Method for producing polythiol compound, method for producing curable composition, and method for producing cured product

Abstract

Provided is a method for producing a polythiol compound, including obtaining one or more polythiol compounds selected from the group consisting of a polythiol compound represented by Formula (3), a polythiol compound represented by Formula (4), and a polythiol compound represented by Formula (5) through steps including: reacting 2-mercaptoethanol with an epihalohydrin in an amount of 1.00 equivalent or more and 1.25 equivalent or less with respect to the 2-mercaptoethanol to obtain a polyol compound represented by Formula (1); and reacting the polyol compound represented by Formula (1) with an alkali metal sulfide in an amount of 1.04 equivalent or more and 1.25 equivalent or less with respect to the 2-mercaptoethanol to obtain a polyol compound represented by Formula (2). ##STR00001##
[in Formula (1), X represents a halogen atom] ##STR00002##

Claims

1. A method for producing a polythiol compound, comprising: reacting 2-mercaptoethanol with an epihalohydrin in an amount of 1.00 equivalent or more and 1.25 equivalent or less with respect to the 2-mercaptoethanol to obtain a polyol compound represented by Formula (1); ##STR00014## [in Formula (1), X represents a halogen atom] reacting the polyol compound represented by Formula (1) with an alkali metal sulfide in an amount of 1.04 equivalent or more and 1.25 equivalent or less with respect to the 2-mercaptoethanol to obtain a polyol compound represented by Formula (2); ##STR00015## reacting the polyol compound represented by Formula (2) with thiourea in the presence of an acid to obtain an isothiuronium salt; hydrolyzing the isothiuronium salt in the presence of a base to obtain a polythiol salt; and converting the polythiol salt into a polythiol with an acid to obtain one or more polythiol compounds selected from the group consisting of a polythiol compound represented by Formula (3), a polythiol compound represented by Formula (4), and a polythiol compound represented by Formula (5) ##STR00016##

2. A method for producing a curable composition, comprising: producing a polythiol compound by the production method according to claim 1; and mixing the produced polythiol compound with a polyiso(thio)cyanate compound to prepare a curable composition.

3. A method for producing a cured product, comprising: producing a curable composition by the production method according to claim 2; and curing the produced curable composition to obtain a cured product.

4. The method for producing a cured product according to claim 3, wherein the curing is carried out by subjecting the curable composition to cast polymerization.

5. The method for producing a cured product according to claim 3, wherein the cured product is a spectacle lens base material.

6. The method for producing a cured product according to claim 4, wherein the cured product is a spectacle lens base material.

Description

EXAMPLES

(1) Next, the present disclosure will be described in greater detail with reference to Examples, but the present disclosure is not limited to the aspects shown in the Examples. Operations and evaluations described below were carried out in air at room temperature (about 20 C. to 25 C.) unless otherwise specified. In addition, % and parts described below are based on mass unless otherwise specified.

Example 1

(2) <Production of Polythiol Compound>

(3) (Step 1)

(4) A total of 96.2 g (1.04 mol) of epichlorohydrin was dropwise added over 1 h to a mixed solution of 78.1 g (1.00 mol) of 2-mercaptoethanol and 2.0 g of triethylamine while keeping the internal temperature at 35 C. to 40 C., and the mixture was aged for 1 h at an internal temperature of 40 C. The aging here and the aging described below were carried out while stirring the reaction solution.

(5) (Step 2)

(6) An aqueous solution prepared by dissolving 124.9 g (0.52 mol) of sodium sulfide nonahydrate in 100 g of pure water was added dropwise over 1 h to the reaction solution after the aging while keeping the internal temperature at 40 C. to 45 C., followed by aging for 1 h at 45 C.

(7) (Step 3)

(8) Next, 303.8 g (3.00 mol) of 36% hydrochloric acid and 190.3 g (2.50 mol) of thiourea were added to the reaction solution, followed by heating and stirring for 9 h at an internal temperature of 110 C.

(9) (Step 4)

(10) After cooling the reaction solution to room temperature, 400 ml of toluene was added, 600.4 g (4.50 mol) of a 30% sodium hydroxide aqueous solution was gradually added and hydrolysis was carried for 4 h out at an internal temperature of 60 C.

(11) (Step 5)

(12) The reaction solution after the hydrolysis was allowed to stand to separate the solution into an aqueous layer and an organic layer, the organic layer was then taken out, and the organic layer was successively washed twice with 100 ml of 36% hydrochloric acid and 100 ml of water. Toluene in the organic layer after washing was distilled off with a rotary evaporator to obtain a polythiol compound in a yield of 174.4 g (yield ratio 95.1%).

(13) In Example 1, in Step 3, the rearrangement reaction occurs as described above, whereby a mixture of the isothiuronium salt having the skeleton of the polythiol compound represented by Formula (3), the isothiuronium salt having the skeleton of the polythiol compound represented by Formula (4), and the isothiuronium salt having the skeleton of the polythiol compound represented by Formula (5) can be obtained. As a result, in Step 5, a mixture of the polythiol compound represented by Formula (3), the polythiol compound represented by Formula (4), and the polythiol compound represented by Formula (5) is obtained. The yield ratio was calculated by the formula
Yield Ratio=[(the abovementioned yield)/(theoretical yield)]100
by using the theoretical yield determined from the theoretical molar yield (0.50 mol) of the polythiol compounds represented by Formulas (3) to (5) obtained from the amount of 2-mercaptoethanol (1.00 mol) used in Step 1.

(14) Mixtures of the polythiol compound represented by Formula (3), the polythiol compound represented by Formula (4), and the polythiol compound represented by Formula (5) are similarly obtained in the Examples and Comparative Examples described hereinbelow. In the below-described Examples and Comparative Examples, the yield ratio was calculated in a similar manner.

(15) The polythiol compounds obtained in the Examples and Comparative Examples were used as they were, without treatment such as purification, for the production of the following cured products and the evaluation of polythiol compounds.

(16) <Production of Cured Product (Plastic Lens) A>

(17) A total of 50.60 parts of xylylene diisocyanate, 0.01 parts of dimethyltin dichloride as a curing catalyst, 0.20 parts of an acidic phosphoric acid ester (JP-506H, manufactured by Johoku Chemical Co., Ltd.) as a releasing agent, and 0.50 parts of an ultraviolet absorber (SEESORB 701, manufactured by Shipro Kasei Kaisha, Ltd.) were mixed and dissolved.

(18) Further, 49.40 parts of the polythiol compound obtained above was added and mixed to obtain a mixed solution. This mixed solution was deaerated for 1 h at 200 Pa, and then filtration was carried out with a PTFE (polytetrafluoroethylene) filter having a pore size of 5.0 m. The filtered mixed solution (curable composition) was injected into a molding die for a lens made of a glass mold having a diameter of 75 mm and 4.00 D and a tape. The molding die was loaded into an electric furnace, gradually heated over 20 h from 15 C. to 120 C., and kept for 2 h for polymerization (curing reaction). After completion of the polymerization, the molding die was removed from the electric furnace and the polymer was released to obtain a cured product (plastic lens). The resulting plastic lens was further annealed for 3 h in an annealing furnace having a furnace temperature of 120 C.

(19) <Production of Cured Product (Plastic Lens) B>

(20) A total of 58.90 parts of dicyclohexylmethane diisocyanate, 0.3 parts of dimethyltin dichloride as a curing catalyst, 0.20 parts of an acidic phosphoric acid ester (JP-506H manufactured by Johoku Chemical Co., Ltd.) as a releasing agent, and 1.00 part of an ultraviolet absorber (SEESORB 701, manufactured by Shipro Kasei Kaisha, Ltd.) were mixed and dissolved.

(21) Further, 41.10 parts of the polythiol compound obtained by the production of the polythiol compound was added and mixed to obtain a mixed solution. This mixed solution was deaerated for 1 h at 200 Pa, and then filtration was carried out with a PTFE (polytetrafluoroethylene) filter having a pore size of 5.0 m. The filtered mixed solution (curable composition) was injected into a molding die for a lens made of a glass mold having a diameter of 75 mm and 4.00 D and a tape. The molding die was loaded into an electric furnace, gradually heated over 20 h from 15 C. to 120 C., and kept for 2 h for polymerization (curing reaction). After completion of the polymerization, the molding die was removed from the electric furnace and the polymer was released to obtain a cured product (plastic lens). The resulting plastic lens was further annealed for 3 h in an annealing furnace having a furnace temperature of 120 C.

Examples 2 to 4, Comparative Examples 1 to 5

(22) Polythiol compounds were obtained by the same method as in Example 1 except that the charged amount of epichlorohydrin in Step 1 and the charged amount of sodium sulfide nonahydrate in Step 2 were changed. The equivalents of epichlorohydrin used in Step 1 and sodium sulfide (sodium sulfide nonahydrate) used in Step 2 with respect to 2-mercaptomethanol used in Step 1 are shown in Table 1.

(23) A cured product A and a cured product B were produced in the same manner as in Example 1 by using the obtained polythiol compound.

(24) [Evaluation Methods]

(25) <Refractive Index of Cured Product (Plastic Lens)>

(26) The refractive index ne of the cured product (plastic lens) produced above was measured by the following method by using a precision refractive index meter KPR-200 manufactured by Shimadzu Corporation.

(27) (1) Using a precision cutting machine Isomet manufactured by Buehler, a test sample in the form of a triangular prism having an angle of 90 between two surfaces in contact with the measuring prism is prepared.

(28) (2) The prepared sample is set in the measuring prism and the refractive index ne is measured under the following measurement conditions.

(29) (Measurement Conditions)

(30) Measurement temperature: 25 C.

(31) Contact liquid: bromonaphthalene

(32) <Glass Transition Temperature of Cured Product (Plastic Lens)>

(33) The glass transition temperature (Tg) of the cured product (plastic lens) produced in the above-described manner was measured by a penetration method using a thermal instrument analyzer TMA 8310 manufactured by Rigaku Corporation. The load at the time of measurement was 10 g, the heating rate was 10 K/min, and an indenter with a diameter of 0.5 mm was used as an indenter for the penetration method.

(34) <Refractive Index of Polythiol Compound>

(35) The refractive index ne of the polythiol compound prepared in the above-described manner was measured using a refractometer RA-500 manufactured by Kyoto Electronics Manufacturing Co., Ltd.

(36) <Thiol Equivalent of Polythiol Compound>

(37) The thiol equivalents of the polythiol compounds obtained in the respective Examples and Comparative Examples were measured by the following method by using an automatic titration device AT-610 manufactured by Kyoto Electronics Manufacturing Co., Ltd.

(38) (1) A total of 0.1 g of the polythiol compound obtained in each Example and Comparative Example are accurately weighed.

(39) (2) The accurately weighed polythiol compound is dissolved in a mixed solvent of 40 ml of chloroform and 20 ml of 2-propanol to prepare a sample for measurement.

(40) (3) Titration of the prepared measurement sample is carried out using a titration solution (0.05 mol/L iodine solution), and an end point is determined.

(41) (4) The thiol equivalent is determined from the titration amount (mL) at the end point by the following formula.
Thiol equivalent=[(Sample amount (g))(Titration solution factor)10000]/Titer (mL)

(42) The above results are shown in Table 1. From the results shown in Table 1, it can be confirmed that the refractive index of the cured product in Examples is improved (improvement of the refractive index ne by 0.02 or more) compared with Comparative Examples.

(43) Further, it can be confirmed that in Examples, the yield ratio and the refractive index of the polythiol compound and the heat resistance of the cured product are all improved compared with Comparative Examples.

(44) The inventors of the present disclosure believe that the thiol equivalent shown in Table 1 is a value that can be used as an index of the purity of the target product in the produced polythiol compound. Details are explained hereinbelow.

(45) The theoretical value of the equivalent for a functional group (for example, a thiol group) of a certain compound can be obtained by dividing the molecular weight of the compound by the number of functional groups contained in one molecule. The polythiol compound represented by Formula (3), the polythiol compound represented by Formula (4), and the polythiol compound represented by Formula (5) are each a tetrafunctional polythiol compound having four thiol groups, and the theoretical value of the equivalent (thiol equivalent) for the thiol group is 92. Meanwhile, as the amount of by-products of trifunctional or less functional thiol compounds other than the above-mentioned three tetrafunctional polythiol compounds, which are the target products in the production of the polythiol compound, increases, the actually measured value of the thiol equivalent greatly exceeds 92. Therefore, the inventors of the present disclosure believe that the thiol equivalent can be used as an index of the purity of the three polythiol compounds which are the target products in the polythiol compounds produced in respective Examples and Comparative Examples. As shown in Table 1, the thiol equivalents of the polythiol compounds prepared in Examples 1 to 4 are closer to the theoretical value 92 than those of the polythiol compounds produced in Comparative Examples 1 to 5. The inventors of the present disclosure presume that the fact that above-mentioned three polythiol compounds, which are the target products, are obtained at high purity is a factor contributing to the improvement of the refractive index of the cured product. In consideration of this point, in one aspect, the measured value of the thiol equivalent of the polythiol compound obtained by the method for producing a polythiol compound according to one aspect of the present disclosure is for example, 92 or more and 100 or less.

(46) However, the above presumption of the inventors of the present disclosure places no limitation on the present disclosure.

(47) TABLE-US-00001 TABLE 1 Cured product A Cured product B Heat Heat resistance, resistance, glass glass Equivalent Polythiol compound transition transition Sodium Refractive Thiol Yield Refractive temperature Refractive temperature Epichlorohydrin sulfide index equivalent ratio index ( C.) index ( C.) Example 1 1.04 1.04 1.6455 97 95.1% 1.669 103 1.602 142 Example 2 1.00 1.04 1.6457 98 93.4% 1.669 104 1.602 141 Example 3 1.00 1.20 1.6452 99 93.6% 1.669 103 1.602 142 Example 4 1.25 1.25 1.6450 99 91.4% 1.668 102 1.601 141 Comparative 1.00 1.00 1.6430 103 87.6% 1.666 99 1.600 139 Example 1 Comparative 1.30 1.30 1.6426 103 85.3% 1.663 97 1.598 136 Example 2 Comparative 0.96 1.10 1.6427 104 82.2% 1.662 96 1.597 137 Example 3 Comparative 1.00 1.34 1.6426 103 84.5% 1.663 97 1.598 138 Example 4 Comparative 1.28 1.04 1.6428 103 83.2% 1.663 98 1.597 137 Example 5

(48) Finally, the above-mentioned aspects are summarized.

(49) According to one aspect, there is provided a method for producing a polythiol compound, including: Step 1 of reacting 2-mercaptoethanol with an epihalohydrin in an amount of 1.00 equivalent or more and 1.25 equivalent or less with respect to the 2-mercaptoethanol to obtain a polyol compound represented by Formula (1); Step 2 of reacting the polyol compound represented by Formula (1) with an alkali metal sulfide in an amount of 1.04 equivalent or more and 1.25 equivalent or less with respect to the 2-mercaptoethanol to obtain a polyol compound represented by Formula (2); Step 3 of reacting the polyol compound represented by Formula (2) with thiourea in the presence of an acid to obtain an isothiuronium salt; Step 4 of hydrolyzing the isothiuronium salt in the presence of a base to obtain a polythiol salt; and Step 5 of converting the polythiol salt into a polythiol with an acid to obtain one or more polythiol compounds selected from the group consisting of a polythiol compound represented by Formula (3), a polythiol compound represented by Formula (4), and a polythiol compound represented by Formula (5).

(50) By subjecting the polythiol compound obtained by the above-mentioned method for producing a polythiol compound to the curing reaction with a polyiso(thio)cyanate compound, it is possible to provide a cured product (polythiourethane resin) having a high refractive index.

(51) In one aspect, the equivalent of epihalohydrin in Step 1 may be 1.20 equivalent or less, may be 1.15 equivalent or less, may be 1.10 equivalent or less, or may be 1.05 equivalent or less with respect to the 2-mercaptoethanol.

(52) In one aspect, the equivalent of the alkali metal sulfide in Step 2 may be 1.20 equivalent or less, may be 1.15 equivalents or less, or may be 1.10 equivalent or less with respect to the 2-mercaptoethanol used in Step 1.

(53) According to further aspect, there is provided a method for producing a curable composition, including: producing a polythiol compound by the abovementioned production method; and mixing the produced polythiol compound with a polyiso(thio)cyanate compound to prepare a curable composition.

(54) According to still further aspect, there is provided a method for producing a cured product, including: producing a curable composition by the abovementioned production method; and curing the produced curable composition to obtain a cured product.

(55) In one aspect, the curing is carried out by subjecting the curable composition to cast polymerization.

(56) In one aspect, the cured product is a spectacle lens base material.

(57) Two or more of the various aspects disclosed in this description can be combined in any combination.

(58) It should be taken into account that the embodiments disclosed herein are exemplary in all respects and are not restrictive. The scope of the present disclosure is defined not by the description above but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

(59) One aspect of the present disclosure is useful in the field of manufacturing various kinds of optical components such as spectacle lenses.