Flame-retardant master batch for PVC cable material with low dust dissipation and high flame retardance and preparation method of flame-retardant master batch

Abstract

The invention discloses a flame-retardant master batch for a PVC cable material with low dust dissipation and high flame retardance and a preparation method of the flame-retardant master batch. The flame-retardant master batch is prepared from the following raw materials in parts by weight: 10-15 parts of polyvinyl chloride resin, 5-10 parts of a plasticizer, 1-3 parts of a filler, 1-2 parts of a stabilizer, 0.5-1.5 parts of a compatilizer, 0.2-0.5 part of a lubricant, 0.1-0.3 part of an antioxidant and 60-90 parts of a flame retardant. According to the invention, the powdery arsenic-containing flame retardant is prepared into PVC base material master batch particles, and a special compatilizer and a standardized production protection system are matched, so that the problem of dissipation of arsenic oxide dust is solved from the source; meanwhile, a low-temperature soft mixing process of an internal mixer is adopted, so that the high-content flame retardant is uniformly dispersed in the PVC base material; the prepared master batch is good in compatibility with the PVC cable material, the oxygen index can be remarkably increased by adding 3% by mass of the master batch, the flame-retardant efficiency and the production cost are both considered, the preparation process is stable, the problems of overmolding and scorching are avoided, and the industrial large-scale production requirement is met.

Description

Technical Field

[0001] This invention relates to the field of wire and cable materials technology, specifically to a flame-retardant masterbatch for PVC cable materials with low dust emission and high flame retardancy, and its preparation method. Background Technology

[0002] Polyvinyl chloride (PVC) has become a core and commonly used material for the insulation sheathing of wires and cables due to its superior mechanical properties, resistance to chemical corrosion, ease of processing, and low cost. It is widely used in the power, rail transportation, and construction industries. With the continuous advancement of global power grid upgrades and urban rail transit infrastructure construction, the PVC cable material market is showing steady growth. According to publicly available market data, the Chinese PVC cable material market reached 140 billion yuan in 2024, accounting for 56% of the global market share. It is projected that the global PVC cable material market will exceed 250 billion yuan by 2030.

[0003] Pure PVC resin has a chlorine content as high as 56.48% and an oxygen index above 45, making it a naturally highly flame-retardant material. However, in the preparation of flexible PVC cable materials, a large amount of flammable plasticizers and other additives must be added to the resin to meet the flexibility requirements for processing and use. This results in a relative decrease in the chlorine content of the PVC cable material and a sharp decline in its flame-retardant performance. The existing national standard HI-90 PVC sheath material is a commonly used flexible PVC cable material in the industry, but its oxygen index is only 24, which is far from meeting the flame-retardant requirements for bundled combustion. Therefore, it is necessary to modify it for flame retardancy by adding flame retardants, which has become a core direction for technological research and development in the industry.

[0004] In existing technologies, antimony trioxide (antimony trioxide) is the most effective flame retardant for PVC cable materials, increasing the oxygen index by 5-7 with just 3-7 parts. However, the market price of pure antimony trioxide (99.8% purity) is as high as 240,000 yuan / ton, significantly increasing the formulation cost of PVC cable materials and hindering large-scale industrial application. To reduce costs, the industry has tried using halogen-free flame retardants such as magnesium hydroxide and aluminum hydroxide, but their flame retardant efficiency is extremely low. An addition of more than 20% is required to slightly improve the oxygen index of PVC cable materials, and excessive addition severely reduces the mechanical properties of PVC cable materials, rendering them unusable. The industry has yet to find a dedicated flame retardant for PVC cable materials that balances flame retardant efficiency and raw material costs.

[0005] Meanwhile, existing flame retardants are all added directly to PVC cable materials in powder form, which has several significant and difficult-to-solve common technical defects: First, most high-efficiency flame retardant powders are toxic or irritating, and their powder form is extremely easy to float in the air, far exceeding the occupational exposure limits specified in "Occupational Exposure Limits for Hazardous Factors in the Workplace Part 1: Chemical Hazardous Factors" (GBZ 2.1-2019). This not only causes health hazards such as respiratory damage to workers, but also seriously pollutes the production environment. Second, the interfacial compatibility between powder flame retardants and PVC resin is generally poor, and problems such as agglomeration and uneven dispersion are prone to occur, resulting in large fluctuations in the flame retardant performance of PVC cable materials, poor product quality stability, and inability to meet the quality requirements of industrial production. Third, the metering and feeding process of powder flame retardants is prone to generating dust, resulting in a large amount of raw material waste. At the same time, the powder is prone to moisture absorption and agglomeration, which brings many inconveniences to transportation, storage, and subsequent feeding. Fourth, the feeding operation of powder flame retardants mostly relies on manual labor, which cannot achieve automated and standardized production, resulting in low production efficiency.

[0006] To address the dust emission problem of powdered flame retardants, existing technologies attempt to formulate flame retardants into masterbatch form. However, these solutions still face significant technical bottlenecks: In existing PVC flame retardant masterbatch formulations, the flame retardant content generally does not exceed 50%, and compatibility issues prevent the uniform dispersion of high-content flame retardants. Furthermore, existing masterbatch granulation processes often employ twin-screw extruders, resulting in significant shear heat effects that can lead to over-plasticization and scorching of the PVC resin, severely impacting the physical and mechanical properties and performance of the masterbatch. Moreover, existing masterbatches often incorporate halogen-free flame retardants, failing to resolve the core issue of low flame retardant efficiency and thus failing to meet the industry's demand for high-efficiency flame-retardant PVC cable materials.

[0007] In addition, existing flame retardant additives for PVC cable materials also have insufficient environmental protection. For example, traditional lead salt stabilizers contain heavy metals, which can easily cause environmental pollution and do not conform to the industry development trend of green chemistry. Furthermore, existing antioxidant systems are mostly single-component, with limited antioxidant effects, resulting in poor storage stability of flame retardant masterbatches and a tendency for the oxygen index to decrease over time, further limiting the industrial application of related products.

[0008] In summary, no existing technology can simultaneously solve multiple core industry challenges, including the difficulty in balancing flame retardant efficiency and cost in PVC cable material flame retardants, the problems of dust dispersion, uneven dispersion, and raw material waste in powder flame retardants, the difficulty in dispersing high-content flame retardants in masterbatches, and the tendency for over-plasticizing and scorching during processing, as well as the poor environmental performance and storage stability of the products. Existing solutions can only address a single pain point and cannot achieve synergistic optimization of multiple performance characteristics. Developing a flame-retardant masterbatch for PVC cable materials and its preparation method that simultaneously possesses low dust dispersion, high flame retardancy, good compatibility, low cost, stable processing, environmental compliance, and convenient storage and transportation has become a pressing technical challenge in this field and an inevitable requirement for industry development. Summary of the Invention

[0009] This invention addresses the aforementioned deficiencies in existing technologies by providing a low-dust-emission, high-flame-retardant masterbatch for PVC cable materials and its preparation method. This invention solves the problem of arsenic oxide dust emission at its source by preparing PVC substrate masterbatch granules from powdered arsenic-containing flame retardant and combining them with a specialized compatibilizer and a standardized production protection system. Simultaneously, a low-temperature, gentle mixing process using a Banbury mixer ensures uniform dispersion of high-content flame retardant in the PVC substrate. The prepared masterbatch exhibits good compatibility with PVC cable materials; an addition of only 3% by weight significantly improves the oxygen index, balancing flame retardant efficiency with production costs. The preparation process is stable, without over-plasticization or scorching issues, meeting the requirements of large-scale industrial production.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a flame-retardant masterbatch for PVC cable materials with low dust emission and high flame retardancy, which is prepared from the following raw materials in parts by weight: 10-15 parts of polyvinyl chloride resin; Plasticizer 5-10 parts; 1-3 parts filler; Stabilizer 1-2 parts; 0.5–1.5 parts of compatibilizer; Lubricant 0.2-0.5 parts; Antioxidant 0.1–0.3 parts; 60-90 parts flame retardant.

[0011] Preferably, the flame retardant is a mixture of antimony trioxide and arsenic trioxide powder, with a mass ratio of antimony trioxide to arsenic trioxide of 1:9. The flame retardant has an average particle size D50 ≤ 2.5 μm and a moisture content ≤ 0.5%, which facilitates uniform dispersion in the resin system.

[0012] Preferably, the polyvinyl chloride resin is S-60 type resin with an average degree of polymerization of 750-850 and a fisheye count of <10 per 400cm. 2The residual polyvinyl chloride monomer content is ≤5μg / g, which has good compatibility with PVC cable material substrate and ensures masterbatch compatibility.

[0013] Preferably, the plasticizer is dioctyl terephthalate with a density of 0.980–0.986 g / cm³. 3 Flash point > 210℃, volume resistivity ≥ 2.0 × 10⁻⁶ 12 Ω • cm, moisture content < 0.15%, excellent electrical properties and good flame retardancy, suitable for the use requirements of cable materials.

[0014] Preferably, the filler is lightweight activated calcium carbonate with a Hunter whiteness ≥96%, an average particle size D50 ≤1.8μm, and a moisture content ≤0.6%, which can improve the mechanical properties of the masterbatch without affecting its flame retardancy.

[0015] Preferably, the stabilizer is a calcium-zinc composite stabilizer with a density of 1.109–1.128 g / cm³. 3 It has a heating loss of less than 1.5%, no heavy metal pollution, and can effectively inhibit the thermal degradation of PVC resin during processing.

[0016] Preferably, the compatibilizer is an ethylene-vinyl acetate copolymer grafted with maleic anhydride (EVA-g-MAH), preferably Formosa Plastics EVA-g-MAH, with a VA content of 18-28% and a grafting rate of 0.8-1.2%, which can significantly improve the interfacial compatibility between the flame retardant and PVC resin and solve the technical problem of uneven dispersion of high-content flame retardants.

[0017] Preferably, the lubricant is a compound system of low-density polyethylene wax, stearic acid, and barium stearate, with a compounding mass ratio of 1:1:1.5; wherein the low-density polyethylene wax has a density of 0.92 g / cm³. 3 It has a melting point of 120–140℃, a number-average molecular weight of 2000–5000, and a viscosity of 1.1 mPa·s at 120℃; stearic acid has a density of 0.84–0.88 g / cm³. 3 Melting point 54–60℃; density of barium stearate 1.14–1.18 g / cm³ 3 It has a melting point of 210–220℃ and a barium content of 19.5–21.5%. This compound system can improve processability, prevent sticking to the machine, and ensure the smooth progress of the granulation process.

[0018] Preferably, the antioxidant is a compound system of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant 1010) and dilauryl thiodipropionate (DLTP) in a mass ratio of 1:1; wherein antioxidant 1010 has a density of 1.15–1.20 g / cm³. 3 Melting point 120℃, loss on heating <1.0%; DLTP density 0.91~0.94g / cm³ 3It has a melting point of 40℃ and a loss on heating of <1.0%. This compound system has a synergistic effect, which can improve the antioxidant properties of the masterbatch and extend its storage and service life.

[0019] This invention also provides a method for preparing the above-mentioned low-dust-emission, high-flame-retardant PVC cable material flame-retardant masterbatch, comprising the following steps: S1. Add polyvinyl chloride resin, plasticizer, filler, stabilizer, compatibilizer, lubricant and antioxidant to a high-speed kneader in the above weight ratio, heat to 90-110℃, and stir and knead at 800r / min for 7-9min to fully soften and mix the resin and each additive. S2. Add the kneaded material from step S1 and the flame retardant to a mixer according to the above weight ratio. Mix at 135-145℃ for 6-8 minutes. After 3-4 minutes of mixing, lift the pressure bar to clean the raw powder in the corner of the mixing chamber for 10-15 seconds to ensure that the flame retardant and the kneaded material are fully mixed. Feed the mixed material into a single-screw granulator for granulation. The screw speed of the single-screw granulator is 50 r / min. It is divided into five heating zones with the following temperatures: Zone 1 55-60℃, Zone 2 65-75℃, Zone 3 80-90℃, Zone 4 90-100℃, and Zone 5 110-120℃. After granulation, air-cooled pellets are cut into pellets with a particle size of 2-3 mm. After drying in a hot air circulating oven, the flame retardant masterbatch for low dust emission and high flame retardancy PVC cable material is obtained.

[0020] Preferably, in step S2, the internal mixer is a tilting internal mixer with a prismatic rotor and a rotor speed of 40-50 r / min; the single screw granulator has a screw diameter of 65 mm and a length-to-diameter ratio of 20:1.

[0021] Preferably, in step S2, the drying process parameters are: hot air circulating oven temperature 60-70℃, wind speed 1.0-1.5m / s, drying time 2-3h, and the moisture content of the masterbatch after drying is ≤0.3%.

[0022] This invention employs a standardized production protection system to control dust emission during the production of flame-retardant masterbatch. Specifically: 1) A fully automated metering and batching system with an accuracy of ±0.1% replaces manual operation, eliminating the need for on-site operation during metering, feeding, and mixing stages; 2) A fully enclosed pipeline batching system is used, maintaining a negative pressure of -0.02 to -0.05 MPa during material transport to reduce the emission of arsenic trioxide dust; 3) H13-grade high-efficiency air filters are installed in the ventilation system of the production workshop, with a filtration efficiency ≥99.95%, ensuring that the dust content in the exhaust air meets the requirements of "Occupational Exposure Limits for Hazardous Factors in the Workplace Part 1: Chemical Hazardous Factors" (GBZ 2.1-2019), with arsenic trioxide dust emission ≤0.01 mg / m³.3 .

[0023] This invention provides a full life-cycle safety protection plan for antimony trioxide-arsenic trioxide mixed powder in flame retardants, as detailed below: 1) Raw material storage and transportation: Antimony trioxide-arsenic trioxide mixed powder is packaged in sealed moisture-proof iron drums and stored in a cool, dry, and ventilated special warehouse, separated from acid and food raw materials. Transportation must comply with the requirements of the "Administrative Measures for the Purchase and Road Transportation Permit of Highly Toxic Chemicals". 2) Production process protection: In addition to the standardized production protection system, production personnel must wear protective equipment such as gas masks, acid and alkali resistant gloves, and protective clothing. Emergency eyewash stations and showers are set up in the production workshop, and arsenic is tested in the workshop air regularly. 3) Product storage and use: The flame retardant masterbatch of this invention is a solid granule, which can be stored at room temperature after being sealed in packaging. No arsenic is released during the storage period. When using it, the material is fed directly by mechanization without the need for manual contact. No arsenic-containing waste gas or waste residue is generated during the cable material processing. 4) Waste and recycling: The masterbatch scraps and defective products generated during the production process must be sealed and collected, and disposed of as hazardous waste after solidification treatment; when the PVC cable material using the masterbatch of this invention is scrapped, the arsenic compounds are solidified and disposed of with the residue during the sorting and recycling of PVC resin, and there is no environmental leakage.

[0024] Compared with the prior art, the technical solution of the present invention has the following advantages: A. This invention uses arsenic-containing flame retardant powder to form PVC substrate masterbatch granules, combined with a standardized production and protection system featuring fully automated metering, closed-pipe batching, and H13-grade high-efficiency air filtration. During production, the amount of arsenic trioxide dust emitted is ≤0.01 mg / m³. 3 It fully complies with the 0.01 mg / m³ limit in the "Occupational Exposure Limits for Hazardous Factors in the Workplace Part 1: Chemical Hazardous Factors" (GBZ2.1-2019). 3 The PC-TWA limit addresses the root cause of the health hazards posed by arsenic trioxide dust emissions, and the masterbatch particles are dust-free, preventing raw material waste. Furthermore, a full life-cycle safety protection plan has been developed to ensure the safe management of raw materials, products, and waste.

[0025] B. The flame retardant of this invention uses a 1:9 mixture of antimony trioxide and arsenic trioxide powder, which has excellent flame retardant efficiency. By adding only 3% by weight of the flame retardant masterbatch of this invention to the national standard HI-90 PVC sheath material formula, its oxygen index can be increased from 24 to over 29.8, meeting the bundled combustion flame retardant requirements in the "Test Method for Burning of Wires and Cables". The amount added is much lower than that of existing halogen-free flame retardant masterbatches (the amount of existing halogen-free flame retardant masterbatches needs to reach more than 20%).

[0026] C. This invention uses PVC as the base material and is combined with a special EVA-g-MAH compatibilizer, which effectively improves the interfacial compatibility between the flame retardant and PVC resin, and ensures good compatibility between the masterbatch and PVC cable material. The process of low-temperature kneading and gentle mixing in an internal mixer greatly reduces the shear heat effect, which not only solves the problem of uneven dispersion of 60-90% high-content flame retardant in the resin system, but also avoids the problems of PVC resin over-plasticization and scorching. The prepared masterbatch does not have stratification or agglomeration after being mixed with PVC cable material.

[0027] D. This invention replaces 90% of pure antimony trioxide with arsenic trioxide, reducing the cost of flame retardant raw materials from 240,000 yuan / ton to 12,000 yuan / ton. Moreover, the amount of masterbatch added is only 3%, which greatly reduces the overall formulation cost of PVC cable material without sacrificing flame retardant efficiency, and has industrial promotion value.

[0028] E. The preparation process of this invention adopts a gradient heating single-screw granulation, standardized air-cooled pelletizing, and hot air circulating oven drying process, resulting in uniform plasticization, good granulation effect, and no over-plasticization or scorching issues during the preparation process, making it suitable for large-scale industrial production. The resulting flame-retardant masterbatch has a tensile strength ≥7.0MPa and an elongation at break ≥100%, exhibiting excellent physical and mechanical properties that meet the processing and usage requirements of PVC cable materials. The masterbatch is in 2-3mm granular form with good flowability. After 72 hours of storage at room temperature (25℃) and 60% humidity, the moisture absorption rate is ≤0.2%, with no clumping, facilitating transportation, storage, and subsequent metering and feeding, thus solving the problem of easy moisture absorption and clumping of powder flame retardants. After 6 months of storage at room temperature, the oxygen index retention rate of the masterbatch is ≥98%, demonstrating excellent storage stability.

[0029] F. This invention uses a calcium-zinc composite stabilizer to replace the traditional lead salt stabilizer, which eliminates heavy metal pollution and meets environmental protection requirements; the production protection system is free of secondary pollution and is in line with the industry development trend of green chemistry. Detailed Implementation

[0030] This invention can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the inventive concept to those skilled in the art. All other embodiments derived by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0031] Basic experimental conditions: Raw material source: In the embodiments and comparative examples of this invention, all raw materials used are commercially available conventional raw materials, and those without specific specifications meet the aforementioned raw material specification requirements of this invention; Equipment parameters: high-speed kneader (speed 0~1000r / min), tilting internal mixer (prismatic rotor, speed 40~50r / min), single screw granulator (screw diameter 65mm, length-to-diameter ratio 20:1), hot air circulating oven; Performance testing methods: (1) Tensile strength and elongation at break: tested according to GB / T 1040.3-2006; (2) Density: Tested according to GB / T 1033.1-2008; (3) Flame retardant content: tested by gravimetric method; (4) Oxygen index: The flame retardant masterbatch was added to the national standard HI-90 PVC sheath material formula at a mass percentage of 3%, and tested according to GB / T 2406.2-2009; (5) Dust emission: The concentration of arsenic trioxide dust in the workplace air during the production process shall be tested in accordance with GB / T 16913-2008; (6) Dispersibility: Add 3% of the masterbatch to HI-90PVC sheath material. After two-roll milling, observe the dispersion state of the flame retardant under a microscope. No agglomeration is qualified, and agglomeration is unqualified.

[0032] (7) Key indicators of raw materials: the number of fish eyes in PVC resin is tested according to GB / T 2914-2008, the residual monomer is tested according to GB / T4615-2013; the volume resistivity of plasticizer is tested according to GB / T 1410-2006; the VA content of compatibilizer is tested according to GB / T12009.2-2009, and the grafting rate is tested by titration.

[0033] Table 1. Test results of key indicators of raw materials in Examples 1-4 Example 1

[0034] This embodiment provides a flame-retardant masterbatch for PVC cable materials with low dust emission and high flame retardancy, which is prepared from the following raw materials in parts by weight: 13.5 parts of S-60 type polyvinyl chloride resin, 7 parts of dioctyl terephthalate, 1.5 parts of light activated calcium carbonate, 1.5 parts of calcium-zinc composite stabilizer, 1 part of EVA-g-MAH (VA content 23%, grafting rate 1.0%), 0.3 parts of compound lubricant (low density polyethylene wax: stearic acid: barium stearate = 1:1:1.5), 0.2 parts of compound antioxidant (antioxidant 1010: DLTP = 1:1), and 75 parts of flame retardant (antimony trioxide: arsenic trioxide = 1:9, D50 = 2.0μm, moisture = 0.3%).

[0035] Its preparation method is as follows: S1. Add the above-mentioned polyvinyl chloride resin, plasticizer, filler, stabilizer, compatibilizer, lubricant and antioxidant to a high-speed kneader in sequence, heat to 110°C, and knead at 800 r / min for 8 minutes to fully soften and mix the resin and each additive. S2. Add the kneaded material from step S1 and the flame retardant to a rotary mixer according to the above weight ratio, and mix at 140°C for 8 minutes. After 4 minutes of mixing, lift the pressure bar to clean the raw powder in the corners of the mixing chamber. Send the mixed material to a single-screw granulator. The temperatures of the five heating zones of the single screw are 55-60°C in zone 1, 65-75°C in zone 2, 80-90°C in zone 3, 90-100°C in zone 4, and 110-120°C in zone 5. After granulation, dry in a hot air circulating oven at 65°C for 2.5 hours. After drying, the moisture content of the masterbatch is 0.2%, resulting in a flame-retardant masterbatch for PVC cable materials with low dust emission and high flame retardancy.

[0036] The production process adopts the standardized production protection system of this invention, and the performance of the produced flame retardant masterbatch is tested. The results are shown in Table 2. Example 2

[0037] This embodiment provides a flame-retardant masterbatch for PVC cable materials with low dust emission and high flame retardancy, which is prepared from the following raw materials in parts by weight: 10 parts of S-60 type polyvinyl chloride resin, 5 parts of dioctyl terephthalate, 1 part of light activated calcium carbonate, 1 part of calcium-zinc composite stabilizer, 0.5 parts of EVA-g-MAH (VA content 18%, grafting rate 0.8%), 0.2 parts of compound lubricant (low density polyethylene wax: stearic acid: barium stearate = 1:1:1.5), 0.1 parts of compound antioxidant (antioxidant 1010: DLTP = 1:1), and 60 parts of flame retardant (antimony trioxide: arsenic trioxide = 1:9, D50 = 2.5μm, moisture = 0.5%).

[0038] Its preparation method is as follows: S1. Add the above raw materials to a high-speed kneader in the order of Example 1, heat to 90°C, and knead at 800 r / min for 7 min to fully soften and mix the resin and each additive. S2. Add the kneaded material from step S1 and the flame retardant to a rotary mixer according to the above weight ratio, and mix at 135°C for 6 minutes. After 3 minutes of mixing, lift the pressure bar to clean the raw powder in the corner of the mixing chamber. Send the mixed material to a single-screw granulator. The temperatures of the five heating zones of the single screw are 55-60°C in the first zone, 65-75°C in the second zone, 80-90°C in the third zone, 90-100°C in the fourth zone, and 110-120°C in the fifth zone. After granulation, dry in a hot air circulating oven at 60°C for 3 hours. After drying, the moisture content of the masterbatch is 0.3%, resulting in a flame-retardant masterbatch for PVC cable materials with low dust emission and high flame retardancy.

[0039] The production protection system is the same as in Example 1. The performance of the prepared flame-retardant masterbatch was tested, and the results are shown in Table 2. Example 3

[0040] This embodiment provides a flame-retardant masterbatch for PVC cable materials with low dust emission and high flame retardancy, which is prepared from the following raw materials in parts by weight: 15 parts of S-60 type polyvinyl chloride resin, 10 parts of dioctyl terephthalate, 3 parts of light activated calcium carbonate, 2 parts of calcium-zinc composite stabilizer, 1.5 parts of EVA-g-MAH (VA content 28%, grafting rate 1.2%), 0.5 parts of compound lubricant (low density polyethylene wax: stearic acid: barium stearate = 1:1:1.5), 0.3 parts of compound antioxidant (antioxidant 1010: DLTP = 1:1), and 90 parts of flame retardant (antimony trioxide: arsenic trioxide = 1:9, D50 = 1.8μm, moisture = 0.2%).

[0041] Its preparation method is as follows: S1. Add the above raw materials to a high-speed kneader in the order of Example 1, heat to 100°C, and knead at 800 r / min for 9 minutes to fully soften and mix the resin and each additive. S2. Add the kneaded material from step S1 and the flame retardant to a rotary mixer according to the above weight ratio, and mix at 145°C for 7 minutes. After 3.5 minutes of mixing, lift the pressure bar to clean the raw powder in the corner of the mixing chamber. Send the mixed material to a single-screw granulator. The temperatures of the five heating zones of the single screw are 55-60°C in zone 1, 65-75°C in zone 2, 80-90°C in zone 3, 90-100°C in zone 4, and 110-120°C in zone 5. After granulation, dry in a hot air circulating oven at 70°C for 2 hours. After drying, the moisture content of the masterbatch is 0.1%, resulting in a flame-retardant masterbatch for PVC cable material with low dust emission and high flame retardancy.

[0042] The production protection system is the same as in Example 1. The performance of the prepared flame-retardant masterbatch was tested, and the results are shown in Table 2. Example 4

[0043] This embodiment provides a flame-retardant masterbatch for PVC cable materials with low dust emission and high flame retardancy, which is prepared from the following raw materials in parts by weight: 13.5 parts of S-60 type polyvinyl chloride resin, 7 parts of dioctyl terephthalate, 1.5 parts of light activated calcium carbonate, 1.5 parts of calcium-zinc composite stabilizer, 1 part of EVA-g-MAH (VA content 20%, grafting rate 1.0%), 0.3 parts of compound lubricant (low density polyethylene wax: stearic acid: barium stearate = 1:1:1.5), 0.2 parts of compound antioxidant (antioxidant 1010: DLTP = 1:1), and 75 parts of flame retardant (antimony trioxide: arsenic trioxide = 1:9, D50 = 2.2μm, moisture = 0.3%).

[0044] The preparation method is the same as in Example 1, and the production of the protective system is the same as in Example 1. The performance of the prepared flame retardant masterbatch was tested, and the results are shown in Table 2.

[0045] Comparative Example 1 A flame-retardant masterbatch for PVC cable materials is identical to that in Example 1 in terms of raw material ratio, preparation method, and production protection system, except that the flame retardant is pure antimony trioxide (content 99.8%, D50=2.0μm, moisture=0.3%), and no arsenic trioxide is added.

[0046] The performance of the prepared flame-retardant masterbatch was tested, and the results are shown in Table 2.

[0047] Comparative Example 2 The existing powder arsenic flame retardant, namely a mixture of antimony trioxide and arsenic trioxide in a mass ratio of 1:9 (D50=2.0μm, moisture=0.3%), is directly added to the national standard HI-90 PVC sheath material formula at an addition amount of 3%, without being made into masterbatch. The production process adopts conventional manual metering and open feeding method.

[0048] Its performance was tested using the same testing method, and the results are shown in Table 2.

[0049] Comparative Example 3 A flame-retardant masterbatch for PVC cable materials has the same raw material ratio as in Example 1, except that EVA-g-MAH compatibilizer is not added. The rest of the preparation method and production protection system are the same as in Example 1.

[0050] The performance of the prepared flame-retardant masterbatch was tested, and the results are shown in Table 2.

[0051] Table 2 Performance test results of Examples 1-4 and Comparative Examples 1-3

[0052] Results analysis: As shown in Table 2, the low-dust-emission, high-flame-retardant PVC cable masterbatches prepared in Examples 1-4 of this invention exhibit excellent physical and mechanical properties. Tensile strength is ≥7.0 MPa, elongation at break is ≥100%, and dispersibility is satisfactory. After adding 3% by weight of HI-90 PVC sheath material, the oxygen index reaches over 29.8, demonstrating excellent flame-retardant effect. The dust emission during production is only 0.02~0.03 mg / m³. 3 It meets national standards, and the cost of flame retardant raw materials is only 12,000 yuan / ton, making it cost-effective.

[0053] Comparative Example 1 uses pure antimony trioxide as a flame retardant. Although its oxygen index and mechanical properties are comparable to those of Example 1, the cost of the flame retardant raw material is as high as 240,000 yuan / ton, which is 20 times that of the present invention, and it has no industrial promotion value.

[0054] Comparative Example 2 uses an existing arsenic-containing flame retardant powder. Although its oxygen index is comparable to that of this invention and its raw material cost is low, it lacks dust protection measures, resulting in a dust emission rate of 6.5 mg / m³. 3 The levels far exceeded national standard limits, and the flame retardant dispersibility was substandard, resulting in large fluctuations in the performance of PVC cable materials.

[0055] Comparative Example 3, without the addition of EVA-g-MAH compatibilizer, had a low dust emission, but the flame retardant dispersibility was unqualified, resulting in a significant decrease in the mechanical properties of the masterbatch. Furthermore, after the addition, the oxygen index of the HI-90 PVC sheath material was only 25.3, and the flame retardant effect was significantly reduced, failing to meet the flame retardant requirements.

[0056] In summary, the flame-retardant masterbatch for PVC cable materials with low dust emission and high flame retardancy prepared by this invention solves the technical problems of dust emission from arsenic-containing flame retardants, uneven dispersion of high-content flame retardants, and difficulty in balancing flame retardant efficiency and cost in the prior art. It has significant technical advantages and industrial promotion value.

[0057] Any aspects not described in this invention are applicable to existing technologies.

[0058] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A flame-retardant masterbatch for PVC cable materials with low dust emission and high flame retardancy, characterized in that, It is prepared from the following raw materials in parts by weight: 10-15 parts of polyvinyl chloride resin; Plasticizer 5-10 parts; 1-3 parts filler; Stabilizer 1-2 parts; 0.5–1.5 parts of compatibilizer; Lubricant 0.2-0.5 parts; Antioxidant 0.1–0.3 parts; 60-90 parts flame retardant; The flame retardant is a mixture of antimony trioxide and arsenic trioxide powder, with a mass ratio of antimony trioxide to arsenic trioxide of 1:

9. The average particle size D50 of the flame retardant is ≤2.5μm, and the moisture content is ≤0.5%.

2. The flame-retardant masterbatch according to claim 1, characterized in that, The polyvinyl chloride resin is type S-60 resin, and the average degree of polymerization of the polyvinyl chloride resin is 750-850, with a fisheye count of <10 per 400cm. 2 The residual polyvinyl chloride monomer content is ≤5μg / g; The plasticizer is dioctyl terephthalate, and the density of dioctyl terephthalate is 0.980–0.986 g / cm³. 3 Flash point > 210℃, volume resistivity ≥ 2.0 × 10⁻⁶ 12 Ω·cm, moisture content <0.15%; The filler is light activated calcium carbonate, and the light activated calcium carbonate has a Hunter whiteness ≥96%, an average particle size D50 ≤1.8μm, and a moisture content ≤0.6%; The stabilizer is a calcium-zinc composite stabilizer, and the density of the calcium-zinc composite stabilizer is 1.109–1.128 g / cm³. 3 The loss on heating is less than 1.5%; The compatibilizer is an ethylene-vinyl acetate copolymer grafted with maleic anhydride (EVA-g-MAH), and the VA content of the compatibilizer is 18-28%, with a grafting rate of 0.8-1.2%.

3. The flame-retardant masterbatch according to claim 1, characterized in that, The lubricant is a compound system of low-density polyethylene wax, stearic acid, and barium stearate, and the mass ratio of low-density polyethylene wax, stearic acid, and barium stearate is 1:1:1.

5.

4. The flame-retardant masterbatch according to claim 3, characterized in that, The density of the low-density polyethylene wax is 0.92 g / cm³. 3 The stearic acid has a melting point of 120–140°C, a number-average molecular weight of 2000–5000, and a viscosity of 1.1 mPa·s at 120°C; the density of the stearic acid is 0.84–0.88 g / cm³. 3 The melting point is 54–60℃; the density of the barium stearate is 1.14–1.18 g / cm³. 3 It has a melting point of 210–220℃ and a barium content of 19.5–21.5%.

5. The flame-retardant masterbatch according to claim 1, characterized in that, The antioxidant is a compound system of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and dilauryl thiodipropionate (DLTP), and the mass ratio of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] to dilauryl thiodipropionate (DLTP) is 1:

1.

6. The flame-retardant masterbatch according to claim 5, characterized in that, The density of the pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] is 1.15–1.20 g / cm³. 3 The melting point is 120℃, and the loss on heating is <1.0%; the density of the dilaurate thiodipropionate (DLTP) is 0.91~0.94g / cm³. 3 It has a melting point of 40℃ and a loss on heating of <1.0%.

7. A method for preparing a flame-retardant masterbatch for low-dust-emission, high-flame-retardant PVC cable materials according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Add polyvinyl chloride resin, plasticizer, filler, stabilizer, compatibilizer, lubricant and antioxidant to a high-speed kneader in the specified proportions, and heat, stir and knead. S2. The kneaded material from step S1 and the flame retardant are added to a mixer in proportion and kneaded. After single-screw granulation and drying in a hot air circulating oven, the flame retardant masterbatch for low dust emission and high flame retardancy PVC cable material is obtained. A standardized production protection system is used to control dust emission during the preparation process.

8. The preparation method according to claim 7, characterized in that, In step S1, the kneading temperature is 90-110℃, the kneading time is 7-9 min, and the rotation speed of the high-speed kneader is 800 r / min.

9. The preparation method according to claim 7, characterized in that, In step S2, the mixing temperature is 135-145℃, the mixing time is 6-8 minutes, and the pressure bar is lifted to clean the raw powder in the corner of the mixing chamber after 3-4 minutes of mixing, with a cleaning time of 10-15 seconds.

10. The preparation method according to claim 7, characterized in that, In step S2, the single screw is divided into five heating zones, with the following temperatures: Zone 1: 55-60℃, Zone 2: 65-75℃, Zone 3: 80-90℃, Zone 4: 90-100℃, and Zone 5: 110-120℃. The screw speed of the single screw granulator is 50 r / min, the pellet size is 2-3 mm, and the moisture content of the dried masterbatch is ≤0.3%.

11. The preparation method according to claim 7, characterized in that, The standardized production protection system includes: 1) A fully automated metering and batching system with an accuracy of ±0.1% is used to replace manual operation, eliminating the need for workers to operate on-site during the metering, feeding, and mixing stages; 2) A fully enclosed pipeline batching system is adopted, and the negative pressure of the pipeline during material transportation is -0.02 to -0.05 MPa; 3) Install H13 grade high-efficiency air filters in the ventilation system of the production workshop, with a filtration efficiency of ≥99.95%, to ensure that the amount of arsenic trioxide dust emitted during production is ≤0.03mg / m³. 3 .

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