JPS6016974B2 - Method for preparing polyolefin resin pellets or particles impregnated with organic peroxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method for preparing polyolefin resin pellets or particles impregnated with an organic peroxide.

Crosslinked polyolefin resins are known to have excellent electrical properties and mechanical properties, and are used in an extremely wide range of applications.

There are various methods for preparing a polyolefin resin composition containing a crosslinking agent to obtain this crosslinked polyolefin resin, but a simple method is to pre-adhere an organic peroxide to a polyolefin resin pellet. It is prized as a preparation method. The applicant has previously proposed a method of impregnating and adhering an organic peroxide to pellets of polyolefin resin (see Japanese Patent Publication No. 39-25792), but this method does not work with pellets or particles of polyolefin resin. The organic peroxide is placed in a mixer, and as the mixing progresses, the organic peroxide melts on the surface of the resin pellet or particles, so-called wetting, and then this permeates into the resin pellet or particles and the process is completed. (Hereinafter, this method will be abbreviated as the "Mabushi-mixing method").

By the way, in this sprinkling mixing method, whether or not a good product in which the organic peroxide is properly impregnated and adhered to the resin pellets or particles can be obtained has a great deal to do with the timing at which the mixing is stopped. In other words, if the mixing process is stopped too early, the organic peroxide will be poorly dispersed, and if this prepared composition is used, there is a concern that the subsequent crosslinking reaction will be non-uniform.On the other hand, if the mixing process is excessive, the preparation process will be interrupted. Powder is generated due to the friction of the resin pellets or particles inside, and this also causes various troubles such as clogging of the piping system later on, which is undesirable.

Conventionally, in this Mabushi mixing method, in order to confirm the timing to stop the above-mentioned mixing process, the mixing naturally takes a certain amount of time and the temperature of the mixed product rises as the mixing end approaches. For example, a timer was set on a mixer, and after a certain period of time, an operator would check the temperature of the mixed product and stop the mixer.

However, with this method, it is difficult to obtain a uniform mixed product because the temperature changes during the above period depending on the type of mixed product and the working environment temperature, and the judgment of the quality of the mixed product differs depending on the worker. In addition, there are disadvantages such as requiring a high degree of skill from the operator.Furthermore, it is extremely difficult to standardize the work of this method due to the above-mentioned changes in mixing time, temperature of the mixed product, etc. .

The inventors were conducting intensive studies on a method for confirming the appropriate time to end this mixing process, and discovered that the load on the mixer suddenly increased while the polyolefin resin pellets or particles were being mixed with the organic peroxide. They found that the time point substantially coincides with the appropriate time to complete the impregnation treatment of the resin pellets or particles with the organic peroxide, and completed the present invention.

That is, this invention provides a method for impregnating and adhering an organic peroxide to a polyolefin resin or particles, in which the polyolefin resin pellets or particles and the organic peroxide are mixed with a mixer, and during the continuation of the mixing, the organic peroxide is An organic peroxide characterized in that the mixing is stopped by detecting a sudden increase in load on the mixer after the peroxide has melted and started to be impregnated and absorbed into the side fat pellets or particles. This is a method for preparing polyolefin resin pellets 3 or particles impregnated with substances. In this invention, the occurrence of the phenomenon in which the load on the mixer, which is the end point of the impregnating and adhering process, suddenly increases can be explained as follows.

That is, in the above-mentioned sprinkling method in which organic peroxide and polyolefin resin pellets or particles are mixed in a mixer, the organic peroxide is heated to a temperature higher than its melting point, thereby melting and gradually forming side fat pellets or particles. It adheres to the surface and begins to wet and become impregnated. During this period, the friction between the side fat pellets or grains in the mixer becomes very small, and the mixing operation proceeds for a certain period with a relatively low load.
Next, when the resin pellets or particles are sufficiently impregnated with organic peroxide, the above-mentioned friction increases rapidly, and this frictional energy causes a sudden increase in the mixing load of the mixer.

Therefore, if the time when the mixing load suddenly increases is taken as the time to stop the impregnation and adhesion treatment, a resin pellet or particle will be obtained in which the entire amount of organic peroxide has been impregnated. In the present invention, the mixing ratio of the polyolefin resin pellets or particles and the organic peroxide is not particularly limited, and the above-mentioned load increase value calculated from the friction property etc. according to the mixing ratio is determined in advance. It is desirable to stop the mixing operation. Further, in this invention, the above-mentioned organic peroxides are not particularly limited, and include dicumyl peroxide, 2.5-dimethyl 2.5-di(tert-butylperoxy)hexane, and 2.5-dimethyl 2.5-dimethyl peroxide. -(tert-butylperoxy)hexane-3,1.3-
Bis(sarybutylperoxy-isopropyl)
Benzene (trade name: Percadox) etc. are used.
Furthermore, in the present invention, other materials such as anti-aging agents or carbon dioxide may be present in the mixed composition of the polyolefin resin pellet and the organic peroxide, if necessary. As the mixer used in the present invention, most of the mixers commonly used for mixing materials of this type can be used, such as a ribbon blender, a Henschel mixer, a soot/goo mixer, and an innolly mixer. As a method for detecting the above-mentioned load increase of these mixers, for example, an increase in the load current or mechanical torque may be detected. As described above, in the method for preparing polyolefin resin pellets or particles impregnated with an organic peroxide, the present invention detects the point at which the mixing load suddenly increases when the two are mixed, and stops the mixing. It was designed so that
Therefore, the timing of the stop will not vary depending on the subjectivity or judgment of the operator, and it can be easily automated by simply adding an automatic stop device to the mixer, which solves the above-mentioned problems. This is something that can be almost eliminated.

Next, examples of this invention will be described.

The compositions of the polyethylene resin pellets and organic peroxide shown in the table were mixed using a mixer (ribbon blender) in the filling amounts shown in the table.

The mixing machine was stopped at S2 as soon as the load current showed signs of increasing, and S2 when the mixing machine showed signs of increasing.

For comparison, the mixer was stopped when the temperature of the mixed product was 70℃.
The test was stopped when the temperature reached 00 or higher, and each mixed product was judged, and the results are shown in the same table. In order to check the degree of powder generation in the above table, 100 pieces of each mixture were collected, shaken through a 10-mesh wire mesh, separated, shaken, and the fallen powder was washed with 500% acetone. The weight of the powder obtained by melting and removing the anti-aging agent was measured.

The results are shown in the table below. According to the results in the table above,
It is clear that in Example 5, good results can be accurately obtained without being affected by the mixture composition, except for the case of excessive mixing after increasing the load, and in the case of Comparative Examples, there are fewer good results and more failures. there were. Reference Example Using the polyethylene mixed composition prepared in Example 2, a conductor with a conductor diameter of 10 cm was extruded and coated to a coating thickness of 2.0 cm, and 21.5 kg/base of pressurized steam was applied. A 600V crosslinked polyethylene insulated wire was manufactured by heating under pressure.

Note that the electric wire manufacturing line list at this time was 12.5/min.
When the gel fraction of the coating layer, heating deformation rate at 120 o'clock, dielectric breakdown voltage, etc. of the obtained crosslinked polyethylene insulated wire were investigated, the gel fraction was 88%, 12%, and 50%.
It was not destroyed by KV and was an extremely benign product.

Claims (1)

[Claims] 1. In a method of impregnating and adhering an organic peroxide to polyolefin resin pellets or particles, the polyolefin resin pellets or particles and the organic peroxide are mixed with a mixer, and during the continuation of the mixing, the organic peroxide is A polyolefin resin impregnated with an organic peroxide, characterized in that the mixing is stopped by detecting an increase in load on a mixer after melting and wetting onto the surface of resin pellets or particles. Method for preparing pellets or particles.