A laser-weldable halogen-free flame-retardant polyamide composite material and its preparation method

Abstract

This invention relates to the field of polymer materials technology, and discloses a laser-weldable halogen-free flame-retardant polyamide composite material and its preparation method, comprising the following components: 35-65 parts of polyamide resin; 5-50 parts of reinforcing material; 5-30 parts of organophosphorus flame retardant; 3-15 parts of phosphate ester flame retardant; and 0.5-5 parts of nano-silica; wherein the particle size of the nano-silica is 5-60 nm. The halogen-free flame-retardant polyamide composite material provided by this invention simultaneously meets the requirements of laser weldability, high flame retardancy, and halogen-free nature, with a laser transmittance ≥28% (1 mm) and a flame-retardant thickness of 1.5 mm meeting the UL94V-0 rating.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a laser-weldable halogen-free flame-retardant polyamide composite material and its preparation method. Background Technology

[0002] Plastic laser welding technology utilizes the heat generated by a high-energy laser beam acting on the material to melt the plastic contact surfaces, thereby bonding molded parts together. Compared to traditional thermoforming, vibration friction welding, and ultrasonic welding processes, it offers significant advantages such as high precision, high efficiency, and low environmental pollution, making it particularly suitable for processing automotive plastic parts. Currently, the new energy vehicle industry is developing rapidly, and the demand for laser welding for components such as electronic component housings, pump bodies, valve bodies, and pipe joints is increasingly strong. Major companies in the industry are leading the shift from traditional welding methods to laser welding.

[0003] Polyamide (PA) materials possess excellent comprehensive properties and, after various functional modifications, are widely used in automotive parts, electronics, and special equipment. Among aliphatic polyamides, PA6 and PA66 are the two with the largest production volume and widest application range, accounting for over 60% of the total production capacity of all types of polyamides. Therefore, laser welding technology for PA6 and PA66 modified composite materials has been successfully applied in these fields. With the implementation of various regulations and increased emphasis on safety, the demand for flame-retardant materials is also increasing. Environmentally friendly halogen-free flame-retardant PA6 and PA66 materials are gaining wider application, with the phosphorus-nitrogen synergistic flame-retardant system being the most mature. However, with the addition of materials such as glass fiber and phosphorus-nitrogen halogen-free flame retardants, the laser transmittance of the composite material decreases sharply. If used as a light-transmitting layer material for laser welding, insufficient light transmittance will be a problem.

[0004] Existing technologies generally achieve laser welding capabilities for halogen-free flame-retardant reinforced materials by adding non-crystalline resins to reduce resin crystallization and improve material transmittance, and by adding specially shaped glass fibers to reduce the refractive index to lasers. For example, patent CN 115678217 obtained a laser-weldable halogen-free flame-retardant reinforced PBT material by adding non-crystalline resin PA6T / 6I and flat glass fibers. However, the non-crystalline resin PA6T / 6I in this solution is significantly more expensive than conventional resins and has a certain impact on the material's heat resistance. The price of flat glass fibers is several times higher than that of conventional glass fibers. These factors greatly limit the material's application range. Furthermore, research on laser welding of halogen-free flame-retardant reinforced PA6 or PA66 materials is rarely reported. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing halogen-free flame-retardant polyamide materials, and to improve the laser transmittance of the material while ensuring cost control and flame retardant performance, thereby providing a laser-weldable halogen-free flame-retardant polyamide composite material.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A laser-weldable halogen-free flame-retardant polyamide composite material, characterized in that, by weight, it comprises the following components:

[0008]

[0009] The particle size of the nano-silica is 5–60 nm.

[0010] The polyamide resin is selected from at least one of polyamide 6 and polyamide 66.

[0011] The glass fiber is an alkali-free glass fiber with a single filament diameter of 8–13 μm.

[0012] The organophosphorus flame retardant is aluminum diethylphosphonate.

[0013] The phosphate ester flame retardant is hydroquinone bis(diphenyl phosphate).

[0014] Preferably, the particle size of the nano-silica is 5–30 nm.

[0015] More preferably, the laser-weldable halogen-free flame-retardant polyamide composite material comprises, by weight, the following components:

[0016]

[0017] The halogen-free flame-retardant polyamide composite material of the present invention can be supplemented with other components according to actual needs. The components may include, but are not limited to, one or a mixture of several of the following: lubricant, release agent, toughening agent, antioxidant, heat stabilizer, light stabilizer, ultraviolet absorber, antistatic agent and coupling agent.

[0018] The present invention also provides a method for preparing the composite material, comprising the following steps: producing the composite material by melt blending extrusion process, using a twin-screw extruder, adding polyamide resin, some or all of glass fiber, organophosphorus flame retardant, phosphate ester flame retardant, nano silica and other processing aids in proportion from the main feed port, adding the remaining glass fiber from the side feed port, and then extruding, cooling and granulating the composite material after melt blending.

[0019] The present invention has the following beneficial effects:

[0020] This invention replaces the nitrogen-based flame retardant in the traditional phosphorus-nitrogen synergistic system by introducing a composition of hydroquinone bis(diphenyl phosphate) and nano-silica with a particle size of 5-60 nm, forming a new synergistic flame retardant system with organophosphorus flame retardants. Hydroquinone bis(diphenyl phosphate) is a solid phosphate ester flame retardant with high transparency and good laser transmittance. Unlike liquid phosphate esters, it does not have a significant plasticizing effect on the material, thus having minimal impact on the material's temperature resistance. Nano-silica can solidify the char layer during the material's combustion process, improving the char layer's strength and further enhancing its ability to block heat transfer and combustible gas exchange. On the other hand, the presence of nano-silica can strengthen the crystallization ability of polyamide materials, reduce crystal thickness, and improve grain regularity, thereby effectively improving the material's laser transmittance. The halogen-free flame-retardant polyamide composite material of this invention can simultaneously meet the requirements of laser weldability, high flame retardancy, and halogen-free properties, with a laser transmittance ≥28% (1 mm) and a flame-retardant thickness of 1.5 mm meeting the UL94 V-0 rating. Detailed Implementation

[0021] The present invention will be further described below with reference to specific embodiments, but the implementation of the present invention is not limited thereto, and is not in particular limited to the types of raw materials used in the following specific embodiments.

[0022] The raw materials used in the following embodiments are as follows:

[0023] PA6: M2400, Guangdong Xinhui Meida Nylon Co., Ltd.;

[0024] PA66: EPR24, Pingdingshan Shenma Engineering Plastics Co., Ltd.;

[0025] Short-cut fiberglass: ECS10-4.5-568H, Jushi Group Co., Ltd.;

[0026] Aluminum diethylphosphonate: Exolit OP1230, Clariant Chemicals Ltd.;

[0027] Hydroquinone bis(diphenyl phosphate): WSFR-PX-220, Zhejiang Wansheng Co., Ltd.;

[0028] Melamine cyanuric acid: MC-25, Hangzhou Jiersi Flame Retardant Chemical Co., Ltd.;

[0029] Melamine polyphosphate: BUDIT 342, Budenheim Fine Chemicals Ltd.;

[0030] Nano-silica: SP-10, Shanghai Huijingya Nanomaterials Co., Ltd.;

[0031] Lubricant: Licowax OP, Clariant Chemicals Ltd.;

[0032] Hindered phenolic antioxidant: IRGANOX 1098, Tianjin Lialong New Material Co., Ltd.

[0033] The weight proportions of raw materials used in the following embodiments and comparative examples are shown in Table 1 and Table 2, respectively.

[0034] In the following examples and comparative examples, each component was weighed according to the formulation amounts in Tables 1 and 2. All raw materials except glass fiber were added to a mixer and mixed until homogeneous. The mixture was then fed into a twin-screw extruder through the main feed port, while the glass fiber was fed in through the side feed port. After melt blending, the mixture was extruded and granulated. Various performance tests were conducted according to the testing standards. The performance test results for each example and comparative example are shown in Tables 1 and 2, respectively.

[0035] The material performance testing standards or methods are as follows:

[0036] Vertical burning performance: Tested according to GB / T 2408-2021 standard, the test strip size is 125mm×13mm×1.5mm;

[0037] Laser transmittance: The test sample was a 60mm×60mm×1.0mm sample. The laser transmittance of the sample was tested using a near-infrared spectrometer (wavelength 980nm, LPKF Laser Electronics GmbH TMG3 plastic laser transmittance tester).

[0038] Table 1. Formulation components and performance test results of the examples.

[0039]

[0040] Table 2 Comparative formulation components and performance test results

[0041]

[0042]

[0043] A comparison of the performance test results of Examples 1-8 in Table 1 and Comparative Examples 1-6 in Table 2 clearly shows that the present invention uses a composition of hydroquinone bis(diphenyl phosphate) and nano-silica to form a new synergistic flame retardant system with organophosphorus flame retardants. The obtained halogen-free flame-retardant polyamide composite material exhibits excellent flame retardant properties (flame retardant rating: UL94 V-0 for 1.5mm thickness) similar to the traditional halogen-free phosphorus-nitrogen system, and also has high laser transmittance (≥28%) and excellent laser welding performance. In contrast, the traditional halogen-free phosphorus-nitrogen flame retardant system (Comparative Examples 1 and 4) has low laser transmittance and poor laser welding performance. The pure organophosphorus flame retardant system without synergy (Comparative Examples 2 and 5) and the synergistic system with only hydroquinone bis(diphenyl phosphate) added (Comparative Example 3) show only average laser transmittance and cannot achieve a V-0 flame retardant rating. The synergistic system with the addition of nano-silica alone (Comparative Example 6) has excellent laser transmittance, but its flame retardancy rating is only V-2.

[0044] Although the above embodiments provide a relatively detailed textual description of the technical concept of the present invention, these textual descriptions are merely simple textual descriptions of the technical concept of the present invention and are not intended to limit the technical concept of the present invention. Any combination, addition, or modification that does not exceed the technical concept of the present invention shall fall within the protection scope of the present invention.

Claims

1. A laser-weldable halogen-free flame-retardant polyamide composite material, characterized in that, By weight, it includes the following components: 35-65 parts of polyamide resin; 5-50 parts glass fiber; 5-30 parts of organophosphorus flame retardant; 3-15 parts of phosphate ester flame retardant; 0.5-5 parts of nano-silica; The nano-silica has a particle size of 5-60 nm; the organophosphorus flame retardant is aluminum diethylphosphonate; The phosphate ester flame retardant is hydroquinone bis(diphenyl phosphate).

2. The laser-weldable halogen-free flame-retardant polyamide composite material according to claim 1, characterized in that, The polyamide resin is selected from at least one of polyamide 6 and polyamide 66.

3. The laser-weldable halogen-free flame-retardant polyamide composite material according to claim 1, characterized in that, The glass fiber is an alkali-free glass fiber with a single filament diameter of 8~13μm.

4. The laser-weldable halogen-free flame-retardant polyamide composite material according to claim 1, characterized in that, The particle size of the nano-silica is 5~30nm.

5. The laser-weldable halogen-free flame-retardant polyamide composite material according to claim 1, characterized in that, By weight, it includes the following components: 45-55 parts of polyamide resin; 15-40 parts glass fiber; 10-20 parts of organophosphorus flame retardant; 5-10 parts of phosphate ester flame retardant; 1-3 parts of nano-silica.

6. The laser-weldable halogen-free flame-retardant polyamide composite material according to claim 1, characterized in that, The components also include one or a mixture of several of the following: lubricant, release agent, toughening agent, antioxidant, heat stabilizer, light stabilizer, ultraviolet absorber, antistatic agent, and coupling agent.

7. A method for preparing a laser-weldable halogen-free flame-retardant polyamide composite material according to any one of claims 1-6, characterized in that, The process includes the following steps: The product is produced using a melt blending extrusion process. A twin-screw extruder is used to add polyamide resin, some or all of the glass fiber, organophosphorus flame retardant, phosphate ester flame retardant, nano silica and other processing aids in proportion from the main feed port. The remaining glass fiber is added from the side feed port. After melt blending, the product is extruded, cooled and granulated to obtain the final product.

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