Preparation of automotive bionic anchoring polypropylene material for improving adhesive force of water transfer printing coating

Abstract

The invention relates to the technical field of high polymer materials, and discloses preparation of an automobile bionic anchoring polypropylene material for improving the adhesive force of a water transfer printing coating, which comprises a polypropylene matrix, a bionic polar anchoring component containing a catechol functional group and a polypropylene block, and an interface migration auxiliary component with the surface tension lower than that of the matrix, the surface tension gradient among the components is utilized to drive the bionic polar anchoring components to be enriched towards the surface of the material in the forming and cooling stage and form a concentration enrichment layer, and catechol functional groups are fixed through the co-crystallization effect between a polypropylene block and a matrix. And interface polarity reconstruction and microscopic anchoring under a treatment-free condition are realized, the influence of a weak interface layer is eliminated, and the bonding stability of a water transfer printing coating in a long-term damp-heat aging environment is improved.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and in particular relates to the preparation of a biomimetic anchoring polypropylene material for automobiles that improves the adhesion of water transfer printing coatings. Background Technology

[0002] Polypropylene resin currently possesses excellent mechanical properties, low density, and superior chemical stability, making it widely used in automotive interior and exterior parts. However, as polypropylene is a typical non-polar polymer material with low surface energy and insufficient interfacial chemical activity, the ink layer generated by the activation of the water transfer printing film is difficult to form effective molecular chain entanglement or chemical bonding with the polypropylene substrate during the water transfer printing process. This leads to the decorative layer easily curling or peeling off at the edges during the drying and shrinkage process. At present, external surface treatments such as flame treatment, plasma modification, or pre-coating with polar primer are mainly used to improve the surface tension of the substrate. However, these external processes increase equipment investment and production cycle, and the treatment effect is affected by the placement time and environmental humidity, which restricts the quality stability of the production process.

[0003] Besides improvements in external processing methods, the industry has attempted to optimize multilayer composite structures to enhance interfacial adhesion. However, shortcomings remain in the internal component control logic. For example, Chinese invention patent CN106626852B discloses a method for forming a laser water transfer composite film, which utilizes adhesive coating between multiple thin films and vacuum aluminizing to achieve interlayer bonding. While this improves the adhesion strength between films, the mechanism is limited to physical adhesion at the external interface. For automotive injection molded parts, this method fails to address the intrinsic non-polar modification problem of polypropylene substrates and struggles to resolve the issue of polar components during the molding process. The polar trap phenomenon in the process; the method of directly adding polar modified components to polypropylene compositions to improve interfacial activity is subject to polar trap constraints. Due to the thermodynamic incompatibility between highly polar modified components and non-polar polypropylene matrix, the modified components tend to be buried inside the substrate during the melting and cooling process, making it difficult to expose effective polar sites on the surface. If the amount of polar component added is increased, excessive precipitation of the component is likely to occur, forming a weak interfacial layer at the interface, which prevents the interfacial stress from being effectively transmitted to the deep part of the substrate, thus deteriorating the coating adhesion.

[0004] Therefore, how to utilize the physicochemical differences between components to induce the enrichment of polar sites on the surface and construct a locked structure that co-crystallizes with the matrix is ​​the technical problem to be solved by this invention. Summary of the Invention

[0005] This invention provides a method for preparing a biomimetic anchoring polypropylene material for automobiles to improve the adhesion of water transfer printing coatings. Based on 100% of the total weight of the biomimetic anchoring polypropylene material, its components and mass percentages include:

[0006] The polypropylene matrix component has a melt index of [missing information]. ;

[0007] The biomimetic polar anchoring component, with a mass percentage of 1% to 8%, is a block copolymer containing polypropylene blocks and catechol functional groups. The melt flow index of the biomimetic polar anchoring component is [missing information]. ,and and The ratio is between 1.5 and 4.5;

[0008] Interface migration aids, with a mass percentage of 0.1% to 1.5%, are present at 25°C. The surface tension below that of the polypropylene matrix component is lower at 25. The surface tension below;

[0009] In the molded cross section of the biomimetic anchoring polypropylene material, due to the surface tension gradient difference between the interface migration auxiliary component and the polypropylene matrix component, the biomimetic polar anchoring component forms a 15-degree angle on the surface of the biomimetic anchoring polypropylene material. Up to 50 A concentration enrichment layer is formed in the depth region, and the co-crystallization structure formed by the polypropylene block and the polypropylene matrix component through intermolecular entanglement enables the spatial positioning of the catechol functional groups within the concentration enrichment layer.

[0010] Preferably, the polypropylene matrix component is isotactic polypropylene or impact copolymer polypropylene with an isotacticity of not less than 96% and a melt index of 15. Up to 35 The number-average molecular weight of the polypropylene blocks in the biomimetic polar anchoring component is 5000 to 15000, and the mass percentage of catechol functional groups in the biomimetic polar anchoring component is 10% to 25%; the interface migration auxiliary component is at 25 The surface tension below is 18 Up to 24 Furthermore, the surface tension difference between it and the polypropylene matrix component is not less than 8. .

[0011] Preferably, the surface distribution density of catechol functional groups in the concentration enrichment layer The following quantitative relationship is satisfied: ,in, The effective mass concentration of catechol functional groups in the concentration enrichment layer per unit area; These are correlation constants pre-defined based on the crystallization kinetics of the polypropylene matrix components; The average cooling rate during the molding and cooling process, in units of... / s; Catechol functional groups via and The synergistic constraints lead to the formation of nanoscale ordered arrangements in the concentration enrichment layer.

[0012] Preferably, the catechol functional group in the biomimetic polar anchoring component is selected from at least one of dopamine structural units, 3,4-dihydroxyphenylpropanol structural units, or catechol-grafted polyethyleneimine units, and the catechol functional group is covalently linked to the end of the polypropylene block.

[0013] Preferably, the melting point of the interface migration auxiliary component is lower than the crystallization initiation temperature of the polypropylene matrix component; the interface migration auxiliary component physically associates with the catechol functional groups in the biomimetic polar anchoring component through intermolecular van der Waals forces, and acts as a carrier for the migration of the biomimetic polar anchoring component to the surface of the biomimetic anchoring polypropylene material.

[0014] Preferably, the polypropylene matrix component further includes a nucleating agent comprising 0.2% to 0.5% of the total weight of the biomimetic anchoring polypropylene material. The nucleating agent is used to increase the crystallization temperature of the polypropylene matrix component, thereby shortening the diffusion time of the biomimetic polar anchoring component in the concentration enrichment layer to lock the molecular phase.

[0015] Preferably, the biomimetic anchoring polypropylene material also includes antioxidants, lubricants, and light stabilizers, and the total content of antioxidants, lubricants, and light stabilizers does not exceed 1.2% of the total weight of the biomimetic anchoring polypropylene material.

[0016] Preferably, the biomimetic polar anchoring component is prepared by an amidation reaction of maleic anhydride-grafted polypropylene and an amino-containing catechol derivative in the molten state, and the biomimetic polar anchoring component is at 1645 It exhibits characteristic infrared absorption peaks of amide carbonyl groups.

[0017] Preferably, the biomimetic anchoring polypropylene material, in its untreated state, exhibits a cross-cut adhesion rating of 0 between its surface and the water transfer ink, and at 80°C... Soak in water for 240 minutes The post-adhesion retention rate is 100%.

[0018] Preferably, the catechol functional groups in the concentration enrichment layer are exposed on the surface of the biomimetic anchoring polypropylene material and are configured to form a chemical chelate with the resin component in the water transfer ink.

[0019] Compared with existing technologies, the biomimetic anchoring polypropylene material for automobiles that improves the adhesion of water transfer printing coatings has the following advantages:

[0020] 1. In the preparation of biomimetic anchoring polypropylene materials, the problem of deep burial of polar sites caused by the random distribution of modified components in the polypropylene matrix is ​​solved by synergistic regulation of surface energy gradient and fluidity gradient. The surface tension difference between the guiding component and the matrix component is used as a thermodynamic driving force to induce the highly fluid biomimetic anchoring component to be directionally transported to the molding surface of the material. Since the biomimetic anchoring component has a higher Brownian motion frequency than the matrix component, it completes enrichment to the outermost layer before advancing and locking the phase at the matrix crystallization front. This results in a high density of active chemical sites on the material surface, achieving improved interfacial wettability and polarity reconstruction under no-treatment conditions.

[0021] 2. The constructed biomimetic anchoring layer achieves deep coupling with the matrix through a molecular chain segment co-crystallization mechanism, avoiding the weak interface layer failure commonly found in conventional surface modification. During the molding and cooling stage, the long polypropylene chain segments in the biomimetic anchoring component undergo intermolecular entanglement with the matrix polypropylene and simultaneously enter the crystal lattice, pinning the end-point catechol functional groups to the surface layer. This root-like anchoring structure enables the resin components in the water transfer ink to not only bind to the surface sites through hydrogen bonding and chemical chelation, but also allows the interfacial stress to be effectively transferred to the depth of the material through the co-crystallized molecular chains, improving the bonding stability of the coating under complex mechanical stress.

[0022] 3. By controlling the spatiotemporal alignment of the migration rate of functional components and the crystallization kinetics of the matrix, the engineering pain points of blooming caused by excessive precipitation of polar substances and the decay of adhesion over time are solved. By limiting the difference in melt index between the anchoring component and the matrix component, the migration process is effectively constrained by the matrix crystallization rate, ensuring that the active sites form a stable and orderly nanoscale arrangement on the surface rather than a random accumulation. This controlled self-organized migration mode maintains the mechanical integrity of the material surface and, based on its excellent resistance to humid heat aging, enables the parts to maintain the substrate-level adhesion strength after long-term immersion in high-temperature hot water. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating the preparation process and microscopic directional anchoring mechanism of the biomimetic anchoring polypropylene material of this invention.

[0024] Figure 2 This is a diagram showing the technical architecture and key parameter configuration of the biomimetic anchoring polypropylene material of this invention. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0026] It should be noted that all directional and positional terms used in this invention, such as: up, down, left, right, front, back, vertical, horizontal, inner, outer, top, bottom, transverse, longitudinal, center, etc., are only used to explain the relative positional relationship and connection between components in a specific state (as shown in the accompanying drawings). They are only for the convenience of describing this invention and do not require that this invention be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention. In addition, the descriptions of "first," "second," etc., in this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0027] In the description of this invention, unless otherwise explicitly specified and limited, the terms installation, connection, and linking should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal communication between two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0028] In the description of this specification, references to the terms "an embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example, and the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0029] This invention provides a method for preparing a biomimetic anchoring polypropylene material for automobiles to improve the adhesion of water transfer printing coatings. By reconstructing the microscopic phase of the polymer composition, a biomimetic polar anchoring component with self-migrating properties is pre-embedded within the polypropylene matrix. The surface tension gradient constructed by the interface migration auxiliary component serves as a driving force, inducing polar sites to directionally accumulate on the material surface during the molding and cooling stage. The polar anchor points are then pinned to the nanoscale region of the surface through co-crystallization between molecular chain segments, thereby achieving both interface polarity reconstruction and physicochemical dual-locking. When isotactic polypropylene is used as the substrate in automotive interior parts, the low surface energy and lack of chemically active sites make it difficult for water transfer printing inks to form effective adhesion at the interface. To address this challenge, this invention employs an isotacticity of at least... Isotactic polypropylene or impact copolymer polypropylene is used as the polypropylene matrix component, and its melt index Set at to Within the specified range, the measurement standard is based on The test conditions are: , The load-bearing capacity of this matrix component forms the main framework of the material, providing impact resistance and processing fluidity for automotive interior parts.

[0030] The non-polar long-chain characteristics of polypropylene limit its affinity with polar water transfer inks, and simple physical blending of polar modifiers easily leads to interfacial failure; in addition, the system introduces a mass percentage of... to The biomimetic polar anchoring component is a block copolymer with polypropylene blocks and catechol functional groups, and has a melt index of [missing information]. The ratio of its melt index to the matrix melt index Limited to to Between these steps, to obtain this component, a grafting rate of [missing information] is selected. to And the melt index is to Using maleic anhydride-grafted polypropylene as a precursor, it was mixed with amino-containing catechol derivatives such as dopamine hydrochloride in xylene solvent, and then... Nucleophilic substitution reaction was performed under isothermal conditions. Monitoring the reaction system down to the infrared spectrum The anhydride absorption peak at that location completely disappeared, and the product was generated at... The modified product exhibiting characteristic absorption peaks of the amide carbonyl group, with the number-average molecular weight of the polypropylene blocks set at [value missing]. to Between these points, the mass percentage of catechin functional groups in the components is: to It is covalently attached to the end of the polypropylene block.

[0031] Conventional polar components are easily buried deep within the matrix during the cooling process of polypropylene melt due to thermodynamic incompatibility, thus failing to exert their interfacial modification effect. To address this site shielding problem, the proposed solution introduces... to Interface migration auxiliary components, in The surface tension is set to to This ensures that the surface tension difference between the surface tension of ... Polytetrafluoroethylene-modified polypropylene wax or perfluoroalkyl-modified polysiloxane was selected as an auxiliary component, and its dropping point temperature was controlled at [temperature range missing]. to To ensure the auxiliary component remains in a molten state before the matrix crystallizes, its melting point is lower than the crystallization initiation temperature of the polypropylene matrix. Through intermolecular van der Waals forces, it physically associates with catechol functional groups, acting as a carrier to drive the biomimetic polar anchoring component to migrate to the molding surface. If the migration process lacks kinetic guidance, surface precipitation or uneven site distribution may occur, thus affecting the coating's bonding stability. This invention achieves spatiotemporal alignment between the migration rate of the functional component and the matrix crystallization kinetics on the surface of the material's molding section. to A concentration enrichment layer is formed in the deep region, and the surface distribution density of catechol functional groups is high. Follow the quantitative relationship ,in This represents the effective distribution density of catechin functional groups on the surface layer, in units of... , These are correlation constants pre-defined based on matrix crystallization kinetics. The average cooling rate during the molding and cooling process, in units of... To control the crystallization kinetics, additional materials are added to the polypropylene matrix. to Nucleating agents are used to increase the crystallization temperature and shorten the diffusion time.

[0032] Calibration correlation constant Gradient cooling injection molding is used, and the average cooling rate is set. exist to Interval, step interval Measure the surface of the sample strip nm to Effective mass concentration of catechols in the nm depth region ,Will and The product is fitted with a linear regression relative to the difference in melt flow index, and the slope of the fitted line is the correlation constant for the current batch. To ensure that the distribution density of catechol functional groups in the concentration enrichment layer reaches the quantitative index during the cooling stage of isotactic polypropylene molding, the preparation process of this material is as follows: isotactic polypropylene, biomimetic polar anchoring components, Interface migration auxiliary components and Nucleating agents are added to a high-speed mixer and mixed at room temperature. Premixing speed The mixture enters with a length-to-diameter ratio of The co-rotating twin-screw extruder has its feeding section temperature set to... to The temperature of the compression section is to The temperature of the metering section is to The die head temperature is The screw speed is controlled to be The mixture undergoes melt blending extrusion, water-cooled strand drawing, and granulation; the resulting granules are then subjected to… Drying The automotive interior parts were then manufactured using injection molding, with the injection pressure set to [value missing]. Mold temperature controlled at The cooling rate is controlled by adjusting the mold temperature. This induces the formation of micro-anchoring structures.

[0033] Example 1: In the injection molding production of an automotive dashboard frame part with a deep cavity structure and a leather-like surface texture, the complex geometry of the part makes it difficult for the active sites generated by flame treatment to cover the deep recesses, causing fluctuations in the interfacial adhesion stability of water transfer ink in the recessed areas of the part. To address the aforementioned technical problem of uneven surface energy distribution, a method is adopted... Polypropylene matrix components, Bionic polar anchoring components and The composition consisting of interface migration aid components is processed.

[0034] The temperature at which the melt fills the cavity and contacts the mold is... During the wall process, the interface migration auxiliary component utilizes its... At that time to The surface tension creates a tension gradient field towards the wall inside the melt. This gradient field is used to guide the biomimetic polar anchoring component to move directionally to the material surface before the matrix component undergoes a crystallization phase transformation. to The depth region, and by adjusting the cooling rate The polypropylene blocks in the biomimetic polar anchoring component have an isotacticity of not less than [a certain value]. The matrix components produce co-crystallization between molecular chains; this co-crystallization anchors the catechol functional groups to the outermost interface of the material, allowing the catechol functional groups to form chemical chelation sites with the polar resin in the covering water transfer ink layer, based on... Standard testing shows that the adhesion level in the deep cavity of the part reaches [a certain level]. And in Soaking in water Afterwards, the interfacial bonding strength remains unchanged.

[0035] Example 2: In the verification process of simulating the service performance of automotive interior parts under humid and hot conditions using a high and low temperature damp heat alternating test chamber, standard specimens were prepared using injection molding. The temperature control accuracy of the test chamber was set to [value missing]. The relative humidity control deviation is no greater than To quantitatively verify the physicochemical anchoring effect on the material surface, scanning electron microscopy was used to... Observation of the surface layer of the sample under accelerating voltage to The topography of the deep region, and using The atomic percentage of surface catechol functional groups was measured using X-ray photoelectron spectroscopy, with experimental data obtained from measured values ​​obtained on a physical experimental platform. To address measurement errors caused by excessive electron beam penetration depth in scanning electron microscopy at a high accelerating voltage of 10 kV, this invention employs an angle-resolved X-ray photoelectron spectroscopy analyzer when calibrating the depth enrichment range. Photoelectron emission angles were set to 15°, 30°, and 45°. Utilizing the physical differences in detection depth at different emission angles, the oxygen concentration gradient distribution curve within the surface range of 15 nm to 50 nm was obtained. This was combined with morphological scanning at a low accelerating voltage of 2 kV to confirm the ordered distribution of catechol functional groups in specific depth regions. Regarding the decision-making path for component ratios and process parameters, the key parameter was identified as the mass percentage of the biomimetic polar anchoring component. Ratio to melt index Its setting needs to balance the polarity density of the material surface layer with the retention rate of the mechanical strength of the substrate. The design considerations lie in achieving a balance between component migration kinetics and matrix crystallization locking rate, when In to Within the specified range, the biomimetic polar anchoring component can reach the material interface and form molecular chain entanglements before the matrix is ​​fully crystallized. If this ratio is lower than [a certain value], [the following occurs]. This results in components being deeply embedded within the matrix due to insufficient diffusion rate, while those with higher diffusion rates remain within the matrix. This leads to excessive segregation of polar components on the surface and the formation of a brittle, weak interface layer. Under this logic, the optimal working window is determined by setting up an experimental group and a control group with gradients.

[0036] In sample groups 1 to 3 of this invention, as exist to Increased distribution density of surface catechol functional groups within a certain range The change trend showed a positive correlation with the amount added, and the measured percentage of oxygen atoms increased from... Upgraded to Left and right, and the adhesion of the hundred grids is in Boil It remained at that level for a long time. It exhibited stable interfacial bonding quality; in control group 3 Set as The initial adhesion force was observed to be And deteriorated to [a certain degree] after aging tests. When the content of polar components exceeds the performance inflection point, excessive interfacial segregation disrupts the co-crystallization integrity between the polypropylene molecular chains on the surface, leading to a decrease in coating bonding stability; the active introduction frequency in the experiment was [missing information]. The electromagnetic harmonics simulate environmental disturbances in an industrial production line. Monitoring data shows that the sample group of this invention contains electromagnetic harmonics in the sensor sampling signal. Under Gaussian white noise conditions, its The calculated value fluctuates less than The stability of the self-migration mechanism driven by the melt index gradient in a non-ideal molding environment was confirmed. Specific experimental data are as follows:

[0037] Table #1: Interfacial characteristic parameters and adhesion test data of materials under different formulation conditions

[0038]

[0039] Experimental results demonstrate that by controlling the melt index ratio of the biomimetic polar anchoring component to the polypropylene matrix component, and in conjunction with the surface tension gradient field constructed by the interface migration auxiliary component, a chemical site enrichment layer can be constructed on the surface of the polypropylene substrate. This site pinning mechanism based on the co-crystallization principle enables the catechol functional groups to form a chemical chelate structure with moisture and heat resistance at the interface with the resin component in the water transfer ink, thus completing the closed-loop verification from the internal formulation adjustment of the material to the surface adhesion performance response.

[0040] Example 3: This example combines Figures 1 to 2 The preparation of a biomimetic anchoring polypropylene material for automobiles, designed to improve the adhesion of water transfer printing coatings, is described below. Figure 1 As shown, this relates to a biomimetic polar anchoring component, which contains catechol functional groups and polypropylene blocks, and its Setting the interfacial migration auxiliary component to 1.5 to 4.5 times that of the matrix component, while having a surface tension lower than that of the matrix component, the component creates a surface tension gradient with the polypropylene matrix component. This provides the thermodynamic driving force for migration during the molding and cooling stage, initiating thermodynamically driven directional migration. This causes the biomimetic polar anchoring component to become directionally enriched outwards, forming a concentration-enriched layer within a 15 nm to 50 nm depth region on the material surface. During the cooling / fixing stage, it exhibits a melt index... The polypropylene matrix component, which provides the main structural support, forms intermolecular entanglement with the polypropylene blocks. The resulting intermolecular co-crystallization structure locks the spatial positioning of the catechol functional groups, ultimately achieving the effect of improving the adhesion of the water transfer coating through chemical chelation and physical anchoring mechanisms.

[0041] like Figure 2As shown, the technical system of this high-adhesion biomimetic anchoring polypropylene material consists of four core dimensions: a polypropylene matrix with isotacticity ≥96% in the raw material composition design; a biomimetic polar anchoring component containing catechol / PP blocks; an interface migration auxiliary component in the form of a low surface tension carrier; and key process parameters, including a temperature of 170°C. Up to 220 The range of twin-screw melt extrusion, melt index matching with MFI ratio control between 1.5 and 4.5, and a rate of 5 / s to 12 / s injection cooling control, the micro-formation mechanism stimulated by the above process and raw materials is manifested as the enrichment of surface concentration in the depth region of 15nm-50nm under the drive of surface tension gradient with tension difference ≥8mN / m, and the locking of active sites through molecular chain co-crystallization.

[0042] Example 4: When the wall thickness is distributed in a stepped manner, i.e., the wall thickness is... to In the injection molding process of automotive door handle components with varying wall thicknesses, the different thermal histories of the material within the mold cavity lead to slow cooling in the thick-walled areas, causing excessive segregation of polar components. This results in inconsistent adhesion stability of water transfer inks at different locations on the component. To address the challenge of interface anchoring failure caused by uneven cooling thermal histories, a mold temperature control method based on crystallization kinetics constraints is adopted to determine the appropriate temperature. Polypropylene matrix components, Bionic polar anchoring components and Processing parameters of the material system composed of interface migration auxiliary components; during injection molding, adjusting the cooling water flow rate of the mold cooling circuit to achieve the average cooling rate at different wall thickness locations of the part. All in to Within the specified range; due to the influence of the isotacticity of the polypropylene matrix components on the release of latent heat of crystallization, the calibration process monitors the pressure drop curve of the melt in the cavity using a hot runner pressure sensor, and calculates the actual cooling performance under the current mold thermal conductivity using the heat conduction equation; the biomimetic polar anchoring component, under the tension gradient traction constructed by the interface migration auxiliary component, utilizes The liquidity provided spans the flow front; when When within the above interval, the correlation constant It was determined by inverse fitting of the surface energy evolution curves under different cooling gradients.

[0043] Using atomic force microscopy to examine the thickness of the workpiece Modulus scanning analysis was performed on the thick-walled surface, and it was observed that on the surface... to A modulus gradient transition layer exists within the depth region; this confirms that the polypropylene blocks in the biomimetic polar anchoring component have an isotacticity of not less than [a certain value]. The polypropylene matrix component forms a co-crystallized structure through molecular chain entanglement; it anchors catechol functional groups to the material surface, increasing the distribution density of surface catechol functional groups. Stay The above, of which The calculation is based on the following formula: ,in, This represents the effective distribution density of catechin functional groups on the surface layer, in units of... , For correlation constants, the numerical value is taken as follows: , The melt flow index of the biomimetic polar anchoring component is taken as a value. , The melt flow index of the polypropylene matrix component is taken as a value. , The average cooling rate during the injection molding process, in units of... After undergoing full-surface water transfer printing decoration, the adhesion of the variable-wall thickness parts in the cross-cut adhesion test at both the thick-wall and thin-wall locations reached a certain level. ; the parts undergo After a period of damp heat aging test, the surface coating did not blister or peel off.

[0044] Example 5: In industrial production conditions involving different batches of isotactic polypropylene matrix components, the surface tension of the matrix components is affected by fluctuations in catalyst activity or differences in molecular weight distribution during raw material production. This deviation affects the response rate of the interface migration aid component in constructing the thermodynamic gradient field. To maintain the uniformity of polar site distribution on the surface, a pre-deployment physical property parameter calibration procedure is adopted. Specifically, before melt processing, the surface tension values ​​of the current batch of polypropylene matrix component and interface migration aid component are measured using a drop contact angle meter. By adjusting the mass percentage of the interface migration aid component, the surface tension difference between the polypropylene matrix component and the interface migration aid component is stabilized. to Within a certain range, the transport efficiency of the interface migration auxiliary component to the biomimetic polar anchoring component is constrained by their mass ratio. In formulation design, the ratio of the mass percentage of the interface migration auxiliary component to the mass percentage of the biomimetic polar anchoring component is set within a locked range of 0.12 to 0.18. This ratio ensures that the non-polar long-chain segments of the auxiliary component can fully coat the catechol functional groups, overcoming the viscosity resistance of the polypropylene matrix while avoiding the formation of a non-co-crystalline impurity weak layer at the interface due to excessive auxiliary component. The surface tension of the polypropylene matrix component is expressed in units of 1000 m². When measured In to At that time, the amount of interfacial migration aid component added was adjusted by calculating the interfacial polar diffusion resistance in the current batch. to To compensate for deviations in thermodynamic driving forces, this proportioning adjustment method based on physical property measurements avoids the influence of differences in raw material sources on the interfacial tension field, ensuring that different batches of materials... The adhesion level remained at [value] after the boiling aging test. , measured When deviation occurs, adjust the amount of interface migration aid component added to correct the thermodynamic driving force, and keep the mass percentage of the interface migration aid component within a certain range. to The intensity of the surface tension gradient field between the matrix and auxiliary components is increased within a certain range to maintain it at a certain level. With a concentration of mN / m or higher, the influence of raw material source differences on the migration rate of biomimetic polar anchoring components is eliminated, and the thickness of the concentration enrichment layer is maintained at a certain level during the molding and cooling stage. nm to nm range.

[0045] When the system faces the condition of cooling efficiency deviation caused by the evolution of mold thermal balance in mass injection molding, the cooling efficiency is improved by adjusting the cooling efficiency below the mold cavity liner. Embedded response frequency not less than Thermocouple sensors monitor the cooling slope of the melt in the crystallization phase transition temperature range in real time and obtain the average cooling rate. Based on the distribution data of catechol functional groups, and considering the thermal inertia of the mold temperature control system during the injection molding cycle, a baseline reference model is established during the start-up phase of the injection molding equipment, and the distribution density of the measured catechol functional groups is compared. The deviation from the target value is assessed using a feedback loop to correct the cooling water valve opening in real time. Based on the energy balance equation, the cooling medium flow rate is adjusted to compensate for the localized temperature rise caused by the release of latent heat of crystallization. With a thickness of The interface of the part is close to ,in, Average cooling rate, in units of , This represents the effective distribution density of catechin functional groups on the surface layer, in units of... The sensor collects temperature signals and inputs them in real-time into the controller's first-in-first-out (FIFO) sliding buffer. This buffer is set to have 50 sampling points. The controller extracts the temperature values ​​from the first and last sampling points in the buffer, calculates the difference, and divides it by a 0.5-second sliding window duration to determine the current real-time average cooling rate. The feedback loop executes as follows: if the measured average cooling rate is lower than the target operating point by 0.5 seconds... Every second, a pulse command is sent to the cooling water proportional control valve to increase the valve opening in steps of 5% of the total stroke, until the measured value returns to the preset 8.5 seconds per second. This control method based on measured heat flow feedback converts the average cooling rate into discrete commands that can be executed by the mold temperature controller, avoiding localized adhesion deviations in large-sized irregularly shaped parts due to differences in thermal history.

[0046] Example 6: In industrial production processes involving parallel injection molding of multi-cavity molds, uneven distribution of cooling water resistance in different cavities leads to differences in the steady-state heat exchange efficiency of each cavity wall, causing inconsistent fluctuations in adhesion performance among different parts from the same production batch. To eliminate heat transfer deviations between cavities, a cavity balance compensation procedure based on a baseline model is adopted. During the mold debugging phase, embedded sensors are used to collect the characteristic thermal response sequences of each cavity and calculate their deviation factor from the global average cooling rate. ,according to The numerical values ​​are used to establish an offline compensation parameter matrix for specific cavities. In actual production, local corrections are forced by independently controlling the proportional regulating valves of each cavity's cooling branch. .

[0047] When the deviation factor of a certain cavity Deviation from preset benchmark value At that time, the controller automatically calculates the current wall heat flux based on the law of conservation of energy and outputs a flow compensation command to adjust the average cooling rate of the area. Compensation to The target operating point, thereby enabling the effective distribution density of catechol functional groups on the surface of all cavity parts. All stable at to Within the specified range; this dynamic compensation mechanism based on the baseline model eliminates the influence of mold structural defects on the interface phase state. After undergoing temperature and humidity cycling tests of equal intensity, the peel strength deviation of the surface decorative layer of all batches of the prepared automotive handle parts was less than [value missing]. This achieves stable and controllable adhesion quality under large-scale production conditions. The biomimetic polar anchoring component and the interface migration aid component work synergistically, regulated by melt index matching and tension gradient, providing polar active sites and co-crystallization segments. The interface migration aid component acts as a thermodynamic carrier; in its absence, isolated micro-regions are formed within the substrate, increasing the surface catechol functional group density. Below mg / m2, melt index ratio deviates to Within a certain range, the molecular chain entanglement and phase locking during the cooling stage cause a time delay, and the active sites generate disordered accumulation in the concentration enrichment layer.

[0048] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit of this application and the scope of protection of this invention, and all of these forms are within the protection scope of this application.

Claims

1. A method for preparing a biomimetic anchoring polypropylene material for automobiles to improve the adhesion of water transfer printing coatings, characterized in that, Based on the total weight of the biomimetic anchoring polypropylene material as 100%, its components and mass percentages include: The polypropylene matrix component has a melt index of [missing information]. ; The biomimetic polar anchoring component, with a mass percentage of 1% to 8%, is a block copolymer containing polypropylene blocks and catechol functional groups. The melt flow index of the biomimetic polar anchoring component is [missing information]. ,and and The ratio is between 1.5 and 4.5; Interface migration aids, with a mass percentage of 0.1% to 1.5%, are present at 25°C. The surface tension below that of the polypropylene matrix component is lower at 25. The surface tension below; In the molded cross section of the biomimetic anchoring polypropylene material, due to the surface tension gradient difference between the interface migration auxiliary component and the polypropylene matrix component, the biomimetic polar anchoring component forms a 15-degree angle on the surface of the biomimetic anchoring polypropylene material. Up to 50 A concentration enrichment layer is formed in the depth region, and the co-crystallization structure formed by the polypropylene block and the polypropylene matrix component through intermolecular entanglement enables the spatial positioning of the catechol functional groups within the concentration enrichment layer.

2. The preparation of a biomimetic anchoring polypropylene material for automobiles to improve the adhesion of water transfer printing coatings according to claim 1, characterized in that, The polypropylene matrix component is isotactic polypropylene or impact copolymer polypropylene with an isotacticity of not less than 96% and a melt flow index of 15. Up to 35 ; The number-average molecular weight of the polypropylene blocks in the biomimetic polar anchoring component is 5000 to 15000, and the mass percentage of catechol functional groups in the biomimetic polar anchoring component is 10% to 25%; the interface migration auxiliary component is 25 The surface tension below is 18 Up to 24 Furthermore, the surface tension difference between it and the polypropylene matrix component is not less than 8. .

3. The preparation of a biomimetic anchoring polypropylene material for automobiles to improve the adhesion of water transfer printing coatings according to claim 1, characterized in that, Surface distribution density of catechol functional groups in the concentration enrichment layer The following quantitative relationship is satisfied: ,in, The effective mass concentration of catechol functional groups in the concentration enrichment layer per unit area; These are correlation constants pre-defined based on the crystallization kinetics of the polypropylene matrix components; The average cooling rate during the molding and cooling process, in units of... / s; Catechol functional groups via and The synergistic constraints lead to the formation of nanoscale ordered arrangements in the concentration enrichment layer.

4. The preparation of a biomimetic anchoring polypropylene material for automobiles to improve the adhesion of water transfer printing coatings according to claim 1, characterized in that, The catechol functional group in the biomimetic polar anchoring component is selected from at least one of dopamine structural units, 3,4-dihydroxyphenylpropanamine structural units, or catechol-grafted polyethyleneimine units, and the catechol functional group is covalently linked to the end of the polypropylene block.

5. The preparation of a biomimetic anchoring polypropylene material for automobiles to improve the adhesion of water transfer printing coatings according to claim 1, characterized in that, The melting point of the interface migration auxiliary component is lower than the crystallization initiation temperature of the polypropylene matrix component. The interface migration aid component physically associates with the catechol functional groups in the biomimetic polar anchoring component through intermolecular van der Waals forces, and acts as a carrier for the migration of the biomimetic polar anchoring component to the surface of the biomimetic anchoring polypropylene material.

6. The preparation of a biomimetic anchoring polypropylene material for automobiles to improve the adhesion of water transfer printing coatings according to claim 1, characterized in that, The polypropylene matrix component also includes a nucleating agent comprising 0.2% to 0.5% of the total weight of the biomimetic anchoring polypropylene material. The nucleating agent is used to increase the crystallization temperature of the polypropylene matrix component, thereby shortening the diffusion time of the biomimetic polar anchoring component in the concentration enrichment layer to lock the molecular phase.

7. The preparation of a biomimetic anchoring polypropylene material for automobiles to improve the adhesion of water transfer printing coatings according to claim 1, characterized in that, The biomimetic anchoring polypropylene material also includes antioxidants, lubricants, and light stabilizers, and the total content of antioxidants, lubricants, and light stabilizers does not exceed 1.2% of the total weight of the biomimetic anchoring polypropylene material.

8. The preparation of a biomimetic anchoring polypropylene material for automobiles to improve the adhesion of water transfer printing coatings according to claim 1, characterized in that, The biomimetic polar anchoring component is prepared by an amidation reaction of maleic anhydride-grafted polypropylene and an amino-containing catechol derivative in the molten state. The biomimetic polar anchoring component is at 1645... It exhibits characteristic infrared absorption peaks of amide carbonyl groups.

9. The preparation of a biomimetic anchoring polypropylene material for automobiles to improve the adhesion of water transfer printing coatings according to claim 1, characterized in that, The biomimetic anchoring polypropylene material, in its untreated state, exhibits a cross-cut adhesion test (0-grade) between its surface and water transfer ink, and the adhesion at 80°C is also low. Soak in water for 240 minutes The post-adhesion retention rate is 100%.

10. The preparation of a biomimetic anchoring polypropylene material for automobiles to improve the adhesion of water transfer printing coatings according to claim 1, characterized in that, The catechol functional groups in the concentration enrichment layer are exposed on the surface of the biomimetic anchoring polypropylene material and are configured to form chemical chelates with the resin components in the water transfer ink.

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