JPS59152367A - Purification of mercaptocarboxylic acid polyhydric alcohol ester - Google Patents

Abstract

PURPOSE:To prepare the titled compound useful as a resin hardener, etc. in high purity, without producing ill-order components, by reacting a specific polyhydric alcohol with mercaptocarboxylic acid, and treating the reaction product with an alcohol and/or an ether. CONSTITUTION:A polyhydric alcohol having 3-6 hydroxyl groups in the molecule is made to react with the mercaptocarboxylic acid of formula I (R1 is H, methyl or ethyl; n is 1-4) or a mercaptocarboxylic acid lower alkyl ester of formula II (R2 is 1-4C alkyl), and the obtained crude mercaptocarboxylic acid polyhydric alcohol ester is purified by treating with an alcohol and/or an ether. There is essentially no discharge of waste water containing organic materials, and the process is economical from industrial viewpoint. A colorless high-quality objective compound free from ill odor can be prepared by this process. The unreacted raw materials can be recycled and reused by the recovery of the solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying mercaptocarboxylic acid polyhydric alcohol esters. Mercaptocarboxylic acid polyhydric alcohol esters are compounds useful as various resin curing agents or resin modifiers.

Known methods for producing mercaptocarboxylic acid polyhydric alcohol esters can be broadly classified into the following two methods.

(1) Direct esterification method: A polyhydric alcohol and a mercaptocarboxylic acid (used in a slight excess of the theoretical amount) are used in the presence of an acidic catalyst, using toluene as a solvent, and the water produced by the reaction is converted into an azeotropic mixture. The reaction is carried out while being removed from the system as After the reaction mixture was cooled to room temperature and thoroughly washed with water, the mercaptocarboxylic acid polyhydric alcohol ester was dissolved into a viscous yellow oil with a considerably high It is obtained with high purity (-sn conversion rate of 98% or more) (!Jiko Sho 39-9071).

(2) Transesterification method: Polyhydric alcohol and mercaptocarboxylic acid lower alkyl ester or mercaptocarboxylic acid lower alkyl ester containing mercaptocarboxylic acid with a weight coefficient of 80 or less, an ester catalyst and mercaptocarboxylic acid lower alkyl ester of 01 ~1
The reaction is carried out in the presence of 0.00 equivalents of water, and dehydration is carried out during the course of the reaction or after the completion of the reaction. After the reaction was completed, the pressure was reduced (101ηmH
Yield 94-9 by distilling off the low-boiling components
5, a pale yellow viscous oil with an SH conversion rate of 90-92 was obtained (Takaikai No. 57-11959).

However, it is quite difficult to proceed quantitatively with this type of esterification reaction, and usually a partial ester in which some of the hydroxyl groups of the polyhydric alcohol are not esterified is produced as a by-product. This partial ester also has a fairly high boiling point like the mercaptocarboxylic acid polyhydric alcohol ester, so it is difficult to remove it by normal distillation operations.

Therefore, the SH conversion rate of mercaptocarboxylic acid polyhydric alcohol ester cannot be obtained by simply distilling off the low boiling point components under reduced pressure (10 mrrtH'? or less) after the completion of the reaction as in the method of known technique (2). It is as low as 92%. This means that although it is possible to remove unreacted mercaptocarboxylic acid and mercaptocarboxylic acid lower alkyl ester by vacuum distillation, the mercaptocarboxylic acid polyhydric alcohol partial ester remains as a distillation residue together with the mercaptocarboxylic acid polyhydric alcohol ester. This is considered to be the reason why the SH conversion rate is low.

As mentioned above, the mercaptocarboxylic acid polyhydric alcohol ester obtained by this method has an SH conversion rate of 90 to 9.
It is difficult to say that the product is completely satisfactory at a low value of 2%.

On the other hand, in the method of known technology (1), after the reaction is completed, the reaction mixture is thoroughly washed with water, and then heated at 150 to 160°C/
By removing low-boiling components at 1 iWmHf, a mercaptocarboxylic acid polyhydric alcohol ester of considerably high purity (SH conversion ratio of 98% or more) was obtained.

However, in this method, the catalyst, unreacted mercaptocarboxylic acid, mercaptocarboxylic acid polyhydric alcohol partial ester, etc. are transferred to the aqueous layer, which poses a problem in the wastewater treatment method. Furthermore, even if the aqueous layer is concentrated to recover the catalyst, mercaptocarboxylic acid, mercaptocarboxylic acid polyhydric alcohol partial ester, etc., a considerable amount of utility is required and it cannot be called an industrial method.

Based on the above-mentioned technical background, the present inventors have conducted intensive studies on purification methods for the purpose of obtaining high-quality mercaptocarboxylic acid polyhydric alcohol esters with high purity and few off-flavor components. As a result, the obtained mercaptocarboxylic acid polyhydric alcohol ester is reacted with alcohol and/or
Alternatively, after treatment with ethers, the low-boiling components are removed under reduced pressure from the separated mercaptocarboxylic acid polyhydric alcohol ester layer, resulting in a colorless and transparent high-quality product with a surprisingly high SH conversion rate of 98% or more, little off-odor components, and It was discovered that mercaptocarboxylic acid polyhydric alcohol ester can be obtained, and the present invention was completed.

That is, the present invention has 6 to 6 hydroxy acids in the molecule (in the formula,
R□ represents a hydrogen atom, a methyl group, or an ethyl group, and n is an integer of 1 to 4), or mercaptocarboxylic acids represented by the general formula (It) (wherein R□ and n represent the general formula (1 ), and R2 has 1 to 1 carbon atoms.
A mercaptocarboxylic acid polyhydric alcohol ester obtained by reacting a mercaptocarboxylic acid lower alkyl ester represented by 4 (representing an alkyl group) with an alcohol and/or an ether. This is a method for purifying carboxylic acid polyhydric alcohol esters.

Examples of polyhydric alcohols having 5 to 6 water groups in the molecule used in the method of the present invention include trimethylolethane, trimethylolpropane, glycerin, tris(2-hydroxyethyl)inocyanurate, and These include ditrimethylolpropane, dipentaerythritol, mannitol, sorbitol, inositol, and adducts of these alkylene oxides (eg, ethylene oxide, propylene oxide, butylene oxide, butyl glycidyl ether, etc.).

Further, as the mercaptocarphonic acid represented by the general formula (1), for example, thioglycolic acid, β-mercaptopropionic acid, α-mercaptopropionic acid, γ-mercaptopropionic acid,
These include mercaptobutyric acid and Δ-mercaptovaleric acid.

Further, as the mercaptocarboxylic acid ester represented by the general formula (Jl), examples of the mercaptocarboxylic acids listed as examples of the general formula (1) include methyl, ethyl, propy7+z, inglovir, butyl, inbutyl,
Tersha 1-rubutyl ester and the like.

In the method of the present invention, the polyhydric alcohol and the general formula (1
) or the mercaptocarboxylic acid represented by the general formula (1
) is reacted with a mercaptocarboxylic acid lower alkyl ester to produce a mercaptocarboxylic acid polyhydric alcohol ester.

This reaction method is not particularly limited, and any known method can be applied. Examples include the above-mentioned direct esterification method and transesterification method.

When the reaction is carried out by a direct esterification method, for example, a polyhydric alcohol and a stoichiometric amount or more of mercaptocarboxylic acid are mixed in an organic solvent capable of forming an azeotrope with water in the presence of an acidic catalyst.
During heating, the water produced by the reaction and the water coexisting in the reaction system are removed by azeotropic distillation.

After the reaction is completed, the organic solvent is recovered to obtain crude mercaptocarboxylic acid polyhydric alcohol esters.

However, when using the transesterification method, polyhydric alcohol and a theoretical amount or more of mercaptocarboxylic acid lower alkyl ester are added to the alkyl ester at a ratio of 01 to 100.
The reaction is carried out in the presence of the same amount of water at a temperature of 20 to 200° C. without a catalyst or with a transesterification catalyst. Water is removed during or after the reaction to obtain crude mercaptocarboxylic acid polyhydric alcohol esters.

In these direct esterification methods or transesterification methods, acid catalysts and transesterification catalysts are usually used.

Such catalysts include, for example, organic sulfonic acids such as methanesulfonic acid, benzenesulfonic acid and laurylsulfonic acid, inorganic acids such as hydrochloric acid and sulfuric acid, dibutyltin oxide, dibutyltin dilaurate, stannous chloride, and sulfuric chloride. tin,
These include organic tin compounds such as dimethyltin dichloride, metal alkoxides such as titanium inopropoxide, and ion exchange resins. These catalysts are usually used in amounts of 0001 to 10 by weight based on the total amount of raw materials.

The crude mercaptocarboxylic acid polyalcohol ester obtained by the reaction as described above is treated with an alcohol and/or an ether.

The crude mercaptocarboxylic acid polyhydric alcohol ester to be treated contains a mercaptocarboxylic acid polyhydric alcohol partial ester, unreacted mercaptocarboxylic acid or mercaptocarboxylic acid lower alkyl ester, an off-flavor component, and an esterification catalyst.

In this way, when treating crude mercaptocarboxylic acid polyhydric alcohol esters with alcohols and/or ethers, the crude mercaptocarboxylic acid polyhydric alcohol esters can be treated with
However, when an ion exchange resin is used as an esterification catalyst, it is necessary to separate and remove the ion exchange resin after the reaction is completed.

The alcohols used in the method of the present invention include, for example, t
(c) Methanol, ethanol, n-propanol, isoglopanol, etc., and ethers include, for example, ethyl ether, diisopropyl ether, dibutyl ether, etc. Cholera may be used not only alone, but also in combination of two or more types, if necessary.

The amount of alcohols and ethers used as these purification solvents varies depending on the type of solvent, the type of mercaptocarboxylic acid polyhydric alcohol ester, etc., but is preferably 0% of the weight of the mercaptocarboxylic acid polyhydric alcohol ester crude product. .1 to 20 times needle, more preferably 02
~15 times the amount. If the amount of solvent is less than 0.1 times the amount,
The solvent dissolves into the mercaptocarboxylic acid polyhydric alcohol, making separation impossible. If the amount of solvent is 20 times or more, the amount of mercaptocarboxylic acid polyhydric alcohol ester itself dissolved in the extraction solvent increases, and the amount of mercaptocarboxylic acid polyhydric alcohol ester obtained per batch decreases, making it less economical. Not on point.

The crude mercaptocarbo/acid polyhydric alcohol ester is thoroughly mixed with a purification solvent to extract impurities.

This extraction can be carried out at room temperature, but also at the reflux temperature of the extraction solvent used. The extraction time is not particularly limited. Usually, the mixture is sufficiently stirred at reflux temperature for 5 to 10 minutes. After the extraction operation, the liquids are separated at room temperature, and volatile components are distilled off under reduced pressure from the mercaptocarboxylic acid polyhydric alcohol ester layer to obtain a high-quality mercaptocarboxylic product that has a JsH conversion rate of 98% or more, has few off-odor components, and is colorless and transparent. It is possible to obtain acid polyhydric alcohol esters.

According to the method of the present invention, crude mercaptocarboxylic acid polyhydric alcohol esters obtained by reacting a polyhydric alcohol with a mercaptocarboxylic acid or a mercaptocarboxylic acid lower alkyl ester, for example, by a direct esterification method or a transesterification method, can be used. , in addition to mercaptocarboxylic acid polyhydric alcohol partial ester, unreacted mercaptocarboxylic acid or mercaptocarboxylic acid lower alkyl ester,
Off-flavor components and common esterification catalysts can be effectively removed at the same time.

In a known method, when unreacted mercaptocarboxylic acid or mercaptocarboxylic acid ester is recovered under reduced pressure while leaving the esterification catalyst in the reaction mixture, the resulting product, mercaptocarboxylic acid polyhydric alcohol ester, turns yellow to brown. This also solves the problem of coloring.

Moreover, the method of the present invention essentially does not emit wastewater containing organic substances, is an industrially economical process, is colorless, removes bad odors originating from off-flavor components, and has a high BH conversion rate. Provides pure and high quality mercaptocarboxylic acid polyhydric alcohol ester. Furthermore, by recovering the solvent from the alcohol and /-1: bamboo ether extraction layer, it is possible to recycle the unreacted raw materials, catalyst, mercaptocarboxylic acid polyhydric alcohol partial ester, etc. to the reaction system, making it possible to make it economical and economical. It is an excellent method in terms of both target and effective use of resources.

Examples and Comparative Examples are shown below, but the present invention is not subject to equivalent limitations thereby.

Example-1 Pentaerythritol 136f (1.0 mol), 2-mercaptoacetic acid ethyl ester 480 r (4.0 mol), water 288 f (16 mol), P-toluenesulfonic acid 6167, a stirrer, N2 blowing pipe The components to be distilled out (mainly water) are charged into a 1L four-bottle flask equipped with a water separator and a thermometer equipped with a reflux condenser on the top. −
ethanol) was collected.

After about 4 hours, the distillate components decreased, so the oil bath temperature was lowered to 1.
When the temperature was raised to 50 to 150°C and the reaction was continued, distillate components (mainly water) came out again and were collected. After about 3 hours, the amount of distillation decreased, so the heating reaction was stopped and the mixture was cooled to room temperature, resulting in colorless liquid 4'IO! ? I got it.

After replacing the water separator with a reflux condenser, 1201 ml of ethanol was added. After stirring for about 5 minutes while heating under reflux, the mixture was transferred to a separating funnel and allowed to cool to room temperature.

The lower layer of pentaerythritol tetrakis (2-mercaptoacetic acid) was collected and the volatile components were distilled off under reduced pressure (1 ommHy or less) to obtain 393 f of a colorless transparent liquid (yield: 91
%) was obtained.

The SH conversion rate measured by the iodine method was 98%, IR
Spectrally, no absorption based on hydroxyl groups was observed;
1H-NMR was also consistent with that of the standard sample. Also,
Although there was a slight characteristic odor, the off-flavor derived from mercaptan was not too bad.

Comparative Example-1 After carrying out the reaction on the same scale and under the same conditions as shown in Example-1, volatile components were distilled off under reduced pressure (~10 mmHy) to obtain 405 f of pale yellow liquid (yield 93.8%). I got it. This one is pentaerythritol tetrakis (
2-mercaptoacetic acid), but absorption based on hydroxyl groups was observed. The SH conversion rate measured by the iodine method was 921.

Example-2 500+++/ equipped with the same equipment as shown in Example-1
? In the four-eye flask, add 4 pentaerythritol filters.
'j (0,25 mol), β-mercagutopropionic acid 117 ? (10 mol), p-toluenesulfonic acid 12 and toluene 2057 were charged, and heating and stirring was continued under reflux under a N2 stream until water 187 was removed by azeotropic distillation with toluene. By recovering toluene from the reaction mixture, a colorless liquid 136f in which a portion of -p-)toluenesulfonic acid was precipitated was obtained. After replacing the water separator with a reflux condenser, methanol 517 was added, and the mixture was heated and stirred at an oil bath temperature of 70°C, then transferred to a separatory funnel, and gradually warmed to room temperature with occasional shaking. After collecting the lower layer of pentaerythritol tetrakis (β-mercaptopropiate) and recovering some methanol, volatile components were further distilled off under reduced pressure (~1 oz++ tut) to obtain 117 f of a colorless transparent liquid (yield: 96%). Ta. The SH conversion rate measured by the iodine method was 985%, and no absorption based on hydroxyl groups was observed in the R spectrum, which coincided with pentaerythritol tetrakis (β-mercaptopropionate). Similarly, 1H-NMR also confirmed that it was pentaerythritol tetrakis (β-mercaptopropionate).

In addition, although there was a slight peculiar aroma, the off-odor derived from mercaptan was not too bad.

Comparative Example-2 A reaction was carried out on the same scale and under the same conditions as shown in Example-2. After the reaction was completed, a small amount of precipitated p-)luenesulfonic acid was removed by filtration. After recovering toluene from r liquid, component (β-mercaptocarboxylic acid) 14.4 f under reduced pressure of 1.01HH7 up to 160°C
(0.14 mol) was distilled off. The residue was colored yellow. This was dissolved in toluene, washed with 1% sodium bicarbonate solution, washed with water and turned over 6 times, and then recovered with l.luene.
．． Components up to 160° C. were distilled off under reduced pressure of 0 mm, H@. As a residue, 118 f (yield 96.6%) of pentaerythritol tetrakis (β-mercaptopropionate) was obtained as a yellow liquid. This product showed an R spectrum consistent with pentaerythritol (β-mercaptopropionate), but absorption based on hydroxyl groups was observed. The SH conversion rate by the iodine method was 94%.

Example 6 In a 500 mg four-eye flask equipped with the same equipment as shown in Example 1, 35.5 f (0.25 mol) of 1,1.1-)limethylolpropane, β-merkaftof 876 mol of ropionic acid (0,825 mol), 11 p-toluenesulfonic acid and 2057 mol of toluene were charged, and N2
Heating and stirring under reflux was continued until approximately 13.5 f of gaseous sewage was removed by azeotropic distillation with toluene. By recovering toluene from the reaction mixture, a colorless liquid 1241i' in which a portion of -p-toluenesulfonic acid was precipitated was obtained. After replacing the water separator with a reflux condenser, 200 y of isopropyl ether was processed, and heating and stirring were continued for 10 minutes under reflux.

The mixture was transferred to a separatory funnel and gradually cooled to room temperature while stirring occasionally. Lower layer 1.1.1-IJ methylolpropane tris (β-mercaptopropionate)
was placed in a flask, 200 f of inople ether was added to the flask, and the heating extraction operation was repeated a total of 5 times including the first time. After the extraction operation with isopropyl ether, 1,1,1-toIJ methylolpropane tris (β-
After recovering some isopropyl ether from the (mercaptopropionate) layer, the pressure was further reduced (~10 m, Hg).
Then, volatile components were distilled off to obtain 846 g (yield: 95 g) of a colorless transparent liquid. The SH conversion rate measured by the iodine method was 9.
81 H-NMR
1, 1.1-) Limethylolglobantris (
β-mercabutogropionate), and no absorption based on hydroxyl groups was observed in the engineering R spectrum.

In addition, although there was a slight characteristic odor, the foreign species derived from mercaptan was not bad.

Comparative Example 6 A reaction was carried out on the same scale and under the same conditions as shown in Example 7. After that, the same treatment as shown in Comparative Example-2 was performed, and the residue was 85.4! i' (yield 96)
1.1.1-trimethylolpropane tris(β-mercaptopropionate) was obtained as a yellow liquid. This is 1,1.1~trimethylolpropane tris (
β-mercaptogropionate), but absorption based on hydroxyl groups was observed. The S H conversion rate by the iodine method was 945%.

patent applicant Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Scope of Claims] Shun A polyhydric alcohol having 6 to 6 hydroxyl groups in the molecule, and a compound of the general formula (1) (wherein R1 represents a hydrogen atom, a methyl group or an ethyl group, and n is 1 to 4 or mercaptocarboxylic acids represented by the general formula C11) (in which R4 and n have the same meanings as in the general formula (1), and R2 represents an alkyl group having 1 to 4 carbon atoms) ) A mercaptocarboxylic acid polyhydric alcohol ester characterized by treating a mercaptocarboxylic acid polyhydric alcohol ester obtained by reacting a mercaptocarboxylic acid lower alkyl ester represented by the formula with an alcohol and/or an ether. kind of purification method.