JPH0366313B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for continuously producing alkyltinthiocarboxylic acid esters. Alkyltin thiocarboxylic acid esters are known stabilizers for vinyl chloride homopolymers and many copolymers. This manufacturing method, for example,
It is described in Houben-Weyl, Methoden der Organischen Chemie, Vol. 6 (1978), pp. 348-350. This is carried out by discontinuous reaction of alkyltin oxides or alkyltin halides, especially alkyltin chlorides, with thiocarboxylic acid esters. This reaction with the alkyltin chloride is preferably carried out in the presence of a base as an acid acceptor under various temperature, time and PH conditions. The preparation of alkyltin thiocarboxylic acid esters from the corresponding alkyltin halides generally involves
For example, it is carried out in the presence of an organic solvent as described in US Pat. No. 2,832,751. It is also known from the literature to carry out this reaction without the presence of a solvent (see US Pat. No. 3,716,568). In batch processes using organic solvents, it is possible to carry out this reaction either at relatively low or higher temperatures. In this reaction, the aqueous phase is usually well and completely separated from the product phase. Also, space/time yield (space/time yield)
refers to the yield of final product from a given volume in a given time, whereas methods performed in the absence of solvent give higher space/time yields. Furthermore, the solvent regeneration step is redundant in this method. Important disadvantages of processes carried out with organic solvents are the rather low space/time yields and the fact that the solvent used has to be removed by distillation from the finishing phase, which saves energy. consumption, contaminating the air used and waste water. Furthermore, the flash point of the product decreases rapidly due to solvent residues, resulting in the need for safer measures in plant equipment. On the other hand, the absence of a solvent in solvent-free processes usually has the disadvantage that only a small separation of the organic product phase from the aqueous phase is possible. This means that
Long standing times also mean loss of product through the formation of mesophases. Furthermore, the difficulty in separating residual water from the organic phase requires relatively long distillation times for the residual water, resulting in a long exposure of the product to heat. For batch reactions of alkyltin halides and thiocarboxylic acid esters, it is necessary to carry out the reaction at low temperatures. Since this reaction is strongly exothermic, the addition of base can only be as fast as the removal of heat through the reaction jacket, which increases reaction times in large-scale production and therefore This results in lower space/time yields. Furthermore, at the beginning of such base addition, the PH of the reaction mixture is in a strongly acidic range (PH 1 or less), and then gradually increases to a neutral range. During the reaction in the acidic range, undesirable saponification reactions occur, for example for thiocarboxylates, which impair the purity of the product. Furthermore, according to the rule of thumb, in batch operations, the final PH
Since the values must be precisely adjusted, uniform production can only be ensured by careful monitoring.
It is known that. Exceeding the PH value results in a decrease in product purity and product loss. The reaction of alkyltin oxides with, for example, thiocarboxylic acid esters requires technically complex intermediate steps of isolation and drying of the alkyltin oxides.
The method described in DE 2209336 is not advantageous because the thin film process requires complex reaction equipment. It is an object of the present invention to provide a continuous process for the production of alkyltinthiocarboxylic acid esters, in which the reactants are mixed under constant pH and over a wide range of temperatures in a simple apparatus with short residence times. Within this range, it is possible to carry out the reaction, if desired, without cooling or removing the heat of reaction and the heat of neutralization, which eliminates the above-mentioned disadvantages of the known processes. Therefore, the method for producing an alkyltin thiocarboxylic acid ester according to the present invention has the following formula: R _x Sn[S(CH ₂ ) _o COOR'] _4-x (1) (wherein 2, R
is a butyl group, an octyl group, a lauryl group or a -
CH ₂ CH ₂ COO-n-C ₄ H ₉ and R' is C 8 -C 16 alkyl. )
In a method for producing an alkyltinthiocarboxylic acid ester represented by the formula (2) R _x SnHal _4-x (2) (formula (where R and x are as defined above and Hal is a chlorine atom, bromine atom or iodine atom), an alkyltin halide represented by the formula (3) HS(CH ₂ ) _o COOR′ ( 3) with a thiocarboxylic acid ester represented by the formula (wherein R′ and n are as defined above) at a constant pH value in the range of 3 to 8 and at a temperature range of 40°C to 80°C. ,
The reaction is carried out continuously in the presence of an aqueous solution of NaOH or KOH and in the absence of an organic solvent. Surprisingly, in contrast to discontinuous processes, only continuous operation does not result in a reduction in product quality. This is because the product is only exposed to high temperatures for a short time and preferably at a constant temperature in the neutral range.
This is because it is a PH value. Therefore, for example 75
A continuous process at 0.degree. C. and PH 6.5 makes it possible to obtain products without loss of quality and with substantially high space/time yields. For example, in Example 1 below, the space/time yield is 2.07 Kg/lh., and the space/time yield of the corresponding batch method is approximately 20 times lower than that of each embodiment of the present invention. This point is indeed a very advantageous effect of the present invention. Furthermore, the desired PH range can be easily adjusted in the entire reaction. The method of the present invention requires two reaction vessels (stirring vessels).
It is carried out by continuous operation in a reaction system containing. The method of the invention also allows the reaction to be carried out at a higher temperature than when following the batch method. When following the batch process, the reaction temperature is generally limited to at most less than 80°C. Furthermore, according to the present invention, continuous reactions can be carried out under adiabatic conditions. In the present invention, the reaction is carried out in a two-stage stirred vessel cascade, the residence time in the first vessel being from 1 to 60 minutes, preferably from 1 to 10 minutes,
Optimally 1 to 5 minutes. The sizes of the containers in the two-stage cascade may be the same or different. Residence times in individual reaction vessels will therefore vary accordingly. The reaction temperature ranges from 40°C to 80°C, preferably
The temperature ranges from 80°C to 50°C to 60°C. By appropriately selecting the temperature at which the reaction vessel is filled with the starting materials, it is possible to carry out the reaction adiabatically. This is achieved by continuous addition of the starting materials at low temperatures, preferably in the range 20°C to 30°C. Since there is no need to remove reaction heat and neutralization heat, cooling energy can be reduced. In the continuous reaction operation according to the invention, a constant PH value in the range of 3 to 8, preferably in the range of 5 to 7, is maintained throughout the entire reaction. this
PH can be adjusted by using a base, eg, monitored with a PH meter. The base used in the method of the present invention is NaOH or
It is an aqueous solution of KOH. These are preferably 10%
It is used as a 50% to 50% aqueous solution. Particularly convenient is an 18 to 20% aqueous sodium hydroxide solution. In the present invention, the reaction is carried out in the absence of any organic solvent such as ether or hydrocarbon. Furthermore, by the method of the present invention, an alkyltin thiocarboxylic acid ester represented by the above formula (1) is produced. In formula (1), R as a butyl group is n-
It may be a butyl group or a t-butyl group, with an n-butyl group being preferred. R as an octyl group is n
-octyl or 2-ethylhexyl, with n-octyl being preferred. R' can be, for example, straight-chain or branched octyl, decyl, dodecyl, tetradecyl and hexadecyl groups and groups from the commercially available alcohol mixtures known as Alfols. The alcohol mixture contains a plurality of alkyl groups having substantially the same number of carbon atoms and is predominantly branched.
The alkyl group is today referred to as "alfyls"
known as. Among the methods of the present invention, the following formula R _x Sn[S(CH ₂ ) _o COOR'] _4-x (where x and n represent 1 or 2, and R is a butyl group, an octyl group, or a group -
CH ₂ CH ₂ COO-n-C ₄ H ₉ and R' represents an alkyl group having 8 to 16 carbon atoms. ) is particularly suitable for producing alkyltinthiocarboxylic esters. The starting materials used in the process of the invention are alkyltin halides and thiocarboxylic acid esters. The alkyltin halides used are chlorides, bromides or iodides, preferably alkyltin chlorides or bromides in an amount of 85 to 115 mol %, based on the thiocarboxylic acid ester. Thiocarboxylic acid esters are known compounds. Particularly preferred are thioglycolic acid esters and thiopropionic acid esters. The continuous reaction can be started in batches, i.e., first the addition of the reagents is started, then an aqueous solution of the base is added to adjust the desired pH range, and finally both the reaction components and the solution of the base are added sequentially. It is effective to do so. The starting materials, alkyltin halide and thiocarboxylic acid ester, may be added to the reactor as a pre-prepared mixture at a temperature of 20°C to 30°C, or may be added separately at different temperatures. The process of the invention may be carried out, for example, by the following procedure: To start the reaction, a suitable alkyltin chloride or mixed chloride and the corresponding thiocarboxylic ester are charged until the latter is approximately half full of the reactor. is pumped into the reactor at a given molar ratio until the While stirring, add the aqueous solution of base until the desired PH value is reached, then start the continuous addition of sodium hydroxide solution, alkyltin chloride (or mixed chlorides) and thiocarboxylic acid ester. When the controlled volume is reached, the reaction mixture is pumped into the second reactor such that the controlled volume is maintained in the second stirred vessel. After an average residence time of 1 to 60 minutes, preferably 1 to 10 minutes and optimally 1 to 5 minutes, the reaction mixture is continuously discharged from the reactor in order to separate the organic phase from the aqueous phase. Separation of water from the reaction mixture discharged from the reactor is preferably carried out by a continuously operating liquid-liquid extractor and by a suitable separation column. Liquid-liquid extractors are conventional separators used in chemical technology. Details of the individual extraction methods are described in Ensyklopadie der technischen Chemie by Ullmann, vol. 2, 4th edition (1972), p. 553. , and details of the individual devices and extractors are described on pages 560-564. Continuously operating liquid-liquid centrifugal extractors are preferably
It is particularly suitable for separating water from the reaction mixture removed from the reactor at 40°C-50°C. It may also be advantageous to dry the product phase isolated in this way continuously, for example by continuous spray drying or with the aid of a thin film or falling film evaporator. Spray drying, thin film or falling film evaporators are also known drying or evaporation systems. Such devices are described, for example, in the above-mentioned article by Ullmann, Volume 2, 4th Edition (1972), pp. 712-713 (spray dryer) and pp. 655--
656 (Thin Film and Falling Film Evaporators). The invention will be explained in more detail with the following examples. The present examples are all examples in which alkyltin thiocarboxylic acid esters were continuously produced using the two-stage cascade reaction system shown in FIG.
As shown in the figure, the reaction system consists of a cascade in which stirring vessel 1 (capacity: 250 ml), which is the first reactor, and stirring vessel 2 (capacity: 1000 ml), which is the second reactor, are connected. A reactant is sent to No. 2 by a pump. Stirring vessel 1 is connected to tanks 11 and 17 for alkyltin halide and thiocarboxylic acid ester via a transport pipe, and receives supplies of these substances, and is also connected to tank 12 via a transport pipe, from which NaOH Receive fluid injection. On the other hand, the stirring vessel 2 is connected to a tank 13 via a transport pipe, from which it receives an additional supply of NaOH liquid, and is also connected to a liquid-liquid extractor 14 via a transport pipe, so that the mixture is extracted after the reaction is completed. Pump into extractor. The extractor 14 is a commercially available centrifugal separator that performs centrifugation without adding additional water, sends the separated product alkyltin thiocarboxylic acid ester to the tank 15, and removes the remaining NaCl solution. is collected in tank 16. Example 1: Mixture of 30 mol% mono-n-octyltin trichloride and 70 mol% di-n-octyltin dichloride
100 parts by weight of 2-ethylhexylthioglycolic acid ester were placed in a reaction system consisting of a cascade of two reactors each equipped with a stirrer, a level meter, a PH meter and a thermometer at a temperature of 60°C. Continuous pressure feeding. A pH of 6.5-7.0 is maintained in the first reactor by simultaneously adding an aqueous sodium hydroxide solution to the reaction with sufficient stirring. The addition of sodium hydroxide is controlled by a PH meter in the first reactor. This reaction mixture is pumped into a second reactor, the volume of which is controlled by a level meter. By controlling the feed and discharge of this reaction mixture, the residence time of the reactants in the first reactor is maintained at 5 minutes. By removing the reaction heat generated during this reaction, the temperature is kept constant at 60° C. in the first and second reactors. Also, in order to maintain a constant pH of 6.9, an aqueous sodium hydroxide solution (very small amount) is introduced into the second reactor (addition controlled by a PH meter). The reactants are then pumped from the second reactor to a liquid-liquid extractor in which the salt-containing aqueous phase is continuously separated from the product. The product is then spray dried and purified by filtration to give 2-ethylhexylmono-n-
A viscous liquid is obtained consisting of a mixture of 30 mol % of octyltin trithioglycolic acid ester and 70 mol % of 2-ethylhexyldi-n-octyltin bisthioglycolic acid ester. This yield is 98% of theory, based on the two starting materials monomer and dioctyltin chloride. Analytical values: Sn (theoretical value): 15.5%; S: 9.0% Sn (actual value): 15.2% S: 8.9% Example 2: 100 parts by weight of mono-n-butyltin trichloride and tetradecylthioglycolic acid 307 parts by weight of ester are continuously pumped into a reaction system consisting of a cascade of two reactors each equipped with a stirrer, a level meter, a PH meter and a thermometer at a temperature of 30.degree. By introducing an aqueous sodium hydroxide solution into the first reactor, about 5
Maintain the PH. This reactant is then pumped into a second reactor, the volume of which is controlled by a level meter. By controlling the feed and discharge of this reaction mixture, the residence time of the reactants in the first reactor is maintained at 2 minutes. By removing the heat of reaction, the temperature in the first and second reactors is maintained not to exceed 50°C. Also, in order to maintain a constant pH of 5, an aqueous sodium hydroxide solution (very small amount) is introduced into the second reactor (addition controlled by a PH meter). The reactants are pumped from the second reactor to a continuously operating liquid-liquid extractor to separate the aqueous phase from the product phase. This product phase is then spray dried and purified by filtration to obtain _a viscous _{liquid of} the formula: n- _C4H9Sn ( _{SCH2COOC14H29} ) ₃ . This yield is based on the starting material, mono-n-butyltin chloride.
It is 96%. Analytical values: Sn (theoretical value): 11.4%; S: 9.3% Sn (measured value): 11.2%; S: 9.1% Example 3: 100 weight of previously produced di-n-octyltin dichloride and 98 parts by weight of 2-ethylhexylthioglycolic acid ester are continuously pumped at room temperature into a reaction system consisting of a cascade of two reactors, each equipped with a stirrer, a level meter, a pH meter and a thermometer. . in the first reactor by simultaneously adding an aqueous sodium hydroxide solution to the reactant with sufficient stirring.
Maintain PH of 6.5-7.0. The addition of sodium hydroxide is controlled by a PH meter in the first reactor. The heat of reaction generated during this reaction is not removed. The reaction temperature is 65°C. (This temperature is determined by the adiabatic mode of operation and depends on the temperature of the starting materials, the mixture of dioctyltin dichloride and 2-ethylhexylthioglycolic acid ester). The reaction mixture is pumped into a second reactor (volume controlled by a level meter).
By controlling the feed and discharge of this reaction mixture, the residence time of the reactants in the first reactor is maintained at 5 minutes. Also, in order to maintain a constant pH of 6.9, an aqueous sodium hydroxide solution (very small amount) is introduced into the second reactor (addition controlled by a PH meter). The reactants are then pumped from the second reactor to a liquid-liquid extractor in which the salt-containing aqueous phase is continuously separated from the product. The product is then spray dried and purified by filtration to give 2-ethylhexyldi-n-
- A viscous liquid consisting of octyltin bisthioglycolic acid ester is obtained. The yield is 97% of theory, based on the starting material di-n-octyltin dichloride. Analytical values: Sn (theoretical value): 15.8%; S: 8.5% Sn (actual value): 15.7%; S: 8.3% In the above examples, the liquid level in stirring container 1 and the liquid level in stirring container 2 are as follows. The liquid level was kept constant using a liquid level control device. The following Tables 1 and 3 are tables showing the flow rates of substances in each transport pipe of the reaction system in the manufacturing process according to Examples 1 and 3. Table 2 is a similar table for a similar example of Example 2 using the material of Example 1.

【table】

【table】

[Table] No starting material could be detected in the reaction mixture or in the product. Further, the content of harmful by-products in the product was extremely small, which was much lower than that in the conventional batch method.
Furthermore, the residence time in stirring vessel 2 was in the range of 0.2 to 0.25 hours. When using the batch method, the reaction temperature was less than 80°C, whereas according to the method of the example, the reaction temperature could be set over a wider range including higher temperatures. Further, the continuous manufacturing method according to this example could be carried out adiabatically. Furthermore, a comparative test between the method according to the present invention and a known batch production method was conducted as follows. Test Example 1 Preparation of ( _C8H17 ) _2Sn [ _SCH2COO -i- _C8H17 ] ₂ A Process according to _Example 3 of U.S. Pat _. No. 3,716,568 Dioctyltin dichloride 100g (0.23 mol) ) and 95 g (0.46 mol) of isooctylthioglycolate were charged into a reaction vessel equipped with a stirrer and cooling capacity. NaOH (40%) liquid 46.1g (0.46
mol) to the mixture slowly and increase the temperature.
Maintained at 45-49°C. After the NaOH addition was complete, the reaction mixture was stirred for 1 hour and then the aqueous phase was removed. The product obtained was a yellow liquid.
Yield: 94% of theory. B. Preparation according to the method of Example 1 of the invention Equivalent amounts of starting materials as in A. above, namely 100 g (0.23 mol) of dioctyltin dichloride, 95 g (0.46 mol) of isooctylthioglycolate and 16
46.1 g of NaOH (40%) diluted to 0.46% solution
mol) and run the reaction at the same temperature (45-49℃).
The above Example 1 process was repeated. The product was obtained as a yellow liquid with a yield of 97% of the ring value. C. The above method A. is described in U.S. Patent Specification No.
The Example 3 method of No. 3,716,568 was modified to some extent to make it truly comparable with the method of the present invention.
That is, as in the present invention, the reaction was carried out without solvent, and the relative amounts of starting materials were approximately matched to those used in the process of the present invention. Furthermore, the reaction temperature was the same for Method A and Method B. 2 Quality Studies During the production of dialkyltin alkylthiocarboxylic acid esters, undesired cyclic by-products are often formed. This results in undesirable precipitation and adversely affects the storage stability of the product. In the case of the above reaction, such a by-product is a compound of formula (1): The content of by-product (1) in both the products obtained by the above methods, A and B, was determined by analysis. The results are given in the table below.

The values given in Table 2 demonstrate that using the continuous process of the invention not only results in better yields, but rather, in particular, a dramatic reduction in undesired by-products. This indicates that the result will be . The stabilizer obtained according to the known batch method contains 4.5% of the by-product of formula (1), whereas the stabilizer obtained according to the method of the present invention contains no by-product. Virtually free (less than 0.5%). Therefore, according to the present invention, it is possible to continuously produce alkyltin thiocarboxylic acid esters using a simple device, in a short residence time, under a constant pH, and in a wide temperature range, and moreover, it is possible to produce alkyltin thiocarboxylic acid esters continuously using a simple device, and in a shorter residence time than in the case of a batch method. The target compound can be obtained in high yield. Moreover, the advantageous effect of the present invention is that the amount of harmful by-products that impede the storage stability of the product can be significantly reduced compared to the batch method, and the target compound can be obtained with very high purity. This is something that can be done.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the reaction system used in the method of the example.

Claims (1)

[Claims] 1 Formula (1) R _x Sn[S(CH ₂ ) _o COOR'] _4-x (1) (where x and n represent 1 or 2, and R
is a butyl group, an octyl group, a lauryl group or a -
CH ₂ CH ₂ COO-n-C ₄ H ₉ and R' is C 8 -C 16 alkyl. )
In the method for producing an alkyltin thiocarboxylic acid ester represented by the formula (2) R _x SnHal _4-x (2) (formula (where R and x are as defined above and Hal is a chlorine atom, bromine atom or iodine atom), an alkyltin halide represented by the formula (3) HS(CH ₂ ) _o COOR′ ( 3) with a thiocarboxylic acid ester represented by the formula (wherein R′ and n are as defined above) at a constant pH value in the range of 3 to 8 and at a temperature range of 40°C to 80°C. ,
A method for producing an alkyltin thiocarboxylic acid ester, which comprises continuous reaction in the presence of an aqueous solution of NaOH or KOH and in the absence of an organic solvent. 2. The method according to claim 1, wherein the reaction is carried out in the reaction system having a residence time of 1 to 10 minutes. 3 The reaction is carried out in the reaction system using 5 to 7
The method according to claim 1, which is carried out at a PH. 4 The reaction is carried out in the reaction system at 50°C to 70°C.
A method according to claim 1, which is carried out in a temperature range of .degree. 5 Add the starting material to the reaction system at 20°C.
2. The method according to claim 1, wherein the reaction is carried out adiabatically. 6. The method according to claim 1, wherein the product removed from the reaction system is separated from the aqueous phase and subsequently dried. 7. The method of claim 6, wherein the product phase removed from the reaction system is separated from the aqueous phase by a continuously operating liquid-liquid extractor or separation column. 8. The method of claim 6, wherein the product phase removed from the reaction system is separated from the aqueous phase by a continuously operating liquid-liquid centrifugal extractor. 9. Process according to claim 6, characterized in that the product phase is dried by continuous spray drying or with the aid of a thin film or falling film evaporator. 10 Formula R _x Sn[S(CH ₂ ) _o COOR'] _4-x (where x and n represent 1 or 2, R
is a butyl group, an octyl group or a group -
CH ₂ CH ₂ COO-n-C ₄ H ₉ and R' is C 8 -C 16 alkyl. )
The method according to claim 1 for producing an alkyltinthiocarboxylic acid ester represented by: