Preparation method of water-based polyisocyanate, channel reaction module and reaction system

Abstract

The invention relates to the technical field of coating curing agents, and provides a preparation method of water-based polyisocyanate, a channel reaction module and a reaction system, and the preparation method of the water-based polyisocyanate.The preparation method of the water-based polyisocyanate comprises the following steps that a hydrophilic modifier and polyisocyanate are fed into the channel reaction module to be subjected to hydrophilic modification treatment, and the water-based polyisocyanate is obtained; and the channel diameter of the channel type reaction module is 6-12 mm. According to the technical scheme, the problem that continuous preparation of the water-based polyisocyanate is difficult to realize in related technologies is solved.

Description

Technical Field

[0001] This invention relates to the field of coating curing agent technology, specifically to a method for preparing waterborne polyisocyanates, a channel reaction module, and a reaction system. Background Technology

[0002] Waterborne polyisocyanates are one of the important raw materials in the field of coating curing agents. Waterborne coatings formed by compounding waterborne polyisocyanates with waterborne hydroxy acrylate resins, waterborne alkyd resins, and waterborne polyester resins have excellent adhesion, abrasion resistance, and hardness, and are widely used in hardware, wood products, electrical appliances, transportation vehicles, and other fields.

[0003] The preparation of waterborne polyisocyanates generally involves reacting hydrophilic small molecules containing hydroxyl or amino groups with some isocyanate groups in oily polyisocyanates to achieve hydrophilic modification of polyisocyanates. The traditional method for preparing waterborne polyisocyanates is mainly the batch reaction method. The main disadvantages of the batch reaction method are: (1) Mass transfer and heat transfer are mainly completed by stirring, resulting in low mass transfer and heat transfer efficiency, leading to low reaction efficiency and long reaction cycle; (2) The batch reaction requires a high reaction temperature and has many side reactions, such as cyclization and polymerization of isocyanates, which leads to a decrease in the content of isocyanate groups in the product and a decrease in the content of effective reactive groups in waterborne polyisocyanates. Especially when the hydrophilic small molecule modifier is a compound containing secondary amine groups, the secondary amine has low activity, the reaction requires a high temperature, and the side reactions are more obvious; (3) The batch reaction method is a batch method and cannot meet the requirements of continuous operation; (4) In order to control the reaction, organic solvents are often used in the process, and the solvent needs to be removed after the reaction, which increases the complexity of the reaction and has poor environmental performance.

[0004] Microchannel reactions, with channels less than 3mm in diameter, reduce the molecular diffusion distance of reactants, resulting in rapid mass transfer. Simultaneously, the microchannel reaction module (channel diameter less than 3mm) has a large specific surface area, strong heat transfer capacity, and enables precise temperature control. Compared to batch reactors, microchannel reactions offer significant advantages in mass and heat transfer, effectively shortening reaction cycles, enabling continuous production, reducing side reactions, improving product quality, and reducing footprint while being safer and more environmentally friendly.

[0005] Although microchannel reactions are widely used in the preparation of polyisocyanates, the hydrophilic modification of polyisocyanates is difficult to achieve due to the more complex characteristics of the raw materials and the types of reactions involved. This is precisely why there are few research reports on the preparation of aqueous polyisocyanates using microchannel reactions. Summary of the Invention

[0006] This invention proposes a method for preparing aqueous polyisocyanates, a channel reaction module, and a reaction system to at least partially solve the above-mentioned technical problems.

[0007] The technical solution of the present invention is as follows: This invention proposes a method for preparing waterborne polyisocyanates, comprising the following steps: feeding a hydrophilic modifier and a polyisocyanate into a channel-type reaction module for hydrophilic modification treatment to obtain waterborne polyisocyanates; The channel diameter of the channel-type reaction module is 6~12 mm.

[0008] As a further technical solution, the hydrophilic modification treatment is carried out at a temperature of 60~150℃ for a time of 300~600s.

[0009] As a further technical solution, the hydrophilic modification treatment includes channel preheating treatment and channel reaction treatment in sequence; the temperature of the channel preheating treatment is 10~50℃ higher than the temperature of the channel reaction treatment, and the time of the channel preheating treatment is 75~150 s.

[0010] As a further technical solution, the mass ratio of the hydrophilic modifier to the polyisocyanate is 4~25:100.

[0011] As a further technical solution, the hydrophilic modifier is a dehydrated hydrophilic modifier.

[0012] As a further technical solution, the aqueous polyisocyanate includes aqueous non-blocked polyisocyanate and aqueous blocked polyisocyanate. When the aqueous polyisocyanate is an aqueous blocked polyisocyanate, the hydrophilic modification treatment further includes a blocking treatment and an emulsification treatment in sequence.

[0013] As a further technical solution, the temperature of the sealing treatment is 40~90℃ and the time is 60~300 s.

[0014] As a further technical solution, during the sealing treatment, the mass ratio of the sealing agent to the hydrophilically modified polyisocyanate is 1:2~4.

[0015] The present invention also proposes a channel reaction module for the preparation method of the aqueous polyisocyanate, wherein the channel diameter is 6-12 mm.

[0016] As a further technical solution, the channels of the channel reaction module include a zigzag or serpentine shape.

[0017] The present invention also proposes a reaction system comprising one of the aforementioned channel reaction modules or multiple channel reaction modules connected in series.

[0018] The working principle and beneficial effects of this invention are as follows: In existing technologies, the advantages of microchannel reactions, such as continuous production and high mass and heat transfer efficiency, stem from their small channel size. The smaller the channel diameter, the larger the specific surface area, and the stronger the mass and heat transfer capacity. However, in this invention, the inventors have overcome this technical bias, discovering that in the continuous preparation process of hydrophilic modification of polyisocyanates, the size of the reaction channel is not necessarily better the smaller it is, but rather there exists an optimal range: a channel diameter of 6-12 mm allows for the continuous preparation of aqueous polyisocyanates through channel-type reactions. Specifically, when the channel diameter of the reaction module is 6-12 mm, it ensures that high-viscosity raw materials can continuously and stably enter the reaction module for hydrophilic modification; on the other hand, it ensures that the raw materials can be uniformly mixed, resulting in more complete hydrophilic modification of the polyisocyanate, thereby preventing subsequent gelation of the aqueous polyisocyanate. Attached Figure Description

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 This is a schematic diagram of the zigzag channel reaction module of the present invention; Figure 2 This is a schematic diagram of the serpentine channel reaction module of the present invention; Figure 3 This is a schematic diagram of the system for preparing aqueous non-blocked polyisocyanates using a liquid hydrophilic modifier according to the present invention; Figure 4 This is a schematic diagram of the system for preparing waterborne non-blocked polyisocyanates using a solid hydrophilic modifier according to the present invention. Figure 5 This is a schematic diagram of the system for preparing aqueous blocked polyisocyanates using liquid hydrophilic modifiers and liquid blocking agents according to the present invention; Figure 6 This is a schematic diagram of the emulsification process of the present invention; Figure 7 This is a schematic diagram of the system for preparing aqueous blocked polyisocyanates using a liquid hydrophilic modifier and a solid blocking agent according to the present invention; Figure 8 This is a schematic diagram of the system for preparing aqueous blocked polyisocyanates using a solid hydrophilic modifier and a liquid blocking agent according to the present invention; Figure 9 This is a schematic diagram of the system for preparing waterborne blocked polyisocyanates using a solid hydrophilic modifier and a solid blocking agent according to the present invention. Figure 10 This is an appearance diagram of the aqueous non-blocked polyisocyanate prepared in Example 1 of the present invention; Figure 11 This is an appearance diagram of the aqueous non-blocked polyisocyanate prepared in Example 2 of the present invention; Figure 12 This is an appearance diagram of the aqueous non-blocked polyisocyanate prepared in Example 3 of the present invention; Figure 13 This is an appearance diagram of the aqueous non-blocked polyisocyanate prepared in Example 4 of the present invention; Figure 14 This is an appearance diagram of the aqueous non-blocked polyisocyanate prepared in Example 5 of the present invention; Figure 15 This is an appearance diagram of the aqueous blocked polyisocyanate prepared in Example 6 of the present invention; Figure 16 This is an appearance diagram of the aqueous blocked polyisocyanate prepared in Example 7 of the present invention; Figure 17 This is an appearance diagram of the aqueous blocked polyisocyanate prepared in Example 8 of the present invention; Figure 18 This is an appearance diagram of the aqueous blocked polyisocyanate prepared in Example 9 of the present invention; Figure 19 This is an appearance diagram of the aqueous blocked polyisocyanate prepared in Example 10 of the present invention; Figure 20 This is an appearance diagram of the aqueous blocked polyisocyanate prepared in Example 15 of the present invention. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] It should be understood that, unless the context clearly indicates otherwise, the terms “comprising,” “including,” or “having” as used herein refer to the presence of an element, but do not exclude the presence or addition of one or more other elements. Furthermore, as used herein, “comprising” and / or “including” indicate the presence of shapes, numbers, steps, operations, members, elements, and / or combinations thereof, and do not exclude the presence or addition of one or more other shapes, numbers, operations, elements, and / or combinations thereof.

[0023] In this application, the numerical range indicated by "~" refers to the range of values ​​specified as the lower and upper limits, respectively, before or after the term. When multiple values ​​for the upper or lower limit of any numerical range are mentioned, the range disclosed herein can be understood as a range with any one of the mentioned upper limits as its upper limit and any one of the mentioned lower limits as its lower limit.

[0024] Isocyanate groups not only readily undergo addition reactions with hydrophilic groups in hydrophilic modifiers, but also readily undergo various side reactions, such as spontaneous dimerization and trimerization to form cross-linked structures like urethane and isocyanurate. This can easily increase the viscosity of waterborne polyisocyanates and even cause gelation, reducing the product quality. Furthermore, if the reaction between the isocyanate groups and the hydrophilic modifier is incomplete, the isocyanate cannot be fully emulsified and dispersed in subsequent applications, affecting the performance of the final coating. How to achieve continuous preparation of waterborne polyisocyanates while further improving their product quality is another technical problem that needs to be solved.

[0025] To make the objectives, technical solutions and advantages of the present invention clearer, the preparation method, channel reaction module and reaction system of aqueous polyisocyanate according to embodiments of the present invention will be described in detail below.

[0026] According to one aspect of the present invention, a method for preparing an aqueous polyisocyanate is provided, comprising the following steps: feeding a hydrophilic modifier and a polyisocyanate into a channel-type reaction module for hydrophilic modification treatment to obtain an aqueous polyisocyanate; the channel diameter of the channel-type reaction module is 6~12 mm.

[0027] The hydrophilic modifier can be at least one of nonionic and anionic hydrophilic modifiers, and is not limited by solid-liquid state. The nonionic hydrophilic modifier can be at least one of polyethylene glycol monomethyl ether, propyl 2,2-dihydroxyformate, and N-methyldiethanolamine with a weight average molecular weight of 200-1000; the anionic hydrophilic modifier can be an organic salt formed by one or more of dimethylolbutyric acid, 2,2-dimethylolpropionic acid, 3-(cyclohexylamine)-1-propanesulfonic acid, 4-(cyclohexylamino)-1-butanesulfonic acid, 2-cyclohexylaminoethanesulfonic acid, 4-aminophenylsulfonic acid, and hydroxyethylsulfonic acid with one or more of triethylamine and N,N-dimethylcyclohexylamine.

[0028] Polyisocyanates can be at least one of aliphatic isocyanates, aliphatic isocyanate trimers, alicyclic isocyanates, alicyclic isocyanate trimers, aromatic isocyanates, and aromatic isocyanate trimers.

[0029] In this invention, based on a channel-type reaction, the hydrophilic modification of polyisocyanates is achieved by reacting the hydrophilic groups in a hydrophilic modifier with some isocyanate groups in the polyisocyanate. Specifically, a channel reaction module with a channel diameter of 6-12 mm is used, solving the problem of continuously and stably feeding raw materials into the reactor during the hydrophilic modification of polyisocyanates, thus realizing the continuous preparation of aqueous polyisocyanates. Compared with the traditional batch reaction, the method for preparing aqueous polyisocyanates in this invention overcomes the disadvantages of low reaction efficiency and long reaction cycle, shortening the reaction cycle of the batch method from 2-3 h to 8-20 min. Furthermore, it is not only easy to achieve continuous production, but also effectively improves the quality of aqueous polyisocyanates, showing significant advantages in terms of production efficiency, safety, and construction costs.

[0030] In one embodiment of the present invention, the hydrophilic modification treatment is performed at a temperature of 60-150°C and for a time of 300-600 seconds. For example, the temperature can be 60°C, 100°C, 120°C, or 150°C; the time can be 300 seconds, 400 seconds, 500 seconds, or 600 seconds, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] In this invention, when the hydrophilic modification treatment temperature is 60~150℃ and the time is 300~600 s, the problem of insufficient hydrophilic modification caused by too low a temperature or too short a time is avoided, ensuring the hydrophilicity of the waterborne polyisocyanate and preventing it from separating in water; at the same time, the side reactions such as self-polymerization of isocyanate groups caused by too high a temperature or too long a time are avoided, thus improving the storage and use performance of the waterborne polyisocyanate.

[0032] In one embodiment of the present invention, the hydrophilic modification treatment sequentially includes channel preheating treatment and channel reaction treatment; the temperature of the channel preheating treatment is 10~50°C higher than the temperature of the channel reaction treatment, and the time of the channel preheating treatment is 75~150s. For example, the temperature of the channel preheating treatment can be 10°C, 30°C, or 50°C higher than the temperature of the channel reaction treatment; the time of the channel preheating treatment can be 75s, 100s, or 150s, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] In this invention, when the channel preheating temperature is 10-50°C higher than the channel reaction temperature, the molecular activity of the hydrophilic modifier can be quickly activated, enabling it to have high reactivity upon entering the reaction stage. This avoids insufficient hydrophilic modification due to delayed reaction initiation caused by insufficient preheating, and also prevents premature side reactions caused by excessively high preheating temperatures, which could lead to instability of the main reaction and affect the product quality of the waterborne polyisocyanate.

[0034] In one embodiment of the present invention, the mass ratio of the hydrophilic modifier to the polyisocyanate is 4 to 25:100, for example, 4:100, 10:100, 20:100, or 25:100, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] In this invention, when the mass ratio of hydrophilic modifier to polyisocyanate is 4~25:100, it can avoid the problem of insufficient hydrophilic modifier leading to insufficient grafting of hydrophilic groups in polyisocyanate, thus affecting the hydrophilicity of waterborne polyisocyanate. It can also prevent excessive consumption of isocyanate groups due to excessive hydrophilic modifier, thus affecting the crosslinking ability of waterborne polyisocyanate.

[0036] In one embodiment of the present invention, the hydrophilic modifier is a dehydrated hydrophilic modifier.

[0037] In this invention, the hydrophilic modifier, after dehydration treatment, can prevent side reactions between its water and polyisocyanates, thereby avoiding the loss of isocyanate groups, increased viscosity of water-based polyisocyanates, and reduced dispersion performance caused by side reactions. The dehydration treatment can be performed using vacuum drying, molecular sieve adsorption dehydration, or inert gas purging and heating, with vacuum drying being the preferred method.

[0038] In one embodiment of the present invention, the aqueous polyisocyanate includes an aqueous non-blocked polyisocyanate or an aqueous blocked polyisocyanate. When the aqueous polyisocyanate is an aqueous blocked polyisocyanate, the hydrophilic modification treatment further includes a blocking treatment and an emulsification treatment in sequence.

[0039] In this invention, the waterborne blocked polyisocyanate refers to a polyisocyanate that has been modified by using a blocking agent to react and remove all remaining isocyanate groups, thus achieving a blocking treatment and deactivating the isocyanate groups at room temperature. When used as a curing agent, under high-temperature baking conditions, the blocked isocyanate groups are unblocked, releasing active isocyanate groups that react with the waterborne resin to complete the curing process.

[0040] The blocking treatment refers to the blocking reaction between the hydrophilically modified polyisocyanate and the blocking agent. The blocking agent can be at least one of methyl ethyl ketone oxime, diethyl malonate, acetylacetone, N-methylaniline, methyl salicylate, phenol, ε-caprolactam, 3,5-dimethylpyrazole, 1,2,4-triazole, 2-hydroxypyridine, 2-methylimidazole, sodium bisulfite, and sodium metabisulfite.

[0041] Emulsification involves mixing the closed-processed product with water, adjusting the pH value, emulsifying, and filtering to break up the aggregated state of the oil phase after the closed-processing and disperse the oil phase into tiny droplets that are uniformly suspended in the aqueous phase, ultimately forming a stable aqueous emulsion.

[0042] In one embodiment of the present invention, the sealing treatment temperature is 40~90℃ and the time is 60~300 s. For example, the temperature can be 40℃, 70℃, or 90℃; the time can be 60 s, 180 s, or 300 s, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] In one embodiment of the present invention, during the sealing treatment, the mass ratio of the sealing agent to the hydrophilically modified polyisocyanate is 1:1 to 1.15, for example, it can be 1:1, 1:1.1, or 1:1.15, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] In this invention, when the mass ratio of the sealant to the hydrophilically modified polyisocyanate is 1:1 to 1.15, a sufficient and appropriate reaction between the two can be achieved. This avoids insufficient sealing due to insufficient sealant dosage, and also prevents the curing process of the water-based sealed polyisocyanate from being delayed due to excessive sealant dosage.

[0045] In one embodiment of the present invention, during the emulsification process, the mass ratio of the product after sealing treatment to water is 1:4 to 8:1, for example, it can be 1:4, 3:1, or 8:1, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0046] In this invention, when the mass ratio of the blocked product to water is 1:4 to 8:1, stable emulsion microparticles can be formed. This avoids both the slow film-forming speed of water-based blocked polyisocyanates due to excessive water usage and the instability of the emulsion system due to insufficient water usage, preventing aggregation or even gelation.

[0047] In one embodiment of the present invention, during emulsification, the pH value is adjusted to 7-9, for example, 7, 8, or 9, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0048] In this invention, an alkali is used to adjust the pH value. The alkali can be at least one of ammonia, N,N-dimethylethanolamine, triethylamine, pyridine, monoethanolamine, and the auxiliary agent AMP-95. When the adjusted pH value is 7-9, the stability of the emulsion system can be ensured. This avoids the deterioration of the emulsion system caused by the hydrolysis of isocyanate groups under acidic conditions, which would affect the use of waterborne blocked polyisocyanates. It also avoids the demulsification of waterborne blocked polyisocyanates under excessively alkaline conditions.

[0049] According to another aspect of the present invention, the present invention also provides a channel reaction module for preparing aqueous polyisocyanates, wherein the channel diameter of the channel reaction module is 6 to 12 mm, for example, 6 mm, 8 mm, or 12 mm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0050] In this invention, the inventors discovered that during the hydrophilic modification of polyisocyanates, the raw materials are difficult to feed continuously and stably due to their inherent characteristics. This is currently the reason why it is difficult to achieve continuous preparation of aqueous polyisocyanates using microchannel reaction modules. Based on this, the inventors found that when the channel diameter of the microchannel reaction module is 6-12 mm, the raw material feeding problem can be solved, enabling continuous preparation of aqueous polyisocyanates. Specifically, within the channel diameter range of this invention, the raw materials are less likely to remain and solidify on the channel walls, reducing damage to the equipment caused by difficult cleaning, extending the equipment's service life, lowering maintenance costs, and improving overall efficiency. The material of the microchannel reaction module can be silicon carbide, Hastelloy, stainless steel, copper, copper alloys, titanium, or titanium alloys, etc.

[0051] In one embodiment of the present invention, the channel of the channel reaction module may be as follows: Figure 1 The figure shown is a broken line.

[0052] In this invention, the zigzag channel enhances the mixing of the hydrophilic modifier and the polyisocyanate. On one hand, as these two raw materials flow within the channel, the zigzag structure continuously alters the flow direction. Each change in direction causes the unevenly distributed raw materials to interpenetrate and collide violently, increasing intermolecular contact and thus promoting thorough mixing. This ensures a more complete and uniform hydrophilic modification reaction at the microscopic level. On the other hand, the zigzag channel improves heat transfer, preventing localized overheating or undercooling and reducing side reactions.

[0053] In one embodiment of the present invention, the channel of the channel reaction module can be as follows: Figure 2 The serpentine channel shown has several reaction spaces and connecting channels that are connected in sequence at intervals, with two adjacent connecting channels located on the left and right sides of the reaction space, respectively.

[0054] In this invention, the serpentine channel can further improve the heat and mass transfer efficiency of the channel reaction module. The longer path and frequent directional changes can promote a more uniform distribution of raw materials and heat, which helps to maintain a stable reaction temperature, reduce the occurrence of side reactions, and ensure the product quality of waterborne polyisocyanates.

[0055] In one embodiment of the present invention, the radius of curvature at the connection between the reaction space and the connecting channel is 15 to 30 mm, for example, 15 mm, 20 mm, 25 mm, or 30 mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0056] In this invention, the connection point between the reaction space and the connecting channel refers to the entire transition area from the connecting channel, where it turns to form an arc-shaped bend, and then connects to the reaction space; the radius of curvature at the connection point refers to the radius of the aforementioned arc-shaped bend. When the radius of curvature at the connection point between the reaction space and the connecting channel is 15~30 mm, the stability of the hydrophilic modification process of polyisocyanates can be maintained, the uniformity of the quality of waterborne polyisocyanates can be guaranteed, and gelation of waterborne polyisocyanates can be further prevented.

[0057] According to another aspect of the invention, the invention also proposes a reaction system comprising one or more of the aforementioned channel reaction modules connected in series.

[0058] In this invention, the reaction system includes one or more channel reaction modules connected in series. The number of channel reaction modules can be determined according to the process flow of the hydrophilic modification treatment. For example, if the hydrophilic modification treatment is carried out in two steps, the number of channel reaction modules is two; if the hydrophilic modification treatment is carried out in three steps, the number of channel reaction modules is three; preferably, if the hydrophilic modification treatment is carried out in four steps, the number of channel reaction modules is four.

[0059] The reaction system can be adjusted according to the solid-liquid state of the hydrophilic modifier, the process flow of the hydrophilic modification treatment, the type of waterborne polyisocyanate, or the solid-liquid state of the blocking agent.

[0060] like Figure 3 The reaction system shown illustrates the process of obtaining waterborne non-blocked polyisocyanates from polyisocyanates through a two-step hydrophilic modification treatment using a liquid hydrophilic modifier. Specifically, the liquid hydrophilic modifier and oily polyisocyanates are pumped into the inlet of the No. 1 channel reaction module by metering gear pumps No. 1 and No. 2, respectively. The hydrophilic modification treatment is then carried out sequentially in the No. 1 and No. 2 channel reaction modules. The product of the hydrophilic modification treatment is sent to the No. 1 storage tank under nitrogen protection, and then pumped into a bag filter by metering gear pump No. 3 for filtration, yielding the waterborne non-blocked polyisocyanates.

[0061] like Figure 4The reaction system shown illustrates the process of obtaining water-based non-blocked polyisocyanates through a four-step hydrophilic modification treatment using a solid hydrophilic modifier. Specifically, the solid hydrophilic modifier and oil-based polyisocyanates are added to dispersion tank #1 and dispersed until the particle size of the solid hydrophilic modifier reaches below 30 μm. The dispersed material is then pumped into storage tank #1 under nitrogen protection by metering gear pump #1, and then into the inlet of reaction module #1 by metering gear pump #2. Hydrophilic modification is then performed sequentially in reaction modules #1, #2, #3, and #4. The product of the hydrophilic modification treatment is sent to storage tank #2 under nitrogen protection, and then pumped into a bag filter by metering gear pump #3 for filtration, yielding water-based non-blocked polyisocyanates.

[0062] like Figure 5 The reaction system shown illustrates the process of obtaining an aqueous blocked polyisocyanate by a four-step hydrophilic modification treatment with a liquid hydrophilic modifier, followed by sequential blocking treatment with a liquid blocking agent and emulsification treatment. Specifically, the liquid hydrophilic modifier and the oily polyisocyanate are pumped into the inlet of the reaction module of channel 1 via metering gear pumps #1 and #2, respectively. The hydrophilic modification treatment is then carried out sequentially in reaction modules #1, #2, #3, and #4. The product after hydrophilic modification, along with the liquid blocking agent pumped in via metering gear pump #3, is fed into reaction module #5 for blocking treatment. The product after blocking treatment is then emulsified to obtain the aqueous blocked polyisocyanate.

[0063] A schematic diagram of emulsification process is shown below. Figure 6 As shown in the figure, the sealed product is sent to storage tank #1, pumped into emulsification tank #1 by metering gear pump #1, water is added and alkali is added to adjust the pH value, emulsified and then pumped into storage tank #2 by metering gear pump #2, and then pumped into bag filter by metering gear pump #3 for filtration to obtain water-based sealed polyisocyanate.

[0064] like Figure 7The reaction system shown illustrates the process of obtaining water-based blocked polyisocyanate by a four-step hydrophilic modification treatment using a liquid hydrophilic modifier, followed by sequential blocking treatment with a solid blocking agent and emulsification treatment. Specifically, the liquid hydrophilic modifier and oil-based polyisocyanate are pumped into the inlet of the No. 1 channel reaction module by metering gear pumps No. 1 and No. 2, respectively. The products undergo hydrophilic modification treatment sequentially in the No. 1, No. 2, No. 3, and No. 4 channel reaction modules. The products after hydrophilic modification are then transferred from the No. 1 storage tank (nitrogen-protected) to the No. 1 dispersion tank (nitrogen-protected). A solid blocking agent is added and dispersed until the particle size of the solid blocking agent reaches below 10 μm. The mixture is then pumped into the No. 2 storage tank (nitrogen-protected) by the No. 3 metering gear pump, and then into the No. 5 channel reaction module (nitrogen-protected) by the No. 4 metering gear pump for blocking treatment. The products after blocking treatment are then emulsified to obtain water-based blocked polyisocyanate.

[0065] like Figure 8 The reaction system shown illustrates the process of obtaining water-based blocked polyisocyanate by a four-step hydrophilic modification treatment with a solid hydrophilic modifier, followed by sequential blocking treatment with a liquid blocking agent and emulsification treatment. Specifically, the solid hydrophilic modifier and oily polyisocyanate are added to a nitrogen-protected dispersion tank (No. 1) and dispersed until the particle size of the solid hydrophilic modifier reaches below 30 μm. The dispersion is then pumped into a nitrogen-protected storage tank (No. 1) by a metering gear pump (No. 1), and then pumped into the inlet of the reaction module (No. 1 channel) by a metering gear pump (No. 2). Hydrophilic modification is then performed sequentially in reaction modules (No. 1, No. 2, No. 3, and No. 4). The product after hydrophilic modification and the liquid blocking agent pumped in by the metering gear pump (No. 3) are sent to the reaction module (No. 5 channel) for blocking treatment. The product after blocking treatment is then emulsified to obtain the water-based blocked polyisocyanate.

[0066] like Figure 9The reaction system shown illustrates the process by which polyisocyanate undergoes four steps of hydrophilic modification with a solid hydrophilic modifier, followed by sequential blocking with a solid blocking agent and emulsification, to obtain an aqueous blocked polyisocyanate. A solid hydrophilic modifier and an oily polyisocyanate were added to a nitrogen-protected dispersion tank (No. 1) and dispersed until the particle size of the solid hydrophilic modifier reached below 30 μm. The mixture was then pumped into a nitrogen-protected storage tank (No. 1) via a metering gear pump (No. 1), and subsequently pumped into the inlet of a reaction module (No. 1). The mixture underwent hydrophilic modification treatment sequentially in reaction modules (No. 1, No. 2, No. 3, and No. 4). The product after hydrophilic modification was transferred from a nitrogen-protected storage tank (No. 2) to a nitrogen-protected dispersion tank (No. 2). A solid blocking agent was added and dispersed until the particle size of the blocking agent reached below 10 μm. This agent was then pumped into a nitrogen-protected storage tank (No. 3) via a metering gear pump (No. 3), and finally pumped into a reaction module (No. 5) via a metering gear pump (No. 4) for sealing treatment. The sealed product was then emulsified to obtain an aqueous blocked polyisocyanate.

[0067] The preparation method, channel reaction module, and reaction system of the aqueous polyisocyanate of the present invention will be described in detail below with reference to examples. The embodiments of the present invention described below can be modified in various forms, and therefore the scope of the invention should not be construed as limited to the embodiments described in detail below. Examples are provided to help those skilled in the art to more readily understand the present invention.

[0068] In the following examples and comparative examples, the polyisocyanate was HT-100, purchased from Wanhua Chemical Group Co., Ltd.; polyethylene glycol monomethyl ether MPEG-750 and polyethylene glycol monomethyl ether MPEG-1000 were purchased from Haian Petrochemical Plant, Jiangsu Province; methyl ethyl ketone oxime, 2-hydroxypyridine and 3,5-dimethylpyrazole were purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; and the hydroxypropyl resin was Bayhydrol® 2427.

[0069] Example 1 A method for preparing an aqueous non-blocked polyisocyanate includes the following steps: Polyethylene glycol monomethyl ether MPEG-750, after vacuum dehydration at 105°C for 30 min, and the polyisocyanate are pumped into the inlet of reaction module #1 via metering gear pumps #1 and #2, respectively. Hydrophilic modification is then performed sequentially in reaction modules #1, #2, #3, and #4 at a constant flow rate. The product of the hydrophilic modification is then transferred to a nitrogen-protected storage tank #1, and subsequently pumped into a bag filter via metering gear pump #3 for filtration, yielding an aqueous non-blocked polyisocyanate, as shown in the image. Figure 10 As shown; The mass ratio of polyethylene glycol monomethyl ether MPEG-750 to polyisocyanate is 25:100; the temperatures of reaction modules 1, 2, 3, and 4 are 110℃, 110℃, 110℃, and 110℃, respectively; the total time in the reaction modules is 600 s; the time in reaction module 1 is 150 s; all reaction modules have the same channel length, are zigzag-shaped, have a channel diameter of 6 mm, and are made of silicon carbide.

[0070] Example 2 The only difference between this embodiment and Embodiment 1 is that in this embodiment, polyethylene glycol monomethyl ether MPEG-750 is replaced with an equal amount of polyethylene glycol monomethyl ether MPEG-550. The appearance of water-based non-blocked polyisocyanates is shown in the figure below. Figure 11 As shown.

[0071] Example 3 The only difference between this embodiment and Embodiment 1 is that in this embodiment, the temperatures of reaction modules 1#, 2#, 3#, and 4# are 110℃, 105℃, 105℃, and 105℃, respectively; the total time in the reaction modules is 600 s, and the time in reaction module 1# is 150 s. The appearance of the aqueous non-blocked polyisocyanate is shown in the figure. Figure 12 As shown.

[0072] Example 4 A method for preparing an aqueous non-blocked polyisocyanate includes the following steps: 2,2-dihydroxymethylpropionic acid and polyisocyanate, after vacuum dehydration at 105℃ for 2 h, are added to a dispersion tank (No. 1) and dispersed at a linear velocity of 4 m / s for 10 min to achieve a particle size of 2,2-dihydroxymethylpropionic acid below 30 μm. The dispersed material is then pumped into a nitrogen-protected storage tank (No. 1) via a metering gear pump (No. 1), and then pumped into the inlet of a reaction module (No. 1). Hydrophilic modification is then performed sequentially in reaction modules (No. 1, No. 2, No. 3, and No. 4) at a constant flow rate. The product of the hydrophilic modification is then sent to a nitrogen-protected storage tank (No. 2), and finally pumped into a bag filter (No. 3) via a metering gear pump (No. 3). Filtration yields an aqueous non-blocked polyisocyanate, as shown in the image. Figure 13 As shown; The mass ratio of 2,2-dihydroxymethylpropionic acid to polyisocyanate was 4:100; the temperatures of reaction modules 1, 2, 3, and 4 were 125℃, 110℃, 110℃, and 110℃, respectively; the total time in the reaction modules was 600 s; the time in reaction module 1 was 150 s. All reaction modules had the same channel length, were zigzag-shaped, had a channel diameter of 6 mm, and were made of silicon carbide.

[0073] Example 5 The only difference between this embodiment and Embodiment 4 is that in this embodiment, the temperatures of reaction modules 1#, 2#, 3#, and 4# are 135℃, 125℃, 125℃, and 125℃, respectively; the total time in the reaction modules is 300 s, and the time in reaction module 1# is 75 s. The appearance diagram is as follows. Figure 14 As shown.

[0074] Example 6 A method for preparing an aqueous closed-cell polyisocyanate includes the following steps: Polyethylene glycol monomethyl ether MPEG-750, after vacuum dehydration at 105°C for 30 min, and the polyisocyanate are pumped into the inlet of reaction module 1 via metering gear pumps #1 and #2, respectively. The polyisocyanate is then subjected to hydrophilic modification treatment sequentially in reaction modules #1, #2, #3, and #4 at a constant flow rate. The hydrophilic-modified product, along with methyl ethyl ketone oxime pumped in via metering gear pump #3, is fed into reaction module #5 for a closed-cell treatment at 90°C for 60 s. The closed-cell product is then fed into storage tank #1, pumped into emulsification tank #1 via metering gear pump #4, and then water and N,N-dimethylethanolamine are added to adjust the pH to 8. After stirring and emulsification, the product is pumped into storage tank #2 via metering gear pump #5, and then into a bag filter via metering gear pump #6. The filtered product yields the aqueous closed-cell polyisocyanate, as shown in the image. Figure 15 As shown; The mass ratio of polyethylene glycol monomethyl ether MPEG-750 to polyisocyanate was 25:100; the temperatures of reaction modules 1, 2, 3, and 4 were 130℃, 120℃, 120℃, and 120℃, respectively; the total time in the reaction modules was 480 s; all reaction modules had the same channel length, were zigzag-shaped, had a channel diameter of 12 mm, and were made of silicon carbide; the mass ratio of methyl ethyl ketone oxime to the hydrophilically modified product was 1:1.1, and the mass ratio of the sealed product to water was 3:2.

[0075] Example 7 The only difference between this embodiment and Embodiment 6 is that in this embodiment, polyethylene glycol monomethyl ether MPEG-750 is replaced with an equal amount of polyethylene glycol monomethyl ether MPEG-1000. The appearance of the water-based blocked polyisocyanate is shown in the figure below. Figure 16 As shown.

[0076] Example 8 The only difference between this embodiment and embodiment 6 is that in this embodiment, the temperatures of reaction modules 1#, 2#, 3#, and 4# are 138℃, 132℃, 132℃, and 125℃, respectively; the total time in the reaction modules is 480 s, and the time in reaction module 1# is 120 s. The appearance diagram of water-based blocked polyisocyanates is shown below. Figure 17 As shown in the figure, the aqueous non-blocked polyisocyanate after water emulsification is milky white.

[0077] Example 9 A method for preparing an aqueous blocked polyisocyanate includes the following steps: Polyethylene glycol monomethyl ether MPEG-750, after vacuum dehydration at 105℃ for 30 min, and the polyisocyanate are pumped into the inlet of the No. 1 channel reaction module via metering gear pumps #1 and #2, respectively. The polyisocyanate is then subjected to hydrophilic modification treatment sequentially in the No. 1, No. 2, No. 3, and No. 4 channel reaction modules at a constant flow rate. The hydrophilic modified product is then transferred from a nitrogen-protected storage tank (No. 1) to a nitrogen-protected dispersion tank (No. 1). 3,5-Dimethylpyrazole is added and dispersed at 1000 rpm for 5 min to achieve a 3,5-dimethylpyrazole particle size below 10 μm. The dispersion is then pumped from the storage tank (No. 2) via metering gear pump #3, and finally into the No. 5 channel reaction module via metering gear pump #4 for further processing at 40℃ and 300℃. The product undergoes a closed-loop process, and after this process, it is sent to storage tank #3. Then, it is pumped into emulsification tank #1 via metering gear pump #5. Water is added, and N,N-dimethylethanolamine is added to adjust the pH to 8. After stirring and emulsification, the product is pumped into storage tank #4 via metering gear pump #6, and then into a bag filter via metering gear pump #7. The filtered product yields an aqueous closed-loop polyisocyanate, as shown in the image. Figure 18 As shown; The mass ratio of polyethylene glycol monomethyl ether MPEG-750 to polyisocyanate was 25:100; the temperatures of reaction modules 1#, 2#, 3#, and 4# were 105℃, 95℃, 95℃, and 95℃, respectively; the total time in the reaction modules was 480 s; each reaction module had the same channel length, a serpentine shape (each channel had several sequentially spaced reaction spaces and connecting channels, with adjacent connecting channels located on the left and right sides of the reaction space), a radius of curvature of 10 mm at the connection between the reaction space and the connecting channel, a channel diameter of 8 mm, and was made of silicon carbide; the mass ratio of 3,5-dimethylpyrazole to the hydrophilically modified product was 1:1.15, and the mass ratio of the sealed product to water was 3:2.

[0078] Example 10 The only difference between this embodiment and Embodiment 9 is that in this embodiment, the temperatures of reaction modules 1#, 2#, 3#, and 4# are 145℃, 95℃, 95℃, and 95℃, respectively; the total time in the channel reaction modules is 480 s, and the time in the 1# channel reaction module is 120 s. The appearance diagram of the aqueous blocked polyisocyanate is shown below. Figure 19 As shown.

[0079] Example 11 The only difference between this embodiment and embodiment 9 is that in this embodiment, the temperatures of reaction modules 1#, 2#, 3#, and 4# are 100℃, 95℃, 95℃, and 95℃, respectively; the total time in the reaction modules is 480 s, and the time in reaction module 1# is 120 s.

[0080] Example 12 The only difference between this embodiment and embodiment 9 is that in this embodiment, the temperatures of reaction modules 1#, 2#, 3#, and 4# are 150℃, 95℃, 95℃, and 95℃, respectively; the total time in the reaction modules is 480 s, and the time in reaction module 1# is 120 s.

[0081] Example 13 The only difference between this embodiment and embodiment 9 is that, in this embodiment, the radius of curvature at the connection between the reaction space and the connecting channel is 40 mm.

[0082] Example 14 The only difference between this embodiment and embodiment 9 is that, in this embodiment, the radius of curvature at the connection between the reaction space and the connecting channel is 15 mm.

[0083] Example 15 The only difference between this embodiment and Embodiment 9 is that, in this embodiment, the radius of curvature at the connection between the reaction space and the connecting channel is 30 mm. The appearance diagram of the water-based closed-type polyisocyanate is shown below. Figure 20 As shown.

[0084] Comparative Example 1 The only difference between this comparative example and Example 1 is that in this example, the channel diameter is 5.5 mm.

[0085] Comparative Example 2 The only difference between this comparative example and Example 1 is that in this example, the channel diameter is 12.5 mm.

[0086] Comparative Example 1 failed to produce an aqueous non-blocked polyisocyanate in a continuous manner.

[0087] The aqueous polyisocyanates prepared in Examples 1-15 and Comparative Example 2 were subjected to the following tests: (1) The aqueous non-blocked polyisocyanates prepared in Examples 1-5 and Comparative Example 2 were mixed, dispersed and emulsified with water at a mass ratio of 1:10. After uniform dispersion, an emulsion was obtained. The emulsions of Examples 1-5 and Comparative Example 2, and the aqueous blocked polyisocyanates in Examples 6-13 were diluted with water by 1000 times by mass, and the particle size was characterized using a laser particle size analyzer. (2) The waterborne polyisocyanate, hydroxypropyl resin and water prepared in Examples 1-15 and Comparative Example 2 were compounded in a mass ratio of 15:65:1 to obtain a waterborne coating. After the waterborne coating was stirred evenly and defoamed, it was applied to the surface of a glass plate. After it was fully cured, the adhesion, hardness and 48-h water immersion resistance of the coating were tested according to Method A in ISO2049:2020, GB / T 6739-2022 and GB / T 1733-1993.

[0088] (3) Visually inspect the appearance, water dispersion state, stability after 30 days of storage, and surface state of the waterborne polyisocyanates prepared in Examples 1-15 and Comparative Example 2.

[0089] The test results are shown in Tables 1 and 2 below.

[0090] Table 1. Test results of waterborne polyisocyanates

[0091] Table 2 Test results of waterborne blocked polyisocyanates

[0092] As can be seen from the test results of Examples 1 to 15 in Tables 1 and 2, the waterborne polyisocyanates prepared by the present invention have good storage and curing properties and good quality. This indicates that the present invention achieves continuous preparation of waterborne polyisocyanates through a channel reaction.

[0093] The comparison between Example 1 and Comparative Examples 1 and 2 shows that continuous preparation of aqueous polyisocyanates can only be achieved through channel-type reactions when the channel diameter of the channel reaction module is 6-12 mm. When the channel diameter is less than 6 mm, continuous preparation of aqueous polyisocyanates is not possible; when the channel diameter is greater than 12 mm, the performance of the aqueous polyisocyanates is poor and gelation occurs.

[0094] Examples 1-5 and Examples 6-13 illustrate that the present invention can prepare both aqueous non-blocked polyisocyanates and aqueous blocked polyisocyanates through channel-type reactions, making it suitable for continuous industrial production.

[0095] A comparison of Examples 11-12 and Examples 9-10 shows that when the channel preheating temperature is 10-50°C higher than the channel reaction temperature, the continuous preparation of water-based polyisocyanates can be achieved, and the product quality can be further improved.

[0096] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. Process for the preparation of aqueous polyisocyanates, characterized in that The method comprises the following steps: feeding a hydrophilic modifier and a polyisocyanate into a channel reaction module for hydrophilic modification treatment to obtain an aqueous polyisocyanate; the channel diameter of the channel reaction module is 6-12 mm.

2. The method of preparing an aqueous polyisocyanate according to claim 1, characterized in that The temperature of the hydrophilic modification treatment is 60-150℃, and the time is 300-600 s.

3. The method of preparing an aqueous polyisocyanate according to claim 2, characterized in that The hydrophilic modification treatment comprises channel preheating treatment and channel reaction treatment in sequence; the temperature of the channel preheating treatment is 10-50℃ higher than that of the channel reaction treatment, and the time of the channel preheating treatment is 75-150 s.

4. The method of producing an aqueous polyisocyanate according to claim 1, characterized by, The mass ratio of the hydrophilic modifier to the polyisocyanate is 4-25:

100.

5. The method of producing an aqueous polyisocyanate according to claim 1, characterized by, The hydrophilic modifier is a dehydrated hydrophilic modifier.

6. The method of producing a waterborne polyisocyanate according to any one of claims 1 to 5, characterized in that, The aqueous polyisocyanate comprises an aqueous non-blocked polyisocyanate and an aqueous blocked polyisocyanate. When the aqueous polyisocyanate is the aqueous blocked polyisocyanate, the hydrophilic modification treatment further comprises, in sequence, a blocking treatment and an emulsification treatment.

7. The method of preparing an aqueous polyisocyanate according to claim 6, characterized in that The temperature of the blocking treatment is 40-90℃, and the time is 60-300 s.

8. Channel reactor module for the preparation of aqueous polyisocyanates according to any one of claims 1 to 7, characterized in that The channel diameter is 6-12 mm.

9. The channel reaction module of claim 8, wherein, The channel of the channel reaction module comprises a zigzag shape or a snake shape.

10. A reaction system characterized by, The method comprises one channel reaction module according to claim 9 or a plurality of channel reaction modules connected in series.

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