Polyisocyanate composition obtained by mixing aliphatic diisocyanate and aromatic diisocyanate

Abstract

The present invention provides a polyisocyanate composition obtained by co-polymerization of an aliphatic diisocyanate and an aromatic diisocyanate. The polyisocyanate composition is prepared by reacting aliphatic and aromatic diisocyanate monomers under the action of a catalyst, and in the composition, the mass ratio of the aromatic isocyanate group to the total isocyanate group is 0.1-0.7.

Description

Technical Field

[0001] The invention belongs to the field of isocyanates, and in particular relates to a polyisocyanate composition obtained by polymixing an aliphatic diisocyanate with an aromatic diisocyanate. Background Art

[0002] Isocyanates can be used to prepare polyurethane coatings. Aliphatic isocyanate products have good yellowing resistance and chemical stability, but their products have a slow drying rate, poor pendulum hardness and poor wiping resistance. Aromatic isocyanate products have a faster drying rate and excellent wiping resistance, but due to the presence of benzene rings, their products have poor yellowing resistance. The polyisocyanate composition of aliphatic (cyclo) / aliphatic diisocyanate and aromatic diisocyanate can combine the advantages of the two to a certain extent to obtain a polyisocyanate composition with excellent yellowing resistance, wiping resistance and drying rate.

[0003] A part of the prior art is a polyisocyanate composition obtained by directly mixing an aliphatic diisocyanate trimer with an aromatic diisocyanate trimer. However, when these polyisocyanate compositions are used as curing agents, the drying rate is uneven due to the difference in reaction rate.

[0004] The other part is a polyisocyanate composition obtained by mixing aliphatic (cyclo) diisocyanate monomers with aromatic diisocyanate monomers and then adding a catalyst to co-polymerize. Although these polyisocyanate compositions have a fast drying speed, they have average yellowing resistance and high viscosity, and require the addition of more solvents. For example, CN103242254B obtains HDI-TDI trimer by mixing HDI and TDI in a certain proportion under the action of a catalyst. After adding 40% diluent to the composition, the viscosity is still 1000cp, which is environmentally unfriendly.

[0005] A part of the polyisocyanate compositions prepared by the prior art is obtained by direct physical mixing. The polyisocyanate compositions obtained by this technology have the defect of inconsistent drying rate when used as curing agents. The polyisocyanate compositions obtained by direct polymerization of two monomers have a general improvement in yellowing resistance and a high viscosity problem. A large amount of solvent needs to be used for dilution before use, which is environmentally unfriendly. Summary of the invention

[0006] The object of the present invention is to provide a polyisocyanate composition obtained by polymixing an aliphatic diisocyanate with an aromatic diisocyanate, which has low viscosity, good yellowing resistance and fast drying rate.

[0007] The inventors have found through research that by controlling the mass ratio of aromatic isocyanate groups to total isocyanate groups in the polyisocyanate composition to be 0.1-0.7, a mixed polyisocyanate composition with low viscosity, good yellowing resistance and fast drying rate can be obtained, thereby completing the present invention.

[0008] In order to achieve the above-mentioned invention object, the specific technical scheme adopted by the present invention is as follows:

[0009] A polyisocyanate composition obtained by co-polymerization of an aliphatic diisocyanate and an aromatic diisocyanate, wherein the mass ratio of unreacted isocyanate groups in aromatic diisocyanate monomers to the total amount of unreacted isocyanate groups in the composition is (0.1-0.7):1, preferably (0.1-0.5):1.

[0010] In the present invention, the aliphatic diisocyanate is one or more of tetramethylene-1,4-diisocyanate, pentamethylene-1,5-diisocyanate (PDI), hexamethylene-1,6-diisocyanate (HDI), and isophorone diisocyanate (IPDI).

[0011] In the present invention, the aromatic diisocyanate is one or more of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and meta-xylylene diisocyanate (XDI).

[0012] Another object of the present invention is to provide a method for preparing the polyisocyanate composition.

[0013] A method for preparing a polyisocyanate composition, the method comprising the following steps:

[0014] S1: Using aliphatic diisocyanate as the starting material, adding a catalyst to react to obtain reaction solution I;

[0015] S2: adding aromatic diisocyanate to the reaction solution I to continue the reaction, and adding a terminator after reaching the reaction end point to obtain a reaction solution II;

[0016] S3: Separating the unreacted diisocyanate monomer in the reaction solution II.

[0017] In the present invention, the catalyst in S1 is a quaternary ammonium salt and / or a quaternary ammonium base, preferably one or more of tetramethylammonium octanoate, tetramethylammonium acetate, trimethylbenzylammonium hydroxide, 2-hydroxypropyltrimethylisooctanoate ammonium salt, and tetramethylammonium hydroxide; preferably, the catalyst is added in an amount of 30-600ppm, preferably 60-400ppm, based on the total mass of the diisocyanate monomer.

[0018] In the present invention, the reaction temperature of S1 is 40-120°C, preferably 50-100°C.

[0019] In the present invention, the terminator in S2 is one or more of phosphoric acid ester and / or sulfuric acid ester terminators, preferably one or more of dibutyl phosphate, dioctyl phosphate, dimethyl sulfate, and p-toluenesulfonic acid; preferably, the terminator is added in an amount of 20-600ppm, preferably 100-400ppm, based on the total mass of the diisocyanate monomer.

[0020] In the present invention, the reaction temperature of S2 is 50-120°C, preferably 60-100°C.

[0021] In the present invention, the mass ratio of aliphatic diisocyanate to aromatic diisocyanate in S2 is 95:5 to 60:40.

[0022] In the present invention, S3 separates the unreacted diisocyanate monomer in the reaction liquid II by thin film evaporation; preferably, the thin film evaporation is a two-stage thin film evaporation, the evaporation temperature is 110-200°C, preferably 120-160°C; the evaporation pressure is 0.1-0.5Torr, preferably 0.1-0.3Torr.

[0023] The researchers of the present invention found in their research that when the content of aromatic isocyanate groups in the polyisocyanate composition accounts for 0.1-0.7 of the total isocyanate group content, the prepared mixed polyisocyanate composition has better drying performance and yellowing resistance. When the content of aromatic isocyanate groups in the total isocyanate group content is less than 0.1, the drying performance of the polyisocyanate composition cannot achieve the desired effect, and when the content of aromatic isocyanate groups in the total isocyanate group content is higher than 0.7, the yellowing resistance of the polyisocyanate composition cannot achieve the desired effect.

[0024] In the above preparation method, aliphatic (cyclic) diisocyanate monomers are used as starting materials, and trimerization reaction is carried out under the action of a catalyst. After the reaction reaches a certain degree, a certain amount of aromatic diisocyanate monomers are added to continue the reaction. After reaching the end point of the reaction, a terminator is added to obtain the desired reaction solution. In this preparation method, the catalyst first triggers the aliphatic (cyclic) diisocyanate monomers because the aliphatic (cyclic) diisocyanate monomers have poor reactivity relative to aromatic diisocyanate monomers. In the first step of the reaction, the catalyst triggers the aliphatic (cyclic) diisocyanate monomers. After the reaction reaches a certain degree, the aromatic diisocyanate monomers are added. The aromatic diisocyanate monomers react with the aliphatic (cyclic) diisocyanate polymer to achieve a similar end-capping effect, and the obtained polyisocyanate composition has a higher proportion of aromatic isocyanate groups.

[0025] If the aliphatic (cyclic) diisocyanate monomers and aromatic diisocyanate monomers are directly mixed and then the catalyst is added, since the reaction activity of aromatic diisocyanate monomers is significantly faster than that of aliphatic (cyclic) diisocyanate monomers, the majority of the catalyst-triggered aromatic diisocyanate monomers with faster reaction activity will be formed, thereby causing the aromatic diisocyanate monomers to polymerize rapidly to form polyisocyanates with larger molecular weights. This results in less participation of aliphatic (cyclic) diisocyanate monomers in the early stage of the reaction, but more participation when the aromatic diisocyanate monomers are almost exhausted, which makes the final polyisocyanate composition have high viscosity and a small proportion of aromatic cyanate groups in the final composition.

[0026] In the early stage of the reaction, the polymer obtained by the aliphatic (cyclic) diisocyanate monomer under the action of the catalyst is as follows. The reaction solution obtained by the first step of the reaction is all saturated carbon chains. In the second step, aromatic diisocyanate monomers are added to the reaction solution. At this time, the active monomers formed with the catalyst are all aliphatic (cyclic) diisocyanates, so that the aromatic diisocyanate monomers react more with aliphatic (cyclic) isocyanates, so that more polyisocyanate compositions similar to those terminated with aromatic diisocyanates are formed, so that the aromatic isocyanate content in the composition is at a lower level, but a faster drying rate can be maintained, which makes the obtained polyisocyanate combination have a faster drying rate and better yellowing resistance. At the same time, the polymer content in the obtained polyisocyanate composition is at a lower level, which also makes the viscosity of the composition at a lower level.

[0027]

[0028] In one embodiment, in the above polyisocyanate composition, the content of aromatic isocyanate groups in the total isocyanate groups can be determined by 13 C-NMR was used to measure the polyisocyanate composition. 13 C-NMR test, taking hexamethylene diisocyanate (HDI) and diphenylmethane diisocyanate (XDI) as examples, by measuring the carbon atom signal areas of the NCO groups of hexamethylene diisocyanate and diphenylmethane diisocyanate near 121.9ppm and 123.3ppm, wherein the peak area A near 123.3ppm is divided by the sum of the peak areas B of the above two areas, the mass ratio of diphenylmethane isocyanate groups to the total isocyanate groups in the polyisocyanate composition can be obtained as C.

[0029] In one embodiment, in the composition, the content of aromatic isocyanate groups in the total isocyanate groups is 0.1-0.7, preferably 0.1-0.5, for example, 0.1, 0.2, 0.3, 0.4, 0.5, etc.

[0030] In one embodiment, technicians can determine the reaction temperature and the selection of catalyst poisons according to different catalysts. The reaction temperature is preferably 40-120°C, preferably 50-100°C.

[0031] In one embodiment, after the reaction is completed, the diisocyanate monomers that have not participated in the reaction are removed by thin film evaporation, extraction, etc. The concentration of the residual unreacted diisocyanate in the obtained polyisocyanate composition may be 2 wt% or less, preferably 1 wt% or less, and more preferably 0.5 wt% or less.

[0032] In one embodiment, the polyisocyanate composition further comprises one or more of the carbamate structure shown in formula (4), the urea structure shown in formula (5), the uretdione structure shown in formula (6), and the iminooxadiazinedione structure shown in formula (7) obtained by trimerization reaction;

[0033]

[0034]

[0035] Among them, the uretdione structure shown in formula (6) is formed by the thermal reaction of two isocyanate groups, and the iminooxadiazinedione structure shown in formula (7) is a side reaction in the process of diisocyanate trimerization, and its content is greatly related to the catalyst used.

[0036] Compared with the prior art, the positive effects of the present invention are:

[0037] (1) A polyisocyanate composition having excellent yellowing resistance and drying rate can be provided without adding any additives, and when used as a curing agent, there will be no uneven drying rate phenomenon.

[0038] (2) By controlling the order of adding materials, the viscosity of the mixed polymer can be kept at a lower level, which is also more friendly to downstream use. DETAILED DESCRIPTION

[0039] The present invention is further described below by means of specific examples. The examples described in the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0040] In the embodiments and comparative examples of the present invention, 13 C-NMR is used to obtain the ratio C of aromatic isocyanate groups to the total isocyanate groups in the polyisocyanate composition.

[0041] 13 C-NMR test conditions

[0042] Device: Bruker Avance 400

[0043] Observation kernel (frequency): 13 C(100MHz)

[0044] Solvent (concentration): CDCl 3 (5 mass / volume %)

[0045] Accumulated times: 2000 times

[0046] Relaxation time: 4s

[0047] <Determination of product viscosity> The viscosity of the products in the examples and comparative examples was measured using a Brookfield RC / S rheometer, rotor model CC-40, constant temperature water bath, and the temperature was controlled at 25±0.1°C. Shear rate 25S -1 -250S -1 .

[0048] <Measurement of Product Chroma> The chroma of the products in Examples and Comparative Examples was measured using a BYK-Gardner GmbH / USA colorimeter.

[0049] <Determination of HDI monomer mass concentration>

[0050] Place a 20mL sample bottle on a digital balance, accurately weigh 1g of the sample and add it. Next, accurately weigh 0.04g of nitrobenzene (internal standard solution) and add it to the sample bottle. Finally, add 9mL of ethyl acetate to the sample bottle and cover it. And, stir it thoroughly to prepare a measurement sample. Perform gas chromatography analysis on the measurement sample under the following conditions to quantify the amount of diisocyanate monomer.

[0051] Equipment: Shimadzu Corporation, "GC-8A"

[0052] Column: "Silicone OV-17" manufactured by Shinwa Chemical Co., Ltd.

[0053] Column oven temperature: 120°C

[0054] Injection / detector temperature: 160°C

[0055] <NCO content (%)>

[0056] The NCO content (%) was determined by neutralizing the isocyanate groups in the measurement sample with an excess of 2 mol / L amine and then back-titrating with 1 mol / L hydrochloric acid.

[0057] <Yellowing resistance test>

[0058] According to the mass ratio of polyisocyanate composition: butyl acetate: xylene: di-n-butyltin dilaurate of 30:34.8:34.8:0.4, the mixture was placed in a 100°C oven for 24 hours, and the chromaticity of the samples before and after the heat treatment was measured. Among them, the chromaticity increase of less than 20% is excellent, the increase of less than 50% is good, the increase of less than 100% is qualified, and the increase of more than 100% is poor.

[0059] <Drying time test>

[0060] Use a linear drying time recorder to read the drying time according to the national standard GB / T 1728.

[0061] <Pendulum hardness test>

[0062] Place the sprayed / scraped sample at room temperature for 15 to 20 minutes, bake at 80°C for 30 minutes, and then place at room temperature for 30 minutes before conducting a pendulum hardness test.

[0063] The main raw material information involved in the embodiments and comparative examples of the present invention and the equipment information involved in the application performance test are as follows:

[0064] HDI: Hexamethylene diisocyanate, Wanhua Chemical

[0065] PDI: Pentamethylene diisocyanate, Mitsui Chemicals

[0066] IPDI: Isophorone diisocyanate, Wanhua Chemical

[0067] TDI: Toluene diisocyanate, Wanhua Chemical

[0068] MDI: Methylene diphenyl diisocyanate, Wanhua Chemical

[0069] XDI: Meta-xylylene diisocyanate, Wanhua Chemical

[0070] 2-Hydroxypropyltrimethylisooctanoate ammonium salt, Evonik

[0071] Trimethylbenzyl ammonium hydroxide, Sigma-Aldrich

[0072] Di-n-butyl phosphate, Sigma-Aldrich

[0073] p-Toluenesulfonic acid, Sigma-Aldrich.

[0074] Three-necked flask, Sichuan Shubo Group Co., Ltd.

[0075] Electric precision mechanical stirring, IKA-RW20

[0076] Digital constant temperature water bath, Guohua Instrument Co., Ltd.

[0077] Pendulum hardness tester, ERICHSEN

[0078] Linear Dryer, Biugeda Precision Instruments (Guangzhou) Co., Ltd.

[0079] [Example 1]

[0080] 900g HDI was heated to 60°C, 1g (0.77mmol) of 20% 2-hydroxypropyltrimethylisooctanoic acid ammonium salt (purchased from Evonik) in n-butanol solution was added, and when the NCO content in the reaction solution reached 43.7%, 100g XDI was added to continue the reaction, and the reaction conversion rate was about 32%. 0.19g (0.90mmol) of di-n-butyl phosphate was added to terminate the reaction. Using a thin film evaporator, it was refined twice at 140°C and 0.1Torr to obtain a polyisocyanate composition T1 with a mixed monomer mass concentration of HDI and XDI of 0.32%.

[0081] The prepared polyisocyanate composition was tested to have a chromaticity of 22 Hazen and a viscosity of 7280 mPa·s (25° C.), and a ratio C of the isocyanate groups of XDI to the total isocyanate groups of 0.16.

[0082] [Example 2]

[0083] 800g of PDI was heated to 80°C, 1g (0.77mmol) of 20% 2-hydroxypropyltrimethylisooctanoic acid ammonium salt (purchased from Evonik) in n-butanol solution was added, and when the NCO content in the reaction solution reached 45.5%, 200g of XDI was added to continue the reaction, and the reaction conversion rate was about 32%. 0.38g (1.80mmol) of di-n-butyl phosphate was added to terminate the reaction. Then, a thin film evaporator was used to purify twice at 130°C and 0.1Torr to obtain a polyisocyanate composition T2 with a mixed monomer mass concentration of PDI and XDI of 0.54%.

[0084] The prepared polyisocyanate composition was tested to have a chromaticity of 24 Hazen and a viscosity of 10245 mPa·s (25° C.). The ratio C of the isocyanate groups of XDI to the total isocyanate groups was 0.28.

[0085] [Example 3]

[0086] 800g HDI was heated to 60°C, 1g (0.77mmol) of 20% 2-hydroxypropyltrimethylisooctanoic acid ammonium salt (purchased from Evonik) in n-butanol solution was added, and when the NCO content in the reaction solution reached 44.5%, 200g TDI was added to continue the reaction, and the reaction conversion rate was about 32%. 0.16g (0.93mmol) of p-toluenesulfonic acid was added to terminate the reaction. Then, a thin film evaporator was used to purify twice at 150°C and 0.2Torr to obtain a polyisocyanate composition T3 with a mixed monomer mass concentration of HDI and TDI of 0.24%.

[0087] The prepared polyisocyanate composition was tested to have a chromaticity of 25 Hazen and a viscosity of 11425 mPa·s (25° C.). The ratio C of the isocyanate groups of TDI to the total isocyanate groups was 0.39.

[0088] [Example 4]

[0089] 700g of HDI was heated to 60°C, and 1g (0.77mmol) of a 20% n-butanol solution of 2-hydroxypropyltrimethylisooctanoic acid ammonium salt (purchased from Evonik) was added. When the NCO content in the reaction solution reached 45.2%, 300g of TDI was added to continue the reaction, and the reaction conversion rate was about 32%. 0.19g (0.90mmol) of di-n-butyl phosphate was added to terminate the reaction. Then, a thin film evaporator was used to purify twice at 160°C and 0.2Torr to obtain a polyisocyanate composition T4 with a mixed monomer mass concentration of HDI and TDI of 0.21%.

[0090] The prepared polyisocyanate composition was tested to have a chromaticity of 28 Hazen and a viscosity of 12632 mPa·s (25° C.). The ratio C of the isocyanate groups of TDI to the total isocyanate groups was 0.50.

[0091] [Example 5]

[0092] 650g of IPDI was heated to 90°C, and 0.6g (0.72mmol) of a 20% n-butanol solution of trimethylbenzyl ammonium hydroxide (purchased from Sigma-Aldrich) was added. When the NCO content in the reaction solution reached 44.2%, 350g of MDI was added to continue the reaction, and the reaction conversion rate was about 32%. 0.18g (0.86mmol) of di-n-butyl phosphate was added to terminate the reaction. Then, a thin film evaporator was used to purify twice at 160°C and 0.2Torr to obtain a polyisocyanate composition T5 with a mixed monomer mass concentration of HDI and MDI of 0.78%.

[0093] The prepared polyisocyanate composition was tested to have a chromaticity of 30 Hazen and a viscosity of 13532 mPa·s (25° C.). The ratio C of the isocyanate groups of MDI to the total isocyanate groups was 0.70.

[0094] [Example 6]

[0095] 950g HDI was heated to 60°C, 1g (0.77mmol) of 20% 2-hydroxypropyltrimethylisooctanoic acid ammonium salt (purchased from Evonik) in n-butanol solution was added, and when the NCO content in the reaction solution reached 43.1%, 50g MDI was added to continue the reaction, and the reaction conversion rate was about 32%. 0.19g (0.90mmol) of di-n-butyl phosphate was added to terminate the reaction. Then, a thin film evaporator was used to purify twice under the conditions of 160°C and 0.2Torr to obtain a polyisocyanate composition T6 with a mass concentration of 0.23% of HDI and MDI mixed monomers.

[0096] The polyisocyanate composition prepared by testing has a chromaticity of 22 Hazen and a viscosity of 5689

[0097] mPa·s (25°C), the ratio C of the isocyanate groups of MDI to the total isocyanate groups is 0.10.

[0098] [Comparative Example 1]

[0099] Compared with Example 3, the difference is that in the first step of the reaction, HDI and TDI are directly mixed and then a catalyst is added to react.

[0100] 800g HDI and 200g TDI were mixed and heated to 60°C, and 1g (0.77mmol) of 20% 2-hydroxypropyltrimethylisooctanoic acid ammonium salt (purchased from Evonik) in n-butanol solution was added. The reaction conversion rate was about 32%, and 0.16g (0.93mmol) of p-toluenesulfonic acid was added to terminate the reaction. Then, a thin film evaporator was used to purify twice under the conditions of 160°C and 0.2Torr to obtain a polyisocyanate composition D1 with a mixed monomer mass concentration of HDI and TDI of 0.65%.

[0101] The prepared polyisocyanate composition was tested to have a chromaticity of 32 Hazen and a viscosity of 48547 mPa·s (25° C.), and a ratio C of the isocyanate groups of TDI to the total isocyanate groups of 0.06.

[0102] [Comparative Example 2]

[0103] Compared with Example 4, the difference is that in the first step of the reaction, HDI and TDI are directly mixed and then a catalyst is added to react.

[0104] 700 g of HDI and 300 g of TDI were mixed and heated to 60° C., 1 g (0.77 mmol) of a 20% n-butanol solution of 2-hydroxypropyltrimethylisooctanoic acid ammonium salt (purchased from Evonik) was added, and the reaction conversion rate was about 32%. 0.19 g (0.90 mmol) of di-n-butyl phosphate was added to terminate the reaction. Then, a thin film evaporator was used to purify twice under the conditions of 160° C. and 0.2 Torr to obtain a polyisocyanate composition D2 with a mixed monomer mass concentration of HDI and TDI of 0.25%.

[0105] The prepared polyisocyanate composition was tested to have a chromaticity of 36 Hazen and a viscosity of 61341 mPa·s (25° C.). The ratio C of the isocyanate groups of TDI to the total isocyanate groups was 0.08.

[0106] [Comparative Example 3]

[0107] Different from all the examples, this comparative example is obtained by trimerization of aliphatic isocyanate.

[0108] 1000g HDI was heated to 60°C, 1g (0.77mmol) of 20% 2-hydroxypropyltrimethylisooctanoic acid ammonium salt (purchased from Evonik) in n-butanol solution was added, the reaction conversion rate was about 32%, and 0.19g (0.90mmol) of di-n-butyl phosphate was added to terminate the reaction. Then, a thin film evaporator was used to purify twice under the conditions of 160°C and 0.2Torr to obtain a polyisocyanate composition D3 with a HDI monomer mass concentration of 0.15%.

[0109] The prepared polyisocyanate composition was tested to have a chromaticity of 18 Hazen and a viscosity of 2105 mPa·s (25° C.). The ratio C of the isocyanate groups of TDI to the total isocyanate groups was 0.

[0110] [Comparative Example 4]

[0111] Different from all the examples, this comparative example is obtained by trimerization of aromatic isocyanate.

[0112] 1000g of TDI was heated to 60°C, and 1g (0.77mmol) of a 20% n-butanol solution of 2-hydroxypropyltrimethylisooctanoic acid ammonium salt (purchased from Evonik) was added. The reaction conversion rate was about 32%, and 0.19g (0.90mmol) of di-n-butyl phosphate was added to terminate the reaction. Then, a thin film evaporator was used to purify twice under the conditions of 160°C and 0.2Torr to obtain a polyisocyanate composition D4 with a TDI monomer mass concentration of 0.83%.

[0113] The prepared polyisocyanate composition was tested to have a chromaticity of 48 Hazen and a viscosity of 74304 mPa·s (25° C.). The ratio C of the isocyanate groups of TDI to the total isocyanate groups was 1.

[0114] Table 1 Evaluation of coating composition properties of polyisocyanate compositions

[0115]

[0116] Comparing the experimental results in the above table, the polyisocyanate compositions in Comparative Examples 1, 2, and 4 have poor yellowing resistance and high product viscosity. Although the polyisocyanate composition prepared in Comparative Example 3 has excellent yellowing resistance, the drying rate is slow. It can be seen that the overall performance of the polyisocyanate composition in Examples 1-6 is relatively good without obvious disadvantages.

[0117] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A polyisocyanate composition obtained by polypolymerization of an aliphatic diisocyanate and an aromatic diisocyanate, characterized in that: The mass ratio of the unreacted isocyanate groups in the aromatic diisocyanate monomer in the composition to the total amount of the unreacted isocyanate groups in the composition is (0.1-0.7):1; The preparation method of the polyisocyanate composition comprises the following steps: S1: Using aliphatic diisocyanate as the starting material, adding a catalyst to react to obtain reaction solution I; S2: adding aromatic diisocyanate to the reaction solution I to continue the reaction, and adding a terminator after reaching the reaction end point to obtain a reaction solution II; S3: Separating the unreacted diisocyanate monomer in the reaction solution II.

2. The polyisocyanate composition according to claim 1, characterized in that The mass ratio of the unreacted isocyanate groups in the aromatic diisocyanate monomer in the composition to the total amount of the unreacted isocyanate groups in the composition is (0.1-0.5):

1.

3. The polyisocyanate composition according to claim 1, characterized in that The aliphatic diisocyanate is one or more of tetramethylene-1,4-diisocyanate, pentamethylene-1,5-diisocyanate (PDI), hexamethylene-1,6-diisocyanate (HDI), and isophorone diisocyanate (IPDI).

4. The polyisocyanate composition according to claim 1 or 2, characterized in that: The aromatic diisocyanate is one or more of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and meta-xylylene diisocyanate (XDI).

5. A method for preparing the polyisocyanate composition according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: S1: Using aliphatic diisocyanate as the starting material, adding a catalyst to react to obtain reaction solution I; S2: adding aromatic diisocyanate to the reaction solution I to continue the reaction, and adding a terminator after reaching the reaction end point to obtain a reaction solution II; S3: Separating the unreacted diisocyanate monomer in the reaction solution II.

6. The preparation method according to claim 5, characterized in that: The catalyst in S1 is a quaternary ammonium salt and / or a quaternary ammonium alkali; And / or, the reaction temperature of S1 is 40-120°C.

7. The preparation method according to claim 6, characterized in that: The catalyst in S1 is one or more of tetramethylammonium octanoate, tetramethylammonium acetate, trimethylbenzylammonium hydroxide, 2-hydroxypropyltrimethylisooctanoate ammonium salt, and tetramethylammonium hydroxide; The catalyst is added in an amount of 30-600 ppm, based on the total mass of the diisocyanate monomer; And / or, the reaction temperature of S1 is 50-100°C.

8. The preparation method according to claim 7, characterized in that: The amount of the catalyst added in S1 is 60-400 ppm, based on the total mass of the diisocyanate monomer.

9. The preparation method according to claim 5, characterized in that: The terminator in S2 is one or more of phosphoric acid ester and / or sulfuric acid ester terminators; And / or, the reaction temperature of S2 is 50-120°C.

10. The preparation method according to claim 9, characterized in that: The terminator in S2 is one or more of dibutyl phosphate, dioctyl phosphate, dimethyl sulfate, and p-toluenesulfonic acid; The terminator is added in an amount of 20-600 ppm, based on the total mass of the diisocyanate monomer; And / or, the reaction temperature of S2 is 60-100°C.

11. The preparation method according to claim 10, characterized in that: The amount of the terminator added in S2 is 100-400 ppm, based on the total mass of the diisocyanate monomer.

12. The preparation method according to claim 5, characterized in that: The mass ratio of the aliphatic diisocyanate in S1 to the aromatic diisocyanate in S2 is 95:5 to 60:

40.

13. The preparation method according to claim 5, characterized in that: S3 separates the unreacted diisocyanate monomer in the reaction solution II by thin film evaporation.

14. The preparation method according to claim 13, characterized in that: The thin film evaporation in S3 is a two-stage thin film evaporation with an evaporation temperature of 110-200° C. and an evaporation pressure of 0.1-0.5 Torr.

15. The preparation method according to claim 14, characterized in that: The thin film evaporation in S3 is a two-stage thin film evaporation with an evaporation temperature of 120-160° C. and an evaporation pressure of 0.1-0.3 Torr.

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