Modified polypropylene, wrapping tape and application of modified polypropylene and wrapping tape in cable joint insulation recovery

Abstract

The invention discloses a modified polypropylene insulating material which comprises a cross-linked structure formed by addition of modified polypropylene through sulfydryl alkene, and the modified polypropylene is polypropylene grafted with a thiol compound. The modified polypropylene insulating material which is compact in material structure and has excellent peel strength and interface breakdown strength is obtained by carrying out thiol compound grafting modification on the surface of polypropylene and further carrying out sulfydryl alkene addition reaction with a polyvinyl compound. The modified polypropylene insulating material disclosed by the invention is used in a wrapping tape, and can construct a winding-increasing insulating structure which is tightly attached between layers and has no physical interface, so that the insulating strength and the long-term operation reliability of cable accessories are greatly improved, and the safety of power transmission and the stability of a power system are guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of power cable accessories, and in particular to a modified polypropylene, a wrapping tape and applications thereof in restoring insulation of a cable joint. Background Art

[0002] As an important power equipment, power cable is an important part of the power transmission and distribution system. Among them, cable joints, as the most used components in cable accessories, are the weak link in the electrical insulation and mechanical properties of cable lines, and are also the key point to improve the safety and reliability of cable line operation.

[0003] At present, the wrapping tape of cable joints is mainly made of thermosetting cross-linked polyethylene (XLPE). Although it has excellent heat resistance, dielectric properties and mechanical properties, it faces the problem of by-products produced during the cross-linking process polluting the environment and being difficult to recycle after retirement, which does not conform to the concept of green environmental protection and sustainable development. Thermoplastic polypropylene materials, with their advantages such as no need for cross-linking in the production process, simple processing technology, and recyclability after retirement, have become an important development direction for environmentally friendly cable insulation materials. With the rapid development of polypropylene cables, the performance requirements for cable joints are also getting higher and higher. However, for thermoplastic polypropylene cables, the cable joints are difficult to manufacture, which restricts the application prospects of polypropylene cables. Summary of the invention

[0004] Based on this, it is necessary to provide a modified polypropylene with excellent peel strength, interface breakdown strength and electrical insulation performance, a wrapping tape and its application in cable joint insulation restoration.

[0005] In a first aspect, the present invention provides a modified polypropylene, wherein the modified polypropylene is prepared by subjecting polypropylene grafted with thiol groups to a thiol-ene addition reaction.

[0006] In some embodiments, the content of grafted thiol group units in the structure of the polypropylene grafted with thiol groups is 10 wt %-15 wt %.

[0007] In some embodiments, the content of mercapto-olefin addition units in the structure of the modified polypropylene is 8 wt %-13 wt %.

[0008] In a second aspect, the present invention also provides a method for preparing a modified polypropylene insulating material, comprising the following steps:

[0009] reacting polypropylene, a thiol compound and a peroxide initiator to obtain polypropylene grafted with a thiol group;

[0010] The cross-linking reaction between the polypropylene grafted with thiol groups and the polyvinyl compound is induced under ultraviolet light to obtain modified polypropylene.

[0011] In some embodiments, the preparation method further satisfies at least one of the following (1) to (8):

[0012] (1) The thiol compound is selected from one or more of allyl mercaptan, n-butyl mercaptan and 1-hexyl mercaptan;

[0013] (2) The peroxide initiator is selected from one or more of dicumyl peroxide, benzoyl peroxide and diisopropyl peroxide;

[0014] (3) The mass ratio of the thiol compound to the peroxide initiator is (1-3): (0.1-0.3);

[0015] (4) reacting the polypropylene, the thiol compound and the peroxide initiator in nitrogen; optionally, the temperature of the nitrogen is 150° C.-180° C.;

[0016] (5) reacting the polypropylene, the thiol compound and the peroxide initiator in nitrogen; optionally, the flow rate of the nitrogen is 10 mL / min-15 mL / min;

[0017] (6) The polyvinyl compound is selected from one or more of divinylbenzene, butadiene, isoprene and p-divinylbenzene;

[0018] (7) The mass ratio of the polypropylene grafted with thiol groups to the polyvinyl compound is (15-20):1; and / or, the equivalent ratio of the thiol groups in the polypropylene grafted with thiol groups to the polyvinyl compound is (1-3) equl:1 equl;

[0019] (8) The wavelength of the ultraviolet light is 200nm-400nm.

[0020] In a third aspect, the present invention further provides a wrapping tape, wherein the wrapping tape comprises the modified polypropylene described above, or comprises the modified polypropylene prepared by the preparation method of the modified polypropylene described above.

[0021] In a fourth aspect, the present invention also provides a wrapping tape composite layer, which is formed by the addition of thiol-ene to a polypropylene wrapping tape grafted with thiol groups and a polyvinyl compound layer, and the polypropylene wrapping tape grafted with thiol groups is respectively laminated on the inner and outer sides of the polyvinyl compound layer.

[0022] In some embodiments, the wrapping tape composite layer further satisfies at least one of the following (1) to (5):

[0023] (1) 1-2 layers of polypropylene with grafted thiol groups are laminated on both sides of the polyvinyl compound layer;

[0024] (2) The single layer thickness of the polypropylene wrapping tape grafted with thiol groups is 450 μm-550 μm;

[0025] (3) The thickness of the polyvinyl compound layer is 170 μm-230 μm;

[0026] (4) The content of grafted thiol group units in the polypropylene wrapping tape grafted with thiol groups is 10-15wt%;

[0027] (5) The content of the mercapto-olefin addition structural unit in the composite layer of the wrapping tape is 8wt%-13wt%.

[0028] In a fifth aspect, the present invention further provides an application of the wrapping tape composite layer in restoring insulation of a cable joint, wherein the wrapping tape composite layer is wrapped around the outside of the cable joint; and / or the wrapping angle of the wrapping tape composite layer wrapped around the cable joint is 30°-40°.

[0029] In some embodiments, the cable joint includes a conductor, and an insulating inner semiconductive layer, an insulating layer, a wrapping tape layer, a restored insulating inner semiconductive layer, a restored insulating outer semiconductive layer and an insulating outer semiconductive layer sequentially stacked and wrapped on the conductor.

[0030] In a sixth aspect, the present invention also provides a cable joint, characterized in that the cable joint comprises a conductor, and an insulating inner semi-conductive layer, an insulating layer, the above-mentioned wrapping tape composite layer, a restored insulating inner semi-conductive layer, a restored insulating outer semi-conductive layer and an insulating outer semi-conductive layer which are sequentially stacked and wrapped on the conductor.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention provides a modified polypropylene, the modified polypropylene comprising a cross-linked structure formed by the addition of mercapto-ene to a grafted thiol group polypropylene. The modified polypropylene provided by the present invention constructs a winding insulation structure with tight interlayer adhesion, the material structure is dense, and has excellent peel strength and interface breakdown strength; further, the modified polypropylene is used in a polypropylene wrapping tape, which can solve the problems of insufficient tightness between the wrapping tapes of the traditional wrapping cable joint, easy delamination, reduced cable insulation life, and erosion of the cable joint, etc. The polypropylene wrapping tape prepared by the modified polypropylene significantly improves the insulation performance and interface resistance of the wrapping tape and the cable joint, replaces the traditional heating and melting resolidification method, avoids the problem of eccentricity of the restored insulation caused by the melting of the material, and the formed physical interface-free insulation layer has a higher insulation strength, realizes the insulation recovery of the wrapping polypropylene factory joint at room temperature, fundamentally solves the problem of creepage caused by insufficient interface tightness, improves the long-term operation reliability of the cable accessories, prolongs the service life of the cable joint, can better adapt to the high voltage environment, and ensures the safety of power transmission and the stability of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the synthesis reaction mechanism of polypropylene grafted with thiol groups.

[0034] Figure 2 This is a schematic diagram of the UV-initiated reaction mechanism of polypropylene grafted with thiol groups and polyvinyl compounds.

[0035] Figure 3 It is a cross-sectional view of the cable joint of the present invention after the insulation is restored.

[0036] Figure 4 It is a schematic diagram of a cable joint with a polypropylene wrapping tape grafted with thiol groups wrapped once.

[0037] Figure 5 Schematic diagram of a cable joint after spraying polyvinyl compound on polypropylene wrapping tape grafted with thiol groups.

[0038] Figure 6 It is a schematic diagram of a cable joint with a polypropylene wrapping tape with thiol groups grafted onto a polyvinyl compound layer for a second time.

[0039] Figure 7 It is a comparison chart of the interface breakdown strength of the wrapping tape samples prepared in Example 1 of the present invention and Comparative Example 1.

[0040] Description of the markings in the figure:

[0041] 11. conductor, 12. insulating inner semiconductive layer, 13. insulating layer, 14. restored insulating inner semiconductive layer, 15. restored insulating outer semiconductive layer, 16. insulating outer semiconductive layer, 21. inner layer of polypropylene wrapping tape grafted with thiol groups, 22. polyvinyl compound layer, 23. outer layer of polypropylene wrapping tape grafted with thiol groups. DETAILED DESCRIPTION

[0042] In order to facilitate the understanding of the present invention, the preferred embodiments of the present invention are given below to describe the present invention more comprehensively. In order to further understand the present invention, the present invention will be described more comprehensively with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0043] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0044] It should be noted that the experimental methods in the following examples of the present invention without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturers. The various commonly used chemical reagents used in the examples are all commercially available products.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0046] Wrapping tape is a strip material used to wrap around the surface of an object. It usually has certain flexibility, insulation, corrosion resistance and other properties. It is widely used for insulation, protection, shielding and other purposes in the fields of wires and cables, pipes, mechanical parts, etc.

[0047] Cable joints need to be heated during production, and the heating process will cause the insulation to melt. Polypropylene is a thermoplastic material, and its mechanical strength is almost lost after melting, which can easily lead to deformation of the insulation structure and poor interface fusion. During the wrapping process, it is difficult for traditional wrapping cable joints to form a tight, continuous insulation structure without physical interfaces, which introduces air, moisture and other impurities, causing insulation degradation and failure, affecting the safe and stable operation of the cable. Therefore, it is urgent to provide a polypropylene wrapping tape with excellent performance to achieve good insulation performance of the cable joint.

[0048] In a first aspect, the present invention provides a modified polypropylene, wherein the modified polypropylene is prepared by subjecting polypropylene grafted with thiol groups to a thiol-ene addition reaction.

[0049] The invention modifies polypropylene, that is, grafts thiol groups into the polypropylene material, and then uses the mercapto-ene addition method through the reaction activity of the thiol group to form a tightly cross-linked three-dimensional network structure of the polypropylene, thereby improving the tight bonding degree between the polypropylene materials, thereby reducing the stratification phenomenon of the materials, and effectively improving the barrier effect of the polypropylene material on external moisture and impurities. Then, the modified polypropylene is used in a cable joint, which can reduce the erosion of the cable joint due to the external environment, and also improves the surface creep phenomenon caused by insufficient interface tightness of the traditional polypropylene material in the cable joint, so as to realize the restoration of insulation of the cable joint.

[0050] In some embodiments, the content of grafted thiol group units in the structure of the polypropylene grafted with thiol groups is 10wt%-15wt%; further, the cross-linked structure obtained after the 10wt%-15wt% grafted content is subjected to mercapto-ene addition has better performance, is more conducive to forming an insulating layer without a physical interface, and restores the insulation performance of the cable joint.

[0051] Furthermore, the content of grafted thiol group units in the structure of the polypropylene grafted with thiol groups includes but is not limited to 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15% or a mass content range formed by any two of the foregoing and any mass content within the range.

[0052] In some embodiments, the content of mercapto-olefin addition units in the structure of the modified polypropylene is 8wt%-13wt%, including but not limited to 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt% or the mass content range formed by any two of the foregoing and any mass content within the range.

[0053] In a second aspect, the present invention further provides a method for preparing modified polypropylene, comprising the following steps:

[0054] reacting polypropylene, a thiol compound and a peroxide initiator to obtain polypropylene grafted with a thiol group;

[0055] The cross-linking reaction between the polypropylene grafted with thiol groups and the polyvinyl compound is induced under ultraviolet light to obtain modified polypropylene.

[0056] In some embodiments, the thiol compound is selected from one or more of allyl mercaptan, n-butyl mercaptan and 1-hexyl mercaptan; further, the modified polypropylene prepared using allyl mercaptan has higher reactivity.

[0057] In some embodiments, the peroxide initiator is selected from one or more of dicumyl peroxide, benzoyl peroxide and diisopropyl peroxide; further, the use of a peroxide initiator has a higher initiation efficiency, can achieve efficient grafting of thiol compounds, and can better control the grafting rate of thiol groups.

[0058] In some embodiments, polypropylene, allyl mercaptan and a peroxide initiator are reacted to obtain polypropylene grafted with a thiol group; during the reaction, the peroxide initiator decomposes to generate free radicals, which can capture hydrogen atoms from the polypropylene molecular chain to form polypropylene free radicals. The carbon-carbon double bonds in allyl mercaptan have high reactivity and react with the polypropylene free radicals to induce a grafting reaction in the polypropylene material. The synthesis reaction mechanism of the polypropylene grafted with a thiol group is as shown in the attached figure. Figure 1 or as follows:

[0059]

[0060] In some embodiments, the mass ratio of the thiol compound to the peroxide initiator is (1-3): (0.1-0.3), including but not limited to 1:0.1, 2:0.1, 3:0.1, 1:0.2, 1:0.3, 3:0.2, 3:0.3 or a ratio range formed by any two of the foregoing and any ratio within the range.

[0061] In some embodiments, the polypropylene, the thiol compound, and the peroxide initiator are reacted in nitrogen.

[0062] In some embodiments, the polypropylene, the thiol compound and the peroxide initiator are reacted in nitrogen at 140°C-180°C, including but not limited to 140°C, 150°C, 160°C, 170°C, 180°C or a ratio range formed by any two of the foregoing and any temperature within the range.

[0063] In some embodiments, the polypropylene, the thiol compound and the peroxide initiator are reacted in nitrogen at a flow rate of 10 mL / min-15 mL / min, including but not limited to 10 mL / min, 11 mL / min, 12 mL / min, 13 mL / min, 14 mL / min, 15 mL / min or a ratio range formed by any two of the foregoing and any temperature within the range.

[0064] In some embodiments, the polyvinyl compound is selected from one or more of divinylbenzene, butadiene, isoprene, and p-divinylbenzene.

[0065] In some embodiments, the mass ratio of the polypropylene grafted with thiol groups to the polyvinyl compound is (15-20):1, including but not limited to 15:1, 16:1, 17:1, 18:1, 19:1, 20:1 or a ratio range formed by any two of the foregoing and any ratio within the range.

[0066] In some embodiments, the equivalent ratio of the thiol groups in the polypropylene grafted with thiol groups and the polyvinyl compound is (1-3) equl:1 equl, including but not limited to 1:1, 1.5:1, 2:1, 2.5:1, 3:1 or a ratio range formed by any two of the foregoing and any ratio within the range.

[0067] In some embodiments, the wavelength of the ultraviolet light is 200nm-400nm, including but not limited to 200nm, 205nm, 225nm, 235nm, 245nm, 265nm, 285nm, 305nm, 325nm, 365nm, 380nm, 400nm or a wavelength range formed by any two of the foregoing and any wavelength within the range.

[0068] In some embodiments, polypropylene grafted with thiol groups and polyvinyl compounds are subjected to a crosslinking reaction under ultraviolet light; in the crosslinking reaction, the irradiation of ultraviolet light triggers a mercapto-ene addition reaction, and the energy of ultraviolet light is used to trigger a polymerization reaction of active groups in the polypropylene grafted with thiol groups, and the prepared modified polypropylene material is tightly combined, which greatly improves the performance of the polypropylene; the synthetic reaction mechanism of the crosslinking reaction is as shown in the attached Figure 2 or as follows:

[0069]

[0070] In a third aspect, the present invention further provides a wrapping tape, which comprises the modified polypropylene described above, or the modified polypropylene prepared by the preparation method of the modified polypropylene described above. The use of the modified polypropylene raw material greatly improves the integrity and sealing of the wrapping tape.

[0071] In a fourth aspect, the present invention also provides a wrapping tape composite layer, which is formed by the addition of thiol-ene to a polypropylene wrapping tape grafted with thiol groups and a polyvinyl compound layer, and the polypropylene wrapping tape grafted with thiol groups is respectively laminated on the inner and outer sides of the polyvinyl compound layer.

[0072] In some embodiments, the wrapping tape composite layer structure includes an attached Figure 3 The polyvinyl compound layer 22 in the middle, the inner layer 21 of the polypropylene wrapping tape grafted with thiol groups stacked on the inner side of the polyvinyl compound layer, and the outer layer 23 of the polypropylene wrapping tape grafted with thiol groups stacked on the outer side of the polyvinyl compound layer; the inner layer 21 of the polypropylene wrapping tape grafted with thiol groups stacked on the inner side of the polyvinyl compound layer and the outer layer 23 of the polypropylene wrapping tape grafted with thiol groups stacked on the outer side of the polyvinyl compound layer are respectively formed with the polyvinyl compound layer 22 by mercapto-ene addition.

[0073] In some embodiments, the polypropylene wrapping tape inner layer 21 with grafted thiol groups stacked on the inner side of the polyvinyl compound layer is as shown in the attached Figure 4 shown.

[0074] In some embodiments, the polyvinyl compound layer 22 in the wrapping tape composite layer structure is as shown in the attached Figure 5 shown.

[0075] In some embodiments, the outer layer 23 of the polypropylene wrapping tape with grafted thiol groups stacked on the outside of the polyvinyl compound layer is as shown in the attached Figure 6 shown.

[0076] In some embodiments, 1-2 layers of polypropylene grafted with thiol groups are laminated on both the inner and outer sides of the polyvinyl compound layer.

[0077] In some embodiments, the thickness of a single layer of the polypropylene wrapping tape grafted with thiol groups is 450 μm-550 μm.

[0078] In some embodiments, the thickness of the polyvinyl compound layer in the wrapping tape composite layer is 170 μm-230 μm.

[0079] In some embodiments, the content of grafted thiol group units in the polypropylene wrapping tape with grafted thiol groups is 10wt-15wt%, including but not limited to 10wt%, 10.5wt%, 11wt%, 11.5wt%, 12wt%, 12.5wt%, 13wt%, 13.5wt%, 14wt%, 14.5wt%, 15wt% or the mass content range formed by any two of the foregoing and any mass content within the range.

[0080] In some embodiments, the content of the mercapto-olefin addition structural unit in the wrapping tape composite layer is 8wt%-13wt%, including but not limited to 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt% or the mass content range formed by any two of the foregoing and any mass content within the range.

[0081] In a fifth aspect, the present invention further provides an application of the wrapping tape composite layer in restoring insulation of a cable joint, wherein the wrapping tape composite layer is wrapped around the outside of the cable joint;

[0082] And / or, in some embodiments, the wrapping angle of the wrapping tape composite layer wrapped around the cable connector is 30°-40°, including but not limited to 30°, 32°, 35°, 38°, 40° or a range formed by any two of the foregoing and any value within the range.

[0083] In some embodiments, the cable joint includes a conductor, and an insulating inner semiconductive layer, an insulating layer, a wrapping tape composite layer, a restored insulating inner semiconductive layer, a restored insulating outer semiconductive layer and an insulating outer semiconductive layer sequentially stacked and wrapped on the conductor.

[0084] As attached Figure 3 As shown, the cable joint comprises a conductor 11, and an insulating inner semiconductive layer 12, an insulating layer 13, a wrapping tape composite layer, a restored insulating inner semiconductive layer 14, a restored insulating outer semiconductive layer 15 and an insulating outer semiconductive layer 16 which are sequentially stacked and wrapped on the conductor 11; the wrapping tape composite layer structure comprises an attached Figure 3 The polyvinyl compound layer 22, the inner layer 21 of the polypropylene wrapping tape with grafted thiol groups stacked on the inner side of the polyvinyl compound layer, and the outer layer 23 of the polypropylene wrapping tape with grafted thiol groups stacked on the inner side of the polyvinyl compound layer, the inner side of the polyvinyl compound layer is close to the conductor, and the outer side of the polyvinyl compound layer is far from the conductor.

[0085] In a sixth aspect, the present invention also provides a cable joint, characterized in that the cable joint comprises a conductor, and an insulating inner semi-conductive layer, an insulating layer, the above-mentioned wrapping tape composite layer, a restored insulating inner semi-conductive layer, a restored insulating outer semi-conductive layer and an insulating outer semi-conductive layer which are sequentially stacked and wrapped on the conductor.

[0086] As attached Figure 3 As shown, the cable joint comprises a conductor 11, and an insulating inner semiconductive layer 12, an insulating layer 13, a wrapping tape composite layer, a restored insulating inner semiconductive layer 14, a restored insulating outer semiconductive layer 15 and an insulating outer semiconductive layer 16 which are sequentially stacked and wrapped on the conductor 11; the wrapping tape composite layer structure comprises an attached Figure 3The polyvinyl compound layer 21, the inner layer 22 of the polypropylene wrapping tape with grafted thiol groups stacked on the inner side of the polyvinyl compound layer, and the outer layer 23 of the polypropylene wrapping tape with grafted thiol groups stacked on the inner side of the polyvinyl compound layer, the inner side of the polyvinyl compound layer is close to the conductor, and the outer side of the polyvinyl compound layer is far from the conductor.

[0087] For experimental parameters not specified in the following specific embodiments, reference is made to the instructions given in the present application document, and reference may also be made to experimental manuals in the art or other experimental methods known in the art, or to experimental conditions recommended by manufacturers.

[0088] The raw materials and reagents involved in the following specific examples can be obtained from commercial sources, or can be prepared by those skilled in the art according to known methods.

[0089] Example 1. Preparation of modified wrapping tape

[0090] The preparation method of the wrapping tape of this embodiment is as follows:

[0091] An aqueous solution containing 70% ethanol, allyl mercaptan, and diisopropylbenzene peroxide (DCP) were mixed uniformly in a mass ratio of 10:3:0.3. A single-layer polypropylene wrapping tape with a thickness of 500 μm was selected and immersed in the above solution. The mixture was stirred thoroughly to ensure full contact. The mixture was then placed in a high-temperature nitrogen atmosphere with a nitrogen flow rate of 10 mL / min and heated at a constant temperature of 150 °C for 15 min to induce a grafting reaction. After the reaction was completed, the wrapping tape was taken out and naturally cooled to obtain a polypropylene wrapping tape grafted with thiol groups. The synthesis reaction mechanism is shown in the attached figure. Figure 1 As shown, the content of thiol group units in the polypropylene wrapping tape grafted with thiol groups is 10wt%-15wt%.

[0092] The polypropylene wrapping tape grafted with thiol groups prepared above is subjected to a crosslinking reaction with divinylbenzene (DB) under ultraviolet light, wherein the equivalent ratio of the thiol groups in the polypropylene grafted with thiol groups to the polyvinyl compound is 2equl:1equl (the mass ratio of the polypropylene wrapping tape grafted with thiol groups to divinylbenzene (DB) is 20:1). The initiation reaction mechanism is as shown in the attached figure. Figure 2 As shown, the UV power is 1641 mW / cm 2 The ultraviolet wavelength is 365 nm, and the ultraviolet irradiation time is 0.5 s to 10 s. The reaction is completed to obtain a modified wrapping tape, in which the content of mercapto-ene addition units is 8wt% to 13wt%.

[0093] Example 2: Preparation of modified wrapping tape

[0094] The preparation method of the wrapping tape of this embodiment is as follows:

[0095] An aqueous solution containing 70% ethanol, allyl mercaptan and diisopropylbenzene peroxide (DCP) were mixed in a mass ratio of 10:3:0.3, a polypropylene wrapping tape with a single layer thickness of 500 μm was selected and immersed in the above solution, and fully stirred to ensure full contact, and then placed in a high-temperature nitrogen atmosphere with a nitrogen flow rate of 10 mL / min and heated at a constant temperature of 150 °C for 15 min to induce a grafting reaction. After the reaction was completed, the wrapping tape was taken out and naturally cooled to obtain a polypropylene wrapping tape grafted with thiol groups, wherein the thiol group unit content in the polypropylene wrapping tape grafted with thiol groups was 10wt%-15wt%.

[0096] The polypropylene wrapping tape grafted with thiol groups prepared above was subjected to a crosslinking reaction with butadiene under ultraviolet light, wherein the equivalent ratio of the thiol groups in the polypropylene grafted with thiol groups to the polyvinyl compound was 2equl:1equl (the mass ratio of the polypropylene wrapping tape grafted with thiol groups to butadiene was 20:1), and the ultraviolet power was 1641 mW / cm 2 The ultraviolet wavelength is 365 nm, and the ultraviolet irradiation time is 0.5 s to 10 s. The reaction is completed to obtain a modified wrapping tape, in which the content of mercapto-ene addition units is 8wt% to 13wt%.

[0097] Example 3: Preparation of modified wrapping tape

[0098] The preparation method of the wrapping tape of this embodiment is as follows:

[0099] An aqueous solution containing 70% ethanol, allyl mercaptan and diisopropylbenzene peroxide (DCP) were mixed in a mass ratio of 10:1:0.3, a polypropylene wrapping tape with a single layer thickness of 500 μm was selected and immersed in the above solution, and fully stirred to ensure full contact, and then placed in a high-temperature nitrogen atmosphere with a nitrogen flow rate of 10 mL / min and heated at a constant temperature of 180 °C for 10 min to induce a grafting reaction. After the reaction was completed, the wrapping tape was taken out and naturally cooled to obtain a polypropylene wrapping tape grafted with thiol groups, wherein the thiol group unit content in the polypropylene wrapping tape grafted with thiol groups was 10wt%-15wt%.

[0100] The polypropylene wrapping tape grafted with thiol groups prepared above was subjected to a crosslinking reaction with divinylbenzene (DB) under ultraviolet light, wherein the equivalent ratio of the thiol groups in the polypropylene grafted with thiol groups to the polyvinyl compound was 2equl:1equl (the mass ratio of the polypropylene wrapping tape grafted with thiol groups to divinylbenzene (DB) was 15:1), and the ultraviolet power was 1641 mW / cm 2The ultraviolet wavelength is 365 nm, and the ultraviolet irradiation time is 0.5 s to 10 s. The reaction is completed to obtain a modified wrapping tape, in which the content of mercapto-ene addition units in the modified wrapping tape is 10wt% to 15wt%.

[0101] Example 4

[0102] The preparation method of the wrapping tape of this embodiment is as follows:

[0103] An aqueous solution containing 70% ethanol, allyl mercaptan and diisopropylbenzene peroxide (DCP) were mixed in a mass ratio of 1:3:0.3, a polypropylene wrapping tape with a single layer thickness of 500 μm was selected and immersed in the above solution, and fully stirred to ensure full contact, and then placed in a high-temperature nitrogen atmosphere with a nitrogen flow rate of 10 mL / min and heated at a constant temperature of 120 °C for 10 min to induce a grafting reaction. After the reaction was completed, the wrapping tape was taken out and naturally cooled to obtain a polypropylene wrapping tape grafted with thiol groups, wherein the content of thiol group units in the polypropylene wrapping tape grafted with thiol groups was 5wt%-8wt%.

[0104] The polypropylene wrapping tape grafted with thiol groups prepared above was subjected to a crosslinking reaction with divinylbenzene (DB) under ultraviolet light, wherein the equivalent ratio of the thiol groups in the polypropylene grafted with thiol groups to the polyvinyl compound was 2equl:1equl (the mass ratio of the polypropylene wrapping tape grafted with thiol groups to divinylbenzene (DB) was 25:1), and the ultraviolet power was 1641 mW / cm 2 The ultraviolet wavelength is 365 nm, and the ultraviolet irradiation time is 0.5 s to 10 s. The reaction is completed to obtain a modified wrapping tape, in which the content of mercapto-ene addition units is less than 8wt%.

[0105] Example 5

[0106] The preparation method of the wrapping tape of this embodiment is as follows:

[0107] An aqueous solution containing 70% ethanol, allyl mercaptan and diisopropylbenzene peroxide (DCP) were mixed in a mass ratio of 10:5:0.1, a polypropylene wrapping tape with a single layer thickness of 500 μm was selected and immersed in the above solution, and fully stirred to ensure full contact, and then placed in a high-temperature nitrogen atmosphere with a nitrogen flow rate of 10 mL / min and heated at a constant temperature of 150 °C for 15 min to induce a grafting reaction. After the reaction was completed, the wrapping tape was taken out and naturally cooled to obtain a polypropylene wrapping tape grafted with thiol groups, wherein the thiol group unit content in the polypropylene wrapping tape grafted with thiol groups was 18wt%-20wt%.

[0108] The polypropylene wrapping tape grafted with thiol groups prepared above was subjected to a crosslinking reaction with divinylbenzene (DB) under ultraviolet light, wherein the equivalent ratio of the thiol groups in the polypropylene grafted with thiol groups to the polyvinyl compound was 2equl:1equl (the mass ratio of the polypropylene wrapping tape grafted with thiol groups to divinylbenzene (DB) was 10:1), and the ultraviolet power was 1641 mW / cm 2 The ultraviolet wavelength is 365 nm, and the ultraviolet irradiation time is 0.5 s to 10 s. The reaction is completed to obtain a modified wrapping tape, in which the content of mercapto-ene addition units is 18wt% to 20wt%.

[0109] Comparative Example 1

[0110] Unmodified, single-layer polypropylene wrapping tape with a thickness of 500 μm.

[0111] Test Example 1: Peel Strength Test of Polypropylene Wrapping Tape

[0112] (1) Test subjects:

[0113] The polypropylene wrapping tapes grafted with thiol groups prepared in Examples 1 to 5 were cut into GPP test pieces (2 pieces) with a length of 150 mm and a width of (20±0.5) mm, respectively. Divinylbenzene (DB) was sprayed on the surfaces of the two GPP test pieces. The DB spraying thickness was 1 mm. The two GPP test pieces sprayed with DB were placed on opposite sides. A finger electrode with a diameter of 25 mm was attached to the interface between the two GPP test pieces so that the two GPP test pieces were closely attached. The high voltage electrode and the grounding electrode were 2 mm apart. GPP-DB-GPP samples were prepared (the samples of Examples 1 to 5 prepared by the same method were respectively recorded as GPP-DB-GPP-1, GPP-DB-GPP-2, GPP-DB-GPP-3, GPP-DB-GPP-4, and GPP-DB-GPP-5). The interface of the GPP-DB-GPP sample was irradiated with ultraviolet light to induce a reaction. The wavelength of the ultraviolet light source was 365 nm and the light power was 1641 mW / cm 2 The sample is irradiated with ultraviolet light for 0.5~10s.

[0114] The polypropylene wrapping tape of Comparative Example 1 was cut into PP test pieces (2 pieces) with a length of 150 mm and a width of (20±0.5) mm. A finger-shaped electrode with a diameter of 25 mm was attached to the interface between the two PP test pieces so that the two PP test pieces were tightly fitted, with the high-voltage electrode and the grounding electrode 2 mm apart. The test pieces were hot-pressed in a flat vulcanizer at 180°C and 15 MPa, and the PP-PP test piece was obtained after cooling.

[0115] (2) Test method:

[0116] Use a fixture to clamp the separation section of the GPP-DB-GPP sample and the PP-PP sample. When the isolation section is separated, the test section is not allowed to separate. The separation angle of the isolation section is 180°. Under the condition of a tensile speed of 50 mm / min, the peel strength test is carried out.

[0117] (3) Test results:

[0118] According to the test results, the peel strength results of the six samples prepared in Examples 1 to 5 and Comparative Example 1 are as follows:

[0119] The peel strength of the GPP-DB-GPP-1 sample was 61 MPa;

[0120] The peel strength of the GPP-DB-GPP-2 sample was 58 MPa;

[0121] The peel strength of the GPP-DB-GPP-3 sample was 54 MPa;

[0122] The peel strength of the GPP-DB-GPP-4 sample was 48 MPa;

[0123] The peel strength of the GPP-DB-GPP-5 sample is 53 MPa.

[0124] The peel strength of the PP-PP sample is 42 MPa.

[0125] Test Example 2: Interfacial Breakdown Strength Test of Polypropylene Wrapping Tape

[0126] (1) Test subjects:

[0127] Experimental Example 1 prepared 6 groups of samples: GPP-DB-GPP-1, GPP-DB-GPP-2, GPP-DB-GPP-3, GPP-DB-GPP-4, GPP-DB-GPP-5 and PP-PP samples.

[0128] (2) Test method:

[0129] The above six groups of samples were subjected to interface breakdown performance tests. Before the experiment, the sample surface was cleaned with anhydrous ethanol and blown dry to keep the sample surface free of impurities and scratches. The test was started after standing at room temperature for 24 hours. The electrodes used were finger-shaped aluminum foil electrodes with an electrode thickness of 0.06 mm and an electrode spacing of 2 mm. The interface pressure was 0.3 MPa, and the voltage was increased at a rate of 0.5 kV / s until the sample interface was broken down. The voltage at this time was recorded as the interface breakdown voltage.

[0130] (3) Test results:

[0131] The breakdown voltage results of the above 6 groups of samples are shown in Table 1:

[0132] Table 1: Interfacial breakdown voltage of polypropylene wrapping tape

[0133]

[0134] It can be seen from the results in Table 1 above that the interfacial breakdown voltage of GPP-DB-GPP-1, GPP-DB-GPP-2, GPP-DB-GPP-3, GPP-DB-GPP-4, and GPP-DB-GPP-5 samples is significantly higher than that of the PP-PP sample of Comparative Example 1, which shows that the polypropylene wrapping tape prepared by the present invention has better performance.

[0135] The breakdown characteristics of GPP-DB-GPP-1 and PP-PP samples are as follows: Figure 7 As shown in the figure, the GPP-DB-GPP-1 sample, which was subjected to the mercapto-ene addition reaction initiated by ultraviolet light, formed a physical interface between the wrapping tapes, avoiding the electric field distortion caused by charge accumulation at the interface, thereby improving the breakdown strength at the interface. The breakdown voltage at the interface of the PP-PP sample was only 5.49 kV.

[0136] Test Example 3: Interface resistance test of polypropylene wrapping tape

[0137] (1) Test subjects:

[0138] Experimental Example 1 prepared 6 groups of samples: GPP-DB-GPP-1, GPP-DB-GPP-2, GPP-DB-GPP-3, GPP-DB-GPP-4, GPP-DB-GPP-5 and PP-PP samples.

[0139] (2) Test method:

[0140] The above six groups of samples were subjected to interface resistance test. Before the experiment, the sample surface was cleaned with anhydrous ethanol and blown dry to keep the sample surface free of impurities and scratches. The test was started after standing at room temperature for 24 hours. The electrode used was a finger-shaped aluminum foil electrode with an electrode thickness of 0.06 mm and an electrode spacing of 2 mm. The sample was placed in a shielded box in a constant temperature box with a test temperature of 30°C and tested with an EST122 picoammeter.

[0141] (3) Test results:

[0142] The test results are shown in Table 2:

[0143] Table 2: Test results of interfacial resistance of polypropylene wrapping tape

[0144]

[0145] It can be seen from the results in Table 2 that the interface resistance of GPP-DB-GPP after ultraviolet light-induced mercapto-ene addition reaction is significantly increased compared with PP-PP. Among them, the interfaces between the wrapping tapes of GPP-DB-GPP-1, GPP-DB-GPP-2, and GPP-DB-GPP-3 are tightly fitted without air gaps, and the interface contact is better, and the interface resistance is significantly increased. The interface resistance of GPP-DB-GPP-4 and GPP-DB-GPP-5 decreases. The main reason is that the grafted content of thiol in the polypropylene wrapping tape exceeds the range of 10-15%, resulting in a certain decrease in the tightness of the interface contact compared with GPP-DB-GPP-1, GPP-DB-GPP-2, and GPP-DB-GPP-3, but it is still better than the performance of PP-PP.

[0146] Application Example 1: Application of wrapping tape composite layer in cable joint insulation restoration

[0147] This application example provides the application of the wrapping tape composite layer in the cable joint insulation restoration, as shown in the attached Figures 3 to 6 As shown, the structure of the composite layer of the wrapping tape includes: a polyvinyl compound layer 22, an inner layer 21 of a polypropylene wrapping tape with grafted thiol groups laminated on the inner side of the polyvinyl compound layer, and an outer layer 23 of a polypropylene wrapping tape with grafted thiol groups laminated on the outer side of the polyvinyl compound layer;

[0148] The polypropylene wrapping tape inner layer 21 grafted with thiol groups stacked on the inner side of the polyvinyl compound layer and the polypropylene wrapping tape outer layer 23 grafted with thiol groups stacked on the outer side of the polyvinyl compound layer are respectively subjected to mercapto-ene addition to the polyvinyl compound layer 22 .

[0149] The application method of the wrapping tape composite layer in the cable joint insulation restoration is as follows:

[0150] The polypropylene wrapping tape grafted with thiol groups prepared in Example 1 is tightly wrapped around the treated cable joint in an overlapping wrapping manner, with a wrapping angle of 30° to 40° and 3 layers, and each layer is compacted without gaps.

[0151] A layer of divinylbenzene (DB) was evenly sprayed on the surface of the inner layer of the polypropylene wrapping tape grafted with thiol groups using a spray gun, with a spraying thickness of about 200 μm and a thickness deviation of ±30 μm, to obtain a divinylbenzene layer.

[0152] An outer layer of polypropylene wrapping tape grafted with thiol groups is again wrapped around the outside of the above-mentioned divinylbenzene layer to be aligned with the inner layer of polypropylene wrapping tape grafted with thiol groups. The wrapping angle is 30°~40°, the number of wrapping layers is 3, and each layer is compacted without gaps.

[0153] Place the wound cable connector under the UV initiator with a UV lamp power of 1641 mW / cm 2 , wavelength is 365 nm, irradiation is 0.5~10 s, the UV-induced reaction is completed, so that the interface between the wrapping tapes is tightly bonded, forming a cable joint without physical interface to restore insulation.

[0154] Application Example 2: Application of the composite layer of wrapping tape in the restoration of insulation of cable joints

[0155] This application example provides the application of the wrapping tape composite layer in the cable joint insulation restoration, as shown in the attached Figures 3 to 6 As shown, the structure of the composite layer of the wrapping tape includes: a polyvinyl compound layer 22, an inner layer 21 of a polypropylene wrapping tape with grafted thiol groups laminated on the inner side of the polyvinyl compound layer, and an outer layer 23 of a polypropylene wrapping tape with grafted thiol groups laminated on the outer side of the polyvinyl compound layer;

[0156] The polypropylene wrapping tape inner layer 21 grafted with thiol groups stacked on the inner side of the polyvinyl compound layer and the polypropylene wrapping tape outer layer 23 grafted with thiol groups stacked on the outer side of the polyvinyl compound layer are respectively subjected to mercapto-ene addition to the polyvinyl compound layer 22 .

[0157] The application method of the wrapping tape composite layer in the cable joint insulation restoration is as follows:

[0158] The polypropylene wrapping tape grafted with thiol groups prepared in Example 2 is tightly wrapped around the treated cable joint in an overlapping wrapping manner, with a wrapping angle of 30° to 40°, 3 wrapping layers, and each layer is compacted without gaps.

[0159] A layer of butadiene was evenly sprayed on the surface of the inner layer of the polypropylene wrapping tape grafted with thiol groups using a spray gun, the spraying thickness was about 200 μm, and the thickness deviation was ±30 μm, to obtain a butadiene layer.

[0160] The polypropylene wrapping tape grafted with thiol groups is again wrapped around the outside of the above-mentioned butadiene layer to be aligned with the inner layer of the polypropylene wrapping tape grafted with thiol groups. The wrapping angle is 30°~40°, the number of winding layers is 3, and each layer is compacted without gaps.

[0161] Place the wound cable connector under the UV initiator with a UV lamp power of 1641 mW / cm 2 , wavelength is 365 nm, irradiation is 0.5~10 s, the UV-induced reaction is completed, so that the interface between the wrapping tapes is tightly bonded, forming a cable joint without physical interface to restore insulation.

[0162] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0163] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A modified polypropylene, characterized in that: The modified polypropylene is prepared by subjecting polypropylene grafted with thiol groups to a mercapto-ene addition reaction.

2. The modified polypropylene according to claim 1, characterized in that The content of grafted thiol group units in the structure of the polypropylene grafted with thiol groups is 10wt%-15wt%; and / or the content of mercapto-olefin addition units in the structure of the modified polypropylene is 8wt%-13wt%.

3. A method for preparing modified polypropylene, characterized in that: The following steps are involved: reacting polypropylene, a thiol compound and a peroxide initiator to obtain polypropylene grafted with a thiol group; The cross-linking reaction between the polypropylene grafted with thiol groups and the polyvinyl compound is induced under ultraviolet light to obtain modified polypropylene.

4. The method for preparing modified polypropylene according to claim 3, characterized in that: The preparation method satisfies at least one of the following (1) to (8): (1) The thiol compound is selected from one or more of allyl mercaptan, n-butyl mercaptan and 1-hexyl mercaptan; (2) The peroxide initiator is selected from one or more of dicumyl peroxide, benzoyl peroxide and diisopropyl peroxide; (3) The mass ratio of the thiol compound to the peroxide initiator is (1-3): (0.1-0.3); (4) reacting the polypropylene, the thiol compound and the peroxide initiator in nitrogen; optionally, the temperature of the nitrogen is 150° C.-180° C.; (5) reacting the polypropylene, the thiol compound and the peroxide initiator in nitrogen; optionally, the flow rate of the nitrogen is 10 mL / min-15 mL / min; (6) The polyvinyl compound is selected from one or more of divinylbenzene, butadiene, isoprene and p-divinylbenzene; (7) The mass ratio of the polypropylene grafted with thiol groups to the polyvinyl compound is (15-20):1; and / or, the equivalent ratio of the thiol groups in the polypropylene grafted with thiol groups to the polyvinyl compound is (1-3) equl:1 equl; (8) The wavelength of the ultraviolet light is 200nm-400nm.

5. A wrapping tape, characterized in that: The raw material for preparing the wrapping tape includes the modified polypropylene described in claim 1 or 2, or the modified polypropylene prepared by the preparation method of the modified polypropylene described in claim 3 or 4.

6. A wrapping tape composite layer, characterized in that: The wrapping tape composite layer is formed by the addition of thiol-grafted polypropylene wrapping tape and a polyvinyl compound layer, and the thiol-grafted polypropylene wrapping tape is stacked on the inner and outer sides of the polyvinyl compound layer respectively.

7. The wrapping tape composite layer according to claim 6, characterized in that: The wrapping tape composite layer also satisfies at least one of the following (1) to (5): (1) 1-2 layers of polypropylene with grafted thiol groups are laminated on both sides of the polyvinyl compound layer; (2) The single layer thickness of the polypropylene wrapping tape grafted with thiol groups is 450 μm-550 μm; (3) The thickness of the polyvinyl compound layer is 170 μm to 230 μm; (4) The content of grafted thiol group units in the polypropylene wrapping tape grafted with thiol groups is 10-15wt%; (5) The content of the mercapto-olefin addition structural unit in the composite layer of the wrapping tape is 8wt%-13wt%.

8. The application of the wrapping tape composite layer in the restoration of insulation of cable joints is characterized by: The composite layer of wrapping tape as claimed in claim 6 or 7 is wrapped around the outside of the cable joint; and / or the wrapping angle of the composite layer of wrapping tape wrapped around the cable joint is 30°-40°.

9. The use according to claim 8, characterized in that: The cable joint comprises a conductor, and an insulating inner semiconductive layer, an insulating layer, a wrapping tape composite layer, a restored insulating inner semiconductive layer, a restored insulating outer semiconductive layer and an insulating outer semiconductive layer which are sequentially stacked and wrapped on the conductor.

10. A cable connector, characterized in that: The cable joint comprises a conductor, and an insulating inner semiconductive layer, an insulating layer, a wrapping tape composite layer as claimed in claim 6 or 7, a restored insulating inner semiconductive layer, a restored insulating outer semiconductive layer and an insulating outer semiconductive layer which are sequentially stacked and wrapped on the conductor.

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