Polyamide composite material, preparation method therefor, and use thereof

Abstract

Disclosed in the present application is a MCA flame-retardant black polyamide composite material capable of high-definition laser marking, which comprises the following components in parts by weight: 50-74 parts of a nylon resin, 20-40 parts of glass fibers, 5-13 parts of a MCA flame retardant, 0.1-0.5 part of carbon black, 0.2-0.6 part of a lubricant, and 0-0.5 part of an antioxidant, the nylon resin being one or two of PA6 and PA66 of which the relative viscosity is 2.0-2.4, and the average particle size of MCA being 5-10 μm. The present application applies the low-viscosity nylon resin, thus ensuring excellent processing flowability; by means of selecting the components in the formula, the problem of non-uniform dispersion during combination use of MCA and carbon black is solved, thus reducing the adverse effect on carbon black dispersity caused by the lubricating effect of MCA, and improving the flame retardance and high CTI performance of the material. Therefore, the present application achieves better high-definition black-on-white laser marking performance while keeping good flame retardance and high CTI. In addition, the present application does not need adding an expensive laser marking agent, graphene and the like for achieving the high-definition black-on-white laser marking and therefore has a low cost.

Description

Polyamide composite material and its preparation method and application

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 29, 2023, with application number 202311851347.2, and invention name “MCA flame-retardant black polyamide composite material capable of high-definition laser marking, its preparation method and application”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention belongs to the field of polymer compositions and relates to a polyamide composite material and a preparation method and application thereof, and specifically relates to a polyamide composite material, an MCA flame-retardant black polyamide composite material capable of high-definition laser marking and a preparation method and application thereof. Background Art

[0003] Polyamide composites are high-performance materials made by adding composite materials such as carbon fiber, glass fiber, and aramid fiber to a polyamide matrix resin. Polyamide composites offer excellent properties such as high strength, high stiffness, low density, corrosion resistance, and heat resistance, and are widely used in aerospace, automotive, electronics, and pharmaceutical industries.

[0004] With the advancement of science and technology, the performance requirements for polyamide composite materials are constantly increasing. This requires increasing the filling amount of the composite material to improve the mechanical properties of the material, reduce the water absorption of nylon to improve the material size and performance stability, and obtain high heat resistance and other properties. However, high filling will lead to a decrease in the flame retardant performance of the material. Conventional nitrogen-based flame retardants (halogen-free flame retardants) cannot achieve higher glow wire flammability index (GWFI) requirements, such as passing 960°C. In order to improve the flame retardant performance, the amount of MCA flame retardant must be further increased. On the one hand, this makes the MCA flame retardant more likely to precipitate. On the other hand, due to the increase in the proportion of flame retardants, the proportion of other components is relatively reduced, thereby reducing other performance of the product.

[0005] Meanwhile, melamine cyanurate (MCA) flame-retardant polyamide composites offer excellent mechanical properties, high flame retardancy, low smoke density, and a comparative tracking index (CTI) of up to 600V. They are widely used in low-voltage electrical appliances, electronics, and home appliances. In particular, low-voltage electrical appliances and 5G applications require laser marking capabilities for their housings.

[0006] Laser marking is a new type of marking technology that uses computer control and has the advantages of fast marking speed, easy operation, environmental protection, and low production cost. It mainly uses a high-energy-density light beam to irradiate the surface of the target object, causing it to undergo physical or chemical changes, thereby obtaining visible text, graphics, symbols, barcodes, or images. At present, halogen-free flame-retardant polyamide composite materials are mainly marked using ultraviolet laser marking machines. Among them, black nitrogen-phosphorus flame-retardant polyamide materials can be used in the 5G1U circuit breaker field due to their good laser marking performance. However, nitrogen-phosphorus flame retardants are expensive, and there is a need for more economical and affordable materials to replace them in the market. MCA is a white crystalline solid, a nitrogen-containing halogen-free environmentally friendly flame retardant, and can also be used as a solid lubricant. It has the advantages of low toxicity, low smoke, and low cost. However, when used in carbon black-modified polyamide composite materials, the marking effect has problems such as yellowing or unclear marking, which limits its application.

[0007] Existing technologies offer two approaches to improving marking performance: graphene masterbatch and high-viscosity resin. However, the graphene masterbatch approach fails to disclose its impact on CTI, and graphene is expensive, leading to high industrial production costs. Some approaches using high-viscosity resins, such as those with relative viscosities of 2.8 or 3.2, fail to demonstrate the flame retardancy of the composite material. Some require the addition of flame retardant synergists and laser marking additives to achieve the claimed improved marking performance. However, high-viscosity resins can lead to poor system fluidity and severe surface fibrillation during injection molding. The addition of other flame retardant synergists and laser marking additives also leads to high composite material costs. Summary of the Invention

[0008] The present invention aims to improve the flame retardancy and precipitation problems under the existing high-filling conditions and provides a polyamide composite material, which is specifically achieved through the following technical solutions:

[0009] The polyamide composite material comprises the following components in parts by weight:

[0010] The average particle size of the MCA is 6 to 10 μm.

[0011] The present applicant unexpectedly discovered that by using MCA with a large average particle size, the flame retardant properties of the material can be reduced while the amount of MCA added is not affected.

[0012] Optionally, the nylon resin is selected from one or more of PA6, PA66, PA6 / 66 or PA66 / 6 with a relative viscosity of 2.0 to 2.5.

[0013] Optionally, the content of the glass fiber is 30 to 40 parts, or 25 to 35 parts, specifically 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 40 parts by weight.

[0014] Optionally, the content of the MCA flame retardant is 6 to 10 parts by weight. Further, the content of the MCA flame retardant is 7 to 10 parts by weight. Specifically, it can be 5, 6, 7, 8, 9, 10, 11, 12, or 13 parts.

[0015] Optionally, the polyamide composite material comprises the following components in parts by weight:

[0016] Optionally, the polyamide composite material comprises the following components in parts by weight:

[0017] Optionally, the sum of the glass fiber and mineral powder is ≤45 parts.

[0018] Optionally, the glass fiber is alkali-free glass fiber.

[0019] Optionally, the lubricant includes one or more of ethylene bisstearamide, calcium stearate, and modified ethylene bisstearamide.

[0020] Optionally, the antioxidant includes one or more of hindered phenols and phosphites.

[0021] Optionally, the antioxidant is a mixture of antioxidant S 9228 and antioxidant 1098 in a mass ratio of 1:1 to 1:3.

[0022] Optionally, the polyamide composite material further comprises 0.02-0.1 parts by weight of a pigment.

[0023] Optionally, the pigment includes one or more of ultramarine blue, cobalt blue, and phthalocyanine blue. As a complementary colorant, the blue pigment can neutralize the yellowing and reddening of the laser marking caused by thermal discoloration of the resin, making the marking tend to be whiter.

[0024] Optionally, the blue pigment is a composite pigment with a mass ratio of ultramarine blue to phthalocyanine blue of 1:1 to 1:3. The composite pigment can further improve the material's resistance to high-temperature yellowing during processing.

[0025] Optionally, the mineral powder includes one or more of talc, ground glass fiber, glass beads, wollastonite, mica, kaolin, and montmorillonite.

[0026] The present application also provides a method for preparing the composite material, comprising the steps of:

[0027] A: First, melt and shear the components except MCA through a screw extruder to obtain a pre-dispersed system;

[0028] B: MCA was added to the pre-dispersed system and sheared and blended by a screw extruder to obtain a well-dispersed composite melt.

[0029] The above preparation method of the present application greatly reduces the precipitation problem of the MCA flame retardant and does not require the addition of an anti-precipitation additive.

[0030] On the other hand, under normal circumstances, in order to better disperse the flame retardant MCA, improve the flame retardant properties of the material, and reduce the amount of flame retardant MCA required to meet the flame retardant requirements, it is preferred to add MCA and other components together to the screw extruder to prepare the composite material. However, the applicant unexpectedly discovered that: MCA has a lubricating effect. After adding the MCA flame retardant, it will reduce the shearing degree of the glass fiber, making the glass fiber retained in the system longer, which in turn leads to a decrease in flame retardant properties. At the same time, the dispersion of the glass fiber is reduced in uniformity due to lubrication, which will make the flame retardant of the product unstable. The special preparation method of this application will not affect the shearing of the glass fiber. The length of the glass fiber in the final material is shorter, the dispersion is more uniform, and the flame retardant properties are more stable.

[0031] Optionally, in the blending step: step A and step B are respectively operated at the main feeding port and the side feeding port of the same screw extruder.

[0032] Optionally, in the blending step: step A and step B are respectively performed in different screw extruders.

[0033] The present application also provides an application of any of the above-mentioned composite material technical solutions, which is used in laser marking black and white parts in the low-voltage electrical appliance field and 5G circuit breaker field.

[0034] Furthermore, the present application provides an application of the above-mentioned polyamide composite material in the manufacture of components in the field of low-voltage electrical appliances.

[0035] The present application adopts MCA with a large average particle size and can obtain considerable flame retardant properties by reducing its addition amount, while solving the flame retardant and precipitation problems caused by high filling, and has unexpected technical effects.

[0036] On the other hand, the present invention aims to solve the problem that the base color of existing MCA flame-retardant black nylon materials is not dark enough and the laser marking is yellow or unclear. It provides a nylon composite material with high clarity of black-on-white laser marking, high CTI, flame retardancy, mechanical properties, and processability, etc. This is achieved through the following technical solutions:

[0037] MCA flame retardant black polyamide composite material capable of high-definition laser marking, comprising the following components in parts by weight:

[0038] The nylon resin has a relative viscosity of 2.0 to 2.4 and is selected from one or both of PA6 and PA66; and the average particle size of the MCA is 6 to 10 μm.

[0039] Optionally, the content of the glass fiber is 20 to 40 parts by weight, further, the content of the glass fiber is 30 to 40 parts, specifically 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 40 parts.

[0040] Optionally, the content of the MCA flame retardant is 6 to 10 parts by weight. Further, the content of the MCA flame retardant is 7 to 10 parts by weight. Specifically, it can be 5, 6, 7, 8, 9, 10, 11, 12, or 13 parts.

[0041] Optionally, the MCA flame-retardant black polyamide composite material capable of high-definition laser marking comprises the following components in parts by weight:

[0042] The nylon resin has a relative viscosity of 2.0 to 2.4 and is selected from one or both of PA6 and PA66; the average particle size of the MCA is 5 to 10 μm, more preferably 6 to 10 μm.

[0043] Optionally, the following components are included in parts by weight:

[0044] Optionally, the following components are included in parts by weight:

[0045] Optionally, the sum of the glass fiber and mineral powder is ≤45 parts.

[0046] When MCA is used as a flame retardant, the smaller the average particle size (such as an average particle size or [D]50 of approximately 1 to 3 microns), the larger its specific surface area and the better the flame retardant effect. While still meeting higher flame retardant requirements, the amount used is reduced, thereby improving the processing precipitation problem caused by the addition of high amounts of MCA. Therefore, it is generally believed in the prior art that MCA with a small average particle size has better flame retardant and precipitation effects than MCA with a large average particle size, and is more preferred. However, during actual use, the applicant unexpectedly discovered that MCA also has a certain lubricating effect. Selecting conventional MCA with a small average particle size that has good flame retardancy will deteriorate the dispersion performance of carbon black, resulting in unstable background color; because carbon black is used as a laser marking additive, poor dispersibility will lead to poor overall marking effect; in addition, because carbon black is used as a black toner, poor dispersibility can easily make the final marking effect darker or other color deviation problems. The present application chose to use MCA with an average particle size of 6-10μm to solve the above problems.

[0047] On the other hand, the applicant unexpectedly discovered that, due to the lubricating effect of MCA, the addition of an MCA flame retardant reduces the shearing of glass fibers, resulting in longer glass fibers remaining in the system, which in turn reduces flame retardancy and causes uneven dispersion of the glass fibers. The applicant's side-feeding of MCA reduces the shearing effect on the glass fibers, resulting in shorter glass fibers in the final material, more even dispersion, and more stable flame retardancy.

[0048] Optionally, the ratio of the MCA flame retardant to carbon black is 15:1 to 40:1.

[0049] Optionally, the glass fiber is alkali-free glass fiber.

[0050] Optionally, the carbon black is medium-high pigment carbon black, which can further improve the blackness of the background material and increase the blackness of the material.

[0051] Optionally, the lubricant includes one or more of ethylene bisstearamide, calcium stearate, and modified ethylene bisstearamide.

[0052] Optionally, the antioxidant includes one or more of hindered phenols and phosphites.

[0053] Optionally, the antioxidant is a mixture of antioxidant S 9228 and antioxidant 1098 in a mass ratio of 1:1 to 1:3.

[0054] Optionally, the mineral powder includes one or more of talc, ground glass fiber, glass beads, wollastonite, mica, kaolin, and montmorillonite.

[0055] Optionally, 0.02-0.1 parts by weight of pigment is also included.

[0056] Optionally, the pigment includes one or more of ultramarine blue, cobalt blue, and phthalocyanine blue. As a complementary colorant, the blue pigment can neutralize the yellowing and reddening of the laser marking caused by thermal discoloration of the resin, making the marking tend to be whiter.

[0057] Optionally, the blue pigment is a composite pigment with a mass ratio of ultramarine blue to phthalocyanine blue of 1:1 to 1:3, thereby further improving the material's resistance to high-temperature yellowing during processing.

[0058] The present application also provides a method for preparing any of the above composite material technical solutions, comprising the blending step:

[0059] A: First, melt and shear the components except MCA through a screw extruder to obtain a pre-dispersed system;

[0060] B: MCA was added to the pre-dispersed system and sheared and blended by a screw extruder to obtain a well-dispersed composite melt.

[0061] Optionally, in the blending step: step A and step B are respectively operated at the main feeding port and the side feeding port of the same screw extruder.

[0062] Optionally, in the blending step: step A and step B are respectively performed in different screw extruders.

[0063] The present application also provides an application of any of the above-mentioned composite material technical solutions, which is used in laser marking black and white parts in the low-voltage electrical appliance field and 5G circuit breaker field.

[0064] Compared to existing technologies, this application utilizes a low-viscosity nylon resin to ensure excellent processing fluidity. The selected formulation components improve the uneven dispersion problem that occurs when MCA and carbon black are used together, reducing the adverse effects of MCA's lubrication on carbon black dispersion and improving the material's flame retardancy and high CTI performance. This results in improved high-definition black-on-white laser marking performance while maintaining excellent flame retardancy and high CTI. This application eliminates the need for expensive laser marking agents, graphene, and other additives to achieve high-definition black-on-white laser marking, resulting in a low-cost solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] FIG1 is an optical microscope photograph of the shell surface of Example 1 ( FIG1 left) and Comparative Example 3 ( FIG1 right). DETAILED DESCRIPTION

[0066] The specific implementation methods of the present application are described in detail below through examples, but the specific implementation of the present application does not limit the technical solution of the present application. Any non-substantial changes such as replacing common technical solutions in the field with the technical solutions described in the examples of the present application are within the scope of protection of the present application.

[0067] The nylon resin in this application may include PA6 / 66 or PA66 / 6 in addition to PA6 and PA66.

[0068] In this application, PA6 / 66 is also called copolymerized polyamide 6, copolymerized nylon 6 resin, and polyamide 6 / 66, that is, it is formed by mixing and polymerizing PA6 monomers or prepolymers with PA66 monomers / prepolymers during the synthesis stage, among which the PA6 monomers or prepolymers account for a relatively high proportion.

[0069] PA66 / 6 is basically the same as it, except that the proportion of polymerized monomers or prepolymers in PA66 is relatively high.

[0070] In the following specific embodiments, the raw materials used are shown below, but this does not limit the source of the products.

[0071] PA6 / CSR / OS Guangdong Xinhui Meida Nylon Co., Ltd. Relative viscosity 1.8

[0072] PA6 / M2000 Guangdong Xinhui Meida Nylon Co., Ltd. Relative viscosity 2.0

[0073] PA6 / M2400 Guangdong Xinhui Meida Nylon Co., Ltd. Relative viscosity 2.4

[0074] PA6 / M2800 Guangdong Xinhui Meida Nylon Co., Ltd. Relative viscosity 2.8

[0075] PA6 / M3200 Guangdong Xinhui Meida Nylon Co., Ltd. Relative viscosity 3.2

[0076] PA66 / EPR24 Shenma Industrial Co., Ltd. Relative viscosity 2.4

[0077] PA6 / 66 Hangzhou Polyshun New Materials Co., Ltd. Relative viscosity 2.5

[0078] Glass Fiber 560A China Jushi Co., Ltd.

[0079] Milled glass fiber (glass fiber powder) 300 mesh Wuhu Chuangsumei New Material Technology Co., Ltd.

[0080] Flame retardant MCA-F Sichuan Fine Chemical Research and Design Institute Average particle size: 6-10 microns

[0081] Flame retardant MCA-12 Sichuan Fine Chemical Research and Design Institute Average particle size: 1-3 microns

[0082] Carbon Black BLACK PEARLS 800 American Cabot Corporation medium and high pigment carbon black

[0083] Antioxidant 1098 Tianjin Li'anlong New Materials Co., Ltd.

[0084] Antioxidant S9228 Dover Chemical, USA

[0085] Lubricant Calcium Stearate Hangzhou Oil and Fat Chemical Co., Ltd.

[0086] Ultramarine Blue 8008 Wenzhou Baise Fine Pigment Chemical Co., Ltd.

[0087] Phthalocyanine Blue K6907 BASF, Germany

[0088] The components and properties of the embodiments and comparative examples are shown in Table 1, Table 2 and Table 3, respectively. The units of each component in the table are parts by weight.

[0089] It should be noted that in each embodiment and comparative example, the antioxidants are 0.2 parts of 1098 and 0.2 parts of S9228, and the lubricant is 0.25 parts of calcium stearate. However, the scope of protection of this application is not limited thereto, and those skilled in the art can make routine adjustments as needed.

[0090] Preparation of resin composition:

[0091] Examples 1 to 12: including the blending step:

[0092] A: First, melt and shear-blend the components except MCA according to the specific examples through a screw extruder to obtain a pre-dispersed system. The pre-dispersed system herein includes a melt, plastic particles, or other processed stock or formed bodies, and does not substantially affect the melt components. B: MCA is added to the pre-dispersed system and shear-blended through a screw extruder to obtain a well-dispersed composite melt. Plastic particles are then prepared through extrusion, cooling, and granulation. Those skilled in the art may also choose to process the plastic particles into other finished or semi-finished products, such as stock or formed bodies, which are equivalent to plastic particles.

[0093] Specifically, in this embodiment, in the blending step: step A and step B are respectively performed in different screw extruders.

[0094] In other embodiments, step A and step B may also be performed at the main feeding port and the side feeding port of the same screw extruder, respectively.

[0095] In the above steps, the aspect ratio of the extruder is 50:1. Specifically, the main engine speed of the extruder is 400-450 rpm, and the temperature of each zone is set to: 40-60°C for zone 1, 210-230°C for zones 2-5, 200-220°C for zones 6-8, and 210-230°C for zones 9-10. Those skilled in the art can select a screw extruder with an aspect ratio in the range of (40:1) to (50:1) according to their needs.

[0096] It should be noted that the basic operations of melting, blending, and extrusion granulation are conventional means used by those skilled in the art in the plastic processing process. The screw combination and process can be set according to the components to be processed and there is no need to elaborate.

[0097] Comparative Example 4: All components were mixed uniformly according to the proportions of each component and added from the main feeding port of a screw extruder. MCA flame-retardant nylon composite material particles were obtained after melt blending and extrusion granulation.

[0098] In the above steps, the aspect ratio of the extruder is 50:1, the main engine speed of the extruder is 400-450 rpm, and the temperature of each zone is set as: 40-60°C for zone 1, 210-230°C for zones 2-5, 200-220°C for zones 6-8, and 210-230°C for zones 9-10.

[0099] Comparative Example 8: All components except carbon black were mixed uniformly according to the proportion of each component, added from the main feeding port of a twin-screw extruder, and a carbon black-free MCA flame-retardant nylon composite material was obtained after melt blending and extrusion granulation.

[0100] The dried particles of the carbon black-free MCA flame-retardant nylon composite material and the carbon black are respectively fed into the main feeding port of the twin-screw extruder, and are melt-blended and extruded into granules to obtain the MCA flame-retardant black nylon composite material.

[0101] In the above steps, the aspect ratio of the extruder is 50:1, the main engine speed of the extruder is 400-450 rpm, and the temperature of each zone is set as: 40-60°C for zone 1, 210-230°C for zones 2-5, 200-220°C for zones 6-8, and 210-230°C for zones 9-10.

[0102] The preparation methods of the remaining comparative examples refer to Examples 1 to 12.

[0103] The performance characterization and testing methods of composite materials are as follows:

[0104] Preparation of test specimens: The pellets of each embodiment and comparative example were dried in an oven at 110°C for 4 to 6 hours, and then injected into standard specimens according to the requirements of each standard at 255 to 265°C for laser marking and other related performance tests. Among them, the laser marking contrast and laser marking effect tests were performed by making laser-marked color plates to test the performance.

[0105] Mechanical properties: Tensile strength is tested according to ISO 527-1:2012 standard using a universal material testing machine; Simple supported beam unnotched impact strength is tested according to ISO179-1:2010 standard using an electronic impact testing machine;

[0106] Flame retardancy: Glow-wire flammability index (GWFI) is tested in accordance with IEC 60695-11-20:2015 standard, at a test temperature of 960°C using a glow-wire tester.

[0107] Electrical properties: Comparative tracking index (CTI) is tested according to IEC60112:2009 standard using a tracking tester;

[0108] Thermal properties: Heat deformation temperature (HDT) is tested in accordance with GB / T 1634.1-2019 standard using an automatic Vicat heat deformation tester;

[0109] Laser marking: The UV-3C ultraviolet laser marking machine of Han's Laser Technology Industry Matrix Co., Ltd. was used for laser marking tests, and the marking speed was 800 mm / sec.

[0110] Laser marking contrast ΔL: A Konica Minolta CM-36dG colorimeter was used to measure the color difference between the marked area (L2) and the unmarked area (L1). The contrast was calculated using ΔL = L2 - L1.

[0111] Laser marking effect: visual inspection, the grades are divided into excellent, good, yellowish, reddish yellow, and dark.

[0112] Appearance rating of injection molded products: The floating fibers on the surface of the color plate are observed under an optical microscope and can be divided into 4 grades: Grade 1 is a high appearance smoothness with no floating fibers and agglomeration; Grade 2 is a high appearance smoothness with a small amount of floating fibers but no agglomeration; Grade 3 is a general appearance smoothness with more floating fibers or a small amount of agglomeration; Grade 4 is a poor appearance smoothness with a large amount of floating fibers or a large amount of agglomeration.

[0113] Table 1 Components and properties of Examples 1 to 12

[0114] Table 2 Components and performance test data of Comparative Examples 1 to 13

[0115] The test results in Table 1 and Table 2 show that obtaining MCA flame retardant black polyamide material with excellent comprehensive performance is related to multiple factors.

[0116] Compared with Example 3, the low-viscosity PA6 component in Example 1 is reduced, and the appearance of the injection molded product is relatively poor.

[0117] Compared with Example 4, the viscosity of the nylon resin in Comparative Examples 1 to 3 has a greater impact on the material's impact resistance, flame retardancy, and the appearance of the injection molded product, laser marking effect, and other properties.

[0118] In Comparative Example 4, the MCA flame retardant was mixed and melt-extruded together. Compared with Example 1, the background color difference value was increased, and the laser marking effect was worse.

[0119] Comparative Example 5 uses a different particle size of MCA flame retardant. Compared with Example 1, the particle size is smaller and the laser marking effect is relatively poor.

[0120] In Comparative Example 8, compared with Example 1, carbon black is extruded separately in steps, and the dispersion of carbon black in the matrix is ​​poor, resulting in the matrix not being black enough and the laser marking being dark.

[0121] FIG1 is an optical microscope photograph of the shell surface of Example 1 ( FIG1 left) and Comparative Example 3 ( FIG1 right), which shows that the dispersion effect of the glass fiber in Example 1 is better than that in Comparative Example 3, that is, Example 1 has a good effect of improving the appearance of floating fibers.

[0122] In an MCA flame-retardant nylon system, under the specific preparation conditions of the examples, when used in conjunction with carbon black in a ratio of (15:1) to (40:1), the black nitrogen-based flame-retardant nylon composite material exhibited a laser marking contrast ΔL exceeding 42, demonstrating excellent overall performance. In Example 5, when the MCA content was 5 phr, the GWFI / 960°C standard could not be consistently passed. However, in some applications, achieving the GWFI / 960°C standard is not necessary and can be used normally.

[0123] The present application scheme gives it good processing performance and appearance performance to a certain extent. The composite material can be used in low-voltage electrical appliances, electrical and electronic equipment, home appliances and other fields.

[0124] Experimental data shows that low-viscosity nylon resins offer excellent fluidity, reducing fiber floating in the shell during injection molding. Using MCA with a larger particle size than those typically used in flame-retardant systems facilitates dispersion within the nylon resin matrix, resulting in better flame retardancy. For the same MCA content, larger particle sizes result in smaller specific surface areas. Similarly, for the same amount of carbon black, the base color of the part appears darker.

[0125] It should be noted that in conventional polyamide MCA flame retardant systems, the MCA particle size used is below 3 microns, with a large specific surface area and low cost.

[0126] Experimental data shows that the weight ratio of MCA is 6 to 10 parts. Too little MCA results in poor flame retardancy and failure to pass the 960°C / 1.5mm GWFI standard. Excessive addition affects the blackness of the nylon matrix. The amount of carbon black added significantly affects the matrix blackness and laser marking performance. Too little carbon black fails to achieve a satisfactory blackness, while too much carbon black results in unclear laser marking. A mixture of antioxidants S9228 and 1098 in a mass ratio of (1:1) to (1:3) can improve the material's resistance to high-temperature yellowing during processing, helping to address yellowing issues in finished products.

[0127] Examples 13 to 19

[0128] The blending steps include:

[0129] A: First, melt and shear-blend the components except MCA according to the specific examples through a screw extruder to obtain a pre-dispersed system. The pre-dispersed system herein includes a melt, plastic particles, or other processed stock or formed bodies, and does not substantially affect the melt components. B: MCA is added to the pre-dispersed system and shear-blended through a screw extruder to obtain a well-dispersed composite melt. Plastic particles are then prepared through extrusion, cooling, and granulation. Those skilled in the art may also choose to process the plastic particles into other finished or semi-finished products, such as stock or formed bodies, which are equivalent to plastic particles.

[0130] Specifically, in this embodiment, in the blending step: step A and step B are respectively performed at the main feeding port and the side feeding port of the same screw extruder.

[0131] In the above steps, the aspect ratio of the extruder is 50:1. Specifically, the main engine speed of the extruder is 400-450 rpm, and the temperature of each zone is set to: 40-60°C for zone 1, 210-230°C for zones 2-5, 200-220°C for zones 6-8, and 210-230°C for zones 9-10. Those skilled in the art can select a screw extruder with an aspect ratio in the range of (40:1) to (50:1) according to their needs.

[0132] It should be noted that the basic operations of melting, blending, and extrusion granulation are conventional means used by those skilled in the art in the plastic processing process. The screw combination and process can be set according to the components to be processed and there is no need to elaborate.

[0133] The preparation methods of Comparative Examples 14 and 15 refer to Comparative Example 4. The preparation methods of the remaining Comparative Examples refer to Examples 13 to 19.

[0134] The performance characterization and testing methods of the composite materials are the same as those of Examples 1 to 12.

[0135] Table 3 Components and properties of Examples 13 to 19 and Comparative Examples 14 to 17

[0136] The test results in Table 3 show that by using MCA with a large average particle size of 6 to 10 microns, the flame retardant properties of the material can be reduced while reducing the amount of MCA added. Specifically:

[0137] In Example 13, 40 parts of glass fiber were added. When 6 parts of MCA were added, the technical effect of GWFI / 960°C 1.0 mm pass was achieved, which was difficult for a person skilled in the art to predict.

[0138] In Example 15, with 40 phr of glass fiber and 5 phr of MCA, the material achieved a GWFI / 960°C 2.0mm pass. This was unexpected for those skilled in the art. Although it did not reach a GWFI / 960°C 1.0mm pass, it still met the requirements for some parts with relatively low requirements and fell within the high flame retardancy range.

[0139] In Examples 15 to 19, by compounding glass fiber and mineral powder, with the reinforcing filler added in an amount of up to 45 parts, and MCA added in an amount of 6 parts, the technical effect of GWFI / 960℃1.0mm passing can be achieved.

[0140] In Comparative Examples 14 and 15, due to limitations in their preparation methods, the technical effect of GWFI / 960°C 1.0 mm pass was not achieved with 40% glass fiber filling and 6 or 7 parts of MCA with an average particle size of 6-10 μm. This also reflects that conventional selections made by those skilled in the art cannot achieve the technical effect of this application, highlighting the unexpected technical effect of this application.

[0141] In Comparative Examples 16 and 17, 7 and 6 parts of MCA with a smaller average particle size were added to 40 and 30 parts of glass fiber filling, respectively. The technical effect of passing GWFI at 960°C at 1.0 mm was not achieved. Although the same preparation method as the examples of this application was used, the smaller the average particle size, the technical effect of the examples of this application was not achieved. This is contrary to the understanding of those skilled in the art: at the same amount of MCA, the smaller the average particle size, the greater the specific surface area, and the better the flame retardant effect. This application has unexpected technical effects.

Claims

1. Polyamide composite material, characterized in that, By weight parts, it includes the following components: The average particle size of the MCA is 6-10 μm.

2. The composite material according to claim 1, characterized in that, Comprising the following components by weight parts:

3. The composite material according to claim 1, characterized in that, Comprising the following components by weight parts:

4. MCA flame-retardant black polyamide composite material with high-definition laser marking, characterized in that, By weight parts, it includes the following components: The nylon resin is one or two of PA6 and PA66 with a relative viscosity of 2.0-2.4; the average particle size of the MCA is 6-10 μm.

5. The composite material according to claim 4, wherein, By weight parts, it includes the following components:

6. The composite material according to claim 5, characterized in that, By weight parts, it includes the following components:

7. The composite material according to any one of claims 4 to 6, characterized in that, The ratio of the MCA flame retardant to the carbon black is (15:1)-(40:1).

8. The composite material according to any one of claims 1 to 6, characterized in that The glass fiber is an alkali-free glass fiber.

9. The composite material according to any one of claims 4 to 6, characterized in that, The carbon black is a medium-high pigment carbon black.

10. The composite material according to any one of claims 1 to 6, characterized in that, The lubricant includes one or more of ethylene bisstearamide, calcium stearate, and ethylene bisstearamide modifier.

11. The composite material according to any one of claims 1 to 6, characterized in that, The antioxidant includes one or more of hindered phenols and phosphite esters.

12. The composite material according to any one of claims 1 to 6, characterized in that, The antioxidant is a mixture of antioxidant S 9228 and antioxidant 1098 with a mass ratio of 1:1-1:

3.

13. The composite material according to claim 3 or 6, characterized in that, The mineral powder includes one or several of talc powder, ground glass fiber, glass microspheres, wollastonite, mica, kaolin, and montmorillonite.

14. The composite material according to any one of claims 1 to 6, characterized in that, It also includes 0.02-0.1 parts by weight of pigment.

15. The composite material according to claim 14, wherein The pigment includes one or more of ultramarine blue, cobalt blue, and phthalocyanine blue.

16. A method for preparing the composite material according to any one of claims 1 to 15, characterized in that, It includes a blending step: A: First, melt and shear-blend the components except MCA according to the raw material components through a screw extruder to obtain a pre-dispersion system; B: Add MCA to the pre-dispersion system and shear-blend through a screw extruder to obtain a well-dispersed composite melt.

17. The preparation method according to claim 16, characterized in that, In the blending step: Step A and Step B are respectively operated at the main feeding port and the side feeding port of the same screw extruder.

18. The preparation method according to claim 16, characterized in that, In the blending step: Step A and Step B are respectively operated in different screw extruders.

19. Use of the composite material according to any one of claims 1 to 15, characterized in that, It is applied to laser marking black-on-white parts in the field of low-voltage electrical appliances and 5G circuit breakers.

20. Use of the composite material according to any one of claims 1 to 3, characterized in that, It is applied to parts in the field of low-voltage electrical appliances.

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