Preparation method for crosslinkable polyethylene

Abstract

The invention provides a preparation method for crosslinkable polyethylene. The method comprises the following steps: under a purification condition, adding an antioxidant in a screw extruder by means of gravity measurement feeding, enabling the antioxidant to contact with low-density polyethylene, then plastifying and filtering, and then granulating by means of underwater strand granulation to obtain clean polyethylene grains; conveying the clean polyethylene grains to a height enabling feeding to be carried out through a self-gravity action during the subsequent steps, by means of water grain conveying through a sealing pipeline, and then dehydrating and drying; under the self-gravity action, conveying the dehydrated and dried clean polyethylene grains into a preheating device and then preheating; under the purification condition, mixing and wetting a crosslinking agent and the preheated clean polyethylene grains by means of gravity measurement feeding to obtain crosslinkable polyethylene grains. The crosslinkable polyethylene prepared by using the method provided by the invention achieves the requirements of an ultra-clean XLPE insulation material.

Description

technical field [0001] The invention relates to a preparation method of crosslinkable polyethylene. Background technique [0002] The molecular structure of polyethylene (PE) is symmetrical, and the dipole moment of the entire molecule is equal to zero. It is a typical non-polar material, so its dielectric constant is very small, and it is an ideal insulating material. Cross-linked polyethylene (XLPE) can greatly improve its creep resistance, corrosion resistance and environmental stress cracking resistance without losing the electrical properties of PE. Other mechanical properties such as tensile strength and low temperature performance also have certain The improvement of XLPE insulation, especially after cross-linking, can greatly improve its heat resistance, thereby increasing its maximum operating temperature and reducing the requirements for short-circuit and overload protection of lines, making XLPE insulation material the first choice for power cable insulation. [...

AI Technical Summary

Problems solved by technology

In this method, the cross-linking agent is added during the extrusion process. After the cross-linking agent is added, it will also be extruded and granulated by a single screw. Therefore, it is unavoidable that DCP will decompose during the single-screw extrusion process, resulting in pre-crosslinking. At the same time, due to the low temperature and high viscosity of the material during the whole process, it is difficult to ensure the uniform dispersion of the added antioxidant and crosslinking agent. Therefore, the XLPE insulating material produced by this method is mainly used for the insulation of medium and low voltage power cables. , mainly used in China for cable grades below 35KV

[0004] CN101456985A has introduced a kind of manufacturing method of ultra-clean cross-linkable polyethylene insulating material, adopt twin-screw extruder to granulate, then mix with DCP method to make XLPE insulating material, this invention does not have to filter in the link of twin-screw granulation Net requirements, only multi-layer stainless steel filter screen mentioned in the embodiment, can not guarantee that the obtained granular premix is ​​ultra-clean; and the invention mixes the prepared granular premix with peroxide efficiently When fully mixed in the container, a large amount of LDPE dust will be produced, and DCP will first enter the LDPE dust, which will affect the uniformity and quality of DCP in the XLPE granules; no measures are taken for the mixing of DCP and the packaging of XLPE insulating materials in this invention Ultra-purification treatment cannot guarantee the ultra-cleanness of the product

The homogenization and absorption link of this invention is to put the particles obtained in the filtration and purification process into the absorption kettle, and add a cross-linking agent in proportion to carry out homogenization and absorption. Obviously, this method cannot guarantee that the particles after filtration and purification are equal to the cross-linking agent. Therefore, the uniformity of the DCP content in each XLPE particle cannot be guaranteed, and the problem of uneven cross-linking occurs during the cable extrusion process; the various production links of the invention also did not adopt any ultra-cleaning treatment, and there is no guarantee product cleanliness

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