阅读说明：本技术 一种具有热塑性绝缘层的电缆 (Cable with thermoplastic insulating layer ) 是由 何金良 袁浩 宋文波 李琦 邵清 胡军 施红伟 周垚 于 2020-10-30 设计创作，主要内容包括：本发明属于电气领域,涉及一种具有热塑性绝缘层的电缆。该电缆包括：至少一个导体以及至少一个围绕所述导体的电绝缘层；其中,所述电绝缘层的材料为至少一种芳香烯烃接枝改性聚丙烯材料；所述芳香烯烃接枝改性聚丙烯材料包括衍生自共聚聚丙烯的结构单元和衍生自苯乙烯类单体的结构单元；以芳香烯烃接枝改性聚丙烯材料的重量为基准,所述芳香烯烃接枝改性聚丙烯材料中衍生自苯乙烯类单体且处于接枝态的结构单元的含量为0.5～14wt％。本发明的电缆具有更高的工作温度,并且,在保证相同电压等级和绝缘水平的条件下,具有电绝缘层厚度更薄、散热更好和重量更小的优点。(The invention belongs to the field of electricity, and relates to a cable with a thermoplastic 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 aromatic olefin graft modified polypropylene material; the aromatic olefin graft modified polypropylene material comprises a structural unit derived from copolymerized polypropylene and a structural unit derived from a styrene monomer; the weight of the aromatic olefin graft modified polypropylene material is taken as a reference, and the content of a structural unit which is derived from a styrene monomer and is in a graft state in the aromatic olefin graft modified polypropylene material is 0.5-14 wt%. 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 grade and insulation level.)

1. A cable having a thermoplastic 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 aromatic olefin graft modified polypropylene material;

the aromatic olefin graft modified polypropylene material comprises a structural unit derived from copolymerized polypropylene and a structural unit derived from a styrene monomer; the content of the structural units derived from the styrene monomer and in a grafted state in the aromatic olefin graft-modified polypropylene material is 0.5-14 wt%, preferably 1-7.5 wt%, and more preferably 1.5-5 wt%, based on the weight of the aromatic olefin graft-modified polypropylene material.

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 aromatic olefin graft-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 aromatic olefin graft-modified polypropylene material has at least one of the following characteristics:

the working temperature of the aromatic olefin graft modified polypropylene material is more than or equal to 90 ℃, and preferably 90-160 ℃;

-the breakdown field strength E of the aromatic olefin graft-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 aromatic olefin graft-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 1.5%, preferably 1.6-40%, more preferably 5-30%, and further preferably 10-20%;

-the direct current volume resistivity p of the aromatic olefin graft modified polypropylene material at 90 ℃ and 15kV/mm field strength_vg≥1.0×10¹³Ω · m, preferably 1.5 × 10¹³Ω·m～1.0×10²⁰Ω·m；

-the direct current volume resistivity p of the aromatic olefin graft modified polypropylene material at 90 ℃ and 15kV/mm field strength_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 1.5 to 50, more preferably 2 to 20, and further preferably 3 to 10;

the dielectric constant of the aromatic olefin graft modified polypropylene material at 90 ℃ and 50Hz is more than 2.0, preferably 2.1-2.5.

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 styrenic monomer is selected from at least one of a monomer having a structure represented by formula I, a monomer having a structure represented by formula II, and a monomer having a structure represented by formula III;

in the formula I, R¹、R²、R³Each independently selected from H, substituted or unsubstituted C₁-C₆Alkyl groups of (a); r⁴-R⁸Each independently selected from H, halogen, hydroxyl, amino, phosphate, sulfonic acid, substituted or unsubstituted C₁-C₁₂Alkyl, substituted or unsubstituted C₃-C₁₂Cycloalkyl, substituted or unsubstituted C₁-C₁₂Alkoxy, substituted or unsubstituted C₁-C₁₂Ester group of (1), substituted or unsubstituted C₁-C₁₂The substituted group is selected from halogen, hydroxyl, amino, phosphate, sulfonic group, C₁-C₁₂Alkyl of (C)₃-C₁₂Cycloalkyl of, C₁-C₁₂Alkoxy group of (C)₁-C₁₂Ester group of (1), C₁-C₁₂An amine group of (a); preferably, R¹、R²、R³Each independently selected from H, substituted or unsubstituted C₁-C₃Alkyl of R⁴-R⁸Each independently selected from H, halogen, hydroxy, amino, substituted or unsubstituted C₁-C₆Alkyl, substituted or unsubstituted C₁-C₆Alkoxy group of (a);

in the formula II, R₁、R₂、R₃Each independently selected from H, substituted or unsubstituted C₁-C₆Alkyl groups of (a); r₄-R₁₀Each independently selected from H, halogen, hydroxyl, amino, phosphate, sulfonic acid, substituted or unsubstituted C₁-C₁₂Alkyl, substituted or unsubstituted C₃-C₁₂Cycloalkyl, substituted or unsubstituted C₁-C₁₂Alkoxy, substituted or unsubstituted C₁-C₁₂Ester group of (1), substituted or unsubstituted C₁-C₁₂The substituted group is selected from halogen, hydroxyl, amino, phosphate, sulfonic group, C₁-C₁₂Alkyl of (C)₃-C₁₂Cycloalkyl of, C₁-C₁₂Alkoxy group of (C)₁-C₁₂Ester group of (1), C₁-C₁₂An amine group of (a); preferably, R₁、R₂、R₃Each independently selected from H, substituted or unsubstituted C₁-C₃Alkyl of R₄-R₁₀Each independently selected from H, halogen, hydroxy, amino, substituted or unsubstituted C₁-C₆Alkyl, substituted or unsubstituted C₁-C₆The substituted radical is selected from halogen, hydroxyl, amino, C₁-C₆Alkyl of (C)₁-C₆Alkoxy group of (a);

in the formula III, R₁’、R₂’、R₃' each is independently selected from H, substituted or unsubstituted C₁-C₆Alkyl groups of (a); r₄’-R₁₀' each is independently selected from H, halogen, hydroxyl, amino, phosphate, sulfonate, substituted or unsubstituted C₁-C₁₂Alkyl, substituted or unsubstituted C₃-C₁₂Cycloalkyl, substituted or unsubstituted C₁-C₁₂Alkoxy, substituted or unsubstituted C₁-C₁₂Ester group of (1), substituted or unsubstituted C₁-C₁₂The substituted group is selected from halogen, hydroxyl, amino, phosphate, sulfonic group, C₁-C₁₂Alkyl of (C)₃-C₁₂Cycloalkyl of, C₁-C₁₂Alkoxy group of (C)₁-C₁₂Ester group of (1), C₁-C₁₂An amine group of (a); preferably, R₁’、R₂’、R₃' each is independently selected from H, substituted or unsubstituted C₁-C₃The alkyl group of (a) is,R₄’-R₁₀' each is independently selected from H, halogen, hydroxy, amino, substituted or unsubstituted C₁-C₆Alkyl, substituted or unsubstituted C₁-C₆The substituted radical is selected from halogen, hydroxyl, amino, C₁-C₆Alkyl of (C)₁-C₆Alkoxy group of (a);

preferably, the styrenic monomer is selected from at least one of styrene, alpha-methylstyrene, 1-vinylnaphthalene, 2-vinylnaphthalene, mono-substituted or poly-substituted styrene, mono-substituted or poly-substituted alpha-methylstyrene, mono-substituted or poly-substituted 1-vinylnaphthalene, and mono-substituted or poly-substituted 2-vinylnaphthalene; the substituted group is preferably selected from the group consisting of halogen, hydroxy, amino, phosphate, sulfonate, C₁-C₈Straight chain alkyl group of (1), C₃-C₈Branched alkyl or cycloalkyl of, C₁-C₆Linear alkoxy of (2), C₃-C₈Branched or cyclic alkoxy of (A), C₁-C₈Linear ester group of (1), C₃-C₈A branched or cyclic ester group of₁-C₈And C is a linear amino group₃-C₈At least one of a branched amine group or a cyclic amine group of (a);

more preferably, the styrenic monomer is selected from at least one of styrene, α -methylstyrene, 2-methylstyrene, 3-methylstyrene and 4-methylstyrene.

12. The cable according to any one of claims 1 to 5, wherein the aromatic olefin graft-modified polypropylene material is prepared by a solid phase graft reaction of a co-polypropylene and a styrenic monomer.

13. The cable according to claim 12, wherein the preparation method of the aromatic olefin graft-modified polypropylene material comprises: and carrying out grafting reaction on the reaction mixture comprising the copolymerized polypropylene and the styrene monomer in the presence of inert gas to obtain the aromatic olefin 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 styrenic monomer is 0.1 to 10:100, preferably 0.5 to 5: 100.

16. The cable according to claim 13, wherein the mass ratio of the styrene-based monomer to the copolymerized polypropylene is 0.5 to 16:100, preferably 1 to 12:100, and more preferably 2 to 10: 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:

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

b. adding a free radical initiator and a styrene 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 dispersant, heating the reaction system to the grafting reaction temperature, and carrying out grafting reaction;

e. and after the reaction is finished, optionally filtering and drying to obtain the aromatic olefin graft modified polypropylene material.

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

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

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 a styrene monomer, optionally adding an interfacial 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. and after the reaction is finished, optionally filtering and drying to obtain the aromatic olefin graft modified polypropylene material.

Technical Field

The invention belongs to the field of electricity, and particularly relates to a cable with a thermoplastic 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 overcome the problem that the existing cable product cannot meet the requirement of stable operation at high temperature and high field intensity, and provides a cable with a thermoplastic insulating layer. The cable adopts an aromatic olefin graft 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 present invention provides a cable having a thermoplastic insulating 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 aromatic olefin graft modified polypropylene material;

the aromatic olefin graft modified polypropylene material comprises a structural unit derived from copolymerized polypropylene and a structural unit derived from a styrene monomer; the content of the structural units derived from the styrene monomer and in a grafted state in the aromatic olefin graft-modified polypropylene material is 0.5-14 wt%, preferably 1-7.5 wt%, and more preferably 1.5-5 wt%, based on the weight of the aromatic olefin 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 aromatic olefin graft-modified polypropylene material, which means that the base material constituting the electrical insulation layer is the aromatic olefin graft-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 aromatic olefin graft-modified polypropylene material. The nature and the amounts of additives used are conventional and known to the person skilled in the art.

The method for producing the electrical insulating layer of the present invention may also be a method which is conventional in the field of cable production, for example, an aromatic olefin graft-modified polypropylene material is mixed with various optional additives, pelletized by a twin-screw extruder, and the resulting pellets are extruded by the extruder to produce an electrical insulating layer. Generally, the conductor shield may be coextruded with pellets of an aromatic olefin graft-modified polypropylene material 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 aromatic olefin graft 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 aromatic olefin graft-modified polypropylene material used in the present invention, the "structural unit" means that it is a part of the graft-modified 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 styrenic monomers" refers to products formed from styrenic monomers, 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 units derived from a styrenic monomer "in the grafted state" refer to structural units derived from a styrenic monomer that form a covalent link (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 graft reaction, preferably a solid phase graft reaction, of a copolymer polypropylene and a styrene monomer. 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 styrenic 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-reacting a copolymerized polypropylene and a styrene-based monomer, and a graft-modified polypropylene pure product obtained by further purifying the product.

According to the present invention, the aromatic olefin graft-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, in terms of electrical properties, the aromatic olefin graft-modified polypropylene material has at least one of the following characteristics:

the working temperature of the aromatic olefin graft modified polypropylene material is more than or equal to 90 ℃, and preferably 90-160 ℃;

-the breakdown field strength E of the aromatic olefin graft-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 aromatic olefin graft-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 1.5%, preferably 1.6-40%, more preferably 5-30%, and further preferably 10-20%;

-the direct current volume resistivity p of the aromatic olefin graft modified polypropylene material at 90 ℃ and 15kV/mm field strength_vg≥1.0×10¹³Ω · m, preferably 1.5 × 10¹³Ω·m～1.0×10²⁰Ω·m；

-the direct current volume resistivity p of the aromatic olefin graft modified polypropylene material at 90 ℃ and 15kV/mm field strength_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 1.5 to 50, more preferably 2 to 20, and further preferably 3 to 10;

the dielectric constant of the aromatic olefin graft modified polypropylene material at 90 ℃ and 50Hz is more than 2.0, preferably 2.1-2.5.

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 styrene monomer can be any monomer styrene compound capable of being polymerized by free radicals, and can be selected from at least one of a monomer with a structure shown in a formula I, a monomer with a structure shown in a formula II and a monomer with a structure shown in a formula III;

in the formula I, R¹、R²、R³Each independently selected from H, substituted or unsubstituted C₁-C₆Alkyl groups of (a); r⁴-R⁸Each independently selected from H, halogen, hydroxyl, amino, phosphate, sulfonic acid, substituted or unsubstituted C₁-C₁₂Alkyl, substituted or unsubstituted C₃-C₁₂Cycloalkyl, substituted or unsubstituted C₁-C₁₂Alkoxy, substituted or unsubstituted C₁-C₁₂Ester group of (1), substituted or unsubstituted C₁-C₁₂The substituted group is selected from halogen, hydroxyl, amino, phosphate, sulfonic group, C₁-C₁₂Alkyl of (C)₃-C₁₂Cycloalkyl of, C₁-C₁₂Alkoxy group of (C)₁-C₁₂Ester group of (1), C₁-C₁₂An amine group of (a); preferably, R¹、R²、R³Each independently selected from H, substituted or unsubstituted C₁-C₃Alkyl of R⁴-R⁸Each independently selected from H, halogen, hydroxy, amino, substituted or unsubstituted C₁-C₆Alkyl, substituted or unsubstituted C₁-C₆Alkoxy group of (a);

in the formula II, R₁、R₂、R₃Each independently selected from H, substituted or unsubstituted C₁-C₆Alkyl groups of (a); r₄-R₁₀Each independently selected from H, halogen, hydroxyl, amino, phosphate, sulfonic acid, substituted or unsubstituted C₁-C₁₂Alkyl, substituted or unsubstituted C₃-C₁₂Cycloalkyl, substituted or unsubstituted C₁-C₁₂Alkoxy, substituted or unsubstituted C₁-C₁₂Ester group of (1), substituted or unsubstituted C₁-C₁₂The substituted group is selected from halogen, hydroxyl, amino, phosphate, sulfonic group, C₁-C₁₂Alkyl of (C)₃-C₁₂Cycloalkyl of, C₁-C₁₂Alkoxy group of (C)₁-C₁₂Ester group of (1), C₁-C₁₂An amine group of (a); preferably, R₁、R₂、R₃Each independently selected from H, substituted or unsubstituted C₁-C₃Alkyl of R₄-R₁₀Each independently selected from H, halogen, hydroxy, amino, substituted or unsubstituted C₁-C₆Alkyl, substituted or unsubstituted C₁-C₆The substituted radical is selected from halogen, hydroxyl, amino, C₁-C₆Alkyl of (C)₁-C₆Alkoxy group of (a);

in the formula III, R₁’、R₂’、R₃' each is independently selected from H, substituted or unsubstituted C₁-C₆Alkyl groups of (a); r₄’-R₁₀' each is independently selected from H, halogen, hydroxyl, amino, phosphate, sulfonate, substituted or unsubstituted C₁-C₁₂Alkyl, substituted or unsubstituted C₃-C₁₂Cycloalkyl, substituted or unsubstituted C₁-C₁₂Alkoxy, substituted or unsubstituted C₁-C₁₂Ester group of (1), substituted or unsubstituted C₁-C₁₂The substituted group is selected from halogen, hydroxyl, amino, phosphate, sulfonic group, C₁-C₁₂Alkyl of (C)₃-C₁₂Cycloalkyl of, C₁-C₁₂Alkoxy group of (C)₁-C₁₂Ester group of (1), C₁-C₁₂An amine group of (a); preferably, R₁’、R₂’、R₃' each is independently selected from H, substituted or unsubstituted C₁-C₃Alkyl of R₄’-R₁₀' each is independently selected from H, halogen, hydroxy, amino, substituted or unsubstituted C₁-C₆Alkyl, substituted or unsubstituted C₁-C₆The substituted radical is selected from halogen, hydroxyl, amino, C₁-C₆Alkyl of (C)₁-C₆Alkoxy group of (2).

Preferably, the styrenic monomer may be selected from at least one of styrene, α -methylstyrene, 1-vinylnaphthalene, 2-vinylnaphthalene, mono-or poly-substituted styrene, mono-or poly-substituted α -methylstyrene, mono-or poly-substituted 1-vinylnaphthalene, and mono-or poly-substituted 2-vinylnaphthalene; the substituted group is preferably selected from the group consisting of halogen, hydroxy, amino, phosphate, sulfonate, C₁-C₈Straight chain alkyl group of (1), C₃-C₈Branched alkyl or cycloalkyl of, C₁-C₆Linear alkoxy of (2), C₃-C₈Is supported byAlkoxy or cyclic alkoxy, C₁-C₈Linear ester group of (1), C₃-C₈A branched or cyclic ester group of₁-C₈And C is a linear amino group₃-C₈At least one of a branched amine group or a cyclic amine group.

More preferably, the styrenic monomer is selected from at least one of styrene, α -methylstyrene, 2-methylstyrene, 3-methylstyrene and 4-methylstyrene.

The aromatic olefin graft modified polypropylene material can be prepared by the solid-phase graft reaction of copolymerization polypropylene and styrene monomers, and specifically can be prepared by the method comprising the following steps: and carrying out grafting reaction on the reaction mixture comprising the copolymerized polypropylene and the styrene monomer in the presence of inert gas to obtain the aromatic olefin 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 active grafting site may be formed on the copolymerized polypropylene in the presence of the styrene-based monomer for grafting, or the active 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 meeting the product characteristics, the dosage of each component in the grafting reaction is not particularly limited, and specifically, the mass ratio of the radical initiator to the styrene monomer can be 0.1-10: 100, and preferably 0.5-5: 100. The mass ratio of the styrene monomer to the copolymerized polypropylene may be 0.5 to 16:100, preferably 1 to 12:100, and more preferably 2 to 10: 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, wherein the interfacial agent is an organic solvent having a swelling effect on polyolefin, and preferably at least one of the following organic solvents having a swelling effect on polypropylene copolymer: 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-C₆FatEther, 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 aromatic olefin graft modified polypropylene material of the invention, the limitation on the styrene monomer and the copolymerized polypropylene is the same as that described above, and the details are not repeated here.

According to the present invention, the preparation method of the aromatic olefin graft 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 styrene 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 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 aromatic olefin graft modified polypropylene material.

More specifically, the preparation method comprises the following steps:

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

b. dissolving a free radical initiator in a styrene monomer 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;

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

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

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

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 a styrene monomer, optionally adding an interfacial 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 aromatic olefin graft modified polypropylene material.

More specifically, the preparation method comprises the following steps:

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

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 styrene monomer, adding 0-30 parts of 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;

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

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 "aromatic olefin graft-modified polypropylene material" of the present invention includes both a product (crude product) directly obtained by graft-reacting a copolymerized polypropylene and a styrene-based monomer and a graft-modified polypropylene purified product obtained by further purifying the product, and therefore, the production process 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 aromatic olefin graft 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 30 to 100%, and more preferably 35 to 80%. The concept of grafting efficiency is well known to those skilled in the art and refers to the amount of styrene grafted per total amount of styrene charged 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 aromatic olefin modified polypropylene particles: the aromatic olefin-modified polypropylene material is mixed with optional additives and pelletized by a twin-screw extruder.

Preparation of conductor shielding layer and electric insulating layer: the conductor shielding material and the aromatic olefin modified polypropylene particles are extruded and coated outside the conductor inner core 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).

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 cable with the thermoplastic 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 aromatic olefin graft 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 cross-sectional view 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 with ethyl acetate for 24 hours, 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 styrenic monomers in the graft-modified polypropylene material, and in the present invention, the calculation formulas for M1 and GE 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 styrene added.

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

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.

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 2g of dibenzoyl peroxide and 100g of styrene, stirring and mixing for 60min, swelling for 4 hours at 40 ℃, heating to 95 ℃, and reacting for 4 hours. After the reaction is finished, nitrogen is blown and cooled to obtain a polypropylene-g-styrene material product C1. 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 at 230 ℃ under a load of 2.16kgThe MFR of (1.54 g/10 min), Tm of 164.9 ℃, the breakdown field strength (90 ℃) of 248kV/mm, and the direct current volume resistivity (90 ℃, 15kV/mm) of 7.25E 12. omega. m, and the 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 2.8g of lauroyl peroxide and 150g of styrene, stirring and mixing for 60min, swelling for 2 hours at 60 ℃, heating to 90 ℃, and reacting for 4 hours. After the reaction is finished, nitrogen is blown and cooled to obtain a polypropylene-g-styrene material product C2. The product obtained was tested for various performance parameters and the results are shown in table 1.

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 1.5g of lauroyl peroxide and 50g of styrene, stirring and mixing for 60min, swelling at 60 ℃ for 2 hours, heating to 85 ℃, and reacting for 4 hours. After the reaction is finished, nitrogen is blown and cooled to obtain a polypropylene-g-styrene material product C3. The product obtained was tested for various performance parameters and the results are shown in table 1.

Example 4

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, DC volume resistivity (90 ℃, 15kV/mm)At 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 4.0g of dibenzoyl peroxide in 100g of acetone, adding the obtained acetone solution into a reaction system, heating to 40 ℃, purging with nitrogen for 30min to remove acetone, adding 100g of p-methylstyrene, stirring and mixing for 30min, swelling at 60 ℃ for 1 hour, heating to 100 ℃, and reacting for 1 hour. After the reaction is finished, nitrogen is blown and cooled to obtain a polypropylene-g-p-methylstyrene material product C4. The product obtained was tested for various performance parameters and the results are shown in table 1.

Example 5

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 0.6g of dibenzoyl peroxide and 30g of styrene, stirring and mixing for 60min, swelling for 4 hours at 40 ℃, heating to 95 ℃, and reacting for 4 hours. After the reaction is finished, nitrogen is blown and cooled to obtain a polypropylene-g-styrene material product C5. The product obtained was tested for various performance parameters and the results are shown in table 1.

Example 6

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 4g of dibenzoyl peroxide and 200g of styrene, stirring and mixing for 60min, swelling for 4 hours at 40 ℃, heating to 95 ℃, and reacting for 4 hours. After the reaction is finished, nitrogen is blown and cooled to obtain a polypropylene-g-styrene material product C6. The product obtained was tested for various performance parameters and the results are shown in table 1.

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 2g of dibenzoyl peroxide and 100g of styrene, stirring and mixing for 60min, swelling for 4 hours at 40 ℃, heating to 95 ℃, and reacting for 4 hours. After the reaction is finished, nitrogen is blown and cooled to obtain a polypropylene-g-styrene material product D1. The product obtained was tested for various performance parameters and the results are shown in table 1.

Comparative example 2

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 12g of dibenzoyl peroxide and 600g of styrene, stirring and mixing for 60min, swelling for 4 hours at 40 ℃, heating to 95 ℃, and reacting for 4 hours. After the reaction is finished, nitrogen is blown and cooled to obtain a polypropylene-g-styrene material product D2. The product obtained was tested for various performance parameters and the results are shown in table 1.

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 100g of polystyrene GPPS-123, and mixed by 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.

Comparing the data of example 1 and comparative example 1, it can be seen that the polypropylene-g-styrene material 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 too high of styrene monomer addition (too high of M1 value) can result in the great reduction of the elongation at break of the obtained polypropylene-g-styrene material, affecting the mechanical properties of the material, and the reduction of the breakdown field strength and the volume resistivity of the material, affecting the electrical properties of the material.

Comparing the data of example 1 and comparative example 3 shows that the mode of blending polystyrene leads to the great reduction of the breakdown field strength and the volume resistivity of the material, and the electrical property of the material is greatly influenced.

In summary, it can be seen from the data in table 1 that the aromatic olefin graft modified 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 graft product is increased compared to the copolymerized polypropylene without grafted styrene monomer, which indicates that the aromatic olefin graft modified 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 a pressing and stranding operation on 76 aluminum monofilaments with the diameter of 2.5mm to obtain the aluminum conductor inner core.

Preparation of aromatic olefin modified polypropylene particles: blending the following components in parts by mass: 100 parts of the aromatic olefin-modified polypropylene material obtained in example 2, 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 ℃.

Preparation of conductor shielding layer and electric insulating layer: the conductor shielding material PSD _ WMP-00012 (Zhejiang Wangman corporation) and the aromatic olefin modified polypropylene particles are extruded and coated outside the conductor inner core through an extruder to form a conductor shielding layer and an electric insulating layer, or the conductor shielding layer, the electric insulating layer and the electric insulating shielding layer (an outer shielding layer) are formed, 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 cable with the thermoplastic insulating layer. The cross-sectional structure of the cable is schematically shown in fig. 1.

A cable having an energy level in the range of 10kV was produced according to the above method based on the material of example 2, with a cable conductor having a cross-sectional area of 400mm²The average thickness of the conductor shielding layer is 1.04mm, the average thickness of the electric insulation layer is 2.53mm, the average thickness of the electric insulation shielding layer is 1.05mm, the average thickness of the metal shielding layer is 0.92mm, the eccentricity of the cable insulation is 5.1%, the average thickness of the armor is 6.00mm, the average thickness of the inner sheath layer is 1.80mm, and the average thickness of the outer sheath layer is 2.45 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 47.5. Cable insulation space charge injection test results: the electric field distortion of the cable was 18.3%. 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 aromatic olefin modified polypropylene particles: blending the following components in parts by mass: 100 parts of the aromatic olefin-modified polypropylene materials obtained in examples 1 and 3 to 6, and 0.3 part of an antioxidant 1010/168/calcium stearate (mass ratio: 2: 1). Granulating by a double-screw extruder at the rotating speed of 300r/min and the granulating temperature of 210 ℃ and 230 ℃.

Preparation of conductor shielding layer and electric insulating layer: the conductor shielding material PSD _ WMP-00012 (Tengman corporation, Zhejiang) and the aromatic olefin modified polypropylene particles are extruded and coated outside the conductor core by an extruder to form a conductor shielding layer and an electric insulating layer, or the conductor shielding layer, the electric insulating layer and the electric insulating shielding layer (an outer shielding layer) are formed, and the extrusion temperature is 160-.

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 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 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.

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 cable with the thermoplastic insulating layer. The cross-sectional structure of the cable is schematically shown in fig. 1.

The energy level is 6-35 kV based on the materials of the embodiment 1 and the embodiments 3-6 respectively according to the methodThe cable has a conductor cross-sectional area of 240-400 mm²The thickness of the conductor shielding layer is 1-3 mm, the thickness of the electric insulation layer is 2-8 mm, the thickness of the electric insulation shielding layer is 0.5-1.5 mm, the thickness of the armor is 0.5-1 mm, the thickness of the inner sheath layer is 1-2 mm, and the thickness of the 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 aromatic olefin graft modified polypropylene material as the main insulating layer has higher working temperature, and can still maintain even higher volume resistivity and stronger puncture resistance at higher working temperature. Compared with the electric insulation layer of the conventional cable, the electric insulation layer made of the aromatic olefin graft 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.