Method of producing polysiloxane from which salts are removed

Abstract

To provide a method of producing polysiloxane reduced in a concentration of salts by removing salts contained in a polysiloxane as impurities with active charcoal, which can be applied to a field related to semiconductors.SOLUTION: A method of producing polysiloxane from which salts are removed includes the steps of: (1) bringing polysiloxane into contact with active charcoal in an organic solvent; and (2) thereafter separating the polysiloxane. The polysiloxane can be applied at a rate of 20-90 mass% based on a total mass of the polysiloxane and the organic solvent, and the active charcoal can be applied at a rate of 3-100 mass% based on a mass of the polysiloxane. A contact temperature with the active charcoal in the step (1) can be adjusted in a range of 5-50°C. A nonpolar organic solvent can be adopted as the organic solvent; benzene, toluene, xylene, mesitylene, and the like can be given as an aromatic hydrocarbon; and octane, nonane, decane, undecane, dodecane, and the like can be given as an aliphatic hydrocarbon. The active charcoal can have an average particle size of 3-200 micron meter.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing polysiloxane from which salts have been removed, and more particularly to a method for removing salts contained in polysiloxane by contacting the polysiloxane with activated carbon in an organic solvent. [Background technology]

[0002] Polysiloxanes are used in a variety of fields, including electrical engineering, machinery, and food. Depending on the application, there are some fields in which the inclusion of impurities in polysiloxane is undesirable. For example, in the electrical field, particularly in the semiconductor-related field, salts contained in polysiloxane can adversely affect electrical properties, so it is desirable for the salt content to be extremely low.

[0003] Polysiloxanes are typically produced by hydrolysis and polycondensation of halogenated silanes. That is, the halogenated silyl group of the halogenated silane is hydrolyzed to generate silanol. When chlorosilane is used as the halogenated silane, hydrochloric acid is by-produced during hydrolysis, and this is used as an acid catalyst to polycondense the silanol to generate polysiloxane. At this time, an alkali (e.g., sodium hydroxide) is used to neutralize the by-produced hydrochloric acid, but salts such as sodium chloride produced by neutralization are incorporated as impurities in the generated polysiloxane, which can cause the above-mentioned problems. Although polysiloxanes vary depending on the type of substituent bonded to silicon, they generally tend to be hydrophobic, while salts are hydrophilic, and there are some process difficulties in removing hydrophilic substances (salts) incorporated into hydrophobic substances (polysiloxanes).

[0004] A conventional refining technology for removing impurities uses activated carbon. For example, there is an invention in which a gas adsorbent made of a calcium-containing composition using seashells, eggshells, etc., containing activated carbon, etc., is used to adsorb formalin, etc. (see Patent Document 1). There is an invention of a method for producing high-purity pyrroloquinoline quinones, which comprises a step of contacting an aqueous medium containing pyrroloquinoline quinones with activated carbon (see Patent Document 2). Also disclosed is an adsorbent that uses activated carbon to remove metals in organic solvents (see Patent Document 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-005195 A [Patent Document 2] JP 2014-193838 A [Patent Document 3] JP 2017-177047 A Summary of the Invention [Problem to be solved by the invention]

[0006] When polysiloxane is brought into contact with activated carbon in an aqueous medium, as described above, polysiloxanes generally tend to be hydrophobic, and therefore the aqueous medium does not penetrate into the interior of the polysiloxane, making it difficult for the activated carbon to reach the interior of the polysiloxane. Also, in those parts of the polysiloxane surface where the aqueous medium has penetrated, salts are ionized by the aqueous medium to form cations and anions, and it is thought that these ionic forms are difficult to adsorb by the activated carbon. In addition, removal by separation or removal using ion exchange resins is difficult to achieve purification to the extremely low salt levels (for example, 10 ppm or less) required in the semiconductor field, etc.

[0007] The present invention provides a method for producing polysiloxane having a reduced concentration of salts, by removing salts contained as impurities in polysiloxane with activated carbon. [Means for solving the problem]

[0008] A first aspect of the present invention relates to a method for producing a polysiloxane from which salts have been removed, the method comprising: a step (1) of contacting a polysiloxane with activated carbon in an organic solvent; and a step (2) of separating the polysiloxane. As a second aspect, the production method according to the first aspect, in which the polysiloxane is applied in a proportion of 20 to 90 mass % based on the total mass of the polysiloxane and the organic solvent; As a third aspect, the method according to the first or second aspect, in which the activated carbon is applied in an amount of 3 to 100% by mass based on the mass of the polysiloxane; As a fourth aspect, the production method according to any one of the first to third aspects, in which the temperature of contact with the activated carbon in the step (1) is adjusted to a range of 5 to 50° C.; As a fifth aspect, the production method according to any one of the first to fourth aspects, in which the organic solvent is a non-polar organic solvent; and According to a sixth aspect, there is provided the method according to any one of the first to fifth aspects, wherein the activated carbon has an average particle size of 3 to 200 micrometers. Effect of the Invention

[0009] In the present invention, salts in the polysiloxane are removed by contacting the polysiloxane with activated carbon in an organic solvent, thereby obtaining a polysiloxane from which salts have been removed. When polysiloxane is contacted with activated carbon in an organic solvent, unlike polysiloxane in an aqueous medium, the organic solvent penetrates into the inside of the polysiloxane, or the polysiloxane dissolves in the organic solvent, and the salts in the polysiloxane can exist as particulate salts without being ionized. It is considered that the salts in the polysiloxane can be removed by adsorbing these minute particulate salts to activated carbon and then separating the polysiloxane from the activated carbon to which the salts are adsorbed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention is a method for producing a polysiloxane from which salts have been removed, comprising the step (1) of contacting a polysiloxane with activated carbon in an organic solvent, and then the step (2) of separating the polysiloxane.

[0011] The polysiloxane used as the raw material in step (1) of the present invention is not particularly limited, and polysiloxanes obtained by various production methods and having various functional groups can be used. For example, when a polysiloxane is produced by hydrolyzing chlorosilane with hydrochloric acid and polycondensing the hydrochloric acid, the polysiloxane obtained through a step of neutralizing the generated hydrochloric acid with an aqueous alkali (e.g., sodium hydroxide) can be used as the polysiloxane in step (1). Examples of the alkali used for the neutralization include sodium hydroxide, potassium hydroxide, and ammonia. The polysiloxane may be a polysiloxane obtained by hydrolysis and polycondensation of a chlorosilane containing an organic functional group. The organic functional group here typically means an organic group other than a chlorine atom, and examples of such groups include alkyl groups such as methyl and ethyl groups, alkenyl groups such as vinyl groups, and aryl groups such as phenyl and 1-naphthyl groups.

[0012] Chlorosilanes are classified into tetrafunctional, trifunctional, difunctional and monofunctional chlorosilanes depending on the number of chlorine atoms bonded to the silicon atom, and the present invention can use chlorosilanes of any functionality. The functionality here refers to the number of chlorine atoms bonded to the silicon atom. An example of a tetrafunctional silane is tetrachlorosilane. Examples of trifunctional silanes include trichlorosilane, alkyltrichlorosilane, alkenyltrichlorosilane, and aryltrichlorosilane. Examples of bifunctional silanes include dichlorosilane, dialkyldichlorosilane, dialkenyldichlorosilane, diaryldichlorosilane, alkylalkenyldichlorosilane, alkylaryldichlorosilane, and alkenylaryldichlorosilane. Examples of monofunctional silanes include chlorosilanes, trialkylchlorosilanes, trialkenylchlorosilanes, triarylchlorosilanes, dialkylalkenylchlorosilanes, dialkylarylchlorosilanes, dialkenylalkylchlorosilanes, dialkenylarylchlorosilanes, diarylalkylchlorosilanes, and diarylalkenylchlorosilanes.

[0013] The raw material silane used in producing polysiloxane may be a single silane or a combination of multiple silanes. When a single silane is used, for example, the above-mentioned tetrafunctional silane, trifunctional silane, difunctional silane, or monofunctional silane may be used alone. In addition, when a plurality of silanes are used in combination, for example, a combination of the above-mentioned tetrafunctional silane and monofunctional silane, a combination of a trifunctional silane and monofunctional silane, a combination of a difunctional silane and monofunctional silane, a combination of a tetrafunctional silane, a trifunctional silane and monofunctional silane, a combination of a trifunctional silane, a difunctional silane and monofunctional silane, or a combination of a tetrafunctional silane, a trifunctional silane, a difunctional silane and a monofunctional silane can be used.

[0014] The alkyl group contained in the silane exemplified above includes alkyl groups having 1 to 10 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an i-propyl group, a butyl group, a pentyl group, and an octyl group. The alkenyl group contained in the above silane includes alkenyl groups having 2 to 10 carbon atoms, such as vinyl groups and propenyl groups (allyl groups). The aryl group contained in the above silane includes aryl groups having 6 to 40 carbon atoms, such as a phenyl group, a naphthyl group, and an anthryl group. These alkyl groups, alkenyl groups and aryl groups may be used in combination. The alkyl groups, alkenyl groups and aryl groups may be substituted with a halogen group, a hydroxy group, a nitro group, a sulfone group, an amino group or the like.

[0015] The polysiloxane may be in a state in which all of the silanol groups (-Si-OH) in the silane are condensed to form siloxane bonds (-Si-O-Si-), in which some or all of the silanol groups are not condensed and exist as silanol groups, or in a mixture of these states. The polysiloxane may have a crosslinked structure in its structure.

[0016] The molecular weight of the polysiloxane used in step (1) is not particularly limited, but for example, polysiloxanes having a weight average molecular weight in the range of 100 to 1,000,000, or 1,000 to 100,000 can be used. The weight average molecular weight can be measured, for example, using a GPC apparatus (EcoSEC, HLC-8320GPC, manufactured by Tosoh Corporation) and a GPC column (Shodex (registered trademark), KF-803L, KF-802, and KF-801, manufactured by Showa Denko K.K.), setting the column temperature to 40° C., using tetrahydrofuran as an eluent (elution solvent), setting the flow rate (flow velocity) to 1.0 mL / min, and using polystyrene (manufactured by Sigma-Aldrich Co.) as a standard sample.

[0017] The content of salts contained in the polysiloxane used in step (1) is not particularly limited, but usually, the content of cations such as sodium is 100 ppm or more, or 200 ppm or more, or 400 ppm or more, and the content of anions such as chlorine is 100 ppm or more, or 200 ppm or more, or 400 ppm or more. Of course, it is possible to use salts in other ranges. Polysiloxanes containing salts may also be used. Usually, the upper limit suitable for treatment is about 1000 ppm. It should be noted that the ions counted as the salt content do not include ions that exist in a free state, but include ions (salts) that are absorbed into the polysiloxane by adsorption or the like and cannot be removed by washing or the like.

[0018] The activated carbon used in the present invention may be in the form of powder or granules. The particle size of the activated carbon may be in the range of 3 to 400 micrometers or 3 to 200 micrometers in average particle size. The average particle size here is a value obtained by measuring a dispersion liquid in which activated carbon is dispersed in water with a laser diffraction / scattering particle size distribution analyzer LA-920 manufactured by Horiba, Ltd. Commercially available activated carbon products can be used, such as those manufactured by Osaka Gas Chemicals Co., Ltd. under the trade name Tokusei Shirasagi and those manufactured by Ajinomoto Co., Inc. under the trade name SD.

[0019] The organic solvent used in the present invention is preferably a solvent that exhibits affinity with the raw material polysiloxane (i.e., unrefined or insufficiently refined) used in step (1) or dissolves the polysiloxane. Among them, the organic solvent is preferably a non-polar organic solvent. As the organic solvent, an aromatic or aliphatic hydrocarbon, or a siloxane-based solvent can be used. Examples of aromatic hydrocarbons include benzene, toluene, xylene, mesitylene, and the like. Examples of aliphatic hydrocarbons include saturated hydrocarbons such as octane, nonane, decane, undecane, and dodecane. An example of the siloxane-based solvent is hexamethyldisiloxane.

[0020] It is preferable that the organic solvent contains as little water as possible, but it is possible for the organic solvent to contain less than 5.0% by volume of water. The reason why it is preferable to use a non-polar organic solvent (e.g., a hydrophobic hydrocarbon) as the organic solvent and to avoid the inclusion of moisture is that the salts contained in the polysiloxane are ionized in the presence of a hydrophilic solvent or water, making it difficult to remove them with activated carbon.

[0021] In step (1), the polysiloxane can be applied in an amount of 5 to 95 mass%, or 20 to 90 mass%, or 40 to 90 mass%, or 50 to 80 mass%, based on the total mass of the polysiloxane and the organic solvent. That is, the polysiloxane can be dispersed or dissolved at the above-mentioned concentration in the liquid consisting of the polysiloxane and the organic solvent. The activated carbon can be applied in an amount of 1 to 200 mass%, 1.5 to 175 mass%, 2.0 to 150 mass%, 1.5 to 125 mass%, or 3 to 100 mass% based on the mass of the polysiloxane. Of course, it is possible to apply the activated carbon in an amount exceeding this range, but this is not efficient because it takes time to separate the activated carbon in the subsequent step (2). Moreover, by applying the activated carbon in an amount within this range, a highly purified polysiloxane can be obtained with good reproducibility.

[0022] In step (1), the temperature at which the polysiloxane in the organic solvent is contacted with the activated carbon can be adjusted, for example, usually within the range of 5 to 50° C., or 10 to 40° C. It is also possible to adjust the contact temperature outside this temperature range, but it is necessary to take into consideration the melting point, boiling point, vapor pressure, etc. of the organic solvent used. The contact time of the polysiloxane with the activated carbon in the organic solvent is preferably adjusted to about 0.001 to 20 hours, or about 0.1 to 10 hours. The contact of polysiloxane with activated carbon can be carried out either batchwise or continuously. In the case of the batchwise method, a vessel equipped with a stirrer is used, and polysiloxane is brought into contact with activated carbon in an organic solvent. This can be done.

[0023] Step (2) is a step of separating the polysiloxane. First, the activated carbon is separated by filtration or the like to obtain an organic solvent solution of the polysiloxane, and then the organic solvent is further removed by distillation or the like to produce a polysiloxane from which salts have been removed.

[0024] To separate the activated carbon and obtain an organic solvent solution of polysiloxane, it is effective to pass the solution through a filter equipped with a filter paper or a membrane filter having a pore size of 1 μm or less. With this method, the activated carbon remains on the filter paper, and the organic solvent solution of polysiloxane can be separated as the filtrate. The organic solvent solution can be passed through by gravity, but it can also be passed through by pressurizing with the pressure of air or an inert gas (e.g., nitrogen gas). When there is a possibility that the polysiloxane may be denatured by contact with air, it is preferable to use an inert gas.

[0025] After the separation of the activated carbon, the organic solvent can be removed by a method of distilling off the organic solvent from the organic solvent solution of the polysiloxane by distillation or the like, and the polysiloxane can be recovered. Although it depends on the organic solvent used, the organic solvent can be removed under normal pressure or reduced pressure (for example, 50 Pa).

[0026] The polysiloxane obtained by the present invention can be a polysiloxane with a reduced salt content, in which the content of sodium or other cations in the polysiloxane is 10 ppm or less, for example, in the range of 0.1 to 10 ppm, and the content of chlorine or other anions in the polysiloxane is 10 ppm or less, for example, in the range of 0.1 to 10 ppm.

[0027] As described above, the present invention shows the reduction of sodium chloride as an example of salts, but it is also possible to remove salts that become particulate in organic solvents, such as metal halides, metal sulfides, metal hydroxides, etc. Examples of these metals include silver, cobalt, chromium, copper, lithium, manganese, nickel, lead, potassium, platinum, tin, aluminum, calcium, iron, manganese, zinc, etc.

[0028] In the present invention, salts are removed using activated carbon. However, if the salts are ionized for some reason and cannot be removed by activated carbon, the salts can be further reduced by alternately contacting the salt with a cation exchange resin and an anion exchange resin after the activated carbon treatment. EXAMPLES

[0029] <Method for analyzing salts (cations, anions) in polysiloxane> Cations were analyzed using an inductively coupled plasma mass spectrometer (ICP-MS). Anions were measured by ion chromatography.

[0030] <Materials used> PS1: Polysiloxane material 1 (commercially available silicone resin, component is polydimethylsiloxane, weight average molecular weight 9,000, contains 130 ppm Na and 220 ppm Cl) PS2: Polysiloxane material 2 (commercially available silicone resin, component is polydimethylsiloxane, weight average molecular weight 7,300, contains 250 ppm Na and 400 ppm Cl)

[0031] AC1: Activated carbon 1 (Osaka Gas Chemicals, product name: Tokusei Shirasagi, average particle size 72 μm) AC2: Activated carbon 2 (manufactured by Ajinomoto Co., Inc., product name: SD, average particle size 75 μm) AC3: Activated carbon 3 (manufactured by Ajinomoto Co., Inc., product name: ZN, average particle size 75 μm) AC4: Activated carbon 4 (manufactured by Futamura Chemical Co., Ltd., product name: Taiko Y, average particle size 35 μm) AC5: Activated carbon 5 (manufactured by Futamura Chemical Co., Ltd., product name: Taiko K, average particle size 35 μm)

[0032] S1: Solvent 1 (toluene, commercially available) S2: Solvent 2 (Exxon Mobil, trade name Isopar-E, main component is a mixture of octane and nonane) S3: Solvent 3 (hexamethyldisiloxane, commercially available) S4: Solvent 4 (methylbutylcarbinol, commercially available)

[0033] Example 1 According to the materials and concentrations shown in Table 1, a polysiloxane solution was prepared by adding a specified amount of polysiloxane material and organic solvent to a 300 ml beaker, to which activated carbon was then added and stirred with a stirrer at a specified temperature for a specified time. Thereafter, the activated carbon was filtered off with filter paper (pore size: 0.5 μm), and the organic solvent was removed by distillation from the polysiloxane solution after the activated carbon filtration to obtain polysiloxane. The salt (cation, anion) contents (residual Na content, residual Cl content) in the obtained polysiloxane were analyzed, and the results are shown in Table 2.

[0034] (Examples 2 to 18, Example 19) Similarly to Example 1, Examples 2 to 18 and Example 19 were carried out using the materials and the like shown in Table 1, and the contents of salts (cations, anions) in the obtained polysiloxanes (amount of residual Na, amount of residual Cl) were analyzed. The results are shown in Table 2.

[0035] In Table 1, the "Type" in the "Polysiloxane Material" column is the type of polysiloxane material 1-2 (PS1 or PS2), and the "Concentration" indicates the concentration (mass %) of the polysiloxane material relative to the total mass of the polysiloxane material and the organic solvent. The "organic solvent" is any of the above solvents 1 to 3 (S1, S2, or S3). In the "activated carbon" column, "type" is the type of activated carbon 1 to 5 (AC1, AC2, AC3, AC4 or AC5) and "addition amount" is the amount added (mass %) relative to the polysiloxane material (mass). The temperature and time are the temperature (° C.) and time (h) at which the polysiloxane material is contacted with the activated carbon in the organic solvent.

[0036] [Table 1]

[0037] [Table 2]

[0038] (Comparative Example 1: Operation using liquid separation treatment (1)) The polysiloxane material 1 (PS1) and toluene (S1) were mixed to prepare a 50% by mass polysiloxane solution, which was then added to a 300 ml separatory funnel. Then, a 10% by mass aqueous sulfuric acid solution was added to the separatory funnel so that the mass ratio of the polysiloxane solution: the aqueous sulfuric acid solution was 50:50, and the polysiloxane solution was collected. This operation (addition of the aqueous sulfuric acid solution and separation) was repeated five times. After five operations, the organic solvent was removed by distillation from the resulting polysiloxane solution to obtain polysiloxane, and the salt (cation, anion) contents (residual Na content, residual Cl content) in the polysiloxane were analyzed. The results are shown in Table 3.

[0039] (Comparative Example 2: Operation using liquid separation treatment (2)) The separation operation (addition of sulfuric acid aqueous solution and separation treatment) of Comparative Example 1 was repeated 10 times. After 10 operations, the organic solvent was removed by distillation from the obtained polysiloxane solution to obtain polysiloxane, and the content of salts (cations, anions) in the polysiloxane (residual Na content, residual Cl content) was analyzed. The results are shown in Table 3.

[0040] (Comparative Example 3: Operation using separation treatment (3)) The separation operation (addition of sulfuric acid aqueous solution and separation treatment) of Comparative Example 1 was repeated 15 times. After 15 operations, the organic solvent was removed by distillation from the obtained polysiloxane solution to obtain polysiloxane, and the content of salts (cations, anions) in the polysiloxane (residual Na content, residual Cl content) was analyzed. The results are shown in Table 3.

[0041] (Comparative Example 4: Operation using ion exchange resin (1)) 30 g of the above polysiloxane material 1 (PS1) and 30 g of methylbutylcarbinol (S4) were added to a 200 ml beaker to prepare a 50% by mass polysiloxane solution. To this was added 6 g of a cation exchange resin (Organo Corporation, product name Amberlyst 15JS-HG Dry), and the mixture was stirred at 100 rpm in a mix rotor at room temperature (23°C) for 4 hours. The cation exchange resin was separated by filtration to obtain a polysiloxane solution. To the obtained polysiloxane solution, 6 g of anion exchange resin (trade name Amberlyst B20-HG Dry, manufactured by Organo Corporation) was added, and the mixture was stirred at 100 rpm in a mix rotor at room temperature (23°C) for 4 hours. The anion exchange resin was separated by filtration to obtain a polysiloxane solution. The organic solvent was removed by distillation from the resulting polysiloxane solution to obtain polysiloxane. The salt (cation, anion) content (residual Na content, residual Cl content) in the resulting polysiloxane was analyzed. The results are shown in Table 3.

[0042] (Comparative Example 5: Operation using ion exchange resin (2)) The same procedure as in Comparative Example 4 was carried out except that the amount of cation exchange resin added was changed from 6 g to 12 g, and the amount of anion exchange resin added was changed from 6 g to 12 g, and the same procedure was carried out as in Comparative Example 4 to obtain polysiloxane, and the contents of salts (cations, anions) in the polysiloxane (residual Na content, residual Cl content) were analyzed. The results are shown in Table 3.

[0043] [Table 3] [Industrial Applicability]

[0044] Polysiloxanes are used in various fields such as electrical engineering, machinery, and food. Depending on the application, there are fields in which the inclusion of impurities in polysiloxane is undesirable. For example, in the electrical field, particularly in the semiconductor-related field, salts contained in polysiloxane can adversely affect electrical properties, and an extremely low salt content is desired. The present invention can provide a polysiloxane that is applicable to fields in which the salt content is extremely low.

Claims

1. A method for removing unionized particulate salts from polysiloxane, comprising the steps of: (1) dissolving a polysiloxane obtained by hydrolyzing and polycondensing a chlorosilane having chlorine atoms bonded to silicon atoms in advance in a solvent containing a nonpolar organic solvent and no water; (2) contacting the polysiloxane with activated carbon in a solution to which only activated carbon is added as a solid component; and (3) separating the polysiloxane.

2. The method for removing salts according to Claim 1, wherein the polysiloxane is applied in a proportion of 20 to 90% by mass based on the total mass of the polysiloxane and the organic solvent.

3. The method for removing salts according to claim 1 or claim 2, wherein activated carbon is applied in a proportion of 3 to 100% by mass based on the mass of polysiloxane.

4. The method for removing salts according to any one of Claims 1 to 3, wherein in step (1), the contact temperature with activated carbon is adjusted to a range of 5 to 50°C.

5. The method for removing salts according to any one of Claims 1 to 4, wherein the activated carbon has an average particle size of 3 to 200 micrometers.

6. The method for removing salts according to any one of claims 1 to 5, wherein the nonpolar organic solvent is at least one selected from the group consisting of toluene, octane, nonane, and hexamethyldisiloxane.

7. The method for removing salts according to any one of claims 1 to 6, wherein the salts are sodium chloride.