High-glowing halogen-free flame-retardant polyamide compositions

Abstract

The present application belongs to the field of polymer composition, and particularly relates to high glow-wire halogen-free flame-retardant polyamide composition. Disclosed is a high glow-wire halogen-free flame-retardant polyamide composition, comprising, by weight parts, polyamide resin 85-92 parts; MCA 8-15 parts; glow-wire improver 0.1-0.4 parts; other additives 0-5 parts; the chemical formula of the glow-wire improver is: M x (HPO4) y zH2O, wherein M is a group II, III main group and transition metal ion; x, y are integers greater than 0, and z is an integer greater than or equal to 0. Compared with the prior art, under the premise of taking MCA as the leading flame-retardant system, the special glow-wire improver only needs a small amount, and the flame-retardant mechanism of MCA contains promoting the rapid dripping of melt drops, taking away heat and self-extinguishing, so that the vertical combustion can be controlled at the UL94 V-0 level, and the glow-wire ignition temperature of the material can be further improved.

Description

Technical Field

[0001] This invention belongs to the field of polymer compositions, specifically relating to a high glow wire halogen-free flame-retardant polyamide composition. Background Technology

[0002] In recent years, fires caused by poor contact, overload, short circuit and overheating of polyamide plastic components inside electronic and electrical equipment have occurred frequently during use. Therefore, it is necessary to implement more stringent glow wire flame retardant standards, that is, the flame retardant performance of plastic parts used in electrical appliances that are left unattended for a long time must meet the UL94 V-0 level, and the material in contact with the glow wire must not ignite within 30 seconds or the burning time must be less than 5 seconds, that is, the GWIT (glow wire ignition temperature) is greater than 750℃.

[0003] Existing technologies for polyamide (also known as nylon) compositions that meet the GWIT 775℃ requirement primarily achieve this through brominated flame retardancy and partial nitrogen-phosphorus flame retardancy, relying on combustion to form a char layer that provides insulation and oxygen barrier properties, thus meeting the high glow wire ignition temperature requirement. However, the low CTI (relative tracking index) and halogen content of brominated flame-retardant polyamide compositions are increasingly limiting their application due to today's trends of demanding high electrical performance and stringent environmental requirements. While nitrogen-phosphorus flame-retardant polyamide compositions in halogen-free flame-retardant systems can also achieve GWIT 775℃ through further improvements in char formation performance, they require higher amounts of flame retardants, resulting in higher material costs.

[0004] Nitrogen-based MCA (melamine cyanurate) flame-retardant polyamide compositions are considered potential alternatives to unattended appliance materials due to their high CTI rating, cost-effectiveness, and environmental friendliness. However, MCA flame-retardant polyamide compositions typically only achieve a UL94 V-0 rating, failing to simultaneously meet the GWIT 775°C flame-retardant requirement. Alternatively, to simultaneously meet both UL94 V-0 and GWIT 775°C requirements, a high MCA content is added, but this leads to decreased mechanical properties and severe exudation during injection molding, necessitating the addition of specific additives to mitigate these adverse effects, resulting in complex formulations and increased costs. Summary of the Invention

[0005] To overcome one of the aforementioned problems in the prior art, the present invention aims to provide a halogen-free flame-retardant polyamide composition that can simultaneously meet UL94 V-0 rating and GWIT 775°C, using MCA as the dominant flame-retardant system. This is achieved through the following technical solution:

[0006] A high glow wire halogen-free flame-retardant polyamide composition, comprising, by weight:

[0007] 85-92 parts of polyamide resin;

[0008] 8-15 copies of MCA;

[0009] 0.1-0.4 parts of heat-enhancing wire agent;

[0010] Other auxiliary agents: 0-5 parts;

[0011] The chemical formula of the hot wire enhancer is: M x (HPO4) y •zH2O, where M is a group II or III main metal ion and a transition metal ion; x and y are integers greater than 0, and z is an integer greater than or equal to 0.

[0012] Optional, by weight, includes:

[0013] 90-92 parts of polyamide resin;

[0014] 8-10 copies of MCA;

[0015] 0.1-0.2 parts of heat-enhancing wire agent;

[0016] The other additives include dispersants, with 0.1 to 1 part of dispersant;

[0017] The MCA is a sheet-like MCA with a D50 size in the range of 0.2μm to 1.5μm, and the dispersant is one or more of spherical alumina, aluminum nitride, boron nitride, silicon dioxide, and titanium dioxide.

[0018] Optional, by weight, includes:

[0019] 85-88 parts of polyamide resin;

[0020] MCA 12-15 parts;

[0021] 0.2-0.4 parts of heat-enhancing wire agent;

[0022] The MCA is a rod-shaped MCA.

[0023] Optionally, the glow wire enhancer includes one or more of titanium hydrogen phosphate, calcium hydrogen phosphate, zirconium hydrogen phosphate, magnesium hydrogen phosphate, titanium hydrogen phosphate hydrate, calcium hydrogen phosphate hydrate, zirconium hydrogen phosphate hydrate, and magnesium hydrogen phosphate hydrate.

[0024] Optionally, the ratio of MCA to the glow wire enhancer is (50~80):1.

[0025] Optionally, the polyamide resin is selected from one or more of PA6, PA66, PA6 / 66 copolymer, PA46, PA610, PA612, and PA1010.

[0026] Optionally, the other additives may include one or more of antioxidants, lubricants, colorants, nucleating agents, toughening agents, light stabilizers, heat stabilizers, and fungicides.

[0027] Optionally, the average particle size of the dispersant is 10 nm to 200 nm.

[0028] Optionally, the dispersant is surface-treated with a coupling agent.

[0029] This application also provides a method for preparing a polyamide composition according to any of the foregoing embodiments, wherein the weighed components are mixed evenly, melt-extruded and granulated by a screw extruder to obtain a high glow wire halogen-free flame-retardant polyamide composition, wherein the screw barrel temperature of the screw extruder is 220-275°C and the screw speed is 300-450 rpm.

[0030] Compared with the prior art, the present invention, in a polyamide composition formulation that does not contain glass fiber, mineral powder or other reinforcing fillers, uses MCA as the dominant flame retardant system and adds M... x (HPO4) y • The glow wire enhancer of zH2O, the present invention requires only a very small amount of glow wire enhancer, combined with the flame retardant mechanism of MCA that promotes rapid dripping of molten droplets, removes heat and self-extinguishes, can achieve the goal of controlling vertical combustion at UL94 V-0 level, and further improve the glow wire ignition temperature of the material, thus obtaining a halogen-free flame retardant polyamide composition that can simultaneously meet UL94 V-0 level and GWIT 775℃.

[0031] This invention achieves UL94 V-0 rating and passes the GWIT 775°C test at a thickness of 0.8 mm. Some composition formulations can even meet the more challenging GWIT 775°C test at a thickness of 3.0 mm. Furthermore, only minor modifications to the original formulation are required, without affecting the original mechanical and processing flow properties of the composition.

[0032] The general formula added in this invention is M x (HPO4) y• The glow wire enhancer of zH2O forms a small amount of NP synergistic flame retardant effect with MCA, improving GWIT performance while maintaining the flame retardant rating of V-0. The possible mechanism is as follows: During combustion, MCA first decomposes and absorbs heat, producing a large amount of inert combustion gases, which lowers the surface temperature of the material and isolates oxygen from the combustible surface. At this time, special hydrogen phosphate metal salts begin to catalyze polymer crosslinking under the influence of heat, forming a viscous melt or a slightly foamed carbon layer, which isolates heat and combustible gases. Simultaneously, it can absorb some of the gases produced by MCA decomposition, forming a porous foamed carbon layer that coats the polymer surface, effectively isolating external heat from the internal polymer and slowing down the decomposition rate. The entire flame-retardant process still involves a rapid formation of molten droplets, and the special hydrogen phosphate metal salts exert a specific degree (weaker than conventional phosphates) of charring effect on the polyamide, having a smaller impact on the molten droplets. Furthermore, the molten droplets carry away a significant amount of heat, lowering the sample surface temperature and extending the time for the special hydrogen phosphate metal salts to decompose, cool, and promote polymer charring. This allows even a very small amount of the special hydrogen phosphate metal salts to pass the GWIT test conditions (a glow wire applied at a specific temperature for 30 seconds, with the flame extinguishing within 5 seconds). In other words, within the same timeframe, a lower temperature allows the small amount of the glow wire enhancer of this invention to remain effective for a longer period. Compared to other nitrogen-based flame-retardant systems that rely solely on gas-phase flame-retardant mechanisms, or nitrogen-phosphorus flame-retardant systems that use a large amount of phosphorus to enhance the glow wire ignition temperature through a combination of gas-phase flame retardancy and charring-promoting flame-retardant mechanisms, this invention uses less MCA and glow wire enhancer overall, resulting in lower cost and better performance. The synergistic effect of this invention's technology is significant.

[0033] In existing technologies, additives used in other systems such as metal phosphate salts and zinc borate to increase the glow wire ignition temperature are applied to MCA-based flame retardant compositions. However, because these additives have a rapid or good charring effect, they negatively impact the droplet formation and rapid dripping of the main flame retardant, MCA, reducing vertical combustion performance and ultimately making it difficult to simultaneously meet the requirements of UL94 V-0 and GWIT 775°C. In contrast, the present invention, with its specially selected hydrogen phosphate metal salt added in small quantities (in a specific ratio), has demonstrated through practical verification that it can enhance the glow wire effect without affecting vertical combustion performance. The specific selection of component combinations and dosages results in a significant improvement in technical performance.

[0034] Furthermore, when the compounding ratio of MCA and glow wire enhancer is (50~80):1, the dual flame retardant requirements of UL94V-0 (0.8mm) and GWIT 775℃ (0.8mm) can be met simultaneously (generally, adding flame retardants that enhance GWIT to the MCA system will reduce the vertical burning rating of the material from V-0 to V-2), which is more conducive to meeting the industry requirements for applying halogen-free flame retardant materials to thin-walled parts. Detailed Implementation

[0035] The specific implementation of this application is described in detail below through examples. However, the specific implementation of this application is not intended to limit the technical solution of this application. Any non-substantial changes, such as replacing common technical solutions in the field, using the technical solutions described in the embodiments of this application are within the protection scope of this application.

[0036] The raw materials used in the examples and comparative examples are all commercially available; unless otherwise specified, the reagents, methods and equipment used in this invention are conventional reagents, methods and equipment in this technical field.

[0037] All embodiments and comparative examples of this invention were prepared by the following method:

[0038] The weighed components are mixed evenly, melt-extruded and granulated by a screw extruder to obtain a high glow wire halogen-free flame-retardant polyamide composition. The screw barrel temperature of the screw extruder is 220-275℃ and the screw speed is 300-450rpm.

[0039] Test strips are prepared according to their respective standards.

[0040] The testing method is as follows:

[0041] Notched impact strength of simply supported beam (KJ / m) 2 Tested according to GB / T1043.1-2008 standard;

[0042] Flame retardancy rating: Standard UL94 test strips with thicknesses of 1.6mm, 0.8mm and 0.4mm were injection molded and tested according to UL94 standards;

[0043] GWIT (Glow Wire Ignition Temperature): Standard IEC 60695-2-13:2021 test strips with thicknesses of 0.8 mm and 3.0 mm were injection molded and tested according to the IEC 60695-2-13:2021 standard.

[0044] It's important to note that GWIT is different from GWFI; substances that improve GWFI cannot necessarily improve GWIT. Specifically: GWFI, or glow-wire flammability index, refers to the highest test temperature of a test sample of a specified thickness in three consecutive tests, and should meet one of the following conditions: (a) the flame or glow of the test sample extinguishes within 30 seconds after the glow wire is removed, and the packaging paper placed under the test sample does not ignite; (b) the test sample does not ignite. GWIT, or glow-wire ignition temperature, refers to the temperature that is 25K higher (30K higher for samples of a specified thickness between 900℃ and 960℃) than the highest temperature at the top of the glow wire that does not ignite in three consecutive tests.

[0045] Processing Exudation: The extent of MCA flame retardant exudation on the mold surface during processing is observed visually. Exudation is categorized as almost no exudation, slight exudation, and severe exudation. Note: 1) MCA exudation is common knowledge in the industry, and skilled personnel can easily evaluate the exudation situation visually; 2) It should be noted that processing exudation does not mean the product is unusable. However, as the amount of exudation increases, mold cleaning during processing becomes more frequent, reducing production efficiency to some extent and not meeting the ideal goals of current mainstream manufacturing companies. Nevertheless, it is still usable.

[0046] The raw materials used in the embodiments and comparative examples of this invention are as follows, but are not limited to these materials:

[0047] PA6 resin: Xinhui M2400;

[0048] PA66 resin: Shenma EPR27;

[0049] PA66 / 6 resin: Huafeng EP26CL;

[0050] Flake-shaped MCA: Jinan Taixing Fine Chemical Co., Ltd. HT-211 1μm;

[0051] Rod-shaped MCA: MCA-100 from Shandong Gaoqi New Material Technology Co., Ltd.;

[0052] Bromine-based flame retardant: Decabromodiphenyl ethane, Shandong Haiwang Chemical Co., Ltd. FR-102WE;

[0053] Bromine-based flame retardant synergist: Antimony trioxide (Sb2O3) 99.50 fine particles from Hunan Xikuangshan Shanxing Antimony Industry Import & Export Co., Ltd.

[0054] Nitrogen-phosphorus flame retardant: Aluminum diethylphosphonate, Zhejiang Xinhua Chemical Co., Ltd. XHPFR-1040;

[0055] Titanium hydrogen phosphate: CAS No. 13772-30-0, commercially available;

[0056] Calcium hydrogen phosphate: CAS No. 7757-93-9, commercially available;

[0057] Zirconium hydrogen phosphate: CAS No. 13772-29-7, commercially available;

[0058] Magnesium hydrogen phosphate hydrate: CAS No. 7782-75-4, commercially available;

[0059] Aluminum phosphate: CAS No. 7784-30-7, commercially available;

[0060] Zinc borate: CAS No. 10361-94-1, commercially available;

[0061] Hydrotalcite: CAS No. 11097-59-9, commercially available;

[0062] Spherical titanium dioxide: Brofos-TiO2-N50 50nm, developed by Bohuas Nanotechnology (Ningbo) Co., Ltd.

[0063] Antioxidant: Antioxidant 1098, commercially available;

[0064] Lubricant: Calcium stearate, commercially available.

[0065] The specific formulations and properties of the compositions in the examples and comparative examples are shown in Tables 1 and 2. In the tables, antioxidants and lubricants are components commonly used by those skilled in the art. The 0.2 parts antioxidant and 0.4 parts lubricant used in the formulations of the examples and comparative examples are not shown again.

[0066] Table 1. Formulations and properties of compositions in Examples 1-10

[0067]

[0068] Table 2. Formulations and properties of the compositions in Comparative Examples 1-14

[0069]

[0070] As can be seen from Tables 1 and 2, compared with Comparative Examples 2-4, adding commonly used glow wire enhancers such as aluminum phosphate, zinc borate, and hydrotalcite to the MCA flame retardant system in Example 1 or Comparative Examples 2-4 cannot increase the GWIT of the MCA flame retardant material to 800°C.

[0071] Compared with Comparative Example 5, Example 1 could not raise the GWIT of the material to 800°C even when compounded with bromine-based and nitrogen-phosphorus heat-increasing wire enhancers.

[0072] Compared with Comparative Example 6, when the amount of glow wire enhancer used in Comparative Example 6 was about 10 times that used in Example 1, GWIT could reach 775°C, but the flame retardancy rating of the composition decreased and could not reach UL94V-0 level with a thickness of 0.8 mm.

[0073] In Comparative Example 12, when 20 parts of MCA and 0.6 parts of titanium hydrogen phosphate were used in combination, a GWIT of 800℃ could be achieved. Although the material can meet the requirements in practical applications, the increased MCA content leads to more precipitates on the mold surface during injection molding, which will increase the frequency of mold cleaning, reduce processing efficiency, and increase the cost of the material system.

[0074] In Comparative Example 14, despite the use of a nitrogen-phosphorus flame retardant system and a large amount of titanium hydrogen phosphate glow wire enhancer, the vertical combustion rating and GWIT still failed to meet the requirements. This is likely due to differences in the carbonization rate or quality of titanium hydrogen phosphate compared to conventional aluminum phosphate. Structurally, the tetrahedral structure of phosphate and hydrogen phosphate differs, which is likely the main reason for the specific differences. Furthermore, hydrogen phosphate is more prone to condensation and dehydration than phosphate, which can further reduce the temperature.

[0075] Examples 2-10 present test data on the variations in the types and contents of resin, MCA, and glow wire improver. The glow wire improver has the technical effect of increasing the glow wire ignition temperature in the corresponding formulation system.

[0076] Comparative Example 1 is a blank control of low-content flake MCA without glow wire enhancer. Comparative Example 7 is experimental data of low-content spherical MCA without glow wire enhancer; the flame retardant rating cannot meet the 0.8mm V-0 requirement. Comparative Examples 8 and 9 are experimental data of commercially available bromine-antimony flame retardant systems with small and large amounts of glow wire enhancer, respectively. This shows that in the bromine-antimony flame retardant system, 5 parts of glow wire enhancer can achieve a GWIT of 800℃, while 0.5 parts of glow wire enhancer can only achieve a GWIT of 775℃.

[0077] Because MCA itself enhances glow wire quality, Comparative Example 10 achieved a flame retardant rating and GWIT 800℃ by adding a large amount of 30 parts of MCA; however, severe precipitation occurred during processing. Comparative Example 11, by reducing the MCA content, only achieved a flame retardant rating of 0.4mm V-2. Although the amount of glow wire enhancer was increased, GWIT 800℃ could not be achieved at a thickness of 3.0mm (the thicker the part, the more difficult it is to achieve GWIT; the thinner the part, the more difficult it is to achieve a flame retardant rating of V-0). Comparative Example 13 used diethylaluminum hypophosphite as the main flame retardant system, with a small amount of MCA as a nitrogen-phosphorus flame retardant system (charring flame retardant mechanism, different from the gas-phase and dripping flame retardant mechanisms of this application). In a formulation with a small amount of glow wire enhancer, both the flame retardant rating and GWIT performance were poor and could not meet the requirements.

[0078] It should be noted that the high glow wire halogen-free flame-retardant polyamide composition described in this invention does not contain glass fiber, mineral powder, or other reinforcing fillers. While glass fiber and other reinforcing fillers provide reinforcement, their "wick effect" makes it more difficult to achieve a UL94 flame retardancy rating of V-0, especially for parts or samples with a thickness of 0.8 mm or less. However, because glass fiber and mineral powder have better temperature resistance, GWIT typically achieves higher temperatures more easily.

[0079] It should be noted that the thicker the test strip, the more difficult it is to achieve the required GWIT temperature. Examples 1-10 of this invention can all meet the GWIT temperature requirement of 800℃ at a thickness of 3.0 mm.

[0080] It should be noted that in this invention, "high glow wire" refers to both the high glow wire ignition temperature and the high glow wire flammability index. As those skilled in the art know, the glow wire flammability index of MCA flame retardant itself is already high enough compared to other flame retardant systems, which is sufficient to meet current requirements.

[0081] It should be noted that the names and specific materials used in the above embodiments can be selected or replaced by those skilled in the art based on their needs, and this does not exceed the scope of protection of this application.

Claims

1. A halogen-free flame-retardant polyamide composition for high glow wire, characterized in that, By weight, it includes: 85-92 parts of polyamide resin; 8-15 copies of MCA; 0.1-0.4 parts of heat-enhancing wire agent; Other auxiliary agents: 0-5 parts; The chemical formula of the hot wire enhancer is: M x (HPO4) y •zH2O, where M is a group II or III main metal ion and a transition metal ion; x, y are integers greater than 0, and z is an integer greater than or equal to 0. The hot wire enhancer includes one or more of titanium hydrogen phosphate, calcium hydrogen phosphate, zirconium hydrogen phosphate, magnesium hydrogen phosphate, titanium hydrogen phosphate hydrate, calcium hydrogen phosphate hydrate, zirconium hydrogen phosphate hydrate, and magnesium hydrogen phosphate hydrate.

2. The polyamide composition according to claim 1, characterized in that, By weight, it includes: 90-92 parts of polyamide resin; 8-10 copies of MCA; 0.1-0.2 parts of heat-enhancing wire agent; The other additives include dispersants, with 0.1 to 1 part of dispersant; The MCA is a sheet-like MCA with a D50 size in the range of 0.2μm to 1.5μm, and the dispersant is one or more of spherical alumina, aluminum nitride, boron nitride, silicon dioxide, and titanium dioxide.

3. The polyamide composition according to claim 1, characterized in that, By weight, it includes: 85-88 parts of polyamide resin; MCA 12-15 parts; 0.2-0.4 parts of heat-enhancing wire agent; The MCA is a rod-shaped MCA.

4. The polyamide composition according to claim 3, characterized in that, The ratio of MCA to the hot wire enhancer is (50~80):

1.

5. The polyamide composition according to any one of claims 1 to 3, characterized in that, The polyamide resin is selected from one or more of PA6, PA66, PA6 / 66 copolymer, PA46, PA610, PA612, and PA1010.

6. The polyamide composition according to any one of claims 1 to 3, characterized in that, The other additives also include one or more of the following: antioxidants, lubricants, colorants, nucleating agents, toughening agents, light stabilizers, heat stabilizers, and mildew inhibitors.

7. The polyamide composition according to claim 2, characterized in that, The average particle size of the dispersant is 10 nm to 200 nm.

8. The polyamide composition according to claim 2, characterized in that, The dispersant is surface-treated with a coupling agent.

9. A method for preparing the polyamide composition according to any one of claims 1 to 8, characterized in that, The weighed components are mixed evenly, melt-extruded and granulated by a screw extruder to obtain a halogen-free flame-retardant polyamide composition. The screw barrel temperature of the screw extruder is 220-275℃ and the screw speed is 300-450rpm.

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