A high-temperature resistant and flame-retardant polyolefin cable compound and its preparation process

Abstract

The present invention discloses a high-temperature resistant and flame-retardant polyolefin cable material and its preparation process, belonging to the field of polyolefin cable materials and their manufacturing. The high-temperature resistant and flame-retardant polyolefin cable material of the present invention is composed of the following raw materials in parts by mass: 50-70 parts of polyolefin resin, 20-40 parts of cardanol grafted polyurethane, 10-25 parts of ionomer, 30-50 parts of composite flame retardant, 1-3 parts of lubricant, and 0.2-1.2 parts of antioxidant; wherein, the polyolefin resin is composed of isotactic polypropylene and multiphase copolymerized polypropylene with a mass ratio of 1:(0.1-0.2), the ionomer is an EMAA copolymer or a SEPS-g-MZn ionomer, and the composite flame retardant is composed of modified polypropylene, magnesium hydroxide, and ammonium polyphosphate. The high-temperature resistant and flame-retardant polyolefin cable material provided by the present invention does not require a cross-linking process, saving production costs, and the production efficiency and quality are easy to control; at the same time, it has excellent mechanical strength, toughness, chemical corrosion resistance, high-temperature resistance, and low-temperature impact resistance, excellent DC breakdown strength and flame retardancy, improving the product quality and service life of the cable material.

Description

Technical Field

[0001] The present invention belongs to the field of polyolefin cable materials and their manufacturing, and particularly relates to a non-crosslinked thermoplastic polypropylene cable material that can meet high-temperature resistance and flame retardancy requirements, as well as a preparation process therefor. Background Art

[0002] With the enhancement of people's awareness of environmental protection and safety, the demand for environmentally friendly cable materials has become increasingly urgent. The development of polymer materials for cable insulation has successively experienced stages such as natural rubber, polyvinyl chloride, polyethylene, crosslinked polyethylene, and ethylene-propylene rubber. Thermosetting crosslinked polyethylene has become the most widely used and highest-yielding cable insulation material because of its low price, good processability, excellent mechanical and electrical properties, and a maximum working temperature of 90 °C when used as cable insulation. However, the crosslinking of XLPE needs to be completed in an inert environment at high temperature and high pressure, with a complex preparation process, low production efficiency, and high energy consumption; XLPE is a thermosetting material and cannot be recycled, resulting in waste of resources and environmental pollution; the crosslinking reaction is prone to generate polar by-products, introducing impurities, leading to a decrease in electrical performance, and is prone to generating internal defects, resulting in insulation breakdown, causing serious accidents such as leakage, short circuit, and power outage.

[0003] Compared with the existing crosslinked polyethylene cable materials, polypropylene has excellent insulation properties, a high temperature resistance grade, does not require crosslinking, and can be plastically recycled. It not only has great advantages in increasing the current-carrying capacity, but also has advantages that XLPE cannot have in simplifying the processing process, reducing costs, increasing production efficiency, and increasing the cable length. However, PP is a non-polar material with disadvantages such as high crystallinity, poor low-temperature impact resistance, poor toughness, low melt viscosity, and high modulus. During the processing process, it is easy to cause uneven distribution of the electric field strength of high-voltage cables due to eccentricity, resulting in unqualified cables. At the same time, under the action of a DC electric field, space charge accumulation will occur, and then the polypropylene insulation material is easily broken down (i.e., easily broken down under high voltage), affecting the application of the cable in a high-voltage environment and reducing the service life; and the mechanical properties are significantly lower than those of XLPE.

[0004] Generally, for high-voltage DC cables, according to the regulations of the national standard GB / T 18380-2008, their flammability needs to meet the standards, and their combustion performance grade also needs to reach Class B1 specified in the national standard GB 31247-2014. As a non-polar polymer, PP has poor compatibility with most flame retardants, including organic phosphates, inorganic aluminum hydroxide, magnesium hydroxide, etc., making it difficult to process. Moreover, it has a high hardness, making the resulting cable feel stiff and prone to cracking. At the same time, the mechanical and mechanical properties of the resulting flame-retardant cable material also cannot meet the requirements, affecting the application of PP cable materials.

[0005] The invention patent CN202210350732.8 discloses a thermoplastic polypropylene DC cable insulating material. By adding an additive containing polar groups to the copolymer-modified PP and grafting double bond groups onto the PP macromolecular chain through an initiator, it mainly solves the influence of antioxidants on space charge accumulation, enabling the PP cable raw material of this invention to have good DC breakdown strength (insulation) and heat resistance and aging resistance. However, no flame retardant or filler components are added in this invention, which does not meet the standard requirements of existing cable materials for smokeless flame retardancy, etc. Moreover, if inorganic flame retardant components are added, it will inevitably affect their compatibility with polypropylene, thereby affecting the final mechanical properties, insulation properties, flame retardancy, etc. of the insulating material. The invention patent CN201410557756.6 discloses a preparation method of a recyclable cable insulating material. After surface treatment of nano-inorganic particles with a silane coupling agent, it is made compatible with thermoplastic polymers (PP / rubber blend and sPP), improving the electrical properties of polypropylene while maintaining good mechanical properties and thermal properties. However, the flame retardant added to this cable material is only 2 - 5 parts, so the flame retardant performance of this cable material is general and it cannot be applied to urban DC cables with flame retardant requirements for DC cables, and there are also limitations in high-voltage DC cables. The invention patent CN201921938940.X discloses a class B flame retardant DC traction cable for a rated voltage of 1500V track. 1 When a large amount of inorganic fillers such as magnesium hydroxide and aluminum hydroxide are filled in the polyolefin sheath material, its low-temperature resistance is significantly reduced, and cracking will occur during long-term use in a low-temperature environment, which makes it difficult to meet the cold resistance requirements of northern cities in China. Summary of the Invention

[0006] The main object of the present invention is to provide a high-temperature resistant and flame retardant polyolefin cable material. This cable material does not require a cross-linking process, has a simple and easy-to-operate preparation process, saves production costs, and is easy to control production efficiency and quality. At the same time, this cable material has excellent mechanical strength, toughness, chemical corrosion resistance, high-temperature and low-temperature impact resistance, significantly improves the DC breakdown strength and flame retardancy of the material, enables the combustion performance of the cable to meet national standards, the cable combustion grade can reach B1 level, and improves the product quality and service life of the cable material.

[0007] To achieve the object of the present invention, the present invention provides a high-temperature resistant and flame-retardant polyolefin cable material, which is composed of the following raw materials in parts by mass: 50-70 parts of polyolefin resin, 20-40 parts of cardanol grafted polyurethane, 10-25 parts of ionomer, 30-50 parts of composite flame retardant, 1-3 parts of lubricant, and 0.2-1.2 parts of antioxidant. Through the appropriate proportioning of the raw materials of the polyolefin cable material, the interaction between the raw material components is ensured, so that the present invention has excellent mechanical strength, electrical insulation, high and low temperature resistance, and flame retardancy. Moreover, the raw materials do not contain halogens, are environmentally friendly, belong to thermoplastic halogen-free low-smoke flame-retardant cable insulating materials, and can ensure that the comprehensive performance meets the national standard requirements.

[0008] The polyolefin resin is composed of isotactic polypropylene and polypropylene random copolymer with a mass ratio of 1:(0.1-0.2). Preferably, the polypropylene random copolymer contains ethylene-propylene rubber (EPR). The present invention combines isotactic polypropylene and polypropylene random copolymer containing ethylene-propylene rubber in an appropriate proportion, which improves the processing melt viscosity of the present invention, is easy to process and form, and significantly improves the mechanical strength, toughness, and low-temperature impact resistance of the present invention, reduces the accumulation or defects of space charge, and enables the present invention to have excellent electrical insulation and high-voltage breakdown strength.

[0009] The ionomer is an EMAA copolymer or SEPS-g-MZn ionomer. Preferably, the ionomer is SEPS-g-MZn ionomer. The addition of the ionomer not only increases the melt viscosity of PP, improves the processing performance of the present invention, and extends the service life of the cable products of the present invention; the use of SEPS-g-MZn ionomer also improves the compatibility between the components of the present invention, and enhances the mechanical strength, toughness, high-temperature resistance, and electrical insulation of the present invention.

[0010] The composite flame retardant is composed of modified polypropylene, magnesium hydroxide, and ammonium polyphosphate. The preferred composite flame retardant combination of the present invention has better compatibility with the polyolefin resin and other components, makes the cable material easy to process, and the products are not easy to crack. It can ensure that the polyolefin cable material can meet the electrical properties required by the present invention, and has excellent mechanical properties. It can also enable the present invention to achieve the flame-retardant and low-smoke properties required by the national standard without containing halogens, and the combustion grade of the cable products of the present invention can reach B1 level.

[0011] Furthermore, the preparation method of the cardanol grafted polyurethane includes the following steps:

[0012] First, add N,N-dimethylcyclohexylamine to the polyurethane emulsion and mix evenly. Then, add benzoyl peroxide (initiator), heat to 80 - 90 °C, and then drop dimethylpentanediamine into the reaction system. After the dropping is completed, react for 2 - 4 h to obtain activated polyurethane. Add the solution obtained by dissolving cardanol in ethyl acetate to the activated polyurethane, stir and react at 50 - 70 °C for 4 - 7 h. Wait until it cools to 40 °C, distill off the solvent in the system under reduced pressure, dry, and grind to obtain the required cardanol-grafted polyurethane.

[0013] In the present invention, polyolefin resin is modified by adding polyurethane in the hope of improving the mechanical strength, elasticity, abrasion resistance, electrical insulation, etc. of polyolefin cable materials. However, polyurethane belongs to a polar material and has poor compatibility with polyolefin resin, which instead reduces the mechanical strength of the present invention and the products are prone to cracking. At the same time, polyurethane is extremely flammable and cannot meet the requirements of the present invention either. After the technical personnel of the present invention graft-treated polyurethane with cardanol, not only the compatibility between polyurethane and components such as polyolefin resin is improved, making the present invention have better mechanical strength, elasticity, abrasion resistance and electrical insulation, but also the high temperature resistance and flame retardancy required by the present invention can be ensured for the cardanol-grafted polyurethane.

[0014] Furthermore, the addition amount of N,N-dimethylcyclohexylamine is 1.2 - 1.8% of the mass of the polyurethane emulsion;

[0015] The addition amount of benzoyl peroxide is 0.3 - 0.6% of the mass of the polyurethane emulsion;

[0016] The addition amount of dimethylpentanediamine is 1.5 - 2.5% of the mass of the polyurethane emulsion;

[0017] The addition amount of cardanol is 4 - 8% of the mass of the polyurethane emulsion.

[0018] Furthermore, the preparation method of the SEPS-g-MZn ionomer is as follows:

[0019] Pre-mix SEPS and an appropriate amount of naphthenic oil evenly, then add MAH monomer and stir for 20 - 30 min. Then, place it under a nitrogen atmosphere, heat to 100 - 120 °C, add AIBN, react for 2 - 5 h, with condensation and reflux, and then perform suction filtration using acetone to obtain the SEPS-g-MH copolymer;

[0020] Add the SEPS-g-MH copolymer and antioxidant to a high-speed mixer, then add zinc stearate, mix at 130 - 140 °C for 5 - 8 min, cool to below 70 °C, and then feed the mixture through a double-cone feeding system to a single-screw extruder for pelletizing to obtain the SEPS-g-MZn ionomer.

[0021] The present invention uses SEPS and MAH in appropriate proportions for grafting treatment, and then combines with zinc ions. The obtained SEPS-g-MZn ionomer can not only improve the melt viscosity of the present invention and enhance the processing performance, but also improve the high-voltage breakdown strength, mechanical properties, etc. of the present invention. If conventional SEBS-g-MZn is directly added to the present invention, although the melt strength and mechanical strength can be improved, the breakdown strength, electrical insulation, low-temperature impact resistance, thermal stability, etc. of the present invention will decrease.

[0022] Furthermore, the mass ratio of the SEPS, MAH monomer and AIBN is 1:(0.07 - 0.09):(0.01 - 0.02);

[0023] The addition amount of zinc stearate is 0.5 - 0.8 wt% of the SEPS-g-MH copolymer.

[0024] Furthermore, the preparation method of the composite flame retardant is as follows:

[0025] Weigh the dried magnesium hydroxide and ammonium polyphosphate respectively, mix them evenly, then add them to the modified polypropylene and stir for 10 - 20 min, and then convey them to a single-screw extruder for extrusion granulation. The temperature of the extruder is set at 160 - 190 °C, and then dry to obtain the composite flame retardant. By processing the composite flame retardant with an appropriate feeding sequence and material ratio, it can ensure that the modified polypropylene and the flame retardant components can be more evenly combined, thereby improving the dispersibility and compatibility of the composite flame retardant in the present invention, and ensuring that the present invention has excellent electrical insulation, mechanical properties and flame retardancy and smoke suppression properties.

[0026] Furthermore, the mass ratio of the modified polypropylene, magnesium hydroxide and ammonium polyphosphate is (0.05 - 0.1):1:(0.5 - 0.7).

[0027] Furthermore, the modified polypropylene is maleic anhydride grafted polypropylene or styrene grafted polypropylene. Using the modified polypropylene of the present invention can significantly improve the dispersibility and compatibility between the composite flame retardant and components such as polyolefin resin, and also improve the DC breakdown strength of the present invention, further ensuring that the present invention has excellent comprehensive performance.

[0028] Furthermore, the lubricant is any one or more of polyethylene wax, magnesium stearate, calcium stearate, ethylene bis-stearamide, aluminum stearate. The selection of the lubricant can make the processing process of the polyolefin cable material have good lubricity, and the obtained product has good appearance and feel, ensuring that the polyolefin cable material has excellent comprehensive performance.

[0029] The antioxidant is any one or two of antioxidant 1010, antioxidant 1076, antioxidant 168, and AO-1010. The antioxidant selected in the present invention can improve the heat-oxygen aging resistance of the polyolefin cable material, and is not easy to discolor or be contaminated.

[0030] The present invention also provides a preparation process for a high-temperature resistant and flame-retardant polyolefin cable material, which specifically includes the following steps:

[0031] Weigh polyolefin resin, ionomer, composite flame retardant, and antioxidant by mass parts, add them to a high-speed mixer, mix for 3-5 minutes under the conditions of 300-500 r / min and 70-80 °C, and then add cardanol grafted polyurethane and lubricant under the stirring rate of 50-80 r / min and mix evenly. Then, through a double-cone feeding system, it is extruded and pelletized by a twin-screw extruder. The temperature of the twin-screw extruder is set at 170-210 °C, and the screw speed is 250-400 rpm to obtain a high-temperature resistant and flame-retardant polyolefin cable material.

[0032] The present invention has achieved the following beneficial effects:

[0033] 1. The polyolefin cable material of the present invention does not require cross-linking, is easy to process, and has the advantages of good mechanical properties, excellent electrical insulation, high resistance to high and low temperatures, good elasticity, and high breakdown strength. The combustion grade of this polyolefin cable material can reach B1 level, the long-term use temperature can be as high as 160 °C, and the cold-resistant temperature can reach -40 °C (the impact resistance meets the standard and does not crack), which fully meets the cold-resistant requirements of northern cities.

[0034] 2. The surface of the polyolefin cable prepared by the present invention is smooth, easy to manufacture, has a low cost, excellent high and low temperature resistance and flame retardant performance, and a wide range of applications. Specific Embodiments

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] In the following examples and comparative examples of the present invention, isotactic polypropylene is selected from isotactic polypropylene RP344P-K of Huajin Chemical Industry;

[0037] Heterophasic copolymerized polypropylene is selected from PPB-M02D of Maoming Petrochemical;

[0038] SEPS is selected from YH4051 of Baling Petrochemical;

[0039] EMAA copolymer is selected from DuPont Surlyn 9320;

[0040] When the modified polypropylene is maleic anhydride grafted polypropylene, it is QB530 selected from Mitsui of Japan (maleic anhydride grafted polypropylene can also be prepared by oneself);

[0041] When the modified polypropylene is styrene grafted polypropylene, it is prepared by oneself, and the preparation method is as follows: put polypropylene powder into a reaction kettle under a nitrogen atmosphere, and then evenly drop the BPO / styrene solution (wherein the usage amount of styrene is 5% of the mass of polypropylene, and the usage amount of BPO is 0.8% of the mass of styrene) into the reaction kettle and stir evenly, heat up to 60 °C and stir for 2 h, then continue to heat up to 90 °C and stir for 1 h, add an appropriate amount of deionized water and keep it for 3 h to make the reaction sufficient, filter, extract in ethyl acetate for 24 h, and dry to obtain the required styrene grafted polypropylene;

[0042] Cardanol is cardanol NC-510 selected from Cardolite;

[0043] The polyurethane emulsion is selected from HYB 6336.

[0044] The high-temperature resistant and flame-retardant polyolefin cable material and its preparation process of the present invention will be described below in conjunction with specific embodiments.

[0045] Example 1

[0046] The preparation process of the high-temperature resistant and flame-retardant polyolefin cable material in Example 1 is as follows:

[0047] Weigh by mass parts, add 50 parts of polyolefin resin, 10 parts of ionomer, 50 parts of composite flame retardant and 0.5 part of antioxidant into a high-speed mixer, mix at 400 r / min and 70 °C for 5 min, and then at a stirring rate of 70 r / min, add 40 parts of cardanol grafted polyurethane and 1.2 parts of lubricant and mix evenly, and extrude and pelletize through a double-cone feeding system to a twin-screw extruder. The temperature of the twin-screw extruder is set at 170 - 210 °C, and the screw speed is 250 - 400 rpm to obtain the high-temperature resistant and flame-retardant polyolefin cable material.

[0048] The above polyolefin resin is composed of isotactic polypropylene and multiphase copolymerized polypropylene with a mass ratio of 5:1.

[0049] The above ionomer is SEPS-g-MZn ionomer, and its preparation method is as follows: pre-mix 1 kg of SEPS (hydrogenated styrene-isoprene-styrene block copolymer) and 150 g of naphthenic oil evenly, then add 90 g of MAH monomer and stir for 30 min, then place it under a nitrogen atmosphere, heat up to 110 °C, add 20 g of AIBN, react for 4 h, carry out condensation reflux, and then carry out suction filtration with acetone to obtain SEPS-g-MH copolymer;

[0050] 1 kg of the above-mentioned SEPS-g-MH copolymer and 3 g of antioxidant 1010 were added to a high-speed mixer and mixed evenly. Then, 8 g of zinc stearate was added, and the mixture was mixed at 450 r / min and 140 °C for 7 min. After cooling to below 70 °C, the mixture was fed through a double-cone feeding system to a single-screw extruder for pelletizing. The temperature of the single-screw extruder was set at 100 - 105 °C for zone 1, 110 - 115 °C for zone 2, 120 - 130 °C for zone 3, and 130 - 135 °C for the die head, obtaining the SEPS-g-MZn ionomer.

[0051] The preparation method of the above-mentioned composite flame retardant is as follows: Mg(OH) 2 and ammonium polyphosphate were dried in an oven at 120 °C for 2 h. Then, 1 kg of Mg(OH) 2 and 700 g of ammonium polyphosphate were mixed evenly, and then added to 50 g of maleic anhydride-grafted polypropylene and stirred for 20 min. Then, it was fed to a single-screw extruder for pelletizing. The temperature of the extruder was set at 160 - 190 °C, and after drying, the composite flame retardant was obtained.

[0052] The above-mentioned antioxidant is antioxidant 1010.

[0053] The preparation method of the above-mentioned cardanol-grafted polyurethane is as follows:

[0054] First, 18 g of N,N-dimethylcyclohexylamine was added to 1 kg of polyurethane emulsion and mixed evenly. Then, 6 g of benzoyl peroxide was added and heated to 80 °C. Then, 25 g of dimethylpentanediamine was dropped into the reaction system. After the dropping was completed, the reaction was carried out for 3 h to obtain the activated polyurethane. The solution obtained by dissolving 80 g of cardanol in ethyl acetate was added to the activated polyurethane, and the mixture was stirred and reacted at 60 °C for 6 h. After cooling to 40 °C, the solvent in the system was removed by vacuum distillation, dried, ground, and the required cardanol-grafted polyurethane was obtained.

[0055] The above-mentioned lubricant is a composition of magnesium stearate and calcium stearate with a mass ratio of 1:1.

[0056] Example 2

[0057] The preparation process of the high-temperature resistant flame retardant polyolefin cable material in this Example 2 is as follows:

[0058] Weighed by mass parts, 70 parts of polyolefin resin, 10 parts of ionomer, 30 parts of composite flame retardant, and 1.2 parts of antioxidant were added to a high-speed mixer and mixed at 400 r / min and 70 °C for 5 min. Then, at a stirring rate of 70 r / min, 20 parts of cardanol-grafted polyurethane and 2.5 parts of lubricant were added and mixed evenly. Then, it was fed through a double-cone feeding system to a twin-screw extruder for pelletizing. The temperature of the twin-screw extruder was set at 170 - 210 °C, and the screw speed was 250 - 400 rpm, obtaining the high-temperature resistant flame retardant polyolefin cable material.

[0059] The above polyolefin resin is composed of isotactic polypropylene and multiphase copolymerized polypropylene with a mass ratio of 10:1.

[0060] The above ionomer is SEPS-g-MZn ionomer, and its preparation method is as follows: 1 kg of SEPS and 150 g of naphthenic oil are pre-mixed evenly, then 70 g of MAH monomer is added and stirred for 20 min, then placed in a nitrogen atmosphere, heated to 100 °C, 10 g of AIBN is added, and the reaction is carried out for 5 h, with condensation and reflux, and then suction filtration is carried out using acetone to obtain SEPS-g-MH copolymer;

[0061] 1 kg of the above SEPS-g-MH copolymer and 3 g of antioxidant AO-1010 are added to a high-speed mixer and mixed evenly, then 7 g of zinc stearate is added, and the mixture is mixed at 450 r / min and 130 °C for 8 min, cooled to below 70 °C, and then the mixture is fed through a double-cone feeding system to a single-screw extruder for pelletizing. The temperature of the single-screw extruder is set at 100 - 105 °C in zone 1, 110 - 115 °C in zone 2, 120 - 130 °C in zone 3, and 130 - 135 °C at the die head to obtain SEPS-g-MZn ionomer.

[0062] The preparation method of the above composite flame retardant is as follows: Mg(OH) 2 and ammonium polyphosphate are dried in an oven at 120 °C for 2 h, then 1 kg of Mg(OH) 2 and 500 g of ammonium polyphosphate are mixed evenly, then added to 100 g of styrene-grafted polypropylene and stirred for 20 min, and then transported to a single-screw extruder for extrusion pelletizing. The temperature of the extruder is set at 160 - 190 °C, and then dried to obtain the composite flame retardant.

[0063] The above antioxidant is antioxidant AO-1010.

[0064] The preparation method of the above cardanol-grafted polyurethane is as follows:

[0065] First, 12 g of N,N-dimethylcyclohexylamine is added to 1 kg of polyurethane emulsion and mixed evenly, then 3 g of benzoyl peroxide is added, and the mixture is heated to 90 °C. Then, 15 g of dimethylpentanediamine is dropped into the reaction system, and after dropping, the reaction is carried out for 2 h to obtain activated polyurethane; the solution obtained by dissolving 40 g of cardanol in ethyl acetate is added to the activated polyurethane, and the mixture is stirred and reacted at 50 °C for 7 h, cooled to 40 °C, and the solvent in the system is removed by reduced pressure distillation, dried, and ground to obtain the required cardanol-grafted polyurethane.

[0066] The above lubricant is a composition of magnesium stearate and polyethylene wax with a mass ratio of 2:1.

[0067] Example 3

[0068] The preparation process of the high-temperature resistant and flame-retardant polyolefin cable material in this Example 3 is as follows:

[0069] Weigh according to parts by mass. Add 55 parts of polyolefin resin, 25 parts of ionomer, 38 parts of composite flame retardant, and 0.8 part of antioxidant into a high-speed mixer, mix for 5 minutes under the conditions of 400 r / min and 80 °C, then add 20 parts of cardanol grafted polyurethane and 2.5 parts of lubricant and mix evenly at a stirring rate of 60 r / min. Then, through a double-cone feeding system, it is extruded and granulated by a twin-screw extruder. The temperature of the twin-screw extruder is set at 170 - 210 °C, and the screw speed is 250 - 400 rpm to obtain the high-temperature resistant and flame-retardant polyolefin cable material.

[0070] The above polyolefin resin is composed of isotactic polypropylene and multiphase copolymerized polypropylene with a mass ratio of 8:1.

[0071] The above ionomer is SEPS-g-MZn ionomer, and its preparation method is as follows: Premix 1 kg of SEPS and 150 g of naphthenic oil evenly, then add 80 g of MAH monomer and stir for 30 minutes. Then, place it in a nitrogen atmosphere, heat up to 120 °C, add 16 g of AIBN, react for 4 hours, carry out condensation reflux, and then use acetone for suction filtration to obtain SEPS-g-MH copolymer;

[0072] Add 1 kg of the above SEPS-g-MH copolymer and 3 g of antioxidant 168 into a high-speed mixer and mix evenly. Then add 5 g of zinc stearate, mix for 5 minutes at 450 r / min and 140 °C, cool to below 70 °C, and then pass the mixture through a double-cone feeding system to a single-screw extruder for extrusion and granulation. The temperature of the single-screw extruder is set at 100 - 105 °C in zone 1, 110 - 115 °C in zone 2, 120 - 130 °C in zone 3, and 130 - 135 °C at the die head to obtain SEPS-g-MZn ionomer.

[0073] The preparation method of the above composite flame retardant is as follows: Respectively dry Mg(OH) 2 and ammonium polyphosphate in an oven at 120 °C for 2 hours. Then mix 1 kg of Mg(OH) 2 and 600 g of ammonium polyphosphate evenly, then add them to 80 g of maleic anhydride grafted polypropylene and stir for 30 minutes, and then convey them to a single-screw extruder for extrusion and granulation. The temperature of the extruder is set at 160 - 190 °C, and dry to obtain the composite flame retardant.

[0074] The above antioxidant is antioxidant 168; the lubricant is magnesium stearate.

[0075] The preparation method of the above cardanol grafted polyurethane is as follows:

[0076] First, add 15 g of N,N-dimethylcyclohexylamine to 1 kg of polyurethane emulsion and mix evenly. Then add 5 g of benzoyl peroxide, heat to 80 °C, and drop 21 g of dimethylpentanediamine into the reaction system. After dropping, react for 3 h to obtain activated polyurethane. Add the solution obtained by dissolving 65 g of cardanol in ethyl acetate to the activated polyurethane, stir and react at 60 °C for 5 h, cool to 40 °C, remove the solvent in the system by vacuum distillation, dry, and grind to obtain the required cardanol-grafted polyurethane.

[0077] Example 4

[0078] The preparation process of the high-temperature resistant and flame-retardant polyolefin cable material in this Example 4 is as follows:

[0079] Weigh by mass parts. Add 56 parts of polyolefin resin, 16 parts of ionomer, 42 parts of composite flame retardant, and 0.8 part of antioxidant to a high-speed mixer, mix at 400 r / min and 80 °C for 5 min, and then add 28 parts of cardanol-grafted polyurethane and 1.8 parts of lubricant and mix evenly at a stirring rate of 60 r / min. Extrude and pelletize through a twin-screw extruder via a double-cone feeding system. The temperature of the twin-screw extruder is set at 170 - 210 °C, and the screw speed is 250 - 400 rpm to obtain the high-temperature resistant and flame-retardant polyolefin cable material.

[0080] The components, ratios, and preparation methods of the above polyolefin resin, ionomer, composite flame retardant, and cardanol-grafted polyurethane are the same as those in Example 3. For details, refer to Example 3.

[0081] The above antioxidant is AO-1010; the lubricant is a composition of magnesium stearate and aluminum stearate with a mass ratio of 1:1.

[0082] Example 5

[0083] The preparation process of the high-temperature resistant and flame-retardant polyolefin cable material in this Example 5 is the same as that in Example 4. For details, refer to Example 4. The difference is that the ionomer in this Example 5 is an EMAA copolymer, selected from PPB-M02D of Maoming Petrochemical.

[0084] Comparative Example 1

[0085] The components and preparation process of the high-temperature resistant and flame-retardant polyolefin cable material in this Comparative Example are the same as those in Example 4. For details, refer to Example 4. The difference is that the polyolefin resin in this Comparative Example 1 is isotactic polypropylene RP344P-K and does not contain polyphase copolymerized polypropylene.

[0086] Comparative Example 2

[0087] The components and preparation process of the high-temperature resistant and flame-retardant polyolefin cable material in this comparative example are the same as those in Example 4, and reference can be made to Example 4 specifically. The difference is that in this Comparative Example 2, the ionomer is SEBS-g-MZn ionomer, and its preparation method is the same as that of the SEPS-g-MZn ionomer in Example 3. The only difference is that SEPS in Example 3 is replaced with SEBS, and the other components and ratios are the same.

[0088] Comparative Example 3

[0089] The components and preparation process of the high-temperature resistant and flame-retardant polyolefin cable material in this comparative example are the same as those in Example 4, and reference can be made to Example 4 specifically. The difference is that in this Comparative Example 3, cardanol grafted polyurethane is not added, and the addition amount of polyolefin resin is 84 parts, that is, the addition sequence is also the same as that in Example 4, and it is added in two times successively. First, 56 parts of polyolefin resin are added, and the rest are added simultaneously with the lubricant.

[0090] Comparative Example 4

[0091] The components and preparation process of the high-temperature resistant and flame-retardant polyolefin cable material in this comparative example are the same as those in Example 4, and reference can be made to Example 4 specifically. The difference is that in this Comparative Example 4, a mixture of cardanol and polyurethane (i.e., cardanol and polyurethane are blended) is added, and the addition amount of cardanol is 6.5% of the mass of polyurethane.

[0092] Comparative Example 5

[0093] The components and preparation process of the high-temperature resistant and flame-retardant polyolefin cable material in this comparative example are the same as those in Example 4, and reference can be made to Example 4 specifically. The difference is that in this Comparative Example 5, the composite flame retardant is a mixture of magnesium hydroxide and ammonium polyphosphate with a mass ratio of 1:0.6.

[0094] Table 1 shows the temperatures of each zone of the twin-screw extruder and the main machine speed during the processing of the raw material formulations in Examples 1-5 and Comparative Examples 1-5, as shown in Table 1 below.

[0095] Table 1 Settings of Temperatures of Each Zone of the Twin-Screw Extruder and the Main Machine Speed

[0096]

[0097] The mechanical properties, electrical insulation, breakdown strength, flame retardancy, high-temperature resistance and other properties of the high-temperature resistant and flame-retardant polyolefin cable materials prepared in the above Examples 1-5 and Comparative Examples 1-5 were tested, and the test results are shown in Tables 2 and 3 below.

[0098] Mechanical properties: Tensile strength and elongation at break were tested according to GB / T 1040.1-2018;

[0099] Electrical insulation: Volume resistivity (20 °C) was tested according to GB / T 1410-2006;

[0100] Heat distortion temperature: Tested according to GB / T 1634-2004, with a heating rate of 120 °C / h and a pressure of 1.8 MPa.

[0101] DC breakdown strength:

[0102] Make a film specimen of polyolefin cable material with a thickness of 100 μm, 6 cm × 12 cm, then place it in a spherical electrode, heat it to 30 °C and keep it for 2 h to fully heat the silicone oil. Use a thermometer to measure and ensure that the temperature at the position of the specimen has no deviation. Carry out the test at a speed of 2 kV / s, measure the breakdown voltage at 5 points, and calculate the DC breakdown strength through the following formula:

[0103]

[0104] In the above formula, E is the DC breakdown strength, with the unit of kV / mm; U is the measured value of the DC breakdown voltage, with the unit of kV; d is the insulation thickness at the breakdown point, with the unit of mm.

[0105] Flame retardancy:

[0106] Detect the limiting oxygen index according to GB / T 2406-2009, with the specimen size of 110×6.5×3 mm; detect the vertical burning performance according to GB / T 2408-2021;

[0107] Low-temperature impact performance: Detect the low-temperature impact embrittlement temperature according to GB / T 5470-2008.

[0108] Table 2 Performance test results of polyolefin cable material examples

[0109]

[0110] Table 3 Performance test results of polyolefin cable material comparative examples

[0111]

[0112] From the results of Examples 1-5 and Comparative Examples 1-5, it can be seen that the high-temperature resistant and flame-retardant polyolefin cable material and its preparation process of the present invention start from the aspects of reducing costs, environmental protection, flame retardancy and insulation, make full use of the characteristics of each raw material itself and the synergistic effect between each component, overcome the deficiencies described in the background technology, ensure that the combustion performance of the polyolefin cable material of the present invention can reach 1.6 mm / V0 (UL94), and further make the combustion performance grade of the prepared cable reach B1 level. At the same time, it can also meet the cold resistance requirement of -40 °C, is convenient to prepare, has a wide application range and low cost, and has the characteristics of good processing performance, high temperature resistance grade, excellent electrical performance, good mechanical performance and strong weather resistance.

[0113] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, 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, it should be considered as the scope described in this specification.

[0114] The above embodiments only express several implementation manners of the present invention, and the description thereof is relatively specific and detailed. However, it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A high temperature resistant flame retardant polyolefin cable material, characterized in that: The polyolefin cable material is composed of the following raw materials in parts by weight: 50-70 parts of polyolefin resin, 20-40 parts of cardanol grafted polyurethane, 10-25 parts of ionomer, 30-50 parts of composite flame retardant, 1-3 parts of lubricant and 0.2-1.2 parts of antioxidant; The polyolefin resin is composed of isotactic polypropylene and heterogeneous copolymer polypropylene in a mass ratio of 1:(0.1-0.2); The ionomer is an EMAA copolymer or a SEPS-g-MZn ionomer; The composite flame retardant is composited from modified polypropylene, magnesium hydroxide and ammonium polyphosphate.

2. The high temperature resistant flame retardant polyolefin cable material according to claim 1, characterized in that: The preparation method of the cardanol grafted polyurethane comprises the following steps: First, N, N-dimethylcyclohexylamine is added to the polyurethane emulsion and mixed evenly, then benzoyl peroxide (initiator) is added, and the mixture is heated to 80-90°C. Then, dimethylpentanediamine is added dropwise to the reaction system, and the mixture is reacted for 2-4 hours to obtain an activated polyurethane. The solution obtained by dissolving cardanol in ethyl acetate is added to the activated polyurethane, and the mixture is stirred and reacted at 50-70°C for 4-7 hours. After the mixture is cooled to 40°C, the solvent in the system is removed by vacuum distillation, and the mixture is dried and ground to obtain the desired cardanol grafted polyurethane.

3. The high temperature resistant flame retardant polyolefin cable material according to claim 2, characterized in that: The amount of N,N-dimethylcyclohexylamine added is 1.2-1.8% of the mass of the polyurethane emulsion; The amount of benzoyl peroxide added is 0.3-0.6% of the mass of the polyurethane emulsion; The amount of dimethylpentanediamine added is 1.5-2.5% of the mass of the polyurethane emulsion; The added amount of the cardanol is 4-8% of the mass of the polyurethane emulsion.

4. The high temperature resistant flame retardant polyolefin cable material according to claim 1, characterized in that: The preparation method of the SEPS-g-MZn ionomer is: SEPS and an appropriate amount of cyclohexane oil were premixed evenly, and then MAH monomer was added and stirred for 20-30 minutes. Then, the mixture was placed under a nitrogen atmosphere, heated to 100-120°C, AIBN was added, reacted for 2-5 hours, condensed and refluxed, and then filtered with acetone to obtain SEPS-g-MH copolymer; The SEPS-g-MH copolymer and the antioxidant are added into a high-speed mixer, and then zinc stearate is added, mixed at 130-140°C for 5-8 minutes, cooled to below 70°C, and then the mixture is extruded and granulated into a single screw through a double-cone feeding system to obtain a SEPS-g-MZn ionomer.

5. The high temperature resistant flame retardant polyolefin cable material according to claim 4, characterized in that: The mass ratio of the SEPS, MAH monomer and AIBN is 1:(0.07-0.09):(0.01-0.02); the amount of zinc stearate added is 0.5-0.8wt% of the SEPS-g-MH copolymer.

6. The high temperature resistant flame retardant polyolefin cable material according to claim 1, characterized in that: The preparation method of the composite flame retardant is as follows: Weigh the dried magnesium hydroxide and ammonium polyphosphate respectively, mix them evenly, then add them into the modified polypropylene and stir for 10-20 minutes, then transport them to a single screw extruder for extrusion granulation, set the extruder temperature to 160-190° C., and dry to obtain a composite flame retardant.

7. The high temperature resistant flame retardant polyolefin cable material according to claim 6, characterized in that: The mass ratio of the modified polypropylene, magnesium hydroxide and ammonium polyphosphate is (0.05-0.1):1:(0.5-0.7).

8. The high temperature resistant flame retardant polyolefin cable material according to claim 7, characterized in that: The modified polypropylene is maleic anhydride grafted polypropylene or styrene grafted polypropylene.

9. The high temperature resistant flame retardant polyolefin cable material according to claim 1, characterized in that: The lubricant is any one or more of polyethylene wax, magnesium stearate, calcium stearate, ethylene bis stearamide, and aluminum stearate; The antioxidant is any one or two of antioxidant 1010, antioxidant 1076, antioxidant 168, and AO-1010.

10. A process for preparing the high temperature resistant flame retardant polyolefin cable material according to any one of claims 1 to 9, characterized in that: The specific steps include: The polyolefin resin, ionomer, composite flame retardant and antioxidant are weighed by mass, added into a high-speed mixer, mixed for 3 to 5 minutes at 300 to 500 r / min and 70 to 80°C, then the cardanol grafted polyurethane and lubricant are added and mixed evenly at a stirring rate of 50 to 80 r / min, and extruded and granulated into a twin-screw extruder through a double-cone feeding system to obtain a high-temperature resistant flame-retardant polyolefin cable material.

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