JPH0430939B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for phosgenating 2,6,2'-triaminoethylhexanoate trihydrochloride, and particularly to a crystallization solvent.

[Conventional technology]

2,6,2'-triaminoethylhexanoate trihydrochloride is used as a raw material for polyurethane by phosgenating dichlorobenzene or monochlorobenzene as a dispersion medium to give an isocyanate.

As a method for producing amino acid aminoalkyl esters, there is a method proposed in JP-A-55-105649. In this method, when amino acid hydrochloride and amino alcohol hydrochloride are heated to react and esterify, hydrogen chloride gas is absorbed into the reaction system in the absence of an organic solvent that forms an azeotrope with water. The product purification method is particularly for the ester from lysine dihydrochloride and ethanolamine hydrochloride, that is, 2,6,2'-triaminoethylhexanoate trihydrochloride.
It is said that a method using a methanol/ethanol mixed solvent as a recrystallization solvent is particularly effective.

[Problem that the invention seeks to solve]

However, when phosgenating the crystals obtained by this method as a raw material to obtain isocyanate, if alcohol is present, a side reaction will occur during the phosgenation process, resulting in adverse effects such as the formation of polymer, so it is necessary to completely remove the alcohol. Yes, it must be dried after crystallization. Furthermore, if the material becomes lumpy due to drying, it will significantly reduce the phosgenation reaction rate, so fine pulverization will be necessary.

As a result of intensive studies to solve this problem, the present inventors found that when purifying 2,6,2'-triaminoethylhexanoate trihydrochloride, the drying and pulverizing steps were omitted and the phosgenation process was carried out. We have discovered a method that can be applied to the above, and have arrived at the present invention.

[Means for Solving the Problems] That is, the present invention provides a method for crystallizing 2,6,2'-triaminoethylhexanoate trihydrochloride using a mixed solution of dichlorobenzene and methanol as a crystallization solvent. , by washing the crystals with dichlorobenzene, the mixture of dichlorobenzene and methanol is replaced with dichlorobenzene, and the obtained wet crystals are subjected to a phosgenation step using dichlorobenzene as a dispersion medium. This is a method for phosgenating 2,6,2'-triaminoethylhexanoate trihydrochloride, which is characterized by:

Lysine dihydrochloride and ethanolamine hydrochloride are reacted by heating in the presence of hydrogen chloride gas, and the target product 2,6,2'-triaminoethylhexano To separate ate trihydrochloride, for example, a mixture of 55-70% methanol and 30-45% dichlorobenzene is used, about 2 to 10 times the weight of the reactants, preferably 2 to 4 times the weight of the reactants. Dissolve, add seed crystals and crystallize. After crystallization, the crystals are separated, and if necessary, the wet crystals are re-dispersed in a methanol/dichlorobenzene mixture having the same composition as that used for crystallization, washed, and the separation process is repeated to increase purity. Next, the wet crystals are redispersed in dichlorobenzene used as a phosgenation solvent, washed, and the process of separating the crystals is repeated to convert the methanol/dichlorobenzene mixture in the wet crystals into dichlorobenzene. The methanol concentration in the wet crystals is preferably 0.05% or less.

The wet crystals thus obtained are subjected to a phosgenation step using dichlorobenzene as a dispersion medium.

Example 214g (1 mol) of the synthesized 2-aminocaprolactam (60% aqueous solution) was mixed with 417g (4 mol) of concentrated hydrochloric acid (35%).
mol) and heated at 100°C for 5 hours for hydrolysis. Then 122g (2 moles) of ethanolamine
was added, and water was distilled off under reduced pressure. This reaction mixture was placed in reaction flask 1 equipped with a stirrer, heated to an internal temperature of 120°C, and residual water was removed under reduced pressure. Next, hydrogen chloride gas was introduced to return the pressure to normal pressure, and hydrogen chloride gas was absorbed for 15 minutes while stirring, and then the reaction was carried out at 120°C for 30 minutes. Then, water produced by the reaction was distilled off under reduced pressure of 10 mmHg or less. Absorption of hydrogen chloride gas, reaction, and distillation of water were repeated 5 to 8 times to obtain a reaction product with an esterification rate of 80%. For 200g of this reactant, methanol 360g
A mixed solution of 240 g of O-dichlorobenzene was added and dissolved, and seed crystals were added to crystallize. The crystals were separated, washed with a methanol/O-dichlorobenzene mixture having the same composition as used during crystallization, and separated. The wet crystals were dispersed in 600 g of O-dichlorobenzene, further washed with O-dichlorobenzene, and the separate operation was repeated four times to convert the methanol/O-dichlorobenzene mixture into O-dichlorobenzene. 152 g wet crystals of substituted 2,6,2'-triaminoethylhexanoate trihydrochloride
(dry weight 80g) was obtained. The content of methanol remaining in this wet crystal was determined by gas chromatography.
It was confirmed that it was 0.05% or less. The shape of the crystals was acicular crystals of about 1 x 10 microns when observed under a microscope, and the redispersibility in O-dichlorobenzene was good. In addition, dry this crystal (5 mmHg, 100℃,
8HR) had a melting point of 162°C.

The structural formula of 2,6,2'-triaminoethylhexanoate trihydrochloride is shown below.

57 g of wet crystals thus obtained (dry weight 30
Add 123 g of O-dichlorobenzene to g), and in a 300 ml four-necked flask equipped with an airtight stirring bar, a thermometer, a gas inlet tube, and a reflux condenser with a gas outlet tube at the tip, add 0.25 to 0.25 g of phosgene gas. Phosgenation was carried out at 140° C. for hours while passing at a flow rate of 0.3 mol/hour, and the time course of the reaction was observed. The reaction rate was 47% at 2.5 hours, 65% at 5 hours, and 86 at 7.5 hours.
%, it was 90% in 10 hours.

For analysis of the samples at each time point, the solvent was distilled off under reduced pressure, and finally, the volatile components were removed by heating to 100°C under a vacuum of 0.01 mmHg, and the sample was dissolved in toluene.
Usual NCO analysis method (add N/10-dibutylamine-toluene solution, allow sufficient reaction, add isopropanol, and back titrate excess dibutylamine with N/10-HCl using bromophenol blue as an indicator. , to quantify NCO groups from the amount consumed).

The structural formula of 2,6,2'-triisocyanate ethylhexanoate obtained by phosgenation is shown below.

Comparative Example 1 A part of the wet crystals containing O-dichlorobenzene of 2,6,2'-triaminoethylhexanoate trihydrochloride obtained in Example was dried under reduced pressure (5 mmHg,
The dried crystals obtained at 100℃, 8HR) were crushed and subjected to phosgenation reaction under the same conditions as in the example. As a result, the reaction rate was 28% in 2.5 hours, 51% in 5 hours, and 7.5
It was 65% for hours, 76% for 10 hours, and 82% for 12.5 hours.

Comparative Example 2 Esterification reaction product 400 obtained under the same conditions as Example
Dissolve g in a mixture of 360 g of methanol and 840 g of ethanol, add seed crystals to crystallize, wash with methanol/ethanol of the same composition, and then vacuum dry (5 to 50 g).
10 mmHg, 80°C, 24 hours) to obtain 170 g of 2,6,2'-triaminoethylhexanoate trihydrochloride. The primary particles of this crystal solidified into agglomerates, and pulverization was required during phosgenation. Further, the results of the phosgenation reaction using this were the same as in Comparative Example 1.

〔Effect of the invention〕

The wet crystals of 2,6,2'-triaminoethylhexanoate trihydrochloride obtained by the method of the present invention can be subjected to phosgenation without drying and pulverizing steps. That is, the washing solvent such as dichlorobenzene contained in the wet crystals can be used as a solvent for phosgenation, and therefore does not require removal by drying or the like. Further, since the primary particles of the crystals do not fuse or become agglomerated due to drying, pulverization is not required, and dispersion in a phosgenation solvent is easy, which is preferable for the phosgenation reaction. In addition, when recovering and recycling the crystallization mother liquor, in the case of alcohols such as methanol and ethanol or isopropanol,
It is difficult to separate them because their boiling points are close to each other, but methanol and dichlorobenzene have the advantage of being easy to separate because they have a large difference in boiling point.

Furthermore, 2,6,2'-triaminoethylhexanoate trihydrochloride has two types of crystals with different crystal forms: an alpha crystal with a melting point of 162°C and a beta crystal with a melting point of 142°C. In order to obtain an isocyanate compound by chemical reaction, the α-crystal has good reaction rate and reaction yield, and the method of the present invention yields the α-crystal. In this case, in the case of β crystals, if the reaction temperature is 125° C. or higher, agglomeration occurs due to half-melting of the crystals, and both reaction rate and reaction yield decrease.

Claims (1)

[Claims] 1. After crystallizing 2,6,2'-tolaminoethylhexanoate trihydrochloride using a mixture of dichlorobenzene and methanol as a crystallization solvent, the crystals are washed with dichlorobenzene to obtain the 2,6,2'-triamino, which is characterized in that a mixture of dichlorobentone and methanol is replaced with dichlorobenzene, and the obtained wet crystals are subjected to a phosgenation step using dichlorobenzene as a dispersion medium. Method for phosgenation of ethylhexanoate trihydrochloride.