1,6-naphthalene dithiol product and method of making same

Abstract

Provided are naphthalene dithiol (or naphthalene dithiol product) having high purity and reduced coloration, and a method for producing the same. The 1,6-naphthalene dithiol (1,6-naphthalene dithiol product) of the present invention has a purity of 99.5% or more in terms of area percentage determined by high performance liquid chromatography, and a content of 0.2% or less of a polymer of 1,6-naphthalene dithiol; and a Gardner color in a molten state of 1 or less. The polymer of the aforementioned 1,6-naphthalene dithiol can be a disulfide of a dimer. Such a 1,6-naphthalene dithiol product can be produced by distilling a crude raw material containing at least 1,6-naphthalene dithiol and a polymer of 1,6-naphthalene dithiol to distill off a distillation fraction containing 1,6-naphthalene dithiol. The crude raw material can be a solid dried product of a crude refined product of 1,6-naphthalene dithiol refined from a reaction mixture.

Description

Technical Field

[0001] This invention relates to a high-purity and colorless 1,6-naphthalenedithiol (or 1,6-naphthalenedithiol product) and its manufacturing method. Background Technology

[0002] Naphthalene dithiol or its derivatives are used in various fields such as optical materials, electrical and electronic materials, and pharmaceuticals as functional materials, raw materials, or reaction intermediates.

[0003] Japanese Patent Publication No. 2008-527413 (Patent Document 1) discloses a display comprising a light-transmitting substrate and a specific hard coating bonded to the substrate. Example 12 of that document describes reacting 2,7-dihydroxynaphthalene with dimethylthiocarbamoyl chloride, drying and heating the resulting dimethylthiocarbamate O-(7-dimethylthiocarbamoyloxy-naphthalene-2-yl) ester, recrystallizing the solid fraction with ethyl acetate to generate dimethylthiocarbamate S-(7-dimethylcarbamoylhydrothio-naphthalene-2-yl) ester, acidifying with hydrochloric acid, filtering the solid fraction, and drying to obtain 2,7-naphthalenediol.

[0004] U.S. Patent No. 2,463,219 (Patent Document 2) discloses a method in which aryl thiols and oxygen are added in a specific ratio to a latex containing a synthetic elastomer prepared by emulsification polymerization, thereby improving the processability of the synthetic elastomer. Examples of aryl thiols in this document include 2,5-dimercapto-naphthalene (1,6-naphthalenediol).

[0005] In the synthesis examples 10 and 11 of U.S. Patent No. 9,170,495 (Patent Document 3), regarding the polymer used to form the photoresist lower layer film, it is described that 9-fluorenone or thioxanone is reacted with 1,6-naphthalenedithiol in the presence of sulfuric acid, and then the resulting phenol monomer is reacted with formaldehyde to obtain the polymer.

[0006] Toshio Nanbara, “Antibacterial and Reactivity of Vinyl Sulfone-Related Compounds (2) (Research on Chemotherapy Agents Against Acid-Inducing Bacteria, Issue 13), Pharmaceutical Journal, 1955, Vol.75, Issue 12, pp.1560-1564 (Non-Patent Literature 1), Fig. 1 describes the synthesis of 1,5-bis(2-(C)-dithiol from naphthalene-1,5-dithiol via 1,5-bis(2-hydroxyethylthio)naphthalene, 1,5-bis(2-chloroethylthio)naphthalene, and 1,5-bis(2-chloroethylsulfonyl)naphthalene.” 1-2 Alkoxy)ethylsulfonyl)naphthalene.

[0007] [Existing Technical Documents]

[0008] [Patent Literature]

[0009] Patent Document 1: Japanese Patent Publication No. 2008-527413 (claims 1 and 6,

[0031] ,

[0038] , Example 12).

[0010] Patent Document 2: U.S. Patent No. 2,463,219 (Claim 1, line 12 of column 5 of the specification).

[0011] Patent Document 3: US Patent No. 9,170,495 (Reaction Scheme 1, Synthesis Examples 10 and 11).

[0012] [Non-patent literature]

[0013] Non-patent literature 1: Toshio Nanbara, “Antibacterial and reactivity of Vinyl Sulfone-related compounds (2) (Research on chemotherapeutic agents against acid-resistant bacteria, No. 13), Pharmaceutical Journal, 1955, Vol. 75, issue 12, pp. 1560-1564 (Fig. 1, experimental part, etc.). Summary of the Invention

[0014] [The problem that the invention aims to solve]

[0015] However, these documents do not describe the properties of 1,6-naphthalenedithiol. Furthermore, naphthalenedithiol is prone to coloring and, due to its highly reactive thiol group, readily forms polymers such as disulfides. Additionally, generally speaking, introducing aromatic rings, especially condensed polycyclic aromatic rings such as naphthalene rings, into the chemical structure increases heat resistance (melting point or boiling point) and refractive index, but tends to decrease solubility. Therefore, the applications of naphthalenedithiol are significantly limited.

[0016] Therefore, the object of the present invention is to provide high-purity naphthalene dithiol (or naphthalene dithiol products) with reduced color intensity and a method for manufacturing the same.

[0017] Another object of the present invention is to provide naphthalene dithiol (or naphthalene dithiol product) that has both high refractive index and high solubility, and a method for manufacturing the same.

[0018] [Methods used to solve problems]

[0019] The inventors focused on naphthalene dithiol, which has a large number of positional isomers, and conducted in-depth research to achieve the aforementioned goal. As a result, they found that among the large number of naphthalene dithiol positional isomers, 1,6-naphthalene dithiol (1,6-form) is different from other positional isomers and has specific properties, exhibiting high refractive index and high solubility even with a low melting point. Based on these findings, they further investigated and found that if crude raw materials containing 1,6-naphthalene dithiol (1,6-form) and its polymer are distilled or evaporated, 1,6-naphthalene dithiol (1,6-form) with extremely high purity and no color can be obtained, thus completing the present invention. The present invention may include the following states [1] to [8].

[0020] That is, the present invention includes [1] a 1,6-naphthalenedithiol (or a 1,6-naphthalenedithiol product) having a purity of 99.5% or more in area percentage as determined by high performance liquid chromatography, and a content of 0.2% or less in the polymer of 1,6-naphthalenedithiol. In addition, the aforementioned 1,6-naphthalenedithiol (or 1,6-naphthalenedithiol product) is almost colorless, and the Gardner color in the molten state is less than 1. In addition, in the aforementioned sample [1], [2] the polymer of 1,6-naphthalenedithiol may be a disulfide of the dimer (disulfide).

[0021] The present invention also includes [3] a method for producing a 1,6-naphthalenedithiol product, which produces a 1,6-naphthalenedithiol product (a high-purity 1,6-naphthalenedithiol product with reduced coloring) from a crude raw material containing a polymer of 1,6-naphthalenedithiol and at least 1,6-naphthalenedithiol. In this method, the aforementioned crude raw material is distilled to produce 1,6-naphthalenedithiol.

[0022] In the method of the aforementioned sample [3], [4] the crude raw material may be a crude purified product of 1,6-naphthalenedithiol obtained from the reaction mixture for the synthesis of 1,6-naphthalenedithiol. In the method of the aforementioned sample [3] or [4], [5] the crude raw material may be a solid dried product of a crude purified product of 1,6-naphthalenedithiol obtained from the reaction mixture for the synthesis of 1,6-naphthalenedithiol. In any of the methods of the aforementioned samples [3] to [5], [6] the crude raw material may be distilled under reduced pressure or vacuum and a distillate containing 1,6-naphthalenedithiol may be distilled. In any of the methods of the aforementioned samples [3] to [6], [7] the crude raw material may be distilled at a pressure of 0.1 to 30 hPa and a distillate at a temperature of 140 to 212°C may be distilled. For example, in any of the methods described in [3] to [7] above, [8] the solid dried product of the aforementioned crude refined product, which is used as crude raw material, can be distilled by single distillation, and a distillate containing 1,6-naphthalene dithiol can be distilled from the top of the distillation apparatus to produce the 1,6-naphthalene dithiol product.

[0023] [Effects of the invention]

[0024] The 1,6-naphthalenedithiol (or 1,6-naphthalenedithiol product) of the present invention, even with the presence of a thiol group, contains very little of the polymers such as the disulfide form of 1,6-naphthalenedithiol, resulting in high purity and almost no coloring. Furthermore, it exhibits high solubility even with a naphthalene ring, thus possessing both high refractive index and high solubility. Additionally, a high-purity 1,6-naphthalenedithiol product with significantly reduced coloring can be produced using a simple distillation process. This 1,6-naphthalenedithiol product can thus be used as a raw material for functional materials (optical materials, etc.) or as a reaction intermediate. Detailed Implementation

[0025] [1,6-Naphthalenedithiol]

[0026] The 1,6-naphthyl dithiol (hereinafter also referred to as the 1,6-body) shown in formula (1) below is a positional isomer of naphthyl dithiol and exhibits the specific properties described below.

[0027]

[0028] That is, the melting point of 2,7-naphthalenedithiol (2,7-form) described in Patent Document 1 is 186 to 188°C, and the melting point of 2,6-naphthalenedithiol (2,6-form) is 196 to 197°C, while the melting point of 1,5-naphthalenedithiol (1,5-form) described in Non-Patent Document 1 is 120 to 121°C. As mentioned above, naphthalenedithiol has a high melting point, and an expected increase in boiling point due to hydrogen bonding of the thiol group is also present. Furthermore, differential scanning calorimeter (DSC) thermal stability data show that the 1,5-form, 2,6-form, and 2,7-form exhibit weight reductions of more than 5% at 176°C, 196°C, and 188°C, respectively. Therefore, it is technically difficult to distill and purify naphthalenedithiol at high temperatures. For example, if vacuum distillation of the 1,5-form, 2,6-form, and 2,7-form is required, the distillation line must be maintained at a high temperature to prevent crystallization. However, if the distillation line is heated to a high temperature, naphthalene dithiol is easily re-evaporated in the distillation line, and the naphthalene dithiol crystallizes in subsequent lines, causing blockages and preventing distillation operations.

[0029] Furthermore, the 1,5-form, 2,6-form, and 2,7-form have low solubility in organic solvents and cannot maintain their crystalline form even when mixed with organic solvents. Therefore, crystallization cannot be used to improve the purity of naphthalene dithiol.

[0030] Alternatively, column chromatography was considered for purification of naphthalene dithiol. However, column chromatography is not suitable for industrial production of naphthalene dithiol. Furthermore, even with column chromatography, the naphthalene dithiol product exhibits significant coloration, making it difficult to obtain a colorless product.

[0031] Further investigation of positional isomers under these conditions revealed that 1,6-naphthalenedithiol (1,6-form) possesses unique properties. Specifically, compared to other positional isomers, the 1,6-form has an extremely low melting point (35-36°C) and a higher refractive index, exhibiting high solubility relative to organic solvents. However, when further exploring purification methods for the 1,6-form using this property, even crystallization of the crude raw material containing 1,6-naphthalenedithiol (1,6-form) failed to improve the purity of the 1,6-form product or reduce its coloration. This is attributed to the fact that naphthalenedithiol is often mixed with or contains polymers such as dimers (disulfides), which typically have lower solubility than naphthalenedithiol itself; trimers and higher polymers are almost insoluble in organic solvents. Therefore, even when 1,6-monomers are purified by crystallization, the prepolymer of the 1,6-monomer crystallizes and precipitates, making it impossible to separate the naphthalene dithiol polymer from the 1,6-monomer. Furthermore, the dimer (disulfide) exhibits the same level of solubility as the 1,6-monomer, thus failing to effectively remove the dimer (disulfide) and the coloring components. Additionally, the 1,6-monomer has high solubility relative to the solvent and is difficult to crystallize; even if it does crystallize, the loss is very high, significantly reducing the yield.

[0032] In addition, the purification of 1,6-bodies by adsorption treatment with activated carbon and the like was also explored, but the coloring components could not be removed, and high-purity 1,6-bodies with less coloring could not be obtained.

[0033] Next, focusing on the fact that polymers such as secondary dimers (disulfides) and trimers or larger polymers are almost non-volatile, it was unexpectedly discovered during the distillation purification of the 1,6-polymer that high-purity 1,6-polymer products could be obtained at relatively low temperatures. Particularly unexpectedly, it was found that coloring components that were also unremovable by column chromatography could be effectively removed, and the purified 1,6-polymer product was almost colorless. This invention was further developed based on these findings.

[0034] That is, the purity of the 1,6-naphthyl dithiol (or 1,6-naphthyl dithiol product) of the present invention, measured by high performance liquid chromatography (HPLC), is 99.5% or more (99.5 to 100%), more preferably 99.7% or more (99.7 to 100%), and more preferably 99.8% or more.

[0035] Furthermore, the content of the 1,6-naphthalenedithiol polymer in the 1,6-naphthalenedithiol product, as a percentage of area by high-performance liquid chromatography (HPLC), is 0.2% or less, preferably 0.15% or less, more preferably 0.1% or less, even more preferably 0.05% or less, and most preferably below the detection limit. The aforementioned polymer can be a dimer (disulfide or disulfide form) of 1,6-naphthalenedithiol. That is, the content of the dimer (disulfide form) can be as described above.

[0036] Furthermore, as mentioned above, the dimer (disulfide) exhibits high solubility similar to the 1,6-mer. In contrast, polymers of trimer or higher are almost insoluble in organic solvents. Therefore, it is generally difficult to quantify the aforementioned polymers of trimer or higher by HPLC.

[0037] Furthermore, the Gardner color of the molten state of the 1,6-naphthalenedithiol (or the 1,6-naphthalenedithiol product) of the present invention is 1 or less. Additionally, the melting point of 1,6-naphthalenedithiol is approximately 35 to 36°C, therefore, the Gardner color of the molten state can be rapidly determined by heating to a temperature above the melting point (a temperature above 40°C, especially 45 to 55°C). The Gardner color is determined by visually comparing the passing color of the Gardner color standard solution as specified in JIS K 0071:1998 "Methods for color testing of chemical products" Part II: Gardner color, with that of the sample, and is indicated by the number of the Gardner color standard solution corresponding to the passing light (color concentration) of the sample. Thus, in the Gardner color, the 1,6-form (or 1,6-form product) of the present invention exhibits a color of at least 1 Gardner color (Gardner color not reaching 1).

[0038] Furthermore, the purified 1,6-naphthalenedithiol (or the 1,6-naphthalenedithiol product) can be crystalline at room temperature (20°C). The melting point of the crystalline 1,6-naphthalenedithiol can be around 35 to 36°C.

[0039] [Method for manufacturing 1,6-naphthalenedithiol]

[0040] [Synthesis or modulation of 1,6-naphthalenedithiol]

[0041] In this invention, the synthesis or preparation method of 1,6-naphthalenedithiol (1,6-body) (or 1,6-naphthalenedithiol product) is not particularly limited and can be applied to reaction products containing the 1,6-body obtained by various methods. Examples of methods for synthesizing or preparing the 1,6-body include publicly known methods for synthesizing naphthalenedithiol, such as methods using 1,6-naphthalenedisulfonic acid or its salts as raw materials.

[0042] In this method, (1) 1,6-naphthalenedisulfonic acid or its salt is reacted with a halogenating agent to prepare 1,6-bis(halosulfonyl)naphthalene, and (2) the generated 1,6-bis(halosulfonyl)naphthalene is reduced in the presence of a reducing agent, thereby preparing 1,6-naphthalenedithiol (1,6-body).

[0043] In the aforementioned (1) halosulfonation reaction, the salt of 1,6-naphthalenedisulfonic acid can be, for example, an alkali metal salt or an ammonium salt. The preferred 1,6-naphthalenedisulfonic acid salt is an alkali metal salt (potassium salt, more preferably sodium salt).

[0044] Examples of halogenating agents include phosgene, phosphorus pentachloride, phosphorus trichloride, phosphorus oxychloride, thioyl chloride, oxalyl chloride, and thionyl chloride. Halogenating agents can be used alone or in combination of two or more. Chlorinating agents such as thionyl chloride are preferred. The ratio of the halogenating agent to 1 mole of 1,6-naphthalenedisulfonic acid or its salt is, for example, 2 to 10 moles, more preferably 2.1 to 5 moles, and more preferably about 2.3 to 3 moles.

[0045] The reaction can be carried out in the presence or absence of a catalyst. Catalysts may include amides such as N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc) (DMF is preferred); pyridines such as pyridine and 4-(N,N-dimethylamino)pyridine; and tertiary amines such as triethylamine. The catalyst can be used alone or in combination of two or more. Amides such as DMF are preferred catalysts. The ratio of catalyst to 1 mole of 1,6-naphthalenedisulfonic acid or its salt is, for example, 0.01 to 10 moles, more preferably 0.01 to 1 mole, more preferably 0.1 to 0.7 moles, and particularly preferably about 0.2 to 0.5 moles. Furthermore, amides such as DMF can form Wilsmeier complexes with chlorinating agents such as thionyl chloride and be converted to sulfonyl chloride.

[0046] The reaction can proceed in the presence or absence of a solvent, which is an inert solvent for the reaction. Examples of solvents include hydrocarbons such as hexane, cyclohexane, toluene, and xylene; halogenated hydrocarbons such as dichloromethane, chloroform, and 1,2-dichloroethane; esters such as methyl acetate and ethyl acetate; ketones such as methyl ethyl ketone and methyl isobutyl ketone; and tetrahydrofuran, dichloromethane, dichloro ... Ethers such as alkanes; nitriles such as acetonitrile and propionitrile; amides such as DMF and DMAc; sulfoxides such as dimethyl sulfoxide, etc. Solvents can be used alone or in combination of two or more as a mixed solvent. Preferred solvents are aromatic hydrocarbons such as toluene and xylene. The solvent ratio is not particularly limited, but is, for example, 10 to 1000 parts by mass relative to 100 parts by mass of 1,6-naphthalenedisulfonic acid or its salt, preferably 100 to 800 parts by mass, and more preferably about 300 to 600 parts by mass.

[0047] The reaction temperature is, for example, 50 to 120°C, more preferably 80 to 110°C, and even more preferably around 90 to 100°C. The reaction time is, for example, 1 to 24 hours, more preferably 2 to 18 hours, and even more preferably around 4 to 12 hours.

[0048] The reaction can be carried out in an air or inert gas environment (e.g., nitrogen; rare gases such as argon and helium), preferably in an inert gas environment. Alternatively, the reaction can be carried out under normal pressure, under pressure, or under reduced pressure.

[0049] After the reaction is complete, the reaction products can be separated and purified by common separation and purification methods such as washing, extraction, concentration, filtration, crystallization, centrifugation, column chromatography, activated carbon treatment, and drying, or a combination of these methods; they can also be used for the aforementioned reduction reaction (2) without separation and purification (e.g., maintaining a solution state). In a preferred method, in order to deactivate the halogenating agent, the operation of adding water to the reaction mixture and stirring, and separating the organic phase and the aqueous phase can be performed at least once or repeated multiple times. In addition, the separated organic phase can optionally be separated and purified by drying, solidification, distillation, crystallization, etc., and used for subsequent reduction reactions. In a preferred state, the separated organic phase can be used for subsequent reduction reactions (2).

[0050] In the aforementioned reduction reaction (2), the type of reducing agent is not particularly limited, and examples include combinations of zinc and acid, tin and acid, tin chloride and acid, lithium aluminum hydride, lithium boron hydride, sodium borohydride, etc. A preferred reducing agent is a combination of zinc (zinc powder, etc.) and acid.

[0051] Examples of acids include inorganic acids such as hydrochloric acid and sulfuric acid, with hydrochloric acid being preferred. The acid can be used alone or in combination of two or more. The ratio of acid to 1 mole of 1,6-bis(halosulfonyl)naphthalene is, for example, 10 to 100 moles, more preferably 40 to 60 moles, and more preferably about 45 to 55 moles. Furthermore, the aforementioned acid can be used as an aqueous solution.

[0052] The ratio of reducing agent to 1 mole of 1,6-bis(halosulfonyl)naphthalene is, for example, 5 to 20 moles, more preferably 8 to 17 moles, and more preferably about 10 to 15 moles.

[0053] The reaction can be carried out in the presence of a solvent, such as the same solvent as that used in the halosulfonation reaction described above (1). Two or more solvents can be used alone or in combination as a mixed solvent. In addition, when using the aforementioned acid, water contained in the form of an aqueous solution can also be used as a solvent. In particular, the reduction reaction (2) is preferably carried out in the presence of water after the reaction is completed, separated from the reaction solvent (hydrophobic aromatic hydrocarbons, etc.). There is no particular limitation on the ratio of solvents, but it is preferably about 500 to 4000 parts by mass relative to 100 parts by mass of 1,6-bis(halosulfonyl)naphthalene.

[0054] The reaction temperature is, for example, 30 to 120°C, more preferably 40 to 100°C, and more preferably about 50 to 80°C. The reaction time is, for example, 0.5 to 24 hours, more preferably 1 to 12 hours, and more preferably about 2 to 5 hours.

[0055] The reaction can be carried out in air, but is preferably carried out in an inert gas environment (such as nitrogen, argon, helium, or other rare gases). Alternatively, the reaction can be carried out under normal pressure, under pressure, or under reduced pressure.

[0056] In addition, if the aforementioned reduction reaction (2) is carried out in the presence of water that can be separated from the reaction solvent, the 1,6-body can be advantageously transferred to the organic phase, which can improve the separation and purification efficiency and accuracy of the 1,6-body.

[0057] [Preparation and distillation of crude raw materials]

[0058] The present invention also includes a method for producing 1,6-polymers (or 1,6-polymer products) by distilling crude feedstock containing 1,6-polymers and at least 1,6-polymers. The polymers contained in the crude feedstock are dimers (disulfides) or trimers or higher.

[0059] Such crude feedstock can serve as a reaction mixture for synthesizing 1,6-polymers. During the distillation of such a reaction mixture, while lighter components such as organic solvents are distilled from the top of the distillation apparatus or column, heavier components containing 1,6-polymers and their polymers remain in the lower part of the apparatus or column. These heavier components often contain impurities such as metallic components (catalyst components, inorganic bases, etc.). Therefore, if the reaction mixture is directly distilled and purified to separate the 1,6-polymer, the separation efficiency of the 1,6-polymer will decrease, and the load on the distillation apparatus will increase.

[0060] Therefore, the crude feedstock is preferably a crude purified product (1,6-body) obtained from the aforementioned reaction mixture. In this crude purification, it is preferable to separate the reaction mixture after the reaction into a crude feedstock (crude purified product) mainly containing the 1,6-body, and other mixtures, and then distill the aforementioned crude feedstock. Alternatively, the reaction mixture may be concentrated.

[0061] In this crude refining process, various separation and refining methods (or treatments) can be used to separate and refine the reaction product (1,6-body) depending on the characteristics of the reaction mixture or concentrated reaction mixture (evaporation characteristics, liquid-liquid properties, alkalinity, precipitation, etc.). These methods include distillation, washing, liquid-liquid extraction or extraction, concentration, neutralization, crystallization or precipitation, solid-liquid separation (filtration, centrifugation, etc.), column chromatography, activated carbon treatment, drying or solidification, etc. These separation and refining methods can be combined to crudely refine (separately refine) the reaction product (1,6-body). For example, the reaction mixture can be distilled in the aforementioned manner, and the aforementioned heavy component can be distilled from the bottom of the distillation apparatus or column. The aforementioned heavy component, used as a crude feedstock, can then be further distilled using the distillation apparatus. However, as mentioned above, even with these separation and refining methods, the separation efficiency of the 1,6-body will decrease, making it difficult to easily produce a high-purity 1,6-body product with reduced color intensity.

[0062] In a preferred method, to reduce the contamination of the crude feedstock (crude purified product) containing the reaction product (1,6-body), the reaction mixture is crudely purified and the crude purified product is distilled. For example, the crude purified product can be obtained through separation operations such as liquid-liquid extraction or extraction, concentration, crystallization or precipitation, solid-liquid separation (filtration, centrifugation, etc.), drying or desiccation, and combinations of these operations. A preferred method for obtaining the crude purified product may employ at least one separation and purification method selected from liquid-liquid extraction and precipitation (or crystallization).

[0063] In the separation (or extraction) process, both a good solvent (highly soluble in the reaction product 1,6-monomer) and a poor solvent (lowly soluble in the reaction product 1,6-monomer) can be used. The reaction mixture must contain at least a good solvent. A poor solvent can be added to the reaction mixture to separate the mixture into an organic phase containing the 1,6-monomer and an aqueous phase. Alternatively, the reaction can be carried out in a reaction system where both good and poor solvents coexist, allowing the reaction mixture to separate into an organic phase and an aqueous phase. The latter approach, where the 1,6-monomer can be extracted or partitioned into the organic phase during separation, is more advantageous from a reaction operation perspective.

[0064] Examples of good solvents include alcohols such as methanol and ethanol; aliphatic hydrocarbons such as hexane and octane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as dichloromethane, chloroform, and 1,2-dichloroethane; esters such as methyl acetate and ethyl acetate; and ketones such as methyl ethyl ketone and methyl isobutyl ketone. These good solvents can be used alone or in combination of two or more as mixed solvents. Aromatic hydrocarbons such as toluene and xylene are preferred good solvents.

[0065] Examples of unsuitable solvents include water. Water is a preferred unsuitable solvent.

[0066] In addition, the separated organic phase (the organic phase from which 1,6-body extracts are extracted) can be used directly as a crude product; the filtrate from the separated organic phase can also be used as a crude product, or the filtrate from which the residue is further washed and combined can be used as a crude product; it can also be concentrated and used as a crude product.

[0067] Alternatively, in the crystallization (or precipitation) operation, the reaction mixture can be concentrated and then crystallized (or precipitated); crystallization can also be performed by cooling in the reaction mixture (which contains at least a poor solvent and forms a homogeneous reaction system at the reaction temperature); or a poor solvent can be added to the reaction mixture and crystallized. Furthermore, since the reaction occurs in a homogeneous system, the reaction mixture usually contains at least a good solvent. Therefore, it is more preferable to add a poor solvent to the reaction mixture and then precipitate or crystallize a product containing 1,6-molecules from the reaction mixture.

[0068] Good solvents, in addition to those mentioned above, include ketones such as acetone; tetrahydrofuran, diacetone, and acetone. Alkane ethers; acetonitrile, propionitrile, and other nitrile compounds; DMF, DMAc, and other amides; dimethyl sulfoxide and other sulfoxides, etc. These good solvents can be used alone or in combination of two or more. Preferred good solvents are aromatic hydrocarbons such as toluene and xylene. Poor solvents (crystallization solvents) can be the same as those mentioned above, with water, methanol, ethanol, etc., being more preferably containing at least water.

[0069] In a more preferred method, taking advantage of the significant differences in the solubility and precipitation properties of the 1,6-body in solvents (poor solvents such as water and good solvents such as hydrocarbons), a crude refined product can be obtained by separating the reaction mixture into an organic phase (or an extract phase) and an aqueous phase, and / or by filtration (including washing of residues) of the precipitate crystallized (or precipitated) from the reaction mixture (reaction system). Specifically, the crude refined product may be the separated organic phase, the filtrate from filtering the organic phase, the filtrate from which residues are optionally washed and combined, or the concentrate from which the organic phase is optionally concentrated to a specific concentration; it may also be the residue from the filtration of solids precipitated or generated from the reaction mixture.

[0070] As mentioned above, the crude product can be a crude raw material containing organic solvents and being liquid at room temperature (20°C) (e.g., the aforementioned organic phase or filtrate, etc., organic solvent solution), or it can be a moist crude raw material that is solid at room temperature (20°C) (e.g., the residue (solid particles) after filtering and separating the precipitated solids).

[0071] The preferred crude refined product is the solid dried product of crude refined product, that is, the crude refined product containing 1,6- and solid at room temperature (20°C) (e.g., the dried product or solidified product of removing solvent from the aforementioned liquid crude raw material (the aforementioned organic solvent solution of the aforementioned organic phase, etc., after separation), or the dried product or solidified product of drying or solidifying a moist substance that is solid at room temperature (20°C).

[0072] The distillation conditions for the crude feedstock can be determined by the composition (types and amounts of low-boiling and high-boiling components, etc.) and form (liquid or solid), utilizing either single distillation (evaporation) or continuous distillation. Furthermore, continuous distillation can utilize plate columns or packed columns, and can be a thin-film distillation apparatus. The theoretical number of layers in the distillation column is, for example, 0 to 100 layers, more preferably 0 to 50 layers, and more preferably about 1 to 10 layers. Reflux can be optionally incorporated into the distillation column, with a reflux ratio, for example, 1 to 100, more preferably 5 to 50, and more preferably about 10 to 20. As described later, a simple distillation apparatus with 0 to 5 layers, especially about 0 to 2 layers, is preferred, and a single distillation apparatus with 0 layers is particularly suitable.

[0073] The aforementioned distillation (including single distillation) can optionally be carried out in an air stream, an inert gas environment (e.g., nitrogen, rare gases, etc.) (or in an air stream), but in a preferred embodiment, although the boiling point of the 1,6-body is lower than that of the positional isomer of naphthalene dithiol, it is still relatively high. Therefore, the crude feedstock is distilled under reduced pressure or vacuum to distill off a fraction containing the 1,6-body. That is, in order to suppress the formation and contamination of the 1,6-body polymer and to distill off the crude feedstock, it is more preferable to distill under reduced pressure (or vacuum distillation) and distill off a fraction containing the 1,6-body. The pressure of the reduced pressure distillation (or vacuum distillation) can be from 0.1 to 30 hPa depending on the distillation temperature (temperature of the distillation apparatus), more preferably from 1 to 25 hPa, more preferably from 5 to 20 hPa, and particularly preferably around 10 to 20 hPa.

[0074] In particular, during the distillation of the aforementioned crude feedstock, it is more preferable to distill the fraction containing 1,6-body at a distillation temperature (or column top temperature) of approximately 140 to 212°C (e.g., 145 to 210°C), more preferably 150 to 210°C, more preferably 160 to 205°C, and especially preferably 170 to 200°C (e.g., 180 to 200°C) under the aforementioned pressure. The distillation temperature (or column top temperature) of the fraction containing 1,6-body is 140 to 200°C, more preferably 140 to 185°C, and more preferably 140 to 170°C (e.g., 140 to 160°C). Furthermore, the aforementioned distillation temperature can be lowered as the pressure decreases during the distillation operation.

[0075] The distillation temperature (internal temperature of the distillation apparatus or bottom temperature of the column) of the aforementioned crude feedstock is sufficient to distill off a fraction containing 1,6-propionate. Depending on the pressure, it can be 160 to 235°C, more preferably 170 to 230°C (e.g., 180 to 225°C), more preferably 190 to 225°C (e.g., 195 to 225°C), and particularly preferably around 200 to 220°C. The aforementioned distillation temperature of the crude feedstock can be 160 to 220°C (e.g., 160 to 205°C), more preferably 160 to 195°C (e.g., 160 to 190°C), and more preferably around 160 to 180°C.

[0076] In a preferred method, distillation (reduced pressure or vacuum distillation) can be carried out at a distillation temperature (internal temperature of the distillation apparatus or bottom temperature of the column) of 160°C to 235°C (e.g., 165 to 230°C) and a pressure of 0.1 to 30 hPa (e.g., 0.5 to 25 hPa) to distill off a fraction containing 1,6-body at a temperature of 140 to 212°C (e.g., 145 to 205°C) and to produce the 1,6-body product.

[0077] Furthermore, if the crude raw material of the aforementioned liquid (the organic phase after separation) and the crude raw material of the aforementioned moist solid (the residue after filtration of precipitates, etc.) are distilled, low-boiling components such as organic solvents can be distilled from the top of the column of the distillation apparatus (single distillation apparatus or continuous distillation apparatus), and a distillate containing 1,6-body can be distilled from the middle or lower part (or the bottom of the column) of the distillation apparatus. The distillate containing 1,6-body from the middle or lower part of the distillation apparatus can be further distilled using a distillation apparatus (e.g., a single distillation apparatus). Although this method requires more distillation apparatus, the purity of the 1,6-body product can be significantly improved by distilling the crude and refined products, and the contamination of coloring components can be suppressed.

[0078] As mentioned above, the distillate containing the 1,6-body can be further purified. However, in this invention, a high-purity, almost colorless 1,6-body product can be produced through a single distillation operation (reduced pressure distillation or vacuum distillation), that is, single distillation under reduced pressure or vacuum. Specifically, if the solid dried product of the crude purified material is continuously distilled by single distillation (single distillation apparatus), the distillate containing the 1,6-body can be distilled from the upper part (top of the column, etc.) of the distillation apparatus (evaporation apparatus), and almost non-volatile polymers such as disulfides can be taken out from the lower part (bottom of the column) of the distillation apparatus (evaporation apparatus). In addition, polymers such as disulfides may remain in the lower part of the distillation apparatus during batch operations. Therefore, the method of this invention preferably includes at least a single distillation operation, which can effectively suppress the contamination of coloring components and significantly improve the purity of the 1,6-body product through the simple operation of single distillation. That is, high-purity, almost colorless 1,6-body can be produced simply by distilling (or recovering) and cooling the aforementioned distillate.

[0079] In addition, the single distillation apparatus (evaporation apparatus) can optionally be used to continuously supply and distill the solid dried material of the crude refined product, or it can be used to batch supply and distill the solid dried material of the crude refined product. The single distillation apparatus (evaporation apparatus) can utilize a device equipped with an evaporator, which may include a heatable evaporator, a supply line connected to the evaporator to supply the solid dried material of the crude refined product in a molten state, a capacitor connected to the upper part (or top) of the aforementioned evaporator to distill off a distillate containing 1,6-body, and a receiver to receive the distillate distilled from the capacitor. Furthermore, the single distillation apparatus (evaporation apparatus) can be a thin-film distillation apparatus (evaporation apparatus) that forms a thin film (a thin film of molten material) of the solid dried material of the crude refined product on the evaporation surface under reduced pressure or vacuum and then distills it; it can also be a downflow thin-film evaporator, a centrifugal thin-film evaporator, etc. In such distillation (or evaporation), the melting point of 1,6-body is low, so distillation (or evaporation) can be performed smoothly even without keeping the capacitor or receiver at a high temperature.

[0080] [Naphthalene derivatives]

[0081] The 1,6-form (or 1,6-form product) of this invention exhibits high purity, significantly reduced coloring due to coloring components, a high refractive index, and high solubility in organic solvents. Therefore, it can be used as a reaction reagent, polymer raw material, etc., to formulate naphthalene derivatives (1,6-form derivatives). These naphthalene derivatives also possess the characteristics of the 1,6-form (or 1,6-form product), exhibiting less coloring and displaying high refractive index and high solubility. For example, compared to other positional isomers (e.g., 1,5-form, 2,6-form, or 2,7-form), the aforementioned 1,6-form (or 1,6-form product) demonstrates superior solubility in organic solvents, readily and efficiently dissolving at high concentrations even at room temperature (around 20°C) to form a homogeneous solution. Therefore, the applications of the aforementioned 1,6-form (or 1,6-form product) can be significantly expanded.

[0082] Organic solvents for the aforementioned 1,6-isocyanate (or 1,6-isocyanate products) include hydrocarbons (aromatic hydrocarbons such as toluene and xylene), halogenated hydrocarbons (chlorinated hydrocarbons such as dichloromethane and chloroform), alcohols (isopropanol, etc.), and ethers (tetrahydrofuran (THF), 1,4-dichloromethane, etc.). Alkanes, glycol ethers (e.g., methyl ceroxythione, ethyl ceroxythione, etc. ceroxythiones, methyl carbitol, ethyl carbitol, etc. carbitols), glycol ether acetates (methyl ceroxythione acetate, ethyl ceroxythione acetate, methyl carbitol acetate, ethyl carbitol acetate, propylene glycol monomethyl ether acetate (PGMEA), etc.), ketones (e.g., acetone, methyl ethyl ketone), esters (ethyl acetate, etc.), nitriles (acetonitrile, etc.), amides (N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), etc.), ureas (1,3-dimethyl-2-imidazolidinedione (DMI), dimethylacrylurea (DMPU), etc.), sulfoxides (e.g., dimethyl sulfoxide, etc.). These organic solvents can be used alone or in combination of two or more as mixed solvents.

[0083] Furthermore, the 1,6-form and its derivatives have high solubility and high refractive index; therefore, if used as polymer raw materials, the proportion of the 1,6-form backbone can be increased, and the refractive index of the polymer can be improved. Additionally, the 1,6-form has an asymmetric structure, allowing for the production of transparent polymers suitable as optical materials. Therefore, the aforementioned 1,6-form (or 1,6-form products) can also be used as various reaction reagents and polymer raw materials due to the highly reactive thiol group; for example, the 1,6-form can be used to formulate polymers via an ene-thiol reaction. Furthermore, the derivatives of the 1,6-form can also be used as reaction reagents and polymer raw materials due to the introduced reactive groups. In a preferred embodiment, the 1,6-form and its derivatives can be used as optical materials.

[0084] Thus, naphthalene derivatives (1,6-body derivatives) can be represented by the following formula (2).

[0085]

[0086] [In the formula, R] 1 Let (2a) to (2e) represent the basis.

[0087]

[0088] (A 1 It is an alkylene group, X 1 R represents an oxygen atom or a sulfur atom. 2 It is an alkyl group, A 2 Indicates a direct bond (single bond) or alkylene group, R 3 R 4 and R 5 Each can be independently represented by a hydrogen atom or an alkyl group, R 6 and R 7 X represents a hydrogen atom or a methyl group, respectively. 2 (This represents an oxygen atom or a sulfur atom, where m1 is an integer greater than or equal to 1, and m2 to m5 represent integers greater than or equal to 0 or 1, respectively.)

[0089] In equations (2a) to (2e), A 1 It can be C 1-6 Alkylenes (especially C) 2-4 Alkylene), X 1 It can be an oxygen atom or a sulfur atom (preferably an oxygen atom).

[0090] R 1 Representative compounds of the group shown in formula (2a) are those in formula (2a) where m1 = 1 to 4 (especially 1 or 2), for example 1,6-bis(hydroxyC) 2-4 Alkylthio)naphthalene, 1,6-bis(hydroxyC) 2-4 Alkoxy C 2-4 Alkylthio)naphthalene, 1,6-bis(mercapto-C) 2-4 Alkylthio)naphthalene, 1,6-bis(mercapto-C) 2-4 Alkyl thio group C 2-4 Alkylthio(naphthalene), etc. The preferred compound is R. 1 Compounds that are hydroxyalkyl, such as 1,6-bis(hydroxyalkylthio)naphthalene [e.g., 1,6-bis(hydroxyethylthio)naphthalene, etc. 1,6-bis(hydroxyC 2-3 Alkylthio(naphthalene, etc.).

[0091] Such compounds can be prepared by reacting the 1,6-disulfide and a reaction component selected from alkoxides, alkyl carbonates, haloalkanols, alkylene sulfides, trithioalkyl carbonates, and haloalkanthiols in solvents such as DMF and DMAc in the presence of an alkali metal hydroxide (such as sodium hydroxide). To suppress the formation of disulfides, the reaction can be carried out in the presence of commonly used reducing agents and / or polymerization inhibitors.

[0092] In equation (2b), R 2 C is either linear or branched. 1-4 Alkyl group. R 1 Representative compounds of the group shown in formula (2b) are those in formula (2b) where m2 = 0 to 4 (more preferably 0 to 2), such as 1,6-bis(C 1-4 alkylthio)naphthalene, 1,6-bis(C 1-4 Alkoxy C 2-4 alkylthio)naphthalene, 1,6-bis(C 1-4 Alkyl thio group C 2-4 Alkylthio(naphthalene), etc. A preferred compound is R. 1 Compounds that are alkylthio or alkylthioalkyl, such as 1,6-bis(methylthio)naphthalene, etc. 1-2 Alkyl thio(naphthalene), etc.

[0093] Such compounds can be prepared by reacting the 1,6-body with alkyl iodides such as alkyl iodides (iodomethane, iodoethane, etc.) in solvents such as dichloromethane, DMF, DMAc in the presence of an alkali metal hydroxide (sodium hydroxide, etc.). To suppress the formation of disulfides, the reaction can be carried out in the presence of commonly used reducing agents and / or polymerization inhibitors.

[0094] R 1 Representative compounds of the group shown in formula (2c) are those in formula (2c) where m3 = 0 to 4 (more preferably 0 to 2) and R 3 R 4 and R 5 Compounds containing hydrogen atoms or methyl groups are preferred, especially those represented by formula (2c) where the group is vinyl or allyl. Examples of such compounds include 1,6-bis(C 2-4 alkenylthio)naphthalene, 1,6-bis(C 2-3 alkenyloxy C 2-3 alkylthio)naphthalene, 1,6-bis(C 2-3 alkenyl thiocyl C 2-3 Alkylthio)naphthalene, etc., preferred compounds include 1,6-bis(vinylthio)naphthalene, 1,6-bis(allylthio)naphthalene, 1,6-bis(isopropenylthio)naphthalene, etc. 1,6-bis(C 2-3 Alkenylthio(naphthalene), etc.

[0095] These compounds can be reacted with alkenyl iodine (allyl iodine, isopropenyl iodine, etc.) in solvents such as dichloromethane, DMF, and DMAc in the presence of alkali metal salts (such as sodium carbonate) and polymerization inhibitors (such as quinones). 2-6 It is prepared by reacting alkenyl iodine (such as alkenyl iodine) with alkenyl iodine. The solvent may contain water.

[0096] R 1 Representative compounds of the group shown in formula (2d) are those in formula (2d) where m4 = 0 to 4 (preferably 0 to 2) and R 6 Compounds containing hydrogen atoms or methyl groups are preferred, especially those with a (meth)acryloyl group as shown in formula (2d). Examples of such compounds include 1,6-bis[(meth)acryloylthio]naphthalene, 1,6-bis[(meth)acryloyloxyethylthio]naphthalene, and 1,6-bis[(meth)acryloyloxyC]naphthalene. 2-3 Alkylthio[naphthalene] etc.; preferred compounds include 1,6-bis(methacryloylthio)naphthalene, etc.

[0097] These compounds can be prepared by reacting the 1,6-form with (meth)acryloyl chloride, (meth)acryloyl bromide, or other (meth)acryloyl halides (preferably methacryloyl halides) in solvents such as dichloromethane, DMF, and DMAc in the presence of polymerization inhibitors (quinones such as methyl quinone).

[0098] R 1 Representative compounds of the group shown in formula (2e) are those in formula (2e) where m5 = 0 to 4 (more preferably 0 to 2) and R 7 It is a hydrogen atom or a methyl group (preferably a hydrogen atom) and X 2 Compounds containing oxygen or sulfur atoms (especially oxygen atoms), preferably with the group shown in formula (2d) being glycidyl, glycidoxy C 2-3 Alkyl compounds. Examples of such compounds include 1,6-bis(epoxypropylthio)naphthalene, 1,6-bis(epoxypropyloxyethylthio)naphthalene, etc. 2-3 Alkylthio(naphthalene), etc. Compounds having the group shown in formula (2e) can be monomers or polymers containing 2 to 10 polymers.

[0099] Such compounds can be modulated by reacting the 1,6-body with epichlorohydrin and other epichlorohydrin halides, or epithiochlorohydrin and other epithiochlorohydrin halides, in the presence of an interphase transfer catalyst such as benzyltributylammonium chloride.

[0100] A preferred derivative of the 1,6-body can be R in the aforementioned formula (2). 1 It is a derivative selected from at least one of hydroxyalkyl, alkyl, alkenyl (vinyl, allyl, etc.), (meth)acryloyl, (meth)acryloyloxyalkyl, glycidyl, and glycidyloxyalkyl. Among the 1,6- derivatives, derivatives having reactive groups such as hydroxyalkyl can be used as monomers of polymers, etc., while derivatives having polymerizable groups such as (meth)acryloyl and glycidyl can be used to form curable resins or compositions thereof.

[0101] (Example)

[0102] The present invention will be further described in detail below with reference to embodiments, but the present invention is not limited to these embodiments. Evaluation methods are presented below.

[0103] [ 1 H-NMR]

[0104] The determination was performed using a JNM-ECZ400 (400MHz) and a JNM-ECA600 (600MHz) instrument manufactured by NEC Corporation. The heavy solvent used was chloroform-d(CDCl3), and the standard substance used was tetramethylsilane (TMS).

[0105] [HPLC purity, disulfide content (dimer content)]

[0106] The area percentage determined by HPLC under the following conditions is used as the HPLC purity and the content of disulfide (dimer). Furthermore, if the content of disulfide (dimer) does not reach the detection limit, it is recorded as "ND".

[0107] HPLC apparatus: Shimadzu Corporation, LC-20A

[0108] Column: YMC-Triart C18 (5μm, 4.6mmφ×150mm)

[0109] Mobile phase: 5% phosphoric acid solution / acetonitrile (acetonitrile 65% → 90%)

[0110] Flow rate: 1.0 ml / min, column temperature: 40℃, detection wavelength: UV210nm.

[0111] [Melting Point]

[0112] Using a melting point measuring apparatus (Buchi "535") according to JIS K 4101 (1993)

[0113] [5.1 Visual Method] The melting point is determined by visual inspection.

[0114] Gardner Chroma

[0115] The sample was kept at 50°C and compared visually with Gardner color standard solution in the molten state, and the color was measured.

[0116] [Refractive Index]

[0117] The refractive index of each sample at 25°C and 589 nm was determined using an Abbe refractometer (ATAGO Co., Ltd., "NAR-1T"). Additionally, the refractive index was determined using the following methods depending on the type of sample.

[0118] [Solubility]

[0119] The solubility of the sample was confirmed by mixing the sample with the specific solvents listed in the table below at a temperature of 25°C. Specifically, a specific amount of solvent was added to the sample until it became insoluble, and the resulting liquid layer (solvent layer) was analyzed by HPLC (Shimadzu Corporation "SPD-20A"), and the concentration of the sample in the liquid layer (solvent layer) (the maximum concentration dissolved) was used as the solubility.

[0120] [Example 1]

[0121] [Synthesis of 1,6-naphthyldithiol (1,6-body)]

[0122]

[0123] In a nitrogen atmosphere, 100 g (300.9 mmol) of disodium 1,6-naphthalenedisulfonate, 451 g of toluene, 8.8 g (0.4 mol / L) of N,N-dimethylformamide, and 89.6 g (2.5 mol / L) of thionyl chloride were added to a 1000 mL flask. The mixture was heated to 100 °C and reacted at 97–102 °C for 8 hours. After the reaction, the mixture was cooled to 30 °C, and 451 g of water was added at 20–30 °C. The mixture was stirred for at least 10 minutes, separated, and the lower aqueous phase was removed. The organic phase was then reacted with 451 g of water in the same manner, stirred for at least 10 minutes, and separated to obtain 622.5 g of a toluene solution of 1,6-naphthalenedisulfonyl chloride (16NDSC) as the organic phase (HPLC purity: 98%, theoretical yield: 97 mol%).

[0124] In a nitrogen atmosphere, 1800 g of toluene and 1439.8 g of 36% hydrochloric acid (48.8 mol / L) were added to a 5000 mL flask, and the temperature was raised to 60 °C. After heating, 622.5 g (291.0 mmol) of the aforementioned 16NDSC toluene solution and 258.8 g (13.6 mol / L) of zinc powder were added in portions over 3 hours and 30 minutes at 60-70 °C, and the reaction was continued at the aforementioned temperature for 1 hour. After the reaction, the mixture was cooled to 30 °C, allowed to stand at 0-30 °C, and then separated, removing the lower aqueous phase. The organic phase was then filtered, and the residue was washed with 33 g of toluene. The resulting filtrate was desolventized and dried under reduced pressure below 45 °C to obtain 50.5 g of solid 1,6-naphthalenedithiol (1,6-monotype) (HPLC: purity 98.3%, disulfide content 1.4%, Gardner color: 5, theoretical yield: 90 mol%).

[0125] [Distillation process]

[0126] 148 g of the solid containing the obtained 1,6-naphthalenedithiol (1,6-body) was added to a distillation apparatus (single distillation apparatus) and distilled at an internal temperature of 162 to 167 °C and a pressure of 0.6 hPa to obtain 144 g of colorless distillate at a top temperature of 141 to 146 °C (yield: 97 mol%, HPLC: purity 100.0%, disulfide “ND”, Gardner color: less than 1).

[0127] Melting point: 35 to 36℃

[0128] Refractive index: 1.722

[0129] 1H-NMR (CDCl3): δ (ppm) 3.57 (s, 1H), 3.61 (s, 1H), 7.31 (dd, J 8.47.4, 1H), 7.40 (dd, J 9.0 1.8, 1H), 7.48 (d, J 7.2,1H), 7.55(d,J8.4,1H), 7.72(d,J 1.8,1H), 8.03(d,J9.0,1H).

[0130] The following table presents the evaluation results of the 1,6-solid product obtained from the distillation operation of Example 1.

[0131] [Table 1]

[0132]

[0133] Examples 2 to 6

[0134] Distillation was performed in the same manner as in Example 1, except that distillation was carried out under the conditions described below, to obtain the 1,6-naphthalene dithiol product. All obtained 1,6-naphthalene dithiol products were HPLC grade: 100.0% purity, disulfide "ND", Gardner color: below 1.

[0135] Example 2: Internal temperature 167℃, pressure 1hPa, and top temperature 146℃.

[0136] Example 3: Internal temperature 200℃, pressure 10hPa, and top temperature 181℃.

[0137] Example 4: Internal temperature 208℃, pressure 15hPa, and top temperature 187℃.

[0138] Example 5: Internal temperature 218℃, pressure 20hPa, and top temperature 194℃.

[0139] Example 6: Internal temperature 234℃, pressure 30hPa, and top temperature 211℃.

[0140] [Comparative Example 1] Crystallization of 1,6-form from methanol

[0141] 25.0 g of crude purified 1,6-naphthalenedithiol (HPLC: purity 98.9%, disulfide 1.1%, Gardner color: 5) and 250.0 g of methanol were added to a 1 L flask. The mixture was stirred and dissolved at 25 °C. The solution was cooled to below 5 °C, and 44.1 g of water was added dropwise, resulting in crystallization. The crystals were obtained by filtration, yielding 18.1 g of a yellow solid (yield: 71 mol%, HPLC: purity 99.3%, disulfide 0.7%, Gardner color: 5).

[0142] In addition, the crude raw material 1,6-naphthalenedithiol was obtained by repeating the same reaction as in Example 1 above. In this example, even when crystallized from methanol, the coloring did not change, so the purification operation was completed with one crystallization operation.

[0143] [Comparative Example 2] Crystallization of 1,6-form from heptane

[0144] 20.0 g of crude purified 1,6-naphthalenedithiol (HPLC: purity 98.9%, disulfide 1.1%, Gardner color: 5) and 229.5 g of heptane were added to a 1 L flask. The mixture was heated to 98 °C and stirred. After stirring, the mixture was slowly cooled to below 5 °C, and crystals precipitated. 7.9 g of a yellow solid was obtained by filtration (yield: 40 mol%, HPLC: purity 98.9%, disulfide 1.1%, Gardner color: 4).

[0145] 7.9 g of the obtained yellow solid and 90.9 g of heptane were added, and the mixture was heated to 98 °C and stirred. After stirring, the mixture was slowly cooled to 5 °C, and crystals precipitated. The crystals were obtained by filtration, yielding 5.9 g of yellow solid (yield: 30 mol%, HPLC: purity 98.9%, disulfide 1.1%, Gardner color: 4).

[0146] The above-described two crystallization operations were performed from heptane, but a high-purity, colorless 1,6-form product was not obtained. In particular, the Gardner color remained unchanged even after two crystallizations.

[0147] [Comparative Example 3] 1,6-form purified by silica gel chromatography

[0148] 20.0 g of crude purified 1,6-naphthyl dithiol (HPLC: purity 98.9%, disulfide 1.1%, Gardner color: 5) was purified by silica gel column chromatography (ethyl acetate / heptane (volume ratio) = 1 / 32) to obtain 14.2 g of pale yellow solid 1,6-naphthyl dithiol (theoretical yield: 72 mol%, HPLC: purity 99.6%, disulfide: 0.3%, Gardner color: 3).

[0149] The obtained solid was further purified by silica gel column chromatography (ethyl acetate / heptane (volume ratio) = 1 / 32) to obtain 10.0 g of pale yellow solid 1,6-naphthalenedithiol (theoretical yield: 50 mol%, HPLC: purity 99.5%, disulfide 0.3%, Gardner color: 3).

[0150] As mentioned above, even after two purification processes using chromatography, the purity and content of disulfide substances cannot be reduced, nor can the coloring components be removed.

[0151] [Comparative Example 4] Adsorption Treatment

[0152] In a nitrogen atmosphere, 250 g of methanol (10 times the amount of the crude purified 1,6-naphthalenedithiol) and 25 g of the crude purified 1,6-naphthalenedithiol (HPLC purity: 100.0%, disulfide "ND", Gardner color: 5) were added to a 1 L flask, and the temperature was raised to 30°C. The mixture was stirred for at least 10 minutes to confirm complete dissolution. 2.5 g of activated carbon ("Hakuhei A" manufactured by Osaka Gas Chemical Co., Ltd.) (10% by mass of the crude purified 1,6-naphthalenedithiol) was added to the resulting solution, and the mixture was stirred for 30 minutes. The mixture was then filtered, and the residue was washed with methanol to obtain 280.2 g of 1,6-naphthalenedithiol solution A (HPLC purity: 99.0%, disulfide: 1.0%), but the coloring components were not removed. 2.5 g of acidic clay (MIZUKALIFE F-1G, manufactured by Mizusawa Chemical Industry Co., Ltd.) was added to the obtained 1,6-naphthalenedithiol solution A (10% by mass relative to the crude refined product of 1,6-naphthalenedithiol) and stirred for at least 30 minutes. The mixture was then filtered, and the residue was washed with methanol to obtain 282.2 g of 1,6-naphthalenedithiol solution B (HPLC purity: 98.5%, disulfide content: 1.5%), but the coloring components were not removed. 2.5 g of the aforementioned acidic clay (10% by mass relative to the crude refined product of 1,6-naphthalenedithiol) was added to the obtained solution B again, and the mixture was stirred for at least 30 minutes. The mixture was then filtered, and the residue was washed with methanol to obtain 282.2 g of 1,6-naphthalenedithiol solution C (HPLC purity: 98.4%, disulfide content: 1.6%), but the coloring components were not removed.

[0153] As mentioned above, even decolorization with activated carbon and acidic clay cannot reduce the purity and the content of disulfide substances, nor can it remove the coloring components.

[0154] [Comparative Example 5] Synthesis of 1,5-form

[0155]

[0156] In a nitrogen atmosphere, 100 g (300.9 mmol) of disodium 1,5-naphthalenedisulfonate, 200 3 g of toluene, 8.8 g (0.4 mol / L) of N,N-dimethylformamide, and 85.9 g (2.4 mol / L) of thionyl chloride were added to a 5 L flask, and the mixture was heated to 100 °C. The temperature was maintained at 97–102 °C in a thermostat for 5 hours. After the reaction, the mixture was cooled to 30 °C, and 451 g of water was added at 20–30 °C with stirring for at least 10 minutes. The lower aqueous phase was separated. 150 g of water was added in the same manner, and the mixture was stirred for at least 10 minutes and separated to obtain the organic phase. The organic phase was filtered, and the residue was washed with 30 g of toluene to obtain 2141.6 g of a toluene solution of 1,5-naphthalenedisulfonyl chloride (15NDSC) (HPLC: purity 96%, theoretical yield: 96 mol%).

[0157] In a nitrogen atmosphere, 580 g of toluene and 1422.1 g of 36% hydrochloric acid (48.4 mol / L) were added to a 10 L flask, and the temperature was raised to 60 °C. After heating, 2141.6 g (289.8 mmol) of the aforementioned 15% NDSC toluene solution and 257.7 g (13.6 mol / L) of zinc powder were added in portions over 1 hour and 30 minutes. The temperature during addition was 60-70 °C, and the reaction was maintained at this temperature in a thermostat for 1 hour. After the reaction, the mixture was cooled to 30 °C and allowed to stand at 0-30 °C. The lower aqueous phase was then separated. The organic phase was then filtered, and the residue was washed with 188 g of toluene. The resulting filtrate was desolventized and dried under reduced pressure below 40 °C to obtain 58.5 g of solid 1,5-naphthalenedithiol (15 molecules) (HPLC: purity 99.4%, disulfide "ND", theoretical yield: 99 mol%).

[0158] [Distillation process]

[0159] 10g of 1,5-naphthalenedithiol (1,5-body) was added to a distillation apparatus (single distillation apparatus) and distilled, yielding a distillate with a boiling point of 150℃ / 0.6hPa. However, crystallization (melting point of 1,5-body of 1,5-body is 120℃) occurred inside the capacitor, blocking the distillation line, thus stopping the process.

[0160] The characteristics of the obtained 1,5-monomer are as follows. Additionally, the 1,5-monomer has a high melting point and is difficult to dissolve, therefore Gardner colorimetry could not be determined, but it exhibits a yellow color.

[0161] Melting point 120 to 121℃

[0162] Refractive index 1.711

[0163] 1 H-NMR (CDCl3): δ (ppm) 3.62 (s, 2H), 7.40 (dd, J 8.4 7.2, 2H), 7.59 (d, J 7.2, 2H), 8.04 (d, J 8.4, 2H).

[0164] [Comparative Example 6] Synthesis of the 2,6-form

[0165]

[0166] In a 1 L flask under nitrogen atmosphere, 100 g (300.9 mmol) of disodium 2,6-naphthalenedisulfonate, 451 g of toluene, 8.8 g (0.4 mol / L) of N,N-dimethylformamide, and 100.3 g (2.8 mol / L) of thionyl chloride were added, and the mixture was heated to 100 °C. The temperature was maintained at 97–102 °C in a thermostat for 8 hours. After the reaction, the mixture was cooled to 30 °C, and 226 g of water was added at 20–30 °C. The mixture was stirred for at least 2 hours and then filtered. The resulting wet crystals were washed with 60 g of toluene and dried to obtain 92.6 g of solid 2,6-naphthalenedisulfonyl chloride (26NDSC) (HPLC: purity 98%, theoretical yield: 93 mol%).

[0167] In a nitrogen atmosphere, 4478 g of toluene and 249.0 g of zinc powder (13.6 mol / L) were added to a 10 L flask, and the temperature was raised to 60 °C. After heating, 92.6 g (279.9 mmol) of 26% NDSC and 692.4 g (24.4 mol / L) of 36% hydrochloric acid were added in portions over 1 hour. The temperature during addition was 60-70 °C, and the reaction was maintained at this temperature in a thermostat for 2 hours. After the reaction, the mixture was filtered, and the residue was washed with 55 g of toluene preheated to 60 °C. The resulting filtrate was separated at 55-60 °C to remove the lower aqueous phase. Then, 221 g of water and 21.0 g (0.74 mol / L) of 36% hydrochloric acid were added, and the temperature was raised to 50 °C. The temperature after heating was maintained at 50-60 °C in a thermostat with stirring for 30 minutes, and the lower aqueous phase was separated. The obtained organic phase was desolventized to 398 g under reduced pressure below 60 °C and cooled to 5 °C. The cooled temperature was maintained at 0 to 5 °C in a constant temperature bath at the aforementioned temperature with stirring for 1 hour, followed by filtration. The obtained wet crystals were washed with 55 g of water and dried, thereby obtaining 40.2 g of solid 2,6-naphthalenedithiol (26 molecules) (HPLC: purity 100.0%, disulfide "ND", theoretical yield: 75 mol%).

[0168] [Distillation process]

[0169] 24 g of 2,6-naphthalenedithiol (2,6-body) was added to the distillation apparatus (single distillation apparatus). During distillation, it began to sublimate at 145 °C / 0.7 hPa (melting point of 2,6-body is 196 to 197 °C) and blocked the distillation line, so the distillation operation was stopped.

[0170] The characteristics of the obtained 2,6-monomer are as follows. Additionally, the 2,6-monomer has a high melting point and is difficult to dissolve, therefore the Gardner color of the 2,6-monomer could not be determined, but it exhibits a yellow color.

[0171] Melting point 196 to 197℃

[0172] Refractive index 1.718

[0173] 1 H-NMR (CDCl3): δ (ppm) 3.58 (s, 2H), 7.32 (dd, J 8.0 1.6, 2H), 7.57 (d, J8.0, 2H), 7.68 (d, J 1.6, 2H).

[0174] [Comparative Example 7] Synthesis of the 2,7-form

[0175]

[0176] In a 1 L flask under nitrogen atmosphere, 100 g (300.9 mmol) of disodium 2,7-naphthalenedisulfonate, 632 g of toluene, 8.8 g (0.4 mol / L) of N,N-dimethylformamide, and 89.5 g (2.5 mol / L) of thionyl chloride were added, and the mixture was heated to 100 °C. The temperature was maintained at 97–102 °C in a thermostat for 3 hours. After the reaction, the mixture was cooled to 30 °C, and 451 g of water was added at 20–30 °C with stirring for at least 10 minutes. The lower aqueous phase was separated. Another 451 g of water was added in the same manner, and the mixture was stirred for at least 10 minutes and separated to obtain 738.6 g of a toluene solution of 2,7-naphthalenedisulfonyl chloride (27NDSC) as the organic phase (HPLC: purity 99%, theoretical yield: 99 mol%).

[0177] In a nitrogen atmosphere, 6507 g of toluene and 1264.3 g of 36% hydrochloric acid (41.9 mol / L) were added to a 10 L flask, and the temperature was raised to 60 °C. After heating, 738.6 g (297.6 mmol) of 27% NDSC toluene solution and 264.7 g (13.6 mol / L) of zinc powder were added in portions over 3 hours and 30 minutes. The temperature during addition was 60-70 °C, and the reaction was maintained at this temperature in a thermostat for 1 hour. After the reaction, the mixture was cooled to 30 °C and allowed to stand at 0-30 °C. The lower aqueous phase was then separated. The organic phase was then filtered, and the residue was washed with 75 g of toluene. The resulting filtrate was desolvated under reduced pressure to 203 g at below 55 °C, and then filtered. The resulting wet crystals were washed with 59 g of toluene and dried to obtain 43.1 g of solid 2,7-naphthalenedithiol (27 bodies) (HPLC: purity 99.5%, disulfide “ND”, theoretical yield: 75 mol%).

[0178] [Distillation process]

[0179] 20 g of 2,7-naphthalenedithiol (2,7-body) was added to the distillation apparatus. During distillation, it began to sublimate at 145 °C / 0.7 hPa (melting point of 2,7-body is 186 to 188 °C) and blocked the distillation line, so the distillation operation was stopped.

[0180] The characteristics of the obtained 2,7-monomeric product are as follows. Additionally, the 2,7-monomeric product has a high melting point and is difficult to dissolve; therefore, the Gardner color of the 2,7-monomeric product could not be determined, but it exhibits a yellow color.

[0181] Melting point 186 to 188℃

[0182] Refractive index 1.721

[0183] 1 H-NMR (CDCl3): δ (ppm) 3.60 (s, 2H), 7.27 (dd, J 8.4 1.2, 2H), 7.58 (d, J1.2, 2H), 7.64 (d, J 8.4, 2H).

[0184] The evaluation results of the naphthalene dithiol products obtained in Examples 1 and Comparative Examples 6 to 8 are presented in the table below. In the table, "THF" stands for tetrahydrofuran, "DMF" for N,N-dimethylformamide, and "PGMEA" for propylene glycol monomethyl ether acetate (the same applies hereinafter). Additionally, as mentioned above, the Gardner colorimetry of the 1,5-form product, 2,6-form product, and 2,7-form product could not be determined.

[0185] [Table 2]

[0186]

[0187] As shown in Table 2, Comparative Example 5 (1,5-monolithic product), which has the lowest refractive index among the comparative examples, exhibits high solubility in all solvents. On the other hand, Example 1 (1,6-monolithic product) has both higher refractive index and solubility than Comparative Example 5 (1,5-monolithic product), especially with significantly higher solubility. In particular, it is soluble in toluene, THF, DMF, and ethyl acetate at concentrations of 90% by mass or higher, and even at concentrations of 85% by mass or higher in PGMEA.

[0188] (Industry availability)

[0189] The 1,6-naphthalenedithiol (or 1,6-naphthalenedithiol product) of the present invention is of high purity and significantly reduces coloration. Furthermore, it also possesses high solubility and high refractive index. Therefore, the 1,6-naphthalenedithiol (or 1,6-naphthalenedithiol product) of the present invention can be used for various applications, such as reagents, raw materials for functional compounds, reaction intermediates, optical materials [e.g., display materials such as antireflective films (e.g., refractive index matching films), refractive index enhancers, fluorescent matting agents, crosslinking agents or crosslinking aids, and other additives (or resin additives)], electrical and electronic materials (photoresist materials such as photoresist underlayer films, organic semiconductor materials, etc.), coating materials or paints (coating compositions for forming hard coatings, etc.). In addition, the 1,6-naphthalenedithiol (or 1,6-naphthalenedithiol product) of the present invention can be used, for example, as a resin raw material or monomer component (e.g., a high refractive index monomer component). Resins that can be formulated from the aforementioned resin raw materials or monomer components include, for example, thermo- (or photo)curable resins such as (meth)acrylic resins, epoxy resins, and diallyl resins; thermoplastic resins such as polyester resins (polyester resins, polyester carbonate resins, polycarbonate resins, polysulfide resins, etc.), polyether resins, polysulfide resins (polyadditions that have undergone the reaction of thiolsenes, etc.), and polyurethane resins (polyurethane resins, polythiourethane resins, etc.).

Claims

1. A 1,6-naphthalene dithiol product, wherein the purity of its area percentage as determined by high performance liquid chromatography is greater than 99.5%, the content of the 1,6-naphthalene dithiol polymer is less than 0.2%, and the Gardner color in the molten state is less than 1.

2. The 1,6-naphthalenedithiol product according to claim 1, wherein the polymer of 1,6-naphthalenedithiol is a disulfide of a dimer.

3. A 1,6-naphthalene dithiol product, which is used to prepare a polymer obtained by reaction with a thiol ene or a 1,6-naphthalene dithiol derivative represented by formula (2) below. The 1,6-naphthalenedithiol product, as determined by high-performance liquid chromatography, has a purity of over 99.5% in terms of area percentage, a 1,6-naphthalenedithiol polymer content of less than 0.2%, and a Gardner color of less than 1 in the molten state. In the formula, R 1 Denotes the basis represented by any of the following equations (2a) to (2e). A 1 Indicates alkylene, X 1 R represents an oxygen atom or a sulfur atom. 2 Indicates alkyl group, A 2 Indicates direct bonding or alkylene bonding, R 3 R 4 and R 5 Each can be independently represented by a hydrogen atom or an alkyl group, R 6 and R 7 X represents a hydrogen atom or a methyl group, respectively. 2 This represents an oxygen atom or a sulfur atom. m1 represents an integer greater than or equal to 1, and m2 to m5 represent integers greater than or equal to 0 or 1, respectively.

4. The 1,6-naphthalene dithiol product according to claim 3, wherein the naphthalene dithiol derivative represented by formula (2) is prepared in an organic solvent.

5. The 1,6-naphthalenedithiol product according to claim 3 or 4, wherein in formulas (2a) to (2e), A 1 C represents 1-6 Alkylene, X 1 Represents oxygen or sulfur atoms. In equation (2a), m1 represents an integer from 1 to 4. In equation (2b), R 2 Indicates linear or branched C 1-4 Alkyl group, m2 represents an integer from 0 to 4. In equation (2c), m3 represents an integer from 0 to 4, and R 3 R 4 and R 5 They represent hydrogen atoms or methyl groups, respectively. In equation (2d), m4 represents an integer from 0 to 4, and R 6 Indicates a hydrogen atom or a methyl group. In equation (2e), m5 represents an integer from 0 to 4, and R 7 X represents a hydrogen atom or a methyl group. 2 It represents an oxygen atom or a sulfur atom.

6. The 1,6-naphthalenedithiol product according to claim 3, wherein in the naphthalenedithiol derivative represented by formula (2), The R 1 The derivative having the group shown in formula (2a) is prepared in an organic solvent in the presence of a base by reacting a 1,6-naphthalene dithiol product with a reactant selected from alkoxides, alkyl carbonates, haloalkanols, alkylene sulfides, trithioalkyl carbonates, and haloalkanthiols. The R 1 Derivatives having the group shown in formula (2b) are prepared in an organic solvent in the presence of a base by reacting a 1,6-naphthalenedithiol product with a haloalkane. The R 1 The derivative having the group shown in formula (2c) is prepared by reacting a 1,6-naphthalene dithiol product with a halide in an organic solvent in the presence of a base and a polymerization inhibitor. The R 1 The derivative having the group shown in formula (2d) is prepared by reacting a 1,6-naphthalenedithiol product with a (meth)acryloyl halide in an organic solvent in the presence of a polymerization inhibitor. The R 1 The derivative having the group shown in formula (2e) is produced by reacting a 1,6-naphthalene dithiol product with an epoxy halopropane and / or an epoxy thiopropane in the presence of an interphase transfer catalyst.

7. The 1,6-naphthalenedithiol product according to claim 3 or 4, wherein the R of formula (2) 1 It is at least one selected from hydroxyalkyl, alkyl, alkenyl, (meth)acryloyl, (meth)acryloyloxyalkyl, epoxypropyl, and epoxypropyloxyalkyl.

8. The 1,6-naphthalenedithiol product according to claim 3 or 4, wherein the polymer of 1,6-naphthalenedithiol is a disulfide of a dimer.

9. The 1,6-naphthalenedithiol product according to claim 3 or 4, wherein the purity of its area percentage determined by high performance liquid chromatography is above 99.8%, the content of the dimer of 1,6-naphthalenedithiol is below 0.05% or does not reach the detection limit, the Gardner color in the molten state is below 1, it is in crystalline form at 20°C, and the melting point is 35 to 36°C.

10. A method for producing a 1,6-naphthalenedithiol product, comprising producing 1,6-naphthalenedithiol from a crude raw material containing a polymer of 1,6-naphthalenedithiol and at least 1,6-naphthalenedithiol, wherein, The manufacturing method involves distilling the aforementioned crude raw materials.

11. The method according to claim 10, wherein the crude feedstock is a crude and refined product of 1,6-naphthalenedithiol refined from the reaction mixture after the synthesis of 1,6-naphthalenedithiol.

12. The method according to claim 10 or 11, wherein the crude feedstock is a solid dried product of a crude refined product of 1,6-naphthalenedithiol obtained from a reaction mixture for synthesizing 1,6-naphthalenedithiol.

13. The method according to claim 10 or 11, wherein the crude feedstock is distilled under reduced pressure or vacuum distilled to distill off a fraction containing 1,6-naphthalenedithiol.

14. The method according to claim 10 or 11, wherein the crude feedstock is distilled at a pressure of 0.1 to 30 hPa and a distillate is obtained at a temperature of 140 to 212°C.

15. The method according to claim 10 or 11, wherein the crude feedstock is a solid dried product of crude refined product of 1,6-naphthalenedithiol obtained from the reaction mixture for synthesizing 1,6-naphthalenedithiol, the solid dried product is subjected to single distillation, and a distillate containing 1,6-naphthalenedithiol is distilled off from the top of the distillation apparatus.

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