and FIG. 3 shows the X-ray diffraction spectrum of the molded product of Comparative Example 3.

Claims (2)

(57) [Claims] 1. A copolymer of propylene having an isotactic pentad fraction of 0.8 or more and having a substantially isotactic structure with a small amount of another olefin, wherein a ratio of a weight average molecular weight to a number average molecular weight. The melting point of the polymer having a melting point measured by heating at 10 ° C./min by differential scanning calorimetry by slow cooling at 100 ° C./min or less after heating and melt-molding a polymer having a Is observed as a peak of X
2θ in the diffraction spectrum observed by X-ray diffraction measurement
An isotactic polypropylene molded article having good transparency, wherein a diffraction line is observed at 20 °. 2. A copolymer of propylene having a substantially isotactic structure having an isotactic pentad fraction of 0.8 or more and a small amount of another olefin, wherein a ratio of a weight average molecular weight to a number average molecular weight. A method for producing an isotactic polypropylene molded article having good transparency, characterized in that a polymer having a molecular weight of 1.5 to 3.5 is melt-molded and then gradually cooled at 100 ° C./min or less.