JPH0445130A - Method for crosslinking syndiotactic polypropylene - Google Patents

Abstract

PURPOSE:To readily crosslink PP having a syndiotactic structure by irradiating a mixture of the syndiotactic structure PP and an alkenylsilane-olefin copolymer with radiative rays. CONSTITUTION:PP is crosslinked by irradiating a mixture of PP having a substantially syndiotactic structure and an alkenyl silane (e.g. vinyl silane or allyl silane)-olefin copolymer with radiative rays.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for crosslinking polypropylene having a syndiotactic structure.

[Prior art]

Isotactic polypropylene is inexpensive and has a relatively good balance of physical properties, and is used for various purposes. On the other hand, the existence of syndiotactic polypropylene has been known for a long time, but the conventional method of low-temperature polymerization using a catalyst consisting of a vanadium compound, ether, and organoaluminum has poor syndiotacticity and has elastomer-like properties. However, it was difficult to say that this represented the inherently syndiotactic characteristics of polypropylene. On the other hand, J, A
, EWEN et al. discovered for the first time that polypropylene with good toughness, with a syndiotactic pentasodide fraction exceeding 0.7, could be obtained using a catalyst consisting of a transition metal compound with an asymmetrical ligand and aluminoxane. (J, As, chem, soc, 19
88, 110.6255-6256), this syndiotactic polypropylene with good stereoregularity has an excellent balance of rigidity and impact resistance, and is at a level that can be used for conventional isotactic polypropylene applications. It is.

[Problem to be solved by the invention]

The syndiotactic polypropylene is more difficult to decompose even when irradiated with radiation than conventional isotactic polypropylene, but compared to polyethylene, it is difficult to crosslink like isotactic polypropylene.

[Means to solve the problem]

The present inventors have completed the present invention by intensively searching for a method for crosslinking polypropylene having a substantially syndiotactic structure by solving the above-mentioned problems.

That is, the present invention is a method for crosslinking syndiotactic polypropylene, which comprises irradiating a mixture of polypropylene and a copolymer of alkenylsilane and olefin having a substantially syndiotactic structure with radiation.

In the present invention, polypropylene having a substantially syndiotactic structure includes not only a homopolymer of propylene having a syndiotactic structure but also a copolymer of propylene and another olefin.

Examples of catalysts used to produce syndiotactic polypropylene include the compounds described in the above-mentioned documents, but even if the catalyst has a different structure, it can produce polypropylene with a syndiotactic pentad fraction of 0.7 or more. You can use it if you can.

As a transition metal compound having an asymmetrical ligand, isopropyl (cyclopentadienyl-
Examples include 1-fluorenyl) hafnium dichloride or isopropyl(cyclopentagenyl-1-fluorenyl) zirconium dichloride, and examples of aluminoxane include (wherein R is a hydrocarbon residue having 1 to 3 carbon atoms). In particular, methylaluminoxane in which R is a methyl group and n is 5 or more, preferably 10 or more is used. The ratio of aluminoxane to the above transition metal compound is 10 to 100.
0,000 mol times, usually 50 to 5,000 mol times.

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 ~ 10
It is generally performed at 0 kg/cd. Preferably the temperature is -100 to 100°C and normal pressure to 50 kg/d.

A preferable molecular weight is generally about 0.1 to 10.0 as the intrinsic viscosity measured in a tetralin solution at 135°C. Regarding the degree of syndiotactic structure, the syndiotactic pentand fraction of the propylene homopolymer is 0.6 or more, preferably 0.7 or more. If it is smaller than 0.6, the properties of crystalline polypropylene are insufficient and the physical properties are poor, which is not preferable. In addition, in copolymers with other olefins, 1,2.4-
)"C-N?IR measured with dichlorohensen solution
The peak intensity observed at about 20.2p9m is 0.3 or more, preferably 0.5 or more of the peak intensity attributable to all methyl groups of the propylene unit. If it is less than 0.3, the physical properties will be poor, which is not preferable.

As other olefins used in the copolymerization, in addition to ethylene, α-olefins having about 4 to 20 carbon atoms can be used. Preferably, butene-1, pentene-1, hexene-1,
Examples include octene-1,4=methylpentene-1. The polymerization ratio to propylene is usually 201
Polymerization is carried out under conditions such that 1 t% or less, more preferably 10 wt.X or less, of other olefins are copolymerized.

In the present invention, an example of the copolymer of alkenylsilane and olefin is shown in Japanese Patent Application No. 193201/1983, but alkenylsilane is a copolymer of at least one
Those having an i-H bond are preferably used, and compounds having a terminal double bond and a 5i-H group in the molecule are exemplified,
Especially general 2〇IC=CH-(CH2) ,,S+l'l
a (in the formula, n is an integer of O to 20), or a compound in which 1 to 2 of its 5i-H bonds are substituted with an alkyl group, or a compound in which 1 to 3 5i-t (in which the bond is chloro) Examples include compounds substituted with vinylpuran, allylsilane, butenylsilane, pentenylsilane, or compounds in which 1 to 2 of the 5i-H bonds of these monomers are substituted with alkyl groups, or 1 to 3 of these monomers are substituted with alkyl groups. S of
Examples include compounds in which 1 to H bonds are substituted with chloro.

Examples of olefins used in copolymerization include olefins having 2 to 20 carbon atoms, such as ethylene, propylene, butene-1, pentene-1, hexene-1,4-methylpentene-1, or mixtures thereof. Mixtures of these with small amounts of higher carbon number olefins are exemplified.

In the present invention, in addition to the catalyst used to polymerize the syndiotactic polypropylene, catalysts used to polymerize the alkenylsilane and olefin include conventionally known catalysts made of titanium trichloride and organoaluminum, and olefins. A catalyst consisting of a transition metal compound and an organometallic compound for the polymerization of can be used without any problem.

As the polymerization method, any of a solvent method using an inert solvent, a bulk polymerization method, and a gas phase polymerization method can be adopted.

As a catalyst consisting of a transition metal compound and an organometallic compound, titanium halide or vanadium halide is preferably used as the transition metal compound, and an organoaluminum compound is preferably used as the organometallic compound. A catalyst system consisting of titanium trichloride obtained by reduction with an organoaluminum or a modified titanium trichloride with an electron-donating compound, an organoaluminum compound and, if necessary, an electron-donating compound such as an oxygen-containing organic compound, and a vanadium halide. Titanium halide, vanadium halide, or vanadium oxyhalide is supported on a catalyst system consisting of L, vanadium oxyhalide, and organic aluminum, or a carrier such as magnesium halide, or a carrier treated with an electron-donating compound. A catalyst system consisting of the transition metal compound catalyst and an organoaluminum compound obtained, and if necessary an electron-donating compound such as an oxygen-containing organic compound, or a reaction product of magnesium chloride and alcohol is dissolved in a hydrocarbon solvent, and then A transition metal compound catalyst obtained by treating it with a precipitant such as titanium chloride to make it insolubilized in a hydrocarbon solvent, optionally treating it with an electron-donating compound such as an ester or ether, and then treating it with a titanium halide. Examples include a catalyst system consisting of an organoaluminum compound, an electron-donating compound such as an oxygen-containing organic compound, etc. (for example, various examples are described in the following documents: Ziegler-Natta Cat).
alysts and polymerizati
on by John Boor Jr.
adesic Press), Journal
of Macrcmorecular 5ie
nce Revisws in Macrosole
cular CheIlistry and Phys
ics, C24(3) 355-385 (1984)
, C25(1) 578597 (1985)).

As the electron-donating compound, oxygen-containing compounds such as ethers, esters, orthoesters, and alkoxy silicon compounds are generally preferred, and alcohols, aldehydes, water, and the like can also be used.

As the organoaluminum compound, trialkylaluminum, dialkylaluminum halide, alkylaluminum sesquihalide, alkyl aluminum civalide can be used, and examples of the alkyl group include methyl group, ethyl group, propyl group, butyl group, hexyl group, etc. Examples of halides include chlorine, bromine, and iodine.

Here, the polymerization ratio of alkenylsilane and olefin is such that it is easy to mix with syndiotactic polypropylene, and the alkenylsilane content in the mixed composition is 0.
There is no particular restriction as long as it can be 0.011 or more, but it is usually preferable that the alkenylsilane content be 30 mol % or less for the purpose of catalytic activity during polymerization or for mixing with syndiotactic polypropylene.

There is no particular limit to the molecular weight of the polymer, but it is preferable from the viewpoint of mixing that it does not have an extremely high molecular weight, for example, an intrinsic viscosity of 10 or more as measured in a tetralin solution at 135°C, and usually an intrinsic viscosity of 0. 1-5
That's about it.

In the present invention, the mixing ratio of the syndiotactic polypropylene and the copolymer of alkenylsilane and olefin is 10wt1 or more, preferably 30wt, based on the syndiotactic polypropylene mixture, in order to express the characteristics of syndiotactic polypropylene. It is more than $1, and the copolymer of alkenylsilane and olefin is 1 because the crosslinking reaction easily occurs.
It is 1% or more, preferably 10-t% or more.

In the present invention, the syndiotactic polypropylene, alkenylsilane, and olefin copolymer are mixed prior to radiation irradiation, but the mixing method is particularly limited.
There is no limit to this, and any method may be used as long as the two can be sufficiently mixed, such as mixing using a normal Henschel machine, melt mixing using a roll or extruder, etc.Normally, the above mixture is molded into a desired shape and then exposed to radiation. It is crosslinked by irradiation.

In the present invention, radiation includes gamma rays, electron beams, X-rays,
Examples include accelerated ions and high-energy electron beams, but gamma rays and X-rays, which have particularly high transparency, are preferably used. Although irradiation can be carried out in air, the crosslinking reaction proceeds more efficiently when carried out in a degassed state or in an inert atmosphere.

There are no particular restrictions on the temperature during irradiation, but irradiation is usually carried out at 50° C. or lower. Furthermore, even more favorable results can be obtained by heat treatment after irradiation, and the heating temperature is preferably higher than the irradiation temperature and lower than the melting point of the polymer9, and is usually carried out at about 80 to 140°C. The higher the heating temperature, the shorter the heating time, usually a few minutes.
For example, at 100° C., one hour is sufficient. As a guideline for heating temperature and heating time, the conditions are such that radicals in the polymer disappear in a relatively short time. The radiation dose is usually 0.01 to 20 Mrad, and if it is less than 0.01 mrad, the crosslinking reaction will not proceed easily;
Irradiation over rad is not more efficient and is not economical.

〔Example〕

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

Example 1 Isopropyl (cyclopentadienyl-1-fluorenyl) zirconium dichloride 0.0.0. Using 2g and 60g of methylaluminoxane (polymerization degree 16.1) manufactured by Toyo Akzo ■, the internal volume was 200.
Polymerization pressure 3 kg/c4-G in autoclave 1, 2
Polymerization was carried out at 0° C. for 2 hours, followed by deashing with methanol and methyl acetoacetate, washing with an aqueous hydrochloric acid solution, and filtration to obtain 6.1 kg of syndiotactic polypropylene. According to C-NMH, this polypropylene has a syndiotactic pentand fraction of 0.928 and 13
The intrinsic viscosity (hereinafter abbreviated as η) measured with a tetralin solution at 5°C is 1.38. Meanwhile, a vibratory mill equipped with four grinding pots each having an internal volume of 41 and containing 9 kg of steel balls with a diameter of 12+e+a is prepared. Magnesium chloride 300g, dimethyl phthalate 75m, titanium tetrachloride 6 under nitrogen atmosphere
0d was added and pulverized for 40 hours. Co-pulverized product 3 thus obtained
00g at 5/! After adding 3.02 liters of toluene, stir at 120"C for 30 minutes, remove the supernatant, and add nitrile X 73.041!, 100
C for 30 minutes, the supernatant liquid was removed again, and the obtained solid content was washed repeatedly with n-hexane to obtain a transition metal catalyst slurry. A portion was sampled and the titanium content was analyzed. However, it was 1.6 wt%.

In an autoclave with an internal volume of 52, put 9° of vinylsilane and 1.5 kg of propylene, add 1.8 Nj2 of hydrogen, and then add 1 g of the above titanium catalyst, 0.2 d of ethylaluminum, 0.05 m of cyclohexylmethyldimethoxysilane, and 100 m of toluene. was added and polymerized at 70°C for 2 hours. After the polymerization, unreacted propylene was purged, the powder was taken out, dried, and weighed to obtain 1080 g of polymer. The η of this copolymer is 1.48, and the vinyl silane content is 1.85 mol χ
Met.

The copolymer was mixed with 8 parts of the non-diotactic polypropylene at a ratio of 20 parts, a phenolic stabilizer was added to the polymer in an amount of 0.1 wt.

For this sort, 2 Mrad of gamma rays were applied at 20°C under nitrogen flow.
2 Mrad was irradiated at /hr. The sort was extracted with boiling xylene for 6 hours and the percentage of extraction residue was 68 w tχ. When the sheet before irradiation was extracted with boiling xylene for 6 hours, the proportion of the extracted residue was 0.5 wtχ.

Example 2 The same procedure as in Example 1 was carried out except that electron beam (v at 750) was irradiated with I Mrad instead of γ ray, and the proportion of boiling xylene extraction residue was 48 wtχ.

Example 3 Polymerization was carried out in the same manner as in Example 1, except that the polymerization was carried out at 50°C by the bulk polymerization method, and the syndiotactic pentad fraction was 0°823.
, a syndiotactic polypropylene having η of 0.92 was obtained. Example 1 was repeated except that 30 parts of a vinylcycine and propylene polymer were used for 70 parts of this polymer. What was the proportion of the boiling xylene extraction residue? It was 2wtχ.

〔Effect of the invention〕

By using the method of the present invention, polypropylene having a syndiotactic structure can be easily crosslinked, and it is industrially valuable.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] 1. A method for crosslinking syndiotactic polypropylene, which comprises irradiating a mixture of polypropylene having a substantially syndiotactic structure and a copolymer of alkenylsilane and olefin with radiation.