Process for producing lignin-based hyperbranched adhesive for high salt service

Abstract

This invention relates to the field of adhesive technology and discloses a production process for lignin-based hyperbranched adhesives for high-salt conditions. The process includes: mixing natural lignin raw materials with an aqueous medium to construct a reactive, low-temperature bulk fluid; constructing a local reaction window using a viscous dissipative energy field generated at the outer edge of a shear stress generating component; injecting modified monomers and crosslinking agents into the window under a pressure gradient formed by the rotation of the shear component, inducing graft copolymerization, and then quenching under a cyclic temperature gradient to lock in a topological structure with a hydrophilic hyperbranched shell and a hydrophobic lignin core. This invention avoids the risk of localized disordered polymerization caused by global heat transfer hysteresis through spatial decoupling of the energy field and temperature field. The resulting topological structure utilizes the steric hindrance effect generated by the outer high-density hydration layer to block the electrostatic shielding of metal cations, thereby improving the homogeneous stability of the adhesive in a high-salt environment.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, and particularly relates to a production process for lignin-based hyperbranched adhesives for high-salt conditions. Background Technology

[0002] Currently, natural lignin contains various phenolic and alcoholic hydroxyl groups, possessing reactivity for developing bio-based adhesives. The industry typically uses hyperbranched polymers to graft and modify lignin, utilizing the high-density end groups and spatial configuration of the hyperbranched structure to improve the curing rate and interfacial wetting performance of lignin adhesives. In deep-sea engineering restoration, plywood applications in seawater-infiltrated environments, or high-salt industrial wastewater seepage prevention and curing, high concentrations of electrolytes such as sodium and magnesium ions in the environmental water produce a strong shielding effect, stripping the hydrated molecular layer around the polymer chain, causing the hydrophobic core of lignin to physically collapse and randomly aggregate, ultimately leading to phase separation or curing failure of the adhesive system. Especially for plywood adhesive layers exposed to seawater, salt ion penetration can trigger microscopic peeling at the adhesive interface. If the adhesive itself does not possess a salt-resistant topology, its wet shear strength will be rapidly lost due to electrolyte attack.

[0003] Conventional production processes employ a path of raw material mixing, global heating reaction, and forced cooling at the end of the reaction, attempting to freeze specific conformations of lignin by reducing system energy. However, in industrial-grade high-viscosity systems, the global heat conduction rate is far lower than the relaxation and rearrangement rate of polymer chains, making it difficult for the cooling action to precisely lock the metastable topological structure. For example, Chinese invention patent application CN114316898A discloses a method for preparing hyperbranched polyamine-modified lignin adhesives. The scheme relies on conventional water bath heating and blending reactions, with the modification logic focusing on the static construction of chemical structures. When dealing with industrial-grade high-viscosity systems, the global heating mode cannot avoid the accumulation of local heat leading to disordered explosive polymerization. The product chain segments are in a state of thermodynamic random entanglement, lacking directional guidance and instantaneous locking of macromolecular topological conformations. When the resulting adhesive encounters extreme high-salt shocks, it cannot block ionic electrostatic shielding through structural steric hindrance effects and is prone to salting-out collapse.

[0004] Therefore, the technical problem to be solved by this invention is how to achieve directional locking of the topological conformation of natural macromolecules in a coupled thermodynamic field and a strong shear flow field, and suppress local explosive polymerization caused by temperature gradient in high viscosity systems. Summary of the Invention

[0005] This invention provides a process for producing lignin-based hyperbranched adhesives for high-salt conditions, comprising the following steps:

[0006] Step 101: Mix natural lignin raw materials with aqueous medium to construct the main reaction fluid, adjust the ambient temperature of the main reaction fluid to 5°C to 15°C, and maintain the main reaction fluid in a homogeneous distribution state under thermal equilibrium.

[0007] Step 102: A local reaction window is constructed using the viscous dissipation energy field generated at the edge of the shear stress generating component located in the reaction space. The rotation speed of the shear stress generating component is 4000 r / min, so that the main reaction fluid generates an active conformation of molecular chain orientation when passing through the local reaction window.

[0008] Step 103: Based on the pressure gradient formed by the shear stress generating component under high-speed rotation, locate the outlet of the material supply path, so that the outlet of the material supply path is located within the local reaction window, and inject hyperbranched modified monomer and crosslinking agent into the local reaction window. The hyperbranched modified monomer is hyperbranched polyethyleneimine or hyperbranched polyester containing multiple active end groups.

[0009] Step 104: The hyperbranched modified monomer undergoes a graft copolymerization reaction with natural lignin raw material under an active conformation, and the reaction product is quenched by the temperature gradient generated by the main reaction fluid in the circulation flow, locking in the formation of a topological structure with a hydrophilic hyperbranched shell and a hydrophobic lignin core.

[0010] Step 105: Monitor the dynamic viscosity and turbidity changes of the reaction system. When the dynamic viscosity reaches the preset viscosity growth termination threshold and the turbidity shows a decreasing trend, stop the operation of the shear stress generating component to obtain the lignin-based hyperbranched adhesive.

[0011] Preferably, step 102 is further refined into the following sub-steps: Step 1021, controlling the local temperature generated by the shear stress generating component within the local reaction window to be 65°C to 85°C, so that a temperature difference gradient of not less than 50°C is formed between the local reaction window and the low-temperature environment where the main reaction fluid is located; Step 1022, using the shear torque provided by the shear stress generating component to induce the molecular chain segments of the natural lignin raw material to produce directional arrangement, and triggering the graft copolymerization reaction within the instantaneous window of directional stretching of the molecular chains.

[0012] Preferably, the natural lignin raw material includes at least one of alkali lignin, sodium lignin sulfonate, or enzymatically hydrolyzed lignin; the crosslinking agent is at least one of epichlorohydrin, formaldehyde, or glutaraldehyde.

[0013] Preferably, in step 103, the radial distance L between the outlet of the material supply path and the outer edge of the shear stress generating component in the horizontal projection direction satisfies the following logical relationship: L = 0.05 × D, where D is the rotation diameter of the shear stress generating component; by limiting the radial distance L, the hyperbranched modified monomer is trapped in the local reaction window by the pressure gradient constraint of the shear stress generating component at the moment it enters the main reaction fluid.

[0014] Preferably, step 101 further includes adding a surfactant to the main reaction fluid to adjust the micelle size of the natural lignin raw material in the aqueous medium, so that the micelle size is maintained between 50 nm and 200 nm, providing physical building blocks for the core construction of the topological structure.

[0015] Preferably, in step 104, cold quenching is achieved by the main reactive fluid leaving the local reaction window and entering the low-temperature region where the ambient temperature is located under the circulatory flow driven by the shear stress generating component; in the topological structure, the outer hydrophilic hyperbranched shell forms a hydration layer, which blocks the electrostatic shielding of the hydrophobic lignin core by electrolyte ions through the steric hindrance effect.

[0016] Preferably, in step 105, the monitoring is further refined into the following sub-steps: Step 1051, acquiring online ultrasonic attenuation sensing data of the reaction system during the polymerization process to convert it into dynamic viscosity data; Step 1052, acquiring online transmission spectral sensing data of the reaction system during the polymerization process to convert it into turbidity data, and determining whether the conversion rate of the graft copolymerization reaction reaches more than 95% based on the mapping correlation slope between the dynamic viscosity data and the turbidity data.

[0017] Preferably, in step 103, the mass ratio of hyperbranched modified monomer to natural lignin raw material is 1:3 to 1:1; by adjusting the mass ratio, the density of hydrophilic end groups on the surface of the topological structure is controlled so that the initial tack strength of the lignin-based hyperbranched adhesive in a saturated saline environment is not less than 1.5 MPa.

[0018] Preferably, the pH of the aqueous medium is adjusted to 10 to 12; by utilizing the solubility characteristics of the alkaline environment on natural lignin raw materials, and in conjunction with the instantaneous high temperature of the local reaction window, the activation efficiency of the crosslinking agent on the phenolic hydroxyl groups in the natural lignin raw materials is improved.

[0019] Preferably, the production process further includes a post-processing step: subjecting the obtained lignin-based hyperbranched adhesive to vacuum devolatilization to remove residual hyperbranched modified monomers, and adjusting the solid content of the lignin-based hyperbranched adhesive to 40% to 60%.

[0020] Compared with existing technologies, the lignin-based hyperbranched adhesive production process of this invention for high-salt conditions has the following advantages:

[0021] 1. In the production of lignin-based hyperbranched adhesives, by spatially decoupling the viscous dissipative energy field and the temperature field, a local high-temperature active micro-reaction window is constructed at the outer edge of the blade. Combined with the low-temperature inert environment of the bulk fluid, the crosslinking reaction is induced to be completed instantaneously when the molecular chains are highly stretched due to shear stress. This mechanism utilizes the temperature gradient generated by fluid circulation to achieve self-limiting termination of the reaction activity, eliminating the risk of local disordered explosive polymerization that is prone to occur in high-viscosity polymerization systems under global heat conduction lag, and improving the stability of the process and the consistency of the product structure in industrial-scale production.

[0022] 2. By leveraging the synergistic effect of hydrophobic shrinkage dynamics provided by the rapid cooling environment and hydrophilic directional tensile stress generated by the ultra-high shear field, a crosslinking agent is introduced under specific physical constraints to achieve topological locking of the spatial arrangement sequence of the lignin hydrophobic framework and hyperbranched hydrophilic network. The resulting product possesses a native core-shell topology. The steric hindrance effect generated by the hydration layer formed by the high-density hydrophilic end groups on the outer layer blocks the electrostatic shielding effect of high-concentration metal cations on the internal framework, enabling the natural material-based adhesive to maintain homogeneous stability in a saturated salt water environment and increasing the critical salting-out concentration of the adhesive.

[0023] 3. By using a dual-source closed-loop monitoring system of dynamic viscosity and real-time turbidity, a mapping relationship is established between the overall rheological properties of the polymerization reaction and the evolution characteristics of the surface phase state, enabling objective determination of the completion node of topology locking. This monitoring mechanism does not rely on a fixed reaction time setting and can automatically compensate for the differences in the untangling state caused by fluctuations in inorganic salt impurities in batches of natural lignin raw materials, ensuring that the final product has a certain bonding strength and resistance to performance degradation in complex service environments such as marine infrastructure repair. Attached Figure Description

[0024] Figure 1 This is a flowchart of the intelligent control and preparation process of lignin-based hyperbranched adhesives under high-salt conditions according to the present invention.

[0025] Figure 2 This is an operational example diagram of the production process of lignin-based hyperbranched adhesives under high-salt conditions according to the present invention. Detailed Implementation

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

[0028] In the description of this invention, unless otherwise explicitly specified and limited, the terms installation, connection, and linking should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal connection of two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0029] In the description of this specification, references to the terms "an embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example, and the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0030] A process for producing lignin-based hyperbranched adhesives for high-salt conditions includes the following steps:

[0031] Step 101: Mix natural lignin raw materials with aqueous medium to construct the main reaction fluid, adjust the ambient temperature of the main reaction fluid to 5°C to 15°C, and maintain the main reaction fluid in a homogeneous distribution state under thermal equilibrium.

[0032] Step 102: A local reaction window is constructed using the viscous dissipation energy field generated at the edge of the shear stress generating component located in the reaction space. The rotation speed of the shear stress generating component is 4000 r / min, so that the main reaction fluid generates an active conformation of molecular chain orientation when passing through the local reaction window.

[0033] Step 103: Based on the pressure gradient formed by the shear stress generating component under high-speed rotation, locate the outlet of the material supply path, so that the outlet of the material supply path is located within the local reaction window, and inject hyperbranched modified monomer and crosslinking agent into the local reaction window. The hyperbranched modified monomer is hyperbranched polyethyleneimine or hyperbranched polyester containing multiple active end groups.

[0034] Step 104: The hyperbranched modified monomer undergoes a graft copolymerization reaction with natural lignin raw material under an active conformation, and the reaction product is quenched by the temperature gradient generated by the main reaction fluid in the circulation flow, locking in the formation of a topological structure with a hydrophilic hyperbranched shell and a hydrophobic lignin core.

[0035] Step 105: Monitor the dynamic viscosity and turbidity changes of the reaction system. When the dynamic viscosity reaches the preset viscosity growth termination threshold and the turbidity shows a decreasing trend, stop the operation of the shear stress generating component to obtain the lignin-based hyperbranched adhesive.

[0036] Preferably, step 102 is further refined into the following sub-steps: Step 1021, controlling the local temperature generated by the shear stress generating component within the local reaction window to be 65°C to 85°C, so that a temperature difference gradient of not less than 50°C is formed between the local reaction window and the low-temperature environment where the main reaction fluid is located; Step 1022, using the shear torque provided by the shear stress generating component to induce the molecular chain segments of the natural lignin raw material to produce directional arrangement, and triggering the graft copolymerization reaction within the instantaneous window of directional stretching of the molecular chains.

[0037] Preferably, the natural lignin raw material includes at least one of alkali lignin, sodium lignin sulfonate, or enzymatically hydrolyzed lignin; the crosslinking agent is at least one of epichlorohydrin, formaldehyde, or glutaraldehyde.

[0038] Preferably, in step 103, the radial distance L between the outlet of the material supply path and the outer edge of the shear stress generating component in the horizontal projection direction satisfies the following logical relationship: L = 0.05 × D, where D is the rotation diameter of the shear stress generating component; by limiting the radial distance L, the hyperbranched modified monomer is trapped in the local reaction window by the pressure gradient constraint of the shear stress generating component at the moment it enters the main reaction fluid.

[0039] Preferably, step 101 further includes adding a surfactant to the main reaction fluid to adjust the micelle size of the natural lignin raw material in the aqueous medium, so that the micelle size is maintained between 50 nm and 200 nm, providing physical building blocks for the core construction of the topological structure.

[0040] Preferably, in step 104, cold quenching is achieved by the main reactive fluid leaving the local reaction window and entering the low-temperature region where the ambient temperature is located under the circulatory flow driven by the shear stress generating component; in the topological structure, the outer hydrophilic hyperbranched shell forms a hydration layer, which blocks the electrostatic shielding of the hydrophobic lignin core by electrolyte ions through the steric hindrance effect.

[0041] Preferably, in step 105, the monitoring is further refined into the following sub-steps: Step 1051, acquiring online ultrasonic attenuation sensing data of the reaction system during the polymerization process to convert it into dynamic viscosity data; Step 1052, acquiring online transmission spectral sensing data of the reaction system during the polymerization process to convert it into turbidity data, and determining whether the conversion rate of the graft copolymerization reaction reaches more than 95% based on the mapping correlation slope between the dynamic viscosity data and the turbidity data.

[0042] Preferably, in step 103, the mass ratio of hyperbranched modified monomer to natural lignin raw material is 1:3 to 1:1; by adjusting the mass ratio, the density of hydrophilic end groups on the surface of the topological structure is controlled so that the initial tack strength of the lignin-based hyperbranched adhesive in a saturated saline environment is not less than 1.5 MPa.

[0043] Preferably, the pH of the aqueous medium is adjusted to 10 to 12; by utilizing the solubility characteristics of the alkaline environment on natural lignin raw materials, and in conjunction with the instantaneous high temperature of the local reaction window, the activation efficiency of the crosslinking agent on the phenolic hydroxyl groups in the natural lignin raw materials is improved.

[0044] Preferably, the production process further includes a post-processing step: subjecting the obtained lignin-based hyperbranched adhesive to vacuum devolatilization to remove residual hyperbranched modified monomers, and adjusting the solid content of the lignin-based hyperbranched adhesive to 40% to 60%.

[0045] Example 1: In deep-sea engineering restoration or high-salinity industrial wastewater seepage prevention and solidification applications, the environmental water contains high concentrations of electrolytes such as sodium and magnesium ions. When lignin-based hyperbranched adhesives prepared using conventional isothermal polymerization processes are applied to this situation, the high concentration of electrolytes strips the hydrated molecular layer around the polymer chains, causing the hydrophobic core of the lignin to physically collapse and aggregate randomly, leading to phase separation and curing failure of the adhesive system. A mixture of natural lignin raw materials and an aqueous medium is used to construct the main reaction fluid. Surfactants are added to this main reaction fluid to adjust the micelle size of the natural lignin raw materials in the aqueous medium to maintain it between 50 nm and 200 nm, and the pH value of the aqueous medium is adjusted to... In this process step (10-12), the surfactant is selected from either sodium dodecylbenzenesulfonate or polyvinyl alcohol. To accurately control the dissolved and dispersed natural lignin macromolecular aggregates within the submicron micelle range of 50 nm to 200 nm in an alkaline pH 10-12 system, the amount of surfactant added is controlled between 0.5% and 1.2% of the total mass of the lignin raw material, ensuring its real-time concentration in the aqueous phase is slightly higher than its critical micelle concentration. Through the self-assembly and directional arrangement of the hydrophilic groups on the outer edge, it provides physical micro-units with high uniformity of specific surface area for subsequent graft crosslinking of hyperbranched modified monomers on their surface. The ambient temperature of the main reaction fluid is also adjusted. The fluid is kept in a homogeneous distribution state under thermal equilibrium at temperatures ranging from 5°C to 15°C. A local reaction window is constructed using the viscous dissipative energy field generated at the edge of the shear stress generating component located in the reaction space. The rotation speed of the shear stress generating component is set to 4000 r / min, and the local temperature generated by the shear stress generating component within the local reaction window is controlled to be maintained between 65°C and 85°C, so that a temperature gradient of no less than 50°C is formed between the local reaction window and the low-temperature environment where the main reaction fluid is located. At an extremely high shear rate of 4000 r / min, the high-viscosity fluid instantly generates a strong non-Newtonian shear thinning effect at the outer edge of the shear stress generating component, forming a layer of extremely low viscosity slip with a thickness on the order of millimeters. The boundary layer, within which the fluid undergoes an instantaneous temperature jump due to extremely high internal friction, and simultaneously, a significant viscosity gradient exists between this boundary layer and the surrounding high-viscosity bulk fluid. This viscosity-jump interface physically constitutes a strong resistance barrier to momentum and heat transfer, thus maintaining the high-temperature state within the surface boundary layer in the overall strong convection environment and preventing it from being instantaneously homogenized and dissipated by the surrounding fluid. The outlet of the material supply path is located based on the pressure gradient formed by the shear stress generating component under high-speed rotation, ensuring that the outlet of the material supply path is within this local reaction window. The radial distance L between the outlet of the material supply path and the outer edge of the shear stress generating component in the horizontal projection direction is set to satisfy the logical relationship L=0.0.5×D, where D is the rotation diameter of the shear stress generating component. By limiting the aforementioned radial distance, the pressure gradient of the shear stress generating component directly confines the hyperbranched modified monomers containing multiple active end groups and the epichlorohydrin crosslinking agent entering the fluid within the local reaction window. The extremely high shear torque provided by the shear stress generating component induces the molecular chain segments of the natural lignin raw material to oriented arrangement, causing the main reaction fluid to produce an active conformation of oriented molecular chain arrangement when passing through the local reaction window. Under the synergistic activation of the instantaneous window of molecular chain oriented stretching and the local instantaneous high temperature, the hyperbranched modified monomers undergo a targeted graft copolymerization reaction with the phenolic hydroxyl groups of the natural lignin raw material.

[0046] The reaction products, along with the bulk reaction fluid, leave the local reaction window and enter the low-temperature region of the ambient temperature during a stirring-driven circulation. This physical temperature gradient quenches the reaction products, causing the reactivity of the epichlorohydrin crosslinking agent to stagnate as the temperature drops sharply. The hydrophobic lignin framework shrinks and solidifies upon cooling, locking in a specific topological structure with a hydrophilic hyperbranched shell and a hydrophobic lignin core. In fact, once the hyperbranched modified monomer and crosslinking agent complete the grafting of lignin phenolic hydroxyl groups within the microsecond-level local high-temperature shear window, the relative molecular mass of the locally grafted macromolecules instantly increases, immediately initiating phase separation at the surface scale in the strong shear region at the outer edge, and the hydrophilic end groups... Under strong flow field directional arrangement, preferentially oriented towards the aqueous phase, micron-sized core-shell micelle prototypes spontaneously form in local micro-regions. As these prototypes circulate with the bulk fluid on a second-scale scale to the low-temperature region, their overall spatial conformation is deeply frozen due to the thermodynamic motion of the polymer chain segments, achieving final overall physical locking. Online ultrasonic attenuation sensing data of the reaction system during the polymerization process is acquired and converted into dynamic viscosity data, while online transmission spectroscopy sensing data is simultaneously acquired and converted into turbidity data. The conversion rate of the graft copolymerization reaction is determined based on the mapping slope between the dynamic viscosity data and the turbidity data, indicating whether it has reached over 95%. When the dynamic viscosity reaches the preset viscosity growth termination threshold and the turbidity continuously shows a certain trend... During the downward trend, the rotation of the shear stress generating component is stopped, the decompression devolatilization reaction system removes the residual free hyperbranched modified monomers, and the solid content of the final system is adjusted to 40% to 60% to obtain the target lignin-based hyperbranched adhesive. The sound velocity and attenuation coefficient of the polymerization reaction system at a specific ultrasonic high frequency, obtained by an online ultrasonic attenuation sensor, are input in real time into the acoustic rheological transformation model of the system microprocessor. This model is based on the classical Stokes-Kirchhoff high-frequency wave extension equation, and establishes the constitutive relationship between the longitudinal wave storage modulus, loss modulus, and dynamic viscosity of the multiphase viscoelastic medium under alternating acoustic stress field. The model is further refined by measuring the relationship between the acoustic attenuation coefficient and the square of the frequency. The macroscopic dynamic viscosity parameter of the system is directly calculated online from the projection slope. At the same time, the transmission light intensity attenuation is collected by the online near-infrared transmission spectrometer in the 800nm ​​to 1100nm band. When the absorbance is calculated to reflect the turbidity of the liquid using the Beer-Lambert law, a set of (3×3) calibration bias compensation coefficient matrices, which are pre-calibrated with standard turbidity liquid and stored in the system, is introduced to filter out the background scattering interference caused by the entanglement of macromolecules themselves, so as to output a standardized actual turbidity parameter that can objectively reflect the concentration consumption state of free monomers and crosslinking agents.In this data conversion process, the system incorporates an acoustic rheological conversion model based on the Stokes-Kirchhoff extended equations. It directly calculates the overall dynamic viscosity parameter using the energy attenuation coefficient of high-frequency ultrasound in a viscoelastic multiphase medium. Simultaneously, it combines Beer-Lambert's law to collect the light intensity attenuation rate of the transmission spectrum in a specific near-infrared band and introduces a compensation coefficient matrix calibrated for the micelle scattering characteristics of natural macromolecules, thereby outputting standardized turbidity parameters. This process decouples the fluid viscosity dissipation energy field from the global heat transfer temperature field in physical space. Local high-temperature, high-shear regions induce cross-linking activation, while the global low-temperature, inert fluid region forcibly blocks reaction propagation, eliminating the risk of localized disordered gelation that is easily triggered in industrial-grade high-viscosity polymerization systems under global heat conduction hysteresis. The resulting adhesive product retains a complete hydrophobic lignin skeleton in the core, while the outer high-density hydrophilic hyperbranched network forms a high-strength hydration layer. The steric hindrance effect blocks the electrostatic shielding of the internal skeleton by high-concentration metal cations, enabling the natural material-based adhesive to maintain homogeneous stability under saturated saline conditions and preserve its original interfacial bonding strength. ;

[0047] Example 2: Industrial wastewater contained an initial concentration of 1.5 mol / L sodium ions and 0.8 mol / L magnesium ions. The fluid transport also experienced dynamic salinity disturbances with environmental noise reaching 15%. A physical testing platform was constructed using a 50L jacketed reactor with 0.1℃ temperature control accuracy and a variable frequency disperser supporting a maximum speed of 6000 r / min. A 45% alkali lignin aqueous solution was extracted as the basic component of the natural lignin raw material. A sample group following the aforementioned parameter range was established. Simultaneously, a temperature control sample group using a global constant temperature 75℃ heating polymerization process was established. A partially deficient control sample group using conventional linear polyamine instead of hyperbranched polyethyleneimine modified monomer was established. An out-of-range control sample group with the shear stress generating component speed set at 5500 r / min was established. Based on this multi-dimensional control system, physicochemical evolution data of each sample group during the polymerization process were collected.

[0048] The mixing and stirring equipment was started to adjust the temperature of the main reaction fluid of the sample group to 10°C. The shear stress generating component was started and its rotation speed was set to 4000 r / min to create a local reaction window with a local temperature of 75°C. The material supply path outlet of the epichlorohydrin crosslinking agent was positioned. The radial distance L between the outlet and the outer edge of the shear stress generating component in the horizontal projection direction was set to satisfy the logical relationship L = 0.05 × D, where D is the rotation diameter of the shear stress generating component. When the radial distance L is limited to a fixed proportional coefficient of 0.05 of the rotation diameter D, the mechanical output of the material supply pipeline is... The inlet is located precisely within the local negative pressure zone formed by the high-speed discharge flow field at the outer edge of the rotor. The proportionality coefficient of 0.05 is an engineering boundary parameter determined based on the fluid dynamics equilibrium within the reactor. When L / D is less than 0.05, the physical outlet of the material pipeline generates extremely high-frequency mechanical tangential fluid pulsations due to its excessive proximity to the high-speed rotating body, easily causing material backflow and clogging of the feed nozzle. Conversely, when L / D is greater than 0.05, the pressure gradient generated by the shear component's discharge has attenuated to less than 15% of the maximum velocity at this distant physical coordinate point, preventing the injected monomers and crosslinking agents from being effectively captured by the vortex negative pressure. The crosslinking agent is directly diffused into the surrounding low-temperature bulk fluid phase, causing global disordered slow polymerization. Therefore, locking the coefficient at 0.05 ensures that the epichlorohydrin crosslinking agent is fully absorbed into the shear dissipation slip layer by the pressure gradient the instant it is sprayed out. This proportionality coefficient of 0.05 is derived from the hydrodynamic equilibrium relationship between the shear field pressure gradient decay curve and the crosslinking agent diffusion rate. Intermediate turbidity data from an online transmission spectrometer were collected. When the reaction time reached 45 minutes, the turbidity index of the sample group of this invention decreased from the initial 15.4 NTU and remained at 2.1 NTU, corresponding to... In the case of hyperbranched networks suppressing the diffusion of free crosslinking agents at low temperatures, the temperature control group, under the same reaction time, was subjected to global high-temperature excitation, resulting in disordered aggregation of free crosslinking agents. Its turbidity index climbed to 89.6 NTU and large-area phase separation occurred. In the case of the out-of-range control group, at an extremely high shear rate of 5500 r / min, its turbidity data rebounded to 18.3 NTU after dropping to 12.5 NTU. This rebound trend reflects the nonlinear degradation effect of mechanical degradation and breakage of covalent bonds in the formed polymer caused by excessive shear stress, confirming the physical boundary of the upper limit parameter of rotation speed.

[0049] The prepared adhesives were collected and coated onto the surface of a standard titanium alloy test substrate. The substrate was then immersed in simulated wastewater with multiple pre-set salinity gradients to collect curing shear strength data. Under a low salinity gradient with a sodium ion concentration of 0.5 mol / L, the curing shear strengths of the present invention's sample group and the partially missing control sample group were 4.85 MPa and 4.12 MPa, respectively. When the sodium ion concentration was increased to a high salinity gradient of 1.75 mol / L, which is superimposed with the peak value of the environmental background noise, the linear structure inside the partially missing control sample group underwent salting out, curling, and collapse, and its curing shear strength decreased exponentially to 0. The sample failed at 95 MPa and underwent brittle fracture. The present invention's sample group, by constructing a steric hindrance effect through an outer high-density hydrophilic hyperbranched polyethyleneimine shell, blocked the electrostatic shielding of the lignin hydrophobic core by metal cations. Its curing shear strength was only mechanically damped and remained stable at 4.62 MPa. The series of test data quantitatively presented the data correlation mechanism between a specific thermodynamic gradient field and hyperbranched monomer grafting in response to the stripping of the hydrated molecular layer by high concentration of metal cations. This confirmed the physical mechanism by which the local reaction window combined with the targeted crosslinking mechanism maintains the adaptability of lignin-based hyperbranched adhesives to high-salt conditions.

[0050] Example 3: In the large-scale continuous production of adhesives for high-salt conditions, the relaxation time of polymer chains and the kinetic parameters of crosslinking reactions within the flow field are subject to parameter constraints. Simply cutting off the reaction based on time parameters leads to topological shifts and uncontrolled gelation between product batches. To calibrate the viscosity growth termination threshold and verify the topological structure, a 45% (w / w) aqueous solution of alkali lignin was extracted to construct the basic reaction fluid. A reaction testing platform integrating an online rotational rheometer and an infrared spectral probe was started. The base temperature of the reaction platform was controlled at 85°C, and the stirring speed was set to 300 r / min. Hyperbranched polyethyleneimine monomers containing multiple active end groups were pumped into the basic reaction fluid at a constant flow rate. The rheometer collected the transient dynamic viscosity data of the fluid in real time, and the infrared spectral probe simultaneously collected the spectral absorption peak area data reflecting the number of characteristic chemical bonds. This spectral absorption peak area is uniquely associated with the number of covalent bonds generated by the graft copolymerization reaction between the phenolic hydroxyl groups on the surface of the natural lignin raw material and the terminal amino groups of the hyperbranched modified monomer. The system matched the transient dynamic viscosity data and the spectral absorption peak area data based on the same time stamp to construct a benchmark mapping between the viscosity growth slope and the reaction conversion rate. Similar to the correlation model; in order to reduce and fuse the dynamic change characteristics of rheological properties and surface phase evolution (turbidity), which are two different physical dimensions and different dimensions, to guide the determination of industrial online endpoints, this invention constructs a dimensionless sliding window mapping correlation slope calculation rule: the microprocessor uses a constant time span Δt as a sliding data sampling window. At the start and end times of each Δt window, the data acquisition module synchronously reads the dynamic viscosity value and the transmission spectrum conversion turbidity value output by the online system. The main control unit calculates the absolute value ΔV of the dynamic viscosity increase within 60 seconds. The ratio of the absolute value of the turbidity decay amplitude ΔT to the value of the turbidity decay amplitude, i.e., according to the formula K=|ΔV / ΔT|, outputs the real-time mapping correlation slope K; where the dynamic viscosity increase ΔV is normalized to the ratio of the viscosity change in the current window to the initial baseline viscosity reference parameter, and the turbidity decay amplitude ΔT is normalized to the ratio of the turbidity change in the current window to the initial turbidity reference parameter, so that the calculated K value becomes a scalar evolution rate parameter that eliminates dimensional interference. Through this dimensionless dimensionality reduction mapping rule, the reliable transformation of multidimensional composite phase trend characteristics into a single numerical endpoint determination benchmark is realized.

[0051] Physical test data show that when the transient dynamic viscosity is less than 2.0 times the initial base viscosity, the area of ​​the spectral absorption peak shows a linear steep increase, which is related to the accelerated stage of the graft copolymerization reaction. When the transient dynamic viscosity reaches 2.5 times the initial base viscosity, the growth slope of the spectral absorption peak area drops sharply and remains at a horizontal plateau, indicating that the highly active reaction sites on the surface of the natural lignin raw material are saturated. When the monomer is continued to be pumped in so that the transient dynamic viscosity reaches more than 3.0 times the initial base viscosity, a sudden increase in light scattering occurs inside the fluid, indicating the initiation point of phase separation caused by excessive crosslinking. It should be noted that the sudden increase in light scattering and the rebound in turbidity when the viscosity reaches more than 3.0 times is due to macroscopic condensation caused by excessive crosslinking. The physical degradation phenomenon of gel precipitation; however, in the normal cross-linking process before gelation, as the hyperbranched monomers and epichlorohydrin cross-linking agent are targeted and grafted onto the lignin skeleton within the shear window, the concentration of free reactive monomers continuously decreases, and the microscopic non-uniform phase distribution within the system converges. This causes the scattering effect of the reaction system on the transmitted light of a specific near-infrared spectrum to continuously decrease with increasing conversion rate. Macroscopically, this manifests as a monotonically decreasing trend in turbidity throughout the entire reaction process, until the reaction conversion rate reaches over 95% and is about to cross the gelation threshold, at which point the turbidity reaches its stable minimum baseline. Therefore, precisely intercepting the viscosity growth termination threshold at 2.5 times the initial base viscosity corresponds precisely to the overall turbidity. The inflection point at the very end of the monotonically decreasing trend, at which point the action is stopped, ensures that the reaction operates entirely within the controlled process envelope of turbidity reduction. The aforementioned nonlinear physical response data calibrates the quantitative mapping boundary between specific viscosity nodes and reaction evolution states. Based on Flory gelation theory and Rayleigh scattering principle, the overall dynamic viscosity of the system increases regularly with the construction of the polymer crosslinking network. The turbidity of the system is dominated by the concentration of free crosslinking agent and monomer, resulting in a negative light scattering response. To transform the benchmark mapping based on infrared spectroscopy into a physical control procedure applicable to online industrial production, the system's main control unit executes the state determination logic: setting the time span as a sliding sampling window Δt, the data acquisition module synchronously reads the dynamic viscosity changes at the start and end times of the sliding sampling window. The conversion rate ΔV and the turbidity change ΔT from the transmission spectrum are used to calculate the real-time mapping correlation slope K based on the formula K=|ΔV / ΔT|. ΔV and ΔT represent the increase in dynamic viscosity and the decrease in turbidity within the set sampling time window, respectively. The calculated K value is used as a dimensionless physical parameter characterizing the liquid phase crosslinking rate. By comparing with the previous offline calibration conversion rate benchmark data of the proton NMR spectrum, the system locks the critical threshold K for the conversion rate to reach 95% as 0.15. During the polymerization process, when the logic comparator determines that the output mapping correlation slope K of three consecutive sliding sampling windows is less than 0.15, it confirms that the conversion rate of the graft copolymerization reaction has crossed the boundary node, and the control center sends a shutdown level signal to the frequency converter to cut off the shear torque input.

[0052] The cold-quenched termination product, which reached the 2.5-fold viscosity growth node, was extracted and its physical morphology was observed using cryo-transmission electron microscopy. The characterization images showed that the product possessed a dense dark-field core and a divergent light-colored halo. The dense dark-field core corresponded to a hydrophobic lignin skeleton that had been physically quenched and solidified, while the divergent light-colored halo corresponded to a highly swollen hydrophilic hyperbranched shell that extended into the outer space. The characterization data verified the specific core-shell topology constructed by the synergistic effect of temperature gradient and viscous dissipation energy field. Combining multidimensional data correlation and characterization results, 2.5 times the initial base viscosity was calibrated as the viscosity growth termination threshold. In industrial production monitoring, the feedback system captured the viscosity threshold signal, triggering the action of stopping monomer injection and starting the cold quenching circuit. This controlled the lignin-based hyperbranched adhesive to avoid excessive cross-linking and to construct the steric structure required for salt precipitation resistance.

[0053] Example 4: When the system is engaged in continuous production of adhesives based on different batches of natural lignin raw materials, fluctuations in the molecular weight of the materials cause initial state baseline drift of the main reaction fluid. Before production, the system calibrates the initial state. The delivery pump injects an alkali lignin aqueous solution into the reactor equipped with an online rheometer and transmission spectrometer. In a pure fluid circulation state without the addition of hyperbranched modified monomers and crosslinking agents, the temperature is adjusted to 10°C and the shear stress generating component is activated to achieve steady-state operation. The control unit collects transient dynamic viscosity and turbidity data within 15 minutes. The microprocessor calculates the arithmetic mean to filter out fluid pulsation noise and writes the obtained average viscosity into the memory as the initial baseline viscosity parameter for that batch of fluid. Simultaneously, the average turbidity value is locked as the initial turbidity reference parameter. .

[0054] After extracting the reference parameters, the sensor scans and obtains the actual rotation diameter D of the shear stress generating component inside the reactor. The main control unit calculates the target positioning data according to the equation L=0.05×D. The servo mechanism drives the material supply path outlet to move and position itself at a spatial coordinate point that satisfies the horizontal radial distance L based on this target positioning data. The calculation module reads the initial basic viscosity reference parameters from the memory. The initial baseline viscosity parameter is multiplied by a constant 2.5 to calculate the dynamic viscosity growth termination threshold for this batch, and the initial turbidity reference parameter is then used. As the zero-point offset compensation input comparator of the spectral monitoring module, after the parameters are written, the control center sends a ready signal to the downstream pipeline to allow material injection.

[0055] Example 5: When the system faces continuous production of adhesives under high-salt conditions, the operation of the shear stress generating component causes the accumulation of viscous heat dissipation in the flow field. This heat accumulation causes the base temperature of the main reactive fluid to rise and drift, thereby compressing the temperature gradient between the local reaction window and the main reactive fluid, triggering the activation of the crosslinking agent in non-target areas. The torque sensor collects the real-time working torque of the shear stress generating component, and the temperature sensor simultaneously collects the real-time main body temperature in the reaction space. The logic operation module converts this real-time working torque into a local viscous heat dissipation rate based on the fluid shear work equation, and then uses this local viscous heat dissipation rate... The cooling compensation load required to maintain the main reaction fluid in the range of 5°C to 15°C is calculated. The fluid shear work equation takes the product of the real-time angular velocity of the servo motor and the current working torque as the total mechanical energy input power. After deducting the known mechanical no-load loss of the stirring bearing transmission system, the power law exponent based on the current fluid rheological characteristics is introduced as the non-Newtonian fluid work conversion coefficient, thereby accurately calculating the net rate at which mechanical energy is converted into fluid internal energy, which is assigned as the local viscous dissipation heat generation rate. The main control unit converts the cooling compensation load into a voltage control signal and outputs it to the servo proportional valve of the reactor cooling jacket to increase the circulation flux of the cooling medium.

[0056] Simultaneously, the logic operation module uses the real-time main temperature as a baseline and superimposes the local viscous dissipation heat generation rate to calculate the transient local temperature at the outer edge of the component generating shear stress. When the transient local temperature is determined to reach 85℃, the main control unit outputs a control command to reduce the operating frequency of the metering pump in the material supply path. This reduces the instantaneous injection amount of epichlorohydrin crosslinking agent, thus suppressing the exothermic local graft copolymerization reaction. Although the reduction in the instantaneous injection amount of crosslinking agent lowers the chemical ratio in terms of macroscopic metering, the material exhibits a state of extremely high molecular-level shear dispersion at 4000 r / min within the local reaction window. In a highly uniform, starved-feed controlled reaction mode, at the microscopic molecular chain scale, high shear stress induces spatial orientation rearrangement of the phenolic hydroxyl groups exposed under a stretched and active conformation in lignin long-chain molecules. This results in a minute stretching of the axial spacing between the grafted and activated sites on the lignin molecular chain surface. At this point, due to the massive three-dimensional nanoscale spherical volume and spatial congestion of the hyperbranched modified monomer's shell caused by its multibranched topological network, its hydrodynamic volume coverage radius is much larger than that of ordinary linear macromolecules. This macromolecular geometry is sufficient to completely cover and bridge the spatial steric hindrance caused by the crosslinking agent. The increased spacing between grafting sites, resulting from the increased density of grafts, replaces some of the structural voids caused by the decrease in covalent bond chemical density through a spatial geometric occupancy effect. Therefore, even when the macroscopic material ratio is dynamically disturbed, the overall spatial integrity of the outer hydrophilic hydration layer and the uniformity of the core-shell topology can still be maintained at the microscopic core-shell interface through cross-scale synergy between physical steric hindrance and chemical grafting. Although the reduction in the instantaneous injection amount of crosslinking agent lowers the overall ratio, the material exhibits a highly uniform, starved-feed controlled reaction mode because the local reaction window maintains an extremely high intensity of molecular-level shear dispersion. This will cause a slight stretching of the axial spacing between the grafting sites on the surface of the lignin molecular chain. The huge three-dimensional spherical volume of the hyperbranched monomer itself is sufficient to completely cover and bridge these spacings in space. Therefore, it will not destroy the overall spatial integrity of the outer hydrophilic hydration layer of the product or the uniformity of the core-shell topology. The thermodynamic dynamic compensation procedure constructs a parameter feedback loop based on mechanical torque parameters and temperature parameters to dynamically correct the heat disturbance generated in the polymerization process, maintain a temperature gradient spatial limit of not less than 50°C, and ensure the physical isolation of the lignin-based hyperbranched adhesive topology by the flow field temperature difference.

[0057] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit of this application and the scope of protection of this invention, and all of these forms are within the protection scope of this application.

Claims

1. A production process for lignin-based hyperbranched adhesives for high-salt conditions, characterized in that, Includes the following steps: Step 101: Mix natural lignin raw materials with aqueous medium to construct the main reaction fluid, adjust the ambient temperature of the main reaction fluid to 5°C to 15°C, and maintain the main reaction fluid in a homogeneous distribution state under thermal equilibrium. Step 102: A local reaction window is constructed using the viscous dissipation energy field generated at the edge of the shear stress generating component located in the reaction space. The rotation speed of the shear stress generating component is 4000 r / min, so that the main reaction fluid generates an active conformation with oriented molecular chain arrangement when passing through the local reaction window. Step 103: Based on the pressure gradient formed by the shear stress generating component under high-speed rotation, locate the outlet of the material supply path, so that the outlet of the material supply path is located within the local reaction window, and inject hyperbranched modified monomer and crosslinking agent into the local reaction window. The hyperbranched modified monomer is hyperbranched polyethyleneimine or hyperbranched polyester containing multiple active end groups. Step 104: The hyperbranched modified monomer undergoes a graft copolymerization reaction with natural lignin raw material under an active conformation, and the reaction product is quenched by the temperature gradient generated by the main reaction fluid in the circulation flow, locking in the formation of a topological structure with a hydrophilic hyperbranched shell and a hydrophobic lignin core. Step 105: Monitor the dynamic viscosity and turbidity changes of the reaction system. When the dynamic viscosity reaches the preset viscosity growth termination threshold and the turbidity shows a decreasing trend, stop the operation of the shear stress generating component to obtain the lignin-based hyperbranched adhesive.

2. The production process of a lignin-based hyperbranched adhesive for high-salt conditions according to claim 1, characterized in that, Step 102 is further refined into the following sub-steps: Step 1021, controlling the local temperature generated by the shear stress generating component within the local reaction window to be 65°C to 85°C, so that a temperature difference gradient of not less than 50°C is formed between the local reaction window and the low-temperature environment where the main reaction fluid is located; Step 1022, using the shear torque provided by the shear stress generating component to induce the molecular chain segments of the natural lignin raw material to produce directional arrangement.

3. The production process of a lignin-based hyperbranched adhesive for high-salt conditions according to claim 1, characterized in that, Natural lignin raw materials include at least one of alkali lignin, sodium lignin sulfonate, or enzymatically hydrolyzed lignin; the crosslinking agent is at least one of epichlorohydrin, formaldehyde, or glutaraldehyde.

4. The production process of a lignin-based hyperbranched adhesive for high-salt conditions according to claim 1, characterized in that, In step 103, the radial distance L between the outlet of the material supply path and the outer edge of the shear stress generating component in the horizontal projection direction satisfies the following logical relationship: L = 0.05 × D, where D is the rotation diameter of the shear stress generating component; by limiting the radial distance L, the hyperbranched modified monomer is trapped in the local reaction window by the pressure gradient constraint of the shear stress generating component at the moment it enters the main reaction fluid.

5. The production process of a lignin-based hyperbranched adhesive for high-salt conditions according to claim 1, characterized in that, In step 101, a surfactant is added to the main reaction fluid to adjust the micelle size of the natural lignin raw material in the aqueous medium, so that the micelle size is maintained between 50 nm and 200 nm, providing physical building blocks for the core construction of the topological structure.

6. The production process of a lignin-based hyperbranched adhesive for high-salt conditions according to claim 1, characterized in that, In step 104, cold quenching is achieved by the main reactive fluid leaving the local reaction window and entering the low-temperature region where the ambient temperature is located under the circulatory flow driven by the shear stress generating component; in the topology, the outer hydrophilic hyperbranched shell forms a hydration layer, which blocks the electrostatic shielding of the hydrophobic lignin core by electrolyte ions through the steric hindrance effect.

7. The production process of a lignin-based hyperbranched adhesive for high-salt conditions according to claim 1, characterized in that, In step 105, the monitoring is further refined into the following sub-steps: Step 1051, acquire online ultrasonic attenuation sensing data of the reaction system during the polymerization process and convert it into dynamic viscosity data; Step 1052, acquire online transmission spectral sensing data of the reaction system during the polymerization process and convert it into turbidity data, and determine whether the conversion rate of the graft copolymerization reaction reaches more than 95% based on the mapping correlation slope between the dynamic viscosity data and the turbidity data.

8. The production process of a lignin-based hyperbranched adhesive for high-salt conditions according to claim 1, characterized in that, In step 103, the mass ratio of hyperbranched modified monomer to natural lignin raw material is 1:3 to 1:1; by adjusting the mass ratio, the density of hydrophilic end groups on the surface of the topological structure is controlled so that the initial tack strength of the lignin-based hyperbranched adhesive in a saturated saline environment is not less than 1.5 MPa.

9. The production process of a lignin-based hyperbranched adhesive for high-salt conditions according to claim 1, characterized in that, The pH of the aqueous medium is adjusted to 10 to 12; by utilizing the solubility properties of the alkaline environment on natural lignin raw materials, and in conjunction with the instantaneous high temperature of the local reaction window, the activation efficiency of the crosslinking agent on the phenolic hydroxyl groups in the natural lignin raw materials is improved.

10. The production process of a lignin-based hyperbranched adhesive for high-salt conditions according to claim 1, characterized in that, The production process also includes a post-processing step: vacuum devolatilization of the obtained lignin-based hyperbranched adhesive and adjustment of the solid content of the lignin-based hyperbranched adhesive to 40% to 60%.

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