Flame-retardant cable and preparation method thereof

Abstract

The invention relates to the technical field of cables, and discloses a flame-retardant cable and a preparation method thereof.The flame-retardant cable comprises a conductor, an insulating layer and a flame-retardant sheath layer; the flame-retardant sheath layer comprises 100 parts by weight of polypropylene, 10-20 parts by weight of an ethylene-vinyl acetate copolymer, 3-8 parts by weight of phosphamide modified soybean oil, 12-20 parts by weight of an inorganic flame retardant and the like; the phosphamide modified soybean oil can improve the compatibility between EVA and polypropylene, so that EVA has a better toughening effect, the soybean oil also has a certain plasticizing and toughening effect, the flexibility of the polypropylene sheath material is improved, and the phosphamide modified soybean oil contains a large amount of flame-retardant phosphamide groups, can be used as a nitrogen-phosphorus flame retardant, and can be used as a flame retardant. By compounding with inorganic flame retardants such as aluminum hydroxide and the like, a good synergistic flame-retardant effect is achieved, and the flame-retardant property of the sheath material is improved.

Description

Technical Field

[0001] This invention relates to the field of cable technology, specifically to a flame-retardant cable and its preparation method. Background Technology

[0002] Flame-retardant cables are mainly used in communication equipment rooms, high-rise buildings, rail transportation, energy and chemical plants, etc. They typically impart flame-retardant properties to the cable sheath to improve its flame-retardant performance. Cable sheaths are mainly made of polyvinyl chloride (PVC), polypropylene (PP), and polyethylene (PE). Among these, polypropylene sheath material has high hardness, low dielectric constant, good temperature resistance, and is not prone to cracking, making it widely used. However, polypropylene has poor flame-retardant properties and relatively low toughness. Therefore, modifying polypropylene for flame retardancy and toughening is of great significance.

[0003] Adding elastomers to polypropylene can improve its toughness. Ethylene-vinyl acetate copolymer (EVA) elastomers have good processing properties, impact resistance, and high-temperature resistance, and are important in the toughening modification of plastics. However, the compatibility between EVA and polypropylene is generally poor, which affects the toughening effect of EVA elastomers. Patent CN110204825B discloses a flame-retardant cable pipe and its preparation method, using polypropylene resin, composite flame retardant, toughening agent, and maleic anhydride-grafted EVA resin as raw materials. The prepared flame-retardant cable pipe has good flame retardancy and mechanical strength, but this patent does not improve the impact resistance of polypropylene, resulting in poor toughness. Summary of the Invention

[0004] Technical problem solved: This invention solves the problem of poor toughness and flame retardant properties of polyethylene sheathing layers for cables.

[0005] The technical solution of the present invention is: a flame-retardant cable, comprising a conductor, an insulation layer and a flame-retardant sheath layer.

[0006] The method for preparing the flame-retardant sheath layer is as follows: (1) Triethylamine and methyl 3-aminopropionate hydrochloride (CAS No. 3196-73-4) were added to dichloromethane, and O,O-dimethylphosphoryl chloride (CAS No. 3196-73-4) was added dropwise. The reaction was stirred under a nitrogen atmosphere, filtered, and the filtrate was distilled under reduced pressure. Then, it was added to methanol, and sodium hydroxide aqueous solution was added dropwise to carry out the hydrolysis reaction. Hydrochloric acid was added dropwise to neutralize the reaction, and dichloromethane was added. After stirring, the mixture was allowed to stand and separate into layers. The aqueous phase was removed, and the oil phase was distilled under reduced pressure and dried. The crude product was separated by column chromatography to obtain dimethoxyphosphorylaminopropionic acid. The reaction formula is as follows: .

[0007] (2) Add dimethoxyphosphorylaminopropionic acid and catalyst to epoxidized soybean oil, stir and react. Add ethyl acetate and water to the solution, stir, and allow to stand for separation. Remove the aqueous phase, distill the oil phase under reduced pressure, and dry to obtain phosphoramide-modified soybean oil. The reaction formula is: .

[0008] (3) Polypropylene, ethylene-vinyl acetate copolymer, phosphoramide-modified soybean oil, inorganic flame retardant and antioxidant are mixed, melt-blended and extruded through a screw extruder to obtain a flame-retardant sheath layer.

[0009] Furthermore, (1) the amount of triethylamine is 146-160 parts by weight, the amount of methyl 3-aminopropionate hydrochloride is 104-114 parts by weight, and the amount of O,O-dimethylphosphoryl chloride is 100 parts by weight.

[0010] Furthermore, in (1), the stirring reaction temperature is 20-30℃ and the reaction time is 2-3h.

[0011] Furthermore, in (1), the hydrolysis reaction temperature is 40-45℃ and the reaction time is 2-4h.

[0012] Furthermore, in (2), the amount of epoxidized soybean oil is 100 parts by weight, the amount of dimethoxyphosphorylaminopropionic acid is 96-160 parts by weight, and the amount of catalyst is 1.8-2.3 parts by weight.

[0013] Furthermore, in (2), the catalyst is triphenylphosphine or N,N-dimethylbenzylamine.

[0014] Furthermore, in (2), the reaction temperature is 115-130℃ and the reaction time is 7-12h.

[0015] Furthermore, the inorganic flame retardant in (3) includes one or more of aluminum hydroxide, magnesium hydroxide, and montmorillonite.

[0016] Furthermore, in (3), the temperature of zones 1-5 of the screw extruder is 170-200℃, and the screw speed is 50-80r / min.

[0017] Furthermore, the amount of polypropylene is 100 parts by weight, ethylene-vinyl acetate copolymer is 10-20 parts by weight, phosphoramide-modified soybean oil is 3-8 parts by weight, inorganic flame retardant is 12-20 parts by weight, and antioxidant is 0.1-0.3 parts by weight.

[0018] The beneficial technical effects of this invention are as follows: The carboxyl group of dimethoxyphosphatidylaminopropionic acid reacts with the epoxy group of epoxidized soybean oil to obtain phosphoramide-modified soybean oil. This modified soybean oil is then compounded with inorganic flame retardants such as polypropylene, ethylene-vinyl acetate copolymer (EVA) elastomer, and aluminum hydroxide to obtain a flame-retardant sheath layer for flame-retardant cables. This phosphoramide-modified soybean oil contains long alkyl chains, similar to the polyolefin backbone structure of polypropylene, and contains a large number of ester groups similar to those in EVA. This allows the modified soybean oil to act as a compatibilizer, improving the compatibility between EVA and polypropylene, giving EVA better toughening properties. Simultaneously, the soybean oil also has a certain plasticizing and toughening effect, significantly improving the flexibility of the polypropylene sheath material and resulting in higher impact strength and flexural strength.

[0019] The phosphoramide-modified soybean oil of this invention contains a large number of flame-retardant phosphoramide groups, which can be used as a nitrogen-phosphorus flame retardant. When combined with inorganic flame retardants such as aluminum hydroxide, it plays a good synergistic flame-retardant role, improves the limiting oxygen index of the sheath material, and has excellent flame-retardant performance. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below. However, it should be understood that the description herein is merely illustrative and not intended to limit the scope of the invention.

[0021] Example 1: A flame-retardant cable, comprising a copper conductor, a polyvinyl chloride insulation layer, and a flame-retardant sheath layer; the method for preparing the flame-retardant sheath layer is as follows: (1) Add 80g of triethylamine and 52g of methyl 3-aminopropionate hydrochloride to 800mL of dichloromethane, add 50g of O,O-dimethylphosphoryl chloride dropwise, stir and react for 3h at 20℃ under nitrogen atmosphere, filter, distill the filtrate under reduced pressure, add it to 900mL of methanol, add 900mL of 6% sodium hydroxide aqueous solution dropwise, heat to 45℃, stir and reflux for 2h, add hydrochloric acid dropwise to neutralize pH to 7, add dichloromethane, stir and let stand to separate the layers, remove the aqueous phase, distill the oil phase under reduced pressure, dry, separate the crude product by column chromatography, the eluent is ethyl acetate in petroleum ether solution, to obtain dimethoxyphosphorylaminopropionic acid.

[0022] (2) Add 126g of dimethoxyphosphoric acid and 2.3g of triphenylphosphine to 100g of epoxidized soybean oil, heat to 115℃, stir and react for 12h, add ethyl acetate and water to the solution, stir and let stand to separate the layers, remove the aqueous phase, distill the oil phase under reduced pressure and dry to obtain phosphoramide modified soybean oil.

[0023] (3) Mix 3kg polypropylene, 300g ethylene-vinyl acetate copolymer, 90g phosphoramide modified soybean oil, 210g aluminum hydroxide, 150g montmorillonite, and 5g antioxidant 1010, and melt blend them through a screw extruder. The temperatures of zones 1-5 are 170℃, 185℃, 195℃, 200℃, and 200℃, and the screw speed is 50r / min. Extrusion molding is then performed to obtain a flame-retardant sheath layer.

[0024] Example 2: A flame-retardant cable, comprising a copper conductor, a polyvinyl chloride insulation layer, and a flame-retardant sheath layer; the method for preparing the flame-retardant sheath layer is as follows: (1) Add 73g of triethylamine and 57g of methyl 3-aminopropionate hydrochloride to 700mL of dichloromethane, add 50g of O,O-dimethylphosphoryl chloride dropwise, stir and react for 2h at 30℃ under nitrogen atmosphere, filter, distill the filtrate under reduced pressure, add it to 900mL of methanol, add 900mL of 6% sodium hydroxide aqueous solution dropwise, heat to 40℃, stir and react for 4h, add hydrochloric acid dropwise to neutralize pH to 7, add dichloromethane, stir and let stand to separate the layers, remove the aqueous phase, distill the oil phase under reduced pressure, dry, separate the crude product by column chromatography, the eluent is ethyl acetate in petroleum ether solution, to obtain dimethoxyphosphorylaminopropionic acid.

[0025] (2) Add 96g of dimethoxyphosphoric acid and 2.2g of triphenylphosphine to 100g of epoxidized soybean oil, heat to 120℃, stir and react for 10h, add ethyl acetate and water to the solution, stir and let stand to separate the layers, remove the aqueous phase, distill the oil phase under reduced pressure and dry to obtain phosphoramide modified soybean oil.

[0026] (3) Mix 3kg polypropylene, 450g ethylene-vinyl acetate copolymer, 160g phosphoramide modified soybean oil, 280g aluminum hydroxide, 200g montmorillonite, and 9g antioxidant 1010, and melt blend them through a screw extruder. The temperatures in zones 1-5 are 170℃, 185℃, 195℃, 200℃, and 200℃, and the screw speed is 50r / min. Extrusion molding is then performed to obtain a flame-retardant sheath layer.

[0027] Example 3: A flame-retardant cable, comprising a copper conductor, a polyvinyl chloride insulation layer, and a flame-retardant sheath layer; the method for preparing the flame-retardant sheath layer is as follows: (1) Add 160g of dimethoxyphosphoric acid (prepared according to the method of Example 1) and 1.8g of N,N-dimethylbenzylamine to 100g of epoxidized soybean oil, heat to 130°C, stir and react for 7h, add ethyl acetate and water to the solution, stir and let stand to separate the layers, remove the aqueous phase, distill the oil phase under reduced pressure and dry to obtain phosphoramide modified soybean oil.

[0028] (2) Mix 3kg polypropylene, 600g ethylene-vinyl acetate copolymer, 240g phosphoramide modified soybean oil, 350g magnesium hydroxide, 250g montmorillonite, and 3g antioxidant 1010, and melt blend them through a screw extruder. The temperatures of zones 1-5 are 170℃, 185℃, 195℃, 200℃, and 200℃, and the screw speed is 80r / min. Extrusion molding is then performed to obtain a flame-retardant sheath layer.

[0029] Comparative Example 1: A cable comprising a copper conductor, a polyvinyl chloride insulation layer, and a sheath layer; the method for preparing the sheath layer is as follows: (1) Mix 3kg polypropylene, 300g ethylene-vinyl acetate copolymer, 210g aluminum hydroxide, 150g montmorillonite and 5g antioxidant 1010, melt blend them through a screw extruder, the temperature of zones 1-5 is 170℃, 185℃, 195℃, 200℃ and 200℃, the screw speed is 50r / min, and extrude to obtain the sheath layer.

[0030] Comparative Example 2: A cable comprising a copper conductor, a polyvinyl chloride insulation layer, and a sheath layer; the method for preparing the sheath layer is as follows: (1) Mix 3kg polypropylene, 300g ethylene-vinyl acetate copolymer, 90g epoxidized soybean oil, 210g aluminum hydroxide, 150g montmorillonite, and 5g antioxidant 1010, and melt blend them through a screw extruder. The temperatures of zones 1-5 are 170℃, 185℃, 195℃, 200℃, and 200℃, and the screw speed is 50r / min. Extrusion molding is then performed to obtain the sheath layer.

[0031] Comparative Example 3: A cable composed of a copper conductor, a polyvinyl chloride insulation layer, and a sheath layer; the method for preparing the sheath layer is as follows: (1) Add 126g of 3-phenylpropionic acid and 2.3g of triphenylphosphine to 100g of epoxidized soybean oil, heat to 115℃, stir and react for 12h, add ethyl acetate and water to the solution, stir and let stand to separate the layers, remove the aqueous phase, distill the oil phase under reduced pressure and dry to obtain modified soybean oil.

[0032] (2) Mix 3kg polypropylene, 300g ethylene-vinyl acetate copolymer, 90g modified soybean oil, 210g aluminum hydroxide, 150g montmorillonite, and 5g antioxidant 1010, and melt blend them through a screw extruder. The temperatures of zones 1-5 are 170℃, 185℃, 195℃, 200℃, and 200℃, and the screw speed is 50r / min. Extrusion molding is then performed to obtain the sheath layer.

[0033] Comparative Example 4: A cable composed of a copper conductor, a polyvinyl chloride insulation layer, and a sheath layer; the method for preparing the sheath layer is as follows: (1) 100g of epoxidized soybean oil and 126g of dimethoxyphosphoric acid (prepared according to the method of Example 1) were stirred and mixed to obtain a phosphoramide-epoxidized soybean oil blend.

[0034] (2) Mix 3kg polypropylene, 300g ethylene-vinyl acetate copolymer, 90g phosphoramide-epoxidized soybean oil blend, 210g aluminum hydroxide, 150g montmorillonite, and 5g antioxidant 1010, and melt blend them through a screw extruder. The temperatures of zones 1-5 are 170℃, 185℃, 195℃, 200℃, and 200℃, and the screw speed is 50r / min. Extrusion molding is then performed to obtain the sheath layer.

[0035] Performance testing: The components are mixed, melt-blended using a screw extruder, extruded and granulated, and then injection molded into test specimens using an injection molding machine. The burning behavior is tested according to GB / T 2406.1-2008 standard, the impact performance is tested according to GB / T 1843-2008 standard, and the flexural performance is tested according to GB / T 9341-2008 standard.

[0036] Table 1 Performance of Sheath Layer Test Samples

[0037] The sheath layer in Comparative Example 1 has low impact strength and flexural strength, and poor toughness. This is mainly because the compatibility between ethylene-vinyl acetate copolymer (EVA) and polypropylene is generally poor, resulting in a low toughening effect of EVA, which is not conducive to improving the toughness of the polypropylene sheath layer.

[0038] Examples 1-3 incorporated phosphoramide-modified soybean oil, which contains long alkyl chains similar to the polyolefin backbone structure of polypropylene and a large number of ester groups similar to EVA. This allows the modified soybean oil to act as a compatibilizer, improving the compatibility between EVA and polypropylene and giving EVA better toughening properties. Simultaneously, soybean oil also has a certain plasticizing and toughening effect, significantly improving the flexibility of the polypropylene sheathing material and resulting in higher impact and flexural strength. Furthermore, the phosphoramide-modified soybean oil contains a large number of flame-retardant phosphoramide groups, which can act as a nitrogen-phosphorus flame retardant. When combined with inorganic flame retardants such as aluminum hydroxide, it exhibits excellent synergistic flame-retardant effects and improves the limiting oxygen index of the sheathing material.

[0039] Comparative Example 2 only added epoxidized soybean oil, which does not contain ester groups, making it difficult to improve the compatibility between EVA and polypropylene. The toughening effect of EVA was poor, and the impact strength and flexural strength of the polypropylene sheath material were lower than those of Example 1. Furthermore, the epoxidized soybean oil does not contain flame-retardant phosphoramide groups, and the limiting oxygen index of the sheath material was lower than that of Example 1, resulting in poor flame retardancy.

[0040] Comparative Example 3 utilizes the reaction of the carboxyl group of 3-phenylpropionic acid with the epoxy group of epoxidized soybean oil to prepare modified epoxidized soybean oil that does not contain flame-retardant phosphoramide groups. The limiting oxygen index of the sheath material is lower than that of Example 1, and the flame retardancy is poor.

[0041] In Comparative Example 4, epoxidized soybean oil and dimethoxyphosphoric acid were physically blended and added to the polypropylene sheath layer. Since epoxidized soybean oil does not contain ester groups, it is difficult to improve the compatibility between EVA and polypropylene. The toughening effect of EVA is not good, and the impact strength and flexural strength of the polypropylene sheath material are lower than those in Example 1.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a flame-retardant cable, characterized in that, The flame-retardant cable includes a conductor, an insulation layer, and a flame-retardant sheath layer; The flame-retardant sheath layer comprises 100 parts by weight of polypropylene, 10-20 parts by weight of ethylene-vinyl acetate copolymer, 3-8 parts by weight of phosphoramide-modified soybean oil, 12-20 parts by weight of inorganic flame retardant, and 0.1-0.3 parts by weight of antioxidant. The preparation method of the phosphoramide-modified soybean oil is as follows: add dimethoxyphosphoric acid and catalyst to epoxidized soybean oil, stir and react, add ethyl acetate and water to the solution, stir and let stand to separate the layers, remove the aqueous phase, distill the oil phase under reduced pressure and dry to obtain phosphoramide-modified soybean oil.

2. The method for preparing the flame-retardant cable according to claim 1, characterized in that, The inorganic flame retardant includes one or more of aluminum hydroxide, magnesium hydroxide, and montmorillonite.

3. The method for preparing the flame-retardant cable according to claim 1, characterized in that, The reaction temperature is 115-130℃, and the reaction time is 7-12h.

4. The method for preparing the flame-retardant cable according to claim 1, characterized in that, The amount of epoxidized soybean oil used is 100 parts by weight, the amount of dimethoxyphosphorylaminopropionic acid is 96-160 parts by weight, and the amount of catalyst is 1.8-2.3 parts by weight.

5. The method for preparing the flame-retardant cable according to claim 4, characterized in that, The catalyst is triphenylphosphine or N,N-dimethylbenzylamine.

6. The method for preparing the flame-retardant cable according to claim 4, characterized in that, The preparation method of the dimethoxyphosphoramidopropionic acid is as follows: triethylamine and methyl 3-aminopropionate hydrochloride are added to dichloromethane, and O,O-dimethylphosphoryl chloride is added dropwise. The mixture is stirred and reacted at 20-30°C for 2-3 hours under a nitrogen atmosphere. After filtration, the filtrate is distilled under reduced pressure and then added to methanol. Sodium hydroxide aqueous solution is added dropwise, and the mixture is heated to 40-45°C and stirred for 2-4 hours. Hydrochloric acid is added dropwise for neutralization, and dichloromethane is added. After stirring, the mixture is allowed to stand and separate into layers. The aqueous phase is removed, and the oil phase is distilled under reduced pressure and dried. The crude product is separated by column chromatography to obtain dimethoxyphosphoramidopropionic acid.

7. The method for preparing the flame-retardant cable according to claim 6, characterized in that, The amount of triethylamine used is 146-160 parts by weight, methyl 3-aminopropionate hydrochloride is 104-114 parts by weight, and O,O-dimethylphosphoryl chloride is 100 parts by weight.

8. The method for preparing the flame-retardant cable according to claim 1, characterized in that, The flame-retardant sheath layer is prepared by mixing polypropylene, ethylene-vinyl acetate copolymer, phosphoramide-modified soybean oil, inorganic flame retardant, and antioxidant, and then melting and extruding the mixture through a screw extruder to obtain the flame-retardant sheath layer.

9. The method for preparing the flame-retardant cable according to claim 8, characterized in that, The temperature of zones 1-5 of the screw extruder is 170-200℃, and the screw speed is 50-80 r / min.

10. A flame-retardant cable obtained by the preparation method according to any one of claims 1-9.

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