JPH11181103A - Crosslinked syndiotactic polypropylene molding and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a crosslinked molding having a specified range of a gel fraction even in the presence of oxygen by irradiating a syndiotactic polypropylene molding with electron beams after or during its molding. SOLUTION: The syndiotactic polypropylene herein mentioned means a substantially syndiotactic polypropylene or its copolymer and is produced by using a catalyst which can give a polypropylene having a syndiotactic pentad fraction of 0.6 or above, desirably 0.7 or above. The molding herein mentioned refers to the one obtained by molding a syndiotactic polypropylene together with, optionally, other resins and a crosslinking aid by an injection molding process or the like process. It includes also a foam prepared by melt extrusion in the presence of a blowing agent or the like, under irradiation with electron beams. The dose of electron beams is 20-1,000 kGy, and the irradiation can be performed by irradiating a molding on a conveyor. The gal fraction of the irradiated molding should be 0.2-90%. The irradiation with electron beams enable the production of a crosslinked syndiotctic polypropylene having excellent heat resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crosslinked syndiotactic polypropylene molded article and a method for producing the same, and more particularly, to a polypropylene molded article having a substantially syndiotactic structure, The present invention relates to a crosslinked syndiotactic polypropylene molded article having good heat resistance by irradiating a ray and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, polypropylene having an isotactic structure has been widely used for various purposes due to its excellent physical properties and chemical properties. Have been. As an improvement method, for example, in the method of irradiating an electron beam to polypropylene, an acrylic ester-based crosslinking aid is required because decomposition proceeds more easily than crosslinking of polypropylene (Japanese Patent Laid-Open No. 1-244828). No.).

As another method, a method of grafting a monomer capable of undergoing a crosslinking reaction by hydrolysis of alkoxyvinylsilane or the like to polypropylene and then crosslinking the same (JP-A-58-117244), A method of obtaining a crosslinked polyolefin by irradiating a mixture of a polyolefin containing alkenylsilane and a polyolefin (Japanese Patent Application Laid-Open No. 2-77455)
Japanese Patent Application Publication No. 6-45717 discloses a method in which a specific copolymer is blended with polypropylene and crosslinked with an electron beam.

On the other hand, polypropylene having a syndiotactic structure has been known for a long time. A. Ewen et al. Discovered for the first time that a catalyst comprising a transition metal compound having an asymmetric ligand and an aluminoxane could obtain a polypropylene having good tacticity such that the syndiotactic pentad fraction exceeded 0.7 (J .Am.Chem.So
c. , Vol. 110, 6255-6256 (198
8)). Syndiotactic polypropylene having good stereoregularity is flexible and excellent in heat resistance, and development of new applications is expected.

[0005] A method of irradiating syndiotactic polypropylene with radiation under specific conditions to increase the molecular weight has been proposed (JP-A-4-218504), but has reached a level where heat resistance is improved. Absent. In addition, the irradiation conditions are limited to the absence of oxygen, and there is a problem that the cost must be increased industrially.

[0006]

However, the syndiotactic polypropylene obtained in this manner is required to have further improved heat resistance depending on the use, similarly to the conventional isotactic polypropylene. The present invention provides a crosslinked syndiotactic polypropylene molded article having excellent heat resistance even in the presence of oxygen.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve such problems, and as a result, have reached the present invention. That is, the present application includes the following inventions or embodiments.

[0008] A syndiotactic polypropylene molded article, or a crosslinked syndiotactic polypropylene molded article having a gel fraction of 0.2 to 90% when irradiated with an electron beam in a molding process of the molded article.

A syndiotactic polypropylene molded article, or a crosslinked syndiotactic polypropylene molded article having a gel fraction of 0.2 to 90% when irradiated with an electron beam in the presence of oxygen during the molding process.

[0010] The irradiation electron dose is 20 to 1000
A crosslinked syndiotactic polypropylene molded article which is kGy or described.

[0011] A method for producing a syndiotactic polypropylene molded article or a crosslinked syndiotactic polypropylene molded article, which comprises irradiating an electron beam during the molding step.

A method for producing a syndiotactic polypropylene molded article or a crosslinked syndiotactic polypropylene molded article, which comprises irradiating the molded article with an electron beam in the presence of oxygen.

When the electron dose to be irradiated is 20 to 1000
A method for producing a crosslinked syndiotactic polypropylene which is kGy or described.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, syndiotactic polypropylene is substantially a polypropylene having a syndiotactic structure, and not only a homopolymer of propylene having a syndiotactic structure but also propylene and other olefins. And a copolymer of

The catalyst used for producing syndiotactic polypropylene is described in the above-mentioned J. Am. A. Examples of the catalyst include a transition metal compound having an asymmetric ligand and an aluminoxane described in Ewen et al.
Even catalysts having different structures can be used as long as they can produce polypropylene having a syndiotactic pentad fraction of 0.5 or more, preferably 0.7.

As the transition metal compound having an asymmetric ligand, isopropyl (cyclopentadienyl-1-fluorenyl) hafnium dichloride or isopropyl (cyclopentadienyl-1) described in the above literature can be used.
-Fluorenyl) zirconium dichloride and the like. Further, as the aluminoxane, the following formula (1)
(Formula 1)

[0017]

Embedded image Or the following formula (2)

[0018]

Embedded image (In these formulas, R is a hydrocarbon residue having 1 to 3 carbon atoms, n
Is an integer of 1 to 50. ) Is exemplified. In particular, n is a methylaluminoxane in which R is a methyl group.
Is 5 or more, preferably 10 or more.

The use ratio of the aluminoxane to the transition metal compound is 10 to 1,000,000 mole times, usually 50 to 100 moles.
５5000 mol times.

The polymerization conditions of propylene are not particularly limited, and 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 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 −100 to 200 ° C., normal pressure to 50 kg
/ Cm ² .

In the present invention, the preferred molecular weight of the syndiotactic polypropylene to be irradiated with an electron beam is 1
The limiting viscosity measured with a 35 ° C. tetralin solution is 0.1
Generally, it is about 5 to about 5.

The degree of syndiotacticity is 0.6 or more, preferably 0.7 or more, as a syndiotactic pentad fraction in the case of a propylene homopolymer. If the syndiotactic pentad fraction is 0.6 or more, the properties as crystalline polypropylene are sufficient,
Good physical properties are preferable.

Further, in the copolymer of propylene and other olefins, 1
¹³ C-NM measured with 2,4-trichlorobenzene solution
In the R absorption spectrum, the peak intensity observed at about 20.2 ppm is 0.3 or more, preferably 0.5 or more, of the peak intensity attributed to all methyl groups of the propylene unit. When this value is 0.3 or more, physical properties are good and preferable.

Examples of α-olefins other than propylene used for copolymerization with propylene include ethylene and α-olefins having 4 to 20 carbon atoms which may be branched. In particular, butene-1, pentene-1,
Hexene-1, octene-1, 4-methylpentene-1
Is preferred. The amount of these α-olefins is preferably at most 20% by weight, particularly preferably at most 10% by weight, based on propylene.

Also, a mixture of syndiotactic polypropylene and other resins may be used as long as the effects of the present invention are not impaired. The mixing ratio is 10 to 10 parts by weight of syndiotactic polypropylene and other resin 10 to 10 parts by weight.
100 parts by weight. Here, the other resin includes, for example, isotactic polypropylene, polyethylene produced by various methods, ethylene / α-olefin copolymer rubber, and the like.

Further, in order to promote crosslinking, a known crosslinking aid can be added. Addition amount is 1-10%
Is preferred. Known crosslinking aids include divinylbenzene, triarylcyanurate, diallylphthalate and the like.

[0027] The syndiotactic polypropylene molded article used in the present invention refers to a commonly used method,
Specifically, a polypropylene having substantially a syndiotactic structure or a mixture of the above-mentioned syndiotactic polypropylene and another resin, a crosslinking aid, for example, an injection molding method, an extrusion molding method, a press molding method and a rotational molding method And the like. In addition, a necessary foaming agent, another resin, and a crosslinking assistant are added, and an electron beam is irradiated while being melt-extruded, and then heated and foamed to obtain a foamed extruded product.

In the present invention, additives usually used for isotactic polypropylene, for example, antioxidants, heat aging agents, ultraviolet absorbers, light stabilizers, nucleating agents, antistatic agents and various inorganic, Organic pigments and the like can also be added.

In the present invention, the irradiation of the electron beam is not particularly limited, but the thickness of the molded body is preferably 30 mm or less. If the thickness of the molded body is less than 30 mm, the electron beam is preferably transmitted to the inside, and depending on the purpose of use of the molded body, the physical properties of the molded body can be changed to desired values by crosslinking only the surface portion. It is. Further, the case where a partially crosslinked product is formed by irradiation at the stage of the pellet also belongs to the embodiment of the present invention.

Here, the dose of the electron beam to be irradiated (absorbed dose)
Is usually 20 to 1000 kGy, preferably in the range of 20 to 800 kGy. In addition, there is no particular limitation on the irradiation method in the molding process of the molded product, and the molded product is usually placed on a conveyor, for example, while irradiating an electron beam from above, or while extruding the sheet by melting. A general method performed by irradiating one or both surfaces with an electron beam can be employed.

The gel fraction of the syndiotactic polypropylene molded product obtained by irradiating an electron beam in this manner has a gel fraction of 0.2.
９０90%, and this was used as an index to be crosslinked.

[0032]

EXAMPLES The present invention will be described more specifically with reference to the following examples. However, this embodiment is merely an example, and the present invention is not limited to these. In addition, the measuring method in an Example is as follows. Gel fraction: 1.0 g of a sample is precisely weighed to 1 mg, wrapped in a 200-mesh wire net, weighed, put into 500 ml of boiling P-xylene, dissolved for 24 hours with stirring, dried under reduced pressure together with the wire net, and weighed. The gel fraction (Equation 1) is calculated by the following calculation.

[0033]

(Equation 1) Example 1 According to JP-A-2-274763, a propylene bulk polymerization method was used in the presence of hydrogen using a catalyst comprising diphenylmethylene (cyclopentadienyl) fluorenylzirconium chloride and methylaluminoxane. This syndiotactic polypropylene is 2
MFI of 30 ° C. and load of 2.16 kg is 3.4 g / 10 m
In, the peak temperature of the crystallization temperature measured by differential scanning calorimetry was 63 ° C, the crystal melting point was 128 ° C, the syndiotactic pentad fraction was 0.804, and the Mw / Mn was 4.0.

The syndiotactic polypropylene thus obtained was added with Irgfos 168 as an antioxidant.
000 ppm, Irganox 1010 at 500 ppm
And mix well with a Henschel mixer, then add
Pelletization was performed at a die temperature of 230 ° C. using a single-screw extruder with a diameter of mm.

The obtained pellets were press-molded at 220 ° C. to obtain a flat plate having a thickness of 1 mm, which was used as a test piece. The flat plate was irradiated with an electron beam having an absorbed dose of 200 kGy using an electron beam irradiation apparatus (Cockcroft-Walton type electron accelerator), and the physical properties of the flat plate were measured. Gel fraction is 10
%Met.

Example 2 Example 1 was the same as Example 1 except that the absorbed dose of electron beam was changed to 400 kGy. The gel fraction was 42%.

Example 3 Example 3 was the same as Example 1 except that the absorbed dose of electron beam was changed to 800 kGy. The gel fraction was 70%.

Comparative Example 1 Example 1 was repeated except that syndiotactic polypropylene was replaced by isotactic propylene homopolymer (manufactured by Mitsui Toatsu Chemicals, Inc., GFL-G, MFI 7 g / 10 min.). Similarly, MFI 50 g /
10 min. Therefore, it is considered that the decomposition occurred without crosslinking.

Comparative Example 2 The same procedure as in Example 1 was carried out except that the absorbed dose of the electron beam was changed to 5 kGy, and the gel fraction was 0%.

[0040]

As shown by the results of the present invention, a film having good heat resistance and good retort resistance by irradiating an electron beam in a molding process of a syndiotactic polypropylene molded article or the molded article, It can be widely used for various industrial parts, for example, insulating layers or protective coating layers of packings, hollow pipes, tubes, electric cables, etc., and components of various composite materials. In addition, the extruded foam can be used for automobile interior parts, home electric parts, shock absorbers, cushions, and the like, and is industrially superior.

Continued on the front page (72) Inventor Nobutaka Uchikawa 3-5-2 Kasumigaseki, Chiyoda-ku, Tokyo Mitsui Chemicals, Inc. (72) Inventor Takeo Inoue 3-5-2 Kasumigaseki, Chiyoda-ku, Tokyo Mitsui Chemicals Inside (72) Inventor Fumio Yoshii 1233 Watanuki-cho, Takasaki City, Gunma Prefecture Inside the Japan Atomic Energy Research Institute Takasaki Research Institute (72) Inventor Keizo Makuuchi 1233 Watanuki-cho, Takasaki City, Gunma Prefecture Japan Atomic Energy Research Institute Takasaki Research Institute (72) Inventor Kazuhiro Nagashima 1233 Watanukicho, Takasaki City, Gunma Prefecture Inside the Japan Atomic Energy Research Institute Takasaki Research Institute

Claims (6)

[Claims] 1. A syndiotactic polypropylene molded article or a crosslinked syndiotactic polypropylene molded article having a gel fraction of 0.2 to 90% when irradiated with an electron beam during the molding step. 2. Molding of a syndiotactic polypropylene molded article or a crosslinked syndiotactic polypropylene molded article having a gel fraction of 0.2 to 90% upon irradiation with an electron beam in the presence of oxygen during the molding process. body. 3. An electron dose for irradiation is 20 to 1000 k.
The crosslinked syndiotactic polypropylene molded article according to claim 1, which is Gy. 4. A method for producing a syndiotactic polypropylene molded article, or a crosslinked syndiotactic polypropylene molded article, which comprises irradiating an electron beam in a molding step of the molded article. 5. A method for producing a crosslinked syndiotactic polypropylene molded article, which comprises irradiating an electron beam in the presence of oxygen during the molding of the syndiotactic polypropylene molded article. 6. An electron dose for irradiation is 20 to 1000 k.
The method for producing a crosslinked syndiotactic polypropylene according to claim 4 or 5, which is Gy.