A method for preparing an environmentally friendly, high-efficiency flame-retardant polyolefin cable sheath material

Abstract

This invention relates to the field of flame retardant preparation technology, and more particularly to a method for preparing an environmentally friendly and highly efficient flame-retardant polyolefin cable sheath material. The invention uses compounds containing primary amino and amide bonds and compounds containing phenyl and phosphoryl chloride groups as raw materials. The reaction is carried out at room temperature for 0.5-1 h, then heated to 45 °C for 3-4 h, and then to 65 °C for 5-6 h. Through a condensation reaction, a phosphoramide macromolecular flame retardant containing phenyl and amide bonds is obtained, with a yield as high as 80.5-95.6%. This flame retardant is added to polyolefin cable sheath material at a mass ratio of 25%, then compounded and extruded to obtain a halogen-free flame-retardant polyolefin cable sheath material. The flame retardant molecule prepared by this invention simultaneously contains phosphorus and nitrogen flame-retardant elements and amide bonds forming a char skeleton. During combustion, it can exert a phosphorus-nitrogen synergistic flame-retardant effect and promote the catalytic char formation of the matrix, which can significantly reduce the heat and toxic gas release of polyolefin cable sheath material during combustion, thereby providing protection for the lives of people in fire scenes.

Description

Technical Field

[0001] This invention relates to the field of flame retardant synthesis and polymer material processing technology, specifically to a method for preparing an environmentally friendly, high-efficiency flame-retardant polyolefin cable sheath material. Background Technology

[0002] Polyolefin materials, such as polyethylene and polypropylene, are widely used in the insulation and sheathing of wires and cables due to their excellent electrical insulation, good chemical resistance, light weight, ease of processing and molding, and low cost. With the acceleration of urbanization and the rapid development of power and communication networks, the use of cables in daily life is increasing daily. However, polyolefin materials are essentially composed of hydrocarbon elements, making them highly flammable. When burning, the flame spreads rapidly, releasing large amounts of heat, dense smoke, and toxic gases (such as carbon monoxide and carbon dioxide), posing a serious threat to people's lives and property. Especially in densely populated or enclosed places such as subways, tunnels, and high-rise buildings, cable fires have become one of the main fire hazards. Therefore, developing polyolefin cable sheathing materials with high-efficiency flame retardant and low-toxicity properties has significant practical and social value.

[0003] Currently, the common method for achieving flame retardancy in polyolefins is to add flame retardants to the matrix. Traditional flame retardant systems mainly include halogenated flame retardants (such as decabromodiphenyl ether) and inorganic filled flame retardants (such as aluminum hydroxide and magnesium hydroxide). Although halogenated flame retardants have high flame retardant efficiency, they release large amounts of toxic and corrosive hydrogen halide gases, as well as highly toxic and carcinogenic substances such as polybrominated dibenzodioxins and polybrominated dibenzofurans during combustion, seriously endangering human life and causing environmental pollution. Therefore, they are gradually being restricted and banned by regulations worldwide. While inorganic metal hydroxide flame retardants are non-toxic, their flame retardant efficiency is relatively low, usually requiring an addition of more than 50% to achieve a satisfactory flame retardant effect. This leads to a sharp deterioration in the mechanical properties (such as tensile strength and elongation at break) and processing performance of cable sheath materials.

[0004] Phosphorus and nitrogen-based flame retardants represent an important development direction for environmentally friendly halogen-free flame retardants. However, traditional small-molecule phosphorus-based flame retardants suffer from high volatility, poor thermal stability, easy migration and precipitation, and poor compatibility with polyolefin matrices. Long-term use can lead to reduced flame retardant effects due to leaching and environmental pollution. Nitrogen-based flame retardants (such as melamine and its derivatives) suffer from insufficient thermal stability, poor water resistance, premature decomposition during material processing, and poor compatibility with polyolefins, affecting the mechanical properties and appearance of the material. A single phosphorus or nitrogen-based flame retardant is insufficient to simultaneously meet the comprehensive requirements of high-performance cable sheath materials.

[0005] The inventors have noted that phosphorus-nitrogen synergistic flame retardant systems are currently a research hotspot in the field of halogen-free flame retardants. By simultaneously introducing phosphorus and nitrogen elements into the molecule, a synergistic effect of "acid source" and "gas source" can be achieved during combustion, promoting the expansion of the polymer matrix into char and forming a dense char layer to insulate against heat and oxygen, thereby achieving highly efficient flame retardancy. Furthermore, designing the flame retardant as a macromolecular structure not only effectively improves its thermal stability and compatibility with the polyolefin matrix but also inhibits the migration and precipitation of small-molecule flame retardants. In addition, introducing rigid groups such as benzene rings and amide bonds and char-forming skeletons into the flame retardant molecule helps to form a stable cross-linked char layer during combustion, further improving flame retardant efficiency.

[0006] Based on this, the present invention designs a novel environmentally friendly phosphorus-nitrogen-based phenylamide macromolecular flame retardant and applies it to polyolefin cable sheath materials, aiming to solve the problems of low flame retardant efficiency, easy migration, and release of large amounts of toxic gases during combustion in the existing technology. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing an environmentally friendly, high-efficiency flame-retardant polyolefin cable sheath material. This method uses compounds containing primary amino and amide bonds and compounds containing phenyl and phosphoryl chloride groups as raw materials, and through a simple polycondensation reaction, yields a phosphorus-nitrogen macromolecular flame retardant with high thermal stability, good compatibility with polyolefins, and integrating acid, gas, and carbon sources. When applied to polyolefin cable sheath materials, it can effectively suppress the release of heat and toxic gases during combustion.

[0008] The objective of this invention is achieved through the following technical solutions.

[0009] This invention relates to a method for preparing an environmentally friendly phosphorus-nitrogen-based phenylamide macromolecular flame retardant and a polyolefin flame-retardant cable sheath material. The specific preparation steps are as follows: (1) Add 25-30 parts by weight of the compound containing primary amino and amide bonds, 10-25 parts by weight of the organic amine and 300-600 parts by weight of the solvent to a three-necked flask equipped with a reflux condenser and mix at room temperature. (2) Mix 20-50 parts by weight of the compound containing phenyl and phosphoryl chloride groups with 20-60 parts by weight of solvent evenly, and slowly add it dropwise over 30-60 minutes through a constant pressure dropping funnel into the three-necked flask obtained in step (1), while keeping the mixture at room temperature and stirring during the dropwise process. (3) After the addition is complete, continue the reaction at room temperature for 0.5-1 h, then raise the temperature of the reaction system to 40-50 °C and react for 3-4 h, then raise the temperature to 60-70 °C and react for 5-6 h; (4) After the reaction is complete, the product system is cooled to room temperature, the generated amine hydrochloride solid is removed by vacuum filtration, the filtrate is subjected to vacuum distillation to recover the organic solvent, and a viscous light yellow crude product is obtained. (5) The crude product obtained in step (4) is dried in a vacuum drying oven at 60~80 ℃ for 20~30 h to obtain a light yellow environmentally friendly phosphorus nitrogen-based phenylamide macromolecular flame retardant with a yield of 80.5~95.6%; (6) Add 70-85 parts by weight of the polyolefin matrix into a mixer or twin-screw extruder and melt blend at 160-180 °C for 5-10 min; (7) Add 15-30 parts by weight of the flame retardant prepared in step (5) to the mixing equipment in step (6) and continue to melt and blend for 10-15 min to make the flame retardant uniformly dispersed in the polyolefin matrix. (8) The blend obtained in step (7) is extruded and granulated by an extruder, and the granules are molded on an injection molding machine or a flat vulcanizing machine to obtain a polyolefin flame-retardant cable sheath material with excellent flame retardant properties and low smoke and halogen-free characteristics.

[0010] The compound containing primary amino and amide bonds in the above steps is preferably one of diaminobenzoyl aniline or M-BAP (CAS No.: 2185036-27-3).

[0011] The organic amine used in the above steps is preferably one of triethylamine, pyridine, or diisopropylethylamine, which serves to absorb the hydrogen chloride produced in the reaction.

[0012] The solvent used in the above steps can be one of tetrahydrofuran (THF), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), acetone, dichloromethane or chloroform, preferably tetrahydrofuran or N,N-dimethylformamide.

[0013] The compound containing phenyl and phosphoryl chloride groups in the above steps is preferably diphenylphosphine chloride.

[0014] The environmentally friendly phosphorus-nitrogen phenylamide macromolecular flame retardant prepared by the above method is a macromolecular compound containing a rigid benzene ring structure, an amide bond carbon skeleton, and phosphorus-nitrogen synergistic flame retardant units in its molecular chain.

[0015] The organic solvent selected in this invention is recyclable, effectively reducing production costs. The reaction process is simple to operate, mild, and reproducible, with outstanding advantages such as high yield and short synthesis cycle. The abundant phosphorus-nitrogen functional groups, benzene rings, and amide bonds in the molecular structure of the prepared phosphorus-nitrogen macromolecular flame retardant endow it with excellent thermal stability, making it an environmentally friendly macromolecular flame retardant with both efficient char formation and synergistic phosphorus-nitrogen flame retardant properties. Its application in cable sheath materials can significantly reduce the heat release rate, total heat release, and the generation of toxic CO2 gas during combustion. This invention provides a practical new technology strategy for the development of halogen-free flame-retardant polyolefin cable materials. Attached Figure Description

[0016] Figure 1 A schematic diagram illustrating the structure of the target macromolecular flame retardant (PNAFR) prepared by the chemical reaction of raw materials diphenylphosphine chloride (DPPC) and M-BAP in Case 1; Figure 2 FT-IR spectra of raw materials diphenylphosphine chloride (DPPC), M-BAP and target macromolecular flame retardant (PNAFR) in Case 1; Figure 3 To implement the target macromolecular flame retardant (PNAFR) in Case 1 1 H NMR spectrum; Figure 4 To implement the target macromolecular flame retardant (PNAFR) in Case 1 31 P NMR spectrum; Figure 5 XPS full spectrum of the target macromolecular flame retardant (PNAFR) in Case 1; Figure 6 The cone calorimetry test heat release rate (HRR) curves of the polyolefin flame retardant cable sheath composite material and substrate with a flame retardant (PNAFR) content of 25 wt% are used to implement Case 1. Figure 7 Cone calorimetry test total heat release (THR) curves of polyolefin flame-retardant cable sheath composite material and substrate with 25 wt% added flame retardant (PNAFR) for Case 1. Figure 8 The cone calorimetry test CO2 generation rate (CO2P) curves of polyolefin flame-retardant cable sheath composite material and substrate with 25 wt% added flame retardant (PNAFR) were used to implement Case 1. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below. It should be noted that, without contradiction, the various embodiments and features of this invention can be combined arbitrarily. Numerous specific details are provided in the following description to help fully understand this invention; however, this invention may also be implemented in other ways different from those described herein. Obviously, the embodiments listed in the specification are only a part of the embodiments of this invention, and not an exhaustive list.

[0018] Implementation Case 1 In a 1000 mL brown three-necked flask equipped with a reflux condenser, 25 g of M-BAP, 10.2 g of triethylamine, and 400 mL of tetrahydrofuran (THF) were added sequentially, and the mixture was stirred at room temperature for 30 min. Separately, 23.7 g of diphenylphosphine chloride (DPPC) was dissolved in 40 mL of THF, and this solution was slowly added dropwise to the three-necked flask over 10 min using a constant-pressure dropping funnel, while maintaining stirring at room temperature during the addition. After the addition was complete, the reaction was continued at room temperature for 30 min; then the oil bath temperature was raised to 45 °C, and the reaction was carried out for 4 h; then the temperature was raised to 65 °C, and the reaction was continued for 5 h. After the reaction was completed, the system was cooled to room temperature, and the generated triethylamine hydrochloride solid was removed by filtration. The filtrate was then subjected to vacuum distillation to recover THF, yielding a viscous crude product. The crude product was dried in a vacuum drying oven at 70 °C for 24 h to obtain an environmentally friendly phosphorus-nitrogen-based phenylamide macromolecular flame retardant (denoted as PNAFR). PNAFR with the same structure can be prepared using any of the raw material ratios within the scope of the instructions. The obtained flame retardant was added to a polyolefin matrix at a mass ratio of 25%, and then melt-blended at 185 °C, extruded, granulated, and molded to obtain a polyolefin flame-retardant cable sheath material.

[0019] Figure 2 To obtain the FT-IR spectra of the raw materials diphenylphosphine chloride (DPPC), M-BAP, and the target macromolecular flame retardant (PNAFR) in Case 1, the raw material DPPC located at 544 cm⁻¹... -1 The characteristic absorption peak of the P-Cl bond disappears in the product PNAFR, while the peaks at 3389 and 3418 cm⁻¹ of M-BAP are absent. -1 The -NH2 double peaks merged into the 3440 cm⁻¹ PNAFR peak. -1 Single peak, and 906 cm⁻¹ in PNAFR -1 The appearance of a new characteristic peak for the PN bond indicates that the P-Cl in DPPC reacts with the -NH2 in M-BAP to form a phosphoramide flame retardant. Furthermore, the product PNAFR retains a peak at 1220 cm⁻¹. -1 The stretching vibration peak of P=O, 3470 cm⁻¹ -1 -OH characteristic peak, 3000~2800 cm⁻¹-1 The CH stretching vibration peak of the benzene ring in the range indicates that the structure of diphenyl phosphate, the phenolic hydroxyl group of the bisphenol A skeleton, and the benzene ring structure were not destroyed after the reaction.

[0020] Figure 3 To implement the target macromolecular flame retardant (PNAFR) in Case 1 1 H NMR spectrum, in PNAFR 1 In the 1H NMR spectrum, a proton peak belonging to the p-NH- bond appeared at 9.69 ppm, a proton peak belonging to the -NH-C=O bond appeared at 8.16 ppm, a proton peak belonging to the phenolic hydroxyl group appeared at 5.12 ppm, and the multiplets between 6.60 and 7.80 ppm were attributed to the proton resonance peaks of hydrogen on the benzene ring (the proton resonance peaks of hydrogen on deuterated chloroform are between 7.10 and 7.30 ppm).

[0021] Figure 4 To implement the target macromolecular flame retardant (PNAFR) in Case 1 31 The P NMR spectrum showed only one strong and sharp phosphorus resonance peak, indicating that the synthesized substance did not contain any byproducts.

[0022] Figure 5 To obtain the XPS full spectrum of the target macromolecular flame retardant (PNAFR) in Case 1, the sharp, strong peak at 284.8 eV is attributed to C 1s, the characteristic peak at 532.0 eV is attributed to O 1s, originating from -OH, P=O, POC, and C=O in the structure, the characteristic peak at 399.5 eV is attributed to N 1s, corresponding to -NH in the molecule, and the characteristic peak at 133.0 eV is attributed to P 2p, corresponding to phosphorus in P=O and PO, proving that the product PNAFR contains C, N, O, and P elements.

[0023] Figure 6 To implement Case 1, the cone calorimetry heat release rate curves of the polyolefin flame-retardant cable sheath composite material and substrate with a flame retardant (PNAFR) content of 25 wt% were obtained. The maximum heat release rate of the polyolefin substrate was 323.8 kW / m. 2 The maximum heat release rate of the polyolefin composite containing 25% PNAFR is 260.1 kW / m². 2 The reduction was 19.7%, indicating that the addition of PNAFR can effectively reduce the heat release rate of polyolefin sheath materials and enhance their flame retardant properties.

[0024] Figure 7To implement Case 1, the smoke generation rate curves of the polyolefin flame-retardant cable sheath composite material and substrate with a flame retardant (PNAFR) content of 25 wt% were obtained from cone calorimetry testing. The maximum total heat release of the polyolefin substrate was 85.1 MJ / m. 2 The maximum total heat release of the polyolefin composite material containing 25% PNAFR was 80.6 MJ / m2, a reduction of 5.3%. This indicates that the addition of PNAFR can effectively reduce the total heat release of the polyolefin sheath material and enhance its flame retardant properties.

[0025] Figure 8 To illustrate the CO generation rate curves of the polyolefin flame-retardant cable sheath composite material and substrate with a flame retardant (PNAFR) content of 25 wt% in Case 1, the peak CO2 generation rate of the polyolefin substrate was 0.189 g / s, while the maximum total heat release of the polyolefin composite material containing 25% PNAFR was 0.172 g / s, a reduction of 9.0%. This indicates that the addition of PNAFR can effectively reduce the total heat release of the polyolefin sheath material and enhance its flame-retardant properties.

[0026] Implementation Case 2 In a 2000 mL brown three-necked flask equipped with a reflux condenser, 27 g of diaminobenzoyl aniline, 20.2 g of triethylamine, and 800 mL of dichloromethane were added sequentially, and the mixture was stirred at room temperature for 30 min. Separately, 47.5 g of diphenylphosphine chloride (DPPC) was dissolved in 80 mL of dichloromethane, and the resulting solution was slowly added dropwise to the flask over 20 min using a constant-pressure dropping funnel, while maintaining stirring at room temperature during the addition. After the addition was complete, the reaction was continued at room temperature for 40 min; then, the temperature was raised to 45 °C in an oil bath for 4 h, and further raised to 65 °C for 5 h. After the reaction was completed, the system was cooled to room temperature, and the generated triethylamine hydrochloride precipitate was removed by vacuum filtration. The filtrate was then distilled under reduced pressure to recover dichloromethane, yielding a crude product. This crude product was dried in a vacuum drying oven at 80 °C for 22 h to obtain an environmentally friendly phosphorus-nitrogen-based phenylamide macromolecular flame retardant (denoted as PNAFR). PNAFR with the same structure can be prepared using the same raw material ratios within the scope of the instructions. The flame retardant is added to the polyolefin matrix at a mass ratio of 25%, and the mixture is melt-blended at 195 °C, extruded and granulated, and finally molded to obtain the polyolefin flame retardant cable sheath material.

Claims

1. A method for preparing an environmentally friendly, high-efficiency flame-retardant polyolefin cable sheath material, characterized in that, Includes the following steps: A phosphorus-nitrogen-based phenylamide macromolecular flame retardant is mixed with a polyolefin matrix at a mass ratio of (15~30):(70~85), and then melt-blended, extruded, granulated, and molded to obtain a polyolefin flame-retardant cable sheath material. The synthesis of the phosphorus-nitrogen phenylamide macromolecular flame retardant includes the following steps: mixing a compound containing primary amino and amide bonds, an organic amine, and a solvent; adding a compound containing phenyl and phosphoryl chloride groups dropwise under stirring at room temperature; reacting at room temperature for 30-60 min; then heating to 40-50 °C and reacting for 3-4 h; then heating to 60-70 °C and reacting for 5-6 h; after the reaction is completed, cooling, filtration, vacuum distillation, and drying are performed to obtain an environmentally friendly phosphorus-nitrogen phenylamide macromolecular flame retardant.

2. The method for preparing an environmentally friendly, high-efficiency flame-retardant polyolefin cable sheath material according to claim 1, characterized in that, The compound containing a primary amino group and an amide bond is preferably diaminobenzoyl aniline or M-BAP (CAS No.: 2185036-27-3).

3. The method for preparing an environmentally friendly, high-efficiency flame-retardant polyolefin cable sheath material according to claim 1, characterized in that, The organic base is preferably triethylamine, pyridine, or diisopropylethylamine.

4. The method for preparing an environmentally friendly, high-efficiency flame-retardant polyolefin cable sheath material according to claim 1, characterized in that, The solvent is preferably tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, acetone, dichloromethane, or chloroform.

5. The method for preparing an environmentally friendly, high-efficiency flame-retardant polyolefin cable sheath material according to claim 1, characterized in that, The compound containing phenyl and phosphoryl chloride groups is preferably diphenylphosphine chloride.

6. The method for preparing an environmentally friendly, high-efficiency flame-retardant polyolefin cable sheath material according to claim 1, characterized in that, The preferred mass ratio of the compound containing primary amino and amide bonds to the compound containing phenyl and phosphoryl chloride groups is 25-30:20-50.

7. The method for preparing an environmentally friendly, high-efficiency flame-retardant polyolefin cable sheath material according to claim 1, characterized in that, The preferred mass ratio of the organic base to the compound containing phenyl and phosphoryl chloride groups is 10-25:20-50.

8. The method for preparing an environmentally friendly, high-efficiency flame-retardant polyolefin cable sheath material according to claim 1, characterized in that, The matrix of the polyolefin cable sheath material is preferably polyethylene or polypropylene granules.

9. The method for preparing an environmentally friendly, high-efficiency flame-retardant polyolefin cable sheath material according to claim 1, characterized in that, The preferred melt blending temperature for the polyolefin flame-retardant cable sheath material is 170~195℃.

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