Flame-retardant heat-resistant PP material for halogen-free low-smoke cable protection tube and preparation method of flame-retardant heat-resistant PP material
By adding cyclic phosphonates, N-alkoxypiperidine derivatives, 2-(2H-benzotriazol-2-yl)-4-methylphenol and toughening agents to PP materials, the problems of flame retardancy, mechanical properties and stability of PP materials were solved, and the efficient preparation of halogen-free, low-smoke flame-retardant and heat-resistant PP materials for cable protection pipes was achieved.
Patent Information
- Application Number
- CN202510971789.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-15
- Publication Date
- 2025-11-11
AI Technical Summary
Existing PP materials have shortcomings in terms of flame retardancy, mechanical properties, halogen-free FR additives, and UV/thermal stability. In particular, high loading of flame retardants weakens mechanical properties, and traditional intumescent flame retardants affect long-term performance during weathering, increasing production costs.
PP materials are prepared by using cyclic phosphonates as halogen-free flame retardants, combined with N-alkoxypiperidine derivatives as flame retardant additives, and adding 2-(2H-benzotriazol-2-yl)-4-methylphenol and 2,6-di-tert-butylhydroquinone as stabilizers, and ultra-high molecular weight polyethylene or nano-silicon as toughening agents, through specific mixing and processing techniques.
It improves the flame retardant properties and UV/thermal stability of PP materials, reduces smoke production, maintains mechanical properties, extends service life, reduces the generation of toxic gases, and lowers production costs.
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Figure CN120923910A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of polymer materials technology, and in particular to a flame-retardant and heat-resistant PP material for halogen-free low-smoke cable protection pipes and its preparation method. Background Technology
[0002] Cable protection conduits are widely used in construction applications. They are used to enclose, wire, and protect electrical wires, cables, or other types of utility lines, and are supplied as rigid or flexible conduits. In today's advocacy for green environmental protection, various sectors have increasingly higher requirements for the quality and performance of electrical wires and cables. Furthermore, fires caused by cable aging are becoming more frequent, necessitating efforts to reduce fire rates. Achieving flame retardancy, minimum smoke density, and the lowest possible halogen content in cables has become a new development direction, thus increasing the demand for halogen-free low-smoke (HFLS) compounds. Currently, the main material used to manufacture conduits is PVC. Although it exhibits good flame retardant properties, its inherent chlorine content causes it to release dense smoke containing toxic and harmful gases when burning, posing a safety concern for public health.
[0003] Therefore, PP emerges as a viable alternative, but due to its highly flammable nature, halogen-free additives are required for flame retardancy to meet the aforementioned standards. Furthermore, when ground-mounted electrical installations are involved, additional UV and thermal stability are needed to enhance their life-cycle performance. Simultaneously, the conduit exhibits requirements in terms of mechanical properties, particularly impact and compression, to effectively promote the protection of the cables it houses. Therefore, it is foreseeable that four key challenges must be addressed to develop PP compounds for large-scale applications: flame retardancy, mechanical properties, halogen-free FR additives, and UV / thermal stability.
[0004] Existing halogen-free flame retardants for PP are typically metal hydroxides and intumescent flame retardants composed of ammonium polyphosphate (APP) and appropriate charring agents (such as pentaerythritol or triazine derivatives). However, when mixed with PP, the metal hydroxide requires a loading of nearly 50 wt%, and the intumescent system requires a loading of nearly 20-30 wt% to achieve V0 in the UL94 test. This high flame retardant content severely weakens the mechanical properties of PP materials. Furthermore, APP is prone to hydrolysis during weathering, thus affecting long-term flame retardancy. To suppress this phenomenon, APP is often specially protected through microencapsulation or coating; however, this significantly increases production costs. Summary of the Invention
[0005] The purpose of this invention is to provide a flame-retardant and heat-resistant PP material for halogen-free low-smoke cable protection pipes and its preparation method, which improves the flame-retardant properties and ultraviolet / thermal stability of PP while ensuring the mechanical properties of the PP matrix, so as to replace PVC in the manufacture of cable protection pipes.
[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A flame-retardant and heat-resistant PP material for halogen-free low-smoke cable protection pipes is composed of the following raw materials in parts by weight: 100-110 parts of polypropylene substrate, 10-15 parts of halogen-free flame retardant, 1-2 parts of flame retardant additive, 1.1-3 parts of stabilizer, 2.1-3 parts of stabilizer, and 3-6 parts of toughening agent.
[0007] Preferably, the halogen-free flame retardant is a cyclic phosphonate.
[0008] Preferably, the selected flame retardant is an N-alkoxypiperidine derivative.
[0009] Preferably, the stabilizer 1 is 2-(2H-benzotriazol-2-yl)-4-methylphenol.
[0010] Preferably, the stabilizer 2 is 2,6-di-tert-butylhydroquinone.
[0011] Preferably, the toughening agent is one or a combination of ultra-high molecular weight polyethylene or nano-silicon.
[0012] This invention also provides a method for preparing flame-retardant and heat-resistant PP material for halogen-free low-smoke cable protection pipes, characterized by comprising the following steps: S1. Accurately weigh the raw materials according to the formula ratio, and simultaneously dry the raw materials in a vacuum drying oven; S2. Pour all solid raw materials into a closed internal mixer in sequence, set the stirring speed to 60 rpm, the mixing time to 6-10 minutes, and the mixing temperature to 180℃. S3. The dry-mixed mixture is melt-extruded and granulated using a twin-screw extruder; S4. Cool the extruded PP composite material in a water bath, then granulate it, and then dry it in a vacuum oven at 80°C for 4 hours to remove any residual moisture.
[0013] Preferably, in S3, the temperature profile of the twin-screw extruder is set as follows: 190°C for the feeding section, 200°C for the conveying section, 205°C for the compression section and the homogenization section, 210°C for the transition section, and 205°C for the die head section, wherein the screw speed is set to 320 r / min.
[0014] Preferably, in step S4, the order of adding raw materials is: polypropylene, flame retardant, flame retardant additive, stabilizer, and toughening agent.
[0015] Preferably, the particle size of the PP material is controlled at 2-5 mm, and the sample is tested for flame retardancy, mechanical properties and UV / thermal stability after preparation to ensure that the design requirements are met.
[0016] In summary, the present invention has the following beneficial effects: Firstly, the halogen-free flame retardant selected in this invention is a cyclic phosphonate. During combustion, the cyclic phosphonate undergoes thermal decomposition, releasing phosphorus free radicals (PO·, HPO·). These free radicals can efficiently capture active free radicals in the flame (such as ·OH, ·H, ·O). At high temperatures, some cyclic phosphonates can promote char formation, effectively blocking heat conduction and oxygen diffusion. Compared with traditional flame retardants, cyclic phosphonates do not produce toxic gases during combustion, and the amount of smoke generated during combustion is significantly reduced. Cyclic phosphonates can be well dispersed into the PP matrix during processing, exhibiting good compatibility and being less prone to precipitation that affects mechanical properties. Furthermore, its cyclic structure gives it a high thermal decomposition temperature (>280℃) and good thermal stability.
[0017] Secondly, the flame retardant additive selected in this invention is an N-alkoxypiperidine derivative (NOR-HAS). When cyclic phosphonates are added alone, their flame retardant effect is limited and the amount added is relatively high (15wt% of the amount added results in a flame retardant rating of V0). However, after the addition of NOR-HAS, it forms a dual radical synergistic system with cyclic phosphonates. This is because NOR-HAS can generate nitrocellulose radicals (NO·) and other amino radicals (such as NH·) through thermal decomposition at high temperatures. At the same time, it can also play an auxiliary role in stabilizing the char layer. More importantly, the loading of NOR-HAS is extremely low. At the same time, because it can generate nitrocellulose radicals, it can endow the material with excellent UV / thermal stability, effectively extending the outdoor service life of the material.
[0018] Thirdly, the present invention, through the addition of stabilizers 2-(2H-benzotriazole-2-yl)-4-methylphenol and 2,6-di-tert-butylhydroquinone, exhibits good thermal stability and antioxidant capacity. They protect the material from oxidative degradation by partially absorbing ultraviolet light through benzotriazole and capturing and neutralizing free radicals through phenolic hydroxyl groups, respectively, thereby further improving the ultraviolet / thermal stability of the material.
[0019] Fourth, by adding toughening agents such as ultra-high molecular weight polyethylene or nano-silicon, this invention significantly improves the toughness, wear resistance, and impact resistance of the material, ensuring that it is not easily broken when subjected to external forces and guaranteeing product quality. Attached Figure Description
[0020] Figure 1 This is a flowchart of the PP material preparation process of the present invention. Detailed Implementation
[0021] The present invention will be further described in detail below with reference to the accompanying drawings.
[0022] Example 1: A flame-retardant and heat-resistant PP material for halogen-free low-smoke cable protection pipes, comprising the following parts by weight of raw materials: 100 parts of polypropylene substrate, 10 parts of halogen-free flame retardant, 1 part of flame retardant additive, 1.1 parts of stabilizer, 2.1 parts of stabilizer, and 3 parts of toughening agent.
[0023] Among them, the halogen-free flame retardant is a cyclic phosphonate (C7H) 14 O6P2); the flame retardant is an N-alkoxypiperidine derivative (NOR-HAS); stabilizer 1 is 2-(2H-benzotriazol-2-yl)-4-methylphenol (C 13 H 12 N2O); stabilizer 2 is 2,6-di-tert-butylhydroquinone (C 15 H 22 O2); the toughening agent is one or a combination of ultra-high molecular weight polyethylene or nano-silicon.
[0024] Preparation methods of flame-retardant and heat-resistant PP materials, such as Figure 1 As shown, it includes the following steps: S1. Weigh the raw materials accurately according to the formula ratio, and dry the raw materials in a vacuum drying oven.
[0025] S2. Pour all solid raw materials into a closed internal mixer in sequence, set the stirring speed to 60 rpm, the mixing time to 6-10 minutes, and the mixing temperature to 180℃.
[0026] S3. The dry-mixed mixture is melt-extruded and granulated using a twin-screw extruder. The temperature profile of the twin-screw extruder is set as follows: feeding section 190℃, conveying section 200℃, compression section 205℃, homogenization section 205℃, transition section 210℃, and die head section 205℃, with the screw speed set to 320 r / min. The low-temperature feeding section ensures that the polypropylene matrix remains solid, preventing premature melting and material blockage. The gradual temperature increase from the feeding section to the die head section promotes uniform melting of polypropylene and other components, ensuring the performance of the composite material. The final high-temperature die head section ensures complete melting of the material and sufficient fluidity.
[0027] S4. The extruded PP composite material is cooled in a water bath, then granulated, and subsequently dried in a vacuum oven at 80°C for 4 hours to remove any residual moisture. In S4, the raw materials are added in the following order: polypropylene, flame retardant, flame retardant additive, stabilizer, and toughening agent. This stepwise addition facilitates the distribution and dispersion of fillers in the PP, prevents agglomeration, and contributes to the stability of the PP's mechanical properties.
[0028] The particle size of the PP material is controlled at 2-5 mm, and after preparation, the sample is tested for flame retardancy, mechanical properties and ultraviolet / thermal stability to ensure that the design requirements are met.
[0029] Example 2 differs from Example 1 in that it is composed of the following raw materials in parts by weight: 100 parts of polypropylene substrate, 10 parts of halogen-free flame retardant, 1.1 parts of stabilizer, 2.1 parts of stabilizer, and 5 parts of toughening agent. This example does not contain flame retardant additives.
[0030] Example 3 differs from Example 1 in that it is composed of the following raw materials in parts by weight: 110 parts of polypropylene substrate, 5 parts of halogen-free flame retardant, 1.5 parts of flame retardant additive, 2 parts of stabilizer, 2.5 parts of stabilizer, and 5 parts of toughening agent.
[0031] Example 4 differs from Example 1 in that it is composed of the following raw materials in parts by weight: 110 parts of polypropylene substrate, 15 parts of halogen-free flame retardant, 2 parts of flame retardant additive, 3 parts of stabilizer, and 6 parts of toughening agent.
[0032] Table 1 shows a comparison of the flame retardant performance test results. Table 2 compares the results of mechanical performance testing and UV / thermal stability testing. This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.
Claims
1. A flame-retardant and heat-resistant PP material for halogen-free low-smoke cable protection pipes, characterized in that: It is composed of the following raw materials in parts by weight: 100-110 parts of polypropylene base material, 10-15 parts of halogen-free flame retardant, 1-2 parts of flame retardant additive, 1.1-3 parts of stabilizer, 2.1-3 parts of stabilizer and 3-6 parts of toughening agent.
2. The flame-retardant and heat-resistant PP material for halogen-free low-smoke cable protection pipes according to claim 1, characterized in that: The halogen-free flame retardant is a cyclic phosphonate.
3. The flame-retardant and heat-resistant PP material for halogen-free low-smoke cable protection pipes according to claim 2, characterized in that: The selected flame retardant additive is an N-alkoxypiperidine derivative.
4. The flame-retardant and heat-resistant PP material for halogen-free low-smoke cable protection pipes according to claim 3, characterized in that: The stabilizer 1 is 2-(2H-benzotriazol-2-yl)-4-methylphenol.
5. The flame-retardant and heat-resistant PP material for halogen-free low-smoke cable protection pipes according to claim 4, characterized in that: The stabilizer 2 is 2,6-di-tert-butylhydroquinone.
6. The flame-retardant and heat-resistant PP material for halogen-free low-smoke cable protection pipes according to claim 5, characterized in that: The toughening agent is one or a combination of ultra-high molecular weight polyethylene or nano-silicon.
7. A method for preparing a flame-retardant and heat-resistant PP material for halogen-free low-smoke cable protection pipe according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Accurately weigh the raw materials according to the formula ratio, and simultaneously dry the raw materials in a vacuum drying oven; S2. Pour all solid raw materials into a closed internal mixer in sequence, set the stirring speed to 60 rpm, the mixing time to 6-10 minutes, and the mixing temperature to 180℃. S3. The dry-mixed mixture is melt-extruded and granulated using a twin-screw extruder; S4. Cool the extruded PP composite material in a water bath, then granulate it, and then dry it in a vacuum oven at 80°C for 4 hours to remove any residual moisture.
8. The method for preparing a flame-retardant and heat-resistant PP material for halogen-free low-smoke cable protection pipe according to claim 7, characterized in that: In S3, the temperature profile of the twin-screw extruder is set as follows: feeding section 190℃, conveying section 200℃, compression section 205℃, homogenization section 205℃, transition section 210℃, and die head section 205℃, wherein the screw speed is set to 320 r / min.
9. The preparation method of a flame-retardant and heat-resistant PP material for halogen-free low-smoke cable protection pipe according to claim 8, characterized in that: In step S4, the order of adding raw materials is: polypropylene, flame retardant, flame retardant additive, stabilizer, and toughening agent.
10. The method for preparing a flame-retardant and heat-resistant PP material for halogen-free low-smoke cable protection pipe according to claim 9, characterized in that: The particle size of the PP material is controlled between 2-5 mm, and after preparation, the sample is tested for flame retardancy, mechanical properties and UV / thermal stability to ensure that the design requirements are met.