阅读说明：本技术 齐格勒-纳塔催化剂的应用、制备电缆工厂软接头及其绝缘层的方法、电缆工厂软接头 (Application of Ziegler-Natta catalyst, method for preparing cable plant flexible joint and insulating layer thereof, and cable plant flexible joint ) 是由 周明瑜 罗艺 刘辉 史善哲 韩正一 于 2020-07-30 设计创作，主要内容包括：本发明涉及一种齐格勒-纳塔催化剂的应用、制备电缆工厂软接头及其绝缘层的方法、制备电缆工厂软接头,所述应用为齐格勒-纳塔催化剂在交联聚乙烯和聚丙烯共聚中的应用。齐格勒-纳塔催化剂可以引发聚乙烯和聚丙烯反应,合成高分子量的PE-b-PP共聚物,并可以精确控制共聚嵌段的长度,得到的共聚物力学性能优异。(The invention relates to an application of a Ziegler-Natta catalyst in copolymerization of crosslinked polyethylene and polypropylene, a method for preparing a cable plant flexible joint and an insulating layer thereof, and a method for preparing a cable plant flexible joint. The Ziegler-Natta catalyst can initiate the reaction of polyethylene and polypropylene to synthesize high molecular weight PE-b-PP copolymer, and can accurately control the length of the copolymerization block, so that the obtained copolymer has excellent mechanical properties.)

1. Use of a ziegler-natta catalyst in the copolymerisation of crosslinked polyethylene and polypropylene.

2. Use of a ziegler-natta catalyst according to claim 1 for the copolymerization of polyethylene and polypropylene, wherein said catalyst is TiCl₄-Al(C₂H₅)₃And/or TiCl₄-Al(C₂H₅)₂Cl。

3. A method for preparing a soft joint insulating layer in a cable factory is characterized by comprising the following steps:

s1, peeling the cross-linked polyethylene insulating layer covering the conductor at the connection position of the factory soft joint into a slope and exposing the inner semi-conductive shielding layer and a section of conductor;

s2, connecting the exposed conductor and recovering the inner semi-conductive shielding layer;

s3, winding a catalyst material belt made of Ziegler-Natta catalyst and polypropylene and/or polyethylene on the insulating layer of the slope;

s4, exhausting all air at the insulating layer wound by the catalyst material strip, and heating the insulating layer;

and S5, extruding polypropylene into the insulating layer wound by the catalyst material tape, melting and copolymerizing the polypropylene and the crosslinked polyethylene, and cooling after the reaction is finished to change the reaction part into a solid state.

4. A method for preparing an insulating layer for a flexible joint in a cable plant according to claim 3, characterized in that the catalyst material tape is prepared by: the ziegler-natta catalyst is mixed with polyethylene or polypropylene and then extruded into a ribbon of catalyst material.

5. The method for preparing the insulation layer of the flexible joint in the cable factory as claimed in claim 3 or 4, wherein the angle between the insulation layer of the slope and the conductor is 25-40 °.

6. The method for preparing the insulation layer of the flexible joint in the cable factory according to any one of claims 3 to 5, wherein the step of surface-deoxidizing and waterproofing the bare conductor is further included before the conductor is connected.

7. The method for preparing an insulation layer for a flexible joint in a cable plant according to any one of claims 3 to 6, wherein the inner semiconductive shield layer is restored with a semiconductive shield tape in step S2.

8. The method of making a cable plant flexible joint insulation according to any one of claims 3 to 7, further comprising the step of grinding the insulation layer of the ramp to a matt surface prior to winding the strip of catalyst material on the insulation layer of the ramp.

9. The method for preparing an insulation layer for a flexible joint in a cable plant according to any one of claims 3 to 8, wherein the air is exhausted with inert gas or nitrogen gas and heated to 180 to 240 ℃ in step S4.

10. The method for preparing an insulation layer for a flexible joint in a cable plant according to any one of claims 3 to 9, wherein the reaction part is changed to a solid state and then is continuously exposed to an inert gas or nitrogen atmosphere for 24 to 36 hours in step S5.

11. A method of making a cable plant flexible joint, comprising the steps of:

preparing a cable plant flexible joint insulation according to the method of any one of claims 3-10;

restoring the outer semiconductive shield layer;

the metal shielding layer, the buffer layer and the outer sheath are recovered.

12. A cable plant flexible joint prepared by the method of claim 11.

Technical Field

The invention relates to the field of power cable accessories, in particular to application of a Ziegler-Natta catalyst, a method for preparing a cable factory soft joint and an insulating layer thereof, and a method for preparing a cable factory soft joint.

Background

An extruded cable using cross-linked polyethylene (XLPE) as a main insulating material is widely used in power systems due to its advantages of simple structure, large transmission capacity, light weight, simple and convenient installation and maintenance, low processing and manufacturing costs, stable operation, etc. Various types of cable accessories are required to make electrical connections between cables and primary electrical equipment to optimize the insulating interface fit between the cables and other components (including other cables) and to dissipate the electric field stress concentration distortions caused by stripping the outer semiconductive shield from the cables. The cable accessories interconnected between the power cables are called cable intermediate joints or cable couplings.

The cable intermediate joint is divided into an integral prefabricated type, a combined prefabricated type and a factory soft joint which is mainly manufactured in a cable factory or on site according to different structural forms of the cable intermediate joint. The main difference between the factory soft joint and the former two is that the factory soft joint mainly adopts the insulating material and the semi-conductive shielding material which are the same as or close to the cable body as the structural material, the manufacturing process is similar to the extrusion process of the cable body, and the external dimension after the manufacturing is nearly the same as the cable body.

In the existing process for manufacturing a factory flexible joint of a crosslinked cable, an insulating layer is mainly manufactured by adopting an injection welding technology for welding, and a melting injection molding extruder, a cladding mold which is almost equal in diameter with a cable core layer (within a cable outer shielding layer) and the like are mainly required on a tool. Because the insulation material of the common extruded cable is a cross-linked polyethylene material, a cross-linking agent is required to be doped in the polyethylene insulation material to complete a cross-linking reaction when the soft joint is used for manufacturing insulation, so that an insulation structure equivalent to cable insulation is finally formed. However, the air inside the mold is coated, and the crosslinking by-products generated during the crosslinking by recovering the insulation are difficult to discharge in the soft joint insulating material, so that the defects of bubbles, impurities and the like are easily formed.

In the traditional chemical materials, similar to the crosslinked polyethylene material, the polypropylene material also has the advantages of high dielectric strength, good insulating property, good heat resistance, equivalent mechanical strength and the like. However, polyethylene and polypropylene, despite having similar hydrocarbon compositions, are incompatible with each other, so that in the case of conventional means, there is always an interface between the cable insulation and the intermediate flexible joint, which are produced using these two materials separately, and finally insulation failure occurs due to interfacial breakdown.

Disclosure of Invention

Therefore, the technical problem to be solved by the present invention is to overcome the defects of the prior art that the interface always exists when the soft joint of the factory is prepared by using polyethylene and polypropylene, thereby providing an application of using the Ziegler-Natta catalyst in the copolymerization of polyethylene and polypropylene.

The invention also provides a method for preparing the soft joint insulating layer in the cable factory.

The invention also provides a method for preparing the soft joint of the cable factory.

The invention also provides a flexible joint for a cable factory.

Therefore, the invention provides an application of the Ziegler-Natta catalyst in the copolymerization of crosslinked polyethylene and polypropylene.

Currently, the vast majority of Polyethylene (PE) and polypropylene (PP) preparations employ heterogeneous chromium and titanium catalysts. Heterogeneous olefin polymerization catalysts have many active sites, each molecule having its own reactivity difference, resulting in polymers of different Molecular Weights (MW), molecular weight distributions and microstructures. In the case of polyethylene and polypropylene, these differences and phase separation inhibit interfacial adhesion and reduce the mechanical properties of the melt blend. In order to solve the problem of the compatibility of polypropylene and polyethylene, a Ziegler-Natta catalyst is found to be used as a polymerization initiator for synthesizing PE-b-PP copolymer with high molecular weight, and the length of a copolymerization block can be accurately controlled. The resulting block amorphous copolymer can act as an additive, thereby increasing the compatibility of the polyethylene and polypropylene.

Further, the catalyst is TiCl₄-Al(C₂H₅)₃And/or TiCl₄-Al(C₂H₅)₂Cl。

The chemical reaction principle is as follows.

Alkylation:

TiCl₄+AlR₃→RTiCl₃+AlR₂Cl

TiCl₄+AlR₂Cl→RTiCl₃+AlRCl₂

RTiCl₃+AlR₃→R₂TiCl₂+AlR₂Cl

homolytic cleavage and reduction of titanium alkyls:

RTiCl₃→TiCl₃+R·

R₂TiCl₂→RTiCl₂+R·

TiCl₄+R·→TiCl₃+RCl

termination of free radicals:

2R → end of coupling or disproportionation.

The invention also provides a method for preparing the soft joint insulating layer in the cable factory, which comprises the following steps:

s1, peeling the cross-linked polyethylene insulating layer covering the conductor at the connection position of the factory soft joint into a slope and exposing the inner semi-conductive shielding layer and a section of conductor;

s2, connecting the exposed conductor and recovering the inner semi-conductive shielding layer;

s3, winding a catalyst material belt made of Ziegler-Natta catalyst and polypropylene and/or polyethylene on the insulating layer of the slope;

s4, exhausting all air at the insulating layer wound by the catalyst material strip, and heating the insulating layer;

and S5, extruding polypropylene into the insulating layer wound by the catalyst material tape, melting and copolymerizing the polypropylene and the crosslinked polyethylene, and cooling after the reaction is finished to change the reaction part into a solid state.

Further, the catalyst material belt is prepared by the following method: the ziegler-natta catalyst is mixed with polyethylene or polypropylene and then extruded into a ribbon of catalyst material.

Furthermore, the included angle between the insulating layer of the slope surface and the conductor is 25-40 degrees.

Furthermore, the method also comprises the step of carrying out surface deoxidation and waterproof treatment on the exposed conductor before the conductor is connected.

Further, the inner semiconductive shield layer is recovered with the semiconductive shield tape in step S2.

Further, before winding the catalyst material belt on the insulating layer of the slope surface, the method also comprises the step of grinding the insulating layer of the slope surface into a rough surface.

Further, in step S4, the air is purged with an inert gas or nitrogen, and the temperature is heated to 180 ℃ to 240 ℃.

Further, in step S5, after the reaction part becomes solid, the reaction part is continuously exposed to an inert gas or nitrogen atmosphere for 24 to 36 hours.

The invention also provides a method for preparing the soft joint of the cable factory, which comprises the following steps:

preparing the insulating layer of the flexible joint of the cable factory according to the method;

restoring the outer semiconductive shield layer;

the metal shielding layer, the buffer layer and the outer sheath are recovered.

The invention also provides the cable factory soft joint prepared by the method.

The technical scheme of the invention has the following advantages:

1. the Ziegler-Natta catalyst can initiate the reaction of polyethylene and polypropylene to synthesize PE-b-PP copolymer with high molecular weight, and can accurately control the length of a copolymerization block, so that the obtained copolymer has excellent mechanical properties.

2. According to the method for preparing the insulating layer of the flexible joint in the cable plant, provided by the invention, the polypropylene material and the polyethylene material are copolymerized in a molten state by using the Ziegler-Natta catalyst, so that the interface between the new insulating material and the old insulating material in the manufacturing process of the flexible joint in the plant can be effectively eliminated, the success rate and the reliability of manufacturing the flexible joint in the plant are directly improved, and the purpose of realizing all functions of the flexible joint in the plant without using a crosslinking reaction is achieved. Because the polyethylene main body material does not need to exhaust in the melting recovery process, only a small amount of exhaust or impurity removal forms exist in the copolymerization area of the polyethylene main body material and the polypropylene material, the manufacturing time of the power cable factory soft joint can be greatly shortened, and the reliability of the factory soft joint can be greatly improved.

3. According to the method for preparing the insulating layer of the flexible joint in the cable plant, the catalyst for the copolymerization reaction of the polypropylene and the polyethylene is accurately placed at the position needing the copolymerization reaction by winding the insulating material base band containing the catalyst, the original crosslinked polyethylene is subjected to decrosslinking by heating the whole material, and the copolymerization reaction is completed with the polypropylene under the action of the catalyst, so that the obtained whole joint does not contain an obvious interface of the polyethylene and the polypropylene any more, and the effect of recovering the whole cable body is achieved.

4. According to the method for preparing the insulating layer of the soft joint in the cable factory, the exposed conductor is subjected to surface deoxidation and waterproof treatment before being connected with the conductor, so that impurities can be contained as little as possible when the conductor is recovered, the problem of heating of the conductor joint caused by poor contact of the conductor or reduction of conductivity at the conductor joint is prevented, and the reliability of conductor connection can be effectively ensured; the insulating layer on the slope surface is polished to be a rough surface, so that the contact between the insulating layer and the catalyst material belt can be increased, the fusion between the catalyst material belt and the cross-linked polyethylene in the reaction process is facilitated, and the reaction is promoted.

5. The method for preparing the insulating layer of the soft joint in the cable plant, provided by the invention, comprises the step of heating the temperature in step S4 to 180-240 ℃, wherein the temperature is the suitable melt polymerization reaction temperature of the polypropylene and the crosslinked polyethylene, and the PE-b-PP copolymer with high molecular weight can be generated in the temperature range.

6. According to the method for preparing the insulating layer of the flexible joint in the cable plant, after the reaction part is changed into the solid state, the reaction part is continuously in the inert gas environment for 24-36 hours, so that the impurities generated in the process of melt copolymerization can be discharged.

7. The flexible joint prepared by the method for preparing the flexible joint of the cable factory is applied to various voltage levels and has no relation with the alternating current or direct current property of a power system.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a cross-sectional view of a cable in embodiment 1 of the present invention;

FIG. 2 is a schematic structural view of the cable treated in step 3) in example 1 of the present invention;

FIG. 3 is a schematic structural diagram of a cable after conductors are connected in step 5) in example 1 of the present invention;

FIG. 4 is a schematic structural diagram of the cable after the inner semiconductive shielding layer is recovered in step 6) of example 1 of the present invention;

fig. 5 is a schematic view of the cable structure after a new insulating layer is formed in step 13) of example 1 of the present invention.

Reference numerals:

1. a conductor; 2. an inner semiconductor shield layer; 3. a crosslinked polyethylene insulating layer; 4. an outer semiconductor shield layer; 5. a metal shielding layer; 6. a buffer layer; 7. an outer sheath; 8. a semiconductive shield tape; 9. and a polypropylene insulating layer.

Detailed Description

The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.