JPH1072428A - Method for producing isocyanate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an isocyanate in improved final yield and excellent operability by producing a urethane from a raw material under specific condition and converting the urethane into isocyanate without separating from the reaction mixture. SOLUTION: The objective isocyanate of formula IV can be produced by reacting (A) an amine of formula I (R<1> is a uni-to trivalent organic group; (n) is 1-3) with (B) a halogenated formate in the presence of (C) a basic compound, adding (D) a halogenated organic silicon compound, preferably a compound of formula II (R<2> to R<4> are each an alkyl, an aryl, etc.; X is a halogen) or (E) a halogenated organic boron compound, preferably a compound of formula III and reacting the compounds. The component C is preferably a t-amine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an isocyanate, and more particularly to a method for producing an isocyanate using an amine without isolating an intermediate urethane.

[0002]

2. Description of the Related Art Conventionally, as a method for producing an isocyanate, there is known a method in which phosgene, diphenyl carbonate, or carbonyldiimidazole is allowed to act on a corresponding amine, or a method in which a carboxylic acid is produced by Curtius rearrangement. Further, a method in which a corresponding diamine compound is once converted into urethane by using a halogenated alkyl formate or a halogenated aryl formate and chlorosilane is used as a catalyst (G. Greber, e.
t. al., Angew. Int. Ed., Vol. 7. No. 12. 941 (196
8)) and the method using catechol borane (VLK Vall
According to i, et. al., J. Org. Chem., Vol. 60.257 (1995)), there is a method in which urethane is thermally decomposed and isocyanated.

[0003] Among them, the method using phosgene is harmful to the human body, and it is preferable to produce isocyanate without using it. On the other hand, in the production method using urethane as a raw material, it is necessary to purify the urethane after synthesizing the urethane from the amine, which increases the number of steps and is not preferable for industrial use. Another problem is that high heat is required for thermal decomposition and that there are many side reactions.

[0004]

Objects and Summary of the Invention The present inventors have conducted various studies on a method for producing an isocyanate using an amine as a raw material. As a result, by performing isocyanation without isolating urethane obtained from the raw material amine under specific conditions, surprisingly, the final yield is improved as compared with urethane formation and isocyanation sequentially, In addition, the inventors have found that they have excellent operability and completed the present invention.

According to the present invention,

Embedded image (R ₁ is an organic group having ₁ to 3 valences, n is an integer of 1 to 3), and in the presence of a basic compound, the following formula

Embedded image (R ₁ and n are the same as above) by reacting an amine represented by the formula (I) with a halogenated formate, and adding an organic silicon halide compound or an organic boron halide compound to the reaction mixture to carry out the reaction. Is provided.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The isocyanate of the present invention is prepared by reacting a corresponding amine with a halogenated formate in the presence of a basic compound, and then adding an organic silicon halide compound or a halogenated organic boron compound as a catalyst. can get.

[Production of urethane] (Amine) As the raw material amine, most of aliphatic and aromatic amines can be used. For example, aniline, methyl aniline, 2,4- or 2,6-diaminotoluene,
Hexamethylenediamine, isophoronediamine, methylcyclohexanediamine, xylylenediamine, isopropylidenebis (4-cyclohexylamine), methylenebis (4-cyclohexylamine), 2,2,4-trimethylhexamethylenediamine, naphthalenediamine, diaminodiphenylmethane, Diaminodiphenyl ether,
3,3′-dimethyl-4,4′-biphenyldiamine, 4,
4'-diamino-2,2'-dimethyl or bis (trifluoromethyl) biphenyl, 1,3- or 1,4-bis (4-aminophenoxy) benzene, 2,2-bis (4-
Aminophenoxyphenyl) propane, 2,2-bis (4
-Aminophenoxyphenyl) hexafluoropropane, 3,3'- or 4,4'-bis (aminophenoxy) diphenylsulfone, triphenylmethanetriaminetris (aminophenyl) thiophosphate, etc. This is not the case.

[0008] The amine concentration in the reaction solution is 1 to 50%, preferably 5 to 40%, and most preferably 10 to 30%. If the concentration is too low, the reaction requires time, which is not practical.
If the concentration is too high, an undesirable side reaction may be caused.

[0009]

Embedded image

[0010]

Embedded image

[0011]

Embedded image

(Halogenated formate) Next, the corresponding amine is reacted with a chloroformate such as methyl chloroformate, ethyl chloroformate, phenyl chloroformate, p-nitrophenyl chloroformate to form an intermediate. Synthesize urethane. Of these, phenyl chloroformate or p-nitrophenyl chloroformate is preferred in order to obtain urethane sufficiently activated to obtain isocyanate. The amount of these formates to be used is 0.8 to 2.
0 equivalent, preferably 1.0 to 1.8 equivalent.

(Basic Compound) In the urethanization, a basic compound is added. An organic base or an inorganic base can be used as a basic compound when either organic silicon or organic boron is used for isocyanation after urethanization, but an organic base is more preferable in terms of solubility in a solvent. Furthermore, tertiary amines such as triethylamine and pyridine are suitable because they do not inhibit the reaction among organic bases. Primary amines and secondary amines are not preferred because they have active hydrogen and may react with the generated isocyanate. The amount of the basic compound used is preferably 1.5 to 4.0 equivalents of the number of moles of the amino group, particularly 1.8.
~ 3.6 equivalents are preferred. These basic compounds are preferably present from the beginning of the reaction, but may be added in portions.

(Solvent) The reaction solvent may be any as long as it can dissolve the amine. Examples thereof include ether compounds such as THF, diethyl ether and dioxane, ketone compounds such as acetone and methyl ethyl ketone, ester compounds such as ethyl acetate, and toluene. , Xylene, aromatic hydrocarbons such as benzene, and halogenated hydrocarbon compounds such as chloroform and methylene chloride. These solvents may be used alone or as a mixture of two or more.

[0015] The reaction temperature is -40 to 70 ° C, preferably-
20 to 50 ° C, optimally 0 to 30 ° C. At −40 ° C. or lower, the reaction hardly proceeds, and at a high temperature of 70 ° C. or higher, side reactions such as condensation may occur.

[Production of Isocyanate] In order to produce an isocyanate from the intermediate urethane obtained as described above, an organic halogen is used as a reaction catalyst without isolating urethane from the reaction solution. A silicon halide compound or an organic boron halide compound is added.

(Organic silicon halide compound) As the organic silicon halide used as the isocyanation catalyst, a compound represented by the following formula is used.

[0018]

Embedded image SiR ₂ R ₃ in R ₄ X (3) Formula, X is Cl, Br, F, a halogen atom such as I,
R ₂ , R ₃ and R ₄ are a lower alkyl group or aryl group having 1 to 3 carbon atoms, an alkoxyl group or a halogen atom, which may be the same or different. Among these, chlorosilanes such as trimethylchlorosilane, triethylchlorosilane, trimethoxychlorosilane, and tetrachlorosilane are particularly preferable, but trimethylchlorosilane is most preferable in terms of ease of handling and price.

The amount of the organosilicon compound used is 0.8 to 2.0 equivalents, preferably 1.0 to 1.8 equivalents of the amino group of the amine used. If the amount is too small, unreacted raw materials may remain. If the amount is too large, it may be difficult to remove it after the completion of the reaction or may cause an undesired side reaction.

When an organosilicon compound is used, the reaction temperature at which the isocyanation reaction proceeds is generally -50 to
Up to 200 ° C, preferably up to -10 to 150 ° C, more preferably up to 20 to 120 ° C, can be appropriately changed depending on the combination of the amine and the organosilicon compound used. If the reaction temperature is too low, the reaction may not proceed at all. Conversely, if the reaction temperature is raised too much or heated for too long, undesired side reactions may occur or the product may be decomposed. It is better to proceed.

(Halogenated Organic Boron Compound) When an organic boron halide compound is used as an isocyanate agent, the following formula is used.

Embedded image Halogenated catecholboranes represented by In the formula, X is a halogen atom such as Cl, Br, F, and I. Specific examples of such a compound include chlorocatechol borane and bromocatechol borane. Among them, chlorocatechol borane is preferable from the viewpoint of ease of handling and price.

Further, since catecholboranes have a higher activity against the thermal decomposition of urethane than the above-mentioned chlorosilanes, a formate other than phenylchloroformate can be used as a reaction reagent for obtaining the urethane. .

The amount of the organoboron halide compound used is 0.8 to 2.0 equivalents of the molar amount of the amino group of the amine used.
In particular, 1.0 to 1.8 equivalents are preferable. If the amount is too small, unreacted raw materials may remain. If the amount is too large, it may be difficult to remove it after the completion of the reaction or may cause an undesired side reaction.

When an organoboron halide compound is used, the reaction temperature at which isocyanation proceeds is generally-
The temperature can be appropriately changed at 50 to 150 ° C, preferably at -30 to 100 ° C, more preferably at -10 to 50 ° C, depending on the combination of the amine, chloroformate and organoboron compound used. If the reaction temperature is too low, the reaction may not proceed at all. Conversely, if the reaction temperature is raised too much or heated for too long, undesired side reactions may occur or the product may decompose. Therefore, the temperature is gradually increased from a low temperature while tracing the reaction by TLC or IR. It is better to let it proceed.

[Purification of Isocyanate] After completion of the reaction, the isocyanate can be isolated and purified by a conventional method. That is, after removing the hydrochloride generated by the reaction and the excess reaction reagent, the product can be purified by a method such as column, recrystallization, or distillation depending on the physical properties of the product.

The method of the present invention can be applied to a polyisocyanate.

The obtained compound was measured for its melting point and identified as a compound of the above formula (1) by mass spectrum and IR spectrum analysis.

[0028]

EXAMPLES The characteristics of the obtained isocyanate were measured as follows. Mass spectrum was measured using Hitachi M80A (manufactured by Hitachi, Ltd.). IR spectrum Measured using IR-810 (manufactured by JASCO Corporation).

[Example 1] 100 equipped with a dropping funnel
1.40 g (15 mmol) of aniline in a 3-mL three-necked flask,
30 mL of toluene and 3.74 g of triethylamine (37 mm
ol). 2.35 g (15 mmol) of phenyl chloroformate was placed in the dropping funnel, and the reaction vessel was cooled to 0 ° C. in an ice bath. Phenyl chloroformate was added dropwise over 5 minutes. After completion of the dropwise addition, the mixture was stirred at 0 ° C. for 30 minutes, and then at room temperature for 1 hour.

Next, trimethylchlorosilane 1.95
g (18 mmol) was added dropwise at room temperature and stirred for 10 minutes. The mixture was stirred for 6 hours while gradually raising the reaction temperature to 60 ° C.

The salt formed was removed by filtration, and the solution was concentrated by an evaporator. The reaction mixture was purified by distillation to obtain 0.90 g (50% yield) of a colorless and transparent liquid.

This compound has a mass spectrum of M ⁺ = 11.
9 molecular ion peaks were observed and 2 in the IR spectrum.
The absorption of the carbonyl group of the isocyanate was observed at 260 cm ^-1 (FIG. 1). Therefore, it was confirmed to be phenyl isocyanate.

Example 2 50 m with a dropping funnel
0.53 g (2.0 mmol) of 1,3-bis (4-aminophenoxy) benzene and methylene chloride 10
mL and 0.81 g (8 mmol) of triethylamine were charged. 0.63 g of phenyl chloroformate (4
mmol) and the reaction vessel was cooled to 0 ° C. in an ice bath. 10
Phenyl chloroformate was added dropwise over a period of minutes, and the mixture was stirred for 30 minutes while returning to room temperature.

Next, 0.64 of trimethylchlorosilane was added.
g (5.9 mmol) was added dropwise at room temperature and stirred for 20 minutes. The solvent was replaced with toluene, and the mixture was stirred for 3 hours while gradually increasing the temperature to 120 ° C. Thereafter, the mixture was stirred at 120 ° C. for 1 hour.

The salt formed was removed by filtration, and the solution was concentrated by an evaporator. The reaction mixture was purified on a flash column to give 0.45 g (66%) of a white solid.
Obtained. This compound had a melting point of 50 ° C., a molecular ion peak of M ⁺ = 344 in the mass spectrum, and absorption of a carbonyl group of the isocyanate was observed at 2270 cm ⁻¹ in the IR spectrum (FIG. 2). Therefore, 1,3-bis [4-
(Isocyanatophenoxy)] benzene.

Example 3 50 m provided with a dropping funnel
0.88 g of 2,2-bis (4-aminophenoxyphenyl) hexafluoropropane (BAPF)
(1.7 mmol), 10 mL of methylene chloride and 1.02 g (10 mmol) of triethylamine were charged. 0.53 g (3.4 mmol) of phenyl chloroformate was placed in the dropping funnel, and the reaction vessel was cooled to 0 ° C. in an ice bath. Phenyl chloroformate was added dropwise over 10 minutes, and the mixture was stirred for 30 minutes while returning to room temperature.

Then, the mixture was ice-cooled again, 0.76 g (4.9 mmol) of chlorocatechol borane was added, and the mixture was stirred for 50 minutes. After raising the reaction temperature to room temperature and stirring for 1 hour, isocyanation proceeded and 0.55 g of a white solid was obtained.
(0.96 mmol) (57% yield).

This compound had a melting point of 137 ° C. Further, a molecular ion peak at M ⁺ = 570 was observed in the mass spectrum, and absorption of a carbonyl group of the isocyanate was observed at 2260 cm ⁻¹ in the IR spectrum (FIG. 3). Therefore, 2,2-bis [4- (4-isocyanatophenoxy) phenyl] hexafluoropropane (BAPF-NC
O) was confirmed.

Comparative Example 1 The same operation as in Example 3 was carried out, except that the urethane was once purified and then the isocyanate was purified.
(BAPF-NCO) was produced. That is, in a 1 L three-necked flask equipped with a dropping funnel, 20 g of BAPF (38.
6 mmol), THF 200 mL, triethylamine 9.58
g (0.095 mol), 14.48 g (0.092 mol) of phenyl chloroformate was placed in the dropping funnel, and the reaction vessel was cooled to 0 ° C. in an ice bath. Phenyl chloroformate was added dropwise over 15 minutes, and the mixture was stirred for 30 minutes while returning to room temperature. The resulting salt was hydrolyzed with 100 mL of water and extracted with chloroform. The organic layer was collected and dried over anhydrous magnesium sulfate. After evaporating the solvent and recrystallizing with toluene, 22.2 g of BAPF-urethane (0.029 m
ol, 75%) as a white solid.

Next, 20.0 g (0.026 mol) of the above BAPF-urethane, 170 mL of methylene chloride, and 7.99 g of triethylamine were placed in a 300 mL two-necked flask.
(0.079 mol). The flask was cooled in an ice bath, and 12.3 g (0.080 mol) of chlorocatechol borane was dissolved in 30.0 mL of methylene chloride and added dropwise over 15 minutes. The ice bath was removed and the mixture was stirred for 2 hours.

100 mL of hexane is added to the reaction mixture,
Insoluble components were removed by filtration. The filtrate was concentrated and purified with a flash column using methylene chloride as a developing solvent. When the solvent was evaporated, 6.3 g of a white solid was obtained.
(0.011 mol, 42%) was obtained. The total yield (based on diamine) in this reaction was 32%, which was lower than the case of Example 3 synthesized in one step (57%).

[0042]

The method of the present invention is very useful in the production of isocyanates in that safe and stable raw materials are used, and isocyanates can be easily obtained. Further, according to the method of the present invention, loss of raw materials due to isolation and purification can be eliminated, the production process can be shortened, the yield of the final target product can be improved, and work safety can be ensured.

[Brief description of the drawings]

FIG. 1 is an infrared absorption spectrum of the isocyanate obtained in Example 1.

FIG. 2 is an infrared absorption spectrum of the isocyanate obtained in Example 2.

FIG. 3 is an infrared absorption spectrum of the isocyanate obtained in Example 3.

Claims (4)

[Claims] 1. The following formula: (Wherein R ₁ is an organic group having ₁ to 3 valences and n is an integer of 1 to 3), in the presence of a basic compound in the production of an isocyanate represented by the following formula: (R ₁ and n are the same as described above) by reacting an amine with a halogenated formate, and adding an organic silicon halide compound or an organic boron compound to the reaction solution to carry out the reaction. Manufacturing method. 2. The organic silicon compound is represented by the following formula: SiR ₂ R ₃ R ₄ X (3) (R ₂ , R ₃ and R ₄ are an alkyl group, an aryl group, an alkoxyl group or a halogen atom, and X is a halogen atom. The production method according to claim 1, wherein 3. An organic boron compound represented by the following formula: 2. The method according to claim 1, wherein X is a halogen atom. 4. The method according to claim 1, wherein the basic compound is a tertiary amine.