A hexamethylene diisocyanate composition and its preparation method and application

Abstract

The present invention relates to a hexamethylene diisocyanate composition and a preparation method and application thereof. The hexamethylene diisocyanate composition comprises hexamethylene diisocyanate and 0.2-500 ppm of a cyclic compound, and the chromaticity change rate after heat treatment at 140°C for 4 hours is less than 8. The polyisocyanate prepared by the hexamethylene diisocyanate composition provided by the present invention has excellent low chromaticity relative stability.

Description

Technical Field

[0001] The invention relates to the technical field of isocyanates, and in particular to an active and relatively stable hexamethylene diisocyanate composition and a preparation method and application thereof. Background Art

[0002] Hexamethylene diisocyanate is an aliphatic isocyanate, which is generally obtained by reacting hexamethylenediamine with phosgene in the industry, and it is particularly advantageous to react in the gas phase. Isocyanate compounds have high reactivity due to the isocyanate group, especially industrial isocyanate products have different reactivity during storage, which affects the preparation of polyisocyanates in the downstream modification step, such as trimer or biuret or uretdione.

[0003] It is known that the stability of isocyanate can be improved by adding stabilizers. For example, U.S. Patent No. 3715381 discloses 2,6-di-tert-butyl-4-methylphenol, and Japanese Patent No. JP2004099523 discloses the stabilizing effect of tetraalkoxysilane on polymeric MDI. The above patent methods all require the addition of other compounds to the product, and also do not provide relevant guidance on the active stability of the product during downstream use.

[0004] Chinese patent CN113980238A discloses the color stabilizing effect of methyl isocyanate basic formamide on xylylene diisocyanate, but does not provide any teaching on the effect on the activity of the product.

[0005] Chinese patent CN112851908A discloses a method for preparing a polyisocyanate containing uretdione groups. The method controls the content of 1-nylon polymer in the removed diisocyanate monomer to prevent the light component from gelling and being unable to be recycled. The impurities are mainly generated by polymerization under the catalytic action of the catalyst for preparing uretdione. No guidance is given on the influence of the activity of normal isocyanate products during storage, and other key impurity influencing factors are not identified. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a hexamethylene diisocyanate composition with relatively stable activity, a preparation method and application thereof. The hexamethylene diisocyanate composition prepared by the present invention has the advantage of relatively stable activity when used as a raw material to prepare polyisocyanate after long-term storage.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] A hexamethylene diisocyanate composition comprises hexamethylene diisocyanate and 0.2-300 ppm of a nitrogen-containing heterocyclic compound.

[0009] The hexamethylene diisocyanate composition, the nitrogen-containing heterocyclic compound comprises any one or a combination of at least two of the following compounds:

[0010] Wherein X is Cl or Br.

[0011] This type of impurities originates from the reaction products of impurities in the raw material amine with phosgene (or bromine-containing phosgene), and can also originate from the reaction products of decomposition products of amine under high-temperature preheating gasification with phosgene (or bromine-containing phosgene).

[0012] The researchers of the present invention have found in their studies that when the hexamethylene diisocyanate composition contains 0.2-300 ppm of the above-mentioned nitrogen-containing heterocyclic compound, the composition can inhibit the polymerization of NCO and has the characteristics of stable activity during storage, especially in the process of being used as a raw material to prepare polyisocyanate, it exhibits a high degree of activity and is relatively stable.

[0013] The content of nitrogen-containing heterocyclic compounds in the hexamethylene diisocyanate composition is 0.2-200 ppm, preferably 0.4-100 ppm.

[0014] The content of the nitrogen-containing heterocyclic compound described in the present invention can be implemented by, but not limited to, the following methods, such as by controlling the reaction conditions, or separation conditions, or additional addition, so that the content of the nitrogen-containing heterocyclic compound can be controlled within the range.

[0015] As is well known to those skilled in the art, the hexamethylene diisocyanate composition can be prepared by subjecting the hexamethylene diamine composition to a phosgenation reaction. Specifically, as the phosgenation reaction, a liquid phase phosgenation method in which the hexamethylene diamine composition reacts with phosgene in a liquid phase or a gas phase phosgenation reaction in which the hexamethylene diamine composition reacts with phosgene in a gas phase can be used. The present invention preferably uses a hexamethylene diamine composition obtained by gas phase phosgenation.

[0016] First, hexamethylenediamine is preheated and gasified in the presence or absence of an inert gas, and reacted with the preheated and gasified phosgene to obtain a hexamethylene diisocyanate composition reaction liquid; the reaction liquid obtained in the above steps is then subjected to phosgene removal, hydrogen chloride removal, and solvent removal treatment to obtain the hexamethylene diisocyanate crude product; finally, the above obtained hexamethylene diisocyanate crude product is subjected to impurity removal and purification to finally obtain the hexamethylene diisocyanate composition product.

[0017] Before the phosgenation reaction, the material stream containing hexamethylenediamine is preheated to above 200°C, preferably 300-520°C; the material stream containing phosgene is preheated to above 200°C, preferably 300-520°C. In the present invention, the material stream containing hexamethylenediamine includes hexamethylenediamine and / or an inert gas such as nitrogen, argon, helium, etc.; the material stream containing phosgene includes fresh phosgene and / or recycled phosgene, and / or optional inert gases such as nitrogen, argon, helium, etc., wherein fresh phosgene refers to phosgene that has not undergone any phosgene-related reaction after phosgene is synthesized from chlorine and carbon monoxide, and recycled phosgene refers to phosgene that has not reacted after the phosgenation reaction and can continue to participate in the phosgenation reaction after separation and purification.

[0018] In the present invention, the reaction of phosgene and hexamethylenediamine is carried out under an absolute pressure of 0.02-0.5Mpa, preferably 0.05-0.2Mpa; the reaction temperature is 200-600°C, preferably 250-500°C.

[0019] If the high-temperature residence time of the amine and phosgene in the reaction zone of the present invention is too long, it is easy to cause the decomposition or polymerization of the amine, phosgene and the target isocyanate, resulting in the occurrence of undesirable side reactions. If the residence time is too short, the contact reaction time of phosgene and amine is insufficient, the reaction is incomplete, and the reaction yield is seriously affected. Therefore, the reaction residence time of the amine and phosgene in the reaction zone of the present invention is 0.02-10s, preferably 0.1-5s.

[0020] A higher molar ratio of phosgene to amino in the present invention is beneficial to the conversion of amine into isocyanate, but will result in a higher phosgene inventory in the system, increase safety risks, and increase costs due to phosgene preheating and condensation. A too low molar ratio of phosgene to amino may lead to poor reaction effect, affect the reaction yield and stable operation of the device. Therefore, the molar ratio of phosgene to amino in the present invention is 2-20:1, preferably 6-10:1.

[0021] The gaseous target isocyanate product passing through the reaction zone is usually at a temperature above 200°C. It is generally absorbed by a capture liquid containing an inert solvent to quench the reaction product to obtain a liquid stream containing isocyanate, which is transferred from the gas phase to the liquid phase. At the same time, part of the hydrogen chloride, unreacted phosgene and by-products will also be distributed in the reaction absorption liquid.

[0022] The temperature of the capture liquid containing the solvent in the present invention is 5 to 200° C., preferably 30 to 160° C. The solvent includes one or more of toluene, xylene, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, methyl benzoate, ethyl benzoate, butyl benzoate, propyl benzoate, chlorobenzene, o-dichlorobenzene, p-chlorotoluene, bromobenzene, etc., but is not limited thereto. These solvents can be used alone or mixed in any proportion.

[0023] In the present invention, the reaction product obtained in the reaction step can be subjected to phosgene removal, hydrogen chloride removal, and solvent removal operations to obtain crude hexamethylene diisocyanate. Phosgene can be used as circulating phosgene to enter the reaction system again after absorption and purification. Part or all of the solvent can be used as a capture liquid for recycling after purification.

[0024] In the present invention, the obtained crude hexamethylene diisocyanate is subjected to impurity removal and purification in the refining and purification step, and finally the hexamethylene diisocyanate composition product is obtained.

[0025] The impurity removal and purification is preferably carried out by distillation purification, which can be carried out by continuous distillation or intermittent distillation. The distillation tower can be a plate tower or a packed tower. The number of distillation towers can be one tower or two towers or more than two towers to achieve the distillation effect, and there is no special limitation on this.

[0026] According to the method of the present invention, in a preferred embodiment, the content of the nitrogen-containing heterocyclic compound in the hexamethylene diisocyanate composition is controlled by continuous distillation. Specifically, the distillation is carried out in a distillation tower, and the theoretical plate number of the distillation tower is preferably 20-40, more preferably 20-30. The top pressure of the distillation tower is preferably 0.5-20kpa, more preferably 1-10kpa. The bottom temperature of the distillation tower is preferably 100-170°C, more preferably 135-155°C. The reflux ratio of the distillation tower is preferably 2-15:1, more preferably 3-7:1. The top extraction of the distillation tower is preferably 4-10wt%, more preferably 4-6wt%.

[0027] According to the method of the present invention, in a preferred embodiment, the crude hexamethylene diisocyanate is fed from the 5th theoretical plate, the enriched liquid of the nitrogen-containing heterocyclic compound is taken out from the top of the distillation tower, and the purified product is taken out through the side line of the distillation tower, and the taking-out position is between the 19th and 20th theoretical plates.

[0028] The composition has the characteristic of stable activity during storage, and especially exhibits the characteristic of high activity and relative stability during the process of being used as a raw material for preparing polyisocyanate.

[0029] The above-mentioned hexamethylene diisocyanate composition containing nitrogen-containing heterocyclic compounds has the characteristic of relatively stable activity during long-term storage, especially in the process of preparing polyisocyanates as raw materials, it shows the characteristic of high activity and relatively stable activity. Such polyisocyanates contain any one or at least two combinations of the following (a)-(e) groups: (a) isocyanurate group, (b) uretdione group, (c) biuret group, (d) carbamate group, (e) urea group, (f) iminooxadiazinedione group, (g) allophanate group, (h) uretonimine group or (i) carbodiimide group.

[0030] Finally, the present invention provides a polyisocyanate composition, which includes but is not limited to a polyisocyanate composition containing an isocyanurate group. The preparation method thereof uses a hexamethylene diisocyanate composition as a raw material, performs a trimerization reaction under the action of a catalyst, adds a terminator to stop the reaction after reaching the reaction endpoint, and then separates to obtain the polyisocyanate composition containing isocyanurate.

[0031] The catalyst is a compound a): at least one of a quaternary ammonium salt, a quaternary ammonium base, and a quaternary phosphonium salt and a compound b): a composition of one or more of a five-membered or six-membered heterocyclic organic compound containing a nitrogen atom, a phosphorus atom, an oxygen atom, or a sulfur atom. Specifically, the compound a is preferably one or more of tetrabutylammonium acetate, tetramethylammonium acetate, tetramethylammonium propionate, tetramethylammonium hydroxide, benzyltrimethylammonium hydroxide, and benzyltriphenylphosphonium chloride; the compound b is preferably one or more of pyrazole, pyridine, imidazole, pyrrole, thiophene, furan, and pyridazine.

[0032] The terminator is an acid compound, including but not limited to at least one of di-n-butyl phosphate, hydrochloric acid, phosphoric acid, dimethyl phosphate, diethyl phosphate, p-toluenesulfonic acid, benzenesulfonic acid, alkylbenzenesulfonic acid, acetyl chloride, and benzoyl chloride.

[0033] The temperature of the trimerization reaction is 60-90°C;

[0034] The mass ratio of hexamethylene diisocyanate to the catalyst is 200-100000:1;

[0035] The amount of the terminator is not particularly limited. Preferably, the mass ratio of hexamethylene diisocyanate to the terminator is 1000-10000:1.

[0036] The beneficial effects of the present invention are:

[0037] According to the method provided by the present invention, the hexamethylene diisocyanate composition having a nitrogen-containing heterocyclic compound content of 0.2-300 ppm can be obtained, and has the characteristic of relatively stable activity during storage, especially in the process of being used as a raw material to prepare polyisocyanate, it exhibits a high degree of relatively stable activity. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with the embodiments, but the present invention is not limited to the listed embodiments, and should also include any other known changes within the scope of the rights claimed by the present invention.

[0039] Raw materials and sources:

[0040] Hexamethylenediamine is an industrial-grade product of INVISTA (Shanghai); phosgene is produced by Wanhua Chemical Group Co., Ltd.; dichlorobenzene, Aladdin, purity 99.5%; tetrabutylammonium acetate, Aladdin, purity 99.5%; pyrazole, Aladdin, purity 99%; anhydrous ethanol, Merck Chemical, purity 99.5%; di-n-butyl phosphate, Aladdin, purity 98.5%; 1-piperidinoyl chloride, TCI, 98%; 1-piperidinoyl bromide, Chem HERE, 98%.

[0041] The test of nitrogen-containing heterocyclic compounds in the hexamethylene diisocyanate composition in the following examples and comparative examples was carried out by gas chromatography. First, the different retention times of the nitrogen-containing heterocyclic compound components in gas chromatography were determined by gas chromatography-mass spectrometry, and the contents were obtained by area normalization method. The test method is as follows:

[0042] The analytical instrument was Agilent 7890B; the chromatographic column model was DB-5 (30m×0.25mm×0.25um); the detector was an FID detector; the injection port temperature was 260°C; the detector temperature was 300°C; the temperature program was from 50°C to 90°C at 10°C / min, maintained for 2 min, from 15°C / min to 180°C, maintained for 2 min, from 20°C / min to 280°C, maintained for 15 min; the injection volume was 0.2ul.

[0043] The product activity test was carried out in the manner of Example 1 in the prepolymer preparation method patent CN112250835B.

[0044] Example 1

[0045] Hexamethylene diisocyanate was prepared by gas phase phosgenation with hexamethylenediamine and phosgene as raw materials.

[0046] The inlet temperature of hexamethylenediamine entering the reactor is 381°C, the inlet temperature of phosgene entering the reactor is 375°C, the reaction pressure is 0.11MPa, the reaction temperature is 467°C, the reaction time is 0.7s, and the molar ratio of phosgene to hexamethylenediamine is 6.7:1. After the reaction product leaves the reaction zone, dichlorobenzene is used for spraying and absorbing at a spraying and absorbing temperature of 35°C to obtain a hexamethylene diisocyanate composition reaction liquid. The reaction liquid is subsequently dephosgenated and desolventized to obtain a crude hexamethylene diisocyanate composition, and the final product is obtained by refining.

[0047] The product is refined by continuous distillation, and the control parameters are as follows:

[0048] The number of theoretical plates of the distillation tower is 32, the pressure at the top of the distillation tower is 1.1 kPa, the temperature at the bottom of the distillation tower is 136°C, the reflux ratio is 6:1, the output from the top of the distillation tower is 6wt%, the crude hexamethylene diisocyanate is fed from the 5th theoretical plate, and the purified product is withdrawn through the side line of the distillation tower, and the withdrawal position is between the 19th and 20th theoretical plates. The content of nitrogen-containing heterocyclic compounds in the obtained product is 0.6 ppm.

[0049] Example 2

[0050] Hexamethylene diisocyanate was prepared by gas phase phosgenation with hexamethylenediamine and phosgene as raw materials.

[0051] The inlet temperature of hexamethylenediamine entering the reactor is 412°C, the inlet temperature of phosgene entering the reactor is 501°C, the reaction pressure is 0.18MPa, the reaction temperature is 521°C, the reaction time is 2.3s, and the molar ratio of phosgene to hexamethylenediamine is 4:1. After the reaction product leaves the reaction zone, dichlorobenzene is used for spraying and absorbing, and the spraying and absorbing temperature is 164°C to obtain a hexamethylene diisocyanate composition reaction liquid. The reaction liquid is subsequently dephosgenated and desolventized to obtain a crude hexamethylene diisocyanate composition, and the final product is obtained by refining.

[0052] The product is refined by continuous distillation, and the control parameters are as follows:

[0053] The number of theoretical plates of the distillation tower is 22, the pressure at the top of the distillation tower is 4.3 kPa, the temperature at the bottom of the distillation tower is 164°C, the reflux ratio is 4:1, the output from the top of the distillation tower is 5 wt%, the crude hexamethylene diisocyanate is fed from the 4th theoretical plate, and the purified product is withdrawn through the side line of the distillation tower, and the withdrawal position is between the 21st and 22nd theoretical plates. The content of nitrogen-containing heterocyclic compounds in the obtained product is 283 ppm.

[0054] Example 3

[0055] Hexamethylene diisocyanate was prepared by gas phase phosgenation with hexamethylenediamine and phosgene as raw materials.

[0056] The inlet temperature of hexamethylenediamine entering the reactor is 310°C, the inlet temperature of phosgene entering the reactor is 423°C, the reaction pressure is 0.04MPa, the reaction temperature is 379°C, the reaction time is 0.08s, and the molar ratio of phosgene to hexamethylenediamine is 12:1. After the reaction product leaves the reaction zone, dichlorobenzene is used for spraying and absorbing, and the spraying and absorbing temperature is 153°C to obtain a hexamethylene diisocyanate composition reaction liquid. The reaction liquid is subsequently dephosgenated and desolventized to obtain a crude hexamethylene diisocyanate composition, and the final product is obtained by refining.

[0057] The product is refined by continuous distillation, and the control parameters are as follows:

[0058] The number of theoretical plates of the distillation tower is 36, the pressure at the top of the distillation tower is 12 kPa, the temperature at the bottom of the distillation tower is 142°C, the reflux ratio is 5:1, the output from the top of the distillation tower is 9wt%, the crude hexamethylene diisocyanate is fed from the 8th theoretical plate, and the purified product is withdrawn through the side line of the distillation tower, and the withdrawal position is between the 22nd and 23rd theoretical plates. The content of nitrogen-containing heterocyclic compounds in the obtained product is 0.3ppm.

[0059] Example 4

[0060] The product obtained in Example 3 was used, and 1-piperidinyl chloride was added thereto to adjust the nitrogen-containing heterocyclic compound content to 52 ppm.

[0061] Example 5

[0062] The product obtained in Example 3 was used, and 1-piperidinyl bromide was added thereto to adjust the content of the nitrogen-containing heterocyclic compound to 94 ppm.

[0063] Hexamethylene diisocyanate was prepared by gas phase phosgenation with hexamethylenediamine and phosgene as raw materials.

[0064] The inlet temperature of hexamethylenediamine entering the reactor is 615°C, the inlet temperature of phosgene entering the reactor is 562°C, the reaction pressure is 0.34MPa, the reaction temperature is 584°C, the reaction time is 13s, and the molar ratio of phosgene to hexamethylenediamine is 1:1. After the reaction product leaves the reaction zone, dichlorobenzene is used for spraying and absorbing at a spraying and absorbing temperature of 170°C to obtain a hexamethylene diisocyanate composition reaction liquid. The reaction liquid is subsequently dephosgenated and desolventized to obtain a crude hexamethylene diisocyanate composition, and the final product is obtained by refining.

[0065] The product is refined by continuous distillation, and the control parameters are as follows:

[0066] The number of theoretical plates of the distillation tower is 16, the pressure at the top of the distillation tower is 0.7 kpa, the temperature at the bottom of the distillation tower is 97°C, the reflux ratio is 2:1, the output from the top of the distillation tower is 2wt%, the crude hexamethylene diisocyanate is fed from the second theoretical plate, and the purified product is withdrawn through the side line of the distillation tower, and the withdrawal position is between the 9th and 10th theoretical plates. The content of nitrogen-containing heterocyclic compounds in the obtained product is 407 ppm.

[0067] Comparative Example 2

[0068] Hexamethylene diisocyanate was prepared by gas phase phosgenation with hexamethylenediamine and phosgene as raw materials.

[0069] The inlet temperature of hexamethylenediamine entering the reactor is 275°C, the inlet temperature of phosgene entering the reactor is 286°C, the reaction pressure is 0.01MPa, the reaction temperature is 311°C, the reaction time is 0.01s, and the molar ratio of phosgene to hexamethylenediamine is 23:1. After the reaction product leaves the reaction zone, dichlorobenzene is used for spraying and absorbing at a spraying and absorbing temperature of 3°C to obtain a hexamethylene diisocyanate composition reaction liquid. The reaction liquid is subsequently dephosgenated and desolventized to obtain a crude hexamethylene diisocyanate composition, and the final product is obtained by refining.

[0070] The product is refined by continuous distillation, and the control parameters are as follows:

[0071] The number of theoretical plates of the distillation tower is 43, the pressure at the top of the distillation tower is 23.1 kPa, the temperature at the bottom of the distillation tower is 174°C, the reflux ratio is 8:1, the output from the top of the distillation tower is 13 wt%, the crude hexamethylene diisocyanate is fed from the 17th theoretical plate, and the purified product is withdrawn through the side line of the distillation tower, and the withdrawal position is between the 32nd and 33rd theoretical plates. The content of nitrogen-containing heterocyclic compounds in the obtained product is 0.1 ppm.

[0072] The following prepolymers are prepared using the hexamethylene diisocyanate compositions obtained in Examples 1-5 and Comparative Examples 1-2, respectively. The prepolymer preparation method is implemented in the manner of Example 1 in patent CN112250835B.

[0073] Preparation of prepolymer

[0074] 5g of a mixture of tetrabutylammonium acetate and pyrazole in a mass ratio of 1:0.8 was dissolved in 20g of anhydrous ethanol to prepare a catalyst composition with a mass concentration of 20%. Under nitrogen protection, 2kg of the hexamethylene diisocyanate composition obtained in the embodiment and comparative example was heated in a 60°C water bath for 1h, and then a catalyst composition with a content of 150ppm (dry weight 0.3g) relative to the hexamethylene diisocyanate monomer was added, and the reaction was continued at 70°C. When the NCO content in the reaction liquid reached 39.3%, the reaction was terminated, and the reaction time was recorded, as shown in Table 1; di-n-butyl phosphate (0.24g) with a content of 120ppm relative to the hexamethylene diisocyanate monomer was added to terminate the reaction.

[0075] The hexamethylene diisocyanate composition was sealed and stored in a nitrogen atmosphere at 25° C. The above-mentioned embodiment was repeated on the 50th day and the 100th day, and the reaction time was recorded respectively. The specific results are shown in Table 1.

[0076]

[0077]

[0078] In summary, by controlling the nitrogen-containing heterocyclic compound in the hexamethylene diisocyanate composition to be 0.2-300 ppm, the composition has the characteristic of relatively stable activity during storage, especially in the process of being used as a raw material to prepare polyisocyanate, it shows a high degree of relatively stable activity.

[0079] The above is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art may make several improvements and supplements without departing from the present invention, and these improvements and supplements should also be regarded as within the protection scope of the present invention.

Claims

1. A hexamethylene diisocyanate composition, characterized in that: The hexamethylene diisocyanate composition comprises hexamethylene diisocyanate and 0.2-300 ppm of a nitrogen-containing heterocyclic compound; the nitrogen-containing heterocyclic compound comprises any one or a combination of at least two of the following compounds: Wherein X is Cl or Br.

2. The composition according to claim 1, characterized in that The content of nitrogen-containing heterocyclic compounds in the hexamethylene diisocyanate composition is 0.2-200 ppm.

3. The composition according to claim 1, characterized in that The content of nitrogen-containing heterocyclic compounds in the hexamethylene diisocyanate composition is 0.4-100 ppm.

4. The method for preparing a hexamethylene diisocyanate composition according to claim 1 or 2, comprising the following steps: preheating hexamethylene diamine in the presence or absence of an inert gas and then gasifying it, and reacting it with the preheated and gasified phosgene to obtain a hexamethylene diisocyanate composition reaction liquid; removing phosgene, dehydrochlorination, and solvent from the reaction liquid obtained in the above steps to obtain the crude hexamethylene diisocyanate; and finally removing impurities and refining the crude hexamethylene diisocyanate obtained to finally obtain the hexamethylene diisocyanate composition product.

5. The preparation method according to claim 4, characterized in that: The preheating temperature of the hexamethylenediamine is above 200° C.; the preheating temperature of the phosgene is above 200° C.

6. The preparation method according to claim 4, characterized in that: The preheating temperature of the hexamethylenediamine is 300-520°C; the preheating temperature of the phosgene is 300-520°C.

7. The preparation method according to claim 4, characterized in that: The inert gas is selected from one or more of nitrogen, argon, and helium; the phosgene includes fresh phosgene and / or recycled phosgene, and optional inert gas, wherein fresh phosgene refers to phosgene that has not undergone any phosgene-related reaction after being synthesized from chlorine and carbon monoxide, and recycled phosgene refers to phosgene that has not reacted after phosgenation reaction and can continue to participate in phosgenation reaction after separation and purification.

8. The preparation method according to claim 7, characterized in that: The optional inert gas is selected from nitrogen, argon and helium.

9. The preparation method according to any one of claims 4 to 8, characterized in that: The reaction of phosgene and hexamethylenediamine is carried out at an absolute pressure of 0.02-0.5 MPa; and / or, the reaction temperature is 200-600° C.; and / or, the reaction residence time of amine and phosgene in the reaction zone is 0.02-10 s.

10. The preparation method according to any one of claims 4 to 8, characterized in that: The reaction of phosgene and hexamethylenediamine is carried out at an absolute pressure of 0.05-0.2 MPa; and / or, the reaction temperature is 250-500° C.; and / or, the reaction residence time of amine and phosgene in the reaction zone is 0.1-5 s.

11. The preparation method according to any one of claims 4 to 8, characterized in that: The molar ratio of phosgene to the amino group in hexamethylenediamine is 2-20:

1.

12. The preparation method according to claim 11, characterized in that: The molar ratio of phosgene to the amino group in hexamethylenediamine is 6-10:

1.

13. The preparation method according to any one of claims 4 to 8, characterized in that: The impurity removal and refining is distillation purification; the distillation is carried out in a distillation tower, the theoretical plate number of the distillation tower is 20-40; and / or the top pressure of the distillation tower is 0.5-20kPa; and / or the bottom temperature of the distillation tower is 100-170°C; and / or the reflux ratio of the distillation tower is 2-15:1; and / or the top extraction amount of the distillation tower is 4-10wt%.

14. The preparation method according to claim 13, characterized in that: The number of theoretical plates of the distillation tower is 20-30; and / or, the pressure at the top of the distillation tower is 1-10 kPa; and / or, the temperature at the bottom of the distillation tower is 135-155° C.; and / or, the reflux ratio of the distillation tower is 3-7:1; and / or, the extraction amount at the top of the distillation tower is 4-6 wt%.

15. A polyisocyanate composition, which uses the hexamethylene diisocyanate composition according to any one of claims 1 to 3 or the hexamethylene diisocyanate composition prepared by the preparation method according to any one of claims 4 to 14 as a raw material, undergoes a trimerization reaction under the action of a catalyst, adds a terminator to stop the reaction after reaching the reaction end point, and then separates to obtain a polyisocyanate composition containing isocyanurate.

16. The composition according to claim 15, characterized in that The catalyst is a combination of compound a): at least one of quaternary ammonium salts, quaternary ammonium bases, and quaternary phosphonium salts and compound b): one or more of five-membered or six-membered heterocyclic organic compounds containing nitrogen atoms, phosphorus atoms, oxygen atoms, or sulfur atoms; the compound b is one or more of pyrazole, pyridine, imidazole, pyrrole, thiophene, furan, and pyridazine; and / or the terminator is an acid compound selected from at least one of di-n-butyl phosphate, hydrochloric acid, phosphoric acid, dimethyl phosphate, diethyl phosphate, benzenesulfonic acid, alkylbenzenesulfonic acid, acetyl chloride, and benzoyl chloride.

17. The composition according to claim 16, characterized in that The compound a is one or more of tetrabutylammonium acetate, tetramethylammonium acetate, tetramethylammonium propionate, tetramethylammonium hydroxide, benzyltrimethylammonium hydroxide, and benzyltriphenylphosphine chloride, and / or the terminator is p-toluenesulfonic acid.

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