Thermoplastic modified insulating material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of polymers, and discloses a thermoplastic modified insulating material as well as a preparation method and application thereof, the preparation method comprises the following steps: mixing polypropylene, a grafting monomer, an initiator, an antioxidant, optional toughening resin, optional dispersing agent and optional other auxiliaries, and melting and mixing to obtain the thermoplastic modified insulating material. According to the invention, polypropylene is subjected to graft modification, so that the prepared thermoplastic insulating resin has good insulating property and mechanical property, and is suitable for insulating materials, especially cable insulating materials.

Description

Technical Field

[0001] The present invention relates to the field of polymer technology, and more specifically, to a thermoplastic modified insulating material and a preparation method and application thereof. Background Art

[0002] Polypropylene is a new type of cable insulation material with great application potential. It has thermoplastic recyclable properties, stronger insulation performance, and can work at higher temperatures. The current mainstream cable insulation material - cross-linked polyethylene cable material has long relied on imports. In recent years, the research on polypropylene used as high-voltage and ultra-high-voltage cables has accelerated significantly, but the mechanical properties of pure polypropylene materials are poor, and the high-temperature electrical properties also need to be improved. Compared with the currently studied modification technologies such as blending, copolymerization and nano-doping, the combination of grafting modification technology and polymer molecular chain regulation technology can achieve a comprehensive improvement in the electrical, mechanical and other properties of polypropylene cable insulation materials, and has the advantages of simple process and stable performance improvement. It has a good application prospect and is currently a research hotspot.

[0003] Publication No. CN105949394A introduces a method of grafting maleic anhydride onto polypropylene to inhibit space charge injection and thus improve electrical properties. However, the application does not introduce the specific properties of polypropylene, and the type of grafted monomer is single, and the preparation method has great limitations.

[0004] Publication Nos. CN115895162A, CN113563527A, and CN113563528A etc. introduce polypropylene insulation materials prepared by combining solid phase or suspension grafting modification technology with polypropylene copolymerization or blending technology. The insulation materials have good high temperature insulation performance and mechanical and processing properties required for cables, and have good application prospects in power cables. However, the grafting technology used therein is solid phase or suspension grafting, and the specific implementation conditions of other grafting methods are not mentioned. Summary of the invention

[0005] The purpose of the present invention is to provide a thermoplastic modified insulating material and a preparation method and application thereof. The present invention obtains a polypropylene insulating material with excellent mechanical properties, insulating properties and processing properties by grafting and optionally toughening polypropylene, thereby meeting the use of dielectric materials for AC and DC transmission cables.

[0006] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a method for preparing a thermoplastic modified insulating material, characterized in that the preparation method comprises: mixing and melt-kneading polypropylene, a grafting monomer, an initiator, an antioxidant, an optional toughening resin, an optional dispersant and optional other additives to obtain the thermoplastic modified insulating material.

[0007] The second aspect of the present invention provides a thermoplastic modified insulating material prepared by the above preparation method.

[0008] The third aspect of the present invention provides the use of the thermoplastic modified insulating material in a dielectric material; preferably in a cable insulation layer material and / or a shielding layer material.

[0009] The technical solution of the present invention has the following beneficial effects:

[0010] (1) The present invention grafts polypropylene to make the prepared thermoplastic insulating resin have good insulating properties and mechanical properties, and is suitable for use in insulating materials, especially in cable insulating materials.

[0011] (2) The present invention effectively improves the diffusion and dispersion uniformity of the initiator and the grafted monomer in the resin by selecting polypropylene of a specific particle size and adopting a premixing method, so that the material obtains more excellent dielectric insulation performance.

[0012] (3) The present invention effectively inhibits side reactions such as polypropylene degradation through the selection of polypropylene, grafting monomers, reaction conditions and compound initiators, so that the material maintains good processing, mechanical and insulation properties.

[0013] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0014] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0015] The first aspect of the present invention provides a method for preparing a thermoplastic modified insulating material, which comprises: mixing and melt-kneading polypropylene, a grafting monomer, an initiator, an antioxidant, an optional toughening resin, an optional dispersant and optional other additives to obtain the thermoplastic modified insulating material.

[0016] According to the present invention, preferably, the preparation method comprises:

[0017] (1) stirring the grafting monomer, the initiator and the optional dispersant to obtain a mixed solution;

[0018] (2) mixing the polypropylene and the mixed solution to obtain prefabricated polypropylene particles;

[0019] (3) The prefabricated polypropylene particles, the antioxidant, the optional toughening resin and the optional other auxiliary agents are mixed and melt-kneaded to obtain the thermoplastic modified insulating material.

[0020] In the present invention, preferably, the mixing operation in step (2) is carried out under inert gas conditions.

[0021] According to the present invention, preferably, the polypropylene is at least one of homopolypropylene, ethylene-propylene random copolymer polypropylene and propylene-butylene random copolymer polypropylene;

[0022] Preferably, the polypropylene has a melt index of 0.01 to 30 g / 10 min at 230° C. and a load of 2.16 kg, more preferably 0.05 to 5 g / 10 min, and more preferably 0.1 to 4 g / 10 min; and a melting point of 140 to 165° C.

[0023] In the present invention, the polypropylene may be at least one of a homopolymer of propylene, a binary copolymer of propylene and an α-olefin having 4 to 8 carbon atoms, and a multi-component copolymer of propylene and an α-olefin having 4 to 8 carbon atoms. α-olefins include but are not limited to at least one of 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene, 1-octene and 1-decene, preferably at least one of 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene; the α-olefin copolymerized with propylene may be one or more. Preferably, it is ethylene and / or butene. When the polypropylene is a copolymer of propylene and α-olefin, the α-olefin content is 0.1 to 25 wt%, preferably 0.5 to 20 wt%, based on the total mass of the polypropylene.

[0024] In the present invention, the polypropylene can be prepared using a multi-active site catalyst such as a Ziegler catalyst, or a single-active site catalyst such as a metallocene catalyst. Propylene homopolymerization or polymerization of propylene and α-olefin can be carried out by any method of liquid phase polymerization such as suspension polymerization, solution polymerization, or gas phase polymerization. The polypropylene can be a homogeneous polymer or a polymer with an "island" structure or a bicontinuous structure. The definitions and concepts of homogeneous and phase separation are well known to professionals in the field.

[0025] According to the present invention, the toughening resin can be one or more of in-vessel alloyed polypropylene, polyethylene, polybutylene, polyolefin elastomer and styrene block copolymer, etc.; preferably, the toughening resin is at least one of polyolefin elastomer, hydrogenated styrene-butadiene block copolymer (SEBS) and in-vessel alloyed polypropylene with a flexural modulus less than 500 MPa;

[0026] The melt index of the toughening resin at 230° C. and a load of 2.16 kg is 0.1 to 20 g / 10 min, preferably 0.5 to 10 g / 10 min, and more preferably 1 to 5 g / 10 min.

[0027] The in-vessel alloy polypropylene is a propylene-based polymer of an island-in-sea structure or a bicontinuous structure, prepared in situ in a reactor by an existing process, comprising a propylene homopolymer and / or a propylene random copolymer matrix component (1) as a matrix phase, and another propylene copolymer component (2) dispersed therein as a dispersed phase. The propylene copolymer component contains one or more ethylene or higher α-olefin comonomers. In the propylene random copolymer, the comonomers are randomly distributed on the main chain of the propylene polymer. Preferably, the propylene copolymer (2) dispersed in the homopolymer or copolymer matrix (1) of the in-vessel alloy polypropylene is substantially amorphous. The term "substantially amorphous" herein means that the propylene copolymer (2) has a lower crystallinity than the homopolymer or copolymer matrix (1). Preferably, the comonomer in the components (1) and (2) of the in-reactor alloyed polypropylene is ethylene or butene, and the comonomer content is 8 to 25 wt%, preferably 10 to 22 wt%; the xylene soluble content is 18 to 75 wt%, preferably 30 to 70 wt%, more preferably 30 to 67 wt%; the flexural modulus is preferably less than 500 MPa, more preferably less than 350 MPa, and further preferably less than 250 MPa.

[0028] The polyethylene refers to an ethylene-based polymer, i.e., a polymer containing at least 50 wt% ethylene based on the total weight of the polymer, such as high-density polyethylene, low-density polyethylene, and linear low-density polyethylene, the definitions and characteristics of which are well known to those skilled in the art.

[0029] The polybutene refers to a butene-based polymer, ie, a polymer containing at least 50 wt% of butene based on the total weight of the entire polymer, and may be a butene homopolymer or a copolymer of butene and other α-olefins.

[0030] The concept of polyolefin elastomer is well known to those skilled in the art, and refers to a non-crosslinked and elastic polyolefin material copolymerized by ethylene and propylene or other α-olefins (such as 1-butene, 1-hexene, 1-octene, etc.). It can be any commercially available ethylene / α-olefin copolymer elastomer (POE or OBC) and its modified product, propylene / α-olefin copolymer elastomer (PBE) and its modified product, ethylene propylene diene rubber (EPR) and its modified product, and ethylene propylene diene rubber (EPDM) and its modified product, which are suitable for the present invention. Including but not limited to Dow's Engage series, ExxonMobile's Exact series, Exxelor series, Vistamaxx series, etc., Dow Chemical's Versify series, etc. It can also be prepared by the methods described in CN101490096A, CN112724303A, CN112724286A, CN102417561A, CN103450403A, CN108384133A, etc. Preferably, the polyolefin elastomer has at least one of the following characteristics: a melt flow rate of 0.5 to 25 g / 10 min, preferably 0.8 to 10 g / 10 min, at 230°C and a load of 2.16 kg; a density of 0.85 to 0.905 g / cm 3 , preferably 0.86 to 0.89 g / cm 3 ; The melting point is greater than 45°C, preferably 50°C to 120°C.

[0031] The styrene block copolymer is a block copolymer formed by polymerization of styrene and one or more other comonomers. The other comonomers may be C2-C10 α-olefins or dienes or other polymerizable monomers containing olefin groups. Preferably, the styrene block copolymer is one or more of styrene-ethylene / butylene-styrene (SEBS) block copolymer, styrene-ethylene / propylene-styrene (SEPS) block copolymer, styrene-butadiene-styrene (SBS) block copolymer, styrene-isoprene-styrene (SIS) block copolymer and acrylonitrile-butadiene-styrene block copolymer. Preferably, the styrene content in the styrene block copolymer ranges from 10wt% to 40wt%, more preferably from 12wt% to 35wt%. The melt flow rate MFR (230°C / 2.16kg) in the styrene block copolymer ranges from 0.01g to 20g / 10min, more preferably from 0.2 to 15g / 10min.

[0032] In the present invention, the flexibility of the insulating material is improved by adding a toughening resin; the toughening resin can be used as a part of the base resin and mixed with polypropylene before the grafting reaction and then grafted; or it can be grafted with a grafting monomer and then mixed with polypropylene; or it can be used as a mixed component and melt-blended with the grafted modified polypropylene to obtain the final product.

[0033] In the present invention, the grafting monomer is a compound containing an olefinic bond and at least one other functional group in one molecule. The so-called other functional groups can be one or more of an aromatic ring, a hydroxyl group, an amino group, an epoxy group, an unsaturated carboxylic acid, an amide group, an imide group, an ester group, an alkoxysilane group, an acyl halide group, a cyano group, an anhydride group, a nitrogen-containing heterocyclic group, an allyl group, etc. Including but not limited to one or more of acrylates, acrylic acid, maleic anhydride, styrene monomers, acrylonitrile, vinyl acetate, vinyl chloride, glycidyl methacrylate, trimethoxysilane, vinyl pyridine, vinylimidazole, vinyl pyrrolidone, etc. Among them, one or more of styrene, triethoxysilane, glycidyl methacrylate and maleic anhydride are preferred. The grafting monomer can be one or more of the above compounds. Preferably, the grafting monomer is at least one of aromatic olefins, anhydrides, acrylic acid and acrylic acid esters; more preferably, it is at least one of styrene, maleic anhydride, glycidyl methacrylate, methyl methacrylate and acrylic acid.

[0034] In the present invention, the grafting monomer can directly participate in the grafting reaction in the form of a monomer, or can be prepolymerized into a polymer form and then participate in the grafting reaction.

[0035] According to the present invention, preferably, the initiator is a peroxide and / or an azo type;

[0036] Preferably, the peroxidation initiator comprises at least one of benzoyl peroxide, dichlorobenzoyl peroxide, dialkyl peroxide, aralkyl peroxide, peroxyester and peroxycarbon ester; more preferably, it is a compound of one or more of dicumyl peroxide (DCP), benzoyl peroxide (BPO), tert-butyl perbenzoate (TBPB) and di-tert-butyl peroxide (DTBP); more preferably, it is a compound of dicumyl peroxide (DCP) and lauroyl peroxide (LPO) or a compound of dicumyl peroxide (DCP) and benzoyl peroxide (BPO).

[0037] According to the present invention, preferably, the antioxidant is selected from at least one of hindered phenol antioxidants, hindered amine antioxidants, phosphite antioxidants and thio antioxidants;

[0038] Preferred are pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)mesitylene, N,N'-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, 2,2'-thiobis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2', At least one of 2-oxalylamino-bis-[ethyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)]propionate, β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 4,4'-thiobis(6-tert-butyl-3-methylphenol), triphenyl phosphite, tris[2,4-di-tert-butylphenyl]phosphite and dilauryl thiodipropionate.

[0039] In the method of the present invention, common processing aids and common additives for wires and cables can be optionally added. Preferably, the other additives include at least one of an anti-degradation agent, a nucleating agent, a lubricant, an anti-aging agent, an anti-copper agent, an ultraviolet light absorber, a flame retardant, a voltage stabilizer and an anti-water tree agent. The dosage of each of the above additives is conventional and known to those skilled in the art.

[0040] In the present invention, the antidegradant includes at least one of styrene, α-methylstyrene, trimethylolpropane triacrylate (TRIS) and divinylbenzene (DVB), preferably styrene. The mass ratio of the antidegradant to the grafting monomer is 0.01 to 1:1. The antidegradant can effectively increase the grafting rate and inhibit the degradation of polypropylene.

[0041] In the present invention, a dispersant may be optionally added, which is mainly used for dispersing and diffusing the initiator and the grafting monomer. The dispersant of the present invention is a liquid dispersant, for example, aromatic hydrocarbon solvents such as benzene, toluene and xylene, aliphatic hydrocarbon solvents such as pentane, hexane, heptane, octane, nonane and decane, alicyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane and decalin, chlorinated hydrocarbons such as chlorobenzene, dichlorobenzene, trichlorobenzene, dichloromethane, chloroform, carbon tetrachloride and tetrachloroethylene, alcohol solvents such as methanol, ethanol, propynol, isopropanol, n-butanol, 2-butanol, isobutanol and tert-butanol, ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone, ester solvents such as ethyl acetate and dimethyl phthalate, ether solvents such as dimethyl ether, ethyl ether, di-n-amyl ether, tetrahydrofuran and dioxyanisole can be mentioned; the amount of the dispersant added is 0 to 20 parts, preferably 0 to 10 parts, relative to 100 parts by mass of the polypropylene.

[0042] In the present invention, preferably, in parts by mass, relative to 100 parts of the polypropylene and the optional toughening resin in total, the amount of the grafting monomer is 0.1-30 parts, preferably 5-25 parts, the amount of the initiator is 0.001-10 parts, preferably 0.1-5 parts, the amount of the antioxidant is 0.1-2 parts, preferably 0.3-0.6 parts, the amount of the dispersant is 0-20 parts, preferably 0-10 parts and the amount of the other auxiliary agents is 0-2 parts, preferably 0-0.6 parts; wherein the mass ratio of the optional toughening resin to the polypropylene is (0-80): (20-100).

[0043] In the present invention, the reaction equipment can be a single screw extruder, a twin screw extruder, a Banbury mixer, a mixer, a rheometer, a kneader and other commonly used melt mixing equipment in the field of polyolefin processing. These methods can be used in combination or alone. Preferably, it is a reactive twin screw extruder or a single screw extruder, more preferably a reactive twin screw extruder, and more preferably a twin screw extruder with a length-to-diameter ratio greater than 25.

[0044] A low melt mixing temperature is not conducive to the grafting reaction, while a high temperature is prone to resin degradation. The melt mixing temperature is 120 to 250°C, preferably 130 to 220°C, and more preferably 160 to 220°C;

[0045] In the present invention, the melt mixing time is 0.1 to 30 minutes, preferably 0.5 to 10 minutes; too short a melt mixing time is not conducive to the conversion rate of the grafting reaction, and too long a time is easy to cause the decomposition of the resin; if the reaction equipment is a twin-screw extruder, the rotation speed is between 50 and 400 rpm, preferably 150 to 250 rpm.

[0046] In the present invention, all raw materials can be fully mixed and added to the reaction equipment at one time, or added to the reaction equipment step by step, or some components can be pre-mixed and then mixed with other components, including but not limited to, after the polypropylene and the optional toughening resin are melted, the grafting monomer is added, and then the mixture of the initiator and the dispersant is added; the polypropylene and the optional toughening resin are mixed with the grafting monomer and then melted, and then the initiator and other optional auxiliary agents are added; the polypropylene and the grafting monomer, initiator, and dispersant are mixed and melted, and then the optional toughening resin is added; the optional toughening resin and the grafting monomer, initiator, and dispersant are mixed and melted, and then mixed with the polypropylene, etc. The pre-mixing of raw materials can adopt the solid or solid-liquid mixing method commonly used in the industry, such as high-speed or low-speed stirring equipment; or a solvent with good solubility for the grafting monomer and the initiator and a low boiling point is selected as a dispersant, and the grafting monomer and the initiator are dissolved and then mixed with the resin, and then the low boiling point solvent is evaporated and recovered to obtain a raw material mixture.

[0047] As a preferred implementation method of the present invention, the implementation method includes:

[0048] (1) stirring an initiator, a grafting monomer and an optional dispersant at 40° C. for 10 to 30 minutes to form a uniform solution;

[0049] (2) sieving polypropylene powder with a particle size of 0.5 to 2 mm;

[0050] (3) adding the solution obtained in step (1) into a mixer containing the polypropylene powder at a rate of 5-20 ml / min, and after the addition is completed, mixing at 40-60° C. for 0.5-2 hours to obtain prefabricated polypropylene particles;

[0051] (4) mixing the prefabricated polypropylene particles, antioxidant, optional toughening resin and optional other additives with a high-speed mixer for 2 to 3 minutes;

[0052] (5) Add the mixture obtained in step (4) into a twin-screw extruder, perform melt mixing, extrusion, cooling and pelletizing at 160-220° C. and 150-220 rpm to obtain a thermoplastic modified insulating material.

[0053] In the above preferred implementation method, the mixing operation in step (3) is preferably carried out under inert gas conditions.

[0054] In the present invention, the polypropylene is preferably a polypropylene powder with a particle size of 0.5 to 2 mm; preferably, the particle size of the polypropylene powder can be controlled to be 0.5 to 2 mm by particle size screening. Common screening methods are well known to those skilled in the art, such as screening by using a mechanical vibrating screen equipped with sieves of different mesh sizes (10 mesh and 35 mesh).

[0055] In the present invention, the diffusion and dispersion uniformity of the grafting monomer and the initiator in the matrix can be effectively improved by screening and premixing the particle size, thereby ensuring the grafting effect and obtaining more excellent dielectric properties.

[0056] The second aspect of the present invention provides a thermoplastic modified insulating material prepared by the above preparation method.

[0057] According to the present invention, preferably, the thermoplastic modified insulating material has at least one of the following physical properties: a xylene soluble content of 0-70wt%, preferably 10-50wt%, more preferably 15-40wt%;

[0058] The melt flow rate at 230°C and 2.16 kg load is 0.01-10 g / 10 min, preferably 0.05-5 g / 10 min;

[0059] The grafting amount is 0.01 to 20 wt%, preferably 0.1 to 15 wt%, and more preferably 1 to 8 wt%;

[0060] The flexural modulus is 150-1600 MPa, preferably 200-800 MPa;

[0061] The breakdown field strength at 105°C is greater than 250 kV / mm, preferably 280 to 800 kV / mm;

[0062] 105℃, 15kV / mm DC volume resistivity is not less than 5×10 13 Ω.m, preferably 9.8×10 13 ~1×10 20 Ω.m;

[0063] 105℃, 50Hz dielectric loss is less than 1×10 -3 , preferably 1×10 -10 ~9×10 -4 .

[0064] The third aspect of the present invention provides the use of the above-mentioned thermoplastic modified insulating material in dielectric materials; preferably in cable insulation layer materials and / or shielding layer materials.

[0065] The thermoplastic modified insulating material prepared by the method of the present invention has good insulation, mechanical and processing properties, and can be used alone or blended with other resin components as insulating materials for wires and cables, including but not limited to the insulation or sheath parts of power cables, communication cables, optical fiber cables, cables for electrical equipment, submersible pump cables, electric vehicle charging cables, wires, etc. It can also be blended with conductive fillers such as graphite, carbon fiber, etc., and used as a semi-conductive material, including but not limited to the shielding layer material of power cables. Preferably, the material prepared by the method of the present invention is suitable for power cables, including the insulating layer and / or shielding layer in extruded cables and polypropylene laminated paper insulated cables, and more preferably the insulating layer and / or shielding layer of extruded power cables.

[0066] As a specific application example, for example, a thermoplastic cable comprises: at least one conductor and at least one electrical insulation layer surrounding the conductor; wherein the material of the electrical insulation layer contains more than 80% of the above-mentioned thermoplastic modified insulation material, preferably 90-100% of the above-mentioned thermoplastic modified insulation material. The cable has at least one cable core, and each of the cable cores comprises, from the inside to the outside, a conductor, an optional conductor shielding layer, an electrical insulation layer, an optional electrical insulation shielding layer, and an optional metal shielding layer. The cable may also include optional armor and / or sheath layers, optional filling layers and / or tape layers, etc. The cable is a DC cable or an AC cable; preferably, the cable is a DC cable.

[0067] The present invention is further described below by examples:

[0068] The following test methods:

[0069] 1. Determination of melt flow rate (melt index) MFR:

[0070] According to the method specified in GB / T 3682-2018, the melt index was measured using a CEAST 7026 melt indexer at 230°C and a load of 2.16 kg.

[0071] 2. Determination of xylene soluble content (XS):

[0072] The test was carried out according to the method specified in GB / T 24282-2009.

[0073] 3. Determination of grafting amount:

[0074] The grafting amount refers to the content of the grafting unit of the thermoplastic polypropylene product in the present invention. 2-4g of the sample is placed in a Soxhlet extractor and extracted with ethyl acetate for 24 hours to remove the unreacted monomer and its homopolymer. The sample is dried and weighed to calculate the parameter grafting amount. The formula is as follows:

[0075]

[0076] In the above formula, MG% is the grafting amount, w0 is the mass of the base resin; w1 is the mass of the grafted product before extraction; and w2 is the mass of the grafted product after extraction.

[0077] 4. Determination of flexural modulus:

[0078] The determination was carried out according to the method specified in GB / T 9341-2008.

[0079] 5. Determination of DC volume resistivity:

[0080] The test was carried out according to the method specified in GB / T 1410-2006. The test temperature was 105°C and the test field strength was 15kV / mm.

[0081] 6. Determination of breakdown field strength:

[0082] The test was carried out according to the method specified in GB / T 1408-2006. The test temperature was 105°C.

[0083] 7. Determination of dielectric loss factor:

[0084] The test was carried out according to the method specified in GB / T 1409-2006. The test temperature was 105°C and the test frequency was 50 Hz.

[0085] In the following examples, the polypropylene used is shown in Table 1 below:

[0086] Table 1

[0087]

[0088] Initiator: benzoyl peroxide (BPO), J&K Technology Co., Ltd.; lauroyl peroxide (LPO), J&K Technology Co., Ltd.; dicumyl peroxide (DCP), Shanghai Aladdin Biochemical Technology Co., Ltd.; 2,5-dimethyl-2,5-bis(tert-butyl peroxide)hexane (DHBP), J&K Technology Co., Ltd.; tert-butyl peroxybenzoate (TBPB), J&K Technology Co., Ltd.;

[0089] Grafting monomer:

[0090] Styrene (St), Bailingwei Technology Co., Ltd.;

[0091] Methyl methacrylate (MMA), Bailingwei Technology Co., Ltd.;

[0092] Glycidyl methacrylate (GMA), Bailingwei Technology Co., Ltd.;

[0093] Maleic anhydride (MAH), Sinopharm Chemical Reagent Co., Ltd.;

[0094] Dispersant: xylene, Bailingwei Technology Co., Ltd.; acetone, Sinopharm Chemical Reagent Co., Ltd.;

[0095] Antioxidants:

[0096] Antioxidant 1035, antioxidant 1010, antioxidant 168, and antioxidant 697 were all purchased from Shanghai Kaiyin Chemical;

[0097] Other additives

[0098] Lubricant: PP wax 2602 (Clariant), PPA 5920A (3M Company, USA);

[0099] Anti-copper agent: MD-1024, MDA-5, Shanghai Kaiyin Chemical;

[0100] Elastomer (toughening resin) is shown in Table 2 below:

[0101] Table 2

[0102]

[0103] Experimental equipment

[0104] Twin screw extruder (HAAKE Rheomex PTW 16OS, L / D=40)

[0105] Example 1

[0106] 1.9g benzoyl peroxide, 17.3g diisopropylbenzene peroxide and 192g styrene were added to a conical flask and stirred magnetically in a water bath at 40°C for 20min to prepare a uniform solution (mixed solution). 2.4kg NS20 powder (particle size of 0.5-2mm) sieved from the middle layer of a sieving machine equipped with 10-mesh and 35-mesh filters was added to a 10L jacketed steel kettle equipped with a spiral ribbon stirring paddle, and the reaction system was sealed and deoxygenated by nitrogen replacement. The mixed solution was added to the steel kettle at a speed of 7.6ml / min, the temperature was 50°C, and the stirring rate was 60rpm. After the addition was completed, the raw materials continued to mix for 1 hour to obtain prefabricated polypropylene particles. Prefabricated polypropylene particles, 7.92g antioxidant 1010 / 168 / calcium stearate (the mass ratio of antioxidant 1010, antioxidant 168 and calcium stearate is 2:2:1) and 3.20g anti-copper agent MD-1024 are mixed in a high-speed mixer for 2 to 3 minutes, and then added to a twin-screw extruder. The temperatures of each section of the extruder are 175°C, 180°C, 190°C, 200°C, 210°C, 210°C, 210°C, 200°C, and 190°C, respectively, and the speed is 160rpm for melt mixing, extrusion, cooling and pelletizing to obtain modified polypropylene particles (thermoplastic modified insulating material) C12.53kg. The performance results are shown in Table 1.

[0107] Example 2

[0108] 1.2g benzoyl peroxide, 9.6g diisopropylbenzene peroxide, 134g glycidyl methacrylate were added to a conical flask and stirred magnetically in a water bath at 40°C for 15min to prepare a uniform solution (mixed solution). 1.8kg of T03 powder sieved from the middle layer of a sieving machine equipped with 10-mesh and 35-mesh filters was added to a 10L jacketed steel kettle equipped with a spiral ribbon stirring paddle, and the reaction system was sealed and deoxygenated by nitrogen replacement. The mixed solution was added to the steel kettle at a speed of 11.0ml / min, the temperature was 45°C, and the stirring rate was 70rpm. After the addition was completed, the raw materials were mixed for 30min to obtain prefabricated polypropylene particles. Prefabricated polypropylene particles, 600g Vistamaxx6102, 9.1g antioxidant (the antioxidants are 1035 and 168, and the mass ratio of 1035 and 168 is 1:1) and 13.0g PP wax 2602 are mixed in a high-speed mixer for 2 to 3 minutes, and then added to a twin-screw extruder. The temperatures of each section of the extruder are 180°C, 190°C, 200°C, 210°C, 210°C, 210°C, 200°C, 190°C, and 185°C, respectively, and the speed is 175rpm for melt mixing, extrusion, cooling and pelletizing to obtain 2.48kg of modified polypropylene particles C2. The performance results are shown in Table 1.

[0109] Example 3

[0110] 1.2 g of benzoyl peroxide, 9.6 g of diisopropylbenzene peroxide and 134 g of glycidyl methacrylate were added into a conical flask and magnetically stirred in a water bath at 40° C. for 15 min to prepare a uniform solution (mixed solution). 1.8 kg of unscreened T03 powder, 600 g of Vistamaxx6102, 9.1 g of antioxidant (the antioxidants are 1035 and 168, and the mass ratio of 1035 and 168 is 1:1), 13.0 g of PP wax 2602 and the above mixed solution were fully mixed in a solid-liquid mixer for 20 minutes, and then added to a twin-screw extruder. The temperatures of each section of the extruder were 180°C, 190°C, 200°C, 210°C, 210°C, 210°C, 200°C, 190°C, and 185°C, respectively, and the speed was 175 rpm for melt mixing, extrusion, cooling and pelletizing to obtain 2.46 kg of modified polypropylene particles C3. The performance results are shown in Table 1.

[0111] Example 4

[0112] 4.9g lauroyl peroxide, 12.3g diisopropylbenzene peroxide, 59g styrene, 90g maleic anhydride and 200ml acetone were added into a conical flask and stirred magnetically for 30min in a water bath at 40℃ to prepare a uniform solution (mixed solution). 2.0kg of FT03S powder sieved from the middle layer of a sieving machine equipped with 10 mesh and 35 mesh filter screens was added into a 10L jacketed steel autoclave equipped with a spiral ribbon stirring paddle, and the reaction system was sealed and deoxygenated by nitrogen replacement. The mixed solution was added into the autoclave at a speed of 15.8ml / min, the temperature was 40℃, the stirring rate was 85rpm, and after the addition was completed, the raw materials were continuously mixed for 35min and vacuumed for 30min to obtain prefabricated polypropylene particles. Prefabricated polypropylene particles, 400g YH506, 7.6g antioxidant 697, 4.8g anti-copper agent MDA-5 and 7.2g white oil were mixed in a high-speed mixer for 2 to 3 minutes, and then added to a twin-screw extruder. The temperatures of each section of the extruder were 170°C, 175°C, 180°C, 190°C, 190°C, 190°C, 190°C, 190°C, 180°C, and 175°C, respectively, and the speed was 200rpm for melt mixing. The mixture was extruded, cooled and pelletized to obtain 2.45kg of modified polypropylene particles C4. The performance results are shown in Table 1.

[0113] Example 5

[0114] 2.6g lauroyl peroxide, 25.3g diisopropylbenzene peroxide and 192g methyl methacrylate were added to a conical flask and stirred magnetically for 30min in a water bath at 40℃ to prepare a uniform solution (mixed solution). 1.3kg of K8003 powder sieved from the middle layer of a sieving machine equipped with 10 mesh and 35 mesh filter screens was added to a 10L jacketed steel kettle equipped with a spiral ribbon stirring paddle, and the reaction system was sealed and nitrogen was replaced for deoxygenation. The mixed solution was added to the steel kettle at a speed of 5.8ml / min, the temperature was 60℃, and the stirring rate was 80rpm. After the addition was completed, the raw materials were mixed for 40min to obtain prefabricated polypropylene particles. Prefabricated polypropylene particles, 1.1 kg NS20 and 10.6 g antioxidant (the antioxidants are 1035 and 168, and the mass ratio of 1035 and 168 is 1:1) are mixed in a high-speed mixer for 2 to 3 minutes, and then added to a twin-screw extruder. The temperatures of each section of the extruder are 165°C, 175°C, 190°C, 200°C, 200°C, 200°C, 190°C, 180°C, and 175°C, respectively, and the speed is 180 rpm for melt mixing, extrusion, cooling and pelletizing to obtain 2.45 kg of modified polypropylene particles C5. The performance results are shown in Table 1.

[0115] Example 6

[0116] The “2.6 g lauroyl peroxide and 25.3 g diisopropylbenzene peroxide” in Example 5 were replaced by “27.9 g diisopropylbenzene peroxide”. The rest was the same as Example 5. 2.44 kg of modified polypropylene particles C6 were prepared. The performance results are shown in Table 1.

[0117] Example 7

[0118] 12.6g of tert-butyl perbenzoate, 92g of acrylic acid and 150ml of xylene were added to a conical flask and stirred magnetically in a water bath at 40°C for 30min to prepare a uniform solution (mixed solution). 1.8kg of GM250E powder sieved from the middle layer of a sieving machine equipped with 10-mesh and 35-mesh filters was added to a 10L jacketed steel kettle equipped with a ribbon stirring paddle, and the reaction system was sealed and deoxygenated by nitrogen replacement. The mixed solution was added to the steel kettle at a speed of 10.5ml / min, the temperature was 50°C, the stirring rate was 66rpm, and after the addition was completed, the raw materials were continued to mix for 50min to obtain prefabricated polypropylene particles. Prefabricated polypropylene particles, 600g Engage 8150 and 11.4g antioxidant 697 were mixed in a high-speed mixer for 2 to 3 minutes and then added to a twin-screw extruder. The temperatures of each section of the extruder were 160°C, 170°C, 180°C, 190°C, 200°C, 200°C, 200°C, 190°C, and 180°C, respectively, and the speed was 150rpm for melt mixing. The mixture was extruded, cooled and pelletized to obtain 2.43kg of modified polypropylene particles C7. The performance results are shown in Table 3.

[0119] Table 3

[0120]

[0121] It can be seen from the examples that the preparation method of the present invention is suitable for the modification of different types of base resins and grafted monomers, and the obtained thermoplastic insulating resin has good insulating properties and mechanical properties, and is suitable for use as an insulating material, especially for use in the insulating layer of a power transmission cable. By comparing Example 2 and Example 3, it can be seen that the use of particle size screening and premixing methods when mixing the raw materials effectively improves the diffusion and dispersion uniformity of the initiator and the grafted monomer in the resin, so that the material obtains more excellent insulating properties. By comparing Example 5 and Example 6, it can be seen that the use of a dual initiator system can significantly inhibit the degradation side reaction in melt grafting and improve the various properties of the material. It can be seen from Example 7 that when the amount of grafted monomer is small, the insulating properties of the material will be slightly reduced.

[0122] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for preparing a thermoplastic modified insulating material, characterized in that: The preparation method comprises: mixing and melt-kneading polypropylene, grafting monomers, initiators, antioxidants, optional toughening resins, optional dispersants and optional other auxiliary agents to obtain the thermoplastic modified insulating material.

2. The preparation method according to claim 1, wherein The preparation method comprises: (1) stirring the grafting monomer, the initiator and the optional dispersant to obtain a mixed solution; (2) mixing the polypropylene and the mixed solution to obtain prefabricated polypropylene particles; (3) The prefabricated polypropylene particles, the antioxidant, the optional toughening resin and the optional other auxiliary agents are mixed and melt-kneaded to obtain the thermoplastic modified insulating material.

3. The preparation method according to claim 1 or 2, wherein The polypropylene is at least one of homopolymer polypropylene, ethylene-propylene random copolymer polypropylene and propylene-butylene random copolymer polypropylene; Preferably, the polypropylene has a melt index of 0.01 to 30 g / 10 min at 230° C. and a load of 2.16 kg, more preferably 0.05 to 5 g / 10 min, and more preferably 0.1 to 4 g / 10 min; and a melting point of 140 to 165° C.

4. The preparation method according to claim 1 or 2, wherein: The toughening resin is at least one of a polyolefin elastomer, a hydrogenated styrene-butadiene block copolymer, and an in-vessel alloy polypropylene having a bending modulus of less than 500 MPa; The melt index of the toughening resin at 230° C. and a load of 2.16 kg is 0.1 to 20 g / 10 min, preferably 0.5 to 10 g / 10 min, and more preferably 1 to 5 g / 10 min.

5. The preparation method according to claim 1 or 2, wherein: The grafting monomer is at least one of aromatic olefins, acid anhydrides, acrylic acid and acrylic esters; preferably at least one of styrene, maleic anhydride, glycidyl methacrylate, methyl methacrylate and acrylic acid.

6. The preparation method according to claim 1 or 2, wherein: The initiator is a peroxide and / or an azo type; Preferably, the peroxidation initiator comprises at least one of benzoyl peroxide, dichlorobenzoyl peroxide, dialkyl peroxide, aralkyl peroxide, peroxyester and peroxycarbon ester; more preferably, it is a mixture of one or more of diisopropyl peroxide, benzoyl peroxide, tert-butyl perbenzoate and di-tert-butyl peroxide; more preferably, it is a mixture of diisopropyl peroxide and lauroyl peroxide or a mixture of diisopropyl peroxide and benzoyl peroxide.

7. The preparation method according to claim 1 or 2, wherein: The antioxidant is selected from at least one of hindered phenol antioxidants, hindered amine antioxidants, phosphite antioxidants and thio antioxidants; Preferred are pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)mesitylene, N,N'-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, 2,2'-thiobis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2', At least one of 2-oxalylamino-bis-[ethyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)]propionate, β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 4,4'-thiobis(6-tert-butyl-3-methylphenol), triphenyl phosphite, tris[2,4-di-tert-butylphenyl]phosphite and dilauryl thiodipropionate.

8. The preparation method according to claim 1 or 2, wherein: The melt mixing equipment is a reactive twin-screw extruder or a reactive single-screw extruder, preferably a reactive twin-screw extruder; more preferably a twin-screw extruder with a length-to-diameter ratio greater than 25; The melt kneading temperature is 120 to 250° C., preferably 130 to 220° C., and more preferably 160 to 220° C.; The polypropylene is preferably a polypropylene powder with a particle size of 0.5 to 2 mm; In parts by mass, relative to 100 parts of the polypropylene and the optional toughening resin in total, the amount of the grafting monomer is 0.1-30 parts, preferably 5-25 parts, the amount of the initiator is 0.001-10 parts, preferably 0.1-5 parts, the amount of the antioxidant is 0.1-2 parts, preferably 0.3-0.6 parts, the amount of the dispersant is 0-20 parts, preferably 0-10 parts, and the amount of the other additives is 0-2 parts, preferably 0-0.6 parts; wherein the mass ratio of the optional toughening resin to the polypropylene is (0-80):(20-100).

9. Thermoplastic modified insulating material prepared according to the preparation method according to any one of claims 1 to 8.

10. The thermoplastic modified insulating material according to claim 9, wherein: The thermoplastic modified insulating material has at least one of the following physical properties: a xylene soluble content of 0-70wt%, preferably 10-50wt%, more preferably 15-40wt%; The melt flow rate at 230°C and 2.16 kg load is 0.01-10 g / 10 min, preferably 0.05-5 g / 10 min; The grafting amount is 0.01 to 20 wt%, preferably 0.1 to 15 wt%, and more preferably 1 to 8 wt%; The flexural modulus is 150-1600 MPa, preferably 200-800 MPa; The breakdown field strength at 105°C is greater than 250 kV / mm, preferably 280 to 800 kV / mm; 105℃, 15kV / mm DC volume resistivity is not less than 5×10 13 Ω.m, preferably 9.8×10 13 ~1×10 20 Ω.m; 105℃, 50Hz dielectric loss is less than 1×10 -3 , preferably 1×10 -10 ~9×10 -4 .

11. Use of the thermoplastic modified insulating material according to claim 9 or 10 in dielectric materials; preferably in cable insulation layer materials and / or shielding layer materials.

Images