Preparation method of aromatic isocyanate dimer
By controlling the crystal size and monomer conversion rate during the preparation of aromatic isocyanate dimers, and by using high-speed shearing and terminator treatment, the problem of polymer contamination in the dimerization of aromatic isocyanates was solved, and the efficient preparation of high-purity urea diketone was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WANHUA CHEM GRP CO LTD
- Filing Date
- 2024-11-12
- Publication Date
- 2026-05-12
AI Technical Summary
In the existing process of aromatic isocyanate dimerization, the urea diketone product contains a large number of polymers and monomers, which affects the purity of the product and requires secondary recrystallization for purification, increasing the difficulty of the process and production investment.
Aromatic isocyanate dimers were prepared in the presence of tertiary phosphine catalysts. High-speed shear stirring was used to control the crystal particle size when crystals precipitated in the reaction system. The conversion rate of aromatic diisocyanate monomers was controlled by adding a terminator at the appropriate time. After filtration and vacuum drying, high-purity aromatic isocyanate dimers were obtained.
It significantly improves the purity of diurea, reduces the polymer level, and achieves a product purity of over 98%, while simplifying the purification process.
Abstract
Description
Technical Field
[0001] This invention relates to an isocyanate dimer, and more particularly to a method for preparing an aromatic isocyanate dimer. Background Technology
[0002] Polyisocyanates, prepared by polymerizing diisocyanate monomers, can effectively reduce the hazards of volatile isocyanate monomers through isocyanate self-polymerization, resulting in structures such as urea diketone, trimers, and iminooxadiazine diketone. Polyisocyanate compositions can be used in a variety of applications, such as vulcanizing auxiliaries, textile accelerators, coatings, and adhesives. In their free state, they are highly reactive, water-sensitive, and readily polymerizable. A useful method for using these materials has been found to be first converting them into isocyanate dimers. Due to their different reactivity, aromatic and aliphatic isocyanate dimers have specific applications in different fields.
[0003] The production of urea diketone by catalyzing the reaction of two isocyanate groups using a dimerizing catalyst (such as tertiary phosphine) is known. However, in many cases, this also results in the formation of higher polymers with more isocyanate groups (hereinafter referred to as "polymers"), reducing the yield of urea diketone. In particular, when aromatic urea diketones are rapidly removed from the reaction medium due to their physical form (e.g., through precipitation), the urea diketone product will contain more polymers and monomers, affecting product purity.
[0004] Patent US2671082A converts isocyanates into addition products containing two isocyanate groups in good yield by contacting aromatic isocyanates with a catalytic amount of a mixed aromatic-aliphatic tertiary phosphine catalyst at a temperature of 0 to 60°C. This method does not require careful control to prevent the formation of undesirable byproducts such as isocyanurates. However, the resulting product still requires secondary recrystallization for purification, increasing the process complexity and production investment. Summary of the Invention
[0005] To address the above technical problems, this invention proposes a method for preparing aromatic isocyanate dimers, which can rapidly obtain products with high urea diketone content and effectively reduce polymer levels.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0007] A method for preparing an aromatic isocyanate dimer, specifically by reacting an aromatic diisocyanate in the presence of a tertiary phosphine catalyst;
[0008] Once crystals begin to precipitate in the reaction system, the crystal particle size is controlled to be 10 μm or less, preferably 0.5-10 μm, by high-speed shear stirring; when the content of aromatic diisocyanate monomer is reduced to 20-80% of the initial content, preferably 30-70%, a terminator is added to terminate the reaction.
[0009] The solid was obtained by filtration and then vacuum dried to remove free monomers and optionally solvents from the solid, thus preparing an aromatic isocyanate dimer.
[0010] This invention controls the crystal particle size in the reaction system by high-speed shear stirring and simultaneously adjusts the conversion rate of aromatic diisocyanate monomers, which can effectively reduce the level of polymers in the product and thus significantly improve the purity of diurea.
[0011] As some preferred examples of the present invention, the aromatic diisocyanate is one or more of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophenyl dimethyl isocyanate (XDI), and dimethyl biphenyl diisocyanate (TODI).
[0012] As some preferred examples of the present invention, the tertiary phosphine catalyst is one or more of trimethylphosphine, triethylphosphine, tripropylphosphine, tri(dimethylamino)phosphine, triisopropylphosphine, tri-n-butylphosphine, tri-tert-butylphosphine, dicyclopentylbutylphosphine, tripentylphosphine, tricyclopentylphosphine, trihexylphosphine, triphenylphosphine, tribenzylphosphine, benzyldimethylphosphine, tricyclohexylphosphine, and tri-n-octylphosphine, more preferably tributylphosphine and / or tri-n-octylphosphine;
[0013] Preferably, the amount of the tertiary phosphine catalyst is 0.001-0.1 wt% of the aromatic diisocyanate, more preferably 0.002-0.05 wt%. If the amount of tertiary phosphine catalyst is greater than 0.1 wt%, the catalytic reaction rate is faster, which easily promotes the formation of more polymers and encapsulates them in the precipitated crystals, reducing the content of urea diketone; while when the catalyst concentration is less than 0.001 wt%, it is difficult to produce precipitable solids or the reaction does not occur during the reaction.
[0014] As some preferred examples of the present invention, the reaction is carried out optionally in the presence of an alcohol co-catalyst; the alcohol co-catalyst is a monohydric or polyhydric alcohol with a relative molecular weight of 32-200, preferably one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-hexanol, octanol, 2-ethyl-1-hexanol, ethylene glycol, propylene glycol, isomeric butanediol, pentanediol, neopentanediol, hexanediol, octanediol, diethylene glycol, 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, glycerol, and trimethylolpropane; the introduction of an alcohol co-catalyst is beneficial to increasing the reaction rate and reducing the amount of tertiary phosphine catalyst used in the reaction.
[0015] Preferably, the alcohol co-catalyst and the tertiary phosphine catalyst are mixed into a solution and then added together to the reaction system, with the amount of alcohol co-catalyst being such that the mass concentration of the tertiary phosphine catalyst in the solution is 5-20 wt%.
[0016] As some preferred examples of the present invention, the reaction is carried out in the presence or absence of a solvent; the solvent is one or more of the following: reactive aromatic hydrocarbons, aliphatic hydrocarbons or their halogenated derivatives, ketones, esters, and amides, preferably one or more of benzene, toluene, xylene, chlorobenzene, o-dichlorobenzene, ethyl acetate, butyl acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, dimethylformamide, dimethylacetamide, acetone, methyl butyl ketone, methyl isobutyl ketone, and cyclohexanone, with benzene, toluene, and xylene being particularly preferred reaction solvents.
[0017] When carrying out the dimerization reaction in this invention, the reaction must be stopped when the mixture reaches the specified aromatic diisocyanate content. Preferably, when the concentration of diisocyanate monomer is 20-80% of the initial amount added, preferably 30-70%, a terminator is added to stop the reaction.
[0018] As some preferred examples of the present invention, the terminating agent is selected from alkylating agents, acyling agents, organic acids, and preferably one or more of dimethyl sulfate, methyl p-toluenesulfonate, benzoyl chloride, p-toluenesulfonyl chloride, phosphoric acid, phosphate ester, sulfonic acid, and sulfonate ester;
[0019] Preferably, the amount of the terminator is 80-150 mol% of the molar amount of the tertiary phosphine catalyst.
[0020] As some preferred examples of the present invention, the reaction temperature is 0-30°C.
[0021] As some preferred examples of the present invention, in the preparation method, a self-absorbing high-speed mixing and shearing device is used to control the crystal particle size to be 10 μm or less; the suitable stirring speed is 600-10000 rpm, preferably 1000-5000 rpm;
[0022] Preferably, the material self-priming high-speed mixing and shearing device is selected from Ika Digital T25, Ika Digital T50 or Yekeey ZJR-5 / 10.
[0023] As some preferred examples of the present invention, the process parameters for vacuum drying are: temperature 30-120℃, vacuum degree 10-500Pa.
[0024] As some preferred examples of the present invention, the obtained aromatic isocyanate dimer has a diisocyanate monomer content of <0.5wt%, a solvent content of <0.5wt%, and a polymer content of <2wt%.
[0025] This invention, by controlling the crystal particle size during the reaction process and simultaneously controlling the conversion rate of aromatic diisocyanate monomers within a certain range, can effectively reduce the content of polymers in the product, achieving a urea diketone purity of over 98%. Detailed Implementation
[0026] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.
[0027] The following testing method is used in the embodiments of the present invention:
[0028] (1) Component content test:
[0029] The raw materials were quantified using gel permeation chromatography (LC-20AD / RID-10A, with MZ-Gel SD plus 10E3A, 5μm (8.0*300mm), MZ-Gel SD plus 500A, 5μm (8.0*300mm), and MZ-Gel SD plus 100A, 5μm (8.0*300mm) in series, Shimadzu; mobile phase: tetrahydrofuran; flow rate: 1.0 mL / min; analysis time: 40 min; column temperature: 35℃). The content of diisocyanate monomers, dimers, and polymers in the system was determined by the area normalization method.
[0030] (2) Average particle size measurement
[0031] Equipment: Malvern Mastersizer 3000E laser particle size analyzer, four-way cuvette, Malvern Panaco; Test method: temperature 25℃, number of scans 3;
[0032] (3) Solvent content test
[0033] The determination was performed by gas chromatography. The analytical conditions were as follows: column: DB-5MS (30m*0.25mm*0.25μm) or equivalent stationary phase size; injection volume: 0.2μL; split ratio: 30:1; injection port temperature: 280℃; carrier gas (N2) flow rate: 1.0mL / min; temperature program: 50℃ for 2 min, then ramped to 200℃ at 15℃ / min and held for 10 min; FID detector temperature: 300℃; hydrogen flow rate: 40mL / min; air flow rate: 400mL / min. Sample preparation: 0.5g of sample was placed in a 20ml glass vial, diluted to 10g with dichloromethane, and the vial was tightly capped and thoroughly mixed.
[0034] The main raw materials used in the following embodiments are as follows:
[0035] 2,4-TDI: Wanhua Chemical, purity > 99%;
[0036] 2,6-TDI: Wanhua Chemical, purity >99%;
[0037] MDI: Wanhua Chemical, purity > 99%;
[0038] XDI: Aladdin, purity > 99%;
[0039] n-Butanol: Aladdin reagent, purity > 99%;
[0040] Ethylene glycol: Aladdin, purity > 98%;
[0041] Isooctyl alcohol: Aladdin, purity >98%
[0042] Tri-n-octylphosphine: Sigma reagent, purity >90%;
[0043] Tri-n-butylphosphine: TCI, purity 95%;
[0044] Tris(dimethylamino)phosphine: Aladdin, purity > 97%;
[0045] Diisooctyl phosphate: Aladdin reagent, purity > 99%;
[0046] Phosphoric acid: Aladdin reagent, 98% purity;
[0047] Benzoyl chloride: Aladdin reagent, purity 98%;
[0048] Methyl p-toluenesulfonate: Aladdin, 98% purity
[0049] Toluene: Aladdin reagent, 99% purity;
[0050] Benzene: Aladdin, 99% purity;
[0051] Butyl acetate: Aladdin reagent, 99% purity.
[0052] Chlorobenzene: Aladdin reagent, purity > 99%.
[0053] Unless otherwise specified in the following examples and comparative examples, the reaction solution was kept under dry nitrogen protection from the time the catalyst was added until the start of the reaction and throughout the entire reaction process. During the reaction, an IkaDigital T50 emulsifier was used to control the crystal particle size.
[0054]
Example 1
[0055] 1200g of 2,4-TDI and 2800g of toluene were mixed at room temperature. 8g of 10wt% tributylphosphine / n-butanol was added as a catalyst. After mixing and dispersing, the system became turbid after about 30 minutes. The reaction temperature was lowered to 10℃, and the stirring speed of the emulsifier was increased to 2000rpm. When the TDI monomer content in the system decreased to 60% of the initial content, the crystal particle size in the turbid liquid was monitored to be 7.3μm. Diisooctyl phosphate with an equimolar amount of tributylphosphine was added, and the mixture was reacted for 30 minutes. After filtration, the product was vacuum dried at 60℃ and 100pa for 3 hours to obtain the urea diketone dimer product.
[0056] The dimer properties prepared in this embodiment are as follows:
[0057] Ureadione: 98.8 wt%
[0058] TDI monomer: 0.2wt%
[0059] Toluene: 0.3 wt%
[0060] Other components (mainly polymers): 0.7 wt%
[0061]
Example 2
[0062] 1200g of XDI and 4800g of benzene were mixed at room temperature. 3g of 20wt% trioctylphosphine / methanol was added as a catalyst. After mixing and dispersion, the system became turbid after about 75 minutes. The reaction temperature was lowered to 0℃ and the stirring speed of the emulsifier was increased to 5000rpm. When the XDI monomer content in the system dropped to 80% of the initial content, the crystal particle size in the turbid liquid was monitored to be 0.7μm. Phosphoric acid with a molar amount of 90mol% of trioctylphosphine was added, and the mixture was mixed and reacted for 30 minutes. The mixture was filtered and dried under vacuum at 80℃ and 400pa for 4 hours to obtain the urea diketone dimer product.
[0063] The dimer properties prepared in this embodiment are as follows:
[0064] Ureadione: 99.3 wt%
[0065] XDI monomer: 0.2wt%
[0066] Benzene: 0.1 wt%
[0067] Other components (mainly polymers): 0.4 wt%
[0068]
Example 3
[0069] 1200g MDI and 1200g ethyl acetate were mixed at room temperature, and 9.6g of 20wt% tris(dimethylamino)phosphine / ethylene glycol was added as a catalyst. After mixing and dispersion, the system became turbid after about 120min. The reaction temperature was lowered to 5℃, and the stirring speed of the emulsifier was increased to 4000rpm. When the MDI monomer content in the system decreased to 20% of the initial content, the crystal particle size in the turbid liquid was monitored to be 9.7μm. Benzoyl chloride with an equimolar amount of tris(dimethylamino)phosphine was added, and the mixture was reacted for 30min. After filtration, the product was vacuum dried at 50℃ and 20pa for 3h to obtain the urea diketone dimer product.
[0070] The dimer properties prepared in this embodiment are as follows:
[0071] Ureadione: 98.1 wt%
[0072] MDI monomer: 0.1 wt%
[0073] Ethyl acetate: 0.2 wt%
[0074] Other components (mainly polymers): 1.6 wt%
[0075]
Example 4
[0076] 1200g of 2,6-TDI and 10800g of chlorobenzene were mixed at room temperature. 2.4g of 20wt% trioctylphosphine / isooctanol was added as a catalyst. After mixing and dispersion, the system became turbid after about 40 minutes. The reaction temperature was lowered to 20℃ and the stirring speed of the emulsifier was increased to 4000rpm. When the TDI monomer content in the system decreased to 70% of the initial content, the crystal particle size in the turbid liquid was monitored to be 5.6μm. 120mol% of methyl p-toluenesulfonate of trioctylphosphine was added, and the mixture was reacted for 30 minutes. The mixture was filtered and dried under vacuum at 50℃ and 100pa for 3 hours to obtain the urea diketone dimer product.
[0077] The dimer properties prepared in this embodiment are as follows:
[0078] Ureadione: 99.4 wt%
[0079] TDI monomer: 0.25wt%
[0080] Chlorobenzene: 0.1 wt%
[0081] Other components (mainly polymers): 0.25 wt%
[0082]
Example 5
[0083] 1200g of 2,4-TDI and 2800g of toluene were mixed at room temperature. 8g of 10wt% tributylphosphine / n-butanol was added as a catalyst. After mixing and dispersing, the system became turbid after about 30 minutes. The reaction temperature was lowered to 10℃, and the stirring speed of the emulsifier was increased to 2000rpm. When the TDI monomer content in the system decreased to 30% of the initial content, the crystal particle size in the turbid liquid was monitored to be 8.2μm. Diisooctyl phosphate with an equimolar amount of tributylphosphine was added, and the mixture was reacted for 30 minutes. After filtration, the product was vacuum dried at 60℃ and 100pa for 3 hours to obtain the urea diketone dimer product.
[0084] The dimer properties prepared in this embodiment are as follows:
[0085] Ureadione: 98.2 wt%
[0086] TDI monomer: 0.2wt%
[0087] Toluene: 0.2 wt%
[0088] Other components (mainly polymers): 1.4 wt%
[0089] Comparative Example 1
[0090] Urea diketone dimer was prepared using a method essentially the same as in Example 1, except that after the system became turbid, the emulsifier speed was maintained at 200 rpm for stirring. When the TDI monomer content in the system dropped to 60% of the initial content, the crystal particle size in the turbid liquid was monitored to be 28 μm.
[0091] The dimer properties prepared in this comparative example are as follows:
[0092] Ureadione: 89.2 wt%
[0093] TDI monomer: 2.3 wt%
[0094] Toluene: 0.5 wt%
[0095] Other components (mainly polymers): 8.0 wt%
[0096] Comparative Example 2
[0097] Urea diketone dimer was prepared using a method essentially the same as in Example 1, except that the stirring speed of the emulsifier was maintained at 2000 rpm, and the reaction was terminated when the TDI monomer content in the system dropped to 15% of the initial content. At this point, the crystal particle size in the reaction solution was 9.8 μm.
[0098] The dimer properties prepared in this comparative example are as follows:
[0099] Ureadione: 75.9 wt%
[0100] TDI monomer: 0.7wt%
[0101] Toluene: 0.6 wt%
[0102] Other components (mainly polymers): 22.8 wt%
[0103] Comparative Example 3
[0104] Urea diketone dimer was prepared using a method essentially the same as in Example 1, except that the stirring speed of the emulsifier was adjusted to 2000 rpm, and the reaction was terminated when the TDI monomer content in the system dropped to 85% of the initial content. At this point, the crystal particle size in the reaction solution was 0.3 μm.
[0105] The dimer properties prepared in this comparative example are as follows:
[0106] Ureadione: 82.5 wt%
[0107] TDI monomer: 11.7 wt%
[0108] Toluene: 0.5 wt%
[0109] Other components (mainly polymers): 5.3 wt%
[0110] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing an aromatic isocyanate dimer, characterized in that, It is prepared by reacting aromatic diisocyanates in the presence of a tertiary phosphine catalyst; Once crystals begin to precipitate in the reaction system, the crystal particle size is controlled to be 10 μm or less, preferably 0.5-10 μm, by high-speed shear stirring; when the content of aromatic diisocyanate monomer is reduced to 20-80% of the initial content, preferably 30-70%, a terminator is added to terminate the reaction. The solid was obtained by filtration and then vacuum dried to remove free monomers and optionally solvents from the solid, thus preparing an aromatic isocyanate dimer.
2. The method for preparing the aromatic isocyanate dimer according to claim 1, characterized in that, The aromatic diisocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophenyl dimethyl isocyanate, and dimethyl biphenyl diisocyanate.
3. The method for preparing the aromatic isocyanate dimer according to claim 1, characterized in that, The tertiary phosphine catalyst is one or more selected from trimethylphosphine, triethylphosphine, tripropylphosphine, tri(dimethylamino)phosphine, triisopropylphosphine, tri-n-butylphosphine, tri-tert-butylphosphine, dicyclopentylbutylphosphine, tripentylphosphine, tricyclopentylphosphine, trihexylphosphine, triphenylphosphine, tribenzylphosphine, benzyldimethylphosphine, tricyclohexylphosphine, and tri-n-octylphosphine. Preferably, the amount of the tertiary phosphine catalyst is 0.001-0.1 wt% of the aromatic diisocyanate, more preferably 0.002-0.05 wt%.
4. The method for preparing the aromatic isocyanate dimer according to any one of claims 1-3, characterized in that, The reaction is carried out in the presence of an alcohol co-catalyst, wherein the alcohol co-catalyst is a monohydric or polyhydric alcohol with a relative molecular weight of 32-200, preferably one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-hexanol, octanol, 2-ethyl-1-hexanol, ethylene glycol, propylene glycol, isomeric butanediol, pentanediol, neopentanediol, hexanediol, octanediol, diethylene glycol, 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, glycerol, and trimethylolpropane; Preferably, the alcohol co-catalyst and the tertiary phosphine catalyst are mixed into a solution and then added together to the reaction system, with the amount of alcohol co-catalyst being such that the mass concentration of the tertiary phosphine catalyst in the solution is 5-20 wt%.
5. The method for preparing the aromatic isocyanate dimer according to any one of claims 1-4, characterized in that, The solvent is one or more of the following: reactive aromatic hydrocarbons, aliphatic hydrocarbons or their halogenated derivatives, ketones, esters, and amides; preferably benzene, toluene, xylene, chlorobenzene, o-dichlorobenzene, ethyl acetate, butyl acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, dimethylformamide, dimethylacetamide, acetone, methyl butyl ketone, methyl isobutyl ketone, and cyclohexanone.
6. The method for preparing the aromatic isocyanate dimer according to any one of claims 1-5, characterized in that, The terminator is selected from alkylating agents, acyling agents, and organic acids, preferably one or more of dimethyl sulfate, methyl p-toluenesulfonate, benzoyl chloride, p-toluenesulfonyl chloride, phosphoric acid, phosphate ester, sulfonic acid, and sulfonate ester; Preferably, the amount of the terminator is 80-150 mol% of the molar amount of the tertiary phosphine catalyst.
7. The method for preparing the aromatic isocyanate dimer according to any one of claims 1-6, characterized in that, The reaction temperature is 0-30℃.
8. The method for preparing the aromatic isocyanate dimer according to any one of claims 1-7, characterized in that, In the preparation method, a self-absorbing high-speed mixing and shearing device is used to control the crystal particle size to 10 μm or less. Preferably, the material self-priming high-speed mixing and shearing device is selected from Ika Digital T25, Ika Digital T50 or Yekeey ZJR-5 / 10.
9. The method for preparing the aromatic isocyanate dimer according to any one of claims 1-8, characterized in that, The process parameters for vacuum drying are: temperature 30-120℃, vacuum degree 10-500Pa.
10. The method for preparing the aromatic isocyanate dimer according to any one of claims 1-9, characterized in that, The obtained aromatic isocyanate dimer contains less than 0.5 wt% diisocyanate monomer, less than 0.5 wt% solvent, and less than 2 wt% polymer.