JPS6021657B2 - Crosslinking agent for high molecular weight polymers - Google Patents

Description

[Detailed description of the invention] The present invention relates to a crosslinking agent for high molecular weight polymers.

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-pressure polyethylene, mixed with an appropriate amount of organic peroxide crosslinking agent, extruded onto the conductor, and then crosslinked. be done.

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, regarding the use of DCP,
This is not to say that there are no problems. For example, from the standpoint of workability, it is desirable to use an extruder to knead polyethylene and DCP, but in order to obtain a homogeneous blend, it is necessary to feed DCP at a constant rate. For this purpose, it is necessary to melt solid DCP, which is difficult to measure, into a liquid state. This not only requires a DCP melting device, but also involves disadvantages such as loss due to decomposition of DCP and the need for safety considerations because DCP is kept in a high-temperature molten state. It also becomes. Furthermore, when handling solid 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. Complex operations such as post-furnace filtration must be added. In view of the current situation, the present inventors have developed a peroxide that exhibits crosslinking properties similar to DCP, that is, has a thermal decomposition temperature close to that of DCP, and has crosslinking performance equivalent to or higher than that of DCP. , and searched for peroxides that are liquid at room temperature. As a result, the product meets all of these conditions and is superior in that it mixes more easily with the high molecular weight polymer in the extruder than DCP, and therefore produces extruded products of superior quality. This led to the discovery of oxide. That is, according to the present invention, Q, Q-
A crosslinking agent for a polymer comprising dimethylbenzyl (Q,Q-dimethyl-p-isopropylbenzyl) peroxide is provided. Q,Q-dimethylbenzyl (Q,Q-
dimethyl-p-isopropylbenzyl) peroxide (
Cumyl-p-isopropyl cumyl peroxide (hereinafter abbreviated as cumyl-p-isopropyl cumyl peroxide) is a peroxide that is liquid at room temperature and has a specific gravity d of approximately 1.00 and a viscosity of approximately 3 $p at 25 qo.

Its half-life is approximately 1 minute at 179 qo and approximately 1 minute at 114 qo.
feeding time, and its activation energy is approximately 34Kca.
l/mol. The most typical method for producing cumyl-p-isopropylcumylberberoxide is to use Q,o-dimethylbenzyl hydroperoxide (cumene hydroperoxide) and Q,Q-dimethyl-p-isopropylbenzyl alcohol, or Q. , o-dimethyl-p-isof.

O-pyrubenzyl hydroperoxide can be easily produced by reacting Q-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, trinesulfonic 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 to 20
It is used in a proportion of 0.5 to 5% by weight, preferably 0.5% to 5% by weight. The reaction temperature is usually 20 to 11,030 qC, preferably 50 to 80 qC. 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. 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 search for a method of coexisting a hydrocarbon solvent such as the one described above in the reaction system and removing water while utilizing azeotropic distillation. 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 carry out such operations smoothly, especially in order to improve the separation from the aqueous layer during neutralization and washing, the reaction mixture must be pretreated with a hydrocarbon having a low boiling point, such as a hydrocarbon with a carbon number of about 5 to 8. 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 about 1 to 1 times the weight of peroxide. After washing the reaction mixture with water, remove it by distillation if low-boiling hydrocarbons were used as described above, and if they contain high-boiling hydrocarbons such as cumene or diisopropylbenzene, perform steam distillation under reduced pressure. It can be removed by doing this.

Further, if necessary, the product can be concentrated under reduced pressure and, if necessary, further filtered through a furnace. Cumil-p-isopropylcumyl peroxide can also be obtained by reaction of cumene hydroperoxide and p-isopropyl-Q-methylstyrene or by reaction of Q,o-dimethyl-p-isopropylbenzyl hydroperoxide and Q-methylstyrene. For example, Tokuiso Sho 52-1
It is advantageous to carry out according to the method disclosed in No. 16207. In the present invention, cumyl-pisopropyl cumyl peroxide is used as a crosslinking agent for high molecular weight polymers.

Unlike DCP, it is liquid at room temperature, so when blended with high molecular weight polymers, it has good quantification and can be blended safely and advantageously.
It is possible to easily obtain a uniform molded product. Also, since it is in liquid form, maintenance and management to prevent contamination by foreign matter is easy. Furthermore, the thermal decomposition temperature is slightly higher than that of DCP, so
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. In addition, since it is easy to mix with a high molecular weight polymer in an extruder, it is particularly advantageous because a homogeneous molded product can be obtained even when high-speed extrusion molding is performed, such as for coating electric wires. The polymer used for crosslinking is resin-like or rubber-like, and specifically, medium-low pressure polyethylene, high pressure polyethylene, polypropylene, poly-1-
Butene, poly4-methyl-1-pentene, ethylene-
Vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, ethylene-propylene copolymer, ethylene-1
-Resinous polymers such as -butene copolymer, ethylene-4-methyl-1-bentene copolymer, propylene-1-butene copolymer, ethylene-propylene copolymer rubber, butyl rubber, chlorinated polyethylene, silicone rubber, propylene-1-butene copolymer Examples include rubbery polymers such as rubber, mixtures of two or more types 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 added in amounts of 0.1% and 1% per weight part of the high molecular weight polymer 10.
It is preferable to mix 0 parts by weight, particularly 0.5 parts by weight, and preferably about 5 parts by weight. Next, examples will be shown.

Example 1 Cumene hydroperoxide (purity 80%) 285 mg (1
．． 4 mol) means Q-dimethyl-p-isopropylbenzyl alcohol (purity 85%) 293 mol (1.4 mol)
was reacted in the presence of a synthetic silica-alumina catalyst for 5 hours at 60°C while blowing nitrogen.

91% cumyl-p-isopropyl cumyl peroxide
was obtained in a yield of . After adding 2 parts of hexane and 3 parts of water to the reaction mixture, the synthetic silica alumina was removed in a furnace.

Next, after washing with 5% NaOH water solution and further washing with water, the oil layer was removed, and the hexane was removed by distillation.
Steam distillation was carried out at 65° C. for ~5 hmH. The mixture was then concentrated at 6500 ml for 9 hmH and filtered through a furnace to obtain liquid peroxide. Its properties are: molecular weight 312, active oxygen content 4.86%, purity 95%, specific gravity (d) 1.00, viscosity (25qo) 34. Zp, half-life 179°C (lmin
), 114qC (1 sail [), activation energy 34. Fox cal/mol. High-pressure polyethylene with a density of 0.921 and a melt index of 1.5 and cumyl-p-isopropyl cumyl peroxide synthesized as described above were fed into an extruder, and while melt-kneaded, a strand of diameter 5 was produced at 12,000 yen. Extruded continuously.

The amount of peroxide is 2 parts by weight per 10 parts by weight of polyethylene.
．． It was supplied at a ratio of 5 parts by weight. Next, crosslinking was carried out in a crosslinker at 195°C for 5 minutes. Continuous extrusion for a long time was possible, and the surface condition of the strands was also good.

Claims (1)

[Scope of Claims] 1 α,α-dimethylbenzyl (α,α-dimethyl p-
A crosslinking agent for polymers consisting of isopropylbenzyl) peroxide. 2 Claim 1 for use in electrically insulating polymers
Crosslinking agent as described. 3. The crosslinking agent according to claim 1 or 2, wherein the high molecular weight polymer is polyethylene. 4. The crosslinking agent according to claim 3, wherein the polyethylene is high-pressure polyethylene.