JP2002146024A - Purification method of organopolysiloxane and organopolysiloxane obtained by the purification method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a purification method capable of easily obtaining a low molecular weight siloxane, particularly an organopolysiloxane having a small content of cyclic siloxane of up to 20 mer in a high yield, and a purification method by the purification method. Provided by the present invention. A following general formula _{^{(1): R 1 a SiO}} (4-a) / 2 (1) ( wherein, R ¹ represents a hydrogen atom, an unsubstituted or substituted hydroxyl group or a C 1-20 one Is a divalent hydrocarbon group, and the value of a is 1.0 to
2.5) can be applied to liquid chromatography using silica gel modified with a hydrocarbon group as a column filler, and a mixed solvent of a non-polar solvent and a polar solvent as an eluent. A purification method for removing low-molecular-weight siloxane contained in the organopolysiloxane by applying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying an organopolysiloxane and to an organopolysiloxane obtained by the method. In particular, the organopolysiloxane purified by this method contains low-molecular-weight siloxane. It is widely used as a base polymer for silicone rubber compounds and silicone oil compounds used in the electric and electronic fields.

[0002]

2. Description of the Related Art Silicone products containing an organopolysiloxane as a main component are easy to handle and have excellent electrical properties and weather resistance. Therefore, they are used as adhesives in the electric and electronic fields or as sealing materials for building materials. It is applied to various uses in various fields. In particular, in the electrical and electronic fields, they are used to fix components and ensure insulation.Since the silicone used in these components is the cause, there is a problem with silicone troubles that hinder conductivity in components with contacts. It has become. This is because the low-molecular siloxane contained in the non-curable or curable silicone composition is volatilized, adheres to the contact, and is caused by an insulating substance such as silica generated by burning with a spark.

[0003] In building materials, the presence of low-molecular-weight siloxane has been a problem because it causes stains around joints. In this case, the low-molecular siloxane in question has a higher molecular weight than that in the electric and electronic fields.

As a method of solving the above problem, there is a method of stripping (heating under reduced pressure) an organopolysiloxane oil serving as a base oil to remove low molecular siloxane. However, in the stripping method, it is difficult to remove a cyclic siloxane of 10-mers or more, and a problem such as generation of a gel-like substance during stripping may occur. In addition, by introducing a special apparatus such as a molecular distillation apparatus, the precision of removing low-molecular siloxane can be increased, but it is insufficient and the yield is not good.

Further, by using an organic solvent incompatible with the organopolysiloxane and mixing in an apparatus capable of liquid separation, the organopolysiloxane and the organic solvent are separated and stripped to remove low molecular siloxane. Although there is a method, the degree of purification is insufficient, and there is a problem in treating an organic solvent used in a large amount, which is not an industrially useful method.

[0006]

SUMMARY OF THE INVENTION In view of this background, an object of the present invention is to provide low-molecular-weight siloxanes, in particular, organopolysiloxanes having a very low content of cyclic siloxanes of 3 to 20 mer in good yield and high yield. And a method for purifying an organopolysiloxane obtainable by the method described above.

[0007]

The present inventors have conducted intensive studies on a method for purifying an organopolysiloxane.
The inventors have found that the above-mentioned problems can be solved by purifying using a predetermined liquid chromatography, and have reached the present invention.

That is, the present invention firstly provides the following general composition formula (1): R ¹ _a SiO _{(4-a) / 2} (1) (wherein R ¹ is a hydrogen atom, a hydroxyl group or a group having 1 to 1 carbon atoms) 20, preferably an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, the value of a is 1.0 to 2.5, preferably 1.2 to 2.1,
More preferably, it is an arbitrary number of 1.5 to 2.05. ) Is subjected to a liquid chromatography using a mixed solvent of a non-polar solvent and a polar solvent as a eluent for a silica gel obtained by modifying the organopolysiloxane represented by a column with a hydrocarbon group as a filler. Removing low molecular siloxane contained in the siloxane,
Preferably, the total of the cyclic siloxanes of 3 to 20 mer is 200 ppm.
It is intended to provide a method for purifying an organopolysiloxane, characterized in that the organopolysiloxane is removed to a value less than 1.

Second, the total content of the cyclic siloxane of 3 to 20 mer purified by this purification method is 200 p.
The present invention provides an organopolysiloxane characterized by being less than pm.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. (Organopolysiloxane) In the present invention, the organopolysiloxane is represented by the following general composition formula (1): R ¹ _a SiO _{(4-a) / 2} (1) (wherein, R ¹ is a hydrogen atom, a hydroxyl group or a carbon atom having 1 carbon atom. -20, preferably an unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms, and the value of a is an arbitrary number of 1.0 to 2.5, preferably 1.2 to 2.1, more preferably 1.5 to 2.05.) Is represented by

Specific examples of the unsubstituted hydrocarbon group having 1 to 20 carbon atoms in R ¹ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group and a tert-
Alkyl groups such as butyl, pentyl, hexyl, heptyl, octyl, and decyl; cyclohexyl;
Cycloalkyl groups such as cycloheptyl group; alkenyl groups such as vinyl group, allyl group, propenyl group, isopropenyl group and butenyl group; aryl groups such as phenyl group and tolyl group; aralkyl groups such as benzyl group and phenylethyl group. Of these, an alkyl group such as a methyl group, a vinyl group and a phenyl group are particularly preferable.

Further, specific examples of the substituted hydrocarbon group having 1 to 20 carbon atoms in R ¹ include at least a part of the hydrogen of the unsubstituted hydrocarbon group, an amino group, an epoxy group,
Carboxyl groups, carbinol groups, methacryl groups, acryl groups, mercapto groups, phenol groups, hydroxyl groups, polyether groups, alkoxy groups, and the like, and those substituted with halogen atoms such as fluorine, chlorine, and bromine are exemplified. Note that R
¹ may be the same or different.

In the organopolysiloxane represented by the above general composition formula (1), the main chain basically consists of repeating diorganosiloxane units represented by R ¹ ₂ SiO _2/2 , and both ends of the molecular chain have R ¹ ₃ are blocked with triorganosiloxy groups and / or (HO) diorgano hydroxy siloxy group represented by R ¹ ₂ SiO _1/2 represented by SiO _1/2, basically linear diorganopolysiloxane It is common to have R ¹ Si
It may have a branched structure containing a monoorganosiloxane unit represented by O _3/2 or a SiO ₂ unit, or may have a three-dimensional network structure.

When the organopolysiloxane represented by the above general composition formula (1) is used as a base polymer for silicone products, the viscosity at 25 ° C. is generally preferably from 0.025 to 500 Pa · s, 0.1Pa ・ s〜100Pa
S is more preferable, and 1 to 100 Pa s is more preferable. When the viscosity is less than 0.025 Pa · s, the cured silicone rubber becomes brittle, and when the viscosity is more than 500 Pa · s, the viscosity of the composition becomes too high, which is disadvantageous in workability.

(Liquid chromatography (hereinafter abbreviated as LC)) In the LC used in the present invention, it is preferable to use a modified silica gel as a column filler.
Modified silica gel is a treatment of silica gel with a hydrocarbon to adsorb and / or bind an aliphatic saturated hydrocarbon group such as an alkyl group represented by a C _n H _{2n + 1} group (n is an integer of 8 to 36) to the silica gel. It was made. Generally, silica gel has a large number of active silanol groups (ie, hydroxyl groups bonded to silicon atoms) on its surface, and since its surface is hydrophilic, it is treated with hydrocarbon to impart hydrophobicity. , LC can significantly improve the separation effect. Such monovalent C ₁₈ H ₃₇ radicals as aliphatic saturated hydrocarbon group is preferably a long chain alkyl group represented by C ₈ H ₁₇ group and C _{3 6} H ₇₃ group, particularly preferably C ₁₈ H ₃₇ group .

When this modified silica gel is used, the desired purified product can be obtained in good yield. It is desirable to use a modified silica gel having a modification rate of 5 to 40%, preferably 10 to 30%, and more preferably a modification rate of 15 to 22%. When ordinary (untreated) silica gel is used, it is difficult to sufficiently purify the organopolysiloxane.

Here, the modification ratio means the ratio (mol%) of the above-mentioned hydrocarbon groups present on the surface of the silica gel after the treatment with the hydrocarbons with respect to the silanol groups present on the surface of the untreated silica gel. If the denaturation ratio is out of the range of 5 to 40%, it becomes difficult to obtain the desired purified product in good yield.

As the eluent used in the present invention, it is preferable to use a mixed solvent of a non-polar solvent and a polar solvent. Non-polar solvents include benzene, toluene,
Typical aromatic hydrocarbon solvents having about 6 to 10 carbon atoms, such as xylene and naphthalene, are typical. As polar solvents, ketone solvents and alcohol solvents such as ketones having 3 to 6 carbon atoms and 1 carbon atoms are preferred. To 6, especially lower alcohols having about 1 to 4 carbon atoms. As the mixed solvent, more specifically, for example, a mixed solvent of an aromatic hydrocarbon and a ketone, a mixed solvent of an aromatic hydrocarbon and an alcohol, and specifically, toluene and acetone, xylene and acetone, toluene and Examples include ethanol, a mixed solvent of toluene and isopropanol, toluene and butanol, and xylene and isopropanol, and a mixed solvent of toluene and acetone is particularly preferable.

In the present invention, the organopolysiloxane to be purified is dissolved in a solvent having the same components as the above eluent and injected into an LC column. Preferred solvents for dissolving the organopolysiloxane are those listed above as the eluent, and particularly a mixed solvent of toluene and acetone.

A method for purifying an organopolysiloxane will be described, for example, in the case of purifying an organopolysiloxane by dissolving the same in a mixed solvent of toluene and acetone. That is, the inside of the LC column is filled with a mixed solvent of toluene and acetone as an eluent, and a solution in which an organopolysiloxane is dissolved in a mixed solvent of toluene and acetone as a sample is injected into the LC column. When developed, low molecular weight siloxanes, especially cyclic siloxanes of 20 mer or less (ie, the following formula:

[0021]

Embedded image (N is an integer of 3 to 20, and R ¹ has the same meaning as described above, and particularly represents a methyl group), and is a cyclic diorganosiloxane of 3 to 20 mer, usually represented by D _{3 to} D ₂ Abbreviated as ₀ . ) Is dissolved in the acetone fraction, and the high molecular weight components are dissolved in the toluene fraction.
By removing toluene, an organopolysiloxane containing no low-molecular siloxane can be obtained.

In the present invention, the low-molecular siloxane is defined as the cyclic siloxane and / or the linear siloxane (that is, diorganopolysiloxane having a triorganosiloxy group blocked at both molecular chain terminals). Having a low molecular weight of about 2 to 20 silicon atoms, particularly those in which all the substituents R ¹ (R ¹ has the same meaning as described above) bonded to a silicon atom are alkyl groups, especially methyl groups. The problem such as silicone troubles is caused by cyclic siloxanes of 3 to 20 mer. According to the invention, this low molecular weight siloxane, in particular the cyclic siloxanes of D _{3 to} D ₂₀ , is reduced to a total of less than 200 ppm, if necessary
It can be purified to pm or less, desirably 30 ppm or less, and further to 10 ppm or less.

[0023]

The present invention will be described below in more detail with reference to examples. The present invention is not limited to these examples. Note that LC
The conditions in are as follows. Soken Chemical Co. Hi-Sep LC Prep A type Column: 20mmΦ × 250mm (diameter × length) Filler: Soken Chemical Co., Ltd. ODS-W 15 / 30μm Eluent: acetone / toluene stepwise washing solution: toluene 100 % Detection: RI (differential refractometer), Range64 Flow rate: 13 mL / min (linear velocity 4.12 cm / min) Temperature: room temperature (25 ° C) Sample A: 2.021 g / (acetone 10 ml + toluene 4 ml) Sample B: 1.999 g / ( Sample C: 2.010 g / (acetone 10 ml + toluene 5 ml)

Example 1 An LC column was filled with a mixed solution of acetone / toluene (volume ratio of 10/4), and a sample A [(dimethylamine having a viscosity of 5 Pa · s at 25 ° C. blocked at both ends with hydroxyl groups) was prepared. 2.021 g of a polysiloxane) mixed with acetone / toluene (10 ml / 4 ml)
Was dissolved in the above-mentioned LC column, developed and, while monitoring with a differential refractometer, an acetone fraction was flowed out and removed, and a toluene fraction was collected.
The toluene in the fractionated toluene fraction was heated at 50 ° C / 1.33 kPa (10
mmHg) for 4 hours to obtain a purified product. The yield was about 95%. In addition, 3 to 2 are contained in the removed toluene.
The content of cyclic siloxane of zero monomer was less than the analytical detection limit of 10 ppm.

Example 2 An LC column was filled with an acetone / toluene mixture (10/5 volume ratio), and the injection sample B [both ends were blocked with vinyl groups and had a viscosity of 5 Pa · s at 25 ° C. 1.999 g of dimethylpolysiloxane was mixed with a mixture of acetone / toluene (10 ml / 5
dissolved in the above-mentioned LC)] is injected into the above LC column,
While developing and monitoring with RI, the acetone fraction was drained off and removed, and then the toluene fraction was collected. Toluene in the fractionated toluene fraction at 50 ° C / 1.33 kPa (10 mm
Hg) for 4 hours to obtain a purified product. Yield about 9
5%. The removed toluene contained 3 to 20.
The content of the monomeric cyclic siloxane was less than the analytical detection limit of 10 ppm.

Example 3 An LC column was filled with a mixed solution of acetone / toluene (volume ratio of 10/5), and an injection sample C [CH ₂ = CH (CH ₃ ) ₂ SiO _{2 was} prepared.
_1/2 unit, including (CH ₃ ) ₃ SiO _1/2 unit and SiO ₂ unit, CH ₂ = C
Total SiO _{2 of} H (CH ₃ ) ₂ SiO _1/2 units and (CH ₃ ) ₃ SiO _1/2 units
The molar ratio to the unit is 0.8, the vinyl group equivalent is 0.9 mol / 100 g, and 2.010 g of a dimethylpolysiloxane-soluble silicone resin is mixed with a mixed solution of acetone / toluene (10 ml).
/ 5 ml) was injected into the above LC column, developed, and monitored by RI to remove the acetone fraction by elution, followed by fractionation of the toluene fraction. Toluene in the fractionated toluene fraction at 50 ° C / 1.33 kP
Removed at a (10 mmHg) for 4 hours to obtain a purified product. The yield was about 95%. In addition, 3 to 2 in the removed toluene
The content of cyclic siloxane of zero monomer was less than the analytical detection limit of 10 ppm.

Comparative Example 1 A 1 L separable flask equipped with a stirrer was charged in a separable flask having a capacity of 5 Pa · s at 25 ° C. with a viscosity of 5 Pa · s and acetone [dimethylpolysiloxane / acetone = 4/6]. (Volume ratio) 800ml], 200
After stirring at rpm for 15 minutes, the mixture was allowed to stand for about 6 hours, the dimethylpolysiloxane phase was collected by liquid separation, and the same operation was repeated five times on the collected dimethylpolysiloxane to obtain residual acetone in the collected dimethylpolysiloxane. At 50 ° C / 1.
It was removed over 4 hours at 33 kPa (10 mmHg) to obtain a purified product. The yield was about 70%.

Comparative Example 2 Using a dimethylpolysiloxane having a viscosity of 5 Pa · s at 25 ° C., both ends of which are blocked with hydroxyl groups, using a molecular distillation apparatus.
Purification was performed at 250 ° C./0.133 Pa (10 ⁻⁴ Torr). The yield was about 80%. The purified products obtained in the above Examples and Comparative Examples were analyzed by gas chromatography under the following conditions. The results are shown in Tables 1 and 2. The following gas chromatography was used.

[0029]

[Table 1] Low molecular siloxane content Unit: ppm * 10>: D ₃ is the detection limit or less for each of the components of the to D _20, the sum of D ₃ to D ₂₀ is less than 10 ppm.

[0030]

[Table 2] Low molecular siloxane content Unit: ppm * 10>: D ₃ is the detection limit or less for each of the components of the to D _10, the sum of D ₃ to D ₁₀ is less than 10 ppm.

[0031]

According to the method for purifying an organopolysiloxane of the present invention, the content of low molecular siloxane is small, especially the total content of cyclic siloxanes of 3 to 20 mer is 200 ppm.
, A high-purity organopolysiloxane with a low yield can be easily obtained in good yield. Therefore, the organopolysiloxane purified according to the present invention and the composition containing the same are useful as sealants, coating agents, potting agents, adhesives, and as building materials in the electric and electronic fields.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hironao Fujiki 1-10 Hitomi, Matsuida-cho, Usui-gun, Gunma Prefecture F-term in the Silicon Electronics Research Laboratory, Shin-Etsu Chemical Co., Ltd. 4J035 BA03 CA01N CA052 CA09K CA11K CA13K CA19K CA26K EB08 LA03 LB02 LB03

Claims (4)

[Claims] 1. The following general composition formula (1): R ¹ _a SiO _{(4-a) / 2} (1) (wherein R ¹ is a hydrogen atom, a hydroxyl group or an unsubstituted or substituted group having 1 to 20 carbon atoms) It is a monovalent hydrocarbon group, and the value of a is 1.0 to
2.5 is any number. ) Is subjected to a liquid chromatography using a mixed solvent of a non-polar solvent and a polar solvent as a eluent for a silica gel obtained by modifying the organopolysiloxane represented by a column with a hydrocarbon group as a filler. A method for purifying an organopolysiloxane, comprising removing low-molecular siloxane contained in the siloxane. 2. The method according to claim 1, wherein the hydrocarbon group of the silica gel modified with a hydrocarbon group is an aliphatic saturated monovalent hydrocarbon group represented by C _n H _{2n + 1} (where n = an integer of 8 to 36). The method for purifying an organopolysiloxane according to claim 1, wherein: 3. The method for purifying an organopolysiloxane according to claim 1, wherein the eluent is a mixed solvent of toluene and acetone. 4. The method according to claim 1, wherein the total content of the cyclic siloxanes of 3 to 20 mer purified by the method for purifying an organopolysiloxane is less than 200 ppm. Organopolysiloxane.