High-temperature-resistant flame-retardant polyolefin cable material and preparation process thereof

Abstract

The invention discloses a high-temperature-resistant flame-retardant polyolefin cable material and a preparation process thereof, and belongs to the field of polyolefin cable materials and manufacturing thereof. The high-temperature-resistant flame-retardant polyolefin cable material is prepared from the following raw materials in parts by mass: 50 to 70 parts of polyolefin resin, 20 to 40 parts of cardanol grafted polyurethane, 10 to 25 parts of ionomer, 30 to 50 parts of composite flame retardant, 1 to 3 parts of lubricant and 0.2 to 1.2 parts of antioxidant, wherein the polyolefin resin is composed of isotactic polypropylene and multiphase co-polypropylene according to a mass ratio of 1: (0.1-0.2), the ionomer is an EMAA copolymer or an SEPS-g-MZn ionomer, and the composite flame retardant is composed of modified polypropylene, magnesium hydroxide and ammonium polyphosphate. The high-temperature-resistant flame-retardant polyolefin cable material provided by the invention does not need a crosslinking process, so that the production cost is saved, and the production efficiency and the quality are easy to control; meanwhile, the cable material has excellent mechanical strength, toughness, chemical corrosion resistance, high-temperature resistance, low-temperature impact resistance, direct-current breakdown strength and flame retardance, the product quality of the cable material is improved, and the service life of the cable material is prolonged.

Description

Technical Field

[0001] The invention belongs to the field of polyolefin cable materials and their manufacture, and in particular relates to a non-crosslinked thermoplastic polypropylene cable material that can meet the requirements of high temperature resistance and flame retardancy and a preparation process thereof. Background Art

[0002] As people's awareness of environmental protection and safety increases, the demand for environmental protection of cable materials has become more urgent. The development of polymer materials for cable insulation has gone through the stages of natural rubber, polyvinyl chloride, polyethylene, cross-linked polyethylene and ethylene propylene rubber. Thermosetting cross-linked polyethylene has low price, good processability, excellent mechanical and electrical properties, and the maximum operating temperature can reach 90°C when used as cable insulation. Therefore, XLPE has now become the most widely used and highest-yield cable insulation material. However, XLPE cross-linking needs to be completed in an inert environment of high temperature and high pressure. The preparation process is complicated, the production efficiency is low, and the energy consumption is high. XLPE is a thermosetting material and cannot be recycled, resulting in a waste of resources and environmental pollution. The cross-linking reaction is prone to generate polar by-products, introduce impurities, and lead to the download of electrical performance, and it is easy to produce internal defects, leading to insulation breakdown, causing leakage, short circuit, power failure and other serious accidents.

[0003] Compared with the existing cross-linked polyethylene cable materials, polypropylene has the characteristics of excellent insulation, high temperature resistance, no need for cross-linking, plasticization and recycling, etc. It not only has great advantages in increasing current carrying capacity, but also simplifies processing technology, reduces costs, increases production efficiency, and increases cable length. It has advantages that XLPE cannot have. However, PP is a non-polar material with high crystallinity, poor low-temperature impact resistance, poor toughness, low melt viscosity, and high modulus. It is easy to deviate from the core during processing, causing uneven distribution of high-voltage cable field strength, resulting in unqualified cables. At the same time, under the action of the DC electric field, space charge accumulation will occur, which makes the polypropylene insulation material easy to be broken down (i.e., high voltage is easy to break down), affecting the application of cables in high-voltage environments and reducing their service life; and the mechanical properties are significantly lower than XLPE.

[0004] Generally, high-voltage DC cables must meet the flammability requirements of the national standard GB / T 18380-2008, and their combustion performance level must also meet the B1 level specified in the national standard GB 31247-2014. PP, as a non-polar polymer, has poor compatibility with most flame retardants, including organic phosphates, inorganic aluminum hydroxide, magnesium hydroxide, etc. It is difficult to process and has high hardness, making the resulting cable feel stiff and easy to crack. At the same time, the mechanical properties of the resulting flame-retardant cable material cannot meet the requirements, which affects the application of PP cable materials.

[0005] Invention patent CN202210350732.8 discloses a thermoplastic polypropylene DC cable insulation material. By adding additives containing polar groups to copolymer-modified PP, double bond groups are grafted onto the PP macromolecular chain through an initiator. It is mainly used to solve the influence of antioxidants on space charge accumulation, so that the PP cable raw material of the invention has better DC breakdown strength (insulation) and heat resistance and aging resistance. However, no flame retardant or filler components are added in the invention, which does not meet the standard requirements of existing cable materials for smokeless flame retardancy, etc., and if inorganic flame retardant components are added, it will inevitably affect its compatibility with polypropylene, thereby causing the final mechanical properties, insulation, flame retardancy, etc. of the insulation material to be affected. Invention patent CN201410557756.6 discloses a method for preparing a recyclable cable insulation material, which treats the surface of nano inorganic particles with a silane coupling agent to make them compatible with thermoplastic polymers (PP / rubber blends and sPP), improves the electrical properties of polypropylene, and maintains good mechanical and thermal properties. However, the flame retardant added to the cable material is only 2-5 parts, so the flame retardant performance of the cable material is general and cannot be applied to urban DC cables that have flame retardant requirements for DC cables, and is also limited in high-voltage DC cables. Invention patent CN201921938940.X discloses a B1-level flame-retardant DC traction cable for rails with a rated voltage of 1500V. 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 when used for a long time in a low temperature environment, which makes it difficult to meet the cold resistance requirements of northern cities in my country. Summary of the invention

[0006] The main purpose of the present invention is to provide a high-temperature resistant and flame-retardant polyolefin cable material. The cable material does not require a cross-linking process, the preparation process is simple and easy to operate, the production cost is saved, and the production efficiency and quality are easy to control; at the same time, the cable material has excellent mechanical strength, toughness, chemical corrosion resistance, high temperature resistance and low temperature impact resistance, and significantly improves the DC breakdown strength and flame retardancy of the material, so that the cable combustion performance meets the national standards, the cable combustion grade can reach B1 grade, and the product quality and service life of the cable material are improved.

[0007] In order to achieve the purpose of the present invention, the present invention provides a high temperature resistant flame retardant polyolefin cable material, which 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 raw materials of the polyolefin cable material are appropriately proportioned to make the raw material components interact with each other, so as to ensure that the present invention has excellent mechanical strength, electrical insulation, high and low temperature resistance and flame retardancy, and the raw materials do not contain halogen, the raw materials are environmentally friendly, and belong to thermoplastic halogen-free low smoke flame retardant cable insulation materials, which can ensure that the comprehensive performance meets the requirements of national standards.

[0008] The polyolefin resin is composed of isotactic polypropylene and multiphase copolymer polypropylene in a mass ratio of 1: (0.1-0.2). Preferably, the multiphase copolymer polypropylene contains ethylene propylene rubber (EPR). The present invention combines isotactic polypropylene and multiphase copolymer polypropylene containing ethylene propylene rubber in an appropriate proportion, thereby improving the processing melt viscosity of the present invention, facilitating processing and molding, and significantly improving the mechanical strength, toughness, and low-temperature impact resistance of the present invention, reducing the accumulation or defects of space charges, and making the present invention have excellent electrical insulation and high-voltage breakdown strength.

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

[0010] The composite flame retardant is a composite of modified polypropylene, magnesium hydroxide and ammonium polyphosphate. The preferred composite flame retardant combination of the present invention has excellent compatibility with polyolefin resin and other components, making the cable material easy to process and the product not easy to crack, ensuring that the polyolefin cable material can meet the electrical properties required by the present invention and has excellent mechanical properties, and can also make the present invention still meet the flame retardancy and low smoke requirements of the national standard under the premise of being halogen-free, and the combustion grade of the cable product of the present invention can reach B1 grade.

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

[0012] 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.

[0013] The present invention modifies polyolefin resin by adding polyurethane, in the hope of improving the mechanical strength, elasticity, wear resistance and electrical insulation of polyolefin cable materials, however, polyurethane is a polar material and has poor compatibility with polyolefin resin, which reduces the mechanical strength of the present invention and makes the product easy to crack; at the same time, polyurethane is extremely flammable and cannot meet the requirements of the present invention. After the technicians of the present invention graft polyurethane with cardanol, not only the compatibility between polyurethane and components such as polyolefin resin is improved, so that the present invention has better mechanical strength, elasticity, wear resistance and electrical insulation, but also the cardanol grafted polyurethane can meet the high temperature resistance and flame retardant properties required by the present invention.

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

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

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

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

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

[0019] 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;

[0020] 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.

[0021] The present invention adopts SEPS and MAH in an appropriate proportion for grafting treatment, and then combines with zinc ions, and the obtained SEPS-g-MZn ionomer can not only improve the melt viscosity of the present invention, improve 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 and thermal stability of the present invention are reduced.

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

[0023] The amount of zinc stearate added 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 minutes, then transport them to a single screw extruder for extrusion granulation, set the extruder temperature to 160-190°C, and dry them to obtain a composite flame retardant. The composite flame retardant is processed using an appropriate feeding sequence and material ratio to ensure that the modified polypropylene and the flame retardant component 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.

[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. The modified polypropylene of the present invention can significantly improve the dispersibility and compatibility between the composite flame retardant and the 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 stearic acid amide, and aluminum stearate. The selection of lubricants can make the polyolefin cable material have good lubricating properties during the processing, and the obtained product has good appearance and feel, ensuring the comprehensive performance of the polyolefin cable material is excellent.

[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-oxidative aging resistance of polyolefin cable materials, and is not easy to change color or pollute.

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

[0031] The polyolefin resin, ionomer, composite flame retardant and antioxidant are weighed by mass, added into a high-speed mixer, mixed for 3-5 minutes at 300-500 r / min and 70-80° C., then the cardanol grafted polyurethane and lubricant are added at a stirring rate of 50-80 r / min and mixed evenly, and extruded into a twin-screw extruder through a double-cone feeding system for granulation, the temperature of the twin-screw extruder is set to 170-210° C., and the screw speed is 250-400 rpm to obtain a high temperature resistant 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 need to be cross-linked, is easy to process, and has the advantages of good mechanical properties, excellent electrical insulation, high high and low temperature resistance, good elasticity, high breakdown strength, etc.; the combustion grade of the polyolefin cable material can reach B1, the long-term use temperature can be as high as 160°C, and the cold-resistant temperature can reach -40°C (impact resistance meets the standard and does not crack), which fully meets the cold-resistant needs of northern cities.

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

[0035] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

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

[0037] The heterogeneous copolymer 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 selected from QB530 of Mitsui of Japan (maleic anhydride grafted polypropylene can also be made by yourself);

[0041] When the modified polypropylene is styrene-grafted polypropylene, it is homemade, and its preparation method is as follows: polypropylene powder is placed in a reactor in a nitrogen atmosphere, and then BPO / styrene solution (wherein the amount of styrene used is 5% of the mass of polypropylene, and the amount of BPO used is 0.8% of the mass of styrene) is uniformly added dropwise to the reactor and stirred evenly, heated to 60°C and stirred for reaction for 2h, and then continued to heat to 90°C and stirred for reaction for 1h, adding an appropriate amount of deionized water and maintaining for 3h to make it fully react, filtering, placing in ethyl acetate for extraction for 24h, and drying to obtain the desired styrene-grafted polypropylene;

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

[0043] Polyurethane emulsion is selected from HYB 6336.

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

[0045] Example 1

[0046] The preparation process of the high temperature resistant flame retardant polyolefin cable material of this embodiment 1 is as follows:

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

[0048] The polyolefin resin is composed of isotactic polypropylene and heterogeneous copolymer polypropylene in a mass ratio of 5:1.

[0049] The above-mentioned ionomer is SEPS-g-MZn ionomer, and its preparation method is as follows: 1 kg of SEPS (hydrogenated styrene-isoprene-styrene block copolymer) and 150 g of cyclohexane oil are pre-mixed evenly, and then 90 g of MAH monomer is added and stirred for 30 min, and then placed in a nitrogen atmosphere, heated to 110° C., 20 g of AIBN is added, reacted for 4 h, condensed and refluxed, and then filtered 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, and then 8 g of zinc stearate was added, mixed at 450 r / min and 140°C for 7 minutes, cooled to below 70°C, and then the mixture was extruded and granulated through a double-cone feeding system to a single screw. The temperature of the single-screw extruder was set to 100-105°C for zone one, 110-115°C for zone two, 120-130°C for zone three, and 130-135°C for the head to obtain a SEPS-g-MZn ionomer.

[0051] The preparation method of the above-mentioned composite flame retardant is as follows: Mg(OH)2 and ammonium polyphosphate are dried in an oven at 120°C for 2h respectively, then 1kg Mg(OH)2 and 700g ammonium polyphosphate are mixed evenly, and then added into 50g maleic anhydride grafted polypropylene and stirred for 20min, and then transported to a single-screw extruder for extrusion granulation, the extruder temperature is set to 160-190°C, and dried to obtain the composite flame retardant.

[0052] The antioxidant is antioxidant 1010.

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

[0054] First, add 18g of N,N-dimethylcyclohexylamine to 1kg of polyurethane emulsion and mix evenly, then add 6g of benzoyl peroxide, heat to 80°C, and then add 25g of dimethylpentanediamine dropwise to the reaction system. After the addition is completed, react for 3 hours to obtain activated polyurethane; add the solution obtained by dissolving 80g of cardanol in ethyl acetate to the activated polyurethane, stir and react at 60°C for 6 hours, cool to 40°C, remove the solvent in the system by reduced pressure distillation, dry, and grind to obtain the desired cardanol grafted polyurethane.

[0055] The lubricant is a composition of magnesium stearate and calcium stearate in a mass ratio of 1:1.

[0056] Example 2

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

[0058] Weigh by mass, add 70 parts of polyolefin resin, 10 parts of ionomer, 30 parts of composite flame retardant and 1.2 parts of antioxidant into a high-speed mixer, mix for 5 minutes at 400 r / min and 70°C, then add 20 parts of cardanol grafted polyurethane and 2.5 parts of lubricant at a stirring rate of 70 r / min, mix evenly, and extrude and granulate into a twin-screw extruder through a double-cone feeding system. The temperature of the twin-screw extruder is set to 170-210°C, and the screw speed is 250-400rpm to obtain a high-temperature resistant flame-retardant polyolefin cable material.

[0059] The polyolefin resin is composed of isotactic polypropylene and heterogeneous copolymer polypropylene in a mass ratio of 10:1.

[0060] The ionomer is SEPS-g-MZn ionomer, and the preparation method thereof is as follows: 1 kg SEPS and 150 g cyclohexane oil are pre-mixed uniformly, and then 70 g MAH monomer is added and stirred for 20 min, and then placed in a nitrogen atmosphere, heated to 100 ° C, 10 g AIBN is added, reacted for 5 h, condensed and refluxed, and then filtered with acetone to obtain a SEPS-g-MH copolymer;

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

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

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

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

[0065] First, add 12g of N,N-dimethylcyclohexylamine to 1kg of polyurethane emulsion and mix evenly, then add 3g of benzoyl peroxide, heat to 90°C, and then drop 15g of dimethylpentanediamine into the reaction system. After the dropwise addition, react for 2h to obtain activated polyurethane; add the solution obtained by dissolving 40g of cardanol in ethyl acetate to the activated polyurethane, stir and react at 50°C for 7h, cool to 40°C, remove the solvent in the system by vacuum distillation, dry, and grind to obtain the desired cardanol grafted polyurethane.

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

[0067] Example 3

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

[0069] Weigh 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 at 400 r / min and 80°C, then add 20 parts of cardanol grafted polyurethane and 2.5 parts of lubricant at a stirring rate of 60 r / min, mix evenly, and extrude and granulate into a twin-screw extruder through a double-cone feeding system. The temperature of the twin-screw extruder is set to 170-210°C, and the screw speed is 250-400rpm to obtain a high temperature resistant flame retardant polyolefin cable material.

[0070] The polyolefin resin is composed of isotactic polypropylene and heterogeneous copolymer polypropylene in a mass ratio of 8:1.

[0071] The above ionomer is SEPS-g-MZn ionomer, and its preparation method is as follows: 1 kg SEPS and 150 g cyclohexane oil are pre-mixed uniformly, and then 80 g MAH monomer is added and stirred for 30 min, and then placed in a nitrogen atmosphere, heated to 120 ° C, 16 g AIBN is added, reacted for 4 h, condensed and refluxed, and then filtered with acetone to obtain SEPS-g-MH copolymer;

[0072] 1 kg of the above-mentioned SEPS-g-MH copolymer and 3 g of antioxidant 168 were added to a high-speed mixer and mixed evenly, and then 5 g of zinc stearate was added, mixed at 450 r / min and 140°C for 5 minutes, cooled to below 70°C, and then the mixture was extruded and granulated through a double-cone feeding system to a single screw. The temperature of the single-screw extruder was set to 100-105°C for zone one, 110-115°C for zone two, 120-130°C for zone three, and 130-135°C for the head to obtain a SEPS-g-MZn ionomer.

[0073] The preparation method of the above-mentioned composite flame retardant is as follows: Mg(OH)2 and ammonium polyphosphate are dried in an oven at 120°C for 2h respectively, then 1kg Mg(OH)2 and 600g ammonium polyphosphate are mixed evenly, and then added into 80g maleic anhydride grafted polypropylene and stirred for 30min, and then transported to a single-screw extruder for extrusion granulation, the extruder temperature is set to 160-190°C, and dried to obtain the composite flame retardant.

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

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

[0076] First, add 15g of N,N-dimethylcyclohexylamine to 1kg of polyurethane emulsion and mix evenly, then add 5g of benzoyl peroxide, heat to 80°C, and then add 21g of dimethylpentanediamine dropwise to the reaction system. After the addition is completed, react for 3 hours to obtain activated polyurethane; add the solution obtained by dissolving 65g of cardanol in ethyl acetate to the activated polyurethane, stir and react at 60°C for 5 hours, cool to 40°C, remove the solvent in the system by reduced pressure distillation, dry, and grind to obtain the desired cardanol grafted polyurethane.

[0077] Example 4

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

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

[0080] The components, proportions and preparation methods of the polyolefin resin, ionomer, composite flame retardant and cardanol grafted polyurethane are the same as those in Example 3, and specific reference is made to Example 3.

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

[0082] Example 5

[0083] The preparation process of the high temperature resistant flame retardant polyolefin cable material of this embodiment 5 is the same as that of embodiment 4, and specific reference is made to embodiment 4. The difference is that the ionomer in this embodiment 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 flame retardant polyolefin cable material of this comparative example are the same as those of Example 4, and specific reference is made to Example 4. The difference is that the polyolefin resin in this comparative example 1 is isotactic polypropylene RP344P-K, and does not contain multiphase copolymerized polypropylene.

[0086] Comparative Example 2

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

[0088] Comparative Example 3

[0089] The components and preparation process of the high temperature resistant flame retardant polyolefin cable material of this comparative example are the same as those of Example 4, and specific reference is made to Example 4. The difference is that no cardanol grafted polyurethane is added in this comparative example 3, and the amount of polyolefin resin added is 84 parts, that is, the order of addition is the same as that of Example 4, which is added in two times, 56 parts of polyolefin resin are added first, and the rest are added at the same time as the lubricant.

[0090] Comparative Example 4

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

[0092] Comparative Example 5

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

[0094] Table 1 shows the temperature of each zone and the main engine speed of the twin-screw extruder during the preparation of the raw material formula in Examples 1-5 and Comparative Examples 1-5, as shown in Table 1 below.

[0095] Table 1 Temperature and main engine speed settings of each zone of twin-screw extruder

[0096]

[0097] The mechanical properties, electrical insulation, breakdown strength, flame retardancy, high temperature resistance and other properties of the high temperature resistant 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 are tested according to GB / T 1040.1-2018;

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

[0100] Heat deformation temperature: tested according to GB / T 1634-2004, heating rate is 120℃ / h, pressure is 1.8MPa;

[0101] DC breakdown strength:

[0102] The polyolefin cable material is made into a 6cm×12cm film sample with a thickness of 100μm, and then placed in a ball electrode. After the temperature is raised to 30℃ and maintained for 2h to fully heat the silicone oil, a thermometer is used to measure to ensure that the temperature at the location of the sample has no deviation. The breakdown voltage at 5 points is measured at a speed of 2kV / s. The DC breakdown strength is calculated by the following formula:

[0103]

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

[0105] Flame retardant:

[0106] According to GB / T 2406-2009, the limit oxygen index is tested, and the sample size is 110×6.5×3mm; according to GB / T2408-2021, the vertical burning performance is tested;

[0107] Low temperature impact performance: Low temperature impact embrittlement temperature is tested 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] It can be seen from the results of Examples 1-5 and Comparative Examples 1-5 that the high temperature resistant flame retardant polyolefin cable material and its preparation process of the present invention, from the perspectives of cost reduction, environmental protection, flame retardant insulation, etc., fully utilize the characteristics of each raw material itself and the synergistic effect between the components, overcome the shortcomings described in the background technology, and ensure that the combustion performance of the polyolefin cable material of the present invention can reach 1.6mm / V0 (UL94), thereby making the combustion performance grade of the prepared cable reach B1 grade, and at the same time can also meet the cold resistance requirements of -40°C, easy preparation, wide range of application, low cost, and have the characteristics of good processing performance, high temperature resistance grade, excellent electrical properties, good mechanical properties, strong weather resistance, etc.

[0113] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0114] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

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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