High-efficiency flame-retardant master batch for nylon 12 and preparation method thereof

Abstract

This invention discloses a high-efficiency flame-retardant masterbatch for nylon 12 and its preparation method. The masterbatch uses nylon 12 as the carrier resin, leveraging its low water absorption, low processing temperature, and excellent flexibility. Through a masterbatch process, the flame retardant is pre-dispersed in nylon 12, overcoming the problems of high processing temperature, high water absorption, insufficient flexibility, and dust pollution and uneven dispersion associated with direct blending processes in existing technologies. The flame-retardant masterbatch provided by this invention can achieve UL94 V-0 flame retardancy at a relatively low addition level, and exhibits good processing stability and surface quality, making it suitable for applications in wire and cable, automotive industry, electronics, 3D printing, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and particularly relates to a high-efficiency flame retardant masterbatch for nylon 12 and its preparation method. Background Technology

[0002] Nylon (polyamide, PA) is an important engineering plastic widely used in electronics, automotive, and rail transportation. Among them, Nylon 66 is currently the most commonly used base material for flame retardant modification, and the related technology is relatively mature.

[0003] Numerous patents have disclosed relevant solutions regarding the flame-retardant modification of nylon. For example, Chinese patent CN119432063A uses nylon 66 as a matrix, adds GF reinforcement, incorporates compound flame retardants and auxiliary flame retardants, and employs a direct blending process to prepare flame-retardant materials, thereby improving the product's flame-retardant performance and resistance to tracking. Chinese patent CN116426009A focuses on the surface treatment of the flame retardant, attempting to improve its compatibility with the nylon matrix to enhance flame-retardant efficiency. However, these solutions still reveal some problems in practical applications.

[0004] Nylon 66 has high water absorption and requires high processing temperatures, which can easily affect the stability of flame retardants. In addition, although the commonly used direct blending process is simple to operate, it has problems such as dust pollution and uneven powder dispersion, resulting in poor batch stability of downstream products.

[0005] To address the aforementioned issues, this invention selects Nylon 12 as the base resin for the flame-retardant masterbatch. Nylon 12 has low water absorption, requiring no strict drying before processing, and its processing temperature is approximately 50°C lower than that of Nylon 66, effectively preventing thermal degradation of the flame retardant at high temperatures. Furthermore, Nylon 12 itself exhibits good flexibility and excellent low-temperature impact resistance, making it more suitable for applications requiring high flexibility, such as cable sheathing and thin-walled components.

[0006] Based on the aforementioned characteristics of nylon 12, this invention uses it as a masterbatch carrier, pre-dispersing flame retardants in nylon 12 melt to prepare high-concentration flame retardant masterbatch, which can both leverage the processing advantages of nylon 12 and avoid the dust and dispersion problems caused by direct blending. Summary of the Invention

[0007] The present invention aims to overcome the problems of high processing temperature, high water absorption and insufficient flexibility of existing flame-retardant nylon materials, as well as the defects of dust pollution, uneven dispersion and unstable feeding in the direct blending process, and provides a high-efficiency flame-retardant masterbatch with nylon 12 as carrier and its preparation method.

[0008] In one aspect, the present invention provides a nylon 12 flame retardant masterbatch, comprising the following components by weight: 100 parts nylon 12; 20-100 parts flame retardant; 0.2-1.0 parts antioxidant; and 0.5-3 parts dispersant.

[0009] In a preferred embodiment, the flame retardant is selected from at least one of nitrogen-based (e.g., melamine cyanurate MCA), organic phosphinate-based (e.g., aluminum diethyl phosphinate AlPi), nitrogen-phosphorus-based (e.g., melamine polyphosphate MPP), phosphorus-based (e.g., red phosphorus masterbatch), or inorganic (e.g., magnesium hydroxide). Preferably, the flame retardant is MCA or AlPi, and more preferably, the flame retardant is a compound system of the two. MCA mainly achieves flame retardancy through condensed phase charring and heat removal by molten droplets, and is characterized by being non-toxic and producing low smoke; AlPi has a dual flame retardant effect of gas-phase free radical capture and condensed phase charring, has high thermal stability, and excellent compatibility with nylon 12. When the two are used in combination, a synergistic effect is formed in the flame retardant mechanism, which can achieve UL94 V-0 flame retardancy at a lower addition amount, while reducing the impact on the mechanical properties of nylon 12.

[0010] In a preferred embodiment, the antioxidant comprises a primary antioxidant and a secondary antioxidant. The primary antioxidant is selected from hindered phenols (such as antioxidants 1010, 1076, and 1098), and the secondary antioxidant is selected from phosphites (such as antioxidants 168, 626, and 9228). The primary antioxidant captures peroxide free radicals, and the secondary antioxidant decomposes hydroperoxides. The two work synergistically to inhibit the thermal oxidative degradation of nylon 12 during high-temperature processing. Preferably, the primary antioxidant is 0.1 to 0.5 parts, and the secondary antioxidant is 0.1 to 0.5 parts.

[0011] In a preferred embodiment, the dispersant is selected from one or more of modified ethylene bis-fatty acid amide (TAF), ethylene bis-stearamide (EBS), calcium stearate, polyethylene wax, and montan wax. This dispersant can reduce the interfacial tension between the flame retardant and the nylon 12 matrix, promote the uniform dispersion of the flame retardant during melt blending, prevent agglomeration, and simultaneously act as an internal lubricant, improving processing fluidity, reducing screw wear, and effectively preventing the flame retardant from precipitating on the product surface, thereby improving the batch stability of product surface quality and flame retardant performance.

[0012] In another aspect, this invention provides a method for preparing the above-mentioned high-efficiency flame-retardant masterbatch for nylon 12. This method is simple, efficient, and easy to scale up for production, and mainly includes the following steps:

[0013] (a) Dry the nylon 12 resin at 80~100℃ for 4~6 hours;

[0014] (b) Weigh nylon 12, flame retardant, antioxidant and dispersant precisely according to the established formula;

[0015] (c) The dried nylon 12 resin is fed into the main feed port of the twin-screw extruder, and the flame retardant, antioxidant and dispersant are added through the side feed.

[0016] (d) Melt blending, extrusion, cooling, and pelletizing are carried out in a melting temperature range of 160~200℃ and a screw speed of 50~200 rpm to obtain the Nylon 12 flame retardant masterbatch.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) In view of the problems of high processing temperature, high water absorption and insufficient flexibility of existing materials, the present invention selects nylon 12 as the matrix. Nylon 12 has low water absorption, does not require strict drying, and avoids flame retardant agglomeration or precipitation due to moisture; the processing temperature is about 50°C lower than that of nylon 66, which prevents thermal degradation of flame retardant; at the same time, nylon 12 has good flexibility, which overcomes the defects of existing materials that are too hard and brittle.

[0019] (2) To address the problems of dust pollution, uneven dispersion, and unstable feeding in the direct blending process, this invention adopts a masterbatch process to pre-disperse the flame retardant in nylon 12 to form granules. Downstream users do not need to contact the powder, eliminating dust pollution; after the flame retardant is pre-dispersed, the downstream processing uniformity is better, avoiding batch differences, bridging, material breakage, and surface precipitation.

[0020] (3) In view of the problem that the addition amount of a single flame retardant is large and affects the mechanical properties, the present invention adopts the MCA and AlPi compound system, and utilizes the synergistic effect of condensed phase char formation and gas phase free radical capture to achieve UL94 V-0 flame retardancy at a lower addition amount, thereby reducing the impact on the mechanical properties of nylon 12.

[0021] (4) In view of the problem that Nylon 12 is prone to thermal oxidation and degradation during high-temperature processing, the present invention adopts a main and auxiliary antioxidant synergistic system to inhibit the degradation reaction and ensure processing stability and storage stability; the dispersant reduces interfacial tension, promotes uniform dispersion of flame retardant, and improves processing fluidity. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and comparative experimental data. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. All other embodiments obtained 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.

[0023] Test methods

[0024] (1) UL94 vertical burning test: conducted according to UL94 standard, with a sample thickness of 1.6 mm;

[0025] (2) Tensile strength test: conducted in accordance with ASTM D638 standard;

[0026] (3) Elongation at break test: conducted in accordance with ASTM D638 standard;

[0027] (4) Surface quality evaluation: Visually observe whether there are white spots, exudates or roughness on the surface of the sample.

[0028] Comparative Example 1

[0029] After drying, Nylon 12 yielded product D-1. D-1 injection-molded samples were then tested. This sample contained no added flame retardants and served as a benchmark for comparing flame retardant performance. Testing showed that the 1.6mm thick sample achieved a UL94 flame retardant rating of HB, exhibiting severe dripping during combustion, rapid flame spread, and no obvious self-extinguishing phenomenon.

[0030] Comparative Example 2

[0031] 100 parts of nylon 12 resin, 30 parts of MCA, 0.3 parts of antioxidant 1010, 0.3 parts of antioxidant 168, and 1.5 parts of dispersant were granulated by twin-screw extrusion to obtain masterbatch D-2. D-2 was then blended with virgin nylon 12 at a 1:4 ratio and injection-molded samples were tested. Test results showed that the 1.6mm sample had a UL94 flame retardancy rating of V-2. After ignition, the flame self-extinguished within seconds, but a large amount of molten material dripped down, igniting the absorbent cotton below. No obvious precipitation was observed on the surface.

[0032] Comparative Example 3

[0033] Masterbatch D-3 was obtained by twin-screw extrusion granulation of 100 parts nylon 66 resin, 30 parts MCA, 20 parts AlPi, 0.3 parts antioxidant 1010, 0.3 parts antioxidant 168, and 1.5 parts dispersant. D-3 was then blended with virgin nylon 66 at a 1:4 ratio and injection-molded samples were tested. Test results showed that the 1.6mm sample had a UL94 flame retardancy rating of V-0, and the flame self-extinguished within 2 seconds after two ignitions, with no molten droplets igniting cotton. However, during processing, obvious white smoke appeared at the twin-screw exhaust port, the extruded strip was yellowish, the injection-molded sample surface was rough, the elongation at break was only 15%, and the sample was easily broken when bent.

[0034] Comparative Example 4

[0035] 100 parts of nylon 12 resin were directly mixed at high speed with 40 parts of MCA, 20 parts of AlPi, 0.3 parts of antioxidant 1010, 0.3 parts of antioxidant 168, and 1.5 parts of dispersant, and then injection molded to prepare a sample, designated D-4. Test results showed that bridging occurred at the injection port during the injection molding process, indicating unstable material feeding. Obvious white spots (flame retardant agglomeration) appeared on the surface of the product, with flame retardant enrichment in some areas. Flame retardant performance showed large batch-to-batch fluctuations; some samples in the same batch reached V-0 level, while others only reached V-2 level, with white powdery substances precipitating on the surface.

[0036] Example 1

[0037] Masterbatch MB-1 was obtained by twin-screw extrusion granulation of 100 parts nylon 12 resin, 40 parts MCA, 20 parts AlPi, 0.3 parts antioxidant 1010, 0.3 parts antioxidant 168, and 1.5 parts dispersant. MB-1 was then blended with virgin nylon 12 at a 1:4 ratio and injection-molded samples were tested. Test results: The 1.6mm sample achieved UL94 V-0 rating; the flame self-extinguished within 1-2 seconds after two ignitions, and no molten droplets ignited cotton. The processing was stable, smokeless, and the sample was milky white. The product surface was smooth with no exudation, tensile strength was 46 MPa, and elongation at break was 110%.

[0038] Example 2

[0039] Masterbatch MB-2 was obtained by twin-screw extrusion granulation of 100 parts nylon 12 resin, 50 parts MCA, 30 parts AlPi, 0.3 parts antioxidant 1076, 0.3 parts antioxidant 168, and 2 parts dispersant. MB-2 was then blended with virgin nylon 12 at a 1:4 ratio and injection-molded specimens were tested. Test results: The 0.8mm thin-walled specimen achieved UL94 V-0 rating; the flame self-extinguished immediately after two ignitions, with no dripping. Torque remained stable during processing, and there was no abnormal odor. The product exhibited good surface gloss, a tensile strength of 44MPa, and an elongation at break of 95%, making it suitable for thin-walled parts.

[0040] Example 3

[0041] Masterbatch MB-3 was obtained by twin-screw extrusion granulation of 100 parts nylon 12 resin, 70 parts MCA, 0.4 parts antioxidant 1010, 0.4 parts antioxidant 168, and 2 parts dispersant. MB-3 was then blended with virgin nylon 12 at a 1:4 ratio and injection-molded samples were tested. Test results: The 1.6mm sample achieved UL94 V-0 rating, exhibited rapid self-extinguishing flame, and showed no ignition from molten droplets. However, the higher MCA content resulted in slightly higher torque during processing and a slightly rougher surface on the sample. The tensile strength of the finished product was 47 MPa, the elongation at break was 105%, and there was no obvious surface exudation, but the cost was higher than the blended system.

[0042] Example 4

[0043] Masterbatch MB-4 was obtained by twin-screw extrusion granulation of 100 parts nylon 12 resin, 40 parts MCA, 20 parts AlPi, 0.3 parts antioxidant 1010, 0.3 parts antioxidant 168, 1.5 parts dispersant, 0.3 parts UV absorber UV-234, and 0.5 parts anti-dripping agent PTFE. MB-4 was then blended with virgin nylon 12 at a 1:4 ratio and injection-molded samples were tested. Test results: The 1.6mm sample achieved UL94V-0 rating, with no dripping and rapid self-extinguishing flame. After 500 hours of xenon lamp aging, the sample surface showed no significant discoloration, the flame retardancy rating remained V-0, and the tensile strength retention rate was over 90%. The addition of the anti-dripping agent prevented any melting dripping during combustion, making it suitable for electronic and electrical applications with strict dripping requirements.

[0044] D-1 none HB The flames spread rapidly and produced severe dripping. ＞200% good D-2 MCA 30 copies V-2 Self-extinguishing within seconds, molten droplets ignited the cotton. 125% good D-3 PA66+MCA / AlPi 50 servings V-0 Self-extinguishing in 2 seconds, no molten droplets 15% rough D-4 Direct blending, MCA / AlPi 60 parts V-2 (fluctuation) Significant batch variations, some with molten droplets 95% white spots, precipitation MB-1 MCA 40+AlPi 20 V-0 Self-extinguishing in 1-2 seconds, no molten droplets. 110% Smooth, no precipitation MB-2 MCA 50+AlPi 30 V-0 (0.8mm) Self-extinguishing immediately, no molten droplets. 95% smooth MB-3 MCA 70 V-0 Rapid self-extinguishing, no dripping. 100% Slightly rough MB-4 MCA 40 + AlPi 20 + Additives V-0 Rapid self-extinguishing without any molten droplets 108% Smooth, no precipitation

[0045] The test results from the above embodiments and comparative examples show that:

[0046] (1) Comparing Comparative Examples 1 to 3, it can be seen that although the flame retardancy rating of Nylon 12 as a carrier (Comparative Example 2) is lower than that of Nylon 66 as a carrier (Comparative Example 3), the Nylon 12 system maintains excellent flexibility (elongation at break 125% vs 15%), and there is no thermal degradation of the flame retardant during processing (no smoke, no yellowing of the strip). This shows that the low processing temperature advantage of Nylon 12 can indeed effectively protect the flame retardant from thermal degradation.

[0047] (2) Comparing Example 1 and Comparative Example 4, it can be seen that under the same flame retardant formulation, the masterbatch process (Example 1) has more stable flame retardant performance (V-0 level vs. V-2 level fluctuation), better surface quality (smooth and no precipitation vs. white spot precipitation), and smoother processing (no bridging) compared with the direct blending process (Comparative Example 4), which fully demonstrates the superiority of the masterbatch process.

[0048] (3) Comparing Example 1 and Comparative Example 3, it can be seen that, under the premise of achieving V-0 flame retardancy, the scheme of the present invention with nylon 12 as the carrier (Example 1) is far superior to the scheme with nylon 66 as the carrier in terms of flexibility (110% vs 15% elongation at break). At the same time, there is no problem of thermal degradation of flame retardant during processing, and the product color and surface quality are also significantly better.

[0049] (4) Comparing Example 1 and Example 3, it can be seen that the MCA / AlPi compound system (Example 1, 60 parts of total flame retardant) achieves the same V-0 flame retardant effect with a lower total addition amount than the single MCA system (Example 3, 70 parts of MCA), and has a smaller processing torque and better surface quality, which confirms the synergistic flame retardant effect between MCA and AlPi.

[0050] (5) Example 4 shows that by adding ultraviolet absorbers and anti-dripping agents on the basis of the present invention, the weather resistance and anti-dripping properties of the product can be further improved while maintaining excellent flame retardant and mechanical properties, thus expanding the application range of the product.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-efficiency flame-retardant masterbatch for nylon 12, characterized in that, By weight, it comprises the following components: 100 parts nylon 12; 20-100 parts flame retardant; 0.2-1.0 parts antioxidant; Dispersant 0.5 to 3 parts.

2. The high-efficiency flame-retardant masterbatch for nylon 12 according to claim 1, characterized in that, The flame retardant is selected from at least one of melamine cyanurate, aluminum diethylphosphinate, melamine polyphosphate, red phosphorus masterbatch, or magnesium hydroxide.

3. The high-efficiency flame-retardant masterbatch for nylon 12 according to claim 2, characterized in that, The flame retardant is a compound system of melamine cyanurate and aluminum diethylphosphonate, with a weight ratio of melamine cyanurate to aluminum diethylphosphonate of (1~5):(1~3).

4. The high-efficiency flame-retardant masterbatch for nylon 12 according to claim 1, characterized in that, The antioxidant includes a primary antioxidant and a secondary antioxidant. The primary antioxidant is selected from hindered phenolic antioxidants, and the secondary antioxidant is selected from phosphite antioxidants. The amount of the primary antioxidant is 0.1 to 0.5 parts, and the amount of the secondary antioxidant is 0.1 to 0.5 parts.

5. The high-efficiency flame-retardant masterbatch for nylon 12 according to claim 5, characterized in that, The primary antioxidant is selected from one or more of antioxidant 1010, antioxidant 1076, and antioxidant 1098; the secondary antioxidant is selected from one or more of antioxidant 168, antioxidant 626, and antioxidant 9228.

6. The high-efficiency flame-retardant masterbatch for nylon 12 according to claim 1, characterized in that, The dispersant is selected from one or more of the following: modified ethylene bis-fatty acid amide, ethylene bis-stearamide, calcium stearate, polyethylene wax, and montan wax.

7. A method for preparing a high-efficiency flame-retardant masterbatch for nylon 12 as described in any one of claims 1 to 6, characterized in that, Includes the following steps: a. Dry the nylon 12 resin at 80~100℃ for 4~6 hours; b. Accurately weigh Nylon 12, flame retardant, antioxidant, and dispersant according to the formula; c. The dried nylon 12 resin is fed into the main feed port of the twin-screw extruder, and the flame retardant, antioxidant and dispersant are added through the side feed. d. Melt blending, extrusion, cooling, and pelletizing are carried out at a melting temperature range of 160~200℃ and a screw speed of 50~200 rpm to obtain the Nylon 12 flame retardant masterbatch.

8. The preparation method according to claim 10, characterized in that, The length-to-diameter ratio of the twin-screw extruder described in step d is 36:1 to 48:

1.

9. The preparation method according to claim 10, characterized in that, The cooling method described in step d is water cooling, with the water temperature controlled at 20~40℃.

10. The preparation method according to claim 10, characterized in that, The pelletizing process described in step d uses air-cooled pelletizing, and the pellet size is controlled at 2~4 mm.