JPH03290438A - Molded article of polypropylene - Google Patents

Abstract

PURPOSE:To obtain a PP molded article having excellent strength and transparency by molding PP having syndiotactic structure. CONSTITUTION:A PP substantially having syndiotactic structure (preferably having >=0.3 ratio of absorption intensity of a peak observed at 20.2ppm in <13>C-NMR observed in a 1,2,4-trichlorotoluene solution to total absorption intensity of whole peaks assigned to methyl group in propylene and <=10wt.% fraction of boiling n-pentane-soluble component) is molded to afford the aimed molded article having a crystal structure of substantially trans-zigzag structure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to molded articles of polypropylene. For more information,
The present invention relates to a polypropylene molded article having a substantially trans-zigzag crystal structure.

[Conventional technique (nei)]

Polypropylene is a lightweight and inexpensive polymer that is used for a variety of purposes, and especially when stretched, it has excellent strength and is used for a variety of purposes.

[Problem to be solved by the invention]

Regarding the crystal structure of polypropylene, it has been shown that isotactic polypropylene has a helical structure, but syndiotactic polypropylene can have a trans-zigzag structure (G, NATTA et al. Makroa et al.
+o1. Chem, , vo175.215 (196
4). However, conventional syndiotactic polypropylene is soluble in hydrocarbon compounds at room temperature, and it is difficult to imagine that it can be used as a molded product of crystalline polypropylene, and a complete trans-zigzag structure has not been identified crystallographically. There was nothing.

[Means for Solving vIN] The present inventors have completed the present invention by intensively searching for a polypropylene molded product having substantially completely trans-zigzag structure and having excellent physical properties to solve the above-mentioned problems.

That is, the present invention is a polypropylene molded product that is formed by molding polypropylene having a substantially syndiotactic structure, and is made of polypropylene that has substantially only a trans-zigzag crystal structure.

The present invention will be further explained by showing an example of its manufacturing method. Most simply, polypropylene with a syndiotactic structure with high stereoregularity, which can be synthesized by the method described below, is melt-molded, rapidly cooled to form a molded product, and then stretched, resulting in a polypropylene with a trans-zigzag crystal structure only. It can be made into a polypropylene molded product. Another method is to stretch syndiotactic polypropylene with a relatively high molecular weight (for example, η of 1.0 or more as described below) to a relatively high degree (for example, by stretching 3 times or more). It is also possible to have only a trans zigzag structure.

The existence of syndiotactic polypropylene has been known for a long time, and it has been purified by low-temperature polymerization with a catalyst consisting of a vanadium compound, ether, and organic aluminum, and has sufficient molding performance. Unlike the highly stereoregular syndiotactic polypropylene described below, those produced by these methods are purified as hydrocarbon-soluble components at room temperature. Therefore, such materials cannot be used in the molded articles of the present invention.J.

A. It was first discovered by EWEN et al. (J, ^-,
Ches+, Soc, 1988, 110.6255-
6256) Polypropylene with good toughness, such as a syndiotactic pentad fraction exceeding 0.7 obtained by a catalyst comprising a transition metal compound having an asymmetrical ligand and an aluminoxane, is preferably used.

In the present invention, the compounds described in the above-mentioned documents can be exemplified as catalysts for producing polypropylene having a substantially syndiotactic structure, but even if the catalyst has a different structure, the homopolymerization of propylene is Any catalyst system that can produce polypropylene having a syndiotactic pentad fraction of 0.7 or more can be used.

As a transition metal compound having an asymmetrical ligand, isopropyl (cyclopentadienyl-
Examples include 1-fluorenyl) hafnium dichloride and isopropyl (cyclopentadienyl-1-fluorenyl) zirconium dichloride. Examples of aluminoxane include RR (wherein R is a hydrocarbon residue having 1 to 3 carbon atoms; Examples of the compounds represented include methylaluminoxane in which R is a methyl group and n is 5 or more, preferably 10 or more.The ratio of aluminoxane to the above transition metal compound is 10 to 1,000,000 times by mole. , usually 50 to 5000 times by mole.

There are no particular restrictions on the polymerization conditions, and solvent polymerization using an inert medium, bulk polymerization without an inert medium, and gas phase polymerization can also be used.The polymerization temperature is -100 to 200°C. Polymerization pressure is normal pressure ~ 1
00 kg/cj is common. Preferably it is -100 to 100° C1 normal pressure to 50 kg/CII. It is also possible to use copolymers with other olefins in small amounts to the extent that the syndiotactic structure is not substantially lost.

Examples of other olefins used in the copolymerization include ethylene or α-olefins having 4 to 2 carbon atoms, specifically butene-1, pentene-1, hexene-1, octene-1,4-methylpentene- 1 etc. are exemplified. The polymerization ratio to propylene is usually 20w.
LX or lower, preferably Powt! The following other olefins are copolymerized under conditions.

In order to use the propylene homopolymer as a molded product, the syndiotactic pentad fraction (A, Zas
+belli et al. Macromolecules vo
+ 6687 (1973), same vol. 8925 (19
75)) is preferably 0.7 or more; if it is less than 0.7, a polypropylene molded product having a substantially perfect trans-zigzag crystal structure cannot be obtained;
More preferably, it is 0°75 or more. In addition, when using a copolymer, the peak intensity observed at about 20.2 pp- based on tetramethylsilane in C-NMR is about 1
The intensity is 0.3 or more, more preferably 0.5 or more of the total methyl group intensity of propylene observed at 9 to 22 pp.

The chain distribution measured by "C-NMR" is a measure of structural disorder in short periods, but in order to improve physical properties, it is necessary to have little structural disorder in long periods, and it is used as a measure for this purpose. There is a boiling n-pentane soluble content, and its value is preferably 10 wtX or less.What is the boiling n-pentane soluble content?Powdered polymer is placed in a Soxhlet extractor and extracted with boiling n-pentane for 6 hours. It is calculated as the ratio of the extracted polymer to the polymer before extraction.

In addition, the polymerization using the above catalyst system is substantially carried out in one step, resulting in a narrow molecular weight distribution (ratio of weight average molecular weight to number average molecular weight measured by gel permeation chromatography at <135°C (hereinafter referred to as Mll/ A polymer whose MN (abbreviated as MN) is usually about 1.5 to 3.5 can be obtained,
3.5 or more by using two types of transition metal compounds (it is effective to use two types of metals such as zirconium and hafnium) or by mixing two or more types of metals with different molecular weights. It is possible to produce compounds with a wide molecular weight distribution, and any compound with a wide molecular weight distribution can be used in the present invention. The preferred molecular weight is generally 0.5 to 20.0 degree as the intrinsic viscosity measured in a tetralin solution at 135°C.

The above-mentioned propylene having a substantially syndiotactic structure is heated and melted and molded into a specific shape. There are no particular restrictions on the molding method, and extrusion molding, injection molding, etc. can be employed.

In the present invention, it is preferable that the molded body be fused to 1
Rapid cooling is performed at a rate of 00° C./win or more, and by using such a material, a substantially transzigzag structure can be easily formed by stretching. Stretching is 100
“It is preferable to carry out at a relatively low temperature below 100°C.
If the temperature exceeds C, the crystal structure changes, which is not preferable. Also, if the cooling is performed slowly, other crystal forms will occur, and unless a high degree of stretching is performed, it is difficult to obtain a substantially transzigzag structure.

In the present invention, a substantially trans zigzag structure means that when a crystal is observed with X-rays, substantially no other crystal structure can be observed; for example, the intensity ratio is about 1 of the diffraction intensity due to the trans zigzag structure. This means that diffraction images due to other crystal structures are observed only at an intensity of /lO or less, and this does not mean that the degree of crystallinity is high.

Of course, it is also possible to use a crystallization nucleating agent during molding. The molded product is then stretched, but there are no particular restrictions on the stretching method, and ordinary uniaxial or biaxial stretching can be used.
Other methods such as roll stretching may also be used, and the stretching ratio is preferably 3.0 times or more, usually 3.0 to
The stretching temperature is about 100 times, which is relatively low. At high temperatures, crystallization of the sheet progresses, making it difficult to obtain only a trans-zigzag structure even if the sheet is stretched. 311 Usually carried out at -10 to 100°C.

Figure 1 shows a fiber photograph taken with an X-ray diffraction Weissenberg camera of the molded article (Example 1) having substantially only a trans-zigzag structure manufactured in this way. The crystal structure is shown in Figure 2.

The crystal structure of the polypropylene molded product of the present invention is a=5.
22, b=11.17, c=5.06λ, and is an orthorhombic crystal.

〔Example〕

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

Example 1 Isopropyl (cyclopentadienyl-1-fluorenyl) zirconium dichloride 0 obtained by lithiation of isopropylcyclopentadienyl-1-fluorene that had bottomed out according to a conventional method, reacting with zirconium tetrachloride, and recrystallizing it. .2g and 30g of methylaluminoxane (polymerization degree 16.1) manufactured by Toyo Akzo ■, internal volume 200.
8 ol of toluene was added to the autoclave in step 1, and the polymerization pressure was 3.
kg/c4-G, polymerized for 2 hours at 20"C, then deashed with methanol and methyl acetoacetate, washed with an aqueous hydrochloric acid solution, and then filtered to obtain 5.6 kg of syndiotactic polypropylene. Polypropylene is “C-
According to NMR, the syndiotactic pentand fraction is 0.
．． 935, and the intrinsic viscosity η measured with a tetralin solution at 135° C. was 1.45.1, and the MN measured with 2.4-trichlorobenzene was 2.2. Calcium stearate and 2,6-di-t-butylphenol were added to this polypropylene at 10/10,000 and 10/10,000, respectively.
After adding 10,000 g of talc and granulating it, it was spun using a 40 mm extruder and a die with 14 holes at a temperature of 220° C. and a screw rotation speed of 64 rpm.

The strands coming out of the string were introduced into a prine at -10°C and rapidly cooled. The thickness of the obtained fiber is 370 D/14
When the book was subjected to a tensile test, the maximum strength was 480 g and the elongation was 68 oz. Further, when stretched 10 times at 25°C, the maximum strength was 780 g, the elongation was 252, and the transparency was extremely good. 120° to this
The maximum strength of the fiber stretched by C (5 times the stretching was used because thread breakage occurs at 6 times) was 680 g, and the elongation was 2 oz. Figure 4 (stretched at 120"C)) is almost defective before stretching, and the one stretched at 25°C has a trans zigzag structure, but the one stretched at 120°C has a trans zigzag structure. Diffraction images other than structures are observed.

〔Effect of the invention〕

The molded article of the present invention has excellent strength and transparency, and is extremely valuable industrially.

[Brief explanation of drawings]

Figure 1 shows the polypropylene molding process of the present invention (Example 1)
This is an example of a photograph of an X-ray diffraction image taken with a Weisenberg camera, and FIG. 2 is a diagram showing its crystal structure. FIG. 3 is a photograph of the fiber before stretching in Example 1, and FIG. 4 is a photograph of the fiber after stretching at 120"C.

Claims (1)

[Scope of Claims] 1. A polypropylene molded product having a substantially trans-zigzag crystal structure obtained by molding polypropylene having a substantially syndiotactic structure. 2. The absorption intensity of the peak observed at about 20.2 ppm in ^1^3C-NMR of polypropylene, which has a substantially syndiotactic structure, measured in a 1,2,4-trichlorotoluene solution is due to the methyl group of propylene. Claim 1: The total absorption intensity of all assigned peaks is 0.3 or more.
The molded article described. 3. The molded article according to claim 1, wherein the polypropylene having a substantially syndiotactic structure has a boiling n-pentane soluble content of 10 wt% or less. 4. The lattice constant of the trans zigzag structure is a=5.22,
The molded article according to claim 1, which is an orthorhombic crystal with b=11.17 and c=5.06 Å.