Environment-friendly polyisocyanate composition and use thereof

Abstract

The present application relates to the technical field of polyisocyanate composition preparation, and provides an environmentally-friendly polyisocyanate composition and application thereof.The polyisocyanate composition of the present application can improve the curing drying time and impact resistance in downstream application.The composition is an end NCO product prepared by reacting materials including toluene diisocyanate and at least two dihydric alcohol compounds with different molecular weights and a number average molecular weight of 400-3000;and the composition does not contain organic solvents, and the free isocyanate monomer content is less than 0.1wt%;when the reaction is carried out, the toluene diisocyanate is first contacted with the dihydric alcohol compound with the lowest molecular weight at 2-92°C for reaction, and then contacted with the remaining dihydric alcohol compounds at 98-180°C for reaction;the molar ratio R1 of the isocyanate groups of the toluene diisocyanate to the hydroxyl groups of the dihydric alcohol compound with the lowest molecular weight is 6-22.

Description

Technical Field

[0001] This invention relates to the field of polyisocyanate composition preparation technology, and in particular to an environmentally friendly polyisocyanate composition and its application. Background Technology

[0002] Toluene diisocyanate (Toluene Diisocyanate) is widely used in coatings, adhesives, and other fields. As an important synthetic raw material, it can be combined with different polyol components to achieve different product properties. Current technologies often calculate the feed ratio to maximize the reaction between isocyanate groups and hydroxyl groups. However, this process leaves residual Toluene Diisocyanate monomers in the system, polluting the environment and harming human health. Patent CN112341595A discloses a method for preparing low-free Toluene Diisocyanate derivatives, such as using thin-film evaporation and extraction to remove unreacted free monomers. However, this system requires the addition of organic solvents to ensure the product's usability, and solvent evaporation introduces new environmental problems. Currently, there is no commercially available environmentally friendly (solvent-free, low-free-monomer) Toluene Diisocyanate derivative product with good workability. Summary of the Invention

[0003] To address at least one deficiency in the prior art, the present invention provides an environmentally friendly polyisocyanate composition and its application. The polyisocyanate composition of the present invention has a viscosity suitable for application without the introduction of organic solvents, and the polyisocyanate composition can improve curing and drying time and impact resistance in downstream applications (e.g., in coatings or adhesives).

[0004] To achieve its objective, the present invention provides the following technical solution:

[0005] This invention provides an environmentally friendly polyisocyanate composition, which is a terminal NCO product obtained by reacting materials including toluene diisocyanate and at least two diol compounds with different molecular weights and number average molecular weights of 400-3000; and the composition does not contain organic solvents and the content of free isocyanate monomers is <0.1wt%.

[0006] Furthermore, during the reaction, the toluene diisocyanate is first reacted with the diol compound with the lowest molecular weight at 2-92°C, and then reacted with the remaining diol compounds at 98-180°C.

[0007] The molar ratio R1 of the isocyanate group of the toluene diisocyanate to the hydroxyl group of the diol compound with the lowest molecular weight is 6-22, preferably 6-20.

[0008] In some embodiments, the molar ratio R2 of the isocyanate group of the toluene diisocyanate to the hydroxyl groups of all the diol compounds is 4-10, preferably 4-9.

[0009] In some embodiments, the diol compound is selected from one or more of polyether diols, polyester diols, polycaprolactone diols, and polycarbonate diols, preferably polyether diols;

[0010] And / or, the toluene diisocyanate is one or more of toluene-2,4-diisocyanate and toluene-2,6-diisocyanate, preferably toluene-2,4-diisocyanate.

[0011] Preferably, the toluene diisocyanate is first reacted with the diol compound with the lowest molecular weight at 2-92°C for 1.5-300 h, preferably 3-300 h.

[0012] Furthermore, the remaining diol compound is a single diol compound, or includes two or more diol compounds with different molecular weights.

[0013] Preferably, when the remaining diol compound is a single diol compound, the remaining diol compound is added to the reaction system and reacted at 98-180°C for 1-15 hours, preferably 2.5-15 hours, and the reaction temperature is preferably 100-180°C.

[0014] Preferably, when the remaining diol compounds include two or more diol compounds with different molecular weights, the diol compounds of different molecular weights are added sequentially in order of increasing molecular weight. After each diol compound of a certain molecular weight is added, the reaction is carried out at 98–180°C for 1–15 hours, and then another diol compound of a certain molecular weight is added and the reaction continues for another 1–15 hours. Preferably, the reaction temperature of the remaining diol compounds after the addition of each molecular weight is 100–180°C, and the reaction time is preferably 2.5–15 hours. More preferably, the remaining diol compounds are reacted at the same reaction temperature after the addition of each molecular weight.

[0015] Preferably, the order of adding raw materials to the reaction system includes: first adding toluene diisocyanate, and then adding the diol compound with the lowest molecular weight to carry out the reaction.

[0016] Preferably, the reaction solution containing the terminal NCO product obtained from the reaction is separated to remove unreacted isocyanate monomers. The separation temperature is 185–240°C, preferably 185–230°C; the separation pressure is 0.1–85 Pa, preferably 0.5–85 Pa.

[0017] The separation is preferably performed using thin-film evaporation.

[0018] Furthermore, no organic solvents are added during the preparation of the composition;

[0019] The organic solvents include, for example, one or more of toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methylcyclohexanone, cyclohexane, n-hexane, tetrahydrofuran, chlorobenzene, dichlorobenzene, dichloromethane, dichloroethane, 1,3-dioxane, methyl acetate, ethyl acetate, butyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, ethyl propionate, propyl propionate, and butyl propionate.

[0020] Furthermore, the viscosity of the polyisocyanate composition at 23°C is 4600–12000 cP.

[0021] The present invention also provides the use of the environmentally friendly polyisocyanate composition described above in the preparation of coatings or adhesives.

[0022] The technical solution provided by this invention has the following beneficial effects:

[0023] The polyisocyanate composition of the present invention is prepared by reacting toluene diisocyanate with two or more diol compounds with different molecular weights between 400 and 3000. The diol with the lowest molecular weight is first reacted with toluene diisocyanate at a low temperature of 2-92°C, and then reacted with the remaining diol compounds with higher molecular weights at a high temperature of 98-180°C. The molar ratio R1 of the isocyanate group of toluene diisocyanate to the hydroxyl group of the diol compound with the lowest molecular weight is controlled to be 6-22. The polyisocyanate composition provided by the present invention has a viscosity suitable for application without the introduction of organic solvents during the preparation process, and can be directly used in downstream applications. Furthermore, the application of the polyisocyanate composition of the present invention in downstream coatings or adhesives helps to improve both drying and curing time and impact resistance. Detailed Implementation

[0024] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The term "and / or" may be used herein to include any and all combinations of one or more of the associated listed items.

[0026] This invention provides an environmentally friendly polyisocyanate composition, which is a terminal NCO product obtained by reacting materials including toluene diisocyanate and at least two diol compounds with different molecular weights; and the composition does not contain organic solvents and the content of free isocyanate monomers is <0.1wt%.

[0027] The number average molecular weight of the diol compound is between 400 and 3000 (e.g., 400, 500, 600, 800, 1000, 1500, 2000, 2500, 3000, etc.);

[0028] Furthermore, during the reaction, toluene diisocyanate is first reacted with the diol compound with the lowest molecular weight at 2-92°C (e.g., 2, 10, 30, 50, 80, 92°C, etc.), and then reacted with the remaining diol compounds at 98-180°C (e.g., 98°C, 110°C, 120°C, 135°C, 150°C, 160°C, 180°C, etc.).

[0029] The molar ratio R1 of the isocyanate group of the toluene diisocyanate to the hydroxyl group of the diol compound with the lowest molecular weight is 6-22, for example, 6, 8, 10, 12, 14, 16, 18, 20, 22, etc., preferably 6-20.

[0030] The polyisocyanate composition of the present invention involves reacting toluene diisocyanate with two or more diol compounds of different molecular weights between 400 and 3000 during its preparation. The diol with the lowest molecular weight is first reacted with toluene diisocyanate at a low temperature of 2-92°C, and then reacted with the remaining diol compounds with higher molecular weights at a high temperature of 98-180°C. The molar ratio R1 of the isocyanate group of toluene diisocyanate to the hydroxyl group of the diol compound with the lowest molecular weight is controlled to be 6-22. The polyisocyanate composition prepared by this method can directly yield a polyisocyanate composition suitable for downstream application. The preparation process does not require the introduction of organic solvents to adjust the viscosity. Moreover, the polyisocyanate composition obtained can be used in downstream coatings or adhesives, which is beneficial for improving both drying and curing time and impact resistance.

[0031] In this invention, the molar ratio R1 of the isocyanate group of toluene diisocyanate to the hydroxyl group of the diol compound with the lowest molecular weight is controlled at 6-22, preferably 6-20. The inventors have found that controlling the molar ratio R1 within this range allows the obtained polyisocyanate composition to achieve both good impact resistance and relatively fast drying and curing time in downstream applications. If the molar ratio R1 is too low, good impact resistance cannot be achieved, while if R2 is too high, the curing and drying time after the product is formulated into coatings or adhesives is too long. Furthermore, in this invention, the toluene diisocyanate is first reacted with the diol compound with the lowest molecular weight at 2-92°C. If the reaction temperature is too high, it is not conducive to obtaining good impact resistance.

[0032] In a preferred embodiment, the toluene diisocyanate is first reacted with the diol compound with the lowest molecular weight at 2-92°C for 1.5-300 h, for example 1.5 h, 10 h, 48 h, 60 h, 80 h, 100 h, 150 h, 200 h, 250 h, 288 h, 300 h, etc., preferably 3-300 h.

[0033] In a preferred embodiment, the molar ratio R2 of the isocyanate group of the toluene diisocyanate to the hydroxyl groups of all the diol compounds is 4-10, for example, 4, 6, 8, 10, etc., more preferably 4-9. Using this preferred molar ratio R2 is beneficial for further improving the application performance of the resulting isocyanate composition.

[0034] In some embodiments, the diol compound is selected from one or more of polyether diols, polyester diols, polycaprolactone diols, and polycarbonate diols, with polyether diols being preferred. Using preferred diols is beneficial for obtaining better impact resistance.

[0035] In some embodiments, the toluene diisocyanate is one or more of toluene-2,4-diisocyanate and toluene-2,6-diisocyanate, preferably toluene-2,4-diisocyanate.

[0036] In some embodiments, the remaining diol compound is a single diol compound, or includes two or more diol compounds with different molecular weights.

[0037] Preferably, when the remaining diol compound is a single diol compound, the remaining diol compound is added to the reaction system and the reaction continues at 98-180°C for 1-15 hours, such as 1 hour, 3 hours, 5 hours, 7 hours, 10 hours, 13 hours, 15 hours, etc., preferably 2.5-15 hours, and the reaction temperature is preferably 100-180°C.

[0038] Preferably, when the remaining diol compounds include two or more diol compounds with different molecular weights, the diol compounds of different molecular weights are added sequentially in order of increasing molecular weight. After each addition of a diol compound, the reaction is carried out at 98–180°C for 1–15 hours, followed by the addition of another diol compound and another 1–15 hours of reaction. The remaining diol compounds are added to the reaction system in the above order of addition and reaction. This preferred method helps to further improve impact resistance and shorten the drying and curing time. Preferably, the reaction temperature for each diol compound after addition is 100–180°C, and the reaction time is preferably 2.5–15 hours. More preferably, the remaining diol compounds are reacted at the same reaction temperature after addition.

[0039] In a preferred embodiment, the order of adding raw materials to the reaction system includes: first adding toluene diisocyanate, and then adding the diol compound with the lowest molecular weight to carry out the reaction.

[0040] Furthermore, in the preparation of the polyisocyanate composition, the reaction solution containing the NCO-terminated product obtained from the reaction is separated to remove unreacted isocyanate monomers. The separation temperature is 185–240°C, preferably 185–230°C; the separation pressure is 0.1–85 Pa, preferably 0.5–85 Pa; and the separation is preferably carried out by thin-film evaporation. Based on toluene diisocyanate, the polyisocyanate prepared according to this invention, after post-processing under the above separation conditions, can yield a polyisocyanate composition with ultra-low free monomer content (free isocyanate monomer content < 0.1 wt%).

[0041] Furthermore, no organic solvent is added during the preparation of the polyisocyanate composition; for example, the organic solvent includes, but is not limited to, one or more of toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methylcyclohexanone, cyclohexane, n-hexane, tetrahydrofuran, chlorobenzene, dichlorobenzene, dichloromethane, dichloroethane, 1,3-dioxane, methyl acetate, ethyl acetate, butyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, ethyl propionate, propyl propionate, and butyl propionate.

[0042] The environmentally friendly polyisocyanate composition provided by this invention has a viscosity of 4600-12000 cP at 23°C and does not contain organic solvents.

[0043] The present invention also provides the use of the environmentally friendly polyisocyanate composition described above in the preparation of coatings or adhesives, wherein the coating is, for example, a polyurethane coating.

[0044] The present invention will be further illustrated by specific embodiments below, but it should not be construed as the present invention being limited thereto.

[0045] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in this technical field can be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0046] The following test methods are used in the embodiments and comparative examples of this invention:

[0047] (1) Test method for the content of free unreacted isocyanate monomers: GB / T18446-2009, and the test was performed by Agilent GC-7890B gas chromatograph;

[0048] (2) NCO content: determined according to standard GB / T 12009.4-1989 using a Metrohm 905 potentiometric titrator;

[0049] (3) Viscosity test method: Dynamic mechanical viscosity was measured using a BrookField DV-IPrime viscometer with an S21 rotor at 23°C;

[0050] (4) Mechanical property test of coating: The polymer (i.e., polyisocyanate composition) is prepared into a coating according to the following "coating preparation method", and then aged in a high temperature environment (135~150℃, 45~55%RH) for 15h. The impact strength (positive impact) of the coating is tested according to GB / T1732-1993.

[0051] Coating preparation method: The prepared polymer and polyol (ACR7502, Tongde Chemical) are mixed at a ratio of 1.02 (NCO / OH) of isocyanate groups in the polymer to hydroxyl groups in polyol ACR7502. The mixture is then adjusted to a solid content of 50wt% using a mixed solvent (composition: ethyl acetate / butyl acetate = 1 / 1 / (mass ratio)) to obtain a polyurethane coating.

[0052] (5) Coating drying performance test: The polyisocyanate composition was prepared according to the above coating preparation method, and the actual drying time of the coating was tested.

[0053] Drying time test: The prepared polyurethane coating was applied to a glass plate (JIS R3202) test piece using a 100μm applicator. The center of the test piece was pinched firmly with the thumb and forefinger until no indentation caused by fingerprints was produced on the glass coating surface and no movement of the coating film was felt. In addition, the coating surface was rubbed quickly and repeatedly with the fingertips until no friction marks were produced (refer to JIS K 5600-1-1). The time elapsed at this point was recorded as an indicator of the evaluation results.

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

[0055] Toluene-2,4-diisocyanate (TDI): Wanhua Chemical, purity >99%;

[0056] PPG-400 (polyether diol): Wanhua Chemical, purity >99%;

[0057] PPG-1000 (polyether diol): Wanhua Chemical, purity >99%;

[0058] PPG-2000 (polyether diol): Wanhua Chemical, purity >99%;

[0059] PCL-2053 (polycaprolactone diol, number average molecular weight 530): Polyren New Materials, purity >99%;

[0060] Polyol: ACR7502, Tongde Chemical, purity >99%;

[0061] Unless otherwise specified, all other raw materials and reagents are available through commercial channels.

[0062] The reactions and separations in the following examples and comparative examples were all carried out in an environment with sufficient dry nitrogen.

[0063] Example 1

[0064] Preparation of polyisocyanate compositions:

[0065] Weigh 1800g of toluene-2,4-diisocyanate, add 906.61g of PPG-1000 to it, and add it completely over 4 hours. React in a water bath at 40°C for 19 hours while stirring. Then add 2296.74g of PPG-2000 to it, and add it completely over 3 hours. React in a water bath at 136°C for 6 hours to obtain a prepolymer reaction solution containing terminal NCO.

[0066] The reaction solution was separated from the residual isocyanate monomers using a thin-film evaporator under the following conditions: separation temperature 188℃, separation pressure 10Pa, and separation time 6min. The heavy components were collected to obtain the polyisocyanate composition.

[0067] In this embodiment, the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl group of PPG-1000 is 11.40, and the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl groups of all the diol compounds added during the reaction is 5.03.

[0068] Example 2

[0069] Preparation of polyisocyanate compositions:

[0070] Weigh 1800g of toluene-2,4-diisocyanate, add 689.02g of PPG-400 to it, and add it completely over 4 hours. React in a water bath at 18°C ​​for 151 hours while stirring. Then add 759.95g of PPG-1000 to it, and add it completely over 1 hour. React in a water bath at 130°C for 9 hours to obtain a prepolymer reaction solution containing terminal NCO.

[0071] The reaction solution was separated from the residual isocyanate monomer using a thin-film evaporator under the following conditions: separation temperature 190℃, separation pressure 0.5 Pa, and separation time 6 min. The heavy components were collected to obtain the polyisocyanate composition.

[0072] In this embodiment, the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl group of PPG-400 is 6.00, and the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl groups of all the diol compounds added during the reaction is 4.16.

[0073] Example 3

[0074] Preparation of polyisocyanate compositions:

[0075] Weigh 1800g of toluene-2,4-diisocyanate, add 311.54g of PPG-400 to it, and add it completely over 5 hours. React in a water bath at 25°C for 205 hours while stirring. Then add 2067.06g of PPG-2000 to it, and add it completely over 2 hours. React in a water bath at 115°C for 12 hours to obtain a prepolymer reaction solution containing terminal NCO.

[0076] The reaction solution was separated from the residual isocyanate monomers using a thin-film evaporator under the following conditions: separation temperature 185℃, separation pressure 20Pa, and separation time 7min. The heavy components were collected to obtain the polyisocyanate composition.

[0077] In this embodiment, the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl group of PPG-400 is 13.27, and the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl groups of all the diol compounds added during the reaction is 5.70.

[0078] Example 4

[0079] Preparation of polyisocyanate compositions:

[0080] Weigh 1800g of toluene-2,4-diisocyanate, add 276.65g of PCL-2053 to it, and add it completely over 5 hours. React in a water bath at 80°C for 49 hours while stirring. Then add 1148.37g of PPG-1000 to it, and add it completely over 5 hours. React in a water bath at 100°C for 15 hours to obtain a prepolymer reaction solution containing terminal NCO.

[0081] The reaction solution was separated from the residual isocyanate monomers using a thin-film evaporator under the following conditions: separation temperature 220℃, separation pressure 80Pa, and separation time 8min. The heavy components were collected to obtain the polyisocyanate composition.

[0082] In this embodiment, the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl group of PCL-2053 is 19.80, and the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl groups of all the diol compounds added during the reaction is 6.19.

[0083] Example 5

[0084] Preparation of polyisocyanate compositions:

[0085] Weigh 1800g of toluene-2,4-diisocyanate, add 266.72g of PPG-400 to it, and add it completely over 7 hours. React in a water bath at 90℃ for 76 hours while stirring. Then add 984.32g of PPG-2000 to it, and add it completely over 5 hours. React in an oil bath at 160℃ for 2.5 hours to obtain a prepolymer reaction solution containing terminal NCO.

[0086] The reaction solution was separated from the residual isocyanate monomers using a thin-film evaporator under the following conditions: separation temperature 230℃, separation pressure 60Pa, and separation time 12min. The heavy components were collected to obtain the polyisocyanate composition.

[0087] In this embodiment, the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl group of PPG-400 is 15.50, and the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl groups of all the diol compounds added during the reaction is 8.92.

[0088] Example 6

[0089] Preparation of polyisocyanate compositions:

[0090] Weigh 1800g of toluene-2,4-diisocyanate, add 510.39g of PPG-400 to it, and add it completely over 8 hours. React in a water bath at 75°C for 4 hours while stirring. Then add 421.85g of PPG-1000 to it, and add it completely over 3 hours. React in an oil bath at 175°C for 2.5 hours while stirring. Then add 1265.55g of PPG-2000 to it, and add it completely over 3 hours. React in an oil bath at 175°C for 2.5 hours to obtain a prepolymer reaction solution containing terminal NCO.

[0091] The reaction solution was separated from the residual isocyanate monomers using a thin-film evaporator under the following conditions: separation temperature 200℃, separation pressure 28Pa, and separation time 15min. The heavy components were collected to obtain the polyisocyanate composition.

[0092] In this embodiment, the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl group of PPG-400 is 8.10, and the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl groups of all the diol compounds added during the reaction is 4.43.

[0093] Example 7

[0094] Preparation of polyisocyanate compositions:

[0095] Weigh 1800g of toluene-2,4-diisocyanate, add 320.15g of PCL-2053 to it, and add it completely over 2 hours. React in a water bath at 60°C for 289 hours while stirring. Then add 671.80g of PPG-1000 to it, and add it completely over 6 hours. React in an oil bath at 150°C for 4 hours while stirring. Then add 723.47g of PPG-2000 to it, and add it completely over 6 hours. React in an oil bath at 150°C for 4 hours to obtain a prepolymer reaction solution containing terminal NCO.

[0096] The reaction solution was separated from the residual isocyanate monomer using a thin-film evaporator under the following conditions: separation temperature 196℃, separation pressure 43Pa, and separation time 5min. The heavy components were collected to obtain the polyisocyanate composition.

[0097] In this embodiment, the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl group of PCL-2053 is 17.11, and the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl groups of all the diol compounds added during the reaction is 6.31.

[0098] Example 8

[0099] Preparation of polyisocyanate compositions:

[0100] Weigh 1800g of toluene-2,4-diisocyanate, add 437.47g of PPG-400 over 6 hours, and react in a water bath at 56°C for 230 hours with stirring. Then add 147.48g of PCL-2053 over 3 hours, and react in an oil bath at 142°C for 3.5 hours with stirring. Next, add 198.76g of PPG-1000 over 3 hours, and react in an oil bath at 142°C for 3.5 hours with stirring. Finally, add 636.02g of PPG-2000 over 3 hours, and react in an oil bath at 142°C for 3.5 hours to obtain a prepolymer reaction solution containing terminal NCO.

[0101] The reaction solution was separated from the residual isocyanate monomers using a thin-film evaporator under the following conditions: separation temperature 185℃, separation pressure 3Pa, and separation time 10min. The heavy components were collected to obtain the polyisocyanate composition.

[0102] In this embodiment, the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl group of PPG-400 is 9.45, and the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl groups of all the diol compounds added during the reaction is 5.47.

[0103] Example 9 (compared to Example 6)

[0104] Preparation of polyisocyanate compositions:

[0105] Weigh 1800g of toluene-2,4-diisocyanate, add 510.39g of PPG-400 to it, and add it completely over 8 hours. React in a water bath at 75°C for 4 hours while stirring. Then add 421.85g of PPG-1000 and 1265.55g of PPG-2000 to it, and add them completely over 3 hours. React in an oil bath at 175°C for 2.5 hours to obtain a prepolymer reaction solution containing terminal NCO.

[0106] The reaction solution was separated from the residual isocyanate monomers using a thin-film evaporator under the following conditions: separation temperature 200℃, separation pressure 28Pa, and separation time 15min. The heavy components were collected to obtain the polyisocyanate composition.

[0107] In this embodiment, the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl group of PPG-400 is 8.10, and the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl groups of all the diol compounds added during the reaction is 4.43.

[0108] Comparative Example 1 (The amount of the lowest molecular weight diol compound added is different compared to Example 1)

[0109] Preparation of polyisocyanate compositions:

[0110] Weigh 1800g of toluene-2,4-diisocyanate, add 2296.74g of PPG-1000 to it, and add it completely over 4 hours. React in a water bath at 40°C for 19 hours while stirring. Then add 2296.74g of PPG-2000 to it, and add it completely over 3 hours. React in a water bath at 136°C for 6 hours to obtain a prepolymer reaction solution containing terminal NCO.

[0111] The reaction solution was separated from the residual isocyanate monomers using a thin-film evaporator under the following conditions: separation temperature 188℃, separation pressure 10Pa, and separation time 6min. The heavy components were collected to obtain the polyisocyanate composition.

[0112] In this comparative example, the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl group of PPG-1000 is 4.50, and the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl groups of all the diol compounds added during the reaction is 3.00.

[0113] Comparative Example 2 (the amount of the lowest molecular weight diol compound added is different compared to Example 1)

[0114] Preparation of polyisocyanate compositions:

[0115] Weigh 1800g of toluene-2,4-diisocyanate, add 397.51g of PPG-1000 to it, and add it completely over 4 hours. React in a water bath at 40°C for 19 hours while stirring. Then add 2296.74g of PPG-2000 to it, and add it completely over 3 hours. React in a water bath at 136°C for 6 hours to obtain a prepolymer reaction solution containing terminal NCO.

[0116] The reaction solution was separated from the residual isocyanate monomers using a thin-film evaporator under the following conditions: separation temperature 188℃, separation pressure 10Pa, and separation time 6min. The heavy components were collected to obtain the polyisocyanate composition.

[0117] In this comparative example, the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl group of PPG-1000 is 26.00, and the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl groups of all the diol compounds added during the reaction is 6.69.

[0118] Comparative Example 3 (compared to Example 1, only one type of diol was added)

[0119] Preparation of polyisocyanate compositions:

[0120] Weigh 1800g of toluene-2,4-diisocyanate, add 906.61g of PPG-1000 to it, and add it over 4 hours. React in a water bath at 40°C for 19 hours while stirring to obtain a prepolymer reaction solution containing terminal NCO.

[0121] The reaction solution was separated from the residual isocyanate monomers using a thin-film evaporator under the following conditions: separation temperature 188℃, separation pressure 10Pa, and separation time 6min. The heavy components were collected to obtain the polyisocyanate composition.

[0122] In this comparative example, the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl group of PPG-1000 is 11.40.

[0123] Comparative Example 4 (compared to Example 1, only one type of diol was added)

[0124] Preparation of polyisocyanate compositions:

[0125] Weigh 1800g of toluene-2,4-diisocyanate and add 2296.74g of PPG-2000 to it. The addition is completed in 3 hours. The mixture is reacted in a water bath at 40°C for 19 hours while being stirred to obtain a prepolymer reaction solution containing terminal NCO.

[0126] The reaction solution was separated from the residual isocyanate monomers using a thin-film evaporator under the following conditions: separation temperature 188℃, separation pressure 10Pa, and separation time 6min. The heavy components were collected to obtain the polyisocyanate composition.

[0127] In this comparative example, the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl group of PPG-2000 is 9.00.

[0128] Comparative Example 5 (compared to Example 1, the lowest molecular weight diol was not reacted at low temperatures)

[0129] Preparation of polyisocyanate compositions:

[0130] Weigh 1800g of toluene-2,4-diisocyanate, add 906.61g of PPG-1000, and add the rest over 4 hours. React in a water bath at 136℃ for 19 hours with stirring. Then add 2296.74g of PPG-2000, and add the rest over 3 hours. React in a water bath at 136℃ for 6 hours to obtain a prepolymer reaction solution containing terminal NCO.

[0131] The reaction solution was separated from the residual isocyanate monomers using a thin-film evaporator under the following conditions: separation temperature 188℃, separation pressure 10Pa, and separation time 6min. The heavy components were collected to obtain the polyisocyanate composition.

[0132] In this comparative example, the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl group of PPG-1000 is 11.40, and the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl groups of all the diol compounds added during the reaction is 5.03.

[0133] Comparative Example 6 (compared to Example 1, the molecular weight of the diol ranged from a minimum of less than 400 to a maximum of greater than 3000)

[0134] Preparation of polyisocyanate compositions:

[0135] Weigh 1800g of toluene-2,4-diisocyanate, add 81.70g of 1,4-butanediol to it, and add it completely over 4 hours. React in a water bath at 40°C for 19 hours while stirring. Then add 4019.29g of PPG-3500 to it, and add it completely over 3 hours. React in a water bath at 136°C for 6 hours to obtain a prepolymer reaction solution containing terminal NCO.

[0136] The reaction solution was separated from the residual isocyanate monomers using a thin-film evaporator under the following conditions: separation temperature 188℃, separation pressure 10Pa, and separation time 6min. The heavy components were collected to obtain the polyisocyanate composition.

[0137] In this comparative example, the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl group of 1,4-butanediol was 11.40, and the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl groups of all the diol compounds added during the reaction was 5.03.

[0138] Comparative Example 7 (Compared to Example 1, all diol compounds were added together for the reaction)

[0139] Preparation of polyisocyanate compositions:

[0140] Weigh 1800g of toluene-2,4-diisocyanate, add 906.61g of PPG-1000 and 2296.74g of PPG-2000 to it, and add them over 3 hours. Then react in a water bath at 136℃ for 6 hours to obtain a prepolymer reaction solution containing terminal NCO.

[0141] The reaction solution was separated from the residual isocyanate monomers using a thin-film evaporator under the following conditions: separation temperature 188℃, separation pressure 10Pa, and separation time 6min. The heavy components were collected to obtain the polyisocyanate composition.

[0142] In this comparative example, the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl group of PPG-1000 is 11.40, and the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl groups of all the diol compounds added during the reaction is 5.03.

[0143] Comparative Example 8

[0144] Preparation of polyisocyanate compositions:

[0145] Weigh 1800g of toluene-2,4-diisocyanate, add 906.61g of PPG-1000 to it, and add it completely over 4 hours. React in a water bath at 0°C for 19 hours while stirring. Then add 2296.74g of PPG-2000 to it, and add it completely over 3 hours. React in a water bath at 136°C for 6 hours to obtain a prepolymer reaction solution containing terminal NCO.

[0146] The reaction solution was separated from the residual isocyanate monomers using a thin-film evaporator under the following conditions: separation temperature 188℃, separation pressure 10Pa, and separation time 6min. The heavy components were collected to obtain the polyisocyanate composition.

[0147] In this comparative example, the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl group of PPG-1000 is 11.40, and the molar ratio of the isocyanate group of toluene-2,4-diisocyanate to the hydroxyl groups of all the diol compounds added during the reaction is 5.03.

[0148] The test results of the content of free unreacted isocyanate monomers (corresponding to "monomers" in Table 1) and viscosity in the polyisocyanate compositions prepared in each example and comparative example are shown in Table 1; the impact resistance and drying time of the polyisocyanate compositions prepared in each example and comparative example after being formulated into polyurethane coatings are shown in Table 1.

[0149] Table 1. Basic Indicators and Performance Test Results of Examples and Comparative Examples

[0150]

[0151] As can be seen from the above experimental results, the present invention uses at least two diols with different molecular weights ranging from 400 to 3000 to react with toluene diisocyanate. During the reaction, toluene diisocyanate is first reacted with the diol compound with the lowest molecular weight at 2-92°C, and then reacted with the remaining diol compounds at 98-180°C. The molar ratio R1 of the isocyanate group of toluene diisocyanate to the hydroxyl group of the diol compound with the lowest molecular weight is controlled to be 6-22. This allows for the production of a polyisocyanate composition with a viscosity of 4600-12000 cP suitable for downstream application without the addition of any organic solvents. Furthermore, the polyurethane coating prepared based on this polyisocyanate composition can achieve a balance between relatively fast drying and curing time and good impact resistance.

[0152] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An environmentally friendly polyisocyanate composition, characterized in that, This composition is a terminal NCO product obtained by reacting materials including toluene diisocyanate and at least two diol compounds with different molecular weights and number average molecular weights of 400-3000; furthermore, no organic solvent is added during the preparation of the composition, and the free isocyanate monomer content is <0.1 wt%. Furthermore, during the reaction, the toluene diisocyanate is first reacted with the diol compound with the lowest molecular weight at 18-92°C, and then reacted with the remaining diol compounds at 98-180°C. The molar ratio R1 of the isocyanate group of the toluene diisocyanate to the hydroxyl group of the diol compound with the lowest molecular weight is 6-22.

2. The environmentally friendly polyisocyanate composition according to claim 1, characterized in that, The molar ratio R1 of the isocyanate group of the toluene diisocyanate to the hydroxyl group of the diol compound with the lowest molecular weight is 6-20.

3. The environmentally friendly polyisocyanate composition according to claim 1, characterized in that, The molar ratio R2 of the isocyanate group of the toluene diisocyanate to the hydroxyl groups of all the diol compounds is 4-10.

4. The environmentally friendly polyisocyanate composition according to claim 3, characterized in that, The molar ratio R2 of the isocyanate group of the toluene diisocyanate to the hydroxyl groups of all the diol compounds is 4-9.

5. The environmentally friendly polyisocyanate composition according to any one of claims 1-4, characterized in that, The diol compound is selected from one or more of polyether diols, polyester diols, polycaprolactone diols, and polycarbonate diols; And / or, the toluene diisocyanate is one or more of toluene-2,4-diisocyanate and toluene-2,6-diisocyanate.

6. The environmentally friendly polyisocyanate composition according to claim 5, characterized in that, The diol compound is selected from polyether diols; And / or, the toluene diisocyanate is toluene-2,4-diisocyanate.

7. The environmentally friendly polyisocyanate composition according to any one of claims 1-4, characterized in that, The toluene diisocyanate is first reacted with the diol compound with the lowest molecular weight at 18-92°C for 1.5-300 h.

8. The environmentally friendly polyisocyanate composition according to claim 7, characterized in that, The toluene diisocyanate is first reacted with the diol compound with the lowest molecular weight at 18-92°C for 3-300 h.

9. The environmentally friendly polyisocyanate composition according to claim 7, characterized in that, The remaining diol compounds are one diol compound, or include two or more diol compounds with different molecular weights.

10. The environmentally friendly polyisocyanate composition according to claim 9, characterized in that, When the remaining diol compound is a single diol compound, the remaining diol compound is added to the reaction system and reacted at 98~180℃ for 1-15 hours.

11. The environmentally friendly polyisocyanate composition according to claim 10, characterized in that, When the remaining diol compound is a single diol compound, the remaining diol compound is added to the reaction system and reacted at 98~180°C for 2.5~15 hours.

12. The environmentally friendly polyisocyanate composition according to claim 10, characterized in that, When the remaining diol compound is a single diol compound, the remaining diol compound is added to the reaction system and reacted at 100~180°C.

13. The environmentally friendly polyisocyanate composition according to claim 9, characterized in that, When the remaining diol compounds include two or more diol compounds with different molecular weights, the various diol compounds with different molecular weights are added in order of increasing molecular weight. After each diol compound with a molecular weight is added, it is reacted at 98~180℃ for 1-15 hours, and then another diol compound with a molecular weight is added and the reaction continues for another 1-15 hours.

14. The environmentally friendly polyisocyanate composition according to claim 13, characterized in that, When the remaining diol compounds include two or more diol compounds with different molecular weights, the reaction temperature after feeding the remaining diol compounds with different molecular weights is 100~180℃ and the reaction time is 2.5~15h.

15. The environmentally friendly polyisocyanate composition according to claim 14, characterized in that, When the remaining diol compounds include two or more diol compounds with different molecular weights, the remaining diol compounds of various molecular weights are reacted at the same reaction temperature after being fed into the reactor.

16. The environmentally friendly polyisocyanate composition according to any one of claims 1-4, characterized in that, The order of adding raw materials to the reaction system includes: first adding toluene diisocyanate, and then adding the diol compound with the lowest molecular weight to carry out the reaction.

17. The environmentally friendly polyisocyanate composition according to any one of claims 1-4, characterized in that, The reaction solution containing the terminal NCO product obtained from the reaction is separated to remove unreacted isocyanate monomers. The separation temperature is 185~240℃ and the separation pressure is 0.1~85Pa.

18. The environmentally friendly polyisocyanate composition according to claim 17, characterized in that, The separation temperature is 185~230℃, and the separation pressure is 0.5~85Pa.

19. The environmentally friendly polyisocyanate composition according to claim 17, characterized in that, The separation is performed using thin-film evaporation.

20. The environmentally friendly polyisocyanate composition according to any one of claims 1-4, characterized in that, The organic solvent includes one or more of toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclohexane, n-hexane, tetrahydrofuran, chlorobenzene, dichlorobenzene, dichloromethane, dichloroethane, 1,3-dioxane, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, ethyl propionate, propyl propionate, and butyl propionate.

21. The environmentally friendly polyisocyanate composition according to any one of claims 1-4, characterized in that, The viscosity of the polyisocyanate composition at 23°C is 4600~12000 cP.

22. Use of the environmentally friendly polyisocyanate composition according to any one of claims 1-21 in the preparation of coatings or adhesives.

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