CN113571233A

CN113571233A - Thermoplastic cable with modified polypropylene insulating layer

Info

Publication number: CN113571233A
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: 2021-10-29
Anticipated expiration: 2040-10-30
Also published as: CN113571233B

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 a structural unit derived from copolymerized polypropylene and a structural unit derived from silane monomers containing alkenyl groups; the content of structural units which are derived from silane monomers containing alkenyl groups and are in a grafted state in the silane graft modified polypropylene material is 0.2-6 wt% based on the weight of the silane graft modified polypropylene material. The cable of the invention has higher working temperature, and has the advantages of thinner thickness of the electric insulating layer, better heat dissipation and smaller weight under the condition of ensuring the same voltage class 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, cross-linked polyethylene is generally adopted by high-voltage direct-current cables at home and abroad as an insulating material, the working temperature is generally 70 ℃, the designed field intensity for long-term working is about 12kV/mm, and the operating environment of cable insulation becomes severer due to further improvement of temperature and electric field intensity along with further improvement of the operating voltage and the transmission capacity of the high-voltage direct-current cables at present, so that higher requirements are provided for the performance of the cable insulating material, namely, the high-voltage direct-current cables still have stronger insulating performance under the conditions of higher temperature and electric field intensity. However, the working temperature of the traditional crosslinked polyethylene reaches its use limit and cannot be further increased, so the development of a dc cable using a novel high-temperature high-field insulating material is urgently needed to meet the requirement of a cable system working under a high-voltage high-capacity condition.

At present, the manufacture of the crosslinked polyethylene insulated direct current cable adopts a three-layer co-extrusion insulated preparation method. The extrusion process mainly comprises three steps of heating and melting, cross-linking (vulcanizing) and cooling forming of the insulating material. The crosslinking initiator is generally used for causing the crosslinking reaction of polyethylene molecules, so that the production process of the cable becomes more complicated, and crosslinking byproduct impurities are inevitably introduced into main insulation due to the introduction of the crosslinking initiator, so that certain negative influence is caused on the insulation performance of the finished cable. In addition, crosslinked polyethylene belongs to thermosetting plastics, cannot be recycled, and the pyrolysis product thereof has great harm to the environment. Therefore, in order to simplify the production process of the cable, improve the final quality of the cable insulation, and eliminate the possible damage 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 cross-linking process thereof, and to realize the manufacturing and engineering application of a 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. The cable adopts a silane grafted modified polypropylene material as a main insulating layer, can still maintain even higher volume resistivity and stronger puncture resistance performance at higher working temperature compared with the existing cable, and simultaneously, the mechanical performance of the cable can also meet the use requirement of the cable.

The invention provides a thermoplastic cable with a modified polypropylene insulation layer, which comprises:

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 a structural unit derived from copolymerized polypropylene and a structural unit derived from silane monomers containing alkenyl groups; the content of the structural unit which is derived from the silane monomer containing the alkenyl and is in a grafted state in the silane graft modified polypropylene material is 0.2-6 wt%, preferably 0.2-2.5 wt% 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, therefore, the invention has no special limitation on the form and specific structure of the cable, and can adopt various cable forms (direct current or alternating current, single core or multi-core) and corresponding various structures which are conventional in the field. In the cable of the invention, except that the electric insulating layer adopts the novel graft modified polypropylene material, other layer structures and other layer materials can be selected conventionally in the field.

The cable of the invention can 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) denotes voltages below 1kV, Medium Voltage (MV) denotes voltages in the range of 1kV to 40kV, High Voltage (HV) denotes voltages above 40kV, preferably above 50kV, and Extra High Voltage (EHV) denotes voltages of at least 230 kV.

According to a preferred embodiment of the present invention, the cable has at least one cable core, and each cable core sequentially includes, 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. The conductor shielding layer, the electric insulation shielding layer and the metal shielding layer can be arranged according to requirements, and are generally used in cables with the voltage of more than 6 kV.

In addition to the above structure, the cable may further include an armor and/or a sheath layer.

The cable of the invention may be a mono-core cable or a multi-core cable, and for multi-core cables, the cable may further comprise a filling layer and/or a tape layer. The filling layer is formed by filling materials among the wire cores. The band layer cladding is in the outside of all sinle silks, guarantees that sinle silk and filling layer are circular, prevents that the sinle silk from being the armor fish tail to play fire-retardant effect.

In the cable of the invention, the conductor is a conductive element, generally made of a metallic material, preferably aluminium, copper or other alloys, comprising one or more metal wires. The direct current resistance and the number of the monofilaments of the conductor meet the requirement of GB/T3956. The preferred conductor adopts a compact stranded circular structure, and the nominal sectional area is less than or equal to 800mm²(ii) a Or a split conductor structure with a nominal cross-sectional area of 1000mm or more²The number of the conductors is not less than 170.

In the cable, the conductor shielding layer can be a covering layer made of polypropylene, polyolefin elastomer, carbon black and other materials, the volume resistivity at 23 ℃ is less than 1.0 omega.m, the volume resistivity at 90 ℃ is less than 3.5 omega.m, and the melt flow rate at 230 ℃ and under a load of 2.16kg is usually 0.01-30 g/10min, preferably 0.05-20 g/10min, further preferably 0.1-10 g/10min, and more preferably 0.2-8 g/10 min; the tensile strength is more than or equal to 12.5 MPa; 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 1.0 mm.

In the cable of the present invention, the material of the electrical insulation layer is at least one silane-grafted modified polypropylene material, which means that the substrate constituting the electrical insulation layer is the silane-grafted modified polypropylene material, and may further comprise additional components such as polymer components or additives, preferably additives such as any one or more of antioxidants, stabilizers, processing aids, flame retardants, water tree retardant additives, acid or ion scavengers, inorganic fillers, voltage stabilizers and copper resistant agents, in addition to the silane-grafted modified polypropylene material. The nature and the amounts of additives used are conventional and known to the person skilled in the art.

The process for producing the electrical insulating layer of the present invention may also be a process which is conventional in the field of cable production, for example, a process in which a silane-grafted modified polypropylene material is mixed with optional various additives, pelletized by a twin-screw extruder, and the resulting pellets are extruded by an extruder to produce an electrical insulating layer. Generally, the conductor shield may be coextruded with the silane-grafted modified polypropylene material pellets to form a structure of conductor shield layer + electrical insulation layer, or to form a structure of conductor shield layer + electrical insulation shield layer. The specific operation can adopt the conventional method and process conditions in the field.

Due to the adoption of the silane grafted modified polypropylene material, 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, and 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 covering layer made of a material such as polypropylene, a polyolefin elastomer, and carbon black, and has a volume resistivity of less than 1.0 Ω · m at 23 ℃ and less than 3.5 Ω · m at 90 ℃. The melt flow rate under the load of 2.16kg at 230 ℃ is 0.01-30 g/10min, preferably 0.05-20 g/10min, further preferably 0.1-10 g/10min, and more preferably 0.2-8 g/10 min; the tensile strength is more than or equal to 12.5 MPa; the elongation at break is more than or equal to 150 percent. The thinnest point thickness of the electric insulation shielding layer is not less than 0.5mm, and the average thickness is not less than 1.0 mm.

In the cable of the invention, the metal shielding layer can be a copper strip shielding layer or a copper wire shielding layer.

In the cable of the invention, the filling layer can be made of high polymer materials, such as PE/PP/PVC or recycled rubber materials.

In the cable of the invention, the belting layer/armor layer is a metal covering layer which is usually 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 metal covering layer/armor layer at room temperature is less than or equal to 1000 omega.m.

In the cable of the invention, the material of the sheath layer can be any one of polyvinyl chloride, polyethylene or low-smoke halogen-free materials. The sheath layer not only comprises an inner sheath layer, but also comprises an outer sheath layer.

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

In the silane-grafted polypropylene material used in the present invention, the "structural unit" means that it is a part of the silane-grafted polypropylene material, and the form thereof is not limited. Specifically, "structural units derived from a co-polypropylene" refers to products formed from a co-polypropylene, including both in "radical" form and "polymer" form. "structural units derived from an alkenyl-containing silane-based monomer" refers to the product formed from an alkenyl-containing silane-based monomer, including both in "radical" form and "monomer" form, as well as "polymer" form. The "structural unit" may be a repeating unit or a non-repeating independent unit.

In the present invention, the structural unit derived from an alkenyl-containing silane-based monomer "in a grafted state" means a structural unit derived from an alkenyl-containing silane-based monomer which forms a covalent bond (graft) with the copolymerized polypropylene.

In the present invention, the term "comonomer" of the copolymerized polypropylene is known to those skilled in the art, and means a monomer copolymerized with propylene.

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

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

According to the present invention, the silane-grafted modified polypropylene material as the material of the electrical insulation layer preferably 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, preferably 0.05-20 g/10min, further preferably 0.1-10 g/10min, and more preferably 0.2-5 g/10 min; the flexural modulus is 20 to 900MPa, and more preferably 50 to 600 MPa; the elongation at break is more than or equal to 200 percent, and preferably the elongation at break is more than or equal to 300 percent; the tensile strength is more than 5MPa, preferably 10-40 MPa.

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

the working temperature of the silane grafted modified polypropylene material is not less than 90 ℃, and preferably 90-160 ℃;

-the breakdown field strength E of the silane-grafted modified polypropylene material at 90 ℃_gThe voltage is more than or equal to 200kV/mm, and preferably 200-800 kV/mm;

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

-the silane grafted modified polypropylene material has a direct current volume resistivity rho at 90 ℃ under a field strength of 15kV/mm_vg≥6×10¹²Ω · m, preferably 6 × 10¹²Ω·m～1.0×10²⁰Ω·m；

-the silane grafted modified polypropylene material has a direct current volume resistivity rho at 90 ℃ under a field strength of 15kV/mm_vgThe direct current volume resistivity rho of the copolymerized polypropylene at 90 ℃ and 15kV/mm field intensity_vRatio of (p)_vg/ρ_vMore than 1, preferably 1.1 to 8.0, more preferably 1.15 to 3, and further preferably 1.2 to 1.8;

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

According to the present invention, the copolymerized polypropylene (base polypropylene in the present invention) is a propylene copolymer containing ethylene or higher alpha-olefin or a mixture thereof. In particular, the comonomer of the copolymerized polypropylene is selected from C other than propylene₂-C₈At least one of alpha-olefins (b) of (a). Said C other than propylene₂-C₈The α -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, and further preferably, the copolymerized polypropylene is composed of propylene and ethylene.

The copolymeric polypropylene of the present invention may be a heterophasic propylene copolymer. The heterophasic propylene copolymer may contain a propylene homopolymer or a propylene random copolymer matrix component (1) and dispersed therein another propylene copolymer component (2). In the propylene random copolymer, the comonomer is randomly distributed in the main chain of the propylene polymer. Preferably, the co-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 a 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 sea-island structure or bicontinuous structure.

Two heterophasic propylene copolymers are known in the art, a heterophasic propylene copolymer containing a propylene random copolymer as matrix phase or a heterophasic propylene copolymer containing a propylene homopolymer as matrix phase. The random copolymer matrix (1) is a copolymer in which the comonomer moieties are randomly distributed 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 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 present invention, in addition to the above-mentioned compositional features, the copolymerized polypropylene has at least one of the following features: the content of the comonomer is 0.5 to 40 mol%, preferably 0.5 to 30 mol%, preferably 4 to 25 wt%, and more preferably 4 to 22 wt%; the xylene soluble content is 2 to 80 wt%, preferably 18 to 75 wt%, more preferably 30 to 70 wt%, and still more preferably 30 to 67 wt%; the content of the comonomer in the soluble substance is 10-70 wt%, preferably 10-50 wt%, more preferably 20-35 wt%; the intrinsic viscosity ratio of the soluble matter to the polypropylene is 0.3 to 5, preferably 0.5 to 3, and more preferably 0.8 to 1.3.

According to the present invention, preferably, the copolymerized polypropylene further has at least one of the following features: the melt flow rate under the load of 2.16kg at 230 ℃ is 0.01-60 g/10min, preferably 0.05-35 g/10min, and further preferably 0.5-8 g/10 min; the melting temperature Tm is 100 ℃ or higher, preferably 110 to 180 ℃, more preferably 110 to 170 ℃, still more preferably 120 to 170 ℃, and still more preferably 120 to 166 ℃. The weight average molecular weight is preferably 20X 10⁴～60×10⁴g/mol. The base polypropylene having a high Tm has satisfactory impact strength and flexibility at both low and high temperatures, and in addition, when the base polypropylene having a high Tm is used, the graft-modified polypropylene of the present invention has an advantage of being able to withstand higher working temperatures. The copolymerized polypropylene of the present invention is preferably a porous granular or powdery resin.

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

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 in the martian petrochemical industry, SPF179 in the zipru petrochemical industry in the china, and the like, and may also be produced by the polymerization processes described in chinese patents CN1081683, CN1108315, CN1228096, CN1281380, CN1132865C, CN102020733A, and the like. Common polymerization processes include the Spheripol process from Basell, the Hypol process from Mitsui oil chemical, 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 silane-based monomer containing alkenyl group of the invention can be any monomeric silane-based compound capable of undergoing polymerization by free radicals, and can be selected from at least one of the silane-based monomers containing alkenyl group selected from the monomers having the structure shown in formula I,

wherein R is₁Is C₂-C₁₂Preferably a monounsaturated alkenyl group; r₂、R₃、R₄Each independently selected from substituted or unsubstituted C₁-C₁₂Linear alkyl, substituted or unsubstituted C of₃-C₁₂Branched alkyl, substituted or unsubstituted C₁-C₁₂Alkoxy, substituted or unsubstituted C₁-C₁₂An acyloxy group of (a); preferably, R₁Is C₂-C₆Preferably a monounsaturated alkenyl group; r₂、R₃、R₄Each independently selected from substituted or unsubstituted C₁-C₆Linear alkyl, substituted or unsubstituted C of₃-C₆Branched alkyl radical of (1), andsubstituted or unsubstituted C₁-C₆Alkoxy, substituted or unsubstituted C₁-C₆An acyloxy group of (1).

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

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

The grafting reaction of the present invention can be carried out by various methods which are conventional in the art, and is preferably a solid phase grafting reaction. For example, the reactive grafting site may be formed on the copolymerized polypropylene in the presence of the alkenyl-containing silane-based monomer for grafting, or the reactive grafting site may be formed on the copolymerized polypropylene first and then treated with the monomer for grafting. The grafting sites may be formed by treatment with a free radical initiator, or by high energy ionizing radiation or microwave treatment. The free radicals produced in the polymer 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-based radical initiator is preferably at least one selected from the group consisting 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 radical initiator is preferably azobisisobutyronitrile and/or azobisisoheptonitrile.

More preferably, the grafting sites are initiated by a peroxide-based free radical initiator and the grafting reaction proceeds further.

In addition, the grafting reaction of the present invention can also be carried out by the methods described in CN106543369A, CN104499281A, CN102108112A, CN109251270A, CN1884326A and CN 101492517B.

On the premise of satisfying the product characteristics, the amount of each component used in the grafting reaction is not particularly limited, and specifically, the mass ratio of the radical initiator to the alkenyl-containing silane monomer may be 0.1 to 10:100, and preferably 0.5 to 6: 100. The mass ratio of the alkenyl-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 invention also has no special limitation on the technical conditions of the grafting reaction, and specifically, the temperature of the grafting reaction can be 30-130 ℃, and preferably 60-120 ℃; the time can 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, which is preferably water or an aqueous solution of sodium chloride. The mass usage amount of the dispersing agent is preferably 50-300% of the mass of the copolymerized polypropylene.

The reaction mixture of the present invention may further comprise an interfacial agent which is an organic solvent having a swelling effect on the polyolefin, preferablyAt least one of the following organic solvents having swelling effect on the co-polypropylene: ether solvents, ketone solvents, aromatic hydrocarbon solvents, and alkane solvents; more preferably at least one of the following organic solvents: chlorobenzene, polychlorinated benzene, C₆Alkane or cycloalkane, benzene, C, or both₁-C₄Alkyl substituted benzene, C₂-C₆Fatty ethers, C₃-C₆Aliphatic ketones, decalins; further preferred is at least one of the following organic solvents: benzene, toluene, xylene, chlorobenzene, tetrahydrofuran, diethyl ether, acetone, hexane, cyclohexane, decahydronaphthalene, heptane. The mass content of the interfacial agent is preferably 1-30% of the mass of the copolymerized polypropylene, and more preferably 10-25%.

The reaction mixture according to the invention may also comprise an organic solvent, preferably comprising C, as solvent for dissolving the solid free-radical initiator₂-C₅Alcohols, C₂-C₄Ethers and C₃-C₅At least one of ketones, more preferably C₂-C₄Alcohols, C₂-C₃Ethers and C₃-C₅At least one ketone, and most preferably at least one of ethanol, diethyl ether and acetone. The mass content of the organic solvent is preferably 1-35% of the mass of the copolymerized polypropylene.

In the preparation method of the silane-grafted modified polypropylene material of the present invention, the definitions of the silane-based monomer containing alkenyl and the polypropylene copolymer are the same as above, and are not repeated herein.

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

in a first aspect, the preparation method comprises the steps of:

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

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

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

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

e. after the reaction is finished, optionally filtering (in the case of using an aqueous phase dispersing agent) and drying to obtain the silane grafted modified polypropylene material.

More specifically, the preparation method comprises the following steps:

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

c. adding 0-30 parts of an 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 graft polymerization temperature of 30-130 ℃, and reacting for 0.5-10 hours;

In a second mode, the preparation method comprises 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 silane monomers containing alkenyl, optionally adding an interface agent, and optionally swelling the reaction system;

e. optionally adding a dispersant, heating the reaction system to the grafting reaction temperature, and carrying out grafting reaction;

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

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

d. adding alkenyl-containing silane monomers, adding 0-30 parts of an interfacial 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 graft 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 a stripping agent at the end of the grafting process. Suitable stripping agents include, but are not limited to, inert gases.

As described above, the "silane-grafted polypropylene material" of the present invention includes both a product (crude product) directly obtained by graft-reacting a copolymerized 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 optionally includes 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 favorable for obtaining the silane grafted and 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%, and 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-based monomer grafted per total amount of silane-based monomer fed to the reaction.

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

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

According to a specific embodiment of the present invention, the preparation method of the cable is as follows:

preparing a conductor: carrying out pressing and stranding operation on a plurality of monofilament conductors (such as aluminum) to obtain conductor inner cores; or performing a wire bundling operation, and then performing a twisting operation on each stranded single-wire conductor to obtain the conductor inner core.

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

Preparation of conductor shielding layer and electric insulating layer: the conductor shielding material and the silane modified polypropylene particles containing alkenyl are formed by co-extrusion coating of an extruder outside an inner core of a conductor to form a conductor shielding layer and an electric insulating layer, or form the conductor shielding layer, the electric insulating layer and the electric insulating shielding layer (an outer shielding layer).

Preparing a metal shielding layer: and (3) winding a copper strip or a copper wire outside the electric insulating layer (the electric insulating shielding layer) to form a metal shielding layer.

Preparing an inner sheath layer: and extruding the sheath layer granules outside the metal shielding layer by an extruder to form an inner sheath layer.

Preparing an armor: the steel wire or steel tape armor is made of galvanized steel/stainless steel/aluminum alloy, the inner layer of the single-layer armor is wound on the inner sheath layer in the left direction or the right direction of the double-layer armor in the outer layer in the left direction, and the steel wire or steel tape armor is tight, so that the gap between the adjacent steel wires/steel tapes is minimum.

Preparing 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 provided by the invention still can 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. Under the condition of ensuring the same voltage grade 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 the 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 by referring to the accompanying drawings.

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

Description of the reference numerals

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

Detailed Description

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

In the following examples and comparative examples:

1. determination of comonomer content in the copolymerized Polypropylene:

comonomer content was determined by quantitative Fourier Transform Infrared (FTIR) spectroscopy. The correlation of the determined comonomer content was calibrated by quantitative Nuclear Magnetic Resonance (NMR) spectroscopy. The basis weight¹³The calibration method for the results obtained by C-NMR spectroscopy was carried out according to a conventional method in the art.

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

the test was carried out using a CRYST-EX instrument from Polymer Char corporation. Heating to 150 deg.C with trichlorobenzene solvent, dissolving, holding at constant temperature for 90min, sampling, testing, cooling to 35 deg.C, holding at constant temperature for 70min, and sampling.

3. Determination of weight average molecular weight of the copolymerized Polypropylene:

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

4. Determination of the melt flow Rate MFR:

measured at 230 ℃ under a load of 2.16kg using a melt index apparatus of type 7026 from CEAST, according to the method specified in GB/T3682-2018.

5. Determination of the melting temperature Tm:

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

6. Determination of the grafting efficiency GE, parameter M1:

and (2) putting 2-4 g of the grafting product into a Soxhlet extractor, extracting for 24 hours by using acetone, removing unreacted monomers and homopolymers thereof to obtain a pure grafting product, drying and weighing, and calculating a parameter M1 and a grafting efficiency GE.

The parameter M1 represents the content of structural units derived from the silane-based monomer containing an alkenyl group in the graft-modified polypropylene material, and the calculation formulas of M1 and GE in the present invention are as follows:

in the above formula, w₀Is the mass of the PP matrix; w is a₁Is the mass of the grafted product before extraction; w is a₂Is the mass of the grafted product after extraction; w is a₃Is the mass of the added silane monomer.

7. Measurement of 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 carried out according to the method defined in GB/T1408-2006.

9. Determination of tensile Strength:

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

12. Determination of dielectric constant and dielectric loss tangent:

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

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

the tests were carried out according to the method specified in appendix A of TICW 7.1-2012. The primary insulation conductivity ratio is equal to the primary insulation conductivity of the cable at 90 ℃ divided by the primary insulation conductivity of the cable at 30 ℃.

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

the cable insulation space charge injection test was performed according to the method specified in appendix B of TICW 7.1-2012.

15. And D, direct-current voltage withstand test:

the cable was continuously pressurized at room temperature for 2 hours with a nominal voltage of 1.85 times negative polarity. No breakdown and discharge phenomena are passed, otherwise no passage is obtained.

16. And (3) load cycle testing:

heating the cable to 90 ℃ at the rated use temperature, adding 1.85 times of rated voltage, pressurizing for 8h, naturally cooling, removing the voltage for 16h, and circulating for 12 days. The occurrence of no breakdown phenomenon is the passing.

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

TABLE A

Name (R)	Description of the invention
		Copolypropylene
1	Self-made by the method described with reference to CN101679557A
		Copolypropylene
2	Self-made by the method described with reference to CN101679557A
		Copolypropylene 3	Self-made by the method described with reference to CN101679557A
Copolypropylene 4	Self-made by the method described with reference to CN101058654A
		Copolypropylene 5	Self-made by the method described with reference to CN101058654A
Copolypropylene 6	Self-made by the method described with reference to CN101058654A
		Polypropylene T30S	Homo-polypropylene ofNational petrochemical and land refining
Dibenzoyl peroxide	Bailingwei Tech Co Ltd (J)&K Chemicals)
		Lauroyl peroxide	Bailingwei Tech Co Ltd (J)&K Chemicals)
Tert-butyl peroxy (2-ethylhexanoate)	Adamas reagent GmbH (adamas-beta)
		Vinyl triethoxy silane	Bailingwei Tech Co Ltd (J)&K Chemicals)
Vinyl triisopropoxysilane	Bailingwei Tech Co Ltd (J)&K Chemicals)
		Vinyl trimethoxy silane	Bailingwei Tech Co Ltd (J)&K Chemicals)
Polyvinyl triethoxy silane	Laboratory self-control

Copolymerized polypropylene 1: the copolymer polypropylene used in example 1.

Copolymerized polypropylene 2: the copolymer polypropylene used in example 2.

Copolymerized polypropylene 3: the copolymer polypropylene used in example 3.

Copolymerized polypropylene 4: the copolymer polypropylene used in example 4.

Copolymerized polypropylene 5: the copolymer polypropylene used in example 5.

Copolymerized polypropylene 6: the copolymer polypropylene used in example 6.

Example 1

Selecting basic copolymerized polypropylene powder with the following characteristics: comonomer ethylene content 18.1 wt%, xylene solubles content 48.7 wt%, comonomer content in solubles 31.9 wt%, solubles/polypropylene intrinsic viscosity ratio 0.89, weight average molecular weight 34.3X 10⁴g/mol, MFR of 1.21g/10min at 230 ℃ under a load of 2.16kg, Tm of 143.4 ℃, breakdown field strength (90 ℃) of 236kV/mm, and direct current volume resistivity (90 ℃, 15kV/mm) of 1.16E 13. omega. m, and fine powder of less than 40 mesh was removed by sieving. Weighing 2.0kg of the basic polypropylene copolymer powder, adding the powder into a 10L reaction kettle with mechanical stirring, sealing the reaction system, and removing oxygen by nitrogen replacement. Adding 2.5g of lauroyl peroxide and 50g of vinyltriethoxysilane, stirring and mixing for 30min, swelling at 40 ℃ for 1 hour, heating to 90 ℃, and reacting for 4 hours. After the reaction is finished, nitrogen is used for blowing, and cooling is carried out, so that a polypropylene-g-vinyl triethoxysilane material product C1 is obtained.

The product obtained 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: comonomer ethylene content 14.7 wt%, xylene solubles content 41.7 wt%, comonomer content in solubles 34.5 wt%, solubles/polypropylene intrinsic viscosity ratio 0.91, weight average molecular weight 36.6X 10⁴g/mol, MFR of 1.54g/10min at 230 ℃ under a load of 2.16kg, Tm of 164.9 ℃, breakdown field strength (90 ℃) of 248kV/mm, and direct current volume resistivity (90 ℃, 15kV/mm) of 7.25E 12. omega. m, and fine powder of less than 40 mesh was removed by sieving. Weighing 2.0kg of the basic polypropylene copolymer powder, adding the powder into a 10L reaction kettle with mechanical stirring, sealing the reaction system, and removing oxygen by nitrogen replacement. Adding 0.9g dibenzoyl peroxide and 20g vinyltriethoxysilane, stirring and mixing for 60min, heating to 90 deg.CAnd the reaction was carried out for 4 hours. After the reaction is finished, nitrogen is used for blowing, and cooling is carried out, so that the polypropylene-g-vinyl triethoxysilane product C2 is obtained.

Example 3

Selecting basic copolymerized polypropylene powder with the following characteristics: comonomer ethylene content 20.1 wt%, xylene solubles content 66.1 wt%, comonomer content in solubles 29.5 wt%, solubles/polypropylene intrinsic viscosity ratio 1.23, weight average molecular weight 53.8X 10⁴g/mol, MFR of 0.51g/10min at 230 ℃ under a load of 2.16kg, Tm of 142.5 ℃, breakdown field strength (90 ℃) of 176kV/mm, and direct current volume resistivity (90 ℃, 15kV/mm) of 5.63E 12. omega. m, and fine powder of less than 40 mesh was removed by sieving. Weighing 2.0kg of the basic polypropylene copolymer powder, adding the powder into a 10L reaction kettle with mechanical stirring, sealing the reaction system, and removing oxygen by nitrogen replacement. Adding 6.0g of lauroyl peroxide and 100g of vinyltriethoxysilane, stirring and mixing for 60min, swelling at 60 ℃ for 1 hour, heating to 90 ℃, and reacting for 4 hours. After the reaction is finished, nitrogen is used for blowing, and cooling is carried out, so that a polypropylene-g-vinyl triethoxysilane material product C3 is obtained.

Example 4

Selecting basic copolymerized polypropylene powder with the following characteristics: comonomer ethylene content 9.3 wt%, xylene solubles content 21.0 wt%, comonomer content in solubles 35.4 wt%, solubles/polypropylene intrinsic viscosity ratio 1.68, weight average molecular weight 30.4X 10⁴g/mol, MFR of 5.69g/10min at 230 ℃ under a load of 2.16kg, Tm of 163.0 ℃, breakdown field strength (90 ℃) of 288kV/mm, and direct current volume resistivity (90 ℃, 15kV/mm) of 1.32E 13. omega. m, and fine powder of less than 40 mesh was removed by sieving. Weighing 2.0kg of the basic polypropylene copolymer powder, adding the powder into a 10L reaction kettle with mechanical stirring, sealing the reaction system, and removing oxygen by nitrogen replacement. 4.5g of tert-butyl peroxy (2-ethylhexanoate) and 120g of vinyltriisopropoxide were addedAnd silane is stirred and mixed for 60min, the temperature is raised to 100 ℃, and the reaction lasts for 1.5 hours. After the reaction is finished, nitrogen is used for blowing, and cooling is carried out, so that a polypropylene-g-vinyl triisopropoxysilane material product C4 is obtained.

Example 5

Selecting basic copolymerized polypropylene powder with the following characteristics: comonomer ethylene content 4.8 wt%, xylene solubles content 19.2 wt%, comonomer content in solubles 17.6 wt%, solubles/polypropylene intrinsic viscosity ratio 1.04, weight average molecular weight 29.2X 10⁴g/mol, MFR of 5.37g/10min at 230 ℃ under a load of 2.16kg, Tm of 163.3 ℃, breakdown field strength (90 ℃) of 322kV/mm, and direct current volume resistivity (90 ℃, 15kV/mm) of 1.36E 13. omega. m, and fine powder of less than 40 mesh was removed by sieving. Weighing 2.0kg of the basic polypropylene copolymer powder, adding the powder into a 10L reaction kettle with mechanical stirring, sealing the reaction system, and removing oxygen by nitrogen replacement. Dissolving 3.7g of lauroyl peroxide in 70g of acetone, adding the obtained acetone solution into a reaction system, heating to 40 ℃, purging with nitrogen for 30min to remove acetone, adding 75g of vinyltriethoxysilane, stirring and mixing for 30min, heating to 85 ℃, and reacting for 4 hours. After the reaction is finished, nitrogen is used for blowing, and cooling is carried out, so that a polypropylene-g-vinyl triethoxysilane material product C5 is obtained.

Example 6

Selecting basic copolymerized polypropylene powder with the following characteristics: comonomer ethylene content 12.6 wt%, xylene solubles content 30.6 wt%, comonomer content in solubles 43.6 wt%, solubles/polypropylene intrinsic viscosity ratio 1.84, weight average molecular weight 27.1X 10⁴g/mol, MFR of 8.46g/10min at 230 ℃ under a load of 2.16kg, Tm of 162.0 ℃, breakdown field strength (90 ℃) of 261kV/mm, and direct current volume resistivity (90 ℃, 15kV/mm) of 9E 12. omega. m, and fine powder of less than 40 mesh was removed by sieving. Weighing the basic polypropylene copolymer powder 2.0kg, addingThe reaction system is sealed in a 10L reaction kettle with mechanical stirring, and oxygen is removed by nitrogen replacement. 5.0g of lauroyl peroxide is dissolved in 100g of vinyltrimethoxysilane and 50g of interfacial agent toluene to form a solution, the solution is stirred and mixed for 30min, the temperature is raised to 95 ℃, 4kg of dispersant water at 95 ℃ is added, and the reaction is carried out for 0.75 hour. After the reaction is finished, cooling, filtering to remove the dispersant water, and vacuum drying at 70 ℃ for 10 hours to obtain a polypropylene-g-vinyltrimethoxysilane material product C6.

Example 7

2.0kg of the basic polypropylene copolymer powder obtained in example 1 was weighed, and the obtained powder was put into a 10L reactor equipped with a mechanical stirrer, and the reaction system was closed and deoxygenated by nitrogen displacement. Adding 7.5g of lauroyl peroxide and 175g of vinyltriethoxysilane, stirring and mixing for 30min, swelling at 40 ℃ for 1 hour, heating to 90 ℃, and reacting for 4 hours. After the reaction is finished, nitrogen is used for blowing, and cooling is carried out, so that a polypropylene-g-vinyl triethoxysilane material product C7 is obtained.

Comparative example 1

Weighing 2.0kg of T30S powder (breakdown field strength (90 ℃) is 347kV/mm, direct current volume resistivity (90 ℃, 15kV/mm) is 1.18E13 omega.m) which is sieved to remove fine powder smaller than 40 meshes, adding the powder into a 10L reaction kettle with mechanical stirring, sealing the reaction system, and removing oxygen by nitrogen replacement. Adding 2.5g of lauroyl peroxide and 50g of vinyltriethoxysilane, stirring and mixing for 60min, swelling at 40 ℃ for 1 hour, heating to 90 ℃, and reacting for 4 hours. After the reaction is finished, nitrogen is used for blowing, and cooling is carried out, so that a polypropylene-g-vinyl triethoxysilane material product D1 is obtained.

Comparative example 2

Selecting basic copolymerized polypropylene powder with the following characteristics: comonomer ethylene content 18.1 wt%, 2Toluene soluble content 48.7 wt%, comonomer content in soluble 31.9 wt%, soluble/copolymerized polypropylene intrinsic viscosity ratio 0.89, weight average molecular weight 34.3X 10⁴g/mol, MFR of 1.21g/10min at 230 ℃ under a load of 2.16kg, Tm of 143.4 ℃, breakdown field strength (90 ℃) of 236kV/mm, and direct current volume resistivity (90 ℃, 15kV/mm) of 1.16E 13. omega. m, and fine powder of less than 40 mesh was removed by sieving. Weighing 2.0kg of the basic polypropylene copolymer powder, adding the powder into a 10L reaction kettle with mechanical stirring, sealing the reaction system, and removing oxygen by nitrogen replacement. Adding 20g of lauroyl peroxide and 400g of vinyltriethoxysilane, stirring and mixing for 60min, swelling at 40 ℃ for 1 hour, heating to 90 ℃, and reacting for 4 hours. After the reaction is finished, cooling and reducing the temperature to obtain a polypropylene-g-vinyl triethoxysilane material product D2.

Comparative example 3

Selecting basic copolymerized polypropylene powder with the following characteristics: comonomer ethylene content 18.1 wt%, xylene solubles content 48.7 wt%, comonomer content in solubles 31.9 wt%, solubles/polypropylene intrinsic viscosity ratio 0.89, weight average molecular weight 34.3X 10⁴g/mol, MFR of 1.21g/10min at 230 ℃ under a load of 2.16kg, Tm of 143.4 ℃, breakdown field strength (90 ℃) of 236kV/mm, and direct current volume resistivity (90 ℃, 15kV/mm) of 1.16E 13. omega. m, and fine powder of less than 40 mesh was removed by sieving. 2.0kg of the above-mentioned basic copolymerized polypropylene powder was weighed and mixed with 50g of polyvinyl triethoxysilane, and mixed by using a screw extruder to obtain a blend D3. The product obtained was tested for various performance parameters and the results are shown in table 1.

The preparation method of the polyvinyl triethoxysilane: 10g of lauroyl peroxide and 200g of vinyltriethoxysilane are dispersed in 800ml of deionized water, stirred and mixed, and the temperature is raised to 90 ℃ for reaction for 4 hours. After the reaction, the reaction system was cooled to room temperature, filtered and dried to obtain 125g of polyvinyltriethoxysilane.

Comparing the data of example 1 and comparative example 1, it can be seen that the polypropylene-g-silane material product obtained by using the powder of T30S as the base powder has too high flexural modulus and poor mechanical properties, and cannot meet the processing requirements of insulating materials.

Comparing the data of example 1 and comparative example 2, it can be seen that the addition of silane-based monomer containing alkenyl group (too high M1 value) can reduce the breakdown field strength and volume resistivity of the obtained polypropylene-g-silane material product, and affect the electrical properties of the material.

Comparing the data of example 1 and comparative example 3, it can be seen that the mode of blending the polyvinyl triethoxysilane instead leads to a great reduction in the breakdown field strength and volume resistivity of the material, which greatly affects the electrical properties of the material.

In summary, it can be seen from the data in table 1 that the silane-grafted polypropylene material of the present invention has good mechanical properties due to the large reduction of the flexural modulus, and the breakdown field strength of the grafted product is increased compared to the polypropylene copolymer without the alkenyl-containing silane monomer, which indicates that the silane-grafted polypropylene material of the present invention has good electrical properties at the same time.

Furthermore, 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 present invention meets the necessary requirements for insulation.

Example A

Preparing a conductor: and (3) carrying out pressing and stranding 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 the alkenyl group-containing silane-modified polypropylene material obtained in example 5, and 0.3 part of an antioxidant 1010/168/calcium stearate (mass ratio 2:2: 1). And (3) granulating by using a double-screw extruder at the rotating speed of 300r/min and the granulating temperature of 210-230 ℃.

Preparing a conductor shielding layer and an insulating layer: the conductor shielding material PSD _ WMP-00012 (Tengman corporation, Zhejiang) and the silane modified polypropylene particles containing alkenyl are subjected to coextrusion coating by an extruder outside a conductor inner core to form a conductor shielding layer and an electric insulating layer, or form the conductor shielding layer, the electric insulating layer and an electric insulating shielding layer (an outer shielding layer), and the extrusion temperature is 190-220 ℃.

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

Preparing an inner sheath layer: PVC pellets (Dongguan sea electronics, Inc.) of grade St-2 were extruded outside the metal shield layer through an extruder to form an inner sheath layer.

Preparing an armor: the 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 wrapped on the inner sheath layer in the left direction, the armor is tight, and the gap between the adjacent steel wires is the minimum.

Preparing an outer sheath layer: PVC granules (Dongguan sea electronic Co., Ltd.) of St-2 were extruded outside the armor by an extruder to form an outer sheath layer.

And finally obtaining the thermoplastic cable with the modified polypropylene insulating layer. The schematic structure of the cable is shown in fig. 1.

A cable having an energy level of 10kV and a conductor cross-sectional area of 400mm was produced according to the above method based on the material of example 5²The 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 insulation eccentricity of the cable is 5.2%, the average thickness of the 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 2.80 mm.

Test example A

The prepared cable was tested. Main insulation conductivity test results of the cable: the electrical conductivity ratio of the cable at 90 ℃ and 30 ℃ was 56.8. Cable insulation space charge injection test results: the electric field distortion of the cable was 17.5%. Direct current withstand voltage test results: 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

Preparing a conductor: and (3) performing a wire bundling operation on the plurality of aluminum single-wire conductors, and then performing a stranding operation on each stranded single-wire conductor 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 the alkenyl group-containing silane-modified polypropylene materials obtained in examples 1 to 4 and examples 6 to 7, and 0.3 part of an antioxidant 1010/168/calcium stearate (mass ratio 2:2: 1). Granulating by a double-screw extruder at the rotating speed of 300r/min and the granulating temperature of 210 ℃ and 230 ℃.

Preparing a conductor shielding layer and an insulating layer: the conductor shielding material PSD _ WMP-00012 (Tengman corporation, Zhejiang) and the silane modified polypropylene particles containing alkenyl are coated outside the inner core of the conductor by co-extrusion through an extruder to form a conductor shielding layer and an electric insulating layer, or form the conductor shielding layer, the electric insulating layer and the electric insulating shielding layer (an outer shielding layer), and the extrusion temperature is 160-220 ℃.

Preparing a metal shielding layer: and (3) performing copper tape wrapping by adopting T1 copper outside the electric insulating layer (the electric insulating shielding layer) to form a metal shielding layer.

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

According to the method, the cable with the energy level in the range of 6-35 kV is prepared on the basis of the materials of the embodiments 1-4 and 6-7, the cross section area of a cable conductor is 240-400 mm2, 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 an 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 1.8 mm.

Test example B

The prepared cable was tested. Main insulation conductivity test results of the cable: the conductivity ratio of each cable at 90 ℃ and 30 ℃ is less than 100. Cable insulation space charge injection test results: the electric field distortion of each cable is less than 20%. Direct current withstand voltage test results: each cable has no breakdown and discharge phenomena and passes through. Load cycle test results: all cables have no breakdown phenomenon and pass 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. Compared with the electric insulation layer of the conventional cable, the electric insulation layer made of the silane grafted modified polypropylene material has the advantages of thinner thickness, better heat dissipation and smaller weight under the condition of ensuring the same voltage grade and insulation level.

Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not 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 described embodiments.

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

Claims

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

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

3. A cable according to claim 2, wherein the cable further comprises an armor and/or jacketing layer.

4. The cable according to claim 2, wherein the cable further comprises a filler layer and/or a tape layer.

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

6. The cable according to any one of claims 1 to 5, 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, preferably 0.05-20 g/10min, further preferably 0.1-10 g/10min, and more preferably 0.2-5 g/10 min; the flexural modulus is 20 to 900MPa, and more preferably 50 to 600 MPa; the elongation at break is more than or equal to 200 percent, and preferably the elongation at break is more than or equal to 300 percent; the tensile strength is more than 5MPa, preferably 10-40 MPa.

7. The cable according to any one of claims 1 to 5, wherein the silane-grafted modified polypropylene material has at least one of the following characteristics:

8. The cable according to any one of claims 1-5, wherein the co-polypropylene has at least one of the following characteristics: the content of the comonomer is 0.5 to 40 mol%, preferably 0.5 to 30 mol%, preferably 4 to 25 wt%, and more preferably 4 to 22 wt%; the xylene soluble content is 2 to 80 wt%, preferably 18 to 75 wt%, more preferably 30 to 70 wt%, and still more preferably 30 to 67 wt%; the content of the comonomer in the soluble substance is 10-70 wt%, preferably 10-50 wt%, more preferably 20-35 wt%; the intrinsic viscosity ratio of the soluble matter to the polypropylene is 0.3 to 5, preferably 0.5 to 3, and more preferably 0.8 to 1.3.

9. The cable according to any one of claims 1-5, 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, preferably 0.05-35 g/10min, and further preferably 0.5-8 g/10 min; the melting temperature Tm is more than 100 ℃, preferably 110-180 ℃, more preferably 110-170 ℃, further preferably 120-170 ℃, and further preferably 120-166 ℃; weight average molecular weight of 20X 10⁴～60×10⁴g/mol。

10. Cable according to any one of claims 1 to 5, wherein the comonomer of the co-polypropylene is selected from C other than propylene₂-C₈At least one of alpha-olefins of (a); preferably, 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; further preferably, the comonomer of the copolymerized polypropylene is ethylene and/or 1-butene; further preferably, the co-polypropylene consists of propylene and ethylene.

11. The cable according to any one of claims 1 to 5, wherein the alkenyl-containing silane-based monomer is at least one selected from monomers having a structure represented by formula I,

wherein R is₁Is C₂-C₁₂Preferably a monounsaturated alkenyl group; r₂、R₃、R₄Each independently selected from substituted or unsubstituted C₁-C₁₂Linear alkyl, substituted or unsubstituted C of₃-C₁₂Branched alkyl, substituted or unsubstituted C₁-C₁₂Alkoxy, substituted or unsubstituted C₁-C₁₂An acyloxy group of (a); preferably, R₁Is C₂-C₆Preferably a monounsaturated alkenyl group; r₂、R₃、R₄Each independently selected from substituted or unsubstituted C₁-C₆Linear alkyl, substituted or unsubstituted C of₃-C₆Branched alkyl, substituted or unsubstituted C₁-C₆Alkoxy, substituted or unsubstituted C₁-C₆An acyloxy group of (a);

12. The cable according to any one of claims 1 to 5, wherein the silane graft-modified polypropylene material is prepared by solid phase grafting reaction of a polypropylene copolymer and an alkenyl-containing silane monomer.

13. The cable according to claim 12, wherein the silane-grafted modified polypropylene material is prepared by a method comprising: and carrying out grafting reaction on a reaction mixture comprising the polypropylene copolymer and the silane monomer containing alkenyl in the presence of inert gas to obtain the silane graft modified polypropylene material.

14. The cable of claim 13, wherein the reaction mixture further comprises a free radical initiator;

preferably, the radical initiator is selected from peroxide-based radical initiators and/or azo-based radical initiators;

the peroxide-based radical initiator is preferably at least one selected from the group consisting 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 radical initiator is preferably azobisisobutyronitrile and/or azobisisoheptonitrile.

15. The cable according to claim 14, wherein the mass ratio of the radical initiator to the alkenyl-containing silane-based monomer is 0.1 to 10:100, preferably 0.5 to 6: 100.

16. The cable according to claim 13, wherein the mass ratio of the alkenyl-containing silane monomer to the polypropylene copolymer is 0.5 to 12:100, preferably 0.8 to 9:100, and more preferably 1 to 6: 100.

17. Cable according to claim 13, wherein the temperature of the grafting reaction is between 30 and 130 ℃, preferably between 60 and 120 ℃; the time is 0.5 to 10 hours, preferably 1 to 5 hours.

18. The cable according to any one of claims 13-17, wherein the reaction mixture further comprises at least one of the following components: the modified polypropylene composite material comprises a dispersing agent, an interface agent and an organic solvent, wherein the mass content of the dispersing agent is 50-300% of the mass of the copolymerized polypropylene, the mass content of the interface agent is 1-30% of the mass of the copolymerized polypropylene, and the mass content of the organic solvent is 1-35% of the mass of the copolymerized polypropylene.

19. The cable according to claim 18, wherein the preparation method comprises the steps of:

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

20. The cable according to claim 18, wherein the preparation method 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.