High-CTI halogen-free flame-retardant PA66 composite material and preparation method thereof

Abstract

The invention discloses a high-CTI (comparative tracking index) halogen-free flame-retardant PA66 (polyamide 66) composite material and a preparation method thereof, and belongs to the technical field of high polymer materials. The composite material comprises the following components in parts by weight: 52-64 parts of PA66 resin, 20-30 parts of glass fibers, 12-15 parts of a phosphorus-based flame retardant, 0.5-1.5 parts of a flame-retardant synergist, 0.3-0.7 part of a lubricant and 0.1-0.5 part of an antioxidant, and the flame-retardant synergist is aliphatic dicarboxylic acid with the carbon atom number greater than or equal to 8. The material surface energy is reduced and electrolyte is repelled through long-carbon-chain hydrophobic groups, and meanwhile, the CTI value is increased to 600 V or above while it is guaranteed that the material reaches the UL94 V0 flame retardant grade (1.6 mm) by utilizing interaction of carboxyl and a PA66 matrix and cooperating with a phosphorus flame retardant. The invention also provides a preparation method of the material, the process is simple, the material is suitable for industrial production, and the product can be widely applied to electronic and electrical components with high safety requirements.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, and in particular relates to a high CTI halogen-free flame-retardant PA66 composite material and its preparation method. Background Technology

[0002] Polyamide 66 (PA66), a widely used engineering plastic, has been extensively applied in various fields such as home appliances, electronics, automotive (including new energy vehicle) parts, rail transportation, and high-voltage power transmission due to its excellent mechanical strength, wear resistance, corrosion resistance, and heat resistance. However, PA66 itself is a flammable material with a limiting oxygen index of only about 24%, making it prone to combustion. Furthermore, potential leakage, short circuits, electric arcs, or electric sparks during circuit use further exacerbate the fire risk.

[0003] In recent years, my country's electronics and electrical appliance industry has continued to develop rapidly. The market has placed higher demands on the strength and dimensional stability of glass fiber reinforced PA66 materials, while also establishing strict standards for their flame retardancy. Especially for unattended electrical appliances, the industry's demand for materials with high tracking index (CTI) is increasingly urgent. This is because if the CTI value of a material is too low, it is very easy to form a conductive path, ultimately leading to a fire hazard.

[0004] To improve the flame retardant properties of PA66, the conventional technique is to add flame retardants to nylon resin. Existing PA66 flame retardant products are mainly divided into two series: halogenated and halogen-free. Halogenated flame retardants often use a bromine-antimony compound system. Although the flame retardant effect is excellent, the smoke density during combustion is high, which can easily lead to poisoning and asphyxiation, posing potential hazards to human health and the environment. Furthermore, with the increasingly stringent EU WEEE and RoHS directives and environmental regulations in various countries, the application of traditional bromine-based flame retardants is severely restricted. In addition, halogenated flame retardants easily migrate to the product surface under the influence of an electric field and generate free radicals, promoting the formation of conductive paths between electrodes. Therefore, replacing halogenated flame retardants with halogen-free flame retardants has become an inevitable trend in the industry. However, the highest CTI value of existing halogen-free flame retardant systems is only around 550 V, which still cannot meet the requirements of high-voltage transmission equipment for a CTI of 600 V or higher. As unattended electrical components move towards modularization and high-performance miniaturization, local operating voltages are constantly increasing, which places more stringent requirements on the CTI performance of halogen-free flame-retardant glass fiber reinforced PA66 materials.

[0005] In summary, developing halogen-free flame-retardant glass fiber reinforced PA66 composite materials with high CTI values ​​is of great practical significance for expanding the application scenarios of flame-retardant nylon materials and promoting the high-quality development of the electronics and electrical industry. Summary of the Invention

[0006] To meet the high CTI value requirements of PA66 products, the primary objective of this invention is to provide a high CTI halogen-free flame-retardant glass fiber reinforced PA66 composite material. This compound employs a technical solution combining a phosphorus-based flame retardant with a long-chain hydrophobic additive, which effectively optimizes the CTI performance of glass fiber reinforced PA66 materials, ultimately achieving a V0 flame retardant rating of 1.6 mm and a CTI value exceeding 600V.

[0007] The specific technical solution to achieve the above-mentioned objectives is as follows: This invention provides a high CTI halogen-free flame-retardant PA66 composite material, which comprises the following raw materials by weight: 52-64 parts of PA66 resin, 20-30 parts glass fiber 12-15 parts of phosphorus-based flame retardant 0.5-1.5 parts of flame retardant synergist. Lubricant 0.3-0.7 parts, Antioxidant 0.1-0.5 parts, The flame retardant synergist is an aliphatic dicarboxylic acid with ≥8 carbon atoms.

[0008] Furthermore, the aliphatic dicarboxylic acid has 10 to 18 carbon atoms.

[0009] Furthermore, the aliphatic dicarboxylic acid is at least one of dodecanoic acid and tetradecanoic acid.

[0010] The aliphatic dicarboxylic acid has a straight-chain structure.

[0011] Furthermore, the ratio of the phosphorus-based flame retardant to the flame retardant synergist is 15:(0.5-1.5).

[0012] Furthermore, the amount of the flame retardant synergist is 0.5-1.0 parts.

[0013] Furthermore, the raw materials of the composite material also contain 0.5-1.0 parts of compatibilizer.

[0014] Furthermore, the compatibilizer is at least one of POE grafted with maleic anhydride, POE grafted with glycidyl methacrylate, and styrene-acrylonitrile grafted with GMA.

[0015] Furthermore, the amount of glass fiber used is 28-30 parts.

[0016] Furthermore, the phosphorus-based flame retardant is at least one of diethylaluminum hypophosphite, triphenyl phosphate, 1,3-phenylene phosphate (2,6-tolyl) tetraester, and bisphenol A-bis(diphenyl phosphate).

[0017] Preferably, the phosphorus-based flame retardant is diethylaluminum hypophosphite. Diethylaluminum hypophosphite requires a small amount to achieve high flame retardant efficiency. During combustion, it generates active free radicals, which significantly improve the flame retardant properties of PA66 by interrupting the combustion chain reaction.

[0018] Furthermore, the flame retardant synergist is a long-chain hydrophobic additive. The molecular structure of this long-chain hydrophobic additive contains both long-chain hydrophobic groups and carboxyl groups. The carboxyl groups react with the amino groups in PA66, improving compatibility. This long-chain hydrophobic additive combines hydrophobic functionality with compatibility with PA66. By reducing the surface energy of the material, it imparts hydrophobic properties, reduces electrolyte adsorption and residue, blocks the formation of conductive pathways, and ultimately improves the CTI value.

[0019] In similar compounds, carbon chain length is positively correlated with hydrophobicity. The longer the carbon chain, the stronger the hydrophobicity, that is, the stronger the ability to repel water molecules. However, after growing to a certain length (above C18), the improvement in hydrophobicity will reach saturation.

[0020] Furthermore, the relative viscosity of the PA66 resin is 2.0 dL / g-2.8 dL / g.

[0021] Preferably, the PA66 resin is a medium-viscosity PA66 with a relative viscosity of 2.7 dL / g.

[0022] Furthermore, the glass fiber is an alkali-free chopped glass fiber with a single filament diameter of 7-15 μm; Preferably, the glass fiber is an alkali-free chopped glass fiber with a single filament diameter of 10 μm.

[0023] Furthermore, the lubricant is selected from at least one of calcium stearate, polyethylene wax, polypropylene wax, stearamide, silicone, ethylene bis-stearamide, ethylene-vinyl acetate copolymer, and ethylene-acrylic acid copolymer.

[0024] Preferably, the lubricant is an ethylene-acrylic acid copolymer.

[0025] Furthermore, the antioxidant includes a primary antioxidant and a secondary antioxidant.

[0026] Preferably, the weight ratio of the primary antioxidant to the secondary antioxidant is 2:1, the hindered phenolic primary antioxidant is antioxidant 1098, and the phosphite secondary antioxidant is 168.

[0027] Another objective of this invention is to provide a method for preparing high CTI halogen-free flame-retardant PA66 composite materials. This method has simple steps, strong operational controllability, stable and uniform product quality, and advantages of high production efficiency and low production cost, making it suitable for large-scale industrial application.

[0028] A method for preparing high CTI halogen-free flame-retardant PA66 composite materials includes the following steps: S1: Weigh each raw material according to the formula weight parts; S2: Mix all raw materials except glass fiber evenly to obtain a premix; S3: The premixed material is added from the main feed port of the twin-screw extruder, and glass fiber is added from the side feed port. After melt blending, extrusion, cooling, pelletizing and drying, the composite material is obtained.

[0029] Furthermore, the mixing speed in step S2 is 500 rpm / min, and the mixing time is 3-5 min; Furthermore, in step S3, the main feed speed of the twin-screw extruder is 400 rpm / min, and the side feed speed is 180 rpm / min; Furthermore, in step S3, the temperatures of each extrusion zone of the twin-screw extruder are: Zone 1 240~255 ℃, Zone 2 245~255 ℃, Zones 3 to 7 265~280 ℃, Zones 8 to 9 240~260 ℃, Zones 10 to 11 230~250 ℃, and the die head 265~280 ℃.

[0030] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses a long-chain hydrophobic additive as a flame retardant synergist, which can reduce the surface energy of the material and make the material surface hydrophobic, thereby reducing the adsorption and spread of electrolyte and blocking the formation of conductive paths. This not only improves the flame retardant performance of glass fiber reinforced PA66, but also further optimizes the CTI of PA66 material to reach over 600V. 2. The preparation method of this invention is simple and easy to implement, and the reaction conditions are mild. A halogen-free flame retardant system is used as the core approach to achieve the flame retardant performance of the material. By compounding a phosphorus-based flame retardant with a long-chain hydrophobic additive, the main flame retardant is responsible for improving flame retardancy, while the synergist is responsible for improving CTI (Chemical Intensity Tolerance). The two do not interfere with each other, promoting a highly efficient synergistic effect and ensuring that the material meets UL94 V standards. While achieving a flame retardant rating of 0 (1.6mm), the CTI value is increased to over 600V; it can effectively avoid the generation of harmful gases and has safe and environmentally friendly characteristics. Detailed Implementation

[0031] To facilitate understanding of the present invention, a more complete description is provided below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this invention includes any and all combinations of one or more of the associated listed items.

[0032] The raw materials used in the embodiments of this invention are sourced from the following sources: (A) PA66: HY1800, Jiangsu Huayang Nylon Co., Ltd.; (B) Glass fiber: chopped glass fiber, ECS10-4.5-568H, China Jushi Co., Ltd.; (C) Phosphorus-based flame retardant: aluminum diethylphosphite, OP1420, BASF; (D) Flame retardant synergists: D-1, tetradecanoic acid, CAS: 821-38-5, commercially available; D-2, dodecadecanoic acid, CAS: 693-23-2, commercially available; (E) Lubricant: A-C540A, Honeywell; (F) Compatibilizers: F-1, glycidyl methacrylate grafted POE (POE-g-GMA), SOG-03, Jia Yi Rong Polymer (Shanghai) Co., Ltd.; F-2, maleic anhydride (MAH) grafted POE (POE-g-MAH), FB521A, Jia Yi Rong Polymer (Shanghai) Co., Ltd. (G) Antioxidants: G-1, primary antioxidant, IRGANOX 1098, BASF; G-2, secondary antioxidant, IRGANOX 168, BASF.

[0033] Example 1 The PA66 composite material of this embodiment is prepared from 53.7 parts PA66 resin, 30 parts glass fiber, 15 parts phosphorus-based flame retardant, 0.5 parts flame retardant synergist, 0.5 parts lubricant, and 0.3 parts antioxidant. The preparation steps of the above PA66 composite material are as follows: S1: Weigh all component raw materials according to the formula weight; S2: Add all components except glass fiber to a high-speed mixer and mix evenly to obtain a premix. The mixing speed is 500 rpm / min and the time is 5 min. S3: The premixed material is added from the main feed port of the twin-screw extruder, and glass fiber is added from the side feed port. After melt blending, extrusion, cooling, pelletizing, and drying, the composite material is obtained. The main feed speed of the twin-screw extruder is 400 rpm / min, and the side feed speed is 180 rpm / min. The temperatures of each extrusion zone of the twin-screw extruder are: Zone 1 240~255 ℃, Zone 2 245~255 ℃, Zones 3 to 7 265~280 ℃, Zones 8 to 9 240~260 ℃, Zones 10 to 11 230~250 ℃, and the die head 265~280 ℃.

[0034] Examples 2-4, Comparative Examples 1-6 The weight proportions of each component are different from those in Example 1, but the preparation method is the same as in Example 1. The specific weight components are shown in Table 1.

[0035] Performance testing Flame retardant performance: Flame retardant performance was tested according to the UL94 test standard using a standard sample with a thickness of 1.6 mm. Compared to the tracking index (CTI): the test sample size was set at 60 mm × 60 mm × 3 mm, and the test was carried out in accordance with the IEC 60112 standard. The electrolyte used was an anhydrous ammonium chloride solution with a mass fraction of 0.1%.

[0036] Table 1. Raw material weight parts and performance test results for Examples 1-4 and Comparative Examples 1-6

[0037] Based on Examples 1 and 2 and Comparative Example 1, it can be seen that the addition of a long-chain hydrophobic additive to PA66 material improves the CTI of the sample. This is because the addition of the hydrophobic additive repels the electrolyte on the material surface, thereby increasing the CTI of PA66 material.

[0038] Combining Examples 1 and 2 with Comparative Example 6, it can be seen that the addition of different types of long-chain hydrophobic additives to PA66 materials resulted in varying degrees of improvement in the CTI (Chip-to-Isolation Temperature) of the samples. This is because different long-chain hydrophobic additives have different effects on the hydrophobicity of the material, and therefore different degrees of repulsion against electrolytes on the material surface, leading to different effects on the CTI of PA66 materials. In general, the longer the carbon chain of the hydrophobic additive, the higher the hydrophobicity, and the higher the CTI value of the PA66 material.

[0039] It should be noted that the CTI test uses 25V as a increment, and the test results can only reflect discrete increment values ​​such as 625V, 650V, and 675V. Therefore, Comparative Example 6, which uses a mixture of 14C and 12C additives, has better hydrophobic properties than Example 2 (pure 12C additives), but it does not reach the threshold of the next increment of 650V. According to the standard, it is still classified as the 625V increment. Therefore, the actual CTI value measured in Comparative Example 6 is the same as that in Example 2.

[0040] Combining Example 1 and Comparative Examples 2 and 3, it can be seen that adding different proportions of the same long-chain hydrophobic additive to PA66 material resulted in varying degrees of improvement in the CTI (Chemical Temperature Index) of the samples. This is because the additive has a limited dispersion in the material, and therefore a limited effect on improving the hydrophobicity of the material.

[0041] Combining Examples 1, 3, and 4, it can be seen that the CTI (Chemical Intensity Tolerance) of the samples varies depending on the type of compatibilizer added to the hydrophobic PA66 material. This is because the groups in the compatibilizer have different reactivity and interaction with the amino and long-chain carboxyl groups of PA66. The epoxy group in the GMA molecule can undergo a rapid ring-opening addition reaction with the carboxyl group, thereby binding with the amino / carboxyl group, while the anhydride in MAH only reacts with the amino group and has no direct stable reaction with the carboxyl group.

[0042] Combining Example 1 and Comparative Example 4, it can be seen that as the glass fiber content decreases and the PA66 content increases, the flame retardant rating of the composite material decreases from V0 to V1, and the CTI decreases to 525.

[0043] Based on Examples 1, 2-3, and 5, it can be seen that hydrophobic long-chain additives need to work synergistically with an appropriate amount of phosphorus-based flame retardants to achieve the flame retardant effect.

[0044] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A high CTI halogen-free flame-retardant PA66 composite material, characterized in that, By weight, it includes the following ingredients: 52-64 parts of PA66 resin, 20-30 parts glass fiber 12-15 parts of phosphorus-based flame retardant 0.5-1.5 parts of flame retardant synergist. Lubricant 0.3-0.7 parts, Antioxidant 0.1-0.5 parts, The flame retardant synergist is an aliphatic dicarboxylic acid with ≥8 carbon atoms.

2. The composite material according to claim 1, characterized in that, The aliphatic dicarboxylic acid has 10 to 18 carbon atoms.

3. The composite material according to claim 2, characterized in that, The aliphatic dicarboxylic acid is at least one of dodecanoic acid and tetradecanoic acid.

4. The composite material according to claim 1, characterized in that, The ratio of the phosphorus-based flame retardant to the flame retardant synergist is 15:(0.5-1.5).

5. The composite material according to claim 1, characterized in that, It also includes 0.5-1.0 parts of compatibilizer.

6. The composite material according to claim 5, characterized in that, The compatibilizer is at least one of POE grafted with maleic anhydride, POE grafted with glycidyl methacrylate, and styrene-acrylonitrile grafted with GMA.

7. The composite material according to claim 1, characterized in that, The amount of glass fiber used is 28-30 parts.

8. The composite material according to claim 1, wherein the phosphorus-based flame retardant is at least one selected from diethylaluminum hypophosphite, triphenyl phosphate, 1,3-phenylene phosphate (2,6-tolyl) tetraester, and bisphenol A-bis(diphenyl phosphate).

9. A method for preparing a composite material as described in any one of claims 1-8, characterized in that, Includes the following steps: S1: Weigh each raw material according to the formula weight parts; S2: Mix all components except glass fiber evenly to obtain a premix; S3: The premix obtained in step S2 is added from the main feed port of the twin-screw extruder, and glass fiber is added from the side feed port. After melt blending, extrusion, cooling, pelletizing and drying, the composite material is obtained.

10. The method according to claim 9, characterized in that, The mixing speed in step S2 is 500 rpm / min, and the mixing time is 3-5 min; the main feed speed of the twin-screw extruder in step S3 is 400 rpm / min, and the side feed speed is 180 rpm / min; the temperatures of each extrusion zone of the twin-screw extruder in step S3 are: zone 1 240~255 ℃, zone 2 245~255 ℃, zones 3 to 7 265~280 ℃, zones 8 to 9 240~260 ℃, zones 10 to 11 230~250 ℃, and the die head 265~280 ℃.

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