CN113571233B

CN113571233B - Thermoplastic cable with modified polypropylene insulating layer

Info

Publication number: CN113571233B
Application number: CN202011190904.7A
Authority: CN
Inventors: 李琦; 袁浩; 宋文波; 何金良; 王宇韬; 胡军; 邵清; 周垚
Original assignee: Sinopec Beijing Research Institute of Chemical Industry; Tsinghua University; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Research Institute of Chemical Industry; Tsinghua University; China Petroleum and Chemical Corp
Priority date: 2020-04-29
Filing date: 2020-10-30
Publication date: 2023-05-09
Anticipated expiration: 2040-10-30
Also published as: CN113571233A

Abstract

The invention belongs to the field of electricity, and relates to a thermoplastic cable with a modified polypropylene insulating layer. The cable includes: at least one conductor and at least one electrically insulating layer surrounding the conductor; wherein the material of the electric insulating layer is at least one silane grafted modified polypropylene material; the silane grafted modified polypropylene material comprises structural units derived from copolymerized polypropylene and structural units derived from alkenyl-containing silane monomers; the content of the structural unit which is derived from the alkenyl-containing silane monomer and is in a grafted state in the silane grafted modified polypropylene material is 0.2 to 6 weight percent based on the weight of the silane grafted modified polypropylene material. The cable has higher working temperature, and has the advantages of thinner thickness of an electric insulation layer, better heat dissipation and smaller weight under the condition of ensuring the same voltage level and insulation level.

Description

Thermoplastic cable with modified polypropylene insulating layer

Technical Field

The invention belongs to the field of electricity, and particularly relates to a thermoplastic cable with a modified polypropylene insulating layer.

Background

At present, the high-voltage direct-current cable at home and abroad generally adopts crosslinked polyethylene as an insulating material, the working temperature is 70 ℃, the long-term working design field intensity is about 12kV/mm, the running environment of cable insulation is more severe due to the further improvement of the temperature and the electric field intensity along with the further improvement of the running voltage and the conveying capacity of the high-voltage direct-current cable, and the high-voltage direct-current cable has higher requirements on the performance of the cable insulating material, namely has stronger insulating performance under the conditions of higher temperature and electric field intensity. However, the working temperature of the conventional crosslinked polyethylene has reached the use limit and cannot be further improved, so that development of a novel direct current cable with high Wen Gaochang insulating material is urgently needed to meet the requirement of the cable system for working under the condition of high voltage and large capacity.

The current manufacture of the crosslinked polyethylene insulated direct current cable adopts a three-layer co-extrusion insulation preparation mode. The extrusion process mainly comprises three steps of heating and melting, crosslinking (vulcanization) and cooling and forming of the insulating material. The crosslinking initiator is generally used for crosslinking the polyethylene molecules, which complicates the production process of the cable, and the introduction of the crosslinking initiator inevitably introduces crosslinking by-product impurities into the main insulation, which can have a certain negative effect on the insulation performance of the finished cable. In addition, crosslinked polyethylene belongs to thermosetting plastics, cannot be recycled, and the pyrolysis products of the crosslinked polyethylene have great harm to the environment. Therefore, in order to simplify the production process flow of the cable, improve the final quality of cable insulation, eliminate the possible harm to the environment, it is necessary to find a novel thermoplastic recyclable cable insulation material and a preparation process thereof, so as to replace the traditional polyethylene material and a crosslinking process thereof, and realize the manufacturing and engineering application of the recyclable insulated power cable with low cost and high performance.

Disclosure of Invention

The invention aims to solve the problem that the existing cable product cannot meet the requirement of stable operation at high temperature and high field intensity, and provides a thermoplastic cable with a modified polypropylene insulating layer. Compared with the existing cable, the cable can still keep even higher volume resistivity and stronger breakdown resistance at higher working temperature, and meanwhile, the mechanical property of the cable can also meet the use requirement of the cable.

The present invention provides a thermoplastic cable having a modified polypropylene insulation layer, the cable comprising:

at least one conductor and at least one electrically insulating layer surrounding the conductor;

wherein the material of the electric insulating layer is at least one silane grafted modified polypropylene material;

the silane grafted modified polypropylene material comprises structural units derived from copolymerized polypropylene and structural units derived from alkenyl-containing silane monomers; the content of the structural unit in the grafted state derived from the alkenyl group-containing silane monomer in the silane graft modified polypropylene material is 0.2 to 6wt%, preferably 0.2 to 2.5wt%, based on the weight of the silane graft modified polypropylene material.

The core of the invention is to use a new material as the electric insulation layer of the cable, so the invention is not particularly limited to the form and specific structure of the cable, and various cable forms (direct current or alternating current, single core or multi-core) and corresponding various structures can be adopted. In the cable, other layer structures and other layer materials can be selected conventionally in the field except that the electric insulating layer is made of a novel grafted modified polypropylene material.

The cable of the invention may be a direct current cable or an alternating current cable; preferably a direct current cable; more preferably, the cable is a medium-high voltage direct current cable or an extra-high voltage direct current cable. In the present invention, low Voltage (LV) means a voltage below 1kV, medium Voltage (MV) means a voltage in the range of 1kV to 40kV, high Voltage (HV) means a voltage above 40kV, preferably above 50kV, and Extra High Voltage (EHV) means a voltage of at least 230 kV.

According to a preferred embodiment of the invention, the cable has at least one cable core, each comprising, in order from inside to outside: a conductor, an optional conductor shield layer, an electrically insulating layer, an optional electrically insulating shield layer, an optional metal shield layer. Wherein, the conductor shielding layer, the electric insulation shielding layer and the metal shielding layer can be arranged according to the requirement, and are generally used in cables with the voltage of more than 6 kV.

In addition to the above structure, the cable may further comprise an armor and/or jacket layer.

The cable of the present invention may be a single core cable or a multi-core cable, for which the cable may further comprise a filler layer and/or a tape layer. The filling layer is formed by filling materials filled between the wire cores. The wrapping tape layer is wrapped on the outer sides of all the wire cores, the wire cores and the filling layer are guaranteed to be round, the wire cores are prevented from being scratched by armor, and the flame-retardant effect is achieved.

In the cable of the invention, the conductor is a conductive element, typically made of a metallic material, preferably aluminum, copper or other alloys, comprising one or more metallic wires. The direct current resistance and the number of monofilaments of the conductor are required to meet the requirements of GB/T3956. The preferred conductor adopts a compressed stranded round structure, and the nominal sectional area is less than or equal to 800mm ² The method comprises the steps of carrying out a first treatment on the surface of the Or a split conductor structure is adopted, and the nominal sectional area is more than or equal to 1000mm ² The number of conductors is not less than 170.

In the cable of the present invention, the conductor shield layer may be a cover layer made of polypropylene, polyolefin elastomer, carbon black or the like, and has a volume resistivity of < 1.0 Ω·m at 23 ℃, a volume resistivity of < 3.5 Ω·m at 90 ℃, and a melt flow rate of usually 0.01 to 30g/10min, preferably 0.05 to 20g/10min, more preferably 0.1 to 10g/10min, and even more preferably 0.2 to 8g/10min at 230 ℃ under a 2.16kg load; the tensile strength is more than or equal to 12.5MPa; the elongation at break is more than or equal to 150 percent. The thickness of the thinnest point of the conductor shielding layer is not less than 0.5mm, and the average thickness is not less than 1.0mm.

In the cable of the present invention, the material of the electrical insulation layer is at least one silane-grafted modified polypropylene material, meaning that the substrate constituting the electrical insulation layer is the silane-grafted modified polypropylene material, and may comprise further components, such as a polymer component or an additive, in addition to the silane-grafted modified polypropylene material, preferably additives, such as any one or more of antioxidants, stabilizers, processing aids, flame retardants, water tree retarding additives, acid or ion scavengers, inorganic fillers, voltage stabilizers and anti-copper agents. The types and amounts of additives are conventional and known to those skilled in the art.

The method for producing an electrical insulating layer of the present invention may also employ a method conventional in the cable production field, for example, mixing a silane-grafted modified polypropylene material with optional various additives, granulating with a twin-screw extruder, and extruding the obtained granules through the extruder to produce an electrical insulating layer. Typically, the conductor shield material may be co-extruded with pellets of silane grafted modified polypropylene material to form a conductor shield layer + electrical insulation layer structure, or to form a conductor shield layer + electrical insulation shield layer structure. Specific operations may employ methods and process conditions conventional in the art.

Because the silane grafted modified polypropylene material is adopted, the thickness of the electric insulating layer can be only 50-95% of the nominal thickness value of the XLPE insulating layer in GB/T12706, preferably, the thickness of the electric insulating layer is 70-90% of the nominal thickness value of the XLPE insulating layer in GB/T12706; the eccentricity is not more than 10%.

In the cable of the present invention, the electrically insulating shield layer may be a cover layer made of polypropylene, polyolefin elastomer, carbon black or the like, and has a volume resistivity of < 1.0 Ω·m at 23 ℃ and a volume resistivity of < 3.5 Ω·m at 90 ℃. The melt flow rate under a load of 2.16kg at 230℃is 0.01 to 30g/10min, preferably 0.05 to 20g/10min, more preferably 0.1 to 10g/10min, still more preferably 0.2 to 8g/10min; the tensile strength is more than or equal to 12.5MPa; the elongation at break is more than or equal to 150 percent. The thinnest point thickness of the electrically insulating shielding layer is not less than 0.5mm, and the average thickness is not less than 1.0mm.

In the cable of the present invention, the metal shielding layer may be a copper tape shielding layer or a copper wire shielding layer.

In the cable of the present invention, the filler layer may be a polymer material such as PE/PP/PVC or recycled rubber material.

In the cable, the wrapping layer/armor layer is a metal covering layer which is made of a copper wire metal cage, a lead or aluminum metal sleeve and the like and wraps the outer surface of the electric insulation shielding layer, and the direct-current volume resistivity of the cable is less than or equal to 1000Ω & m at room temperature.

In the cable of the present invention, the material of the sheath layer may be any one of polyvinyl chloride, polyethylene or low smoke halogen-free material. The sheath layer includes both an inner sheath layer and an outer sheath layer.

The above layer structures can be prepared by conventional methods in the art. For example, the conductor shield, the electrical insulation, and the jacket layer may be formed by extrusion coating through an extruder, and the metal shield and armor may be formed by wrapping.

In the silane-grafted modified polypropylene material used in the present invention, the "structural unit" means that it is a part of the silane-grafted modified polypropylene material, and the form thereof is not limited. In particular, "structural units derived from a copolymerized polypropylene" refers to products formed from the copolymerized polypropylene, including both "radical" forms and "polymeric" forms. "structural units derived from alkenyl-containing silane-based monomers" refers to products formed from alkenyl-containing silane-based monomers, including both "radical" forms and "monomer" forms and also "polymer" forms. The "structural units" may be repeating units or may be non-repeating independent units.

In the present invention, the structural unit derived from the alkenyl group-containing silane-based monomer "in a grafted state" means a structural unit derived from the alkenyl group-containing silane-based monomer forming a covalent bond (grafting) with the copolymer.

In the present invention, the meaning of "comonomer" of the polypropylene copolymer is known to the person skilled in the art and refers to a monomer copolymerized with propylene.

According to the invention, the grafted modified polypropylene material is preferably prepared by grafting reaction, preferably solid phase grafting reaction, of copolymerized polypropylene and an alkenyl-containing silane monomer. The grafting reaction of the present invention is a radical polymerization reaction, and thus, the "in a grafted state" means a state in which a reactant forms a connection with another reactant after radical polymerization. The connection includes both direct and indirect connections.

During the grafting reaction, the alkenyl-containing silane-based monomer may polymerize to form a certain amount of ungrafted polymer. The term "grafted modified polypropylene material" of the present invention includes both a product (crude product) directly obtained by grafting reaction of a copolymer polypropylene and an alkenyl-containing silane-based monomer and a pure product of the grafted modified polypropylene obtained by further purifying the product.

According to the invention, the silane-grafted modified polypropylene material as the electrical insulation layer material preferably has at least one of the following characteristics: the melt flow rate under a load of 2.16kg at 230℃is 0.01 to 30g/10min, preferably 0.05 to 20g/10min, more preferably 0.1 to 10g/10min, still more preferably 0.2 to 5g/10min; the flexural modulus is 20 to 900MPa, more preferably 50 to 600MPa; the elongation at break is more than or equal to 200 percent, preferably more than or equal to 300 percent; the tensile strength is more than 5MPa, preferably 10-40 MPa.

Further, in terms of electrical properties, the silane grafted modified polypropylene material has at least one of the following characteristics:

the working temperature of the silane grafted modified polypropylene material is more than or equal to 90 ℃, preferably 90-160 ℃;

-the breakdown field strength E of the silane grafted modified polypropylene material at 90 °c _g More than or equal to 200kV/mm, preferably 200-800 kV/mm;

-the breakdown field strength E of the silane grafted modified polypropylene material at 90 °c _g The change rate delta E/E of the breakdown field intensity obtained by dividing the difference delta E of the breakdown field intensity E of the copolymerization polypropylene at 90 ℃ by the breakdown field intensity E of the copolymerization polypropylene at 90 ℃ is more than 0.7%, preferably 0.8-40%, more preferably 2-20%, and even more preferably 6-15%;

-the direct current volume resistivity ρ of the silane grafted modified polypropylene material at 90 ℃, 15kV/mm field strength _vg ≥6×10 ¹² Omega.m, preferably 6X 10 ¹² Ω·m～1.0×10 ²⁰ Ω·m；

-the direct current volume resistivity ρ of the silane grafted modified polypropylene material at 90 ℃, 15kV/mm field strength _vg DC volume resistivity ρ with the copolymer polypropylene at 90 ℃ and 15kV/mm field strength _v Ratio ρ of (2) _vg /ρ _v Greater than 1, preferably 1.1 to 8.0, more preferably 1.15 to 3, still more preferably 1.2 to 1.8;

the silane grafted modified polypropylene material has a dielectric constant at 90 ℃ at 50Hz of more than 2.0, preferably between 2.1 and 2.5.

According to the present invention, the copolymerized polypropylene (base polypropylene in the present invention) is a propylene copolymer containing ethylene or higher α -olefin or a mixture thereof. In particular, the polypropylene copolymerThe comonomer is selected from C other than propylene ₂ -C ₈ At least one of the alpha-olefins of (a). Said C other than propylene ₂ -C ₈ The alpha-olefins of (a) include, but are not limited to: at least one of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene, preferably ethylene and/or 1-butene, further preferably the copolymerized polypropylene consists of propylene and ethylene.

The copolymer polypropylene of the present invention may be a heterophasic propylene copolymer. The heterophasic propylene copolymer may contain a propylene homopolymer or propylene random copolymer matrix component (1), and a further propylene copolymer component (2) dispersed therein. In propylene random copolymers, the comonomer is randomly distributed in the backbone of the propylene polymer. Preferably, the copolymerized polypropylene of the present invention is a heterophasic propylene copolymer prepared in situ (in situ) in the reactor by existing processes.

According to a preferred embodiment, the heterophasic propylene copolymer comprises a propylene homopolymer matrix or random copolymer matrix (1), and dispersed therein a propylene copolymer component (2) comprising one or more ethylene or higher alpha-olefin comonomers. The heterophasic propylene copolymer may be of islands-in-the-sea or bicontinuous structure.

Two heterophasic propylene copolymers are known in the art, heterophasic propylene copolymers containing a propylene random copolymer as matrix phase or heterophasic propylene copolymers containing a propylene homopolymer as matrix phase. The random copolymer matrix (1) is a copolymer formed by the random distribution of comonomer moieties on the polymer chain, in other words, consisting of an alternating sequence of two monomer units of random length (comprising a single molecule). Preferably the comonomer in the matrix (1) is selected from ethylene or butene. It is particularly preferred that the comonomer in the matrix (1) is ethylene.

Preferably, the propylene copolymer (2) dispersed in the homo-or copolymer matrix (1) of the heterophasic propylene copolymer is substantially amorphous. The term "substantially amorphous" means herein that the propylene copolymer (2) has a lower crystallinity than the homopolymer or copolymer matrix (1).

According to the invention, in addition to the above compositional features, the copolypropylene has at least one of the following features: the comonomer content is 0.5 to 40mol%, preferably 0.5 to 30mol%, preferably 4 to 25wt%, more preferably 4 to 22wt%; the xylene solubles content is 2 to 80wt%, preferably 18 to 75wt%, further preferably 30 to 70wt%, more preferably 30 to 67wt%; the comonomer content in the solubles is 10 to 70wt%, preferably 10 to 50wt%, more preferably 20 to 35wt%; the intrinsic viscosity ratio of the soluble substance to the polypropylene is 0.3 to 5, preferably 0.5 to 3, more preferably 0.8 to 1.3.

According to the present invention, preferably, the copolymerized polypropylene further has at least one of the following characteristics: the melt flow rate under a load of 2.16kg at 230℃is 0.01 to 60g/10min, preferably 0.05 to 35g/10min, more preferably 0.5 to 8g/10min; the melting temperature Tm is 100℃or higher, preferably 110 to 180℃and more preferably 110 to 170℃and still more preferably 120 to 166 ℃. The weight average molecular weight is preferably 20X 10 ⁴ ～60×10 ⁴ g/mol. The base polypropylene having a high Tm has satisfactory impact strength and flexibility at both low and high temperatures, and in addition, the graft modified polypropylene of the present invention has an advantage of being able to withstand higher working temperatures when using the base polypropylene having a high Tm. The polypropylene copolymer of the present invention is preferably a porous particulate or powdery resin.

According to the present invention, preferably, the copolymerized polypropylene further has at least one of the following characteristics: the flexural modulus is 10 to 1000MPa, preferably 50 to 600MPa; the elongation at break is more than or equal to 200 percent, and the elongation at break is more than or equal to 300 percent. Preferably, the tensile strength of the copolymer polypropylene is greater than 5MPa, preferably from 10 to 40MPa.

The polypropylene copolymer of the present invention may include, but is not limited to, any commercially available polypropylene powder suitable for the present invention, such as NS06, SPF179, etc. of chinese petrochemical, marchantia, and may also be produced by the polymerization processes described in chinese patents CN1081683, CN1108315, CN1228096, CN1281380, CN1132865C, CN102020733a, etc. Common polymerization processes include the Spheripol process from Basell, the Hypol process from Sanjing, the Borstar PP process from Borealis, the Unipol process from DOW chemical, the Innovene gas phase process from INEOS (original BP-Amoco), and the like.

The alkenyl-containing silane monomer can be any monomer silane compound capable of being polymerized by free radicals, can be selected from at least one of monomers with a structure shown in a formula I,

Wherein R is ₁ Is C ₂ -C ₁₂ Alkenyl groups of (a), preferably monounsaturated alkenyl groups; r is R ₂ 、R ₃ 、R ₄ Each independently selected from substituted or unsubstituted C ₁ -C ₁₂ Straight-chain alkyl, substituted or unsubstituted C ₃ -C ₁₂ Branched alkyl, substituted or unsubstituted C ₁ -C ₁₂ Alkoxy, substituted or unsubstituted C ₁ -C ₁₂ An acyloxy group of (a); preferably, R ₁ Is C ₂ -C ₆ Alkenyl groups of (a), preferably monounsaturated alkenyl groups; r is R ₂ 、R ₃ 、R ₄ Each independently selected from substituted or unsubstituted C ₁ -C ₆ Straight-chain alkyl, substituted or unsubstituted C ₃ -C ₆ Branched alkyl, substituted or unsubstituted C ₁ -C ₆ Alkoxy, substituted or unsubstituted C ₁ -C ₆ Is an acyloxy group.

More preferably, the alkenyl-containing silane-based monomer is at least one selected from the group consisting of vinyltriethoxysilane, vinyltrimethoxysilane, vinyltriisopropoxysilane, vinyltri-t-butoxysilane, vinyltriacetoxysilane, methylvinyldimethoxysilane, ethylvinyldiethoxysilane, allyltriethoxysilane, allyltrimethoxysilane, allyltriisopropoxysilane, vinyltris (β -methoxyethoxy) silane, allyltris (β -methoxyethoxy) silane, allyltri-t-butoxysilane, allyltriacetoxysilane, methallyldimethoxysilane, and ethylallyldiethoxysilane.

The silane grafted modified polypropylene material can be prepared from copolymerized polypropylene and alkenyl-containing silane monomers through a solid-phase grafting reaction, and specifically can be prepared by a method comprising the following steps: and (3) in the presence of inert gas, carrying out grafting reaction on a reaction mixture comprising the copolymerized polypropylene and the silane monomer containing alkenyl to obtain the silane grafted modified polypropylene material.

The grafting reaction of the present invention can be carried out by referring to various methods conventional in the art, and is preferably a solid phase grafting reaction. For example, active grafting sites are formed on the copolymer polypropylene in the presence of the alkenyl-containing silane-based monomer for grafting, or the copolymer polypropylene is first formed with active grafting sites and then treated with the monomer for grafting. The grafting sites may be formed by treatment with a free radical initiator or by treatment with high energy ionizing radiation or microwaves. The free radicals in the polymer, which are generated as a result of the chemical or radiation treatment, form grafting sites on the polymer and initiate the polymerization of the monomers at these sites.

Preferably, the grafting sites are initiated by a free radical initiator and the grafting reaction is further carried out. In this case, the reaction mixture further comprises a free radical initiator; further preferably, the radical initiator is selected from peroxide-based radical initiators and/or azo-based radical initiators.

Wherein the peroxide radical initiator is preferably at least one selected from dibenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, lauroyl peroxide, t-butyl peroxybenzoate, diisopropyl peroxydicarbonate, t-butyl peroxy2-ethylhexanoate and dicyclohexyl peroxydicarbonate; the azo-based free radical initiator is preferably azobisisobutyronitrile and/or azobisisoheptonitrile.

More preferably, the grafting sites are initiated by peroxide-based free radical initiators and the grafting reaction is further carried out.

Furthermore, the grafting reaction of the present invention may also be carried out by the methods described in CN106543369A, CN104499281A, CN102108112A, CN109251270A, CN1884326a and CN 101492517B.

The amount of each component used in the grafting reaction of the present invention is not particularly limited on the premise of satisfying the above-mentioned product characteristics, and specifically, the mass ratio of the radical initiator to the alkenyl group-containing silane-based monomer may be 0.1 to 10:100, preferably 0.5 to 6:100. The mass ratio of the alkenyl group-containing silane monomer to the copolymerized polypropylene may be 0.5 to 12:100, preferably 0.8 to 9:100, and more preferably 1 to 6:100.

The technological conditions of the grafting reaction are not particularly limited either, and specifically, the temperature of the grafting reaction may be 30 to 130 ℃, preferably 60 to 120 ℃; the time may be 0.5 to 10 hours, preferably 1 to 5 hours.

In the present invention, the "reaction mixture" includes all materials added to the grafting reaction system, and the materials may be added at one time or at different stages of the reaction.

The reaction mixture of the present invention may also include a dispersant, preferably water or an aqueous solution of sodium chloride. The mass amount of the dispersing agent is preferably 50-300% of the mass of the polypropylene copolymer.

The reaction mixture of the present invention may further comprise an interfacial agent which is an organic solvent having a swelling effect on polyolefin, preferably at least one of the following organic solvents having a swelling effect on copolymerized polypropylene: ether solvents, ketone solvents, aromatic hydrocarbon solvents, and alkane solvents; more preferably at least one of the following organic solvents: chlorobenzene, polychlorinated benzene, C ₆ The alkane or cycloalkane, benzene, C ₁ -C ₄ Alkyl-substituted benzene, C ₂ -C ₆ Fatty ethers, C ₃ -C ₆ Aliphatic ketones, decalin; further preferred is at least one of the following organic solvents: benzene, toluene, xylene, chlorobenzene, tetrahydrofuran, diethyl ether, acetone, hexane, cyclohexane, decalin, heptane. The mass content of the interfacial agent is preferably 1 to 30% by mass, more preferably 10 to 25% by mass, of the polypropylene copolymer.

The reaction mixture according to the invention may also comprise an organic solvent, preferably comprising C, as solvent for dissolving the solid free-radical initiator ₂ -C ₅ Alcohols, C ₂ -C ₄ Ethers and C ₃ -C ₅ At least one of the ketones, more preferably comprising C ₂ -C ₄ Alcohols, C ₂ -C ₃ Ethers and C ₃ -C ₅ At least one of the ketones, most preferably at least one of ethanol, diethyl ether and acetone. The mass content of the organic solvent is preferably 1 to 35% of the mass of the polypropylene copolymer.

In the preparation method of the silane grafted modified polypropylene material, the limitation of the alkenyl-containing silane monomer and the copolymerized polypropylene is the same as the previous description, and the description is omitted here.

According to the invention, the preparation method of the silane grafted modified polypropylene material can be selected from one of the following modes:

in one mode, the preparation method comprises the following steps:

a. placing the polypropylene copolymer in a closed reactor for inert gas replacement;

b. adding a free radical initiator and an alkenyl-containing silane monomer into the closed reactor, and stirring and mixing;

c. optionally adding an interfacial agent, and optionally swelling the reaction system;

d. optionally adding a dispersing agent, heating the reaction system to a grafting reaction temperature, and carrying out grafting reaction;

e. After the reaction is finished, the silane grafted modified polypropylene material is obtained by optionally filtering (in the case of using an aqueous dispersing agent) and drying.

More specifically, the preparation method comprises the following steps:

b. dissolving a free radical initiator in an alkenyl-containing silane monomer to prepare a solution, adding the solution into a closed reactor filled with polypropylene copolymer, and stirring and mixing;

c. adding 0-30 parts of interfacial agent, and optionally swelling the reaction system at 20-60 ℃ for 0-24 hours;

d. adding 0-300 parts of dispersing agent, heating the system to the grafting polymerization temperature of 30-130 ℃ and reacting for 0.5-10 hours;

In a second mode, the preparation method includes the following steps:

b. mixing an organic solvent and a free radical initiator, and adding the mixture into the closed reactor;

c. removing the organic solvent;

d. adding an alkenyl-containing silane monomer, optionally adding an interfacial agent, and optionally swelling the reaction system;

e. Optionally adding a dispersing agent, heating the reaction system to a grafting reaction temperature, and carrying out grafting reaction;

f. after the reaction is finished, the silane grafted modified polypropylene material is obtained by optionally filtering (in the case of using an aqueous dispersing agent) and drying.

More specifically, the preparation method comprises the following steps:

b. mixing an organic solvent and a free radical initiator to prepare a solution, and adding the solution into a closed reactor filled with the polypropylene copolymer;

c. purging with an inert gas or removing the organic solvent by vacuum;

d. adding silane monomer containing alkenyl, adding 0-30 parts of interface agent, and optionally swelling the reaction system at 20-60 ℃ for 0-24 hours;

e. adding 0-300 parts of dispersing agent, heating the system to the grafting polymerization temperature of 30-130 ℃ and reacting for 0.5-10 hours;

According to the process of the invention, if volatile components are present in the system after the end of the reaction, the process of the invention preferably comprises a step of devolatilization, which can be carried out by any conventional method, including vacuum extraction or the use of stripping agents at the end of the grafting process. Suitable stripping agents include, but are not limited to, inert gases.

As described above, the "silane-grafted modified polypropylene material" of the present invention includes both a product (crude product) directly obtained by grafting a copolymer polypropylene and an alkenyl group-containing silane-based monomer and a pure product of the graft-modified polypropylene obtained by further purifying the product, and therefore, the preparation method of the present invention may optionally include a step of purifying the crude product. The purification may be carried out by various methods conventional in the art, such as extraction.

The grafting efficiency of the grafting reaction is not particularly limited, but the higher grafting efficiency is more beneficial to obtaining the silane grafted modified polypropylene material with the required performance through one-step grafting reaction. Therefore, the grafting efficiency of the grafting reaction is preferably controlled to be 5 to 100%, more preferably 5 to 60%. The concept of grafting efficiency is well known to those skilled in the art and refers to the amount of silane monomer grafted on/total amount of silane monomer charged in the reaction.

The inert gas of the present invention may be various inert gases commonly used in the art, including but not limited to nitrogen, argon.

The cable of the present invention may be manufactured through various manufacturing processes conventional in the art, and the present invention is not particularly limited thereto.

According to one embodiment of the invention, the cable is prepared as follows:

preparation of conductors: performing compacting and twisting operation on a plurality of monofilament conductors (such as aluminum) to obtain a conductor inner core; or performing wire bundling operation, and then twisting each monofilament conductor after wire bundling to obtain the conductor inner core.

Preparation of alkenyl-containing silane-modified polypropylene particles: the alkenyl-containing silane-modified polypropylene is mixed with optional additives and pelletized using a twin screw extruder.

Preparation of conductor shielding layer and electrical insulation layer: the conductor shielding material and the silane modified polypropylene particles containing alkenyl are subjected to coextrusion cladding outside the conductor inner core through an extruder to form a conductor shielding layer and an electric insulation layer, or to form the conductor shielding layer, the electric insulation layer and the electric insulation shielding layer (outer shielding layer).

Preparation of a metal shielding layer: copper strips or copper wires are wrapped outside the electric insulating layer (electric insulating shielding layer) to form the metal shielding layer.

Preparation of an inner sheath layer: and extruding the sheath layer granules outside the metal shielding layer through an extruder to form an inner sheath layer.

Preparation of armor: the galvanized steel/stainless steel/aluminum alloy is used for manufacturing steel wires or steel tape armors, the single-layer armors or the double-layer armors are wound on the inner sheath layer in the right direction and the outer layer in the left direction, and the steel wires or steel tape armors are tightly wound so that the gaps between adjacent steel wires/steel tapes are minimized.

Preparation of an outer sheath layer: and extruding the sheath layer granules outside the armor through an extruder to form an outer sheath layer.

Finally, the thermoplastic cable with the modified polypropylene insulating layer is prepared.

Compared with the existing cable, the cable can still maintain even higher volume resistivity and stronger breakdown resistance at higher working temperature, and meanwhile, the mechanical property of the cable can also meet the use requirement of the cable. Under the condition of ensuring the same voltage level and insulation level, the electric insulation layer made of the silane grafted modified polypropylene material has the advantages of thinner thickness, better heat dissipation, smaller weight and the like compared with the electric insulation layer of a conventional cable. Therefore, the cable has a wider application range.

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

Drawings

Exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

Fig. 1 is a schematic structural view of a cable according to an embodiment of the present invention.

Description of the reference numerals

1-conductors; 2-a conductor shield layer; 3-an electrically insulating layer; 4-an electrically insulating barrier layer; a 5-metal shielding layer; 6-an inner sheath layer; 7-armoring; 8-an outer sheath layer.

Detailed Description

The following describes specific embodiments of the present invention in detail. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.

In the following examples and comparative examples:

1. determination of comonomer content in the Co-Polypropylene:

comonomer content was determined by quantitative Fourier Transform Infrared (FTIR) spectroscopy. The correlation of the determined comonomer content is calibrated by quantitative Nuclear Magnetic Resonance (NMR) spectroscopy. The basis of quantification ¹³ The method of calibrating the results obtained by C-NMR spectroscopy is performed according to a conventional method in the art.

2. Determination of xylene solubles content in the copolymer polypropylene, comonomer content in the solubles, and intrinsic viscosity ratio of the solubles/copolymer polypropylene:

the test was performed using a CRYST-EX instrument from Polymer Char. Dissolving with trichlorobenzene solvent at 150deg.C, maintaining the temperature for 90min, sampling, cooling to 35deg.C, maintaining the temperature for 70min, and sampling.

3. Measurement of the weight average molecular weight of the copolymer polypropylene:

the sample was dissolved in 1,2, 4-trichlorobenzene by gel permeation chromatography (PL-GPC 220 type of Polymer Laboratory) and the concentration was 1.0mg/ml, as measured by high temperature GPC. The test temperature was 150℃and the solution flow rate was 1.0ml/min. The molecular weight of polystyrene is used as an internal reference to make a standard curve, and the molecular weight and molecular weight distribution of the sample are calculated according to the outflow time.

4. Determination of melt flow Rate MFR:

the measurement was carried out by using a CEAST model 7026 melt index apparatus at 230℃under a load of 2.16kg according to the method specified in GB/T3682-2018.

5. Determination of melting temperature Tm:

the melting process and crystallization process of the material were analyzed using a differential scanning calorimeter. The specific operation is as follows: under the protection of nitrogen, 5-10 mg of samples are measured by adopting a three-stage temperature rise and fall measuring method from 20 ℃ to 200 ℃, and the melting and crystallization processes of the materials are reflected by the change of heat flow, so that the melting temperature Tm is calculated.

6. Determination of grafting efficiency GE, parameter M1:

2-4 g of the grafted product is put into a Soxhlet extractor, extracted for 24 hours by acetone, unreacted monomers and homopolymers thereof are removed, and the pure grafted product is obtained, dried and weighed, and parameters M1 and grafting efficiency GE are calculated.

The parameter M1 represents the content of structural units derived from alkenyl-containing silane monomers in the grafted modified polypropylene material, and in the invention, the calculation formulas of M1 and GE are as follows:

in the above formula, w ₀ Is the mass of the PP matrix; w (w) ₁ Is the quality of grafted products in advance; w (w) ₂ Is the quality of the grafted product after extraction; w (w) ₃ Is the mass of the silane monomer.

7. Measurement of the direct-current volume resistivity:

the measurement was carried out according to the method specified in GB/T1410-2006.

8. Determination of breakdown field strength:

the measurement was performed according to the method specified in GB/T1408-2006.

9. Determination of tensile Strength:

the measurement was carried out according to the method specified in GB/T1040.2-2006.

10. Determination of flexural modulus:

the measurement was carried out according to the method specified in GB/T9341-2008.

11. Determination of elongation at break:

the measurement was carried out according to the method specified in GB/T1040-2006.

12. Measurement of dielectric constant and dielectric loss tangent:

the measurement was carried out according to the method specified in GB/T1409-2006.

13. Determination of the main insulation conductivity (resistivity) ratio of the cable:

the test was performed according to the method specified in TICW 7.1-2012 appendix A. The main insulation conductivity ratio is equal to the main insulation conductivity of the cable at 90 ℃ divided by the main insulation conductivity of the cable at 30 ℃.

14. Cable insulation space charge injection test (measurement of electric field distortion rate):

cable insulation space charge injection experiments were performed according to the method specified in tisw 7.1-2012 appendix B.

15. Direct current withstand voltage test:

the cable was continuously pressurized with 1.85 times of the negative rated voltage for 2 hours at normal temperature. And if no breakdown or discharge phenomenon occurs, the electric power passes through, otherwise, the electric power does not pass through.

16. Load cycle test:

the cable is heated to 90 ℃ at the rated use temperature, is pressurized for 8 hours by adding 1.85 times of rated voltage, is naturally cooled and is removed from the voltage for 16 hours, and is circulated for 12 days. No breakdown phenomenon occurs, namely passing.

The raw materials used in the examples are described in table a below.

Table A

Name of the name	Description of the invention
		Polypropylene copolymer
1 ×	Homemade method described with reference to CN101679557a
		Polypropylene copolymer 2 x	Homemade method described with reference to CN101679557a
Polypropylene copolymer 3	Homemade method described with reference to CN101679557a
		Copolymerized polypropylene 4 ×	Homemade method described with reference to CN101058654a
5 x of copolypropylene	Homemade method described with reference to CN101058654a
		Copolymerized polypropylene 6 ×	Homemade method described with reference to CN101058654a
Polypropylene T30S	Homo-polypropylene and China petrochemical sea-level refining
		Dibenzoyl peroxide	"Bailingwei technology Co., ltd (J)&K Chemicals)
Lauroyl peroxide	"Bailingwei technology Co., ltd (J)&K Chemicals)
		Tert-butyl peroxy (2-ethylhexanoate)	Adamas reagent Co., ltd (adamas-beta)
Vinyl triethoxysilane	"Bailingwei technology Co., ltd (J)&K Chemicals)
		Vinyl triisopropoxysilane	"Bailingwei technology Co., ltd (J)&K Chemicals)
Vinyl trimethoxy silane	"Bailingwei technology Co., ltd (J)&K Chemicals)
		Polyethylene triethoxysilane	Self-made laboratory

* Copolymer polypropylene 1: the polypropylene copolymer used in example 1.

* Copolymer polypropylene 2: the polypropylene copolymer used in example 2.

* Copolymer polypropylene 3: the polypropylene copolymer used in example 3.

* Copolymer polypropylene 4: the polypropylene copolymer used in example 4.

* Copolymer polypropylene 5: the polypropylene copolymer used in example 5.

* Copolymer polypropylene 6: the polypropylene copolymer used in example 6.

Example 1

Selecting basic copolymerized polypropylene powder with the following characteristics: comonomer ethylene content 18.1wt%, xylene solubles content 48.7wt%, comonomer content 31.9wt%, solubles/copolymerized polypropylene intrinsic viscosity ratio 0.89, weight average molecular weight 34.3X10 ⁴ g/mol, MFR at 230℃under a load of 2.16kg of 1.21g/10min, tm=143.4℃and breakdown field strength (90 ℃) of 236kV/mm, DC volume resistivity (90)15 kV/mm) is 1.16E13 Ω -m, and the fine powder smaller than 40 meshes is removed by sieving. 2.0kg of the basic polypropylene copolymer powder is weighed and added into a 10L reaction kettle with mechanical stirring, a reaction system is closed, and nitrogen is replaced for deoxidization. 2.5g of lauroyl peroxide and 50g of vinyltriethoxysilane were added, stirred and mixed for 30min, swollen for 1 hour at 40 ℃, heated to 90℃and reacted for 4 hours. After the reaction is finished, nitrogen purging and cooling are carried out to obtain a polypropylene-g-vinyl triethoxysilane material product C1.

The resulting product was tested for various performance parameters and the results are shown in table 1.

Example 2

Selecting basic copolymerized polypropylene powder with the following characteristics: the ethylene content of the comonomer is 14.7wt%, the xylene solubles content is 41.7wt%, the comonomer content in the solubles is 34.5wt%, the intrinsic viscosity ratio of the solubles/the copolymerized polypropylene is 0.91, and the weight average molecular weight is 36.6X10 ⁴ g/mol, MFR at 230 ℃,2.16kg load of 1.54g/10min, tm=164.9 ℃, breakdown field strength (90 ℃) of 248kV/mm, direct current volume resistivity (90 ℃,15 kV/mm) of 7.25E12 Ω·m, and sieving to remove fine powder smaller than 40 meshes. 2.0kg of the basic polypropylene copolymer powder is weighed and added into a 10L reaction kettle with mechanical stirring, a reaction system is closed, and nitrogen is replaced for deoxidization. 0.9g of dibenzoyl peroxide and 20g of vinyltriethoxysilane are added, stirred and mixed for 60min, and the temperature is raised to 90 ℃ for reaction for 4 hours. After the reaction is finished, nitrogen purging and cooling are carried out to obtain a polypropylene-g-vinyl triethoxysilane material product C2.

Example 3

Selecting basic copolymerized polypropylene powder with the following characteristics: comonomer ethylene content 20.1wt%, xylene solubles content 66.1wt%, comonomer content 29.5wt%, solubles/copolymerized polypropylene intrinsic viscosity ratio 1.23, weight average molecular weight 53.8X10 ⁴ g/mol, MFR at 230℃under a load of 2.16kg of 0.51g/10min, tm=142.5℃and breakdown field strength (90 ℃) of 176kThe volume resistivity of the direct current (90 ℃ C., 15 kV/mm) is 5.63E12 ohm.m, and the fine powder smaller than 40 meshes is removed by sieving. 2.0kg of the basic polypropylene copolymer powder is weighed and added into a 10L reaction kettle with mechanical stirring, a reaction system is closed, and nitrogen is replaced for deoxidization. 6.0g of lauroyl peroxide and 100g of vinyltriethoxysilane are added, stirred and mixed for 60min, swelled for 1 hour at 60 ℃, heated to 90 ℃ and reacted for 4 hours. After the reaction is finished, nitrogen purging and cooling are carried out to obtain a polypropylene-g-vinyl triethoxysilane material product C3.

Example 4

Selecting basic copolymerized polypropylene powder with the following characteristics: 9.3wt% of comonomer ethylene, 21.0wt% of xylene solubles, 35.4wt% of comonomer in the solubles, an intrinsic viscosity ratio of the solubles/the copolymerized polypropylene of 1.68, a weight average molecular weight of 30.4X10 ⁴ g/mol, MFR at 230 ℃,2.16kg load of 5.69g/10min, tm= 163.0 ℃, breakdown field strength (90 ℃) of 288kV/mm, direct current volume resistivity (90 ℃,15 kV/mm) of 1.32E13 Ω & m, and sieving to remove fine powder smaller than 40 meshes. 2.0kg of the basic polypropylene copolymer powder is weighed and added into a 10L reaction kettle with mechanical stirring, a reaction system is closed, and nitrogen is replaced for deoxidization. 4.5g of tert-butyl peroxy (2-ethylhexanoate) and 120g of vinyltriisopropoxysilane were added, stirred and mixed for 60min, heated to 100℃and reacted for 1.5 hours. After the reaction is finished, nitrogen purging and cooling are carried out to obtain a polypropylene-g-vinyl triisopropoxy silane material product C4.

Example 5

Selecting basic copolymerized polypropylene powder with the following characteristics: comonomer ethylene content 4.8wt%, xylene solubles content 19.2wt%, comonomer content 17.6wt% in the solubles, solubles/copolymerized polypropylene intrinsic viscosity ratio 1.04, weight average molecular weight 29.2×10 ⁴ g/mol, MFR at 230℃under a load of 2.16kg5.37g/10min, tm=163.3 ℃, breakdown field strength (90 ℃) 322kV/mm, direct current volume resistivity (90 ℃,15 kV/mm) 1.36E13 Ω & m, and fine powder smaller than 40 meshes is removed by sieving. 2.0kg of the basic polypropylene copolymer powder is weighed and added into a 10L reaction kettle with mechanical stirring, a reaction system is closed, and nitrogen is replaced for deoxidization. 3.7g of lauroyl peroxide is dissolved in 70g of acetone, the obtained acetone solution is added into a reaction system, the temperature is raised to 40 ℃, the acetone is removed by nitrogen purging for 30min, 75g of vinyltriethoxysilane is added, stirring and mixing are carried out for 30min, the temperature is raised to 85 ℃, and the reaction is carried out for 4 hours. After the reaction is finished, nitrogen purging and cooling are carried out to obtain a polypropylene-g-vinyl triethoxysilane material product C5.

Example 6

Selecting basic copolymerized polypropylene powder with the following characteristics: comonomer ethylene content 12.6wt%, xylene solubles content 30.6wt%, comonomer content 43.6wt% in the solubles, solubles/copolymerized polypropylene intrinsic viscosity ratio 1.84, weight average molecular weight 27.1X10 ⁴ g/mol, MFR at 230 ℃,2.16kg load is 8.46g/10min, tm=162.0 ℃, breakdown field strength (90 ℃) is 261kV/mm, direct current volume resistivity (90 ℃,15 kV/mm) is 9E12 Ω & m, and fine powder smaller than 40 meshes is removed by sieving. 2.0kg of the basic polypropylene copolymer powder is weighed and added into a 10L reaction kettle with mechanical stirring, a reaction system is closed, and nitrogen is replaced for deoxidization. 5.0g of lauroyl peroxide was dissolved in 100g of vinyltrimethoxysilane and 50g of toluene as an interface agent to form a solution, the solution was stirred and mixed for 30 minutes, the temperature was raised to 95 ℃, 4kg of dispersant water at 95 ℃ was added, and the reaction was carried out for 0.75 hours. After the reaction is finished, cooling, filtering to remove dispersant water, and vacuum drying for 10 hours at 70 ℃ to obtain a polypropylene-g-vinyl trimethoxy silane material product C6.

Example 7

2.0kg of the base polypropylene copolymer powder of example 1 was weighed and added to a 10L reaction kettle with mechanical stirring, the reaction system was closed, and oxygen was removed by nitrogen substitution. 7.5g of lauroyl peroxide and 175g of vinyltriethoxysilane were added, stirred and mixed for 30min, swollen for 1 hour at 40℃and heated to 90℃for 4 hours. After the reaction is finished, nitrogen purging and cooling are carried out to obtain a polypropylene-g-vinyl triethoxysilane material product C7.

Comparative example 1

2.0kg of T30S powder (with breakdown field strength (90 ℃) of 347kV/mm and direct-current volume resistivity (90 ℃) of 1.18E13 omega-m) which is sieved and removed into fine powder smaller than 40 meshes is weighed and added into a 10L reaction kettle with mechanical stirring, a reaction system is closed, and oxygen is removed by nitrogen replacement. 2.5g of lauroyl peroxide and 50g of vinyltriethoxysilane were added, stirred and mixed for 60min, swollen for 1 hour at 40 ℃, heated to 90℃and reacted for 4 hours. After the reaction is finished, nitrogen purging and cooling are carried out to obtain a polypropylene-g-vinyl triethoxysilane material product D1.

Comparative example 2

Selecting basic copolymerized polypropylene powder with the following characteristics: comonomer ethylene content 18.1wt%, xylene solubles content 48.7wt%, comonomer content 31.9wt%, solubles/copolymerized polypropylene intrinsic viscosity ratio 0.89, weight average molecular weight 34.3X10 ⁴ g/mol, MFR at 230 ℃,2.16kg load of 1.21g/10min, tm=143.4 ℃, breakdown field strength (90 ℃) of 236kV/mm, direct current volume resistivity (90 ℃,15 kV/mm) of 1.16E13 Ω·m, and sieving to remove fine powder smaller than 40 meshes. 2.0kg of the basic polypropylene copolymer powder is weighed and added into a 10L reaction kettle with mechanical stirring, a reaction system is closed, and nitrogen is replaced for deoxidization. 20g of lauroyl peroxide and 400g of vinyltriethoxysilane are added, stirred and mixed for 60min, swelled for 1 hour at 40 ℃, heated to 90 ℃ and reacted for 4 hours. After the reaction is finished, cooling to obtain polypropylene-g-vinyl Triethoxysilane material product D2.

Comparative example 3

Selecting basic copolymerized polypropylene powder with the following characteristics: comonomer ethylene content 18.1wt%, xylene solubles content 48.7wt%, comonomer content 31.9wt%, solubles/copolymerized polypropylene intrinsic viscosity ratio 0.89, weight average molecular weight 34.3X10 ⁴ g/mol, MFR at 230 ℃,2.16kg load of 1.21g/10min, tm=143.4 ℃, breakdown field strength (90 ℃) of 236kV/mm, direct current volume resistivity (90 ℃,15 kV/mm) of 1.16E13 Ω·m, and sieving to remove fine powder smaller than 40 meshes. 2.0kg of the above base polypropylene powder was weighed, mixed with 50g of polyethylene triethoxysilane, and mixed using a screw extruder to obtain a blend D3. The resulting product was tested for various performance parameters and the results are shown in table 1.

The preparation method of the polyethylene triethoxysilane comprises the following steps: 10g of lauroyl peroxide and 200g of vinyltriethoxysilane are dispersed in 800ml of deionized water, stirred and mixed, heated to 90 ℃ and reacted for 4 hours. After the reaction was completed, the reaction system was cooled to room temperature, and 125g of polyvinyl triethoxysilane was obtained after filtration and drying.

As can be seen from the data of comparative example 1 and comparative example 1, the flexural modulus of the obtained polypropylene-g-silane material product is too high and the mechanical properties of the material are poor to meet the processing requirements of the insulating material by adopting the T30S powder as the basic powder.

As can be seen from comparing the data of example 1 and comparative example 2, an excessively high addition amount of the alkenyl group-containing silane-based monomer (an excessively high M1 value) results in a decrease in breakdown field strength and volume resistivity of the resulting polypropylene-g-silane material product, affecting the electrical properties of the material.

As can be seen from comparing the data of example 1 and comparative example 3, the mode of blending the polyvinyl triethoxysilane instead causes the breakdown field strength and the volume resistivity of the material to be greatly reduced, and the electrical properties of the material are greatly affected.

From the data in table 1, it can be seen that the greatly reduced flexural modulus makes the silane grafted modified polypropylene material of the present invention have good mechanical properties, and the breakdown field strength of the grafted product is improved compared with the copolymerized polypropylene without grafted alkenyl-containing silane monomer, which indicates that the silane grafted modified polypropylene material of the present invention has good electrical properties.

In addition, as can be seen from the dielectric constant and dielectric loss data, the graft modification does not affect the dielectric constant and dielectric loss of the material, and the material of the invention meets the necessary conditions for insulation.

Example A

Preparation of conductors: and (3) performing compacting and twisting operation on 76 aluminum monofilaments with the diameter of 2.5mm to obtain the aluminum conductor inner core.

Preparation of alkenyl-containing silane-modified polypropylene particles: blending the following components in parts by mass: 100 parts of alkenyl silane modified polypropylene material obtained in example 5 and 0.3 part of antioxidant 1010/168/calcium stearate (mass ratio of 2:2:1). Granulating by a double-screw extruder at the speed of 300r/min and the granulating temperature of 210-230 ℃.

Preparation of a conductor shielding layer and an insulating layer: the conductor shielding material PSD_WMP-00012 (Zhejiang Wanma Co., ltd.) and the alkenyl-containing silane modified polypropylene particles are formed by coextrusion cladding outside a conductor inner core through an extruder to form a conductor shielding layer and an electric insulation layer, or form the conductor shielding layer, the electric insulation layer and the electric insulation shielding layer (outer shielding layer), wherein the extrusion temperature is 190-220 ℃.

Preparation of a metal shielding layer: and (3) wrapping the copper wires outside the electric insulating layer (electric insulating shielding layer) by adopting 25T 1 copper metal wires with the diameter of 0.3mm to form the metal shielding layer.

Preparation of an inner sheath layer: PVC particles (Dongguan sea Innovative electronics Co., ltd.) of St-2 brand are extruded outside the metal shield layer through an extruder to form an inner jacket layer.

Preparation of armor: a single-layer steel wire armor is made of 50 304 stainless steel wires with the diameter of 6.0mm, the single-layer steel wire armor is wound on an inner sheath layer in the left direction, the armor is tight, and the gap between adjacent steel wires is minimum.

Preparation of an outer sheath layer: PVC particles (Dongguan sea Innovative electronics Co., ltd.) of St-2 were extruded through an extruder outside the armor to form an outer jacket layer.

Finally, the thermoplastic cable with the modified polypropylene insulating layer is obtained. The structure of the cable is schematically shown in fig. 1.

A cable with an energy level of 10kV was produced according to the method described above on the basis of the material of example 5, the cable conductor cross-sectional area being 400mm ² The average thickness of the conductor shielding layer is 1.05mm, the average thickness of the electric insulation layer is 2.95mm, the average thickness of the electric insulation shielding layer is 1.18mm, the average thickness of the metal shielding layer is 0.95mm, the cable insulation eccentricity is 5.2%, the average thickness of armor is 5.95mm, the average thickness of the inner sheath layer is 2.44mm, and the average thickness of the outer sheath layer is 2.80mm.

Test case A

The resulting cable was tested. Main insulation conductivity test results of the cable: the cable had a conductivity ratio of 56.8 at 90℃and 30 ℃. Cable insulation space charge injection test results: the electric field distortion of the cable was 17.5%. Direct current withstand voltage test result: the cable has no breakdown and discharge phenomena and passes through. Load cycle test results: the cable has no breakdown phenomenon and passes through.

Example B

Preparation of conductors: and (3) carrying out wire bundling operation on a plurality of aluminum monofilament conductors, and then, carrying out twisting operation on each monofilament conductor after wire bundling to obtain the aluminum conductor inner core.

Preparation of alkenyl-containing silane-modified polypropylene particles: blending the following components in parts by mass: 100 parts of alkenyl-containing silane modified polypropylene material obtained in examples 1-4 and examples 6-7, and 0.3 part of antioxidant 1010/168/calcium stearate (mass ratio 2:2:1). Granulating with a twin-screw extruder at a speed of 300r/min and a granulating temperature of 210-230 ℃.

Preparation of a conductor shielding layer and an insulating layer: the conductor shielding material PSD_WMP-00012 (Zhejiang Wanma Co., ltd.) and the alkenyl-containing silane modified polypropylene particles are formed into a conductor shielding layer and an electric insulation layer or a conductor shielding layer, an electric insulation layer and an electric insulation shielding layer (outer shielding layer) outside a conductor inner core through coextrusion cladding by an extruder, wherein the extrusion temperature is 160-220 ℃.

Preparation of a metal shielding layer: and (3) carrying out copper strip wrapping outside the electric insulating layer (electric insulating shielding layer) by adopting T1 copper to form the metal shielding layer.

Preparation of armor: the steel wire armor with the nominal diameter of 1.25mm is made of 304 stainless steel, and is wrapped on the inner sheath layer from the left direction of single-layer armor, so that the armor is tight, and the gap between adjacent steel wires is minimized.

According to the method, cables with energy levels in the range of 6-35 kV are respectively prepared based on the materials of the examples 1-4 and the examples 6-7, wherein the sectional area of a cable conductor is 240-400 mm < 2 >, the thickness of a conductor shielding layer is 1-3 mm, the thickness of an electric insulation layer is 2-8 mm, the thickness of the electric insulation shielding layer is 0.5-1.5 mm, the thickness of an armor is 0.5-1 mm, the thickness of an inner sheath layer is 1-2 mm, and the thickness of an outer sheath layer is not less than 1.8mm.

Test case B

The resulting cable was tested. Main insulation conductivity test results of the cable: the conductivity ratio of each cable is less than 100 at 90 ℃ and 30 ℃. Cable insulation space charge injection test results: the electric field distortion of each cable is less than 20%. Direct current withstand voltage test result: each cable has no breakdown and discharge phenomena and passes through. Load cycle test results: each cable has no breakdown phenomenon and passes through.

Therefore, compared with the existing cable, the cable adopting the silane grafted modified polypropylene material as the main insulating layer has higher working temperature, and can still maintain even higher volume resistivity and stronger breakdown resistance at higher working temperature. Under the condition of ensuring the same voltage level and insulation level, the electric insulation layer made of the silane grafted modified polypropylene material has the advantages of thinner thickness, better heat dissipation and smaller weight compared with the electric insulation layer of a conventional cable.

The foregoing description of embodiments of the invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the various embodiments described.

The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.

Claims

1. A thermoplastic cable having a modified polypropylene insulation layer, the cable comprising:

the silane grafted modified polypropylene material comprises structural units derived from copolymerized polypropylene and structural units derived from alkenyl-containing silane monomers; the content of the structural unit which is derived from the alkenyl-containing silane monomer and is in a grafted state in the silane grafted modified polypropylene material is 0.2 to 6 weight percent based on the weight of the silane grafted modified polypropylene material.

2. Cable according to claim 1, wherein the content of structural units derived from alkenyl-containing silane-based monomers in the grafted state in the silane-grafted polypropylene material is from 0.2 to 2.5 wt.%, based on the weight of the silane-grafted polypropylene material.

3. The cable according to claim 1, wherein the cable has at least one cable core, each comprising, in order from inside to outside: a conductor, an optional conductor shield layer, an electrically insulating layer, an optional electrically insulating shield layer, an optional metal shield layer.

4. A cable according to claim 3, wherein the cable further comprises an armouring and/or sheathing layer.

5. A cable according to claim 3, wherein the cable further comprises a filler layer and/or a tape layer.

6. The cable of claim 1, wherein the cable is a direct current cable or an alternating current cable.

7. The cable of claim 6, wherein the cable is a direct current cable.

8. The cable according to any one of claims 1-7, wherein the silane grafted modified polypropylene material has at least one of the following characteristics: the melt flow rate under the load of 2.16kg at 230 ℃ is 0.01-30 g/10min; the flexural modulus is 20-900 MPa; the elongation at break is more than or equal to 200%; the tensile strength is more than 5MPa.

9. The cable of claim 8 wherein the silane grafted modified polypropylene material has a melt flow rate of 0.05 to 20g/10min at 230 ℃,2.16kg load.

10. The cable of claim 9 wherein the silane grafted modified polypropylene material has a melt flow rate of 0.1 to 10g/10min at 230 ℃,2.16kg load.

11. The cable of claim 10 wherein the silane grafted modified polypropylene material has a melt flow rate of 0.2 to 5g/10min at 230 ℃, under a 2.16kg load.

12. The cable of claim 8 wherein the silane grafted modified polypropylene material has a flexural modulus of 50 to 600MPa.

13. The cable of claim 8 wherein the silane grafted modified polypropylene material has an elongation at break of greater than or equal to 300%.

14. The cable of claim 8 wherein the silane grafted modified polypropylene material has a tensile strength of 10 to 40MPa.

15. The cable according to any one of claims 1-7, wherein the silane grafted modified polypropylene material has at least one of the following characteristics:

the working temperature of the silane grafted modified polypropylene material is more than or equal to 90 ℃;

-the breakdown field strength E of the silane grafted modified polypropylene material at 90 °c _g ≥200kV/mm；

-the breakdown field strength E of the silane grafted modified polypropylene material at 90 °c _g A breakdown field strength change rate delta E/E obtained by dividing a difference delta E between the breakdown field strength E of the polypropylene copolymer and the breakdown field strength E of the polypropylene copolymer at 90 ℃ by the breakdown field strength E of the polypropylene copolymer at 90 ℃ is more than 0.7%;

-the direct current volume resistivity ρ of the silane grafted modified polypropylene material at 90 ℃, 15kV/mm field strength _vg ≥6×10 ¹² Ω·m；

-the direct current volume resistivity ρ of the silane grafted modified polypropylene material at 90 ℃, 15kV/mm field strength _vg DC volume resistivity ρ with the copolymer polypropylene at 90 ℃ and 15kV/mm field strength _v Ratio ρ of (2) _vg/ ρ _v Greater than 1;

-the silane grafted modified polypropylene material has a dielectric constant at 90 ℃ at 50Hz of more than 2.0.

16. The cable of claim 15 wherein the silane grafted modified polypropylene material has an operating temperature of 90 to 160 ℃.

17. The cable of claim 15 wherein the silane grafted modified polypropylene material has a breakdown field strength E at 90 degrees c _g Is 200-800 kV/mm.

18. The cable of claim 15 wherein the silane grafted modified polypropylene material has a breakdown field strength E at 90 degrees c _g The change rate delta E/E of the breakdown field intensity obtained by dividing the difference delta E of the breakdown field intensity E of the copolymerization polypropylene at 90 ℃ by the breakdown field intensity E of the copolymerization polypropylene at 90 ℃ is 0.8-40%.

19. The cable of claim 18 wherein the silane grafted modified polypropylene material has a breakdown field strength E at 90 degrees c _g The change rate delta E/E of the breakdown field intensity obtained by dividing the difference delta E of the breakdown field intensity E of the copolymerization polypropylene at 90 ℃ by the breakdown field intensity E of the copolymerization polypropylene at 90 ℃ is 2-20%.

20. The cable of claim 19 wherein the silane grafted modified polypropylene material has a breakdown field strength E at 90 degrees c _g The change rate delta E/E of the breakdown field intensity obtained by dividing the difference delta E of the breakdown field intensity E of the copolymerization polypropylene at 90 ℃ by the breakdown field intensity E of the copolymerization polypropylene at 90 ℃ is 6-15%.

21. The cable of claim 15, wherein the silane grafted modified polypropylene material has a direct current volume resistivity ρ at 90 ℃ at a field strength of 15kV/mm _vg Is 6 multiplied by 10 ¹² Ω·m～1.0×10 ²⁰ Ω·m。

22. The cable of claim 15, wherein the silane grafted modified polypropylene material has a direct current volume resistivity ρ at 90 ℃ at a field strength of 15kV/mm _vg DC volume resistivity ρ with the copolymer polypropylene at 90 ℃ and 15kV/mm field strength _v Ratio ρ of (2) _vg/ ρ _v 1.1 to 8.0.

23. The cable of claim 22, wherein the silane grafted modified polypropylene material has a direct current volume resistivity ρ at 90 ℃ at a field strength of 15kV/mm _vg DC volume resistivity ρ with the copolymer polypropylene at 90 ℃ and 15kV/mm field strength _v Ratio ρ of (2) _vg/ ρ _v 1.15 to 3.

24. The cable of claim 23, wherein the silane grafted modified polypropylene material has a direct current volume resistivity ρ at 90 ℃ at a field strength of 15kV/mm _vg DC volume resistivity ρ with the copolymer polypropylene at 90 ℃ and 15kV/mm field strength _v Ratio ρ of (2) _vg/ ρ _v 1.2 to 1.8.

25. The cable of claim 15 wherein the silane grafted modified polypropylene material has a dielectric constant of 2.1 to 2.5 at 90 ℃ at 50 Hz.

26. The cable according to any one of claims 1-7, wherein the co-polypropylene has at least one of the following characteristics: the comonomer content is 0.5 to 40mol%; the content of xylene solubles is 2-80 wt%; the content of comonomer in the soluble matters is 10-70 wt%; the intrinsic viscosity ratio of the soluble matters to the polypropylene is 0.3-5.

27. Cable according to claim 26, wherein the comonomer content of the copolypropylene is 0.5 to 30mol%.

28. Cable according to claim 27, wherein the comonomer content of the copolypropylene is 4 to 25wt%.

29. Cable according to claim 28, wherein the comonomer content of the copolypropylene is 4 to 22wt%.

30. The cable of claim 26 wherein the copolymerized polypropylene has a xylene solubles content of 18-75 wt%.

31. Cable according to claim 30, wherein the copolymerized polypropylene has a xylene solubles content of 30-70 wt%.

32. Cable according to claim 31, wherein the copolymerized polypropylene has a xylene solubles content of 30-67 wt%.

33. Cable according to claim 26, wherein the comonomer content in the solubles of the copolypropylene is 10 to 50wt%.

34. Cable according to claim 33, wherein the comonomer content in the solubles of the copolypropylene is 20 to 35wt%.

35. The cable of claim 26 wherein the copolymer polypropylene has a soluble to polypropylene intrinsic viscosity ratio of 0.5 to 3.

36. The cable of claim 35 wherein the copolymer polypropylene has a soluble to polypropylene intrinsic viscosity ratio of 0.8 to 1.3.

37. The cable according to any one of claims 1-7, wherein the co-polypropylene has at least one of the following characteristics: the melt flow rate under the load of 2.16kg at 230 ℃ is 0.01-60 g/10min; the melting temperature Tm is above 100 ℃; weight average molecular weight of 20X 10 ⁴ ～60×10 ⁴ g/mol。

38. The cable of claim 37 wherein the melt flow rate of the co-polypropylene is from 0.05 to 35g/10min at 230 ℃ under a 2.16kg load.

39. The cable of claim 38 wherein the melt flow rate of the copolymer polypropylene is from 0.5 to 8g/10min at 230 ℃ under a 2.16kg load.

40. The cable of claim 37 wherein the copolymerized polypropylene has a melting temperature Tm of 110-180 ℃.

41. The cable of claim 40 wherein the copolymerized polypropylene has a melting temperature Tm of 110-170 ℃.

42. The cable of claim 41 wherein the copolymerized polypropylene has a melting temperature Tm of 120-170 ℃.

43. The cable of claim 42 wherein the copolymerized polypropylene has a melting temperature Tm of 120-166 ℃.

44. Cable according to any one of claims 1 to 7, wherein the comonomer of the copolypropylene is selected from C other than propylene ₂ -C ₈ At least one of the alpha-olefins of (a).

45. The cable of claim 44 in which the comonomer of the copolymerized polypropylene is selected from at least one of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene.

46. The cable of claim 45 wherein the comonomer of the copolymerized polypropylene is ethylene and/or 1-butene.

47. The cable of claim 46 in which the copolymerized polypropylene consists of propylene and ethylene.

48. The cable according to any one of claims 1 to 7, wherein the alkenyl group-containing silane-based monomer is selected from at least one of monomers having a structure represented by formula I,

Wherein R is ₁ Is C ₂ -C ₁₂ Alkenyl of (c); r is R ₂ 、R ₃ 、R ₄ Each independently selected from substituted or unsubstituted C ₁ -C ₁₂ Straight-chain alkyl, substituted or unsubstituted C ₃ -C ₁₂ Branched alkyl, substituted or unsubstituted C ₁ -C ₁₂ Alkoxy, substituted or unsubstituted C ₁ -C ₁₂ Is an acyloxy group.

49. The cable of claim 48 wherein R ₁ Is a monounsaturated alkenyl group.

50. The cable of claim 48 wherein R ₁ Is C ₂ -C ₆ Alkenyl groups of (c).

51. The cable of claim 50 wherein R ₁ Is monounsaturated alkene.

52. The cable of claim 48 wherein R ₂ 、R ₃ 、R ₄ Each independently selected from substituted or unsubstituted C ₁ -C ₆ Straight-chain alkyl, substituted or unsubstituted C ₃ -C ₆ Branched alkyl, substituted or unsubstituted C ₁ -C ₆ Alkoxy, substituted or unsubstituted C ₁ -C ₆ Is an acyloxy group.

53. The cable of claim 48 in which the alkenyl-containing silane-based monomer is selected from at least one of vinyltriethoxysilane, vinyltrimethoxysilane, vinyltriisopropoxysilane, vinyltri-t-butoxysilane, vinyltriacetoxysilane, methylvinyldimethoxysilane, ethylvinyldiethoxysilane, allyltriethoxysilane, allyltrimethoxysilane, allyltriisopropoxysilane, vinyltris (β -methoxyethoxy) silane, allyltris (β -methoxyethoxy) silane, allyltri-t-butoxysilane, allyltriacetoxysilane, methallyldimethoxysilane, and ethylallyldiethoxysilane.

54. The cable according to any one of claims 1-7, wherein the silane grafted modified polypropylene material is prepared from a copolypropylene and an alkenyl-containing silane-based monomer by a solid phase grafting reaction.

55. The cable of claim 54 wherein the silane grafted modified polypropylene material is prepared by a process comprising: and (3) in the presence of inert gas, carrying out grafting reaction on a reaction mixture comprising the copolymerized polypropylene and the silane monomer containing alkenyl to obtain the silane grafted modified polypropylene material.

56. The cable of claim 55 wherein the reaction mixture further comprises a free radical initiator.

57. The cable of claim 56 wherein the radical initiator is selected from peroxide-based radical initiators and/or azo-based radical initiators.

58. The cable of claim 57 in which the peroxide-based free radical initiator is selected from at least one of dibenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, lauroyl peroxide, t-butyl peroxybenzoate, diisopropyl peroxydicarbonate, t-butyl peroxy (2-ethylhexanoate), and dicyclohexyl peroxydicarbonate; the azo free radical initiator is azo diisobutyronitrile and/or azo diisoheptonitrile.

59. The cable of claim 56 wherein the mass ratio of free radical initiator to alkenyl-containing silane-based monomer is from 0.1 to 10:100.

60. The cable of claim 59 in which the mass ratio of free radical initiator to alkenyl-containing silane-based monomer is from 0.5 to 6:100.

61. The cable of claim 55 in which the mass ratio of the alkenyl-containing silane-based monomer to the copolymerized polypropylene is from 0.5 to 12:100.

62. The cable of claim 61 wherein the mass ratio of the alkenyl group-containing silane-based monomer to the copolymerized polypropylene is 0.8-9:100.

63. The cable of claim 62 in which the mass ratio of the alkenyl-containing silane-based monomer to the copolymerized polypropylene is 1-6:100.

64. The cable of claim 55 wherein the grafting reaction is at a temperature of 30-130 ℃; the time is 0.5-10 h.

65. The cable of claim 64 wherein the grafting reaction is at a temperature of 60-120 ℃; the time is 1-5 h.

66. The cable according to any one of claims 55-65, wherein the reaction mixture further comprises at least one of the following components: the mass content of the dispersing agent is 50-300% of the mass of the polypropylene copolymer, the mass content of the interfacial agent is 1-30% of the mass of the polypropylene copolymer, and the mass content of the organic solvent is 1-35% of the mass of the polypropylene copolymer.

67. The cable of claim 66, wherein the method of making comprises the steps of:

e. and after the reaction is finished, optionally filtering and drying to obtain the silane grafted modified polypropylene material.

68. The cable of claim 66, wherein the method of making comprises the steps of:

c. removing the organic solvent;

f. and after the reaction is finished, optionally filtering and drying to obtain the silane grafted modified polypropylene material.