A preparation method of polyurethane rigid foam thermal insulation material

Abstract

The present invention relates to the technical field of thermal insulation materials, and in particular to a method for preparing a polyurethane rigid foam thermal insulation material. The method comprises the following steps: mixing polyol and nano-silicon dioxide by a high-shear emulsifier to generate a first raw material; respectively adding the first raw material, a second raw material and isocyanate into a high-pressure foaming machine in proportion; adjusting the temperature to a first temperature, reacting for 20 minutes to form a first mixture; adjusting the temperature to a second temperature, reacting for 10 minutes to form 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, determining whether a peak value is delayed, and determining whether a catalyst should be added; and controlling the release of a temperature-sensitive cross-linking inhibitor based on a reaction temperature value monitored by an infrared thermal imager to determine whether the reaction of the finished thermal insulation material is complete. The present invention effectively improves the thermal insulation effect of the material while improving the accuracy of preparing the polyurethane rigid foam thermal insulation material.

Description

Technical Field

[0001] The present invention relates to the technical field of heat-insulating material preparation, in particular to a method for preparing a polyurethane rigid foam heat-insulating material. Background Art

[0002] In actual applications, polyurethane rigid foam insulation materials need to face various complex environmental conditions, such as high temperature, low temperature, high humidity, mechanical impact, etc. These environmental factors will affect the service life and performance stability of the material. By optimizing the preparation parameters of polyurethane rigid foam, such as raw material ratio, foaming temperature, catalyst dosage, etc., its 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-saving standards.

[0003] Chinese patent application publication number CN118240173A discloses a process for preparing a high-strength polyurethane thermal insulation material. This invention, belonging to the field of thermal insulation materials, employs a ring-opening crosslinking reaction between a quaternary ammonium epoxy triphenyl-s-triazine crosslinker and the hydroxymethyl groups of starch using tin tetrachloride as a catalyst. The resulting modified starch aerogel is then freeze-dried to produce a modified starch aerogel. The numerous hydroxyl groups in the modified starch aerogel serve as polymerization sites for graft polymerization with diisocyanate compounds and polyether polyols, resulting in a high-strength polyurethane thermal insulation material grafted with the starch aerogel. This enhances the interfacial compatibility between the starch aerogel and the polyurethane, and the modified starch aerogel exhibits higher mechanical strength, minimizing the impact of the modified starch aerogel on the mechanical properties of the polyurethane, while maintaining excellent mechanical properties. This process also reduces the thermal conductivity of the polyurethane material, improving its thermal insulation performance and enhancing its antibacterial properties.

[0004] This shows that the existing technology generates a large number of hydroxyl groups to form higher mechanical strength, reduce the closed porosity inside the material, and weaken the thermal insulation effect. Summary of the Invention

[0005] To this end, the present invention provides a method for preparing a polyurethane rigid foam thermal insulation material, which is used to overcome the problem in the prior art that a large amount of hydroxyl groups are generated to form higher mechanical strength, reduce the closed porosity inside the material, and weaken the thermal insulation effect.

[0006] To achieve the above object, the present invention provides a method for preparing a polyurethane rigid foam thermal insulation material, comprising:

[0007] Mixing polyol and nano-silicon dioxide through a high shear emulsifier to generate a first raw material;

[0008] The first raw material, the second raw material and the isocyanate are added into a high-pressure foaming machine in proportion, wherein the second raw material includes a blowing agent, a catalyst, a surfactant, a flame retardant and a temperature-sensitive cross-linking inhibitor;

[0009] After adjusting the temperature to a first temperature, the first raw material, the second raw material, and isocyanate are mixed by the high-pressure foaming machine, injected into a mold by an intermittent method, and reacted for 20 minutes to form a first mixture;

[0010] Adjusting the temperature to a second temperature, monitoring the reaction progress of the first mixture by infrared spectroscopy, adjusting the amount of catalyst, and reacting for 10 minutes to generate a second mixture;

[0011] adjusting the temperature to a third temperature in combination with microwave-assisted heating, curing the second mixture for 20 minutes, collecting a dielectric constant using a dielectric constant sensor, calculating and generating a dielectric loss factor, and determining whether a peak value is delayed based on the dielectric loss factor to determine whether to add additional catalyst;

[0012] The overheating area is determined based on the reaction temperature value monitored by the infrared thermal imager, and the release of the temperature-sensitive cross-linking inhibitor is controlled according to the distribution of the overheating area to determine whether the reaction of the finished insulation material is complete.

[0013] Furthermore, the process of monitoring the reaction progress of the first mixture according to infrared spectroscopy and adjusting the amount of the catalyst includes:

[0014] Determine the standard reaction conversion curve corresponding to different catalyst concentrations;

[0015] The decay rate of the isocyanate group in the first mixture is collected by infrared spectroscopy to calculate the reaction conversion rate;

[0016] 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 based on the comparison result;

[0017] The preset rate difference is positively correlated with the hydroxyl concentration in the first mixture.

[0018] Furthermore, the process of mixing the polyol and the nano-silicon dioxide through the high shear emulsifier to generate the first raw material includes:

[0019] Drying the nano-silica in a vacuum oven at 80-100° C. for 4-6 hours;

[0020] The polyol and the nano-silica are mixed and added into the high shear emulsifier, the speed is set to 8000-12000 rpm, and the mixture is processed for 5-10 minutes;

[0021] Increase the speed to 20,000 rpm and continue processing for 15 to 30 minutes to generate a dispersion;

[0022] placing the dispersion in a vacuum degassing machine and degassing at a vacuum degree of -0.09 MPa for 15 to 30 minutes to generate the first raw material;

[0023] Wherein, the operating temperature of the high shear emulsifier is maintained below 40° C. through a circulating water cooling system.

[0024] Furthermore, the process of injecting the mixture into the mold by an intermittent method and reacting for 20 minutes to form the first mixture includes:

[0025] Adjusting the temperature to the first temperature, setting the working pressure of the high-pressure foaming machine to 10 MPa-15 MPa, and mixing the first raw material, the second raw material, and the isocyanate to form a premix;

[0026] Injecting the premix into a mold in several portions;

[0027] Close the mold and let it react for 20 minutes.

[0028] Further, the temperature is adjusted to the second temperature, the reaction progress of the first mixture is monitored by infrared spectroscopy, the amount of catalyst is adjusted, and the process of generating the second mixture after the reaction for 10 minutes includes:

[0029] Adjusting the temperature to the second temperature, detecting the NCO peak area by infrared spectroscopy, and recording the initial NCO peak area and the NCO peak area at each time;

[0030] The NCO decrease rate is calculated using the NCO peak area at each moment, the NCO decrease rate is compared with a preset rate, and whether to add the catalyst is determined based on the comparison result;

[0031] After reacting for 10 minutes, the final NCO peak area was recorded, and whether a second mixture was generated was determined based on the final NCO peak area;

[0032] The preset rate is positively correlated with the initial concentration of the catalyst.

[0033] Furthermore, after 10 minutes of reaction, the final NCO peak area is recorded, and whether a second mixture is generated is determined based on the final NCO peak area, wherein:

[0034] Calculating a reaction ratio based on the final NCO peak area and the initial NCO peak area, comparing the reaction ratio with a preset ratio, and determining whether to extend the reaction time or generate a second mixture based on the comparison result;

[0035] The preset ratio is positively correlated with the total concentration of the catalyst.

[0036] Furthermore, the temperature is adjusted to the third temperature in combination with microwave-assisted heating, the second mixture is cured for 20 minutes, a dielectric constant is collected by a dielectric constant sensor, a dielectric loss factor is calculated and generated, and a peak value is determined to be delayed based on the dielectric loss factor to determine whether to add a catalyst. The process includes:

[0037] transferring the second mixture to a microwave reaction chamber, and adjusting the temperature to the third temperature using the microwave-assisted heating;

[0038] The dielectric constant is collected by the dielectric constant sensor, the dielectric loss factor is calculated and generated at each moment, the maximum value of the dielectric loss factor is selected as the reaction peak, and the time corresponding to the reaction peak is recorded as the peak time;

[0039] Whether the reaction is delayed is determined based on the peak time, and whether the catalyst is insufficient is determined based on the reaction peak.

[0040] Furthermore, whether the reaction is delayed is determined based on the peak time, and whether the catalyst is insufficient is determined based on the reaction peak, wherein:

[0041] If the peak time is greater than or equal to the preset time, it is determined that the reaction is delayed;

[0042] If the reaction peak value is less than or equal to a preset peak value, it is determined that the catalyst is insufficient;

[0043] The preset time is positively correlated with the mold setting temperature, and the reaction peak is positively correlated with the total amount of reaction raw materials.

[0044] Furthermore, based on the reaction temperature value monitored by the infrared thermal imager, the release of the temperature-sensitive cross-linking inhibitor is controlled to determine whether the reaction of the finished thermal insulation material is complete. The process includes:

[0045] Using an infrared thermal imager to monitor the reaction temperature values ​​of various areas of the mold, and determining the overheating area based on the reaction temperature;

[0046] releasing the temperature-sensitive cross-linking inhibitor in the overheated area;

[0047] When the reaction temperature of the overheating area decreases to become a non-overheating area, the release of the temperature-sensitive cross-linking inhibitor is stopped, and it is determined that the reaction of the finished thermal insulation material is completed.

[0048] Furthermore, the components for preparing the polyurethane rigid foam insulation material include, by weight: 100 parts of polyol, 1 to 5 parts of nano-silica, 100 to 120 parts of isocyanate, 10 to 20 parts of foaming agent, 0.5 to 3 parts of catalyst, 1 to 3 parts of surfactant, 10 to 20 parts of flame retardant and 0.5 to 2 parts of temperature-sensitive cross-linking inhibitor.

[0049] Compared with the prior art, the beneficial effect of the present invention lies in that the present invention monitors the reaction progress of the first mixture according to infrared spectroscopy and adjusts the catalyst dosage. When infrared monitoring shows that the -NCO consumption rate is lower than the preset value, the catalyst is automatically added to accelerate the cross-linking reaction and avoid premature volatilization of the foaming agent, which causes the collapse of the foam cells. The traditional method for preparing polyurethane rigid foam insulation materials may not be able to accurately control the reaction process, resulting in unstable product quality. The present invention can accurately grasp the reaction progress through infrared spectroscopy monitoring and catalyst dosage adjustment, thereby more accurately controlling the reaction conditions, making the prepared polyurethane rigid foam insulation material more stable and uniform in performance, and improving the accuracy of preparation. An accurate preparation process helps to improve the performance of polyurethane rigid foam insulation materials. Accurate control of the reaction process can avoid waste of raw materials due to incomplete reaction or overreaction, reduce production costs, monitor the reaction progress in real time and adjust the catalyst dosage in time, so that the reaction can always be in an efficient state, shorten the production cycle, improve production efficiency, and improve the accuracy of the preparation of polyurethane rigid foam insulation materials.

[0050] Furthermore, in the present invention, the first raw material is generated by mixing the polyol and the nano-silica through the high-shear emulsifier. The uniform dispersion of nano-silica in the polyol is one of the key factors to ensure the performance of 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 serves as a reaction medium, which 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 with the high-shear emulsifier can provide a stable reaction environment for subsequent reactions, further improving the accuracy of preparation. The uniform dispersion of nano-silica can significantly improve the mechanical properties and thermal insulation properties of polyurethane rigid foam. The uniform mixture can reduce defects and uneven structures inside the material, improve the overall performance and service life of the material, and further improve the accuracy of preparation of polyurethane rigid foam thermal insulation materials.

[0051] Furthermore, in the present invention, an intermittent method is adopted to inject the material into the mold, and a first mixture is formed after 20 minutes of reaction. The intermittent method of injecting the material into the mold can accurately control the amount and time of adding the raw materials, avoiding uneven distribution caused by one-time injection. This precise control helps to ensure that the reaction is carried out uniformly in the mold, thereby improving the accuracy of the preparation. By forming the first mixture after 20 minutes, it can be ensured that the reaction is carried out under stable conditions. Such stable reaction conditions help to improve the repeatability and consistency of the reaction, further improving the accuracy of the preparation. The intermittent method of injecting the material into the mold and the reaction time of 20 minutes 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 insulation material, such as thermal insulation performance, mechanical properties, etc., further improving the accuracy of the preparation of the polyurethane rigid foam insulation material.

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

[0053] Furthermore, in the present invention, the dielectric constant is collected by a dielectric constant sensor, and the dielectric loss factor is calculated and generated. The peak value is determined to be delayed based on the dielectric loss factor to determine whether a catalyst should be added. The dielectric constant is monitored in real time by the dielectric constant sensor, and the dielectric loss factor is calculated, so that the degree of reaction can be accurately monitored. This precise monitoring helps to ensure that the reaction is carried out under the expected conditions, thereby improving the accuracy of the preparation. According to the monitoring results of the dielectric loss factor, it is possible to determine in real time whether the peak value is delayed and decide whether to add a catalyst. This real-time adjustment can avoid product performance differences caused by incomplete reaction or overreaction, further improving the accuracy of the preparation. By precisely controlling the reaction progress, it can ensure that the performance of the polyurethane rigid foam insulation material is 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 insulation material.

[0054] Furthermore, the present invention controls the release of the temperature-sensitive cross-linking inhibitor by monitoring the reaction temperature value based on an infrared thermal imager to determine whether the reaction of the finished thermal insulation material is complete. The infrared thermal imager can monitor the temperature changes during the reaction in real time and accurately, especially the occurrence of temperature peaks. This precise monitoring helps to ensure that the reaction is carried out under the expected conditions, thereby improving the accuracy of the preparation. By controlling the release of the temperature-sensitive cross-linking 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 a reaction or excessive cross-linking, further improving the accuracy of the preparation. By precisely controlling the reaction temperature and the degree of cross-linking, it can ensure that the performance of the polyurethane rigid foam thermal insulation material is more uniform and stable, further improving the accuracy of the preparation of the polyurethane rigid foam thermal insulation material. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a flow chart of the method for preparing the polyurethane rigid foam thermal insulation material of the present invention;

[0056] Figure 2 A logic diagram for adjusting the amount of catalyst used in the first mixture according to an embodiment of the present invention;

[0057] Figure 3 A flow chart showing the mixing and generation of a first raw material according to an embodiment of the present invention;

[0058] Figure 4 This is a logic diagram for determining whether to generate a second mixture according to an embodiment of the present invention. DETAILED DESCRIPTION

[0059] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention.

[0060] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0061] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside", and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is only for the 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. Therefore, it cannot be understood as a limitation on the present invention.

[0062] Furthermore, it should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0063] See also Figure 1 As shown, it is a flow chart of a method for preparing a polyurethane rigid foam thermal insulation material of the present invention. An embodiment of the present invention provides a method for preparing a polyurethane rigid foam thermal insulation material, comprising:

[0064] Step S1, mixing polyol and nano-silicon dioxide through a high shear emulsifier to generate a first raw material;

[0065] Step S2, adding the first raw material, the second raw material and the isocyanate into a high-pressure foaming machine in proportion, wherein the second raw material includes a blowing agent, a catalyst, a surfactant, a flame retardant and a temperature-sensitive cross-linking inhibitor;

[0066] Step S3, after adjusting the temperature to the first temperature, mixing the first raw material, the second raw material and the isocyanate through a high-pressure foaming machine, injecting into a mold by an intermittent method, and reacting for 20 minutes to form a first mixture;

[0067] Step S4, adjusting the temperature to a second temperature, monitoring the reaction progress of the first mixture by infrared spectroscopy, adjusting the amount of catalyst, and reacting for 10 minutes to generate a second mixture;

[0068] Step S5, adjusting the temperature to a third temperature in combination with microwave-assisted heating, curing the second mixture for 20 minutes, collecting the dielectric constant using a dielectric constant sensor, calculating and generating a dielectric loss factor, and determining whether the peak value is delayed based on the dielectric loss factor to determine whether to add additional catalyst;

[0069] Step S6, determining the overheating area based on the reaction temperature value monitored by the infrared thermal imager, controlling the release of the temperature-sensitive cross-linking inhibitor according to the distribution of the overheating area, and determining whether the reaction of the finished insulation material is complete.

[0070] See also Figure 2 As shown in FIG. , which is a logic diagram for adjusting the catalyst dosage of the first mixture according to an embodiment of the present invention, in step S4, the reaction progress of the first mixture is monitored according to infrared spectroscopy, and the process of adjusting the catalyst dosage includes:

[0071] Determine the standard reaction conversion curve corresponding to different catalyst concentrations;

[0072] The decay rate of the isocyanate group in the first mixture is collected by infrared spectroscopy to calculate the reaction conversion rate;

[0073] 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 based on the comparison result;

[0074] It is understood that isocyanate group (-NCO) has a characteristic absorption peak in infrared spectrum (2270–2250 ), its peak area decay is linearly related to the decrease in -NCO concentration. During the reaction, the peak area gradually weakens with the consumption of -NCO groups. By real-time acquisition of the -NCO peak area changes, the reaction conversion rate can be accurately calculated. The reaction rate can be calculated through the reaction conversion rate, realizing dynamic tracking of the reaction process.

[0075] It is understood that the reaction rate of the first mixture is ,in, is the reaction conversion rate, t is the time (unit: min), and the reaction rate of the standard curve is ,in, 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.

[0076] If the rate difference is less than or equal to the preset rate difference, it is determined to increase the amount of catalyst;

[0077] If the rate difference is greater than the preset rate difference, it is determined to maintain the current response;

[0078] 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 that the amount of catalyst is increased.

[0079] If the rate difference is 0.08% / min and is greater than the preset rate difference, it is determined that the current reaction is maintained.

[0080] The preset rate difference is positively correlated with the concentration of hydroxyl groups in the first mixture.

[0081] It can be understood that the greater the concentration of hydroxyl groups in the first mixture, the faster the reaction will be at the same catalyst dosage, so the preset rate difference is positively correlated with the concentration of hydroxyl groups in the first mixture.

[0082] Preferably, the hydroxyl concentration in the first mixture is 0.5 mol / L, and the preset rate difference is 0.02% / min;

[0083] The hydroxyl concentration in the first mixture is 1.0 mol / L, and the preset rate difference is 0.05% / min;

[0084] The hydroxyl concentration in the first mixture is 1.5 mol / L, and the preset rate difference is 0.08% / min.

[0085] Specifically, the present invention monitors the reaction progress of the first mixture according to infrared spectroscopy and adjusts the catalyst dosage. If the infrared monitoring shows that the -NCO consumption rate is lower than the preset value, the catalyst is automatically added to accelerate the cross-linking reaction and avoid premature volatilization of the foaming agent, which causes the collapse of the foam cells. The traditional method for preparing polyurethane rigid foam thermal insulation materials may not be able to accurately control the reaction process, resulting in unstable product quality. The present invention can accurately grasp the reaction progress through infrared spectroscopy monitoring and catalyst dosage adjustment, thereby more accurately controlling the reaction conditions, making the prepared polyurethane rigid foam thermal insulation material more stable and uniform in performance, and improving the accuracy of preparation. An accurate preparation process helps to improve the performance of polyurethane rigid foam thermal insulation materials. Accurate control of the reaction process can avoid waste of raw materials due to incomplete reaction or overreaction, reduce production costs, monitor the reaction progress in real time and adjust the catalyst dosage in time, so that the reaction can always be in an efficient state, shorten the production cycle, improve production efficiency, and improve the accuracy of the preparation of polyurethane rigid foam thermal insulation materials.

[0086] See also Figure 3 As shown, it is a flow chart of mixing and generating the first raw material according to an embodiment of the present invention. In step S1, the process of mixing polyol and nano-silicon dioxide by a high shear emulsifier to generate the first raw material includes:

[0087] Step S101, drying the nano-silicon dioxide in a vacuum oven at 80-100° C. for 4-6 hours;

[0088] Step S102: Add the polyol and nano-silica mixture to a high shear emulsifier, set the speed to 8000-12000 rpm, and process for 5-10 minutes;

[0089] Step S103, increasing the rotation speed to 20,000 rpm and continuing the process for 15 to 30 minutes to generate a dispersion;

[0090] Step S104, placing the dispersion in a vacuum degassing machine and degassing at a vacuum degree of -0.09 MPa for 15 to 30 minutes to generate a first raw material;

[0091] Among them, the operating temperature of the high shear emulsifier is maintained below 40°C through a circulating water cooling system.

[0092] It is understandable that the high specific surface area of ​​nano-silica enables it to form a strong interfacial interaction when in contact with polyols, significantly improving the mechanical properties of the mixture; nanoparticles are easy to agglomerate, and the strong shear force of the high shear emulsifier can overcome the attraction between particles and achieve uniform dispersion at the nanoscale.

[0093] Specifically, in the present invention, the first raw material is generated by mixing polyol and nano-silica through a high-shear emulsifier. The uniform dispersion of nano-silica in the polyol is one of the key factors to ensure the performance of polyurethane rigid foam. The use of a 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 serves as a reaction medium, which 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 in a high-shear emulsifier can provide a stable reaction environment for subsequent reactions, further improving the accuracy of preparation. The uniform dispersion of nano-silica can significantly improve the mechanical properties and thermal insulation properties of polyurethane rigid foam. The uniform mixture can reduce defects and uneven structures inside the material, improve the overall performance and service life of the material, and further improve the accuracy of preparation of polyurethane rigid foam thermal insulation materials.

[0094] Specifically, in step S3, the process of injecting the mixture into the mold by the intermittent method and reacting for 20 minutes to form the first mixture includes:

[0095] Adjusting the temperature to the first temperature, setting the working pressure of the high-pressure foaming machine to 10 MPa-15 MPa, and mixing the first raw material, the second raw material and the isocyanate to form a premix;

[0096] Pour the premix into the mold in several portions;

[0097] Close the mold and let it react for 20 minutes.

[0098] It is understandable that, preferably, the first temperature is 25° C., which is close to room temperature. This can ensure a moderate reaction rate between isocyanate and polyol, avoid violent reaction at high temperature leading to uncontrolled foaming, and extend the operation time of the premix.

[0099] Specifically, the present invention adopts an intermittent method to inject into the mold, and forms a first mixture after 20 minutes of reaction. The intermittent method of injecting into the mold can accurately control the amount and time of raw materials added, avoiding uneven distribution caused by one-time injection. This precise control helps to ensure that the reaction is carried out evenly in the mold, thereby improving the accuracy of preparation. By forming the first mixture after 20 minutes, it can be ensured that the reaction is carried out under stable conditions. Such stable reaction conditions help to improve the repeatability and consistency of the reaction, further improving the accuracy of preparation. The intermittent method of injecting into the mold and the reaction time of 20 minutes can ensure the uniform distribution and reaction of the raw materials in the mold. This uniformity helps to improve the performance of polyurethane rigid foam insulation materials, such as thermal insulation performance, mechanical properties, etc., further improving the accuracy of preparation of polyurethane rigid foam insulation materials.

[0100] Specifically, in step S4, the temperature is adjusted to the second temperature, the reaction progress of the first mixture is monitored by infrared spectroscopy, the amount of catalyst is adjusted, and the process of generating the second mixture after the reaction for 10 minutes includes:

[0101] Adjusting the temperature to the second temperature, detecting the NCO peak area by infrared spectroscopy, and recording the initial NCO peak area and the NCO peak area at each time;

[0102] The NCO decrease rate is calculated using the NCO peak area at each moment, and the NCO decrease rate is compared with the preset rate to determine whether to add catalyst based on the comparison result;

[0103] After 10 minutes of reaction, the final NCO peak area was recorded, and whether the second mixture was generated was determined based on the final NCO peak area;

[0104] Preferably, the second temperature is 40°C-50°C.

[0105] It can be understood that the NCO decrease rate is the difference between the NCO peak areas measured at adjacent moments divided by the time difference between the adjacent moments.

[0106] If the NCO decrease rate is greater than or equal to the preset rate, the reaction is determined to be normal;

[0107] If the NCO decreasing rate is less than the preset rate, it is determined that the catalyst should be added;

[0108] In a specific embodiment, the preset rate is set to 15 a.u. / min. If the NCO decrease rate is 19 a.u. / min, which is greater than the preset rate, the reaction is determined to be normal.

[0109] If the NCO decreasing rate is 13a.u. / min, which is less than the preset rate, it is determined that the catalyst should be added;

[0110] The preset rate is positively correlated with the initial catalyst concentration.

[0111] It can be understood that the higher the initial concentration of the catalyst, the faster the reaction, so the preset rate is positively correlated with the initial concentration of the catalyst.

[0112] Preferably, the initial concentration of the catalyst is 0.01% and the preset rate is 5 a.u. / min;

[0113] The initial catalyst concentration was 0.03% and the preset rate was 12 a.u. / min;

[0114] The initial catalyst concentration was 0.05% and the preset rate was 20 a.u. / min.

[0115] See also Figure 4As shown, it is a logic diagram for determining whether a second mixture is generated according to an embodiment of the present invention. In step S4, after reacting for 10 minutes, the final NCO peak area is recorded, and whether a second mixture is generated is determined based on the final NCO peak area, wherein:

[0116] Calculate a 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 generate a second mixture based on the comparison result;

[0117] It is understandable that .

[0118] If the reaction ratio is less than the preset ratio, it is determined that the reaction time is extended;

[0119] If the reaction ratio is greater than or equal to the preset ratio, it is determined that a second mixture is generated;

[0120] In a specific embodiment, the preset ratio is set to 0.9, and if the reaction ratio is 0.84, which is less than the preset ratio, it is determined that the reaction time is extended;

[0121] If the reaction ratio is 0.92 and is greater than the preset ratio, it is determined that the second mixture is generated.

[0122] The preset ratio is positively correlated with the total catalyst concentration.

[0123] It can be understood that the greater the total catalyst concentration, the faster the reaction. Under the same reaction time, the final NCO peak area is larger, so the preset ratio is positively correlated with the total catalyst concentration.

[0124] Preferably, the total catalyst concentration is 0.05 mol / L, and the preset ratio is 0.6;

[0125] If the total catalyst concentration is 0.06 mol / L, the preset ratio is 0.8;

[0126] The total catalyst concentration is 0.07 mol / L, and the preset ratio is 0.9.

[0127] It is understandable that, when it is determined that the reaction time should be extended, the reaction time can be optionally extended by 5 minutes before measuring the reaction ratio.

[0128] Specifically, in the present invention, by recording the final NCO peak area, determining whether a second mixture is generated based on the final NCO peak area, and recording the NCO peak area through infrared spectroscopy analysis, the consumption of NCO groups during the reaction process can be accurately monitored. This precise monitoring helps to ensure that the reaction is carried out under the expected conditions, thereby improving the accuracy of the preparation. According to the monitoring results of the NCO peak area, the reaction conditions can be adjusted or the reactants can be supplemented in real time. This real-time adjustment can avoid product performance differences caused by incomplete reaction or overreaction, further improving the accuracy of the preparation. By precisely controlling the reaction progress, the performance of the polyurethane rigid foam insulation material can be ensured to be more uniform and stable. For example, the uniform consumption of NCO groups can improve the thermal insulation and mechanical properties of the material, further improving the accuracy of the preparation of the polyurethane rigid foam insulation material.

[0129] Specifically, in step S5, the temperature is adjusted to a third temperature in combination with microwave-assisted heating, the second mixture is cured for 20 minutes, a dielectric constant is collected by a dielectric constant sensor, a dielectric loss factor is calculated and generated, and a peak value is determined to be delayed based on the dielectric loss factor to determine whether to add a catalyst. The process includes:

[0130] transferring the second mixture to a microwave reaction chamber, and adjusting the temperature to a third temperature using microwave-assisted heating;

[0131] The dielectric constant is collected by the dielectric constant sensor, and the dielectric loss factor at each moment is calculated and generated. The maximum value of the dielectric loss factor is selected as the reaction peak, and the time corresponding to the reaction peak is recorded as the peak time;

[0132] The peak time is used to determine whether the reaction is delayed, and the reaction peak is used to determine whether the catalyst is insufficient.

[0133] Preferably, the third temperature is 60°C-65°C.

[0134] It is understandable that microwaves directly heat polar molecules through dielectric loss, and the heating rate is 3 to 5 times faster than traditional heating. The temperature uniformity is better and can be accurately controlled to ±2°C to avoid local overheating.

[0135] It is understandable 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 reaction peak value.

[0136] It can be understood that dielectric loss factor = dielectric constant x tanδ, where tanδ is the loss tangent value, which represents the proportion of viscous loss.

[0137] Specifically, in step S5, it is determined whether the reaction is delayed based on the peak time, and whether the catalyst is insufficient based on the reaction peak.

[0138] If the peak time is greater than or equal to the preset time, the reaction is determined to be delayed;

[0139] If the reaction peak value is less than or equal to the preset peak value, it is determined that the catalyst is insufficient;

[0140] In a specific embodiment, the preset time is set to 8 minutes. If the peak time is 12 minutes, which is greater than the preset time, it is determined that the response is delayed.

[0141] In a specific embodiment, the preset peak value is set to 150 a.u., and if the reaction peak value is 128 a.u., which is smaller than the preset peak value, it is determined that the catalyst is insufficient.

[0142] The preset time is positively correlated with the mold setting temperature, and the reaction peak is positively correlated with the total amount of reaction raw materials.

[0143] It is understandable that the higher the mold setting temperature is, the higher the starting temperature of the reaction is and the faster the reaction is. Therefore, the preset time is positively correlated with the mold setting temperature.

[0144] Preferably, the mold temperature is set to 60 degrees Celsius and the preset time is 10 minutes;

[0145] The mold temperature is set to 63 degrees Celsius and the preset time is 9 minutes;

[0146] The mold temperature is set to 65 degrees Celsius and the preset time is 8 minutes;

[0147] It can be understood that the greater the total amount of reaction raw materials, the greater the reaction peak.

[0148] Preferably, the total amount of reaction raw materials is 20 kg, and the reaction peak is 150 a.u.;

[0149] The total amount of reaction raw materials is 40 kg, and the reaction peak is 300 a.u.;

[0150] The total amount of reaction raw materials is 60 kg, and the reaction peak is 450 a.u.

[0151] Specifically, in the present invention, the dielectric constant is collected by a dielectric constant sensor, the dielectric loss factor is calculated and generated, and the peak value is determined to be delayed based on the dielectric loss factor to determine whether to add a catalyst. The dielectric constant is monitored in real time by the dielectric constant sensor, and the dielectric loss factor is calculated, so as to accurately monitor the progress of the reaction. This precise monitoring helps to ensure that the reaction is carried out under the expected conditions, thereby improving the accuracy of the preparation. According to the monitoring results of the dielectric loss factor, it is possible to determine in real time whether the peak value is delayed and decide whether to add a catalyst. This real-time adjustment can avoid product performance differences caused by incomplete reaction or excessive reaction temperature value, further improving the accuracy of the preparation. By precisely controlling the reaction progress, it can ensure that the performance of the polyurethane rigid foam insulation material is 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 insulation material.

[0152] Specifically, in step S6, based on the reaction temperature value monitored by the infrared thermal imager, the release of the temperature-sensitive cross-linking inhibitor is controlled to determine whether the reaction of the finished thermal insulation material is complete. The process includes:

[0153] Use an infrared thermal imager to monitor the reaction temperature values ​​of each area of ​​the mold and determine the overheating area based on the reaction temperature;

[0154] Releases temperature-sensitive cross-linking inhibitors in overheated areas;

[0155] When the reaction temperature in the overheating area decreases to the non-overheating area, the release of the temperature-sensitive cross-linking inhibitor is stopped, and it is determined that the reaction of the finished thermal insulation material is completed.

[0156] If the reaction temperature is greater than or equal to the preset temperature, the area corresponding to the reaction temperature is determined to be an overheating area;

[0157] If the reaction temperature is lower than the preset temperature, the area corresponding to the reaction temperature is determined to be a non-overheated area;

[0158] 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, then the region corresponding to the reaction temperature is determined to be an overheated region.

[0159] If the reaction temperature is 64° C., which is lower than the preset temperature, the region corresponding to the reaction temperature is determined to be a non-overheating region.

[0160] The preset temperature is positively correlated with the total catalyst concentration.

[0161] It is understandable that the higher the total catalyst concentration, the more intense the reaction and the correspondingly higher the reaction temperature, so the preset temperature is positively correlated with the total catalyst concentration.

[0162] Preferably, the total concentration of the catalyst is 0.05 mol / L, and the preset temperature is 65°C;

[0163] The total catalyst concentration is 0.06 mol / L, so the preset temperature is 70°C;

[0164] The total catalyst concentration is 0.07 mol / L, and the preset temperature is 80°C.

[0165] It is understandable that the polyurethane foaming reaction is a highly exothermic reaction. The reaction rate increases by 2-4 times for every 10°C increase in temperature. Excessive local temperature will lead to the formation of hard and brittle "burned" areas, increased thermal conductivity of the insulation material, deterioration of mechanical properties, and excessive volatilization of the CO2 foaming agent generated by the reaction of isocyanate and water, resulting in bubble collapse or uneven size. The accumulated heat may cause explosion or overheating damage to the equipment. The effect of the temperature-sensitive cross-linking inhibitor is similar to a "temperature switch", which can intervene immediately when overheating occurs and exit intervention when it is not overheating, to avoid obstruction of the global reaction.

[0166] Specifically, the present invention controls the release of temperature-sensitive cross-linking inhibitors by monitoring the reaction temperature value based on an infrared thermal imager to determine whether the reaction of the finished insulation material is complete. The infrared thermal imager can monitor the temperature changes during the reaction in real time and accurately, especially the occurrence of temperature peaks. This precise monitoring helps to ensure that the reaction is carried out under the expected conditions, thereby improving the accuracy of the preparation. By controlling the release of temperature-sensitive cross-linking inhibitors, 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 cross-linking, further improving the accuracy of the preparation. By precisely controlling the reaction temperature and the degree of cross-linking, the performance of the polyurethane rigid foam insulation material can be ensured to be more uniform and stable, further improving the accuracy of the preparation of the polyurethane rigid foam insulation material.

[0167] Specifically, the components for preparing polyurethane rigid foam insulation materials include, by weight: 100 parts of polyol, 1 to 5 parts of nano-silica, 100 to 120 parts of isocyanate, 10 to 20 parts of foaming agent, 0.5 to 3 parts of catalyst, 1 to 3 parts of surfactant, 10 to 20 parts of flame retardant and 0.5 to 2 parts of temperature-sensitive cross-linking inhibitor. Example

[0168] The components for preparing the polyurethane rigid foam insulation material include, by weight, 100 kg of polyol, 3 kg of nano-silica, 110 kg of isocyanate, 15 kg of blowing agent, 1.75 kg of catalyst, 2 kg of surfactant, 15 kg of flame retardant, and 1.25 kg of temperature-sensitive cross-linking inhibitor. The polyurethane rigid foam insulation material was prepared according to the above technical scheme, and the preset peak value was calculated to be 800 a.u., and the catalyst concentration was adjusted. The results are shown in Table 1.

[0169] Table 1 Comparison results of preset stirring parameter adjustments

[0170]

[0171] From the finished product structures of Examples 1 to 3 above, it can be concluded that Example 1 was not prepared using the technical solution of the present invention. Example 2 was prepared using the technical solution of the present invention, but without the addition of a catalyst. Example 3 was prepared using the technical solution of the present invention, and a catalyst was added based on the reaction peak value generated by the dielectric constant calculation.

[0172] Thus far, the technical solutions of the present invention have been described in conjunction with 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 may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

Claims

1. A method for preparing a polyurethane rigid foam thermal insulation material, characterized in that: include: Mixing polyol and nano-silicon dioxide through a high shear emulsifier to generate a first raw material; The first raw material, the second raw material and the isocyanate are added into a high-pressure foaming machine in proportion, wherein the second raw material includes a blowing agent, a catalyst, a surfactant, a flame retardant and a temperature-sensitive cross-linking inhibitor; After adjusting the temperature to a first temperature, the first raw material, the second raw material, and isocyanate are mixed by the high-pressure foaming machine, injected into a mold by an intermittent method, and reacted for 20 minutes to form a first mixture; Adjusting the temperature to a second temperature, monitoring the reaction progress of the first mixture by infrared spectroscopy, adjusting the amount of catalyst, and reacting for 10 minutes to generate a second mixture; adjusting the temperature to a third temperature in combination with microwave-assisted heating, curing the second mixture for 20 minutes, collecting a dielectric constant using a dielectric constant sensor, calculating and generating a dielectric loss factor, and determining whether a peak value is delayed based on the dielectric loss factor to determine whether to add additional catalyst; Determining overheating areas based on reaction temperature values ​​monitored by an infrared thermal imager, controlling the release of the temperature-sensitive cross-linking inhibitor according to the distribution of the overheating areas, and determining whether the reaction of the finished insulation material is complete; The process of adjusting the temperature to the third temperature in combination with microwave-assisted heating, curing the second mixture for 20 minutes, collecting the dielectric constant by a dielectric constant sensor, calculating and generating a dielectric loss factor, and determining whether the peak value is delayed based on the dielectric loss factor to determine whether to add a catalyst includes: transferring the second mixture to a microwave reaction chamber, and adjusting the temperature to the third temperature using the microwave-assisted heating; The dielectric constant is collected by the dielectric constant sensor, the dielectric loss factor is calculated and generated at each moment, the maximum value of the dielectric loss factor is selected as the reaction peak, and the time corresponding to the reaction peak is recorded as the peak time; Determine whether the reaction is delayed based on the peak time, and determine whether the catalyst is insufficient based on the reaction peak, wherein: 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 a preset peak value, it is determined that the catalyst is insufficient; The preset time is positively correlated with the mold setting temperature, and the reaction peak is positively correlated with the total amount of reaction raw materials.

2. The method for preparing the polyurethane rigid foam thermal insulation material according to claim 1, wherein: The process of monitoring the reaction progress of the first mixture according to infrared spectroscopy and adjusting the amount of catalyst includes: Determine the standard reaction conversion curve corresponding to different catalyst concentrations; The decay rate of the isocyanate groups in the first mixture is collected by infrared spectroscopy to calculate 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 based on the comparison result; The preset rate difference is positively correlated with the hydroxyl concentration in the first mixture.

3. The method for preparing the polyurethane rigid foam thermal insulation material according to claim 2, wherein: The process of mixing the polyol and the nano-silicon dioxide 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; The polyol and the nano-silica are mixed and added into the high shear emulsifier, the speed is set to 8000-12000 rpm, and the mixture is processed for 5-10 minutes; Increase the speed to 20,000 rpm and continue processing for 15 to 30 minutes to generate a dispersion; placing the dispersion in a vacuum degassing machine and degassing at a vacuum degree of -0.09 MPa for 15 to 30 minutes to produce the first raw material; Wherein, the operating temperature of the high shear emulsifier is maintained below 40° C. through a circulating water cooling system.

4. The method for preparing the polyurethane rigid foam thermal insulation material according to claim 3, characterized in that: The process of injecting the mixture into the mold by the intermittent method and reacting for 20 minutes to form the first mixture includes: Adjusting the temperature to the first temperature, setting the working pressure of the high-pressure foaming machine to 10 MPa-15 MPa, and mixing the first raw material, the second raw material, and the isocyanate to form a premix; Injecting the premix into a mold in several portions; Close the mold and let it react for 20 minutes.

5. The method for preparing the polyurethane rigid 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 by infrared spectroscopy, adjusting the amount of catalyst, and generating the second mixture after the reaction for 10 minutes includes: Adjusting the temperature to the second temperature, detecting the NCO peak area by infrared spectroscopy, and recording the initial NCO peak area and the NCO peak area at each time; The NCO decrease rate is calculated using the NCO peak area at each moment, the NCO decrease rate is compared with a preset rate, and whether to add the catalyst is determined based on the comparison result; After 10 minutes of reaction, the final NCO peak area was recorded, and whether a second mixture was generated was determined based on the final NCO peak area; The preset rate is positively correlated with the initial concentration of the catalyst.

6. The method for preparing the polyurethane rigid foam thermal insulation material according to claim 5, characterized in that: After 10 minutes of reaction, the final NCO peak area is recorded, and whether a second mixture is generated is determined based on the final NCO peak area, wherein: Calculating a reaction ratio based on the final NCO peak area and the initial NCO peak area, comparing the reaction ratio with a preset ratio, and determining whether to extend the reaction time or generate a second mixture based on the comparison result; The preset ratio is positively correlated with the total concentration of the catalyst.

7. The method for preparing the polyurethane rigid foam thermal insulation material according to claim 6, characterized in that: The process of controlling the release of the temperature-sensitive cross-linking inhibitor based on the reaction temperature value monitored by the infrared thermal imager to determine whether the reaction of the finished insulation material is complete includes: Using an infrared thermal imager to monitor the reaction temperature values ​​of various areas of the mold, and determining the overheating area based on the reaction temperature; releasing the temperature-sensitive cross-linking inhibitor in the overheated area; When the reaction temperature in the overheating zone decreases to a non-overheating zone, the release of the temperature-sensitive cross-linking inhibitor is stopped, and it is determined that the reaction of the finished thermal insulation material is completed.

8. The method for preparing the polyurethane rigid foam thermal insulation material according to claim 7, characterized in that: The components for preparing the polyurethane rigid foam thermal insulation material include, by weight: 100 parts of polyol, 1 to 5 parts of nano-silicon dioxide, 100 to 120 parts of isocyanate, 10 to 20 parts of foaming agent, 0.5 to 3 parts of catalyst, 1 to 3 parts of surfactant, 10 to 20 parts of flame retardant and 0.5 to 2 parts of temperature-sensitive cross-linking inhibitor.

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