A method of stabilizing a stored polyisocyanate composition

Abstract

This invention belongs to the field of polyisocyanate technology, and particularly relates to a method for stably storing polyisocyanate compositions. The method comprises the following steps: placing the polyisocyanate composition in a metal packaging drum or an IBC container, controlling the storage temperature between -15 and 40°C, to obtain a stable polyisocyanate composition product. This method ensures high stability of the polyisocyanate composition product during storage.

Description

Technical Field

[0001] This invention belongs to the field of polyisocyanate technology, and particularly relates to a method for stabilizing the storage of polyisocyanate compositions. Background Technology

[0002] As is well known, polyurethane resin coatings possess excellent abrasion resistance, chemical resistance, and stain resistance. In particular, polyisocyanates derived from aliphatic (cyclic) isocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate exhibit excellent weather resistance. Therefore, these polyisocyanates are often used as room-temperature or heat-curing polyurethane coatings for painting and repairing buildings, automobiles, aircraft, ships, and cross-sea bridges.

[0003] Currently, methods for preparing polyisocyanates from aromatic, aliphatic, or cycloaliphatic diisocyanate monomers in the presence of a catalyst are known. The advantages and disadvantages of various catalyst systems are described in detail in the literature, for example, in scientific literature J. Prakt. Chem. 336(1994) 185-200, patent documents CN201410002995.5, CN95113103.6, CN200310120368.3, CN200310120121.1, CN200910128728.1, and CN201280059016.9.

[0004] However, the main drawback of polyisocyanates prepared by existing processes is that the monomer increases rapidly or the turbidity increases rapidly during storage, which seriously affects the long-distance transportation of the product and its downstream use.

[0005] Therefore, it is of great significance to study how to obtain storage-stable polyisocyanate compositions without using any additives. Summary of the Invention

[0006] The purpose of this invention is to provide a method for stable storage of polyisocyanate compositions, addressing the aforementioned problems in the prior art. This method is simple to operate and can obtain stable polyisocyanate compositions without the use of any additives, effectively solving the problems of free monomers and unstable turbidity that occur during storage and downstream use of polyisocyanate compositions prepared by existing methods.

[0007] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0008] In a first aspect, a method for stably storing a polyisocyanate composition is provided, comprising the steps of: placing the polyisocyanate composition in a metal packaging drum or an IBC container, and controlling the storage temperature at -15 to 40°C (e.g., -14°C, -12°C, -10°C, -8°C, -6°C, -5°C, -4°C, -2°C, -1°C, 0°C, 1°C, 2°C, 5°C, 8°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 38°C) to obtain a stable (e.g., stable free monomer content and stable turbidity) polyisocyanate composition product.

[0009] According to the method provided by the present invention, in some embodiments, the metal packaging drum is selected from drums with an inner wall of 304 stainless steel, drums with an inner wall of tinplate, drums with an inner wall of galvanized steel, drums with an inner wall of tin-plated steel, and metal drums with an inner wall that has been passivated or contain an inner coating substance.

[0010] In this article, the volume of the metal packaging drum can be one or more of the following specifications: 20L, 60L, and 200L.

[0011] In some implementations, the IBC container is made of one or more of high-density polyethylene, polypropylene, polytetrafluoroethylene, polyvinyl chloride, polycarbonate, polylactic acid, polyurethane, and polyamide.

[0012] Our investigation revealed a surprising finding: by storing polyisocyanate (POC) compositions in metal drums or IBC containers at a temperature controlled between -15°C and 40°C, the stability of the final product was significantly improved. Further research showed that at lower temperatures, POC compositions precipitate insoluble solid particles. After prolonged storage, these particles agglomerate and are difficult to dissolve even upon returning to room temperature, forming turbidity and affecting downstream applications. At higher temperatures, some unstable groups in the POC composition decompose into monomers, leading to product defects and impacting sales and downstream customer use. By storing POC compositions in metal drums or IBC containers at a temperature controlled between -15°C and 40°C, we can prevent the precipitation of insoluble solid particles and the formation of turbidity, as well as the decomposition of unstable groups into monomers. This ensures high stability of the POC composition in terms of free monomer content and turbidity during storage.

[0013] In this document, the preparation process of the polyisocyanate composition can be based on existing technology, and the polyisocyanate reaction solution suitable for the method of this invention can be a polyisocyanate reaction solution prepared by any method; this invention does not impose any specific limitations. According to the method provided by this invention, in some embodiments, the preparation method of the polyisocyanate composition includes the following steps:

[0014] (1) React isocyanate monomers with polyols by contacting them, or allow isocyanate monomers to undergo self-polymerization.

[0015] (2) After the reaction reaches the set conversion rate, add a terminator or do not add a terminator to the system to end the reaction and obtain the polyisocyanate reaction solution.

[0016] (3) Optionally, the obtained polyisocyanate reaction solution is separated by an evaporator;

[0017] (4) Optionally, the separated heavy components are diluted with a solvent or not to obtain a polyisocyanate composition product.

[0018] The method of preparing the isocyanate monomer used to prepare the polyisocyanate reaction solution is not important for the implementation of the preparation method of the present invention. It includes isocyanate monomers that can be produced with or without phosgene or any other method, such as aromatic, aliphatic and / or alicyclic organic isocyanates, which are organic diisocyanates or organic polyisocyanates that contain 4-20 carbon atoms in addition to NCO groups in the carbon skeleton.

[0019] In some embodiments, the isocyanate monomer in step (1) is selected from one or more of aromatic organic isocyanates, aliphatic organic isocyanates, and alicyclic organic isocyanates, preferably from one or more of hexamethylene diisocyanate, isophorone diisocyanate, cyclohexyldimethylene diisocyanate, phenyldimethylene diisocyanate, dicyclohexylmethane diisocyanate, norbornene dimethylene diisocyanate, cyclohexyl diisocyanate, lysine diisocyanate, tetramethylphenyldimethylene diisocyanate, 2,4,4-trimethylhexane diisocyanate, toluene diisocyanate, methylcyclohexyl diisocyanate, naphthalene diisocyanate, terephthalic diisocyanate, diphenylmethane diisocyanate, and polymethylene polyphenyl polyisocyanate.

[0020] In some implementations, step (1) is carried out in the presence or absence of a catalyst. Different preparation methods may be used for different types of polyisocyanate compositions or polyisocyanate reaction solutions, and the catalysts, reaction conditions, etc., selected in each method can be chosen according to the chosen preparation method.

[0021] The "achieving the set conversion rate" mentioned in step (2) can be understood as a conversion rate preset according to the product to be obtained. Different types of polyisocyanate products require different conversion rates, which is well known to those skilled in the art and will not be elaborated here.

[0022] In some embodiments, the total content of polyisocyanate in the polyisocyanate reaction solution in step (2) is 5-80 wt% (e.g., 6 wt%, 10 wt%, 15 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 60 wt%, 65 wt%, 75 wt%), preferably 20-70 wt%.

[0023] In some embodiments, the polyisocyanate reaction solution in step (2) includes a polyisocyanate containing one or more of the following structures: isocyanurate, carbamate, urethane, biuret, iminooxadiazine dione, urea dione, carbodiimide, and urea ketimide. For example, the polyisocyanate reaction solution may be a trimer polyisocyanate reaction solution, a polyisocyanate reaction solution containing a biuret structure, or a polyisocyanate reaction solution containing a urea dione structure.

[0024] In step (3), the separation treatment of the polyisocyanate reaction solution by an evaporator is a conventional operation in the art, and the present invention does not impose specific limitations. In some embodiments, when the separation treatment by an evaporator is performed in step (3), the evaporator is a scraped evaporator.

[0025] In some implementations, the scraped evaporator is a thin-film evaporator and / or a short-path evaporator.

[0026] Thin-film evaporators and short-path evaporators, for example, include a rotor with scrapers and an evaporator shell with a heating jacket. The material to be separated is evenly dispersed on the inner wall of the evaporator shell by a disperser located at the top of the evaporator. The material flows down naturally due to gravity, and the rotor with scrapers rotates at a constant speed, scraping the material into a thin liquid film. Low-boiling-point free monomers escape from the liquid film, and the obtained unvolatile heavy components and a small amount of free monomers can enter the next separation unit. The evaporator shell with the heating jacket is heated by heated heat transfer oil or steam to provide heat to the material to be separated.

[0027] In some implementations, the evaporator is used in a single stage and / or in two stages in series, preferably in a single stage.

[0028] In some implementations, the process conditions for the evaporator separation process in step (3) include: a separation temperature of 100-200℃ (e.g., 110℃, 120℃, 130℃, 140℃, 150℃, 155℃, 160℃, 165℃, 170℃, 175℃, 190℃), and a separation vacuum of 5-200PaA (e.g., 6Pa, 8Pa, 10Pa, 15Pa, 20Pa, 25Pa, 30Pa, 40Pa, 50Pa, 60Pa, 80Pa, 90Pa, 100Pa, 120Pa, 150Pa, 180Pa).

[0029] In this invention, different types of polyisocyanate compositions can be prepared using different processes. For example:

[0030] In the first embodiment, the method for preparing the trimer polyisocyanate composition includes the following steps:

[0031] (11) Under an inert atmosphere, the isocyanate monomer is added to the reaction vessel and heated. After the system is heated to the reaction temperature, catalyst I is added (e.g., dropwise) to carry out the polymerization reaction. The NCO% of the reaction solution is monitored and measured. When the NCO% value drops to a suitable value (e.g., 35-45%), terminator I is added to terminate the reaction to obtain the trimer polyisocyanate reaction solution.

[0032] (12) The trimeric polyisocyanate reaction solution obtained in the above steps is separated by a separation device (e.g., a combination of a thin film evaporator and a short-path evaporator) to obtain the heavy component, namely the trimeric polyisocyanate composition.

[0033] The trimer polyisocyanate reaction solution includes one or more polyisocyanates containing isocyanurate, urethane, urethane, iminooxadiazine dione, urea dione, carbodiimide, and urea ketimide structures, preferably including polyisocyanates containing isocyanurate, urethane, urethane, iminooxadiazine dione, urea dione, carbodiimide, and urea ketimide structures.

[0034] In some examples, the catalyst I described in step (11) is a quaternary ammonium base and / or a quaternary ammonium salt catalyst, preferably selected from organic weak acid salts of choline hydroxide, trimethylhydroxyethyl ammonium hydroxide, tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, tetrapropyl ammonium hydroxide, tetrabutyl ammonium hydroxide, benzyltrimethyl ammonium hydroxide, 1-adamantyl ammonium hydroxide, hexamethylbisammonium hydroxide, tetraalkyl ammonium (e.g., tetramethyl ammonium, tetraethyl ammonium, etc.) and tetramethyl octanoic acid ammonium, organic weak acid salts of trimethylhydroxypropyl ammonium (e.g., formic acid, acetic acid, decanoic acid, etc.), and trimethylhydroxyethyl ammonium (e.g., formic acid, acetic acid, decanoic acid, etc.).

[0035] The organic weak acid salts of tetraalkylammonium mentioned herein may be tetramethylammonium formate, tetramethylammonium acetate, tetramethyldecanoate, tetraethylammonium formate, tetraethylammonium acetate, or tetraethyldecanoate; the organic weak acid salts of trimethylhydroxypropylammonium may be trimethylhydroxypropylammonium formate, trimethylhydroxypropylammonium acetate, or trimethylhydroxypropyldecanoate; and the organic weak acid salts of trimethylhydroxyethylammonium may be trimethylhydroxyethylammonium formate, trimethylhydroxyethylammonium acetate, or trimethylhydroxyethyldecanoate.

[0036] In some examples, the amount of catalyst I added is 0.001 wt% to 0.2 wt% of the weight of the isocyanate monomer (e.g., 0.0025 wt%, 0.005 wt%, 0.01 wt%, 0.04 wt%, 0.06 wt%, 0.08 wt%, 0.1 wt%, 0.125 wt%, 0.15 wt%, 0.18 wt%).

[0037] The catalyst I can be used as a pure substance or optionally dissolved in an alcohol at any concentration. As a diluent for the catalyst, the alcohol can be, but is not limited to, monohydric alcohols and / or dihydric alcohols; the monohydric alcohol is selected from one or more of C1-C10 aliphatic alcohols, aryl aliphatic alcohols, aromatic alcohols, aliphatic phenols, aryl aliphatic phenols, and aromatic phenols, more preferably existing in the form of straight-chain, branched, or cyclic alcohols or phenols; the dihydric alcohol can be, but is not limited to, ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1, 5-Pentanediol, 1,2-Pentanediol, 1,3-Pentanediol, 1,4-Pentanediol, neopentanediol, 1,6-Hexanediol, 1,7-Heptanediol, 1,8-Octandiol, 1,9-Nonanediol, 1,10-Decanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylenediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octandiol, and 2,2-diethyl-1,3-propanediol.

[0038] In some examples, the terminator I in step (11) is selected from organic acids and / or acylating agents, preferably one or more of formic acid, benzoic acid, benzoyl chloride, dibutyl phosphate and di(2-ethylhexyl) phosphate.

[0039] Those skilled in the art will understand that different types of polymerization catalysts used in the reaction system will result in different amounts of terminator. In the reaction system of the present invention, the amount of terminator I added is determined to deactivate polymerization catalyst I in the system.

[0040] In some examples, the reaction temperature of step (11) is 30-100°C (e.g., 35°C, 50°C, 60°C, 70°C, 90°C), preferably 40-80°C.

[0041] In some examples, the separation device in step (12) can be a scraped film evaporator; the scraping system of the scraped film evaporator can be a roller type or a scraper type, and the evaporator can be a thin film evaporator or a short-path evaporator. The process conditions for the separation treatment include: the separation temperature of the scraped film evaporator is 140-180℃ (e.g., 145℃, 155℃, 160℃, 175℃), and the absolute separation pressure is 5-200Pa (e.g., 6Pa, 10Pa, 20Pa, 50Pa, 100Pa, 150Pa, 180Pa).

[0042] The free monomer content in the recombinant trimer polyisocyanate composition obtained after separation treatment is less than or equal to 0.1 wt% based on the mass of the composition.

[0043] In the second embodiment, the preparation method of the TDI-TMP polyisocyanate composition includes the following steps:

[0044] (21) Prepolymerization reaction to obtain reaction solution: Polyol compound and toluene diisocyanate are mixed and reacted in the first reactor;

[0045] (22) The material obtained in step (21) above enters the second reactor for reaction;

[0046] (23) The material obtained in step (22) above is separated by a separation device to remove unreacted toluene diisocyanate monomers and obtain heavy components;

[0047] (24) The heavy component (i.e., the polyisocyanate composition) obtained in step (23) above is diluted with a solvent to obtain a polyisocyanate composition solution.

[0048] In some examples, the components of the polyol compound in step (21) can be added separately to the reaction vessel and mixed with toluene diisocyanate for reaction, or the components can be premixed before reacting with toluene diisocyanate; the premixing method includes mixing in a pipeline mixer or mixing in a premixing tank in advance, preferably using a pipeline mixer for mixing.

[0049] In some examples, in step (21), the material can be introduced into the reactor at room temperature for reaction, or it can be preheated before being introduced into the reactor for reaction. Preferably, the material is preheated to 60-100°C before being introduced into the reactor for reaction.

[0050] In some examples, in step (21), the reaction temperature of the material in the first reactor is 100-170°C, preferably 100-150°C. The higher the temperature, the smaller the difference in activity of the isocyanate functional groups of 2,4-TDI and 2,6-TDI, the greater the molecular disorder in the product, and the less likely the product is to precipitate during low-temperature storage, but the higher the color number of the product will be, affecting downstream use.

[0051] In some examples, in step (21), the average residence time of the material in the first reactor is 3-30 minutes, preferably 5-15 minutes.

[0052] In some examples, in step (21), stabilizers and additives may be added to reduce product color variations; these stabilizers and additives are common additives in the polyisocyanate field, and include, but are not limited to: antioxidants, sterically hindered phenolic substances (e.g., antioxidant BHT, antioxidant 1010, antioxidant 1076, antioxidant, antioxidant 1135, etc.), phosphite substances (e.g., tri(nonylphenyl) phosphite, tri(2,4-di-tert-butylphenyl) phosphite, etc.), ultraviolet absorbers (e.g., benzotriazoles, salicylates, benzophenones, etc.), and hindered amine light stabilizers (e.g., 2,2,6,6-tetramethylpyridine, etc.).

[0053] In some examples, the method of preparing the toluene diisocyanate monomer as a raw material in step (21) is not important to the implementation of the present invention, including the use of toluene diisocyanate monomers produced by means of phosgene or any other method, wherein the toluene diisocyanate preferably comprises 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, wherein the mass ratio of the 2,4-toluene diisocyanate and 2,6-toluene diisocyanate is 60:40-95:5, preferably 75:25-85:15.

[0054] In some examples, in step (21), the polyol compound includes TMP and DEG, and may optionally include one or more of other di, tri, or tetraols having a molecular weight of 62 to 200, such as, but not limited to, ethylene glycol, 1,2-propanediol, methylpropanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentanediol, 1,6-hexanediol, 2-ethylhexanediol, trimethylolethane, glycerol, and pentaerythritol.

[0055] In some examples, the mass ratio of TMP to DEG in the polyol compound of step (21) is 1:1-5:1, preferably 2:1-4:1.

[0056] In some examples, the mass ratio of TMP to DEG in the polyol compound of step (21) is 1:1-5:1, preferably 2:1-4:1. If other polyols are included in addition to TMP and DEG, the mass ratio of the total mass of the other polyols to the mass of TMP is 1:5-1:50.

[0057] In this article, the ratio of polyol compound to toluene diisocyanate is a conventional choice in the field and will not be elaborated further.

[0058] In some examples, in step (22), the reaction temperature of the material in the second reactor is 60-100°C, preferably 60-80°C.

[0059] In some examples, in step (22), the average residence time of the material in the second reactor is 2-20 hours, preferably 5-10 hours.

[0060] In some examples, in step (23), the obtained reaction solution is separated to remove unreacted toluene diisocyanate monomers; in some examples, the separation treatment for removing unreacted isocyanate monomers is a conventional operation in the art and is not particularly limited thereto; the separation device used may be, for example, an extraction device, a rotary evaporator, a short-path evaporator or a thin-film evaporator or a combination thereof, to remove residual unreacted isocyanate monomers until the isocyanate monomer content in the product is low, for example, based on the mass of the composition, the unreacted isocyanate monomer content is ≤0.5wt%, for example, less than or equal to 0.4wt%, less than or equal to 0.2wt%.

[0061] In some examples, in step (24), the obtained heavy component polyisocyanate composition can be diluted with an organic solvent to obtain a polyisocyanate composition solution. The organic solvent used can be one or more of toluene, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate and propylene glycol methyl ether acetate, preferably ethyl acetate.

[0062] In some examples, in step (24), the solid content of the polyisocyanate composition solution is 30-80 wt%, preferably 50-80 wt%.

[0063] In some examples, in step (24), the diluted organic solvent is preheated to 30-80°C, preferably 50-70°C.

[0064] In a second aspect, there is an application of a stable-stored polyisocyanate composition obtained by the method described above, wherein the stable-stored polyisocyanate composition, after being sealed with a sealing agent, is used in the preparation of polyurethane coatings or polyurethane adhesives.

[0065] In some examples, the stable-storage polyisocyanate products are used in various additive systems and various isocyanate raw material systems, preferably in the fields of oil-based polyurethane paints, water-based polyurethane materials, and yellowing-resistant polyurethane materials.

[0066] In the applications to which this invention pertains, the specific processes and techniques for preparing polyurethane coatings or polyurethane adhesives after the stable-stored polyisocyanate composition is sealed with a sealing agent can be achieved by conventional means in the art, and will not be elaborated here.

[0067] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0068] In the preparation of polyisocyanate compositions, this invention, by placing them in metal packaging drums or IBC containers and controlling the storage temperature between -15 and 40°C, yields isocyanate composition products with excellent storage stability (the products exhibit high stability in terms of free monomer content and turbidity). Detailed Implementation

[0069] To provide a detailed understanding of the technical features and content of this invention, preferred embodiments will be described in more detail below. While preferred embodiments are described in the examples, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply.

[0070] <Testing Methods>

[0071] (1) Determination of the content of free isocyanate monomers:

[0072] Isocyanate raw materials were quantified using gel permeation chromatography (LC-20AD / RID-10A, columns: MZ-Gel SD plus 10E3A, 5μm (8.0*300mm), MZ-Gel SD plus 500A, 5μm (8.0*300mm), MZ-Gel SD plus 100A, 5μm (8.0*300mm) in series, Shimadzu; mobile phase: tetrahydrofuran; flow rate: 1.0 mL / min; analysis time: 40 min; column temperature: 35℃). The area of ​​polymers and monomers in the test system was determined by the area normalization method. The isocyanate monomer content (%) was calculated as S(isocyanate monomer peak area) / S(sum of peak areas of all components) * 100%.

[0073] (2) NCO% content test: The test was conducted in accordance with standard GB / T 12009.4;

[0074] (3) Method for determining product color number: Based on the method of GB / T 3143-1982, the color number is measured in a 50mm disposable rectangular cuvette using HACH Lange's LICO 400.

[0075] (4) Method for determining the turbidity of the product: The turbidity was determined using a Hach 2100N turbidity meter from the United States.

[0076] The chemical raw materials used in the following examples and comparative examples are as follows; unless otherwise specified, all other raw materials are common commercially available materials:

[0077] 1,6-Hexamethylene diisocyanate ( HDI), Wanhua Chemical;

[0078] Toluene diisocyanate ( TDI-80), Wanhua Chemical;

[0079] Trimethylolpropane (TMP), diethylene glycol (DEG), purity ≥99%, Sigma-Aldrich;

[0080] Tetraethylammonium hydroxide solution (25 wt%, methanol solution), Sigma Aldrich;

[0081] Di(2-ethylhexyl) phosphate: purity > 98.5%, Aladdin reagent.

[0082] Unless otherwise specified, in the following examples and comparative examples, the reaction solution was kept under a dry nitrogen atmosphere from the start of the reaction until the addition of the catalyst and throughout the entire reaction process. Unless otherwise stated, all percentages in this document are by mass.

[0083] Example 1 of preparation of polyisocyanate composition products:

[0084] 1000g of 1,6-hexamethylene diisocyanate (HDI) was added to a reaction apparatus and heated to 70°C. 5g of tetraethylammonium hydroxide solution (25wt% methanol solution) was added to initiate the polymerization reaction. The NCO% content of the reaction solution was monitored and measured. When the NCO% content of the reaction solution reached 40wt%, 0.16g of di(2-ethylhexyl) phosphate was added to terminate the reaction, yielding an HDI trimer polyisocyanate reaction solution. The total polyisocyanate content in this reaction solution was 42wt%.

[0085] The HDI trimer polyisocyanate reaction solution obtained above was passed into a two-stage series evaporator for separation. The separation temperature of the first-stage thin-film evaporator was 155±2.5℃ and the separation vacuum was 100Pa absolute pressure. The separation temperature of the second-stage short-path evaporator was 155±2.5℃ and the separation vacuum was 20Pa absolute pressure. Unreacted free isocyanate monomers were removed to obtain the heavy component, namely the HDI trimer polyisocyanate composition containing the isocyanurate structure.

[0086] The prepared HDI trimer polyisocyanate composition was tested and found to have a color number of 15 Hazen, a turbidity of 0.24 NTU, and a free HDI monomer content of 0.08 wt%.

[0087] Example 2 of preparation of polyisocyanate composition products:

[0088] The continuous reaction system consists of two jacketed reactors connected in series. The first reactor has a volume of 10L, and the second reactor has a volume of 500L. The temperature of the first reactor is set at 130±2℃, and the temperature of the second reactor is set at 70±2℃. The two reactors are pre-filled with 5L and 300L of toluene diisocyanate (TDI-80), respectively. The temperature of each reactor is controlled by jacket heating and internal coil heat transfer, and the reaction proceeds isothermally. Then, TDI (pre-filled with...) is added continuously. Antioxidant BHT (equivalent to 300 ppm of TDI by mass), TMP, and DEG were added to the first reactor at a weight ratio of 20:2:1. All materials were preheated to 80±1℃, and the feed flow rate was controlled. The average residence time of the materials in the first reactor was 10 minutes. The mixture was then overflowed into the second reactor, where the average residence time was 10 hours, yielding a polyisocyanate reaction solution. The total polyisocyanate content in this reaction solution was 63 wt%.

[0089] The polyisocyanate reaction solution obtained above was separated by a two-stage thin-film evaporator. The separation temperature of the first-stage thin-film evaporator was 170±2.5℃ and the absolute pressure of separation was 100Pa. The separation temperature of the second-stage thin-film evaporator was 170±2.5℃ and the absolute pressure of separation was 20Pa. Unreacted free TDI monomers in the reaction system were removed to obtain the heavy component, namely the polyisocyanate composition containing TDI adducts.

[0090] The separated heavy components are then added to ethyl acetate preheated to 70°C, mixed thoroughly, and cooled to 30°C to obtain the polyisocyanate composition product with a solid content of 75 wt%.

[0091] The prepared polyisocyanate composition was tested and found to have a color number of 23 Hazen, a turbidity of 0.56 NTU, and a free TDI monomer content of 0.18 wt%.

[0092]

Storage Example

[0093] The polyisocyanate composition products prepared in the above product preparation example were filled into 200L stainless steel drums and high-density polyethylene IBC ton containers for storage using a filling machine. The storage conditions are shown in Table 1. The experimental results are shown in Table 1.

[0094] Table 1 Storage conditions and experimental results

[0095]

[0096]

[0097] As can be seen from the test data of the examples and comparative examples in Table 1, by placing the polyisocyanate composition in a metal packaging drum or IBC tonne drum and controlling the storage temperature at -15 to 40°C, the present invention can control the free monomer content in the obtained polyisocyanate composition to below 0.3 wt%, and the turbidity to below 0.6 NTU, thus exhibiting high stability.

[0098] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the spirit of the invention.

Claims

1. A method for stabilizing and storing a polyisocyanate composition, characterized in that, The steps are as follows: the polyisocyanate composition is placed in a metal packaging drum or an IBC ton container, and the storage temperature is controlled between -15 and 40°C to obtain a stable polyisocyanate composition product.

2. The method according to claim 1, characterized in that, The metal packaging drums are selected from drums with an inner wall of 304 stainless steel, drums with an inner wall of tinplate, drums with an inner wall of galvanized steel, drums with an inner wall of tinplate, and metal drums with an inner wall that has been passivated or contain an inner coating substance.

3. The method according to claim 1 or 2, characterized in that, The IBC container is made of one or more of the following materials: high-density polyethylene, polypropylene, polytetrafluoroethylene, polyvinyl chloride, polycarbonate, polylactic acid, polyurethane, and polyamide.

4. The method according to any one of claims 1-3, characterized in that, The preparation method of the polyisocyanate composition includes the following steps: (1) React isocyanate monomers with polyols by contacting them, or allow isocyanate monomers to undergo self-polymerization. (2) After the reaction reaches the set conversion rate, add a terminator or do not add a terminator to the system to end the reaction and obtain the polyisocyanate reaction solution. (3) Optionally, the obtained polyisocyanate reaction solution is separated by an evaporator; (4) The separated heavy components are diluted with solvent or not to obtain the polyisocyanate composition product.

5. The method according to claim 4, characterized in that, The isocyanate monomer in step (1) is selected from one or more of aromatic organic isocyanates, aliphatic organic isocyanates, and alicyclic organic isocyanates, preferably from one or more of hexamethylene diisocyanate, isophorone diisocyanate, cyclohexyldimethylene diisocyanate, phenyldimethylene diisocyanate, dicyclohexylmethane diisocyanate, norbornene dimethylene diisocyanate, cyclohexyl diisocyanate, lysine diisocyanate, tetramethylphenyldimethylene diisocyanate, 2,4,4-trimethylhexane diisocyanate, toluene diisocyanate, methylcyclohexyl diisocyanate, naphthalene diisocyanate, terephthalic diisocyanate, diphenylmethane diisocyanate, and polymethylene polyphenyl polyisocyanate.

6. The method according to claim 4 or 5, characterized in that, Step (1) is carried out under conditions with or without a catalyst.

7. The method according to any one of claims 4-6, characterized in that, In step (2), the total content of polyisocyanate in the polyisocyanate reaction solution is 5-80 wt%, preferably 20-70 wt%.

8. The method according to any one of claims 4-7, characterized in that, The polyisocyanate reaction solution in step (2) includes polyisocyanates containing one or more of the following structures: isocyanurate structure, carbamate structure, urethane structure, biuret structure, iminooxadiazine dione structure, urea dione structure, carbodiimide structure, and urea ketimide structure.

9. The method according to any one of claims 4-8, characterized in that, In step (3), when the evaporator is used for separation, the evaporator is a scraped evaporator. Preferably, the scraped evaporator is a thin-film evaporator and / or a short-path evaporator.

10. The application of the stable-stored polyisocyanate composition obtained by the method of any one of claims 1-9, characterized in that, The stable-stored polyisocyanate composition is used in the preparation of polyurethane coatings or polyurethane adhesives after being sealed with a sealing agent.

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