Preparation method of environment-friendly formaldehyde-free glue

Abstract

The invention relates to the technical field of environment-friendly glue, in particular to a preparation method of environment-friendly formaldehyde-free glue, which comprises the following steps: when a first mixed solution is prepared, monitoring light transmittance, and dynamically adjusting heating power or stirring rate to prepare a second mixed solution; furthermore, batch performance fluctuation and product defects caused by uneven initial mixing are reduced; when the first glue solution is prepared from the second mixed solution, the first viscosity change rate is monitored, and the alkali liquor adding rate or the emulsion adding rate is dynamically adjusted to prepare the second glue solution, so that the bonding strength and the stability of the final glue are improved; when the formaldehyde-free glue is prepared from the second glue solution, second viscosity change rate monitoring is performed, and the addition rate of the cross-linking agent is dynamically adjusted to prepare the formaldehyde-free glue, so that the formaldehyde-free glue which does not contain formaldehyde and is excellent and stable in comprehensive performance is obtained. According to the invention, the quality uniformity and high quality of the glue finished product can be ensured by adjusting the preparation parameters in real time.

Description

Technical Field

[0001] This invention relates to the field of environmentally friendly adhesives, and in particular to a method for preparing an environmentally friendly formaldehyde-free adhesive. Background Technology

[0002] With increasing public awareness of health and environmental protection, the residue and release of toxic and harmful substances such as formaldehyde in interior decoration materials, especially engineered wood products and their adhesives, have attracted much attention. Formaldehyde has been identified as a carcinogen by the World Health Organization, and long-term exposure can cause serious damage to the human respiratory and immune systems. Therefore, the development and application of truly environmentally friendly "formaldehyde-free adhesives" has become an urgent need for the industry.

[0003] Currently, several formaldehyde-free adhesive technologies have emerged in the market aimed at replacing traditional urea-formaldehyde and phenolic adhesives. Chinese Patent Publication No. CN115820208A discloses a process for preparing formaldehyde-free adhesive. This process involves mixing plant protein glue, vinyl acetate copolymer emulsion, water-soluble polyvinyl alcohol, and water-based high-molecular-weight isocyanate in a mixer to obtain raw material A; then crushing and grinding borax into powder, adding water glass, and mixing and grinding again to obtain raw material B; mixing raw material A and raw material B, and then sequentially adding a water-retaining agent, defoamer, flame retardant powder, preservative, and thickener to prepare the final adhesive product. This technology, by introducing bio-based raw materials, eliminates the generation of formaldehyde and benzene-based organic solvents at the source, aligning with environmental trends. However, this technology lacks real-time monitoring and analysis of the adhesive preparation process, making it impossible to ensure the stability and viscosity of the produced adhesive. This results in high production costs and difficulty in guaranteeing the uniformity of the final adhesive product.

[0004] Therefore, there is an urgent need for an environmentally friendly, formaldehyde-free adhesive preparation method that can monitor the preparation process in real time to ensure that the quality of the prepared adhesive meets expectations and that the production cost is low. Summary of the Invention

[0005] Therefore, this invention provides a method for preparing an environmentally friendly formaldehyde-free adhesive, which solves the problem that the existing technology lacks a process for real-time monitoring and analysis of the formaldehyde-free adhesive preparation process, resulting in high production costs and difficulty in ensuring the quality uniformity of the final adhesive product.

[0006] To achieve the above objectives, the present invention provides a method for preparing an environmentally friendly formaldehyde-free adhesive, comprising: Plant-based protein powder, polyvinyl alcohol, and water were added to a reaction vessel, heated, and stirred to obtain a first mixture. The transmittance of the first mixture during the heating and stirring process was monitored to determine the transmittance of the first mixture. The heating power or stirring rate during the heating and stirring process is adjusted in real time based on the light transmittance. After adjusting the heating power or stirring rate, a second mixture is prepared, and an alkaline solution and a vinyl acetate copolymer emulsion are added to the second mixture at a preset rate for modification and compounding. During the addition of alkali solution and vinyl acetate copolymer emulsion, the first viscosity change rate corresponding to the second mixture is monitored, and the alkali solution addition rate or emulsion addition rate is adjusted in real time based on the first viscosity change rate to obtain the first adhesive solution. The corresponding viscosity of the first adhesive, the corresponding viscosity of the second mixture, and the adjusted alkali addition rate or emulsion addition rate are obtained to determine the initial addition rate of the crosslinking agent. A crosslinking agent is added to the first adhesive solution at the initial addition rate to perform gelation treatment, and the second viscosity change rate of the first adhesive solution is monitored during the addition process. The addition rate of the crosslinking agent is adjusted in real time based on the second viscosity change rate to prepare formaldehyde-free adhesive.

[0007] Furthermore, the process of adjusting the heating power or stirring rate in real time during the heating and stirring process based on the transmittance includes: Based on the comparison result of the transmittance and the transmittance threshold, the heating power or the stirring rate in the current preparation process of the first mixture is adjusted in real time, wherein, If the transmittance is less than or equal to the lower limit of the transmittance threshold, determine and obtain the fluid heat change curve and fluid shear change curve corresponding to the preparation process of the first mixture, and increase the heating power and increase the stirring rate based on the fluid heat change curve and the fluid shear change curve. If the light transmittance is greater than the upper limit of the light transmittance threshold and the duration is greater than the preset duration, it is determined to reduce the heating power and the stirring rate.

[0008] Furthermore, the process of increasing the heating power based on the fluid heat change curve and increasing the stirring rate based on the fluid shear change curve includes: Based on the fluid heat change curve, several instantaneous heat slopes are determined, and the absolute value of the mean is calculated to obtain the mean heat slope. Based on the comparison between the mean heat slope and the preset mean heat slope, the increase in heating power is determined. Based on the fluid shear change curve, several instantaneous shear slopes are determined, and the absolute value of the mean is calculated to obtain the mean shear slope. Based on the comparison between the mean shear slope and the preset mean shear slope, the increase in the stirring rate is determined.

[0009] Furthermore, the process of reducing the heating power and the stirring rate includes: The reduction range of the heating power and the stirring rate is determined based on the comparison between the light transmittance difference and the preset light transmittance difference, wherein the reduction range of the heating power and the stirring rate are both positively correlated with the light transmittance difference. Wherein, the transmittance difference is the difference between the transmittance and the upper limit of the transmittance threshold.

[0010] Furthermore, the process of adjusting the alkali addition rate or emulsion addition rate in real time based on the first viscosity change rate includes: During the preparation of the first adhesive, the first viscosity values ​​of the second mixture at several first time points are collected to plot the first viscosity change curve, and the first viscosity change rate during the preparation process is determined based on the first viscosity change curve. Based on the comparison between the first viscosity change rate and the first viscosity change threshold, the alkali addition rate or the emulsion addition rate during the preparation of the first adhesive solution are adjusted in real time, wherein... If the first viscosity change rate is less than the lower limit of the first viscosity change threshold, determine to increase the alkali addition rate; If the first viscosity change rate is greater than the upper limit of the first viscosity change threshold, the emulsion addition rate is reduced.

[0011] Furthermore, the process of increasing the rate of alkali addition includes, The alkali addition rate is increased based on the comparison between the first viscosity change difference and the preset first viscosity change difference. Wherein, the first viscosity change difference is the difference between the lower limit of the first viscosity change threshold and the first viscosity change rate, and the increase in the alkali addition rate is positively correlated with the first viscosity change difference; The process of reducing the emulsion addition rate includes, The emulsion addition rate is reduced based on the comparison result between the second viscosity change difference and the preset second viscosity change difference; Wherein, the second viscosity change difference is the difference between the first viscosity change rate and the upper limit of the first viscosity change threshold, and the decrease in the emulsion addition rate is positively correlated with the second viscosity change difference.

[0012] Furthermore, the process of adjusting the addition rate of the crosslinking agent in real time based on the second viscosity change rate includes: In the preparation process of the formaldehyde-free adhesive, the second viscosity values ​​of the first adhesive at several second time points are collected to plot the second viscosity change curve, and the second viscosity change rate in the preparation process is determined based on the second viscosity change curve. The addition rate of the crosslinking agent in the preparation process of the formaldehyde-free adhesive is adjusted in real time based on the comparison result between the second viscosity change rate and the second viscosity change threshold. If the second viscosity change rate is less than the lower limit of the second viscosity change threshold, determine to increase the addition rate; If the second viscosity change rate is greater than the upper limit of the second viscosity change threshold, the addition rate is determined to be reduced.

[0013] Furthermore, the process of increasing the addition rate includes: The addition rate of the crosslinking agent is increased based on the comparison between the third viscosity change difference and the preset third viscosity change difference. The third viscosity change difference is the difference between the lower limit of the second viscosity change threshold and the second viscosity change rate, and the increase in the addition rate is positively correlated with the third viscosity change difference.

[0014] Furthermore, the process of reducing the addition rate includes: The addition rate is reduced based on the comparison result between the fourth viscosity change difference and the preset fourth viscosity change difference; The fourth viscosity change difference is the difference between the second viscosity change rate and the upper limit of the second viscosity change threshold, and the decrease in the addition rate is positively correlated with the fourth viscosity change difference.

[0015] Further, the components of each raw material by weight are as follows: 25 parts of the plant-based protein powder, 10 parts of the polyvinyl alcohol, 37 parts of the water, 4 parts of the alkaline solution, 20 parts of the vinyl acetate copolymer emulsion, and 2.5 parts of the crosslinking agent.

[0016] Compared with existing technologies, the beneficial effects of the preparation method of the environmentally friendly formaldehyde-free adhesive of the present invention are as follows: During the preparation of the first mixture, transmittance is monitored, and the heating power or stirring rate is dynamically adjusted to prepare the second mixture, thereby reducing batch performance fluctuations and product defects caused by uneven initial mixing; during the preparation of the first adhesive from the second mixture, a first viscosity change rate is monitored, and the alkali addition rate or emulsion addition rate is dynamically adjusted to prepare the first adhesive, thereby improving the bonding strength and stability of the final adhesive; during the preparation of the formaldehyde-free adhesive from the first adhesive, a second viscosity change rate is monitored, and the crosslinking agent addition rate is dynamically adjusted based on the monitoring results to prepare a formaldehyde-free adhesive with excellent and stable comprehensive performance. This preparation method can ensure both the production cost of the final adhesive product and the uniformity and high quality of the finished adhesive.

[0017] Furthermore, this invention also adjusts the heating power or stirring rate in real time based on the comparison between light transmittance and light transmittance threshold. When it is determined that the heating power needs to be increased, the fluid heat change curve is acquired and the corresponding average heat slope is determined. Then, based on the comparison between the average heat slope and the preset average heat slope, the increase in heating power is accurately determined. When it is determined that the stirring rate needs to be increased, the fluid shear change curve is acquired and the corresponding average shear slope is determined. Then, based on the comparison between the average shear slope and the preset average shear slope, the increase in stirring rate is accurately determined. When it is determined that the heating power and stirring rate need to be reduced, the light transmittance difference is acquired and compared with the preset light transmittance difference, and combined with the comparison between the duration and the preset duration, to accurately determine the reduction in heating power and stirring rate. This ensures the high uniformity and batch consistency of the initial material mixing, actively avoids the risk of insufficient mixing, local overheating, or excessive shearing, and improves the quality stability of the final adhesive.

[0018] Furthermore, the present invention also adjusts the alkali addition rate or emulsion addition rate in real time based on the comparison between the first viscosity change rate and the first viscosity change threshold; when it is determined that the alkali addition rate needs to be increased, the first viscosity change difference is obtained and compared with a preset first viscosity change difference, thereby accurately determining the increase in the alkali addition rate; when it is determined that the emulsion addition rate needs to be decreased, the second viscosity change difference is obtained and compared with a preset second viscosity change difference, thereby accurately determining the decrease in the emulsion addition rate; thus, it is possible to adjust the viscosity growth rate during the preparation of the first adhesive so that the reaction state of the first adhesive reaches a relatively ideal state.

[0019] Furthermore, the present invention also adjusts the addition rate of the crosslinking agent in real time based on the comparison between the second viscosity change rate and the second viscosity change threshold; when it is determined that the addition rate of the crosslinking agent needs to be increased, a third viscosity change difference is obtained and compared with a preset third viscosity change difference to accurately determine the increase in the crosslinking agent; when it is determined that the addition rate of the crosslinking agent needs to be decreased, a fourth viscosity change difference is obtained and compared with a preset fourth viscosity change difference to accurately determine the decrease in the crosslinking agent; in this way, the viscosity growth rate during the preparation process of formaldehyde-free adhesive can be adjusted so that the crosslinking reaction is stable and controlled, thereby ensuring that the final adhesive product has excellent performance and batch stability. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the preparation method of the environmentally friendly formaldehyde-free adhesive in an embodiment of the present invention; Figure 2 This is a schematic diagram of the modules used to implement the preparation method of environmentally friendly formaldehyde-free adhesive in an embodiment of the present invention; Figure 3This is a logic diagram for adjusting heating power or stirring rate based on the comparison result of light transmittance and light transmittance threshold in an embodiment of the present invention. Figure 4 This is a logic diagram for adjusting the alkali addition rate or emulsion addition rate based on the comparison result between the first viscosity change rate and the first viscosity change threshold in an embodiment of the present invention. Figure 5 This is a logic diagram showing how the addition rate of the crosslinking agent is adjusted based on the comparison between the second viscosity change rate and the second viscosity change threshold in an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0022] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0023] It should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0024] In this embodiment, the components of each raw material by weight are as follows: 25 parts plant-based protein powder, 10 parts polyvinyl alcohol, 37 parts water, 4 parts alkali solution, 20 parts vinyl acetate copolymer emulsion, and 2.5 parts crosslinking agent. Parts by weight refers to a dimensionless unit expressing the relative mass ratio between components. The ratio of plant-based protein powder:polyvinyl alcohol:water is 25:10:37, meaning that if 25 grams of plant-based protein powder is used in the formula, then 10 grams of polyvinyl alcohol and 37 grams of water should be used accordingly. The actual mass can be scaled up or down proportionally as needed.

[0025] In other embodiments, 1.5 parts of thickener and 0.5 parts of defoamer are added for final adjustment to eliminate bubbles or pores generated during the preparation of the formaldehyde-free adhesive.

[0026] The plant-based protein powder can be at least one of soybean gum or corn protein gum; polyvinyl alcohol is used as the adhesive matrix or protective colloid; the alkali solution is sodium hydroxide solution or sodium silicate solution; the vinyl acetate copolymer emulsion is obtained by copolymerizing vinyl acetate with ethylene / acrylate; the crosslinking agent is water-based isocyanate or aziridine crosslinking agent; and the thickener is a water-based polyacrylic acid thickener.

[0027] Please see Figure 1 The diagram shown is a schematic flowchart of the preparation method of the environmentally friendly formaldehyde-free adhesive in an embodiment of the present invention. The process includes at least the following steps: S1: Add plant-based protein powder, polyvinyl alcohol and water to a reaction vessel, heat and stir to obtain the first mixture; S2: Monitor to determine the transmittance of the first mixture during the heating and stirring process; S3: Adjust the heating power or stirring rate in real time during the heating and stirring process based on light transmittance; S4: After adjusting the heating power or stirring rate, a second mixture is prepared, and alkali solution is added for modification and vinyl acetate copolymer emulsion is added for compounding. S5: During the addition of alkaline solution and vinyl acetate copolymer emulsion, monitor the first viscosity change rate corresponding to the second mixture; S6: Adjust the alkali addition rate or emulsion addition rate in real time based on the first viscosity change rate to obtain the first adhesive solution; S7: Obtain the corresponding viscosity of the first adhesive, the corresponding viscosity of the second mixture, and the adjusted alkali addition rate or emulsion addition rate to determine the initial addition rate of the crosslinking agent. S8: Add crosslinking agent to the first adhesive solution at the initial addition rate for gelation treatment, and monitor the second viscosity change rate of the first adhesive solution during the addition process; S9: Adjust the addition rate of the crosslinking agent in real time based on the second viscosity change rate to prepare formaldehyde-free adhesive.

[0028] Please see Figure 2 As shown, this is a schematic diagram of the modules used in an embodiment of the present invention for implementing an environmentally friendly formaldehyde-free adhesive preparation method, including a preparation module, a data acquisition module, a reaction control module, and a process execution module, wherein... The preparation module includes a mixing reaction unit, a modification and compounding unit, and a gelling treatment unit. The mixing reaction unit performs step S1, receiving plant-based protein powder, polyvinyl alcohol, and water from a material conveying system, and heating and stirring them in a reaction vessel to obtain a first mixture. The heating and stirring of the first mixture are then adjusted to obtain a second mixture. The modification and compounding unit performs step S4, receiving the first mixture from the first mixing reaction unit and sequentially performing alkali modification and emulsion compounding to obtain a first adhesive. The gelling treatment unit performs step S7, receiving the first adhesive from the modification and compounding unit and adding a crosslinking agent at the initial addition rate for gelling treatment, ultimately preparing a formaldehyde-free adhesive. The data acquisition module, connected to the preparation module, includes an optical sensing unit, a flow meter, and a viscosity sensing unit. The optical sensing unit performs step S2, monitoring the transmittance of the first mixture in real time during heating and stirring. The flow meter performs step S4, detecting the alkali addition rate or emulsion addition rate in real time during modification and compounding. The viscosity sensing unit performs steps S5 and S8, respectively, monitoring the viscosity data of the second mixture and the first adhesive in real time during the preparation process. The reaction control module, connected to the data acquisition module, is used to execute steps S3, S6, and S9. Specifically, based on the real-time transmittance feedback from the data acquisition module, calculations and judgments are performed to generate a first control command for adjusting the heating power or stirring rate to ensure the homogenization reaction process of the first mixture. Based on the viscosity data feedback from the data acquisition module, a first viscosity change rate is calculated in real-time, and calculations and judgments are performed to generate a second control command for adjusting the addition rate of alkali solution or vinyl acetate copolymer emulsion to precisely control the modified compounding reaction process. Based on the viscosity information feedback from the data acquisition module, a second viscosity change rate is calculated in real-time, and calculations and judgments are performed to generate a third control command for adjusting the addition rate of the crosslinking agent to ultimately ensure that the adhesive performance meets the standards. The initial addition rate of the crosslinking agent can be calculated based on the viscosity information corresponding to the first adhesive, the viscosity information corresponding to the second mixture, and the adjusted alkali solution addition rate or emulsion addition rate feedback from the data acquisition module. The process execution module is connected to the reaction control module and the preparation module, and includes a first execution unit, a second execution unit, and a third execution unit. The first execution unit dynamically adjusts the heating power of the heating mechanism and the stirring rate of the stirring mechanism in the mixing reaction unit according to a first control command. The second execution unit precisely controls the rate of the first metering pump adding alkali solution to the modified compounding unit and the rate of the second metering pump adding vinyl acetate copolymer emulsion according to a second control command. The second execution unit precisely controls the rate of the third metering pump adding crosslinking agent to the gelation treatment unit according to a third control command. In other embodiments, a fourth metering pump rate for adding thickener is also provided; controlling the addition rate of the fourth metering pump for adding thickener to the first adhesive solution enhances the viscosity of the formaldehyde-free adhesive.

[0029] The optical sensing unit includes a photoelectric sensor or a near-infrared spectral probe. A light beam is emitted from a light source and passes through the first mixture. The receiver detects the intensity of the transmitted light to determine the transmittance B. The viscosity sensing unit includes a rotary (or vibratory) viscometer. The probe is immersed in the second mixture and the first adhesive solution. The viscosity data is directly calculated by measuring the torque required to maintain a constant rotational speed (or constant amplitude vibration).

[0030] Please see Figure 3 As shown, this is a logic diagram for adjusting heating power or stirring rate based on the comparison result of transmittance and transmittance threshold in an embodiment of the present invention. Specifically, a transmittance threshold B0 is set and compared with transmittance B. Based on the comparison result, the heating power or stirring rate can be adjusted accurately and correspondingly, thereby more precisely intervening in the preparation process of the first mixture, thus achieving protective adjustment and energy-saving optimization. Based on the specific material system, glue process target, and detection method, and through preliminary experimental optimization, the range of transmittance threshold B0 is exemplarily set to 78% to 85%, and the corresponding lower limit B1 = 78% and the corresponding upper limit B2 = 85% in the transmittance threshold B0. The comparison process based on transmittance B with B1 and B2 is as follows: If B is less than B1, it is determined that the components in the first mixture are not sufficiently dissolved and dispersed, resulting in turbidity of the solution and strong scattering of light, thus causing a low transmittance B. In this case, the transmittance B can be improved by increasing the heating power to promote molecular thermal motion or by increasing the stirring rate to break up particle agglomerates. Specifically, the fluid heat change curve during heating and the fluid shear change curve during stirring of the first mixture are obtained during the preparation process. Then, the heating power of the heating mechanism is adjusted based on the fluid heat change curve, and the stirring rate of the stirring mechanism is adjusted based on the fluid shear change curve.

[0031] If B is greater than B2, it is determined that the solution in the first mixture is too clear, resulting in a high light transmittance and thus a high transmittance B. When the transmittance B is high, local overheating or excessive shearing of the first mixture is likely to occur. Therefore, it is necessary to reduce the heating power or stirring rate for protective intervention, thereby reducing thermal damage and energy waste. When determining whether to reduce the heating power or stirring rate, it is also necessary to compare the duration with the preset duration. The duration refers to the time required for the first mixture to remain stable after monitoring that the corresponding B is greater than B2 during the preparation of the first mixture. A preset duration is set and compared with the duration as a dual judgment condition. While B is greater than B2, the duration must also be greater than the preset duration. This indicates that there is a risk of overheating or excessive shearing in the current preparation process. Therefore, it is necessary to reduce the heating power and simultaneously reduce the stirring rate to avoid denaturation of plant-based protein powder or degradation of polyvinyl alcohol molecular chains due to continuous overheating, or to prevent damage to the formed colloidal network structure due to excessive and unnecessary mechanical shearing force. This ensures the bonding strength, stability, and durability of the final formaldehyde-free adhesive.

[0032] The preset duration is set based on two principles: first, it must be able to filter out normal signal fluctuations caused by the transient mixing of the first mixture or detection noise to avoid false alarms; second, it must be shorter than the time it takes for the first mixture to begin to deteriorate under substandard process conditions to ensure timely intervention. For example, the preset duration can be set to 3 minutes, which can reliably avoid misjudgment and ensure that process adjustment is completed before substantial damage to material properties occurs.

[0033] If B is greater than or equal to B1 and less than or equal to B2, it is determined that the dissolution and dispersion process in the preparation of the first mixture has reached the optimal state. At this time, the process execution module maintains the current heating power and stirring rate.

[0034] Specifically, during the preparation stage of the first mixture, the data acquisition module acquires data once per second. This module includes an immersion PT100 temperature sensor and an online rheometer. The immersion PT100 temperature sensor obtains the real-time temperature of the first mixture, and the online rheometer... The shear rate of the first mixture during flow is obtained. The data acquisition module continuously collects data for 2 minutes, totaling 120 data points. The real-time temperature is multiplied by the total heat capacity of the first mixture to obtain the real-time heat value, thereby generating a fluid heat change curve. At the same time, the shear rate generated by the first mixture under the action of the stirring mechanism is directly used as a variable reflecting the mechanical rotation intensity of the first mixture to generate a fluid shear change curve.

[0035] Based on the fluid heat change curve, with each 15-second time window (i.e., 15 data points), the instantaneous heat slope within this window is calculated using linear least squares fitting. Its physical meaning is the rate of change of system heat per unit time; a positive value indicates heat release, and a negative value indicates heat absorption. Eight instantaneous heat slopes are calculated consecutively, and the arithmetic mean of the absolute values ​​of all slopes is obtained as the mean heat slope K. This mean K reflects the average drastic degree of heat change within that time period; the smaller K is, the more gradual the heat change and the less kinetic the dissolution. Through previous process optimization experiments, it was determined that when the dissolution and dispersion processes are in an ideal state, the average rate of heat change should be stable within a specific range. Therefore, a preset mean heat slope K0 is determined. When the transmittance B is less than the lower limit B1 of the transmittance threshold B0, the increase in heating power of the heating mechanism is determined based on the comparison between the mean heat slope K and the preset mean heat slope K0.

[0036] In one specific embodiment, in order to more accurately determine the increase in heating power, the preset average heat slope K0 can be divided into a first preset average heat slope K1 and a second preset average heat slope K2. For example, K1 = 0.03 kW / s and K2 = 0.05 kW / s are set. Then, the comparison process between the average heat slope K and K1 and K2 is as follows: If K is less than or equal to K1, a first heating power adjustment command is generated, determining to increase the heating power of the heating mechanism by 600W based on the original heating power. For a mixing system with a total volume of 100L, the initial heating power of the heating mechanism is exemplarily set to 20kW, then the increased heating power is 20.6kW. If K is greater than K1 and less than or equal to K2, a second heating power adjustment command is generated, determining to increase the heating power of the heating mechanism by 400W based on the original heating power. If K is greater than K2, a third heating power adjustment command is generated, determining to increase the heating power of the heating mechanism by 300W based on the original heating power. The more drastic the heat change of the first mixture, the weaker the corresponding increase in heating power needs to be.

[0037] Simultaneously, the fluid shear change curves were subjected to the same windowing process (every 15 seconds), and the instantaneous shear slope within each window was calculated. The arithmetic mean of the absolute values ​​of the eight instantaneous shear slopes was also calculated to obtain the mean shear slope W. This mean W characterizes the stability of the hybrid dynamic state during stirring; the larger W is, the more unstable the stirring state of the first mixture. Similarly, a preset mean shear slope W0 was determined through previous process optimization experiments. When the transmittance B is greater than the upper limit B2 of the transmittance threshold B0, the increase in the stirring power of the stirring mechanism was determined based on the comparison between the mean shear slope W and the preset mean shear slope W0.

[0038] In one specific embodiment, to more accurately determine the increase in stirring rate, the preset average shear slope W0 can be divided into a first preset average shear slope W1 and a second preset average shear slope W2, with W1 exemplarily set to 0.35s. -2 W2 = 0.5s -2 The comparison process based on the mean shear slope W with W1 and W2 is as follows: If W is less than or equal to W1, a first stirring rate adjustment command is generated, determining to increase the stirring rate of the stirring mechanism by 8 rpm. For a mixing system with a total volume of 100L, the initial stirring rate of the stirring mechanism is exemplarily set to 60 rpm, so the increased stirring rate is 68 rpm. If W is greater than W1 and less than or equal to W2, a second stirring rate adjustment command is generated, increasing the stirring rate of the stirring mechanism by 5 rpm. If W is greater than W2, a third stirring rate adjustment command is generated, increasing the stirring rate of the stirring mechanism by 3 rpm. The more violent the rotational fluctuations of the first mixture, the weaker the corresponding increase in stirring rate needs to be.

[0039] Specifically, the transmittance difference F is the difference between transmittance B and the upper limit B2 of the transmittance threshold B0. When the transmittance difference F is larger, the corresponding transmittance B is also larger, which indicates that the risk of local overheating or excessive shearing in the current preparation stage is greater. The heating mechanism needs to reduce the heating power to a greater extent, and the stirring mechanism also needs to reduce the stirring rate to a greater extent. Therefore, the heating power and stirring rate decrease as the transmittance difference F increases.

[0040] In one specific embodiment, a preset transmittance difference value F0 is set and compared with a transmittance difference value F. Based on the comparison result, the reduction range of the heating power of the heating mechanism and the reduction range of the stirring rate of the stirring mechanism are determined. The preset transmittance difference value F0 is divided into a first preset transmittance difference value F1 and a second preset transmittance difference value F2. For example, F1=3% and F2=6%. Based on the comparison between F and F1 and F2, when F is less than or equal to F1, a fourth heating power adjustment command is generated, determining that the heating power of the heating mechanism is reduced by 150W from the original heating power. For a mixing system with a total volume of 100L, the initial heating power of the heating mechanism is set to 20kW, and the reduced heating power is 20.15kW. When F is greater than F1 and less than or equal to F2, a fifth heating power adjustment command is generated, determining that the heating power of the heating mechanism is reduced by 300W from the original heating power. When F is greater than F2, a sixth heating power adjustment command is generated, determining that the heating power of the heating mechanism is reduced by 500W from the original heating power.

[0041] Simultaneously, when F is less than or equal to F1, a fourth stirring rate adjustment command is generated, determining to reduce the stirring rate of the stirring mechanism by 3 rpm from its original stirring rate; whereby, if the initial stirring rate of the stirring mechanism is exemplarily set to 60 rpm, the reduced stirring rate is 57 rpm. When F is greater than F1 and less than or equal to F2, a fifth stirring rate adjustment command is generated, determining to reduce the stirring rate of the stirring mechanism by 5 rpm from its original stirring rate. When F is greater than F2, a sixth stirring rate adjustment command is generated, determining to reduce the stirring rate of the stirring mechanism by 7 rpm from its original stirring rate.

[0042] It should be noted that adjusting the heating power or stirring rate will not negatively affect the preparation process of the second mixture, and the adjustment range is within a safe and controllable range. The commands for adjusting the heating power and the commands for adjusting the stirring rate are both first control commands. It is understood that the increase or decrease in heating power and the increase or decrease in stirring rate can also be set to other acceptable values ​​to ensure that the transmittance B is effectively changed, thereby achieving a level greater than or equal to the lower limit B1 and less than or equal to the upper limit B2.

[0043] Please see Figure 4 As shown, this is a logic diagram for adjusting the alkali addition rate or emulsion addition rate based on the comparison result of the first viscosity change rate and the first viscosity change threshold in an embodiment of the present invention. Specifically, during the preparation of the first adhesive, the preparation process is monitored by a data acquisition module, which can collect the first viscosity values ​​of the second mixture at several first time points. The module can be set to collect the first viscosity value every two seconds, collecting 20 first viscosity values. The reaction control module plots a first viscosity change curve based on the 20 collected first viscosity values, and then uses the least squares method to determine a fitted straight line with the smallest overall error compared to all data points. Based on the slope of this fitted straight line, the corresponding first viscosity change rate H is determined. A first viscosity change threshold H0 is then set and compared with the first viscosity change rate H to adjust the alkali addition rate or emulsion addition rate in real time.

[0044] The first viscosity change threshold H0 was determined through preliminary process experiments. This first viscosity change threshold H0 includes a lower limit H1 and an upper limit H2, which are set as an example. ,in, This represents the rate of viscosity change over time; the comparison process based on the first viscosity change rate H with H1 and H2 is as follows: If H is less than H1, it means that the viscosity growth rate is relatively slow when preparing the first emulsion. This indicates that the current reaction system is not active enough and the alkali modification reaction is not sufficient. It cannot provide enough active sites or a suitable reaction environment for subsequent emulsion copolymerization. Therefore, it is necessary to increase the alkali addition rate to improve the alkali modification reaction while keeping the emulsion addition rate constant.

[0045] If H is greater than H2, it means that the viscosity growth rate is relatively fast when preparing the first emulsion. This indicates that the current reaction is too vigorous and there is a risk of gelation. The excessively rapid viscosity growth is due to excessive denaturation and aggregation of proteins caused by excessive alkali, or the emulsion participating in cross-linking too quickly in an overly active system. Therefore, it is necessary to reduce the emulsion addition rate to reduce the amount of polymerizable monomers entering the reaction system, moderate the copolymerization rate, and keep the alkali addition rate constant.

[0046] If H is greater than or equal to H1 and less than or equal to H2, the reaction state in the current preparation of the first adhesive solution is considered to be relatively ideal, and the current alkali addition rate and emulsion addition rate are maintained.

[0047] In one specific embodiment, a preset first viscosity change difference Y0 is set and compared with the first viscosity change difference Y to determine the adjustment range of the alkali addition rate. The first viscosity change difference Y is the difference between the lower limit H1 of the first viscosity change threshold and the first viscosity change rate H. When the first viscosity change difference Y is larger, the corresponding first viscosity change rate H is smaller, which indicates that the viscosity growth rate is slower when preparing the first adhesive. At this time, a larger alkali addition rate is required to improve the alkali modification reaction. Therefore, the increase in the alkali addition rate increases with the increase of the first viscosity change difference Y.

[0048] To more accurately determine the increase in the alkali addition rate, the preset first viscosity change difference Y0 can be divided into a first preset first viscosity change difference Y1 and a second preset first viscosity change difference Y2, as exemplarily set. The comparison process based on the first viscosity change difference Y with Y1 and Y2 is as follows: If Y is less than or equal to Y1, a first alkali addition rate adjustment command is generated, and the first metering pump is controlled to increase its addition rate by 5% based on the original rate; where the original addition rate of the first metering pump is 50 ml / min, the increased addition rate is 52.5 ml / min. If Y is greater than Y1 and less than or equal to Y2, a second alkali addition rate adjustment command is generated, and the first metering pump is controlled to increase its addition rate by 10% based on the original rate. If Y is greater than Y2, a third alkali addition rate adjustment command is generated, and the first metering pump is controlled to increase its addition rate by 15% based on the original rate.

[0049] In one specific embodiment, a preset second viscosity change difference value R0 is also set and compared with the second viscosity change difference value R to determine the adjustment range of the reduction in the emulsion addition rate. The second viscosity change difference value R is the difference between the first viscosity change rate H and the upper limit value H2 of the first viscosity change threshold. When the second viscosity change difference value R is larger, the corresponding first viscosity change rate H is larger, which indicates that the viscosity growth rate is faster when preparing the first adhesive. In order to avoid the risk of gelation, a smaller emulsion addition rate is required to mitigate the copolymerization reaction. Therefore, the reduction range of the emulsion addition rate increases with the increase of the second viscosity change difference value R.

[0050] To more accurately determine the reduction in the emulsion addition rate, the preset second viscosity change difference R0 can be divided into a first preset second viscosity change difference R1 and a second preset second viscosity change difference R2, as exemplarily set. The comparison process based on the second viscosity change difference R with R1 and R2 is as follows: If R is less than or equal to R1, a first emulsion addition rate adjustment command is generated, and the second metering pump is controlled to reduce its addition rate by 6% from the original rate; where the original addition rate of the second metering pump is 200 ml / min, the reduced addition rate is 188 ml / min. If R is greater than R1 and less than or equal to R2, a second emulsion addition rate adjustment command is generated, and the second metering pump is controlled to reduce its addition rate by 8% from the original rate. If R is greater than R2, a third emulsion addition rate adjustment command is generated, and the second metering pump is controlled to reduce its addition rate by 15% from the original rate.

[0051] It should be noted that adjusting the alkali addition rate or emulsion addition rate will not negatively affect the preparation process of the first adhesive, and the adjustment range is within a safe and controllable range. The instructions used to adjust the alkali addition rate and emulsion addition rate are both secondary control instructions. It is understood that the adjustment range for increasing the alkali addition rate and decreasing the emulsion addition rate can also be set to other suitable values ​​to ensure that the first viscosity change rate H can be adjusted to be greater than or equal to H1 and less than or equal to H2.

[0052] Please see Figure 5As shown, this is a logic decision diagram for adjusting the addition rate of the crosslinking agent based on the comparison result of the second viscosity change rate and the second viscosity change threshold in an embodiment of the present invention. Specifically, in the preparation process of formaldehyde-free adhesive, the preparation process is also monitored by a data acquisition module, which can collect the second viscosity values ​​of the first adhesive at several second time nodes. Specifically, the second viscosity value is collected every two seconds, and 20 second viscosity values ​​are collected. The reaction control module plots a second viscosity change curve based on the 20 collected second viscosity values, and then uses the least squares method to determine a fitting straight line with the smallest overall error with all data points. Based on the slope of the fitting straight line, the corresponding second viscosity change rate M is determined. Then, a second viscosity change threshold M0 is set and compared with the second viscosity change rate M to adjust the addition rate of the crosslinking agent in real time.

[0053] The second viscosity change threshold M0 was determined through preliminary process experiments. This threshold includes a lower limit M1 and an upper limit M2. For example, M1 = 1.2 Pa·s / min and M2 = 1.5 Pa·s / min. The comparison process between M and M1 and M2 is as follows: If M is less than M1, it is determined that the viscosity increase is too slow when preparing formaldehyde-free adhesive, indicating that the crosslinking reaction is insufficient. Therefore, the addition rate of the crosslinking agent can be increased in real time to meet the intermolecular crosslinking point formation rate.

[0054] If M is greater than M2, it is determined that the viscosity increases too quickly when preparing formaldehyde-free adhesive, which poses a risk of uncontrolled gelation. Therefore, the excessively violent reaction can be weakened by reducing the addition rate of the crosslinking agent in real time.

[0055] If M is greater than or equal to M1 and less than or equal to M2, it is determined that the viscosity growth rate is in a relatively stable range when preparing formaldehyde-free adhesive, the crosslinking reaction is stable and controlled, and the initial addition rate of the current crosslinking agent is maintained.

[0056] In one specific embodiment, a preset third viscosity change difference U0 is set and compared with the third viscosity change difference U to determine the increase in the crosslinking agent addition rate. The third viscosity change difference U is the difference between the lower limit M1 of the second viscosity change threshold and the second viscosity change rate M. When the third viscosity change difference U is larger, the corresponding second viscosity change rate M is smaller, which indicates that the viscosity growth rate is slower when preparing formaldehyde-free adhesive. At this time, a faster crosslinking agent addition rate is required to improve the crosslinking reaction progress. Therefore, the adjustment range of the crosslinking agent addition rate increases with the increase of the third viscosity change difference U.

[0057] To more accurately determine the increase in the crosslinking agent addition rate, the preset third viscosity change difference U0 can be divided into a first preset third viscosity change difference U1 and a second preset third viscosity change difference U2. For example, U1 = 0.08 Pa·s / min and U2 = 0.12 Pa·s / min. The comparison process between the third viscosity change difference U0 and U1 and U2 is as follows: If U is less than or equal to U1, a first crosslinking agent addition rate adjustment command is generated, and the third metering pump is controlled to increase its addition rate by 8% based on the initial addition rate; where the initial addition rate of the third metering pump is 30 ml / min, the adjusted addition rate is 32.4 ml / min. If U is greater than U1 and less than or equal to U2, a second crosslinking agent addition rate adjustment command is generated, and the third metering pump is controlled to increase its addition rate by 15% based on the initial addition rate. If U is greater than U2, a third crosslinking agent addition rate adjustment command is generated, and the third metering pump is controlled to increase its addition rate by 23% based on the initial addition rate.

[0058] In one specific embodiment, a preset fourth viscosity change difference value V0 is also set and compared with the fourth viscosity change difference value V to determine the reduction in the crosslinking agent addition rate. Here, the fourth viscosity change difference value V is the difference between the second viscosity change rate M and the upper limit value M2 in the second viscosity change threshold. When the fourth viscosity change difference value V is larger, the corresponding second viscosity change rate M is larger, which indicates that the viscosity increases faster when preparing formaldehyde-free adhesive. At this time, a slower crosslinking agent addition rate is required to weaken the overly violent reaction. Therefore, the reduction in the crosslinking agent addition rate increases with the increase of the fourth viscosity change difference value V.

[0059] To more accurately determine the decrease in the crosslinking agent addition rate, the preset fourth viscosity change difference V0 can be divided into a first preset fourth viscosity change difference V1 and a second preset fourth viscosity change difference V2. For example, V1 = 0.11 Pa·s / min and V2 = 0.17 Pa·s / min. The comparison process between the fourth viscosity change difference V0 and V1 and V2 is as follows: If V is less than or equal to V1, a fourth crosslinking agent addition rate adjustment command is generated, and the third metering pump is controlled to reduce its addition rate by 5% from the initial rate; where the initial addition rate of the third metering pump is 30 ml / min, the adjusted addition rate is 28.5 ml / min. If V is greater than V1 and less than or equal to V2, a fifth crosslinking agent addition rate adjustment command is generated, and the third metering pump is controlled to reduce its addition rate by 8% from the initial rate. If V is greater than V2, a sixth crosslinking agent addition rate adjustment command is generated, and the third metering pump is controlled to reduce its addition rate by 12% from the initial rate.

[0060] It should be noted that adjusting the addition rate of the crosslinking agent will not negatively affect the preparation process of the formaldehyde-free adhesive, and the adjustment range is within a safe and controllable range. The instruction used to adjust the addition rate of the crosslinking agent is the third control instruction. It is understood that the adjustment range for increasing or decreasing the addition rate of the crosslinking agent can also be set to other acceptable values ​​to ensure that the second viscosity change rate M can be adjusted to be greater than or equal to M1 and less than or equal to M2.

[0061] To better illustrate the preparation process of environmentally friendly formaldehyde-free adhesive, the present invention will be further described below with reference to specific embodiments. Example

[0062] During the preparation process, the changes in the first mixture during heating and stirring were monitored in real time to obtain the transmittance of the first mixture, B=75%. Furthermore, by collecting data on several instantaneous heat slopes and calculating the average heat slope K = 0.025 kW / s, a first heating power adjustment command is generated to control the heating mechanism to adjust the heating power; and by collecting data on several instantaneous shear slopes and calculating the average shear slope W = 0.4 s. -2 The second stirring rate adjustment command is generated to control the stirring mechanism to adjust the stirring rate. Furthermore, after adjusting the heating power and stirring rate, several first viscosity values ​​are collected and calculated to obtain the first viscosity change rate H = 0.83 Pa·s / min; the second viscosity change difference R = 0.03 Pa·s / min is then calculated, and a first emulsion addition rate adjustment command is generated to control the second metering pump to adjust the emulsion addition rate. Furthermore, after keeping the alkali addition rate constant and adjusting the emulsion addition rate, several second viscosity values ​​were collected and calculated to obtain the second viscosity change rate M = 1.63 Pa·s / min; the fourth viscosity change difference V = 0.13 Pa·s / min was then calculated, and a fifth crosslinking agent addition rate adjustment command was generated to control the third metering pump to adjust the crosslinking agent addition rate, and finally, formaldehyde-free glue was prepared. Example

[0063] During the preparation process, the changes of the first mixture during heating and stirring were monitored in real time to obtain the transmittance of the first mixture B=81%, and to determine the current heating power and stirring rate to be maintained. Further, data from several first viscosity values ​​are collected and calculated to obtain the first viscosity change rate H = 0.4 Pa·s / min; the first viscosity change difference Y = 0.1 Pa·s / min is then calculated, and a second alkali addition rate adjustment command is generated to control the first metering pump to adjust the alkali addition rate. Furthermore, after keeping the emulsion addition rate constant and adjusting the alkali addition rate, several second viscosity values ​​were collected and calculated to obtain the second viscosity change rate M = 1.15 Pa·s / min; the third viscosity change difference U = 0.05 Pa·s / min was then calculated, and the first crosslinking agent addition rate adjustment command was generated to control the third metering pump to adjust the crosslinking agent addition rate, and finally, formaldehyde-free adhesive was prepared.

[0064] Control group, Example 3: The difference between this and Example 1 lies in the fact that the average heat slope K = 0.025 kW / s and the average shear slope W = 0.4 s were calculated. -2 When the first heating power adjustment command was generated, the second stirring rate adjustment command was not generated; and when the fourth viscosity change difference V=0.13Pa·s / min was calculated, the fifth crosslinking agent addition rate adjustment command was not generated. The rest was the same as in Example 1.

[0065] Control group, Example 4: The difference between this and Example 2 is that when the first viscosity change rate H = 0.4 Pa·s / min was calculated, the first viscosity change difference was not calculated; and when the third viscosity change difference U = 0.05 Pa·s / min was calculated, the first crosslinking agent addition rate adjustment command was not generated. The rest is the same as Example 2.

[0066] Based on the formaldehyde-free adhesive products from Examples 1-4, performance tests were conducted according to the following standard methods: Dry bond strength: Beech veneer plywood was prepared according to GB / T 17657-2013 "Test methods for physical and chemical properties of wood-based panels and veneer wood-based panels", and the dry compressive shear strength was determined.

[0067] Wet bond strength (water resistance): As per the above standard, after immersing the specimen in hot water at (63±2)℃ for 3 hours, the wet compressive shear strength is determined.

[0068] Storage stability: The adhesive was sealed and stored at (25±1)℃ for 30 days, and its viscosity change rate (compared to the initial viscosity) and whether layering or gelation occurred were tested.

[0069] Pot life: The time required for the adhesive to reach 150% of its initial viscosity when left at 25°C.

[0070] Please see Table 1 below for specific data.

[0071] Table 1. Experimental results of Examples 1-4 ; Results analysis: As can be seen from the data in Table 1, the dynamic feedback adjustment method based on transmittance, average thermal slope, average shear slope, first viscosity change rate, and second viscosity change rate in this embodiment has a significant effect on improving the overall performance of formaldehyde-free adhesive.

[0072] Both Examples 1 and 2, employing a complete dynamic adjustment process, exhibited excellent performance across all indicators. Example 1, by real-time adjustment of heating power, stirring rate, vinyl acetate copolymer emulsion addition rate, and crosslinking agent addition rate, achieved optimal control of the reaction process, resulting in the highest dry and wet bond strength, as well as optimal storage stability and pot life, validating the effectiveness of the core control logic of this example. Example 2, after achieving the transmittance target, maintained the initial parameters and dynamically adjusted the alkali addition rate for the first viscosity change rate and the crosslinking agent addition rate for the second viscosity change rate. Its overall performance was slightly lower than Example 1, but still significantly better than the control group, demonstrating the advantage of targeted adjustments based on the actual reaction state.

[0073] The control group, which omitted key dynamic adjustment steps, exhibited significant performance shortcomings. In Example 3, only the heating power was adjusted when changes in heat and shear slope were detected, without adjusting the stirring rate. Furthermore, the addition of crosslinking agent was omitted in the later stages of the reaction, resulting in insufficient mixing uniformity and incomplete final crosslinking network integrity. This manifested as a significant decrease in wet bond strength (water resistance), poor storage stability (significant viscosity increase), and a significantly shortened pot life, demonstrating that precise control of stirring and later crosslinking is crucial for adhesive durability and stability. In Example 4, the alkali addition rate was not adjusted based on the first viscosity change rate in the initial stage of the reaction, and crosslinking agent adjustment was also omitted in the later stages, leading to imprecise control of the reaction process. Its dry strength and pot life were the weakest among the control groups.

[0074] In summary, by fully implementing Examples 1 and 2 of the present invention regarding the preparation method of environmentally friendly formaldehyde-free adhesive, the adhesive synthesis reaction is ensured to be in a highly efficient, uniform, and controllable state, thereby simultaneously improving the bonding strength (especially water resistance) and storage and processing performance (high stability and long pot life) of the final product (formaldehyde-free adhesive), providing a reliable solution for the preparation of high-performance environmentally friendly adhesives.

[0075] Any technologies not mentioned in the above embodiments are applicable to existing technologies.

[0076] It is understood that no specific limitation is made to any preset parameter or critical parameter in the embodiments of the present invention, and the above values ​​are not limited thereto. Those skilled in the art can make corresponding adjustments to the preset parameters or critical parameters according to actual needs, analysis of historical data, or equipment usage.

[0077] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for preparing an environmentally friendly formaldehyde-free adhesive, characterized in that, include: Plant-based protein powder, polyvinyl alcohol, and water were added to a reaction vessel, heated, and stirred to obtain a first mixture. The transmittance of the first mixture during the heating and stirring process was monitored to determine the transmittance of the first mixture. The heating power or stirring rate during the heating and stirring process is adjusted in real time based on the light transmittance. After adjusting the heating power or stirring rate, a second mixture is prepared, and an alkaline solution and a vinyl acetate copolymer emulsion are added to the second mixture at a preset rate for modification and compounding. During the addition of alkali solution and vinyl acetate copolymer emulsion, the first viscosity change rate corresponding to the second mixture is monitored, and the alkali solution addition rate or emulsion addition rate is adjusted in real time based on the first viscosity change rate to obtain the first adhesive solution. The viscosity of the first adhesive, the viscosity of the second mixture, and the adjusted alkali addition rate or emulsion addition rate are obtained to determine the initial addition rate of the crosslinking agent. A crosslinking agent is added to the first adhesive solution at the initial addition rate to perform gelation treatment, and the second viscosity change rate of the first adhesive solution is monitored during the addition process. The addition rate of the crosslinking agent is adjusted in real time based on the second viscosity change rate to prepare formaldehyde-free adhesive.

2. The method for preparing the environmentally friendly formaldehyde-free adhesive according to claim 1, characterized in that, The process of adjusting the heating power or stirring rate in real time based on the transmittance includes: Based on the comparison result of the transmittance and the transmittance threshold, the heating power or the stirring rate in the current preparation process of the first mixture is adjusted in real time, wherein, If the transmittance is less than or equal to the lower limit of the transmittance threshold, determine and obtain the fluid heat change curve and fluid shear change curve corresponding to the preparation process of the first mixture, and increase the heating power and increase the stirring rate based on the fluid heat change curve and the fluid shear change curve. If the light transmittance is greater than the upper limit of the light transmittance threshold and the duration is greater than the preset duration, then the heating power and the stirring rate are reduced.

3. The method for preparing the environmentally friendly formaldehyde-free adhesive according to claim 2, characterized in that, The processes of increasing the heating power based on the fluid heat change curve and increasing the stirring rate based on the fluid shear change curve include: Based on the fluid heat change curve, several instantaneous heat slopes are determined, and the absolute value of the mean is calculated to obtain the mean heat slope. Based on the comparison between the mean heat slope and the preset mean heat slope, the increase in heating power is determined. Based on the fluid shear change curve, several instantaneous shear slopes are determined, and the absolute value of the mean is calculated to obtain the mean shear slope. Based on the comparison between the mean shear slope and the preset mean shear slope, the increase in the stirring rate is determined.

4. The method for preparing the environmentally friendly formaldehyde-free adhesive according to claim 2, characterized in that, The process of reducing the heating power and the stirring rate includes: The reduction range of the heating power and the stirring rate is determined based on the comparison between the light transmittance difference and the preset light transmittance difference, wherein the reduction range of the heating power and the stirring rate are both positively correlated with the light transmittance difference. Wherein, the transmittance difference is the difference between the transmittance and the upper limit of the transmittance threshold.

5. The method for preparing the environmentally friendly formaldehyde-free adhesive according to claim 2, characterized in that, The process of adjusting the alkali addition rate or emulsion addition rate in real time based on the first viscosity change rate includes: During the preparation of the first adhesive, the first viscosity values ​​of the second mixture at several first time points are collected to plot the first viscosity change curve, and the first viscosity change rate during the preparation process is determined based on the first viscosity change curve. Based on the comparison between the first viscosity change rate and the first viscosity change threshold, the alkali addition rate or the emulsion addition rate during the preparation of the first adhesive solution are adjusted in real time, wherein... If the first viscosity change rate is less than the lower limit of the first viscosity change threshold, determine to increase the alkali addition rate; If the first viscosity change rate is greater than the upper limit of the first viscosity change threshold, the emulsion addition rate is reduced.

6. The method for preparing the environmentally friendly formaldehyde-free adhesive according to claim 5, characterized in that, The process of increasing the alkaline solution addition rate includes, The alkali addition rate is increased based on the comparison between the first viscosity change difference and the preset first viscosity change difference. Wherein, the first viscosity change difference is the difference between the lower limit of the first viscosity change threshold and the first viscosity change rate, and the increase in the alkali addition rate is positively correlated with the first viscosity change difference; The process of reducing the emulsion addition rate includes, The emulsion addition rate is reduced based on the comparison result between the second viscosity change difference and the preset second viscosity change difference; Wherein, the second viscosity change difference is the difference between the first viscosity change rate and the upper limit of the first viscosity change threshold, and the decrease in the emulsion addition rate is positively correlated with the second viscosity change difference.

7. The method for preparing the environmentally friendly formaldehyde-free adhesive according to claim 5, characterized in that, The process of adjusting the addition rate of the crosslinking agent in real time based on the second viscosity change rate includes: In the preparation process of the formaldehyde-free adhesive, the second viscosity values ​​of the first adhesive at several second time points are collected to plot the second viscosity change curve, and the second viscosity change rate in the preparation process is determined based on the second viscosity change curve. The addition rate of the crosslinking agent in the preparation process of the formaldehyde-free adhesive is adjusted in real time based on the comparison result between the second viscosity change rate and the second viscosity change threshold. If the second viscosity change rate is less than the lower limit of the second viscosity change threshold, determine to increase the addition rate; If the second viscosity change rate is greater than the upper limit of the second viscosity change threshold, the addition rate is determined to be reduced.

8. The method for preparing the environmentally friendly formaldehyde-free adhesive according to claim 7, characterized in that, The process of increasing the addition rate includes: The addition rate of the crosslinking agent is increased based on the comparison between the third viscosity change difference and the preset third viscosity change difference. The third viscosity change difference is the difference between the lower limit of the second viscosity change threshold and the second viscosity change rate, and the increase in the addition rate is positively correlated with the third viscosity change difference.

9. The method for preparing the environmentally friendly formaldehyde-free adhesive according to claim 7, characterized in that, The process of reducing the addition rate includes: The addition rate of the crosslinking agent is reduced based on the comparison between the fourth viscosity change difference and the preset fourth viscosity change difference. The fourth viscosity change difference is the difference between the second viscosity change rate and the upper limit of the second viscosity change threshold, and the decrease in the addition rate is positively correlated with the fourth viscosity change difference.

10. The method for preparing the environmentally friendly formaldehyde-free adhesive according to claim 1, characterized in that, The components of each raw material by weight are as follows: 25 parts of plant-based protein powder, 10 parts of polyvinyl alcohol, 37 parts of water, 4 parts of alkali solution, 20 parts of vinyl acetate copolymer emulsion, and 2.5 parts of crosslinking agent.

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