CN107814996B

CN107814996B - Preparation method of crosslinkable polyethylene modified material

Info

Publication number: CN107814996B
Application number: CN201610825763.9A
Authority: CN
Inventors: 孙小杰; 陈学连; 李亚飞; 孙苗苗; 梁文斌; 赖世燿
Original assignee: China Energy Investment Corp Ltd; National Institute of Clean and Low Carbon Energy
Current assignee: Shenhua Beijing New Material Technology Co ltd
Priority date: 2016-09-14
Filing date: 2016-09-14
Publication date: 2020-12-01
Anticipated expiration: 2036-09-14
Also published as: CN107814996A

Abstract

The invention relates to the field of crosslinkable polyethylene preparation, and discloses a preparation method of a crosslinkable polyethylene modified material. The method comprises the following steps: (1) mixing a mixture containing polyethylene a, a cross-linking agent, a cross-linking auxiliary agent, an antioxidant, a lubricant and a cross-linking stabilizer to prepare a cross-linkable polyethylene master batch; based on the total amount of the crosslinkable polyethylene master batch, the total content of the crosslinking agent and the crosslinking assistant is 12-27 wt%; (2) respectively adding the crosslinkable polyethylene master batch, the polyethylene b and the toughening component into a double-screw extruder for melt blending to obtain a crosslinkable polyethylene modified material; and taking the total amount of the crosslinkable polyethylene modified material as a reference, wherein the total content of the crosslinking agent and the crosslinking assistant is 0.008-0.05 wt%. The crosslinking reaction does not occur in the preparation process, and the obtained crosslinkable polyethylene modified material does not contain any gel.

Description

Preparation method of crosslinkable polyethylene modified material

Technical Field

The invention relates to the field of crosslinkable polyethylene preparation, and in particular relates to a preparation method of a crosslinkable polyethylene modified material.

Background

The crosslinkable polyethylene modifier is a composition generally containing polyethylene, a crosslinking agent, an auxiliary agent, an antioxidant, a lubricant and the like, and can be further processed and produced to be applied to the fields of sheet extrusion, foaming, rotational molding and the like, so that the crosslinkable polyethylene modifier is receiving more and more attention. However, in the process of preparing the crosslinkable polyethylene modified material by mixing the composition, because the composition contains the crosslinking agent and the crosslinking assistant, under the action of heat, shear and pressure, the composition is easy to crosslink, so that the obtained modified material contains gel, and the subsequent processing and use are influenced. Therefore, in industrial production, how to ensure that the composition is uniformly mixed in the process of extruding and mixing into the crosslinkable polyethylene modified material, but the crosslinking effect does not occur in advance, and the obtained crosslinkable polyethylene modified material does not contain gel, does not influence subsequent processing operation, and is a subject which needs to be researched and solved urgently.

CN203919665U A screw combination for producing high-performance polypropylene filled composite material, comprising two screws with same structure which are meshed with each other, wherein the two screws rotate in the same direction, each screw comprises a spline shaft, a screw element fixedly sleeved on the spline shaft and a kneading element, the screw element comprises a plurality of forward screw blocks and a plurality of reverse screw blocks distributed along the length direction of the spline shaft, the meshing element comprises a plurality of forward kneading blocks and a plurality of reverse kneading blocks distributed along the length direction of the spline shaft, and is characterized in that the forward screw blocks comprise 56/56, 72/72, 96/96, 56/56A, 112/56SK, 112/112SK, the reverse screw blocks comprise 56/28L, and the forward kneading blocks comprise K60 DEG/5/56, K45 °/5/56, K60 °/4/56, K30 °/7/72, ZME16/32, the reverse kneading block comprising K45 °/5/36L, the screw elements on the spline shaft and the kneading elements being arranged in this order: 56/56A, 112/56SK, 112/112SK, 112/56SK, 96/96, 72/72, 56/56, K30 °/7/72, K45 °/5/56, K60 °/4/56, 56/56, 56/56, K90 °/5/56, K45 °/5/36L, 96/96, 96/96, 72/72, 56/56, 96/96, 96/96, 72/72, 56/56, 56/56, K45 °/5/56, K60 °/4/56, K90 °/5/56, 56/56, 56/56, ZME16/32, E16/32, 56/56, 56/56, K45 °/5/56, K45 °/5/56, K45 °/5/56, K45 °/5/36L, 56/56, 56/56, K45 °/5/56, K45 °/5/56, K90 °/5/56, 56/28L, 96/96, 96/96, 96/96, 72/72, 72/72, 56/56, 56/56, 56/56. The utility model discloses a have the special piece of kneading of ZME to other kneading piece matched with modes, improve the distribution and the dispersion effect of combined material in polypropylene for the end product can possess mechanical properties such as excellent tensile strength and bending strength when keeping good impact toughness, and can improve combined material's output, practiced thrift the energy. The invention mainly improves the dispersion through the saw-toothed meshing blocks, belongs to a strong shearing combination and is not suitable for processing and mixing the crosslinkable polyethylene modified material.

CN102529062B discloses a screw combination for extrusion processing of nylon without drying the nylon, which comprises an extruder and is characterized in that the extruder is provided with two screw (1) combinations with the same structure, the screw (1) comprises a spline shaft (2) with splines, a thread element (3) and a kneading element (4), inner holes of the thread element (3) and the kneading element (4) are provided with spline grooves (5) corresponding to the splines on the spline shaft (2), and a plurality of different forward and reverse thread elements (3) and a plurality of different forward and reverse kneading elements (4) are fixed; the two screw rods (1) have the same rotation direction, and the phase difference of the two screw rods (1) is 90 degrees; each screw is: (A) a solid conveying section, a melting section, a mixing section, a gas exhausting section and a homogenizing section. The invention provides a screw combination which saves the drying treatment before processing nylon (polyamide PA), saves energy and has low cost and is used for extrusion processing nylon without drying the nylon. But mainly aims at the combined design of materials easy to absorb water, and the screw combination enables the water in the nylon (polyamide PA) to be fully volatilized, so that the mechanical property of the nylon is kept stable. But are not suitable for processing and mixing of crosslinkable polyethylene modifiers.

CN105291402A discloses a screw combination for processing nano powder master batches, which comprises a double-screw extruder and a machine barrel arranged on the double-screw extruder; two parallel screws (6) are arranged in the machine barrel, and each screw (6) is provided with a plurality of screw parts with different specifications; the screw rods (6) are symmetrically arranged in the machine barrel and have the same rotation direction, one end of each screw rod (6) is connected with a screw rod bearing (7), and the screw rods (6) are driven to rotate by the screw rod bearings (7); the method is characterized in that: the screw (6) comprises a spline shaft (6-1) with a spline, a thread element (6-2) and a kneading element (6-3); the inner bores of the thread element (6-2) and the kneading element (6-3) are provided with spline grooves (6-4) corresponding to the splines on the spline shaft (6-1); the screw elements (6-2) with different forward directions and reverse directions and the kneading elements (6-3) with different forward directions and reverse directions are sequentially arranged on the spline shaft (6-1), the two ends of the spline shaft (6-1) fix the arranged screw elements (6-2) and the kneading elements (6-3), one end of the screw (6) is provided with a screw head (6-5) matched with the notch of the spline groove (6-4), and the other end of the screw (6) is fixedly connected through a screw bearing (7); the outer diameter of the screw head (6-5) is smaller than the outer diameter of the screw (6). But are not suitable for processing and mixing of crosslinkable polyethylene modifiers.

CN104448461A discloses a preparation method of crosslinkable polyethylene, which comprises (a) adding an antioxidant into a screw extruder in a gravity metering feeding mode under a purification condition, plasticizing and filtering after contacting with low-density polyethylene, and granulating in an underwater granulation mode to obtain clean polyethylene particles; (b) conveying the clean polyethylene particles to a height which can enable the polyethylene particles to be fed in the subsequent steps under the action of self weight by adopting a water particle conveying mode, and then dehydrating and drying the polyethylene particles; (c) preheating the dehydrated and dried polyethylene clean particles under the action of self weight; (d) under the purification condition, a cross-linking agent and the preheated polyethylene clean particles are mixed and infiltrated by adopting a gravity metering feeding mode.

Disclosure of Invention

The invention aims to overcome the defect that the crosslinkable polyethylene material obtained by premature initiation of a crosslinking reaction contains a crosslinking structure when the crosslinkable polyethylene material is prepared in the prior art, and provides a preparation method of a crosslinkable polyethylene modified material.

In order to achieve the above object, the present invention provides a method for preparing a crosslinkable polyethylene modifier, comprising: (1) mixing a mixture containing polyethylene a, a cross-linking agent, a cross-linking auxiliary agent, an antioxidant, a lubricant and a cross-linking stabilizer to prepare a cross-linkable polyethylene master batch; based on the total amount of the crosslinkable polyethylene master batch, the total content of the crosslinking agent and the crosslinking assistant is 12-27 wt%; (2) respectively adding the crosslinkable polyethylene master batch, the polyethylene b and the toughening component into a double-screw extruder for melt blending to obtain a crosslinkable polyethylene modified material; and taking the total amount of the crosslinkable polyethylene modified material as a reference, wherein the total content of the crosslinking agent and the crosslinking assistant is 0.8-3 wt%.

Through the technical scheme, the crosslinkable polyethylene master batch containing the crosslinking agent, various auxiliaries and the like is prepared by step-by-step preparation, wherein the crosslinking agent and the crosslinking auxiliaries are high in content; then the crosslinkable polyethylene master batch, a large amount of polyethylene and toughening components are extruded to be melt blended, the content of the crosslinking agent and the crosslinking auxiliary agent is reduced, the uniform dispersion of various auxiliary agents can be facilitated, and the melt blending process is carried out under the condition of no crosslinking reaction, so that the crosslinking structure in the obtained crosslinkable polyethylene modified material is effectively overcome.

Further, in a twin-screw extruder for extrusion melt blending, the screws used have a specific screw combination, especially in the melting section part of the screws, the arrangement and combination mode of the thread elements and the kneading elements is specially set, so that the friction heat of the crosslinkable polyethylene master batch, the polyethylene b and the toughening component in the extrusion process is small, and the obtained crosslinkable polyethylene modified material does not contain any gel.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is a schematic view of the overall structure of a screw;

FIG. 2 is a schematic view of a threaded element;

FIG. 3 is a schematic view of the structure of the kneading elements.

Description of the reference numerals

1. Screw 2, splined shaft 3, threaded element 4, kneading element

5. Spline groove A, solid conveying section B, melting section C and mixing section

D. Exhaust section E, homogenization section

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The invention provides a preparation method of a crosslinkable polyethylene modified material, which comprises the following steps: (1) mixing a mixture containing polyethylene a, a cross-linking agent, a cross-linking auxiliary agent, an antioxidant, a lubricant and a cross-linking stabilizer to prepare a cross-linkable polyethylene master batch; based on the total amount of the crosslinkable polyethylene master batch, the total content of the crosslinking agent and the crosslinking assistant is 12-27 wt%; (2) respectively adding the crosslinkable polyethylene master batch, the polyethylene b and the toughening component into a double-screw extruder for melt blending to obtain a crosslinkable polyethylene modified material; and taking the total amount of the crosslinkable polyethylene modified material as a reference, wherein the total content of the crosslinking agent and the crosslinking assistant is 0.8-3 wt%.

In the preparation method provided by the invention, the step (1) is used for obtaining the crosslinkable polyethylene master batch containing various additives such as a crosslinking agent and the like, and the content concentration of the various additives in the crosslinkable polyethylene master batch is higher. The mixing temperature for preparing the crosslinkable polyethylene master batch is lower than the temperature for the crosslinking reaction of the crosslinking agent and the crosslinking assistant, but the polyethylene a can be molten. Preferably, in the step (1), the polyethylene a, the crosslinking agent, the crosslinking assistant, the antioxidant, the lubricant and the crosslinking stabilizer are fully mixed in a high-speed mixer until the mixture is uniform, for example, for 3-5 min; and then mixing the mixture by a double-screw extruder, and extruding and granulating to obtain the crosslinkable polyethylene master batch. The temperature of each temperature section of the twin-screw extruder is preferably set to 130 to 145 ℃, and the rotation speed of the screw is preferably set to 60 to 350 rpm. A conventional twin-screw extruder can be used, for example, the diameter of the screw is 36 to 96mm, and the length-diameter ratio (the ratio of the length to the diameter of the screw) is (36 to 48): 1. in the process of mixing in the extrusion granulation process, the temperature of the twin-screw extruder is not suddenly increased or the current of the extruder is not suddenly increased, which can indicate that no crosslinking reaction occurs in the extrusion granulation process.

According to the present invention, in step (1), the polyethylene a is preferably selected from high density polyethylene and/or low density polyethylene.

Preferably, the density of the high-density polyethylene is 0.94-0.965 g/cm³And a Melt Index (MI) of 1 to 20g/10min at 190 ℃ under a load of 2.16 kg. The high-density polyethylene is polyethyleneAs a known substance, 8007(HDPE, melt index of 8.2g/10min, density of 0.963 g/cm) from Shenhuabaotian coal-to-liquids Co., Ltd is commercially available³)。

Preferably, the density of the low-density polyethylene is 0.91-0.935 g/cm³And a melt index at 190 ℃ under a load of 2.16kg of 1 to 20g/10 min. The low density polyethylene is a known substance and can be purchased from 2426H (LDPE, melt index 2.1g/10min, density 0.924 g/cm) of Shenhua Baotou coal-to-liquids GmbH³)。

According to the invention, the components are fed in step (1) to obtain a crosslinkable polyethylene masterbatch with a high concentration of the sum of the crosslinking agent and the crosslinking assistant. Preferably, in the step (1), relative to 100 parts by weight of the polyethylene a, 20 to 25 parts by weight of the crosslinking agent, 5 to 10 parts by weight of the crosslinking assistant, 2 to 15 parts by weight of the antioxidant, 5 to 15 parts by weight of the lubricant, and 1 to 5 parts by weight of the crosslinking stabilizer are used.

In the present invention, the crosslinking agent may be at least one selected from dicumyl peroxide, benzoyl peroxide, dicumyl hydroperoxide, t-butyl hydroperoxide, 2, 5-dimethyl-2, 5-di-t-butyl hexane peroxide, 2, 5-dimethyl-2, 5-di-t-butyl peroxy-3-yne, diacyl peroxide, di-t-butyl peroxide, alkyl hydroperoxide, dilauroyl peroxide, methyl ethyl ketone peroxide, and cyclohexanone peroxide.

In the present invention, the crosslinking assistant may be at least one selected from the group consisting of poly-1, 2-butadiene, diallyl terephthalate (DATP), Divinylbenzene (DVB), triallyl cyanurate (TAC), triallyl cyanurate (TAP), and triallyl isocyanate (TAIC). Wherein the weight average molecular weight of the poly-1, 2-butadiene is 0.7-9 ten thousand.

In the present invention, the antioxidant may be a conventional one, and is preferably the antioxidant 1010 and/or the antioxidant 168. The antioxidant is a known substance and can be obtained commercially by national pharmaceutical group chemical reagents limited.

In the present invention, the lubricant may be of conventional choice, preferably a polyethylene wax, such as is commercially available from honeywell corporation.

In the present invention, the crosslinking stabilizer is a radical inhibitor, preferably a polymerization inhibitor of a phenol, quinone or aromatic nitro compound, more preferably at least one selected from tris (2,2,6, 6-tetramethylpiperidinyloxy) phosphite, 2-bis (4-tert-octylphenyl) -1-picrylhydrazine and nitroxyl radical piperidinol.

In the preparation method provided by the invention, the step (2) is used for diluting the crosslinkable polyethylene master batch, so that the concentration of various auxiliary agents contained in the crosslinkable polyethylene master batch, especially the concentration of the crosslinking agent and the crosslinking auxiliary agent can meet the composition requirement of the obtained crosslinkable polyethylene modified material, and the crosslinkable polyethylene modified material can be suitable for further processing.

In the step (2) of the invention, the crosslinkable polyethylene master batch, the polyethylene b and the toughening component are preferably added into the double-screw extruder at the same time from different feed inlets. And feeding the crosslinkable polyethylene master batch, the polyethylene b and the toughening component according to a certain proportion, preferably, in the step (2), the polyethylene b accounts for 500-1000 parts by weight and the toughening component accounts for 35-400 parts by weight relative to 100 parts by weight of the crosslinkable polyethylene master batch. I.e. it may be the polyethylene b: the toughening component: the weight ratio of the crosslinkable polyethylene master batch is (5-10): (0.35-4): 1.

according to the invention, step (2) can be used to dilute the concentration of various additives, especially the cross-linking agent and the cross-linking additive, in the crosslinkable polyethylene masterbatch, and the polyethylene b can be selected from the same polyethylene as the polyethylene a, or the polyethylene b and the polyethylene a can be selected from different polyethylenes according to the requirement. Preferably, the polyethylene b is selected from high density polyethylene and/or low density polyethylene; preferably, the density of the high-density polyethylene is 0.94-0.965 g/cm³A melt index at 190 ℃ under a load of 2.16kg of 1 to 20g/10 min; the density of the low-density polyethylene is 0.91-0.935 g/cm³And a melt index at 190 ℃ under a load of 2.16kg of 1 to 20g/10 min. The high density polyethylene is a known substance, and can be purchased from 8007(HDPE, melt index of 8.2g/10min, density of 0.963 g/cm) of Shenhuabaotiao coal-to-liquids Co., Ltd³). The known low-density polyethylene can be obtained as 2426H (LDPE, melt index 2.1g/10min, density 0.924 g/cm) of Shenhua Baotou coal-to-liquids GmbH³)。

According to the invention, the toughening component can play a role in improving the toughness of the material, and preferably, the toughening component is selected from at least one of linear low-density polyethylene, ethylene-octene copolymer and ethylene propylene diene monomer.

Preferably, the linear low density polyethylene has a density of 0.91 to 0.935g/cm³And a melt index at 190 ℃ under a load of 2.16kg of 1 to 20g/10 min. The linear low density polyethylene is known and can be purchased from 7042(LLDPE, melt index 2g/10min, density 0.92 g/cm) of Shenhua Baotou coal-to-liquids Co., Ltd³) 8320 from Daqing petrochemical company (LLDPE, melt index 20g/10min, density 0.926 g/cm)³)。

Preferably, in the ethylene-octene copolymer, the content of an octenyl structure may be 20 to 30 wt%, the number average molecular weight of the ethylene-octene copolymer (POE) may be 7000 to 20000, the melt index may be 2 to 7g/10min, and the density may be 0.75 to 0.95g/cm³. The ethylene-octene copolymer is known and is commercially available as POE8200 from the Dow chemical company.

Preferably, the ethylene-propylene-diene monomer rubber is a terpolymer of ethylene, propylene and a non-conjugated diene, wherein the non-conjugated diene may be Ethylidene Norbornene (ENB) or dicyclopentadiene (DCPD). The ethylene propylene diene monomer has an ethylene propylene ratio of 80: 20 to 50: 50, the ENB content is 0.5-10 wt%. The Mooney viscosity (125 ℃) of the ethylene propylene diene monomer is 20-100. The ethylene propylene diene monomer is a known substance and is commercially available from the Dow chemical company.

In the preparation method provided by the invention, further, a specially set screw combination is preferably selected for the double-screw extruder used in the step (2), so that the cross-linkable polyethylene master batch, the polyethylene b and the toughening component are subjected to stable and uniform screw meshing shearing action and generate less friction heat in the process of melt blending in the double-screw extruder, and thus, the uniform melt blending of materials can be completed without causing the cross-linking agent and the cross-linking auxiliary agent to generate a cross-linking reaction.

According to the present invention, preferably, in the step (2), as shown in fig. 1, the screw combination in the twin-screw extruder comprises two screws 1 with the same structure and meshed with each other; the screw 1 comprises a spline shaft 2, a thread element 3 and a kneading element 4; a plurality of different forward and reverse-rotation screw elements 3 and a plurality of different forward and reverse-rotation kneading elements 4 are sleeved on the spline shaft 2 through spline grooves 5 formed in respective inner bores.

According to the invention, the threaded element 3 has an internal bore with a splined groove 5, as shown in fig. 2. Preferably, the lead of the screw element 3 is 44 to 96mm, and the length of the screw element 3 is 44 to 96 mm. In the invention, X/Y can be used for representing that the thread element is a positive thread element, X/YL can be used for representing that the thread element is a reverse thread element, and X/YA can be used for representing a starting thread element; where X represents the lead of the threaded element and Y represents the length of the threaded element.

According to the invention, as shown in fig. 3, the kneading elements 4 have an inner bore with splined grooves 5, and the kneading elements 4 can be composed of a plurality of kneading blocks. The kneading blocks are arranged in a staggered way. The external shape of the cross section of the vertical inner hole of the kneading block is approximately oval. Preferably, the offset angle of the kneading elements 4 is 30 to 60 °, the length of the kneading elements 4 is 44 to 56mm, and the number of kneading blocks of the kneading elements 4 is 4 to 6. In the present invention, the forward kneading elements may be represented by θ/n/m, and the reverse kneading elements may be represented by θ/n/mL; where θ represents the dislocation angle of the kneading elements, n represents the number of kneading blocks, and m represents the length of the entire kneading elements.

According to the present invention, each screw 1 preferably comprises a solid conveying section a, a melting section B, a kneading section C, a degassing section D and a homogenizing section E, which are divided in this order from the driving end toward the tip end of the screw 1.

In the present invention, the solid conveying section a is used for conveying materials (such as crosslinkable polyethylene master batch, polyethylene b and toughening component) from a feeding port and preventing flash. In the solid conveying section, a larger material containing space is required to be arranged in the solid conveying section so as to adapt to the adjustment of the feeding amount and prevent the materials from accumulating at the feeding port to generate flash. Besides the conveying function, the solid conveying section can also compact loose powdery materials or improve the fullness of granular materials in the screw so as to promote the melting and plasticizing of the materials in the next section. Therefore, the volume of the groove of the screw element 3 at this stage changes from large to small along the driving end of the screw 1 to the end, and the lead of the thread of the screw element 3 gradually changes from large to small. Preferably, the solid conveying section of the present invention employs medium thread grooves, large lead, positive thread. For example, in a preferred embodiment, the arrangement of the plurality of screw elements 3 constituting the solid conveying section is 56/56a, 96/96, 96/96, 72/72, 72/72, 56/56, 44/44 in order from the driving end to the end of the screw 1.

In the invention, the melting section B is used for fully melting and homogenizing materials through heat transfer and friction shearing. In this section, the material begins to melt and mix after being subjected to a certain compression through the solid conveying section a. The heat source for melting the material comes from two sources, namely external heating provided by barrel heating and shearing heat of a screw. The shear heat of the screw is generated by virtue of the high shear action produced by the elements of the segment. Preferably, the melting section B contains at least two sets of intermeshing sections, each intermeshing section containing at least 2 kneading elements 4; at least one screw element 3 is contained between the meshing sections; the melting section contains at least one counter-rotating threaded element 3. The plastic granulate can be melt-plasticized by means of the high shear of the kneading elements 4 and the back-flow compression of the counter-rotating screw elements 3.

According to the invention, the melting section preferably comprises at least two sets of intermeshing sections, each set of intermeshing sections comprising at least 1 kneading element 4; at least one screw element 3 is contained between the meshing sections; the melt section contains at least one reverse flight element or one reverse kneading element.

Preferably, when the melt section contains engaging sections containing reverse kneading elements, the number of immediately adjacent forward kneading elements does not exceed 1, which can provide a more suitable blending effect and prevent the occurrence of crosslinking.

Preferably, when the melt zone contains an intermeshing zone not containing a reverse kneading element, the number of the forward kneading elements is not less than 2, which can provide a more suitable blending effect and prevent the occurrence of crosslinking.

In the present invention, a preferable embodiment constituting the melting section may be such that the arrangement of the plurality of screw elements 3 and kneading elements 4 constituting the melting section is 45 °/5/56, 45 °/5/56, 45 °/56/56, 44/44, 45 °/5/56, 60 °/4/56, 56/56, 44/44, 60 °/4/44, 45 °/5/56L in order from the solid conveying section a toward the end of the screw 1.

In the invention, the mixing section C has the mixing function of distributivity and dispersibility, so that the molten material is further refined and uniform. The material is in a molten state after passing through the melting section, the mixing of the components in the material starts from melting, the sizes of various polymers are further and rapidly changed in the melting process, and the sizes of the various polymers are from macro particles of a primary millimeter level to micron levels at the end of melting. Because the particles in the material from the melting section are basically melted and plasticized, the particles enter the mixing section and are mainly dispersed. The kneading elements 4 and the screw elements 3 are arranged alternately in the mixing section to form a moderate shear kneading zone to avoid the phenomenon of shear overheating. For example, in a preferred embodiment, the plurality of screw elements 3 and kneading elements 4 constituting the kneading section C are arranged in the order of 56/56, 44/44, 44/44, 44/44, 45 °/5/44, 45 °/5/44, 45 °/5/44, 56/56, 56/56, 44/44, 44/44, 45 °/5/44, 45 °/5/56, 56/56 from the melting section B toward the end of the screw 1.

In the present invention, the exhaust section D is used to exhaust impurities such as moisture and low molecular weight substances. In the exhaust section, the flow characteristic of the material is that the material in a completely molten state is compressed and then suddenly decompressed, and the volatile material is quickly volatilized under the vacuum condition to be separated from the melt. Preferably, the venting section may employ a medium lead screw element 3 to form a low fill and thin melt zone with an exposed free surface of material to facilitate gas venting. For example, in a preferred embodiment, the arrangement of the plurality of screw elements 3 constituting the degassing section D is 56/56, 44/44, 44/44 in the order from the kneading section C toward the end of the screw 1.

In the invention, the homogenizing section E is used for conveying and pressurizing to establish certain pressure, so that the material at the die orifice arranged at the outlet of the double-screw extruder has certain density, and the material is convenient to discharge. And meanwhile, the homogenizing section E further mixes the materials, and finally the aim of smoothly extruding and granulating is fulfilled. Preferably, the homogenization section can be pressurized by a lead progression or a groove progression of the threaded element 3. For example, in a preferred embodiment, the arrangement of the plurality of screw elements 3 and kneading elements 4 constituting the homogenizing section E is 45 °/5/44, 60 °/4/44, 64/64, 64/64, 44/44, 44/44 in the order from the exhaust section D toward the end of the screw 1.

According to the invention, the two screws 1 are preferably turned in the same direction; when the two screws 1 rotate, the phase difference is 90 degrees.

According to the invention, the diameter of the screw 1 is preferably 36-96 mm, and the length-diameter ratio is (36-48): 1. in a preferred embodiment, the screw 1 has a diameter of 65mm and a length to diameter ratio of 36: 1.

in the present invention, two screws 1 are placed in the barrel of a twin-screw extruder. A heating zone is coated outside the cylinder. From the driving end to the end of the screw 1, the heating zones are arranged equidistantly from the first heating zone to the ninth heating zone, as shown in fig. 1.

In the invention, the melt blending in the step (2) is realized, and the temperature of the heating zone of the double-screw extruder can be set to be 140-145 ℃. In one preferred embodiment, the temperatures of the heating zones from the first heating zone to the ninth heating zone are set to 140 ℃, 145 ℃ and 145 ℃. The rotation speed of the screw 1 may be 100 to 300rpm, and preferably 200rpm in one embodiment.

In the present invention, the melt blending in step (2) is performed, and the melt temperature of the extrudate is higher than the set temperature of the heating zone, but the method of using the crosslinkable polyethylene masterbatch provided by the present invention can still ensure that no crosslinked structure is formed in the finally obtained crosslinkable polyethylene modifier.

The preparation method provided by the invention can also comprise the step of granulating the molten melt extruded by the twin-screw extruder in the step (2) by an underwater granulator, and then drying the molten melt for 2-4 hours at 80-100 ℃ to obtain the crosslinkable polyethylene modified material.

In the present invention, when the melt blending of step (2) is performed, the morphology of the extrudate extruded from the extruder and the gel content of the final crosslinkable polyethylene modifier can be observed to evaluate the effect of the method of the present invention. The gel content of the crosslinkable polyethylene modified material can be measured by a method for measuring the content of xylene insoluble substances, and whether a crosslinked structure is formed in the crosslinkable polyethylene modified material is judged. Preferably, the crosslinkable polyethylene modifier has a gel content of 0% by weight.

In the invention, when the melt blending in the step (2) is carried out, the current of the extruder can reflect the magnitude of the screw torque in the extrusion process and whether the extrusion is difficult or not, and is in direct proportion to the viscosity of the extrudate. When the current of the extruder is large, the fact that the viscosity of an extrudate is large and the screw torque of the extruder is large can be reflected, which shows that materials in the extruder need to consume more energy for extrusion, and the materials are more difficult to process compared with the materials with small current of the extruder under the same condition.

The present invention will be described in detail below by way of examples.

In the following examples, the gel content of the crosslinkable polyethylene modifier was determined by measuring the xylene insoluble content;

the materials in the following examples and comparative examples,

HDPE (DMDA8007, melt index 8.3g/10min, density 0.963 g/cm)³) Shenhua Baotou coal oil Co., Ltd;

LLDPE (DMDA7042, melt index 2g/10min, density 0.92 g/cm)³) Shenhua Baotou coal oil Co., Ltd;

LLDPE (8320, melt index of 20g/10min, density of 0.926 g/cm)³) Daqing petrochemical company;

POE (8200, melt index of 5g/10min, density of 0.87 g/cm)³) Dow chemical company;

the cross-linking agent is di-tert-butyl peroxide, J & K Scientific;

the crosslinking coagent was triallyl isocyanurate (TAIC) (technical grade), J & K Scientific;

the crosslinking stabilizer is tris (2,2,6, 6-tetramethylpiperidine nitroxide free radical) phosphite, J & K Scientific;

antioxidant 1010, antioxidant 168: chemical agents of the national drug group, ltd;

polyethylene wax (A-C316A), HoNiverl.

Example 1

(1) 50kg of high-density polyethylene powder (DMDA8007), 11.25kg of di-tert-butyl peroxide, 3.75kg of triallyl isocyanurate, 3kg of antioxidant 1010, 3kg of antioxidant 168, 2kg of polyethylene wax (A-C316A), 2.5kg of tris (2,2,6, 6-tetramethylpiperidine nitroxide free radical) phosphite are mixed in a high-speed mixer for 5 minutes, and the mixture is added into an extruder to be extruded at 145 ℃ to prepare the crosslinkable polyethylene master batch.

(2) 500kg of high-density polyethylene, 200kg of linear low-density polyethylene (DMDA7042) and 50kg of crosslinkable polyethylene master batch are put into three different weightless scales, the high-density polyethylene, the linear low-density polyethylene and the crosslinkable polyethylene master batch are fed into a 65-type (screw diameter 65mm) homodromous parallel twin-screw extruder (TSE 65, Nanjing Ruiya extrusion machinery equipment Co., Ltd.) according to the mass ratio of 10:4:1 to be extruded to prepare the crosslinkable polyethylene modified material, the temperatures of 9 sections of heating zones of the extruder are respectively 140 ℃, 140 ℃, 145 ℃, 145 ℃, 145 ℃, 145 ℃, 145 ℃, and 200rpm, the melt flowing out of the twin-screw extruder is cut into granules by an underwater granulator and is sucked into a drying bin for drying for 2 hours at 80 ℃, and the crosslinkable polyethylene modified material is obtained.

The screw combination used by the twin-screw extruder in the step (2) sequentially comprises the following steps from the screw transmission end to the tail end:

(solid conveying section a)56/56a, 96/96, 96/96, 72/72, 72/72, 56/56, 44/44; (melting section B)45 °/5/56, 45 °/5/56, 45 °/5/56, 44/44, 45 °/5/56, 60 °/4/56, 56/56, 44/44, 60 °/4/44, 45 °/5/56L; (mixing section C)56/56, 44/44, 44/44, 44/44, 45 °/5/44, 45 °/5/44, 45 °/5/44, 56/56, 56/56, 44/44, 44/44, 45 °/5/44, 45 °/5/56, 56/56; (exhaust stage D)56/56, 44/44, 44/44; (homogenizing section E)45 °/5/44, 60 °/4/44, 64/64, 64/64, 44/44, 44/44.

The melt temperature exiting the extruder, the extruder current, the extrudate state, and the gel content of the resulting crosslinkable polyethylene modifier are shown in table 1.

Comparative example 1

Adding 11.25kg of di-tert-butyl peroxide, 3.75kg of triallyl isocyanurate, 3kg of antioxidant 1010, 3kg of antioxidant 168, 2kg of polyethylene wax (A-C316A) and 2.5kg of tris (2,2,6, 6-tetramethylpiperidine nitroxide free radical) phosphite into a high-speed mixer, mixing for 5min to serve as an auxiliary composition, and adding into a weight loss scale-1;

550kg of high-density polyethylene is conveyed to a weight loss scale-2 in an empty way, and 200kg of linear low-density polyethylene (DMDA7042) is conveyed to a weight loss scale-3 in an empty way;

mixing the assistant composition, the high-density polyethylene and the linear low-density polyethylene according to the weight ratio of 0.51: 11: 4, feeding the mixture into a 65-type co-rotating parallel double-screw extruder for extrusion to prepare crosslinkable polyethylene master batches, wherein the temperatures of 9 sections of heating zones of the extruder are respectively 140 ℃, 140 ℃, 145 ℃, 145 ℃, 145 ℃, 145 ℃, 145 ℃, 200rpm, the melt flowing out of the double-screw extruder is granulated by an underwater granulator, and is sucked into a drying bin for drying for 2 hours at 80 ℃ to obtain the crosslinkable polyethylene modified material.

Comparative example 2

(solid conveying section a)56/56a, 96/96, 96/96, 72/72, 72/72, 56/56, 44/44; (melting section B)56/56, 60 °/5/56, 56/56, 44/44, 45 °/5/56, 60 °/4/56, 56/56, 44/44, 60 °/4/44, 45 °/5/56L; (mixing section C)56/56, 44/44, 44/44, 44/44, 44/44, 45 °/5/44, 45 °/5/44, 56/56, 56/56, 44/44, 44/44, 45 °/5/44, 45 °/5/56, 56/56; (exhaust stage D)56/56, 44/44, 44/44; (homogenizing section E)45 °/5/44, 60 °/4/44, 64/64, 64/64, 44/44, 44/44.

Example 2

(1) 50kg of high-density polyethylene (DMDA8007) powder, 10kg of di-tert-butyl peroxide, 5kg of triallyl isocyanurate, 2kg of antioxidant 1010, 2kg of antioxidant 168, 4.5kg of polyethylene wax (A-C316A) and 2kg of tris (2,2,6, 6-tetramethylpiperidine nitroxide free radical) phosphite are put into a high-speed mixer to be mixed for 5min, and the mixture is added into an extruder to be extruded at 140 ℃ to prepare the crosslinkable polyethylene master batch.

(2) Putting 500kg of high-density polyethylene, 100kg of linear low-density polyethylene (8320) and 50kg of crosslinkable polyethylene master batch into three different weightless scales, blanking the high-density polyethylene, the linear low-density polyethylene and the crosslinkable polyethylene master batch into a 65-type co-rotating parallel double-screw extruder according to the mass ratio of 10:2:1, and extruding to prepare a crosslinkable polyethylene modified material, wherein the temperatures of 9 sections of heating zones of the extruder are respectively 140 ℃, 140 ℃, 145 ℃, 145 ℃, 145 ℃, 145 ℃, 145 ℃, 145 ℃, 200rpm, the melt flowing out of the double-screw extruder is granulated by an underwater granulator, and is sucked into a drying bin for drying at 80 ℃ for 2 hours, so as to obtain the crosslinkable polyethylene modified material.

(solid conveying section a)56/56a, 96/96, 96/96, 72/72, 72/72, 56/56, 44/44; (melting section B)45 °/5/56, 45 °/5/56, 56/56, 44/44, 45 °/5/56, 60 °/4/56, 56/56, 44/44, 60 °/4/44, 45 °/5/56L; (mixing section C)56/56, 44/44, 44/44, 44/44, 44/44, 45 °/5/44, 45 °/5/44, 56/56; (exhaust section D)56/56, 44/44, 44/44, 45 °/5/44, 45 °/5/56, 56/56, 56/56, 44/44, 44/44; (homogenizing section E)45 °/5/44, 60 °/4/44, 64/64, 64/64, 44/44, 44/44.

Comparative example 3

Firstly, adding 10kg of di-tert-butyl peroxide, 5kg of triallyl isocyanurate, 2kg of antioxidant 1010, 2kg of antioxidant 168, 4.5kg of polyethylene wax (A-C316A) and 2kg of tris (2,2,6, 6-tetramethylpiperidinyloxy free radical) phosphite into a high-speed mixer, mixing for 5min to serve as an auxiliary composition, and then adding into a weight loss scale-1;

550kg of high-density polyethylene is conveyed to a weight loss scale-2 in an empty state, and 100kg of linear low-density polyethylene (8320) is conveyed to a weight loss scale-3 in an empty state;

mixing the assistant composition, the high-density polyethylene and the linear low-density polyethylene according to the weight ratio of 0.51: 11: feeding the materials in a mass ratio of 2 into a 65-type co-rotating parallel double-screw extruder, extruding to prepare the crosslinkable polyethylene master batch, wherein the temperatures of 9 sections of heating zones of the extruder are respectively 140 ℃, 140 ℃, 145 ℃, 145 ℃, 145 ℃, 145 ℃, 145 ℃, and 200rpm, the melt flowing out of the double-screw extruder is granulated by an underwater granulator, and is sucked into a drying bin at 80 ℃ to be dried for 2 hours, so as to obtain the crosslinkable polyethylene modified material.

(solid conveying section a)56/56a, 96/96, 96/96, 72/72, 72/72, 56/56, 44/44; (melting section B)45 °/5/56, 45 °/5/56, 45 °/5/56, 44/44, 45 °/5/56, 60 °/4/56, 56/56, 60 °/4/44, 60 °/4/44, 45 °/5/56L; (mixing section C)56/56, 44/44, 44/44, 44/44, 45 °/5/44, 45 °/5/44, 45 °/5/44, 56/56, 56/56, 44/44, 44/44, 45 °/5/44, 45 °/5/56, 56/56; (exhaust stage D)56/56, 44/44, 44/44; (homogenizing section E)45 °/5/44, 60 °/4/44, 64/64, 64/64, 44/44, 44/44.

Example 3

(1) 50kg of high-density polyethylene powder (DMDA8007), 11.25kg of di-tert-butyl peroxide, 3.75kg of triallyl isocyanurate, 3kg of antioxidant 1010, 3kg of antioxidant 168, 2.5kg of polyethylene wax (A-C316A), 2kg of tris (2,2,6, 6-tetramethylpiperidine nitroxide free radical) phosphite are mixed in a high-speed mixer for 5min, and the mixture is added into an extruder to be extruded at 135 ℃ to prepare the crosslinkable polyethylene master batch.

(2) 300kg of high-density polyethylene, 17.5kg of ethylene-octene copolymer (POE8200) and 50kg of crosslinkable polyethylene master batch are put into three different weight loss scales, the high-density polyethylene, the ethylene-octene copolymer and the crosslinkable polyethylene master batch are fed into a 65-type co-rotating parallel double-screw extruder according to the mass ratio of 6:0.35:1 for extrusion to prepare the crosslinkable polyethylene modified material, the temperature of 9 sections of heating zones of the extruder is respectively 140 ℃, 140 ℃, 145 ℃, 145 ℃, 145 ℃, 145 ℃, 145 ℃, 145 ℃, 200rpm, the melt flowing out of the double-screw extruder is cut into granules by an underwater granulator, and the granules are sucked into a drying bin for drying for 2 hours at 80 ℃ to obtain the crosslinkable polyethylene modified material.

Comparative example 4

Adding 11.25kg of di-tert-butyl peroxide, 3.75kg of triallyl isocyanurate, 3kg of antioxidant 1010, 3kg of antioxidant 168, 2.5kg of polyethylene wax (A-C316A) and 2kg of tris (2,2,6, 6-tetramethylpiperidine nitroxide free radical) phosphite into a high-speed mixer, mixing for 5min to serve as an auxiliary composition, and adding into a weight loss scale 1;

350kg of high-density polyethylene is empty and sent to a weight loss scale 2, and 17.5kg of ethylene-octene copolymer (POE8200) is added to a weight loss scale 3;

feeding the auxiliary agent composition, high-density polyethylene and ethylene-octene copolymer into a 65-type co-rotating parallel double-screw extruder according to the mass ratio of 0.51:7:0.35, extruding to prepare crosslinkable polyethylene master batches, wherein the temperatures of 9 sections of heating zones of the extruder are respectively 140 ℃, 140 ℃, 145 ℃, 145 ℃, 145 ℃, 145 ℃, 145 ℃, 145 ℃, 145 ℃, 200rpm, and the rotating speed of the extruder is 200rpm, granulating a melt flowing out of the double-screw extruder by an underwater granulator, and sucking the melt into a drying bin at 80 ℃ for drying for 2 hours to obtain the crosslinkable polyethylene modified material.

Comparative example 5

(solid conveying section a)56/56a, 96/96, 96/96, 72/72, 72/72, 56/56, 44/44; (melting section B)45 °/5/56, 45 °/5/56, 45 °/5/56, 44/44, 45 °/5/56, 60 °/4/56, 56/56, 60 °/4/44, 60 °/4/44, 45 °/5/56L; (mixing section C)56/56, 44/44, 44/44, 44/44, 45 ℃/5/44, 45 °/5/44, 45 °/5/44, 56/56, 56/56, 44/44, 44/44, 45 °/5/44, 45 °/5/56, 56/56; (exhaust stage D)56/56, 44/44, 44/44; (homogenizing section E)45 °/5/44, 60 °/4/44, 64/64, 64/64, 44/44, 44/44.

TABLE 1

Table 1 shows the melt temperature, extruder current, extrusion morphology of the extrudate and gel content of the resulting crosslinkable polyethylene modifier when the crosslinkable polyethylene masterbatch, polyethylene and toughening component were extruded in a twin screw extruder equipped with screws of different shear thread combinations.

As can be seen from the results in Table 1, examples 1-3 can ensure that the extrudate is completely molten, i.e., the crosslinkable polyethylene modifier can be well molten and uniformly mixed. Under this premise, the melt temperature of the extrudates in examples 1-3 were all lower than the comparative example, and the gel content of the extrudate was 0 wt%, indicating that no crosslinking occurred during extrusion. Further observation of the extruder current values shows that the extrudate has a low viscosity and is not difficult to process when good melting as described above is achieved in the examples.

In contrast, in comparative examples 1-4, the extrudate morphology did not melt, or even cross-link, and did not provide good melting of the cross-linkable polyethylene modifier, and the mixing effect was poor.

Comparative example 1 corresponds to example 1, but the various materials were fed by direct feeding extrusion of polyethylene, crosslinking agent, crosslinking aid, antioxidant, lubricant, crosslinking stabilizer, etc. Table 1 shows that no fully melted extrudate was obtained. The feeding method of comparative example 1 allows materials of different physical states to be melt blended in an extruder without being previously prepared in the form of master batches. Because the auxiliary agent is in a liquid state and the material is solid powder or particles, the material mixing is not uniform, the shearing is weakened in the extrusion process, and the melting state is poor. There is also a loss of material.

Comparative example 2 corresponds to example 1 in which, although master batches were prepared first, only one forward kneading element (60 °/5/56) was contained in the screw combination different from example 1 (containing three kneading elements) except for the meshing zone at the beginning of the melting zone in the screw combination used without reverse kneading elements, and therefore the screw combination of the melting zone was different, and as a result, the melt blending effect achieved was weakened and complete melting of the material could not be achieved.

The amount of each material fed in comparative example 3 corresponds to example 2, but the method of feeding each material was direct feeding, and the screw combination used in comparative example 3, which is different from that of example 2, was a strong shear combination (60 °/4/44, 60 °/4/44, 45 °/5/56L), which caused the melt temperature to rise and crosslinking to occur.

The feed rate of comparative example 4 corresponds to that of example 3, but the feed method is different, no masterbatch is produced, polyethylene and various additives are fed directly into the extruder, and white infusions can be found in the extrudate, i.e. the elastomer is shear-weak at the screw combination and cannot be shear-melted effectively.

The material dosage and the method of dosage in comparative example 5 corresponded to example 3, but with the screw thread combination adjusted, with a strong shear combination (60 °/4/44, 60 °/4/44, 45 °/5/56L), the extruded extrudate was rough surfaced and partially cross-linked.

In the embodiment, by adopting the feeding method disclosed by the invention, the crosslinkable polyethylene master batch is prepared firstly, then is subjected to melt blending with the polyethylene and the toughening component, and is combined with adjustment of the thread combination of the melting section, so that a larger safe processing interval can be provided in the process of preparing the crosslinkable polyethylene modified material, the shearing heat is greatly reduced, the volatilization of the auxiliary agent is less, and the crosslinkable polyethylene modified material with the gel content of 0 and no crosslinking structure is obtained. The cross-linked polyethylene with high cross-linking degree can be prepared by using the cross-linked polyethylene modifier.

Claims

1. A preparation method of a crosslinkable polyethylene modifier comprises the following steps:

(1) mixing a mixture containing polyethylene a, a cross-linking agent, a cross-linking auxiliary agent, an antioxidant, a lubricant and a cross-linking stabilizer to prepare a cross-linkable polyethylene master batch; based on the total amount of the crosslinkable polyethylene master batch, the total content of the crosslinking agent and the crosslinking assistant is 12-27 wt%;

(2) respectively adding the crosslinkable polyethylene master batch, the polyethylene b and the toughening component into a double-screw extruder for melt blending to obtain a crosslinkable polyethylene modified material; based on the total amount of the crosslinkable polyethylene modified material, the total content of the crosslinking agent and the crosslinking assistant is 0.8-3 wt%;

in the step (1), the mixing temperature of the crosslinkable polyethylene master batch is lower than the temperature of the crosslinking reaction of the crosslinking agent and the crosslinking assistant agent;

the crosslinking stabilizer is a polymerization inhibitor of phenols, quinones or aromatic nitro compounds;

in the step (2), the screw combination in the double-screw extruder comprises two mutually meshed screws (1) with the same structure;

the screw (1) comprises a spline shaft (2), a thread element (3) and a kneading element (4);

the plurality of screw elements (3) with different forward rotations and reverse rotations and the plurality of kneading elements (4) with different forward rotations and reverse rotations are sleeved on the spline shaft (2) through spline grooves (5) arranged on respective inner holes;

each screw (1) comprises a solid conveying section (A), a melting section (B), a mixing section (C), an exhaust section (D) and a homogenizing section (E) which are sequentially divided from the transmission end of the screw (1) to the tail end;

said melting section (B) containing at least one reverse flighted element or one reverse kneading element;

the gel content of the crosslinkable polyethylene modifier is 0 wt%.

2. The preparation method according to claim 1, wherein in the step (1), the crosslinking agent is 20 to 25 parts by weight, the crosslinking assistant is 5 to 10 parts by weight, the antioxidant is 2 to 15 parts by weight, the lubricant is 5 to 15 parts by weight, and the crosslinking stabilizer is 1 to 5 parts by weight, based on 100 parts by weight of the polyethylene a.

3. The production method according to claim 1 or 2, wherein in step (1), the polyethylene a is selected from a high density polyethylene and/or a low density polyethylene.

4. The method according to claim 3, wherein the high density polyethylene has a density of 0.94 to 0.965g/cm³A melt index at 190 ℃ under a load of 2.16kg of 1 to 20g/10 min; the density of the low-density polyethylene is 0.91-0.935 g/cm³And a melt index at 190 ℃ under a load of 2.16kg of 1 to 20g/10 min.

5. The preparation method according to claim 1, wherein in the step (2), the polyethylene b is 500 to 1000 parts by weight and the toughening component is 35 to 400 parts by weight with respect to 100 parts by weight of the crosslinkable polyethylene masterbatch.

6. The production method according to claim 1 or 5, wherein, in the step (2), the polyethylene b is selected from a high density polyethylene and/or a low density polyethylene.

7. The method according to claim 6, wherein the high density polyethylene has a density of 0.94 to 0.965g/cm³19 under a load of 2.16kgThe melt index at 0 ℃ is 1-20 g/10 min; the density of the low-density polyethylene is 0.91-0.935 g/cm³And a melt index at 190 ℃ under a load of 2.16kg of 1 to 20g/10 min.

8. The production method according to claim 1 or 2, wherein the toughening component is selected from at least one of linear low density polyethylene, ethylene-octene copolymer, and ethylene-propylene-diene monomer rubber; the cross-linking agent is selected from at least one of dicumyl peroxide, benzoyl peroxide, dicumyl hydroperoxide, diacyl peroxide, di-tert-butyl peroxide, alkyl hydroperoxide, dilauroyl peroxide, methyl ethyl ketone peroxide and cyclohexanone peroxide; the crosslinking assistant is selected from at least one of poly (1, 2-butadiene), diallyl terephthalate, divinylbenzene, triallyl cyanurate and triallyl isocyanate; the crosslinking stabilizer is at least one selected from tris (2,2,6, 6-tetramethylpiperidinyloxy) phosphite, 2-bis (4-tert-octylphenyl) -1-picrylhydrazine and nitroxide radical piperidinol.

9. The production method according to claim 1, wherein the lead of the screw element (3) is 44 to 96mm, and the length of the screw element (3) is 44 to 96 mm; the dislocation angle of the kneading element (4) is 30-60 degrees, the length of the kneading element (4) is 44-56 mm, and the number of kneading blocks of the kneading element (4) is 4-6.

10. The production process according to claim 1, wherein the melting section contains at least two sets of engaging sections, each engaging section containing at least 1 kneading element (4);

at least one screw element (3) is contained between the engagement sections.

11. The production method according to any one of claims 1, 9 and 10, wherein the directions of rotation of the two screws (1) are the same; when the screw rod (1) rotates, the phase difference of the two screw rods (1) is 90 degrees.

12. The preparation method according to claim 11, wherein the screw (1) has a diameter of 36 to 96mm and an aspect ratio of (36 to 48): 1.