Preparation method of rigid polyurethane foam thermal insulation material

Abstract

The invention relates to the technical field of thermal insulation materials, in particular to a preparation method of a rigid polyurethane foam thermal insulation material, which comprises the following steps: mixing polyol and nano silicon dioxide through a high-shear emulsifying machine to generate a first raw material; respectively adding the first raw material, the second raw material and isocyanate into a high-pressure foaming machine in proportion; adjusting the temperature to a first temperature, and reacting for 20 minutes to form a first mixture; adjusting the temperature to a second temperature, and reacting for 10 minutes to generate a second mixture; adjusting the temperature to a third temperature, curing the second mixture for 20 minutes, collecting a dielectric constant, calculating and generating a dielectric loss factor, and judging whether a peak value is delayed or not so as to judge whether a catalyst is supplemented or not; based on a reaction temperature value monitored by the infrared thermal imager, controlling the release of the temperature-sensitive crosslinking inhibitor, and judging whether the reaction of the finished thermal insulation material is completed or not; according to the invention, the thermal insulation effect of the material is effectively improved, and the preparation accuracy of the rigid polyurethane foam thermal insulation material is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of thermal insulation materials, and particularly to a preparation method of rigid polyurethane foam thermal insulation materials. Background Art

[0002] Rigid polyurethane foam thermal insulation materials need to face various complex environmental conditions in practical applications, such as high temperature, low temperature, high humidity, mechanical shock, etc. These environmental factors will affect the service life and performance stability of the materials. By optimizing the preparation parameters of rigid polyurethane foam, such as raw material ratio, foaming temperature, catalyst dosage, etc., the thermal conductivity can be further reduced and the thermal insulation performance can be improved, so that it can better meet the requirements of building energy conservation standards.

[0003] Chinese Patent Application Publication No.: CN118240173A discloses a preparation process of high-strength polyurethane thermal insulation materials. The invention discloses a preparation process of high-strength polyurethane thermal insulation materials, belonging to the technical field of thermal insulation materials. Using stannic chloride as a catalyst, an epoxy quaternary ammonium salt triphenylmelamine crosslinking agent reacts with the hydroxymethyl of starch by ring-opening crosslinking reaction, and after freeze-drying treatment, a modified starch aerogel is obtained. Its large number of hydroxyl groups can be used as polymerization reaction sites to carry out graft polymerization reaction with diisocyanate compounds and polyether polyols, thereby obtaining a high-strength polyurethane thermal insulation material grafted with starch aerogel, enhancing the interfacial compatibility between starch aerogel and polyurethane, and the modified starch aerogel has higher mechanical strength, so that the modified starch aerogel has little influence on the mechanical properties of polyurethane, and the polyurethane thermal insulation material still has good mechanical properties. It reduces the thermal conductivity and heat conduction of polyurethane materials, which is beneficial to improving the thermal insulation performance of the materials. At the same time, it improves the antibacterial performance of polyurethane thermal insulation materials.

[0004] It can be seen that in the prior art, a large number of hydroxyl groups are generated to form higher mechanical strength, reducing the internal closed cell rate of the material and weakening the heat insulation effect. Summary of the Invention

[0005] Therefore, the present invention provides a preparation method of rigid polyurethane foam thermal insulation materials to overcome the problem in the prior art that a large number of hydroxyl groups are generated to form higher mechanical strength, reducing the internal closed cell rate of the material and weakening the heat insulation effect.

[0006] To achieve the above object, the present invention provides a preparation method of rigid polyurethane foam thermal insulation materials, including: Mixing polyol and nano-silica through a high-shear emulsifier to generate a first raw material; Adding the first raw material, a second raw material and isocyanate into a high-pressure foaming machine in proportion, and the second raw material includes a foaming agent, a catalyst, a surfactant, a flame retardant and a temperature-sensitive crosslinking inhibitor; After adjusting the temperature to the first temperature, the first raw material, the second raw material and isocyanate are mixed by the high-pressure foaming machine and injected into the mold by the batch method. After reacting for 20 minutes, a first mixture is formed. Adjust the temperature to the second temperature, monitor the reaction progress of the first mixture by infrared spectroscopy, adjust the catalyst dosage, and generate a second mixture after reacting for 10 minutes. Combine microwave-assisted heating to adjust the temperature to the third temperature, cure the second mixture for 20 minutes, collect the dielectric constant by a dielectric constant sensor, calculate the dielectric loss factor, and determine whether the peak is delayed based on the dielectric loss factor to determine whether to add a catalyst. Determine the overheated area based on the reaction temperature value monitored by the infrared thermal imager, control the release of the temperature-sensitive crosslinking inhibitor according to the distribution of the overheated area, and determine whether the reaction of the finished thermal insulation material is completed.

[0007] Further, the process of adjusting the catalyst dosage according to the reaction progress of the first mixture monitored by infrared spectroscopy includes: Determine the standard reaction conversion rate curve corresponding to different catalyst concentrations. Collect the attenuation rate of isocyanate groups in the first mixture by infrared spectroscopy and calculate the reaction conversion rate. Calculate the rate difference between the reaction conversion rate and the standard reaction conversion rate corresponding to the same catalyst concentration, compare it with the preset rate difference, and determine whether to increase the catalyst dosage according to the comparison result. The preset rate difference is positively correlated with the hydroxyl concentration in the first mixture.

[0008] Further, the process of mixing the polyol and the nano-silica by the high-shear emulsifier to generate the first raw material includes: Dry the nano-silica in a vacuum oven at 80-100 °C for 4-6 hours. Mix the polyol and the nano-silica and add them to the high-shear emulsifier, set the rotation speed at 8000-12000 rpm, and process for 5-10 minutes. Increase the rotation speed to 20000 rpm and continue to process for 15-30 minutes to generate a dispersion. Place the dispersion in a vacuum degassing machine and degas it at a vacuum degree of -0.09 MPa for 15-30 minutes to generate the first raw material. Among them, the working temperature of the high-shear emulsifier is maintained below 40 °C by a circulating water cooling system.

[0009] Further, the process of injecting into the mold by the batch method and forming a first mixture after reacting for 20 minutes includes: Adjust the temperature to the first temperature, set the working pressure of the high-pressure foaming machine to 10 MPa - 15 MPa, and mix the first raw material, the second raw material and the isocyanate to generate a premix; Inject the premix into the mold in several portions; Close the mold and let it stand for reaction for 20 minutes.

[0010] Further, adjust the temperature to the second temperature, monitor the reaction progress of the first mixture by infrared spectroscopy, adjust the catalyst dosage, and the process of generating the second mixture after reacting for 10 minutes includes: Adjust the temperature to the second temperature, detect the NCO peak area by infrared spectroscopy, and record the initial NCO peak area and the NCO peak areas at each moment; Calculate the NCO decline rate using the NCO peak areas at each moment, compare the NCO decline rate with the preset rate, and determine whether to supplement the catalyst according to the comparison result; After reacting for 10 minutes, record the final NCO peak area, and determine whether the second mixture is generated according to the final NCO peak area; The preset rate is positively correlated with the initial catalyst concentration.

[0011] Further, after reacting for 10 minutes, record the final NCO peak area, and determine whether the second mixture is generated according to the final NCO peak area, wherein, Calculate the reaction ratio using the final NCO peak area and the initial NCO peak area, compare the reaction ratio with the preset ratio, and determine whether to extend the reaction time or generate the second mixture according to the comparison result; The preset ratio is positively correlated with the total catalyst concentration.

[0012] Further, combine microwave-assisted heating to adjust the temperature to the third temperature, cure the second mixture for 20 minutes, collect the dielectric constant through a dielectric constant sensor, calculate the dielectric loss factor, and the process of determining whether to supplement the catalyst based on the dielectric loss factor to determine whether the peak is delayed includes: Transfer the second mixture to the microwave reaction cavity, and use the microwave-assisted heating to adjust the temperature to the third temperature; Collect the dielectric constant through the dielectric constant sensor, calculate the dielectric loss factors at each moment, select the maximum value of the dielectric loss factors as the reaction peak, and record the moment corresponding to the reaction peak as the peak time; Determine whether the reaction is delayed according to the peak time, and determine whether the catalyst is insufficient according to the reaction peak.

[0013] Further, determine whether the reaction is delayed according to the peak time, and determine whether the catalyst is insufficient according to the reaction peak value, where if the peak time is greater than or equal to the preset time, it is determined that the reaction is delayed; if the reaction peak value is less than or equal to the preset peak value, it is determined that the catalyst is insufficient; the preset time is positively correlated with the set temperature of the mold, and the reaction peak value is positively correlated with the total amount of reaction raw materials.

[0014] Further, based on the reaction temperature value monitored by the infrared thermal imager, control the release of the temperature-sensitive crosslinking inhibitor. The process of determining whether the reaction of the finished thermal insulation material is completed includes: Use an infrared thermal imager to monitor the reaction temperature values of each area of the mold, and determine the overheated area based on the reaction temperature; Release the temperature-sensitive crosslinking inhibitor in the overheated area; When the reaction temperature in the overheated area decreases and becomes a non-overheated area state, stop releasing the temperature-sensitive crosslinking inhibitor, and determine that the reaction of the finished thermal insulation material is completed.

[0015] Further, by weight, the components for preparing the rigid polyurethane foam thermal insulation material include: 100 parts of polyol, 1-5 parts of nano-silica, 100-120 parts of isocyanate, 10-20 parts of foaming agent, 0.5-3 parts of catalyst, 1-3 parts of surfactant, 10-20 parts of flame retardant, and 0.5-2 parts of temperature-sensitive crosslinking inhibitor.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows. The present invention adjusts the catalyst dosage by monitoring the reaction progress of the first mixture according to infrared spectroscopy. Infrared monitoring shows that the -NCO consumption rate is lower than the preset value, and the catalyst is automatically added to accelerate the crosslinking reaction and avoid the collapse of the cell structure caused by the premature volatilization of the foaming agent. The traditional preparation method of rigid polyurethane foam thermal insulation materials may not be able to precisely control the reaction process, resulting in unstable product quality. However, the present invention can precisely master the reaction progress through infrared spectroscopy monitoring and catalyst dosage adjustment, thereby more accurately controlling the reaction conditions, making the prepared rigid polyurethane foam thermal insulation material more stable and uniform in performance, improving the preparation accuracy. The accurate preparation process helps to improve the performance of the rigid polyurethane foam thermal insulation material. Precise control of the reaction process can avoid waste of raw materials caused by incomplete or excessive reactions, reduce production costs. Real-time monitoring of the reaction progress and timely adjustment of the catalyst dosage can keep the reaction in a highly efficient state, shorten the production cycle, improve production efficiency, and improve the preparation accuracy of the rigid polyurethane foam thermal insulation material.

[0017] Furthermore, in the present invention, the polyol and the nano-silica are mixed by the high-shear emulsifier to generate the first raw material. The uniform dispersion of nano-silica in the polyol is one of the key factors to ensure the performance of the polyurethane rigid foam. The use of the high-shear emulsifier can significantly improve the dispersion effect of nano-silica, avoid local performance differences caused by uneven dispersion, and thus improve the accuracy of preparation. The uniform mixture as the reaction medium can ensure the uniform progress of the subsequent reaction. The uniformity of the reaction directly affects the performance of the final product. The first raw material generated by mixing with the high-shear emulsifier can provide a stable reaction environment for the subsequent reaction and further improve the accuracy of preparation. The uniform dispersion of nano-silica can significantly improve the mechanical properties and thermal insulation properties of the polyurethane rigid foam. The uniform mixture can reduce the defects and uneven structures inside the material, improve the overall performance and service life of the material, and further improve the accuracy of the preparation of the polyurethane rigid foam thermal insulation material.

[0018] Furthermore, in the present invention, the intermittent injection method is adopted to inject into the mold. After reacting for 20 minutes, the first mixture is formed. The intermittent injection method into the mold can precisely control the addition amount and addition time of the raw materials, avoid uneven distribution caused by one-time injection. This precise control helps to ensure the uniform progress of the reaction in the mold, thereby improving the accuracy of preparation. By forming the first mixture after 20 minutes, it can ensure that the reaction proceeds under stable conditions. This stable reaction condition helps to improve the repeatability and consistency of the reaction and further improve the accuracy of preparation. The intermittent injection method into the mold and the 20-minute reaction time can ensure the uniform distribution and reaction of the raw materials in the mold. This uniformity helps to improve the performance of the polyurethane rigid foam thermal insulation material, such as thermal insulation performance, mechanical properties, etc., and further improves the accuracy of the preparation of the polyurethane rigid foam thermal insulation material.

[0019] Furthermore, in the present invention, the final NCO peak area is recorded, and whether the second mixture is generated is determined according to the final NCO peak area. By recording the NCO peak area through infrared spectroscopy analysis, the consumption of NCO groups during the reaction process can be precisely monitored. This precise monitoring helps to ensure that the reaction proceeds under the expected conditions, thereby improving the accuracy of preparation. According to the monitoring results of the NCO peak area, the reaction conditions can be adjusted in real time or reactants can be supplemented. This real-time adjustment can avoid product performance differences caused by incomplete reaction or overreaction and further improve the accuracy of preparation. By precisely controlling the reaction progress, it can ensure that the performance of the polyurethane rigid foam thermal insulation material is more uniform and stable. For example, the uniform consumption of NCO groups can improve the thermal insulation performance and mechanical properties of the material, and further improve the accuracy of the preparation of the polyurethane rigid foam thermal insulation material.

[0020] Furthermore, in the present invention, the dielectric constant is collected by a dielectric constant sensor, and the dielectric loss factor is calculated and generated. Based on the dielectric loss factor, it is determined whether the peak value is delayed to determine whether to supplement the catalyst. By using the dielectric constant sensor to monitor the dielectric constant in real time and calculate the dielectric loss factor, the progress of the reaction can be accurately monitored. Such accurate monitoring helps to ensure that the reaction proceeds under the expected conditions, thereby improving the accuracy of the preparation. According to the monitoring results of the dielectric loss factor, it can be determined in real time whether the peak value is delayed and decide whether to supplement the catalyst. Such real-time adjustment can avoid product performance differences caused by incomplete or excessive reactions, and further improve the accuracy of the preparation. By precisely controlling the reaction progress, the performance of the rigid polyurethane foam thermal insulation material can be ensured to be more uniform and stable. For example, the uniform progress of the reaction can improve the thermal insulation performance and mechanical properties of the material, further improving the accuracy of the preparation of the rigid polyurethane foam thermal insulation material.

[0021] Furthermore, in the present invention, based on the reaction temperature value monitored by an infrared thermal imager, the release of the temperature-sensitive crosslinking inhibitor is controlled to determine whether the reaction of the finished thermal insulation material is completed. The infrared thermal imager can monitor the temperature change during the reaction in real time and accurately, especially the appearance of the temperature peak. Such accurate monitoring helps to ensure that the reaction proceeds under the expected conditions, thereby improving the accuracy of the preparation. By controlling the release of the temperature-sensitive crosslinking inhibitor, the reaction rate and degree can be adjusted in real time. Such real-time control can avoid product performance differences caused by too fast reaction or excessive crosslinking, and further improve the accuracy of the preparation. By precisely controlling the reaction temperature and crosslinking degree, the performance of the rigid polyurethane foam thermal insulation material can be ensured to be more uniform and stable, further improving the accuracy of the preparation of the rigid polyurethane foam thermal insulation material. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a flowchart of the preparation method of the rigid polyurethane foam thermal insulation material of the present invention; Figure 2 is a logic diagram for adjusting the catalyst dosage of the first mixture in the embodiment of the present invention; Figure 3 is a flowchart of mixing to generate the first raw material in the embodiment of the present invention; Figure 4 is a logic diagram for determining whether the second mixture is generated in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] In order to make the objectives and advantages of the present invention clearer, the present invention will be further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principle of the present invention and do not limit the protection scope of the present invention.

[0025] It should be noted that in the description of the present invention, the terms indicating directions or positional relationships such as "upper", "lower", "left", "right", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings. This is only for convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0026] In addition, it should also be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. 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 directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0027] Please refer to Figure 1 as shown, which is a flowchart of the preparation method of the polyurethane rigid foam thermal insulation material of the present invention. The embodiments of the present invention provide a preparation method of a polyurethane rigid foam thermal insulation material, including: Step S1, mixing a polyol and nano-silica through a high-shear emulsifier to generate a first raw material; Step S2, respectively adding the first raw material, the second raw material, and an isocyanate into a high-pressure foaming machine in proportion. The second raw material includes a foaming agent, a catalyst, a surfactant, a flame retardant, and a temperature-sensitive crosslinking inhibitor; Step S3, adjusting the temperature to a first temperature, and then mixing the first raw material, the second raw material, and the isocyanate through the high-pressure foaming machine, and injecting them into a mold by an intermittent method. After reacting for 20 minutes, a first mixture is formed; Step S4, adjusting the temperature to a second temperature, monitoring the reaction progress of the first mixture through infrared spectroscopy, adjusting the dosage of the catalyst, and generating a second mixture after reacting for 10 minutes; Step S5, combining microwave-assisted heating to adjust the temperature to a third temperature, curing the second mixture for 20 minutes, collecting the dielectric constant through a dielectric constant sensor, calculating to generate a dielectric loss factor, and determining whether the peak is delayed based on the dielectric loss factor to determine whether to supplement the catalyst; Step S6, determining the overheated area based on the reaction temperature value monitored by an infrared thermal imager, controlling the release of the temperature-sensitive crosslinking inhibitor according to the distribution of the overheated area, and determining whether the reaction of the finished thermal insulation material is completed.

[0028] Please refer to Figure 2 shown in the figure, which is the logic diagram for adjusting the catalyst dosage of the first mixture in the embodiment of the present invention. In step S4, according to the infrared spectrum to monitor the reaction progress of the first mixture, the process of adjusting the catalyst dosage includes: Determine the standard reaction conversion rate curve corresponding to different catalyst concentrations; Collect the attenuation rate of isocyanate groups in the first mixture through infrared spectroscopy, and calculate the reaction conversion rate; Calculate the rate difference between the reaction conversion rate and the standard reaction conversion rate corresponding to the same catalyst concentration, compare it with the preset rate difference, and determine whether to increase the catalyst dosage according to the comparison result; It can be understood that isocyanate groups (-NCO) have characteristic absorption peaks (2270–2250 ) in the infrared spectrum, and the attenuation of its peak area is linearly related to the decrease in -NCO concentration. During the reaction process, this peak area gradually weakens as the -NCO groups are consumed. By collecting the change in the -NCO peak area in real time, the reaction conversion rate can be accurately calculated, and the reaction rate can be calculated through the reaction conversion rate to achieve dynamic tracking of the reaction process.

[0029] It can be understood that the reaction rate of the first mixture is , where is the reaction conversion rate, t is the time (unit: min), and the reaction rate of the standard curve is , where is the standard reaction conversion rate, t is the time (unit: min), and the rate difference = the reaction rate of the first mixture - the reaction rate of the standard curve.

[0030] If the rate difference is less than or equal to the preset rate difference, it is determined to increase the catalyst dosage; If the rate difference is greater than the preset rate difference, it is determined to maintain the current reaction; In a specific embodiment, the preset rate difference is set to 0.05% / min. If the rate difference is -0.2% / min, which is less than the preset rate difference, it is determined to increase the catalyst dosage; If the rate difference is 0.08% / min, which is greater than the preset rate difference, it is determined to maintain the current reaction.

[0031] The preset rate difference is positively correlated with the hydroxyl concentration in the first mixture.

[0032] It can be understood that the greater the hydroxyl concentration in the first mixture, the faster the reaction under the same catalyst dosage. Therefore, the preset rate difference is positively correlated with the hydroxyl concentration in the first mixture.

[0033] Preferably, the hydroxyl concentration in the first mixture is 0.5 mol / L, and the preset rate difference is 0.02% / min; The hydroxyl concentration in the first mixture is 1.0 mol / L, and the preset rate difference is 0.05% / min; The hydroxyl concentration in the first mixture is 1.5 mol / L, and the preset rate difference is 0.08% / min.

[0034] Specifically, the present invention adjusts the catalyst dosage by monitoring the reaction progress of the first mixture according to infrared spectroscopy. Infrared monitoring shows that the -NCO consumption rate is lower than the preset value, and the catalyst is automatically added to accelerate the cross-linking reaction and avoid the collapse of cell holes caused by the premature volatilization of the blowing agent. The traditional preparation method of rigid polyurethane foam thermal insulation materials may not be able to precisely control the reaction process, resulting in unstable product quality. However, the present invention can accurately master the reaction progress through infrared spectroscopy monitoring and catalyst dosage adjustment, thereby more accurately controlling the reaction conditions, making the prepared rigid polyurethane foam thermal insulation materials more stable and uniform in performance, and improving the accuracy of preparation. An accurate preparation process helps to improve the performance of rigid polyurethane foam thermal insulation materials. Precise control of the reaction process can avoid waste of raw materials caused by incomplete or excessive reactions, reduce production costs, and real-time monitoring of the reaction progress and timely adjustment of the catalyst dosage can keep the reaction in a highly efficient state, shorten the production cycle, improve production efficiency, and improve the accuracy of the preparation of rigid polyurethane foam thermal insulation materials.

[0035] Please refer to Figure 3 As shown, it is a flowchart of the mixing to generate the first raw material in an embodiment of the present invention. In step S1, the process of mixing polyol and nano-silica by a high-shear emulsifier to generate the first raw material includes: Step S101, drying the nano-silica in a vacuum oven at 80 - 100 °C for 4 - 6 hours; Step S102, mixing the polyol and nano-silica and adding them to the high-shear emulsifier, setting the rotation speed at 8000 - 12000 rpm, and processing for 5 - 10 minutes; Step S103, increasing the rotation speed to 20000 rpm and continuing to process for 15 - 30 minutes to generate a dispersion; Step S104, placing the dispersion in a vacuum degassing machine and degassing at a vacuum degree of -0.09 MPa for 15 - 30 minutes to generate the first raw material; Among them, the working temperature of the high-shear emulsifier is maintained below 40 °C through a circulating water cooling system.

[0036] It is understandable that the high specific surface area of nano-silica enables it to form strong interfacial interactions when contacting with polyols, significantly improving the mechanical properties of the mixture. Nano-particles tend to agglomerate, and through the strong shearing force of a high-shear emulsifier, the attractive force between particles can be overcome to achieve uniform dispersion at the nano-scale.

[0037] Specifically, in the present invention, the first raw material is generated by mixing polyols and nano-silica through a high-shear emulsifier. The uniform dispersion of nano-silica in polyols is one of the key factors to ensure the performance of rigid polyurethane foam. The use of a high-shear emulsifier can significantly improve the dispersion effect of nano-silica, avoiding local performance differences caused by uneven dispersion, thereby improving the preparation accuracy. The uniform mixture as the reaction medium can ensure the uniform progress of subsequent reactions. The uniformity of the reaction directly affects the performance of the final product. The first raw material generated by mixing through a high-shear emulsifier can provide a stable reaction environment for subsequent reactions, further improving the preparation accuracy. The uniform dispersion of nano-silica can significantly improve the mechanical properties and thermal insulation properties of rigid polyurethane foam. The uniform mixture can reduce the defects and uneven structures inside the material, improving the overall performance and service life of the material, and further improving the preparation accuracy of rigid polyurethane foam thermal insulation materials.

[0038] Specifically, in step S3, the process of forming the first mixture by injecting into the mold in batches and reacting for 20 minutes includes: Adjust the temperature to the first temperature, set the working pressure of the high-pressure foaming machine at 10 MPa - 15 MPa, and mix the first raw material, the second raw material and isocyanate to generate a premix; Inject the premix into the mold in several portions; Close the mold and let it stand and react for 20 minutes.

[0039] It is understandable that, preferably, the first temperature is 25 °C. 25 °C is close to room temperature, which can not only ensure the appropriate reaction rate between isocyanate and polyols, avoid out-of-control foaming caused by violent reactions at high temperatures, but also extend the operation time of the premix.

[0040] Specifically, in the present invention, by using the intermittent injection method into the mold, a first mixture is formed after reacting for 20 minutes. The intermittent injection method into the mold can precisely control the addition amount and addition time of the raw materials, avoiding uneven distribution caused by one-time injection. This precise control helps to ensure the uniform progress of the reaction in the mold, thereby improving the accuracy of preparation. By forming the first mixture after 20 minutes, it can ensure that the reaction proceeds under stable conditions. Such stable reaction conditions contribute to improving the repeatability and consistency of the reaction, further enhancing the accuracy of preparation. The intermittent injection method into the mold and the 20-minute reaction time can ensure the uniform distribution and reaction of the raw materials in the mold. This uniformity helps to improve the properties of the rigid polyurethane foam thermal insulation material, such as thermal insulation performance, mechanical properties, etc., further improving the accuracy of the preparation of the rigid polyurethane foam thermal insulation material.

[0041] Specifically, in step S4, the temperature is adjusted to the second temperature, and the reaction progress of the first mixture is monitored by infrared spectroscopy. The process of adjusting the catalyst dosage and generating the second mixture after reacting for 10 minutes includes: Adjust the temperature to the second temperature, detect the NCO peak area by infrared spectroscopy, and record the initial NCO peak area and the NCO peak areas at each moment; Calculate the NCO decline rate using the NCO peak areas at each moment, compare the NCO decline rate with the preset rate, and determine whether to supplement the catalyst according to the comparison result; After reacting for 10 minutes, record the final NCO peak area, and determine whether the second mixture is generated according to the final NCO peak area; Preferably, the second temperature is 40°C - 50°C.

[0042] It can be understood that the NCO decline rate is the difference between the NCO peak areas measured at adjacent moments divided by the time difference between adjacent moments.

[0043] If the NCO decline rate is greater than or equal to the preset rate, it is determined that the reaction is normal; If the NCO decline rate is less than the preset rate, it is determined to supplement the catalyst; In a specific embodiment, the preset rate is set to 15 a.u. / min. If the NCO decline rate is 19 a.u. / min, which is greater than the preset rate, it is determined that the reaction is normal; If the NCO decline rate is 13 a.u. / min, which is less than the preset rate, it is determined to supplement the catalyst; The preset rate is positively correlated with the initial catalyst concentration.

[0044] It can be understood that the higher the initial catalyst concentration, the faster the reaction. Therefore, the preset rate is positively correlated with the initial catalyst concentration.

[0045] Preferably, the initial catalyst concentration is 0.01%, and the preset rate is 5 a.u. / min; The initial catalyst concentration is 0.03%, and the preset rate is 12 a.u. / min; The initial catalyst concentration is 0.05%, and the preset rate is 20 a.u. / min.

[0046] Please refer to Figure 4 As shown, it is the logic diagram for determining whether the second mixture is generated in the embodiment of the present invention. In step S4, after reacting for 10 minutes, record the final NCO peak area, and determine whether the second mixture is generated according to the final NCO peak area, where Calculate the reaction ratio based on the final NCO peak area and the initial NCO peak area, compare the reaction ratio with the preset ratio, and determine whether to extend the reaction time or generate the second mixture according to the comparison result; It can be understood that .

[0047] If the reaction ratio is less than the preset ratio, it is determined to extend the reaction time; If the reaction ratio is greater than or equal to the preset ratio, it is determined to generate the second mixture; In a specific embodiment, the preset ratio is set to 0.9. If the reaction ratio is 0.84, which is less than the preset ratio, it is determined to extend the reaction time; If the reaction ratio is 0.92, which is greater than the preset ratio, it is determined to generate the second mixture.

[0048] The preset ratio is positively correlated with the total catalyst concentration.

[0049] It can be understood that the greater the total catalyst concentration, the faster the reaction. Under the same reaction time, the greater the final NCO peak area. Therefore, the preset ratio is positively correlated with the total catalyst concentration.

[0050] Preferably, when the total catalyst concentration is 0.05 mol / L, the preset ratio is 0.6; When the total catalyst concentration is 0.06 mol / L, the preset ratio is 0.8; When the total catalyst concentration is 0.07 mol / L, the preset ratio is 0.9.

[0051] It can be understood that in the state of determining to extend the reaction time, optionally, extend the reaction time by 5 minutes and then measure the reaction ratio.

[0052] Specifically, in the present invention, by recording the final NCO peak area and determining whether to generate the second mixture based on the final NCO peak area, and recording the NCO peak area through infrared spectrum analysis, the consumption of NCO groups during the reaction process can be accurately monitored. This accurate monitoring helps to ensure that the reaction proceeds under the expected conditions, thereby improving the accuracy of preparation. According to the monitoring results of the NCO peak area, the reaction conditions can be adjusted in real time or reactants can be supplemented. This real-time adjustment can avoid product performance differences caused by incomplete or excessive reactions, and further improve the accuracy of preparation. By precisely controlling the reaction progress, the performance of the rigid polyurethane foam thermal insulation material can be ensured to be more uniform and stable. For example, the uniform consumption of NCO groups can improve the thermal insulation performance and mechanical properties of the material, further improving the accuracy of the preparation of the rigid polyurethane foam thermal insulation material.

[0053] Specifically, in step S5, the temperature is adjusted to the third temperature in combination with microwave-assisted heating, the second mixture is cured for 20 minutes, the dielectric constant is collected by a dielectric constant sensor, the dielectric loss factor is calculated, and the process of determining whether to supplement the catalyst based on the dielectric loss factor includes: Transfer the second mixture to the microwave reaction cavity and use microwave-assisted heating to adjust the temperature to the third temperature; Collect the dielectric constant by a dielectric constant sensor, calculate the dielectric loss factor at each moment, select the maximum value of the dielectric loss factor as the reaction peak, and record the moment corresponding to the reaction peak as the peak time; Determine whether the reaction is delayed according to the peak time, and determine whether the catalyst is insufficient according to the reaction peak.

[0054] Preferably, the third temperature is 60°C - 65°C.

[0055] It can be understood that microwaves directly heat polar molecules through dielectric loss, and the heating rate is 3 to 5 times faster than traditional heating, and the temperature uniformity is better, which can be accurately controlled to ±2°C to avoid local overheating.

[0056] It can be understood that even if the peak time is normal, if the catalyst concentration is lower than the critical value, the reaction rate peak cannot reach the expected value, resulting in a low maximum value of the reaction peak.

[0057] It can be understood that the dielectric loss factor = dielectric constant × tanδ, where tanδ is the tangent of the loss angle, which represents the proportion of viscous loss.

[0058] Specifically, in step S5, determine whether the reaction is delayed according to the peak time, and determine whether the catalyst is insufficient according to the reaction peak, where If the peak time is greater than or equal to the preset time, it is determined that the reaction is delayed; If the reaction peak value is less than or equal to the preset peak value, it is determined that the catalyst is insufficient. In a specific embodiment, the preset time is set to 8 min. If the peak time is 12 min, which is greater than the preset time, it is determined that the reaction is delayed.

[0059] In a specific embodiment, the preset peak value is set to 150 a.u. If the reaction peak value is 128 a.u., which is less than the preset peak value, it is determined that the catalyst is insufficient.

[0060] The preset time is positively correlated with the set temperature of the mold, and the reaction peak value is positively correlated with the total amount of reaction raw materials.

[0061] It can be understood that the greater the set temperature of the mold, the greater the starting temperature of the reaction, and the faster the reaction. Therefore, the preset time is positively correlated with the set temperature of the mold.

[0062] Preferably, the set temperature of the mold is 60 °C and the preset time is 10 minutes; The set temperature of the mold is 63 °C and the preset time is 9 minutes; The set temperature of the mold is 65 °C and the preset time is 8 minutes; It can be understood that the greater the total amount of reaction raw materials, the greater the reaction peak value.

[0063] Preferably, the total amount of reaction raw materials is 20 kg and the reaction peak value is 150 a.u.; The total amount of reaction raw materials is 40 kg and the reaction peak value is 300 a.u.; The total amount of reaction raw materials is 60 kg and the reaction peak value is 450 a.u.

[0064] Specifically, in the present invention, the dielectric constant is collected by a dielectric constant sensor, the dielectric loss factor is calculated and generated, and based on the dielectric loss factor, it is determined whether the peak is delayed to determine whether to supplement the catalyst. By monitoring the dielectric constant in real time through the dielectric constant sensor and calculating the dielectric loss factor, the progress of the reaction can be accurately monitored. This accurate monitoring helps to ensure that the reaction proceeds under the expected conditions, thereby improving the accuracy of the preparation. According to the monitoring results of the dielectric loss factor, it can be determined in real time whether the peak is delayed and whether to supplement the catalyst. This real-time adjustment can avoid product performance differences caused by incomplete reactions or excessive reaction temperature values, further improving the accuracy of the preparation. By precisely controlling the reaction progress, the performance of the polyurethane rigid foam thermal insulation material can be ensured to be more uniform and stable. For example, the uniform progress of the reaction can improve the thermal insulation performance and mechanical properties of the material, further improving the accuracy of the preparation of the polyurethane rigid foam thermal insulation material.

[0065] Specifically, in step S6, based on the reaction temperature value monitored by the infrared thermal imager, the release of the temperature-sensitive crosslinking inhibitor is controlled. The process of determining whether the reaction of the finished thermal insulation material is completed includes: Use an infrared thermal imager to monitor the reaction temperature values of each area of the mold, and determine the overheated area based on the reaction temperature; Release the temperature-sensitive crosslinking inhibitor in the overheated area; When the reaction temperature in the overheated area decreases and becomes a non-overheated area state, stop releasing the temperature-sensitive crosslinking inhibitor, and determine that the reaction of the finished thermal insulation material is completed.

[0066] If the reaction temperature is greater than or equal to the preset temperature, it is determined that the area corresponding to the reaction temperature is the overheated area; If the reaction temperature is less than the preset temperature, it is determined that the area corresponding to the reaction temperature is the non-overheated area; In a specific embodiment, the preset temperature is set to 70 °C. If the reaction temperature is 84 °C, which is greater than the preset temperature, it is determined that the area corresponding to the reaction temperature is the overheated area; If the reaction temperature is 64 °C, which is less than the preset temperature, it is determined that the area corresponding to the reaction temperature is the non-overheated area.

[0067] The preset temperature is positively correlated with the total catalyst concentration.

[0068] It can be understood that the higher the total catalyst concentration, the more intense the reaction, and the higher the corresponding reaction temperature. Therefore, the preset temperature is positively correlated with the total catalyst concentration.

[0069] Preferably, when the total catalyst concentration is 0.05 mol / L, the preset temperature is 65 °C; When the total catalyst concentration is 0.06 mol / L, the preset temperature is 70 °C; When the total catalyst concentration is 0.07 mol / L, the preset temperature is 80 °C.

[0070] It can be understood that the polyurethane foaming reaction is a strong exothermic reaction. For every 10 °C increase in temperature, the reaction rate increases by 2 - 4 times. Excessive local temperature will cause the formation of hard and brittle "scorching" areas, an increase in the thermal conductivity of the thermal insulation material and deterioration of mechanical properties, excessive volatilization of the CO2 foaming agent generated by the reaction of isocyanate and water, resulting in cell collapse or uneven cell size, and the accumulated heat may cause explosive polymerization or overheating damage to the equipment. The temperature-sensitive crosslinking inhibitor has an effect similar to a "temperature switch", which can intervene immediately when overheated and withdraw from intervention when not overheated, avoiding obstruction of the global reaction.

[0071] Specifically, in the present invention, based on the reaction temperature value monitored by an infrared thermal imager, the release of the temperature-sensitive crosslinking inhibitor is controlled to determine whether the reaction of the finished thermal insulation material is completed. The infrared thermal imager can monitor the temperature change during the reaction in real time and accurately, especially the appearance of the temperature peak. This accurate monitoring helps to ensure that the reaction proceeds under the expected conditions, thereby improving the accuracy of preparation. By controlling the release of the temperature-sensitive crosslinking inhibitor, the reaction rate and degree can be adjusted in real time. This real-time control can avoid product performance differences caused by too fast reaction or excessive crosslinking, and further improve the accuracy of preparation. By precisely controlling the reaction temperature and crosslinking degree, the performance of the rigid polyurethane foam thermal insulation material can be ensured to be more uniform and stable, further improving the accuracy of the preparation of the rigid polyurethane foam thermal insulation material.

[0072] Specifically, by weight, the components for preparing the rigid polyurethane foam thermal insulation material include: 100 parts of polyol, 1 - 5 parts of nano-silica, 100 - 120 parts of isocyanate, 10 - 20 parts of foaming agent, 0.5 - 3 parts of catalyst, 1 - 3 parts of surfactant, 10 - 20 parts of flame retardant, and 0.5 - 2 parts of temperature-sensitive crosslinking inhibitor. Example

[0073] By weight, the components for preparing the rigid polyurethane foam thermal insulation material include: 100 kg of polyol, 3 kg of nano-silica, 110 kg of isocyanate, 15 kg of foaming agent, 1.75 kg of catalyst, 2 kg of surfactant, 15 kg of flame retardant, and 1.25 kg of temperature-sensitive crosslinking inhibitor. The rigid polyurethane foam thermal insulation material is prepared according to the above technical scheme, and the preset peak value is calculated to be 800 a.u., and the catalyst concentration is adjusted. The results are shown in Table 1.

[0074] Table 1 Comparison results of adjusted preset stirring parameters

[0075] From the finished product structure results of the above Examples 1 - 3, it can be concluded that in Example 1, the present invention's technical scheme is not adopted for preparation. In Example 2, the present invention's technical scheme is adopted for preparation, but no additional catalyst is added. In Example 3, the present invention's technical scheme is adopted for preparation, and at the same time, the catalyst is additionally added according to the reaction peak value calculated based on the dielectric constant.

[0076] So far, the technical scheme of the present invention has been described in combination with the preferred embodiments shown in the drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical schemes after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A preparation method of a rigid polyurethane foam thermal insulation material, characterized in that, Comprising: Mixing a polyol and nano-silica through a high-shear emulsifier to generate a first raw material; Adding the first raw material, a second raw material, and isocyanate into a high-pressure foaming machine in proportion, wherein the second raw material includes a foaming agent, a catalyst, a surfactant, a flame retardant, and a temperature-sensitive crosslinking inhibitor; After adjusting the temperature to a first temperature, mixing the first raw material, the second raw material, and isocyanate through the high-pressure foaming machine, injecting them into a mold by an intermittent method, and forming a first mixture after reacting for 20 minutes; Adjusting the temperature to a second temperature, monitoring the reaction progress of the first mixture through infrared spectroscopy, adjusting the catalyst dosage, and generating a second mixture after reacting for 10 minutes; Combined with microwave-assisted heating, adjusting the temperature to a third temperature, curing the second mixture for 20 minutes, collecting the dielectric constant through a dielectric constant sensor, calculating to generate a dielectric loss factor, and determining whether the peak is delayed based on the dielectric loss factor to determine whether to supplement the catalyst; Determining an overheated area based on the reaction temperature value monitored by an infrared thermal imager, controlling the release of the temperature-sensitive crosslinking inhibitor according to the distribution of the overheated area, and determining whether the reaction of the finished thermal insulation material is completed.

2. The preparation method of the rigid polyurethane foam thermal insulation material according to claim 1, wherein The process of adjusting the catalyst dosage according to the reaction progress of the first mixture monitored by infrared spectroscopy includes: Determining a standard reaction conversion rate curve corresponding to different catalyst concentrations; Collecting the attenuation rate of isocyanate groups in the first mixture through infrared spectroscopy and calculating the reaction conversion rate; Calculating the rate difference between the reaction conversion rate and the standard reaction conversion rate corresponding to the same catalyst concentration, comparing it with a preset rate difference, and determining whether to increase the catalyst dosage according to the comparison result; The preset rate difference is positively correlated with the hydroxyl concentration in the first mixture.

3. The preparation method of the rigid polyurethane foam thermal insulation material according to claim 2, characterized in that, The process of mixing the polyol and the nano-silica through the high-shear emulsifier to generate the first raw material includes: Drying the nano-silica in a vacuum oven at 80 - 100 °C for 4 - 6 hours; Mixing the polyol and the nano-silica and adding them into the high-shear emulsifier, setting the rotation speed at 8000 - 12000 rpm, and processing for 5 - 10 minutes; Increasing the rotation speed to 20000 rpm and continuing to process for 15 - 30 minutes to generate a dispersion; Placing the dispersion in a vacuum degassing machine and degassing it at a vacuum degree of -0.09 MPa for 15 - 30 minutes to generate the first raw material; Wherein, the working temperature of the high-shear emulsifier is maintained below 40 °C through a circulating water cooling system.

4. The preparation method of the rigid polyurethane foam thermal insulation material according to claim 3, wherein, The process of injecting into a mold by an intermittent method and forming a first mixture after reacting for 20 minutes includes: Adjusting the temperature to the first temperature, setting the working pressure of the high-pressure foaming machine at 10 MPa - 15 MPa, and mixing the first raw material, the second raw material, and the isocyanate to generate a premix; Injecting the premix into the mold in several portions; Closing the mold and standing for reaction for 20 minutes.

5. The preparation method of the rigid polyurethane foam thermal insulation material according to claim 4, characterized in that, The process of adjusting the temperature to the second temperature, monitoring the reaction progress of the first mixture through infrared spectroscopy, adjusting the catalyst dosage, and generating a second mixture after reacting for 10 minutes includes: Adjust the temperature to the second temperature, detect the NCO peak area by infrared spectroscopy, and record the initial NCO peak area and the NCO peak areas at each moment; Calculate the NCO decline rate using the NCO peak areas at each moment, compare the NCO decline rate with a preset rate, and determine whether to supplement the catalyst according to the comparison result; After reacting for 10 minutes, record the final NCO peak area, and determine whether the second mixture is formed according to the final NCO peak area; The preset rate is positively correlated with the initial catalyst concentration.

6. The preparation method of the rigid polyurethane foam thermal insulation material according to claim 5, characterized in that, After reacting for 10 minutes, record the final NCO peak area, and determine whether the second mixture is formed according to the final NCO peak area, where Calculate the reaction ratio based on the final NCO peak area and the initial NCO peak area, compare the reaction ratio with a preset ratio, and determine whether to extend the reaction time or form the second mixture according to the comparison result; The preset ratio is positively correlated with the total catalyst concentration.

7. The preparation method of the rigid polyurethane foam thermal insulation material according to claim 6, characterized in that The process of adjusting the temperature to the third temperature by combining microwave-assisted heating, curing the second mixture for 20 minutes, collecting the dielectric constant by a dielectric constant sensor, calculating the dielectric loss factor, and determining whether the peak is delayed based on the dielectric loss factor to determine whether to supplement the catalyst includes: Transfer the second mixture to a microwave reaction chamber, and use the microwave-assisted heating to adjust the temperature to the third temperature; Collect the dielectric constant by the dielectric constant sensor, calculate the dielectric loss factor at each moment, select the maximum value of the dielectric loss factor as the reaction peak, and record the moment corresponding to the reaction peak as the peak time; Determine whether the reaction is delayed according to the peak time, and determine whether the catalyst is insufficient according to the reaction peak.

8. The preparation method of the rigid polyurethane foam thermal insulation material according to claim 7, characterized in that, Determine whether the reaction is delayed according to the peak time, and determine whether the catalyst is insufficient according to the reaction peak, where If the peak time is greater than or equal to the preset time, it is determined that the reaction is delayed; If the reaction peak is less than or equal to the preset peak, it is determined that the catalyst is insufficient; The preset time is positively correlated with the mold set temperature, and the reaction peak is positively correlated with the total amount of reaction raw materials.

9. The preparation method of the rigid polyurethane foam thermal insulation material according to claim 8, characterized in that, Based on the reaction temperature value monitored by an infrared thermal imager, controlling the release of the temperature-sensitive crosslinking inhibitor, and the process of determining whether the reaction of the finished thermal insulation material is completed includes: Use an infrared thermal imager to monitor the reaction temperature values of each area of the mold, and determine the overheated area based on the reaction temperature; Release the temperature-sensitive crosslinking inhibitor in the overheated area; When the reaction temperature in the overheated area decreases to a non-overheated area state, stop releasing the temperature-sensitive crosslinking inhibitor, and determine that the reaction of the finished thermal insulation material is completed.

10. The preparation method of the rigid polyurethane foam thermal insulation material according to claim 9, characterized in that, By weight, the components for preparing the rigid polyurethane foam thermal insulation material include: 100 parts of polyol, 1 - 5 parts of nano-silica, 100 - 120 parts of isocyanate, 10 - 20 parts of foaming agent, 0.5 - 3 parts of catalyst, 1 - 3 parts of surfactant, 10 - 20 parts of flame retardant, and 0.5 - 2 parts of temperature-sensitive crosslinking inhibitor.

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