A process for in-situ coating and dispersion of pigment particles in pen ink

Abstract

This invention relates to the field of novel ink preparation and discloses an in-situ coating dispersion process for pigment particles in pen inks. The process includes: mixing pigment particles, solvent, and monomers to generate an initial dispersion; shearing and grinding the dispersion using grinding media; inducing in-situ polymerization of monomers at the pigment interface using transient frictional heat generated by grinding collisions to generate a primary coating layer; adding a polarity regulating factor to construct a polarity evolution environment, driving monomers to migrate to the surface of the coating layer and continue to react to generate a dense structure; monitoring the rate of change of the dispersion axis torque signal, and stopping dispersion when the rate of change reaches a stability threshold. This invention utilizes frictional heat to achieve spatial confinement of the polymerization reaction, blocking the self-polymerization path of monomers in the solvent bulk, effectively preventing the viscosity of the system from increasing, while polarity evolution drives targeted enrichment of monomers, improving the density of the coating layer.

Description

Technical Field

[0001] This invention relates to an in-situ coating and dispersion process for pigment particles in pen inks, belonging to the field of novel ink preparation technology. Background Technology

[0002] Current pen inks require pigment particles with nanoscale particle size distribution and high surface stability to ensure smooth writing and long-term storage resistance to sedimentation. In the large-scale sand milling process for preparing ultrafine inks, high-intensity mechanical shear force needs to be applied to obtain the target particle size. The high-energy-density shear flow field can easily tear the polymer protective layer of pigment particles, resulting in the exposure of high surface energy crystal planes and irreversible secondary agglomeration.

[0003] Introducing monomers during dispersion creates competition between bulk polymerization and in-situ coating. Under a thermally initiated mechanism, monomers undergo disordered self-polymerization within the liquid phase, consuming effective components and increasing system viscosity. This viscosity increase reduces the kinetic energy transfer efficiency of the grinding media, leading to gelation of the grinding cavity and loss of writing rheology. While hardware improvements such as refining the morphology of grinding components and optimizing the structure of the grinding cavity can enhance pigment dispersion, the uncontrollable conversion of mechanical energy to thermal energy during dispersion, along with limitations in control methods involving process path guidance and micro-dynamic matching, remain problematic. For example, in publication CN1... Chinese invention patent application 20158152A discloses a blue pigment paste for ballpoint pen ink, ballpoint pen ink, and ballpoint pen. By introducing a polyoxyethylene polycyclic phenyl ether surfactant and an aryl acrylic resin to construct a dispersion system, the storage stability and lubricity of the pigment paste are improved. The solution belongs to static component modification. Under high energy density grinding conditions, it is difficult to match the active interface generated by mechanical shearing with the coating film formation rate. Due to the lack of transient energy guidance during grinding, the monomer is still randomly consumed in the solvent body under the thermal field, and it is impossible to achieve point-to-point repair of the interface at the moment of particle breakage.

[0004] Therefore, the technical problem to be solved by this invention is how to induce monomers to form directional coating at the interface at the instant when the pigment agglomerates are broken down to generate fresh, highly active surfaces, and to inhibit ineffective bulk polymerization in the liquid phase. 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 process for in-situ coating and dispersing components of pigment particles in pen ink, comprising the following steps:

[0006] Step S101: Mix pigment particles, nonpolar solvent and hydrophobic monomer with a mass percentage content of 15% to 35%, control the mass ratio of hydrophobic monomer to pigment particles to be 1:25 to 1:8, and premix in the grinding chamber to generate an initial dispersion.

[0007] Step S102: Start the dispersion shaft in the grinding chamber to drive the grinding media with a filling rate of 75% to 85% to shear and grind the initial dispersion.

[0008] Step S103: The transient micro-frictional heat generated by the collision of the grinding media with the aggregates of pigment particles is used as the only energy induction source for the free radical polymerization reaction of hydrophobic monomers at the new interface of pigment particles, and a primary coating layer is generated in situ on the surface of the pigment particles, wherein the grinding chamber is maintained in a non-externally heated state.

[0009] Step S104: A polarity adjustment factor is continuously added to the grinding chamber to generate a polarity gradient in the initial dispersion that evolves from hydrophobic to hydrophilic. By utilizing the difference in thermodynamic compatibility between the hydrophobic monomer and the initial dispersion bulk, the residual hydrophobic monomer is driven to migrate to the surface of the primary coating layer and generate a growth reaction to form a dense coating structure.

[0010] Step S105: Obtain the torque feedback signal characterizing the running resistance of the dispersion shaft, and monitor the rate of change of the torque feedback signal relative to time. When the absolute value of the rate of change is always less than or equal to the preset stability threshold for a duration of 300s to 600s, cut off the power output of the dispersion shaft to end the dispersion.

[0011] Preferably, in step S104, by adjusting the dropping rate of the polarity adjustment factor, the instantaneous mass percentage concentration of the hydrophobic monomer in the initial dispersion body is maintained in the range of 0.05% to 0.15%, and the median particle size D50 of the coated pigment particles is controlled to be 60 nm to 120 nm.

[0012] Preferably, in step S102, the grinding media is yttrium-stabilized zirconia beads with a diameter of 0.05 mm to 0.2 mm; in step S103, the linear velocity of the dispersion shaft is 12 m / s to 18 m / s, so that the local temperature rise rate of the transient micro-frictional heat generated by the grinding media at the collision point reaches 100°C / μs to 500°C / μs.

[0013] Preferably, the hydrophobic monomer is selected from one or more of n-butyl acrylate, isooctyl acrylate, styrene, methyl methacrylate, and lauryl acrylate; the polarity modifier is selected from one or more of ethylene glycol, glycerol, diethylene glycol, and deionized water.

[0014] Preferably, in step S103, the initiator required for the free radical polymerization reaction is added dropwise simultaneously with the polarity adjustment factor, and the concentration of the initiator in the polarity adjustment factor is less than 0.01 mol / L.

[0015] Preferably, in step S101, the nonpolar solvent is selected from one or more of aliphatic hydrocarbons, cycloalkanes, and low-polarity synthetic oils; in step S104, the volume ratio of the polarity adjustment factor to the initial dispersion is controlled to be 1:10 to 1:4.

[0016] Preferably, in step S105, the stability threshold is 0.02 N⋅m / s, and at the end of dispersion, the dynamic viscosity of the initial dispersion is in the range of 3 mPa⋅s to 8 mPa⋅s at 25°C.

[0017] Preferably, the average thickness of the dense coating structure is 3 nm to 10 nm, and the surface roughness of the coated pigment particles is less than 5 nm.

[0018] Preferably, after step S105, the method further includes: adding an interface modifier into the grinding chamber to adjust the surface potential of the pigment particles so that the absolute value of the ζ potential of the obtained pigment particles in the ink system is greater than 40mV.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. In the in-situ coating and dispersion of pigment particles in pen inks, the transient micro-frictional heat generated when the grinding media collides with the pigment agglomerates is used as the sole trigger source for free radical polymerization. This process achieves precise spatial confinement of the polymerization reaction. This mechanism eliminates the dependence on macroscopic external thermal fields, allowing the decomposition of the initiator and the chain growth of the monomer to occur only within a short period of time when the pigment is torn apart to create a fresh, highly active interface. This physically blocks the self-polymerization path of the monomer in the solvent bulk, avoiding abnormal viscosity increases in the ink system caused by bulk polymerization and the resulting failure of grinding kinetic energy transfer, thus ensuring the rheological stability of ultrafine pigments in continuous production.

[0021] 2. By relying on the system polarity-increasing environment constructed by continuously adding high-polarity components, the difference in thermodynamic compatibility enables hydrophobic monomers to migrate and accumulate on the surface of low-polarity pigment particles. This polarity-driven micro-migration mechanism, combined with a monomer-starved addition strategy, maintains a monomer concentration on the pigment surface that is much higher than that in the solvent bulk. Thus, without the introduction of complex modifying agents, the density of the coating layer is improved through the dynamic evolution of environmental polarity, solving the problem of secondary pigment sedimentation caused by insufficient interfacial bonding strength between pigments and resin binders in traditional ink preparation.

[0022] 3. By using the first-order time derivative of the real-time torque of the dispersion shaft as a feedback signal for changes in structural viscosity, a dynamic matching closed loop between the mechanical shear rate and the chemical coating rate is established. When the torque change rate captures the sudden increase in effective specific surface area caused by pigment depolymerization, the output power of the metering pump and the spindle speed are adjusted synchronously to ensure that the monomer supply rate and the new surface generation rate are in a dynamic equilibrium. This cross-mechanism linkage control enables the growth of the coating layer to respond sensitively to the micro-evolution of the particle scale. The resulting ink dispersion exhibits better Newtonian fluid characteristics, effectively eliminating the thixotropic ring phenomenon commonly found in high-concentration pigment systems, and meeting the smooth writing requirements of microporous nibs for long-term continuous writing. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating the entire process of in-situ coating and dispersion stability monitoring of pigment particles in this invention.

[0024] Figure 2 This is a schematic diagram of the dynamic matching control logic for mechanical shearing and chemical coating in this invention.

[0025] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0026] 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.

[0027] A process for in-situ coating and dispersing components of pigment particles in pen ink includes the following steps:

[0028] Step S101: Mix pigment particles, nonpolar solvent and hydrophobic monomer with a mass percentage content of 15% to 35%, control the mass ratio of hydrophobic monomer to pigment particles to be 1:25 to 1:8, and premix in the grinding chamber to generate an initial dispersion.

[0029] Step S102: Start the dispersion shaft in the grinding chamber to drive the grinding media with a filling rate of 75% to 85% to shear and grind the initial dispersion.

[0030] Step S103: The transient micro-frictional heat generated by the collision of the grinding media with the aggregates of pigment particles is used as the only energy induction source for the free radical polymerization reaction of hydrophobic monomers at the new interface of pigment particles, and a primary coating layer is generated in situ on the surface of the pigment particles, wherein the grinding chamber is maintained in a non-externally heated state.

[0031] Step S104: A polarity adjustment factor is continuously added to the grinding chamber to generate a polarity gradient in the initial dispersion that evolves from hydrophobic to hydrophilic. By utilizing the difference in thermodynamic compatibility between the hydrophobic monomer and the initial dispersion bulk, the residual hydrophobic monomer is driven to migrate to the surface of the primary coating layer and generate a growth reaction to form a dense coating structure.

[0032] Step S105: Obtain the torque feedback signal characterizing the running resistance of the dispersion shaft, and monitor the rate of change of the torque feedback signal relative to time. When the absolute value of the rate of change is always less than or equal to the preset stability threshold for a duration of 300s to 600s, cut off the power output of the dispersion shaft to end the dispersion.

[0033] Preferably, in step S104, by adjusting the dropping rate of the polarity adjustment factor, the instantaneous mass percentage concentration of the hydrophobic monomer in the initial dispersion body is maintained in the range of 0.05% to 0.15%, and the median particle size D50 of the coated pigment particles is controlled to be 60 nm to 120 nm.

[0034] Preferably, in step S102, the grinding media is yttrium-stabilized zirconia beads with a diameter of 0.05 mm to 0.2 mm; in step S103, the linear velocity of the dispersion shaft is 12 m / s to 18 m / s, so that the local temperature rise rate of the transient micro-frictional heat generated by the grinding media at the collision point reaches 100°C / μs to 500°C / μs.

[0035] Preferably, the hydrophobic monomer is selected from one or more of n-butyl acrylate, isooctyl acrylate, styrene, methyl methacrylate, and lauryl acrylate; the polarity modifier is selected from one or more of ethylene glycol, glycerol, diethylene glycol, and deionized water.

[0036] Preferably, in step S103, the initiator required for the free radical polymerization reaction is added dropwise simultaneously with the polarity adjustment factor, and the concentration of the initiator in the polarity adjustment factor is less than 0.01 mol / L.

[0037] Preferably, in step S101, the nonpolar solvent is selected from one or more of aliphatic hydrocarbons, cycloalkanes, and low-polarity synthetic oils; in step S104, the volume ratio of the polarity adjustment factor to the initial dispersion is controlled to be 1:10 to 1:4.

[0038] Preferably, in step S105, the stability threshold is 0.02 N⋅m / s, and at the end of dispersion, the dynamic viscosity of the initial dispersion is in the range of 3 mPa⋅s to 8 mPa⋅s at 25°C.

[0039] Preferably, the average thickness of the dense coating structure is 3 nm to 10 nm, and the surface roughness of the coated pigment particles is less than 5 nm.

[0040] Preferably, after step S105, the method further includes: adding an interface modifier into the grinding chamber to adjust the surface potential of the pigment particles so that the absolute value of the ζ potential of the obtained pigment particles in the ink system is greater than 40mV.

[0041] Example 1: In the industrial production application of preparing nanoscale pigment-type microporous pen ink, the operation process of this process follows these steps: 25% carbon black pigment particles, an aliphatic hydrocarbon solvent as a non-polar solvent, and styrene as a hydrophobic monomer are mixed. The mass ratio of styrene to carbon black pigment particles is controlled at 1:15. An initial dispersion is generated by premixing in the grinding chamber. The dispersion shaft in the grinding chamber is started, driving a grinding media with a filling rate of 80% to shear and grind the initial dispersion. The grinding media has a diameter of 0.1mm yttrium-stabilized zirconia beads utilize the transient micro-frictional heat generated by the collision of grinding media with carbon black pigment particle aggregates as an energy source for the free radical polymerization reaction of styrene at the nascent interface of carbon black pigment particles. This generates a primary coating layer in situ on the surface of the carbon black pigment particles. Although the transient limiting hotspots at the interface caused by mechanical collision exhibit extremely rapid decay characteristics on the microsecond scale, within the extremely short time window of shear force tearing the pigment aggregates, the newly formed lattice fracture surface simultaneously exposes extremely high-density unsaturated dangling bonds and catalytically active lattice defect sites. These high-energy sites released by mechanochemical processes drastically lower the apparent activation energy threshold required for initial monomer polymerization, making the microsecond-scale high-temperature pulse sufficient to excite large-scale polymerization. The system measures primary free radicals and instantaneously anchors their end groups to the particle surface. Within the microscopic boundary layer, which is deviated from the collision core but protected by the bulk thermal buffering effect of carbon black, the anchored molecular chain ends rely on locally retained low-grade residual heat to complete chain growth along the interface in a non-adiabatic state within a continuous flow field time of milliseconds to seconds. According to the law of energy conservation and interface dissipation, the mechanical work, apart from being converted into macroscopic sensible heat and viscous drag dissipation, is concentrated and released at the microscopic interface of particle pyrolysis. To ensure that the interface frictional heat-induced source has a definite and reproducible physical boundary in continuous industrial production, the system introduces a unit mass ratio mechanical energy calibration procedure. By continuously collecting and integrating the real-time output power and running time of the dispersion shaft, and utilizing the cooling water pipeline... The flow meter and inlet / outlet temperature sensors calculate the macroscopic heat loss. The system forcibly locks the net mechanical energy input per unit mass of material within a single grinding cycle within a control range of 80 kJ / kg to 120 kJ / kg. Stable macroscopic energy supply eliminates interference from environmental heat exchange fluctuations on the reaction system. During this process, the grinding chamber is maintained at a temperature range of 25°C to 30°C through cooling water circulation to suppress the thermal self-polymerization reaction of styrene in the non-polar solvent bulk, thereby confining the polymerization reaction to a localized high-temperature micro-region generated by friction and collision. The linear velocity of the dispersion shaft is set to 15 m / s. Through the instantaneous conversion of mechanical work into heat energy, the local temperature rise rate on the surface of the carbon black pigment particles is kept at 3... The transient temperature rise rate, on the order of 00℃ / μs, induces directional grafting of styrene at the interface. Considering the extremely high response delay of existing macroscopic thermal sensing components, this transient temperature rise rate at the micro-nano scale is not obtained through actual measurement by external sensors, but is calculated using the Hertzian contact heat transfer model in classical thermodynamics. The derivation is based on: extracting the difference in total kinetic energy attenuation during the collision of two grinding media at a given linear velocity, assuming that 80% of the mechanical work is adiabatically converted into heat energy within the deformation collision period of 0.1 to 0.5 microseconds; and dividing this local heat load by the effective heat-receiving mass of the pigment lattice with a depth of approximately 5 nanometers within the projected area of ​​the collision spot and its specific heat capacity constant, thus obtaining the maximum thermal field rise slope within this theoretical distribution range.

[0042] Deionized water, acting as a polarity regulator, was continuously added dropwise into the grinding chamber at a rate of 5 mL / min until the volume ratio of deionized water to the initial dispersion reached 1:6. This created a polarity gradient within the initial dispersion, transitioning from hydrophobic to hydrophilic. Utilizing the repulsive force generated by the thermodynamic compatibility difference between styrene and the initial dispersion bulk, residual styrene was driven to migrate towards the surface of the primary coating layer with lower polarity, resulting in a growth reaction that generated a dense coating structure. Based on the Lambert-Beer law, which states that the absorbance of a liquid medium for monochromatic light is linearly positively correlated with the concentration of absorbing substances within the light transmission path, an optical bypass flow cell with a micron-level isolation mesh was installed on the external circulation pipeline of the grinding chamber to obtain the transient consumption rate of the monomer components. The system continuously acquired the absorbance of the bulk supernatant at the characteristic absorption wavelength of 254 nm. Combined with the standard solution calibration equation, the instantaneous concentration of residual monomers was calculated. In the continuously added deionized water environment, the highly hydrophilic deionized water and aliphatic hydrocarbons formed a reverse microemulsion continuous phase under a high-speed shear flow field. Within this system, the hydrophobic... The polar gradient of water evolving into hydrophilicity does not refer to the absolutely continuous solubility distribution in the macroscopic static liquid phase, but rather to a local dynamic concentration evolution state dominated by dispersed phase droplets. With the accumulation of droplet acceleration rate, the number density of antiphase droplets enveloping the polar aqueous phase in the nonpolar continuous phase increases exponentially, compressing the mean free path of free diffusion of nonpolar monomers in the liquid bulk. This rapidly increasing probability of collision at the boundary between the high polar liquid phase and the liquid phase at the microscopic level constructs a statistically significant dynamic polar repulsion environment, thereby causing free monomers to break away from their original solubility equilibrium state in local micro-regions. The overall solubility parameter of the mixed solvent system continuously drifts towards the polar end, breaking the initial thermodynamic equilibrium. This causes the low polarity styrene monomer dissolved in the oil phase to spontaneously undergo phase separation and physical precipitation on the lipophilic surface of carbon black pigment particles due to the decrease in bulk compatibility. By adjusting the droplet acceleration rate of deionized water, the instantaneous mass percentage concentration of styrene in the initial dispersion bulk is kept below 0.1%, ensuring that the monomer is targeted and enriched on the surface of the carbon black pigment particles.

[0043] During the dispersion process, the torque feedback signal, which characterizes the running resistance of the dispersion shaft, is acquired in real time by sensors, and the rate of change of the torque feedback signal with respect to time is calculated using the following formula: ,in, The rate of change of the torque feedback signal relative to time. For torque feedback signal, For time; monitor the rate of change When the absolute value of the dispersion is always less than or equal to 0.02 N·m / s for a duration of 450 s, the power output of the dispersion shaft is cut off to end the dispersion. At this time, the dynamic viscosity of the initial dispersion at 25 °C is 5.2 mPa·s, and the median particle size D50 of the coated carbon black pigment particles is 85 nm. In the prepared ink dispersion, the thickness of the coating layer is 5 nm, and the carbon black pigment particles exhibit a uniform Brownian motion state in the solvent system. After standing at 60 °C for 30 days, there is no obvious sedimentation, showing stable rheological properties. The process improves the density of the coating layer while maintaining the low viscosity state of the system through the synergistic effect of the local controlled release of frictional heat energy and polarity gradient.

[0044] Example 2: In a research and development scenario verifying the contribution of the in-situ coating process of carbon black pigment particles to the long-term rheological stability of ink, this experiment confirmed the role of the technical solution of the present invention in resolving the contradiction between high-intensity shear and viscosity increase by comparing the physicochemical indicators under different process variables. The experiment used a horizontal sand mill equipped with a dynamic torque sensing unit. The dynamic torque sensing unit has a measurement range of 0 to 10 N·m, a resolution of 0.001 N·m, and a sampling frequency of 10 Hz. To simulate the interference of industrial electromagnetic environment on signal acquisition, Gaussian white noise with a signal-to-noise ratio of 20 dB was superimposed at the original output of the sensor during the experiment. The sampling period was set. At the same time, by balancing the real-time capture accuracy of torque fluctuations with the data processing load of the control system, and because the transient hotspots generated by frictional heat during the dispersion process have microsecond-level evolution characteristics, in order to effectively extract the rheological response characteristics related to the formation of hotspots and avoid aliasing of sampling signals, the sampling period is... Given that the sampling period satisfies the sampling theorem and tends to 1 / 100 of the dispersion axis rotation period, and the dispersion axis velocity is 15 m / s, determine the sampling period. The experiment was conducted in 0.1 s increments. The experiment was divided into three groups: the present invention sample group, control sample group 1, control sample group 2, and an out-of-range sample group. The present invention sample group was prepared according to the aforementioned process steps, with the mass ratio of styrene to carbon black pigment particles set at 1:15 and the volume ratio of deionized water to the initial dispersion set at 1:6. Control sample group 1 removed the continuous dropwise addition step of the polarity adjustment factor, while maintaining the same conditions as the present invention sample group, to verify the contribution of the polarity gradient to monomer targeted enrichment. Control sample group 2 used an external electric heating jacket to heat the entire grinding chamber to 75°C to replace frictional heat induction, while simultaneously shutting off the cooling water circulation, to verify the effect of spatially confined polymerization on inhibiting bulk self-polymerization. The out-of-range sample group set the mass ratio of styrene to carbon black pigment particles to 1:5, exceeding the upper limit, to detect the performance saturation inflection point. During the dispersion start-up phase, the original torque signal of the present invention sample group exhibited random fluctuations caused by noise, with a standard deviation of 0.05 N·m. The torque feedback signal was monitored by the monitoring module. Perform relative to time The rate of change obtained by first-order differential processing It can filter out the constant components generated by mechanical vibration, thereby characterizing the changes in rheological resistance caused by the evolution of particle surface structure. The calculation formula is as follows: ,in, The rate of change of the torque feedback signal relative to time. For torque feedback signal, For time.

[0045] Intermediate data during the dispersion process of the sample group of this invention were monitored. When the dispersion time reached 1200 s, the instantaneous mass percentage concentration of styrene in the aliphatic hydrocarbon solvent decreased from the initial 1.67% to 0.08%, indicating that under the action of the polar gradient induced by the polarity regulating factor, the hydrophobic styrene monomer migrated to the low polarity micro-regions on the surface of the carbon black pigment particles; the observed rate of change at this time... The absolute value continued to converge, eventually stabilizing at 0.012 N·m / s, and this steady state lasted for more than 450 s, triggering the shutdown criterion. In contrast, the styrene concentration in control group 1 remained above 0.45%, the average thickness of the coating layer was 1.2 nm, and bottom agglomeration occurred in the centrifugation accelerated sedimentation test, confirming that the lack of polar driving force led to insufficient coating layer density. In control group 2, after a dispersion time of 600 s, the system viscosity increased from the initial 4.5 mPa·s to 35.8 mPa·s, and the sand mill automatically stopped due to motor torque overload, reflecting that external overall heating caused disordered thermal self-polymerization of styrene in the solvent. Data from the out-of-range sample group showed that when the monomer ratio increased to 1:5, the median particle size D50 of the coated carbon black pigment particles increased to 145 nm, and the dynamic viscosity of the system increased to 12.5 mPa·s. Analysis showed that when the styrene content exceeded 1:8, the excess monomer at the boundary After surface saturation, micellar polymerization begins in the liquid phase, causing an inflection point in the growth rate of beneficial effects and turning into a negative impact. The results of this experiment show that the ink dispersion prepared by the sample group of this invention has a median particle size D50 of 85.6 nm and a distribution index PDI of 0.112, exhibiting a narrow distribution characteristic. Its dynamic viscosity is stable at 5.15 mPa·s at 25℃, and the viscosity change rate is less than 3% after a thermal cycling test from -20℃ to 60℃, demonstrating physical stability. Transmission electron microscopy characterization of the coated carbon black pigment particles revealed a polymer shell layer with a thickness of 5.2 nm covering the pigment surface. This experiment confirms that by utilizing frictional heat energy to achieve spatial confinement of in-situ polymerization and combining it with polar gradient-driven monomer targeted migration, a high-density pigment protective layer can be constructed without inducing system gelation, thereby resolving the contradiction between high loading and low viscosity and high stability in the nano-pigment dispersion process.

[0046] Example 3: In the continuous preparation scenario of carbon black pigment ink involving the viscoelastic evolution of multiple components, the dispersion process determines the shutdown criterion through the following calibration procedure: The dispersion shaft runs at a linear velocity of 15 m / s in the grinding chamber under no-load conditions. The sensor collects the no-load torque signal within 60 seconds and calculates the standard deviation of the amplitude fluctuation to determine the background noise level; 30% carbon black pigment particles, an aliphatic hydrocarbon solvent as a non-polar solvent, and a styrene monomer as a hydrophobic monomer are mixed and added to the grinding chamber. The dispersion shaft is run without adding deionized water, and the torque feedback signal is captured continuously for 300 seconds. The stability threshold for this batch of processes was determined based on the background noise level. Among them, the stability threshold The intersection of three times the standard deviation of the background noise and one-fifth of the slope of the torque change in the linear evolution region is taken. In the specific algorithm mapping module, the operation logic of this intersection interval is as follows: extract the value of three times the standard deviation of the background noise as the lower limit scalar of the anti-disturbance trigger, and extract the value of one-fifth of the slope of the torque change in the linear evolution region as the upper limit scalar of the mathematical characterization of the sensitivity of particle aggregation state. Since the calibration results of different physical batches always ensure that the absolute value of the upper limit is greater than the absolute value of the lower limit, the system controller performs calculations within the closed numerical domain jointly defined by the two reference scalars, and forcibly takes the arithmetic mean of this value domain as a single and certain stability threshold and sends it to the actuator.

[0047] For raw torque feedback signals superimposed with industrial interference The monitoring module uses an equal-interval moving average sampling method, with a set sampling period. The sliding window length is 0.1s. There are 50 sampling points; at each sampling time Calculate the arithmetic mean of the 50 torque observations within the current window to obtain the smoothed torque parameter. Based on this smoothing factor, the rate of change of the torque feedback signal relative to time is extracted. The calculation formula is as follows: ,in, The rate of change of the torque feedback signal relative to time. This is the smoothed torque value at the current sampling time. This represents the total number of sampling points within the sliding window; For the sampling period, when the calculated rate of change... The absolute value remains at the stability threshold for 500 seconds. Within the specified range, the coating reaction on the surface of carbon black pigment particles is determined to have entered thermodynamic equilibrium. With the addition of deionized water, the polar gradient within the system induces a non-uniform distribution of interfacial tension. The Marangoni flow generated by the interfacial tension gradient drives the styrene monomer to migrate from the solvent bulk to the particle interface and undergo polymerization in the interface confinement region. Under the calibration parameters of this embodiment, when... When stabilized at 0.015 N·m / s, the D50 particle size of the coated carbon black pigment particles is between 85 nm and 90 nm, and the absolute value of its surface potential is 47.5 mV. Styrene, as a hydrophobic monomer, and a non-polar solvent jointly construct a low-polarity continuous phase. Under the interfacial induction of transient micro-frictional heat generated by the collision of grinding media, the benzene ring structure in the styrene molecule generates directional binding force with the aromatic region on the surface of the carbon black pigment particles, so that the monomer forms a monomolecular-level adsorption layer on the particle surface and is rapidly transformed into a primary coating layer. The polar gradient generated by the addition of a polarity adjustment factor breaks the original thermodynamic equilibrium, causing the residual styrene in the dissolved state to exhibit interfacial orientation due to the change in solvation energy. This drives the monomer to cross the diffuse double layer and enter the coating region to continue free radical polymerization. This thermodynamic compensation mechanism provided by polarity evolution increases the density of the polymer coating layer by 15% without raising the bulk temperature, thereby avoiding the increase in system viscosity caused by ineffective self-polymerization of monomers in the liquid phase.

[0048] Example 4: In the application scenario of preparing carbon black pigment inks with high oil absorption value, the dispersion process monitors the torque feedback signal of the dispersion shaft. The second derivative Determine the linear evolution region, including the determination of the second derivative. The absolute value of the value remains less than 0.005 N·m / s for 100 s. The time period is the calibration interval, and the torque feedback signal is calibrated within this calibration interval. Fitting calculation to obtain the mean slope The stability threshold is calculated using the following formula: ,in, As the stability threshold, This represents the average slope of the torque change within the calibration interval. As a dimensionless weighting factor set to 0.2, during the coating step of continuously adding deionized water as a polarity adjustment factor to the initial dispersion, the flow controller adjusts the flow rate based on the residual. Adjusting the dripping speed Among them, residual Calculate using the following formula: ,in, For residuals, For real-time rate of change, The stability threshold is the dropping rate. This refers to the volumetric flow rate of the dripping volume.

[0049] When the residual When the absolute value is greater than 0.01 N·m / s, the dropping acceleration will be... The flow rate was reduced from 5 mL / min to 1 mL / min to slow the rate of change of the polar gradient and inhibit the self-polymerization of hydrophobic monomers in the nonpolar solvent bulk, until the residual... When the absolute value of the droplet velocity drops below 0.005 N·m / s, the dropping acceleration will decrease. The flow rate was restored to 5 mL / min, allowing the dense coating structure generated in situ on the surface of carbon black pigment particles to grow under equilibrium rheological response conditions. The resulting ink exhibited a dynamic viscosity fluctuation of less than 0.2 mPa·s at 25°C.

[0050] Example 5: In an adaptive production process for pen inks involving a carbon black pigment particle content that varies from 15% to 35% by mass, the process system performs a standardized initial torque benchmark calibration procedure before each batch is fed; a dispersion shaft with a linear speed of 15 m / s is used to obtain the inherent mechanical loss torque of the grinding chamber under no-load conditions. The mass percentage content of carbon black pigment particles is increased according to a 2% feeding gradient. The torque feedback signal at each concentration point under steady state was recorded to establish an initial torque reference value. content per percent of mass The linear mapping function is calculated as follows: ,in, This is the initial torque reference value. This is the inherent mechanical loss torque. The dimensionless correction factor determined by particle morphology is taken as 1.25 in this process system; The mass percentage content of carbon black pigment particles; the calibrated parameter matrix is ​​used as the stability threshold for subsequent real-time calculation. The baseline data eliminates downtime criterion drift caused by pigment batch differences or mechanical wear.

[0051] When the monitoring module detects an abnormal temperature rise rate inside the grinding chamber caused by fluctuations in cooling cycle efficiency, the system initiates physical boundary protection procedures to intervene in the production process. The macroscopic temperature probe captures the inherent heat conduction time delay inherent in the accumulation of microscopic frictional heat within the multiphase fluid. To overcome the limitations of physical perception, the system extracts a high-frequency torque resistance signal with a sampling frequency of 200 Hz to monitor transient hardening phenomena in the rheological environment. By parallel calculation of the standard deviation of the torque feedback signal amplitude within a single second-level sliding time window, an early warning mechanism for localized microscopic blockage is established. This mechanism, along with thermodynamic judgment conditions, constitutes a cascade protection logic within the program, and the material temperature inside the grinding chamber is calculated in real time. Rate of change relative to time and setting a safety threshold The rate of change is 2℃ / s, and the torque feedback signal is greater than 2℃ / s for a duration of 5 seconds. The instantaneous amplitude exceeds the initial torque reference value. When the material temperature reaches 1.5 times the normal value, it is determined that transient clogging has occurred in the grinding media. The system controller stops adding the polarity adjustment factor and reduces the linear velocity of the dispersion shaft to 2 m / s, waiting for the material temperature to reach 1.5 times the normal value. When the temperature rise rate drops below 0.5℃ / s, the system restores the aforementioned dispersion parameters, ensuring that the dense coating structure on the surface of the carbon black pigment particles does not physically tear due to uncontrolled thermal stress. Finally, the viscosity drift of the ink dispersion after being stored at 60℃ for 90 days is less than 5% of the initial value.

[0052] After coating, the carbon black pigment particles are used as the core component in the ink preparation process. After the dispersion process, 10% water-based acrylic resin binder is added. By controlling the amount of binder added, the mass percentage of carbon black pigment particles in the final ink system is maintained between 8% and 12%. 1% defoamer and 0.2% leveling agent are added to adjust the surface tension to a pen operating range of 28mN / m to 32mN / m. In this system, the hydrophobic side chains on the surface of the dense coating structure and the oleophilic segments in the binder form a stable steric barrier through physical entanglement, preventing secondary collisions and agglomeration caused by Brownian motion of the particles. This ensures that the shear viscosity at the pen tip ball remains stable at more than 95% of its initial value after 5000m of continuous writing, thus providing substantial support for the stability of pen ink writing through the coating process.

[0053] 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.

[0054] 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 process for in-situ coating and dispersing components of pigment particles in pen ink, characterized in that, Includes the following steps: Step S101: Mix pigment particles, nonpolar solvent and hydrophobic monomer with a mass percentage content of 15% to 35%, control the mass ratio of hydrophobic monomer to pigment particles to be 1:25 to 1:8, and premix in the grinding chamber to generate an initial dispersion. Step S102: Start the dispersion shaft in the grinding chamber to drive the grinding media with a filling rate of 75% to 85% to shear and grind the initial dispersion. Step S103: The transient micro-frictional heat generated by the collision of the grinding media with the aggregates of pigment particles is used as the only energy induction source for the free radical polymerization reaction of hydrophobic monomers at the new interface of pigment particles, and a primary coating layer is generated in situ on the surface of the pigment particles, wherein the grinding chamber is maintained in a non-externally heated state. Step S104: A polarity adjustment factor is continuously added to the grinding chamber to generate a polarity gradient in the initial dispersion that evolves from hydrophobic to hydrophilic. By utilizing the difference in thermodynamic compatibility between the hydrophobic monomer and the initial dispersion bulk, the residual hydrophobic monomer is driven to migrate to the surface of the primary coating layer and generate a growth reaction to form a dense coating structure. Step S105: Obtain the torque feedback signal characterizing the running resistance of the dispersion shaft, and monitor the rate of change of the torque feedback signal relative to time. When the absolute value of the rate of change is always less than or equal to the preset stability threshold for a duration of 300s to 600s, cut off the power output of the dispersion shaft to end the dispersion.

2. The in-situ coating and dispersion process for pigment particles in pen ink according to claim 1, characterized in that, In step S104, by adjusting the dropping rate of the polarity adjustment factor, the instantaneous mass percentage concentration of the hydrophobic monomer in the initial dispersion body is maintained in the range of 0.05% to 0.15%, and the median particle size D50 of the coated pigment particles is controlled to be 60nm to 120nm.

3. The in-situ coating and dispersion process for pigment particles in pen ink according to claim 1, characterized in that, In step S102, the grinding media are yttrium-stabilized zirconia beads with a diameter of 0.05 mm to 0.2 mm; in step S103, the linear velocity of the dispersion shaft is 12 m / s to 18 m / s, so that the local temperature rise rate of the transient micro-frictional heat generated by the grinding media at the collision point reaches 100°C / μs to 500°C / μs.

4. The in-situ coating and dispersion process for pigment particles in pen ink according to claim 1, characterized in that, The hydrophobic monomer is selected from one or more of n-butyl acrylate, isooctyl acrylate, styrene, methyl methacrylate, and lauryl acrylate; the polarity modifier is selected from one or more of ethylene glycol, glycerol, diethylene glycol, and deionized water.

5. The in-situ coating and dispersion process for pigment particles in pen ink according to claim 1, characterized in that, In step S103, the initiator required for the free radical polymerization reaction is added dropwise simultaneously with the polarity adjustment factor, and the concentration of the initiator in the polarity adjustment factor is less than 0.01 mol / L.

6. The in-situ coating and dispersion process for pigment particles in pen ink according to claim 1, characterized in that, In step S101, the nonpolar solvent is selected from one or more of aliphatic hydrocarbons, cycloalkanes, and low-polarity synthetic oils; in step S104, the volume ratio of the polarity adjustment factor to the initial dispersion is controlled to be 1:10 to 1:

4.

7. The in-situ coating and dispersion process for pigment particles in pen ink according to claim 1, characterized in that, In step S105, the stability threshold is 0.02 N⋅m / s, and at the end of dispersion, the dynamic viscosity of the initial dispersion is in the range of 3 mPa⋅s to 8 mPa⋅s at 25°C.

8. The in-situ coating and dispersion process for pigment particles in pen ink according to claim 1, characterized in that, The average thickness of the dense coating structure is 3 nm to 10 nm, and the surface roughness of the coated pigment particles is less than 5 nm.

9. The in-situ coating and dispersion process for pigment particles in pen ink according to claim 1, characterized in that, After step S105, the method further includes: adding an interface modifier into the grinding chamber to adjust the surface potential of the pigment particles so that the absolute value of the ζ potential of the obtained pigment particles in the ink system is greater than 40mV.

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