A thermoplastic composite molding compound and its cold push molding process

Abstract

This invention relates to the field of polymer compound compositions and discloses a thermoplastic composite molding compound and its cold push molding process, comprising: providing a molding compound containing a semi-crystalline matrix, a rigid filler, and an interfacial crystallization responder; the responder is a specific conversion rate esterification product of hyperbranched polyester and straight-chain saturated fatty acid, forming an amphiphilic interfacial layer containing unreacted hydroxyl groups and long-chain side chains on the filler surface; heating the molding compound to a semi-solid state and applying high pressure, causing the interfacial layer to preferentially dissociate and slip under shear exceeding the yield threshold to fill the mold; after depressurization, the shape is locked by in-situ recrystallization of the side chains. This invention achieves orthogonal decoupling of low-temperature fluid slip and room-temperature rigid locking by constructing a stress-responsive interfacial eutectic intercalation structure, solving the problem of inverted flowability and modulus in cold push molding, and suppressing dimensional springback by utilizing a phase change mechanism.

Description

Technical Field

[0001] This invention relates to a thermoplastic composite molding compound and its cold push molding process, belonging to the technical field of polymer compound compositions. Background Technology

[0002] Currently, the mainstream molding methods for semi-crystalline thermoplastic resin-based composites such as polypropylene and polyamide are melt injection molding or hot pressing. Although these processes are mature, they suffer from limitations such as high energy consumption, long cycle times, and susceptibility to thermal degradation. Cold push molding, as a highly efficient near-net-shape forming technology, has great potential in industrial manufacturing due to its ability to force flow under high pressure at temperatures below the melting point. This is especially true for tooling manufacturing, such as automotive molds, fixtures, ship models, and product models, which are sensitive to production cycles. If cold push molding can replace traditional metal cutting or wood stacking, it will reduce manufacturing costs and improve iteration efficiency. However, existing semi-crystalline thermoplastic composites cannot meet the above requirements. The stringent requirements for material performance in the high-end tooling field stem from the inverse contradiction between rheological properties and mechanical rigidity. Traditional formulations often use plasticizers or reduce the molecular weight of the matrix to improve processing fluidity at low temperatures. While this solves the mold filling problem, it sacrifices the integrity of the material's crystalline regions and bulk modulus, resulting in insufficient rigidity of the parts. These parts cannot withstand the high-pressure loads of stamping dies or carbon fiber composite molding dies during service. At the same time, elastic deformation of polymer chain segments dominates during low-temperature molding, and entropy elastic recovery occurs after pressure relief. This dimensional springback phenomenon makes it impossible for materials to meet the micron-level dimensional accuracy control standards of automotive fixtures and precision ship models.

[0003] To overcome the shortcomings of the aforementioned mold materials in terms of rigidity and precision, the industry has attempted to improve the performance of the template by modifying the resin matrix formulation. However, existing technologies mostly focus on relying on complex chemical cross-linking and curing to achieve dimensional stability, neglecting the balance between processing efficiency and molding cycle. For example, Chinese invention patent CN102746619B discloses a synthetic resin template and its production process. Its technical solution involves multi-step mixing and vacuum kneading of epoxy resin, polysulfide glue, polyurethane, and fillers such as alumina and silica, followed by vacuum curing for 10 to 14 hours and 90 to 11 hours of curing. While the method of preparing resin templates by baking at 0 degrees Celsius utilizes the interpenetrating network structure of epoxy resin and polyurethane to improve the hardness and temperature resistance of the material to some extent, its process is still a typical thermosetting chemical reaction molding process. It involves a curing and baking cycle of up to tens of hours, resulting in huge energy consumption and low production efficiency. Furthermore, it cannot achieve rapid reversible molding at low temperatures through physical phase change mechanisms. This traditional process, which relies on chemical cross-linking, is difficult to solve the high-efficiency production requirements of modern mold manufacturing for immediate use, and it cannot provide an effective reference for solving the problem of dimensional springback of thermoplastic matrices under cold push-out processes.

[0004] Therefore, the technical problem to be solved by this invention is how to construct a thermoplastic composite material system that can overcome the contradiction between fluidity and modulus inversion in cold push molding, and effectively suppress dimensional springback while achieving rapid mold filling at low temperature, so as to meet the stringent manufacturing requirements of rapid prototyping molds and high-precision industrial tooling. Summary of the Invention

[0005] To address the problems mentioned in the background art, the technical solution of the present invention is as follows: A thermoplastic composite molding compound, comprising:

[0006] The semi-crystalline thermoplastic resin matrix is ​​a continuous phase, the particulate rigid inorganic filler is dispersed in the semi-crystalline thermoplastic resin matrix, and the hyperbranched polyester modifier is coated on the surface of the particulate rigid inorganic filler.

[0007] Hyperbranched polyester modifiers are those with terminal hydroxyl groups and a theoretical hydroxyl value of [value missing]. The third-generation hyperbranched polyester with a carbon atom number of to The esterification products of straight-chain saturated fatty acids, wherein the hydroxyl conversion rate of the esterification products is... to Hyperbranched polyester modifiers form hydrogen bonds with active sites on the surface of particulate rigid inorganic fillers through residual hydroxyl groups at the ends of molecular chains, thereby constructing an amphiphilic slip layer with long-chain aliphatic side chains on the surface of particulate rigid inorganic fillers.

[0008] exist to At the molding temperature, the aliphatic side chains in the amphiphilic slip layer are in a molten state, transforming the particulate rigid inorganic filler into micro-rolling units lubricated by the amphiphilic slip layer, and reducing the yield stress of the thermoplastic composite molding material at the molding temperature. to between;

[0009] During the cooling stage after the thermoplastic composite molding compound is filled under pressure, the aliphatic side chains in the hyperbranched polyester modifier undergo in-situ interfacial eutectic with the semi-crystalline thermoplastic resin matrix, forming a thickness of [missing information] at the interface between the granular rigid inorganic filler and the semi-crystalline thermoplastic resin matrix. to The eutectic intercalation locking structure locks the deformation of the semi-crystalline thermoplastic resin matrix after shear stress removal.

[0010] Preferably, the granular rigid inorganic filler is selected from hollow glass microspheres or ceramic microspheres; the average particle size of the granular rigid inorganic filler is [missing information]. to Furthermore, the mass percentage of granular rigid inorganic fillers in thermoplastic composite molding compounds is [missing information]. to The coating density of hyperbranched polyester modifier on the surface of granular rigid inorganic filler is the corresponding density per square meter of granular rigid inorganic filler surface area. to Hyperbranched polyester modifiers; in And the shear rate is not less than Under certain conditions, the apparent viscosity of thermoplastic composite molding compound decreases nonlinearly and monotonically with increasing shear rate.

[0011] Preferably, the total weight of the thermoplastic composite molding compound is... The content of hyperbranched polyester modifier by weight is: weight parts to The content of granular rigid inorganic filler by weight is: weight parts to The remainder is a semi-crystalline thermoplastic resin matrix, in parts by weight; wherein the content of hyperbranched polyester modifier is... The value varies with the hydroxyl conversion rate. It decreases as it rises, that is, when for hour, for to ;when for hour, for to .

[0012] Preferably, the semi-crystalline thermoplastic resin matrix is ​​selected from polypropylene, polyethylene, and polyamide. One or more of polybutylene terephthalate; the carbon chain length of the aliphatic side chain in the hyperbranched polyester modifier matches the length of the main chain repeating unit of the semi-crystalline thermoplastic resin matrix.

[0013] Preferably, the thermoplastic composite molding compound is in The rheological properties under these conditions follow the Bingham fluid model: ;in, Shear stress, unit: ; The yield stress of the thermoplastic composite molding compound, in units of ; This is the plastic viscosity coefficient, in units of... ; Shear rate, in units of .

[0014] Preferably, the melting point of the hyperbranched polyester modifier is lower than that of the semi-crystalline thermoplastic resin matrix. to ;exist At the molding temperature, the hyperbranched polyester modifier is a liquid fluid. At room temperature, the hyperbranched polyester modifier is a crystalline solid, and the thermoplastic composite molding compound has a diameter of to Injection molding granules, in The flexural modulus under the condition is not less than Furthermore, the products formed by cold extrusion are in The linear shrinkage rate within is lower than .

[0015] Preferably, the hyperbranched polyester modifier is prepared by the following steps: mixing third-generation hyperbranched polyester with linear saturated fatty acids in a specific ratio. to The molar ratio of the mixture is 1:1, and the temperature is 1:1. to And the vacuum degree is greater than or equal to Under suitable conditions, a melt esterification reaction was carried out, and the hydroxyl conversion rate was achieved by measuring the amount of water removed during the reaction. to .

[0016] Preferably, it also includes one or more of antioxidants, internal lubricants, and nucleating agents; the mass percentage of antioxidants is [missing information]. to The mass percentage of internal lubricant is to The nucleating agent is selected from sorbitol derivatives or organophosphates.

[0017] Preferably, the surface of the granular rigid inorganic filler is pre-coated with a silane coupling agent, which has amino or epoxy groups to fix the residual hydroxyl groups of the hyperbranched polyester modifier to the surface of the granular rigid inorganic filler through covalent bonds or hydrogen bonds.

[0018] A cold push molding process for thermoplastic composite molding materials includes the following steps:

[0019] Step 111: Preheat the thermoplastic composite molding compound to... to This transforms the hyperbranched polyester modifier into a molten state and coats the surface of the granular rigid inorganic filler to form an amphiphilic slip layer;

[0020] Step 112: Place the preheated thermoplastic composite molding material into the mold cavity and apply molding pressure so that the shear stress on the thermoplastic composite molding material is greater than the yield stress. And induce the thermoplastic composite molding compound to fill the mold cavity;

[0021] Step 113: Press the filled thermoplastic composite molded material and cool it to room temperature. During the cooling process, the aliphatic side chains in the hyperbranched polyester modifier undergo eutectic reaction with the semi-crystalline thermoplastic resin matrix to form a eutectic intercalation locking structure.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. In thermoplastic composite molding and cold push molding, the esterification reaction conversion rate of the interface crystallization response agent is limited to the range of 65% to 75%. A stress-responsive interface eutectic layer is constructed between the semi-crystalline resin matrix and the rigid filler. The specific conversion rate retains the polar hydroxyl groups to anchor the modifier to the filler surface. An appropriate amount of long alkyl side chains are grafted into the matrix lattice edge to form physical cross-linking. Based on the dual anchoring structure of the specific reaction degree, the interface eutectic layer of the molding material preferentially dissociates and exhibits fluid slip only when the cold push processing conditions exceed a specific shear threshold. The rigid connection is reconstructed by restoring the side chain eutectic in the static state after stress removal. This solves the technical contradiction of sacrificing the intrinsic crystallinity of the matrix to improve the rigidity of the finished product in the existing technology. It enables the cold push part to obtain excellent filling performance while maintaining the high energy storage modulus of engineering plastics.

[0024] 2. By utilizing the size matching between C18 to C22 straight-chain alkyl side chains and the helical chain segments of the matrix, a shape locking mechanism based on interfacial crystallization phase transition is established. This differs from existing technologies that rely on the entropy elastic relaxation of polymer amorphous region chain segments for shaping. At the moment of decompression of the interfacial layer, the long alkyl side chains are rapidly recrystallized in situ to generate physical locking force, which suppresses the tendency of natural springback after deformation of the matrix molecular chain. The liquid-solid phase transition locking is completed instantly, so that the mold material maintains the micro-stress balance after cold push forming. The shrinkage rate and warpage of the part are controlled within the precision tolerance range, overcoming the problem of elastic recovery dimensional stability in cold forming process.

[0025] 3. This invention enhances the intelligent rheological properties of composite materials through controlled reactions of conventional chemical raw materials. Modifier molecules achieve spontaneous equilibrium within a 65% to 75% conversion rate range, improving the wettability of inorganic fillers and the intercalation ability into the organic matrix, forming a uniform and stable core-shell structure. Based on a stoichiometric control preparation strategy, it avoids the introduction of expensive special monomers or complex post-processing steps, ensuring consistent quality in industrial-grade continuous production equipment for molding materials. This makes high-rigidity cold-push molding materials economically feasible for large-scale industrial application. Furthermore, the invention constructs an interface slip layer, transforming the traditional integral shear flow of polymers into a filler-induced particle flow mode. The high-pressure shear field during cold-push molding, along with the low yield strength of the interface eutectic layer, transforms rigid fillers into micro-rolling units, driving the surrounding semi-solid matrix to achieve rapid cavity filling. This reduces the frictional heat-generating shear viscosity during the flow process of the high-filler system, allowing the molding material to achieve dense molding at a temperature far below the matrix melting point. This eliminates the need for a full-melting and full-cooling enthalpy exchange process, shortening the molding cycle and reducing production energy consumption.

[0026] 4. The interfacial crystallization responsive agent of the present invention constructs a stable amphiphilic interfacial layer. This structure endows the mold material with excellent matrix compatibility. Under the premise of ensuring cold extrusion molding performance, the mold material system can be used as an open formulation platform. According to the different working conditions of automotive molds, outdoor inspection tools or high-temperature molds, lubricants to increase fluidity, reinforcing agents to improve hardness, as well as functional excipients such as fire retardants, high-temperature resistant agents, and UV stabilizers can be flexibly added. This on-demand formulation characteristic enables the present invention to adapt to a wide range of application scenarios from precision inspection tools to heavy-duty stamping dies through simple component adjustments.

[0027] 5. This invention achieves a leapfrog transformation of molding materials from irreversible chemical curing to reversible physical phase change, exhibiting significant recyclability and environmental friendliness. Compared to traditional thermosetting mold materials in the background technology that rely on chemical cross-linking, cannot be remelted and reused after molding, and easily cause environmental pollution, the semi-crystalline thermoplastic system adopted in this invention is based on a physical crystallization / desorption phase change mechanism, enabling the molding material to still have complete secondary processing capabilities after completing specific tooling tasks. This realizes the essential evolution of mold materials from disposable consumables to recyclable industrial assets. This reusability not only eliminates the environmental pollution pressure caused by thermosetting waste landfill from the source, but also greatly reduces the raw material cost of single manufacturing through efficient closed-loop resource recycling. Combined with the extremely short molding cycle of the cold push process, it achieves deep synergy between green environmental protection, cost reduction and material reduction, and production efficiency in mold manufacturing. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the cold push molding process and the interfacial eutectic response mechanism of the thermoplastic composite molding material of the present invention;

[0029] Figure 2 This is a comparison diagram of the shear stress-strain curves and rheological yield properties of the molding material under different hydroxyl conversion rates according to the present invention.

[0030] Figure 3 This is a schematic diagram of the integrated system module and closed-loop monitoring of the thermoplastic composite molding material preparation and cold push molding of the present invention. Detailed Implementation

[0031] The following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Any modifications or substitutions made by those skilled in the art to the technical solutions of the invention after reading the specification and based on the teachings of the invention shall fall within the scope of protection of the claims of the invention.

[0032] This specific embodiment provides a thermoplastic composite molding compound and its cold push molding process, which is composed of a semi-crystalline thermoplastic resin matrix, a rigid inorganic filler, and an interfacial crystallization response agent anchored on the surface of the filler, by melt blending. The semi-crystalline thermoplastic resin matrix, as the continuous phase, is selected with a melt index of [insert melt index here]. to Isotactic polypropylene or polyamide, and rigid inorganic fillers with an average particle size of [missing information]. to And the compressive strength is higher than Hollow glass microspheres or ceramic microspheres, with the interfacial crystallization response agent having a theoretical hydroxyl value. The third-generation hydroxyl-terminated hyperbranched polyester with a carbon chain length of to The product of the melt esterification reaction of straight-chain saturated fatty acids, wherein the third-generation hydroxyl-terminated hyperbranched polyester is specifically a quasi-spherical topological macromolecule constructed by the polycondensation reaction of the core unit trimethylolpropane (TMP) and the branched monomer 2,2-bis-methylolpropionic acid (bis-MPA). The straight-chain saturated fatty acid can be stearic acid or docosanoic acid. The carbon chain length must meet the interface crystallization matching criterion with the lattice parameters of the semi-crystalline thermoplastic resin matrix. The characteristic period length of the helical chain segment of the semi-crystalline thermoplastic resin matrix is... Numerical analysis was performed on unmodified pure resin matrix samples using wide-angle X-ray diffraction (WAXD) at 25 degrees Celsius. The periodic distance of repeating units along the fiber axis of the polymer chain crystal region was calculated using the Bragg equation and the interplanar spacing of the characteristic crystal peaks in the diffraction pattern. The theoretical length of the grafted side chains was also determined. The physical constants of carbon-carbon bond length of 0.154 nm and bond angle of 109.5 degrees in the all-trans conformation are calculated by geometric projection and used as the geometric constraint benchmark for side chain embedding into matrix lattice defects.

[0033] The preparation of interfacial crystallization responsive agents follows strict stoichiometry and conversion rate control procedures. Under isothermal conditions, using p-toluenesulfonic acid as a catalyst, a third-generation hydroxyl-terminated hyperbranched polyester, branched from a trimethylolpropane core and 2,2-dimethylolpropionic acid, was melt-esterified with a straight-chain saturated fatty acid. The acid value of the system was monitored in real time during the reaction, and the hydroxyl conversion rate was calculated accordingly. When the hydroxyl conversion rate fell into a certain range... to The reaction is terminated immediately when the value falls within the specified range. The hydroxyl conversion rate of the melt esterification reaction is calculated based on the real-time acid value of the system and the molar ratio of the feed materials, according to the GB / T6743 standard. Every 10 minutes during the preparation process, the melt in the titration vessel is sampled to obtain the instantaneous acid value. The amount of residual carboxyl groups is calculated by subtracting the instantaneous acid value from the initial total amount of carboxyl groups in the fed linear saturated fatty acids, yielding the amount of carboxyl groups consumed in the reaction. The ratio of this consumption amount to the theoretical total amount of hydroxyl groups in the third-generation hydroxyl-terminated hyperbranched polyester is defined as the instantaneous hydroxyl conversion rate. When the value falls within the preset process window of 65% to 75%, the reactor cooling coil is opened and liquid nitrogen is injected to terminate the reaction. Within this conversion rate range, the interfacial crystallization response agent exhibits a specific amphiphilic structure, i.e., containing... to unreacted hydroxyl groups and to The grafted side chains, with unreacted hydroxyl groups as polar anchoring groups, are used to adsorb onto the surface of rigid inorganic fillers through chemical bonding or hydrogen bonding; the grafted side chains, as non-polar crystalline segments, are used to insert into the lattice edge of the semi-crystalline thermoplastic resin matrix during the cooling process of mold preparation, thereby forming an interfacial eutectic intercalation structure.

[0034] The preparation process of thermoplastic composite molding compound includes two steps: filler surface modification and melt blending. Rigid inorganic fillers and interfacial crystallization responsive agents are added to a high-speed mixer and mixed at a temperature higher than the melting point of the interfacial crystallization responsive agent. This allows the interfacial crystallization responsive agent to melt and uniformly coat the filler surface, forming a layer with a thickness of [missing information]. to A continuous interface layer is formed by melt blending surface-modified rigid inorganic fillers with a semi-crystalline thermoplastic resin matrix in a co-rotating twin-screw extruder. The blend is then extruded, water-cooled, and pelletized to obtain thermoplastic composite molding compound granules. In these granules, the semi-crystalline thermoplastic resin matrix accounts for the remainder, and the rigid inorganic filler accounts for a certain percentage. weight parts to The content of the interfacial crystallization response agent is (parts by weight). weight parts to By weight, the interfacial eutectic intercalation structure has a yield strength lower than that of the bulk crystalline region of the semi-crystalline thermoplastic resin matrix, forming a stress-responsive slip layer. The cold push molding process of this thermoplastic composite molded material utilizes the thixotropic properties of the interfacial layer to achieve low-temperature flow and room-temperature locking. The process involves heating the thermoplastic composite molded material to a pre-plasticizing temperature, lower than the melting point of the semi-crystalline thermoplastic resin matrix. to This allows the mold material to be in a semi-solid state. Then, the semi-solid mold material is placed at the mold cavity inlet and an application of pressure higher than [amount missing]. Under the extrusion pressure and high-pressure shearing, when the shear stress exceeds the interfacial eutectic yield threshold, the grafted side chains in the interfacial eutectic intercalation structure orient and untangle, transforming into a quasi-liquid slip layer. At this time, the rigid inorganic filler, in a particle flow mode, drives the surrounding matrix to quickly fill the mold cavity. After filling is completed and the extrusion pressure is removed, the shear rate inside the mold material returns to zero. In an environment where the mold temperature is lower than the pre-plasticizing temperature, the grafted side chains utilize the surface of the rigid inorganic filler as a confined nucleation template. to Within a timeframe of several orders of magnitude, in-situ epitaxial growth and recrystallization occur, reconstructing the interfacial eutectic intercalation structure. The physical locking force generated by this rapid recrystallization process inhibits the entropy elastic recovery of the amorphous chain segments in the semi-crystalline thermoplastic resin matrix, thereby locking the shape of the molded part and eliminating dimensional springback.

[0035] Example 1: In the high-speed cold push forming production scenario of precision electronic structural components, the production environment requires the forming cycle to be compressed to [a certain value]. Within this range, the manufactured parts must possess superior qualities. To meet the dimensional accuracy requirements of subsequent automated assembly, existing polypropylene-based composite materials face severe processing challenges under such conditions. When high filler content is used to increase modulus, the material's properties below its melting point... At cold push temperatures, the fluidity is extremely poor, leading to incomplete mold filling or equipment overload. If the fluidity is improved by reducing the molecular weight of the matrix, the part will spring back after demolding due to stress relaxation in the amorphous region, resulting in dimensional deviations exceeding [a certain threshold]. This method cannot meet the precision tolerance requirements. Therefore, this embodiment uses a method based on melt flow index... isotactic polypropylene matrix, average particle size A thermoplastic composite molding compound composed of hollow glass microspheres and a specific interfacial crystallization responsive agent addresses the above challenges. The interfacial crystallization responsive agent has a hydroxyl conversion rate controlled at [value missing]. The esterification product of third-generation hydroxyl-terminated hyperbranched polyester and stearic acid is produced by heating the molding compound to [temperature missing]. That is, below the melting point of the matrix. It is in a semi-solid pre-plasticized state, and then applied. Under the extrusive pressure, the internal shear stress of the molding material rapidly increases and exceeds the interfacial eutectic yield threshold. The stearic acid side chain crystalline regions of the interfacial layer preferentially dissociate under the high shear field, forming a quasi-liquid slip layer on the surface of the rigid glass microspheres. This reduces the internal friction between particles, induces the microspheres to transform into rolling units, and drives the high-viscosity matrix in a particle flow mode. It completes the dense filling of complex cavities.

[0036] When the pressure holding ends and the extrusion pressure is released, the internal shear rate of the die material instantly returns to zero, because the die temperature is set to... Located in the rapid crystallization temperature range of stearic acid side chains, the dissociated side chains utilize the anchoring effect of residual hydroxyl groups on the surface of the microbeads as a confined nucleation template. In-situ recrystallization occurs within the matrix, a rapid phase transition process that reconstructs the interfacial eutectic intercalation structure. The resulting physical locking force effectively freezes the movement of the matrix molecular chains and inhibits the entropic elastic recovery of amorphous chain segments. After demolding, the molded part is inspected by a coordinate measuring machine, and the critical dimensional deviations are controlled within... Within, and the tensile storage modulus remains at above.

[0037] Example 2: To verify the technical effect of the thermoplastic composite molding compound of the present invention under non-melting processing conditions, a verification test platform simulating an industrial-grade cold push molding process was constructed, equipped with a material barrel temperature control precision (temperature control accuracy). ) and pushing speed (speed control precision) The experiment used a high-pressure capillary rheometer and a precision mold system capable of applying and maintaining a constant mold closing pressure. The semi-crystalline thermoplastic resin matrix used in the experiment was isotactic polypropylene (melt index 100%). The rigid inorganic filler is hollow glass microspheres (average particle size). The core objective of the experiment is to quantitatively evaluate the combined effects of the introduction of interfacial crystallization response agents and key synthesis parameters (hydroxyl conversion rate) on the low-temperature fluidity, dimensional stability and mechanical rigidity of the molding compound.

[0038] To systematically investigate the nonlinear regulatory effect of hydroxyl conversion rate, a key parameter, on interfacial properties, a multi-dimensional control system was introduced in the experimental design. The sample groups in this invention used hydroxyl conversion rates controlled at various levels. , and The interface crystallization responsive agent was used for modification; three control groups were set up: control group 1 did not add any interface modifier (blank control), control group 2 used an interface modifier with a hydroxyl conversion rate of 100%. The modifier was below the lower limit of the range, and the control group 3 used a hydroxyl conversion rate of [missing information]. The modifier exceeded the upper limit of the range, and the mass fraction of rigid inorganic filler was uniformly set to [value missing] in all sample groups. The amount of interface modifier added is uniformly set as follows: The test process tested each sample group at... (below the melting point of the matrix) The apparent viscosity at ) and the shear rate set to To simulate the high shear conditions during cold extrusion molding, each sample group was cold extruded into standard tensile specimens under the same conditions. After demolding, Let it stand in the environment Hours, using a laser scanner to measure the dimensional shrinkage rate in the length direction, and according to The standard test tensile storage modulus was performed, and the test results are summarized in Table 1.

[0039] Table 1: Effect of Hydroxyl Conversion Rate of Interface Modifier on Molding Properties

[0040]

[0041] Referring to Table 1, the data exhibit a non-linear variation. Control group 1, lacking interfacial lubrication, showed extremely high viscosity at low temperatures and significant dimensional shrinkage after molding due to matrix stress relaxation. While control group 2 showed some viscosity reduction, its low conversion rate resulted in excessively high polarity and poor compatibility with the matrix. This not only failed to effectively reduce shrinkage but also caused a significant decrease in modulus due to interfacial defects. In contrast, samples 1 to 3 of this invention showed... to Within the conversion rate range, the apparent viscosity drops sharply. Below, the dimensional shrinkage rate is controlled at... Within this range, the modulus is increased to The performance leap within this range indicates that only within this specific conversion window can the interface modifier simultaneously achieve effective anchoring of the filler (retaining hydroxyl groups) and crystallization intercalation of the matrix (the effect of long side chains), thereby providing lubrication under high shear and rigid locking at rest. When the conversion rate is further increased... In (control group 3), due to insufficient residual hydroxyl groups, the modifier fell off the filler surface, the lubrication and locking effects failed, and all performance indicators showed a deterioration inflection point.

[0042] Example 3: This example combines Figures 1 to 3 This document describes a thermoplastic composite molding compound and its cold push molding process, such as... Figure 1 As shown, the raw material components, including a semi-crystalline matrix, rigid filler, and interfacial crystallization responsive agent, are metered. Subsequently, an interfacial eutectic intercalation structure is constructed and a brush-like topology is formed through melt blending and extrusion. The material is then subjected to semi-solid pre-plasticizing heating, with the temperature controlled 20-50°C below the melting point. By preserving the physical cross-linking points of the crystalline region, a high-pressure shearing and pushing force greater than 50 MPa is applied to make the shear stress greater than the interface eutectic yield threshold. Under this condition, a quasi-liquid slip layer is formed, the grafted side chains are de-entangled, and the rigid filler fills the mold cavity in a particle flow mode. Finally, after the pressure relief and in-situ recrystallization step, the side chains are epitaxially grown and the interface eutectic intercalation structure is reconstructed after shearing removal, thereby obtaining a molded part that suppresses entropy elastic recovery and eliminates dimensional springback.

[0043] like Figure 2 As shown in the figure, the curves of shear stress versus shear strain at different hydroxyl conversion rates are displayed. The horizontal axis represents the shear strain in the range of 0 to 0.96 MPa, and the vertical axis represents the shear stress in the range of 0 to 2.5 MPa. The figure contains three curves, corresponding to the solid line for 70% hydroxyl conversion, the dashed line for 65% hydroxyl conversion, and the dotted line for 75% hydroxyl conversion, respectively. Figure 3 As shown, the system comprises four main parts: a raw material supply unit, a compounding and modification unit, a cold extrusion molding unit, and a quality monitoring unit. The raw material supply unit is responsible for accurately metering the semi-crystalline resin matrix polypropylene / polyamide, rigid inorganic filler glass microspheres / ceramic microspheres, and interface crystallization response agent hyperbranched polyester esterification products according to the formula, and then physically feeding them to the compounding and modification unit. The compounding and modification unit uses a high-speed mixer with interface coating and anchoring functions and a twin-screw extruder with melt blending and granulation functions to process the materials and then convey the composite particles to the cold extrusion molding unit. The cold extrusion molding unit includes a pre-plasticizing heating device that keeps the material in a semi-solid billet state, a high-pressure extrusion system that uses shear flow enhancement and slip mechanism, and a precision molding die that uses an in-situ recrystallization locking mechanism to finally output high-rigidity precision parts. At the same time, the quality monitoring unit monitors the apparent viscosity of the melt through an online rheometer and feeds back the process parameters to the twin-screw extruder to achieve closed-loop control.

[0044] Example 4: To determine the optimal addition window of the interfacial crystallization response agent in thermoplastic composite molding compounds, and to balance the competition between low-temperature rheology and room-temperature mechanical stiffness, a series of verification experiments with gradient addition amounts were designed. All experiments used a melt flow index of [missing information]. Isotactic polypropylene was used as the matrix, and hollow glass microspheres were used as the filler, with a fixed filling amount of [missing information]. The weight percentage was determined by selecting the hydroxyl conversion rate prepared in Example 1. Interfacial crystallization responsive agents were prepared by maintaining consistent extrusion granulation process parameters, with the contents of the interfacial crystallization responsive agents being respectively... Parts by weight Parts by weight Parts by weight Parts by weight and Five independent sample groups were prepared by weight, and two key performance indicators were tested on each sample group: one was the spiral flow length test simulating the cold push process, and the test temperature was set at [temperature value missing]. Injection pressure is The first is used to characterize the ultimate filling capacity at low temperatures; the second is the standard flexural modulus test. The experiments were conducted in an environment that was used to characterize the rigidity retention rate of the material. The results are summarized in Table 2.

[0045] Table 2: Effect of Interface Crystallization Response Agent Addition Amount on Rheological and Mechanical Properties of Mold Material

[0046]

[0047] Referring to Table 2, the data reveals a specific physical threshold between the amount of interface modifier and performance; when the amount added is only... At the weight percentage (gradient group 1), the spiral flow length is extremely short, indicating that the modifier is insufficient to form a continuous coating layer on the filler surface. A significant amount of direct contact remains between the glass microspheres and the matrix, leading to high internal friction. When the addition amount increases to... At a weight percentage (gradient group 2), the flow length exhibits a step increase, indicating that the percolation threshold for interfacial lubrication has been reached, forming a complete slip layer. to Within the weight range (gradient group 2 to 4), the flow length steadily increases with increasing addition amount, while the flexural modulus remains constant. The high levels mentioned above indicate that the excessive modifier is mainly concentrated in the interfacial region to thicken the slip layer, without penetrating into the matrix. However, when the addition amount reaches... At the weight percentage (gradient group 5), although the flowability reached saturation, the flexural modulus showed a precipitous drop. This indicates that excessive modifier molecules had overflowed the interfacial region and entered the interior of the polypropylene matrix. The long alkyl chains interfered with the crystallinity and density of the matrix itself, producing a typical bulk plasticizing effect, confirming... to The parts by weight represent the preferred formulation range that can simultaneously achieve super-lubricity of the interface and zero plasticization of the matrix, thus providing direct engineering basis for limiting the numerical range.

[0048] Example 5: To ensure the performance consistency and reliability of the thermoplastic composite molding compound of the present invention in different batches and under different service environments, a standardized interface performance calibration and quality control procedure was established. The core of this procedure is to quantitatively evaluate the grafting efficiency of the interface crystallization responder and its ability to regulate interface slip behavior through controlled rheological testing, thereby providing an objective basis for quality monitoring during the production process. Specifically, samples are randomly selected from the molding compound particles of the batch to be tested, and steady-state shear tests are performed in a precision rheometer. The test temperature is set to... Shear rate range covers to By recording the curve of shear stress versus shear rate and fitting the experimental data using the Bingham fluid model, the yield stress value of this batch of mold material was calculated.

[0049] Based on statistical analysis of a large amount of historical experimental data, a qualified judgment range for yield stress was established. When the measured yield stress is lower than the preset lower limit, it indicates that the interface layer bonding is too weak or the modifier content is too high, which may lead to interface peeling after molding. When the measured yield stress is higher than the preset upper limit, it indicates that the interface layer lubrication is insufficient or the modifier grafting rate is too low, which may lead to difficulties in cold push molding. Only when the measured value falls within the qualified range can the interface structure of the batch of mold material be judged to be successfully constructed and can proceed to the subsequent molding process. For unqualified batches, the esterification reaction termination point or modifier addition ratio of the next production cycle is adjusted according to the deviation direction until the indicators return to normal. This closed-loop control mechanism effectively eliminates performance deviations caused by raw material fluctuations or process disturbances, ensuring that the excellent fluidity of the final product under low temperature and high shear and the high rigidity under room temperature static conditions can be stably reproduced.

[0050] Example 6: To ensure that the interfacial properties of thermoplastic composite molding materials remain consistent during long-term production and to avoid quality risks caused by process parameter drift, an online monitoring and feedback adjustment procedure based on rheological characteristics was established. The apparent viscosity stability of the melt was used as the core monitoring indicator. An online rheometer installed on the extruder die head was used to collect the viscosity data of the molding material at a specific shear rate in real time, thereby providing an immediate quantitative decision-making basis for process fine-tuning during production.

[0051] In the specific implementation process, the melt temperature of the extruder head is set to... And keep the shear rate of the online rheometer constant at The system continuously records the apparent viscosity value of the melt, with a sampling frequency set to [value missing]. Based on statistical analysis of a large amount of experimental data from the previous period, the standard viscosity reference value under this operating condition was established as [value missing]. And set the allowable fluctuation range as When the viscosity value monitored in real time is consistently higher than Exceed At a certain time, if the system determines that the dispersion or grafting efficiency of the interface modifier has decreased, it will automatically trigger a feedback mechanism to... The mixing temperature in the middle section of the extruder is gradually increased at a rate until the viscosity value returns to the normal range; conversely, when the viscosity value remains below a certain level... If the system determines that the matrix is ​​excessively degraded or the interface layer slips too much, it will reduce the screw speed or feeding speed accordingly. This online closed-loop control mechanism effectively compensates for the interference caused by raw material batch fluctuations and changes in ambient temperature, ensuring that the final molded material particles always have stable rheological response characteristics in subsequent cold push molding.

[0052] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A thermoplastic composite molding material, characterized in that, Comprise: a semi-crystalline thermoplastic resin matrix as a continuous phase, a particulate rigid inorganic filler dispersed in the semi-crystalline thermoplastic resin matrix, and a hyperbranched polyester modifier coated on the surface of the particulate rigid inorganic filler; Hyperbranched polyester modifiers are those with terminal hydroxyl groups and a theoretical hydroxyl value of [value missing]. The third-generation hyperbranched polyester with a carbon atom number of to The esterification products of straight-chain saturated fatty acids, wherein the hydroxyl conversion rate of the esterification products is... to Hyperbranched polyester modifiers form hydrogen bonds with active sites on the surface of particulate rigid inorganic fillers through residual hydroxyl groups at the ends of molecular chains, thereby constructing an amphiphilic slip layer with long-chain aliphatic side chains on the surface of particulate rigid inorganic fillers. At to molding temperature, the aliphatic side chains in the amphiphilic slip layer are in a molten state, which converts the particulate rigid inorganic filler into micro-rolling units lubricated by the amphiphilic slip layer, and makes the yield stress of the thermoplastic composite molding material at the molding temperature between to ; During the cooling stage of the thermoplastic composite mold material after being pressurized to fill the mold, the aliphatic side chains in the hyperbranched polyester modifier undergo interfacial in-situ co-crystallization with the semi-crystalline thermoplastic resin matrix to form a co-crystalline intercalation locking structure with a thickness of 1-100 nm at the interface between the particulate rigid inorganic filler and the semi-crystalline thermoplastic resin matrix, the co-crystalline intercalation locking structure locking the deformation of the semi-crystalline thermoplastic resin matrix after the removal of the shear stress. to co-crystalline intercalation locking structure locking the deformation of the semi-crystalline thermoplastic resin matrix after the removal of the shear stress.

2. The thermoplastic composite molding material of claim 1, wherein The particulate rigid inorganic filler is selected from hollow glass microbeads or ceramic microspheres; the average particle size of the particulate rigid inorganic filler is to , and the mass percentage of the particulate rigid inorganic filler in the thermoplastic composite material is to ; the coating density of the hyperbranched polyester modifier on the surface of the particulate rigid inorganic filler is to of the hyperbranched polyester modifier per square meter of the surface area of the particulate rigid inorganic filler; under the condition that and the shear rate is not less than , the apparent viscosity of the thermoplastic composite material monotonously decreases in a nonlinear manner with the increase of the shear rate.

3. The thermoplastic composite molding material of claim 1, wherein The total weight of the thermoplastic composite molding compound is The content of hyperbranched polyester modifier by part is weight parts to The content of granular rigid inorganic filler by weight is: weight parts to The remainder is a semi-crystalline thermoplastic resin matrix, in parts by weight; wherein the content of hyperbranched polyester modifier is... The value varies with the hydroxyl conversion rate. It decreases as it rises, that is, when for hour, for to ;when for hour, for to .

4. The thermoplastic composite molding material of claim 1, wherein The semi-crystalline thermoplastic resin matrix is selected from one or more of polypropylene, polyethylene, polyamide , polybutylene terephthalate; the carbon chain length of the aliphatic side chains in the hyperbranched polyester modifier matches the length of the backbone repeat units of the semi-crystalline thermoplastic resin matrix.

5. The thermoplastic composite molding material of claim 1, wherein The rheological properties of the thermoplastic composite molding material under follow the Bingham fluid model: wherein is the shear stress in ; is the yield stress of the thermoplastic composite molding material in ; is the plastic viscosity coefficient in ; is the shear rate in .

6. The thermoplastic composite molding material of claim 1, wherein The melting point of the hyperbranched polyester modifier is lower than the melting point of the semi-crystalline thermoplastic resin matrix To ; at the molding temperature of , the hyperbranched polyester modifier is a liquid fluid, at the normal temperature environment of , the hyperbranched polyester modifier is a crystalline solid, and the thermoplastic composite molding material is an injection molding particle with a diameter of to , the bending modulus of which under the condition of is not less than , and the linear shrinkage of the product after cold push molding within is less than .

7. The thermoplastic composite molding material of claim 1, wherein The hyperbranched polyester modifier is prepared by mixing the third generation hyperbranched polyester with a linear saturated aliphatic acid in a molar ratio of to , carrying out a melt esterification reaction under conditions of a temperature of to and a vacuum degree of or more, and making the hydroxyl conversion rate reach to by measuring the amount of water released in the reaction.

8. The thermoplastic composite molding material of claim 1, wherein Also including one or more of an antioxidant, an internal lubricant, a nucleating agent; the mass percentage of the antioxidant is to , the mass percentage of the internal lubricant is to , the nucleating agent is selected from sorbitol derivatives or organic phosphates.

9. The thermoplastic composite molding material of claim 2, wherein the thermoplastic resin is a polyamide resin. the surface of the particulate rigid inorganic filler is pre-coated with a silane coupling agent having an amino or epoxy group for fixing the residual hydroxyl groups of the hyperbranched polyester modifier to the surface of the particulate rigid inorganic filler through covalent bonds or hydrogen bonds.

10. A cold push forming process for a thermoplastic composite mold material as defined in claim 1, wherein, Comprise the following steps: Step 111, preheating the thermoplastic composite mold material to to converting the hyperbranched polyester modifier into a molten state and coating the surface of the particulate rigid inorganic filler to form an amphiphilic slip layer; Step 112, placing the preheated thermoplastic composite mold material into the mold cavity and applying a forming pressure, so that the thermoplastic composite mold material is subjected to a shear stress greater than the yield stress and inducing the thermoplastic composite mold material to fill the mold cavity; Step 113, the filled thermoplastic composite material is pressure maintained and cooled to room temperature, and during the cooling process, the eutectic intercalation locking structure is formed by the eutectic reaction between the aliphatic side chains in the hyperbranched polyester modifier and the semi-crystalline thermoplastic resin matrix.

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