Method for separating and recovering polythiol

Abstract

To provide a technique for separating and recovering polythiol compounds contained in an aqueous solution from the aqueous solution.SOLUTION: Provided is a method for separating and recovering a polythiol compound, the method including the step of mixing an aqueous solution containing a polythiol compound with an inorganic salt or an aqueous solution containing an inorganic salt, and salting out the polythiol compound.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for separating and recovering a polythiol compound dissolved in an aqueous solution. [Background technology]

[0002] Polythiol compounds, which have two or more thiol groups in one molecule, are used as crosslinking agents and curing agents for various resins such as epoxy resins, urethane resins, acrylic resins, allyl resins, vinyl resins, unsaturated polyesters, polybutadienes, etc. In particular, cured products containing epoxy resins have good adhesion, chemical resistance, low shrinkage, and excellent physical properties, and are useful compounds that have been widely used in paints, adhesives, etc. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] China Patent Application Publication No. 109180926 Summary of the Invention [Problem to be solved by the invention]

[0004] Polythiol compounds have many thiol groups in one molecule, and therefore are highly hydrophilic. Therefore, they are soluble in water and difficult to separate from the aqueous solution. In addition, wastewater containing such thiol compounds is harmful, and therefore needs to be rendered harmless in the wastewater treatment process, but this requires a great deal of effort. The object of the present invention is to provide a technology for separating and recovering polythiol compounds contained in an aqueous solution from the aqueous solution. [Means for solving the problem]

[0005] The present invention is a method for separating and recovering a polythiol compound, comprising the steps of mixing an aqueous solution containing a polythiol compound with an inorganic salt or an aqueous solution containing an inorganic salt, and salting out the polythiol compound. Effect of the Invention

[0006] By using the method of the present invention, the polythiol compound dissolved in the aqueous solution can be separated and further recovered. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] The method for separating and recovering a polythiol compound of the present invention includes a step of mixing an aqueous solution containing a polythiol compound with an inorganic salt or an aqueous solution containing an inorganic salt to salt out the polythiol compound.

[0008] The polythiol compound preferably has a polyether moiety represented by the following general formula (1) in the main chain and a structural unit represented by the following formula (2) at the terminal. R 1 [-(R 2 O) n ] m - (1) -CH2CH(OH)CH2-SH (2).

[0009] In formula (1), R 1 is a residue of a polyamine or polyalcohol having 10 or less carbon atoms with a hydrogen atom removed, and R 2 is an alkylene group having a carbon number of 2 to 6. n is an integer of 1 to 200, and preferably 1 to 100. m is an integer of 2 to 8, and preferably 2 to 5.

[0010] Examples of the polyamine include triethanolamine and ethylenediamine.

[0011] Examples of the polyhydric alcohol include glycerin, trimethylolpropane, trimethylolethane, hexanetriol, diglycerin, pentaerythritol, triethanolamine, sucrose, etc. Among the above polyols, glycerin, trimethylolpropane, and trimethylolethane are particularly preferred.

[0012] The polyhydric amines and the polyhydric alcohols may be used alone or in combination.

[0013] R 2 Examples of the alkylene include ethylene, n-propylene, isopropylene, n-butylene, and isobutylene.

[0014] A method for synthesizing the polythiol compound of the present invention will be specifically described below.

[0015] The polythiol compound in the present invention can be obtained by reacting a polyether polyol having the structure of formula (1) with epichlorohydrin to synthesize a chloropolyether intermediate, and then reacting the chloropolyether intermediate thus obtained with sodium hydrosulfide.

[0016] In the present invention, the intermediate chloropolyether is obtained by first reacting a polyether polyol having the structure of formula (1) with epichlorohydrin in the presence of a Lewis acid catalyst.

[0017] The Lewis acid catalyst may be BF3, AlCl3, SbCl5, SnCl4, TiCl4, FeBr3, FeCl3, or ZnCl2. These Lewis acids may be used alone or in combination.

[0018] The amount of the Lewis acid catalyst used is preferably 0.1% by mass to 10% by mass, and more preferably 0.3% by mass to 5% by mass, of the polyether polyol.

[0019] The molar ratio of the epichlorohydrin to the polyether polyol is preferably 2.0 to 10.0, and more preferably 2.5 to 6.0.

[0020] The reaction temperature between the epichlorohydrin and the polyether polyol is preferably 40 to 150°C, and more preferably 60 to 100°C.

[0021] The reaction time is preferably from 1 to 100 hours, and more preferably from 2 to 10 hours.

[0022] Next, the polythiol compound is obtained by reacting the chloropolyether with sodium hydrosulfide in a hydrogen sulfide atmosphere.

[0023] In the above reaction, it is preferable to use a phase transfer catalyst, since this can further accelerate the reaction and is expected to improve productivity.

[0024] As the phase transfer catalyst, a quaternary ammonium salt and a quaternary phosphonium salt can be preferably used.

[0025] Examples of the quaternary ammonium salt include tetrabutylammonium fluoride, benzyltributylammonium chloride, benzyltriethylammonium chloride, benzyltrimethylammonium chloride, tetra-n-butylammonium chloride, tetraethylammonium chloride, methyltributylammonium chloride, benzyltri-n-butylammonium bromide, benzyltriethylammonium bromide, benzyltrimethylammonium bromide, n-octyltrimethylammonium bromide, hexyltrimethylammonium bromide, tetrabutylammonium bromide, tetraethylammonium bromide, tetradecyltrimethyl ... Preferred are tetrabutylammonium bromide, tetra-n-propylammonium bromide, tetraoctylammonium bromide, tetrabutylammonium iodide, tetraethylammonium iodide, tetra-n-propylammonium iodide, trimethylphenylammonium iodide, tetrabutylammonium hydrogen sulfate, benzyltrimethylammonium hydroxide, phenyltrimethylammonium hydroxide, tetrabutylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydrogen sulfate, and tetrabutylammonium tetrafluoroborate.

[0026] Examples of quaternary phosphonium salts include tetrabutylphosphonium fluoride, benzyltributylphosphonium chloride, benzyltriethylphosphonium chloride, benzyltrimethylphosphonium chloride, tetra-n-butylphosphonium chloride, tetraethylphosphonium chloride, methyltributylphosphonium chloride, benzyltri-n-butylphosphonium bromide, benzyltriethylphosphonium bromide, benzyltrimethylphosphonium bromide, n-octyltrimethylphosphonium bromide, hexyltrimethylphosphonium bromide, tetrabutylphosphonium bromide, tetraethylphosphonium bromide, tetradecyltrimethyl ... Preferred are tetrabutylphosphonium bromide, tetra-n-propylphosphonium bromide, tetraoctylphosphonium bromide, tetrabutylphosphonium iodide, tetraethylphosphonium iodide, tetra-n-propylphosphonium iodide, trimethylphenylphosphonium iodide, tetrabutylphosphonium hydrogen sulfate, benzyltrimethylphosphonium hydroxide, phenyltrimethylphosphonium hydroxide, tetrabutylphosphonium hydroxide, tetraethylphosphonium hydroxide, tetrapropylphosphonium hydroxide, tetrabutylphosphonium hydrogen sulfate, tetrabutylphosphonium tetrafluoroborate, and the like.

[0027] More preferred examples of the phase transfer catalyst include tetraethylammonium bromide, tetrabutylammonium bromide, tetrabutylammonium iodide, tetrabutylammonium hydrogen sulfate, tetrabutylphosphonium bromide, tetraoctylammonium bromide, benzyltriethylammonium chloride, and methyltributylammonium chloride.

[0028] These phase transfer catalysts may be used alone or in combination of two or more kinds.

[0029] When the phase transfer catalyst is used, the amount used is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, of the chloropolyether.

[0030] In the present invention, the substitution reaction between the chloropolyether and sodium hydrosulfide is preferably carried out in a hydrogen sulfide atmosphere. By carrying out the reaction in a hydrogen sulfide atmosphere, it is advantageous to suppress side reactions. The pressure of the hydrogen sulfide gas is not particularly specified, but it may be under normal pressure or under pressure.

[0031] The molar ratio of the chloropolyether to sodium hydrosulfide is preferably 0.5 to 3.0, and more preferably 0.9 to 1.5.

[0032] The sodium hydrosulfide is preferably used as an aqueous solution, and the concentration of the aqueous sodium hydrosulfide solution is preferably 10 to 70% by mass, and more preferably 15 to 50% by mass.

[0033] The temperature of the substitution reaction is preferably 70 to 120°C, and more preferably 80 to 100°C.

[0034] The time period for the substitution reaction is preferably from 2 to 100 hours, and more preferably from 5 to 20 hours.

[0035] In the present invention, it is preferable to carry out post-treatment after the substitution reaction. In the post-treatment, the crude product obtained by the substitution reaction is washed with water for the first time and separated, the pH value is adjusted to 3 to 7, and then washed with water for the second time and separated to obtain a washed crude product. Furthermore, the washed crude product is subjected to vacuum conditions to remove water, thereby obtaining a polythiol compound.

[0036] Specifically, after obtaining the crude product, the first washing with water is carried out. A certain amount of water is added to the crude product to wash it with water. The amount of water is preferably 1 to 3 times the mass of the crude product. The temperature of the water washing is preferably 50 to 100°C.

[0037] Thereafter, the pH value is adjusted to 3 to 7. A method for adjusting the pH value is preferably to add an acid. In the present invention, the acid is not particularly limited, but a mineral acid such as sulfuric acid or hydrochloric acid, or an organic acid such as acetic acid, propionic acid, oxalic acid, malonic acid, or citric acid can be used.

[0038] After adjusting the pH value, a liquid separation operation is performed to obtain a crude product. Then, a second water washing is performed, and a certain amount of water is added to the crude product to perform water washing. The amount of water added is preferably 1 to 3 times the mass of the crude product. The water washing temperature is preferably 50 to 100°C. After the second water washing, a liquid separation operation is performed again to obtain a crude product.

[0039] After obtaining a crude product by washing with water, water is removed under vacuum conditions, such as a degree of vacuum of -0.095 MPa or less and a temperature of 60 to 80°C.

[0040] Since a large amount of water is used in the washing process of the post-treatment, a large amount of aqueous solution containing thiol compounds is generated. Since wastewater containing these thiol compounds is harmful, it is necessary to render it harmless in a wastewater treatment process, which requires a great deal of effort.

[0041] By using the method of the present invention, the polythiol compound can be separated and recovered from the aqueous solution, thereby reducing the labor required for the wastewater treatment process.

[0042] A method for separating and treating a polythiol compound dissolved in an aqueous solution will be specifically described.

[0043] In the present invention, an inorganic salt or an aqueous solution containing an inorganic salt is mixed with an aqueous solution containing a polythiol compound to salt out the polythiol compound, and then a liquid separation operation is performed to separate and recover the aqueous solution and the polythiol compound.

[0044] The aqueous solution containing the polythiol compound may be the aqueous solution generated in the post-treatment step.

[0045] In the present invention, examples of inorganic salts include phosphates such as sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium metaphosphate, trisodium phosphate, potassium dihydrogen phosphate, dipotassium phosphate, sodium polyphosphate, and sodium pyrophosphate, carbonates such as sodium carbonate, sodium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, and ammonium carbonate, metal chlorides such as sodium chloride, potassium chloride, magnesium chloride, and calcium chloride, sodium sulfate, sodium sulfite, and sodium hydrogen sulfite. Metal chlorides are preferred, and sodium sulfate and sodium chloride are more preferred.

[0046] The inorganic salts may be used alone or in combination.

[0047] As a method for mixing the aqueous solution containing the polythiol compound with the inorganic salt, the inorganic salt may be added to the aqueous solution containing the polythiol compound, or conversely, the aqueous solution containing the polythiol compound may be added to the inorganic salt.

[0048] The inorganic salt may be mixed as a solid, as an aqueous solution in which the inorganic salt is dissolved in water, or as a supersaturated slurry solution.

[0049] In this case, when mixing as an aqueous solution, if the salt concentration in the aqueous solution is too low, the effect of salting out decreases. Therefore, the higher the salt concentration after mixing, the better. It is preferable to adjust the salt concentration in the aqueous solution after mixing to be 5% by mass or more, preferably 10% by mass or more, and more preferably 15% by mass or more.

[0050] When the aqueous solution containing the polythiol compound is mixed with the inorganic salt, the mixing may be performed in a state where the polythiol compound is in an insoluble state coexisting in the aqueous solution.

[0051] After mixing an aqueous solution containing the polythiol compound with an inorganic salt and then performing liquid-liquid separation of the oil phase and the water phase, the polythiol compound in the aqueous solution can be separated and removed. At this time, the polythiol compound separated from the water phase can be recovered as a product.

Example

[0052] Examples and comparative examples are shown below to specifically describe the present invention. In the following examples, when the raw materials were not specifically specified, general reagents purchased from reagent manufacturers were used. Also, the concentration of the polythiol compound in the aqueous solution was measured by the following HPLC analysis.

[0053] <HPLC Analysis Conditions> Column: YMC-Pack (registered trademark) ODS-A303 250 mm × 4.6 mm φ (YMC CO., LTD.) Mobile phase A solution: 0.05% phosphoric acid aqueous solution (phosphoric acid: HPLC grade) Mobile phase B solution: acetonitrile (HPLC grade) Gradient: 0 min (98:2) → 5 min (98:2) → 15 min (10:90) → 33 min (10:90) → 34 min (98:2) → 60 min (98:2) Detector: UV (λ = 215 nm) Flow rate: 1.0 ml / min Temperature: 40°C Injection volume: 10 μl Retention time: Peaks from 12 minutes to 20 minutes were totaled and calculated as the polythiol compound.

[0054] [Example 1] To 100 g of an aqueous solution containing 6% by mass of the polythiol compound and 2% by mass of sodium chloride, 30 g of powdered sodium chloride was added and completely dissolved. The concentration of sodium chloride in the aqueous solution after dissolution was 26% by mass. Liquid-liquid separation was performed to separate the water phase and the oil phase, and the content of the polythiol compound in the aqueous solution was measured to be 0.4%. 5.4 g of the polythiol compound could be separated and recovered.

[0055] [Example 2] 100g of an aqueous solution containing 6% by mass of polythiol compound and 2% by mass of sodium chloride was added to and mixed with 100g of an aqueous solution containing 25% by mass of sodium chloride. The concentration of sodium chloride in the aqueous solution after dissolution was 14% by mass. The content of polythiol compound in the aqueous solution was measured by separating the aqueous phase from the oil phase and finding that it was 2.1%. 1.9g of polythiol compound was separated and recovered.

[0056] [Example 3] 100g of a slurry-state sodium chloride aqueous solution was added to 100g of an aqueous solution containing 6% by mass of polythiol compound and 2% by mass of sodium chloride and mixed. The concentration of sodium chloride in the aqueous solution after dissolution was 19% by mass. The content of polythiol compound in the aqueous solution was measured by separating the aqueous phase from the oil phase through liquid-liquid separation and found to be 1.5%. 3.0g of polythiol compound was separated and recovered.

[0057] [Example 4] 25 g of powdered sodium sulfate anhydrate was added to 100 g of an aqueous solution containing 6 mass % of polythiol compound and 2 mass % of sodium chloride, and completely dissolved. The concentration of sodium sulfate in the aqueous solution after dissolution was 21 mass %. The aqueous phase and oil phase were separated by liquid-liquid separation, and the content of polythiol compound in the aqueous solution was measured to be 0.6%. 4.7 g of polythiol compound was separated and recovered.

[0058] [Comparative Example 1] 100g of an aqueous solution containing 6% by mass of polythiol compound and 2% by mass of sodium chloride was mixed with 100g of an aqueous solution containing 5% by mass of sodium chloride. The concentration of sodium chloride in the aqueous solution after dissolution was 4% by mass. Almost no polythiol compound was separated and recovered.

[0059] [Comparative Example 2] 100g of an aqueous solution containing 6% by mass of polythiol compound and 2% by mass of sodium chloride was mixed with 100g of an aqueous solution containing 2% by mass of sodium sulfate. The concentration of sodium sulfate in the aqueous solution after dissolution was 1% by mass. Almost no polythiol compound was separated and recovered.

[0060] [Comparative Example 3] 100 g of pure water was added to 100 g of an aqueous solution containing 6% by mass of a polythiol compound and 2% by mass of sodium chloride, and mixed. The concentration of sodium chloride in the aqueous solution after dissolution was 1% by mass. The polythiol compound could not be separated and recovered at all.

Claims

1. A method for separating and recovering a polythiol compound, comprising the steps of mixing an aqueous solution containing a polythiol compound with an inorganic salt or an aqueous solution containing an inorganic salt, and salting out the polythiol compound.

2. The polythiol compound is R １ [-(R ２ O) ｎ ] ｍ - (However, R １ is a residue obtained by removing a hydrogen atom from a polyhydric amine or polyhydric alcohol having 10 or less carbon atoms, R ２ is an alkylene group having 2 to 6 carbon atoms, n is an integer from 1 to 200, and m is an integer from 2 to 8. and a polyether moiety represented by the formula: ２ CH(OH)CH ２ The method for separating and recovering a polythiol according to claim 1, which has a structural unit represented by -SH.

3. The method for separating and recovering a polythiol according to claim 1 or 2, wherein the inorganic salt concentration in the aqueous solution after mixing the inorganic salt or the aqueous solution containing the inorganic salt is 10 mass% or more.

4. The method for separating and recovering a polythiol according to claim 1 or 2, wherein the inorganic salt is at least one selected from the group consisting of sodium chloride, sodium sulfate, and magnesium sulfate.