A polypropylene composite material for laser engraving and a method for producing the same

Abstract

The application discloses a kind of polypropylene composite material for laser engraving and preparation method thereof, by polypropylene resin 50-90 parts, composite laser sensitive agent 15-16 parts, toughening compatilizer 5-15 parts, filler 0-10 parts, antioxidant 0.2-0.4 parts, lubricant 0.1-0.3 parts are prepared according to weight parts, wherein: the composite laser sensitive agent is compounded by inorganic laser sensitive agent and organic carbonization accelerator.The synergistic effect of composite laser sensitive additive and specific grafting rate toughening compatilizer, polypropylene is used for LDS when multiple technical contradictions such as laser insensitive, filler dispersion difficult, weak interface combination and toughness deterioration are systematically solved, so that material simultaneously has excellent LDS performance, high mechanical strength and good processing fluidity.

Description

Technical Field

[0001] This invention relates to the field of polymer material modification and electronic manufacturing technology, specifically a polypropylene composite material for laser engraving and its preparation method. Background Technology

[0002] Laser direct engraving (LDS) technology creates catalytically active patterns on plastic surfaces containing special fillers using laser scanning, followed by selective electroless plating to directly fabricate three-dimensional circuits, achieving a high degree of integration between structural components and circuit carriers. This technology has been widely applied in fields such as smart cars and high-end consumer electronics. However, currently, commercially available LDS materials are almost entirely limited to a few resin systems such as ABS, PC / ABS alloys, or PA. While these materials have mature processing techniques, they each suffer from inherent defects such as insufficient heat resistance, high cost, and high hygroscopicity, limiting their application in a wider range of scenarios.

[0003] Polypropylene (PP), as the most widely produced general-purpose plastic, combines low density, excellent chemical resistance, and easy processing, making it widely used in the automotive and home appliance industries. However, using PP in LDS faces three interrelated technical obstacles: First, PP has extremely low absorption of typical near-infrared lasers (such as 1064 nm), and inherently lacks laser-sensitive properties; second, most high-efficiency laser-sensitive fillers are polar inorganic materials with poor compatibility with the PP matrix, easily agglomerating, leading not only to uneven laser activation but also severely weakening coating adhesion due to the thin interface; third, after introducing a considerable proportion of fillers to obtain sufficient laser response, the toughness and melt flowability of PP often deteriorate significantly, making it difficult to meet the stringent requirements for comprehensive mechanical properties of structurally integrated components.

[0004] To address the aforementioned issues, existing technologies include modification schemes involving laser marking of polypropylene, but these only aim to create surface markings and cannot form a conductive catalytic layer sufficient to initiate chemical plating. Other schemes focus on optimizing the laser transmittance of PP for welding and other joining processes, but their technical goals are the opposite of the high-efficiency localized energy deposition required for LDS. Therefore, there is an urgent need to develop a comprehensive material solution that can systematically address the series of problems faced by PP in LDS applications, including weak absorption, poor dispersion, weak interfaces, and reduced toughness. Summary of the Invention

[0005] In view of this, the present invention provides a polypropylene composite material for laser engraving and its preparation method. Through the synergistic effect of composite laser-sensitive additives and toughening compatibilizers with specific grafting ratios, the multiple technical contradictions of polypropylene in laser insensitivity, difficult filler dispersion, weak interfacial bonding and toughness deterioration when used for LDS are systematically solved, so that the material has excellent LDS performance, high mechanical strength and good processing fluidity.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention discloses a polypropylene composite material for laser engraving, which is prepared by weight of 50-90 parts of polypropylene resin, 15-16 parts of composite laser sensitizer, 5-15 parts of toughening compatibilizer, 0-10 parts of filler, 0.2-0.4 parts of antioxidant, and 0.1-0.3 parts of lubricant, wherein the composite laser sensitizer is a compound of inorganic laser sensitizer and organic carbonization accelerator.

[0007] As a further aspect of the present invention: the toughening compatibilizer has a grafting rate of 0.5%. 1.2% maleic anhydride-grafted polyolefin elastomer.

[0008] As a further aspect of the present invention, the weight ratio of the inorganic laser sensitizer to the organic carbonization accelerator is (9.5:1) to (15:1).

[0009] As a further aspect of the present invention: the polypropylene resin is compounded from high-flowability copolymer polypropylene and high-toughness copolymer polypropylene in a 1:1 weight ratio; the high-flowability copolymer polypropylene has a melt flow rate of 30-100 g / 10 min at 230°C and 2.16 kg, and the high-toughness copolymer polypropylene has a notched cantilever beam impact strength ≥20 kJ / m. 2 .

[0010] As a further aspect of the present invention: the inorganic laser sensitizer is antimony-doped tin dioxide with an average particle size of 0.3-1.0 μm; the organic carbonization promoter is copper phthalocyanine.

[0011] As a further aspect of the present invention: the filler is a sheet-like filler, which is wet-synthesized mica with a diameter-to-thickness ratio greater than 20:1.

[0012] As a further aspect of the present invention: the notched impact strength of its cantilever beam is ≥20 kJ / m 2 The flexural modulus is ≥1500MPa, and the melt flow rate at 230℃ and 2.16kg is ≥10 g / 10min.

[0013] As a further aspect of the present invention: after the polypropylene composite material is engraved with near-infrared laser and chemically plated with copper, the resistivity of the resulting metallized pattern is not greater than 0.5 Ω / cm.

[0014] Secondly, the present invention discloses a method for preparing the above-mentioned polypropylene composite material for laser engraving, comprising the following steps: The composite laser-sensitive additive is premixed with a portion of toughening compatibilizer, and then melt-extruded and granulated to obtain the additive masterbatch. The polypropylene resin, the remaining toughening compatibilizer, and the additive masterbatch are mixed evenly to obtain a premix. The premixed material is fed into a twin-screw extruder and melt-blended, extruded, and granulated at a processing temperature of 170-210℃ and a screw speed of 300-500 rpm to obtain the polypropylene composite material for laser engraving.

[0015] Thirdly, the present invention discloses the application of the polypropylene composite material for laser engraving as described above in the manufacture of intelligent automotive interior parts or intelligent home appliance housing components with integrated conductive circuits.

[0016] Compared with the prior art, the beneficial effects of the present invention are: First, this invention solves the technical challenges of PP-based LDS materials at the system level for the first time. Existing technologies mostly focus on improving single properties, making it difficult to simultaneously address multiple interdependent aspects such as laser activation efficiency, filler dispersion, interfacial adhesion, and mechanical toughness. This invention, through a dual synergistic design of an inorganic / organic composite activation system and an elastomer compatibilizer with precisely optimized grafting rates, simultaneously addresses three dimensions: energy absorption-conversion, micro-graphitized structure construction, and macro-interface engineering. This comprehensively and synergistically solves the technical chain challenges of using PP in LDS, and the overall technical approach is non-obvious.

[0017] Secondly, it achieves a revolutionary balance between functionality and mechanical properties. Traditionally, high levels of functional additives used to obtain sufficient LDS response lead to material embrittlement. This invention leverages the dispersing, coupling, and toughening effects of POE-g-MAH with a specific grafting ratio. While introducing functional fillers, it enables the composite material to simultaneously possess excellent LDS performance, high toughness, and good processing flowability, meeting the stringent requirements for comprehensive performance in structural-functional integrated components.

[0018] Third, the raw materials used in this invention are all mass-produced industrial products, and the preparation process is fully compatible with existing plastic modification production lines, requiring no additional special equipment. Compared to the current LDS solution, which must use imported engineering plastics (such as PC / ABS, PA), this invention achieves the same or even better performance while significantly lowering raw material and processing costs, giving it strong market competitiveness. Detailed Implementation

[0019] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0021] In addition, unless otherwise specified, the preparation processes in the following embodiments are all conventional methods in the prior art, and therefore will not be described in detail; unless otherwise specified, the parts in the following embodiments refer to parts by weight.

[0022] The reagents used in this embodiment and their suppliers are as follows: Polypropylene resins: PP-HF (high-flow copolymer polypropylene, MFR (230℃ / 2.16kg) = 65 g / 10min), manufactured by Sinopec Shanghai Petrochemical Co., Ltd., grade M1200H; PP-HT (high-toughness copolymer polypropylene, cantilever beam notched impact strength ≈ 35 kJ / m 2 The manufacturer of the product (MFR (230℃ / 2.16kg) = 25 g / 10min) is SK Chemicals Co., Ltd. of South Korea, and the product name is BX3920.

[0023] Composite laser-sensitive additives: The inorganic phase is antimony-doped tin dioxide (ATO) with an average particle size D50 of 0.5 μm, manufactured by Shanghai Naio Nanotechnology Co., Ltd., with the grade ATO-P500; the organic phase is industrial-grade copper phthalocyanine (CuPc), manufactured by BASF China Ltd., with the grade Heliogen® Blue K7090.

[0024] Surface treatment agent: Silane coupling agent KH-550 (γ-aminopropyltriethoxysilane), manufactured by Nanjing Shuguang Chemical Group Co., Ltd., with a purity of ≥98%.

[0025] Before use, the surface is pretreated with a 1.0% (by weight of powder) silane coupling agent KH-550 ethanol solution.

[0026] Toughening compatibilizers: POE-g-MAH (maleic anhydride grafting rate 0.8%, MFR (190℃ / 2.16kg) = 5 g / 10min) is manufactured by Ningbo Nengzhiguang New Material Technology Co., Ltd., brand name N-812; PP-g-MAH (maleic anhydride grafting rate 0.9%, used as a control sample) is manufactured by Jiayirong Polymer (Shanghai) Co., Ltd., brand name CMG-9801.

[0027] Filler: Wet-process synthetic mica (average diameter-to-thickness ratio >30:1, D50=10μm), manufactured by Chuzhou Wanqiao Sericite Powder Factory, grade QM-12.

[0028] Other additives: Antioxidant (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl)phosphite in a 1:1 ratio), all manufactured by BASF China Ltd.; Lubricant calcium stearate, industrial grade, manufactured by Huzhou Linghu Xinwang Chemical Co., Ltd., brand name SA-Ca-01.

[0029] The reagents described above are only for illustrating the source and composition of the reagents used in the experiments of this invention, so as to provide full disclosure, and do not imply that the invention cannot be achieved by using other similar reagents or reagents provided by other suppliers.

[0030] The performance testing standards are as follows: Melt flow rate (MFR): Tested according to ISO 1133 standard at 230°C / 2.16 kg.

[0031] Flexural properties (flexural modulus): tested according to ISO 178 standard.

[0032] Notched impact strength of cantilever beam: tested according to ISO 180 / 1A standard.

[0033] The coating adhesion is rated according to the ASTM D3359 standard cross-cut adhesion test, with 0 being the best and 5 being the worst.

[0034] Dynamic thermomechanical analysis (DMA): Using thin film stretching mode, the test temperature range is -80℃ to 120℃. The loss factor (tanδ) is analyzed as a function of temperature to characterize interfacial interactions and material damping properties.

[0035] LDS processing and performance evaluation: 1. Laser engraving: Using a 1064 nm wavelength fiber laser marking machine, a parallel line array with a line width of 50 μm and a spacing of 200 μm was engraved in the central area of ​​a 100 mm × 100 mm × 2 mm flat sample surface. Through parameter optimization, the optimal process conditions were determined to be: power 15 W, scanning speed 2000 mm / s. 2. Chemical Copper Plating: The standard alkaline chemical copper plating process is adopted, and the process is as follows: alkaline degreasing (50℃, 5min) → water washing → acid washing (10% volume fraction sulfuric acid solution, room temperature, 2min) → water washing → activation (using commercially available colloidal palladium activator, palladium concentration 50 ppm, diluted at a volume ratio of 1:9, soaking at 40℃ for 5min) → water washing → chemical copper plating (basic composition of plating solution: copper sulfate pentahydrate 8 g / L, formaldehyde (37%) 15 ml / L, disodium ethylenediaminetetraacetate 30 g / L, pH adjusted to 12.8 with sodium hydroxide, temperature 55±1℃, plating time 30min) → water washing → hot air drying.

[0036] 3. LDS Performance Characterization: The sheet resistance of the circuit after electroless copper plating was measured using a four-probe tester and converted to resistivity per unit length (Ω / cm). Adhesion was tested using the cross-cut adhesion test (tape method) according to Method B of ASTM D3359 and rated (0 being the best, 5 the worst). The width and edge morphology of the engraved lines were observed and measured using a laser confocal microscope.

[0037] Material characterization methods: Raman spectroscopy: Using a 532 nm laser, the spectra of micro-regions on the surface of the laser-engraved sample are acquired to analyze the characteristic peaks of the carbonized products: D peak (~1350 cm⁻¹). -1 (representing disordered carbon or defects) and the G peak (~1580 cm⁻¹) -1 (Represents the ordered vibration of the graphite lattice). The degree of graphitization and structural defect density of the carbonized layer are evaluated by calculating its intensity ratio (ID / IG). The lower the ID / IG value, the higher the degree of graphitization.

[0038] Thermogravimetric analysis (TGA): Under a nitrogen atmosphere, the sample was heated from 50°C to 800°C at a heating rate of 10°C / min. The thermogravimetric curve of the sample was recorded, and the mass retention rate (char residue) at 600°C was read to evaluate the thermal stability of the composite material and its char-forming ability at high temperatures.

[0039] The preparation methods of Examples 1-6 and Comparative Examples 1-6 were all carried out according to the following general steps: (1) Masterbatch preparation: Weigh the surface-treated composite laser sensitizer (a mixture of ATO and CuPc) and 30% of the total weight of the toughening compatibilizer added in the formula according to the formula in Table 1, and mix them in a high-speed mixer for 5 minutes. The mixture is melt-extruded by a co-rotating twin-screw extruder, water-cooled, and pelletized to obtain LDS additive concentrated masterbatch. The twin-screw extruder has a medium-low shear combination screw configuration with a length-to-diameter ratio of 44:1; the temperature settings are: 170℃ in zone 1, 180℃ in zone 2, 190-200℃ in zones 3 to 7, and 205℃ at the die head; the screw speed is 400 rpm; and the vacuum degree is maintained above -0.07 MPa.

[0040] (2) Preparation of composite materials: According to the formula shown in Table 1, all polypropylene resin, the remaining toughening compatibilizer, the above-prepared additive concentrate masterbatch, wet-process mica, antioxidant, and lubricant were put into a high-speed mixer and mixed for 5 minutes to obtain a premix. The premix was fed into a twin-screw extruder (screw configuration is a medium-low shear combination, length-to-diameter ratio 44:1; temperature settings: zone 1 170℃, zone 2 180℃, zones 3 to 7 190-200℃, die head 205℃; screw speed 400 rpm; vacuum degree maintained above -0.07 MPa), and after melt mixing, extrusion, water cooling, pelletizing, and drying at 80℃ for 4 hours, the final composite material particles were obtained.

[0041] (3) Test strip preparation: The dried composite material particles are injection molded into ISO standard mechanical property test strips and LDS performance test plates (100mm×100mm×2mm) on a standard injection molding machine.

[0042] The performance test results are shown in Table 1.

[0043] Table 1

[0044] Note: “—” in the table indicates that the test was not performed or is not required.

[0045] Comparing Example 1 with Comparative Examples 1-3, it can be seen that: Comparative Example 1, lacking CuPc, cannot form a continuous conductive circuit at all, proving that the organic carbonization promoter is a necessary component for forming a conductive carbonized layer. In Comparative Example 2, the ATO:CuPc ratio is 17:1, exceeding the upper limit, with a resistivity of 3.2 Ω / cm, an ID / IG value of 1.22, and a residual carbon content of 6.8%, resulting in decreased LDS performance, indicating that insufficient organic phase ratio cannot fully induce graphitization. In Comparative Example 3, the ATO:CuPc ratio is 8:1, below the lower limit, with a resistivity of 3.8 Ω / cm and an ID / IG value of 1.35, also showing poor performance, indicating that excessive organic phase interferes with the uniform absorption and conversion of laser energy. The resistivity of Examples 1-3 is ≤0.65 Ω / cm, the ID / IG value is ≤1.12, and the residual carbon content is ≥7.5%, fully meeting the performance requirements.

[0046] Comparative Example 1 and Comparative Examples 4-6: Comparative Example 5, without toughening compatibilizer, has an impact strength of only 4.8 kJ / m. 2 Furthermore, it is completely non-conductive, indicating that the toughening compatibilizer not only affects mechanical properties but also directly influences the activation of LDS. In Comparative Example 4, replacing POE-g-MAH with an equal amount of PP-g-MAH resulted in an impact strength of only 8.5 kJ / m². 2 The LDS adhesion was grade 2-3, indicating that while PP-g-MAH has some compatibility, it lacks elastic toughening effect and sufficient interfacial buffering capacity. Comparative Example 6, using PP-g-MAH but without POE-g-MAH, had an impact strength of only 5.5 kJ / m. 2 With a resistivity of 4.2Ω / cm and an LDS adhesion rating of only 3, it is further confirmed that the synergistic effect of the present invention cannot be achieved by using PP-g-MAH alone.

[0047] Example 1 (POE-g-MAH, 0.8% grafting rate): Impact strength 26.8 kJ / m 2 With an adhesion rating of 0, it fully demonstrates the irreplaceable nature of the dispersion-coupling-toughening triad of POE-g-MAH with a specific grafting ratio.

[0048] Application Example: To verify the reliability of the material in practical application, the composite material of Example 1 was used to injection mold a curved air conditioning vent hidden touch-sensitive decorative strip component for a certain brand of new energy vehicle. In a predetermined area on the surface of this component, a diamond-shaped grid circuit for capacitive touch control (line width / spacing = 50μm / 200μm) was engraved using the aforementioned LDS process, and chemical copper plating (copper layer thickness approximately 5μm) was completed. Tests showed that the surface sheet resistance of the integrated circuit was <0.1 Ω / □, the touch function was sensitive, and it met the design specifications. To further assess its long-term reliability, the finished component was placed in a constant temperature and humidity test chamber at 85°C and 85% relative humidity (RH) for a continuous 1000-hour aging test. After the test, the surface plating of the component remained intact, with no blistering, peeling, or discoloration. The adhesion test using the cross-cut adhesion test maintained the highest level (level 0), and the circuit function was normal.

[0049] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0050] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. A polypropylene composite material for laser engraving, characterized in that, It is prepared by weight of 50-90 parts of polypropylene resin, 15-16 parts of composite laser sensitizer, 5-15 parts of toughening compatibilizer, 0-10 parts of filler, 0.2-0.4 parts of antioxidant, and 0.1-0.3 parts of lubricant, wherein the composite laser sensitizer is a compound of inorganic laser sensitizer and organic carbonization accelerator.

2. The polypropylene composite material for laser engraving according to claim 1, characterized in that, The toughening compatibilizer has a grafting rate of 0.5%. 1.2% maleic anhydride-grafted polyolefin elastomer.

3. The polypropylene composite material for laser engraving according to claim 1, characterized in that, The weight ratio of the inorganic laser sensitizer to the organic carbonization accelerator is (9.5:1) to (15:1).

4. The polypropylene composite material for laser engraving according to claim 1, characterized in that, The polypropylene resin is a blend of high-flowability copolymer polypropylene and high-toughness copolymer polypropylene in a 1:1 weight ratio; the high-flowability copolymer polypropylene has a melt flow rate of 30-100 g / 10 min at 230℃ and 2.16 kg, and the high-toughness copolymer polypropylene has a notched cantilever beam impact strength ≥20 kJ / m. 2 .

5. The polypropylene composite material for laser engraving according to claim 1, characterized in that, The inorganic laser sensitizer is antimony-doped tin dioxide with an average particle size of 0.3-1.0 μm; the organic carbonization promoter is copper phthalocyanine.

6. The polypropylene composite material for laser engraving according to claim 1, characterized in that, The filler is a sheet-like filler, which is wet-synthesized mica with a diameter-to-thickness ratio greater than 20:

1.

7. The polypropylene composite material for laser engraving according to claim 1, characterized in that, Its cantilever beam notched impact strength ≥20 kJ / m 2 The flexural modulus is ≥1500 MPa, and the melt flow rate at 230℃ and 2.16 kg is ≥10 g / 10 min.

8. The polypropylene composite material for laser engraving according to claim 1, characterized in that, The resistivity of the lines of the metallized pattern obtained after near-infrared laser engraving and chemical copper plating of the polypropylene composite material is no greater than 0.5 Ω / cm.

9. The method for preparing the polypropylene composite material for laser engraving according to any one of claims 1-8, characterized in that, Includes the following steps: The composite laser-sensitive additive is premixed with a portion of toughening compatibilizer, and then melt-extruded and granulated to obtain the additive masterbatch. The polypropylene resin, the remaining toughening compatibilizer, and the additive masterbatch are mixed evenly to obtain a premix. The premixed material is fed into a twin-screw extruder and melt-blended, extruded, and granulated at a processing temperature of 170-210℃ and a screw speed of 300-500rpm to obtain the polypropylene composite material for laser engraving.

10. The use of the polypropylene composite material for laser engraving as described in any one of claims 1-8 in the manufacture of intelligent automotive interior parts or intelligent home appliance housing components with integrated conductive circuits.

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