JPH0488028A - Method for crosslinking polypropylene - Google Patents

Abstract

PURPOSE:To improve crosslinking rate of polypropylene without using any catalyst by heating a mixture of PP having syndiotactic configuration and a copolymer of an alkenylsilane and propylene in the presence of water. CONSTITUTION:A mixture of PP (preferably having 0.1-5 intrinsic viscosity) substantially having syndiotactic configuration and a copolymer of an alkenylsilane and propylene is heated to preferably >=50 deg.C in water to crosslink polypropylene.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for crosslinking polypropylene.

More specifically, the present invention relates to a method for crosslinking polypropylene with improved crosslinking speed.

[Prior art]

Polypropylene is inexpensive, has a relatively good balance of physical properties, and is used for a variety of 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 of vanadium compounds, ethers, and aluminum catalysts has poor syndiotactic properties and has poor elastomer 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 pentad fraction exceeding 0.7, could be obtained using a catalyst consisting of a transition metal compound with an asymmetrical ligand and aluminoxane. (J, A, [1WEN, J, Am, Ch
em, Soc, , 19B8.110.6255-6
256). This syndiotactic polypropylene with good stereoregularity has an excellent balance of locking properties and impact resistance, and is at a level that can be fully used for conventional isotactic polypropylene applications.

On the other hand, it has long been known that a crosslinking reaction proceeds by heating a copolymer of alkenylsilane, propylene, and ethylene in the presence of water (USP 364/1306).

[Problem to be solved by the invention]

The copolymer of alkenylsilane-stopped propylene and ethylene mentioned above has a relatively slow crosslinking speed, and in particular, the copolymer of crystalline alkenylsilane and propylene has the problem that it does not easily crosslink even when combined with a catalyst. It is thought that the use of crosslinked polymers may limit the scope of use of crosslinked polymers, and it has been desired to develop a crosslinking method that has a sufficient crosslinking rate without using a catalyst.

[Means for Solving the Problems] The present inventors have diligently searched for a method for solving the above problems and easily crosslinking polypropylene, and have completed the present invention.

That is, the present invention is a method for crosslinking polypropylene, which comprises heating a mixture of polypropylene having a substantially syndiotactic structure and a copolymer of alkenylsilane and propylene in the presence of water.

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 literature, 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 alumitsugisan include RR (wherein R is a hydrocarbon residue having 1 to 3 carbon atoms). Examples of the compounds shown above include methylaluminoxane in which R is a methyl group and n is 5 or more, preferably 10 or more. The ratio of aluminoxane used to the above transition metal compound is 10 to 1,000,000 times, usually 50 to 5,000 times by mole.

Furthermore, there are no particular limitations on polymerization conditions, and solvent polymerization using an inert medium, bulk polymerization in which an inert medium is not substantially present, and gas phase polymerization can also be used. The polymerization temperature is -100 to 200°C; the polymerization pressure is normal pressure to
It is common to use 100 kg/cffl. Preferably -100~100°C1 normal pressure~50kg/clI
It is l.

A preferable molecular weight is generally about 0.1 to 10.0 as the intrinsic viscosity measured in a tetralin solution at 135°C. As for the degree of syndiotactic structure, in a propylene homopolymer, the syndiotactic pentad fraction is 0.6 or more, preferably 0.7 or more. If it is smaller than 0.6, the characteristics as crystalline polypropylene are insufficient and the physical properties are poor, which is not preferable. In addition, in copolymers with other olefins, 1, 2.
"C-NM measured with 4-1-lichlorobenzene solution"
The peak intensity observed at about 20.2 ppm for R is 0.3 of the peak intensity attributed to all methyl groups in the propylene unit.
It is preferably 0.5 or more. 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 2Qw
Polymerization is carried out under conditions such that t% or less, more preferably 10wtX or less, of other olefins are copolymerized.

In the present invention, an example of a copolymer of alkenylsilane and propylene is shown in Japanese Patent Application No. 193201/1983, but alkenylsilane is a copolymer of at least one 5
Those having an i-II bond are preferably used, and the terminal 2
Compounds having a double bond and an S i -It group in the molecule are exemplified, particularly -Noshiro+12C=CI+-(C1,). 5
A compound represented by ill+ (in the formula, n is an integer of 0 to 20), or a compound in which 1 to 2 of its S i -H bonds are substituted with an alkyl group, or a compound in which 1 to 3 S i -H bonds are substituted with an alkyl group
Examples include compounds in which the bond is substituted with chloro, specifically vinylsilane, allylsilane, butenylsilane, pentenylsilane, or 5i-II of these monomers.
Examples include compounds in which one to two bonds are substituted with alkyl groups, or compounds in which one to three 5i-II bonds are substituted with chlorine, and particularly preferred are compounds having S i -If bonds.

As the copolymer of the present invention, those copolymerized with other olefins can also be used, and examples of olefins used in copolymerization include olefins having 2 or 4 to 20 carbon atoms, and specifically, ethylene, phthene-1, Penten-1,
It is also possible to copolymerize hexene-1,4-methylpentene-1 and the like with propylene up to about 2Qwtχ.

In the present invention, in addition to the catalyst used to polymerize the syndiotactic polypropylene, catalysts used to polymerize the alkenylsilane and propylene include conventionally known catalysts made of titanium trichloride and organoaluminium, and propylene. 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 the following methods can be employed: a container method using an inert solvent, a bulk polymerization method, and a gas phase polymerization method.

As the catalyst composed 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. For example, titanium trichloride obtained by reducing titanium tetrachloride with metallic aluminum, hydrogen, or organoaluminum, or titanium trichloride obtained by modifying these with electron-donating compounds, organoaluminum compounds, and, if necessary, electron-donating compounds such as oxygen-containing organic compounds. A catalyst system consisting of a compound, a catalyst system consisting of a vanadium halide, or a vanadium oxyhalide and an organoaluminum, or a carrier such as magnesium halide, or a carrier such as a magnesium halide, or a carrier treated with an electron-donating compound, and a titanium halide or a vanadium halide. , a catalyst system consisting of a transition metal compound catalyst obtained by supporting barium-dium oxyhalide, an organoaluminium compound, an electron-donating compound such as an oxygen-containing organic compound, or a reaction product of magnesium chloride and alcohol. It is dissolved in a hydrocarbon solvent and then treated with a precipitant such as titanium tetrachloride to make it insoluble in the hydrocarbon solvent.
Catalyst system consisting of a transition metal compound catalyst obtained by treatment with an electron-donating compound such as ether and then treatment with titanium halide, an organoaluminium compound, and if necessary an electron-donating compound such as an oxygen-containing organic compound. (For example, various examples are described in the following documents. Ziegler-Natta Cat
alysts and polymerizati
on by John Boor Jr.
academic Press), Journal of
Macromolecule 5ience Re
views in Macromolecular C
hemistry and physics, C24 (3
) 355-385 (1984), c25(1)
57B-597 (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, 1-realkylaluminum, dialkylaluminum halide, al:toluluminum sesquihalide, and alkylaluminum civalide can be used, and the alkyl group is a methyl group,
Examples include ethyl group, propyl group, butyl group, hexyl group, etc., and examples of halides include chlorine, bromine, and iodine.

Here, the polymerization ratio of alkenylsilane and propylene is not particularly limited as long as it can be easily mixed with syndiotactic polypropylene, but it is usually 0.1 to 10 mol χ
The alkenylsilane content is more preferably about 0.5 to 5 mol χ.

There is no particular restriction on the molecular weight of the polymer, but it is preferable from the viewpoint of mixing that it has 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 has an intrinsic viscosity of 0. 1~
It is about 5.

In the present invention, the mixing ratio of the syndiotactic polypropylene and the copolymer of alkenylsilane and propylene is 5 wt% or more relative to the mixture of syndiotactic polypropylene, from the viewpoint of easy crosslinking. The proportion of syndiotactic polypropylene in the mixture should be 95 wt % or less in order to fully exhibit its properties as a crosslinked polymer and to facilitate crosslinking.

In the present invention, the syndiotactic polypropylene and the copolymer of alkenylsilane and propylene are mixed prior to heat treatment in the presence of water, but there are no particular restrictions on the mixing method, such as mixing by ordinary Henschel, rolling, Any method may be used as long as the two can be sufficiently mixed, such as melt mixing using an extruder. Although it is of course possible to use the catalyst suitable for water crosslinking described in the above-mentioned literature in this mixing, according to the present invention, crosslinking easily proceeds even without using a catalyst in combination.

Usually, the mixture is crosslinked by shaping it into a desired shape and then heating it in the presence of water. The heating temperature is 50
℃ or higher is sufficient, but if necessary, it can be set to a relatively high temperature below the deformation temperature of the mixed metal.

〔Example〕

The present invention will be further explained by showing examples below.

Example 1 Isopropyl (cyclopentadienyl-1-fluorenyl) zirconium dichloride 0.0.0. 2g and 60g of methylaluminoxane (polymerization degree 16.1.) manufactured by Toso Akzo■, and the internal volume was 20.
Polymerization pressure 3kg/c+fl-G in autoclave 01
The polymer was 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 6.1 kg of syndiotactic polypropylene. According to C-IJMR, this polypropylene has a syndioctic bentad fraction of 0.928, and an intrinsic viscosity (hereinafter abbreviated as η) measured in a tetralin solution at 135°C of 1°38. Ball 9kg
Internal volume of 4f! .

Prepare a vibrating mill equipped with four grinding pots. 300g of magnesium chloride and 75m of dimethyl phthalate in each pot under nitrogen atmosphere! , 60 m2 of titanium tetrachloride was added and pulverized for 40 hours. 300 g of the co-pulverized material thus obtained was placed in a flask at 5°C, and 3.0 g of toluene was added. Or! , was stirred at 120°C for 30 minutes, the supernatant liquid was removed, and toluene 3. The mixture was stirred at 100'C for 30 minutes, the supernatant liquid was removed again, and the resulting solid content was repeatedly washed with n-hexano to obtain a transition metal catalyst slurry. When a part of the sample was sampled and the titanium content was analyzed, it was found to be 1.6 wt%.

In an autoclave with an internal volume of 51, 90 g of nylsilane and 1.5 kg of propylene were placed, and 1.8 Nj2 of hydrogen was added thereto. Then, 200 mg of the above titanium catalyst, 0.2 ml of l-ethylaluminum, 0.05 d of cyclohexylmethyldimethoxysilane, and 100 mg of toluene were added. The dispersed material 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. This copolymer had a η of 1.48 and a vinylsilane content of 185 mol χ.

Mix 80 parts of the copolymer to 20 parts of the syndiotactic polypropylene, add 0.1 wt% of phenolic stabilizer to the polymer, and granulate at 220°C to a thickness of 1.
A 1 mm injection seam was prepared.

This sheet was treated with boiling water for 6 hours. When the sheet was extracted with boiling xylene for 6 hours, the proportion of the extracted residue was 0.5 wt % before treatment with boiling water and 72 wt χ after treatment.

Comparative Example 1 When a similar experiment was carried out by granulating and molding only the copolymer, the proportion of boiling xylene extraction residue was 1.8 w before boiling water treatment.
t%, and even after treatment it was only 3 wt%.

Example 2 The same procedure as Example 1 was carried out except that 80 parts of syndiotactic polypropylene and 20 parts of copolymer were mixed, and the ratio of boiling xylene extraction residue was 0.1 w before boiling water treatment.
t%, and 22.5 wt% after treatment.

〔Effect of the invention〕

By using the method of the present invention, polypropylene can be easily crosslinked and is extremely valuable industrially.

Claims (1)

[Claims] A method for crosslinking polypropylene, which comprises heating a mixture of polypropylene having a substantially syndiotactic structure and a copolymer of alkenylsilane and propylene in the presence of water.