Flame-retardant polyethylene sheath material for high-speed small section and preparation method thereof
Patent Information
- Application Number
- CN202611147614.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-30
- Publication Date
- 2026-10-30
AI Technical Summary
然而，聚磷酸铵极性强，与非极性聚乙烯基体不相容，添加足量后导致熔体粘度急剧升高，高速挤出时发生熔体破裂、表面粗糙，无法实现稳定生产，现有硅烷偶联剂等物理表面处理改善效果微弱，不能从根本上解决相容性问题
（1）本发明采用有机化聚磷酸铵作为阻燃剂，通过离子交换反应将聚磷酸铵中部分铵根阳离子置换为含长链烷基的季铵盐阳离子，使阻燃剂粒子表面原位形成与聚乙烯基体热力学相容的柔性长链烷基层，这一化学改性消除了无机阻燃剂粒子的高表面能和高极性，使有机化聚磷酸铵在聚乙烯基体中的分散尺度达到亚微米级，界面张力显著降低，熔体流动速率得到提高，同时，表面锚接的长链烷基在高温剪切加工中发挥内润滑作用，降低了阻燃剂粒子之间及粒子与加工设备壁面之间的摩擦，提高了发生熔体破裂的临界剪切速率，护套料在190℃、2.16kg条件下熔体流动速率可达2.0g/10min以上，能够在450m/min线速度下稳定挤出壁厚0.45mm的护套，表面光滑，壁厚偏差≤±0.02mm。
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Abstract
Description
Technical Field
[0001] This invention relates to the field of cable sheath materials technology, specifically to flame-retardant polyethylene sheath material for high-speed, small-section applications and its preparation method. Background Technology
[0002] The sheath thickness of small-section, thin-walled cables is typically 0.3mm to 0.8mm, requiring an extrusion speed greater than 300m / min. Polyethylene is the preferred substrate for these cables, but it is flammable, necessitating the introduction of intumescent flame retardants such as ammonium polyphosphate. However, ammonium polyphosphate is highly polar and incompatible with the non-polar polyethylene matrix. Adding sufficient amounts leads to a sharp increase in melt viscosity, causing melt fracture and surface roughness during high-speed extrusion, making stable production impossible. Existing physical surface treatments such as silane coupling agents offer only minor improvements and cannot fundamentally solve the compatibility problem. Summary of the Invention
[0003] This invention addresses the problems in the prior art by providing a flame-retardant polyethylene sheath material for high-speed, small-section applications and its preparation method. The specific technical solution is as follows: On one hand, the present invention provides a flame-retardant polyethylene sheath material for high-speed, small-section applications, comprising the following raw materials in parts by weight: 100 parts of matrix resin; 25 to 35 parts of organically modified ammonium polyphosphate; 8 to 15 parts of charring agent; Antioxidant 0.2 to 1.0 parts; Processing lubricant: 0.8 parts to 2.0 parts; The organically modified ammonium polyphosphate is prepared by an ion exchange reaction between ammonium polyphosphate and a long-chain alkyl quaternary ammonium salt, wherein the cation of the long-chain alkyl quaternary ammonium salt has the general formula [R1R2R3R4N]. + In the formula, R1 is a straight-chain or branched alkyl group with 12 to 22 carbon atoms, and R2, R3, and R4 are each independently selected from alkyl or benzyl groups with 1 to 4 carbon atoms.
[0004] As a further technical solution of the present invention, the long-chain alkyl quaternary ammonium salt is at least one of hexadecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, octadecyldimethylbenzylammonium chloride, and docosyltrimethylammonium chloride.
[0005] As a further technical solution of the present invention, in the organic ammonium polyphosphate, the molar amount of quaternary ammonium salt cations participating in ion exchange accounts for 8% to 20% of the total molar amount of ammonium cations in the original ammonium polyphosphate.
[0006] As a further technical solution of the present invention, the matrix resin comprises linear low-density polyethylene or metallocene linear low-density polyethylene, and the melt mass flow rate of the matrix resin at 190°C and 2.16 kg is 1.5 g / 10 min to 4.0 g / 10 min.
[0007] As a further technical solution of the present invention, the char-forming agent is at least one of pentaerythritol, dipentaerythritol, sorbitol or starch.
[0008] As a further technical solution of the present invention, the total weight of the antioxidant and the processing lubricant is 1.0 to 3.0 parts.
[0009] On the other hand, the present invention also provides a method for preparing flame-retardant polyethylene sheath material for high-speed, small-section applications, comprising the following steps: S1. Preparation of organic ammonium polyphosphate: Ammonium polyphosphate powder is dispersed in water, and a long-chain alkyl quaternary ammonium salt aqueous solution is added under stirring at 50℃~70℃. The reaction is carried out for 1 hour to 3 hours, and then filtered, washed and dried to obtain organic ammonium polyphosphate powder. S2. Mix the matrix resin, the organic ammonium polyphosphate obtained in step S1, the charring agent, the antioxidant and the processing lubricant according to the weight parts to obtain the mixture; S3. The mixture is melt-blended and extruded in a twin-screw extruder at 140℃~170℃ to obtain the final product.
[0010] As a further technical solution of the present invention, the long-chain alkyl quaternary ammonium salt aqueous solution in step S1 is added by dripping, and the dripping time is controlled between 0.5 hours and 2 hours.
[0011] The beneficial effects of this invention are as follows: (1) This invention uses organic ammonium polyphosphate as a flame retardant. Through ion exchange reaction, some ammonium cations in the ammonium polyphosphate are replaced with quaternary ammonium salt cations containing long-chain alkyl groups. This allows a flexible long-chain alkyl layer that is thermodynamically compatible with the polyethylene matrix to be formed in situ on the surface of the flame retardant particles. This chemical modification eliminates the high surface energy and high polarity of inorganic flame retardant particles, allowing the dispersion scale of organic ammonium polyphosphate in the polyethylene matrix to reach the submicron level. The interfacial tension is significantly reduced, and the melt flow rate is improved. At the same time, the long-chain alkyl groups anchored on the surface play an internal lubricating role in high-temperature shearing processing, reducing the friction between flame retardant particles and between particles and the wall of the processing equipment, and increasing the critical shear rate at which melt fracture occurs. The melt flow rate of the sheath material can reach more than 2.0 g / 10 min at 190℃ and 2.16 kg. It can stably extrude a sheath with a wall thickness of 0.45 mm at a linear velocity of 450 m / min. The surface is smooth and the wall thickness deviation is ≤ ±0.02 mm.
[0012] (2) By controlling the cation replacement rate of quaternary ammonium salt within the range of 8% to 20%, this invention not only fully improves compatibility and flowability, but also retains a sufficient number of ammonium ion active sites in ammonium polyphosphate, ensuring the release of non-flammable gases and the flame retardant effect of promoting char formation when heated. Under the same conditions of flame retardant addition, the limiting oxygen index of the sheath material can reach more than 32%, the tensile strength is ≥11.7MPa, and the elongation at break is ≥395%, achieving a balance between high flame retardancy, excellent mechanical properties and high processing flowability. Detailed Implementation
[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments.
[0014] Example of preparation of organically modified ammonium polyphosphate; Preparation Example 1 100g of ammonium polyphosphate was dispersed in 800mL of deionized water and heated to 60℃ with stirring. 12g of hexadecyltrimethylammonium chloride was dissolved in 150mL of deionized water and added dropwise to the ammonium polyphosphate slurry at a uniform rate over 1 hour. The mixture was kept at 60℃ and stirred for another 2 hours. After the reaction was complete, the mixture was filtered. The filter cake was washed three times with approximately 300mL of deionized water at 60℃ each time, dried under vacuum at 80℃ and -0.095MPa for 12 hours, and then pulverized through a 200-mesh sieve to obtain the organic ammonium polyphosphate. Elemental analysis showed that the quaternary ammonium salt cation replacement rate was approximately 12%.
[0015] Preparation Example 2 100g of ammonium polyphosphate was dispersed in 800mL of deionized water and stirred until heated to 60℃. 10g of octadecyldimethylbenzylammonium chloride was dissolved in 150mL of deionized water and added dropwise to the ammonium polyphosphate slurry at a uniform rate over 1 hour. The reaction was continued at 60℃ with stirring for 2 hours. After the reaction was complete, the mixture was filtered. The filter cake was washed three times with approximately 300mL of deionized water at 60℃ each time, dried under vacuum at 80℃ and -0.095MPa for 12 hours, and then pulverized through a 200-mesh sieve to obtain organophosphate ammonium. The replacement rate was approximately 9%.
[0016] Preparation Example 3 100g of ammonium polyphosphate was dispersed in 800mL of deionized water and stirred until heated to 60℃. 18g of docosyltrimethylammonium chloride was dissolved in 150mL of deionized water and added dropwise to the ammonium polyphosphate slurry at a uniform rate over 2 hours. The reaction was continued at 60℃ with stirring for 3 hours. After the reaction was complete, the mixture was filtered. The filter cake was washed three times with approximately 300mL of deionized water at 60℃ each time, dried under vacuum at 80℃ and -0.095MPa for 12 hours, and then pulverized through a 200-mesh sieve to obtain organophosphate ammonium. The replacement rate was approximately 18%.
[0017] Example 1
[0018] Formula (parts by weight): The matrix resin consists of 100 parts of metallocene linear low-density polyethylene and 30 parts of linear low-density polyethylene. Prepare 30 parts of the organophosphated ammonium obtained in Example 1; Pentaerythritol 12 parts; 0.5 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; 0.4 parts of dilauryl thiodipropionate; 1.1 parts of polyethylene wax.
[0019] Preparation method: All the above raw materials are put into a high-speed mixer and mixed at 800 rpm and 80°C for 15 minutes. The mixture is then fed into a twin-screw extruder and melt-blended, extruded and granulated in a temperature range of 140°C to 170°C to obtain the sheathing material.
[0020] Example 2
[0021] Formula (parts by weight): 100 parts of matrix resin, all of which are metallocene linear low-density polyethylene; 25 parts of the organic polyphosphate ammonium obtained in Example 2 were prepared; 10 parts of dipentaerythritol; 0.3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]; 1.5 parts zinc stearate.
[0022] Preparation method: All the above raw materials are put into a high-speed mixer and mixed at 800 rpm and 80°C for 15 minutes. The mixture is then fed into a twin-screw extruder and melt-blended, extruded and granulated in a temperature range of 140°C to 170°C to obtain the sheathing material.
[0023] Example 3
[0024] Formula (parts by weight): The matrix resin consists of 100 parts of metallocene linear low-density polyethylene and 30 parts of linear low-density polyethylene. 35 parts of the organically modified ammonium polyphosphate obtained in Example 3 were prepared; Pentaerythritol 8 parts; 0.8 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]; 2.0 parts of polyethylene wax.
[0025] Preparation method: All the above raw materials are put into a high-speed mixer and mixed at 800 rpm and 75°C for 18 minutes. The mixture is then fed into a twin-screw extruder and melt-blended, extruded and granulated in a temperature range of 140°C to 170°C to obtain the sheathing material.
[0026] Comparative Example 1 Formula (parts by weight): The matrix resin consists of 100 parts of metallocene linear low-density polyethylene and 30 parts of linear low-density polyethylene. 30 parts of unmodified ammonium polyphosphate; Pentaerythritol 12 parts; 0.5 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; 0.4 parts of dilauryl thiodipropionate; 1.1 parts of polyethylene wax.
[0027] Preparation method: All the above raw materials are put into a high-speed mixer and mixed at 800 rpm and 80°C for 15 minutes. The mixture is then fed into a twin-screw extruder and melt-blended, extruded and granulated in a temperature range of 140°C to 170°C to obtain the sheathing material.
[0028] Comparative Example 2 Preparation of low-replacement-rate organic ammonium polyphosphate: 100g of ammonium polyphosphate was dispersed in 800mL of deionized water and stirred until heated to 60℃. 5g of hexadecyltrimethylammonium chloride was dissolved in 150mL of deionized water and added dropwise to the ammonium polyphosphate slurry at a uniform rate over 1 hour. The mixture was stirred and reacted at 60℃ for 2 hours. After the reaction was complete, the mixture was filtered. The filter cake was washed three times with approximately 300mL of deionized water at 60℃ each time, dried under vacuum at 80℃ and -0.095MPa for 12 hours, and then pulverized through a 200-mesh sieve to obtain organic ammonium polyphosphate with a replacement rate of approximately 5%.
[0029] Sheath material formulation (parts by weight): The matrix resin consists of 100 parts of metallocene linear low-density polyethylene and 30 parts of linear low-density polyethylene. 30 parts of the above-mentioned low-replacement-rate organic polyphosphate ammonium; Pentaerythritol 12 parts; 0.5 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; 0.4 parts of dilauryl thiodipropionate; 1.1 parts of polyethylene wax.
[0030] Preparation method: All the above raw materials are put into a high-speed mixer and mixed at 800 rpm and 80°C for 15 minutes. The mixture is then fed into a twin-screw extruder and melt-blended, extruded and granulated in a temperature range of 140°C to 170°C to obtain the sheathing material.
[0031] Comparative Example 3 Preparation of high-replacement-rate organically modified ammonium polyphosphate: 100g of ammonium polyphosphate was dispersed in 800mL of deionized water and heated to 60℃ with stirring. 30g of hexadecyltrimethylammonium chloride was dissolved in 150mL of deionized water and added dropwise to the ammonium polyphosphate slurry at a uniform rate over 1 hour. The reaction was maintained at 60℃ with stirring for 3 hours. After the reaction was completed, the mixture was filtered, and the filter cake was washed three times with approximately 300mL of deionized water at 60℃ each time. The cake was then dried under vacuum at 80℃ and -0.095MPa for 12 hours, pulverized, and passed through a 200-mesh sieve to obtain organically modified ammonium polyphosphate with a replacement rate of approximately 27%.
[0032] Sheath material formulation (parts by weight): The matrix resin consists of 100 parts of metallocene linear low-density polyethylene and 30 parts of linear low-density polyethylene. 30 parts of the above-mentioned high-replacement-rate organic polyphosphate ammonium; Pentaerythritol 12 parts; 0.5 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; 0.4 parts of dilauryl thiodipropionate; 1.1 parts of polyethylene wax.
[0033] Preparation method: All the above raw materials are put into a high-speed mixer and mixed at 800 rpm and 80°C for 15 minutes. The mixture is then fed into a twin-screw extruder and melt-blended, extruded and granulated in a temperature range of 140°C to 170°C to obtain the sheathing material.
[0034] Comparative Example 4 Formula (parts by weight): The matrix resin is 100 parts, all of which is high-density polyethylene; Prepare 30 parts of the organophosphated ammonium obtained in Example 1; Pentaerythritol 12 parts; 0.5 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; 0.4 parts of dilauryl thiodipropionate; 1.1 parts of polyethylene wax.
[0035] Preparation method: All the above raw materials are put into a high-speed mixer and mixed at 800 rpm and 80°C for 15 minutes. The mixture is then fed into a twin-screw extruder and melt-blended, extruded and granulated in a temperature range of 140°C to 170°C to obtain the sheathing material.
[0036] Performance testing methods The melt flow rate was tested according to GB / T3682.1-2018, under conditions of 190℃ and a load of 2.16kg.
[0037] The limiting oxygen index was tested according to GB / T2406.2-2009, with a sample thickness of 3.0 mm.
[0038] Tensile strength and elongation at break were tested according to GB / T1040.3-2006, with a tensile rate of 250 mm / min.
[0039] High-speed extrusion evaluation: The extrusion was carried out on a single-screw extruder with a die gap of 0.45 mm, an extrusion temperature of 140℃~170℃, a screw speed of 35 rpm, and a sheath with a wall thickness of 0.45 mm extruded at a linear velocity of 450 m / min. The surface quality was visually observed and the wall thickness deviation was measured with a micrometer.
[0040] The performance of the sheath materials prepared in Examples 1-3 and Comparative Examples 1-4 were tested, and the test results are shown in Table 1.
[0041]
[0042] Table 1 Note: " / " indicates that a continuous and complete sample could not be obtained due to severe melt fracture and frequent wire breaks.
[0043] Examples 1-3 all adopted the technical solution of the present invention, with MFRs of 2.6 g / 10 min, 3.0 g / 10 min, and 2.4 g / 10 min, respectively. The limiting oxygen index was greater than 32%, the tensile strength was 11.7-12.5 MPa, the elongation at break was 395%-430%, and the extrusion surface at 450 m / min was smooth with a wall thickness deviation of ≤ ±0.02 mm. This indicates that the sheath material of the present invention has high fluidity, high flame retardancy, and excellent processing performance.
[0044] Comparative Example 1 used unmodified ammonium polyphosphate, with an MFR of only 1.1 g / 10 min. During extrusion, it suffered severe melt fracture and frequent wire breakage, proving that without organic modification, it is impossible to meet the requirements of high-speed thin-wall extrusion.
[0045] Comparative Example 2 used organic polyphosphate ammonium with a replacement rate of about 5% and an MFR of 1.6 g / 10 min. Slight sharkskin appeared on the extruded surface, and the wall thickness deviation increased to ±0.05 mm. This proves that when the replacement rate is less than 8%, the long-chain alkyl coverage density on the flame retardant particle surface is insufficient, which cannot fully improve compatibility and flowability.
[0046] Comparative Example 3 used organic ammonium polyphosphate with a replacement rate of about 27%, with an MFR of 2.6 g / 10 min and a smooth extrusion surface, but the limiting oxygen index dropped to 28.9%, proving that when the replacement rate is higher than 20%, too many ammonium ions are replaced, resulting in a deterioration of flame retardancy.
[0047] Comparative Example 4 used high-density polyethylene with an MFR of only 0.8 g / 10 min, and the overall MFR was only 0.5 g / 10 min. Severe melt fracture occurred during extrusion, proving that the fluidity of the base resin itself is the basis for achieving high-speed extrusion. If the MFR is less than 1.5 g / 10 min, it cannot be implemented.
[0048] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it.
Claims
1. A flame-retardant polyethylene sheath material for high-speed, small-section applications, characterized in that, Including the following parts by weight of raw materials: 100 parts of matrix resin; 25 to 35 parts of organically modified ammonium polyphosphate; 8 to 15 parts of charring agent; Antioxidant 0.2 to 1.0 parts; Processing lubricant: 0.8 parts to 2.0 parts; The organically modified ammonium polyphosphate is prepared by an ion exchange reaction between ammonium polyphosphate and a long-chain alkyl quaternary ammonium salt, wherein the cation of the long-chain alkyl quaternary ammonium salt has the general formula [R1R2R3R4N]. + In the formula, R1 is a straight-chain or branched alkyl group with 12 to 22 carbon atoms, and R2, R3, and R4 are each independently selected from alkyl or benzyl groups with 1 to 4 carbon atoms.
2. The flame-retardant polyethylene sheath material for high-speed, small-section applications according to claim 1, characterized in that: The long-chain alkyl quaternary ammonium salt is at least one of hexadecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, octadecyldimethylbenzylammonium chloride, and docosyltrimethylammonium chloride.
3. The flame-retardant polyethylene sheath material for high-speed, small-section applications according to claim 1, characterized in that: In the organic ammonium polyphosphate, the molar amount of quaternary ammonium salt cations participating in ion exchange accounts for 8% to 20% of the total molar amount of ammonium cations in the original ammonium polyphosphate.
4. The flame-retardant polyethylene sheath material for high-speed, small-section applications according to claim 1, characterized in that: The matrix resin comprises linear low-density polyethylene or metallocene linear low-density polyethylene, and the melt mass flow rate of the matrix resin at 190°C and 2.16 kg is 1.5 g / 10 min to 4.0 g / 10 min.
5. The flame-retardant polyethylene sheath material for high-speed, small-section applications according to claim 1, characterized in that: The charring agent is at least one of pentaerythritol, dipentaerythritol, sorbitol, or starch.
6. The flame-retardant polyethylene sheath material for high-speed, small-section applications according to claim 1, characterized in that: The total weight of the antioxidant and processing lubricant is 1.0 to 3.0 parts.
7. A method for preparing flame-retardant polyethylene sheath material for high-speed, small-section applications, characterized in that, Includes the following steps: S1. Preparation of organic ammonium polyphosphate: Ammonium polyphosphate powder is dispersed in water, and a long-chain alkyl quaternary ammonium salt aqueous solution is added under stirring at 50℃~70℃. The reaction is carried out for 1 hour to 3 hours, and then filtered, washed and dried to obtain organic ammonium polyphosphate powder. S2. Mix the matrix resin, the organic ammonium polyphosphate obtained in step S1, the charring agent, the antioxidant and the processing lubricant according to the weight parts to obtain the mixture; S3. The mixture is melt-blended and extruded in a twin-screw extruder at 140℃~170℃ to obtain the final product.
8. The method for preparing high-speed, small-section flame-retardant polyethylene sheath material according to claim 7, characterized in that: The long-chain alkyl quaternary ammonium salt aqueous solution mentioned in step S1 is added dropwise, and the dropwise addition time is controlled between 0.5 hours and 2 hours.