CN-122011587-A - Dynamic crosslinked polypropylene cable insulating material with thermo-mechanical stability and preparation method thereof

Abstract

The invention discloses a dynamic crosslinked polypropylene cable insulating material with thermo-mechanical stability and a preparation method thereof, belonging to the technical field of high-voltage cable insulating materials. According to the invention, polypropylene is taken as a matrix, reactive sites are introduced through maleic anhydride grafted polypropylene, and a thiourethane dynamic covalent bond is generated by reacting a multi-mercapto compound with isocyanate under the catalysis of organic base, so that the reprocessing performance of the material is endowed. Meanwhile, organic small molecules or oligomers containing strong polar groups are introduced into the system as deep trap regulating units, the deep trap regulating units are uniformly dispersed in a matrix to form deep level electron trapping centers, electrons injected under the action of an electric field can be effectively trapped by the traps, the concentration and mobility of free carriers are greatly reduced, and finally the polypropylene cable insulating material with higher thermo-mechanical performance, deep trap regulating capability and reworkability is obtained.

Inventors

• YANG KAI
• LI JIANYING
• SUN HAOFEI
• HAN YANHUA
• Yun Xiahaoyue
• ZHANG XIN
• MAO CHEN
• YANG DINGGE
• HOU ZHE
• JU ZELI
• PU LU
• SHEN JING
• SUN XIN
• WU KANGNING
• DANG WENQIANG
• ZHANG YAN
• YANG BO

Assignees

• 国网陕西省电力有限公司电力科学研究院
• 国网(西安)环保技术中心有限公司

Dates

Publication Date

20260512

Application Date

20260311

Claims (10)

1. 1. The dynamic crosslinked polypropylene cable insulating material with the thermal mechanical stability is characterized by comprising the following raw materials, by mass, 100 parts of polypropylene, 5-20 parts of maleic anhydride grafted polypropylene, 0.5-5 parts of a multi-mercapto compound, 0.2-3 parts of isocyanate, 0.1-1.5 parts of a deep trap regulating unit and 0.01-0.2 part of an organic base catalyst; The deep trap regulating and controlling unit is a polar compound containing triazine, imide, fluorine aromatic ring or nitrile group.
2. 2. The dynamic crosslinked polypropylene cable insulation material with thermo-mechanical stability according to claim 1, wherein the polypropylene is selected from isotactic polypropylene, syndiotactic polypropylene or atactic polypropylene; the grafting amount of the maleic anhydride in the maleic anhydride grafted polypropylene is 0.3-1.5wt%.
3. 3. The dynamic crosslinked polypropylene cable insulation material with thermal mechanical stability according to claim 1, wherein the multi-mercapto compound is selected from the group consisting of a binary mercapto compound selected from the group consisting of 1, 2-ethanedithiol, 1, 3-propanedithiol, 1, 4-butanedithiol, 1, 5-pentanedithiol, 1, 6-hexanedithiol, 1, 8-octanedithiol, 1, 10-decanedithiol, 1, 4-benzenedithiol, 4' -thiobisthiophenol and 3, 6-dioxa-1, 8-octanedithiol, or a multi-mercapto compound selected from the group consisting of trimethylol propane tris (3-mercaptopropionate), pentaerythritol tetrakis (3-mercaptobutyrate) or trimethylol ethane tris (3-mercaptopropionate).
4. 4. The dynamic crosslinked polypropylene cable insulation material with thermal mechanical stability according to claim 1, wherein the isocyanate is selected from aliphatic isocyanate, aromatic isocyanate or polyfunctional isocyanate, wherein the aliphatic isocyanate is selected from hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate or 1, 4-butylene diisocyanate, the aromatic isocyanate is selected from toluene diisocyanate, diphenylmethane diisocyanate, p-phenylene diisocyanate or 1, 3-phenylene diisocyanate, and the polyfunctional isocyanate is selected from hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, diphenylmethane diisocyanate trimer or polyisocyanate prepolymer.
5. 5. The dynamic crosslinked polypropylene cable insulation material with thermo-mechanical stability according to claim 1, wherein the deep trap regulating unit is selected from melamine, cyanuric acid, pyromellitic dianhydride derivatives, bisphenol a type polyimide oligomers, p-cyanobenzoic acid, dicyanobiphenyl or 4,4' - (hexafluoroisopropyl) diphthalic anhydride.
6. 6. The dynamic crosslinked polypropylene cable insulation material with thermo-mechanical stability according to claim 1, wherein the organic base catalyst is selected from tertiary amines, imidazoles or strong base organic catalysts.
7. 7. The dynamic crosslinked polypropylene cable insulation material with thermal mechanical stability according to claim 1, wherein dynamic crosslinking bonds of the dynamic crosslinked polypropylene cable insulation material are thiocarbamate bonds, the density of the dynamic crosslinking bonds is 0.05-0.15 mmol/g, and the gel content of the dynamic crosslinked polypropylene cable insulation material is 50-75%.
8. 8. A method for preparing the dynamic cross-linked polypropylene cable insulation material with thermo-mechanical stability according to any one of claims 1 to 7, comprising the following steps: And (3) melting and mixing polypropylene and maleic anhydride grafted polypropylene, then adding a multi-mercapto compound, isocyanate and a deep trap regulating unit, continuing the melting reaction, and then extruding, granulating, cooling and drying to obtain the dynamic crosslinked polypropylene cable insulating material with thermo-mechanical stability.
9. 9. The method of claim 8, wherein the melt mixing is performed at a temperature of 190 ℃ and the melt mixing apparatus is a twin screw extruder.
10. 10. A reprocessing method of a dynamic crosslinked polypropylene cable insulation material with thermal mechanical stability according to any one of claims 1 to 7, comprising the steps of crushing the dynamic crosslinked polypropylene cable insulation material, and hot-pressing at 200 ℃ and 5 to 15MPa for 1 to 2 hours to obtain the reprocessed dynamic crosslinked polypropylene cable insulation material.

Description

Dynamic crosslinked polypropylene cable insulating material with thermo-mechanical stability and preparation method thereof Technical Field The invention belongs to the technical field of high-voltage cable insulating materials, and particularly relates to a dynamic crosslinked polypropylene cable insulating material with thermo-mechanical stability and a preparation method thereof. Background With the rapid development of socioeconomic performance and the continuous increase of electrification level, the worldwide electricity demand continues to increase. New energy grid connection, remote power transmission and urban load density improvement make the position of a high-voltage transmission system in an electric power infrastructure increasingly important. In order to reduce line loss, improve transmission efficiency, and realize large-capacity and long-distance transmission, high-voltage direct current (HVDC) transmission technology is widely used. Compared with alternating current transmission, direct current transmission has the advantages of low line loss, long transmission distance, strong controllability and the like, so that the consumption of the high-voltage direct current cable is increased year by year, and the high-voltage direct current cable is particularly outstanding in submarine cables, urban underground power grids and new energy source transmission projects. In a hvdc cable system, insulating material is a central factor determining the reliability and service life of the cable. At present, cross-linked polyethylene (XLPE) is widely applied to the field of high-voltage direct-current cables as a main-current cable insulating material. XLPE forms a three-dimensional network structure through chemical crosslinking, and has excellent thermal stability and mechanical strength under high temperature conditions. However, with the increasing green manufacturing concepts and recycling economy requirements, the problem of non-recyclability of XLPE materials is increasingly pronounced. The cross-linked structure of XLPE material is an irreversible chemical bond, once the cross-linking is completed, the XLPE material is difficult to melt and process again, and the waste material is difficult to recycle. Meanwhile, peroxide initiators are generally required to be used in the cross-linking process of XLPE, small molecule byproducts such as methane, acetophenone and the like are generated, and long-time degassing treatment is required, so that the production period is increased, and the electrical property and environmental safety of the material are possibly influenced. Therefore, the development of recyclable and environment-friendly cable insulation materials is an important direction of industry development. In this context, polypropylene (PP) is becoming a potential candidate for replacement of XLPE due to its good electrical insulation properties, low dielectric loss, high volume resistivity and melt reworkable properties. The polypropylene as thermoplastic material has the advantages of cyclic utilization, short processing period, no cross-linking byproducts and the like, and accords with the development trend of green manufacturing. Accordingly, in recent years, studies on polypropylene insulation materials for high voltage direct current cables have been increasing. However, conventional isotactic polypropylene belongs to the typical thermoplastic semi-crystalline materials, which have insufficient thermo-mechanical stability under high temperature conditions. When the cable runs at 90-105 ℃ or even higher temperature for a long time, the polypropylene is easy to form relaxation, the stability of a crystal structure is reduced, and the storage modulus is obviously reduced, so that the dimensional stability and the mechanical supporting capability of the insulating layer are affected. In addition, under the long-term action of a high-voltage direct-current electric field, the phenomenon of space charge accumulation is easy to occur in polypropylene. Because of imbalance among carrier injection, migration and capture processes, a charge accumulation area is formed in the material, so that electric field distribution is distorted, local electric field intensity is increased, and local breakdown is caused, and safe operation of the cable is seriously affected. The above problems are increasingly pronounced as the voltage class increases and the run time increases. In order to improve the thermo-mechanical stability of polypropylene, chemical crosslinking methods, such as peroxide crosslinking or irradiation crosslinking, are generally adopted in the prior art to enable the polypropylene to form a three-dimensional crosslinked network structure, thereby improving the high-temperature mechanical property. However, the chemically crosslinked polypropylene, like XLPE, loses its melt processibility and cannot be reused, contrary to the concept of green sustainable development. In addition, the degree