WO2023240938A1

WO2023240938A1 - Reversibly crosslinked polyethylene cable material and preparation method therefor

Info

Publication number: WO2023240938A1
Application number: PCT/CN2022/135845
Authority: WO
Inventors: 刘小燕; 陈旭; 王霞; 魏福庆; 李丽; 邓守军; 段宏义; 樊洁; 李广全; 于国滨
Original assignee: 中国石油天然气股份有限公司
Priority date: 2022-06-17
Filing date: 2022-12-01
Publication date: 2023-12-21
Also published as: CN117285769A

Abstract

Provided in the present application are a reversibly crosslinked polyethylene cable material and a preparation method therefor. The raw materials of the reversibly crosslinked polyethylene cable material in the present application comprise a polyethylene copolymer and a coupling agent, wherein the polyethylene copolymer is obtained by copolymerizing polymerization monomers, the polymerization monomers comprising ethylene, and vinyl-benzaldehyde and/or a vinyl-benzaldehyde derivative, and the coupling agent is selected from polybasic primary amine compounds. The reversibly crosslinked polyethylene cable material of the present invention has the advantages of excellent heat resistance and wide process window.

Description

A reversible cross-linked polyethylene cable material and its preparation method

This application requests the priority of the Chinese patent application submitted to the China Patent Office on June 17, 2022, with the application number 202210684782. incorporated herein by reference.

Technical field

This application belongs to the technical field of polymer materials and relates to a reversibly cross-linked polyethylene cable material and its preparation method.

Background technique

Polyethylene has good insulation, easy processability, low temperature resistance and aging resistance. It is an excellent electrical insulation material, but it also has shortcomings such as low temperature resistance and poor creep resistance. After polyethylene is cross-linked, its molecular structure changes from a two-dimensional structure to a three-dimensional network structure. Its electrical properties, heat resistance and physical strength can be greatly improved, broadening its application scope.

Traditional polyethylene cross-linking methods mainly include peroxide cross-linking, radiation cross-linking and silane cross-linking, etc. However, the above cross-linking methods are all irreversible cross-linking, thus losing valuable thermoplasticity and making the cable material unable to be processed and processed again. recycle and re-use.

Dynamic covalent bonds refer to covalent bonds that can be reversibly broken/bonded after being exposed to specific stimuli (such as heat, light, and pH). The polymer cross-linked network formed by this can achieve topological rearrangement under external influence. It has been reported that reversibly cross-linked polyolefins can be obtained through DA reaction. For example, patent CN111072858A reports a polyethylene resin with side groups as cyclopentadiene groups. The polymerized monomers of the polyethylene resin include ethylene and cyclopentadiene-containing monomers. group of α-olefins, in which the cyclopentadiene groups on the α-olefin monomer are reacted through DA so that the resulting polyethylene resin has a reversibly cross-linked network structure. The resin reverses when heated to above 160°C. The reaction decrosslinks the polyethylene, giving the material thermoplasticity. In addition, patent WO2019024633A1 also reports a styrenic copolymer with reversible cross-linking bonds. The copolymer is obtained by reacting a styrenic copolymer with a furyl group and a multifunctional maleimide derivative through DA. A styrenic copolymer with reversible cross-linking bonds. This patent also provides the application of this copolymer in cable materials. The reversible cross-linking bonds of this copolymer can be broken at high temperatures, giving the cable material secondary processing properties. , can be used repeatedly.

However, in many current situations, due to the large current transmission per unit cross-sectional area, high calorific value, and high long-term operating temperature of the conductor, higher requirements are placed on the heat resistance level of the insulating material, and the DA type reversible cross-linking has been reported The heat resistance of polyethylene cable material is poor, and the viscosity of the cable material drops suddenly when it is decross-linked, which limits its application in working environments with higher temperatures.

Contents of the invention

This application provides a reversibly cross-linked polyethylene cable material, which has the advantages of excellent heat resistance and wide processing window.

This application also provides a method for preparing a reversibly cross-linked polyethylene cable material. This method can simply and quickly prepare a reversibly cross-linked polyethylene cable material with excellent heat resistance and a wide processing window.

The first aspect of this application provides a reversibly cross-linked polyethylene cable material, the raw materials of which include polyethylene copolymer and coupling agent;

The polymerized monomers include ethylene, and vinylbenzaldehyde and/or vinylbenzaldehyde derivatives;

The coupling agent is selected from polybasic primary amine compounds.

The reversible cross-linked polyethylene cable material as above, wherein the coupling agent is selected from compounds of formula (I):

H ₂ NR ¹ -NH ₂ formula (I)

In formula (I), R ¹ is selected from a C1 to C12 alkyl group, a C6 to C12 substituted or unsubstituted aryl group, or a C6 to C12 substituted or unsubstituted heteroaryl group;

Wherein, the substituents in the substituted aryl group or the substituted heteroaryl group are selected from C1 to C3 alkyl groups or halogens.

The above-mentioned reversibly cross-linked polyethylene cable material, wherein R ¹ is selected from C2 or C3 linear alkyl groups.

The reversible cross-linked polyethylene cable material as above, wherein the vinyl benzaldehyde derivative is selected from a vinyl benzaldehyde compound containing at least one C1-C6 alkyl substituted on the benzene ring.

The reversible cross-linked polyethylene cable material as above, wherein the mass ratio of the polyethylene copolymer to the coupling agent is 100: (1-20).

The reversibly cross-linked polyethylene cable material as described above, wherein the polyethylene copolymer includes 70% to 93% of ethylene units and 5% to 29% of vinyl benzaldehyde units and/or vinyl benzene based on molar content. Formaldehyde derivative unit.

The reversibly cross-linked polyethylene cable material as above, wherein the polyethylene copolymer is a low-density polyethylene copolymer.

The reversibly cross-linked polyethylene cable material as described above, wherein the raw materials of the cable material also include antioxidants;

The mass ratio of polyethylene copolymer, coupling agent and antioxidant is 100: (2～15): (0.3～0.7).

The second aspect of the present application provides a method for preparing the reversibly cross-linked polyethylene cable material as described above, which includes: mixing the raw materials of the cable material to obtain a mixture; and extruding the mixture to obtain the reversible cross-linked polyethylene cable material. Cross-linked polyethylene cable material.

The preparation method as mentioned above, wherein the temperature of the extrusion treatment is 190-230°C.

The implementation of this application will have at least the following beneficial effects:

1. In this application, the aldehyde group on the side chain of the polyethylene copolymer reacts with the amino group in the coupling agent to obtain a polyethylene cable material with an imine bond covalently cross-linked network structure. The cable material has excellent heat resistance. .

2. When the polyethylene cable material of this application is decross-linked, the viscosity of the cable material decreases slowly, which greatly broadens the processing window temperature and processing stability of the cable material, making the processing process simpler and easier to control.

3. The preparation method of the reversibly cross-linked polyethylene cable material of the present application can obtain the above-mentioned reversibly cross-linked polyethylene cable material with excellent heat resistance and wide processing window by simply mixing and extruding the cable material raw materials. , this method has the advantage of being simple and easy to operate.

Description of the drawings

Figure 1 is a comparison chart of the infrared spectra of the cable materials of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3;

Figure 2 is a comparison chart of the infrared spectra of the cable materials of Example 1 and Comparative Example 4.

Detailed ways

The present application will be described in further detail below with reference to specific embodiments. It should be understood that the following examples are only for illustrating and explaining the present application, and should not be construed as limiting the protection scope of the present application. All technologies implemented based on the above contents of this application are covered by the scope of protection intended by this application.

The first aspect of this application provides a reversibly cross-linked polyethylene cable material, wherein the raw materials of the cable material include polyethylene copolymer and coupling agent; the polyethylene copolymer is obtained by copolymerization of polymerized monomers, and the polymerized monomers include ethylene, and Vinyl benzaldehyde and/or vinyl benzaldehyde derivatives; the coupling agent is selected from polyvalent primary amine compounds.

Wherein, the polymerized monomer includes ethylene, and in addition to ethylene, it also includes at least one of vinyl benzaldehyde and vinyl benzaldehyde derivatives.

The substitution position of the vinyl group on the benzaldehyde is not particularly limited in this application. For example, it may be o-vinylbenzaldehyde, m-vinylbenzaldehyde or p-vinylbenzaldehyde. Among them, the derivatives of vinyl benzaldehyde refer to compounds in which an alkyl substituent is connected to the benzene ring of vinyl benzaldehyde.

The polyethylene copolymer of the present application contains an aldehyde group (-CHO) on the side group, and the coupling agent is a polyvalent primary amine compound. The coupling agent contains at least two amino groups (-NH ₂ ), and the aldehyde group and the amino group carry out Schiff interaction. Alkaline reaction can produce reversibly cross-linked polyethylene with a dynamic imine bond cross-linked network.

Although the polyethylene cable material with dissociated dynamic covalent cross-linking network represented by D-A reaction can be processed again, it has problems of narrow processing window and sudden viscosity drop during de-crosslinking, which limits its use in high-temperature environments. application and processing difficulty. The reversibly cross-linked polyethylene cable material of this application has a dynamic imine bond cross-linked network and has good heat resistance. When de-cross-linking, the viscosity of the cable material gradually decreases with the increase of temperature, making the processing process simple. Easy to control.

In this application, the copolymerization process of polymerized monomers is a free radical polymerization process, and a peroxide initiator can be added to the copolymerization reaction to initiate the polymerization reaction. In order to control the polyethylene copolymer obtained by copolymerization to have an appropriate molecular weight, a small amount of molecular weight regulator needs to be added to the polymerization system. The molecular weight regulator can be selected from molecular weight regulators commonly used in this field, including but not limited to propylene, butene or Propane, etc., preferably propylene. The added amount of the molecular weight regulator is 0 to 5000 ppm, preferably 1000 to 3000 ppm.

In a specific embodiment, the coupling agent is selected from compounds of formula (I):

H ₂ NR ¹ -NH ₂ formula (I)

Specifically, the C1-C12 alkyl group can be a straight-chain alkyl group or a branched-chain alkyl group with 1 to 12 carbon atoms, including but not limited to methyl, ethyl, n-propyl, isopropyl, n-butyl base, tert-butyl, isobutyl, sec-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, etc. The C1-C6 alkyl group can be a linear or branched chain alkyl group with 1 to 6 carbon atoms, including but not limited to methyl, ethyl, n-propyl, isopropyl, n-butyl, tert. Butyl, isobutyl, sec-butyl, n-pentyl, n-hexyl, etc. The C1-C3 alkyl group can be a straight-chain alkyl group or a branched-chain alkyl group with 1 to 3 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, etc.

Except for special exceptions, "aryl" refers to an unsaturated, aromatic, monocyclic or polycyclic substituent that is fused or covalently connected; "heteroaryl" refers to a substituent containing 1 to 4 heteroatoms. Aryl groups, typical heteroatoms include nitrogen, oxygen, and sulfur.

C6-C12 aryl groups include but are not limited to phenyl, naphthyl, biphenyl, etc.; C6-C12 heteroaryl groups include but are not limited to pyrrolyl, pyridyl, pyrazolyl, imidazolyl, oxazolyl, iso Oxazolyl, pyrimidinyl, purinyl, indolyl, etc.

Further, R1 in formula (I) is selected from C2 or C3 linear alkyl groups, that is, ethyl or n-propyl groups.

In a specific embodiment, the vinyl benzaldehyde derivative is selected from vinyl benzaldehyde compounds containing at least one C1-C6 alkyl group substituted on the benzene ring. Furthermore, the C1-C6 alkyl-substituted vinyl benzaldehyde compound is preferably a methyl-substituted vinyl benzaldehyde compound.

In a specific embodiment, the mass ratio of the polyethylene copolymer to the coupling agent in the raw materials of the cable material of the present application is 100: (1-20).

In a specific embodiment, the polyethylene copolymer includes 70% to 93% of ethylene units and 5% to 29% of vinylbenzaldehyde units and/or vinylbenzaldehyde derivative units according to molar content. Wherein, the polyethylene copolymer includes 5% to 29% of vinyl benzaldehyde units and/or the vinyl benzaldehyde derivative units include the polyethylene copolymer with a molar content of vinyl benzaldehyde units of 5% to 29%. The molar content of vinylbenzaldehyde derivative units in the copolymer is 5% to 29%, and the sum of the molar content of vinylbenzaldehyde units and vinylbenzaldehyde derivative units in the polyethylene copolymer is 5% to 29% three conditions. Specifically, the molar content of ethylene units, vinylbenzaldehyde and their derivative units in the copolymer can be measured by infrared spectroscopy. For example, the molar content of the aldehyde group in the copolymer can be measured by infrared spectroscopy. The molar content of the aldehyde group is The content of vinylbenzaldehyde and its derivative units can be determined.

The polyethylene copolymer of this application is preferably a low-density polyethylene copolymer. Low-density polyethylene is also called high-voltage polyethylene, with a density of 0.91g/cm ³ to 0.93g/cm ³ . It has excellent electrical insulation properties and good mechanical properties. performance, excellent cost performance, low cost and other advantages.

In a specific embodiment, the low-density polyethylene copolymer of the present application can be prepared using the following preparation method:

Add polymerized monomers to the high-pressure polyethylene reactor, causing the polymerized monomers to undergo a first-stage polymerization reaction at 280°C to 300°C to obtain a first polymerization product; causing the first polymerization product to undergo a second-stage polymerization reaction at 285°C to 295°C. A two-stage polymerization reaction is performed to obtain a second polymerization product; the second polymerization product is subjected to a third-stage polymerization reaction at 280°C to 290°C to obtain a third polymerization product; the third polymerization product is subjected to a third-stage polymerization reaction at 270°C to 285°C. Four-stage polymerization reaction produces low-density polyethylene copolymer.

The above-mentioned four different stages of polymerization reactions are all initiated by organic peroxides. The organic peroxides are injected at four points through an injection pump to initiate four stages of polymerization reactions respectively.

Before adding the polymerized monomer into the high-pressure polyethylene reactor, a step of preheating the polymerized monomer is also included. Preferably, the temperature of the preheated polymerized monomer is 160°C to 170°C, and more preferably 165°C.

The raw materials of the cable material in this application also include antioxidants. Cross-linked polyolefins are prone to aging when used in cable material insulation materials, thereby deteriorating their cross-linking characteristics, mechanical properties and thermal stability. Adding antioxidants can Delay the oxidative aging of oxides.

The antioxidant in this application is preferably at least one of hindered phenolic antioxidants and phosphorous acid antioxidants. Among them, hindered phenolic antioxidants include but are not limited to monovalent hindered phenols, polyvalent hindered phenols, such as dibutylhydroxytoluene BHT, antioxidant 1024, antioxidant 3114, antioxidant 1010, antioxidant 1330; phosphorous acid Antioxidants refer to phosphite antioxidants, including but not limited to phenol-free phosphite antioxidants, low-phenol phosphite antioxidants, phenol-containing phosphite antioxidants, such as Oxygen 168.

Further, the mass ratio of polyethylene copolymer, coupling agent and antioxidant is 100: (2～15): (0.3～0.7). For example, in a specific embodiment, 80,000 ppm of coupling agent and 4,000 ppm of antioxidant are added to each kilogram of polyethylene copolymer, where ppm represents the mass of coupling agent and antioxidant in the polyethylene copolymer. parts per million of the mass of the ethylene copolymer, then in the above embodiment, the mass ratio of the polyethylene copolymer, coupling agent and antioxidant is 100:8:0.4.

The second aspect of this application provides a method for preparing the above-mentioned reversibly cross-linked polyethylene cable material. The method includes: mixing the raw materials of the cable material to obtain a mixture; and extruding the mixture to obtain the reversibly cross-linked polyethylene cable material. .

First, the components of the cable material are mixed in a mixer to obtain a mixture; then the mixture is sent to an extruder for mixing and then extrusion.

After extrusion, the extrudate is also cooled, pelletized, and dried to obtain the reversibly cross-linked polyethylene cable material of the present application.

The mixer of the present application can be a high-speed mixer, and the extruder includes but is not limited to a single-screw extruder or a twin-screw extruder.

Furthermore, the mixing of cable materials can be completed at 0 to 50°C.

Further, the temperature of the extrusion treatment is 190 to 230°C. At this temperature, the extrusion process not only completes the molding process of polyethylene cable materials, but also promotes the reaction between the aldehyde groups in the polyethylene copolymer and the amino groups in the coupling agent, completing the imine bonding of the polyethylene copolymer. Covalent cross-linking process.

The reversible cross-linked polyethylene cable material and its preparation method provided in this application will be further described in detail below with reference to specific examples.

It should be noted that in the following examples, unless otherwise specified, the raw materials used can be commercially purchased or prepared by conventional methods. Experimental methods without specifying specific conditions are conventional methods and conventional conditions well known in the art. .

Example 1

The preparation method of reversibly cross-linked polyethylene cable material in this embodiment includes the following steps:

1) A tubular high-pressure polyethylene reactor with four reaction zones is used as the reaction device. The temperatures of the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone are 295°C, 285°C, and 285°C respectively. ℃, 275℃, the reactor pressure is set to 285Mpa, ethylene and 2-vinylbenzaldehyde are introduced into the reactor at a flow rate of 50t/h and 2.95t/h respectively for preheating, so that the reaction of the preheated materials The temperature reaches 165°C, and the material is passed through the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone in sequence. At the same time, the molecular weight regulator is introduced at the entrance of the first reaction zone at a flow rate of 100kg/h. The initiator was injected into the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone at four points through the injection pump. The total amount of initiator added was 0.17t/h to initiate the 4-stage polymerization reaction to prepare A low-density polyethylene copolymer was obtained, and the aldehyde group content in the copolymer was 6.31 mol%;

Among them, the initiator is di-tert-butyl peroxide and the molecular weight regulator is propylene.

2) Add the low-density polyethylene copolymer prepared in step 1), coupling agent, and antioxidant into a high-speed mixer, and mix the above components uniformly at high speed to obtain a mixture. The mixture was extruded through a 35-type twin-screw extruder (Belonkoya Nanjing Machinery Co., Ltd.) at 200°C. The extruded product was cooled by circulating water, and then pelletized by a pelletizer. The pellets were dried and screened. Obtain reversibly cross-linked polyethylene cable material;

Among them, the coupling agent is ethylenediamine, and the antioxidant is a mixture obtained by mixing hindered phenol antioxidant 1010 and phosphite antioxidant 168 at a mass ratio of 2:1; the amount of coupling agent added is based on per kilogram. The low-density polyethylene copolymer is added at 80,000 ppm, and the antioxidant is added at 4,000 ppm per kilogram of low-density polyethylene copolymer.

Example 2

1) A tubular high-pressure polyethylene reactor with four reaction zones is used as the reaction device. The temperatures of the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone are 300°C, 297°C, and 290°C respectively. ℃, 280℃, the reactor pressure is set to 285Mpa, and ethylene and 3-vinylbenzaldehyde are introduced into the reactor at a flow rate of 50t/h and 4.51t/h respectively for preheating, so that the reaction of the preheated materials The temperature reaches 165°C, and the material is passed through the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone in sequence. At the same time, the molecular weight regulator is introduced at the entrance of the first reaction zone at a flow rate of 150kg/h. The initiator was injected into the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone at four points through the injection pump. The total amount of the initiator added was 0.20t/h to initiate the 4-stage polymerization reaction to prepare A low-density polyethylene copolymer was obtained, and the aldehyde group content in the copolymer was 11.45 mol%;

Among them, the initiator is tert-butyl peroxyacetate and the molecular weight regulator is propylene.

Among them, the coupling agent is propylene diamine, and the antioxidant is a mixture obtained by mixing hindered phenol antioxidant 1010 and phosphite antioxidant 168 at a mass ratio of 1:1; the amount of coupling agent added is based on per kilogram. The low-density polyethylene copolymer is added at 90,000 ppm, and the antioxidant is added at 5,000 ppm per kilogram of low-density polyethylene copolymer.

Example 3

1) A tubular high-pressure polyethylene reactor with four reaction zones is used as the reaction device. The temperatures of the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone are 300°C, 295°C, and 290°C respectively. ℃, 285℃, the reactor pressure is set to 290Mpa, ethylene and 2-vinylbenzaldehyde are introduced into the reactor at a flow rate of 50t/h and 2.43t/h respectively for preheating, so that the reaction of the preheated materials The temperature reaches 165°C, and the material is passed through the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone in sequence. At the same time, the molecular weight regulator is introduced at the entrance of the first reaction zone at a flow rate of 150kg/h. The initiator was injected into the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone at four points through the injection pump. The total amount of initiator added was 0.18t/h to initiate the 4-stage polymerization reaction to prepare A low-density polyethylene copolymer was obtained, and the aldehyde group content in the copolymer was 5.79 mol%;

Among them, the initiator is tert-butyl peroxypivalate and the molecular weight regulator is propylene.

Among them, the coupling agent is 1,2-propylenediamine, and the antioxidant is a mixture obtained by mixing hindered phenol antioxidant 1010 and phosphite antioxidant 168 in a mass ratio of 2:0.5; the addition of coupling agent The amount added is 60,000ppm per kilogram of low-density polyethylene copolymer, and the amount of antioxidant is 4,500ppm per kilogram of polyethylene.

Example 4

1) A tubular high-pressure polyethylene reactor with four reaction zones is used as the reaction device. The temperatures of the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone are 300°C, 295°C, and 290°C respectively. ℃, 285℃, the reactor pressure is set to 285Mpa, ethylene and 2-vinylbenzaldehyde are introduced into the reactor at a flow rate of 50t/h and 2.43t/h respectively for preheating, so that the reaction of the preheated materials The temperature reaches 165°C, and the material is passed through the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone in sequence. At the same time, the molecular weight regulator is introduced at the entrance of the first reaction zone at a flow rate of 50kg/h. The initiator was injected into the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone at four points through the injection pump. The total amount of the initiator added was 0.20t/h to initiate the 4-stage polymerization reaction to prepare A low-density polyethylene copolymer was obtained, and the aldehyde group content in the copolymer was 10.65 mol%;

2) Add coupling agent and antioxidant to the low-density polyethylene copolymer prepared in step 1) and mix uniformly at high speed, and mix the above components uniformly at high speed to obtain a mixture. The mixture was extruded through a 35-type twin-screw extruder (Belonkoya Nanjing Machinery Co., Ltd.) at 200°C. The extruded product was cooled by circulating water, and then pelletized by a pelletizer. The pellets were dried and screened. Obtain reversibly cross-linked polyethylene cable material;

Among them, the coupling agent is 1,3-propylenediamine, and the antioxidant is a mixture obtained by mixing hindered phenol antioxidant 1010 and phosphite antioxidant 168 at a mass ratio of 1:1; the addition of coupling agent The amount added is 70,000ppm per kilogram of low-density polyethylene copolymer, and the amount of antioxidant is 4,000ppm per kilogram of low-density polyethylene copolymer.

Example 5

The reversibly cross-linked polyethylene cable material obtained in Example 4 was again added to a 35-type twin-screw extruder (Belonkoya Nanjing Machinery Co., Ltd.) for melting. The melting section temperature of the extruder was 200°C. The melt was heated at 200°C. ℃, the extruded product is cooled in a circulating water bath and pelletized, and then dried and screened to obtain the final product.

Example 6

The reversibly cross-linked polyethylene cable material obtained in Example 5 was again added to a 35-type twin-screw extruder (Belonkoa Nanjing Machinery Co., Ltd.) for melting. The melting section temperature of the extruder was 200°C. The melt was heated at 200°C. ℃, the extruded product is cooled in a circulating water bath and pelletized, and then dried and screened to obtain the final product.

Example 7

1) A tubular high-pressure polyethylene reactor with four reaction zones is used as the reaction device. The temperatures of the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone are 296°C, 287°C, and 285°C respectively. ℃, 280℃, the reactor pressure is set to 285Mpa, and ethylene and 2-methyl-4-vinylbenzaldehyde are introduced into the reactor at a flow rate of 50t/h and 3.24t/h respectively for preheating. The reaction temperature of the final material reaches 165°C, and the material is passed through the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone in sequence, and at the same time, the inlet of the first reaction zone is passed at a flow rate of 110kg/h. Add the molecular weight regulator, and inject the initiator into the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone at four points through the injection pump. The total amount of initiator added is 0.18t/h, initiating 4 A low-density polyethylene copolymer was prepared through step polymerization, and the aldehyde group content in the copolymer was 10.34 mol%;

Among them, the coupling agent is p-phenylenediamine, and the antioxidant is a mixture obtained by mixing hindered phenol antioxidant 1010 and phosphite antioxidant 168 in a mass ratio of 2:1; the amount of coupling agent added is based on Add 90,000ppm per kilogram of low-density polyethylene copolymer, and add 4,500ppm of antioxidant per kilogram of low-density polyethylene copolymer.

Example 8

1) A tubular high-pressure polyethylene reactor with four reaction zones is used as the reaction device. The temperatures of the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone are 295°C, 288°C, and 287°C respectively. ℃, 275℃, the reactor pressure is set to 285Mpa, and ethylene and 2-methyl-4-vinylbenzaldehyde are introduced into the reactor at a flow rate of 50t/h and 4.86t/h respectively for preheating. The reaction temperature of the final material reaches 165°C, and the material is passed through the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone in sequence, and at the same time, the inlet of the first reaction zone is passed at a flow rate of 150kg/h. Add the molecular weight regulator, and inject the initiator into the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone at four points through the injection pump. The total amount of initiator added is 0.20t/h, initiating 4 A low-density polyethylene copolymer was prepared through step polymerization, and the aldehyde group content in the copolymer was 14.51 mol%;

Among them, the coupling agent is 2-methyl-p-phenylenediamine, and the antioxidant is a mixture obtained by mixing hindered phenol antioxidant 1010 and phosphite antioxidant 168 in a mass ratio of 2:1; The addition amount is 110,000ppm per kilogram of low-density polyethylene copolymer, and the addition amount of antioxidant is 5,000ppm per kilogram of low-density polyethylene copolymer.

Example 9

1) A tubular high-pressure polyethylene reactor with four reaction zones is used as the reaction device. The temperatures of the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone are 298°C, 288°C, and 287°C respectively. ℃, 275℃, the reactor pressure is set to 285Mpa, and ethylene and 2-vinylbenzaldehyde are introduced into the reactor at a flow rate of 50t/h and 4.12t/h respectively for preheating, so that the reaction of the preheated materials The temperature reaches 165°C, and the material is passed through the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone in sequence. At the same time, the molecular weight regulator is introduced at the entrance of the first reaction zone at a flow rate of 130kg/h. The initiator was injected into the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone at four points through the injection pump. The total amount of initiator added was 0.18t/h to initiate the 4-stage polymerization reaction to prepare A low-density polyethylene copolymer was obtained, and the aldehyde group content in the copolymer was 12.17 mol%;

Among them, the coupling agent is 2-chloro-p-phenylenediamine, and the antioxidant is a mixture obtained by mixing hindered phenol antioxidant 1010 and phosphite antioxidant 168 in a mass ratio of 2:1; the addition of coupling agent The amount added is 75,000ppm per kilogram of low-density polyethylene copolymer, and the amount of antioxidant added is 7,000ppm per kilogram of low-density polyethylene copolymer.

Comparative example 1

1) A tubular high-pressure polyethylene reactor with four reaction zones is used as the reaction device. The temperatures of the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone are 295°C, 285°C, and 285°C respectively. ℃, 275℃, the reactor pressure is set to 285Mpa, and ethylene is introduced into the reactor at a flow rate of 50t/h for preheating, so that the reaction temperature of the preheated material reaches 165℃, and the material is passed through the first reaction zone, second reaction zone, third reaction zone, and fourth reaction zone. At the same time, the molecular weight regulator is introduced at the inlet of the first reaction zone at a flow rate of 100kg/h, and the initiator is injected into the first reaction zone at four points through the injection pump. In the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone, the total amount of initiator added is 0.17t/h, initiating the 4-stage polymerization reaction to prepare low-density polyethylene;

2) In a high-speed mixer, mix the low-density polyethylene prepared in step 1) and the antioxidant at high speed to obtain a mixture. The mixture was extruded through a 35-type twin-screw extruder (Belonkoya Nanjing Machinery Co., Ltd.) at 200°C. The extruded product was cooled by circulating water, and then pelletized by a pelletizer. The pellets were dried and screened. Get polyethylene;

Among them, the antioxidant is a mixture of hindered phenol antioxidant 1010 and phosphite antioxidant 168 at a mass ratio of 2:1; the amount of antioxidant added is 4000ppm per kilogram of low-density polyethylene.

Comparative example 2

1) Step 1) of this comparative example is consistent with step 1) of Example 1;

2) Add the low-density polyethylene copolymer prepared in step 1) and the antioxidant into a high-speed mixer, and mix the above components uniformly at high speed to obtain a mixture. The mixture was extruded through a 35-type twin-screw extruder (Belonkoya Nanjing Machinery Co., Ltd.) at 200°C. The extruded product was cooled by circulating water, and then pelletized by a pelletizer. The pellets were dried and screened. Obtain 2-vinylbenzaldehyde graft-modified polyethylene;

Among them, the antioxidant is a mixture of hindered phenol antioxidant 1010 and phosphite antioxidant 168 at a mass ratio of 2:1; the amount of antioxidant added is 4000 ppm per kilogram of polyethylene.

Comparative example 3

1) Step 1) of this comparative example is consistent with step 1) of comparative example 1;

2) Add the low-density polyethylene and antioxidant prepared in step 1) into a high-speed mixer, and mix the above components uniformly at high speed to obtain a mixture. The mixture was extruded through a 35-type twin-screw extruder (Belonkoya Nanjing Machinery Co., Ltd.) at 200°C. The extruded product was cooled by circulating water, and then pelletized by a pelletizer. The pellets were dried and screened. Obtain polyethylene pellets;

3) Mix the polyethylene granules prepared in step 2) with a peroxide cross-linking agent, and then absorb, cool, and package to obtain cross-linked polyethylene cable material;

Among them, the peroxide cross-linking agent is di-tert-butyl peroxide, and the added amount of the peroxide cross-linking agent is 80,000 ppm per kilogram of polyethylene pellets.

Comparative example 4

The preparation method of the reversibly cross-linked polyethylene cable material of this comparative example includes the following steps:

1) A tubular high-pressure polyethylene reactor with four reaction zones is used as the reaction device. The temperatures of the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone are 295°C, 285°C, and 285°C respectively. , 275℃, the reactor pressure is set to 285MPa, ethylene and 6-furan-1-hexene are introduced into the reactor at a flow rate of 50t/h and 2.95t/h respectively for preheating, so that the preheated material The reaction temperature reaches 165°C, and the materials are passed through the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone in sequence. At the same time, the molecular weight regulator is introduced at the entrance of the first reaction zone at a flow rate of 100kg/h. , inject the initiator into the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone at four points through the injection pump. The total amount of initiator added is 0.17t/h to initiate the 4-stage polymerization reaction. Prepare low-density polyethylene copolymer;

2) Add the low-density polyethylene copolymer, coupling agent, and antioxidant mentioned in step 1) into a high-speed mixer, and mix the above components at high speed to obtain a mixture. The mixture was extruded through a 35-type twin-screw extruder (Belonkoya Nanjing Machinery Co., Ltd.) at 200°C. The extruded product was cooled by circulating water, and then pelletized by a pelletizer. The pellets were dried and screened. Obtain reversibly cross-linked polyethylene cable material;

Among them, the coupling agent is 1,6-bis(maleimido)hexane, and the antioxidant is obtained by mixing hindered phenol antioxidant 1010 and phosphite antioxidant 168 at a mass ratio of 2:1. The mixture; the coupling agent is added in an amount of 80,000ppm per kilogram of low-density polyethylene copolymer, and the antioxidant is added in an amount of 4,000ppm per kilogram of low-density polyethylene copolymer.

Test example 1

Conduct an infrared spectrum test on the cable materials of Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4. The test method is: press the sample above the melting temperature into a sheet with a thickness of less than 2 mm, and pass the Fourier transform Transform infrared spectroscopy (FT-IR) was used to analyze the characteristic peaks of the sample.

Figure 1 is a comparison chart of the infrared spectra of the cable materials of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3; Figure 2 is a comparison chart of the infrared spectra of the cable materials of Example 1 and Comparative Example 4.

Comparative Example 1 is an uncrosslinked low-density polyethylene cable material, Comparative Example 2 is a low-density polyethylene copolymer cable material prepared from ethylene and vinyl benzaldehyde, and Comparative Example 3 is an irreversibly cross-linked low-density polyethylene cable. Material, Example 1 is a low-density polyethylene copolymer cable material prepared by ethylene and vinyl benzaldehyde with reversible cross-linking of imine bonds. As can be seen from Figure 1, the cable material of Comparative Example 2 has an aldehyde group absorption peak at 1725cm ^-1 , indicating that vinyl benzaldehyde is polymerized to the polyethylene chain; the cable material of Example 1 appears at 1627cm ^-1 The C=N bond absorption peak is detected, indicating that the cable material of Example 1 contains an imine bond covalently cross-linked network.

Example 4 is a reversibly cross-linked polyethylene cable material prepared by DA reaction. As can be seen from Figure 2, the cable material of Comparative Example 4 has an in-plane bending vibration absorption peak of cyclic molecules at 1197 cm ^-1 . The formation of ring structures is illustrated.

Test example 2

The cable materials obtained in the above examples and comparative examples were tested for the following parameters:

1. Melt flow rate (MFR): measured in accordance with GB/T 3682.1-2018 at 190°C and 2.16kg load.

2. Density: tested in accordance with GB/T 1033.2.

3. Tensile strength: tested in accordance with GB/T 1040.3-2006.

4. Elongation at break: tested in accordance with GB/T 1040.3-2006.

5. Vicat softening temperature: tested according to GB/T1633-2000.

6. Intermediate point constant: tested in accordance with GB/T1409-2006.

7. Intermediate point loss tangent: tested in accordance with GB/T1409-2006.

The test results of the above parameters are shown in Table 1.

Table 1

1) Compared with the low-density polyethylene prepared in Comparative Example 1, the tensile strength, elongation at break, and Vicat softening temperature of Examples 1 to 9 are significantly improved. Compared with the low-density polyethylene with pre-embedded cross-linking agent (Comparative Example 3), the performance of Examples 1 to 9 is better than that of Comparative Example 3, especially because the cumbersome process steps of pre-embedded cross-linking agent are reduced. Compared with Comparative Example 3, Examples 1 to 9 show a significant decrease in the point constant and point loss tangent of the cable material.

2) From the comparison of Example 4, Example 5 and Example 6, it can be seen that the material properties of the cable material of the present application remain basically unchanged after multiple processing treatments. This is due to the properties of the cable material of the present application. Thermal reversible cross-linking function allows the cross-linked structure of the cable material to be stably restored after repeated processing. This is completely different from the permanent cross-linked network formed by traditional cross-linked polyethylene, thus giving the cross-linked polymer excellent thermoplastic properties.

3) The Vicat softening temperatures of the cable materials in Examples 1 to 9 of the present application are all higher than those in Comparative Examples 1 to 4, which indicates that the cable materials of the present application have excellent heat resistance.

In addition, thanks to the characteristics of associative dynamic covalent bonds, even above the Vicat softening temperature, the low-density polyethylene copolymer in the cable material of the present application still has a cross-linked structure, which reduces the melt viscosity of the material. Slowly, greatly broadening the processing temperature window and processing stability. The thermally reversible cross-linked polyethylene prepared by this application fully meets the requirements for use of high-voltage polyethylene cable materials.

To sum up, when the cable material of the present application is melted and processed, it has the remarkable characteristics of de-crosslinking at high temperature (during processing) and easy processing, and cross-linking is formed at low temperature (after molding), and has excellent various properties.

The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still implement the foregoing implementations The technical solutions described in the examples are modified, or some or all of the technical features are equivalently replaced; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions in the embodiments of the present application.

Claims

A reversibly cross-linked polyethylene cable material, wherein the raw materials of the cable material include polyethylene copolymer and coupling agent;

The polyethylene copolymer is obtained by copolymerization of polymerized monomers; the polymerized monomers include ethylene, vinyl benzaldehyde and/or vinyl benzaldehyde derivatives;

The coupling agent is selected from polybasic primary amine compounds.
The reversibly cross-linked polyethylene cable material according to claim 1, wherein the coupling agent is selected from compounds of formula (I):

H 2 NR 1 -NH 2 formula (I)

In formula (I), R 1 is selected from a C1 to C12 alkyl group, a C6 to C12 substituted or unsubstituted aryl group, or a C6 to C12 substituted or unsubstituted heteroaryl group;

Wherein, the substituents in the substituted aryl group or the substituted heteroaryl group are selected from C1 to C3 alkyl groups or halogens.
The reversibly cross-linked polyethylene cable material according to claim 1, wherein R1 is selected from C2 or C3 linear alkyl groups.
The reversibly cross-linked polyethylene cable material according to any one of claims 1 to 3, wherein the derivative of vinyl benzaldehyde is selected from the group consisting of vinyl benzaldehyde containing at least one C1-C6 alkyl substituted on the benzene ring. compound.
The reversibly cross-linked polyethylene cable material according to any one of claims 1 to 4, wherein the mass ratio of the polyethylene copolymer to the coupling agent is 100: (1-20).
The reversibly cross-linked polyethylene cable material according to any one of claims 1 to 5, wherein the polyethylene copolymer includes 70% to 93% of ethylene units and 5% to 29% of vinylbenzene based on molar content. Formaldehyde units and/or vinylbenzaldehyde derivative units.
The reversibly cross-linked polyethylene cable material according to any one of claims 1 to 6, wherein the polyethylene copolymer is a low-density polyethylene copolymer.
The reversibly cross-linked polyethylene cable material according to claim 7, wherein the low-density polyethylene copolymer is prepared by a method including the following steps:

Add polymerized monomers to the high-pressure polyethylene reactor, causing the polymerized monomers to undergo a first-stage polymerization reaction at 280°C to 300°C to obtain a first polymerization product; causing the first polymerization product to undergo a second-stage polymerization reaction at 285°C to 295°C. A two-stage polymerization reaction is performed to obtain a second polymerization product; the second polymerization product is subjected to a third-stage polymerization reaction at 280°C to 290°C to obtain a third polymerization product; the third polymerization product is subjected to a third-stage polymerization reaction at 270°C to 285°C. Four-stage polymerization reaction produces low-density polyethylene copolymer.
The reversibly cross-linked polyethylene cable material according to claim 8, wherein before adding the polymerized monomer into the high-pressure polyethylene reactor, it includes the step of preheating the polymerized monomer, and the temperature of the preheated polymerized monomer is It is 160℃~170℃.
The reversibly cross-linked polyethylene cable material according to any one of claims 1 to 9, wherein the raw materials of the cable material further include an antioxidant.
The reversibly cross-linked polyethylene cable material according to claim 10, wherein the mass ratio of polyethylene copolymer, coupling agent and antioxidant is 100: (2～15): (0.3～0.7).
A method for preparing a reversibly cross-linked polyethylene cable material according to any one of claims 1 to 11, which includes: mixing the raw materials of the cable material to obtain a mixture; and extruding the mixture to obtain The reversible cross-linked polyethylene cable material.
The preparation method according to claim 12, wherein the temperature of the extrusion treatment is 190-230°C.