High-temperature-resistant high-weld-strength PC / PBT laser welding material and preparation method thereof

Abstract

The application discloses a kind of high-temperature-resistant high welding strength PC / PBT laser welding materials and preparation method thereof, belong to high polymer modified composite material technical field, the material contains siloxane copolymer polycarbonate according to proportioning ratio, high specific viscosity polybutylene terephthalate, epoxy modified flat glass fiber, complex ester exchange inhibitor, high heat-resistant polyester grafting toughening agent, near-infrared response type interface compatibilizer and auxiliary agent;Preparation uses raw material pre-drying, feeds in sub-site, segmented temperature control blending, double-stage vacuum devolatilization process.The application uses the above-mentioned one kind of high-temperature-resistant high welding strength PC / PBT laser welding material and preparation method thereof, by formula and process synergistic optimization, crack the performance contradiction of conventional material heat resistance, laser light transmittance and welding strength, material heat distortion temperature increases, room temperature laser welding tensile shear strength is improved, can be widely used in automobile, electronic and electrical etc. High-temperature working condition precision welding parts.

Description

Technical Field

[0001] This invention relates to the field of polymer modified composite materials technology, and in particular to a high-temperature resistant and high-weld-strength PC / PBT laser welding material and its preparation method. Background Technology

[0002] Polycarbonate / polybutylene terephthalate (PC / PBT) alloys combine the excellent impact resistance and dimensional stability of PC with the good chemical resistance and processing fluidity of PBT, making them widely used in automotive parts, electronics, precision instruments, and other fields. In recent years, laser welding technology, with its advantages of being non-contact, having high welding precision, good sealing, and high production efficiency, has gradually become the mainstream joining process for plastic parts, leading to a continuous increase in demand for PC / PBT alloy materials suitable for laser welding. Especially in high-temperature service scenarios such as automotive engine compartments and high-voltage electrical modules, materials not only need to meet the light transmittance requirements of laser welding but also need to possess high heat resistance and welding reliability under long-term high temperatures, placing higher demands on the overall performance of the materials.

[0003] Currently, laser-weldable PC / PBT materials are mostly adapted for welding by adjusting the proportion of the matrix resin and adding laser absorbers. However, this approach generally suffers from multiple performance contradictions: to ensure the near-infrared transmittance of the upper layer material, the proportion of amorphous PC is usually increased, resulting in a generally low heat distortion temperature that cannot meet the requirements of high-temperature conditions; PC and PBT are prone to transesterification reactions during high-temperature blending, causing molecular chain breakage and performance degradation. Single transesterification inhibitors have limited inhibitory effects, and some organic inhibitors can interact with grafted toughening agents, weakening the toughening effect; in glass fiber reinforced systems, the refractive index difference between conventional circular glass fibers and the matrix is ​​large, resulting in severe light scattering and a significant reduction in transmittance. Furthermore, the glass fiber-matrix interface is weak, and interface debonding is prone to occur at high temperatures, leading to a sharp drop in weld strength.

[0004] In summary, existing technologies cannot simultaneously achieve high heat resistance, high light transmittance, and high welding strength, and their high-temperature welding reliability is insufficient, making them unsuitable for the stringent application requirements of high-end fields. Summary of the Invention

[0005] The purpose of this invention is to provide a high-temperature resistant, high-weld-strength PC / PBT laser welding material and its preparation method to solve the above-mentioned problems.

[0006] This invention provides a high-temperature resistant and high-weld-strength PC / PBT laser welding material, comprising the following components by weight: 25-40 parts polycarbonate resin, 35-55 parts polybutylene terephthalate resin, 15-30 parts modified flat glass fiber, 0.6-1.2 parts compounded transesterification inhibitor, 3-8 parts high-temperature toughening agent, 0.2-0.8 parts near-infrared responsive interface compatibilizer, 0.2-0.5 parts composite antioxidant, and 0.1-0.5 parts processing aid; The modified flat glass fiber is a flat, alkali-free glass fiber with a cross-section treated with an epoxy silane coupling agent, and its aspect ratio is 3:1 to 6:1. The near-infrared responsive interface compatibilizer is an epoxy-functionalized styrene-ethylene-butene-styrene copolymer grafted with perylene dyes, which has an absorption rate of ≥60% for laser wavelengths of 980–1064 nm.

[0007] Preferably, the polycarbonate resin is a siloxane copolymer polycarbonate, with the siloxane segment mass percentage being 3% to 8%; the intrinsic viscosity of the polybutylene terephthalate resin is 0.9 to 1.2 dL / g, and the terminal carboxyl group value is ≤20 mol / t.

[0008] Preferably, the compound transesterification inhibitor is prepared by compounding triphenyl phosphite and anhydrous sodium dihydrogen phosphate in a mass ratio of 1:1 to 2:1.

[0009] Preferably, the high-temperature toughening agent is a copolymer of poly(1,4-cyclohexanediethanol terephthalate) grafted with maleic anhydride, with a grafting rate of 0.8% to 1.2%.

[0010] Preferably, the composite antioxidant is composed of hindered phenolic primary antioxidant and phosphite secondary antioxidant in a mass ratio of 1:1 to 1:2.

[0011] Preferably, the processing aid is at least one of pentaerythritol stearate or ethylene bis-stearamide.

[0012] Preferably, it also includes 0.3 to 1.0 parts of low-absorption black pigment, wherein the low-absorption black pigment is at least one of perylene black or anthraquinone black.

[0013] The material has a heat distortion temperature ≥155℃ and a test condition of 1.82MPa; its laser welding tensile shear strength at room temperature is ≥45MPa, and its weld strength retention rate at 150℃ is ≥70%. When the amount of modified flat glass fiber added is 15-20 parts by weight, the transmittance of the material to 980nm laser is ≥28% at a thickness of 1.5mm; when the amount of modified flat glass fiber added is 20-30 parts by weight, the transmittance of the material to 980nm laser is ≥24% at a thickness of 1.5mm.

[0014] A method for preparing the high-temperature resistant and high-weld-strength PC / PBT laser welding material as described above is provided, comprising the following steps: Step 1: Pre-dry the polycarbonate resin and polybutylene terephthalate resin separately, and control the moisture content to ≤0.02%; weigh the dried resin, anhydrous sodium dihydrogen phosphate, high-temperature toughening agent, near-infrared responsive interface compatibilizer, composite antioxidant and processing aid according to the formula, and put them into a high-speed mixer to mix evenly to obtain a premix. Step 2: The premixed material is added to the main feed port of the twin-screw extruder, and the modified flat glass fiber is added from the side feed port of the fourth zone of the extruder. Triphenyl phosphite is quantitatively injected from the end of the fourth zone of the extruder through a pressurized liquid metering pump. The twin-screw extruder is divided into a feeding section, a melting section, a reaction section, and a homogenization section along the feeding direction. The temperatures of each section are set to 220-230℃, 245-255℃, 255-265℃, and 245-255℃, respectively, and the die head temperature is 245-255℃. Step 3: After melt blending and two-stage vacuum devolatilization, the material is extruded, stretched, water-cooled, and pelletized to obtain semi-finished particles. The semi-finished particles are placed in a forced-air drying oven at 80-100℃ for 4-6 hours to dry, and the particle moisture content is controlled to be ≤0.02% to obtain the finished material.

[0015] Preferably, the pre-drying conditions in step 1 are as follows: polycarbonate resin is dried at 120°C for 6-8 hours by forced air drying, and polybutylene terephthalate resin is dried at 110°C for 4-6 hours by forced air drying; the speed of the high-speed mixer is 800-1200 rpm, the mixing time is 3-5 minutes, and the mixing temperature is controlled at 40-60°C.

[0016] Preferably, in step 2, the screw length-to-diameter ratio of the twin-screw extruder is 40:1 to 48:1, the screw speed is 300 to 450 rpm, and the total residence time of the material in the extruder is 60 to 120 s.

[0017] Therefore, the present invention employs the above-mentioned high-temperature resistant and high-weld-strength PC / PBT laser welding material and its preparation method, which has the following beneficial effects: (1) By using siloxane copolymer PC and high intrinsic viscosity PBT as the matrix, and matching the refractive index with the matrix, the additional light scattering loss caused by the toughening components is avoided; epoxy modified flat glass fiber is used to replace conventional round glass fiber, which greatly reduces the interfacial light scattering. With the graded matching of glass fiber content and light transmittance, in a 15-20 part glass fiber system, the light transmittance of 1.5 mm thick material to 980 nm laser is ≥28%, and the heat distortion temperature of the material is stable at ≥155℃, which solves the technical contradiction between heat resistance and laser transmittance in the traditional system.

[0018] (2) An inhibitor system composed of triphenyl phosphite and anhydrous sodium dihydrogen phosphate in a ratio of 1:1 to 2:1 is adopted. The residual catalyst is efficiently chelated and the transesterification reaction is inhibited through the synergistic mechanism of inorganic chelation and organic blocking. Combined with the inhibitor site injection design in the preparation process, the high-temperature contact time between the organic inhibitor and the grafted toughening agent is shortened, the consumption of the active functional groups of the toughening agent by the organic inhibitor is greatly reduced, the toughening effect is avoided, and the thermal stability and impact toughness of the system are ensured at the same time.

[0019] (3) Introducing a near-infrared responsive interface compatibilizer with both interface compatibilization and near-infrared selective absorption functions, which can be directionally enriched at the welding interface, promote deep interpenetration and entanglement of interface molecular chains, and strengthen the weld bonding force; epoxy-modified flat glass fiber forms a chemical bond interface with the matrix, and is not prone to interface debonding at high temperature. Under the synergistic effect of the two, the tensile shear strength of the material at room temperature laser welding is ≥45MPa, and the weld strength retention rate at 150℃ is ≥70%, which can be adapted to long-term high-temperature service scenarios.

[0020] (4) Through the process design of segmented temperature control, short residence time and two-stage vacuum devolatilization, the low temperature in the front stage suppresses the transesterification side reaction, and the moderate temperature rise in the middle stage promotes the compatibilization main reaction, while reducing glass fiber shear damage and additive volatilization loss. The overall process is compatible with general twin-screw extrusion equipment, the product performance is stable and controllable, and it has a good foundation for industrial mass production.

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0022] Figure 1 This is a comparison diagram of the heat distortion temperature properties of Examples 1-4 and Comparative Examples 1-4 in the present invention, which describes a high-temperature resistant and high-weld-strength PC / PBT laser welding material and its preparation method. Figure 2 This is a comparison diagram of the room temperature welding tensile shear strength properties of Examples 1-4 and Comparative Examples 1-4 in the present invention, which describes a high-temperature resistant and high-weld-strength PC / PBT laser welding material and its preparation method. Figure 3 This is a comparison chart of the high-temperature welding strength retention rate of Examples 1-4 and Comparative Examples 1-4 in the present invention, which describes a high-temperature resistant and high-welding-strength PC / PBT laser welding material and its preparation method. Detailed Implementation

[0023] To better understand the above technical solutions, a detailed description of the solutions will be provided below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0025] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0026] This invention provides a high-temperature resistant, high-weld-strength PC / PBT laser welding material, comprising the following components by weight: 25-40 parts polycarbonate resin, 35-55 parts polybutylene terephthalate resin, 15-30 parts modified flat glass fiber, 0.6-1.2 parts compounded transesterification inhibitor, 3-8 parts high-temperature toughening agent, 0.2-0.8 parts near-infrared responsive interface compatibilizer, 0.2-0.5 parts composite antioxidant, and 0.1-0.5 parts processing aid; The modified flat glass fiber is a flat, alkali-free glass fiber with a cross-section treated with an epoxy silane coupling agent, and its aspect ratio is 3:1 to 6:1. The near-infrared responsive interface compatibilizer is an epoxy-functionalized styrene-ethylene-butene-styrene copolymer grafted with perylene dyes, which has an absorption rate of ≥60% for laser wavelengths of 980–1064 nm.

[0027] The polycarbonate resin is a siloxane copolymer polycarbonate with a siloxane segment mass ratio of 3% to 8%; the intrinsic viscosity of the polybutylene terephthalate resin is 0.9 to 1.2 dL / g, and the terminal carboxyl group value is ≤20 mol / t.

[0028] The compound transesterification inhibitor is prepared by compounding triphenyl phosphite and anhydrous sodium dihydrogen phosphate in a mass ratio of 1:1 to 2:1.

[0029] The high-temperature toughening agent is a copolymer of poly(1,4-cyclohexanediethanol terephthalate) grafted with maleic anhydride, with a grafting rate of 0.8% to 1.2%.

[0030] The compound antioxidant is composed of hindered phenolic primary antioxidant and phosphite secondary antioxidant in a mass ratio of 1:1 to 1:2.

[0031] The processing aid is at least one of pentaerythritol stearate or ethylene bis-stearamide.

[0032] It also includes 0.3 to 1.0 parts of low-absorption black pigment, wherein the low-absorption black pigment is at least one of perylene black or anthraquinone black.

[0033] The material's heat distortion temperature is ≥155℃, and the test condition is 1.82MPa; the laser welding tensile shear strength at room temperature is ≥45MPa, and the weld strength retention rate at 150℃ is ≥70%. When the amount of modified flat glass fiber added is 15-20 parts by weight, the transmittance of the material to 980nm laser is ≥28% at a thickness of 1.5mm; when the amount of modified flat glass fiber added is 20-30 parts by weight, the transmittance of the material to 980nm laser is ≥24% at a thickness of 1.5mm.

[0034] Specifically, a blend of siloxane-copolymerized polycarbonate and high intrinsic viscosity polybutylene terephthalate (PPT) is used as the matrix resin. The siloxane-copolymerized polycarbonate incorporates siloxane segments into its molecular chain, which possess excellent thermal stability and low-temperature flexibility, significantly improving the resin's heat distortion temperature and impact resistance. Simultaneously, the amorphous structure of polycarbonate provides a good near-infrared transmittance basis for the material, a prerequisite for laser welding. PPT has a higher molecular weight and more complete crystallinity, effectively improving the mechanical strength, chemical corrosion resistance, and heat resistance of the alloy system. Furthermore, by controlling the terminal carboxyl group value at a low level, it reduces the active sites that could trigger transesterification reactions from the source, lowering the probability of transesterification reactions during high-temperature blending. The proportional blending of these two components balances the material's transmittance, heat resistance, mechanical properties, and processing fluidity, providing a performance foundation for the synergistic effect of subsequent functional components.

[0035] A transesterification inhibition system employing triphenyl phosphite and anhydrous sodium dihydrogen phosphate in a mass ratio of 1:1 to 2:1 is used to inhibit the transesterification reaction while avoiding the negative impact of a single organic inhibitor on the toughening agent. Anhydrous sodium dihydrogen phosphate, an inorganic weak acid salt, can chelate residual titanium-based polymerization catalysts in polybutylene terephthalate through strong coordination, thereby passivating the catalytically active centers of the transesterification reaction at its source. It does not react with the maleic anhydride functional groups of the toughening agent, thus not weakening the compatibilizing effect of the toughening agent. This component is premixed with the matrix resin and exerts its chelating effect in the early stages of melting. Triphenyl phosphite, an organic phosphite compound, can capture free radicals generated during high-temperature processing, terminating the chain reaction of transesterification, and simultaneously decompose hydrogen peroxide in the system, helping to improve the thermo-oxidative stability of the material. By controlling the ratio of the two compounds, the proportion of organic phosphite is reduced while ensuring the efficiency of transesterification inhibition. This reduces the probability of esterification reaction between organic phosphite and the toughening agent anhydride group, thus balancing the transesterification inhibition effect and toughening performance. This solves the technical problem that a single organic inhibitor would reduce the impact performance of the system.

[0036] A high-temperature toughening agent was adopted using a copolymer of poly(1,4-cyclohexanediethanol) terephthalate (PTA) grafted with maleic anhydride. PTA contains rigid cyclohexanediethanol structural units in its molecular chain, exhibiting extremely high heat resistance. Its Vicat softening point is significantly higher than that of conventional polyester toughening agents, and its addition to the system does not lower the overall heat distortion temperature of the material, thus meeting the core requirement of high-temperature resistance. Furthermore, PTA belongs to the same polyester family as polybutylene terephthalate (PBPT), has similar solubility parameters, and exhibits excellent compatibility with the matrix resin. It can form a uniformly sized island-like dispersion structure, without producing a significant light scattering interface, and has minimal impact on laser transmittance. The grafted maleic anhydride functional groups can chemically react with the terminal hydroxyl groups of polycarbonate and the terminal carboxyl groups of PBPT during high-temperature blending, forming chemical bonds between the toughening agent and the matrix, achieving compatibilization and effectively improving the material's impact strength and interfacial bonding. By controlling the grafting rate between 0.8% and 1.2%, the toughening agent can be guaranteed to have sufficient reactivity, while avoiding problems such as decreased dispersibility and excessive polarity caused by excessive grafting.

[0037] Flat-section glass fibers treated with epoxy-based silane coupling agents are used as the reinforcing phase to address the inherent defects of conventional circular glass fibers from three dimensions: optical, mechanical, and dimensional stability. The refractive index difference between conventional circular glass fibers and the resin matrix causes multi-directional refraction and reflection at the circular interface, resulting in strong light scattering and significantly reducing laser transmittance. Flat-section glass fibers, however, align along the melt flow direction during injection molding, with their flat planes parallel to the part surface. When near-infrared laser light is incident perpendicularly, the refraction angle at the glass fiber interface is significantly reduced, drastically decreasing the light scattering intensity and effectively improving the material's near-infrared transmittance. Controlling the cross-sectional aspect ratio to 3:1–6:1 ensures low light scattering while preventing excessive breakage and loss of the flat structure during processing. The epoxy-based silane coupling agent introduces epoxy functional groups onto the glass fiber surface, chemically bonding with the end groups of the matrix resin and the active groups of the compatibilizer. This significantly improves the interfacial bonding strength between the glass fiber and the matrix, preventing interface debonding at high temperatures and thus enhancing the material's high-temperature mechanical properties and weld strength retention. In addition, oriented flat glass fibers can reduce the anisotropy of the parts, reduce molding warpage, ensure the bonding accuracy of the welding surfaces, and indirectly improve the quality stability of laser welding.

[0038] Perylene-based dye-grafted epoxy-functionalized styrene-ethylene-butene-styrene copolymers are used as near-infrared responsive interfacial compatibilizers, simultaneously achieving the dual functions of interfacial compatibilization and weld interface strengthening. The styrene segments of the styrene-ethylene-butene-styrene block copolymer exhibit good compatibility with polycarbonate, while the ethylene-butene segments provide toughening effects. The grafted epoxy functional groups can undergo ring-opening reactions with the terminal hydroxyl and carboxyl groups of the matrix resin, strengthening the interfacial bonding and improving the compatibility and impact toughness of the alloy system. The grafted perylene-based dyes exhibit strong absorption characteristics in the commonly used laser welding wavelength range of 980–1064 nm, and due to the interfacial activity of the compatibilizer molecules, they spontaneously accumulate at the glass fiber-matrix interface and the subsequent welding fusion interface of the parts during blending. During laser welding, after the near-infrared laser penetrates the upper material and reaches the welding interface, the perylene-based dyes enriched at the interface selectively absorb the laser energy and rapidly convert it into heat energy. This promotes the full melting of the resin at the welding interface, causing deep interpenetration and entanglement of the molecular chains on both sides, significantly improving the welding strength. This component is directionally enriched at the interface, eliminating the need for a high content of laser absorber added to the matrix as a whole. Therefore, it does not reduce the laser transmittance of the material itself, resolving the performance contradiction between traditional laser absorbers and transmittance. Controlling its absorption rate for 980–1064 nm lasers to ≥60% ensures sufficient energy conversion efficiency, while the low addition amount does not significantly affect the heat resistance and appearance of the material matrix.

[0039] A composite antioxidant system combining hindered phenols and phosphites is employed. The hindered phenolic primary antioxidant captures alkoxy and alkyl free radicals generated during high-temperature processing, terminating the oxidation chain reaction; the phosphite secondary antioxidant decomposes hydroperoxides in the system. The two work synergistically to effectively inhibit the thermo-oxidative degradation of the resin during high-temperature blending, ensuring the molecular weight and performance stability of the material.

[0040] Processing aids such as pentaerythritol stearate or ethylene bis-stearamide can reduce the internal friction of the melt and the adhesion between the melt and the equipment, improve processing fluidity and plasticization uniformity, and promote the uniform dispersion of various functional components in the matrix. In addition, they can improve the surface finish of the product, reduce surface diffuse reflection, and indirectly improve laser transmittance and weld surface flatness.

[0041] Perylene black or anthraquinone black was selected as the low-absorption black pigment. Perylene black and anthraquinone black are organic black dyes, and their molecular structure determines that they have strong absorption in the visible light band, which can achieve a uniform black appearance; while they have high transmittance in the near-infrared laser band of 980-1064nm and extremely low light absorption loss. Therefore, while meeting the requirements for black appearance coloring, they have basically not affected the light transmittance of the material for laser welding.

[0042] A method for preparing the high-temperature resistant and high-weld-strength PC / PBT laser welding material as described above is provided, comprising the following steps: Step 1: Pre-dry the polycarbonate resin and polybutylene terephthalate resin separately; dry the polycarbonate resin at 120℃ for 6-8 hours and the polybutylene terephthalate resin at 110℃ for 4-6 hours, controlling the moisture content to ≤0.02%; weigh the dried resin, anhydrous sodium dihydrogen phosphate, high-temperature toughening agent, near-infrared responsive interface compatibilizer, composite antioxidant and processing aid according to the formula, and put them into a high-speed mixer to mix evenly to obtain a premix; the speed of the high-speed mixer is 800-1200 rpm, the mixing time is 3-5 minutes, and the mixing temperature is controlled at 40-60℃.

[0043] Step 2: The premixed material is added to the main feed port of the twin-screw extruder. Modified flat glass fiber is added from the side feed port of zone 4 of the extruder. Triphenyl phosphite is quantitatively injected from the end of zone 4 of the extruder through a pressurized liquid metering pump. The twin-screw extruder is divided into a feeding section, a melting section, a reaction section, and a homogenization section along the feeding direction. The temperatures of each section are set to 220-230℃, 245-255℃, 255-265℃, and 245-255℃, respectively, and the die head temperature is 245-255℃. The screw length-to-diameter ratio of the twin-screw extruder is 40:1 to 48:1, the screw speed is 300-450 rpm, and the total residence time of the material in the extruder is 60-120 s.

[0044] Step 3: After melt blending and two-stage vacuum devolatilization, the material is extruded, stretched, water-cooled, and pelletized to obtain semi-finished particles. The semi-finished particles are placed in a forced-air drying oven at 80-100℃ for 4-6 hours to dry, and the particle moisture content is controlled to be ≤0.02% to obtain the finished material.

[0045] Specifically, the preparation process and formulation system are deeply synergistic. Through a combination of site-specific feeding, segmented temperature control, low-damage processing, and two-stage devolatilization, the functions of each component are maximized. The specific mechanism is as follows: Raw material pre-drying: Both polycarbonate and polybutylene terephthalate contain ester bonds, which are prone to hydrolysis and degradation when exposed to water at high temperatures, leading to molecular chain breakage and performance deterioration. A targeted pre-drying process controls the moisture content of the raw materials to below 0.02%, preventing hydrolysis reactions during processing and ensuring the intrinsic properties of the matrix resin.

[0046] Inhibitor feeding at specific sites: Anhydrous sodium dihydrogen phosphate is added along with the main resin feedstock, allowing it to fully contact and chelate residual catalysts in the early stages of melting, thus passivating transesterification activity in advance; Triphenyl phosphite is injected at the end of the melting section via a pressurized liquid metering pump, significantly shortening its high-temperature residence time, reducing volatilization loss, and lowering the probability of high-temperature reaction between it and the toughening agent anhydride groups, thus avoiding weakening the toughening effect. The liquid injection method also ensures its uniform dispersion in the melt.

[0047] Segmented temperature control: The extrusion process is divided into a feeding section, a melting section, a reaction section, and a homogenization section. The feeding and melting sections use relatively low temperatures to reduce transesterification side reactions while ensuring sufficient resin plasticization. The reaction section slightly increases the temperature to provide sufficient activation energy for the interfacial reaction between the compatibilizer and the resin, promoting full compatibilization. The homogenization section moderately lowers the temperature to stabilize the melt viscosity and ensure stable extrusion. This design resolves the process contradiction between "low temperature required to inhibit transesterification" and "high temperature required to promote compatibilization," achieving a synergistic effect of suppressing side reactions and promoting the main reaction.

[0048] Low-damage glass fiber side-feeding process: Flat glass fibers are fed from the middle side feed port, avoiding the strong shear area of ​​the feeding section. With the help of a weak shear screw element, the cross-sectional shape and aspect ratio of the flat glass fibers are preserved to the greatest extent, avoiding excessive breakage of the glass fibers and loss of low light scattering and high reinforcement.

[0049] Two-stage vacuum devolatilization: A two-stage vacuum system is used to sequentially remove moisture, volatile additives, small molecules, residual monomers and oligomers generated by transesterification from the system, reducing bubbles and low-molecular-weight impurities in the melt, avoiding weld defects caused by bubbles during welding, and improving the stability of welding strength and weld sealing.

[0050] Finished product drying: The finished particles are dried to control the moisture content and ensure that the product will not have problems such as silver streaks or degradation due to moisture during subsequent injection molding. At the same time, it ensures that the welding surface is flat and dense, and improves the consistency of welding quality.

[0051] To provide a clearer and more detailed description of the high-temperature resistant, high-weld-strength PC / PBT laser welding material and its preparation method provided by this invention, specific embodiments will be described below.

[0052] The raw material parameters used in the following examples and comparative examples are as follows: Polycarbonate resin: siloxane copolymer polycarbonate, with siloxane segments accounting for 5% by mass, and melt flow rate of 10 g / 10 min (test conditions: 300℃, 1.2 kg). Polybutylene terephthalate resin: intrinsic viscosity is 1.0 dL / g, and terminal carboxyl group value is 15 mol / t; Modified flat glass fiber: Flat cross-section alkali-free glass fiber with a cross-sectional aspect ratio of 4:1, treated with an epoxy silane coupling agent. Compound transesterification inhibitor: It is composed of triphenyl phosphite and anhydrous sodium dihydrogen phosphate in a set mass ratio, and the median particle size D50 of anhydrous sodium dihydrogen phosphate is ≤5μm; High-temperature toughening agent: Poly(1,4-cyclohexanediethanol terephthalate) grafted with maleic anhydride copolymer, with a grafting rate of 1.0%, Vicat softening point ≥160℃, and refractive index of 1.56; Near-infrared responsive interface compatibilizer: epoxy-functionalized styrene-ethylene-butene-styrene copolymer grafted with perylene dyes, with an absorption rate of ≥60% for 980-1064nm wavelength laser light; Compound antioxidant: It is a mixture of hindered phenolic primary antioxidant and phosphite secondary antioxidant in a mass ratio of 1:1.5; Processing aid: Pentaerythritol stearate; Low-absorption black pigment: Perylene black, light transmittance ≥70% at 1064nm wavelength; Example 1 The high-temperature resistant and high-weld-strength PC / PBT laser welding material of this embodiment comprises, by weight, 30 parts of polycarbonate resin, 45 parts of polybutylene terephthalate resin, 18 parts of modified flat glass fiber, 0.8 parts of compound transesterification inhibitor, 5 parts of high-temperature toughening agent, 0.5 parts of near-infrared responsive interface compatibilizer, 0.4 parts of composite antioxidant, and 0.3 parts of processing aid; the mass ratio of triphenyl phosphite to anhydrous sodium dihydrogen phosphate in the compound transesterification inhibitor is 1.5:1.

[0053] The preparation method is as follows: Step 1: Dry the polycarbonate resin in a 120℃ forced-air drying oven for 7 hours and the polybutylene terephthalate resin in a 110℃ forced-air drying oven for 5 hours, controlling the moisture content of both to be ≤0.02%; Weigh the dried resin, anhydrous sodium dihydrogen phosphate, high-temperature toughening agent, near-infrared responsive interface compatibilizer, composite antioxidant and processing aid according to the formula, put them into a high-speed mixer, and mix for 4 minutes at a speed of 1000 rpm and a temperature of 50℃ to obtain a premix; Step 2: The premixed material is added to the main feed port of the twin-screw extruder, and the modified flat glass fiber is added from the side feed port of zone 4 of the extruder. Triphenyl phosphite is quantitatively injected from the end of zone 4 of the extruder through a pressurized liquid metering pump. The twin-screw extruder is divided into a feeding section, a melting section, a reaction section, and a homogenization section along the feeding direction. The temperatures of each section are set to 225℃, 250℃, 260℃, and 250℃, respectively, and the die head temperature is 250℃. The screw length-to-diameter ratio of the twin-screw extruder is 44:1, the screw speed is 380 rpm, and the total residence time of the material in the extruder is 90 s. Step 3: After melt blending and two-stage vacuum devolatilization, the material is extruded, stretched, water-cooled, and pelletized to obtain semi-finished particles; the semi-finished particles are placed in a 90℃ forced-air drying oven for 5 hours to dry, and the particle moisture content is controlled to be ≤0.02% to obtain the finished material.

[0054] Example 2 The high-temperature resistant and high-weld-strength PC / PBT laser welding material of this embodiment comprises, by weight, 28 parts of polycarbonate resin, 38 parts of polybutylene terephthalate resin, 25 parts of modified flat glass fiber, 1.0 part of compound transesterification inhibitor, 6 parts of high-temperature toughening agent, 0.6 parts of near-infrared responsive interface compatibilizer, 0.4 parts of composite antioxidant, and 0.4 parts of processing aid; the mass ratio of triphenyl phosphite to anhydrous sodium dihydrogen phosphate in the compound transesterification inhibitor is 2:1.

[0055] The preparation method in this embodiment is completely consistent with that in Example 1.

[0056] Example 3 The high-temperature resistant and high-weld-strength PC / PBT laser welding material of this embodiment comprises, by weight, 29 parts of polycarbonate resin, 43 parts of polybutylene terephthalate resin, 20 parts of modified flat glass fiber, 0.9 parts of compounded transesterification inhibitor, 5 parts of high-temperature toughening agent, 0.5 parts of near-infrared responsive interface compatibilizer, 0.3 parts of composite antioxidant, 0.3 parts of processing aid, and 0.7 parts of low-absorption black pigment; the mass ratio of triphenyl phosphite to anhydrous sodium dihydrogen phosphate in the compounded transesterification inhibitor is 1:1.

[0057] The preparation method in this embodiment is the same as in Example 1. The low-absorption black pigment is added together with anhydrous sodium dihydrogen phosphate and premixed in a high-speed mixer.

[0058] Example 4 The high-temperature resistant and high-weld-strength PC / PBT laser welding material of this embodiment comprises, by weight, 35 parts of polycarbonate resin, 36 parts of polybutylene terephthalate resin, 22 parts of modified flat glass fiber, 0.7 parts of compound transesterification inhibitor, 4 parts of high-temperature toughening agent, 0.3 parts of near-infrared responsive interface compatibilizer, 0.3 parts of composite antioxidant, and 0.2 parts of processing aid; the mass ratio of triphenyl phosphite to anhydrous sodium dihydrogen phosphate in the compound transesterification inhibitor is 1.8:1.

[0059] The preparation method in this embodiment is completely consistent with that in Example 1.

[0060] Comparative Example 1 This comparative example uses conventional glass fiber reinforced PC / PBT laser welding material. By weight, the components include: 32 parts polycarbonate resin, 45 parts polybutylene terephthalate resin, 18 parts ordinary round glass fiber, 0.8 parts triphenyl phosphite, 5 parts MBS toughening agent, 0.2 parts ordinary near-infrared laser absorber, 0.4 parts composite antioxidant, and 0.3 parts processing aid.

[0061] The product is prepared using a conventional blending process: all resins, additives and glass fibers are fed into a twin-screw extruder through the main feed port. The temperature of each section of the barrel is uniformly set to 250℃, the die head temperature is 250℃, the screw speed is 350rpm, and the total residence time is 160s. The finished product is obtained by single-stage vacuum devolatilization, extrusion granulation and drying.

[0062] Comparative Example 2 The formulation of this comparative example is basically the same as that of Example 1, except that the near-infrared responsive interface compatibilizer is replaced with an equal mass of ordinary bulk-dispersed near-infrared laser absorber, and the other components and contents are the same.

[0063] The preparation method of this comparative example is the same as that of Example 1.

[0064] Comparative Example 3 The formulation of this comparative example is basically the same as that of Example 1, except that the high-temperature toughening agent is replaced with an equal mass of polyethylene terephthalate-1,4-cyclohexanediethanol ester grafted maleic anhydride copolymer (Vicat softening point 115°C), and the other components and contents are the same.

[0065] The preparation method of this comparative example is the same as that of Example 1.

[0066] Comparative Example 4 The formulation of this comparative example is completely the same as that of Example 1, except for the preparation process: all the compound transesterification inhibitors are added with the resin from the main feed port, the temperature of each section of the barrel is uniformly set to 255°C, single-stage vacuum devolatilization is adopted, the total residence time of the material is 160s, and the rest of the process is the same as that of Example 1.

[0067] Performance testing: Testing standards: Heat distortion temperature: tested according to GB / T 1634.2-2019, load 1.82MPa; Near-infrared transmittance: Tested using a near-infrared spectrophotometer, with a sample thickness of 1.5 mm and a test wavelength of 980 nm; Tensile shear strength of room temperature laser welding: Overlapped specimens were prepared using a 980nm semiconductor laser with an overlap area of ​​10mm×10mm, and tested according to GB / T 1040.2-2018. 150℃ weld strength retention rate: The weld strength of the sample was tested after heat treatment at 150℃ for 2 hours, and the ratio with the strength at room temperature was calculated. Notched impact strength of simply supported beams: tested according to GB / T 1043.1-2008, test temperature 23℃; The test results are shown in Table 1 below.

[0068] Table 1 Performance test results of Examples 1-4 and Comparative Examples 1-4

[0069] Examples 1-4 cover mainstream application scenarios such as low glass fiber transmittance, high glass fiber reinforced, and black-colored types, achieving a synergistic improvement in heat resistance, laser transmittance, and welding reliability. All samples exhibited stable heat distortion temperatures, making them suitable for long-term high-temperature service scenarios such as automotive engine compartments and high-voltage electrical modules. The low glass fiber system, at a thickness of 1.5 mm, achieved a near-infrared transmittance of over 28% at 980 nm, making it suitable for direct use as a laser welding transmittance layer. The high glass fiber system maintained a transmittance of over 24%, further enhancing structural strength and heat resistance. Examples 1-4 showed room-temperature laser welding tensile shear strength exceeding 45 MPa, and a weld strength retention rate exceeding 70% at 150°C, effectively addressing the industry pain point of rapid weld failure under high-temperature conditions.

[0070] Compared with Comparative Example 1, which uses conventional industry solutions, this embodiment improves heat distortion temperature, near-infrared transmittance, room temperature welding strength, and high-temperature strength retention rate by using flat glass fibers to reduce light scattering, high-heat-resistant toughening agents to balance toughness and heat resistance, interfacial compatibilizers to directionally strengthen welds, and compound inhibitors to synergistically inhibit transesterification degradation.

[0071] Comparative Example 2 showed a significant decrease in transmittance, weld strength, and high-temperature retention rate when the near-infrared responsive interfacial compatibilizer was replaced with an equal amount of conventional bulk-dispersed laser absorber. Conventional laser absorbers are uniformly dispersed in the matrix, resulting in the overall consumption of laser energy, which cannot be concentrated on the weld interface and lacks interfacial compatibilization. The interfacial compatibilizer of this invention can spontaneously accumulate at the weld, concentrating and converting laser energy and strengthening the interfacial bonding, thus possessing the dual effects of weld strengthening and toughening enhancement.

[0072] Comparative Example 3 replaced the high heat-resistant polyester toughening agent with a conventional low heat-resistant grafted toughening agent. While the impact performance of both was similar, the heat distortion temperature of Comparative Example 3 decreased by 20°C, failing to meet high-temperature application requirements. This demonstrates the value of selecting high heat-resistant toughening agents containing a rigid cyclohexane structure, as they can achieve reaction compatibilization without reducing the overall heat resistance of the material, achieving a performance balance of toughening without sacrificing heat resistance.

[0073] Comparative Example 4 used the exact same formulation as this scheme, but employed a conventional blending process, resulting in a significant decline in all performance characteristics. Under conventional processes, the prolonged high-temperature contact time between the inhibitor and toughening agent consumes active functional groups, weakening the compatibilization effect. Simultaneously, the longer high-temperature residence time exacerbates transesterification degradation, and single-stage devolatilization cannot fully eliminate internal defects in the system. The site-specific feeding, segmented temperature control, and two-stage devolatilization process of this invention are deeply matched with the formulation's innovative points, achieving synergistic effects by suppressing side reactions and reducing internal defects.

[0074] Therefore, this invention employs the aforementioned high-temperature resistant and high-weld-strength PC / PBT laser welding material and its preparation method. By using a matrix of siloxane copolymerized PC and high intrinsic viscosity PBT, combined with a high-temperature toughening agent whose refractive index matches the matrix, additional light scattering loss caused by the toughening components is avoided. Epoxy-modified flat glass fibers are used instead of conventional round glass fibers, significantly reducing interfacial light scattering. With graded matching of glass fiber content and transmittance, in a 15-20 part glass fiber system, the transmittance of a 1.5 mm thick material to 980 nm laser is ≥28%, while the material's heat distortion temperature stably reaches above 155℃. This resolves the technical contradiction of the trade-off between heat resistance and laser transmittance in traditional systems. An inhibitor system composed of triphenyl phosphite and anhydrous sodium dihydrogen phosphate in a ratio of 1:1 to 2:1 is used to efficiently chelate residual catalyst and inhibit transesterification reaction through a synergistic mechanism of inorganic chelation and organic blocking. Combined with the inhibitor site injection design in the preparation process, the high-temperature contact time between the organic inhibitor and the grafted toughening agent is shortened, which greatly reduces the consumption of active functional groups of the toughening agent by the organic inhibitor, avoids the toughening effect being offset, and simultaneously ensures the thermal stability and impact toughness of the system.

[0075] A near-infrared responsive interface compatibilizer, possessing both interface compatibilization and near-infrared selective absorption functions, is introduced. This compatibilizer can be directionally enriched at the welding interface, promoting deep interpenetration and entanglement of interface molecular chains and strengthening weld bonding. Epoxy-modified flat glass fibers form a chemically bonded interface with the matrix, making them less prone to interface debonding at high temperatures. With the synergistic effect of these two components, the material exhibits a room-temperature laser welding tensile shear strength ≥45MPa and a weld strength retention rate ≥70% at 150℃, making it suitable for long-term high-temperature service scenarios. Through a process design involving segmented temperature control, short residence time, and two-stage vacuum devolatilization, the initial low-temperature stage suppresses transesterification side reactions, while the moderate temperature rise in the middle stage promotes the compatibilization main reaction, simultaneously reducing glass fiber shear damage and additive volatilization loss. The overall process is compatible with general-purpose twin-screw extrusion equipment, ensuring stable and controllable product performance and providing a solid foundation for industrial mass production.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A high-temperature resistant, high-weld-strength PC / PBT laser welding material, characterized in that, By weight, it includes the following components: 25-40 parts polycarbonate resin, 35-55 parts polybutylene terephthalate resin, 15-30 parts modified flat glass fiber, 0.6-1.2 parts compounded transesterification inhibitor, 3-8 parts high-temperature toughening agent, 0.2-0.8 parts near-infrared responsive interface compatibilizer, 0.2-0.5 parts composite antioxidant, and 0.1-0.5 parts processing aid; The modified flat glass fiber is a flat, alkali-free glass fiber with a surface treated with an epoxy silane coupling agent; The near-infrared responsive interface compatibilizer is an epoxy-functionalized styrene-ethylene-butene-styrene copolymer grafted with perylene dyes.

2. The high-temperature resistant and high-weld-strength PC / PBT laser welding material according to claim 1, characterized in that, The polycarbonate resin is a siloxane copolymer polycarbonate with a siloxane segment mass ratio of 3% to 8%; the intrinsic viscosity of the polybutylene terephthalate resin is 0.9 to 1.2 dL / g, and the terminal carboxyl group value is ≤20 mol / t.

3. The high-temperature resistant and high-weld-strength PC / PBT laser welding material according to claim 1, characterized in that, The compound transesterification inhibitor is prepared by compounding triphenyl phosphite and anhydrous sodium dihydrogen phosphate in a mass ratio of 1:1 to 2:

1.

4. The high-temperature resistant and high-weld-strength PC / PBT laser welding material according to claim 1, characterized in that, The high-temperature toughening agent is a copolymer of poly(1,4-cyclohexanediethanol terephthalate) grafted with maleic anhydride, with a grafting rate of 0.8% to 1.2%.

5. The high-temperature resistant and high-weld-strength PC / PBT laser welding material according to claim 1, characterized in that, The compound antioxidant is composed of hindered phenolic primary antioxidant and phosphite secondary antioxidant in a mass ratio of 1:1 to 1:

2.

6. The high-temperature resistant and high-weld-strength PC / PBT laser welding material according to claim 1, characterized in that, The processing aid is at least one of pentaerythritol stearate or ethylene bis-stearamide.

7. The high-temperature resistant and high-weld-strength PC / PBT laser welding material according to claim 1, characterized in that, The product also includes 0.3 to 1.0 parts by weight of low-absorption black pigment, wherein the low-absorption black pigment is at least one of perylene black or anthraquinone black.

8. A method for preparing a high-temperature resistant, high-weld-strength PC / PBT laser welding material as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Pre-dry the polycarbonate resin and polybutylene terephthalate resin separately, and control the moisture content to ≤0.02%; weigh the dried resin, anhydrous sodium dihydrogen phosphate, high-temperature toughening agent, near-infrared responsive interface compatibilizer, composite antioxidant and processing aid according to the formula, and put them into a high-speed mixer to mix evenly to obtain a premix. Step 2: The premixed material is added to the main feed port of the twin-screw extruder, and the modified flat glass fiber is added from the side feed port of the fourth zone of the extruder. Triphenyl phosphite is quantitatively injected from the end of the fourth zone of the extruder through a pressurized liquid metering pump. The twin-screw extruder is divided into a feeding section, a melting section, a reaction section, and a homogenization section along the feeding direction. The temperatures of each section are set to 220-230℃, 245-255℃, 255-265℃, and 245-255℃, respectively, and the die head temperature is 245-255℃. Step 3: After melt blending and two-stage vacuum devolatilization, the material is extruded, stretched, water-cooled, and pelletized to obtain semi-finished particles. The semi-finished particles are placed in a forced-air drying oven at 80-100℃ for 4-6 hours to dry, and the particle moisture content is controlled to be ≤0.02% to obtain the finished material.

9. The method for preparing a high-temperature resistant, high-weld-strength PC / PBT laser welding material according to claim 8, characterized in that, The pre-drying conditions in step 1 are as follows: polycarbonate resin is dried at 120℃ for 6-8 hours by forced air drying, and polybutylene terephthalate resin is dried at 110℃ for 4-6 hours by forced air drying; the speed of the high-speed mixer is 800-1200 rpm, the mixing time is 3-5 minutes, and the mixing temperature is controlled at 40-60℃.

10. The method for preparing a high-temperature resistant, high-weld-strength PC / PBT laser welding material according to claim 8, characterized in that, In step 2, the screw length-to-diameter ratio of the twin-screw extruder is 40:1 to 48:1, the screw speed is 300 to 450 rpm, and the total residence time of the material in the extruder is 60 to 120 s.

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