Modified polypropylene and preparation method thereof, insulating material and cable

Abstract

The invention discloses modified polypropylene and a preparation method thereof, an insulating material and a cable. The modified polypropylene is formed by co-polypropylene through coordination of a sulfydryl grafting monomer and gold particles. According to the modified polypropylene disclosed by the invention, co-polypropylene is taken as a matrix, the matrix contains a sulfydryl-gold coordination bond, a deep trap is formed, and a dynamic reversible point cross-linked network is constructed in the matrix, so that molecular chain movement at a high temperature can be limited to a certain extent, creep deformation in long-term operation is reduced, and the service life of the modified polypropylene is prolonged. And the sulfydryl-gold coordination bond can be recombined at a local damage part through heating, has a self-repairing function, and is endowed with better short-term overload resistance and long-term high-temperature resistance. The modified polypropylene provided by the invention can be applied to a cable as an insulating material to maintain the stability of an insulating layer structure, improve the power transmission capability, prolong the service life of the cable, realize melt processing or recycling of an out-of-service cable, and meet the requirements of environment-friendly cables.

Description

Technical Field

[0001] This application relates to the field of power cable materials technology, and in particular to a modified polypropylene and its preparation method, insulating materials, and cables. Background Technology

[0002] Power cables, as the core carrier of electrical energy transmission, play an irreplaceable role in the modern energy system. Polypropylene (PP) has received widespread attention as an environmentally friendly insulation material to replace cross-linked polyethylene (XLPE). PP boasts advantages such as excellent insulation performance, no need for cross-linking, high operating temperature, and recyclability, significantly reducing carbon emissions and offering energy-saving benefits. Furthermore, the insulation layer can be recycled after cable decommissioning, providing environmental advantages. Simultaneously, PP is free of gel, degassing-induced pores, and small-molecule chemical impurities, exhibiting high purity and natural water-tree resistance, with performance limits exceeding those of XLPE. However, in practical applications, homopolymer PP exhibits excessive rigidity and poor impact resistance. To meet the requirements of cable use and manufacturing processes, it needs to be toughened and softened to reduce the flexural modulus of the prepared copolymer PP. However, this generally results in poor temperature resistance and electrical properties. Therefore, resolving the contradiction between the impact resistance, temperature resistance, and electrical properties of copolymer PP as cable insulation material is expected to overcome the bottleneck in the development of ultra-high voltage cable insulation technology and represents an important direction for the development of power cable technology. Summary of the Invention

[0003] Therefore, it is necessary to provide a modified polypropylene with good impact resistance, high temperature resistance and good electrical properties, its preparation method, and its use as an insulating material in cables to achieve excellent power transmission performance.

[0004] In a first aspect, this application provides a modified polypropylene, which is formed by copolymerizing polypropylene and coordinating it with gold particles via a mercapto-grafted monomer.

[0005] In some embodiments, the copolymer polypropylene is selected from one or both of impact copolymer polypropylene and random copolymer polypropylene.

[0006] In some embodiments, the modified polypropylene comprises, by weight parts, 40-100 parts copolymer polypropylene, 0.005-0.3 parts initiator, 0.5-3 parts mercapto graft monomer and 0.1-1 parts gold particles.

[0007] In some embodiments, the modified polypropylene comprises, by weight parts, 100 parts copolymer polypropylene, 0.01-0.1 parts initiator, 0.5-3 parts mercapto graft monomer and 0.2-0.6 parts gold particles.

[0008] In some embodiments, the modified polypropylene further satisfies at least one of the features shown in (1) to (5) below:

[0009] (1) The initiator includes one or more of benzoyl peroxide, dicumyl peroxide, bis(2,5-diphenylene oxide), azobisisobutyronitrile, and di-tert-butyl peroxide;

[0010] (2) The mercapto graft monomers include one or more of allyl mercaptan, n-propane mercaptan, butenyl mercaptan, 2-buten-1-thiol, (Z)-1,4-dimercaptobut-2-ene, 2-cyclopropene-1-thiol, 2-buten-1,4-dithiol, 2-methyl-2-propene mercaptan, 3-buten-2-thiol and isoprene mercaptan.

[0011] (3) The grafting rate of the thiol monomer in the structure of the modified polypropylene is 0.5%-10%;

[0012] (4) The particle size of the gold particles is 5nm-60nm;

[0013] (5) The gold particles are spherical, star-shaped, rod-shaped, triangular or tetrahedral in shape.

[0014] Secondly, this application also provides a method for preparing modified polypropylene, comprising the following steps:

[0015] Modified polypropylene is prepared by mixing and melting the copolymerized polypropylene, the mercapto-grafted monomer, and the gold particles;

[0016] Optionally, an initiator may be added during the mixing process.

[0017] Thirdly, this application also provides an insulating material, the composition of which includes modified polypropylene and additives, wherein the modified polypropylene includes the modified polypropylene provided in the first aspect of this application.

[0018] In some embodiments, the insulating material further satisfies at least one of the features shown in (1) to (3) below:

[0019] (1) By mass, the insulating material comprises 40-105 parts of modified polypropylene and 0.01-0.6 parts of additives;

[0020] (2) The adjuvants include antioxidants;

[0021] Optionally, the antioxidant includes one or more of antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 1035, and antioxidant 300;

[0022] Optionally, the amount of antioxidant added is 0.01-0.6 parts by weight.

[0023] Fourthly, this application also provides the use of modified polypropylene and / or insulating materials in cables, wherein the modified polypropylene includes the modified polypropylene provided in the first aspect of this application, and the insulating material includes the insulating material provided in the third aspect of this application.

[0024] Fifthly, this application also provides a cable comprising the modified polypropylene provided in the first aspect of this application, or the insulating material provided in the third aspect of this application;

[0025] Optionally, the cable is a DC cable.

[0026] Compared with traditional technologies, the beneficial effects of the technical solution in this application include:

[0027] This application provides a modified polypropylene, which is formed by copolymerizing polypropylene and coordinating it with thiol-grafted monomers and gold particles. On one hand, the modified polypropylene provided in this application contains thiol-gold coordination bonds in its structure, constructing a dynamic and reversible point crosslinking network within the polypropylene. This endows it with superior short-term overload resistance and long-term high-temperature resistance. Furthermore, the constructed dynamic point crosslinking network can, to a certain extent, restrict molecular chain movement at high temperatures, reducing creep deformation during long-term operation, thereby improving impact resistance. When used as an insulating material in cable insulation layers, it can maintain the structural stability of the insulation layer.

[0028] On the other hand, the gold particles introduced in the modified polypropylene structure provided in this application can form deep traps in the polypropylene matrix. Free electrons can be captured by the surface defect states of the gold particles, reducing carrier mobility, forming a local shielding effect, reducing the risk of electric field distortion, and the gold particles are connected to the copolymerized polypropylene matrix by coordination bonds, optimizing interface compatibility and reducing interface charge accumulation.

[0029] Furthermore, the thiol-gold coordination bonds in the modified polypropylene structure provided in this application can undergo bond recombination at localized damage sites through heating, achieving a certain degree of self-repair function and extending service life. Therefore, when applied to cables, the constructed dynamic reversible point cross-linked network enables the melting and processing or recycling of retired cables, reducing production energy consumption and waste pollution, thus meeting the requirements for environmentally friendly cables. Attached Figure Description

[0030] Figure 1 The volume resistivity of the modified polypropylene provided in Examples 1, 2 and Comparative Example 1 of this application.

[0031] Figure 2 The diagram shows the Weibull distribution of the DC breakdown strength of the modified polypropylene provided in Examples 1, 2 and Comparative Example 1 of this application at 30°C.

[0032] Figure 3The diagram shows the Weibull distribution of the DC breakdown strength of the modified polypropylene provided in Examples 1, 2 and Comparative Example 1 of this application at 70°C. Detailed Implementation

[0033] To facilitate understanding of this application, preferred embodiments of this application are provided below for a more comprehensive description of the technical solutions of this application. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to enable a more thorough and complete understanding of the disclosure of this application.

[0034] It should be noted that the experimental methods in the following examples of this application without specifying specific conditions are generally based on conventional conditions or conditions recommended by the manufacturers. Various commonly used chemical reagents used in the examples are all commercially available products.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0036] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this document; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, stating that a parameter is an integer ≥2 is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, stating that a parameter is an integer selected from "2-10" is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0037] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0038] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0039] Unless otherwise specified, the terms "comprising," "containing," and "including" as used in this application can be open-ended or closed-ended. In open-ended cases, for example, "comprising," "containing," and "including" can mean that other members, elements, or method steps not listed can also be included, or that only the listed members, elements, or method steps can be included.

[0040] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". Further, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0041] In this application, unless otherwise specified, A (e.g., B) means that B is a non-limiting example of A, and it is understood that A is not limited to B.

[0042] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0043] In this application, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0044] In this application, if the unit of a data range is only followed by the right endpoint, it means that the units of the left and right endpoints are the same.

[0045] Polypropylene (PP) materials possess advantages such as excellent insulation properties, no need for cross-linking, high operating temperature, and melt reusability. Compared to cross-linked polyethylene (XLPE), PP materials exhibit superior performance and can be recycled after cable decommissioning, significantly reducing carbon emissions and offering energy-saving and environmental benefits. Furthermore, PP materials are free from gelation, degassing-induced pores, and small-molecule chemical impurities, possessing high purity and natural water-tree resistance, with performance limits exceeding those of XLPE. PP materials represent a crucial direction for the development of power cable technology, replacing XLPE.

[0046] However, in practical applications, homopolymer polypropylene is too rigid and cannot be directly used as cable insulation material, requiring toughening and softening. Thanks to the development of in-reactor polypropylene alloying technology, petrochemical companies can synthesize impact copolymer polypropylene (IPC) containing an intrinsic rubber phase, effectively reducing the material's flexural modulus to meet the requirements of cable use and manufacturing processes. However, toughened polypropylene materials generally suffer from poor temperature resistance and electrical properties. For example, the ethylene propylene rubber phase introduced into impact copolymer polypropylene (IPC) reduces the material's insulation performance and temperature resistance. The rubber phase negatively impacts the temperature resistance and electrical properties of impact copolymer polypropylene, potentially leading to more significant space charge accumulation under an electric field, easily causing electric field distortion and breakdown risk. Under long-term use and short-term overload conditions, thermomechanical properties deteriorate, and this performance degradation becomes more pronounced with increasing rubber phase content.

[0047] Therefore, this application provides a modified polypropylene that resolves the contradiction between the impact resistance, temperature resistance, and electrical properties of polypropylene materials as cable insulation.

[0048] In a first aspect, this application provides a modified polypropylene, which is formed by copolymerizing polypropylene and coordinating it with gold particles via a mercapto-grafted monomer.

[0049] The modified polypropylene structure provided in this application uses copolymer polypropylene as the matrix. Through the formation of coordination bonds between the thiol groups grafted onto the copolymer polypropylene and gold particles (Au), a dynamic and reversible point cross-linking network is constructed within the copolymer polypropylene molecular chain. This significantly improves the heat extension temperature and high-temperature thermomechanical stability of the copolymer polypropylene. Furthermore, the gold particles introduced into the copolymer polypropylene macromolecular chain form deep traps within the copolymer polypropylene matrix. Free electrons can be captured by the surface defect states of the gold particles, reducing carrier mobility and effectively lowering the electrical conductivity of the copolymer polypropylene. This also creates a local shielding effect, reducing the risk of electric field distortion and increasing the breakdown field strength of the copolymer polypropylene. Moreover, the coordination bonds between the gold particles and the copolymer polypropylene matrix optimize interfacial compatibility and reduce interfacial charge accumulation. When applied to insulation materials and cables, it exhibits excellent impact resistance, temperature resistance, and electrical properties, providing superior power transmission performance.

[0050] The modified polypropylene provided in this application possesses a dynamic and reversible point cross-linking network. The resulting mercapto-gold particle coordination bonds can be recombined at localized damage sites through heating, achieving a certain degree of self-repair and extending service life. It also exhibits reprocessable characteristics, maintaining material properties even after multiple processing cycles. This further enables the melting and recycling of decommissioned cables, reducing production energy consumption and waste pollution, thus meeting the requirements for environmentally friendly cables.

[0051] As a non-limiting example, in some embodiments, the copolymer polypropylene is selected from one or both of impact copolymer polypropylene and random copolymer polypropylene.

[0052] The introduction of an ethylene propylene rubber phase into the structure of impact copolymer polypropylene (IPC) reduces the insulation performance and temperature resistance of the material. The rubber phase has a negative impact on the temperature resistance and DC performance of impact copolymer polypropylene, and the impact is even greater on the high voltage DC performance. This may lead to a more significant problem of space charge accumulation in impact copolymer polypropylene under a high voltage DC electric field, which can easily cause electric field distortion and breakdown risk. Under long-term use and short-term overload, there is a problem of thermomechanical property degradation, and this performance degradation is more significant with the increase of rubber phase content. Therefore, the modified polypropylene with the structure described in this application is particularly suitable for impact copolymer polypropylene (IPC) where R is impact copolymer polypropylene (IPC). The dynamic reversible point crosslinking network constructed by the mercapto-gold coordination bond in the structure of formula (1) can significantly improve the temperature resistance of impact copolymer polypropylene (IPC). The introduction of gold particles into the macromolecular chain of impact copolymer polypropylene (IPC) creates deep traps within the IPC matrix, effectively improving the electrical properties of IPC.

[0053] In some embodiments, the modified polypropylene comprises, by weight parts, 40-100 parts copolymer polypropylene, 0.005-0.3 parts initiator, 0.5-3 parts mercapto graft monomer and 0.1-1 parts gold particles.

[0054] In some embodiments, the modified polypropylene comprises, by weight parts, 100 parts copolymer polypropylene, 0.01-0.1 parts initiator, 0.5-3 parts mercapto graft monomer and 0.2-0.6 parts gold particles.

[0055] In some embodiments, the initiator includes one or more of benzoyl peroxide (BPO), dicumyl peroxide (DCP), bis(2,5-diphenyl)propane (AD), azobisisobutyronitrile (AIBN), and di-tert-butyl peroxide (DTBP).

[0056] In some embodiments, the thiol grafting monomer includes one or more of allyl mercaptan, n-propane mercaptan, butenyl mercaptan, 2-buten-1-thiol, (Z)-1,4-dimercaptobut-2-ene, 2-cyclopropene-1-thiol, 2-buten-1,4-dithiol, 2-methyl-2-propene mercaptan, 3-buten-2-thiol, and isoprene mercaptan.

[0057] In some embodiments, the grafting rate of the thiol monomer in the structure of the modified polypropylene is 0.5wt%-10wt%. As a non-limiting example, it includes, but is not limited to, 0.5wt%, 1wt%, 2wt%, 5wt%, 8wt%, 10wt%, or any range formed by both of the foregoing and any value within that range.

[0058] The particle size of the gold particles used in the modified polypropylene significantly affects the performance of the modified polypropylene. In some embodiments, the particle size of the gold particles is 5nm-60nm. Within this particle size range, a suitable number of coordination sites and crosslinking active sites can be formed, resulting in a suitable crosslinking density. This allows the particles to be uniformly dispersed in the matrix, effectively resolving the contradiction between impact resistance, temperature resistance, and electrical properties. When the particle size of the gold particles is less than 5nm, the number of mononuclear coordination sites and crosslinking active sites is insufficient, leading to inadequate crosslinking density and a failure to effectively improve temperature resistance and electrical properties. When the particle size of the gold particles is greater than 50nm, the mononuclear crosslinking density is high, resulting in excessively rigid molecular chains and a significant decrease in impact resistance. Furthermore, excessively large particle sizes can easily lead to agglomeration, causing excessively high local stress, which can easily trigger electric field distortion and breakdown risks, and cause overload phenomena. As a non-limiting example, it includes, but is not limited to, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, or any range formed by both of the foregoing and any value within that range. Furthermore, in some embodiments, a gold particle size of 20nm-50nm can better achieve the technical effects of this application.

[0059] The shape of the gold particles used in the modified polypropylene also has a significant impact on the performance of the modified polypropylene. Different gold particle shapes have different numbers of coordination sites, crosslinking active sites, and uniform distribution, thus affecting the arrangement of the copolymerized polypropylene chains after point crosslinking, resulting in different performance effects. As a non-limiting example, in some embodiments, the gold particles are spherical, star-shaped, rod-shaped, triangular, or tetrahedral.

[0060] Secondly, this application also provides a method for preparing modified polypropylene, comprising the following steps:

[0061] Modified polypropylene is prepared by mixing and melting the copolymerized polypropylene, mercapto-grafted monomer, and gold particles.

[0062] In some embodiments, an initiator is added during the mixing process.

[0063] In some embodiments, the method for preparing the modified polypropylene includes the following steps:

[0064] S10. Mix the copolymer polypropylene, initiator and grafting monomer, and carry out the grafting reaction to prepare mercapto-grafted copolymer polypropylene.

[0065] S20. The thiol-grafted copolymer polypropylene is mixed and melted with gold particles to prepare modified polypropylene.

[0066] In step S10, the initiator decomposes, and the copolymerized polypropylene generates free radicals. These free radicals can abstract hydrogen atoms from the copolymerized polypropylene backbone to form free radicals. The thiol grafting monomer has high reactivity and undergoes an addition reaction with the copolymerized polypropylene free radicals, thus initiating the grafting reaction.

[0067] In some embodiments, in step S10, the grafting rate is 0.5wt%-10wt%. Within this grafting rate range, the crosslinking density at coordination sites with gold particles can be better controlled, thereby obtaining excellent modified polypropylene properties. As a non-limiting example, the grafting rate includes, but is not limited to, 0.5wt%, 1wt%, 2wt%, 5wt%, 8wt%, 10wt%, or any range formed by both of the foregoing and any value within that range.

[0068] In some embodiments, in step S10, the grafting reaction temperature is 180°C-230°C, which allows for better control of the thiol grafting rate of the copolymer polypropylene. As a non-limiting example, the temperature includes, but is not limited to, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, or any range thereof and any value within that range.

[0069] In some embodiments, in step S10, after the grafting reaction is completed, the material is extruded using a twin-screw extruder.

[0070] In some embodiments, the temperature of the twin-screw extruder is 180°C-230°C. As a non-limiting example, the temperature includes, but is not limited to, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, or any range formed by either of the foregoing and any value within that range.

[0071] In some embodiments, the twin-screw extruder has a rotational speed of 60 rpm to 200 rpm. As a non-limiting example, the rotational speed includes, but is not limited to, 60 rpm, 80 rpm, 100 rpm, 120 rpm, 150 rpm, 180 rpm, 200 rpm, or any range formed by either of the foregoing and any value within that range.

[0072] In some embodiments, the prepared mercapto-grafted copolymer polypropylene in step S10 further needs to be dried, which, as a non-limiting example, can be vacuum drying.

[0073] In some embodiments, the drying temperature of the prepared mercapto-grafted copolymer polypropylene is 80°C-100°C. As a non-limiting example, the temperature includes, but is not limited to, 80°C, 85°C, 90°C, 95°C, 100°C, or any range thereof and any value within such range.

[0074] In some embodiments, the drying time of the prepared mercapto-grafted copolymer polypropylene is 5h-20h. As a non-limiting example, it includes, but is not limited to, 5h, 8h, 10h, 12h, 15h, 18h, 20h or any range formed by both of the foregoing and any value within the range.

[0075] In some embodiments, in step S20, the gold particles also need to be pretreated, specifically by washing the gold particles and then refluxing them in a non-polar solvent to obtain the gold particles.

[0076] In some embodiments, in step S20, the melting temperature is 180°C-230°C. As a non-limiting example, the temperature includes, but is not limited to, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, or any range formed by either of the foregoing and any value within that range.

[0077] In some embodiments, in step S20, the rotation speed of the melting process is 30 rpm to 200 rpm. As a non-limiting example, the rotation speed includes, but is not limited to, 30 rpm, 40 rpm, 50 rpm, 60 rpm, 80 rpm, 100 rpm, 120 rpm, 150 rpm, 180 rpm, 200 rpm, or any range formed by any two of the foregoing and any value within the range.

[0078] In some embodiments, in step S20, the melting time is 5 min to 20 min. As a non-limiting example, the rotation speed includes, but is not limited to, 5 min, 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, or any range formed by either of the foregoing and any value within that range.

[0079] Thirdly, this application also provides an insulating material, the composition of which includes modified polypropylene and additives, wherein the modified polypropylene includes the modified polypropylene provided in the first aspect of this application.

[0080] In some embodiments, the modified polypropylene in the insulating material is 40-105 parts by weight, including but not limited to 40 parts, 50 parts, 55 parts, 60 parts, 70 parts, 80 parts, 90 parts, 100 parts, 105 parts or any range formed by both of the foregoing and any value within the range.

[0081] In some embodiments, the additives in the insulating material are 0.01-0.6 parts by weight, including but not limited to 0.01 parts, 0.05 parts, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, or any range formed by any two of the foregoing and any value within the range.

[0082] In some embodiments, the adjuvant includes an antioxidant. As a non-limiting example, the antioxidant includes one or more of antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]), antioxidant 1076 (octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), antioxidant 168 (tris[2,4-di-tert-butylphenyl]phosphite), antioxidant 1035 (2,2'-thiobis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]), and antioxidant 300 (4,4'-thiobis(6-tert-butyl-3-methylphenol)).

[0083] In some embodiments, the insulating material comprises, by weight, 0.01-0.6 parts modified polypropylene and 0.01-0.6 parts antioxidant.

[0084] Fourthly, this application also provides the use of modified polypropylene and / or insulating materials in cables, wherein the modified polypropylene includes the modified polypropylene provided in the first aspect of this application, and the insulating material includes the insulating material provided in the third aspect of this application.

[0085] Fifthly, this application also provides a cable comprising the modified polypropylene provided in the first aspect of this application, or the insulating material provided in the fourth aspect of this application.

[0086] In some embodiments, the cable is a DC cable.

[0087] For experimental parameters not specified in the following specific embodiments, please refer to the guidelines given in this application document first, or refer to experimental manuals or other experimental methods known in the art, or refer to the experimental conditions recommended by the manufacturer.

[0088] The raw materials and reagents involved in the following specific embodiments can be obtained commercially or prepared by those skilled in the art using known methods.

[0089] The types and sources of some of the reagents and raw materials involved in the embodiments of this application are as follows:

[0090] Impact copolymer polypropylene resin (purchased from Sinopec Yanshan Petrochemical Company, model K8003, 2.5 g / 10min), initiator (Noryon Perkadox, DCP), allyl mercaptan (CAS No.: 870-23-5), and gold nanoparticles (Zhongke Keyou, particle size 10nm-60nm, spherical).

[0091] Example 1

[0092] The raw materials for preparing the modified polypropylene in this embodiment, by mass parts, include:

[0093] 100 parts of impact-resistant copolymer polypropylene resin K8003

[0094] Initiator DCP 0.03 parts,

[0095] 2.4 parts of allyl mercaptan

[0096] Antioxidant 1010 0.3 parts, and

[0097] 0.6 parts of gold nanoparticles (20nm, spherical).

[0098] The preparation method of the modified polypropylene is as follows:

[0099] The temperature range of the twin-screw extruder is set to 180, 190, 200, 210, 210, 200, and 200℃, and the rotation speed is set to 120 rpm. After the temperature of each area of ​​the screw stabilizes, the impact copolymer polypropylene resin, antioxidant 1010, initiator DCP, and allyl mercaptan are uniformly mixed according to the mass fraction and then fed into the twin-screw extruder using a loss-in-weight feeder. The material extruded from the die is then water-cooled and pelletized.

[0100] The above materials were vacuum dried at 80℃ for 12 hours to remove residual moisture and ungrafted allyl mercaptan from the materials. Using the Ellman method, 5,5'-dithiobis(2-nitrobenzoic acid) reagent was added to allow it to undergo a mercapto-disulfide bond exchange reaction with the mercapto groups. The grafting rate of mercapto groups in the impact copolymer polypropylene resin was determined by measuring the absorbance of the reaction product 2-nitro-5-mercaptobenzoic acid. The test results showed that the grafting rate of mercapto groups in the impact copolymer polypropylene resin reached 0.5wt%-10wt%.

[0101] 20 nm gold nanoparticles were acid-washed with HNO3 for 30 minutes to remove surface oxides, and then ultrasonically cleaned with ethanol and acetone in sequence, with the solvent replaced by xylene. The mixture was refluxed at 110 °C for 4 hours. Impurities in the gold nanoparticles were removed by centrifugation, and the purified gold nanoparticles were dispersed in xylene. 0.1% magnesium stearate (by weight of the gold nanoparticles) was added and ultrasonically treated. The gold nanoparticles were then removed and vacuum-dried at 80 °C for 12 hours to prepare pretreated gold nanoparticles.

[0102] The vacuum-dried mercapto-grafted impact-resistant copolymer polypropylene resin and the pretreated nano-gold particles were placed in a mixer and melt-mixed at 190°C and 60 rpm for 10 min to prepare modified polypropylene.

[0103] Example 2

[0104] The raw materials for preparing the modified polypropylene in this embodiment, by mass parts, include:

[0105] 100 parts of impact-resistant copolymer polypropylene resin K8003

[0106] Initiator DCP 0.03 parts,

[0107] 1.6 parts of allyl mercaptan

[0108] Antioxidant 1010 0.3 parts, and

[0109] 0.4 parts of gold nanoparticles (20nm, spherical).

[0110] The preparation method of the modified polypropylene is the same as that in Example 1.

[0111] Example 3

[0112] The raw materials for preparing the modified polypropylene in this embodiment, by mass parts, include:

[0113] 100 parts of impact-resistant copolymer polypropylene resin K8003

[0114] Initiator DCP 0.03 parts,

[0115] 1.2 parts of allyl mercaptan

[0116] Antioxidant 1010 0.3 parts, and

[0117] 0.3 parts of gold nanoparticles (20nm, spherical).

[0118] The preparation method of the modified polypropylene is the same as that in Example 1.

[0119] Example 4

[0120] The raw materials for preparing the modified polypropylene in this embodiment, by mass parts, include:

[0121] 100 parts of impact-resistant copolymer polypropylene resin K8003

[0122] Initiator DCP 0.03 parts,

[0123] 0.8 parts of allyl mercaptan

[0124] Antioxidant 1010 0.3 parts, and

[0125] 0.2 parts of gold nanoparticles (20nm, spherical).

[0126] The preparation method of the modified polypropylene is the same as that in Example 1.

[0127] Example 5

[0128] The raw materials for preparing the modified polypropylene in this embodiment, by mass parts, include:

[0129] 100 parts of impact-resistant copolymer polypropylene resin K8003

[0130] Initiator DCP 0.03 parts,

[0131] 4 parts of allyl mercaptan

[0132] Antioxidant 1010 0.3 parts, and

[0133] 0.6 parts of gold nanoparticles (20nm, spherical).

[0134] The preparation method of the modified polypropylene is the same as that in Example 1.

[0135] Example 6

[0136] The raw materials for preparing the modified polypropylene in this embodiment, by mass parts, include:

[0137] 100 parts of impact-resistant copolymer polypropylene resin K8003

[0138] Initiator DCP 0.03 parts,

[0139] 2.4 parts of allyl mercaptan

[0140] Antioxidant 1010 0.3 parts, and

[0141] 1.5 parts of gold nanoparticles (20nm, spherical).

[0142] The preparation method of the modified polypropylene is the same as that in Example 1.

[0143] Example 7

[0144] The raw materials for preparing the modified polypropylene in this embodiment, by mass parts, include:

[0145] 100 parts of impact-resistant copolymer polypropylene resin K8003

[0146] Initiator DCP 0.03 parts,

[0147] 4 parts of allyl mercaptan

[0148] Antioxidant 1010 0.3 parts, and

[0149] 1.5 parts of gold nanoparticles (20nm, spherical).

[0150] The preparation method of the modified polypropylene is the same as that in Example 1.

[0151] Example 8

[0152] The raw materials for preparing the modified polypropylene in this embodiment, by mass parts, include:

[0153] 100 parts of impact-resistant copolymer polypropylene resin K8003

[0154] Initiator DCP 0.03 parts,

[0155] 2.4 parts of allyl mercaptan

[0156] Antioxidant 1010 0.3 parts, and

[0157] 0.6 parts of gold nanoparticles (60nm, spherical).

[0158] The preparation method of the modified polypropylene is the same as that in Example 1.

[0159] Example 9

[0160] The raw materials for preparing the modified polypropylene in this embodiment, by mass parts, include:

[0161] 100 parts of impact-resistant copolymer polypropylene resin K8003

[0162] Initiator DCP 0.03 parts,

[0163] 2.4 parts of allyl mercaptan

[0164] Antioxidant 1010 0.3 parts, and

[0165] 0.6 parts of gold nanoparticles (10nm, spherical).

[0166] The preparation method of the modified polypropylene is the same as that in Example 1.

[0167] Comparative Example 1

[0168] Uncrosslinked impact copolymer polypropylene resin K8003 was hot-pressed into samples of various sizes in a flat vulcanizing machine at 190℃ and 15MPa for comparative testing.

[0169] Comparative Example 2

[0170] By mass fraction, the raw materials for preparing the modified polypropylene in this comparative example do not contain added gold nanoparticles; the remaining raw materials and their contents are the same as in Example 1. The preparation method for the modified polypropylene in this comparative example does not include the treatment of gold nanoparticles or point crosslinking; the remaining preparation steps are basically the same as in Example 1.

[0171] Comparative Example 3

[0172] The raw materials for preparing the modified polypropylene in this comparative example, by mass parts, include:

[0173] 100 parts of impact-resistant copolymer polypropylene resin K8003

[0174] Antioxidant 1010 0.3 parts, and

[0175] One part of gold nanoparticles.

[0176] The preparation method of the modified polypropylene in this comparative example does not include the grafting treatment of impact copolymer polypropylene resin, and the remaining preparation steps are basically the same as those in Example 1.

[0177] Application Example 1: Mechanical Property Testing of Modified Polypropylene

[0178] The modified polypropylene prepared in the examples and comparative examples was hot-pressed into sheet samples with a thickness of 1 mm and cut into dumbbell-shaped samples. The mechanical properties were tested according to the test method of GB / T 1040.3-2006. The test results are shown in Table 1.

[0179] Table 1: Test results of mechanical properties of modified polypropylene

[0180]

[0181] As shown in Table 1, compared to the comparative examples, the examples all exhibited increased tensile strength and decreased elongation at break, demonstrating better impact resistance. The increase in the amount of thiol monomer and gold nanoparticles had a greater impact on the mechanical properties of the point-crosslinked polypropylene, and the amount of thiol monomer and gold nanoparticles was positively correlated with the crosslinking density of the copolymerized polypropylene. Compared to Comparative Example 1, Comparative Example 2 (grafted only with thiol groups), and Comparative Example 3 (doped only with gold nanoparticles), the impact resistance of the materials was only slightly enhanced, but not significantly changed, further demonstrating that the increased tensile strength of the materials prepared in the examples came from the crosslinking of gold-sulfur bonds. Examples 5-9 showed a slight decrease in tensile strength compared to Examples 1-4, attributed to the mismatch in reactant concentrations and the unevenness of the crosslinking network density. Unreacted thiol groups or gold nanoparticle monomers were present in Examples 5 and 6, which acted as impurities, reducing material uniformity. In Example 7, the excessively high crosslinking density led to decreased material toughness, causing the tensile process to enter the stress hardening stage earlier, resulting in decreased mechanical properties. In Example 8, the excessively large size of the gold nanoparticles led to excessive bonding between the gold nanoparticles and the thiol-grafted polypropylene backbone, resulting in concentrated cross-linking and uneven distribution of the cross-linked network, thus deteriorating the mechanical properties. In Example 9, the excessively small size of the gold nanoparticles resulted in too few polypropylene backbones being cross-linked with them, leading to a decrease in the cross-linking effect.

[0182] Application Example 2: Temperature Resistance Test of Modified Polypropylene

[0183] The modified polypropylene prepared in the examples and comparative examples was subjected to temperature resistance tests. The specific test methods are as follows:

[0184] (1) Heat resistance elongation temperature test: The modified polypropylene prepared in the examples and comparative examples was hot-pressed into sheet samples with a thickness of 1 mm and cut into dumbbell-shaped samples. The heat resistance elongation temperature test under a load of 0.2 MPa was carried out. The temperature was gradually increased from 150 °C, and the temperature was held for 15 min after each 2 °C increase. The temperature at which the load elongation reached 60% was taken as the heat resistance elongation temperature.

[0185] (2) Melt flow index: The melt flow index of the modified polypropylene prepared in the examples and comparative examples was measured at 230°C and 2.16 kg.

[0186] The test results obtained using the above testing method are shown in Table 2.

[0187] Table 2: Test results of heat resistance elongation temperature of modified polypropylene

[0188]

[0189] As shown in Table 2, compared to the comparative examples, the modified polypropylene prepared in the examples of this application exhibits a significantly improved heat extension temperature. This improvement can be attributed to the formation of a gold-sulfur crosslinked network between the gold nanoparticles and the thiol monomers, which enhances the thermomechanical stability of the material at high temperatures. Compared to Examples 1-4, the heat extension temperatures in Examples 5-9 are lower, attributed to excessive material and uneven crosslinking. In Examples 5 and 6, the excessively high content of thiol or gold nanoparticles, resulting in either too many or too few molecular chains reacting with individual gold nanoparticles, both lead to decreased crosslinking uniformity. In Example 8, there is excessively high local crosslinking, while in Example 9, the density of the gold nanoparticle crosslinked network is too low, both resulting in a decrease in heat extension temperature. In Example 7, the degree of crosslinking is too high, and the melt flow rate is too low, making it unsuitable for processing in practical applications.

[0190] The decrease in the heat resistance extension temperature in Comparative Example 2 may be related to the reduction of the regularity of the copolymer polypropylene molecular chain by the thiol side group. The increase in the heat resistance extension temperature in Comparative Example 3 may be related to the physical cross-linking of the copolymer polypropylene by the gold nanoparticles. However, in general, the gold sulfur point cross-linking network of this application has a greater improvement in the heat resistance of the copolymer polypropylene.

[0191] As the amount of thiol monomer and gold nanoparticles increases, the melt flow rate gradually decreases. This is related to the point crosslinking network constructed by gold-sulfur bonds. Although the viscosity increases, it still retains thermoplasticity and can be used for cable insulation extrusion. When the amount of thiol monomer and / or gold nanoparticles is too high (as in Examples 5-7), the crosslinking density of the copolymer polypropylene is too high, resulting in excessively high material viscosity, which has a significant impact on the molding extrusion of cable insulation. When the particle size of the gold nanoparticles is too large or too small (as in Examples 8-9), excessively large gold nanoparticles will induce locally excessively dense crosslinking networks, leading to a decrease in material uniformity. Insufficiently small gold nanoparticles cannot connect enough polypropylene molecular chains, resulting in excessively low crosslinking density. Comparative Examples 2-3 show that the increase in melt flow rate in the examples is largely due to the gold-sulfur point crosslinking network, rather than solely due to grafting and nanocomposite properties.

[0192] Application Example 3: Electrical Property Testing of Modified Polypropylene

[0193] The modified polypropylene prepared in Examples 1-2 and Comparative Example 1 was subjected to electrical performance testing. The specific testing methods are as follows:

[0194] (1) Volume resistivity: The modified polypropylene prepared in Examples 1-2 and Comparative Example 1 was hot-pressed into a thin film sample with a thickness of 0.3 mm. The volume resistivity of the sample was tested at 30 and 70 °C under an electric field of 20 kV / mm using a three-electrode high-resistivity meter.

[0195] (2) DC breakdown strength: The modified polypropylene prepared in Examples 1-2 and Comparative Example 1 was hot-pressed into thin film samples with a thickness of 0.1 mm. The DC breakdown strength of the three samples was tested using a DC breakdown device. The breakdown test electrode was a cylindrical electrode with a diameter of 25 mm. The sample and the electrode were immersed in silicone oil for the experiment. The experiment was conducted at 30℃ and 70℃, and the voltage rise rate was 1 kV / s.

[0196] The test results obtained using the above testing method are attached. Figure 1 Appendix Figure 2 and attached Figure 3 .

[0197] See attached Figure 1In Examples 1 and 2, the point-crosslinked modified copolymer polypropylene showed significantly improved volume resistivity at both 30°C and 70°C compared to the unmodified copolymer polypropylene, with the improvement being more pronounced at higher temperatures. This may be because the melting of the elastomer phase in pure impact copolymer polypropylene at high temperatures lowers the carrier migration barrier, leading to a decrease in volume resistivity. For the point-crosslinked modified copolymer polypropylene, on the one hand, the gold-sulfur crosslinks dispersed within the polypropylene can bond the elastomer phase to the copolymer polypropylene phase molecules, hindering the melting and relaxation of the elastomer phase; on the other hand, both the gold nanoparticles and the thiol monomers possess deep trap introduction capabilities, which can suppress carrier migration and improve volume resistivity by trapping charges.

[0198] See appendix Figure 2 and attached Figure 3 Modified copolymer polypropylene, which relies on gold-sulfur bond crosslinking, has a higher DC breakdown field strength, larger shape parameters, smaller dispersion, and stronger material reliability.

[0199] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above 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.

[0200] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A modified polypropylene, characterized in that, The modified polypropylene is formed by copolymerizing polypropylene and coordinating it with gold particles via a mercapto-grafted monomer.

2. The modified polypropylene according to claim 1, characterized in that, The copolymer polypropylene is selected from one or both of impact copolymer polypropylene and random copolymer polypropylene.

3. The modified polypropylene according to claim 1, characterized in that, The modified polypropylene comprises, by weight, 40-100 parts copolymer polypropylene, 0.005-0.3 parts initiator, 0.5-3 parts mercapto graft monomer and 0.1-1 parts gold particles.

4. The modified polypropylene according to claim 3, characterized in that, The modified polypropylene comprises, by weight, 100 parts copolymer polypropylene, 0.01-0.1 parts initiator, 0.5-3 parts mercapto graft monomer and 0.2-0.6 parts gold particles.

5. The modified polypropylene according to claim 3 or 4, characterized in that, The modified polypropylene also satisfies at least one of the following characteristics (1) to (5): (1) The initiator includes one or more of benzoyl peroxide, dicumyl peroxide, bis(2,5-diphenylene oxide), azobisisobutyronitrile, and di-tert-butyl peroxide; (2) The mercapto graft monomers include one or more of allyl mercaptan, n-propane mercaptan, butenyl mercaptan, 2-buten-1-thiol, (Z)-1,4-dimercaptobut-2-ene, 2-cyclopropene-1-thiol, 2-buten-1,4-dithiol, 2-methyl-2-propene mercaptan, 3-buten-2-thiol and isoprene mercaptan. (3) The grafting rate of the thiol monomer in the structure of the modified polypropylene is 0.5%-10%; (4) The particle size of the gold particles is 5nm-60nm; (5) The gold particles are spherical, star-shaped, rod-shaped, triangular or tetrahedral in shape.

6. The method for preparing modified polypropylene according to any one of claims 1 to 5, characterized in that, The following steps are involved: Modified polypropylene is prepared by mixing and melting the copolymerized polypropylene, the mercapto-grafted monomer, and the gold particles; Optionally, an initiator may be added during the mixing process.

7. An insulating material, characterized in that, The insulating material comprises modified polypropylene and additives, wherein the modified polypropylene includes the modified polypropylene according to any one of claims 1 to 5.

8. The insulating material according to claim 7, characterized in that, The insulating material also satisfies the following characteristics as shown in (1) and / or (2): (1) By mass, the insulating material comprises 40-105 parts of modified polypropylene and 0.01-0.6 parts of additives; (2) The adjuvants include antioxidants; Optionally, the antioxidant includes one or more of antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 1035, and antioxidant 300; Optionally, the amount of antioxidant added is 0.01-0.6 parts by weight.

9. The use of modified polypropylene and / or insulating materials in cables, wherein the modified polypropylene comprises the modified polypropylene according to any one of claims 1 to 5, and the insulating material comprises the insulating material according to claim 7 or 8.

10. A cable, characterized in that, The cable comprises the modified polypropylene as described in any one of claims 1 to 5, or the insulating material as described in claim 7 or 8; Optionally, the cable is a DC cable.

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