JP3181704B2 - Method for producing cross-linked molded article of polyolefin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a gradient material having a different degree of cross-linking depending on the location of a molded product. More specifically, the present invention relates to a method for producing a cross-linked molded article of polyolefin having a gradient in cross-linking degree by mixing a specific copolymer and a catalyst and subjecting the mixture to heat-melt molding.

[0002]

2. Description of the Related Art Crosslinking of a polyolefin for the purpose of improving mechanical properties, improving solvent resistance, improving heat resistance and the like is widely performed. Various methods have already been proposed as a method of crosslinking, and a method using an alkenylsilane copolymer is excellent from the viewpoint of ease of crosslinking, a wide range of crosslinking density, physical properties, and the like.

[0003]

In the method using alkenylsilane, the crosslink density can be changed in a wide range, but it is necessary to use a so-called gradient material having different crosslink densities in the same molded product. Therefore, development of a method for producing such a molded product is desired.

[0004]

Means for Solving the Problems The present inventors have solved the above problems, and have earnestly studied a method for producing a molded article having a gradient in crosslink density, and completed the present invention.

That is, the present invention relates to a composition containing an alkenylsilane and olefin copolymer, a rhodium salt and
The general formula (Chem. 5)

Embedded image (Wherein R ¹ and R ² are the same or different and have 1 to 12 carbon atoms)
A hydride residue, n is an integer of 0 to 3, M is titanium, zirconium
Metal selected from uranium and hafnium. ) Period
A component containing a catalyst selected from alkoxy compounds of Group IVB metals is mixed, and the ratio of the catalyst in each part of the molded article is adjusted.
This is a method for producing a cross-linked molded article of polyolefin having a gradient in the degree of cross-linking, which is characterized by performing heat-melt molding so as to form a gradient.

In the present invention, alkenyl silanes having at least one Si—H bond are preferably used, for example, a compound represented by the following general formula (Chemical Formula 1):

[0007]

Embedded image H ₂ C = CH— (CH ₂ ) _n —SiH _P R _3-P (where n is 0 to 12, p is 1 to 3, and R is a hydrocarbon residue having 1 to 12 carbon atoms). ) Can be exemplified, specifically, vinyl silane,
Examples thereof include allylsilane, butenylsilane, pentenylsilane, and compounds in which H of Si—H bond in some of these monomers is substituted with chloro.

As the olefin, a compound represented by the following general formula (Formula 2):

[0009]

Embedded image H ₂ CHCH—R (where R is hydrogen or a hydrocarbon residue having 1 to 12 carbon atoms)
Can be exemplified, specifically, ethylene, propylene, butene
In addition to α-olefins such as -1, pentene-1, hexene-1, 2-methylpentene, heptene-1, and octene-1, styrene or a derivative thereof is also exemplified.

In the present invention, the copolymer of olefin and alkenylsilane can be produced by a bulk polymerization method or a gas phase polymerization method in addition to a solvent method using an inert solvent. Further, a catalyst comprising a transition metal compound and an organometallic compound is generally used as a catalyst used in the production. A titanium halide is preferably used as the transition metal compound, and an organoaluminum compound is preferably used as the organometallic compound.

Specifically, titanium trichloride obtained by reducing titanium tetrachloride with metallic aluminum, hydrogen or organic aluminum is modified with an electron donating compound, an organic aluminum compound, and if necessary, an oxygen-containing organic compound. A transition metal compound catalyst obtained by supporting a titanium halide on a catalyst system comprising an electron donating compound such as a magnesium halide or a carrier obtained by treating them with an electron donating compound, and an organoaluminum compound. A catalyst system comprising an electron-donating compound such as an oxygen-containing organic compound, or a reaction product of magnesium chloride and an alcohol is dissolved in a hydrocarbon solvent, and then treated with a precipitant such as titanium tetrachloride to form a hydrocarbon solvent. Insolubilize and treat with an electron-donating compound such as an ester or ether if necessary. Examples of the catalyst system include a transition metal compound catalyst and an organoaluminum compound obtained by a method of treatment with titanium logenide and an electron-donating compound such as an oxygen-containing organic compound as required (for example, various types of compounds described in the following documents). Examples are described: Ziegler-Natta Ca
talysts and Polymerization by John Boor Jr (Academi
c Press), Journal of Macromorecular Science Reviews
in MacromolecularChemistry and Physics, C24 (3) 355
-385 (1984) and C25 (1) 578-597 (1985)).

Alternatively, the polymerization can be carried out using a catalyst comprising a transition metal catalyst soluble in a hydrocarbon solvent and an aluminoxane.

As the electron donating compound, oxygen-containing compounds such as ethers, esters, orthoesters and alkoxysilicon compounds can be preferably exemplified, and alcohols, aldehydes and water can also be used.

As the organoaluminum compound, trialkylaluminum, dialkylaluminum halide, alkylaluminum sesquihalide, and alkylaluminum dihalide can be used. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and a hexyl group. Illustrative examples of the halide include chlorine, bromine and iodine. Aluminoxane, which is an oligomer to a polymer obtained by reacting the above-mentioned organoaluminum with water or water of crystallization, can also be used.

Here, the polymerization ratio of the alkenyl silane and the olefin is usually about 0.1 to 30 mol%, preferably about 30 to 30 mol%, from the viewpoint of increasing the degree of crosslinking.
0.5 to 10 mol%. When it is used in a mixture with another olefin polymer, the content is 1 to 20 mol%.

Although the molecular weight of the polymer is not particularly limited, from the viewpoint of improving the physical properties of the molded product, the higher the molecular weight, the higher the degree of crosslinking even with a small alkenylsilane content. In terms of moldability, if the molecular weight is too high, the moldability deteriorates. Therefore, the intrinsic viscosity measured with a tetralin solution at 135 ° C. is preferably 0.5 to 0.5.
It is about 10 and particularly preferably about 1.0 to 5.0.

A graft copolymer obtained by graft-polymerizing an alkenylsilane onto a polyolefin (for example, a polyolefin used as a mixture as described below) can also be used for the purpose of the present invention. There is no particular limitation on the method of grafting the alkenyl silane to the method, and the method and conditions used for ordinary graft copolymerization can be used, and usually the polyolefin and alkenyl silane used are radical initiators in the presence of a radical initiator such as peroxide. The graft copolymerization can be easily performed by heating to a temperature equal to or higher than the decomposition temperature.

In the present invention, the polyolefin used by mixing with the above-mentioned copolymer, if necessary, is an olefin represented by the above general formula (Formula 2), specifically, ethylene,
Propylene, butene-1, pentene-1, hexene-1, 2-methylpentene, heptene-1, octene-1, and other α-olefins, homopolymers of styrene or a derivative thereof, mutual random copolymers, or Examples thereof include a so-called block copolymer produced by first copolymerizing an olefin alone or a small amount of another olefin, and then copolymerizing two or more olefins.

The methods for producing these polyolefins are already known, and various brands are available on the market. Alternatively, the alkenyl silane can be produced by using the same method as that for producing the copolymer of olefin and alkenyl silane except that alkenyl silane is not used.

In the present invention, if necessary, a compound containing at least two unsaturated bonds can be used in combination. Examples of such a compound include aromatic compounds such as divinylbenzene, diisopropenylbenzene and diallylbenzene. Examples include vinyl compounds, unsaturated esters such as ethylene glycol dimethacrylate and ethylene glycol diacrylate, and polymers such as polybutadiene and polyisoprene. Any compound having at least two reactive unsaturated bonds can be used. Things are also available.

The catalyst used in the present invention is a rhodium salt such as a triphenylphosphine complex of rhodium chloride, or an alkoxy compound of a Group IVB metal of the Periodic Table represented by the following general formula (Formula 3) such as a titanate ester.
It is .

[0022]

Embedded image _{^{R 1 n M (OR 2)}} 4-n ( wherein R ^1, R ² is a hydrocarbon residue of the same or different carbon atoms 1 to 12, n is an integer of from 0 to 3, M is titanium , Zirconium, hafnium.)

What is important in the present invention is that components containing the above-mentioned alkenylsilane / olefin copolymer and catalyst are prepared in advance, and the two components are mixed while changing their ratio and molded by heating and melting. Therefore, as long as the alkenylsilane / olefin copolymer and the catalyst are not mixed, the composition of each component is freely determined. For example, as one component, a copolymer of an alkenylsilane and an olefin alone or a stabilizer such as an antioxidant, and further, if necessary, a pellet made of a compound containing at least two unsaturated bonds, and one component Examples thereof include mixing a catalyst into a polyolefin or using a catalyst solution in which the catalyst is dissolved in a liquid unsaturated compound.

The molding may be carried out by any molding method as long as the ratio of the catalyst, alkenylsilane and olefin copolymer in each part of the molded product is inclined, and examples include injection molding, extrusion molding and press molding. Is done. Here, the concentration of the alkenylsilane in the mixture is 0.01 to 20 mol%, and the preferred concentration of the catalyst varies depending on the catalyst used, but is usually about 1 ppm to 1%. The molding temperature is not particularly limited, and may be at the ordinary molding temperature of polyolefin, and is usually at 150 to 300 ° C.

In the present invention, crosslinking can be further promoted by subjecting the molded article obtained by the above method to a heat treatment at a temperature of 100 ° C. or higher and a deformation temperature of the molded article or lower. The heating temperature is preferably high as long as the molded product is not deformed, but is preferably 100 to 200 ° C., particularly preferably 1 to 200 ° C.
00-160 ° C.

[0026]

The present invention will be further described with reference to examples.

Example 1 A vibrating mill equipped with four crushing pots having a capacity of 4 liters and containing 9 kg of steel balls having a diameter of 12 mm was prepared. Under a nitrogen atmosphere, 300 g of magnesium chloride, 60 ml of tetraethoxysilane and 45 ml of α, α, α-trichlorotoluene were added to each pot.
ml was added and crushed for 40 hours. Co-ground product 300 thus obtained
g in a 5 liter flask, 1.5 liters of titanium tetrachloride and 1.5 liters of toluene are added.
After stirring for minutes, the supernatant was removed. Add 1.5 liters of titanium tetrachloride and 1.5 liters of toluene again,
The mixture was stirred at 100 ° C. for 30 minutes, and then the supernatant was removed. Thereafter, the solid content was repeatedly washed with n-hexane to obtain a transition metal catalyst slurry. When a part was sampled and analyzed for titanium content, the titanium content was 1.9 wt%.

In a 5 liter autoclave, under a nitrogen atmosphere, 40 ml of toluene, 100 mg of the above transition metal catalyst, 0.128 ml of diethylaluminum chloride, 0.06 ml of methyl p-toluate and 0.20 ml of triethylaluminum were placed, and 1.5 kg of propylene and 80 g of vinylsilane were added. Plus hydrogen
After injection of 0.5N liter, polymerization was carried out at 75 ° C for 2 hours. After polymerization, unreacted propylene was purged, and the powder was taken out and dried to obtain 480 g of powder.

The resulting powder has an intrinsic viscosity of 2.35 measured in a tetralin solution at 135 ° C., and the melting point and crystallization temperature are maximized by raising or lowering the temperature at 10 ° C./min using a differential thermal analyzer. It was a crystalline propylene copolymer having a melting point of 156 ° C. and a crystallization temperature of 120 ° C. when measured as a peak temperature. According to elemental analysis, it contained 1.3 wt% of a vinylsilane unit.

0.5 g, 0.2 g, 0.1 g, and 0.05 g of n-butyl titanate were mixed with 100 g of the obtained copolymer, and the mixtures were sequentially arranged to form a 20 cm × 5 cm × 2 mm press sheet at 250 ° C. × 150 kg / cm ² . This molded product was cut into 5 cm pieces in the length direction, and the ratio of the extraction residue extracted with boiling xylene for 12 hours in each part was measured.
It was 2,45%. When the molded product was heated at 140 ° C. for 1 hour, the proportions of the extraction residues extracted with boiling xylene for 12 hours were 99, 91, 85 and 62%, respectively. Thus, a material having a gradient in crosslink density could be formed.

Example 2 A copolymer having an intrinsic viscosity of 2.40 and containing 0.15 wt% of vinylsilane was obtained in the same manner as in Example 1 except that the amount of vinylsilane used was changed to 10 g. 0.1 g of triphenylphosphine complex of rhodium chloride with respect to 100 g of the obtained copolymer, 0.1 g.
Each of 05g, 0.01g and 0.005g was mixed and molded in the same manner as in Example 1, and the proportion of the extraction residue extracted with boiling xylene for 12 hours in each part was measured to be 78, 71, 34 and 11%. Was. When this molded article was heated at 140 ° C. for 1 hour, the proportions of the extraction residues extracted with boiling xylene for 12 hours were 96, 88, 56 and 28%, respectively. Thus, a material having a gradient in crosslink density could be formed.

[0032]

By carrying out the method of the present invention, a crosslinked molded article of a polyolefin having a gradient in the degree of crosslinking can be easily obtained, which is extremely valuable industrially.

Claims (1)

(57) [Claims] 1. A component containing a copolymer of alkenylsilane and olefin, a salt of rhodium and a compound represented by the following general formula:
4) [of 4] (Wherein R ¹ and R ² are the same or different and have 1 to 12 carbon atoms)
A hydride residue, n is an integer of 0 to 3, M is titanium, zirconium
Metal selected from uranium and hafnium. ) Period
A component containing a catalyst selected from alkoxy compounds of Group IVB metals is mixed, and the ratio of the catalyst in each part of the molded article is adjusted.
A method for producing a cross-linked molded article of a polyolefin having a gradient in cross-linking degree, wherein the cross-linking is performed by heat-melt molding so as to form a slope.