Water tree resistant modified propylene-based thermoplastic insulating material, method of making and use thereof

Abstract

The application belongs to the technical field of polymers, and discloses a kind of water treeing resistance modified propylene-based thermoplastic insulating material and its preparation method and application, the thermoplastic insulating material contains the grafting modified propylene polymer of oxygen-containing polar monomer and optional second monomer, propylene polymer, auxiliary agent and optional elastomer;Thermoplastic insulating material, the content of oxygen-containing polar monomer and optional second monomer structural unit in grafting state is 0.1-6wt%, the content of xylene soluble is 0-70wt%, and the gel content is less than 2wt%;The melt flow rate of thermoplastic insulating material under 230℃, 2.16kg load is 0.2-7g / 10min;The bending modulus of thermoplastic insulating material is 150-1600MPa.The thermoplastic insulating material has good water treeing resistance, and is suitable for long-term use under high temperature and high field strength.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of polymers, and in particular relates to a water treeing resistant modified propylene-based thermoplastic insulating material, a preparation method of the water treeing resistant modified propylene-based thermoplastic insulating material, and an application of the water treeing resistant modified propylene-based thermoplastic insulating material in a cable. BACKGROUND

[0002] In order to meet the requirements of environmental protection and sustainable development, the research on a new recyclable non-crosslinked polyolefin cable insulating material has become a hot spot in the field of insulating materials. Polypropylene has become the most concerned research direction due to its excellent electrical insulation performance and low price. The cable will be eroded by air or moisture in the soil under long-term work, water trees are formed, and the insulation performance and mechanical performance are deteriorated, thereby greatly shortening the service life of the cable. Therefore, it has high practical value to develop a water treeing resistant thermoplastic cable insulating material.

[0003] Patent document US20140363671 provides a cable with an epoxy group modified non-crosslinked polyolefin insulating layer, and mentions that the introduction of the epoxy group can improve the water tree resistance of the insulating material, but does not describe the specific effect and corresponding insulating material performance parameters. Moreover, due to the preparation method and the characteristics of the epoxy group, the insulating layer material will produce gel under the influence of heat and moisture in processing and operation, which has adverse effects on its electrical performance and recyclability.

[0004] Patent document CN111354507A provides a water treeing resistant cable, and the insulating layer thereof is composed of a material based on thermoplastic polypropylene and at least one oxygen-containing compound with a melting temperature greater than 110 DEG C, which effectively prevents the precipitation of traditional liquid phase or small molecule water treeing resistant agents during processing. However, due to the polarity gap between the oxygen-containing compound and the polyolefin, the dispersion problem caused by the aggregation of polar groups may easily occur under the addition amount, thereby affecting the water treeing resistance effect. SUMMARY

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to provide a water treeing resistant modified propylene-based thermoplastic insulating material, a preparation method and application thereof. The thermoplastic insulating material has good water treeing resistance and is suitable for long-term use under high temperature and high field strength.

[0006] The first aspect of the present application provides a water treeing resistant modified propylene-based thermoplastic insulating material, which contains a propylene polymer grafted with an oxygen-containing polar monomer and an optional second monomer, an optional propylene polymer, an auxiliary agent, and an optional elastomer;

[0007] The content of the oxygen-containing polar monomer and the optional second monomer in the grafting state in the thermoplastic insulating material is 0.1-6wt%, the content of xylene-soluble matter is 0-70wt%, and the gel content is less than 2wt%; the melt flow rate of the thermoplastic insulating material under a load of 2.16kg at 230℃ is 0.2-7g / 10min; and the flexural modulus of the thermoplastic insulating material is 150-1600MPa.

[0008] The second aspect of the present application provides a preparation method of the above-mentioned water-tree-resistant modified propylene-based thermoplastic insulating material, which comprises the following steps:

[0009] 1) mixing the propylene polymer grafted and modified by the oxygen-containing polar monomer and the optional second monomer, the optional propylene polymer, the auxiliary agent and the optional elastomer, melt-extruding and granulating;

[0010] 2) after the granules are processed into a shape, annealing and heat-treating to obtain the thermoplastic insulating material.

[0011] The third aspect of the present application provides the application of the above-mentioned water-tree-resistant modified propylene-based thermoplastic insulating material in a cable.

[0012] The thermoplastic insulating material of the present application has good water-tree-resistant performance and is suitable for long-term use under high temperature and high field strength. The water-tree-resistant performance of the insulating material can be effectively improved by selecting the propylene polymer grafted and modified by the oxygen-containing polar monomer and the optional second monomer as the raw material. In addition, the water-tree-resistant performance of the insulating material can be further improved by heat-treating the product after shaping.

[0013] Other features and advantages of the present application will be described in detail in the following specific embodiments. DETAILED DESCRIPTION

[0014] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0015] According to the first aspect of the present application, the present application provides a water-tree-resistant modified propylene-based thermoplastic insulating material, which contains a propylene polymer grafted and modified by an oxygen-containing polar monomer and an optional second monomer, an optional propylene polymer, an auxiliary agent and an optional elastomer;

[0016] The content of the oxygen-containing polar monomer and the optional second monomer in the grafted state in the thermoplastic insulating material is 0.1-6wt%, the content of xylene-soluble matter is 0-70wt%, and the gel content is less than 2wt%; the melt flow rate of the thermoplastic insulating material under a load of 2.16kg at 230°C is 0.2-7g / 10min; and the flexural modulus of the thermoplastic insulating material is 150-1600MPa.

[0017] Preferably, the content of the oxygen-containing polar monomer and the optional second monomer in the grafted state in the thermoplastic insulating material is 0.5-5wt%, preferably 1-4wt%, the content of xylene-soluble matter is 0.5-65wt%, and the gel content is 0-1wt%; the melt flow rate of the thermoplastic insulating material under a load of 2.16kg at 230°C is 0.5-5g / 10min, preferably 1-3.5g / 10min; and the flexural modulus of the thermoplastic insulating material is 200-1200MPa, preferably 400-1000MPa.

[0018] In the present application, the propylene polymer can be a homogenous or heterogeneous propylene homopolymer or copolymer, and the content of the comonomer in the propylene polymer is 0-25wt%, preferably 0-20wt%; the melt flow rate of the propylene polymer under a load of 2.16kg at 230°C is 0.5-10g / 10min, preferably 1-7g / 10min, and the melting temperature Tm is 110-180°C, preferably 120-170°C.

[0019] According to the present application, the comonomer of the propylene copolymer can be at least one selected from the group consisting of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene, preferably ethylene and / or 1-butene.

[0020] In the present application, the oxygen-containing polar monomer is at least one selected from the group consisting of siloxane monomers containing unsaturated double bonds, acrylate monomers, acid anhydride monomers and acrylic monomers; preferably acrylate monomers and / or acid anhydride monomers; more preferably methyl methacrylate monomers, hydroxypropyl methacrylate monomers or maleic anhydride.

[0021] In the present application, the second monomer is an aromatic olefin monomer, preferably styrene.

[0022] According to the present application, the thermoplastic insulating material contains at least one propylene polymer grafted with an oxygen-containing polar monomer and an optional second monomer. That is, the propylene polymer grafted with an oxygen-containing polar monomer and an optional second monomer in the thermoplastic insulating material can be a propylene polymer grafted with a single oxygen-containing polar monomer and an optional second monomer, or a propylene polymer grafted with two or more oxygen-containing polar monomers and optional second monomers.

[0023] The propylene polymer grafted with the oxygen-containing polar monomer and optional second monomer according to the present application can be prepared by using conventional methods in the prior art, as long as the use requirements are met. Preferably, the propylene polymer grafted with the oxygen-containing polar monomer and optional second monomer is prepared by using the following method:

[0024] a. placing the propylene polymer in a closed reactor, and performing inert gas replacement;

[0025] b. adding a free radical initiator and the oxygen-containing polar monomer and optional second monomer into the closed reactor, and stirring and mixing;

[0026] c. optionally adding a co-swelling agent, and optionally allowing the reaction system to swell;

[0027] d. optionally adding a dispersing agent, allowing the reaction system to be heated to a grafting reaction temperature, and performing grafting reaction;

[0028] e. optionally filtering and drying the reaction product, to obtain the propylene polymer grafted with the oxygen-containing polar monomer and optional second monomer.

[0029] According to the present application, the inert gas can be various inert gases commonly used in the art, including but not limited to nitrogen, argon.

[0030] In the present application, the free radical initiator is selected from peroxide type free radical initiators; the peroxide type free radical initiator is preferably selected from at least one of dibenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, lauroyl peroxide, dodecanoyl peroxide, tert-butyl benzene percarboxylate, diisopropyl peroxydicarbonate, tert-butyl peroxy(2-ethylhexanoate), and dicyclohexyl peroxydicarbonate.

[0031] According to the present application, the amount of the oxygen-containing polar monomer and optional second monomer can be 1-10% by mass based on the mass of the propylene polymer, preferably 1.5-9%, and more preferably 1.7-7%. When the second monomer is contained, the amount of the second monomer can be determined as needed, and preferably, the amount of the oxygen-containing polar monomer is more than 20 wt% of the total amount of the oxygen-containing polar monomer and second monomer.

[0032] The mass ratio of the amount of the free radical initiator to the amount of the oxygen-containing polar monomer and optional second monomer is 0.1-6:100, and preferably 0.5-5:100.

[0033] According to the present application, the co-swelling agent is an organic solvent having a swelling effect on the olefin polymer, and the co-swelling agent is preferably at least one selected from the group consisting of benzene, toluene, xylene, chlorobenzene, tetrahydrofuran, diethyl ether, acetone, hexane, cyclohexane, decalin and heptane. The amount of the co-swelling agent is 1 to 30%, preferably 10 to 25%, based on the mass of the propylene polymer.

[0034] In the present application, the swelling conditions include that the swelling temperature can be 30 to 60°C and the time can be 1 to 5 hours.

[0035] The dispersant is water or an aqueous sodium chloride solution. The water is deionized water, and the aqueous sodium chloride solution can be used at any conventional concentration. The amount of the dispersant is 50 to 300%, based on the mass of the propylene polymer.

[0036] In the present application, the temperature of the grafting reaction is 80 to 130°C, preferably 85 to 120°C, and the time is 0.5 to 10 hours, preferably 1 to 6 hours.

[0037] According to the present application, all the materials in the grafting reaction system can be added at once or at different stages of the reaction.

[0038] According to the present application, the auxiliary agent contains an antioxidant and optionally a processing aid.

[0039] The antioxidant is at least one selected from the group consisting of hindered phenol-based antioxidants, hindered amine-based antioxidants, phosphite-based antioxidants and thio-based antioxidants. The antioxidant is preferably at least one selected from the group consisting of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol ester, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)mesitylene, N,N'-bis[p-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, 2,2'-thiobis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2',2-oxamidyl-bis-[ethyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)]propionate, n-octadecyl 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.

[0040] The processing aid is at least one selected from the group consisting of fluorine-containing compounds, polypropylene waxes, polyethylene waxes, fatty acid esters and mineral oils, and is preferably at least one selected from the group consisting of polypropylene waxes, fatty acid esters and mineral oils.

[0041] In the present application, the elastomer is preferably selected from at least one of POE, PBE, EPR, EPDM, SEBS and SBS.

[0042] According to the second aspect of the present application, the present application provides a preparation method of the above-mentioned water treeing resistant modified propylene-based thermoplastic insulating material, which comprises the following steps:

[0043] 1) mixing the propylene polymer modified by the oxygen-containing polar monomer and the optional second monomer, the optional propylene polymer, the auxiliary agent and the optional elastomer, melt-extruding and granulating;

[0044] 2) after the granules are processed into a shape, annealing heat treatment is performed to obtain the thermoplastic insulating material.

[0045] According to the present application, the auxiliary agent contains the antioxidant and the optional processing aid, the amount of the propylene polymer modified by the oxygen-containing polar monomer and the optional second monomer is more than 50%, preferably more than 55%, and more preferably more than 60%, based on the total mass of the propylene polymer modified by the oxygen-containing polar monomer and the optional second monomer, the propylene polymer and the elastomer; the amount of the antioxidant is more than 2000 ppm, and is preferably 3000-5000 ppm; when the processing aid is contained, the amount of the processing aid is 0.5-4%, and is preferably 0.8-2%.

[0046] In addition, according to the product needs, other auxiliary agents such as voltage stabilizers, anti-aging agents, copper-resistant agents and the like can be added, and the types and amounts of the other auxiliary agents are conventional and known to those skilled in the art.

[0047] In the present application, the melt-extrusion granulation can be performed by using the conventional equipment in the prior art, and a twin-screw extruder is preferably used. The temperature of the melt-extrusion granulation can be 180-250°C, preferably 185-230°C, and more preferably 190-220°C.

[0048] According to the present application, the temperature of the heat treatment is 50-120°C, preferably 60-110°C, and more preferably 80-100°C; and the time of the heat treatment is 2-12 hours, preferably 2.5-10 hours, and more preferably 3-8 hours.

[0049] The third aspect of the present application provides the use of the above-mentioned water treeing resistant modified propylene-based thermoplastic insulating material in cables.

[0050] The thermoplastic insulating material of the present application can be used as an insulating material and the like in the field of cables, and the specific use mode can be performed according to the conventional insulating material.

[0051] The substances and parameters not defined in the present application can be selected according to the prior art, and are conventional technical means in the art.

[0052] The application will be further illustrated in connection with the following examples. However, the application is not limited by these examples.

[0053] In the following preparation examples, examples and comparative examples, the relevant data are obtained according to the following test methods:

[0054] 1. Determination of comonomer content in propylene polymer:

[0055] The comonomer content is determined by quantitative Fourier transform infrared (FTIR) spectroscopy. The correlation of the determined comonomer content is calibrated by quantitative nuclear magnetic resonance (NMR) spectroscopy. The results obtained by quantitative 13 The calibration method of the results obtained by C-NMR spectroscopy is carried out according to the conventional method in the art.

[0056] 2. Determination of xylene solubles content (XS):

[0057] The test is carried out according to the method specified in GB / T 24282-2009.

[0058] 3. Determination of grafting degree GD (n)

[0059] 2-4 g of the grafting product is placed into a Soxhlet extractor and extracted with an organic solvent (ethyl acetate is used for aromatic olefin monomers, acrylic ester monomers, acid anhydrides; acetone is used for silane monomers) for 24 hours to remove unreacted monomers and their homopolymers, to obtain a pure grafting product, which is dried and weighed to calculate the parameter grafting degree GD. (n) The grafting degree GD represents the grafting rate of the propylene polymer containing the oxygen-containing polar monomer and the optional second monomer in the material. The content of the structural unit containing the oxygen-containing polar monomer and the optional second monomer in the thermoplastic insulating material and in the grafted state. In the present application, the calculation formula of GD is as follows:

[0060]

[0061]

[0062] In the above formula, w0 is the mass of the propylene polymer; w1 is the mass before extraction of the grafting product; w2 is the mass after extraction of the grafting product. In the case where the thermoplastic insulating material contains more than one grafting product, m n1 is the mass of the propylene polymer modified by the first oxygen-containing polar monomer and the optional second monomer in the material, m n2 is the mass of the propylene polymer modified by the second oxygen-containing polar monomer and the optional second monomer, and so on; m 产品 is the mass of the thermoplastic insulating material.

[0063] 4. Determination of melt flow rate (melt index) MFR:​

[0064] Determined according to the method specified in GB / T 3682-2018, using a CEAST model 7026 melt indexer at 230°C under a load of 2.16 kg.

[0065] 5. Determination of the melting temperature (melting point) Tm:

[0066] The melting process and crystallization process of the material were analyzed using a differential scanning calorimeter. The specific operation was as follows: under the protection of nitrogen, 5-10 mg of sample was measured from 20°C to 200°C using a three-stage temperature measurement method, and the change of heat flow was used to reflect the melting and crystallization process of the material, so as to calculate the melting temperature Tm.

[0067] 6. Determination of the bending modulus:

[0068] Determined according to the method specified in GB / T 9341-2008.

[0069] 7. Determination of the gel content:

[0070] Determined according to the method specified in ASTM-D2765.

[0071] 8. Determination of water treeing:

[0072] According to the method described in "Design of Real-time Observation System for Water Treeing Aging of Crosslinked Polyethylene Insulation" (Li Xiufeng, Insulating Materials, 2017, 50(6)) and the water tree observation equipment, the sample was prepared into a 40mm x 40mm x 1mm flat panel sample, and after being treated as required, it was placed in a 1.8mol / L NaCl solution, and a high-frequency voltage with an effective value of 4kV and a frequency of 3kHz was continuously applied at room temperature in an environment with an air humidity of 60-70%. The sample was immersed in silicone oil and observed and recorded the initial initiation time of water treeing in the direction of the electric field using an optical microscope.

[0073] The reagents used in the preparation examples, examples and comparative examples are as follows:

[0074] Benzoyl peroxide (BPO), B-lab Scientific Co., Ltd.;

[0075] Lauryl peroxide (LPO), B-lab Scientific Co., Ltd.;

[0076] Tert-butyl 2-ethylhexanoate peroxide (OT), Adamas Reagent Co., Ltd.;

[0077] Styrene (St), B-lab Scientific Co., Ltd.;

[0078] Methyl methacrylate (MMA), B-lab Scientific Co., Ltd.;

[0079] Hydroxypropyl methacrylate (HPMA), Boleny Technology Co., Ltd.

[0080] Maleic anhydride (MAH), Boleny Technology Co., Ltd.

[0081] Xylene, Boleny Technology Co., Ltd.

[0082] Butyl acrylate (BA), Boleny Technology Co., Ltd.

[0083] Antioxidants: antioxidant 1035, antioxidant 1010, antioxidant 168, antioxidant 697, Shanghai Kaijin Chemical Industry Co., Ltd.

[0084] Processing aids (lubricants): PP wax 2602 (Clariant), PPA5920A (3M Company, USA);

[0085] Elastomers: Vistamaxx 6102, Vistamaxx 6202, Exxon Mobil;

[0086] Propylene polymers, as shown in Table 1:

[0087] Table 1

[0088]

[0089] Preparation Examples 1-5

[0090] The propylene polymer powder is weighed and added to a reaction kettle with mechanical stirring. The reaction system is closed and deoxygenated by nitrogen replacement. The initiator and the mixture of oxygen-containing polar monomer and optional second monomer are added and stirred with the powder for 15-20 minutes. The dispersant or swelling aid is optionally added. The materials are weighed in parts by mass, and the temperature is raised to the reaction temperature for 1-6 hours. After the reaction is completed, the temperature is cooled down. The dispersant water is optionally filtered out, and the product is dried at 70°C for 4 hours to obtain the propylene polymer grafted with oxygen-containing polar monomer and optional second monomer. The specific reaction conditions and product properties are shown in Table 2.

[0091] Comparative Preparation Example 1

[0092] Comparative Preparation Example 1 is different from Preparation Example 5 in that the amount of oxygen-containing polar monomer is increased, the amount of initiator and dispersant is also increased, and the grafting reaction time is prolonged. The specific reaction conditions and product properties are shown in Table 2.

[0093] Table 2

[0094]

[0095] Examples 1-6

[0096] The oxygen-containing polar monomer and optional second monomer grafted modified propylene polymer (modified propylene polymer), propylene polymer, antioxidant, processing aid and optional elastomer are weighed out in parts by mass, mass percent or mass ppm, mixed well by high-speed mixer, and then fed into a twin-screw extruder for melt extrusion and granulation to obtain a thermoplastic insulating material. After sample preparation according to the requirements in the test method, annealing heat treatment is performed. The specific preparation conditions and material properties of each example are shown in Table 3 and Table 4, respectively.

[0097] Comparative Examples 1-5

[0098] Comparative Example 1 differs from Example 1 in that no heat treatment is performed, and the rest are the same. Comparative Example 2 differs from Example 1 in that unmodified propylene polymer is used instead of the modified propylene polymer in Example 1, and the rest are the same. Comparative Example 3 differs from Example 1 in that the annealing heat treatment time is shorter, and the rest are the same. Comparative Example 4 differs from Example 1 in that the annealing heat treatment temperature is higher, and the rest are the same. Comparative Example 5 differs from Example 5 in that the sample prepared in Comparative Preparation Example 1 is used, and the rest are the same. The specific preparation conditions and material properties of each comparative example are shown in Table 3 and Table 4, respectively.

[0099] Table 3

[0100]

[0101] Table 4

[0102]

[0103] The materials prepared in each example and comparative example are subjected to water tree resistance performance testing, and the results are shown in Table 5.

[0104] Table 5

[0105]

[0106] By comparing the examples and comparative examples, it can be seen that the growth of water tree branches of the samples obtained by the present application is effectively inhibited. Comparing the data of Example 1 and Comparative Example 1, it can be seen that the initial time of water tree branches of the sample without annealing treatment is significantly earlier than that of the sample after annealing treatment. Comparing the data of Example 1 and Comparative Example 2, it can be seen that the use of ungrafted modified polypropylene results in poor water tree resistance performance of the product. Comparing the data of Example 1 and Comparative Example 3, it can be seen that a short annealing time does not improve the water tree resistance performance of the sample. Comparing the data of Example 1 and Comparative Example 4, it can be seen that a high annealing temperature does not improve the water tree resistance performance of the sample. Comparing Comparative Example 5 and Example 5, it can be seen that a monomer content that is too high results in a high gel content of the product and poor water tree resistance performance.

[0107] Having described various embodiments of the application, it is to be understood that the above description is meant to be illustrative only, and that many modifications and variations of the embodiments are possible without departing from the scope and spirit of the described embodiments. Many modifications and variations of the described embodiments are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims and their equivalents, the described embodiments can be practiced otherwise than as specifically described.

Claims

1. A water tree resistant modified propylene-based thermoplastic insulating material, characterized in that, The thermoplastic insulating material contains propylene polymer grafted with oxygen-containing polar monomer and optional second monomer, optional propylene polymer, auxiliary agent and optional elastomer; The content of the oxygen-containing polar monomer and optional second monomer in the thermoplastic insulating material is 0.1-6wt%, the content of xylene soluble is 0-70wt%, and the content of gel is less than 2wt%; the melt flow rate of the thermoplastic insulating material under 230℃ and 2.16kg load is 0.2-7g / 10min; the bending modulus of the thermoplastic insulating material is 150-1600MPa; The thermoplastic insulating material is obtained by a preparation method comprising the following steps: 1) mixing propylene polymer grafted with oxygen-containing polar monomer and optional second monomer, optional propylene polymer, auxiliary agent and optional elastomer, melt extruding and granulating; 2) after processing the granules into a shape, annealing heat treatment is performed to obtain the thermoplastic insulating material; The temperature of the heat treatment is 50-120℃; the time of the heat treatment is 2-12 hours.

2. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 1, wherein, The content of the oxygen-containing polar monomer and optional second monomer in the thermoplastic insulating material is 0.5-5wt%, the content of xylene soluble is 0.5-65wt%, and the content of gel is 0-1wt%; the melt flow rate of the thermoplastic insulating material under 230℃ and 2.16kg load is 0.5-5g / 10min; the bending modulus of the thermoplastic insulating material is 200-1200MPa.

3. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 2, wherein, The content of the oxygen-containing polar monomer and optional second monomer is 1-4wt%.

4. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 2 wherein, The melt flow rate of the thermoplastic insulating material under 230℃ and 2.16kg load is 1-3.5g / 10min.

5. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 2 wherein, The bending modulus of the thermoplastic insulating material is 400-1000MPa.

6. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 1, wherein, The propylene polymer is propylene homopolymer or propylene copolymer, and the content of comonomer in the propylene polymer is 0-25wt%; the melt flow rate of the propylene polymer under 230℃ and 2.16kg load is 0.5-10g / 10min, and the melting temperature Tm is 110-180℃; The oxygen-containing polar monomer is at least one of siloxane monomer, acrylate monomer, acid anhydride monomer and acrylic monomer containing unsaturated double bond; The second monomer is aromatic olefin monomer.

7. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 6 wherein, The content of comonomer in the propylene polymer is 0-20wt%.

8. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 6 wherein, The melt flow rate of the propylene polymer under 230℃ and 2.16kg load is 1-7g / 10min, and the melting temperature Tm is 120-170℃.

9. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 6 wherein, The comonomer of the propylene copolymer is at least one of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene.

10. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 9, wherein, The comonomer of the propylene copolymer is ethylene and / or 1-butene.

11. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 6 wherein, The oxygen-containing polar monomer is acrylate monomer and / or acid anhydride monomer.

12. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 11, wherein, The oxygen-containing polar monomer is methyl methacrylate monomer, hydroxypropyl methacrylate monomer or maleic anhydride.

13. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 6 wherein, The second monomer is styrene.

14. The water tree resistant modified polypropylene based thermoplastic insulating material according to any one of claims 1-13, wherein, A propylene polymer grafted with at least one oxygen-containing polar monomer and optionally a second monomer in a thermoplastic insulating material.

15. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 14, wherein, The propylene polymer grafted with at least one oxygen-containing polar monomer and optionally a second monomer is prepared by the following method: a. placing the propylene polymer in a closed reactor and performing inert gas replacement; b. adding a free radical initiator and the oxygen-containing polar monomer and the optional second monomer to the closed reactor and stirring to mix; c. optionally adding a co-solvent and optionally swelling the reaction system; d. optionally adding a dispersant, heating the reaction system to a grafting reaction temperature, and performing the grafting reaction; e. optionally filtering and drying the reaction product to obtain the propylene polymer grafted with the oxygen-containing polar monomer and the optional second monomer.

16. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 15, wherein, The free radical initiator is selected from peroxide-based free radical initiators; The amount of the oxygen-containing polar monomer and the optional second monomer is 1-10% based on the mass of the propylene polymer; The mass ratio of the amount of the free radical initiator to the amount of the oxygen-containing polar monomer and the optional second monomer is 0.1-6:

100.

17. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 16, wherein, The peroxide-based free radical initiator is selected from at least one of dibenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, lauroyl peroxide, dodecanoyl peroxide, tert-butyl peroxybenzoate, diisopropyl peroxydicarbonate, tert-butyl peroxy(2-ethylhexanoate), and dicyclohexyl peroxydicarbonate.

18. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 16, wherein, The amount of the oxygen-containing polar monomer and the optional second monomer is 1.5-9% based on the mass of the propylene polymer.

19. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 18, wherein, The amount of the oxygen-containing polar monomer and the optional second monomer is 1.7-7% based on the mass of the propylene polymer.

20. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 16, wherein, The mass ratio of the amount of the free radical initiator to the amount of the oxygen-containing polar monomer and the optional second monomer is 0.5-5:

100.

21. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 16, wherein, The co-solvent is selected from at least one of benzene, toluene, xylene, chlorobenzene, tetrahydrofuran, diethyl ether, acetone, hexane, cyclohexane, decalin, and heptane; and the amount of the co-solvent is 1-30% based on the mass of the propylene polymer; The temperature of the swelling is 30-60°C, and the time is 1-5 hours; The dispersant is water or an aqueous sodium chloride solution; and the amount of the dispersant is 50-300% based on the mass of the propylene polymer; The temperature of the grafting reaction is 80-130°C; and the time is 0.5-10 hours.

22. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 21, wherein, The amount of the co-solvent is 10-25% based on the mass of the propylene polymer.

23. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 21, wherein, The temperature of the grafting reaction is 85-120°C; and the time is 1-6 hours.

24. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 1, wherein, The auxiliary agent contains an antioxidant and optionally a processing aid; The antioxidant is selected from at least one of hindered phenol-based antioxidants, hindered amine-based antioxidants, phosphite-based antioxidants, and thio-based antioxidants; The processing aid is selected from at least one of fluorine-containing compounds, polypropylene waxes, polyethylene waxes, fatty acid esters, and mineral oils.

25. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 24, wherein, The antioxidant is at least one of tetrakis [beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid] pentaerythritol ester, 2, 2'-methylenebis (4-methyl-6-tert-butylphenol), 2, 4, 6-tris (3', 5'-di-tert-butyl-4'-hydroxybenzyl) mesitylene, N, N'-bis [beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl] hydrazine, 2, 2'-thiobis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid], 2', 2-oxamidyl-bis- [ethyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate], n-octadecyl beta- (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, dilauryl thiodipropionate.

26. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 24, wherein, The processing aid is at least one of polypropylene wax, fatty acid ester and mineral oil.

27. The water tree resistant modified polypropylene based thermoplastic insulating material of claim 24, wherein, The elastomer is at least one of POE, PBE, EPR, EPDM, SEBS and SBS.

28. A process for the preparation of the water tree retardant modification of the propylene-based thermoplastic insulating material according to any one of claims 1 to 27, characterized in that, The preparation method comprises the following steps: 1) mixing the propylene polymer grafted and modified by the oxygen-containing polar monomer and the optional second monomer, the optional propylene polymer, the aid and the optional elastomer, melt-extruding and granulating; 2) after the granules are processed and shaped, annealing heat treatment is performed to obtain the thermoplastic insulating material; The temperature of the heat treatment is 50-120℃; the time of the heat treatment is 2-12 hours.

29. The method of making a water tree resistant modified polypropylene thermoplastic insulating material of claim 28 wherein, The aid contains the antioxidant and the optional processing aid, the amount of the propylene polymer grafted and modified by the oxygen-containing polar monomer and the optional second monomer is more than 50% based on the total mass of the propylene polymer grafted and modified by the oxygen-containing polar monomer and the optional second monomer, the propylene polymer and the elastomer; the amount of the antioxidant is greater than 2000ppm; the amount of the processing aid is 0.5-4%; The temperature of the melt-extruding and granulating is 180-250℃; The temperature of the heat treatment is 60-110℃; the time of the heat treatment is 2.5-10 hours.

30. The method of making a water tree resistant modified polypropylene thermoplastic insulating material of claim 29 wherein, The amount of the propylene polymer grafted and modified by the oxygen-containing polar monomer and the optional second monomer is greater than 55%.

31. The method of making a water tree resistant modified polypropylene thermoplastic insulating material of claim 30 wherein, The amount of the propylene polymer grafted and modified by the oxygen-containing polar monomer and the optional second monomer is greater than 60%.

32. The method of making a water tree resistant modified polypropylene thermoplastic insulating material of claim 29 wherein, The amount of the antioxidant is 3000-5000ppm.

33. The method of making a water tree resistant modified polypropylene thermoplastic insulating material of claim 29 wherein, The amount of the processing aid is 0.8-2%.

34. The method of making a water tree resistant modified polypropylene based thermoplastic insulating material of claim 29 wherein, The temperature of the melt-extruding and granulating is 185-230℃.

35. The method of making a water tree resistant modified polypropylene thermoplastic insulating material of claim 34 wherein, The temperature of the melt-extruding and granulating is 190-220℃.

36. The method of making a water tree resistant modified polypropylene based thermoplastic insulating material of claim 29 wherein, The temperature of the heat treatment is 80-100℃; the time of the heat treatment is 3-8 hours.

37. The application of the water tree resistant modified propylene-based thermoplastic insulating material in claim 1-27, the water tree resistant modified propylene-based thermoplastic insulating material prepared by the preparation method in claim 28-36 in a cable.

Images