Halogen-free flame-retardant nylon 6 material for electronic connector as well as preparation method and application of halogen-free flame-retardant nylon 6 material

Abstract

The invention discloses a halogen-free flame-retardant nylon 6 material for an electronic connector as well as a preparation method and application of the halogen-free flame-retardant nylon 6 material. The material is prepared from PA6 resin, and the modified PA6 material also contains melamine cyanurate and a flame-retardant synergist, the flame retardant synergist comprises nano-scale antimony trioxide and hollow glass beads; the melamine cyanurate is melamine cyanurate prepared by a semi-dry method, and the particle size of the melamine cyanurate is 1.1-1.5 [mu] m; the intrinsic viscosity of the PA6 resin is 2.2 to 2.6. The flame-retardant synergistic effect of the melamine cyanurate MCA, the nanoscale antimony trioxide and the hollow glass beads is achieved, meanwhile, the melamine cyanurate prepared through a semi-dry method is selected, the particle size of the melamine cyanurate is controlled to range from 1.1 micrometers to 1.5 micrometers, and therefore the modified PA6 material can have the excellent flame-retardant performance, mechanical performance and electrical performance at the same time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, in particular to a halogen-free flame-retardant nylon 6 material for electronic connectors and a preparation method and application thereof. BACKGROUND

[0002] As one of the most widely used engineering plastics, nylon 6 (PA6) is often used as a functional part of automobiles, machinery and electronic and electrical products. Although nylon 6 has certain self-extinguishing properties, it is still flammable (oxygen index 24%) and melts and drips during combustion, and in special environments such as live work, there are hidden dangers such as electric leakage, short circuit, electric arc and electric spark, and once a fire occurs, the consequences are unpredictable, so it is a major trend in the industry to prepare polyamides with excellent flame retardance.

[0003] Halogen-containing flame retardants have good effects but poor electrical properties, and when used in electrical equipment, they can easily cause short circuits, and when halogen-containing flame retardants are used, a large amount of toxic smoke is generated during the combustion of nylon 6 materials, causing secondary disasters in production and application, and also causing negative effects on the human body and the environment. Red phosphorus flame-retardant nylon has a large performance weakening and color limitation.

[0004] Melamine cyanurate (MCA) is a polymer that relies on hydrogen bonds and is very stable at 300℃, begins to sublimate at around 350℃ but does not undergo main decomposition, and at 430℃-450℃, a large amount of endothermic decomposition occurs, releasing non-combustible gas and forming carbon, thereby achieving flame retardation. It is a high-efficiency additive-type flame retardant for nylon, and its itself and decomposition products are low in toxicity. However, at present, it is often added to PA66 on the market, and the PA66 material modified by flame retardance is used as an electronic connector material, but the price of PA66 is significantly higher than that of PA6, resulting in an increase in material cost. In addition, the gas-phase flame-retardant mechanism is easy to cause a large amount of melt dripping during the combustion of the base material, causing secondary combustion, that is, the flame retardance of the material needs to be improved.

[0005] If it is added to PA6 in order to reduce the cost, it is found that the flame retardance is not enough, and the electrical and mechanical properties of the PA6 material need to be further improved in order to be applicable to the field of electronic connectors. SUMMARY

[0006] In view of the shortcomings and deficiencies of the prior art, the present application provides an improved halogen-free flame-retardant nylon 6 material. The halogen-free flame-retardant nylon 6 material has excellent flame retardance, electrical properties and mechanical properties, and is low in cost, and can be used in the field of electronic connectors.

[0007] To achieve the above-mentioned purposes, the technical scheme adopted by the present application is as follows: The application discloses a modified PA6 material for electronic connectors, which comprises a PA6 resin, and further comprises melamine cyanurate and a flame-retardant synergist; the flame-retardant synergist comprises nano-sized antimony trioxide and hollow glass microbeads; the melamine cyanurate is semi-dry prepared melamine cyanurate with a particle size of 1.1-1.5 microns; and the PA6 resin has a characteristic viscosity of 2.2-2.6.

[0008] In some embodiments, the hollow glass microbeads have a particle size of 20-100 microns.

[0009] In some embodiments, the nano-sized antimony trioxide has a particle size of 30-50 nanometers.

[0010] In some embodiments, the PA6 resin has a melt index of 30-60 g / 10 min at 235 DEG C / 2.16 kg. The PA6 resin with the melt index in the range is used as a base resin, the flowability of the base material is improved, the flame retardant MCA and the flame-retardant synergist are fully dispersed, and thus a better flame-retardant effect is achieved.

[0011] In some embodiments, the modified PA6 material comprises 6-10% of the melamine cyanurate, 0.4-1.5% of the nano-sized antimony trioxide and 0.5-2.5% of the hollow glass microbeads by weight percentage.

[0012] In some embodiments, the modified PA6 material further comprises at least one of a nucleating agent, a coupling agent, an antioxidant and a lubricant.

[0013] In some embodiments, the modified PA6 material further comprises a nucleating agent, a coupling agent, an antioxidant and a lubricant.

[0014] In some embodiments, the modified PA6 material comprises 85-95% of the PA6 resin, 6-10% of the melamine cyanurate, 0.4-1.5% of the nano-sized antimony trioxide, 0.5-2.5% of the hollow glass microbeads, 0.1-0.5% of the nucleating agent, 0.2-1.0% of the coupling agent, 0.1-1.0% of the antioxidant and 0.1-1.0% of the lubricant by weight percentage, and the sum of the weight percentages of all components is 100%.

[0015] In some embodiments, the nucleating agent is at least one of sodium benzoate, nano-sized silicon dioxide and sodium phenylphosphinate. When the nucleating agent is sodium benzoate, the flame-retardant stability and the mechanical properties of the material can be further improved with a very small amount of addition.

[0016] In some embodiments, the coupling agent is selected from at least one of an amine group-containing silane coupling agent, an epoxy group-containing silane coupling agent, and an ethylene agent silane coupling agent.

[0017] In some embodiments, the coupling agent is at least one of KH-550, KH-560, KH-792, and A-171.

[0018] In some embodiments, the antioxidant is one or both of antioxidant 1010 and antioxidant 168; preferably, the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 at a mass ratio of 1:1.

[0019] In some embodiments, the lubricant is a combination of one or more of stearic acid, a stearate, and ethylene bis-stearamide.

[0020] In some embodiments, the modified PA6 material has a UL94 flame retardancy of V0 level, a tracking resistance passing 525V level, a tensile strength of 70-80 MPa, a bending strength of 98-110 MPa, a bending modulus of 2800-3100 MPa, and a notched impact strength of 6.7-8 kJ / m 2 . It can be seen that the modified PA6 material of the present application can simultaneously have excellent flame retardant performance, electrical performance, and mechanical performance.

[0021] Preferably, the modified PA6 material has a tracking resistance passing 600V level.

[0022] The present application also provides a preparation method of the modified PA6 material for electronic connectors as described above, which comprises the following steps: 1) mixing the PA6 resin and the coupling agent to obtain a first mixture; 2) mixing the remaining raw materials and adding them to the first mixture to obtain a second mixture; and 3) extruding and granulating the second mixture to obtain the modified PA6 material for electronic connectors.

[0023] Further, the extrusion is performed in a twin-screw extruder.

[0024] The present application also provides the use of the modified PA6 material for electronic connectors as described above for electronic connectors.

[0025] Compared with the prior art, the present application has the following advantages: 1) The modified PA6 material of the present application has excellent flame retardant performance, electrical performance, and mechanical performance, and is low in cost, and can be used in the field of electronic connectors.

[0026] 2) Compared with traditional flame-retardant PA66 materials, the present application uses PA6, which is more cost-effective, as the base resin, thereby reducing the cost of the material.

[0027] 3) The application can make the modified PA6 material have excellent flame retardant performance, mechanical properties and electrical properties by the flame retardant synergistic effect of melamine cyanurate MCA and nano-sized antimony trioxide, hollow glass microspheres, and by selecting the semi-dry method to prepare the melamine cyanurate and controlling the particle size of the melamine cyanurate to 1.1-1.5 μm.

[0028] 4) The hollow glass microspheres as the flame retardant synergistic agent have a hollow inside and are filled with inert gas, which can prevent high-voltage breakdown, improve the voltage resistance of the material, and improve the electrical properties of the material, so that the material can be used in the field of electronic connectors. DETAILED DESCRIPTION

[0029] In the flame retardation of nylon materials, halogen-containing flame retardants have good effect but poor electrical properties, and are easy to cause short circuit when used in electrical equipment. When halogen-containing flame retardants are used, a large amount of toxic smoke is generated during the combustion of nylon 6 material, which causes secondary disasters in production and application, and has negative effects on the human body and the environment. Red phosphorus flame-retardant nylon has a large performance weakening and color limitation. Melamine cyanurate (MCA) is more used in PA66 materials due to its low toxicity and decomposition products, but its flame retardant performance is not enough, and a large amount of molten droplets is generated during combustion, which is easy to cause secondary combustion. In addition, PA66 material is expensive and has high cost.

[0030] In the traditional MCA flame-retardant PA6 experiment, the molten droplets have high heat content, which directly ignites the dehydrated cotton during the combustion and dripping process in the form of flame dripping or in the form of non-flame dripping, and ignites the dehydrated cotton in the form of high heat. That is, the flame retardant performance cannot meet the requirements of electrical equipment, especially electronic connectors. In addition, the electrical properties of the material, such as voltage resistance and mechanical properties, need to be improved.

[0031] The present application produces a flame-retardant synergistic effect through melamine cyanurate MCA and nanoscale antimony trioxide, hollow glass microspheres, and improves the flame-retardant performance of the modified material together, and can guarantee the mechanical properties and electrical properties at the same time. When MCA is added alone, the combustion product of the modified PA6 material is a fluffy structure, the surface is discontinuous, and there are a large number of cavities, which cannot achieve the role of a protective layer, and the addition of nanoscale antimony trioxide can catalyze the cracking of the PA6 resin matrix, so that the combustion product forms a dense carbon layer on the surface of the PA6 resin, and then the flame-retardant performance is improved. The resin matrix is converted from gas-phase flame retardation of MCA to condensed-phase flame retardation, promotes carbonization, avoids contact with air, and improves the flame-retardant performance. In addition, the hollow glass microspheres are hollow inside and filled with inert gas, which can be released during the combustion of the modified material, thereby diluting the oxygen concentration around the modified material, and further improving the flame-retardant performance of the modified material. The composite flame retardant composed of the three components makes the initial decomposition temperature of the PA6 material advance, and the combustion heat is uniformly released, so as not to cause a large combustion heat in a short time to cause a fire. And the addition of nanoscale antimony trioxide and hollow glass microspheres makes the modified material directly convert from depolymerization decomposition to carbonization decomposition when ignited, effectively inhibits combustion and dripping, and improves the comprehensive flame-retardant performance of the material.

[0032] In addition, the hollow glass microspheres are a kind of thin-walled closed spherical particles with hollow, low density, high temperature resistance, heat insulation, high electrical insulation strength and other excellent properties. Since the hollow glass microspheres have a uniform hollow structure and are filled with inert gas inside, the material has very excellent electrical properties, can prevent high-voltage breakdown, can achieve high electrical performance, and has a low cost.

[0033] The present application will be further described below in conjunction with examples. However, the present application is not limited to the following examples. The implementation conditions used in the examples can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are the conventional conditions in the industry. The technical features involved in each embodiment of the present application can be combined with each other as long as they do not conflict with each other.

[0034] Example 1 The present embodiment provides a modified nylon 6 material, the raw material composition of which is shown in Table 1, and the preparation method thereof is as follows: 1) According to the formula (mass fraction) in Table 1, first weigh each raw material, then put the PA6 chips and MCA into a 120℃ oven, and dry for 2 hours. After drying and cooling, add the raw material PA6 into a mixer, and treat with a coupling agent to make the surface contain polar functional groups. Then add antimony trioxide and hollow glass microspheres, and weigh the other raw material additives according to the formula proportion, and put them into a high-speed mixer for mixing; 2) The mixed material is granulated by a twin-screw extruder. The temperature settings for zones 1-10 are 200℃, 210℃, 230℃, 240℃, 245℃, 245℃, 245℃, 250℃, 250℃, and 260℃, respectively. The main screw speed is 360r / min, and the feed rate is 25kg / h. Nylon 6 material is finally obtained.

[0035] In Table 1, PA6 resins are: 1) Sumitomo 1013B resin (Japan): intrinsic viscosity is 2.4, melt index is 30-60 g / 10 min at 235℃ / 2.16 kg; 2) YH800 resin: intrinsic viscosity is 2.7, melt index is 15-29 g / 10 min at 235℃ / 2.16 kg. MCA: 1) Semi-dry MCA-15: Commercially available from Sichuan Fine Chemical Research Institute, prepared using a semi-dry method, particle size 1.1-1.5 μm; 2) Semi-dry MCA-10: Commercially available from Sichuan Fine Chemical Research Institute, prepared using a semi-dry method, particle size less than 1.1 μm; 3) Semi-dry MCA-25: Commercially available from Sichuan Fine Chemical Research Institute, prepared using a semi-dry method, particle size 1.5-1.8 μm; 4) Wet MCA-15: Commercially available from Shandong Taixing New Materials Co., Ltd., prepared using a wet method, particle size 1.1-1.5 μm.

[0036] Antimony trioxide (Sb₂O₃): 1) Nano-sized antimony trioxide: particle size 30-50 nm; 2) Ordinary antimony trioxide: micron-sized; Hollow glass microspheres: particle size 20-100 micrometers, commercially available from 3M; Solid glass microspheres: particle size 20-100 micrometers, commercially available from Sovitec.

[0037] In Table 1, "-" indicates that the component is not present.

[0038] Examples 2-4 This embodiment provides a nylon 6 material, which is basically the same as that in embodiment 1, except that the raw material composition or dosage is different, as shown in Table 1 below.

[0039] Comparative Examples 1-6 This comparative example provides a comparative nylon 6 material, which is basically the same as Example 1, except that the raw material composition or dosage is different, as shown in Table 1 below.

[0040] In Comparative Example 1, the nylon 6 resin was replaced with YH800 resin instead of 1013B resin, i.e., nylon 6 resin with lower intrinsic viscosity was used as the matrix; in Comparative Example 2, the semi-dry MCA-15 was replaced with wet MCA-15, both with basically the same particle size but different preparation processes; in Comparative Example 3, the semi-dry MCA-15 was replaced with semi-dry MCA-10, i.e., semi-dry MCA with smaller particle size was used; in Comparative Example 4, the semi-dry MCA-15 was replaced with semi-dry MCA-25, i.e., semi-dry MCA with larger particle size was used; in Comparative Example 5, nano-sized Sb2O3 was replaced with micron-sized Sb2O3; in Comparative Example 6, hollow glass microspheres were replaced with solid glass microspheres; in Comparative Example 7, no Sb2O3 was added; and in Comparative Example 8, no hollow glass microspheres were added. The modified nylon 6 materials prepared in each embodiment and comparative example were subjected to performance tests. Specifically, the following tests were conducted: (1) Tensile strength and elongation at break tests: The samples were prepared by injection molding according to ISO527-2 standard.

[0041] (2) Bending strength and bending modulus test: The specimens were prepared by injection molding machine according to ISO178 standard.

[0042] (3) Cantilever beam notch impact test: The specimen was prepared by injection molding machine according to ISO180 standard.

[0043] (4) Tracking Ingress Test (CTI) of the material: Tested according to GB / T-2012, with a voltage level set every 25V. The solution is a 0.1% ammonium chloride solution.

[0044] (5) The flame retardant properties of the material were tested according to UL94. A vertical burning tester was used to apply two flames for 10 seconds to the bottom of the vertically placed sample (130mm×13mm×1.6mm), and the burning phenomenon was recorded. Five samples were tested in each group, and the average value was taken.

[0045] The results are shown in Table 2 below. As shown in Table 2, compared with Comparative Example 1, the modified nylon 6 material of Example 1 exhibits superior flame retardant and mechanical properties (Comparative Example 1 has a longer flame combustion time). This indicates that using the nylon 6 resin with the specific intrinsic viscosity of this invention as the matrix can improve the flame retardant and mechanical properties of the modified material. This is because the nylon 6 resin of this invention has a moderate intrinsic viscosity and better processing fluidity, allowing flame retardants such as MCA and antimony trioxide to be more uniformly dispersed in the resin matrix. This, in turn, improves the flame retardant performance and reduces stress concentration caused by the addition of flame retardants, resulting in better mechanical properties of the composite material.

[0046] Compared to Comparative Example 2, the modified nylon 6 material of Example 1 exhibits superior flame retardant properties, demonstrating that using the semi-dry MCA of this invention as the base flame retardant provides better flame retardant performance compared to using wet MCA. This is because semi-dry MCA primarily consists of plate-like or near-spherical MCA crystals, which have better heat resistance than other crystal forms. In other words, semi-dry MCA has better heat resistance than wet MCA, thus allowing it to exert superior flame retardant properties when added to nylon 6.

[0047] Compared with Comparative Examples 3-4, the modified nylon 6 material of Example 1 exhibits superior flame retardant properties, demonstrating that the semi-dry MCA with the specific particle size of this invention can achieve better flame retardant performance. This is because if the particle size of the MCA flame retardant is too small, it is difficult to disperse uniformly in the PA6 matrix resin and it is prone to agglomeration; conversely, if the particle size is too large, it is difficult to achieve sufficient compatibility with the resin material, both of which impair the flame retardant performance.

[0048] Compared to Comparative Example 5, the modified nylon 6 material in Example 1 exhibits superior flame retardant properties. This demonstrates that the use of nano-sized Sb₂O₃, compared to micron-sized Sb₂O₃, enables a more synergistic flame-retardant effect between antimony trioxide and MCA, resulting in superior flame retardant performance of the modified PA6 material. This is because the specific surface area of ​​nano-sized Sb₂O₃ (typically >30 m²) is significantly higher. 2 / g) is much larger than the micrometer scale (<5 m) 2 The surface area of ​​Sb2O3 is larger in the polymer matrix, which improves the efficiency of catalytic carbonization and gas-phase free radical capture by 3-5 times; while the specific surface area of ​​micron-sized Sb2O3 is smaller, and the catalytic carbonization effect is worse.

[0049] Compared to Comparative Example 6, the modified nylon 6 material of Example 1 exhibits superior flame retardant and electrical properties, demonstrating that the hollow glass microspheres of this invention, compared to solid glass microspheres, can significantly improve the flame retardant and electrical properties of the modified PA6 material. This is because the hollow glass microspheres are hollow and filled with an inert gas, which can be released during combustion of the modified material, thereby diluting the oxygen concentration around the material and further enhancing its flame retardant properties. Furthermore, the gaseous interior of the hollow glass microspheres results in poor electrical conductivity, leading to a higher voltage breakdown resistance level for the modified material. Therefore, the hollow glass microspheres and MCA have a synergistic flame retardant effect and simultaneously improve the tracking resistance of the modified material.

[0050] Compared to Comparative Examples 7-8, the modified nylon 6 material in Example 1 exhibits superior flame retardant properties, demonstrating a synergistic flame-retardant effect of the MCA, nano-antimony trioxide, and hollow glass microspheres in this application. When neither nano-antimony trioxide nor hollow glass microspheres are added, the flame retardant properties of the modified material are inferior to those with all three additives. This is because when MCA is added alone, the combustion products of the modified PA6 material have a loose structure, a discontinuous surface, and numerous voids, failing to provide a protective layer. However, the addition of nano-antimony trioxide catalyzes the decomposition of the PA6 resin matrix, resulting in a dense char layer formed on the PA6 resin surface from the gas-phase flame retardant properties of MCA, thus improving flame retardant performance. The resin matrix transforms from gas-phase flame retardancy (MCA) to condensed-phase flame retardancy, promoting char formation and preventing contact with air, thereby enhancing flame retardant performance. Hollow glass microspheres contain inert gases, which have a good synergistic effect during combustion. Furthermore, the hollow structure of the glass microspheres improves the voltage resistance of the material. Therefore, MCA, nano-sized antimony trioxide, and hollow glass microspheres can produce a synergistic effect in flame retardancy.

[0051] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention.

[0052] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A modified PA6 material for electronic connectors, comprising PA6 resin, characterized in that: The modified PA6 material also contains melamine cyanurate and a flame retardant synergist; the flame retardant synergist includes nano-sized antimony trioxide and hollow glass microspheres; the melamine cyanurate is melamine cyanurate prepared by a semi-dry method and has a particle size of 1.1-1.5 μm; the intrinsic viscosity of the PA6 resin is 2.2-2.

6.

2. The modified PA6 material for electronic connectors according to claim 1, characterized in that: The hollow glass microspheres have a particle size of 20-100 μm; and / or the nano-sized antimony trioxide has a particle size of 30-50 nm.

3. The modified PA6 material for electronic connectors according to claim 1, characterized in that: The melt flow index of the PA6 resin at 235℃ / 2.16kg is 30-60g / 10min.

4. The modified PA6 material for electronic connectors according to claim 1, characterized in that: By weight percentage, the modified PA6 material contains 6%-10% melamine cyanurate, 0.4%-1.5% nano-sized antimony trioxide, and 0.5%-2.5% hollow glass microspheres.

5. The modified PA6 material for electronic connectors according to claim 1, characterized in that: The modified PA6 material further includes at least one of a nucleating agent, a coupling agent, an antioxidant, and a lubricant; preferably, the modified PA6 material further includes a nucleating agent, a coupling agent, an antioxidant, and a lubricant.

6. The modified PA6 material for electronic connectors according to claim 5, characterized in that: By weight percentage, the modified PA6 material contains 85%-95% PA6 resin, 6%-10% melamine cyanurate, 0.4%-1.5% nano-sized antimony trioxide, 0.5%-2.5% hollow glass microspheres, 0.1%-0.5% nucleating agent, 0.2%-1.0% coupling agent, 0.1%-1.0% antioxidant, and 0.1%-1.0% lubricant, with the sum of the weight percentages of all components being 100%.

7. The modified PA6 material for electronic connectors according to claim 5, characterized in that: The nucleating agent is selected from at least one of sodium benzoate, nano silica, and sodium phenyl hypophosphite; and / or, the coupling agent is selected from at least one of amine-containing silane coupling agents, epoxy-containing silane coupling agents, and ethylene-containing silane coupling agents; and / or, the antioxidant is selected from one or two of antioxidant 1010 and antioxidant 168; preferably, the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1; and / or, the lubricant is selected from one or more combinations of stearic acid, stearate, and ethylene bis-stearamide.

8. The modified PA6 material for electronic connectors according to claim 1, characterized in that: The modified PA6 material has a UL94 flame retardancy rating of V0, a ​​tracking resistance rating of 525V, a tensile strength of 70-80 MPa, a flexural strength of 98-110 MPa, a flexural modulus of 2800-3100 MPa, and a notched impact strength of 6.7-8 kJ / m. 2 .

9. The method for preparing the modified PA6 material for electronic connectors according to any one of claims 1-8, characterized in that: The preparation method includes the following steps: 1) mixing the PA6 resin and coupling agent to obtain a first mixture; 2) mixing the remaining raw materials and adding them to the first mixture to obtain a second mixture; 3) extruding and granulating the second mixture to obtain the modified PA6 material for electronic connectors.

10. Use of the modified PA6 material for electronic connectors according to any one of claims 1-8 in electronic connectors.

Images