Two-step method for preparing peroxide crosslinked polyethylene pipe

Abstract

The invention provides a two-step method for preparing a peroxide crosslinked polyethylene pipe. The method adopts two steps of primary crosslinking and post crosslinking; during the process of primary crosslinking, polyethylene is melted, plasticized, molded and partially crosslinked; a machine head can be very short, so that the extrusion resistance is small; continuous extrusion can be carriedout by using a screw extruder; the bulk density of the pipe wall is uniform, so that the scorch phenomenon is avoided; an odorless peroxide crosslinking agent can be used, so that sanitary performanceof pipes is good; the time required by crosslinking is short and the extrusion speed is high; the primary crosslinking is matched with the post crosslinking to jointly construct a long cross-linked interval which enables the crosslinking to be more adequate.

Description

technical field [0001] The invention belongs to a method for manufacturing plastic products, in particular to a two-step method for manufacturing peroxide crosslinked polyethylene pipes. Background technique [0002] The creep resistance and heat resistance of cross-linked high-density polyethylene are significantly improved compared with uncross-linked high-density polyethylene. The pipes made of it are called cross-linked polyethylene (PEX) pipes and are widely used in In the hot and cold water system. There are three kinds of PEX pipes that have been commercialized, namely, PEXa pipe-peroxide cross-linked polyethylene pipe; PEXb pipe-silane cross-linked polyethylene pipe; PEXc pipe-irradiation cross-linked polyethylene pipe. [0003] The manufacture of synchronous cross-linked PEXa pipes is extruded by a plunger extruder. The cross-linking process is completed at the same time as the melting and plasticization of the material and the forming of the tube embryo, which can...

AI Technical Summary

Problems solved by technology

However, the energy consumption is extremely high, and the pipe wall is affected by the fusion line. During the extrusion process, not only must the material be melted and plasticized well, but also the crosslinking agent must not be decomposed prematurely (scorch), and the operation is difficult. Great, the choice of cross-linking agent According to the book of cross-linking agents, DYBP (2,5, methyl, 2,5, [tert-butyl, peroxy], alkyne-3) is the only one, and its odor is serious , The hygienic performance is poor, the pipe is cross-linked in hot air, the surface thermal oxidation is obvious, and the fire is inevitable;

[0005] Microwave post-crosslinking method is extruded by screw extruder, which can be extruded at high speed, but DYBP must also be used as crosslinking agent, which has serious odor, poor hygienic performance, and the phenomenon of "scorch" cannot be avoided. More conductive materials need to be added, and the performance of the material will drop significantly

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