Polyamide composition as well as preparation method and application thereof

Abstract

The invention relates to a polyamide composition as well as a preparation method and application thereof. The polyamide composition comprises the following components: polyamide resin, biotite, an MCA flame retardant and carbon black. The polyamide composition disclosed by the invention is good in flame retardant property and is a material with high blackness, the whiteness of a laser marking area is high, and the contrast ratio of the laser marking area and an unmarked area is high; the method is very suitable for preparing workpieces, such as electric appliance shells, which have requirements on flame retardance and blackness and need to form marks through laser marking and require the marks to play a role of safety key identification.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and more specifically, to a polyamide composition, its preparation method, and its application. Background Technology

[0002] Polyamide resins possess excellent mechanical properties, barrier properties, heat resistance, abrasion resistance, and chemical corrosion resistance. Their composite materials are widely used in machinery manufacturing, household appliances, power tools, electronic appliances, and transportation.

[0003] Melamine cyanurate (MCA) has a high nitrogen content and decomposes upon heating to produce non-flammable gases such as NH3, H2O, N2, CO2, and H2NCN. These gases have endothermic, cooling, and diluting properties, and are commonly used as flame retardant modifiers for thermoplastic resins. Furthermore, due to its wide availability, MCA offers better cost-effectiveness compared to traditional bromine-antimony flame retardants and organophosphorus flame retardants, making it widely used in low-voltage electrical appliances, electronics, and household appliances.

[0004] Due to their crystallinity and water absorption properties, polyamide materials typically exhibit a matte finish. Adding MCA (methyl methacrylate), a white substance, further complicates achieving high-blackness flame-retardant nylon products. Furthermore, these products may require laser marking (e.g., appliance casings), necessitating a bright white marking area. However, current technology struggles to simultaneously achieve flame retardancy, high blackness, and laser marking: the addition of MCA hinders blackness enhancement, while increasing carbon black dosage typically improves it. However, excessive carbon black negatively impacts laser marking, resulting in marks that appear yellowish or darker with infrared laser marking, and in severe cases, carbonization and blackening, making it difficult to form white marks and resulting in poor marking quality. Furthermore, forming white markings only meets the general readability requirements. With the improvement of safety standards and regulations, a high contrast between the black casing and the white markings is required (i.e., a large difference between the L value of the marked area and the L value of the unmarked area) to meet the requirements of safety-critical markings (such as warnings). However, using only carbon black to achieve laser marking often results in a white marking, but it is still difficult to meet the high contrast requirement and thus cannot serve as a safety-critical marking.

[0005] Currently, there are no reports in the industry of simultaneously achieving the three effects of high blackness of MCA flame-retardant polyamide materials, easy formation of white marks by laser marking, and high contrast between the marked and unmarked areas. Summary of the Invention

[0006] The primary objective of this invention is to overcome the problems or defects existing in the current technology and to provide a polyamide composition.

[0007] A further object of the present invention is to provide a method for preparing the above-described polyamide composition.

[0008] A further object of the present invention is to provide the application of the above-described polyamide composition in the preparation of automotive parts.

[0009] The above-mentioned objective of this invention is achieved through the following technical solution:

[0010] A polyamide composition comprising the following components in parts by weight: 69-90 parts of polyamide resin, Biotite 1.8-5 parts, 6-10 parts of MCA flame retardant (melamine cyanurate), Carbon black 0.05~0.15 parts, The MCA flame retardant has an average particle size of 5~10μm, and the carbon black has an average particle size of 5~40nm.

[0011] To avoid issues such as noticeably yellowish, dark, or even carbonized markings on polyamide compositions during laser marking, the inventors of this invention controlled the amount of carbon black used within a certain range. However, within this range, the amount of carbon black was insufficient to cause the polyamide composition itself to be noticeably blackened.

[0012] The inventors of this invention discovered that by adding a certain amount of biotite and controlling the average particle size of carbon black within a certain range, the polyamide composition itself can achieve sufficient blackness. The laser-marked area of ​​the polyamide composition exhibits high whiteness and improves the contrast between the marked and unmarked areas. This is because: in this polyamide composition formulation, carbon black has a significantly higher light absorption effect than biotite. Laser marking primarily involves carbon black absorbing light and generating heat, causing the material to foam and form the marked area. Biotite, on the other hand, achieves material staining without significant light absorption and heat generation, thus preventing the marked area from becoming noticeably yellow, dark, or even carbonized, resulting in a high-white mark. Furthermore, the addition of biotite increases the difference in L-value between the marked and unmarked areas, leading to high contrast. Simultaneously, controlling the average particle size of carbon black within this range facilitates blackening the material, making laser marking easier to form white marks, and ensuring high contrast between the marked and unmarked areas. If the average particle size of carbon black is too large, all of the above properties of the material are detrimental.

[0013] To achieve flame-retardant properties, this invention also incorporates MCA flame retardant. The inventors discovered that controlling the average particle size of the MCA flame retardant within a certain range prevents agglomeration, thus allowing the polyamide composition to exhibit good flame-retardant properties. Furthermore, the MCA flame retardant within this average particle size range has a small specific surface area, preventing significant consumption of carbon black with a specific average particle size. This allows the polyamide composition to maintain good blackness and effectively foam during laser marking, resulting in a distinctly white appearance. It also ensures high contrast between the marked and unmarked areas of the polyamide composition.

[0014] The polyamide composition of the present invention has good flame retardant properties, is a material with high blackness, and is easy to form white marks by laser marking. Moreover, the contrast between the laser-marked area and the unmarked area is high, making it very suitable for manufacturing parts that require flame retardant properties and blackness, need to form marks by laser marking, and require the marks to play a key safety identification role, such as electrical appliance housings.

[0015] In this invention, polyamide resin is used as the main resin, and its mass fraction in the polyamide composition is more than 75%.

[0016] In this invention, the amount of polyamide resin can be 70, 72, 74, 76, 78, 80, 82, 84, 86, or 88 parts by weight, or any range formed by any two of the above values; the amount of biotite can be 1.8, 2.0, 2.2, 2.4, 2.8, 3.0, 3.2, 3.5, 3.8, 4.0, 4.2, 4.5, 4.8, or 5.0 parts by weight, or any range formed by any two of the above values; the amount of MCA flame retardant can be 6, 7, 8, 9, or 10 parts by weight, or any range formed by any two of the above values; and the amount of carbon black can be 0.05, 0.06, 0.08, 0.10, 0.12, or 0.15 parts by weight, or any range formed by any two of the above values.

[0017] Preferably, the polyamide resin is at least one of PA66, PA6, PA56, PA12, PA610 or PA1012.

[0018] Preferably, the relative viscosity of the polyamide resin is 2.0 to 4.0, for example, it can be 2.0, 2.2, 2.4, 2.5, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8 or 4.0, or any range formed by any two of the above values.

[0019] In this invention, the relative viscosity of the polyamide resin can be measured according to the standard GB / T 12006.1-2009 "Plastics Polyamide Part 1: Determination of Viscosity Number", with the test conditions being: 96% H2SO4 and a temperature of 25℃.

[0020] Preferably, the biotite has a mesh size of 1200-3500.

[0021] In this invention, the mesh size of biotite can be obtained by sieving through a sieve.

[0022] More preferably, the biotite has a mesh size of 2000-3000 mesh. Controlling it within this range results in a darker polyamide composition, higher whiteness in the laser-marked area, and higher contrast between the marked and unmarked areas.

[0023] Preferably, the biotite in the polyamide composition is 1.5% to 6.3% by mass; specifically, it can be 1.5%, 1.6%, 1.7%, 1.8%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 5.8%, 6.0%, 6.3%, or any range formed by any two of the above values.

[0024] More preferably, the biotite in the polyamide composition comprises 3.8% to 4.9% by mass. Controlling the biotite mass percentage within this range results in a higher contrast between the marked and unmarked areas of the polyamide composition.

[0025] Preferably, the whiteness value of the biotite is ≤28, specifically 24~28. The whiteness of the biotite can be measured according to GB / T23774-2009.

[0026] In this invention, the MCA flame retardant can be either commercially available or homemade.

[0027] Preferably, the process of making MCA flame retardant is as follows: cyanuric acid and melamine are mixed, reacted and nucleated in the presence of water at 50-60°C, and then kept at 85-105°C for 2-6 hours to obtain the MCA flame retardant.

[0028] More preferably, the mixing process involves adding a melamine solution to a cyanuric acid solution.

[0029] More preferably, the addition rate is ≤5 L / min, for example, it can be 1~5 L / min.

[0030] More preferably, the concentration of the melamine solution is 1-3 wt%; the concentration of the cyanuric acid solution is 1-3 wt%.

[0031] More preferably, the molar ratio of cyanuric acid to melamine is 1.01 to 1.05:1.

[0032] More preferably, after the heat preservation, a drying step is also included.

[0033] More preferably, the drying process is as follows: first, keep warm at 35~45℃ for 1~3 hours, then keep warm at 50~70℃ for 1~3 hours, and then keep warm at 75~95℃ for 0.5~2 hours.

[0034] In this invention, the average particle size of both MCA flame retardant and carbon black can be measured by a Darwin particle size analyzer. The specific operation method is as follows: take 1g of sample and add it to 500mL of ethanol solution (the volume ratio of water to ethanol is 1:1), disperse it by ultrasonic vibration to obtain a suspension, and then put the suspension into the Darwin particle size analyzer for testing.

[0035] In this invention, the average particle size of the MCA flame retardant can be 5.0, 5.1, 5.2, 6.0, 7.0, 8.0, 9.0, 9.8 or 10.0 μm, or any range formed by any two of the above values.

[0036] Preferably, the average particle size of the MCA flame retardant is 8~9.8μm. Controlling it within this range results in a darker polyamide composition, higher whiteness in the laser-marked area, and higher contrast between the marked and unmarked areas.

[0037] Preferably, the MCA flame retardant in the polyamide composition is 6% to 12% by mass, specifically 6%, 7%, 8%, 9%, 10%, 11%, 12%, or any two of the above values ​​within a range.

[0038] In this invention, the average particle size of carbon black can be 5, 6, 8, 10, 12, 15, 18, 20, 24, 28, 30, 32, 35, 38 or 40 nm, as well as any range formed by any two of the above values.

[0039] In this invention, the average particle size of the carbon black is 12-20 nm. By controlling it within this range, the whiteness of the laser-marked area of ​​the obtained polyamide composition is higher, and the contrast between the marked area and the unmarked area is also higher.

[0040] Preferably, the carbon black in the polyamide composition is 0.05% to 0.18% by mass; specifically, it can be 0.05%, 0.06%, 0.08%, 0.10%, 0.12%, 0.15%, 0.16%, 0.18%, or any range formed by any two of the above values.

[0041] Preferably, the mass percentage of carbon black relative to the MCA flame retardant is 0.5% to 2.5%; specifically, it can be 0.5%, 0.6%, 0.8%, 1.0%, 1.2%, 1.5%, 1.6%, 1.8%, 2.0%, 2.2%, 2.5%, or any range formed by any two of the above values.

[0042] Preferably, the polyamide composition further includes 0-2 parts of other additives.

[0043] More preferably, the other additives are at least one of antioxidants, lubricants, or nucleating agents.

[0044] More preferably, the antioxidant is at least one of a primary antioxidant or a secondary antioxidant.

[0045] More preferably, the primary antioxidant is at least one of hindered phenolic antioxidants, hindered amine antioxidants, or organosulfur antioxidants.

[0046] More preferably, the auxiliary antioxidant is at least one of phosphonates or disodium hydrogen phosphate.

[0047] More preferably, the lubricant is at least one of stearate lubricant, erucamide lubricant, or oleamide lubricant.

[0048] More preferably, the nucleating agent is at least one of talc, aromatic amide nucleating agents, and organophosphate nucleating agents.

[0049] The preparation method of the above polyamide composition includes the following steps: mixing the components, melt extruding, and granulating to obtain the polyamide composition.

[0050] Preferably, the temperature of the melt extrusion is 220~280℃; the screw length-to-diameter ratio of the extruder for the melt extrusion is 35~50:1, and the screw speed is 300~600r / min.

[0051] The application of the above-mentioned polyamide composition in the preparation of connectors, coil frames, electrical housings, switches, etc. is also within the scope of protection of this invention.

[0052] A polyamide component is made from the above-mentioned polyamide composition.

[0053] Preferably, the polyamide part includes an un-laser-marked area and a laser-marked area, wherein the L value of the un-laser-marked area is ≤27 and the L value of the laser-marked area is ≥61.

[0054] More preferably, the L value of the un-laser-marked area is 25~27, and the L value of the laser-marked area is 61~63.

[0055] More preferably, the difference between the L value of the laser-marked area and the L value of the unmarked area is ≥34, for example, it can be 34~38.

[0056] Compared with the prior art, the beneficial effects of the present invention are: The polyamide composition of the present invention has good flame retardant properties, is a material with high blackness, has high whiteness in the laser-marked area, and has high contrast between the laser-marked area and the unmarked area. It is very suitable for manufacturing parts that require flame retardant properties and blackness, need to form markings by laser marking, and require the markings to play a key safety identification role (such as warnings), such as electrical appliance housings. Detailed Implementation

[0057] To more clearly and completely describe the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Various changes can be made within the scope of the claims of the present invention.

[0058] The reagents used in the various embodiments and comparative examples of this invention are described below: Polyamide resin 1#: PA66 EP-158, relative viscosity 2.8, Huafeng Group Co., Ltd.; Polyamide resin #2: PA66 EPR24, relative viscosity 2.4, Shenma Industrial Co., Ltd.; Polyamide resin #3: PA6 HY-2500A, relative viscosity 2.5, Haiyang Technology Co., Ltd.; Biotite #1: 2000 mesh, Shijiazhuang Chenxing Industrial Co., Ltd.; Biotite #2: 1250 mesh, Lingshou County Tuolin Mineral Products Processing Plant; Biotite #3: 3000 mesh, Shijiazhuang Chenxing Industrial Co., Ltd.; MCA flame retardant #1: Homemade, process as follows: A cyanuric acid solution (2 wt%) was added to a high-pressure reactor, followed by a melamine solution (2 wt%) at a rate of ≤5 L / min. The molar ratio of cyanuric acid in the cyanuric acid solution to melamine in the melamine solution was 1.03:1. Using deionized water as the medium, nucleation was initiated at a reaction temperature of 55°C, then the temperature was raised to 105°C (T) and held for 4 hours (T t) to allow crystal growth. The mixture was then cooled to 30°C. The reactants were filtered, washed with deionized water, and filtered again. This process was repeated several times. The reactants were then subjected to step drying (drying at 40°C for 2 hours, then at 60°C for 2 hours, and finally at 80°C for 1 hour) to avoid rapid high-temperature drying that could cause particle cracking. Finally, the mixture was allowed to cool naturally to room temperature to obtain MCA flame retardant 1#, which has an average particle size of 8.0 μm. MCA flame retardant #2: self-made, the process differs from that of MCA flame retardant #1 in that: the temperature T is 85℃, the time t is 2 hours; the average particle size of MCA flame retardant #2 is 5.2μm; MCA flame retardant 3#: self-made, the process differs from MCA flame retardant 1# in that: time t is 6 hours; the average particle size of MCA flame retardant 3# is 9.6μm; MCA flame retardant 4#: self-made, the process differs from MCA flame retardant 1# in that: the temperature T is 75℃, the time t is 1.5 hours; the average particle size of MCA flame retardant 4# is 2.5μm; MCA flame retardant 5#: self-made, the process differs from that of MCA flame retardant 1# in that: the temperature T is 110℃, the time t is 7 hours; the average particle size of MCA flame retardant 5# is 12.5μm; MCA flame retardant A#: MCA-F, Sichuan Jingshida Technology Co., Ltd., with an average particle size of 7.5μm; Carbon Black 1#: CSX865, Cabot (China) Investment Co., Ltd., average particle size 19nm; Carbon Black #2: FW200, Evonik Degussa (China) Investment Co., Ltd., average particle size 13nm; Carbon black #3: #10, Mitsubishi Chemical Co., Ltd., average particle size 35nm; Carbon black #4: #25, Mitsubishi Chemical Co., Ltd., average particle size 47nm; Other adjuvant 1#: Antioxidant, N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine, commercially available; Unless otherwise specified, all components (e.g., other additives 1#) used in the parallel examples and comparative examples are the same commercially available products.

[0059] The polyamide compositions of the embodiments and comparative examples of the present invention were prepared by the following preparation method: (1) Weigh each component according to the proportion, put each component into a high-speed mixer, and mix them evenly to obtain a mixture; (2) The mixture is fed into a twin-screw extruder. The extruder temperature is set in the following order: 160℃, 240℃, 270℃, 265℃, 240℃, 230℃, 230℃, 240℃, 250℃, 270℃. The rotation speed is 400r / min and the screw length-to-diameter ratio is 40:1. The polyamide composition is obtained by melt extrusion and granulation.

[0060] The polyamide compositions provided in the embodiments and comparative examples of the present invention were subjected to performance testing according to the following test methods: 1) Blackness test: The injection molded sample size is a square plate of 60mm × 60mm × 2.0mm. The Lab value is measured using an X-Rite benchtop spectrophotometer, and the L value (L1) is recorded. 2) Flame retardancy rating test: conducted in accordance with UL 94 standard, with test strip dimensions of 125mm×13mm×1.6mm; 3) Whiteness test of laser marking area: Using an infrared laser marking machine (Han's EP-12), the marking current, marking frequency, marking step size and other parameters were adjusted to find the marking process with the highest whiteness of the polyamide composition of each embodiment and comparative example. The Lab value of the marking area (circle with a diameter of 30mm) was measured with an X-rite benchtop spectrophotometer, and the L value (L2) with the highest whiteness was recorded.

[0061] 4) Contrast: Calculate the difference between L2 and L1 above. L represents the contrast ratio; the larger the difference, the higher the contrast ratio.

[0062] Examples 1-14 Examples 1-14 provide a series of polyamide compositions, the formulations of which are shown in Tables 1 and 2.

[0063] Table 1. Formulations (parts by weight) for Examples 1-10

[0064] Table 2 Formulations (parts by weight) for Examples 11-14

[0065] Comparative Examples 1-6 Comparative Examples 1-6 provide a series of polyamide compositions, the formulations of which are shown in Table 3.

[0066] Table 3. Formulations (parts by weight) for Comparative Examples 1-6

[0067] The properties of the polyamide compositions of each embodiment and comparative example were determined according to the test methods mentioned above, and the test results are shown in Table 4.

[0068] Table 4 Performance test results of the polyamide compositions in each example and comparative example

[0069] As can be seen from Table 4: The polyamide compositions of Examples 1-14 all have a blackness of 27.0 or below, a flame retardancy rating of V-0, a maximum whiteness of 61.0 or above in the laser-marked area, and a difference of L value between the marked and unmarked areas of 34.0 or above. This indicates that the polyamide compositions of the present invention have good flame retardant properties, are high blackness materials, easily form white marks after laser marking, and have high contrast between the marked and unmarked areas.

[0070] The particle size of the MCA flame retardant added in Comparative Example 1 was too small, resulting in a large specific surface area of ​​the MCA flame retardant. This led to excessive consumption of carbon black by adsorption by the MCA flame retardant, resulting in insufficient blackness of the polyamide composition, as well as inconspicuous laser marking and foaming of the polyamide composition, low maximum whiteness, and poor white marking effect. Furthermore, the contrast between the marked and unmarked areas was low.

[0071] The particle size of the MCA flame retardant added in Comparative Example 2 was too large, which caused the polyamide composition to drip during the flame retardancy test, resulting in poor flame retardancy performance. Furthermore, the highest whiteness of the laser-marked area was lower than that of Examples 1, 6, and 7. In addition, the contrast between the marked and unmarked areas was not high.

[0072] The carbon black particles added in Comparative Example 3 were too large, resulting in the polyamide composition not being black enough. Although the laser-marked area had a certain degree of whiteness, the contrast between the marked and unmarked areas was not high.

[0073] Comparative Example 4 did not add biotite, resulting in the polyamide composition being insufficiently black. Although the highest whiteness of the laser-marked area was high, the contrast between the marked and unmarked areas was low.

[0074] The addition of too much carbon black in Comparative Example 5 resulted in a low maximum whiteness in the laser-marked area of ​​the polyamide composition. Although the polyamide composition itself (the unmarked area) had high blackness, the contrast between the marked and unmarked areas was very low.

[0075] Comparative Example 6 did not add biotite and added too much carbon black. Although the polyamide composition was black enough, the highest whiteness of the laser-marked area was low, and the contrast between the marked and unmarked areas was very low.

[0076] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A polyamide composition, characterized in that, The components include the following parts by weight: 69-90 parts of polyamide resin, Biotite 1.8-5 parts, 6-10 parts of MCA flame retardant, Carbon black 0.05~0.15 parts, The MCA flame retardant has an average particle size of 5~10μm, and the carbon black has an average particle size of 5~40nm.

2. The polyamide composition according to claim 1, characterized in that, The polyamide resin is at least one of PA66, PA6, PA56, PA12, PA610, or PA1012.

3. The polyamide composition according to claim 1, characterized in that, The relative viscosity of the polyamide resin is 2.0~4.

0.

4. The polyamide composition according to claim 1, characterized in that, The biotite has a mesh size of 1200-3500.

5. The polyamide composition according to claim 1, characterized in that, The biotite in the polyamide composition is 1.5% to 6.3% by mass.

6. The polyamide composition according to claim 1, characterized in that, The polyamide composition further includes 0-2 parts of other additives; preferably, the other additives are at least one of antioxidants, lubricants or nucleating agents.

7. A method for preparing the polyamide composition according to any one of claims 1 to 6, characterized in that, The process includes the following steps: mixing the components, melt extruding, and granulating to obtain the polyamide composition.

8. Use of the polyamide composition according to any one of claims 1 to 6 in the preparation of connectors, coil frames, electrical housings or switches.

9. A polyamide component, characterized in that, It is prepared from the polyamide composition according to any one of claims 1 to 6.

10. The polyamide part according to claim 9, characterized in that, The polyamide part has an unmarked area and a marked area, wherein the L value of the unmarked area is ≤27 and the L value of the marked area is ≥61.

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