Low-smoke low-halogen flame-retardant medium-low-temperature fire-resistant PVC (polyvinyl chloride) cable sheath material and preparation method thereof

Abstract

The invention discloses a low-smoke low-halogen flame-retardant medium and low temperature fire-resistant PVC cable sheath material and a preparation method thereof, and belongs to the technical field of wire and cable materials. The sheath material is prepared by taking PVC resin as a matrix, matching with a compound stabilizer, an environment-friendly plasticizing system, a flame-retardant synergistic system, a fire-resistant additive and a functional filler, and performing premixing, melt extrusion, cooling and granulation. According to the invention, food contact grade acetyl tributyl citrate (ATBC), epoxy fatty acid methyl ester and other environment-friendly plasticizers are adopted to replace traditional plasticizers, and a magnesium hydroxide-cerium oxide flame-retardant synergistic system is innovatively compounded, so that the product has the advantages of low smoke, low halogen, high flame retardance, fire resistance, wide temperature range, stability and the like, and can be stably used for a long time at the temperature of-20 DEG C to 105 DEG C. The preparation process is simple, easy to industrialize and suitable for the field of high-safety-level wire and cable sheaths.

Description

Technical Field

[0001] This invention relates to the field of wire and cable materials technology, specifically to a low-smoke, low-halogen, environmentally friendly, non-toxic, and highly flame-retardant fire-resistant PVC cable sheath material suitable for medium and low temperature environments and high safety requirements, as well as its preparation process. Background Technology

[0002] Polyvinyl chloride (PVC) cable materials are widely used in the wire and cable industry due to their low cost, readily available raw materials, corrosion resistance, and good insulation properties. However, traditional PVC sheathing materials generally suffer from the following technical challenges: 1. Poor environmental performance: When burned, it releases a large amount of hydrogen halide gas and dense smoke, which not only corrodes precision equipment, but also causes "secondary disasters" and seriously endangers the safety of personnel evacuation. It does not meet the safety standards of modern green building materials. 2. Insufficient flame retardancy and fire resistance: It is prone to rapid combustion and dripping under high temperature flame attack, and has a short fire resistance time, which cannot effectively block the spread of fire and protect the cable core when a fire occurs; 3. Limited temperature range adaptability: It is prone to hardening and cracking in low temperature environments (such as below -20℃), losing its mechanical protective performance; while in high temperature environments (such as above 105℃), it is prone to softening and deformation, making it difficult to meet the requirements for long-term stable use under harsh working conditions.

[0003] Although some halogen-free flame-retardant materials have emerged in the market, it is often difficult to achieve a balance between compatibility with the PVC matrix, mechanical properties, and cost. Therefore, based on the excellent mechanical and electrical properties of PVC itself, developing an environmentally friendly PVC cable sheath material that combines high flame retardancy and fire resistance with adaptability to a wide temperature range has become an urgent need for industry upgrading. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned defects of the prior art and provide a PVC cable sheath material with low smoke and low halogen content, excellent flame retardant and fire resistant properties, and stable performance in the medium and low temperature range, as well as its preparation method. Technical solution

[0005] To achieve the above objectives, the present invention provides the following technical solution: A low-smoke, low-halogen, flame-retardant, medium- and low-temperature fire-resistant PVC cable sheath material is prepared from the following raw material components in parts by weight: • PVC resin: 100 parts; • Composite stabilizer: 2.5-4.5 parts; • Low-smoke plasticizer: 8-15 parts; • Flame retardant synergistic system: 15-25 parts; • Refractory additives: 5-10 parts; • Functional filler: 10-20 parts; Other adjuvants: 0.5-2 parts; The flame retardant synergistic system is composed of magnesium hydroxide flame retardant and cerium oxide synergist in a mass ratio of 4:1; the fire refractory additive is at least one of ammonium polyphosphate or red phosphorus; and the low-smoke plasticizer is at least one of epoxy fatty acid methyl ester, acetylsic acid tributyl ester, and epoxy linseed oil.

[0006] Preferably, the PVC resin is a polyvinyl chloride homopolymer or copolymer resin with an average degree of polymerization of 800-1300.

[0007] Preferably, the composite stabilizer is a mixture of a calcium-zinc composite stabilizer and an organotin stabilizer. More preferably, the mass ratio of the calcium-zinc composite stabilizer to the organotin stabilizer is 1:1.

[0008] Preferably, the functional filler is ultrafine calcium carbonate or silica with a surface treated with a coupling agent. The coupling agent can be a silane coupling agent or a titanate coupling agent.

[0009] Preferably, the limiting oxygen index of the sheath material is ≥32%, the vertical flammability rating reaches VW-1 standard, and the operating temperature range is -20℃ to 105℃.

[0010] The present invention also provides a method for preparing the above-mentioned low-smoke, low-halogen, flame-retardant, medium- and low-temperature fire-resistant PVC cable sheath material, comprising the following steps: (1) Premixing: Weigh out the PVC resin, composite stabilizer and low smoke plasticizer by weight, put them into a high-speed mixer, and mix at 80℃-100℃ for 5-10 minutes until uniform; (2) Adding fillers and flame retardant system: Add flame retardant synergistic system, refractory additives and functional fillers to the mixture, and continue mixing for 3-5 minutes; (3) Melt extrusion: The mixture is fed into a twin-screw extruder, and the temperature is controlled at 160℃-180℃ for melt plasticization, compounding and extrusion; (4) Cooling and granulation: The extruded melt is cooled, dried and granulated to obtain the finished product.

[0011] Preferably, in step (3), the length-to-diameter ratio of the twin-screw extruder is 30-40:1, and the screw speed is 300-500 r / min. Beneficial effects

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. High Flame Retardancy and Fire Resistance: This invention employs a flame-retardant synergistic system composed of magnesium hydroxide and cerium oxide in a specific ratio. Its mechanism of action lies in the fact that magnesium hydroxide decomposes and absorbs heat during combustion, generating water vapor to dilute oxygen, while cerium oxide, as a synergist, catalyzes and promotes the formation of a denser and more stable char layer, effectively isolating heat and oxygen, thereby achieving highly efficient flame retardancy and anti-dripping properties. The resulting material has a limiting oxygen index ≥32%, and through the VW-1 vertical burning test, it rapidly self-extinguishes in a flame without dripping, effectively blocking the spread of combustion.

[0013] 2. Wide Temperature Range Applicability: Through scientific selection of environmentally friendly plasticizers and functional fillers, the formula solves the traditional temperature sensitivity problem of PVC, allowing for long-term stable use in harsh environments ranging from -20℃ to 105℃, maintaining excellent mechanical protection properties. Its tensile strength is ≥15MPa, and its elongation at break is ≥200%.

[0014] 3. Green and environmentally friendly: The formula completely eliminates traditional phthalate plasticizers and adopts non-toxic and environmentally friendly plasticizing systems such as ATBC and epoxy fatty acid methyl esters. It is phthalate-free, has low migration, low smoke and low halogen content, and complies with EU REACH and domestic food contact safety standards.

[0015] 4. Stable process: The preparation process is simple and controllable, the batch stability of the product is high, it is easy to carry out large-scale industrial production, and it has significant economic and social benefits. Preparation process flow description

[0016] The preparation process of the low-smoke, low-halogen flame-retardant PVC cable sheath material described in this invention.

[0017] Process: 1—Weighing and batching raw materials; 2—High-speed premixing; 3—Mixing of flame retardant and filler system; 4—Twin-screw melt extrusion; 5—Water cooling; 6—Air drying; 7—Pelletizing; 8—Finished product packaging. Detailed Implementation

[0018] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention in any way. Example

[0019] A low-smoke, low-halogen, flame-retardant, medium- and low-temperature fire-resistant PVC cable sheath material, with the following raw material formula (parts by weight): • PVC resin (degree of polymerization 1000): 100 parts • Composite stabilizer (calcium zinc: organotin = 1:1): 3.5 parts • Low-smoke plasticizer (epoxy fatty acid methyl ester): 12 parts • Flame retardant synergistic system (magnesium hydroxide:cerium oxide = 4:1): 20 parts • Refractory additive (ammonium polyphosphate): 8 parts • Functional filler (coupling-treated calcium carbonate): 15 parts • Antioxidant: 1 part Preparation method: 1. Add the above-mentioned PVC resin, composite stabilizer, and low-smoke plasticizer to a high-speed mixer and mix at 85°C for 8 minutes; 2. Add the flame retardant synergist system, refractory additives, fillers, and antioxidants, and mix for 4 minutes; 3. Feed the extruder into a twin-screw extruder with a length-to-diameter ratio of 35:1, screw speed of 400 r / min, and temperature settings for each zone of 160 / 170 / 180 / 175 / 170℃; 4. Cool, air-cool, and granulate to obtain the finished product. Example

[0020] It is basically the same as Example 1, except that the flame retardant synergistic system is adjusted to 25 parts and the fire refractory additive is adjusted to 5 parts.

[0021] Test results show that the flame retardant performance has been slightly improved, with an LOI of 33.5%, but the cost has increased slightly. Example

[0022] It is basically the same as Example 1, except that the low-smoke plasticizer is changed to acetylsicottide tributyl ester (ATBC), and the dosage is 10 parts.

[0023] The product exhibits superior resistance to temperature aging, non-toxic and environmentally friendly properties, meets food contact safety standards, and has optimal thermal stability.

[0024] Comparative Example 1 It uses conventional PVC resin, combined with lead salt stabilizer, DOP plasticizer and common flame retardant system.

[0025] Test results showed that it had high smoke density and hydrogen halide release, with an LOI of only 22%, failing to meet the VW-1 standard, and was prone to brittleness upon low-temperature impact.

[0026] Performance test comparison Test Item Example 1 Example 3 Comparative Example 1 Limiting Oxygen Index (LOI): ≥32.5% ≥33% <22% Vertical Combustion Rating VW-1 Pass VW-1 Pass Fail Low-temperature embrittlement temperature ≤-20℃ ≤-22℃ -5℃ Tensile strength (MPa) ≥16 ≥16.5 ≥14 Elongation at break (%) ≥220 ≥230 ≥180 Environmentally friendly, non-toxic, low-smoke, food-grade, non-toxic, highly toxic, high-smoke As shown in the table above, compared with Comparative Example 1, the sheath materials of Examples 1 and 3 of the present invention have improved the limiting oxygen index by more than 10 percentage points, achieved the highest VW-1 rating in vertical combustion, and significantly improved low-temperature toughness, while also achieving low toxicity and environmental friendliness. This demonstrates that the present invention, through the synergistic effect of a specific formulation, successfully resolves the contradiction between the high smoke and high toxicity of traditional PVC cable materials and their poor flame retardancy and weather resistance.

[0027] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A low-smoke, low-halogen, flame-retardant, medium- and low-temperature fire-resistant PVC cable sheath material, characterized in that, It is prepared from the following raw material components in parts by weight: 100 parts of PVC resin; 2.5-4.5 parts of composite stabilizer; 8-15 parts of low-smoke plasticizer; 15-25 parts of flame retardant synergistic system; 5-10 parts of refractory additives; 10-20 parts of functional filler; The flame retardant synergistic system is composed of magnesium hydroxide flame retardant and cerium oxide synergist in a mass ratio of 4:1; the fire refractory additive is at least one of ammonium polyphosphate or red phosphorus; and the low-smoke plasticizer is at least one of epoxy fatty acid methyl ester, acetylsic acid tributyl ester, and epoxy linseed oil.

2. The low-smoke, low-halogen, flame-retardant, medium- and low-temperature fire-resistant PVC cable sheath material according to claim 1, characterized in that, The PVC resin is a polyvinyl chloride homopolymer or copolymer resin with an average degree of polymerization of 800-1300.

3. The low-smoke, low-halogen, flame-retardant, medium- and low-temperature fire-resistant PVC cable sheath material according to claim 1, characterized in that, The composite stabilizer is a combination of calcium-zinc composite stabilizer and organotin stabilizer.

4. The low-smoke, low-halogen, flame-retardant, medium- and low-temperature fire-resistant PVC cable sheath material according to claim 3, characterized in that, The mass ratio of the calcium-zinc composite stabilizer to the organotin stabilizer is 1:

1.

5. The low-smoke, low-halogen, flame-retardant, medium- and low-temperature fire-resistant PVC cable sheath material according to claim 1, characterized in that, The functional filler is ultrafine calcium carbonate or silica with a surface treated with a coupling agent.

6. The low-smoke, low-halogen, flame-retardant, medium- and low-temperature fire-resistant PVC cable sheath material according to claim 5, characterized in that, The coupling agent is a silane coupling agent or a titanate coupling agent.

7. A method for preparing the low-smoke, low-halogen, flame-retardant, medium- and low-temperature fire-resistant PVC cable sheath material as described in any one of claims 1-6, characterized in that, Includes the following steps: (1) Premixing: Weigh out the PVC resin, composite stabilizer and low smoke plasticizer by weight, put them into a high-speed mixer, and mix them at 80℃-100℃ for 5-10 minutes until uniform; (2) Adding fillers and flame retardant system: Add flame retardant synergistic system, refractory additives and functional fillers to the mixture and continue mixing for 3-5 minutes; (3) Melt extrusion: The mixture is fed into a twin-screw extruder, and the temperature is controlled at 160℃-180℃ for melt plasticization, compounding and extrusion; (4) Cooling and granulation: The extruded melt is cooled, dried and granulated to obtain the finished product.

8. The preparation method according to claim 7, characterized in that, In step (3), the length-to-diameter ratio of the twin-screw extruder is 30-40:1, and the screw speed is 300-500 r / min.