A storage-stable polyisocyanate composition

Abstract

The present application provides a storage stable polyisocyanate composition. The composition is a polyisocyanate composition obtained from an aliphatic diisocyanate or a cycloaliphatic diisocyanate and a dihydric alcohol, the integral area of the peak of the component with a weight average molecular weight of 550±80 accounting for 0.1-5% of the total peak area of GPC, the integral area of the peak of the component with a weight average molecular weight of 450±80 accounting for 10-70% of the total peak area of GPC, and the viscosity of the polyisocyanate composition being not more than 2000 mPa·s. The isocyanate composition has good storage stability, and the monomer content increases by ≤0.1% at 50°C for 30 days based on the quality of the polyisocyanate product.

Description

Technical Field

[0001] This invention belongs to the field of polyisocyanates, and specifically relates to a storage-stable polyisocyanate composition. Background Technology

[0002] Isocyanate homopolymers containing urea diketone groups have very low viscosity, making them excellent as crosslinking agents in water-based, low-solvent, high-solids coating compositions. They are also widely used as solvent substitutes for diluents in curing agents.

[0003] Currently, methods for preparing polyisocyanates containing urea diketone groups from aromatic, aliphatic, or cycloaliphatic diisocyanate monomers in the presence of a catalyst are known, and the advantages and disadvantages of various dimerization catalysts or catalyst systems are discussed in detail in various literatures.

[0004] CN1334264A discloses a method for improving the storage stability of urea diketone polyisocyanate by adding substituted urea or substituted amide during the reaction process. However, other problems still arise during storage, such as rapid increase in product viscosity. Additionally, when the added substituted urea has a small molecular weight, a small amount may enter the light component condenser during separation, affecting monomer recycling.

[0005] CN110305294A discloses a method for controlling the acid content in the terminator to be ≤300ppm (calculated as hydrogen chloride). The prepared polyisocyanate has a monomer content increase of ≤0.1wt% after 6 months of storage at below 40°C. However, when the storage temperature is increased to 50°C, the monomer increase rate is significantly accelerated.

[0006] CN1511858A discloses a method for preparing urea diketone that allows high-content urea diketone products to maintain a monomer content of less than 0.5% after storage at 50°C for 6 months. However, the reaction temperature needs to be controlled below 40°C, which significantly reduces the reaction efficiency.

[0007] The main drawback of existing processes for preparing urea diketone polyisocyanates is that they undergo re-decomposition into isocyanate monomers during storage, resulting in high levels of free isocyanate monomers. This negatively impacts the performance of downstream products and is harmful to operators and the environment during construction, severely affecting the use of urea diketone polyisocyanate curing agents. In practical applications, raising the storage stability temperature of urea diketone polyisocyanates to 50°C is beneficial for product storage and downstream construction. Summary of the Invention

[0008] The purpose of this invention is to provide a polyisocyanate composition in which the content of free monomers increases only slightly during storage at 50°C, thus meeting the needs of downstream applications and occupational health and safety.

[0009] To achieve the above-mentioned objectives, the polyisocyanate composition provided by this invention adopts the following technical solution:

[0010] A polyisocyanate composition, said composition being a polyisocyanate composition obtained by reacting an aliphatic diisocyanate and / or an alicyclic diisocyanate with a diol having ≤20 carbon atoms, said composition:

[0011] a. The integrated area of ​​the component peak with a weight-average molecular weight of 550±80 accounts for 0.1-5% of the total peak area, preferably 0.2-3%;

[0012] b. The integrated area of ​​the peak of the component with a weight average molecular weight of 450±80 accounts for 10-70% of the total peak area, preferably 20-60%.

[0013] In this invention, the peaks of the different molecular weight components were obtained by gel permeation chromatography (GPC).

[0014] In this invention, the viscosity of the polyisocyanate composition is less than or equal to 2000 mPa·s, preferably less than or equal to 1000 mPa·s.

[0015] In this invention, the aliphatic diisocyanate and / or alicyclic diisocyanate are organic diisocyanates whose carbon skeleton contains 4-20 carbon atoms in addition to the NCO group. Preferably, the isocyanate is selected from one or more of hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), cyclohexyl diisocyanate (HMDI), dicyclohexylmethane diisocyanate (HXDI), norbornene diisocyanate (NBDI), cyclohexyl diisocyanate (CHDI), and 2,4,4-trimethylhexamethylene diisocyanate (TMHDI), and more preferably hexamethylene diisocyanate.

[0016] In this invention, the diol is a diol with ≤10 carbon atoms, preferably one or more of ethylene glycol, propylene glycol, butanediol, hexanediol, and octanediol.

[0017] In a preferred embodiment, the amount of the diol used is 0-5% of the weight of the starting isocyanate used, preferably 0.1-5%, more preferably 0.5-3%.

[0018] In this invention, the content of free isocyanate monomers in the composition increases by ≤0.1wt% after being stored at 50°C for 30 days, based on the total mass of the polyisocyanate composition.

[0019] Another object of the present invention is to provide a method for preparing a polyisocyanate composition.

[0020] A method for preparing the above-mentioned polyisocyanate composition, wherein the method is preparation method A or preparation method B.

[0021] In this invention, preparation method A includes the following steps:

[0022] S1-1: Reaction of excess organic isocyanate with diol yields a prepolymer reaction solution;

[0023] S1-2: Add a catalyst to the prepolymer reaction solution. After the reaction reaches the set conversion rate, add a terminator to terminate the reaction.

[0024] S1-3: Remove unreacted organic isocyanate monomers to obtain polyisocyanate products.

[0025] In this invention, preparation method B includes the following steps:

[0026] S2-1: Excess organic isocyanate reacts with diol to obtain a prepolymer reaction solution, and the unreacted organic isocyanate monomers are removed.

[0027] S2-2: Add a catalyst to the organic isocyanate. After the reaction reaches the set conversion rate, add a terminator to terminate the reaction and remove the unreacted organic isocyanate monomers.

[0028] S2-3: The product of S2-1 is mixed with the product of S2-1 to obtain the polyisocyanate product.

[0029] In this invention, the reaction temperature of S1-1 and S2-1 is 80-120°C, preferably 100-110°C; the reaction time is 0.5-4 hours, preferably 1-2 hours.

[0030] In this invention, the catalysts for S1-2 and S2-2 are tertiary phosphine, preferably one or more of trimethylphosphine, triethylphosphine, tripropylphosphine, triisopropylphosphine, tri-n-butylphosphine, tri-tert-butylphosphine, dicyclopentylbutylphosphine, tripentylphosphine, tricyclopentylphosphine, trihexylphosphine, triphenylphosphine, tribenzylphosphine, benzyldimethylphosphine, tricyclohexylphosphine, and tri-n-octylphosphine, more preferably tributylphosphine and / or tri-n-octylphosphine.

[0031] When the inventors performed component structure analysis on the reaction solution of the polyisocyanate composition using a high-performance gel chromatography instrument, they were surprised to find that the peaks of the component with a weight average molecular weight of 550±80 and the component with a weight average molecular weight of 450±80 significantly affected the storage stability of the product.

[0032] The content of the component peak with a weight-average molecular weight of 550±80 is mainly determined by the prepolymerization process and the activity of the diol. When the integral area of ​​the component peak with a weight-average molecular weight of 550±80 accounts for 0.1% to 5% of the total peak area, the storage stability of the product can be significantly improved. Its content can be controlled by regulating the prepolymerization process, or by separating the prepolymerization solution and adding the separated product to the final product. When the ratio of the peak area of ​​the component peak with a weight-average molecular weight of 550±80 to the total peak area is less than 0.1%, the increase in monomer content during storage at 50℃ cannot be suppressed; when the ratio is greater than 5%, white flocculent matter will appear during storage, affecting downstream product applications.

[0033] In the preparation of the polyisocyanate composition of this invention, the elution peak with a weight-average molecular weight of 450±80 corresponds to the presence of a large amount of urea diketone structure. The content of this structure affects the viscosity of the product and the content of monomers in the system. To prepare a high content of urea diketone structure, a tertiary phosphine catalyst is preferably selected, which has the following structure:

[0034]

[0035] R1, R2, and R3 are independently selected from aliphatic or aromatic substituents. The amount of catalyst used is typically 0.01-1 wt% of the amount of the starting diisocyanate used, preferably 0.05-0.5 wt%.

[0036] In this invention, the catalyst tertiary phosphine is a nucleophile that is easily oxidized by oxygen in the air. It must be strictly deoxygenated and protected with an inert gas during use. For example, trioctylphosphine will undergo a violent oxidation reaction if exposed to air, generating trioctylphosphine oxide.

[0037] In the method of this invention, the peak area of ​​the component with a weight-average molecular weight of 450±80 can be adjusted by adjusting the conversion rate in the system. When the ratio of the remaining mass of isocyanate in the system to the total mass of isocyanate monomers in the system reaches 10%-80%, preferably 30%-70%, a terminator is added to terminate the reaction, so that the content of the separated polyisocyanate can be controlled at 10-70%, preferably 20-60%. The catalyst poison used is dimethyl sulfate, methyl p-toluenesulfonate, phosphate ester, acyl chloride, sulfur or peroxide, etc. The amount of catalyst poison required to terminate the reaction depends on the amount of catalyst used in the system. The amount of terminator is 80-120% of the number of moles of catalyst used in the reaction.

[0038] After the reaction is complete, unreacted monomers can be separated using one or more of the following methods: flash evaporator, falling film evaporator, thin-film evaporator, and short-path evaporator, to remove isocyanate monomers from the system. In the polyisocyanate composition, the content of unreacted isocyanate monomers is preferably less than 0.5 wt%, more preferably less than 0.3 wt%. Since diurea polyisocyanate is easily decomposed at high temperatures, to reduce the decomposition of diurea polyisocyanate, the separation temperature needs to be controlled at 120-150°C, and the residence time of the material at high temperature should be ≤30 min, preferably ≤20 min.

[0039] The unconverted diisocyanate obtained through separation can be returned to the reactor to participate in the reaction, or it can be treated by distillation or rectification before participating in the reaction. In the method of the present invention, it is preferable to return it directly to the reactor to participate in the reaction without distillation or rectification.

[0040] Furthermore, stabilizers and additives can be added wherever needed in the method of the present invention. These stabilizers and additives are conventional in the field of polyisocyanates. They include: antioxidants, hindered phenols (such as 2,6-di-tert-butyl-4-methylphenol, octadecyl 3,5-di-tert-butyl-4-hydroxyphenylpropionate, etc.), phosphites (such as tri(nonylphenyl) phosphite, tri(2,4-di-tert-butylphenyl) phosphite, etc.), ultraviolet absorbers (such as benzotriazoles, salicylates, benzophenones, etc.), hindered amine light stabilizers (such as 2,2,6,6-tetramethylpyridine), etc.

[0041] The polyisocyanate products prepared by the method of the present invention can be used to prepare single-component and multi-component polyurethane coatings or adhesives, and can be used with di or polyisocyanate products prepared by prior art, such as mixtures of di or polyisocyanates containing biuret, carbamate, urethane, isocyanurate and iminooxadiazine dione.

[0042] This invention also relates to polyurethane coatings and polyurethane adhesives, and other related products prepared using the method of this invention, which contain polyisocyanates. Furthermore, the polyisocyanates prepared using the method of this invention can be used to prepare other related products such as polyurethane coatings and polyurethane adhesives after being sealed with a sealing agent.

[0043] Compared with the prior art, the present invention has the following positive effects:

[0044] Polyisocyanates containing high urea diketone content tend to decompose into free isocyanate monomers during storage. This invention significantly improves the storage stability of the product at 50°C by controlling the content of the integrated area of ​​the peaks of the components with a weight average molecular weight of 550±80 and 450±80 in the polyisocyanate. The resulting urea diketone polyisocyanate product exhibits a free isocyanate monomer content increase of ≤0.1wt% (calculated based on the polyisocyanate product) after 30 days of storage below 50°C, demonstrating good storage stability. Attached Figure Description

[0045] Figure 1 The image shows the gel chromatography spectrum of Example 1. Peak 5 has a weight-average molecular weight of 550±80, and peak 6 has a weight-average molecular weight of 450±80. Detailed Implementation

[0046] The following embodiments will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed embodiments, but should also include any other well-known modifications within the scope of the claims of the present invention. The specific application of the present invention is not limited to the applications mentioned in the examples. Simple modifications made to the present invention by those skilled in the art based on the concept of the present invention are all within the scope of protection claimed by the present invention.

[0047] The following testing method is used in the embodiments of the present invention:

[0048] (1) The peak areas of the component with a weight-average molecular weight of 550±80 and the peak areas of the component with a weight-average molecular weight of 450±80 were determined 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, with polystyrene as a standard, mobile phase: tetrahydrofuran; flow rate: 1.0mL / min; analysis time: 40min, column temperature: 35℃), using a differential detector for determination. Isocyanate raw materials were quantified, and the area of ​​polymers and monomers in the system was determined by the area normalization method. The reaction conversion rate (%) = S (monomer peak area) / S (sum of peak areas of each component) * 100%.

[0049] (2) High performance liquid chromatography, equipped with a UV detector or diode array detector. The recommended instrument model is Shimadzu 20AT. Chromatographic column: Waters XSelect T3 (4.6*250mm, 5um). Mobile phase is A (water) and mobile phase is B (methanol). Flow rate: 1ml / min. Analysis time: 50min. Column temperature: 40℃. Use a 258nm UV detector for analysis.

[0050] Gradient elution conditions:

[0051]

[0052] Sample preparation: Place 500 mg of sample in a 10 ml volumetric flask, add derivatizing solution (100 g benzyl alcohol dissolved in a 1000 ml volumetric flask, add 3 g dibutyltin dilaurate and dilute to 1000 ml with dichloromethane) to the mark, shake well, seal well, and place in a 50 °C oven for 3 hours. After cooling, perform sample analysis.

[0053] (3) Viscosity determination: Dynamic mechanical viscosity was measured using a BrookField DV-I Prime viscometer with an S21 rotor at 25°C.

[0054] The raw material information used in the following embodiments is as follows:

[0055] Hexamethylene diisocyanate (HDI): Wanhua Chemical, purity > 99%;

[0056] 2-Ethyl-1,3-hexanediol: Aladdin reagent, purity > 99%;

[0057] Tri-n-octylphosphine: Sigma reagent, purity > 95%;

[0058] Diisooctyl phosphate: Aladdin reagent, purity > 98.5%;

[0059] n-Butanol: Aladdin, 99% purity;

[0060] Tetramethylammonium hydroxide: Sigma reagent, purity ≥95%, crystals;

[0061] 1,3-Butanediol: Aladdin reagent, purity > 99.5%;

[0062] Tributylphosphine: Aladdin reagent, purity > 95%;

[0063] Dibutyl phosphate: Aladdin reagent, purity > 95%.

[0064] Unless otherwise specified in the following examples and comparative examples, the reaction solution was kept under a dry nitrogen atmosphere from before the reaction until the addition of the catalyst and throughout the entire reaction process. Unless otherwise stated, all percentages are by mass, and all pressures are absolute pressures.

[0065] Example 1

[0066] Preparation method A was used.

[0067] S1-1: 15g of 2-ethyl-1,3-hexanediol was added to 1000g of hexamethylene diisocyanate under stirring at 100℃ and the reaction was carried out for 1 hour.

[0068] S1-2: Cool to 60℃, add 2.5g of trioctylphosphine, and quantitatively monitor the ratio of the remaining mass M1 of HDI in the reaction system to the total mass M of added HDI by gel chromatography; when the remaining mass M1 of HDI in the system accounts for 50% of the total mass M of added HDI, add diisooctyl phosphate (molar ratio of 1:1 with trioctylphosphine) and heat to 80℃ for 2 hours to terminate the reaction;

[0069] S1-3: Unreacted HDI in the reaction system was removed by two-stage thin-film evaporator distillation at a temperature of 140℃ and a pressure of 0.3mbar to obtain polyisocyanate composition 1 containing urea diketone groups.

[0070] Example 2

[0071] Preparation method B was used.

[0072] S2-1: 1000g of hexamethylene diisocyanate (M) was added to 30g of 2-ethyl-1,3-hexanediol under stirring at 100°C. The reaction was carried out for 4 hours to obtain a prepolymer reaction solution. The reaction solution was then subjected to two-stage thin-film evaporator distillation at 140°C and 0.3mbar to remove unreacted HDI from the reaction system, resulting in a polyisocyanate composition with a monomer content of less than 0.5%.

[0073] S2-2: Weigh 1000g of HDI and heat it to 60℃. Add 2.5g of trioctylphosphine and quantitatively monitor the ratio of the remaining mass M1 of HDI in the reaction system to the total mass M of added HDI by gel chromatography. When the remaining mass M1 of HDI in the system accounts for 50% of the total mass M of added HDI, add diisooctyl phosphate (molar ratio of 1:1 with trioctylphosphine) and heat to 80℃ for 2 hours to terminate the reaction. Remove unreacted HDI in the reaction system by two-stage thin-film evaporator distillation at 140℃ and 0.3mbar to obtain a polyisocyanate composition containing ureidone groups.

[0074] S2-3: The polyisocyanate of S2-1 is blended into the polyisocyanate product containing urea diketone groups of S2-2, with a mixing mass ratio of the former to the latter of 5:95, to obtain polyisocyanate composition 2.

[0075] Example 3

[0076] The steps are the same as in Example 1, except that when the remaining mass M1 of HDI in the system accounts for 30% of the total mass M of added HDI, diisooctyl phosphate (molar ratio of 1:1 with trioctylphosphine) is added to terminate the process, and after separation, a polyisocyanate composition 3 containing urea diketone groups is obtained.

[0077] Example 4

[0078] S1-1: 1000g of hexamethylene diisocyanate (HDI) was added to 10g of 1,3-butanediol under stirring at 80℃, and the reaction was carried out for 1 hour.

[0079] S1-2: Then cool to 60℃, add 3g of tributylphosphine, and quantitatively monitor the ratio of the remaining mass M1 of HDI in the reaction system to the total mass M of added HDI by gel chromatography; when the remaining mass M1 of HDI in the system accounts for 50% of the total mass M of added HDI, add dibutyl phosphate (molar ratio of 1:1 with tributylphosphine) and heat to 80℃ for 2 hours to terminate the reaction;

[0080] S1-3: Unreacted HDI in the reaction system was removed by two-stage thin-film evaporator distillation at a temperature of 140℃ and a pressure of 0.3mbar to obtain a polyisocyanate composition 4 containing urea diketone groups.

[0081] Comparative Example 1

[0082] Prepare a polyisocyanate without a component with a weight-average molecular weight of 550±80.

[0083] Weigh 1000g of HDI and heat it to 60℃. Add 2.5g of trioctylphosphine and quantitatively monitor the ratio of the remaining mass M1 of HDI in the reaction system to the total mass M of added HDI by gel chromatography. When the remaining mass M1 of HDI in the system accounts for 50% of the total mass M of added HDI, add diisooctyl phosphate (molar ratio of 1:1 with trioctylphosphine) and heat to 80℃ for 2 hours to terminate the reaction. Remove unreacted HDI in the reaction system by two-stage thin-film evaporator distillation at 140℃ and 0.3mbar to obtain polyisocyanate composition 5 containing ureidone groups.

[0084] Comparative Example 2

[0085] In order to control the content of 550±80 weight average molecular weight, the polyisocyanate in S2-1 of Example 2 was used for adjustment to prepare a polyisocyanate composition with a high content of 550±80 weight average molecular weight. 40g of the polyisocyanate composition in step 1 of Example 2 and 160g of the composition in Comparative Example 1 were mixed in a ratio of 20:80 and mixed evenly to obtain polyisocyanate composition 6.

[0086] Comparative Example 3

[0087] A polyisocyanate composition with a low weight-average molecular weight of 450±80 was prepared.

[0088] Dilute the catalyst by taking 0.4g of tetramethylammonium hydroxide, adding 9.6g of n-butanol, mixing thoroughly, and preparing a 4% catalyst solvent.

[0089] 1000 g of hexamethylene diisocyanate (HDI) was added to the reaction mixture at 60 °C with stirring, along with 15 g of n-butanol. The reaction was allowed to proceed for 1 hour, then the temperature was raised to 90 °C, and 0.6 g of tetramethylammonium hydroxide-butanol was added. The proportion of HDI consumed (M1) to the total added HDI (M) was quantitatively monitored by gel permeation chromatography. When the consumed HDI (M1) reached 50% of the total added HDI (M), dibutyl phosphate (1:1 molar ratio with tetramethylammonium hydroxide) was added to terminate the reaction. Unreacted HDI was removed by two-stage thin-film evaporator distillation at 160 °C and 0.3 mbar to obtain a polyisocyanate composition with a peak content of approximately 0.5% at a weight-average molecular weight of 450 ± 80.

[0090] The above composition is mixed with 10% of polyisocyanate composition-5 to obtain polyisocyanate composition 7.

[0091] Comparative Example 4

[0092] A polyisocyanate composition with a high weight-average molecular weight of 450±80 was prepared.

[0093] 1000 g of hexamethylene diisocyanate (HDI) was added sequentially with 15 g of 2-ethyl-1,3-hexanediol under stirring at 100 °C. The reaction was carried out for 1 hour, then cooled to 60 °C, and 2.5 g of trioctylphosphine was added. The proportion of the remaining mass M1 of HDI in the reaction system to the total mass M of added HDI was quantitatively monitored by gel chromatography. When the remaining mass M1 of HDI in the system accounted for 90% of the total mass M of added HDI, diisooctyl phosphate (molar ratio of 1:1 with trioctylphosphine) was added and the system was heated to 80 °C and held for 2 hours to terminate the reaction. Unreacted HDI in the reaction system was removed by two-stage thin-film evaporator distillation at 140 °C and 0.3 mbar to obtain a polyisocyanate composition 8 containing ureidone groups.

[0094] The characterization results of polyisocyanate compositions 1-8 are shown in the table below:

[0095]

[0096]

[0097] Polyisocyanate compositions 1-8 were placed in an oven at 50°C and stored for 30 days for storage stability testing. The results are shown in the table below:

[0098] Examples / Comparative Examples Initial monomer content / % Monomer content (%) at 50℃ for 30 days Monomer content increase / % Sample status Polyisocyanate component 1 0.1 0.18 0.08 clarify Polyisocyanate component 2 0.1 0.19 0.09 clarify Polyisocyanate component 3 0.1 0.2 0.1 clarify Polyisocyanate component 4 0.1 0.18 0.08 clarify Comparison of polyisocyanate component 5 0.1 0.75 0.65 clarify Comparison of polyisocyanate component 6 0.1 0.18 0.08 turbid Comparison of polyisocyanate component 7 0.08 0.13 0.05 clarify Comparison of polyisocyanate components 8 0.2 0.55 0.30 clarify

[0099] The component peak with a weight-average molecular weight of 450±80 affected the storage stability of polyisocyanates. Higher concentrations tended to lead to higher monomer content in the system, as shown in comparative polyisocyanate composition 5, where the monomer content increased rapidly. However, lower concentrations did not cause a significant increase in monomer content, as shown in polyisocyanate composition 7. When the peak content of the component with a weight-average molecular weight of 450±80 was between 10% and 70%, the component with a weight-average molecular weight of 550±80 could regulate the monomer content during storage. However, higher concentrations resulted in poor compatibility, as shown in the results of comparative polyisocyanate 6, where turbidity occurred during storage.

Claims

1. A polyisocyanate composition, characterized in that, The composition is a polyisocyanate composition obtained from aliphatic diisocyanate and / or alicyclic diisocyanate and a dihydric alcohol with ≤20 carbon atoms, the composition: a. the integral area of the component peak with a weight average molecular weight of 550±80 accounts for 0.1-5% of the total peak area; b. the integral area of the component peak with a weight average molecular weight of 450±80 accounts for 10-70% of the total peak area; The aliphatic diisocyanate and / or alicyclic diisocyanate is an organic diisocyanate containing 4-20 carbon atoms in the carbon skeleton in addition to the NCO group; The peak area is measured using gel chromatography technology, LC-20AD / RID-10A, the chromatographic column is MZ-Gel SDplus10E3A, 5μm (8.0*300mm), MZ-Gel SDplus 500A 5μm (8.0*300mm), MZ-Gel SDplus100A 5μm (8.0*300mm) in series, Shimadzu, polystyrene is used for standard sample, the mobile phase is tetrahydrofuran; the flow rate is 1.0mL / min; the analysis time is 40min, the column temperature is 35℃, the differential detector is used for measurement, the isocyanate raw material is quantified, the areas of the polymers and monomers in the system are determined by area normalization method, and the reaction conversion rate (%) = S (monomer peak area) / S (sum of areas of each component peak) *100%.

2. The polyisocyanate composition according to claim 1, characterized in that, The composition: a. the integral area of the component peak with a weight average molecular weight of 550±80 accounts for 0.2-3% of the total peak area; b. the integral area of the component peak with a weight average molecular weight of 450±80 accounts for 20-60% of the total peak area.

3. The polyisocyanate composition according to claim 1 or 2, characterized in that The viscosity of the polyisocyanate composition is less than or equal to 2000mPa·s.

4. The polyisocyanate composition according to claim 3, characterized in that The viscosity of the polyisocyanate composition is less than or equal to 1000mPa·s.

5. The polyisocyanate composition according to claim 1, characterized in that, The aliphatic diisocyanate and / or alicyclic diisocyanate is selected from one or more of hexamethylene diisocyanate, isophorone diisocyanate, cyclohexyl dimethylene diisocyanate, dicyclohexyl methane diisocyanate, norbornane dimethylene diisocyanate, cyclohexyl diisocyanate and 2,4,4-trimethyl hexane diisocyanate.

6. The polyisocyanate composition according to claim 5, characterized in that The aliphatic diisocyanate is hexamethylene diisocyanate.

7. The polyisocyanate composition according to claim 1 or 2, characterized in that, The dihydric alcohol is a dihydric alcohol with ≤10 carbon atoms.

8. The polyisocyanate composition according to claim 7, characterized in that The dihydric alcohol is one or more of ethylene glycol, propylene glycol, butylene glycol, hexylene glycol and octylene glycol.

9. The polyisocyanate composition according to claim 1 or 2, characterized in that, The free isocyanate monomer content of the composition increases by ≤0.1wt% after being stored at 50℃ for 30 days, based on the total mass of the polyisocyanate composition.

10. A process for the preparation of the polyisocyanate composition according to any one of claims 1 to 9, characterized in that, The method is preparation method A or preparation method B; The preparation method A comprises the following steps: S1-1: reacting an excess of organic diisocyanate with a dihydric alcohol to obtain a prepolymerization liquid; S1-2: adding a catalyst to the prepolymerization liquid, and after the reaction reaches a set conversion rate, adding a terminator to terminate the reaction; S1-3: removing the unreacted organic isocyanate monomer to obtain a polyisocyanate product; The preparation method B comprises the following steps: S2-1: reacting excess organic isocyanate with dihydric alcohol to obtain a prepolymerization liquid, and removing unreacted organic isocyanate monomers; S2-2: adding a catalyst to the organic isocyanate, adding a terminating agent to terminate the reaction after the reaction reaches a set conversion rate, and removing unreacted organic isocyanate monomers; S2-3: mixing the product of S2-1 with the product of S2-1 to obtain a polyisocyanate product.

11. The method of claim 10, wherein, The reaction temperature of S1-1 and S2-1 is 80-120°C; and the reaction time is 0.5-4 hours.

12. The method of claim 11, wherein, The reaction temperature of S1-1 and S2-1 is 100-110°C; and the reaction time is 1-2 hours.

13. The method of claim 10, wherein, The catalyst of S1-2 and S2-2 is a tertiary phosphine.

14. The method of claim 13, wherein, The catalyst of S1-2 and S2-2 is one or more of trimethyl phosphine, triethyl phosphine, tripropyl phosphine, triisopropyl phosphine, tri-n-butyl phosphine, tri-t-butyl phosphine, dicyclopentyl butyl phosphine, triamyl phosphine, tricyclopentyl phosphine, trihexyl phosphine, triphenyl phosphine, tribenzyl phosphine, benzyl dimethyl phosphine, tricyclohexyl phosphine, tri-n-octyl phosphine.

15. The method of claim 14, wherein, The catalyst of S1-2 and S2-2 is tri-n-butyl phosphine and / or tri-n-octyl phosphine.

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