JPS627188B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to novel peroxides. More specifically, the present invention relates to a liquid peroxide suitable for crosslinking electrically insulating polymers.

Electrical insulation layers used to cover electric wires, cables, etc. are generally made of high-voltage polyethylene.
It is formed by extrusion coating a mixture of this and an appropriate amount of an organic peroxide crosslinking agent onto a conductor, followed by crosslinking. Dicumyl peroxide (hereinafter abbreviated as DCP) is often used as an organic peroxide crosslinking agent because it does not decompose during extrusion coating and efficiently crosslinks polyethylene during crosslinking. However, the use of DCP is not without its problems. For example polyethylene and DCP
From the viewpoint of workability, it is desirable to use an extruder to knead the mixture, but in order to obtain a homogeneous mixture,
It is necessary to supply DCP at a constant rate. To do this, solid DCP, which is difficult to measure, must be melted into a liquid state. This not only requires a DCP melting device, but also suffers from disadvantages such as loss due to decomposition of DCP and the need for safety considerations since DCP is kept in a high-temperature molten state. Become. Even more solid
When handling DCP, foreign matter such as dust often gets mixed in, and such foreign matter that has a negative effect on the quality of the insulating layer must be removed in advance. It is necessary to add complicated operations.

In view of this current situation, the present inventors have developed a peroxide that exhibits crosslinking properties similar to DCP, that is, its thermal decomposition temperature is close to that of DCP, and its crosslinking performance is equal to or higher than that of DCP. We searched for peroxides that are liquid at room temperature. As a result, it satisfies all of these conditions, and moreover, it mixes with high molecular weight polymers more easily in the extruder than DCP.
Therefore, we have discovered a peroxide that is superior in that extrusion molded products of excellent quality can be obtained. That is, according to the present invention, α·α-dimethylbenzyl (α·α-dimethyl-m-isopropylbenzyl) peroxide is provided.

α・α-Dimethylbenzyl (α・α-dimethyl-m-isopropylbenzyl) peroxide (hereinafter abbreviated as cumyl-m-isopropylcumyl peroxide) has a specific gravity d ²⁵ ₄ of approximately 1.00 and a viscosity at 25°C of approximately 33 CP. It is a peroxide that is liquid at room temperature. Its half-life is approximately 1 minute at 180℃ and approximately 10 hours at 112℃, and its activation energy is approximately
It is 33Kcal/mol.

The most typical method for producing cumyl-m-isopropyl cumyl peroxide is α・
α-dimethylbenzyl hydroperoxide (cumene hydroperoxide) and α・α-dimethyl-m
-isopropylbenzyl alcohol, or α・α
It can be easily produced by reacting -dimethyl-m-isopropylbenzyl hydroperoside and α·α-dimethylbenzyl alcohol in the presence of an acidic catalyst. Although the reaction ratio between the raw material hydroperoxide and the raw material alcohol is arbitrary, it is usually preferable that the alcohol/hydroperoxide (molar ratio) is about 1.0 to 1.3.
As the acidic catalyst, silica alumina, acid clay, silica magnesia, alumina boria, zinc chloride, aluminum sulfate, nickel sulfate, sulfuric acid, toluenesulfonic acid, etc. can be used. The amount of catalyst used varies depending on the type of catalyst; for example, in the case of a solid catalyst, it is usually used in a proportion of 0.1 to 20% by weight, preferably 0.5 to 5% by weight. The reaction temperature is usually 20 to 110°C, preferably 50 to 80°C. Although the reaction is preferably carried out without a solvent, a solvent inert to the reaction such as cumene or diisopropylbenzene may be used. Although it varies depending on the type of catalyst used, it is generally preferable to constantly remove water generated during the reaction. As a method for removing water, there are known methods such as reacting while blowing an inert gas such as nitrogen,
A method of removing water by entraining it with nitrogen, or a method of reducing the pressure of the reaction system to remove water by evaporation, etc. can be adopted. Alternatively, it is also possible to adopt a method in which a hydrocarbon solvent such as that described above is present in the reaction system and water is removed while utilizing azeotropic distillation.

After the reaction between alcohol and hydroperoxide is completed, the acidic catalyst is removed from the reaction mixture by oxidation or neutralization, and preferably washed with water.
In order to carry out such operations smoothly, and in particular to improve separation from the aqueous layer during neutralization and water washing, the reaction mixture is preliminarily treated with a hydrocarbon of a low boiling point, for example, a hydrocarbon having about 5 to 8 carbon atoms. It is preferable to dilute it with a similar amount. For example, pentane, hexane, cyclohexane, benzene, etc. can be suitably used. It is preferable to use such hydrocarbons in an amount of about 1 to 10 times the weight of the peroxide.

After washing the reaction mixture with water, as above, if low boiling hydrocarbons were used, they were removed by distillation, and if they contained high boiling hydrocarbons such as cumene or diisopropylbenzene, they were steam distilled under reduced pressure. It can be removed by doing the following. Further, if necessary, the product can be concentrated under reduced pressure and, in some cases, further filtered.

Cumyl-m-isopropylcumyl peroxide is also produced by the reaction of cumene hydroperoxide and m-isopropyl-α-methylstyrene or α.
It can also be obtained by the reaction of α-dimethyl-m-isopropylbenzyl hydroperoxide and α-methylstyrene. For example, it is advantageous to carry out the method according to the method disclosed in Japanese Patent Application No. 52-116027.

The cumyl-m-isopropyl cumyl peroxide of the present invention is useful as a crosslinking agent for high molecular weight polymers. In particular, unlike DCP, it is liquid at room temperature, so when it is blended into a high molecular weight polymer, it has good meterability and can be blended safely and advantageously, making it possible to easily obtain uniform molded products. Also, since it is in liquid form, maintenance and management to prevent contamination by foreign matter is easy.
Furthermore, since the thermal decomposition temperature is slightly higher than that of DCP, the processing temperature before crosslinking, for example, the extrusion temperature of the high molecular weight polymer, can be increased, and processability can be improved. Furthermore, regarding crosslinking efficiency
It has performance equal to or better than DCP. Furthermore, since it is easy to mix with a high molecular weight polymer in an extruder, it is particularly advantageous in that homogeneous molded products can be obtained even in high-speed extrusion molding such as electric wire coating.

The polymers used for crosslinking are resin-like or rubber-like, and specifically include medium-low pressure polyethylene, high-pressure polyethylene, poly-1-butene, ethylene-vinyl acetate copolymer, and ethylene-vinyl acetate copolymer.
Acrylic ester copolymer, ethylene-propylene copolymer, ethylene-1-butene copolymer,
ethylene-4-methyl-1-pentene copolymer,
Resin-like polymers such as propylene-1-butene copolymer, ethylene-propylene copolymer rubber, butyl rubber, chlorinated polyethylene, silicone rubber, rubber-like polymers such as propylene-1-butene copolymer rubber, two or more types of Examples include mixtures of resinous polymers, mixtures of two or more types of rubbery polymers, and mixtures of resinous polymers and rubbery polymers. When used for crosslinking, the peroxide of the present invention is preferably added in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the polymer.
It is preferable to add about 0.5 to 5 parts by weight.

The peroxide of the present invention is also effective as a decomposition accelerator for peroxide-decomposable polymer compounds such as polypropylene and poly-4-methyl-1-pentene, or as a polymerization initiator for radical polymerization.

Next, examples will be shown.

Example 1 266 g of cumene hydroperoxide (purity 80%)
(1.4 mol) and 293 g (1.4 mol) of α・α-dimethyl-m-isopropylbenzyl alcohol (purity 85%) in the presence of 10 g of synthetic silica alumina catalyst.
The reaction was carried out at 60° C. for 5 hours while blowing nitrogen. cumyl-m-isopropyl cumyl peroxide is 91
% yield.

To this reaction mixture were added 2 hexane and 30 ml of water, and the mixture was filtered to remove synthetic silica alumina. Next, after washing with 5% NaOH aqueous solution and further washing with water, the oil layer was removed, and the hexane was removed by distillation.
Steam distillation was performed at 30-50 mmHg and 65°C. Then, it was concentrated under conditions of 5 mmHg and 65°C and filtered to obtain liquid peroxide. Its properties are molecular weight 312, active oxygen content 4.77%, purity 93.2%, _specific gravity ( ^d254 )
1.00, viscosity (25℃) 33.0CP, half-life 180℃
(1min), 112℃ (10hr), activation energy
It was 33.1 Kcal/mol.

High-pressure polyethylene having a density of 0.921 and a melt index of 1.5 and the synthesized peroxide were fed into an extruder, and strands with a diameter of 5 mm were continuously extruded at 120° C. while melt-kneading. The peroxide was supplied in a proportion of 2.5 parts by weight per 100 parts by weight of polyethylene. Next, crosslinking was performed at 195°C for 5 minutes using a crosslinker.

Continuous extrusion for a long period of time was possible, and the surface condition of the strands was also good. Also, the gel fraction (90℃
(insoluble matter when immersed in toluene for 6 hours) is
It was 89%.

Claims (1)

[Claims] 1 α·α-dimethylbenzyl (α·α-dimethyl-m-isopropylbenzyl) peroxide.