JPS627187B2 - - 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 standpoint 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 disadvantages such as loss due to decomposition of DCP and the need for filtration for security reasons, since DCP is kept in a high-temperature molten state. It will also happen. Even more solid
When handling DCP, foreign matter such as dust is often mixed in, and such foreign matter that adversely affects 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-methylbenzyl) peroxide is provided.

α・α-dimethylbenzyl (α・α-dimethyl-m-methylbenzyl) peroxide (hereinafter abbreviated as cumyl-m-simylperoxide) is
Specific gravity ^d254 is approximately 1.0, viscosity _at 25℃ is 25~
26CP is a liquid peroxide at room temperature. Its half-life is about 1 minute at 178°C and about 10 hours at 114°C, and its activation energy is about 35 Kcal/mol.

The most typical method for producing walnut m-simyl peroxide is to prepare α,α-dimethylbenzyl hydroperoxide (cumene hydroperoxide) and α,α-dimethyl-m-methylbenzyl alcohol, or α,α-dimethyl. It can be easily produced by reacting -m-methylbenzyl hydroperoxide and α·α-dimethylbenzyl alcohol in the presence of an acidic catalyst. The reaction ratio between raw material hydroperoxide and raw material alcohol is arbitrary, but usually alcohol/
The hydroperoxide (molar ratio) is preferably 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, for solid catalysts, it is usually 0.1
from 20% by weight, preferably from 0.5 to 5% by weight
used at a rate of 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 cymene 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. There are well-known methods for removing water, such as a method in which the reaction is carried out while blowing in an inert gas such as nitrogen, and water is removed by entraining it with nitrogen, or a method in which the pressure of the reaction system is reduced and water is removed 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.

When using cumyl-m-simyl peroxide as a crosslinking agent for polymers, α・α-dimethylbenzyl (α・α-dimethyl-p-methylbenzyl) peroxide (hereinafter abbreviated as cumyl-p-simyl peroxide) is used. It may be used in combination with. For example, the weight ratio of m-form/p-form is 50/
50 to 100/0, preferably 55/45 to 80/
A range of 20 can be suitably used.

cumyl-m-simyl peroxide and cumyl-p
- When preparing a mixture of simyl peroxides, the step 2 for preparing the cumyl-m-simyl peroxides
Instead of α·α-dimethyl-m-methylbenzyl alcohol or α·α-dimethyl-m-methylbenzyl hydroperoxide in the process, a mixture of the respective m-, p-isomers can be used.

After the condensation reaction between alcohol and hydroperoxide is completed, the acidic catalyst is removed from the reaction mixture by filtration or neutralization, and preferably washed with water. In order to perform these operations smoothly, especially to ensure good separation from the aqueous layer during neutralization and washing,
It is desirable to dilute the reaction mixture in advance with a hydrocarbon having a low boiling point, for example, a hydrocarbon having about 5 to 8 carbon atoms. 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, if a low-boiling hydrocarbon is used as described above, it is removed by distillation, and if it contains a high-boiling hydrocarbon such as cumene or cymene, it is steam distilled under reduced pressure. It can be removed by doing this. Further, if necessary, the product can be concentrated under reduced pressure and, in some cases, further filtered.

Reaction of walnut-m-simylperoxide or cumene hydroperoxide with m-methyl-α-methylstyrene or α・α-dimethyl-m-
It can also be obtained by the reaction of methylbenzyl 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-simyl peroxide of the present invention is useful as a crosslinking agent for high molecular weight polymers. especially
Unlike DCP, it is liquid at room temperature, so when it is blended into a high molecular weight polymer, it has good meterability, can be blended safely and advantageously, and uniform molded products can be easily obtained. Furthermore, since it is in liquid form, maintenance and management to prevent contamination by foreign matter is easy. Further DCP
Since the thermal decomposition temperature is slightly higher, 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, in terms of crosslinking efficiency, it has performance equivalent to or higher than that of 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 useful as a decomposition accelerator for peroxide-decomposable polymers such as polypropylene and poly-4-methyl-1-pentene, or as a polymerization initiator for radical polymerization.

Next, examples will be shown.

Example 1 285 g of cumene hydroperoxide (purity 80%)
(1.4 mol) and α・α-dimethyl-m-methylbenzyl alcohol (purity 85%) 247 g (1.4 mol)
were reacted in the presence of 10 g of synthetic silica alumina catalyst at 60° C. for 5 hours while blowing nitrogen. Cumyl-m-simyl peroxide was obtained with a yield of 92%.

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 284, active oxygen content 5.10%, purity 90.5%, specific gravity (d ²⁵ ₄ )
1.01, viscosity (25℃) 25.3CP, half-life 178℃
(1min), 114℃ (10hr), activation energy
It was 34.6 Kcal/mol.

Example 2 In Example 1, instead of α·α-dimethyl-m-methylbenzyl alcohol, a mixture of α·α-dimethyl-m-methylbenzyl alcohol and α·α-dimethyl-p-methylbenzyl alcohol (m- A mixture of cumyl-m-simyl peroxide and cumyl-p-simyl peroxide (m-isomer/p-isomer = 65/35) was carried out in the same manner as in Example 1, except that cumyl-m-simyl peroxide and cumyl-p-simyl peroxide were used (m-isomer/p-isomer = 65/35). ) was obtained. Its properties are molecular weight 284, active oxygen content 4.82%, purity
85.6%, specific gravity ( ^d254 ) 1.02 _, viscosity (25℃)
27.5CP, half-life 177℃ (1min), 113℃ (10hr),
The activation energy was 34.9 Kcal/mol.

High-pressure polyethylene having a density of 0.921 and a melt index of 1.5 and the peroxide of Example 1 or Example 2 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.

In either case, continuous extrusion for a long period of time was possible, and the surface condition of the strands was also good. The gel fraction (insoluble content when immersed in toluene at 90°C for 6 hours) was 88% in all cases.

Claims (1)

[Scope of Claims] 1 α·α-dimethylbenzyl (α·α-dimethyl-m-methylbenzyl) peroxide. 2. The peroxide according to claim 1, which contains not more than the same weight of α·α-dimethylbenzyl (α·α-dimethyl-p-methylbenzyl) peroxide.