A polyisocyanate composition, process for its preparation and use thereof

Abstract

This invention provides a polyisocyanate composition, its preparation method, and its application. The polyisocyanate composition is derived from aliphatic isocyanates, and its functionality distribution ratio (f-ratio) is 0.05-0.15; f-ratio = (X4 + X5) / X1, where X1, X4, and X5 represent the molar content of aliphatic isocyanate trimers, nonameliters, and polymers in the polyisocyanate composition, respectively. Through the design and precise control of the functionality distribution ratio, this invention enables the polyisocyanate composition to possess appropriate NCO values ​​and viscosity, exhibiting excellent curing and processing properties. Its curing speed is significantly accelerated, effectively shortening the construction cycle. While significantly improving the application strength and hardness of the cured product, it maintains excellent flexibility, achieving superior overall performance.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a polyisocyanate composition, its preparation method, and its application. Background Technology

[0002] Polyisocyanates are versatile curing agents with high reactivity, finding wide application in coatings, adhesives, sealants, and other fields. Based on the different skeletal structures linked to the isocyanate groups, polyisocyanates are broadly classified into aromatic and aliphatic categories. Among them, aliphatic polyisocyanates, compared to aromatic polyisocyanates containing unsaturated groups, possess superior weather resistance and resistance to yellowing, making them more attractive and competitive in the market.

[0003] Isophorone diisocyanate (IPDI), as a member of the aliphatic isocyanate family, includes a unique aliphatic ring structure in its molecular structure, resulting in superior molecular rigidity and lipophilicity. Simultaneously, IPDI has a low saturated vapor pressure, making it more environmentally friendly. Trimers prepared from IPDI exhibit good thermal stability, wear resistance, and corrosion resistance, and are currently widely used as curing agents in high-end furniture, the automotive industry, the aerospace industry, and sporting goods, demonstrating extremely high commercial value.

[0004] Given the high value of IPDI trimer, its preparation method is also an important research topic in the industry. For example, CN103626955A discloses a method for trimerizing alicyclic diisocyanates. IPDI undergoes polymerization under the action of a catalyst, and the reaction is terminated when the NCO in the reaction system reaches the target value. Monomers are removed by means of vacuum distillation or thin-film distillation to obtain the trimer product. This product can be added to a solvent or made into powder for use as a curing agent. The study "Trimerization Research of Isophorone Diisocyanate" indicates that IPDI does not only generate trimers during polymerization, but forms a mixed system with trimers as the main component and containing pentamers, heptamers, and other high molecular weight polymers. Due to the influence of steric hindrance, its gel permeation chromatography (GPC) pattern usually shows a decreasing trend in the content of trimers, pentamers, heptamers, nine- to higher polymers. Therefore, under current technological conditions, the polymer content in the prepared products is generally low, which significantly restricts the application strength and curing speed of the cured products. This is especially true in industrial protection and construction applications, where the actual curing speed and application strength of the cured products are significantly insufficient. Increasing the polymer content to improve application strength requires further increasing the polymerization degree of IPDI, but this strategy leads to a decrease in the trimer content of the polymerized product, a surge in product viscosity, causing inconvenience in practical applications, and a significant reduction in the flexibility of the cured product, thus creating a prominent contradiction between processing performance and material mechanical properties.

[0005] Therefore, developing an isocyanate curing agent with fast curing speed and good processing performance, and whose cured product has high application strength and excellent flexibility, is an urgent problem to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a polyisocyanate composition, its preparation method, and its application. By designing the functionality distribution ratio, the polyisocyanate composition possesses excellent crosslinking properties, curing properties, and processing properties, with faster curing speed and significantly improved hardness and application strength of the cured product, while also exhibiting excellent flexibility.

[0007] To achieve this objective, the present invention employs the following technical solution: In a first aspect, the present invention provides a polyisocyanate composition derived from an aliphatic isocyanate, wherein the functionality distribution ratio of the polyisocyanate composition is 0.05-0.15; the formula for calculating the functionality distribution ratio is shown in Formula A: f-ratio=(Χ4+Χ5) / Χ1 (Formula A)

[0008] In Formula A, f-ratio represents the functionality distribution ratio, Χ1 represents the molar content of aliphatic isocyanate trimer in the polyisocyanate composition, Χ4 represents the molar content of aliphatic isocyanate nonamerm in the polyisocyanate composition, and Χ5 represents the molar content of aliphatic isocyanate polymer in the polyisocyanate composition.

[0009] The aliphatic isocyanate polymer has the structure shown in Formula I: Formula I; Wherein, R represents a divalent residue derived from aliphatic isocyanates; n is an integer greater than 3.

[0010] This invention has discovered that the trimer content, as a major component of polyisocyanate compositions, is a key factor affecting core physicochemical parameters such as viscosity and NCO value. Therefore, effectively increasing the polymer content in the composition while maintaining a suitable trimer content has become a pressing technical challenge in this field. Based on this, this invention conducts in-depth research on the compositional distribution of polyisocyanate compositions, proposing the functionality distribution ratio as a key parameter. By designing a functionality distribution ratio within the range of 0.05-0.15, a specific functionality distribution relationship is established between the nonamer, polymer, and trimer, resulting in higher functionality of the polyisocyanate composition. This composition exhibits excellent crosslinking, curing, and processing properties, significantly accelerating curing speed, effectively shortening the construction cycle, and effectively balancing crosslinking density and flexibility, providing higher mechanical strength. While significantly improving the application strength and hardness of the cured product, it still maintains excellent flexibility.

[0011] As a preferred embodiment of the present invention, the functionality distribution ratio f-ratio of the polyisocyanate composition is 0.05-0.15, for example, it can be 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13 or 0.14, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0012] As a preferred embodiment of the present invention, the polyisocyanate composition comprises the following components in molar amounts: Aliphatic isocyanate trimers: 72.5%-74.5% Aliphatic isocyanate pentamers: 12.5%-16% Aliphatic isocyanate heptamers 3.5%-5%, Aliphatic isocyanate nonamers 2%-5.5%, Aliphatic isocyanate polymers 2.5%-5%.

[0013] As a preferred technical solution of the present invention, the compositional distribution of the polyisocyanate composition is designed to achieve a suitable content level of trimer, while simultaneously controlling the content of pentamer, heptamer, nonamerm, and higher polymers. In particular, the molar content of nonamerm and higher polymers is selectively increased. Through precise control of the compositional distribution, the polyisocyanate composition achieves appropriate NCO value and viscosity, exhibiting excellent functionality, including comprehensive improvements in crosslinking performance, curing performance, and processing performance. Its curing speed is significantly accelerated, effectively shortening the construction cycle. While significantly improving the application strength and hardness of the cured product, it still maintains excellent flexibility, resulting in superior overall performance.

[0014] In this invention, the structure of the aliphatic isocyanate trimer is as follows: .

[0015] The structure of the aliphatic isocyanate pentamer is as follows: .

[0016] The structure of the aliphatic isocyanate heptamer is as follows: .

[0017] The structure of the aliphatic isocyanate nonmer is as follows: .

[0018] The aliphatic isocyanate polymer has the structure shown in Formula I: Formula I.

[0019] In Formula I, n is an integer greater than 3, such as 4, 5, 6, 7, 8, 9, or 10.

[0020] In the aforementioned structure, R represents a divalent residue derived from an aliphatic isocyanate.

[0021] For example, if the aliphatic isocyanate is isophorone diisocyanate (IPDI), then R in the aforementioned structure is... The aliphatic isocyanate is dicyclohexylmethane diisocyanate (HMDI), then R in the aforementioned structure is... The aliphatic isocyanate is 1,4-diisocyanate cyclohexane, then R in the aforementioned structure is... ;in, The linking site of the representative group.

[0022] It should be noted that the aliphatic isocyanate polymers are a general term for a class of polymers with the structure shown in Formula I, all of which have an odd degree of polymerization. For example, when n is 4, it is an aliphatic isocyanate undecimer; when n is 5, it is an aliphatic isocyanate thiedemer; when n is 6, it is an aliphatic isocyanate decimer, and so on. This is because it is necessary to react with two molecules of aliphatic isocyanate monomers on the basis of oligomers (oligomers with an odd degree of polymerization) to form a stable six-membered ring structure in order to increase the degree of polymerization. Products with an even degree of polymerization cannot exist stably.

[0023] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0024] In this invention, the molar content of aliphatic isocyanate trimer in the polyisocyanate composition is 72.5%-74.5%, for example, it can be 72.6%, 72.8%, 73%, 73.2%, 73.5%, 73.8%, 74%, 74.2% or 74.4%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0025] The polyisocyanate composition contains an aliphatic isocyanate pentamer molar content of 12.5%-16%, for example, 12.8%, 13%, 13.2%, 13.5%, 13.8%, 14%, 14.2%, 14.5%, 14.8%, 15%, 15.2%, 15.5%, or 15.8%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0026] The molar content of aliphatic isocyanate heptamer in the polyisocyanate composition is 3.5%-5%, for example, it can be 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.5%, 4.6% or 4.8%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0027] The molar content of aliphatic isocyanate nonmer in the polyisocyanate composition is 2%-5.5%, for example, it can be 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, or 5.4%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0028] The molar content of aliphatic isocyanate polymer in the polyisocyanate composition is 2.5%-5%, for example, it can be 2.6%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5% or 4.8%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0029] As a preferred embodiment of the present invention, the aliphatic isocyanate includes any one or a combination of at least two of isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), and 1,4-diisocyanate cyclohexane.

[0030] As a preferred embodiment of the present invention, the mass content (NCO value) of the NCO groups in the polyisocyanate composition is 10%-15%, for example, it can be 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14% or 14.5%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but 11%-13% is preferred.

[0031] For example, the mass content of NCO groups in the polyisocyanate composition is determined by hydrochloric acid-di-n-butylamine chemical titration, specifically the mass content of NCO groups in a polyisocyanate composition solution with a solid content of 70% (preferably with butyl acetate as the solvent).

[0032] Preferably, the viscosity of the polyisocyanate composition is 500-1500 mPa·s, for example, it can be 600 mPa·s, 800 mPa·s, 1000 mPa·s, 1100 mPa·s, 1200 mPa·s, 1300 mPa·s or 1400 mPa·s, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but preferably 700-1400 mPa·s.

[0033] For example, the viscosity is obtained by testing at 23°C, specifically the viscosity of a polyisocyanate composition solution with a solid content of 70% (preferably with butyl acetate as the solvent).

[0034] In a second aspect, the present invention provides a method for preparing the polyisocyanate composition as described in the first aspect, the method comprising: Aliphatic isocyanates undergo a first polymerization reaction in the presence of a first catalyst until the mass content of NCO groups in the system is 27.8%-29.8%, yielding the crude product. The crude product was purified to obtain an isocyanate prepolymer. The isocyanate prepolymer undergoes a second polymerization reaction in the presence of a phosphate ester catalyst to obtain the polyisocyanate composition.

[0035] This invention reveals that conventional trimeric polyisocyanate products have the highest trimer content, while the content of pentameric, heptameric, nonmeric, and other polymers decreases with increasing degree of polymerization. These products exhibit significantly insufficient curing speed and application strength of the cured product. Therefore, this invention proposes a method for preparing a polyisocyanate composition, comprising two polymerization reactions. The first polymerization reaction results in a high NCO value, and the crude product is purified to obtain an isocyanate prepolymer. This prepolymer undergoes a second polymerization reaction catalyzed by a phosphate ester catalyst, further increasing the proportion of polymers in the product through self-polymerization. This results in a polyisocyanate composition with an NCO value and trimer content comparable to conventional products, along with a specific functionality distribution. The content of nonmeric and higher polymers is 3-5 times higher than that of conventional products, significantly accelerating the curing speed as a curing agent. The resulting cured product exhibits significantly improved hardness and application strength while maintaining excellent flexibility.

[0036] As a preferred embodiment of the present invention, the second polymerization reaction is carried out under entropy-increasing conditions, which include solvent dilution and / or heating and stirring. That is, under the conditions of solvent dispersion and / or heating and stirring, the entropy value of the reaction system is effectively increased, slightly increasing the collision probability of pentamers, heptamers, nonamers and other molecules, thereby increasing the possibility of higher polymer formation. Finally, under the action of the phosphate ester catalyst, the polymer is repolymerized to obtain the polyisocyanate composition with a higher proportion of polymers.

[0037] In this invention, a phosphate ester catalyst is used to catalyze the second polymerization reaction. The oxygen atom in the phosphoryl group (P=O) has a lone pair of electrons, exhibiting Lewis base (nucleophilic) properties. It can attack the highly electron-deficient carbon atom in the isocyanate group (RN=C=O) to form an activated zwitterionic intermediate ((RO)2P). + -OC(=O)-N - -R), this intermediate more readily attacks another isocyanate molecule, thereby initiating a trimerization or polymerization chain reaction. This catalytic process proceeds slowly under heating or prolonged conditions, which is milder than conventional trimerization catalysts such as quaternary ammonium bases and quaternary ammonium salts, and is more conducive to achieving the technical objectives of this invention. After the second polymerization reaction is completed, as the temperature drops to the storage temperature, the residual trace amounts of phosphate ester catalyst in the system will no longer continue to catalyze the reaction, but will remain in the product, acting as a polymerization inhibitor, and will not adversely affect the product composition and performance.

[0038] In the preparation method described above, the endpoint of the first polymerization reaction is determined by detecting the content of NCO groups in the system. At the endpoint, the mass content (NCO value) of NCO groups in the system is 27.8%-29.8%, for example, it can be 27.9%, 28%, 28.2%, 28.4%, 28.5%, 28.6%, 28.8%, 29%, 29.2%, 29.4%, 29.5%, 29.6%, or 29.7%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0039] In this invention, the aliphatic isocyanate (monomer) used as a raw material can be fresh aliphatic isocyanate and / or recycled aliphatic isocyanate, preferably including a combination of fresh aliphatic isocyanate and aliphatic isocyanate.

[0040] Preferably, the mass content of fresh aliphatic isocyanate in the aliphatic isocyanate (monomer) is 10%-90%, for example, it can be 20%, 30%, 40%, 50%, 60%, 70% or 80%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but preferably 30%-70%.

[0041] Preferably, the first polymerization reaction includes a raw material pretreatment step, which includes: feeding fresh aliphatic isocyanate and recycled aliphatic isocyanate into a degassing tower for distillation purification to reduce the content of impurities such as CHI (NCO-R-Cl) and HCl.

[0042] Preferably, the temperature of the raw material pretreatment is 50-120℃, for example, it can be 60℃, 70℃, 80℃, 90℃, 100℃ or 110℃, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, and 80-110℃ is further preferred.

[0043] Preferably, the raw material pretreatment time is 30-120 min, for example, it can be 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min or 110 min, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, and 60-100 min is further preferred.

[0044] As a preferred embodiment of the present invention, the first catalyst comprises a quaternary ammonium salt and / or a quaternary ammonium base, preferably any one or a combination of at least two of tetraalkyl quaternary ammonium salt, trialkylaryl quaternary ammonium salt, tetraalkyl quaternary ammonium base, and trialkylaryl quaternary ammonium base, and more preferably a trialkylaryl quaternary ammonium base.

[0045] For example, the quaternary ammonium salt includes any one or a combination of at least two of trimethylhydroxypropylammonium decanoate, trimethylhydroxypropylammonium formate, trimethylhydroxyethylammonium formate, trimethylhydroxyethylammonium acetate, and trimethylhydroxyethylammonium decanoate.

[0046] For example, the quaternary ammonium base includes any one or a combination of at least two of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, methyltriethylammonium hydroxide, dimethyldiethylammonium hydroxide, trimethylpropylammonium hydroxide, methyltributylammonium hydroxide, benzyltrimethylammonium hydroxide, and benzyltriethylammonium hydroxide.

[0047] Preferably, the first catalyst is mixed with a solvent to prepare a first catalyst solution for use in the first polymerization reaction.

[0048] Preferably, the solvent in the first catalyst solution includes an alcohol solvent, which may be a monohydric alcohol and / or a polyhydric alcohol, including but not limited to: any one or a combination of at least two of methanol, ethanol, n-propanol, and isopropanol.

[0049] As a preferred embodiment of the present invention, the mass of the first catalyst is 50-500 ppm, based on the mass of the aliphatic isocyanate as 100%, for example, it can be 80 ppm, 100 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm, 400 ppm or 450 ppm, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0050] In this invention, the term "ppm" means parts per million, and 1 ppm is one part per million.

[0051] The reaction mechanism of the first polymerization reaction is as follows: ① The first catalyst acts as a nucleophile to activate NCO groups to form an active intermediate; ② The active intermediate attacks other free NCO groups to form a dimer intermediate, which cannot stably form a ring; ③ The unstable dimer intermediate attacks other free NCO groups to form a trimer intermediate; ④ The trimer intermediate spontaneously deactivates the first catalyst to form a stable six-membered ring structure, which is the trimer; ④ The free NCO outside the trimer can also be attacked by the first catalyst, forming a ring again to form a pentamer, heptamer, etc., and so on until a higher polymer is formed.

[0052] Preferably, the first polymerization reaction is carried out under stirring conditions.

[0053] As a preferred embodiment of the present invention, the temperature of the first polymerization reaction is 50-120°C, for example, it can be 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C or 115°C, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range. Preferably, it is 80-115°C, and more preferably 95-110°C.

[0054] In this invention, the endpoint of the first polymerization reaction is when the mass content of NCO groups in the system is 27.8%-29.8%. After reaching the endpoint, no additional terminator is required. The reaction is terminated by rapidly heating the system to 125-140°C (e.g., 128°C, 130°C, 132°C, 135°C, 138°C, etc.) to deactivate the first catalyst at high temperature.

[0055] As a preferred embodiment of the present invention, the purification process includes sequential vacuum circulation pretreatment and distillation. The vacuum circulation pretreatment removes residual first catalyst and its possible decomposition products (e.g., quaternary ammonium cations, tertiary amine molecules, etc.) from the crude product, preventing the first catalyst and its decomposition products from affecting the second polymerization reaction. The distillation removes unreacted aliphatic isocyanate monomers, and the distilled aliphatic isocyanate monomers are recycled into the first polymerization reaction; the distillate fraction obtained is the isocyanate prepolymer.

[0056] As a preferred technical solution of the present invention, the vacuum pretreatment method includes: first, subjecting the crude product to vacuum circulation, then replacing it with an inert gas, and then drawing a vacuum to complete the vacuum pretreatment.

[0057] Preferably, the vacuum pretreatment is performed in a buffer vessel.

[0058] As a preferred embodiment of the present invention, the temperature of the vacuum cycle is 40-80°C, for example, it can be 45°C, 50°C, 55°C, 60°C, 65°C, 70°C or 75°C, as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0059] As a preferred embodiment of the present invention, the vacuum cycle time is 0.5-2 h, for example, it can be 0.8 h, 1 h, 1.2 h, 1.4 h, 1.5 h, 1.6 h or 1.8 h, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0060] Preferably, the pressure of the vacuum circulation is ≤1 mbar, for example, it can be 0.1 mbar, 0.2 mbar, 0.3 mbar, 0.4 mbar, 0.5 mbar, 0.6 mbar, 0.7 mbar, 0.8 mbar or 0.9 mbar, etc.

[0061] As a preferred embodiment of the present invention, the number of times the inert gas is replaced is 1-5 times, for example, 1 time, 2 times, 3 times, 4 times or 5 times.

[0062] For example, the inert gas includes any one of N2, Ar, and He.

[0063] Preferably, the re-vacuuming to a pressure ≤1 mbar can be, for example, 0.1 mbar, 0.2 mbar, 0.3 mbar, 0.4 mbar, 0.5 mbar, 0.6 mbar, 0.7 mbar, 0.8 mbar, or 0.9 mbar.

[0064] As a preferred embodiment of the present invention, the distillation pressure is ≤20 Pa, for example, it can be 1 Pa, 2 Pa, 4 Pa, 5 Pa, 6 Pa, 8 Pa, 10 Pa, 12 Pa, 14 Pa, 15 Pa, 16 Pa or 18 Pa, as well as specific point values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific point values ​​included in the range.

[0065] As a preferred embodiment of the present invention, the distillation temperature is 160-210℃, for example, it can be 165℃, 170℃, 175℃, 180℃, 185℃, 190℃, 195℃, 200℃ or 205℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0066] As a preferred technical solution of the present invention, the distillation includes: passing the product obtained by vacuum pretreatment through a falling film evaporator and a thin film evaporator under the conditions of pressure ≤20 Pa and temperature 160-210℃ to remove unreacted aliphatic isocyanate (monomer), wherein the aliphatic isocyanate (monomer) is recycled, and the fraction after distillation is the isocyanate prepolymer.

[0067] As a preferred embodiment of the present invention, the isocyanate prepolymer comprises the following components in molar content: Aliphatic isocyanate trimers 74%-78%, Aliphatic isocyanate pentamers 16%-18%, Aliphatic isocyanate heptamers 4%-5%, Aliphatic isocyanate nonmer 1%-2%, Aliphatic isocyanate polymers 0-1%.

[0068] Preferably, the molar content of aliphatic isocyanate trimer in the isocyanate prepolymer is 74%-78%, for example, it can be 74.2%, 74.5%, 74.8%, 75%, 75.2%, 75.5%, 75.8%, 76%, 76.2%, 76.5%, 76.8%, 77%, 77.2%, 77.5%, or 77.8%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0069] Preferably, the molar content of aliphatic isocyanate pentamers in the isocyanate prepolymer is 16%-18%, for example, it can be 16.2%, 16.4%, 16.5%, 16.6%, 16.8%, 17%, 17.2%, 17.4%, 17.5%, 17.5% or 17.8%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0070] Preferably, the molar content of aliphatic isocyanate heptamers in the isocyanate prepolymer is 4%-5%, for example, it can be 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8% or 4.9%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0071] Preferably, the molar content of aliphatic isocyanate nonmer in the isocyanate prepolymer is 1%-2%, for example, it can be 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8% or 1.9%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0072] Preferably, the molar content of aliphatic isocyanate polymer in the isocyanate prepolymer is 0-1%, for example, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% or 0.9%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0073] In this invention, the isocyanate prepolymer undergoes a second polymerization reaction under the action of a phosphate ester catalyst, causing the trimer, pentamer, heptamer and other components to polymerize under the catalysis of the phosphate ester catalyst to form polymers of different sizes. Due to the entropy-increasing environment, the probability of the trimer reacting with the pentamer, the trimer reacting with the heptamer and other components is increased, thereby increasing the content of polymers in the final product.

[0074] As a preferred embodiment of the present invention, the second polymerization reaction is carried out in the presence of a solvent.

[0075] As a preferred embodiment of the present invention, the isocyanate prepolymer and solvent are mixed to obtain a mixture; a phosphate ester catalyst solution is added to the mixture to carry out a second polymerization reaction to obtain the polyisocyanate composition.

[0076] Preferably, the mixing is carried out under stirring conditions.

[0077] Preferably, the mixing temperature is 60-80℃, for example, it can be 62℃, 65℃, 68℃, 70℃, 72℃, 75℃ or 78℃, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0078] Preferably, the mixing time is 0.5-1 h, for example, 0.6 h, 0.7 h, 0.8 h or 0.9 h, and specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific point values ​​included in the range.

[0079] As a preferred embodiment of the present invention, the mass content of isocyanate prepolymer in the mixture is 10%-90%, for example, it can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 80% or 85%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but preferably 20%-60%.

[0080] As a preferred embodiment of the present invention, the solvent includes any one or a combination of at least two of aromatic solvents, ester solvents, and ketone solvents, preferably any one or a combination of at least two of toluene, xylene, butyl acetate, propylene glycol methyl ether acetate, ethyl acetate, propyl acetate, acetone, cyclohexanone, and methyl isobutyl ketone.

[0081] As a preferred embodiment of the present invention, the phosphate ester catalyst includes any one or a combination of at least two of dibutyl phosphate, dimethyl phosphate, diethyl phosphate, di(2-ethylhexyl) phosphate, and diphenyl phosphate.

[0082] As a preferred embodiment of the present invention, the solvent in the phosphate ester catalyst solution includes any one or a combination of at least two of butyl acetate, propylene glycol methyl ether acetate, ethyl acetate, propyl acetate, and propylene glycol methyl ether propionate, preferably butyl acetate.

[0083] As a preferred embodiment of the present invention, the mass content of the phosphate ester catalyst in the phosphate ester catalyst solution is 30%-70%, for example, it can be 35%, 40%, 45%, 50%, 55%, 60% or 65%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0084] As a preferred embodiment of the present invention, the mass content of the phosphate ester catalyst in the second polymerization reaction system is 1-1000 ppm, for example, it can be 10 ppm, 30 ppm, 50 ppm, 80 ppm, 100 ppm, 150 ppm, 180 ppm, 200 ppm, 250 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm or 900 ppm, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range. Preferably, it is 10-300 ppm, and more preferably 20-200 ppm.

[0085] It should be noted that the total mass of the second polymerization reaction system is 100%, that is, the total mass of isocyanate prepolymer, solvent, phosphate catalyst and solvent is 100%, and the mass of phosphate catalyst is 1-1000 ppm.

[0086] Preferably, the second polymerization reaction is carried out under stirring conditions.

[0087] As a preferred embodiment of the present invention, the temperature of the second polymerization reaction is 80-130°C, for example, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, or 125°C, as well as specific values ​​between the above-mentioned values. For space limitations and for the sake of brevity, the present invention will not exhaustively list all the specific values ​​included in the range, but 100-120°C is further preferred. If the temperature of the second polymerization reaction is lower than this temperature range, the catalytic effect will be reduced or even ineffective; if the temperature of the second polymerization reaction is higher than this range, side reactions such as ureadione / carboimide will be triggered.

[0088] As a preferred embodiment of the present invention, the time for the second polymerization reaction is 10-17 h, for example, it can be 10.5 h, 11 h, 11.5 h, 12 h, 12.5 h, 13 h, 13.5 h, 14 h, 14.5 h, 15 h, 15.5 h, 16 h or 16.5 h, as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0089] Preferably, during the second polymerization reaction, the product composition is checked every 1 hour until the composition reaches the acceptable range, and the reaction is terminated by cooling to obtain the polyisocyanate composition.

[0090] For example, the product composition is detected by liquid chromatography.

[0091] Preferably, the reaction is terminated by cooling to ≤50℃ (e.g., 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 48℃, or 49℃). The second polymerization reaction stops automatically after the temperature decreases, without the need for additional terminator.

[0092] As a preferred embodiment of the present invention, the preparation method includes the following steps: (1) The aliphatic isocyanate was subjected to a first polymerization reaction at 50-120°C in the presence of a first catalyst until the mass content of NCO groups in the system was 27.8%-29.8%, and the crude product was obtained. (2) The crude product is subjected to vacuum circulation treatment at 40-80℃ for 0.5-2 h, and then replaced with inert gas 1-5 times, and then vacuumed to ≤1 mbar to obtain the pretreated product; the pretreated product is distilled under pressure ≤20 Pa and temperature of 160-210℃ to obtain isocyanate prepolymer. (3) The isocyanate prepolymer is mixed with a solvent to obtain a mixture; the mass content of the isocyanate prepolymer in the mixture is 10%-90%; A phosphate ester catalyst solution is added to the mixture to make the mass content of the phosphate ester catalyst in the system 1-1000 ppm, and the polymerization reaction is carried out at 80-130℃ for 10-17 h to obtain the polyisocyanate composition.

[0093] Thirdly, the present invention provides the use of the polyisocyanate composition as described in the first aspect and the polyisocyanate composition prepared by the preparation method as described in the second aspect in polyurethane products or polyurea products.

[0094] Fourthly, the present invention provides a polyurethane coating comprising a hydroxyl-containing resin and a curing agent, wherein the curing agent comprises at least one of the polyisocyanate composition as described in the first aspect and a polyisocyanate composition prepared by the preparation method described in the second aspect.

[0095] Compared with the prior art, the present invention has at least the following beneficial effects: (1) In the polyisocyanate composition provided by the present invention, the trimer has a suitable content level, and the contents of pentamer, heptamer, nonamer and polymer are controlled, especially increasing the contents of nonamer and polymer. Through the design and precise directional control of the composition distribution, the polyisocyanate composition has appropriate NCO value and viscosity. On the basis of excellent curing performance and processing performance, the hardness and application strength of the cured product are significantly improved, and it also has excellent flexibility. At the same time, the curing speed of the polyisocyanate composition is significantly accelerated, which can shorten the construction cycle and achieve rapid curing in relatively unfavorable construction environments, thus obtaining excellent comprehensive performance.

[0096] (2) The polyisocyanate composition provided by the present invention can be used in polyurethane coatings to make the curing time of the coating ≤22 min. Its curing speed is about 20% higher than that of conventional tripolyisocyanate, effectively shortening the construction cycle. The formed coating film maintains excellent flexibility while increasing the hardness to 3H-4H, significantly improving the comprehensive application strength, so that it can meet the application requirements of industrial buildings and other fields with higher requirements for hardness and other properties. Attached Figure Description

[0097] Figure 1 GPC spectrum of the polyisocyanate composition provided in Example 1; Figure 2 GPC spectrum of the polyisocyanate composition provided in Comparative Example 1; Figure 3 This is a GPC overlay comparison diagram of the polyisocyanate compositions in Example 1 and Comparative Example 1. Detailed Implementation

[0098] To facilitate understanding of the present invention, specific embodiments are provided to further illustrate the technical solution of the present invention. Those skilled in the art should understand that the embodiments are merely illustrative of the present invention and should not be considered as specific limitations thereof.

[0099] In one specific embodiment, the functionality distribution ratio f-ratio of the polyisocyanate composition is 0.05-0.15; f-ratio=(Χ4+Χ5) / Χ1, where Χ1, Χ4, and Χ5 represent the molar content of aliphatic isocyanate trimer, nonamerm, and polymer in the polyisocyanate composition, respectively.

[0100] In one specific embodiment, the polyisocyanate composition comprises the following components in molar amounts: Aliphatic isocyanate trimers: 72.5%-74.5% Aliphatic isocyanate pentamers: 12.5%-16% Aliphatic isocyanate heptamers 3.5%-5%, Aliphatic isocyanate nonamers 2%-5.5%, Aliphatic isocyanate polymers 2.5%-5%.

[0101] In one specific embodiment, the method for preparing the polyisocyanate composition includes the following steps: (S1) Raw material pretreatment: Fresh aliphatic isocyanate and recycled aliphatic isocyanate are fed into a degassing tower in a certain proportion and purified by distillation at a higher temperature to reduce the content of impurities such as CHI and HCl, and obtain mixed raw materials.

[0102] (S2) First polymerization reaction: The mixed raw materials are fed into a stirred reactor and heated to 50-120°C. Then, a certain amount of the first catalyst solution is slowly added dropwise to carry out the first polymerization reaction. The catalyst dosage is adjusted in time according to the reaction rate. When the mass content of NCO groups in the system is 27.8%-29.8%, the temperature is rapidly raised to 125-140°C to deactivate the catalyst and terminate the reaction to obtain the crude product.

[0103] (S3) Purification treatment: ① Vacuum circulation pretreatment: Transfer the crude product to a buffer vessel, rapidly cool it to 40-80℃, control the vacuum pressure inside the vessel to ≤1 mbar, circulate it with a suitable feed rate for 0.5-2 h, then replace it with inert gas 1-5 times, and then evacuate it to ≤1 mbar to remove the residual first catalyst and its possible decomposition products in the system, and obtain the pretreated product; ② Distillation: Under the conditions of pressure ≤20 Pa and temperature of 160-210℃, pass the pretreated product through a falling film evaporator and a thin film evaporator to remove unreacted aliphatic isocyanates (monomers), the separated monomers are recycled, and the fraction after distillation is used as isocyanate prepolymer.

[0104] (S4) Second polymerization reaction: The isocyanate prepolymer is pumped into a stirred reactor containing a certain proportion of solvent using a high-temperature pump and stirred evenly. The temperature is controlled at 60-80℃ and stirred for 0.5-1 h to ensure dispersion effect, resulting in a mixture. The phosphate ester catalyst solution is added to the stirred reactor in one go through the solvent inlet and stirred at 80-130℃ for 10-17 h. During this period, the product composition is tested every 1.0 h (the sampling and testing interval can be shorter when the endpoint is approached). When the composition reaches the qualified range, the temperature is lowered to <50℃ and stirred for 0.5 h to terminate the reaction, resulting in the polyisocyanate composition.

[0105] The detection methods involved in the following specific embodiments of the present invention are as follows: (1) Mass content of NCO groups (NCO value) The detection was performed using hydrochloric acid-di-n-butylamine chemical titration, with electrode model DGi113-SC.

[0106] (2) Components of polyisocyanate composition and isocyanate prepolymer Detection was performed using liquid chromatography, specifically a gel permeation liquid chromatograph (GPC) system: Agilent 1260 Infinity II; column: Shodex GPC KF-802.5; column temperature: 40℃; detection wavelength: 210 nm; mobile phase: tetrahydrofuran; flow rate: 1.0 mL / min; injection volume: 5 μL; the sample was diluted with ethyl acetate for detection, and the chromatogram was processed using the area normalization method.

[0107] Molar content of each component: This refers to the molar percentage of each component, specifically the molar amount of each component divided by the total molar amount. The molar amount of each component is calculated from the area of ​​each component after normalization by GPC area, using the following formula: Χ1=ω1 / (M1·n 总 );Χ2=ω2 / (M2·n 总 ); Χ3=ω3 / (M3·n 总);Χ4=ω4 / (M4·n 总 );Χ5=ω5 / (M5·n 总 ); Wherein, Χ1, Χ2, Χ3, Χ4, and Χ5 represent the molar content of aliphatic isocyanate trimers, pentamers, heptamers, nonamers, and polymers in the polyisocyanate composition, respectively; ω1, ω2, ω3, ω4, and ω5 represent the mass content of aliphatic isocyanate trimers, pentamers, heptamers, nonamers, and polymers, respectively, obtained by GPC; M1, M2, M3, and M4 represent the molecular weights of aliphatic isocyanate trimers, pentamers, heptamers, and nonamers, respectively; M5 is the average molecular weight of the aliphatic isocyanate polymer, measured by GPC; n 总 This represents the total molar quantity.

[0108] Functionality ratio (f-ratio): It is the molar ratio, specifically the ratio of the sum of nonamers and polymers to the molar content of trimers. A suitable functionality ratio can balance crosslinking density and flexibility, providing higher mechanical strength.

[0109] (3) Viscosity The test was conducted using a BROOKFIELD-RSX rheometer at a temperature of 23℃.

[0110] (4) Curing speed The curing time of polyurethane coatings was tested according to the method shown in standard GB / T 1728-1979. The shorter the curing time, the faster the curing speed.

[0111] (5) Hardness The fully cured paint film was tested using a Biuged BGD 507 / 2 electric pencil hardness tester, according to the method shown in standard GB / T 6739-2022.

[0112] (6) Flexibility Test the fully cured paint film according to the method shown in standard GB / T 1731-2020, and observe whether there are any patterns, cracks and peeling phenomena in the paint film; if there are no patterns, cracks and peeling phenomena within the minimum radius (1 mm), record it as "no abnormality".

[0113] In the following specific embodiments of the present invention, all raw materials for which no preparation method is provided are conventional commercially available chemicals that can be purchased through market channels.

[0114] The following will describe in detail the polyisocyanate composition and its preparation method according to the present invention using several examples, but the polyisocyanate composition and its preparation method are not limited to these examples.

[0115] Example 1 A polyisocyanate composition and its preparation method thereof, the preparation method comprising the following steps: (S1) Raw material pretreatment: Take 1000 g of fresh IPDI and 500 g of recycled IPDI into a four-necked flask, keep warm at 60℃, stir and vacuum for 20 min, then replace with nitrogen 3 times, and then heat to 90℃ and stabilize for 30 min to obtain IPDI mixed raw material.

[0116] (S2) First polymerization reaction: Under stirring conditions, a first catalyst solution (40 wt% benzyltrimethylammonium hydroxide in methanol, wherein the mass of benzyltrimethylammonium hydroxide is 150 ppm of the mass of IPDI) is added to the IPDI mixed raw material. The reaction temperature is controlled at 95°C for the first polymerization reaction. When the NCO value of the system drops to 28.8%, the system is rapidly heated to 130°C and kept at that temperature for 30 min to terminate the reaction and obtain the crude product.

[0117] (S3) Purification treatment: The crude product is circulated under vacuum at 70°C at a rate of 100 mL / min for 1 h; after the circulation, it is replaced three times with high-purity N2, and finally vacuumed to ≤1 mbar to remove the first catalyst and its possible decomposition products to obtain the pretreated product; then the pretreated product is distilled at 170°C to obtain the isocyanate prepolymer, wherein the molar content of IPDI trimer is 76.19%, the molar content of IPDI pentamer is 17.06%, the molar content of IPDI heptamer is 4.73%, the molar content of IPDI nonamer is 1.35%, and the molar content of IPDI polymer is 0.67%.

[0118] (S4) Second polymerization reaction: The isocyanate prepolymer and n-butyl acetate were stirred and mixed at 60°C in a mass ratio of 7:3. After uniform dissolution, a phosphate catalyst solution (30 wt% diethyl phosphate in butyl acetate solution) was added dropwise to the system to make the mass content of the phosphate catalyst in the system 40 ppm. Then the temperature was rapidly raised to 110°C and stirred for 12 h under a nitrogen atmosphere. Subsequently, the temperature was lowered to 30°C and stirred for 0.5 h to terminate the reaction, and the polyisocyanate composition was obtained. Its component information and related parameters are shown in Table 1.

[0119] Example 2 A polyisocyanate composition and its preparation method thereof, the preparation method comprising the following steps: (S1) Raw material pretreatment: Same as step (S1) in Example 1.

[0120] (S2) First polymerization reaction: Under stirring conditions, a first catalyst solution (40 wt% benzyltrimethylammonium hydroxide in methanol, wherein the mass of benzyltrimethylammonium hydroxide is 150 ppm of the mass of IPDI) is added to the IPDI mixed raw material. The reaction temperature is controlled at 95℃ for the first polymerization reaction. When the NCO value of the system drops to 29.4%, the system is rapidly heated to 130℃ and kept at that temperature for 30 min to terminate the reaction and obtain the crude product.

[0121] (S3) Purification treatment: The crude product is circulated under vacuum at 70°C at a rate of 100 mL / min for 1 h; after the circulation, it is replaced three times with high-purity N2, and finally vacuumed to ≤1 mbar to remove the first catalyst and its possible decomposition products to obtain the pretreated product; then the pretreated product is distilled at 170°C to obtain the isocyanate prepolymer, wherein the molar content of IPDI trimer is 77.70%, the molar content of IPDI pentamer is 16.12%, the molar content of IPDI heptamer is 4.38%, the molar content of IPDI nonamer is 1.22%, and the molar content of IPDI polymer is 0.58%.

[0122] (S4) Second polymerization reaction: The isocyanate prepolymer and n-butyl acetate were stirred and mixed at 60°C in a mass ratio of 7:3. After uniform dissolution, a phosphate catalyst solution (30 wt% diethyl phosphate in butyl acetate solution) was added dropwise to the system to make the mass content of the phosphate catalyst in the system 40 ppm. Then the temperature was rapidly raised to 110°C and stirred under a nitrogen atmosphere for 11.2 h. Subsequently, the temperature was lowered to 30°C and stirred for 0.5 h to terminate the reaction, and the polyisocyanate composition was obtained. Its component information and related parameters are shown in Table 1.

[0123] Example 3 A polyisocyanate composition and its preparation method thereof, the preparation method comprising the following steps: (S1) Raw material pretreatment: Same as step (S1) in Example 1.

[0124] (S2) First polymerization reaction: Under stirring conditions, a first catalyst solution (40 wt% benzyltrimethylammonium hydroxide in methanol, wherein the mass of benzyltrimethylammonium hydroxide is 150 ppm of the mass of IPDI) is added to the IPDI mixed raw material. The reaction temperature is controlled at 95℃ for the first polymerization reaction. When the NCO value of the system drops to 28.2%, the system is rapidly heated to 130℃ and kept at that temperature for 30 min to terminate the reaction and obtain the crude product.

[0125] (S3) Purification treatment: The crude product is circulated under vacuum at 70°C at a rate of 100 mL / min for 1 h; after the circulation, it is replaced three times with high-purity N2, and finally vacuumed to ≤1 mbar to remove the first catalyst and its possible decomposition products to obtain the pretreated product; then the pretreated product is distilled at 170°C to obtain the isocyanate prepolymer, wherein the molar content of IPDI trimer is 74.74%, the molar content of IPDI pentamer is 17.97%, the molar content of IPDI heptamer is 4.98%, the molar content of IPDI nonamer is 1.59%, and the molar content of IPDI polymer is 0.72%.

[0126] (S4) Second polymerization reaction: The isocyanate prepolymer and n-butyl acetate were stirred and mixed at 60°C in a mass ratio of 7:3. After uniform dissolution, a phosphate catalyst solution (30 wt% dibutyl phosphate in butyl acetate solution) was added dropwise to the system to make the mass content of the phosphate catalyst in the system 40 ppm. Then the temperature was rapidly raised to 110°C and stirred for 12.5 h under a nitrogen atmosphere. Subsequently, the temperature was lowered to 30°C and stirred for 0.5 h to terminate the reaction, and the polyisocyanate composition was obtained. Its component information and related parameters are shown in Table 1.

[0127] Example 4 A polyisocyanate composition and its preparation method thereof, the preparation method comprising the following steps: (S1) Raw material pretreatment: Same as step (S1) in Example 1.

[0128] (S2) First polymerization reaction: Under stirring conditions, a first catalyst solution (40 wt% benzyltrimethylammonium hydroxide in methanol, wherein the mass of benzyltrimethylammonium hydroxide is 150 ppm of the mass of IPDI) is added to the IPDI mixed raw material. The reaction temperature is controlled at 90°C for the first polymerization reaction. When the NCO value of the system drops to 29.8%, the system is rapidly heated to 130°C and kept at that temperature for 30 min to terminate the reaction and obtain the crude product.

[0129] (S3) Purification treatment: The crude product is circulated under vacuum at 70°C at a rate of 100 mL / min for 1 h; after the circulation, it is replaced three times with high-purity N2, and finally vacuumed to ≤1 mbar to remove the first catalyst and its possible decomposition products to obtain the pretreated product; then the pretreated product is distilled at 170°C to obtain the isocyanate prepolymer, wherein the molar content of IPDI trimer is 77.64%, the molar content of IPDI pentamer is 16.25%, the molar content of IPDI heptamer is 4.22%, the molar content of IPDI nonamer is 1.29%, and the molar content of IPDI polymer is 0.60%.

[0130] (S4) Second polymerization reaction: The isocyanate prepolymer and n-butyl acetate were stirred and mixed at 60°C in a mass ratio of 7:3. After uniform dissolution, a phosphate catalyst solution (30 wt% butyl acetate solution of di(2-ethylhexyl) phosphate) was added dropwise to the system to make the mass content of the phosphate catalyst in the system 20 ppm. Then the temperature was rapidly raised to 110°C and stirred for 16 h under a nitrogen atmosphere. Subsequently, the temperature was lowered to 30°C and stirred for 0.5 h to terminate the reaction, and the polyisocyanate composition was obtained. Its component information and related parameters are shown in Table 1.

[0131] Example 5 A polyisocyanate composition and its preparation method thereof, the preparation method comprising the following steps: (S1) Raw material pretreatment: Same as step (S1) in Example 1.

[0132] (S2) First polymerization reaction: Under stirring conditions, a first catalyst solution (40 wt% benzyltrimethylammonium hydroxide in methanol, wherein the mass of benzyltrimethylammonium hydroxide is 150 ppm of the mass of IPDI) is added to the IPDI mixed raw material. The reaction temperature is controlled at 100℃ for the first polymerization reaction. When the NCO value of the system drops to 28.5%, the system is rapidly heated to 130℃ and kept at that temperature for 30 min to terminate the reaction and obtain the crude product.

[0133] (S3) Purification treatment: The crude product is circulated under vacuum at 70°C at a rate of 100 mL / min for 1 h; after the circulation, it is replaced three times with high-purity N2, and finally vacuumed to ≤1 mbar to remove the first catalyst and its possible decomposition products to obtain the pretreated product; then the pretreated product is distilled at 170°C to obtain the isocyanate prepolymer, wherein the molar content of IPDI trimer is 77.69%, the molar content of IPDI pentamer is 16.30%, the molar content of IPDI heptamer is 4.18%, the molar content of IPDI nonamer is 1.28%, and the molar content of IPDI polymer is 0.55%.

[0134] (S4) Second polymerization reaction: The isocyanate prepolymer and n-butyl acetate were stirred and mixed at 60°C in a mass ratio of 7:3. After uniform dissolution, a phosphate catalyst solution (30 wt% diphenyl phosphate in butyl acetate solution) was added dropwise to the system to make the mass content of the phosphate catalyst in the system 160 ppm. Then the temperature was rapidly raised to 110°C and stirred for 14 h under a nitrogen atmosphere. Subsequently, the temperature was lowered to 30°C and stirred for 0.5 h to terminate the reaction, and the polyisocyanate composition was obtained. Its component information and related parameters are shown in Table 1.

[0135] Example 6 A polyisocyanate composition and its preparation method thereof, the preparation method comprising the following steps: (S1) Raw material pretreatment: Same as step (S1) in Example 1.

[0136] (S2) First polymerization reaction: Under stirring conditions, a first catalyst solution (40 wt% benzyltrimethylammonium hydroxide in methanol, wherein the mass of benzyltrimethylammonium hydroxide is 150 ppm of the mass of IPDI) is added to the IPDI mixed raw material. The reaction temperature is controlled at 95°C for the first polymerization reaction. When the NCO value of the system drops to 29.29%, the system is rapidly heated to 130°C and kept at that temperature for 30 min to terminate the reaction and obtain the crude product.

[0137] (S3) Purification treatment: The crude product is circulated under vacuum at 70°C at a rate of 100 mL / min for 1 h; after the circulation, it is replaced three times with high-purity N2, and finally vacuumed to ≤1 mbar to remove the first catalyst and its possible decomposition products to obtain the pretreated product; then the pretreated product is distilled at 170°C to obtain the isocyanate prepolymer, wherein the molar content of IPDI trimer is 77.31%, the molar content of IPDI pentamer is 16.01%, the molar content of IPDI heptamer is 4.66%, the molar content of IPDI nonamer is 1.08%, and the molar content of IPDI polymer is 0.94%.

[0138] (S4) Second polymerization reaction: The isocyanate prepolymer and n-butyl acetate were stirred and mixed at 60°C in a mass ratio of 7:3. After uniform dissolution, a phosphate catalyst solution (30 wt% dimethyl phosphate in butyl acetate solution) was added dropwise to the system to make the mass content of the phosphate catalyst in the system 30 ppm. Then the temperature was rapidly raised to 110°C and stirred for 10 h under a nitrogen atmosphere. Subsequently, the temperature was lowered to 30°C and stirred for 0.5 h to terminate the reaction, and the polyisocyanate composition was obtained. Its component information and related parameters are shown in Table 1.

[0139] Comparative Example 1 A polyisocyanate composition and its preparation method thereof, the preparation method comprising the following steps: (S1) Raw material pretreatment: Same as step (S1) in Example 1.

[0140] (S2) First polymerization reaction: Under stirring conditions, a first catalyst solution (40 wt% benzyltrimethylammonium hydroxide in methanol, wherein the mass of benzyltrimethylammonium hydroxide is 150 ppm of the mass of IPDI) is added to the IPDI mixed raw material. The reaction temperature is controlled at 95°C for the first polymerization reaction. When the NCO value of the system drops to 26.5%, the system is rapidly heated to 130°C and kept at that temperature for 30 min to terminate the reaction and obtain the crude product.

[0141] (S3) Purification treatment: The crude product was circulated under vacuum at 70°C at a rate of 100 mL / min for 1 h. After the circulation, it was replaced with high-purity N2 three times, and finally vacuumed to ≤1 mbar to remove the first catalyst and its possible decomposition products to obtain the pretreated product. The pretreated product was then distilled at 170°C to obtain the isocyanate prepolymer, which was mixed with n-butyl acetate at a mass ratio of 7:3 to obtain the polyisocyanate composition. Its component information and related parameters are shown in Table 1.

[0142] Comparative Example 2 A polyisocyanate composition and its preparation method thereof, the preparation method comprising the following steps: (S1) Raw material pretreatment: Same as step (S1) in Example 1.

[0143] (S2) First polymerization reaction: Under stirring conditions, a first catalyst solution (40 wt% benzyltrimethylammonium hydroxide in methanol, wherein the mass of benzyltrimethylammonium hydroxide is 150 ppm of the mass of IPDI) is added to the IPDI mixed raw material. The reaction temperature is controlled at 95°C for the first polymerization reaction. When the NCO value of the system drops to 29.83%, the system is rapidly heated to 130°C and kept at that temperature for 30 min to terminate the reaction and obtain the crude product.

[0144] (S3) Purification treatment: The crude product is circulated under vacuum at 70°C at a rate of 100 mL / min for 1 h; after the circulation, it is replaced three times with high-purity N2, and finally vacuumed to ≤1 mbar to remove the first catalyst and its possible decomposition products to obtain the pretreated product; then the pretreated product is distilled at 170°C to obtain the isocyanate prepolymer, wherein the molar content of IPDI trimer is 79.01%, the molar content of IPDI pentamer is 15.42%, the molar content of IPDI heptamer is 4.60%, the molar content of IPDI nonamer is 0.74%, and the molar content of IPDI polymer is 0.23%.

[0145] (S4) Second polymerization reaction: The isocyanate prepolymer and n-butyl acetate were stirred and mixed at 60°C in a mass ratio of 7:3. After uniform dissolution, a phosphate catalyst solution (30 wt% diethyl phosphate in butyl acetate solution) was added dropwise to the system to make the mass content of the phosphate catalyst in the system 40 ppm. Then the temperature was rapidly raised to 110°C and stirred for 11 h under a nitrogen atmosphere. Subsequently, the temperature was lowered to 30°C and stirred for 0.5 h to terminate the reaction, and the polyisocyanate composition was obtained. Its component information and related parameters are shown in Table 1.

[0146] Comparative Example 3 A polyisocyanate composition and its preparation method thereof, the preparation method comprising the following steps: (S1) Raw material pretreatment: Same as step (S1) in Example 1.

[0147] (S2) First polymerization reaction: Under stirring conditions, a first catalyst solution (40 wt% benzyltrimethylammonium hydroxide in methanol, wherein the mass of benzyltrimethylammonium hydroxide is 150 ppm of the mass of IPDI) is added to the IPDI mixed raw material. The reaction temperature is controlled at 95°C for the first polymerization reaction. When the NCO value of the system drops to 27.78%, the system is rapidly heated to 130°C and kept at that temperature for 30 min to terminate the reaction and obtain the crude product.

[0148] (S3) Purification treatment: The crude product is circulated under vacuum at 70°C at a rate of 100 mL / min for 1 h; after the circulation, it is replaced three times with high-purity N2, and finally vacuumed to ≤1 mbar to remove the first catalyst and its possible decomposition products to obtain the pretreated product; then the pretreated product is distilled at 170°C to obtain the isocyanate prepolymer, wherein the molar content of IPDI trimer is 71.81%, the molar content of IPDI pentamer is 18.94%, the molar content of IPDI heptamer is 6.23%, the molar content of IPDI nonamer is 2.05%, and the molar content of IPDI polymer is 0.97%.

[0149] (S4) Second polymerization reaction: The isocyanate prepolymer and n-butyl acetate were stirred and mixed at 60°C in a mass ratio of 7:3. After uniform dissolution, a phosphate ester catalyst solution (30 wt% diethyl phosphate in butyl acetate solution) was added dropwise to the system to make the mass content of the phosphate ester catalyst in the system 40 ppm. Then the temperature was rapidly raised to 110°C and stirred for 13 h under a nitrogen atmosphere. Subsequently, the temperature was lowered to 30°C and stirred for 0.5 h to terminate the reaction, and the polyisocyanate composition was obtained. Its component information and related parameters are shown in Table 1.

[0150] In Table 1, the component information (molar content of aliphatic isocyanate trimer, aliphatic isocyanate pentamer, aliphatic isocyanate heptamer, aliphatic isocyanate nonamer, and aliphatic isocyanate polymer) and the functionality distribution ratio (f-ratio) of each polyisocyanate composition were obtained by gel-liquid chromatography (GPC) and calculation. For example, the GPC spectrum of the polyisocyanate composition provided in Example 1 is shown below. Figure 1 As shown, the GPC spectrum of the polyisocyanate composition provided in Comparative Example 1 is as follows. Figure 2 As shown, the GPC overlay comparison diagrams of the two are as follows: Figure 3 As shown in the figure, the peak positions from right to left are trimer, pentamer, heptamer, nonamer, and polymer. It can be clearly seen that, under the condition that the trimer content is similar, the content of polymer in Example 1 is significantly higher than that of the conventional product in Comparative Example 1.

[0151] Table 1 The polyurethane coating of the present invention will be described in detail below with several application examples, but the polyurethane coating is not limited to these application examples.

[0152] Application Example 1 A polyurethane coating comprising a hydroxyl-containing resin (commercially available, Dongsheng 1253 resin) and a curing agent, said curing agent comprising a combination of HDI trimer (commercially available NHUNATE® NT3300) and a polyisocyanate composition derived from Example 1.

[0153] The polyurethane coating is prepared as follows: 21.0 g of polyisocyanate composition and 49.0 g of HDI trimer are added to 30.0 g of butyl acetate and stirred evenly at 60°C. Then, 30% butyl acetate diluted Dongsheng 1253 resin is added at a molar ratio of NCO:OH = 1:1 and stirred thoroughly to obtain the polyurethane coating.

[0154] The polyurethane coating was applied to a 304 tinplate sheet, and the curing speed was tested according to the method shown in standard GB / T 1728-1979. After the coating film was fully cured, its hardness and flexibility were tested, and the test data are shown in Table 2.

[0155] Application Example 2-6, compared with Application Example 1-3 A polyurethane coating differs from Application Example 1 only in that the polyisocyanate composition used is derived from Examples 2-6 and Comparative Examples 1-3, respectively. Performance tests were conducted using the same method as in Application Example 1, and the data are shown in Table 2.

[0156] Table 2 As shown in Tables 1 and 2, the polyisocyanate composition provided by this invention improves its functionality by adjusting the functionality distribution ratio to 0.05-0.15, while maintaining a suitable molar content of aliphatic isocyanate trimers, and increasing the molar content of nonamerrers and polymers. The polyisocyanate composition has suitable NCO values ​​and viscosity, and when used to prepare polyurethane coatings, it shortens the curing speed to within 22 minutes, more preferably within 20 minutes, which is about 20% faster than the conventional product of Comparative Example 1, effectively shortening the construction cycle. Simultaneously, its film hardness is increased to 3H-4H, significantly higher than Comparative Example 1, while maintaining a comparable level of flexibility, resulting in a significant improvement in the application strength of the polyisocyanate composition.

[0157] In Comparative Example 2, the functionality distribution ratio of the polyisocyanate composition was <0.05, and its properties were similar to those of the conventional product in Comparative Example 1. No significant improvement was observed in curing speed or application strength. In Comparative Example 3, the functionality distribution ratio was >0.15, resulting in a significant increase in product viscosity. Although the curing speed and hardness of the resulting paint film were improved, fine mesh patterns appeared at the minimum bending radius in the flexibility test, indicating a significant decrease in flexibility and consequently, a reduction in overall application performance.

[0158] The present invention has been illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A polyisocyanate composition, characterized in that, The polyisocyanate composition is derived from aliphatic isocyanates, and the functionality distribution ratio of the polyisocyanate composition is 0.05-0.

15. The formula for calculating the functionality distribution ratio is shown in Equation A: f-ratio = (Χ4+Χ5) / Χ1 (Formula A); Wherein, f-ratio represents the functionality distribution ratio, Χ1 represents the molar content of aliphatic isocyanate trimer in the polyisocyanate composition, Χ4 represents the molar content of aliphatic isocyanate nonamerm in the polyisocyanate composition, and Χ5 represents the molar content of aliphatic isocyanate polymer in the polyisocyanate composition. The aliphatic isocyanate polymer has the structure shown in Formula I: Equation I; Wherein, R represents a divalent residue derived from aliphatic isocyanates; n is an integer greater than 3.

2. The polyisocyanate composition according to claim 1, characterized in that, The polyisocyanate composition comprises the following components in molar amounts: Aliphatic isocyanate trimers: 72.5%-74.5% Aliphatic isocyanate pentamers: 12.5%-16% Aliphatic isocyanate heptamers 3.5%-5%, Aliphatic isocyanate nonamers 2%-5.5%, Aliphatic isocyanate polymers 2.5%-5%.

3. The polyisocyanate composition according to claim 1 or 2, characterized in that, The aliphatic isocyanate includes any one or a combination of at least two of isophorone diisocyanate, dicyclohexylmethane diisocyanate, and 1,4-diisocyanate cyclohexane. And / or, the NCO group content in the polyisocyanate composition is 10%-15% by mass, preferably 11%-13%.

4. A method for preparing the polyisocyanate composition according to any one of claims 1-3, characterized in that, The preparation method includes: Aliphatic isocyanates undergo a first polymerization reaction in the presence of a first catalyst until the mass content of NCO groups in the system is 27.8%-29.8%, yielding the crude product. The crude product was purified to obtain an isocyanate prepolymer. The isocyanate prepolymer undergoes a second polymerization reaction in the presence of a phosphate ester catalyst to obtain the polyisocyanate composition.

5. The preparation method according to claim 4, characterized in that, The first catalyst comprises any one or a combination of at least two of tetraalkyl quaternary ammonium salts, trialkylaralkyl quaternary ammonium salts, tetraalkyl quaternary ammonium bases, and trialkylaralkyl quaternary ammonium bases; And / or, based on the mass of the aliphatic isocyanate as 100%, the mass of the first catalyst is 50-500 ppm; And / or, the temperature of the first polymerization reaction is 50-120°C, preferably 80-115°C, and more preferably 95-110°C.

6. The preparation method according to claim 4, characterized in that, The purification process includes sequential vacuum circulation pretreatment and distillation; Preferably, the vacuum pretreatment method includes: first, subjecting the crude product to vacuum circulation, then replacing it with an inert gas, and then drawing a vacuum to complete the vacuum pretreatment; Preferably, the temperature of the vacuum cycle is 40-80°C; Preferably, the vacuum cycle time is 0.5-2 hours; Preferably, the pressure of the distillation is ≤20 Pa; Preferably, the distillation temperature is 160-210℃; Preferably, the isocyanate prepolymer comprises the following components in molar amounts: Aliphatic isocyanate trimers 74%-78%, Aliphatic isocyanate pentamers 16%-18%, Aliphatic isocyanate heptamers 4%-5%, Aliphatic isocyanate nonmer 1%-2%, Aliphatic isocyanate polymers 0-1%.

7. The preparation method according to claim 4, characterized in that, The second polymerization reaction is carried out in the presence of a solvent; Preferably, the isocyanate prepolymer and solvent are mixed to obtain a mixture; a phosphate ester catalyst solution is added to the mixture to carry out a second polymerization reaction to obtain the polyisocyanate composition; Preferably, the mass content of isocyanate prepolymer in the mixture is 10%-90%, more preferably 20%-60%; Preferably, the solvent includes any one or a combination of at least two of aromatic solvents, ester solvents, and ketone solvents; more preferably, it includes any one or a combination of at least two of toluene, xylene, butyl acetate, propylene glycol methyl ether acetate, ethyl acetate, propyl acetate, acetone, cyclohexanone, and methyl isobutyl ketone. Preferably, the phosphate ester catalyst includes any one or a combination of at least two of dibutyl phosphate, dimethyl phosphate, diethyl phosphate, di(2-ethylhexyl) phosphate, and diphenyl phosphate; Preferably, the mass content of the phosphate ester catalyst in the second polymerization reaction system is 1-1000 ppm, more preferably 10-300 ppm, and even more preferably 20-200 ppm; Preferably, the temperature of the second polymerization reaction is 80-130°C, more preferably 100-120°C; Preferably, the second polymerization reaction takes 10-17 h.

8. The preparation method according to any one of claims 4-7, characterized in that, The preparation method includes the following steps: (1) The aliphatic isocyanate was subjected to a first polymerization reaction at 50-120°C in the presence of a first catalyst until the mass content of NCO groups in the system was 27.8%-29.8%, and the crude product was obtained. (2) The crude product is subjected to vacuum circulation treatment at 40-80℃ for 0.5-2 h, and then replaced with inert gas 1-5 times, and then vacuumed to ≤1 mbar to obtain the pretreated product; the pretreated product is distilled under pressure ≤20 Pa and temperature of 160-210℃ to obtain isocyanate prepolymer. (3) The isocyanate prepolymer is mixed with a solvent to obtain a mixture; the mass content of the isocyanate prepolymer in the mixture is 10%-90%; A phosphate ester catalyst solution is added to the mixture to make the mass content of the phosphate ester catalyst in the system 1-1000 ppm, and the polymerization reaction is carried out at 80-130℃ for 10-17 h to obtain the polyisocyanate composition.

9. The use of a polyisocyanate composition according to any one of claims 1-3, or a polyisocyanate composition prepared by any one of claims 4-8, in polyurethane products or polyurea products.

10. A polyurethane coating, characterized in that, The polyurethane coating comprises a hydroxyl-containing resin and a curing agent, wherein the curing agent comprises at least one of the polyisocyanate compositions as described in any one of claims 1-3 and the polyisocyanate compositions prepared by the preparation method as described in any one of claims 4-8.

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