JPS5854138B2 - Method for producing a mixture of mercaptopropionate and dimethylthiodipropionate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for preparing mixtures of methyl mercaptopropionate and dimethyl mono- and/or -thiodipropionate, and more particularly to the preparation of mixtures of methyl mercaptopropionate and dimethyl mono- and/or -thiodipropionate, which are useful in applications such as sealants. The present invention relates to a method for producing an intermediate of (alkylene)-polyester-poly(sulfide)-polythiol.

Poly(oxyalkylene)-polyester-poly(sulfide)-polythiols are widely known as shown in US Pat. No. 3,817,936.

However, the production of this material by the method described in this patent is quite difficult, requiring corrosion-resistant equipment such as glass-lined reactors, and the resulting product features stabilization to avoid gelation on storage. In JP-A No. 53-31795 (this application is a divisional application of this application), in the presence of a transesterification catalyst, the formula (a); containing alkyl groups, R is hydrogen or ft/, n is an integer having a numerical value from 1 to 5, and the total number of carbon atoms in all R and R/ groups is not more than 15 carbons per molecule. and at least one alkylmercaptocarboxylate of the formula (b); where n, R and R/ are as defined above, r is an integer from 1 to 5, - or poly-thiodicarboxylate containing at least one dialkyl mono- or poly-
Thiodicarboxylate; alkyl or H that is 20 or less, and m
is an integer from 1 to 10); where Y is a hydrocarbon having at least two carbon atoms per moiety and a valence equal to the value of at least one poly(oxyalkylene)-polyol prepared by reacting with at least one polyol of A method for making poly(oxyalkylene)-polyester-t'lJ(sulfide)-polythiols having two or more pendant thiol groups is described.

The present invention relates to a method for producing a mixture of the mercaptocarboxylate shown in (a) above and the dialkylthiodicarboxylate shown in (b).

The term poly(oxyalkylene)-polyester-poly(sulfide)-polysulfide is a generic term for all such mixtures where sulfide is mono- or polysulfide and poly means a chain of 2 to 5 sulfur atoms. means.

Examples of useful alkyl mercaptocarboxylates are methyl mercaptoacetate, methyl 2-mercaptopropionate, methyl 3-mercaptopropionate, ethyl 4-mercaptobutyrate, n-butyl 6-mercaptohexanoate, isopropyl 6-mercapto. undecanoate, n-pentyl 6-mercap) 2-(2.2
-dimethylpropyl)undecanoate, t-butyl 2
Mercapto-2-methyl-heptanoate, methyl 3.
3-dimethyl-6-mercaptohexanoate, n-propyl-6-merka7'')-2.23.3.4.4.
Contains 5,5,6-nonamethylheptaate, etc.

Specific examples of useful dialkylthiodicarboxylates are dimethylthiodiacetate, dimethyl 3,3'-thiodipropionate, diethyl 4,4'-thiodibutyrate,
Di-n-butyl 6,6'-thiodihexanoate, diisopropyl 6,6'-thioundecanoate, di-n-
pentyl 6,6'-thiobisC2-(2,2-dimethylpropyl)undecanoate], di-t-butyl-2.
2'-thiobis(2-methyl-heptanoate), dimethyl 66'-thiobis(3,3-dimethylhexanoate di-n-propyl 6,6'-thiobis(2,2,33
・4,4,5,5,6-nonamethylheptanoate),
Contains dimethyl ester of 3-[(carboxymethyl)thio]propionic acid.

It is sometimes also desirable to have a small amount of dialkyl dithiodicarboxylate present in the mixture of alkyl mercaptocarboxylate and dialkyl thiodicarboxylate.

This mixture is within the scope of this invention.

As an example of this, the present invention provides for the reaction of methyl acrylate and hydrogen sulfide in the presence of an addition catalyst to produce methyl mercaptopropionate in a suitable ratio such that it can be used directly in the transesterification reaction as described above. and dimethyl mono- and/or di-thiodipropionate.

Although it is possible to carry out the desired reaction of hydrogen sulfide and methyl acrylate in the absence of a catalyst, it is highly preferred to use an additional catalyst to facilitate the reaction.

Useful addition catalysts include well known organic or inorganic bases such as hydroxide, dimethylamine, triethylamine, N-N-diethylaniline, pyridine, 3-ethyl-4-methylpyridine, and the like.

Ammonium hydroxide is currently preferred.

In the reaction of methyl acrylate with hydrogen sulfide using the aforementioned addition catalysts, it is often desirable to use cocatalysts containing lower alcohols and sulfur and/or water.

It has been found that sulfur, especially in combination with water, greatly increases the ratio of methyl mercaptopropionate to dimethyl mono- and/or di-thiodipropionate.

In the absence of sulfur and/or water, the desired high proportions of methyl mercaptopropionate are not formed even in the presence of excess H2S, but according to the desired reaction described above, they were produced by varying the proportion of hydrogen sulfide. Make some changes in the proportion of methyl mercaptopropionate.

Thus, by using sulfur and/or water to substantially increase the amount of methyl mercaptopropionate produced, and then varying the amount of hydrogen sulfide used, the reaction can be adjusted to the exact ratio desired. You can fine-tune it to suit your needs.

In the process described above, the addition of hydrogen sulfide to methyl acrylate is carried out in the presence or absence of a diluent.

It is preferred here to use diluents consisting of: lower alcohols of the formula R'OH, in which R' is as defined above; saturated aliphatic, saturated cycloaliphatic or Aromatic hydrocarbons; cyclic or acyclic ethers containing 4 to 8 carbon atoms.

Exemplary diluents include methanol, ethanol, isopropanol, pentane, hexane, isooctane, cyclohexane, benzene, toluene, xylene, diethyl ether, -)-t-7''thyl ether, tetrahydrofuran, and p-dioxane.

Alcohol is preferred as diluent here, and methanol is the alcohol of choice.

The alcohol is generally 1-50% based on the total weight of hydrogen sulfide, alkyl ester and alcohol. Preferably it is used in an amount within the range of 5-25% by weight.

More can be used if desired as long as at least about 1% is used since excess amounts have no particular detrimental effect.

The addition of hydrogen sulfide to methyl acrylate is carried out depending on what conditions of temperature, pressure and time are desired to obtain the desired result.

Temperatures in the range of 25 to 150°C are generally useful for this reaction; however, due to the often exothermic nature of the reaction, it is desirable to provide external cooling capabilities to the reactor.

The pressures useful for this reaction are generally between 200 and 200
0 psig (1350 to 13500 kPa) and preferably in the range of 200 to 500 psig (1350 to 3450 kPa).

Reaction times of 1 minute to 24 hours are generally useful, but
A time of 30 minutes to 5 hours is preferred.

Hydrogen sulfide and methyl acrylate are generally used in amounts ranging from 0.5 to 10 moles of hydrogen sulfide per mole of acrylic ester, and preferably H2 per mole of ester.
S is used in amounts ranging from 1 to 3 moles.

Any amount of diluent can be used during the addition reaction that produces the desired result.

Preferably, 0.3 to 1 part by weight of diluent is used per part by weight of acrylic ester.

An effective amount of catalyst is usually used in the range of 0.0001 to 0.1 parts by weight of catalyst per part by weight of acrylic ester, but any amount can be used.

The preferred range of catalyst amount is 0.00% catalyst per part by weight of acrylic ester. OOl to 0.05 parts by weight.

Sulfur is generally sulfur o, ooo per part by weight of ester.
i to 0.1, preferably 0.001 to 0.05
It is used in addition reactions in amounts ranging from parts by weight.

Water is generally 0.0001 to 0 per part by weight of ester.
．． 2, preferably used in the addition reaction in an amount ranging from 0.004 to 0.1 part by weight.

Following the addition of hydrogen sulfide to methyl acrylate, it is desirable to remove volatile diluents, unreacted starting materials, and volatile by-products.

This is easily accomplished by flushing out unwanted volatile components of the reaction mixture.

The resulting residue, ie a mixture containing a major portion of methylmercaptopropionate and dimethylthiodipropionate with a small amount of dimethyldithiodipropionate, is then used directly for the transesterification reaction.

In addition to producing a higher proportion of methyl mercaptopropionate, the presence of sulfur in the cocatalyst also produces some dimethyl mono- and/or di-thiodipropionate, and by using this mixture (oxyalkylene)-polyester-poly(monosulfide)
- Poly(disulfide) - Polythiol, Poly(oxyalkylene) - Polyester - Poly(monosulfite)
-Contributes to the production of poly(disulfide)-poly(trisulfide) polythiol, etc.

However, using the mixtures prepared as described above, it is possible to avoid the careful control of the addition reaction necessary to obtain the desired ratio of esters in the reaction product or to carry out the transesterification reaction more precisely than is possible. It is desirable to adjust the ratio of mixed ester to

In some cases, the reaction product mixture resulting from the addition reaction of hydrogen sulfide to methyl acrylate is fractionally distilled to obtain a fraction enriched in either methyl mercaptopropionate or dimethyl thiodipropionate.

Appropriate amounts of product fractions are then combined to provide a mixture that provides exactly the desired ratios of methyl mercaptopropionate and dimethyl thiodipropionate for the subsequent transesterification reaction.

If sulfur is used in the preparation of mixed esters, a small amount, usually 2 to 10 sulfur, based on the total mixed ester
As a result of the presence of % by weight of dithiodiesters, poly(oxyalkylene)-polyester-poly(monosulfide)-poly(disulfide)-polythiols can be prepared.

EXAMPLE 1 The run below (Run 1) shows the production of methyl 3-mercaptopropionate, dimethylthiodipropionate and dimethyldithiopropionate.

Methanol (600 mA), concentrated ammonium hydroxide (2.8 wt.%
NH3,21,6f), sulfur (12g) and hydrogen sulfide (816S') were charged.

Methyl acrylate (13761) was introduced into the stirred reactor over a period of 45 minutes.

During this reaction period, the temperature of the reaction mixture was varied from 23°C to 53°C.
while increasing the pressure to 1650 kPa (16,9k
g/c4G) to 1150 kPa (11,9k
g/crAG).

After stirring for an additional 30 minutes, the reactor was vented to release excess hydrogen sulfide and the remaining reaction solution was transferred to a fractionator.

A total of 5 runs were performed as described above.

The resulting reaction mixture was combined prior to fractional distillation.

Both parts (5889 g) = 50) liters (Hg) pressure, 87
-93°C boiling range, which contained 98.6% by weight of methyl 3-mercaptopropionate (GL
C1, i.e., analyzed by gas-liquid chromatography).

The undistilled pot residue (3005y) contained 85% by weight dimethylthiodipropionate and 15% by weight dimethyldithiodipropionate (analyzed by GLC).

EXAMPLE 1 Methanol, ammonium hydroxide, sulfur and hydrogen sulfide were used in the same amounts using the same reactor and the same charging process as in Example I.

30 to 40 methyl methacrylate (1376f)
Added to the stirred reactor for a minute.

Addition of methyl acrylate was followed by stirring for 15 minutes.

The reaction solutions for six consecutive runs were then combined and the methanol distilled.

The remaining reaction product containing methylmercaptopropionate, dimethylthiodipropionate and dimethyldithiodipropionate in a weight ratio of 67.3/27.8/4.9 respectively (by GLC) was filtered.

Example ■ The following pilot plant run was conducted under essentially the same conditions as Example ■ except that it was scaled up to a larger volume.

3.4 kg of Heiou inside the 1895J glass-lined reactor
and 136'k of methanol along with approximately 80 gallons of hydrogen sulfide.
g and 136 kg of concentrated ammonium hydroxide (28% by weight NH3) were charged.

Then, over a period of 2 hours, 409J of methyl acrylate was charged into the reactor.

Over the duration of the reaction, the temperature of the reaction mixture was increased from 29°C to about 48°C, while the pressure was increased to about 2100 kPa (2
1,5kg/crrtG) to approximately 1150 kPa
(11.9kg/c4G).

After another hour of reaction time, the reactor was vented to release excess hydrogen sulfide, then a reflux condenser was attached to the top of the reactor, and the reactor was heated to a temperature of about 162°C to remove water and methanol. kicked out.

This was then cooled and the resulting product containing mixed esters of methyl 3-mercaptopropionate and dimethyl thiodipropionate was charged to a holding drum.

Examples ■ Water; hydrogen sulfide (816♂, 24 mol), ammonia (6
,Of) without heating or cooling performance 3.791
A series of runs were performed by charging a stainless steel autoclave and pumping methyl acrylate (1376f, 16 moles) into the reactor.

The time required for the maximum temperature to be reached and the corresponding pressure drop were recorded.

After charging the acrylate, small samples were periodically removed for analysis by gas liquid chromatography (GLC) to determine when the reaction was complete.

When the GLC analysis showed no further change in reactant to product ratio, unreacted hydrogen sulfide was allowed to flash.

Data obtained from these runs (based on GLC analysis)
is summarized below: (0 methanol per mole of methyl acrylate solution (2)
Per mole of methyl acrylate? (3) Time in minutes required for methyl acrylate addition to the reactor (4) Time in minutes from start of methyl acrylate addition to maximum temperature (5) kg/kg/min from start of methyl acrylate addition to temperature peak Pressure drop in caG (6) Time in minutes from the end of methyl acrylate addition to discharge from the reactor and flushing of hydrogen sulfide.

(7) Area percentage measured by gas-liquid chromatography 1 (8) R is CH30-C-CH2CH2-.

(9) Left at room temperature overnight before completion.

Claims (1)

[Claims] 1. Methyl acrylate and hydrogen sulfide are combined with sulfur and/or
or in the presence of a co-catalyst consisting of water and a lower alcohol,
1. A method for producing a mixture of methyl mercaptopropionate and dimethyl mono- and (or) di-thiodipropionate, characterized in that the reaction is carried out using an addition catalyst. 2 The above sulfur is 0 per part by weight of methyl acrylate.
．． 0.002 to 0.05 parts by weight of said water per part by weight of methyl acrylate.
A method according to claim 1, wherein the method is present in an amount ranging from 4 to 0.1 parts by weight. 3. A process according to claim 1 or 2, wherein said alcohol is present in the range from 0.04 to 0.4 parts by weight per part by weight of methyl acrylate. 4. The method according to claims 1 to 3, wherein the alcohol is methanol. 5. A process according to any one of claims 1 to 3, wherein said hydrogen sulfide is used in an amount ranging from 1 to 3 moles of hydrogen sulfide per mole of methyl acrylate. 6. A method according to any one of claims 1 to 5, wherein the addition catalyst is ammonium hydroxide. 7. Process according to claim 6, using concentrated ammonium hydroxide as catalyst and sulfur as promoter.