Preparation method of automobile high-brightness decorative strip with high weather resistance and gloss persistence

Abstract

The invention relates to the technical field of preparation of polymer modified materials, and discloses a preparation method of an automobile high-brightness decorative strip with high weather resistance and gloss persistence, and the method comprises the following steps: premixing perfluorohexane and triphenyl phosphite, injecting into a melting system containing polycarbonate, polymethyl methacrylate and lanthanum acetylacetonate catalyst, and carrying out melt extrusion to obtain the automobile high-brightness decorative strip with high weather resistance and gloss persistence. Lanthanum acetylacetonate is used for inducing a two-phase interface to generate an in-situ ester exchange reaction, a block copolymer with a compatibilization effect is generated, a dispersed phase domain region is effectively reduced, the blackness and the surface glossiness of the material are improved, meanwhile, local transient cooling of a melt is achieved through the phase change flash evaporation effect of perfluorohexane, and the flame retardance of the material is improved. And in cooperation with the chelating passivation effect of triphenyl phosphite on the center of the rare earth catalyst, thermal degradation of a polymer chain in the processing and service process is inhibited. According to the invention, in-situ ester exchange, phase change flash evaporation and chemical passivation are cooperated, so that thermal degradation is inhibited while interfacial compatibility is enhanced, and high gloss and long-acting weather resistance of the decorative strip are realized.

Description

Technical Field

[0001] This invention relates to the field of polymer modified material technology, specifically to a method for preparing high-gloss automotive trim strips with high weather resistance and gloss durability. Background Technology

[0002] As a key component of a vehicle's appearance, the surface quality of automotive exterior trim directly affects the vehicle's visual appeal. Therefore, materials must possess extremely high surface gloss, deep blackness, and excellent outdoor weather resistance. Polycarbonate and polymethyl methacrylate alloys, through complementary components, can simultaneously achieve good mechanical strength, heat resistance, and surface hardness, making them the mainstream solution for achieving a high-gloss, paint-free finish.

[0003] However, in practical applications, polycarbonate and polymethyl methacrylate (PMMA) are thermodynamically incompatible systems. The large interfacial tension between the two leads to coarse dispersed phase domains. During injection molding, due to drastic changes in the shear field, flow marks, silver streaks, or obvious phase separation haze easily form on the material surface, making it difficult to achieve the deep texture of piano black. Although introducing transesterification catalysts can induce chemical bonding at the interface between the two phases to generate compatibilizing block structures and improve compatibility, PMMA is extremely sensitive to heat. The high-temperature processing accompanying the catalytic reaction often triggers disordered depolymerization of the molecular chains.

[0004] This degradation process not only releases a large amount of monomer volatiles, causing microbubbles on the surface of the product, but also poses a more serious problem: the residual activity of the catalyst. Existing extrusion processes lack effective reaction termination methods. Residual active rare earth or metal ions in the alloy matrix continue to catalyze the photo-oxidative degradation and hydrolysis of the polymer chains during subsequent injection molding and long-term outdoor service. This uncontrollable chemical activity causes the molecular chains to break and generate chromophores after UV irradiation or high-temperature and humid aging, ultimately resulting in rapid gloss decay, yellowing, and embrittlement and cracking of the trim surface, severely limiting the service life of high-performance automotive trims. Therefore, how to achieve transient control of the reaction process and complete catalytic activity lock-in while ensuring interfacial compatibilization efficiency is a pressing technical challenge in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing high-gloss automotive trim strips with high weather resistance and gloss durability. This method solves the problems of surface quality defects caused by poor compatibility between the two phases in existing polycarbonate and polymethyl methacrylate alloy systems, as well as polymer thermal degradation and weather resistance deterioration caused by catalyst residues during processing.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a high-gloss automotive trim strip with high weather resistance and gloss durability, comprising the following steps:

[0007] S1. Mix perfluorohexane and triphenyl phosphite at a mass ratio of 2 to 8:1 until a homogeneous and transparent mixture is formed. Then transfer the mixture to a storage tank and seal it for later use.

[0008] S2. Mix polycarbonate resin, polymethyl methacrylate resin, lanthanum acetylacetonate, high-pigment carbon black and hindered amine light stabilizer evenly, and add to the main feed port of the twin-screw extruder.

[0009] S3. Set the temperature of the reaction section of the twin-screw extruder so that the material undergoes melt blending and in-situ transesterification block reaction under the catalysis of lanthanum acetylacetone.

[0010] S4. The mixture described in step S1 is continuously injected into the melt inside the twin-screw extruder using a side high-pressure pump.

[0011] S5. The material enters the sealed zone of the twin-screw extruder, where the phase change flash evaporation effect of perfluorohexane reduces the local temperature of the melt, while triphenyl phosphite passivates the residual lanthanum acetylacetone.

[0012] S6. After the material is vacuum-treated to remove perfluorohexane vapor and volatiles, it is extruded from the die head, cooled, pelletized and dried.

[0013] S7. The dried material is then processed into high-gloss automotive trim strips using an injection molding process.

[0014] By adopting the above technical solution, this invention introduces a process combining in-situ chemical reaction and physical transient control during twin-screw extrusion. Lanthanum acetylacetonate initiates transesterification between polycarbonate and polymethyl methacrylate at the interface, generating a compatibilizing block copolymer. This enhances the adhesion between the two phases, reduces diffuse reflection caused by phase separation, and results in a material exhibiting uniform surface gloss and blackness.

[0015] Meanwhile, by injecting a mixture of perfluorohexane and triphenyl phosphite laterally, the low boiling point of perfluorohexane generates a transient phase change endothermic reaction in the melt, which can quickly remove the local enthalpy of the melt to suppress the occurrence of side reactions.

[0016] While physically cooling the material, triphenyl phosphite chelates and passivates the rare earth catalyst center, blocking the polymer chain thermal degradation process that may occur in the later stages of processing and injection molding, thus essentially ensuring the material's weather resistance and gloss stability.

[0017] The mechanism of this invention is as follows:

[0018] Regarding the in-situ transesterification compatibilization process:

[0019] In step S3, lanthanum acetylacetonate acts as an transesterification catalyst, with its rare-earth metal center coordinating with the carbonate groups of polycarbonate (PC) and the ester groups of polymethyl methacrylate (PMMA). Under a shear field of 235–255 °C, chain segmentation and recombination occur at the two-phase interface. In this process, the catalyst... It forms an unstable coordination intermediate with the ester group, effectively reducing the activation energy of the reaction;

[0020] Subsequently, the terminal hydroxyl or carbonate groups of the PC segments exchange with the methyl ester groups in the PMMA chains, generating PC-b-PMMA block copolymers in situ. Because these newly formed copolymers are oriented and enriched in the interfacial region, they can reduce interfacial tension and refine the dispersed domain regions of PMMA, thereby eliminating macroscopic surface haze by forming a stable microstructure.

[0021] Regarding the synergistic effect of thermodynamic regulation and chemical passivation:

[0022] In steps S4 and S5, perfluorohexane is introduced to precisely truncate the reaction kinetics. Perfluorohexane has a boiling point of only 56°C at atmospheric pressure. When it enters the high-temperature melt under high pressure, it experiences a dramatic absorption effect of latent heat of vaporization due to the sudden pressure drop. Since this medium does not chemically react or swell with the polymer components, the cavitation effect generated by its phase transition can drive the triphenyl phosphite (TPP) to achieve full spatial dispersion within microseconds.

[0023] Under this cooling effect, the local temperature of the melt drops by more than 30°C within 3 seconds, causing the kinetic energy of the system to rapidly decrease below the threshold for transesterification and PMMA depolymerization, thus forcibly terminating the reaction process. Simultaneously, the uniformly distributed TPP utilizes its strong coordination groups to... The formation of a highly thermally stable complex causes the catalyst to lose its coordination ability with ester groups, thus achieving physical shielding and chemical locking of the catalyst activity.

[0024] In addition, TPP, as a secondary antioxidant, can further clean up hydrogen peroxide in the system and synergistically construct a long-lasting anti-aging system with hindered amine light stabilizers, avoiding photo-oxidative degradation of molecular chains during service.

[0025] Preferably, in step S1, the step of forming a uniform and transparent mixture includes: turning on the stirrer at 20-25°C and setting the speed to 100-200 rpm, then adding triphenyl phosphite dropwise; maintaining constant temperature stirring for 10-15 minutes, and transferring the mixture to a plunger pump storage tank with piston pressure by nitrogen pressure delivery.

[0026] By adopting the above technical solution, controlled stirring at room temperature ensures that perfluorohexane and triphenyl phosphite are molecularly miscible, and the chemical composition of the system is kept constant by a pressure delivery system, so as to avoid the impact of fluctuations in the proportion of volatile components on the subsequent cooling effect.

[0027] Preferably, in S2, the weight parts of each material are as follows: polycarbonate resin: 60-80 parts; polymethyl methacrylate resin: 20-40 parts; lanthanum acetylacetonate: 0.05-0.15 parts; high-pigment carbon black: 0.3-0.8 parts; hindered amine light stabilizer: 0.1-0.3 parts.

[0028] By adopting the above technical solution, the rigidity and optical performance of the material were balanced through ratio optimization. Under the premise of ensuring that lanthanum acetylacetonate provides sufficient catalytic activity, a stable polymer alloy matrix was constructed by combining the synergistic effect of light stabilizer and passivator.

[0029] Preferably, in S3, the reaction temperature of the first to fifth zones of the twin-screw extruder is set to be constant at 235–255°C, and the screw speed is set to 300–500 rpm.

[0030] By adopting the above technical solution, and by maintaining a specific level of thermal energy and shear strength, it is ensured that the material has completed the expected in-situ compatibilization reaction before entering the quenching zone, thus laying the foundation for the formation of a stable microstructure.

[0031] Preferably, in step S4, when the melt is conveyed to the sixth zone of the extruder, 1.0 to 2.0 parts of the mixture described in step S1 are injected based on 100 parts of the total weight of the polycarbonate resin and polymethyl methacrylate resin described in step S2, and the injection pressure is set to 3.0 to 8.0 MPa.

[0032] By adopting the above technical solution, the physical state of perfluorohexane is controlled by high-pressure injection, enabling it to generate a higher intensity of flash expansion work when entering the low-pressure zone, thereby improving the dispersion uniformity of the passivating agent and the cooling rate of the melt.

[0033] Preferably, in S5, the material enters the melt sealing zone of the seventh zone, and the back pressure in this zone is maintained at 1.5 to 3.0 MPa by adjusting the die head pressure valve.

[0034] By adopting the above technical solution, a relatively closed phase change chamber is constructed inside the extruder using controlled back pressure, which prolongs the reaction time of perfluorohexane endothermic reaction and triphenyl phosphite chelation catalyst, ensuring the complete quenching of the reaction.

[0035] Preferably, in S6, the material enters the eighth and ninth zones, respectively, and the two-stage vacuum system is activated to control the absolute pressure to 300-800 Pa and 100-400 Pa, respectively.

[0036] By adopting the above technical solution, through graded gradient vacuuming, the perfluorohexane vapor and reaction residues that have completed their functional mission are completely removed, thus avoiding interference from trace bubbles in the material on the surface gloss of the injection molded parts.

[0037] This invention provides a method for preparing high-gloss automotive trim strips with high weather resistance and gloss durability. It offers the following advantages:

[0038] 1. This invention utilizes lanthanum acetylacetonate to induce an in-situ transesterification reaction between polycarbonate and polymethyl methacrylate during twin-screw extrusion, generating a compatibilizing block copolymer at the interface between the two phases. This copolymer effectively reduces interfacial tension, decreases the domain size of the dispersed phase, and forms a stable phase structure, thereby improving the gloss and blackness of the material surface and solving the surface fogging and flow mark problems that are prone to occur in conventional physical blending systems.

[0039] 2. This invention utilizes the phase change flash evaporation effect of perfluorohexane injected under high pressure from the side to rapidly absorb the enthalpy of the melt in the sealed melt zone, achieving transient cooling at the thermodynamic level. This temperature control mechanism can forcibly terminate unnecessary transesterification reactions in the later stages and effectively inhibit the thermal depolymerization of polymethyl methacrylate at high temperatures, reducing the generation of monomer residues and small molecule volatiles, and ensuring the stability of the melt mass flow rate.

[0040] 3. This invention utilizes the vaporization and expansion of perfluorohexane to rapidly disperse triphenyl phosphite in the melt, enabling it to undergo strong coordination chelation with the rare earth catalyst center. This chemical passivation method completely seals off the catalyst's activity, preventing molecular chain degradation caused by residual catalytic activity during injection molding and subsequent use. Combined with the synergistic protection of hindered amine light stabilizers, this significantly enhances the color retention and weather resistance of the trim strips under long-term photo-oxidative environments. Attached Figure Description

[0041] Figure 1 This is a schematic diagram comparing the thermodynamic response parameters and melt degradation indexes of various embodiments and comparative examples of the present invention;

[0042] Figure 2 This is a schematic diagram comparing the glass transition temperature shift data based on DSC thermal analysis according to the present invention;

[0043] Figure 3 This is a bar chart comparing the cooling amplitudes of various embodiments and comparative examples of the present invention;

[0044] Figure 4 This is a bar chart comparing the melt flow rates of various embodiments and comparative examples of the present invention.

[0045] Figure 5This is a bar chart comparing the volatile residue MMA content of various embodiments and comparative examples of the present invention;

[0046] Figure 6 This is a bar chart showing the multi-angle comparison of gloss and color brightness of various embodiments and comparative examples of the present invention.

[0047] Figure 7 This is a bar chart comparing the impact strength and accelerated aging stability of various embodiments and comparative examples of the present invention. Detailed Implementation

[0048] Please see the appendix Figure 1 -Appendix Figure 7 .

[0049] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0050] The polycarbonate resin (CAS No. 25037-45-0) is a bisphenol A type polycarbonate homopolymer. Its melt flow rate under test conditions of 300℃ and 1.2kg is 10.0g / 10min, and its weight-average molecular weight ranges from 22,000 to 25,000.

[0051] Polymethyl methacrylate resin (CAS No. 9011-14-7) is an amorphous homopolymer prepared by suspension polymerization. Its melt flow rate is 2.0 g / 10 min under test conditions of 230℃ and 3.8 kg, and its light transmittance is greater than 92%.

[0052] Lanthanum acetylacetonate (CAS No. 14284-88-9) is a commercially available analytical grade solid powder with a purity greater than 99.0%.

[0053] Triphenyl phosphite (CAS No. 101-02-0) is a commercially available pure liquid with a purity greater than 99.0%.

[0054] Perfluorohexane (CAS No. 355-42-0) is a high-purity perfluorocarbon fluorinated liquid with a boiling point of 56°C at normal pressure and a purity greater than 99.0%.

[0055] High-pigment carbon black (CAS No. 1333-86-4) has a native particle size range of 15nm to 25nm.

[0056] The hindered amine light stabilizer (CAS No. 41556-26-7) is bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, with an effective content greater than 96.0%.

[0057] Example 1:

[0058] This embodiment provides a method for preparing a high-gloss automotive trim material, including the following steps:

[0059] S1. In an explosion-proof, sealed mixing vessel at 22°C and normal pressure, first measure and add 35 kg of perfluorohexane using a level gauge, turn on the anchor-type agitator and set the speed to 150 rpm, then slowly add 10 kg of triphenyl phosphite dropwise over 3 minutes using a dropping tank; maintain a constant temperature of 22°C and stir for 12 minutes. After a homogeneous and transparent mixture is formed, transfer it to a piston pump storage tank with piston pressure using nitrogen pressure transfer and seal it for later use.

[0060] S2. Add 70 parts of polycarbonate resin (PC), 30 parts of polymethyl methacrylate resin (PMMA), 0.1 parts of lanthanum acetylacetonate, 0.5 parts of high-pigment carbon black and 0.2 parts of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate to a high-speed mixer and mix at 800 rpm for 5 minutes. After mixing evenly, add the mixture to the main feed port of a twin-screw extruder.

[0061] S3. Set the reaction temperature of the first to fifth zones of the twin-screw extruder to be constant at 245℃ and the screw speed to 400rpm, so that the material undergoes melt blending and in-situ transesterification block reaction under the catalysis of lanthanum acetylacetone.

[0062] S4. When the melt is delivered to the sixth zone of the extruder, 1.5 parts of the mixture are continuously injected by a side high-pressure pump, with the injection pressure set to 5.0 MPa.

[0063] S5. The material enters the melt sealing zone of the seventh zone. The back pressure of this zone is maintained at 2.0MPa by adjusting the pressure valve of the die head. The local temperature of the melt is rapidly reduced to 210℃ within 3s by utilizing the endothermic effect of the sudden boiling of perfluorohexane. At the same time, triphenyl phosphite is uniformly dispersed and passivates the center of the residual catalyst.

[0064] S6. The material enters zones eight and nine, where a two-stage vacuum system is activated, controlling the absolute pressures to 500 Pa and 200 Pa respectively. A high-capacity vacuum pump, combined with a condensation recovery device, efficiently removes perfluorohexane vapor and volatiles. The material is extruded through a die head (set temperature 225℃), cooled in a 35℃ constant-temperature water bath, and pelletized. The resulting pellets are placed in a honeycomb dehumidifying dryer and continuously dried at 105℃ for 4 hours to ensure the material moisture content is below 0.02%.

[0065] S7. Input the dried material into the precision injection molding machine, set the barrel temperature to: Zone 1 240℃, Zone 2 255℃, Zone 3 265℃, nozzle 260℃; set the mold temperature to 105℃ (using rapid cooling and heating mold temperature control technology); set the injection pressure to 110MPa, the holding pressure to 85MPa, the holding time to 8s, and the cooling time to 15s to obtain the finished high-gloss automotive trim strip.

[0066] Example 2:

[0067] This embodiment provides a method for preparing a high-gloss automotive trim material, including the following steps:

[0068] S1. In an explosion-proof, sealed mixing vessel at 20°C and normal pressure, first add 30 kg of perfluorohexane, start stirring and set the speed to 100 rpm, then slowly add 5 kg of triphenyl phosphite; maintain a constant temperature of 20°C and stir for 10 min. After a uniform and transparent mixture is formed, transfer it to a piston pump storage tank with piston pressure by nitrogen pressure transfer and seal it for later use.

[0069] S2. Mix 60 parts of polycarbonate resin, 40 parts of polymethyl methacrylate resin, 0.05 parts of lanthanum acetylacetonate, 0.3 parts of high-pigment carbon black and 0.1 parts of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate in a high-speed mixer until homogeneous, and then add the mixture to the main feed port of a twin-screw extruder.

[0070] S3. Set the reaction temperature of the first to fifth zones of the twin-screw extruder to 235℃ and the screw speed to 300rpm to guide the material to melt and undergo preliminary reaction.

[0071] S4. When the melt is delivered to the sixth zone of the extruder, 1.0 part of the mixture is injected by a high-pressure pump, and the injection pressure is set to 3.0 MPa.

[0072] S5. The material enters the melt sealing zone of the seventh zone, and the back pressure in this zone is maintained at 1.5MPa. The perfluorohexane phase change flash evaporation absorbs a large amount of latent heat, causing the local temperature of the melt to drop rapidly to 200℃, rapidly freezing the reaction morphology and terminating the transesterification reaction.

[0073] S6. The material enters the vacuum devolatilization zone, with absolute pressures controlled at 300 Pa and 100 Pa respectively. The devolatilized melt is extruded through a die head (temperature 215℃), cooled by circulating water at 25℃, and then pelletized. The pellets are dried in a hot air circulating oven at 100℃ for 6 hours.

[0074] S7. The injection molding process is set as follows: the barrel temperature from the feeding section to the nozzle is 235℃, 245℃, 255℃, and 250℃ respectively; the mold temperature is 90℃; the injection pressure is 95MPa; the injection speed is medium speed (40mm / s); the holding pressure is 70MPa; and the cooling time is 20s.

[0075] Example 3:

[0076] This embodiment provides a method for preparing a high-gloss automotive trim material, including the following steps:

[0077] S1. In an explosion-proof, sealed mixing vessel at 25°C and normal pressure, first add 40 kg of perfluorohexane, start stirring and set the speed to 200 rpm, then slowly add 15 kg of triphenyl phosphite; maintain a constant temperature of 25°C and stir for 15 min. After a uniform and transparent mixture is formed, transfer it to a piston pump storage tank with piston pressure by nitrogen pressure transfer and seal it for later use.

[0078] S2. Mix 80 parts of polycarbonate resin, 20 parts of polymethyl methacrylate resin, 0.15 parts of lanthanum acetylacetonate, 0.8 parts of high-pigment carbon black and 0.3 parts of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate in a high-speed mixer, and then add the mixture to the main feed port of a twin-screw extruder.

[0079] S3. Set the reaction temperature of the first to fifth zones of the twin-screw extruder to 255℃ and the screw speed to 500rpm to promote full in-situ ester exchange between components.

[0080] S4. When the melt is delivered to the sixth zone of the extruder, 2.0 parts of the mixture are continuously injected by a side high-pressure pump, with the injection pressure set to 8.0 MPa.

[0081] S5. The material enters the melt sealing zone of the seventh zone, maintaining a back pressure of 3.0 MPa. The local temperature of the melt is reduced to 222°C by the violent flash evaporation of perfluorohexane, and the catalyst is completely chelated by triphenyl phosphite.

[0082] S6. The vacuum absolute pressure is set to 800Pa and 400Pa. The melt is extruded through the die head (temperature 230℃), cooled by 45℃ warm water strips, and pelletized by a pelletizer. The pellets are dried in a vacuum drying oven at 110℃ for 3 hours.

[0083] S7. Injection molding process settings: barrel temperature 250℃ in zone 1, 265℃ in zone 2, 275℃ in zone 3, nozzle 270℃; mold temperature 115℃ to eliminate weld lines; injection pressure 130MPa, injection speed high speed (80mm / s), holding pressure 100MPa, holding time 10s.

[0084] Example 4:

[0085] This embodiment provides a method for preparing a high-gloss automotive trim material, including the following steps:

[0086] S1. At 21°C, add 32kg of perfluorohexane to the reactor, set the stirring speed to 120rpm, and add 8kg of triphenyl phosphite dropwise. Stir at a constant temperature for 11min. After a uniform and transparent mixture is formed, transfer it to a piston pump storage tank with piston pressure by nitrogen pressure transfer and seal it for later use.

[0087] S2. Mix 65 parts of polycarbonate resin, 35 parts of polymethyl methacrylate resin, 0.08 parts of lanthanum acetylacetonate, 0.4 parts of high-pigment carbon black and 0.15 parts of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and add it to the main feed port of the extruder.

[0088] S3. Set the temperature of the first to fifth zones of the twin-screw extruder to 240℃ and the screw speed to 350rpm.

[0089] S4. Inject 1.2 parts of the mixture into the sixth zone using a high-pressure pump, with the injection pressure set at 4.5 MPa.

[0090] S5. Set the back pressure to 1.8 MPa in the seventh zone, and cool the melt to 205°C by using the latent heat of liquid vaporization to freeze the microscopic phase morphology and achieve uniform passivation.

[0091] The absolute vacuum pressures in zones S6, 8, and 9 were set to 400 Pa and 150 Pa, respectively. After removing volatiles, the material was extruded, cooled, and pelletized to obtain trim material granules, which were then dried at 105°C for 5 hours.

[0092] S7. Injection molding process settings are as follows: barrel temperature 245℃ in zone 1, 255℃ in zone 2, 260℃ in zone 3, nozzle 255℃; mold temperature 100℃; injection pressure 105MPa, holding pressure 80MPa, cooling time 18s.

[0093] Example 5:

[0094] This embodiment provides a method for preparing a high-gloss automotive trim material, including the following steps:

[0095] S1. At 24℃, add 38kg of perfluorohexane to the reactor, set the stirring speed to 180rpm, and add 12kg of triphenyl phosphite dropwise; stir at a constant temperature for 14min, and after a uniform and transparent mixture is formed, transfer it to a piston pump storage tank with piston pressure by nitrogen pressure delivery and seal it for later use.

[0096] S2. Mix 75 parts of polycarbonate resin, 25 parts of polymethyl methacrylate resin, 0.12 parts of lanthanum acetylacetonate, 0.7 parts of high-pigment carbon black and 0.25 parts of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and add it to the main feed port of the extruder.

[0097] S3. Set the temperature of the first to fifth zones of the twin-screw extruder to 250℃ and the screw speed to 450rpm.

[0098] S4. Inject 1.8 parts of the mixture into the sixth zone, and set the injection pressure to 6.5 MPa.

[0099] S5. Set the back pressure to 2.8 MPa in the seventh zone, and rapidly cool the melt to 218°C to quickly freeze the reaction morphology and freeze the reaction kinetics.

[0100] S6. The vacuum absolute pressure is set to 700Pa and 300Pa. The melt is extruded through the die head (temperature 228℃), water-cooled and pelletized, and then dried in a dehumidifying dryer at 108℃ for 4.5h.

[0101] S7. Injection molding process settings are as follows: barrel temperature 255℃ in zone 1, 265℃ in zone 2, 270℃ in zone 3, nozzle 265℃; mold temperature 110℃; injection pressure 120MPa, holding pressure 90MPa, holding time 9s.

[0102] Comparative Example 1:

[0103] Compared with Example 1, the difference is that lanthanum acetylacetone catalyst is not added during the S2 dry mixing process, while the other components and process steps are the same.

[0104] Comparative Example 2:

[0105] Compared with Example 1, the difference is that perfluorohexane is not used in S1, but 10 kg of triphenyl phosphite (TPP) is directly injected as liquid; correspondingly, in S4, the lateral injection volume is only pure TPP (equivalent to 0.33 parts), and the injection pressure is reduced to atmospheric pressure injection (0.1 MPa), and the rest are the same.

[0106] Comparative Example 3:

[0107] Compared with Example 1, the difference is that in S1, perfluorohexane is replaced with an equal mass of high-boiling-point mineral oil (boiling point > 300°C), while the remaining process steps (including high-pressure injection) are the same.

[0108] Comparative Example 4:

[0109] Compared with Example 1, the difference lies in the following: the feeding sequence and injection position of triphenyl phosphite (passivating agent) are changed. The lateral injection in S4 and the back pressure control of the sealing area in S5 are cancelled. An equivalent amount of pure triphenyl phosphite is added in S2 along with the main resin material (and lanthanum acetylacetone) from the main feed port, while the remaining process temperatures remain the same.

[0110] Test Example 1:

[0111] Experimental steps:

[0112] The experimental subjects were selected from the modified polycarbonate alloy particles prepared in Examples 1-5 above, and the comparative sample particles prepared in Comparative Examples 1-4.

[0113] During the extrusion production process, a K-type thermocouple pressure integrated sensor, which is pre-embedded in the melt flow channel of the seventh zone (the rear section of the micro-orifice injection zone) of the twin-screw extruder, is used to collect the temperature fluctuation of the melt before and after passing the lateral injection point in real time.

[0114] Record the melt reference temperature before injection (end of zone 6). The melt stability temperature after flash injection (end of zone 7) Calculate the transient cooling amplitude .

[0115] The collected particles were dried in a vacuum drying oven at 100℃ for 4 hours to remove trace amounts of adsorbed moisture.

[0116] The melt flow rate (MFR) of each group of samples was determined using a melt flow indexer (according to GB / T3682-2000 standard) at 260℃ and 2.16kg load.

[0117] The content (ppm) of residual polymethyl methacrylate depolymerization monomer (MMA) in each group of particles was determined by headspace sampling using gas chromatography-mass spectrometry (GC-MS) to quantify the degree of degradation.

[0118] Each sample was tested in parallel 5 times. After removing outliers, the arithmetic mean was taken. The test results are shown in Table 1.

[0119] Table 1: Test Results of Thermodynamic Response Parameters and Melt Degradation Indicators

[0120] Sample number Temperature drop (°C) Melt flow rate (MFR) (g / 10min) Volatile residue MMA content (ppm) Example 1 34.2 8.2 115.4 Example 2 35.8 7.9 98.2 Example 3 33.1 9.1 142.7 Example 4 34.7 8.5 121.3 Example 5 32.4 8.8 133.5 Comparative Example 1 5.2 6.4 108.6 Comparative Example 2 4.8 15.6 455.2 Comparative Example 3 2.1 18.2 522.0 Comparative Example 4 3.5 11.4 288.4

[0121] From Table 1, we can obtain:

[0122] According to Table 1 and Figure 1 The experimental data shown demonstrates the logical rigor of this process scheme in controlling the thermal stability of the PC / PMMA alloy system. As can be observed from the cooling amplitudes in Table 1, after the injection of perfluorohexane in Examples 1-5, the melts all exhibited a drastic cooling response exceeding 30°C. In contrast, Comparative Examples 2 and 3, which did not contain perfluorohexane or replaced it with mineral oil, showed cooling amplitudes below 5°C, primarily due to sensible heat exchange within the cryogenic liquid itself.

[0123] This significant temperature difference confirms the effectiveness of the medium's sudden boiling (phase change flash evaporation) mechanism in this scheme, namely, utilizing the extremely high latent heat of vaporization to remove the energy of the melt, thereby achieving a precipitous cooling at the thermodynamic level.

[0124] Regarding melt stability, the MFR values ​​of Examples 1-5 remained within a reasonable range of 7.9 to 9.1 g / 10 min with minimal fluctuations, indicating that the macromolecular chain segments were well protected in the later stages of extrusion.

[0125] In contrast, Comparative Example 3 (lacking effective cooling effect) showed a significantly higher MFR value of 18.2 g / 10 min, while its MMA monomer release reached a high of 522.0 ppm. This indicates that even with the presence of a passivating agent, the La(acac)3-catalyzed side reactions and the heat-sensitive depolymerization of PMMA itself can still occur rapidly at high temperatures in the absence of transient cooling intervention. Although Comparative Example 1 had a lower MFR value, this was due to the complete absence of a catalyst, resulting in the lack of an effective compatibilization reaction and failing to meet the performance requirements of high-performance alloys.

[0126] It is noteworthy that, in Comparative Example 2, with only TPP chemical passivation agent added and without perfluorohexane assistance, the MFR (15.6 g / 10 min) was significantly higher than that of the Example. This reveals the hysteresis of simple chemical mixing under high viscosity melts and proves that the cavitation explosion dispersion proposed in this invention is a key prerequisite for achieving rapid locking of catalytic active centers of TPP at the microscopic level.

[0127] Based on the above indicators, this scheme, through dual locking of heat dissipation and chemical kinetics, successfully suppressed the thermal degradation trend of the polymer bulk while ensuring the in-situ compatibilization strength, laying the microstructural foundation for obtaining a material with high gloss and low impurity content.

[0128] Test Example 2:

[0129] Experimental steps:

[0130] The experimental subjects were modified polycarbonate alloy particles prepared in Examples 1-5 and Comparative Examples 1-4, with each sample amount being approximately 5-10 mg.

[0131] The sample to be tested was placed in an aluminum crucible and thermally scanned using a differential scanning calorimeter (DSC214) under a nitrogen atmosphere, with the nitrogen flow rate set to 20 mL / min.

[0132] First, the temperature is increased from room temperature to 280°C at a rate of 20°C / min, and then held at 280°C for 3 minutes to eliminate residual thermal history and internal stress of the polymer during extrusion pelletizing.

[0133] The temperature was then cooled to 40°C at a rate of 10°C / min. After the baseline stabilized, a second temperature-scanning operation was started, with the temperature-scanning rate set at 10°C / min. Heat flow curves were collected from 40°C to 200°C.

[0134] Identify the two glass transition steps on the heat flow curve and record the glass transition temperatures of the PMMA-enriched phase. Glass transition temperature of PC-enriched phase .

[0135] Calculate the difference in the two-phase transition temperature. The smaller the difference, the higher the degree of interphase wetting and interfacial fusion between components. This is used to evaluate the realization effect of the molecular rivet mechanism. The test results are shown in Table 2.

[0136] Table 2: Glass transition temperature shift data based on DSC thermal analysis

[0137] Sample number PMMA phase (°C) PC phase (°C) Two-phase temperature difference (°C) Example 1 118.42 142.15 23.73 Example 2 119.57 143.21 23.64 Example 3 117.13 141.68 24.55 Example 4 118.86 142.74 23.88 Example 5 117.65 141.92 24.27 Comparative Example 1 108.24 149.33 41.09 Comparative Example 2 114.52 144.67 30.15 Comparative Example 3 113.81 145.26 31.45 Comparative Example 4 115.34 143.91 28.57

[0138] From Table 2, we can obtain:

[0139] According to Table 2 and Figure 2 Analysis of experimental data shows that the process proposed in this invention, which involves in-situ reaction initiated by La(acac)3 and combined with space fluid intervention, significantly improves the thermodynamic compatibility of PC and PMMA. Examples 1-5 The values ​​were all stable within the range of 23.64 to 24.55 °C. Compared with the theoretically huge temperature difference between the pure PC and PMMA components, this significant temperature difference convergence phenomenon confirms that a highly active block copolymer was indeed generated at the interface.

[0140] This copolymer acts as a molecular-level rivet, breaking the originally extremely high interfacial tension between the two components, causing the originally independent phase regions to undergo deep interweaving of molecular chain segments.

[0141] A closer look at the comparative data reveals that Comparative Example 1, which contains no catalytic components, exhibits a temperature difference of up to 41.09℃ between its two phases, essentially maintaining the original state of the two resins before mixing. This indicates that simple physical blending cannot achieve compatibilization at the microscopic level.

[0142] The data from Comparative Examples 2 and 3 further reveal the profound impact of sudden boiling dispersion on the reaction quality; although both components contain catalysts, the TPP passivator cannot achieve millisecond-level uniform distribution throughout the system due to the lack of efficient phase change dispersion of perfluorohexane.

[0143] This localized loss of control or delayed desensitization leads to The temperature remained above 30°C, indicating poor uniformity of the interfacial compatibilization reaction and failure to achieve a unified thermal response behavior in terms of macroscopic properties.

[0144] Furthermore, the data from Comparative Example 4 (28.57°C) indicate that if the passivating agent is added prematurely without lateral injection, the compatibilization reaction will be terminated prematurely before the optimal conversion rate is reached.

[0145] Examples 1-5 are able to maintain an extremely narrow temperature difference range, mainly due to the full utilization of the high enthalpy latent heat of the PC melt to activate the interfacial reaction in the pre-extrusion stage, and the use of perfluorohexane flash evaporation to instantly freeze the structure at a determined cavity location.

[0146] This precise control over reaction timing and interfacial dynamics enables the material to exhibit single and consistent physical properties on a macroscopic scale, fundamentally solving the problems of phase separation flow marks and surface white fog that easily occur in automotive high-gloss trim under complex injection molding conditions.

[0147] Test Example 3:

[0148] Experimental steps:

[0149] The experimental subjects were alloy particles prepared in Examples 1-5 and Comparative Examples 1-4, which were molded into optical testing standard samples with a thickness of 3 mm by a precision injection molding machine under the same process parameters.

[0150] According to GB / T9754 standard, a multi-angle gloss meter was used to measure the center and upper and lower edge areas of the test sample. The gloss values ​​(GU) at incident angles of 20°, 60° and 85° were recorded and the arithmetic mean was taken.

[0151] Using an integrating sphere spectrophotometer, under a D65 standard light source and a 10° field of view setting, the color space parameters of each sample surface were measured, the lightness L value was extracted, and the depth of the material's base blackness was examined.

[0152] The sample was placed in a standard color matching light box. Under uniform diffuse reflection lighting conditions, the testers observed whether there were flow marks, silver streaks, microbubbles, and cloud-like phase separation defects on the surface. An objective comprehensive appearance score (out of 100 points) was given in combination with the surface flatness. The test results are shown in Table 3.

[0153] Table 3: Multi-angle gloss and macroscopic appearance quality evaluation data

[0154] Sample number 20° Gloss (GU) 60° Gloss (GU) 85° Gloss (GU) Lightness L value Overall Appearance Rating Example 1 92.4 98.1 99.3 25.18 96 Example 2 91.7 97.4 98.6 26.04 95 Example 3 90.9 96.6 97.2 26.92 91 Example 4 92.1 97.8 98.4 25.66 94 Example 5 91.2 96.9 97.8 26.31 92 Comparative Example 1 68.3 74.5 81.2 34.75 58 Comparative Example 2 75.6 82.1 86.4 31.22 67 Comparative Example 3 72.4 79.8 85.1 33.41 64 Comparative Example 4 82.5 88.3 91.6 29.84 81

[0155] From Table 3, we can obtain:

[0156] According to the data in Table 3, the example groups locked by in-situ reaction assisted by high-pressure flash evaporation of perfluorohexane have a clear technical advantage in terms of macroscopic optical performance. The 60° gloss of Examples 1-5 generally exceeds 96 GU, and the lightness L value is controlled in the low range below 27, which visually presents a deep, highly reflective texture rarely seen in existing paint-free materials.

[0157] In conventional production, when injection molding high-viscosity alloy materials, the dramatic change in mold filling shear force often leads to the aggregation of dispersed phases and the formation of diffuse reflection zones on the mold surface. In contrast, this method synthesizes block structures through in-situ interfacial reactions induced by La(acac)3.

[0158] This structure directly constrains the sliding of the PMMA phase in the processing flow field, maintaining the smoothness of the phase interface from both mechanical and thermodynamic perspectives. This translates into a decrease in scattering rate and an optimization of light transmission absorption rate during gloss measurement.

[0159] The degradation characteristics of the optical parameters in the comparative example demonstrate the engineering significance of the transition from physical mixing to chemical fluid control. In Comparative Example 1, significant large-scale phase separation occurred after the catalyst was removed, with the L value rising to 34.75 and the material surface exhibiting a grayish-white, foggy appearance, confirming that extruder shearing alone is insufficient to establish a microscopically stable phase region.

[0160] Comparative Examples 2 and 3, which involve the intervention of the quenching stage in the stripping process, show that the reaction of a single chemical structure is also constrained by the mass transfer process of the medium. Whether it is the lack of perfluorohexane burst decomposition leading to insufficient TPP end-capping efficiency, or the lack of latent heat removal causing continuous thermal oxidation of the polymer end, such local reaction distortions leave microbubbles and yellowing marks on the molded parts, lowering the overall appearance score.

[0161] Tests show that coupling chemical quenching with microscopic thermodynamic explosion is not only a necessary step for reaction convergence, but also a prerequisite for giving long-process composite materials a high-quality, paint-free finish.

[0162] Test Example 4:

[0163] Experimental steps:

[0164] The resin materials obtained by extrusion granulation in Examples 1-5 and Comparative Examples 1-4 were collected and injection molded into standard mechanical specimens with dimensions of 80mm×10mm×4mm and standard flat plate test pieces with dimensions of 100mm×100mm×3mm using an injection molding machine.

[0165] A type A notch was milled into the mechanical spline using machining equipment, leaving a remaining width of 8.0 mm. The cantilever beam notched impact strength (kJ / m²) was measured using a pendulum impact testing machine at 23℃ and 50% relative humidity. 2 For each sample, 10 roots were tested to obtain the average distribution.

[0166] The standard flat plate test specimen was placed in the xenon lamp aging test chamber, and the irradiance was set to a wavelength of 340nm according to the ISO4892-2 standard. The black plate temperature was controlled at 65℃, and a continuous light irradiation and intermittent water spray cycle program was applied (the cycle was set to 102min light irradiation + 18min light irradiation and water spray). The total test time was 1000h.

[0167] Before and after the aging test, the Lab three-dimensional color space coordinates of the central area of ​​the plate were measured using an integrating sphere colorimeter, and the color difference value was calculated to characterize the degree of matrix degradation and yellowing.

[0168] The gloss of the sample surface at a 60° incident angle was re-measured using a multi-angle gloss meter after 1000 hours of aging. The gloss was divided by the initial 60° gloss before aging, and the gloss retention rate (%) of each group of materials was calculated and recorded. The test results are shown in Table 4.

[0169] Table 4: Test data on macroscopic mechanical toughness and accelerated aging thermo-photo-oxidative stability

[0170] Sample number <![CDATA[Izod impact strength (kJ / m 2 )]]> Color difference after 1000 hours of aging Gloss retention rate after aging (%) Example 1 51.4 1.34 94.2 Example 2 47.8 1.86 92.6 Example 3 53.6 1.22 95.8 Example 4 49.3 1.57 93.4 Example 5 50.7 1.48 94.9 Comparative Example 1 17.3 4.25 68.7 Comparative Example 2 29.8 6.84 55.3 Comparative Example 3 24.1 8.51 48.7 Comparative Example 4 38.6 3.52 76.5

[0171] From Table 4, we can obtain:

[0172] Based on the data in Table 4, the fluid-interventional spatial quenching process and block reaction mechanism proposed in this invention establish a long-term stable morphology at the material level that balances mechanical load-bearing capacity and resistance to oxidation degradation. From a mechanical performance perspective, the notched impact strength of the cantilever beams in Examples 1-5 all ranges from 47.8 to 53.6 kJ / m. 2 A high-level platform.

[0173] In the twin-screw reaction section, the two-phase polymer melt forms a high-density PC-b-PMMA molecular rivet connection with the help of La(acac)3 catalysis. This eliminates the microscopic voids caused by poor compatibility and acts as a stress transfer bridge in the impact fracture process, making the material exhibit energy absorption characteristics similar to tough metals.

[0174] In Comparative Example 1, due to the lack of catalytic conditions that induce cross-linking, the interfacial tension between the heterophase layers resulted in a loosely stacked physical state of the internal molecular chains. Under transient impact loads, this made them highly susceptible to crazing at the interfaces and rapid breakage, with an impact strength of only 17.3 kJ / m. 2 .

[0175] The resistance of the material's micro-segments to deep ultraviolet light and thermal ablation further reveals the necessity of precise temperature control and chemical locking during the reaction stage. Comparative Examples 2 and 3 failed to achieve a tight closed loop in the polymer backbone; after 1000 hours of high-temperature light cycling, the degradation process on the surface of these two samples was extremely severe.

[0176] In the absence of high-speed phase change freezing of perfluorohexane or when it is replaced only by low-boiling-point sensible heat, the inhibitor TPP is free in the local area of ​​the high-viscosity melt. The transesterification catalytic centers that are not promptly passivated and locked, along with the accumulation of extrusion heat, force the PMMA main chain to undergo disordered depolymerization reaction from the end group.

[0177] Because the surface of the injection molded part is covered with these kinds of cut-off unstable free radical remnants and free monomer structures, conjugated double bond chromophores are rapidly generated under photo-oxidation attack, inducing yellowing, causing the color difference to soar to over 6.84, and the gloss retention rate to drop to less than 60% due to micro-cracks on the surface.

[0178] This approach physically removes these two defects at their source, using the transient thermodynamic freezing generated by microporous injection to forcibly block the spread of the depolymerization reaction, and in conjunction with TPP, achieves full-space deadlock of catalytic activity.

[0179] Not only was no perceptible macroscopic color shift observed in the series of examples (<1.9), but the gloss retention rate also remained above 92%, fully demonstrating that this mechanism avoids the overdraft of back-end service stability by the front-end synthesis and successfully transforms molecular-level intervention into a substantial extension of the actual service life of polymer alloys.

Claims

1. A method for preparing a high-gloss automotive trim strip with high weather resistance and gloss durability, characterized in that, Includes the following steps: S1. Mix perfluorohexane and triphenyl phosphite at a mass ratio of 2 to 8:1 until a homogeneous and transparent mixture is formed. Then transfer the mixture to a storage tank and seal it for later use. S2. Mix polycarbonate resin, polymethyl methacrylate resin, lanthanum acetylacetonate, high-pigment carbon black and hindered amine light stabilizer evenly, and add to the main feed port of the twin-screw extruder; S3. Set the temperature of the reaction section of the twin-screw extruder so that the material undergoes melt blending and in-situ transesterification block reaction under the catalysis of lanthanum acetylacetone. S4. The mixture described in step S1 is continuously injected into the melt inside the twin-screw extruder using a side high-pressure pump; S5. The material enters the sealed zone of the twin-screw extruder, where the phase change flash evaporation effect of perfluorohexane is used to reduce the local temperature of the melt, and the triphenyl phosphite is used to passivate the residual lanthanum acetylacetone. S6. After the material is vacuum-treated to remove perfluorohexane vapor and volatiles, it is extruded from the die head, cooled, pelletized and dried. S7. The dried material is then processed into the high-gloss automotive trim strip through injection molding.

2. The method for preparing a high-gloss automotive trim strip with high weather resistance and gloss durability according to claim 1, characterized in that, In S1, the step of forming a homogeneous and transparent mixture includes: At 20–25°C, start stirring and set the speed to 100–200 rpm, then add triphenyl phosphite dropwise; maintain constant temperature stirring for 10–15 min, and transfer the solution to a plunger pump reservoir with piston pressure by nitrogen pressure delivery.

3. The method for preparing a high-gloss automotive trim strip with high weather resistance and gloss durability according to claim 1, characterized in that, In S2, the weight fractions of each material are: Polycarbonate resin: 60-80 parts; Polymethyl methacrylate resin: 20-40 parts; Lanthanum acetylacetone: 0.05–0.15 parts; High-pigment carbon black: 0.3–0.8 parts; Hindered amine light stabilizer: 0.1 to 0.3 parts.

4. The method for preparing a high-gloss automotive trim strip with high weather resistance and gloss durability according to claim 1, characterized in that, In S2, polycarbonate resin, polymethyl methacrylate resin, lanthanum acetylacetonate, high-pigment carbon black and hindered amine light stabilizer are added to a high-speed mixer and mixed at 800 rpm for 5 minutes. After being mixed evenly, the mixture is added to the main feed port of a twin-screw extruder.

5. The method for preparing a high-gloss automotive trim strip with high weather resistance and gloss durability according to claim 1, characterized in that, In S2, the polycarbonate resin is a bisphenol A type polycarbonate homopolymer with a melt flow rate of 9.0–11.0 g / 10 min under test conditions of 300°C and 1.2 kg, and a weight-average molecular weight range of 22,000 to 25,000; the polymethyl methacrylate resin is an amorphous homopolymer prepared by suspension polymerization with a melt flow rate of 1.5–2.5 g / 10 min under test conditions of 230°C and 3.8 kg, and a light transmittance greater than 92%.

6. The method for preparing a high-gloss automotive trim strip with high weather resistance and gloss durability according to claim 1, characterized in that, The primary particle size range of the high-pigment carbon black is 15 nm to 25 nm; the hindered amine light stabilizer is bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate.

7. The method for preparing a high-gloss automotive trim strip with high weather resistance and gloss durability according to claim 1, characterized in that, In S3, the reaction temperature of the first to fifth zones of the twin-screw extruder is set to be constant at 235–255°C, and the screw speed is set to 300–500 rpm. The material undergoes in-situ transesterification under the catalysis of lanthanum acetylacetone.

8. The method for preparing a high-gloss automotive trim strip with high weather resistance and gloss durability according to claim 1, characterized in that, In step S4, when the melt is conveyed to the sixth zone of the extruder, 1.0 to 2.0 parts of the mixture described in step S1 are injected based on 100 parts of the total weight of the polycarbonate resin and polymethyl methacrylate resin described in step S2, and the injection pressure is set to 3.0 to 8.0 MPa.

9. The method for preparing a high-gloss automotive trim strip with high weather resistance and gloss durability according to claim 1, characterized in that, In S5, the material enters the melt sealing zone of the seventh zone. The back pressure in this zone is maintained at 1.5 to 3.0 MPa by adjusting the pressure valve of the die head. The latent heat of vaporization of perfluorohexane is used to cool the local temperature of the melt by more than 30°C within 3 seconds, thereby terminating the transesterification reaction.

10. The method for preparing a high-gloss automotive trim strip with high weather resistance and gloss durability according to claim 1, characterized in that, In S6, the material enters the eighth and ninth zones, where two-stage vacuum systems are activated to control the absolute pressures at 300–800 Pa and 100–400 Pa, respectively, to remove perfluorohexane vapor and volatiles. The material is then extruded through a die head, cooled in a water bath, pelletized, and dried at 100–110°C for 3–6 hours.

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