阅读说明：本技术 适用于高速加工的电缆护套用聚乙烯组合物及其制备方法 (Polyethylene composition suitable for high-speed processing for cable sheath and preparation method thereof ) 是由 王群涛 郭锐 王日辉 高凌雁 *** 许平 唐岩 苑东兴 石晶 于 2018-07-16 设计创作，主要内容包括：本发明涉及一种适用于高速加工的电缆护套用聚乙烯组合物及其制备方法,属于聚乙烯改性技术领域。本发明所述的适用于高速加工的电缆护套用聚乙烯组合物,包括以下重量份数的原料：聚乙烯树脂100份,抗氧剂0.2-0.5份,反应剂0.06-0.1份,炭黑母料5-8份。所述反应剂为马来酰亚胺类哌啶基氧化物。本发明所述的适用于高速加工的电缆护套用聚乙烯组合物,临界剪切速率、熔体强度及ESCR性能均得到显著提高,有利于提高电缆护套料的加工性能和使用寿命；本发明同时提供了简单易行、节能环保的制备方法。(The invention relates to a polyethylene composition for a cable sheath suitable for high-speed processing and a preparation method thereof, belonging to the technical field of polyethylene modification. The polyethylene composition for the cable sheath suitable for high-speed processing comprises the following raw materials in parts by weight: 100 parts of polyethylene resin, 0.2-0.5 part of antioxidant, 0.06-0.1 part of reactant and 5-8 parts of carbon black master batch. The reactant is maleimide piperidyl oxide. The polyethylene composition for the cable sheath suitable for high-speed processing provided by the invention has the advantages that the critical shear rate, the melt strength and the ESCR (environmental protection chemical resistance) performance are all remarkably improved, the processability of the cable sheath material is favorably improved, and the service life of the cable sheath material is prolonged; the invention also provides a simple, energy-saving and environment-friendly preparation method.)

1. A polyethylene composition suitable for high-speed processing of cable sheaths is characterized by comprising the following raw materials in parts by weight: 100 parts of polyethylene resin, 0.2-0.5 part of antioxidant, 0.06-0.1 part of reactant and 5-8 parts of carbon black master batch;

the reactant is maleimide piperidyl oxide.

2. The polyethylene composition for cable jackets suitable for high speed processing according to claim 1, characterized in that: the polyethylene resin is a copolymer of ethylene and 1-hexene or 1-butene and 1-hexene.

3. The polyethylene composition for cable jackets suitable for high speed processing according to claim 2, characterized in that: the polyethylene resin is produced by adopting a gas phase method process and a modified chromium catalyst, the reaction temperature is 93-95 ℃, and the reaction pressure is 2.0-2.1 MPa.

4. The polyethylene composition for cable jackets suitable for high speed processing according to claim 1, characterized in that: the density of the polyethylene resin is 0.930-0.935g/cm³(ii) a The mass flow rate of the melt under the load of 2.16 kilograms is 0.35 to 0.55g/10 min; the weight average molecular weight is 11-14 ten thousandThe molecular weight distribution is 23.0-26.0; the relative degree of branching is from 0.66 to 0.74.

5. The polyethylene composition for cable jackets suitable for high speed processing according to claim 1, characterized in that: the polyethylene resin is in the form of powder, and has an average particle diameter of 0.60-0.65mm and a bulk density of 0.37-0.39g/cm³。

6. The polyethylene composition for cable jackets suitable for high speed processing according to claim 1, characterized in that: the antioxidant is a mixture of hindered phenol antioxidant and phosphite antioxidant.

7. The polyethylene composition for cable jackets suitable for high speed processing according to claim 1, characterized in that: the mass content of the carbon black in the carbon black master batch is 50%.

8. The polyethylene composition for cable jackets suitable for high speed processing according to claim 1, characterized in that: the maleimide piperidyl oxide is one or two of 4-maleimide-tetramethylpiperidine oxide or 1-oxy-3-maleimide-tetramethylpiperidine oxide.

9. A process for preparing a polyethylene composition suitable for high speed processing of cable jackets according to any of claims 1 to 8, characterized by comprising the steps of:

(1) putting the polyethylene resin and the antioxidant into a high-speed mixer, stirring and mixing, stopping stirring, adding the reactant, and stirring again; stopping the machine, adding the carbon black master batch and then stirring;

(2) and (2) adding the material added with the carbon black master batch in the step (1) and stirred into a double-screw extruder for melting, plasticizing, extruding and granulating to obtain the polyethylene composition for the cable sheath suitable for high-speed processing.

10. The method for preparing a polyethylene composition for a cable jacket suitable for high speed processing according to claim 9, wherein: in the step (1), the reaction agent is added and stirred at the stirring temperature of 50-60 ℃.

Technical Field

The invention relates to a polyethylene composition for a cable sheath suitable for high-speed processing and a preparation method thereof, belonging to the technical field of polyethylene modification.

Background

Optical cables require an outer protective layer due to the constraints of the application or use environment. The outer protective layer aims at playing the protective roles of water resistance, moisture insulation, corrosion resistance, accidental damage prevention, even insulation and the like. This outer protective layer is commonly referred to as a "jacket". The material used to produce the "jacket" is referred to as the "jacket material".

Environmental Stress Cracking Resistance (ESCR) is a very important performance requirement for polyethylene sheathing materials, which directly affects the service life of electrical and optical cables. Polyethylene is very sensitive to environmental stresses, particularly in the presence of polar liquids, due to its own structural problems. Underground sewage is complex in composition and often contains surfactants such as detergents. The underground full-plastic cable is usually soaked with underground sewage in the manhole. When the cable or cable is bent in the manhole, the polyethylene sheath is stressed and, in addition to a long-term contact with polar liquids, cracks occur in the surface. To ensure long-term service life of the cable jacket, the material should have excellent ESCR properties.

Melt strength, which reflects the elongation and sag resistance of polymer melts, is a very important property in determining the processing and shaping of materials. The melt strength is related to the degree of entanglement of the molecular chains, the higher the degree of entanglement, the higher the melt strength. The sheath material needs high melt strength to prevent melt fracture during molding, so that the requirement of high-speed traction processing is met, and the processing efficiency is improved. Meanwhile, the sheath material should have excellent processability, so that the product has good appearance, and the product is generally characterized by the critical shear rate, and the higher the critical shear rate is, the material is not easy to generate melt fracture in the processing process, so that the product has good appearance.

A certain number of long branched chains are formed in the molecular chain of the polyethylene resin, which is beneficial to increasing the entanglement degree of the molecular chain, can improve the environmental stress cracking resistance and the melt strength of the resin, and meets the requirements of the resin in harsh use conditions and high-speed processing fields. At present, polyolefin production enterprises mainly introduce long-chain branches into molecular chains by means of adjusting catalysts, polymerization process technologies and the like, but the technical process is complex, the molecular chain structure is difficult to control, and the cost is high.

CN 102120845A discloses a polyethylene sheath material, in particular to a polyethylene sheath material for optical cables. The high-density polyethylene resin antioxidant is prepared from high-density polyethylene resin, medium-density polyethylene resin, linear low-density polyethylene resin and an antioxidant processing aid through weighing, mixing, extruding, granulating, drying and packaging.

CN201110325136 discloses a long-chain branched polyethylene resin, which is prepared from polyethylene, organic peroxide, vinyl functional monomer, and crosslinking inhibitor as raw materials, wherein the mass ratio of the raw materials is as follows based on the amount of polyethylene: polyethylene, organic peroxide is 100: 0.05-0.30; polyethylene, vinyl functional monomer 100: 1.0-4.0; polyethylene and a crosslinking inhibitor, wherein the crosslinking inhibitor is 100: 0.5-1.5. The invention also discloses a preparation method of the polyethylene resin.

Disclosure of Invention

The invention aims to provide a polyethylene composition for a cable sheath, which is suitable for high-speed processing, has obviously improved critical shear rate, melt strength and ESCR performance, and is beneficial to improving the processing performance and prolonging the service life of the cable sheath material; the invention also provides a simple, energy-saving and environment-friendly preparation method.

The polyethylene composition for the cable sheath suitable for high-speed processing comprises the following raw materials in parts by weight: 100 parts of polyethylene resin, 0.2-0.5 part of antioxidant, 0.06-0.1 part of reactant and 5-8 parts of carbon black master batch.

Preferably, the feed comprises the following raw materials in parts by weight: 100 parts of polyethylene resin, 0.3-0.4 part of antioxidant, 0.07-0.09 part of reactant and 5-7 parts of carbon black master batch.

The polyethylene resin is a copolymer of ethylene and 1-hexene or 1-butene and 1-hexene. The polyethylene resin is produced by adopting a gas phase method process and a modified chromium catalyst, the reaction temperature is 93-95 ℃, and the reaction pressure is 2.0-2.1 MPa.

The density of the polyethylene resin is 0.930-0.935g/cm³Preferably 0.932-0.934 g/cm³The material is ensured to have basic cracking resistance while meeting the requirement of mechanical strength, and the use requirement is met.

The melt Mass Flow Rate (MFR) of the PE resin under the load of 2.16kg is 0.35-0.55g/10min, and preferably 0.40-0.52g/10 min; the molecular weight (Mw/MD) distribution D is from 23.0 to 26.0, preferably from 23.5 to 25.5. The MFR and the D influence the processability and the mechanical strength of the resin, and the polyethylene resin with the performance parameters ensures that the material has good processability while having certain mechanical strength.

The weight average molecular weight (Mw) of the PE-RT resin is 11-14 ten thousand, preferably 11.5-13.3 ten thousand; the relative degree of branching is from 0.66 to 0.74, preferably from 0.68 to 0.72. Mw and relative branching affect the reaction effectiveness and cooperativity of the reactants, i.e., the number and distribution of long chain branches introduced into the resin.

The PE-RT resin is in the form of powder, the average grain diameter is 0.60-0.65mm, and the bulk density is 0.37-0.39g/cm³And the dispersion of the auxiliary agent and the introduction of long-chain branches are facilitated.

When polyethylene is in contact with air, it is oxidized by a chemical reaction with oxygen in the air, which is a typical radical reaction. The antioxidant is added into polyethylene and can react with oxidation free radicals R and ROO generated by oxidation in the material to interrupt the growth of an active chain, so that the degradation and aging processes of the plastic material are effectively inhibited or reduced, and the service life of the plastic product is prolonged. The antioxidant is a mixture of hindered phenol antioxidant and phosphite antioxidant, and the mixing ratio is preferably 1: 1. Amine antioxidants hinder the chain reaction effect of the reactants with the resin and are not favorable for introducing long chain branches.

The hindered phenol antioxidant is tetra [ methyl-beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ] pentaerythritol ester, beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) n-octadecyl propionate, 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene or 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) -1,3, 5-triazine-2, 4,6(1H,3H,5H) -trione; the phosphite antioxidant is tris [2, 4-di-tert-butylphenyl ] phosphite, bis (2, 4-di-tert-butylphenol) pentaerythritol diphosphite or pentaerythritol distearate diphosphite.

The carbon black master batch contains 50% of carbon black by mass, and can be uniformly dispersed in the composition, so that the composition is ensured to have good ultraviolet aging resistance.

The reactant is maleimide piperidyl oxide. Preferably, the maleimide oxide is one or two of 4-maleimide-tetramethylpiperidine oxide and 1-oxy-3-maleimide-tetramethylpiperidine oxide, and the mixing mass ratio is 1:1 when the maleimide oxide and the 1-oxy-3-maleimide-tetramethylpiperidine oxide are mixed.

The preparation method of the polyethylene composition for the cable sheath suitable for high-speed processing comprises the following steps:

(1) putting polyethylene resin and an antioxidant into a high-speed mixer, stirring and mixing, stopping stirring, adding a reactant, and stirring at the temperature of 50-60 ℃; stopping the machine, adding the carbon black master batch and then stirring;

(2) and (2) adding the material added with the carbon black master batch in the step (1) and stirred into a double-screw extruder for melting, plasticizing, extruding and granulating to obtain the polyethylene composition for the cable sheath suitable for high-speed processing.

In the steps, the first three components are mixed, then the stirring is stopped, and then the reactant is added, so that the reactant is favorably and uniformly dispersed in the resin and fully reacted with the resin, and the content and the performance of the long-chain branch in the resin are improved; the carbon black master batch is added after the machine is stopped, and the advantages that the carbon black master batch is granular material, other raw materials are powder material, and the auxiliary agent and the powder material are reacted and uniformly dispersed.

The polyethylene compositions produced according to the invention have the following performance parameters:

the melt strength is more than or equal to 0.23N, the critical shear rate is more than or equal to 1300s < -1 >, and the environmental stress cracking resistance (50 ℃,10 percent TX < -10 >) is more than 1800 h.

The invention has the following beneficial effects:

(1) according to the invention, by limiting the molecular structure and components of the resin, maleimide piperidyl oxide is added into polyethylene, and long-chain branch chains are introduced into the molecular chain of the resin through blending and melt extrusion, so that the critical shear rate, the melt strength and the ESCR (ethylene styrene-butadiene-styrene copolymer) performance of the composition are improved, and the processing performance and the service life of the cable sheath material are improved;

(2) the preparation method of the polyethylene composition is energy-saving and environment-friendly, and is simple and feasible.

Detailed Description

The present invention is further illustrated by the following examples, which are not intended to limit the practice of the invention.