JP2005255629A - Method for producing 1,3,5,7-tetramethylcyclosiloxane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing highly pure 1,3,5,7-tetramethylcyclotetrasiloxane having a reduced 1,3,5-trimethylcyclotrisiloxane content. <P>SOLUTION: This method for producing the 1,3,5,7-tetramethylcyclotetrasiloxane comprises heating a chain or cyclic methylhydrogenpolysiloxane in the presence of a catalyst. Therein, when a gas containing the 1,3,5,7-tetramethylcyclotetrasiloxane and 1,3,5-trimethylcyclotrisiloxane is condensed, a part or all parts of the non-condensed phase are removed from the condensation system to produce the highly pure 1,3,5,7-tetramethylcyclotetrasiloxane. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing 1,3,5,7-tetramethylcyclotetrasiloxane used as a raw material in the silicone industry.

  As a method for producing cyclosiloxane by disproportionating polysiloxane, a method using an acidic or alkaline catalyst is generally known. However, such a method using an acidic or alkaline catalyst has severe reaction conditions and is not advantageous for industrially stable production.

  As a method for producing cyclosiloxane by disproportionation under neutral conditions, for example, the production of cyclosiloxane by thermal decomposition of polysiloxane is known, but this method requires a very high temperature of about 300 ° C. This method is also not an advantageous method for industrially stable production. In addition, as a disproportionation method under neutral conditions, a method using a transition metal catalyst is known. However, this method requires the use of an expensive metal catalyst such as Pt or Pd, and a cost viewpoint is also considered. This is not an industrially advantageous method.

  As a method for producing 1,3,5,7-tetramethylcyclotetrasiloxane, for example, a method of hydrolytic condensation of organosilanes having two hydrolyzable groups on silicon such as methyldichlorosilane is generally used. Are known. However, under such hydrolysis condensation reaction conditions, the reaction system becomes acidic and harsh, which is not advantageous for industrially stable production.

  In particular, in the production of cyclic oligosiloxanes containing Si-H groups, Si-H groups are very reactive under such acidic conditions, and react with water or silanol groups coexisting in the reaction system, The yield of the target compound is low. In order to solve this problem, the following methods (A) or (B) have been proposed.

  That is, (a) methyldichlorosilane is hydrolyzed in the presence of a mixed solvent of tetrahydrofuran and a hydrocarbon solvent (Patent Document 1), and (b) dichlorodisiloxane is hydrolyzed in the presence of t-butyl alcohol. This is a decomposition method (Patent Document 2).

  However, in order to obtain a cyclic oligosiloxane as a product with a high yield in the method (a), it is necessary to use benzene as a hydrocarbon solvent. This may be a problem when it is put to practical use.

  In the method (b), since dichlorodisiloxane used as a raw material is not a general-purpose raw material, the availability of the raw material becomes a problem when the present technology is generally implemented. There is a problem in that general technology lacks generality.

  As another production method of 1,3,5,7-tetramethylcyclotetrasiloxane, by reacting a chain polysiloxane or a highly polymerized cyclic polysiloxane in the presence of an acidic or alkaline catalyst under various conditions. A method has been proposed.

  Examples of the method using an acidic catalyst include (c) a method of reacting a Si-H group-containing polysiloxane in the presence of water and activated clay (Patent Document 3), and (d) methylhydrogen polysiloxane in the presence of an acid catalyst. A method of reacting by heating under (Patent Document 4), (e) a method of contacting organopolysiloxane with a heated fixed catalyst bed under reduced pressure (Patent Document 5), and (f) methylhydrogenpolysiloxane. There are a method in which the reaction is carried out in the presence of an organodisiloxane having a high boiling point (Patent Document 6) and a method in which (g) an organohydrogenpolysiloxane is reacted in the presence of aluminum chloride (Patent Document 7).

  Examples of the method using an alkaline catalyst include (h) a method using an alkali metal carbonate as a catalyst (Patent Document 8) and (ii) a method using an alkali metal silanolate as a catalyst (Patent Document 9).

  When an acid catalyst or an alkali catalyst as described above is used, there is a problem that the reaction system gels due to a stability problem with the Si—H group.

  As a means for solving this problem, it is possible to carry out the reaction under the simple conditions of neutral conditions and relatively low temperatures using raw materials that can be obtained at low cost, and especially in the case of a system containing Si-H groups. As a method for producing a cyclic oligosiloxane, which is practical when carried out industrially without gelation, a production method comprising heating a chain or cyclic polysiloxane in the presence of a metal alkoxide ( There exists patent document 10). Using this reaction, 1,3,5,7-tetramethylcyclotetrasiloxane can be produced.

However, when these chain polysiloxanes or cyclic polysiloxanes with a high degree of polymerization are reacted in the presence of an acidic catalyst, an alkaline catalyst or a metal alkoxide catalyst, those having higher boiling points than the same substance can be cut by a distillation column. However, 1,3,5-trimethylcyclotrisiloxane having a low boiling point is recovered together with 1,3,5,7-tetramethylcyclotetrasiloxane in a receiver after reactive distillation, and 1,3,5,7-tetra It has been found that there is a problem in terms of obtaining methylcyclotetrasiloxane with high purity.
Japanese Patent Laid-Open No. 6-80680 JP-A-7-285974 Japanese Patent Application No.54-13480 JP-A-55-11697 JP-A-2-129192 JP-A-7-242678 JP-A-7-316167 Japanese Examined Patent Publication No. 45-15036 Japanese Patent Publication No.33-2149 JP 2000-159783 A

  Accordingly, an object of the present invention is to provide a method for producing 1,3,5,7-tetramethylcyclotetrasiloxane having a high purity with a reduced content of 1,3,5-trimethylcyclotrisiloxane.

In order to solve such a problem, the present inventors have intensively studied and obtained by heating a chain or cyclic methylhydrogenpolysiloxane in the presence of an acidic catalyst, an alkali catalyst, or a metal alkoxide, By removing 1,3,5-trimethylcyclotrisiloxane from a product based on 3,5-trimethylcyclotrisiloxane and 1,3,5,7-tetramethylcyclotetrasiloxane, , 5,7-tetramethylcyclotetrasiloxane has been found to be produced with improved purity, and the present invention has been achieved.
That is,
Heating methylhydrogenpolysiloxane in the presence of a catalyst;
Producing a system comprising gaseous 1,3,5,7-tetramethylcyclotetrasiloxane and gaseous 1,3,5-trimethylcyclotrisiloxane;
A part of the gaseous 1,3,5,7-tetramethylcyclotetrasiloxane and the gaseous 1,3,5-trimethylcyclotrisiloxane is condensed, and 1,3,5,5 contained in the system Step 2 for separating 7-tetramethylcyclotetrasiloxane and 1,3,5-trimethylcyclotrisiloxane into a condensed phase and a non-condensed phase,
Removing a part or all of 1,3,5,7-tetramethylcyclotetrasiloxane and 1,3,5-trimethylcyclotrisiloxane contained in the non-condensed phase from the condensing part where the condensed phase exists Including 3,
The weight ratio to 1,3,5-trimethylcyclotrisiloxane is greater than the weight ratio of 1,3,5,7-tetramethylcyclotetrasiloxane to gaseous 1,3,5-trimethylcyclotrisiloxane in Step 1 A method for producing 1,3,5,7-tetramethylcyclotetrasiloxane (Claim 1).

1,3,5,7-tetramethylcyclotetrasiloxane and 1,3,5-trimethyl contained in the non-condensed phase via a space installed above the space where the system generated in Step 1 is present The manufacturing method (Claim 2) according to claim 1, wherein a part or all of the cyclotrisiloxane is discharged from the condensing part.

  2. The production method according to claim 1, wherein the amount of condensation is controlled by changing the temperature of the condensed refrigerant in step (Claim 3).

  According to the present invention, 1,3,5,7-tetramethylcyclotetrasiloxane can be produced with high purity by a simple method without newly installing a separation apparatus such as a distillation column.

Hereinafter, the present invention will be described in detail.

The methyl hydrogen polysiloxane used in the present invention is not particularly limited.

In particular,
Me ₃ SiO— (MeHSiO) x -SiMe ₃ ,
Me ₂ PhSiO— (MeHSiO) x -SiMe ₂ Ph,
MeHSi (OH) O- (MeHSiO) x-SiMe (OH) H,
(Here, x represents a number of 4 to 1000, preferably a number of 20 to 500, and more preferably a number of 30 to 200).

（ここでいうｘは３〜１０００の数を表し、好ましくは３〜１００の数を表し、さらに好ましくは４〜１０の数を表す。）等が挙げられる。

本発明で用いる触媒は、特に限定されるものではないが、例えば、酸性触媒、アリカリ触媒、金属アルコキシド触媒が挙げられる。

(Where x represents a number of 3 to 1000, preferably 3 to 100, and more preferably 4 to 10).

Although the catalyst used by this invention is not specifically limited, For example, an acidic catalyst, an antkari catalyst, and a metal alkoxide catalyst are mentioned.

  The acidic catalyst used in the present invention is not particularly limited, and examples thereof include hydrochloric acid, sulfuric acid, nitric acid, trifluoromethanesulfonic acid, activated clay, and Lewis acid such as aluminum chloride.

  The alkaline catalyst used in the present invention is not particularly limited, and examples thereof include alkali metal carbonates such as sodium carbonate and potassium carbonate, and alkali metal silanolates.

  The metal alkoxide catalyst used in the present invention is not particularly limited.

（式中Ｒ1は一価の置換または非置換の炭化水素基であり、炭化水素基の例としては前記一般式（Ｉ）のＲ¹に同じであり、Ｙ¹およびＹ²は炭素数が１〜８のアルキル基、アリール基、あるいはアルコキシ基、Ｍは２価乃至４価の金属元素で表され、ｒおよびｓは０、１、２、３、４であり、ｒ＋ｓは２乃至４である）で表すことができる。これらのうち、好ましくはＭがＡｌ、Ｔｉ、Ｚｒ、Ｓｎ、Ｚｎである金属アルコキシドが用いられ、さらに好ましくはＭがＡｌ、Ｔｉ、Ｚｒである金属アルコキシドが用いられ、最も好ましくはアルミニウムアルコキシドが用いられる。

(Wherein R1 is a substituted or unsubstituted monovalent hydrocarbon group, examples of the hydrocarbon group are the same as R ¹ in the general formula (I), Y ¹ and Y ² are carbon atoms 1 ˜8 alkyl group, aryl group or alkoxy group, M is represented by a divalent to tetravalent metal element, r and s are 0, 1, 2, 3, 4 and r + s is 2 to 4 ). Of these, metal alkoxides in which M is preferably Al, Ti, Zr, Sn, Zn are used, more preferably metal alkoxides in which M is Al, Ti, Zr are used, and aluminum alkoxides are most preferably used. It is done.

  Specific examples include aluminum triethoxide, aluminum triisopropoxide, aluminum tributoxide, aluminum trisecondary butoxide, aluminum diisopropoxysecondary butoxide, aluminum diisopropoxyacetylacetonate, aluminum disecondary butoxyacetylacetate. Narate, aluminum diisopropoxyethyl acetoacetate, aluminum di-secondary butoxyethyl acetoacetate, aluminum trisacetylacetonate, aluminum trisethylacetoacetate, aluminum acetylacetonate bisethylacetoacetate, titanium tetraethoxide, titanium Tetraisopropoxide, Titanium tetrabutoxide, Titanium diisopropoxybisacetylacetonate, Titanium diiso Ropoxybisethylacetoacetate, titanium tetra-2-ethylhexyl oxide, titanium diisopropoxybis (2-ethyl-1,3-hexanediolate), titanium dibutoxybis (triethanolaminato), zirconium tetrabutoxide, zirconium Tetraisopropoxide, zirconium tetramethoxide, zirconium tributoxide monoacetylacetonate, zirconium dibutoxide bisacetylacetonate, zirconium butoxide trisacetylacetonate, zirconium tetraacetylacetonate, zirconium tributoxide monoethylacetoacetate, zirconium di Butoxide bisethyl acetoacetate, zirconium butoxide trisethyl acetoacetate, zirconium tetraethyl Acetoacetate, it is. In addition, cyclic 1,3,5-triisopropoxycyclotrialuminoxane and the like can also be used. Of these, aluminum triisopropoxide, aluminum tri-secondary butoxide, aluminum diisopropoxyethyl acetoacetate, aluminum disecondary butoxyethyl acetoacetate, aluminum trisacetylacetonate, titanium tetraisopropoxide, titanium tetra Butoxide and zirconium tetrabutoxide are used. Most preferred is aluminum triisopropoxide. These metal alkoxides may be used alone or in combination at any ratio.

  The amount of the metal alkoxide used in the present invention can be variously selected according to the reaction rate, but is generally 0.01 to 10 parts by weight, preferably 0.01 to 5 parts by weight, more preferably 0.01 based on the starting polysiloxane. Up to 1 part by weight can be used.

  The reaction temperature in the present invention may be any temperature at which the reaction proceeds. When metal alkoxide is used as a catalyst, a temperature of 60 to 300 ° C. is generally used, but side reactions are suppressed and the reaction is efficient. A temperature of 100-200 ° C. is preferred for good progress.

  The reaction of the present invention can be carried out under normal pressure or reduced pressure. However, it is preferred to carry out the reaction under reduced pressure in order to efficiently distill off the product and proceed the reaction efficiently at a relatively low temperature. In this case, for example, the reaction can be carried out under a reduced pressure of 10 to 300 mmHg.

  In the reaction of the present invention, an appropriate solvent can be used as necessary. As the solvent, a solvent that does not have chemical reactivity with the catalyst to be used and has a higher boiling point than the cyclic oligosiloxane to be produced can be used. Specific examples of the solvent include decane, dodecane, mineral oil, mesitylene, diethylene glycol diethyl ether, diethylene glycol dibutyl ether and the like. Any amount can be used.

  In the reaction of the present invention, the raw polysiloxane and the catalyst are mixed, and if necessary, heated and reacted, then the product can be purified by distillation or the like, and the reaction is carried out while the product is distilled off sequentially during the reaction. You can also. In order to suppress side reactions, it is desirable to carry out the reaction while successively distilling the product. When distilling off the product, a rectifying column such as various packed columns can be used as necessary. When a rectification column is used, the purity of the product can be increased. In this case, however, it is possible to suppress the mixing of substances having a higher boiling point than 1,3,5,7-tetramethylcyclotetrasiloxane, but 1,3,5-trimethylcyclotrisiloxane having a low boiling point is the target product. It will be collected together with things.

  The condensation of the gas carried out in the present invention involves mixing the raw material polysiloxane and the catalyst, and if necessary, heating and reacting the gas containing 1,3,5,7-tetramethylcyclotetrasiloxane outside the reactor. By condensing, a liquid containing 1,3,5,7-tetramethylcyclotetrasiloxane is produced. The structure of the condenser can be of any type such as a multi-tube type, a plate type, a spiral type, etc. The installation direction can be set vertically, horizontally, or obliquely at any angle. The gas flowing into the condenser from the gas inlet contacts the medium through which the refrigerant is passed and condenses, and the condensate falls downward due to gravity, but the uncondensed gas remains at that position. When gas continuously flows into the condenser, uncondensed gas, that is, gas having a high concentration of 1,3,5-trimethylcyclotrisiloxane stays above the gas inlet of the condenser. Therefore, it is desirable that the gas outlet is located higher than the gas inlet.

  The condensation temperature is determined by the temperature of the refrigerant passing through the condensing part, and can be any temperature, but is -20 ° C to 80 ° C, more preferably -10 ° C to 50 ° C. Since the amount of condensation can be controlled by changing the condensation temperature, the higher the condensation temperature, the lower the boiling point of the relatively low boiling point 1,3,5-trimethylcyclotrisiloxane. It is possible to obtain 5,7-tetramethylcyclotetrasiloxane products. However, if the condensation temperature is too high, there is an economic balance because the yield is reduced because the total amount that is condensed and produced is reduced.

  As a method for removing the gas that has not been completely condensed, it may be released into the atmosphere as it is, or it may be condensed and discarded as a liquid. Further, 1,3,5,7-tetramethylcyclotetrasiloxane is separated by distillation, or the liquid condensed in the deep trap is reacted with 1,3,5-trimethylcyclotrisiloxane polysiloxane and a catalyst. It is also possible to carry out a recovery operation such as adding to the liquid.

  The present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples.

(Example 1)
A thermometer, a magnetic stirrer, and a rectifying column (6 mm McMahon (outer diameter 17 mm × packing length 30 mm), thermometer installed at the top) were connected to a 2 L eggplant flask.

  At the top of the rectifying column, a distillation head (a device having an adjustment cock for the condensing part and the distillation / distillation ratio, a finger condenser with a length of 16 cm and a refrigerant temperature of 35 ° C.) is installed. A 50 mL four-necked round bottom flask equipped with a distillate collector was installed on the outlet side.

  A line was drawn from the top of the distillation head and connected to a vacuum pump through a cryogenic trap cooled with ethanol cooled with dry ice.

In the above eggplant flask, 1303 g of trimethylsilylpolymethylhydrogensiloxane at both ends represented by Me ₃ SiO— (MeHSiO) ₄₀ —SiMe ₃ and 1.30 g of aluminum triisopropoxide are placed, and an oil at 150 ° C. at normal pressure. Heated in bath for 30 minutes. Subsequently, the system was maintained at a reduced pressure of 50 mmHg while the eggplant flask was heated in an oil bath of 150 to 160 ° C., and the reflux head was fully refluxed by tilting the cock of the distillation head toward the return side for 10 minutes.

  Thereafter, the first fraction was collected for 5 minutes (with all the distillation head cocks tilted to the distillation side), and fraction A was placed in a 50 mL four-necked round bottom flask equipped with a distillate collector on the distillation side. Obtained.

  Thereafter, at a distillation temperature of 60 ° C., a fraction distilled under a return distillation / distillation condition in which the cock was tilted by 45 ° C. from the neutral position to the reflux side was recovered over 9 hours to obtain 393 g of fraction B.

  As a result of analysis by gas chromatography, the obtained fraction had a composition of 3.3% by weight of 1,3,5-trimethylcyclotrisiloxane and 92.6% by weight of 1,3,5,7-tetramethylcyclotetrasiloxane. Had.

  The liquid fraction collected in the trap was 51.4 g, and as a result of analysis, 1,3,5-trimethylcyclotrisiloxane was 57% by weight and 1,3,5,7-tetramethylcyclotetrasiloxane was 42% by weight. Had a composition.

In addition to the liquid, gelled solids remained in the deep trap. It is presumed that 1,3,5-trimethylcyclotrisiloxane contained in a large amount in the gas not condensed in the condensing part was gelled.
(Example 2)
A 50 L eggplant flask was connected to a thermometer, a magnetic stirrer, and a rectifying column (20-stage older show). A round bottom flask was installed. Connected to the top of the distillation head is a vertical condenser (cooling water temperature 0 to 5 ° C.) that cools the refrigerant through a serpentine tube. It was connected to a vacuum pump through a cold trap.

Into the flask, 50 kg of trimethylsilylpolymethylhydrogensiloxane at both ends represented by Me ₃ SiO— (MeHSiO) ₄₀ —SiMe ₃ and 50 g of aluminum triisopropoxide were placed, and the flask was heated in an oil bath at 150 to 160 ° C. While maintaining the system at a reduced pressure of 40 mmHg, the whole was refluxed.

  A fraction distilled at a distillation temperature of 50 to 52 ° C. was recovered over 30 hours under the condition of a reflux ratio (return / distillation ratio) of 3 to obtain a 45 kg fraction. As a result of analysis by gas chromatography, the obtained fraction had a composition of 4% by weight of 1,3,5-trimethylcyclotrisiloxane and 96% by weight of 1,3,5,7-tetramethylcyclotetrasiloxane. The liquid fraction collected in the trap was 1 kg. As a result of the analysis, the composition of 49% by weight of 1,3,5-trimethylcyclotrisiloxane and 49% by weight of 1,3,5,7-tetramethylcyclotetrasiloxane was obtained. Had. A large amount of gelled material adhered to the rubber pipe and the vinyl chloride pipe between the upper part of the condenser and the trap. It is presumed that 1,3,5-trimethylcyclotrisiloxane contained in a large amount in the gas not condensed in the condensing part was gelled.

(Comparative Example 1)
A thermometer, a magnetic stirrer, and a rectifying column (6 mm McMahon (outer diameter 17 mm × packing length 30 mm), thermometer installed at the top) were connected to a 2 L eggplant flask.

  Distillation head (with a condensing unit and return / distillation ratio adjustment cock, 16cm long finger condenser, refrigerant temperature -1 ° C) and distillate on the distillation side A 50 mL four-necked round bottom flask equipped with a collector was installed.

  A 50 mL four-neck round bottom flask equipped with a distillate collector was connected to a vacuum pump through a cryogenic trap cooled with ethanol cooled with dry ice.

In a flask, 1303 g of trimethylsilylpolymethylhydrogensiloxane at both ends represented by Me ₃ SiO— (MeHSiO) ₄₀ —SiMe ₃ and 1.30 g of aluminum triisopropoxide were placed in an oil bath at 150 ° C. at normal pressure. For 30 minutes.

  Subsequently, while the flask was heated in an oil bath at 150 to 160 ° C., the system was kept at a reduced pressure of 50 mmHg, and all the cocks of the distillation head were brought down to the distillation side for 10 minutes for total reflux.

  Thereafter, the first distillation is collected for 5 minutes (all the head cocks are tilted to the distillation side), and then the distillation / distillation is performed at a distillation temperature of 60 ° C and the cock is turned 45 ° C from the neutral position to the reflux side. The fraction distilled under conditions was collected over 9 hours to obtain 315 g of a fraction.

  As a result of analysis by gas chromatography, the obtained fraction had a composition of 9.7% by weight of 1,3,5-trimethylcyclotrisiloxane and 87.4% by weight of 1,3,5,7-tetramethylcyclotetrasiloxane. Had.

By removing uncondensed gas from the upper part of the condenser from Examples 1 and 2 and Comparative Example 1, the boiling point is lower than that of 1,3,5,7-tetramethylcyclotetrasiloxane, and it is difficult to condense. A gas having a higher concentration of 3,5-trimethylcyclotrisiloxane than the concentration of gas introduced into the condenser is discharged out of the system, and as a result, high-purity 1,3,5,7-tetramethylcyclotetrasiloxane is obtained. be able to.

  Also, from Examples 1 and 2, by increasing the condensation temperature and reducing the amount of condensation, a gas rich in 1,3,5-trimethylcyclotrisiloxane was discharged out of the system, and as a result, high purity 1,3 , 5,7-tetramethylcyclotetrasiloxane can be obtained.

Claims (3)

Methyl hydrogen polysiloxane is heated in the presence of a catalyst to produce a system comprising gaseous 1,3,5,7-tetramethylcyclotetrasiloxane and gaseous 1,3,5-trimethylcyclotrisiloxane. Step 1,
A part of the gaseous 1,3,5,7-tetramethylcyclotetrasiloxane and the gaseous 1,3,5-trimethylcyclotrisiloxane is condensed, and 1,3,5,5 contained in the system Step 2 for separating 7-tetramethylcyclotetrasiloxane and 1,3,5-trimethylcyclotrisiloxane into a condensed phase and a non-condensed phase,
Removing a part or all of 1,3,5,7-tetramethylcyclotetrasiloxane and 1,3,5-trimethylcyclotrisiloxane contained in the non-condensed phase from the condensing part where the condensed phase exists Including 3,
The weight ratio to 1,3,5-trimethylcyclotrisiloxane is greater than the weight ratio of 1,3,5,7-tetramethylcyclotetrasiloxane to gaseous 1,3,5-trimethylcyclotrisiloxane in Step 1 A method for producing 1,3,5,7-tetramethylcyclotetrasiloxane. 1,3,5,7-tetramethylcyclotetrasiloxane and 1,3,5-trimethyl contained in the non-condensed phase via a space installed above the space where the system generated in Step 1 is present The manufacturing method according to claim 1, wherein a part or all of the cyclotrisiloxane is discharged from the condensing part.   The production method according to claim 1, wherein the amount of condensation is controlled by changing the temperature of the condensed refrigerant in step 2.